Nanomedicine for glaucoma: liposomes provide sustained release of latanoprost in the eye

Purpose: To report the development and therapeutic evaluation of a liposomal nanocarrier for sustained release of latanoprost, in the rabbit eye. Methods: We fabricated latanoprost-loaded egg-phosphatidylcholine (EggPC) liposomes using the film hydration technique. The delivery vehicles were nano-sized (Z avg = 109 ± 18 nm), had a narrow poly dispersity index (PDI = 0.19 ± 0.04), and a very high loading efficiency (94% ± 5%). Based on in vitro data, we evaluated this formulation for lowering intraocular pressure (IOP) in rabbit eyes. Following a single subconjunctival injection of the latanoprost loaded formulation, the eyes were clinically monitored and the IOP recorded. Results: Latanoprost-loaded EggPC liposomes demonstrated a high drug/lipid mole ratio of 0.181, remained stable for at least 6 months on storage (4°C), and at least 1 month at 25°C. A slow and sustained release of 60% of latanoprost was achieved by 14 days in the in vitro release study. The same formulation demonstrated a greater sustained IOP lowering effect compared with daily administration of topical latanoprost beyond 90 days (4.8 ± 1.5 vs 2.5 ± 0.9 mmHg; P < 0.001). No signs of inflammation were evident in the eyes from slit-lamp examination analysis. Conclusion: The loading required for a long-term sustained delivery of latanoprost for up to 90 days in the rabbit eyes was achieved with EggPC liposomes. A single injection of latanoprost-loaded EggPC liposomes can lower the IOP for up to 90 days, with a greater IOP lowering effect than daily topical administration of latanoprost.Published versio

Sustained Release of an Anti-Glaucoma Drug: Demonstration of Efficacy of a Liposomal Formulation in the Rabbit Eye

Topical medication remains the first line treatment of glaucoma; however, sustained ocular drug delivery via topical administration is difficult to achieve. Most drugs have poor penetration due to the multiple physiological barriers of the eye and are rapidly cleared if applied topically. Currently, daily topical administration for lowering the intra-ocular pressure (IOP), has many limitations, such as poor patient compliance and ocular allergy from repeated drug administration. Poor compliance leads to suboptimal control of IOP and disease progression with eventual blindness. The delivery of drugs in a sustained manner could provide the patient with a more attractive alternative by providing optimal therapeutic dosing, with minimal local toxicity and inconvenience. To investigate this, we incorporated latanoprost into LUVs (large unilamellar vesicles) derived from the liposome of DPPC (di-palmitoyl-phosphatidyl-choline) by the film hydration technique. Relatively high amounts of drug could be incorporated into this vesicle, and the drug resides predominantly in the bilayer. Vesicle stability monitored by size measurement and DSC (differential scanning calorimetry) analysis showed that formulations with a drug/lipid mole ratio of about 10% have good physical stability during storage and release. This formulation demonstrated sustained release of latanoprost in vitro, and then tested for efficacy in 23 rabbits. Subconjunctival injection and topical eye drop administration of the latanoprost/liposomal formulation were compared with conventional daily administration of latanoprost eye drops. The IOP lowering effect with a single subconjunctival injection was shown to be sustained for up to 50 days, and the extent of IOP lowering was comparable to daily eye drop administration. Toxicity and localized inflammation were not observed in any treatment groups. We believe that this is the first demonstration, in vivo, of sustained delivery to the anterior segment of the eye that is safe and efficacious for 50 days

Cell-mimicking polyethylene glycol-diacrylate based nanolipogel for encapsulation and delivery of hydrophilic biomolecule

Lipid based nanoparticulate formulations have been widely used for the encapsulation and sustain release of hydrophilic drugs, but they still face challenges such as high initial burst release. Nanolipogel (NLG) emerges as a potential system to encapsulate and deliver hydrophilic drug while suppressing its initial burst release. However, there is a lack of characterization of the drug release mechanism from NLGs. In this work, we present a study on the release mechanism of hydrophilic Dextran-Fluorescein Isothiocyanate (DFITC) from Poly (ethylene glycol) Diacrylate (PEGDA) NLGs by using different molecular weights of PEGDA to vary the mesh size of the nanogel core, drawing inspiration from the macromolecular crowding effect in cells, which can be viewed as a mesh network of undefined sizes. The effect is then further characterized and validated by studying the diffusion of DFITC within the nanogel core using Fluorescence Recovery after Photobleaching (FRAP), on our newly developed cell derived microlipogels (MLG). This is in contrast to conventional FRAP works on cells or bulk hydrogels, which is limited in our application. Our work showed that the mesh size of the NLGs can be controlled by using different Mw of PEGDA, such as using a smaller MW to achieve higher crosslinking density, which will lead to having smaller mesh size for the crosslinked nanogel, and the release of hydrophilic DFITC can be sustained while suppressing the initial burst release, up to 10-fold more for crosslinked PEGDA 575 NLGs. This is further validated by FRAP which showed that the diffusion of DFITC is hindered by the decreasing mesh sizes in the NLGs, as a result of lower mobile fractions. These findings will be useful for guiding the design of PEGDA NLGs to have different degree of suppression of the initial burst release as well as the cumulative release, for a wide array of applications. This can also be extended to other different types of nanogel cores and other nanogel core-based nanoparticles for encapsulation and release of hydrophilic biomolecules

Pushing the envelope in tissue engineering: Ex vivo production of thick vascularized cardiac extracellular matrix constructs

