Armando Silva-Cunha

New vehicle based on a microemulsion for topical ocular administration of dexamethasone

Aim: Eye drops are the most used dosage form by the ocular route, in spite of their low bioavailability. Due to their properties and numerous advantages, microemulsions are promising systems for topical ocular drug delivery. They can increase water solubility of the drug and enhance drug absorption into the eye. The present study describes the development and characterization of an oil‐in‐water microemulsion containing dexamethasone and the evaluation of its pharmacokinetics in rabbits after topical ocular application.

Montmorillonite clay-based polyurethane nanocomposite as local triamcinolone acetonide delivery system

Biodegradable polyurethane was synthesized by preparing aqueous polyurethane dispersion having poly(caprolactone) and poly(ethylene glycol) as soft segments. Montmorillonite particles were delaminated within the waterborne polyurethane to produce a nanocomposite. The triamcinolone acetonide (TA), an important corticoid drug, was dispersed into the nanocomposite followed by a drying step to produce an implantable drug delivery system. Infrared (FTIR) results demonstrated that the original chemical structure of the TA was preserved after incorporation into the nanocomposite. Wide angle (WAXS) and small angle X-ray scattering (SAXS) results suggested that TA and clay do not dramatically change the morphology phase of the polymer although they can interact with each other. The presence of montmorillonite particles in the nanocomposite reduced the rate of TA release as compared to the pure polyurethane and enhanced the mechanical properties of the polymer. The overall results indicate that montmorillonite clay-based polyurethane nanocomposite could be potentially applied as local TA delivery system.

In vitro and in vivo ocular biocompatibility of electrospun poly(ɛ-caprolactone) nanofibers.

Biocompatibility is a requirement for the development of nanofibers for ophthalmic applications. In this study, nanofibers were elaborated using poly(ε-caprolactone) via electrospinning. The ocular biocompatibility of this material was investigated. MIO-M1 and ARPE-19 cell cultures were incubated with nanofibers and cellular responses were monitored by viability and morphology. The in vitro biocompatibility revealed that the nanofibers were not cytotoxic to the ocular cells. These cells exposed to the nanofibers proliferated and formed an organized monolayer. ARPE-19 and MIO-M1 cells were capable of expressing GFAP, respectively, demonstrating their functionality. Nanofibers were inserted into the vitreous cavity of the rats eye for 10days and the in vivo biocompatibility was investigated using Optical Coherence Tomography (OCT), histology and measuring the expression of pro-inflammatory genes (IL-1β, TNF-α, VEGF and iNOS) (real-time PCR). The OCT and the histological analyzes exhibited the preserved architecture of the tissues of the eye. The biomaterial did not elicit an inflammatory reaction and pro-inflammatory cytokines were not expressed by the retinal cells, and the other posterior tissues of the eye. Results from the biocompatibility studies indicated that the nanofibers exhibited a high degree of cellular biocompatibility and short-term intraocular tolerance, indicating that they might be applied as drug carrier for ophthalmic use.

Evaluation of water-in-oil-in-water multiple emulsion and microemulsion as potential adjuvants for immunization with rabies antigen

Water-in-oil-in-water (W/O/W) multiple emulsions and microemulsions have been studied as potential candidates to be formulated as adjuvants. In this work their application as adjuvants for rabies virus immunization was studied. The humoral response, the effective dose 50 and histology for the developed formulations were evaluated in mice and compared with those from traditional adjuvants. The microemulsion and W/O/W multiple emulsion adjuvants developed were able to induce humoral response in mice and the serum showed good in vivo protection. Compared to the other adjuvants evaluated, microemulsion was shown to be the best candidate for rabies immunization as it presented good potency against the virus and did not appear to cause any local reaction.

Development and characterization of an intraocular biodegradable polymer system containing cyclosporine-A for the treatment of posterior uveitis

The aim of this study was to synthesize and characterize the biodegradable intraocular implants based on poly (D,L-lactide-co-glycolide) (PLGA 75:25) with Cyclosporine-A (CyA) and to evaluate their in vitro drug delivery profile. Thermal analysis was conducted by using Thermogravimetry (TG) and Differential Scanning Calorimetry (DSC). Phase analysis and crystallinity of the polymer-CyA samples were assessed through X ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). Finally, microstructure and morphology of the systems were investigated by Scanning Electron Microscopy (SEM). The results showed that CyA was successfully incorporated into PLGA network with drug loading of approximately 31.6%. Also, based on FTIR and thermal analyses (TGA/DSC) no significant physical-chemical interaction was detected at the micro-nanoscale level between polymer/drug. SEM micrographs have indicated a uniform drug distribution in PLGA matrix. XRD patterns have showed that the incorporated semi-crystalline structure of CyA has not significantly altered the polymeric mainly amorphous network. In addition, the results have confirmed the chemical and biological drug stability, the drug distribution into the polymeric matrix and the possibility of cyclosporine prolonged delivery system profile.

Tacrolimus-loaded PLGA implants: in vivo release and ocular toxicity.

