Bio

Bio


Heilshorn's interests include biomaterials in regenerative medicine, engineered proteins with novel assembly properties, microfluidics and photolithography of proteins, and synthesis of materials to influence stem cell differentiation. Current projects include tissue engineering for spinal cord and blood vessel regeneration, designing injectable materials for use in stem cell therapies, and the design of microfluidic devices to study the directed migration of cells (i.e., chemotaxis).

Academic Appointments


Honors & Awards


  • New Investigator Award, Petroleum Research Fund, American Chemical Society (2009)
  • CAREER Award, National Science Foundation (2009)
  • New Innovator Award, National Institutes of Health (2009)

Professional Education


  • PhD, Caltech, Chemical Engineering (2004)
  • MS, Caltech, Chemical Engineering (2000)
  • BS, Georgia Tech, Chemical Engineering (1998)

Research & Scholarship

Current Research and Scholarly Interests


Protein engineering
Tissue engineering
Regenerative medicine
Biomaterials

Teaching

2013-14 Courses


Postdoctoral Advisees


Publications

Journal Articles


  • Microfluidic Investigation of BDNF-Enhanced Neural Stem Cell Chemotaxis in CXCL12 Gradients SMALL Xu, H., Heilshorn, S. C. 2013; 9 (4): 585-595

    Abstract

    In vivo studies have suggested that gradients of CXCL12 (aka stromal cell-derived factor 1?) may be critical for neural stem cell (NSC) migration during brain development and neural tissue regeneration. However, traditional in vitro chemotaxis tools are limited by unstable concentration gradients and the inability to decouple cell migration directionality and speed. These limitations have restricted the reproducible and quantitative analysis of neuronal migration, which is required for mechanism-based studies. Using a microfluidic gradient generator, nestin and Sox-2 positive human embryonic NSC chemotaxis is quantified within a linear and stable CXCL12 gradient. While untreated NSCs are not able to chemotax within CXCL12 gradients, pre-treatment of the cells with brain-derived neurotrophic factor (BDNF) results in significant chemotactic, directional migration. BDNF pre-treatment has no effect on cell migration speed, which averages about 1 ?m min(-1). Quantitative analysis determines that CXCL12 concentrations above 9.0 nM are above the minimum activation threshold, while concentrations below 14.7 nM are below the saturation threshold. Interestingly, although inhibitor studies with AMD 3100 revealed that CXCL12 chemotaxis requires receptor CXCR4 activation, BDNF pre-treatment is found to have no profound effects on the mRNA levels or surface presentation of CXCR4 or the putative CXCR7 scavenger receptor. The microfluidic study of NSC migration within stable chemokine concentration profiles provides quantitative analysis as well as new insight into the migratory mechanism underlying BDNF-induced chemotaxis towards CXCL12.

    View details for DOI 10.1002/smll.201202208

    View details for Web of Science ID 000315103300013

    View details for PubMedID 23109183

  • Building stem cell niches from the molecule up through engineered peptide materials NEUROSCIENCE LETTERS Lampe, K. J., Heilshorn, S. C. 2012; 519 (2): 138-146

    Abstract

    The native stem cell niche is a dynamic and complex microenvironment. Recapitulating this niche is a critical focus within the fields of stem cell biology, tissue engineering, and regenerative medicine and requires the development of well-defined, tunable materials. Recent biomaterial design strategies seek to create engineered matrices that interact with cells at the molecular scale and allow on-demand, cell-triggered matrix modifications. Peptide and protein engineering can accomplish these goals through the molecular-level design of bioinductive and bioresponsive materials. This brief review focuses on engineered peptide and protein materials suitable for use as in vitro neural stem cell niche mimics and in vivo central nervous system repair. A key hallmark of these materials is the immense design freedom to specify the exact amino acid sequence leading to multi-functional bulk materials with tunable properties. These advanced materials are engineered using rational design strategies to recapitulate key aspects of the native neural stem cell niche. The resulting materials often combine the advantages of biological matrices with the engineering control of synthetic polymers. Future design strategies are expected to endow these materials with multiple layers of bi-directional feedback between the cell and the matrix, which will lead to more advanced mimics of the highly dynamic neural stem cell niche.

    View details for DOI 10.1016/j.neulet.2012.01.042

    View details for Web of Science ID 000306146800009

    View details for PubMedID 22322073

  • Improving Viability of Stem Cells During Syringe Needle Flow Through the Design of Hydrogel Cell Carriers TISSUE ENGINEERING PART A Aguado, B. A., Mulyasasmita, W., Su, J., Lampe, K. J., Heilshorn, S. C. 2012; 18 (7-8): 806-815

    Abstract

    Cell transplantation is a promising therapy for a myriad of debilitating diseases; however, current delivery protocols using direct injection result in poor cell viability. We demonstrate that during the actual cell injection process, mechanical membrane disruption results in significant acute loss of viability at clinically relevant injection rates. As a strategy to protect cells from these damaging forces, we hypothesize that cell encapsulation within hydrogels of specific mechanical properties will significantly improve viability. We use a controlled in vitro model of cell injection to demonstrate success of this acute protection strategy for a wide range of cell types including human umbilical vein endothelial cells (HUVEC), human adipose stem cells, rat mesenchymal stem cells, and mouse neural progenitor cells. Specifically, alginate hydrogels with plateau storage moduli (G') ranging from 0.33 to 58.1 Pa were studied. A compliant crosslinked alginate hydrogel (G'=29.6 Pa) yielded the highest HUVEC viability, 88.9% ± 5.0%, while Newtonian solutions (i.e., buffer only) resulted in 58.7% ± 8.1% viability. Either increasing or decreasing the hydrogel storage modulus reduced this protective effect. Further, cells within noncrosslinked alginate solutions had viabilities lower than media alone, demonstrating that the protective effects are specifically a result of mechanical gelation and not the biochemistry of alginate. Experimental and theoretical data suggest that extensional flow at the entrance of the syringe needle is the main cause of acute cell death. These results provide mechanistic insight into the role of mechanical forces during cell delivery and support the use of protective hydrogels in future clinical stem cell injection studies.

    View details for DOI 10.1089/ten.tea.2011.0391

    View details for Web of Science ID 000302137200013

    View details for PubMedID 22011213

  • Essential Regulation of CNS Angiogenesis by the Orphan G Protein-Coupled Receptor GPR124 SCIENCE Kuhnert, F., Mancuso, M. R., Shamloo, A., Wang, H., Choksi, V., Florek, M., Su, H., Fruttiger, M., Young, W. L., Heilshorn, S. C., Kuo, C. J. 2010; 330 (6006): 985-989

    Abstract

    The orphan G protein-coupled receptor (GPCR) GPR124/tumor endothelial marker 5 is highly expressed in central nervous system (CNS) endothelium. Here, we show that complete null or endothelial-specific GPR124 deletion resulted in embryonic lethality from CNS-specific angiogenesis arrest in forebrain and neural tube. Conversely, GPR124 overexpression throughout all adult vascular beds produced CNS-specific hyperproliferative vascular malformations. In vivo, GPR124 functioned cell-autonomously in endothelium to regulate sprouting, migration, and developmental expression of the blood-brain barrier marker Glut1, whereas in vitro, GPR124 mediated Cdc42-dependent directional migration to forebrain-derived, vascular endothelial growth factor-independent cues. Our results demonstrate CNS-specific angiogenesis regulation by an endothelial receptor and illuminate functions of the poorly understood adhesion GPCR subfamily. Further, the functional tropism of GPR124 marks this receptor as a therapeutic target for CNS-related vascular pathologies.

