Instructor, Cardiothoracic Surgery
Amphiphilic bovine serum albumin-poly(methyl methacrylate) conjugate forms nanoparticles with the uniform size of ~100 nm by self-assembling. Loaded with the hydrophobic anti-tumor drug camptothecin, the nanoparticle efficiently delivers drugs into cancer cells, and thus inhibits ~79% of tumor growth in animals compared with free drug.
View details for DOI 10.1002/smll.201200889
View details for Web of Science ID 000312214400004
View details for PubMedID 22888073
We describe a new temperature and electric field dual-stimulus responsive nanoparticle system for programmed drug delivery. Nanoparticles of a conducting polymer (polypyrrole) are loaded with therapeutic pharmaceuticals and are subcutaneously localized in vivo with the assistance of a temperature-sensitive hydrogel (PLGA-PEG-PLGA). We have shown that drug release from the conductive nanoparticles is controlled by the application of a weak, external DC electric field. This approach represents a novel interactive drug delivery system that can show an externally tailored release profile with an excellent spatial, temporal, and dosage control.
View details for DOI 10.1021/nn203430m
View details for Web of Science ID 000299368300029
View details for PubMedID 22111891
Ischemic heart disease is the leading cause of death worldwide. Recent studies suggest that adipose tissue-derived stem cells (ASCs) can be used as a potential source for cardiovascular tissue engineering due to their ability to differentiate along the cardiovascular lineage and to adopt a proangiogenic phenotype. To understand better ASCs' biology, we used a novel 3D culture device. ASCs' and b.END-3 endothelial cell proliferation, migration, and vessel morphogenesis were significantly enhanced compared to 2D culturing techniques. ASCs were isolated from inguinal fat pads of 6-week-old GFP+/BLI+ mice. Early passage ASCs cells (P3-P4), PKH26-labeled murine b.END-3 cells or a co-culture of ASCs and b.END-3 cells were seeded at a density of 1 × 10(5) on three different surface configurations: (a) a 2D surface of tissue culture plastic, (b) Matrigel, and (c) a highly porous 3D scaffold fabricated from inert polystyrene. VEGF expression, cell proliferation, and tubulization, were assessed using optical microscopy, fluorescence microscopy, 3D confocal microscopy, and SEM imaging (n = 6). Increased VEGF levels were seen in conditioned media harvested from co-cultures of ASCs and b.END-3 on either Matrigel or a 3D matrix. Fluorescence, confocal, SEM, bioluminescence revealed improved cell, proliferation, and tubule formation for cells seeded on the 3D polystyrene matrix. Collectively, these data demonstrate that co-culturing ASCs with endothelial cells in a 3D matrix environment enable us to generate prevascularized tissue-engineered constructs. This can potentially help us to surpass the tissue thickness limitations faced by the tissue engineering community today.
View details for DOI 10.1002/jbm.a.33113
View details for PubMedID 21630430
New strategies for skin regeneration are needed to address the significant medical burden caused by cutaneous wounds and disease. In this study, pullulan-collagen composite hydrogel matrices were fabricated using a salt-induced phase inversion technique, resulting in a structured yet soft scaffold for skin engineering. Salt crystallization induced interconnected pore formation, and modification of collagen concentration permitted regulation of scaffold pore size. Hydrogel architecture recapitulated the reticular distribution of human dermal matrix while maintaining flexible properties essential for skin applications. In vitro, collagen hydrogel scaffolds retained their open porous architecture and viably sustained human fibroblasts and murine mesenchymal stem cells and endothelial cells. In vivo, hydrogel-treated murine excisional wounds demonstrated improved wound closure, which was associated with increased recruitment of stromal cells and formation of vascularized granulation tissue. In conclusion, salt-induced phase inversion techniques can be used to create modifiable pullulan-collagen composite dermal scaffolds that augment early wound healing. These novel biomatrices can potentially serve as a structured delivery template for cells and biomolecules in regenerative skin applications.
View details for DOI 10.1089/ten.tea.2010.0298
View details for Web of Science ID 000287801600005
View details for PubMedID 20919949
Evolving evidence suggests a possible role for adipose stromal cells (ASCs) in adult neovascularization, although the specific cues that stimulate their angiogenic behavior are poorly understood. We evaluated the effect of hypoxia, a central mediator of new blood vessel development within ischemic tissue, on proneovascular ASC functions. Murine ASCs were exposed to normoxia (21% oxygen) or hypoxia (5%, 1% oxygen) for varying lengths of time. Vascular endothelial growth factor (VEGF) secretion by ASCs increased as an inverse function of oxygen tension, with progressively higher VEGF expression at 21%, 5%, and 1% oxygen, respectively. Greater VEGF levels were also associated with longer periods in culture. ASCs were able to migrate towards stromal cell-derived factor (SDF)-1, a chemokine expressed by ischemic tissue, with hypoxia augmenting ASC expression of the SDF-1 receptor (CXCR4) and potentiating ASC migration. In vivo, ASCs demonstrated the capacity to proliferate in response to a hypoxic insult remote from their resident niche, and this was supported by in vitro studies showing increasing ASC proliferation with greater degrees of hypoxia. Hypoxia did not significantly alter the expression of endothelial surface markers by ASCs. However, these cells did assume an endothelial phenotype as evidenced by their ability to tubularize when seeded with differentiated endothelial cells on Matrigel. Taken together, these data suggest that ASCs upregulate their proneovascular activity in response to hypoxia, and may harbor the capacity to home to ischemic tissue and function cooperatively with existing vasculature to promote angiogenesis.
View details for DOI 10.1634/stemcells.2008-0276
View details for Web of Science ID 000263032400030
View details for PubMedID 18974212