Abstract Purpose: To evaluate the in vivo release and ocular toxicity of a tacrolimus-loaded PLGA intravitreal implant. Methods: Tacrolimus-loaded PLGA implants were inserted into the vitreous cavity of rabbits’ eye. At different time points, the vitreous was retrieved and the concentration of tacrolimus released from the implants was determined. Clinical examination was performed to evaluate the implant tolerance. Results: PLGA implants provided controlled and prolonged release of tacrolimus. Approximately 99.97% of the drug was released from the devices at 6 weeks. Ophthalmic examination revealed no evidence of toxic effects of implants. Conclusions: Tolerance and feasibility of the tacrolimus-loaded PLGA implants, as sustained intraocular drug delivery systems, were demonstrated.

Montmorillonite clay based polyurethane nanocomposite as substrate for retinal pigment epithelial cell growth

The subretinal transplantation of retinal pigment epithelial cells (RPE cells) grown on polymeric supports may have interest in retinal diseases affecting RPE cells. In this study, montmorillonite based polyurethane nanocomposite (PU-NC) was investigated as substrate for human RPE cell growth (ARPE-19 cells). The ARPE-19 cells were seeded on the PU-NC, and cell viability, proliferation and differentiation were investigated. The results indicated that ARPE-19 cells attached, proliferated onto the PU-NC, and expressed occludin. The in vivo ocular biocompatibility of the PU-NC was assessed by using the HET-CAM; and through its implantation under the retina. The direct application of the nanocomposite onto the CAM did not compromise the vascular tissue in the CAM surface, suggesting no ocular irritancy of the PU-NC film. The nanocomposite did not elicit any inflammatory response when implanted into the eye of rats. The PU-NC may have potential application as a substrate for RPE cell transplantation.

Evaluation of the effects of thalidomide-loaded biodegradable devices in solid Ehrlich tumor.

Regarding thalidomides effects in cancer and the problems related to its physicochemical characteristics and toxic effects, we proposed a new biodegradable polymeric implant to this drug. In this paper, we evaluate the antiangiogenic activity and antitumor effect of thalidomide when incorporated in poly-lactide-co-glycolide (PLGA) implants in an animal model for Ehrlich tumor. This dosage form permits the prolonged drug release. The biodegradable implants could reduce the blood vessel in a chorioallantoic membrane (CAM) model. When applied to the Ehrlich tumor model, implant also showed to reduce the number of vessels. It was also observed to reduce areas of inflammation and increases the area of necrosis in the group of thalidomide implant. A 47% reduction in tumor volume was observed in the thalidomide implant group, which is discussed in relation to literature reported results of thalidomide conventional administration ways.

Bevacizumab-loaded polyurethane subconjunctival implants: effects on experimental glaucoma filtration surgery.

PURPOSE Vascular endothelial growth factor (VEGF) may contribute to the scarring process resulting from glaucoma filtration surgery, since this cytokine may stimulate fibroblast proliferation. The aim of this study was to describe a new bevacizumab-loaded polyurethane implant (BPUI) and to evaluate its effectiveness as a new drug delivery system of anti-VEGF antibody in a rabbit model of glaucoma filtration surgery. METHODS An aqueous dispersion of polyurethane was obtained via the conventional process. Bevacizumab (1.5 mg) was then incorporated into the dispersion and was subsequently dried to form the polymeric films. Films with dimensions of 3×3×1 mm that either did (group BPUI, n=10) or did not contain bevacizumab (group PUI, n=10) were implanted in the subconjunctival space, at the surgical site in 1 eye of each rabbit. The in vitro bevacizumab release was evaluated using size-exclusion high-performance liquid chromatography (HPLC), and the in vivo effects of the drug were investigated in a rabbit experimental trabeculectomy model by examining the bleb characteristics and collagen accumulation, and by performing immunohistological analyses of VEGF expression. RESULTS HPLC showed that only 10% of the bevacizumab in the implants had been released by postoperative day 5. In vivo studies demonstrated that the drug had no adverse effects; however, no significant differences in either the bleb area score or the collagen deposit intensity between the group PUI and the group that BPUI were observed. Moreover, the group BPUI presented a significantly lower proportion of VEGF-expressing fibroblasts than group PUI (0.17±0.03 vs. 0.35±0.05 cells/field, P=0.005). CONCLUSIONS This study demonstrated that bevacizumab release from the BPUIs only occurred for a short time probably from the surface of the films. Nevertheless, they were well tolerated in rabbit eyes and reduced the number of VEGF-expressing fibroblasts.

Biodegradable implants for ocular delivery of anti-inflammatory drug

The treatment of vitreoretinal diseases is limited, and there are currently new drug delivery approaches being reported for increasing drug bioavailability. Intraocular implants can release drugs directly into the posterior segment of the eye and maintain long-term vitreous concentrations of drugs within the therapeutic range. The objective of this pilot study was to investigate the in vitro and in vivo short-term safety and pharmacokinetic behavior of a dexamethasone implant that is inserted into the vitreous using a new technique that does not require surgery. The results showed that the developed device prolonged the release of dexamethasone within therapeutic levels, both in vitro and in vivo. Furthermore, the implant was not associated with retinal histological changes or elevated intraocular pressure in normal rabbits’ eyes. Controlled animal studies are underway to test the efficacy of the implant in diseased eyes.