    View details for DOI 10.1126/science.1196554

    View details for Web of Science ID 000284118000049

    View details for PubMedID 21071672

  • Two-component protein-engineered physical hydrogels for cell encapsulation PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Foo, C. T., Lee, J. S., Mulyasasmita, W., Parisi-Amon, A., Heilshorn, S. C. 2009; 106 (52): 22067-22072

    Abstract

    Current protocols to encapsulate cells within physical hydrogels require substantial changes in environmental conditions (pH, temperature, or ionic strength) to initiate gelation. These conditions can be detrimental to cells and are often difficult to reproduce, therefore complicating their use in clinical settings. We report the development of a two-component, molecular-recognition gelation strategy that enables cell encapsulation without environmental triggers. Instead, the two components, which contain multiple repeats of WW and proline-rich peptide domains, undergo a sol-gel phase transition upon simple mixing and hetero-assembly of the peptide domains. We term these materials mixing-induced, two-component hydrogels. Our results demonstrate use of the WW and proline-rich domains in protein-engineered materials and expand the library of peptides successfully designed into engineered proteins. Because both of these association domains are normally found intracellularly, their molecular recognition is not disrupted by the presence of additional biomolecules in the extracellular milieu, thereby enabling reproducible encapsulation of multiple cell types, including PC-12 neuronal-like cells, human umbilical vein endothelial cells, and murine adult neural stem cells. Precise variations in the molecular-level design of the two components including (i) the frequency of repeated association domains per chain and (ii) the association energy between domains enable tailoring of the hydrogel viscoelasticity to achieve plateau shear moduli ranging from approximately 9 to 50 Pa. Because of the transient physical crosslinks that form between association domains, these hydrogels are shear-thinning, injectable, and self-healing. Neural stem cells encapsulated in the hydrogels form stable three-dimensional cultures that continue to self-renew, differentiate, and sprout extended neurites.

    View details for DOI 10.1073/pnas.0904851106

    View details for Web of Science ID 000273178700008

    View details for PubMedID 20007785

  • Dynamic, three-dimensional pattern formation within enzyme-responsive hydrogels Advanced Materials Straley KS, Heilshorn SC 2009; 21 (41): 4148-4152
  • Independent tuning of multiple biomaterial properties using protein engineering Soft Matter Straley KS, Heilshorn SC 2009; 5: 114-124
  • Design of three-dimensional engineered protein hydrogels for tailored control of neurite growth ACTA BIOMATERIALIA Lampe, K. J., Antaris, A. L., Heilshorn, S. C. 2013; 9 (3): 5590-5599

    Abstract

    The design of bioactive materials allows tailored studies probing cell-biomaterial interactions, however, relatively few studies have examined the effects of ligand density and material stiffness on neurite growth in three-dimensions. Elastin-like proteins (ELPs) have been designed with modular bioactive and structural regions to enable the systematic characterization of design parameters within three-dimensional (3-D) materials. To promote neurite out-growth and better understand the effects of common biomaterial design parameters on neuronal cultures we here focused on the cell-adhesive ligand density and hydrogel stiffness as design variables for ELP hydrogels. With the inherent design freedom of engineered proteins these 3-D ELP hydrogels enabled decoupled investigations into the effects of biomechanics and biochemistry on neurite out-growth from dorsal root ganglia. Increasing the cell-adhesive RGD ligand density from 0 to 1.9×10(7)ligands ?m(-3) led to a significant increase in the rate, length, and density of neurite out-growth, as quantified by a high throughput algorithm developed for dense neurite analysis. An approximately two-fold improvement in total neurite out-growth was observed in materials with the higher ligand density at all time points up to 7 days. ELP hydrogels with initial elastic moduli of 0.5, 1.5, or 2.1kPa and identical RGD ligand densities revealed that the most compliant materials led to the greatest out-growth, with some neurites extending over 1800?m by day 7. Given the ability of ELP hydrogels to efficiently promote neurite out-growth within defined and tunable 3-D microenvironments these materials may be useful in developing therapeutic nerve guides and the further study of basic neuron-biomaterial interactions.

    View details for DOI 10.1016/j.actbio.2012.10.033

    View details for Web of Science ID 000315536000019

    View details for PubMedID 23128159

  • Protein-Engineered Injectable Hydrogel to Improve Retention of Transplanted Adipose-Derived Stem Cells ADVANCED HEALTHCARE MATERIALS Parisi-Amon, A., Mulyasasmita, W., Chung, C., Heilshorn, S. C. 2013; 2 (3): 428-432

    Abstract

    Improved retention of transplanted stem cells is achieved through minimally invasive delivery in MITCH, a mixing-induced two-component hydrogel that was engineered to possess shear-thinning and self-healing thixotropic properties. MITCH, an ideal injectable cell-delivery vehicle, supports 3D stem-cell culture, resulting in high cell viability and physiologically relevant cell morphology.

    View details for DOI 10.1002/adhm.201200293

    View details for Web of Science ID 000315899900004

    View details for PubMedID 23184882

  • Tuning colloidal association with specific peptide interactions SOFT MATTER Schoen, A. P., Hommersom, B., Heilshorn, S. C., Leunissen, M. E. 2013; 9 (29): 6781-6785

    View details for DOI 10.1039/c3sm50230a

    View details for Web of Science ID 000321273000023

  • Complex chemoattractive and chemorepellent Kit signals revealed by direct imaging of murine mast cells in microfluidic gradient chambers INTEGRATIVE BIOLOGY Shamloo, A., Manchandia, M., Ferreira, M., Mani, M., Nguyen, C., Jahn, T., Weinberg, K., Heilshorn, S. 2013; 5 (8): 1076-1085

    Abstract

    Besides its cooperating effects on stem cell proliferation and survival, Kit ligand (KL) is a potent chemotactic protein. While transwell assays permit studies of the frequency of migrating cells, the lack of direct visualization precludes dynamic chemotaxis studies. In response, we utilize microfluidic chambers that enable direct observation of murine bone marrow-derived mast cells (BMMC) within stable KL gradients. Using this system, individual Kit+ BMMC were quantitatively analyzed for migration speed and directionality during KL-induced chemotaxis. Our results indicated a minimum activating threshold of ∼3 ng ml(-1) for chemoattraction. Analysis of cells at KL concentrations below 3 ng ml(-1) revealed a paradoxical chemorepulsion, which has not been described previously. Unlike chemoattraction, which occurred continuously after an initial time lag, chemorepulsion occurred only during the first 90 minutes of observation. Both chemoattraction and chemorepulsion required the action of G-protein coupled receptors (GPCR), as treatment with pertussis toxin abrogated directed migration. These results differ from previous studies of GPCR-mediated chemotaxis, where chemorepulsion occurred at high ligand concentrations. These data indicate that Kit-mediated chemotaxis is more complex than previously understood, with the involvement of GPCRs in addition to the Kit receptor tyrosine kinase and the presence of both chemoattractive and chemorepellent phases.

