PhD, University Paris Descartes, France, Ophthalmology/Toxicology (2015)
PhD, Federal University Minas Gerais, Brasil, Biomaterials (2015)
In this study, an in situ forming corneal stromal substitute based on collagen type I crosslinked by bio-orthogonal strain-promoted azide-alkyne cycloaddition (SPAAC) is presented. The crosslinked collagen gel has greater transparency compared to non-crosslinked collagen gels. The mechanical properties of the gels are controlled by changing functional group ratios and conjugated collagen concentrations. Higher concentrations of conjugated collagen yield enhances mechanical properties, where the storage modulus increases from 42.39 ± 8.95 to 112.03 ± 3.94 Pa after SPAAC crosslinking. Encapsulated corneal keratocytes grow within the SPAAC-crosslinked gels and corneal keratinocytes are supported on top of the gel surfaces. SPAAC-crosslinked gels support more favorable and stable keratinocyte morphology on their surface compared to non-crosslinked gels likely as a result of more optimal substrate stiffness, gel integrity, and resistance to degradation. SPAAC-crosslinked collagen gels with and without encapsulated keratocytes applied to rabbit corneas in an organ culture model after keratectomy exhibit surface epithelialization with multilayered morphology. The novel in situ forming gel is a promising candidate for lamellar and defect reconstruction of corneal stromal tissue.
View details for PubMedID 30106514
View details for DOI 10.1021/acscentsci.8b00470
Drug ocular toxicity is a field that requires attention. Clindamycin has been injected intravitreally to treat ocular toxoplasmosis, the most common cause of eye posterior segment infection worldwide. However, little is known about the toxicity of clindamycin to ocular tissues. We have previously showed non intraocular toxicity in rabbit eyes of poly(lactic-co-glycolic acid) (PLGA) implants containing clindamycin hydrochloride (CLH) using only clinical macroscotopic observation. In this study, we investigated the in vivo biocompatibility of CLH-PLGA implants at microscotopic, cellular and molecular levels.Morphology of ARPE-19 and MIO-M1 human retinal cell lines was examined after 72 h exposure to CLH-PLGA implant. Drug delivery system was also implanted in the vitreous of rat eyes, retinal morphology was evaluated in vivo and ex vivo. Morphology of photoreceptors and inflammation was assessed using immunofluorescence and real-time PCR.After 72 h incubation with CLH-PLGA implant, ARPE-19 and MIO-M1 cells preserved the actin filament network and cell morphology. Rat retinas displayed normal lamination structure at 30 days after CLH-PLGA implantation. There was no apoptotic cell and no loss in neuron cells. Cones and rods maintained their normal structure. Microglia/macrophages remained inactive. CLH-PLGA implantation did not induce gene expression of cytokines (IL-1β, TNF-α, IL-6), VEGF, and iNOS at day 30.These results demonstrated the safety of the implant and highlight this device as a therapeutic alternative for the treatment of ocular toxoplasmosis.
View details for DOI 10.1007/s11095-017-2118-2
View details for Web of Science ID 000399164800015
View details for PubMedID 28224388
In the treatment of traumatic injuries, burns, and ulcers of the eye, inadequate epithelial tissue healing remains a major challenge. Wound healing is a complex process involving the temporal and spatial interplay between cells and their extracellular milieu. It can be impaired by a variety of causes including infection, poor circulation, loss of critical cells and/or proteins, and a deficiency in normal neural signaling (e.g. neurotrophic ulcers). Ocular anatomy is particularly vulnerable to lasting morbidity from delayed healing, whether it be scarring or perforation of the cornea, destruction of the conjunctival mucous membrane, or cicatricial changes to the eyelids and surrounding skin. Therefore, there is a major clinical need for new modalities for controlling and accelerating wound healing, particularly in the eye. Collagen matrices have long been explored as scaffolds to support cell growth as both two-dimensional coatings and substrates, as well as three-dimensional matrices. Meanwhile, the immobilization of growth factors to various substrates has also been extensively studied as a way to promote enhanced cellular adhesion and proliferation. Herein we present a new strategy for photochemically immobilizing growth factors to collagen using riboflavin as a photosensitizer and exposure to visible light (~458 nm). epidermal growth factor (EGF) was successfully bound to collagen-coated surfaces as well as directly to endogenous collagen from porcine corneas. The initial concentration of riboflavin and EGF, as well as the blue light exposure time, were keys to the successful binding of growth factor to these surfaces. The photocrosslinking reaction increased EGF residence time on collagen surfaces over seven days. EGF activity was maintained after the photocrosslinking reaction with a short duration of pulsed blue light exposure time. Bound EGF accelerated in vitro corneal epithelial cell proliferation and migration and maintained normal cell phenotype. Additionally, the treated surfaces were cytocompatible, and the photocrosslinking reaction was proven to be safe, preserving nearly 100% cell viability. These results suggest that this general approach is safe and versatile may be used for targeting and immobilizing bioactive factors onto collagen matrices in a variety of applications, including in the presence of live, seeded cells or in vivo onto endogenous extracellular matrix collagen.