Functional vascularization is a prerequisite for cardiac tissue engineering of constructs with physiological thicknesses. We previously reported the successful preservation of main vascular conduits in isolated thick acellular porcine cardiac ventricular ECM (pcECM). We now unveil this scaffold's potential in supporting human cardiomyocytes and promoting new blood vessel development ex vivo, providing long-term cell support in the construct bulk. A custom-designed perfusion bioreactor was developed to remodel such vascularization ex vivo, demonstrating, for the first time, functional angiogenesis in vitro with various stages of vessel maturation supporting up to 1.7 mm thick constructs. A robust methodology was developed to assess the pcECM maximal cell capacity, which resembled the human heart cell density. Taken together these results demonstrate feasibility of producing physiological-like constructs such as the thick pcECM suggested here as a prospective treatment for end-stage heart failure. Methodologies reported herein may also benefit other tissues, offering a valuable in vitro setting for "thick-tissue" engineering strategies toward large animal in vivo studies.Israeli Science Foundation/1563/10Singapore National Research Foundatio

Accelerating the Translation of Nanomaterials in Biomedicine

Due to their size and tailorable physicochemical properties, nanomaterials are an emerging class of structures utilized in biomedical applications. There are now many prominent examples of nanomaterials being used to improve human health, in areas ranging from imaging and diagnostics to therapeutics and regenerative medicine. An overview of these examples reveals several common areas of synergy and future challenges. This Nano Focus discusses the current status and future potential of promising nanomaterials and their translation from the laboratory to the clinic, by highlighting a handful of successful examples

Accelerating the Translation of Nanomaterials in Biomedicine

Due to their size and tailorable physicochemical properties, nanomaterials are an emerging class of structures utilized in biomedical applications. There are now many prominent examples of nanomaterials being used to improve human health, in areas ranging from imaging and diagnostics to therapeutics and regenerative medicine. An overview of these examples reveals several common areas of synergy and future challenges. This Nano Focus discusses the current status and future potential of promising nanomaterials and their translation from the laboratory to the clinic, by highlighting a handful of successful examples

Biocompatibility and Biodegradation Studies of Subconjunctival Implants in Rabbit Eyes

Sustained ocular drug delivery is difficult to achieve. Most drugs have poor penetration due to the multiple physiological barriers of the eye and are rapidly cleared if applied topically. Biodegradable subconjunctival implants with controlled drug release may circumvent these two problems. In our study, two microfilms (poly [d,l-lactide-co-glycolide] PLGA and poly[d,l-lactide-co-caprolactone] PLC were developed and evaluated for their degradation behavior in vitro and in vivo. We also evaluated the biocompatibility of both microfilms. Eighteen eyes (9 rabbits) were surgically implanted with one type of microfilm in each eye. Serial anterior-segment optical coherence tomography (AS-OCT) scans together with serial slit-lamp microscopy allowed us to measure thickness and cross-sectional area of the microfilms. In vitro studies revealed bulk degradation kinetics for both microfilms, while in vivo studies demonstrated surface erosion kinetics. Serial slit-lamp microscopy revealed no significant inflammation or vascularization in both types of implants (mean increase in vascularity grade PLGA50/50 12±0.5% vs. PLC70/30 15±0.6%; P = 0.91) over a period of 6 months. Histology, immunohistochemistry and immuno-fluorescence also revealed no significant inflammatory reaction from either of the microfilms, which confirmed that both microfilms are biocompatible. The duration of the drug delivery can be tailored by selecting the materials, which have different degradation kinetics, to suit the desired clinical therapeutic application

Hemocompatilibilization of biopolymer systems

The primary goals of this project were achieved. These included the development of a reliable method to evaluate the interaction of blood cells with polymer films; the quantification of the attachment and proliferation of endothelial cells with biodegradable polymer films; the development of 3 independent surface modification methods that enhanced endothelialization rates; the identification of key factors that govern the growth of endothelial cells on polymers.ARC 4/0

Hentocontpatilibilization of biopolydler systems

The primary goals of this project were achieved. These included the development of a reliable method to evaluate the interaction of blood cells with polymer films; the quantification of the attachment and proliferation of endothelial cells with biodegradable polymer films; the development of 3 independent surface modification methods that enhanced endothelialization rates; the identification of key factors that govern the growth of endothelial cells on polymers. Additional work on the interaction of polymeric nanoparticles with blood cells also revealed some interesting results, including the definition of surface features that inhibit particle uptake by phagocytic cells.ARC 4/0

Cosolvent effects on the drug release and depot swelling in injectable in situ depot-forming systems

Although injectable depot-forming solutions have been commercialized, the factors that influence the overall release kinetics from such systems are still not fully understood. In this work, we address the effect of cosolvent on the issue of excessive burst release of potent bioactives from injectable depot-forming solutions. Specifically, we have evaluated the influence of addition of a relatively hydrophobic cosolvent (triacetin) to more hydrophilic biocompatible solvents such as dimethyl sulfoxide (DMSO) and N-methyl-2-pyrrolidone (NMP) on the burst release. Drug release and solvent release results demonstrate that high burst release that occurred when only hydrophilic solvent was used as solvent was significantly reduced by adding triacetin as a cosolvent. The profiles of drug release were in good agreement with the profiles of the hydrophilic solvent DMSO or NMP release, and the suppression of the burst by triacetin addition is due to the suppression of the solvent release. Surprisingly, the swelling of the depot increased with triacetin amount and the depot morphology became more porous compared with the absence of triacetin. Usage of hydrophobic solvent as a cosolvent to reduce the burst release was shown to be more effective on the hydrophobic PdlLA depot and less effective on the relatively hydrophilic RG502 depot