    View details for DOI 10.1039/c3ib40025e

    View details for Web of Science ID 000322076800007

    View details for PubMedID 23835699

  • Sequence-Specific Crosslinking of Electrospun, Elastin-Like Protein Preserves Bioactivity and Native-Like Mechanics ADVANCED HEALTHCARE MATERIALS Benitez, P. L., Sweet, J. A., Fink, H., Chennazhi, K. P., Nair, S. V., Enejder, A., Heilshorn, S. C. 2013; 2 (1): 114-118

    View details for DOI 10.1002/adhm.201200115

    View details for Web of Science ID 000315121900009

    View details for PubMedID 23184558

  • Spontaneous cardiomyocyte differentiation of mouse and embryoid bodies regulated by hydrogel crosslink density. Biomaterials Science Chung, C., Pruitt, B. L., Heilshorn, S. C. 2013; 10 (1): 1082-1090
  • Dynamic remodelling of disordered protein aggregates is an alternative pathway to achieve robust self-assembly of nanostructures SOFT MATTER Schoen, A. P., Cordella, N., Mehraeen, S., Arunagirinathan, M. A., Spakowitz, A. J., Heilshorn, S. C. 2013; 9 (38): 9137-9145

    View details for DOI 10.1039/c3sm50830g

    View details for Web of Science ID 000324423700012

  • Chemotaxis of human induced pluripotent stem cell-derived endothelial cells AMERICAN JOURNAL OF TRANSLATIONAL RESEARCH Huang, N. F., Dewi, R. E., Okogbaa, J., Lee, J. C., Jalilrufaihah, A., Heilshorn, S. C., Cooke, J. P. 2013; 5 (5): 510-U96

    Abstract

    This study examined the homing capacity of human induced pluripotent stem cell-derived endothelial cells (iPSC-ECs) and their response to chemotactic gradients of stromal derived factor-1α (SDF). We have previously shown that EC derived from murine pluripotent stem cells can home to the ischemic hindlimb of the mouse. In the current study, we were interested to understand if ECs derived from human induced pluripotent stem cells are capable of homing. The homing capacity of iPSC-ECs was assessed after systemic delivery into immunodeficient mice with unilateral hindlimb ischemia. Furthermore, the iPSC-ECs were evaluated for their expression of CXCR4 and their ability to respond to SDF chemotactic gradients in vitro. Upon systemic delivery, the iPSC-ECs transiently localized to the lungs but did not home to the ischemic limb over the course of 14 days. To understand the mechanism of the lack of homing, the expression levels of the homing receptor, CXCR4, was examined at the transcriptional and protein levels. Furthermore, their ability to migrate in response to chemokines was assessed using microfluidic and scratch assays. Unlike ECs derived from syngeneic mouse pluripotent stem cells, human iPSC-ECs do not home to the ischemic mouse hindlimb. This lack of functional homing may represent an impairment of interspecies cellular communication or a difference in the differentiation state of the human iPSC-ECs. These results may have important implications in therapeutic delivery of iPSC-ECs.

    View details for Web of Science ID 000323539100004

    View details for PubMedID 23977410

  • Engineered Protein Templates Synthesize Inorganic Nanomaterials CHEMICAL ENGINEERING PROGRESS Schoen, A. P., Schoen, D. T., Huggins, K. N., Adhimoolam, A. M., Heilshorn, S. C. 2012; 108 (12): 47-50
  • Tetrakis(hydroxymethyl) Phosphonium Chloride as a Covalent Cross-Linking Agent for Cell Encapsulation within Protein-Based Hydrogels BIOMACROMOLECULES Chung, C., Lampe, K. J., Heilshorn, S. C. 2012; 13 (12): 3912-3916

    Abstract

    Native tissues provide cells with complex, three-dimensional (3D) environments comprised of hydrated networks of extracellular matrix proteins and sugars. By mimicking the dimensionality of native tissue while deconstructing the effects of environmental parameters, protein-based hydrogels serve as attractive, in vitro platforms to investigate cell-matrix interactions. For cell encapsulation, the process of hydrogel formation through physical or covalent cross-linking must be mild and cell compatible. While many chemical cross-linkers are commercially available for hydrogel formation, only a subset are cytocompatible; therefore, the identification of new and reliable cytocompatible cross-linkers allows for greater flexibility of hydrogel design for cell encapsulation applications. Here, we introduce tetrakis(hydroxymethyl) phosphonium chloride (THPC) as an inexpensive, amine-reactive, aqueous cross-linker for 3D cell encapsulation in protein-based hydrogels. We characterize the THPC-amine reaction by demonstrating THPC's ability to react with primary and secondary amines of various amino acids. In addition, we demonstrate the utility of THPC to tune hydrogel gelation time (6.7±0.2 to 27±1.2 min) and mechanical properties (storage moduli ?250 Pa to ?2200 Pa) with a recombinant elastin-like protein. Lastly, we show cytocompatibility of THPC for cell encapsulation with two cell types, embryonic stem cells and neuronal cells, where cells exhibited the ability to differentiate and grow in elastin-like protein hydrogels. The primary goal of this communication is to report the identification and utility of tetrakis(hydroxymethyl) phosphonium chloride (THPC) as an inexpensive but widely applicable cross-linker for protein-based materials.

    View details for DOI 10.1021/bm3015279

    View details for Web of Science ID 000312035000004

    View details for PubMedID 23151175

  • Protein-Engineered Biomaterials to Generate Human Skeletal Muscle Mimics ADVANCED HEALTHCARE MATERIALS Sengupta, D., Gilbert, P. M., Johnson, K. J., Blau, H. M., Heilshorn, S. C. 2012; 1 (6): 785-789

    View details for DOI 10.1002/adhm.201200195

    View details for Web of Science ID 000315120500014

    View details for PubMedID 23184832

  • Multifunctional Materials through Modular Protein Engineering ADVANCED MATERIALS Dimarco, R. L., Heilshorn, S. C. 2012; 24 (29): 3923-3940

    Abstract

    The diversity of potential applications for protein-engineered materials has undergone profound recent expansion through a rapid increase in the library of domains that have been utilized in these materials. Historically, protein-engineered biomaterials have been generated from a handful of peptides that were selected and exploited for their naturally evolved functionalities. In recent years, the scope of the field has drastically expanded to include peptide domains that were designed through computational modeling, identified through high-throughput screening, or repurposed from wild type domains to perform functions distinct from their primary native applications. The strategy of exploiting a diverse library of peptide domains to design modular block copolymers enables the synthesis of multifunctional protein-engineered materials with a range of customizable properties and activities. As the diversity of peptide domains utilized in modular protein engineering continues to expand, a tremendous and ever-growing combinatorial expanse of material functionalities will result.