View details for PubMedID 28799757
Surface modifications with tethered growth factors have mainly been applied to synthetic polymeric biomaterials in well-controlled, acellular settings, followed by seeding with cells. The known bio-orthogonality of copper-free click chemistry provides an opportunity to not only use it in vitro to create scaffolds or pro-migratory tracks in the presence of living cells, but also potentially apply it to living tissues directly as a coupling modality in situ. In this study, we studied the chemical coupling of growth factors to collagen using biocompatible copper-free click chemistry and its effect on the enhancement of growth factor activity in vitro. We verified the characteristics of modified epidermal growth factor (EGF) using mass spectrometry and EGF/EGF receptor binding assay, and chemical immobilization of EGF on collagen was also evaluated by copper-free click chemistry using surface x-ray photoelectron spectroscopy (XPS), surface plasmon resonance (SPR) spectroscopy, and enzyme-linked immunosorbent assay (ELISA). We found that the anchoring was non-cytotoxic, biocompatible, and sufficiently rapid for clinical application. Moreover, the surface-immobilized EGF has significant effects on epithelial cell attachment and proliferation. Our results demonstrate the possibility of copper-free click chemistry as a tool for covalent bonding of growth factors to extracellular matrix collagen and the potential effectiveness of immobilized EGF in this setting. This approach is a novel and potentially clinically useful application of copper-free click chemistry as a way of directly anchoring growth factors to collagen and foster epithelial wound healing.
View details for PubMedID 28598594
Ocular toxoplasmosis may result in uveitis in the posterior segment of the eye, leading to severe visual complications. Clindamycin-loaded poly(lactide-co-glycolide) (PLGA) implants could be applied to treat the ocular toxoplasmosis. In this study, the pharmacokinetic profiles of the drug administrated by PLGA implants and by intravitreal injections in rabbits' eyes were evaluated. The implant released the drug for 6 weeks while the drug administrated by intravitreal injections remained in the vitreous cavity for 2 weeks. Compared to the injected drug, the implants containing clindamycin had higher values of area under the curve (AUC) (39.2 vs 716.7 ng week mL(-1)) and maximum vitreous concentration (Cmax) (8.7 vs 13.83 ng mL(-1)). The implants prolonged the delivery of clindamycin and increased the contact of the drug with the eyes' tissues. Moreover, the in vivo ocular biocompatibility of the clindamycin-loaded PLGA implants was evaluated regarding to the clinical examination of the eyes and the measurement of the intraocular pressure (IOP) during 6 weeks. The implantable devices caused no ocular inflammatory process and induced the increase of the IOP in the fourth week of the study. The IOP augmentation could be related to the maximum concentration of clindamycin released from the implants. In conclusion, the PLGA implants based on clindamycin may be a therapeutic alternative to treat ocular toxoplasmosis.
View details for DOI 10.1016/j.jpba.2014.08.023
View details for Web of Science ID 000347277500044
View details for PubMedID 25459934
A simple and accurate method including liquid-liquid extraction and protein precipitation procedures from silicone oil and aqueous humor samples followed by high-performance liquid chromatography (HPLC-UV) was developed and validated to determine the pharmacokinetic profile of triamcinolone acetonide in silicone oil and aqueous humor of rabbits' eyes submitted to the pars plana vitrectomy surgery. The method was successfully applied to quantify the drug remaining in silicone oil and aqueous humor (LOQ range of 1μg/mL). The triamcinolone acetonide remained in silicone oil and aqueous humor of vitrectomized rabbits' eyes for four weeks after the intravitreal injections.
View details for DOI 10.1016/j.jpba.2013.10.025
View details for Web of Science ID 000330487000004
View details for PubMedID 24252721
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