    View details for DOI 10.1002/adma.201200051

    View details for Web of Science ID 000307048200002

    View details for PubMedID 22730248

  • Mechanisms of Vascular Endothelial Growth Factor-Induced Pathfinding by Endothelial Sprouts in Biomaterials TISSUE ENGINEERING PART A Shamloo, A., Xu, H., Heilshorn, S. 2012; 18 (3-4): 320-330

    Abstract

    A critical property of biomaterials for use in regenerative medicine applications is the ability to promote angiogenesis, the formation of new vascular networks, to support regenerating tissues. Recent studies have demonstrated that a complex interplay exists between biomechanical and biochemical regulators of endothelial cell sprouting, an early step in angiogenesis. Here, we use a microfluidic platform to study the pathfinding behaviors induced by various stable vascular endothelial growth factor (VEGF) gradients during sprouting morphogenesis within biomaterials. Quantitative, time-lapse analysis of endothelial sprouting demonstrated that the ability of VEGF to regulate sprout orientation during several stages of sprouting morphogenesis (initiation, elongation, and turning navigation) was biomaterial dependent. Identical VEGF gradients induced different types of coordinated cell movements depending on the density of the surrounding collagen/fibronectin matrix. In denser matrices, sprouts were more likely to have an initial orientation aligned parallel to the VEGF gradient. In contrast, in less dense matrices, sprouts were more likely to initially misalign with the VEGF gradient; however, these sprouts underwent significant turning and navigation to eventually reorient to be parallel to the VEGF gradient. These less dense matrices required shallower VEGF gradients and demonstrated lower activating VEGF thresholds to induce proper sprout alignment and pathfinding. These results encourage the future use of microfluidic platforms to probe fundamental aspects of matrix effects on angiogenesis, to screen biomaterials for angiogenic potential, and to design ex vivo tissues with aligned vascular networks.

    View details for DOI 10.1089/ten.tea.2011.0323

    View details for Web of Science ID 000300003300010

    View details for PubMedID 21888475

  • The intestinal stem cell markers Bmi1 and Lgr5 identify two functionally distinct populations PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Yan, K. S., Chia, L. A., Li, X., Ootani, A., Su, J., Lee, J. Y., Su, N., Luo, Y., Heilshorn, S. C., Amieva, M. R., Sangiorgi, E., Capecchi, M. R., Kuo, C. J. 2012; 109 (2): 466-471

    Abstract

    The small intestine epithelium undergoes rapid and continuous regeneration supported by crypt intestinal stem cells (ISCs). Bmi1 and Lgr5 have been independently identified to mark long-lived multipotent ISCs by lineage tracing in mice; however, the functional distinctions between these two populations remain undefined. Here, we demonstrate that Bmi1 and Lgr5 mark two functionally distinct ISCs in vivo. Lgr5 marks mitotically active ISCs that exhibit exquisite sensitivity to canonical Wnt modulation, contribute robustly to homeostatic regeneration, and are quantitatively ablated by irradiation. In contrast, Bmi1 marks quiescent ISCs that are insensitive to Wnt perturbations, contribute weakly to homeostatic regeneration, and are resistant to high-dose radiation injury. After irradiation, however, the normally quiescent Bmi1(+) ISCs dramatically proliferate to clonally repopulate multiple contiguous crypts and villi. Clonogenic culture of isolated single Bmi1(+) ISCs yields long-lived self-renewing spheroids of intestinal epithelium that produce Lgr5-expressing cells, thereby establishing a lineage relationship between these two populations in vitro. Taken together, these data provide direct evidence that Bmi1 marks quiescent, injury-inducible reserve ISCs that exhibit striking functional distinctions from Lgr5(+) ISCs and support a model whereby distinct ISC populations facilitate homeostatic vs. injury-induced regeneration.

    View details for DOI 10.1073/pnas.1118857109

    View details for Web of Science ID 000298950200030

    View details for PubMedID 22190486

  • Photoreactive elastin-like proteins for use as versatile bioactive materials and surface coatings JOURNAL OF MATERIALS CHEMISTRY Raphel, J., Parisi-Amon, A., Heilshorn, S. C. 2012; 22 (37): 19429-19437

    Abstract

    Photocrosslinkable, protein-engineered biomaterials combine a rapid, controllable, cytocompatible crosslinking method with a modular design strategy to create a new family of bioactive materials. These materials have a wide range of biomedical applications, including the development of bioactive implant coatings, drug delivery vehicles, and tissue engineering scaffolds. We present the successful functionalization of a bioactive elastin-like protein with photoreactive diazirine moieties. Scalable synthesis is achieved using a standard recombinant protein expression host followed by site-specific modification of lysine residues with a heterobifunctional N-hydroxysuccinimide ester-diazirine crosslinker. The resulting biomaterial is demonstrated to be processable by spin coating, drop casting, soft lithographic patterning, and mold casting to fabricate a variety of two- and three-dimensional photocrosslinked biomaterials with length scales spanning the nanometer to millimeter range. Protein thin films proved to be highly stable over a three-week period. Cell-adhesive functional domains incorporated into the engineered protein materials were shown to remain active post-photo-processing. Human adipose-derived stem cells achieved faster rates of cell adhesion and larger spread areas on thin films of the engineered protein compared to control substrates. The ease and scalability of material production, processing versatility, and modular bioactive functionality make this recombinantly engineered protein an ideal candidate for the development of novel biomaterial coatings, films, and scaffolds.

    View details for DOI 10.1039/c2jm31768k

    View details for Web of Science ID 000308099900010

    View details for PubMedID 23015764

  • Hydrogel crosslinking density regulates temporal contractility of human embryonic stem cell-derived cardiomyocytes in 3D cultures SOFT MATTER Chung, C., Anderson, E., Pera, R. R., Pruitt, B. L., Heilshorn, S. C. 2012; 8 (39): 10141-10148

    Abstract

    Systematically tunable in vitro platforms are invaluable in gaining insight to stem cell-microenvironment interactions in three-dimensional cultures. Utilizing recombinant protein technology, we independently tune hydrogel properties to systematically isolate the effects of matrix crosslinking density on cardiomyocyte differentiation, maturation, and function. We show that contracting human embryonic stem cell-derived cardiomyocytes (hESC-CMs) remain viable within four engineered elastin-like hydrogels of varying crosslinking densities with elastic moduli ranging from 0.45 to 2.4 kPa. Cardiomyocyte phenotype and function was maintained within hESC embryoid bodies for up to 2 weeks. Interestingly, increased crosslinking density was shown to transiently suspend spontaneous contractility. While encapsulated cells began spontaneous contractions at day 1 in hydrogels of the lowest crosslinking density, onset of contraction was increasingly delayed at higher crosslinking densities up to 6 days. However, once spontaneous contraction was restored, the rate of contraction was similar within all materials (71 ± 8 beats/min). Additionally, all groups successfully responded to electrical pacing at both 1 and 2 Hz. This study demonstrates that encapsulated hESC-CMs respond to 3D matrix crosslinking density within elastin-like hydrogels and stresses the importance of investigating temporal cellular responses in 3D cultures.

    View details for DOI 10.1039/c2sm26082d

    View details for Web of Science ID 000308882800024

  • Template Engineering Through Epitope Recognition: A Modular, Biomimetic Strategy for Inorganic Nanomaterial Synthesis JOURNAL OF THE AMERICAN CHEMICAL SOCIETY Schoen, A. P., Schoen, D. T., Huggins, K. N., Arunagirinathan, M. A., Heilshorn, S. C. 2011; 133 (45): 18202-18207

    Abstract

    Natural systems often utilize a single protein to perform multiple functions. Control over functional specificity is achieved through interactions with other proteins at well-defined epitope binding sites to form a variety of functional coassemblies. Inspired by the biological use of epitope recognition to perform diverse yet specific functions, we present a Template Engineering Through Epitope Recognition (TEThER) strategy that takes advantage of noncovalent, molecular recognition to achieve functional versatility from a single protein template. Engineered TEThER peptides span the biologic-inorganic interface and serve as molecular bridges between epitope binding sites on protein templates and selected inorganic materials in a localized, specific, and versatile manner. TEThER peptides are bifunctional sequences designed to noncovalently bind to the protein scaffold and to serve as nucleation sites for inorganic materials. Specifically, we functionalized identical clathrin protein cages through coassembly with designer TEThER peptides to achieve three diverse functions: the bioenabled synthesis of anatase titanium dioxide, cobalt oxide, and gold nanoparticles in aqueous solvents at room temperature and ambient pressure. Compared with previous demonstrations of site-specific inorganic biotemplating, the TEThER strategy relies solely on defined, noncovalent interactions without requiring any genetic or chemical modifications to the biomacromolecular template. Therefore, this general strategy represents a mix-and-match, biomimetic approach that can be broadly applied to other protein templates to achieve versatile and site-specific heteroassemblies of nanoscale biologic-inorganic complexes.

    View details for DOI 10.1021/ja204732n

    View details for Web of Science ID 000297381200043

    View details for PubMedID 21967307

  • Molecular-Level Engineering of Protein Physical Hydrogels for Predictive Sol-Gel Phase Behavior BIOMACROMOLECULES Mulyasasmita, W., Lee, J. S., Heilshorn, S. C. 2011; 12 (10): 3406-3411

    Abstract

    Predictable tuning of bulk mechanics from the molecular level remains elusive in many physical hydrogel systems because of the reliance on nonspecific and nonstoichiometric chain interactions for network formation. We describe a mixing-induced two-component hydrogel (MITCH) system, in which network assembly is driven by specific and stoichiometric peptide-peptide binding interactions. By integrating protein science methodologies with a simple polymer physics model, we manipulate the polypeptide binding interactions and demonstrate the direct ability to predict the resulting effects on network cross-linking density, sol-gel phase behavior, and gel mechanics.

    View details for DOI 10.1021/bm200959e

    View details for Web of Science ID 000295602600006

    View details for PubMedID 21861461

  • Protein-engineered biomaterials: Nanoscale mimics of the extracellular matrix BIOCHIMICA ET BIOPHYSICA ACTA-GENERAL SUBJECTS Romano, N. H., Sengupta, D., Chung, C., Heilshorn, S. C. 2011; 1810 (3): 339-349

    Abstract

    Traditional materials used as in vitro cell culture substrates are rigid and flat surfaces that lack the exquisite nano- and micro-scale features of the in vivo extracellular environment. While these surfaces can be coated with harvested extracellular matrix (ECM) proteins to partially recapitulate the bio-instructive nature of the ECM, these harvested proteins often exhibit large batch-to-batch variability and can be difficult to customize for specific biological studies. In contrast, recombinant protein technology can be utilized to synthesize families of 3 dimensional protein-engineered biomaterials that are cyto-compatible, reproducible, and fully customizable.Here we describe a modular design strategy to synthesize protein-engineered biomaterials that fuse together multiple repeats of nanoscale peptide design motifs into full-length engineered ECM mimics.Due to the molecular-level precision of recombinant protein synthesis, these biomaterials can be tailored to include a variety of bio-instructional ligands at specified densities, to exhibit mechanical properties that match those of native tissue, and to include proteolytic target sites that enable cell-triggered scaffold remodeling. Furthermore, these biomaterials can be processed into forms that are injectable for minimally-invasive delivery or spatially patterned to enable the release of multiple drugs with distinct release kinetics.Given the reproducibility and flexibility of these protein-engineered biomaterials, they are ideal substrates for reductionist biological studies of cell-matrix interactions, for in vitro models of physiological processes, and for bio-instructive scaffolds in regenerative medicine therapies. This article is part of a Special Issue entitled Nanotechnologies - Emerging Applications in Biomedicine.

    View details for DOI 10.1016/j.bbagen.2010.07.005

    View details for Web of Science ID 000287470900012

    View details for PubMedID 20647034

  • Vacuum soft lithography to direct neuronal polarization SOFT MATTER Nevill, J. T., Mo, A., Cord, B. J., Palmer, T. D., Poo, M., Lee, L. P., Heilshorn, S. C. 2011; 7 (2): 343-347

    View details for DOI 10.1039/c0sm00869a

    View details for Web of Science ID 000286110900005

  • High Speed Water Sterilization Using One-Dimensional Nanostructures NANO LETTERS Schoen, D. T., Schoen, A. P., Hu, L., Kim, H. S., Heilshorn, S. C., Cui, Y. 2010; 10 (9): 3628-3632

    Abstract

    The removal of bacteria and other organisms from water is an extremely important process, not only for drinking and sanitation but also industrially as biofouling is a commonplace and serious problem. We here present a textile based multiscale device for the high speed electrical sterilization of water using silver nanowires, carbon nanotubes, and cotton. This approach, which combines several materials spanning three very different length scales with simple dying based fabrication, makes a gravity fed device operating at 100000 L/(h m(2)) which can inactivate >98% of bacteria with only several seconds of total incubation time. This excellent performance is enabled by the use of an electrical mechanism rather than size exclusion, while the very high surface area of the device coupled with large electric field concentrations near the silver nanowire tips allows for effective bacterial inactivation.

    View details for DOI 10.1021/nl101944e

    View details for Web of Science ID 000281498200068

    View details for PubMedID 20726518

  • Protein-Engineered Biomaterials: Highly Tunable Tissue Engineering Scaffolds TISSUE ENGINEERING PART B-REVIEWS Sengupta, D., Heilshorn, S. C. 2010; 16 (3): 285-293

    Abstract

    A common goal in tissue engineering is to attain the ability to tailor specific cell-scaffold interactions and thereby gain control over cell behavior. The tunable nature of protein-engineered biomaterials enables independent tailoring of a range of biomaterial properties, creating an attractive alternative to synthetic polymeric scaffolds or harvested natural scaffolds. Protein-engineered biomaterials are comprised of modular peptide domains with various functionalities that are encoded into a DNA plasmid, transfected into an organism of choice, and expressed and purified to yield a biopolymer with exact molecular-level sequence specification. Because of the modular design strategy of protein-engineered biomaterials, these scaffolds can be easily modified to enable optimization for specific tissue engineering applications. By including multiple peptide domains with different functionalities in a single, modular biomaterial, the scaffolds can be designed to mimic the diverse properties of the natural extracellular matrix, including cell adhesion, cell signaling, elasticity, and biodegradability. Recently, the field of protein-engineered biomaterials has expanded to include functional modules that are not normally present in the extracellular matrix, thus expanding the scope and functionality of these materials. For example, these modules can include noncanonical amino acids, inorganic-binding domains, and DNA-binding sequences. The modularity, tunability, and sequence specificity of protein-engineered biomaterials make them attractive candidates for use as substrates for a variety of tissue engineering applications.

    View details for DOI 10.1089/ten.teb.2009.0591

    View details for Web of Science ID 000278640000002

    View details for PubMedID 20141386

  • Local and Long-Range Reciprocal Regulation of cAMP and cGMP in Axon/Dendrite Formation SCIENCE Shelly, M., Lim, B. K., Cancedda, L., Heilshorn, S. C., Gao, H., Poo, M. 2010; 327 (5965): 547-552

    Abstract

    Cytosolic cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP) often mediate antagonistic cellular actions of extracellular factors, from the regulation of ion channels to cell volume control and axon guidance. We found that localized cAMP and cGMP activities in undifferentiated neurites of cultured hippocampal neurons promote and suppress axon formation, respectively, and exert opposite effects on dendrite formation. Fluorescence resonance energy transfer imaging showed that alterations of the amount of cAMP resulted in opposite changes in the amount of cGMP, and vice versa, through the activation of specific phosphodiesterases and protein kinases. Local elevation of cAMP in one neurite resulted in cAMP reduction in all other neurites of the same neuron. Thus, local and long-range reciprocal regulation of cAMP and cGMP together ensures coordinated development of one axon and multiple dendrites.

    View details for DOI 10.1126/science.1179735

    View details for Web of Science ID 000274020500029

    View details for PubMedID 20110498

  • The Interplay between Biomechanical and Biochemical Factors Regulates Lumen Formation and Navigation of Endothelial Cell Sprouts PROCEEDINGS OF THE ASME SUMMER BIOENGINEERING CONFERENCE, 2010 Shamloo, A., Heilshorn, S. C. 2010: 429-430
  • Biomaterial Design Strategies for the Treatment of Spinal Cord Injuries JOURNAL OF NEUROTRAUMA Straley, K. S., Foo, C. W., Heilshorn, S. C. 2010; 27 (1): 1-19

    Abstract

    The highly debilitating nature of spinal cord injuries has provided much inspiration for the design of novel biomaterials that can stimulate cellular regeneration and functional recovery. Many experts agree that the greatest hope for treatment of spinal cord injuries will involve a combinatorial approach that integrates biomaterial scaffolds, cell transplantation, and molecule delivery. This manuscript presents a comprehensive review of biomaterial-scaffold design strategies currently being applied to the development of nerve guidance channels and hydrogels that more effectively stimulate spinal cord tissue regeneration. To enhance the regenerative capacity of these two scaffold types, researchers are focusing on optimizing the mechanical properties, cell-adhesivity, biodegradability, electrical activity, and topography of synthetic and natural materials, and are developing mechanisms to use these scaffolds to deliver cells and biomolecules. Developing scaffolds that address several of these key design parameters will lead to more successful therapies for the regeneration of spinal cord tissue.

    View details for DOI 10.1089/neu.2009.0948

    View details for Web of Science ID 000273983200001

    View details for PubMedID 19698073

  • Matrix density mediates polarization and lumen formation of endothelial sprouts in VEGF gradients LAB ON A CHIP Shamloo, A., Heilshorn, S. C. 2010; 10 (22): 3061-3068

    Abstract

    Endothelial cell (EC) sprouting morphogenesis is a critical step during angiogenesis, the formation of new blood vessels from existing conduits. Here, three-dimensional sprouting morphogenesis was examined using in vitro microfluidic devices that enabled the separate and simultaneous tuning of biomechanical and soluble biochemical stimuli. Quantitative analysis of endothelial sprout formation demonstrated that the ability of vascular endothelial growth factor (VEGF) to regulate stable sprout formation was mediated by the density of the surrounding collagen/fibronectin matrix. The coordinated migration and proliferation of multiple ECs to form stable sprouts were enhanced at intermediate matrix densities (1.2-1.9 mg ml(-1)), while lower densities resulted in uncoordinated migration (0.3-0.7 mg ml(-1)) and higher densities resulted in broad cell clusters that did not elongate (2.7 mg ml(-1)). Within the permissive range of matrix biomechanics, higher density matrices resulted in shorter, thicker, and slower-growing sprouts. The sprouts in higher density matrices also were more likely to polarize towards higher VEGF concentrations, included more cells per cross-sectional area, and demonstrated more stable lumen formation compared to sprouts in lower density matrices. These results quantitatively demonstrate that matrix density mediates VEGF-induced sprout polarization and lumen formation, potentially by regulating the balance between EC migration rate and proliferation rate.

    View details for DOI 10.1039/c005069e

    View details for Web of Science ID 000283600900006

    View details for PubMedID 20820484

  • Dynamic, 3D-Pattern Formation Within Enzyme-Responsive Hydrogels ADVANCED MATERIALS Straley, K. S., Heilshorn, S. C. 2009; 21 (41): 4148-?
  • Gradient lithography of engineered proteins to fabricate 2D and 3D cell culture micro environments BIOMEDICAL MICRODEVICES Wang, S., Foo, C. W., Warrier, A., Poo, M., Heilshorn, S. C., Zhang, X. 2009; 11 (5): 1127-1134

    Abstract

    Spatial patterning of proteins is a valuable technique for many biological applications and is the prevailing tool for defining microenvironments for cells in culture, a required procedure in developmental biology and tissue engineering research. However, it is still challenging to achieve protein patterns that closely mimic native microenvironments, such as gradient protein distributions with desirable mechanical properties. By combining projection dynamic mask lithography and protein engineering with non-canonical photosensitive amino acids, we demonstrate a simple, scalable strategy to fabricate any user-defined 2D or 3D stable gradient pattern with complex geometries from an artificial extracellular matrix (aECM) protein. We show that the elastic modulus and chemical nature of the gradient profile are biocompatible and allow useful applications in cell biological research.

    View details for DOI 10.1007/s10544-009-9329-1

    View details for Web of Science ID 000270679400019

    View details for PubMedID 19495986

  • Independent tuning of multiple biomaterial properties using protein engineering SOFT MATTER Straley, K. S., Heilshorn, S. C. 2009; 5 (1): 114-124

    View details for DOI 10.1039/b808504h

    View details for Web of Science ID 000263272100015

  • Design and adsorption of modular engineered proteins to prepare customized, neuron-compatible coatings. Frontiers in neuroengineering Straley, K. S., Heilshorn, S. C. 2009; 2: 9-?

    Abstract

    Neural prosthetic implants are currently being developed for the treatment and study of both peripheral and central nervous system disorders. Effective integration of these devices upon implantation is a critical hurdle to achieving function. As a result, much attention has been directed towards the development of biocompatible coatings that prolong their in vivo lifespan. In this work, we present a novel approach to fabricate such coatings, which specifically involves the use of surface-adsorbed, nanoscale-designed protein polymers to prepare reproducible, customized surfaces. A nanoscale modular design strategy was employed to synthesize six engineered, recombinant proteins intended to mimic aspects of the extracellular matrix proteins fibronectin, laminin, and elastin as well as the cell-cell adhesive protein neural cell adhesion molecule. Physical adsorption isotherms were experimentally determined for these engineered proteins, allowing for direct calculation of the available ligand density present on coated surfaces. As confirmation that ligand density in these engineered systems impacts neuronal cell behavior, we demonstrate that increasing the density of fibronectin-derived RGD ligands on coated surfaces while maintaining uniform protein surface coverage results in enhanced neurite extension of PC-12 cells. Therefore, this engineered protein adsorption approach allows for the facile preparation of tunable, quantifiable, and reproducible surfaces for in vitro studies of cell-ligand interactions and for potential application as coatings on neural implants.

    View details for DOI 10.3389/neuro.16.009.2009

    View details for PubMedID 19562090

  • Endothelial cell polarization and chemotaxis in a microfluidic device LAB ON A CHIP Shamloo, A., Ma, N., Poo, M., Sohn, L. L., Heilshorn, S. C. 2008; 8 (8): 1292-1299

    Abstract

    The directed migration of endothelial cells is an early and critical step in angiogenesis, or new blood vessel formation. In this study, the polarization and chemotaxis of human umbilical vein endothelial cells (HUVEC) in response to quantified gradients of vascular endothelial growth factor (VEGF) were examined. To accomplish this, a microfluidic device was designed and fabricated to generate stable concentration gradients of biomolecules in a cell culture chamber while minimizing the fluid shear stress experienced by the cells. Finite element simulation of the device geometry produced excellent agreement with the observed VEGF concentration distribution, which was found to be stable across multiple hours. This device is expected to have wide applicability in the study of shear-sensitive cells such as HUVEC and non-adherent cell types as well as in the study of migration through three-dimensional matrices. HUVEC were observed to chemotax towards higher VEGF concentrations across the entire range of concentrations studied (18-32 ng mL(-1)) when the concentration gradient was 14 ng mL(-1) mm(-1). In contrast, shallow gradients (2 ng mL(-1) mm(-1)) across the same concentration range were unable to induce HUVEC chemotaxis. Furthermore, while all HUVEC exposed to elevated VEGF levels (both in steep and shallow gradients) displayed an increased number of filopodia, only chemotaxing HUVEC displayed an asymmetric distribution of filopodia, with enhanced numbers of protrusions present along the leading edge. These results suggest a two-part requirement to induce VEGF chemotaxis: the VEGF absolute concentration enhances the total number of filopodia extended while the VEGF gradient steepness induces filopodia localization, cell polarization, and subsequent directed migration.

    View details for DOI 10.1039/b719788h

    View details for Web of Science ID 000258572400009

    View details for PubMedID 18651071

  • LKB1/STRAD promotes axon initiation during neuronal polarization CELL Shelly, M., Cancedda, L., Heilshorn, S., Sumbre, G., Poo, M. 2007; 129 (3): 565-577

    Abstract

    Axon/dendrite differentiation is a critical step in neuronal development. In cultured hippocampal neurons, the accumulation of LKB1 and STRAD, two interacting proteins critical for establishing epithelial polarity, in an undifferentiated neurite correlates with its subsequent axon differentiation. Downregulation of either LKB1 or STRAD by siRNAs prevented axon differentiation, and overexpression of these proteins led to multiple axon formation. Furthermore, interaction of STRAD with LKB1 promoted LKB1 phosphorylation at a PKA site S431 and elevated the LKB1 level, and overexpressing LKB1 with a serine-to-alanine mutation at S431 (LKB1(S431A)) prevented axon differentiation. In developing cortical neurons in vivo, downregulation of LKB1 or overexpression of LKB1(S431A) also abolished axon formation. Finally, local exposure of the undifferentiated neurite to brain-derived neurotrophic factor or dibutyryl-cAMP promoted axon differentiation in a manner that depended on PKA-dependent LKB1 phosphorylation. Thus local LKB1/STRAD accumulation and PKA-dependent LKB1 phosphorylation represents an early signal for axon initiation.

    View details for DOI 10.1016/j.cell.2007.04.012

    View details for Web of Science ID 000246373600022

    View details for PubMedID 17482549

  • Lithographic patterning of photoreactive cell-adhesive proteins JOURNAL OF THE AMERICAN CHEMICAL SOCIETY Carrico, I. S., Maskarinec, S. A., Heilshorn, S. C., Mock, M. L., Liu, J. C., Nowatzki, P. J., Franck, C., Ravichandran, G., Tirrell, D. A. 2007; 129 (16): 4874-?

    View details for DOI 10.1021/ja070200b

    View details for Web of Science ID 000245782800009

    View details for PubMedID 17397163

  • Cell-binding domain context affects cell behavior on engineered proteins BIOMACROMOLECULES Heilshorn, S. C., Liu, J. C., Tirrell, D. A. 2005; 6 (1): 318-323

    Abstract

    A family of artificial extracellular matrix proteins developed for application in small-diameter vascular grafts is used to examine the importance of cell-binding domain context on cell adhesion and spreading. The engineered protein sequences are derived from the naturally occurring extracellular matrix proteins elastin and fibronectin. While each engineered protein contains identical CS5 cell-binding domain sequences, the lysine residues that serve as cross-linking sites are either (i) within the elastin cassettes or (ii) confined to the ends of the protein. Endothelial cells adhere specifically to the CS5 sequence in both of these proteins, but cell adhesion and spreading are more robust on proteins in which the lysine residues are confined to the terminal regions of the chain. These results may be due to altered protein conformations that affect either the accessibility of the CS5 sequence or its affinity for the alpha(4)beta(1) integrin receptor on the endothelial cell surface. Amino acid choice outside the cell-binding domain can thus have a significant impact on the behavior of cells cultured on artificial extracellular matrix proteins.

    View details for DOI 10.1021/bm049627q

    View details for Web of Science ID 000226344300041

    View details for PubMedID 15638535

  • Comparative cell response to artificial extracellular matrix proteins containing the RGD and CS5 cell-binding domains BIOMACROMOLECULES Liu, J. C., Heilshorn, S. C., Tirrell, D. A. 2004; 5 (2): 497-504

    Abstract

    This study addresses endothelial cell adhesion and spreading on a family of artificial extracellular matrix (aECM) proteins designed for application in small-diameter vascular grafts. The aECM proteins contain domains derived from elastin and from fibronectin. aECM 1 contains the RGD sequence from the tenth type III domain of fibronectin; aECM 3 contains the fibronectin CS5 cell-binding domain. Negative control proteins aECM 2 and 4 are scrambled versions of aECM 1 and 3, respectively. Competitive peptide inhibition studies and comparisons of positive and negative control proteins confirm that adhesion of HUVECs to aECM proteins 1 and 3 is sequence specific. When subjected to a normal detachment force of 780 pN, 3-fold more HUVECs remained adherent to aECM 1 than to aECM 3. HUVECs also spread more rapidly on aECM 1 than on aECM 3. These results (i) indicate that cellular responses to aECM proteins can be modulated through choice of cell-binding domain and (ii) recommend the RGD sequence for applications that require rapid endothelial cell spreading and matrix adhesion.

    View details for DOI 10.1021/bm034340z

    View details for Web of Science ID 000220109200032

    View details for PubMedID 15003012

  • Endothelial cell adhesion to the fibronectin CS5 domain in artificial extracellular matrix proteins BIOMATERIALS Heilshorn, S. C., DiZio, K. A., Welsh, E. R., Tirrell, D. A. 2003; 24 (23): 4245-4252

    Abstract

    This study examines the spreading and adhesion of human umbilical vein endothelial cells (HUVEC) on artificial extracellular matrix (aECM) proteins containing sequences derived from elastin and fibronectin. Three aECM variants were studied: aECM 1 contains lysine residues periodically spaced within the protein sequence and three repeats of the CS5 domain of fibronectin, aECM 2 contains periodically spaced lysines and three repeats of a scrambled CS5 sequence, and aECM 3 contains lysines at the protein termini and five CS5 repeats. Comparative cell binding and peptide inhibition assays confirm that the tetrapeptide sequence REDV is responsible for HUVEC adhesion to aECM proteins that contain the CS5 domain. Furthermore, more than 60% of adherent HUVEC were retained on aECM 1 after exposure to physiologically relevant shear stresses (

    View details for DOI 10.1016/S0142-9612(03)00294-1

    View details for Web of Science ID 000184239500017

    View details for PubMedID 12853256

  • Liquid personal cleansing compositions which contain a  complex coacervate for improved sensory perception Assignee: The Procter & Gamble Company. Glenn, R. W., Sine, M. R., Evans, M. D., Carethers, M. E., Heilshorn, S. C. 2000

Books and Book Chapters


  • Microfluidic devices for quantifying the role of soluble gradients in early angiogenesis Mechanical and Chemical Signaling in Angiogenesis Benitez, P., Heilshorn, S. C. edited by Reinhart-King, C. A. Heidelberg, Germany, Springer.. 2013: 1
  • Protein-Engineered Hydrogels. Biomaterials Surface Science Raphel, J., Parisi-Amon, A. P., Heilshorn, S. C. edited by Taubert, A., Mano, J., Rodriquez-Cabello, J. C. Mannheim, Germany, Wiley-VCH Verlag.. 2012: 1
  • Hydrogels from Protein Engineering Biomimetic Approaches for Biomaterials Development Greenwood-Goodwin, M., Heilshorn, S. C. edited by Mano, J. F. Mannheim, Germany, Wiley-VCH Verlag.. 2012: 1
  • Engineered Protein Biomaterials. Biomedical Engineering Handbook Parisi-Amon, A., Heilshorn, S. C. edited by Bronzino, J. D., Peterson, D. R., FIsher, J. P. Boca Raton, FL, CRC Press. 2012; 4th: 1
  • Protein-Engineered Biomaterials: Synthesis and Characterization. Comprehensive Biomaterials. Mulyasasmita, W., Heilshorn, S. C. edited by Ducheyne, P., Healy, K., Hutmacher, D. W. Oxford, UK, Elsevier Science.. 2011: 1
  • Protein Engineered Biomaterials. Protein Engineering. Wong, C. P., Heilshorn, S. C. edited by Park, S. J., Cochran, J. R. Boca Raton, FL, CRC Press. 2010: 1

Conference Proceedings


  • Formation and properties of magnetic chains for 100nm nanoparticles used in separations of molecules and cells Wilson, R. J., Hu, W., Fu, C. W., Koh, A. L., Gaster, R. S., Earhart, C. M., Fu, A., Heilshorn, S. C., Sinclair, R., Wang, S. X. ELSEVIER SCIENCE BV. 2009: 1452-1458

    Abstract

    Optical observations of 100 nm metallic magnetic nanoparticles are used to study their magnetic field induced self assembly. Chains with lengths of tens of microns are observed to form within minutes at nanoparticle concentrations of 10(10) per mL. Chain rotation and magnetophoresis are readily observed, and SEM reveals that long chains are not simple single particle filaments. Similar chains are detected for several 100 nm commercial bio-separation nanoparticles. We demonstrate the staged magnetic condensation of different types of nanoparticles into composite structures and show that magnetic chains bind to immunomagnetically labeled cells, serving as temporary handles which allow novel magnetic cell manipulations.

    View details for DOI 10.1016/j.jmmm.2009.02.066

    View details for Web of Science ID 000265278000028

    View details for PubMedID 20161001

  • Designer Protein-Based Scaffolds for Neural Tissue Engineering Straley, K., Heilshorn, S. C. IEEE. 2009: 2101-2102

    Abstract

    A key attribute missing from many current biomaterials is the ability to independently tune multiple biomaterial properties without simultaneously affecting other material parameters. Because cells are well known to respond to changes in the initial elastic modulus, degradation rate, and cell adhesivity of a biomaterial, it is critical to develop synthetic design strategies that allow decoupled tailoring of each individual parameter in order to systematically optimize cell-scaffold interactions. We present the development of a family of biomimetic scaffolds composed of chemically crosslinked, elastin-like proteins designed to support neural regeneration through a combination of cell adhesion and cell-induced degradation and remodeling. Through use of a modular protein-design strategy, a range of biomaterials is created that allows independent tuning over the initial elastic modulus, degradation rate, cell adhesivity, and neurite outgrowth. By combining these engineered proteins into composite structures, biomaterials are created with 3D patterns that emerge over time in response to cell-secreted enzymes. These dynamic 3D structures enable the delivery of multiple drugs with precise spatial and temporal resolution and also enable the design of biomaterials that adapt to changing scaffold needs.

    View details for Web of Science ID 000280543601259

    View details for PubMedID 19964779

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