A novel MMC-loaded pHEMA drainage device for the treatment of glaucoma: in vitro and in vivo studies

Mevacor/Poly(vinyl acetate/2-hydroxyethyl methacrylate) as Solid Solution: Preparation, Solubility Enhancement and Drug Delivery

Mevacor/Poly(vinyl acetate-co-2-hydroxyethyl methacrylate) drug carrier systems (MVR/VAC-HEMA) containing different Mevacor (MVR) contents were prepared in one pot by free radical copolymerization of vinyl acetate with 2-hydroxyethyl methacrylate using an LED lamp light in the presence of camphorquinone as a photoinitiator and Mevacor as a drug filler. The prepared material was characterized by FTIR, 1H NMR, DSC, SEM and XRD methods. Different parameters influencing the efficiency in the Mecvacor-water solubility and the drug delivery of this system, such as the swelling capacity of the carrier, the amount of Mevacor loaded and the pH medium have been widely investigated. The results obtained revealed that the Mevacor particles were uniformly dispersed in their molecular state in the copolymer matrix forming a solid solution; the cell toxicity of the virgin poly(vinyl acetate-co-2-hydroxy ethyl methacrylate) (VAC-HEMA) and MVR/VAC-HEMA drug carrier system exhibited no significant effect on their viability when between 0.25 and 2.00 wt% was loaded in these materials; the average swelling capacity of VAC-HEMA material in water was found to be 45.16 wt%, which was practically unaffected by the pH medium and the solubility of MVR deduced from the release process reached more than 22 and 37 times that of the powder dissolved directly in pH 1 and 7 media, respectively. The in vitro MVR release kinetic study revealed that the MVR/VAC-HEMA system containing 0.5 wt% MVR exhibited the best performance in the short gastrointestinal transit (GITT), while that containing 2.0 wt% is for the long transit as they were able to considerably reduce the minimum release of this drug in the stomach (pH1).

Animal models and drug candidates for use in glaucoma filtration surgery: A systematic review

Glaucoma, a degenerative disease of the optic nerve, is the leading cause of irreversible blindness worldwide. Currently, there is no curative treatment. The only proven treatment is lowering intraocular pressure (IOP), the most important risk factor. Glaucoma filtration surgery (GFS) can effectively lower IOP. However, approximately 10% of all surgeries fail yearly due to excessive wound healing, leading to fibrosis. GFS animal models are commonly used for the development of novel treatment modalities. The aim of the present review was to provide an overview of available animal models and anti-fibrotic drug candidates. MEDLINE and Embase were systematically searched. Manuscripts until September 1st^, 2021 were included. Studies that used animal models of GFS were included in this review. Additionally, the snowball method was used to identify other publications which had not been identified through the systematic search. Two hundred articles were included in this manuscript. Small rodents (e.g. mice and rats) are often used to study the fibrotic response after GFS and to test drug candidates. Due to their larger eyes, rabbits are better suited to develop medical devices. Novel drugs aim to inhibit specific pathways, e.g. through the use of modulators, monoclonal antibodies, aqueous suppressants or gene therapy. Although most newly studied drugs offer a higher safety profile compared to antimetabolites, their efficacy is in most cases lower when compared to MMC. Current literature on animal models and potential drug candidates for GFS were summarized in this review. Future research should focus on refining current animal models (for example through the induction of glaucoma prior to undertaking GFS) and standardizing animal research to ensure a higher reproducibility and reliability across different research groups. Lastly, novel therapies need to be further optimized, e.g. by conducting more research on the dosage, administration route, application frequency, the option of creating combination therapies, or the development of drug delivery systems for sustained release of anti-fibrotic medication.

Glaucoma drainage devices: a review of the past, present, and future

Glaucoma drainage devices are more frequently being used for glaucoma filtering surgeries, even those at low risk for failure with trabeculectomy. There are 4 major devices available: the Molteno, Baerveldt, Krupin, and Ahmed. The Molteno and Baerveldt are non-valved implants, while the Krupin and Ahmed are valved. The success rates of the different valves are about equal at approximately 70% with a mean intraocular pressure (IOP) lowering of at least 50% from the pre-operative IOP. Unfortunately, the failure rate is about 10% per year, leading to only 50% functional drainage devices at 5 years. Therefore, research on the biomaterials, shape, and technique of drainage implant surgery is being done in hopes of increasing long term success rates.

Carbodiimide cross-linked hyaluronic acid hydrogels as cell sheet delivery vehicles: characterization and interaction with corneal endothelial cells

It was reported that cell-adhesive gelatin discs have been successfully used as delivery vehicles for intraocular grafting of bioengineered corneal endothelial cell sheets. Development of alternative biomaterials to bovine-based gelatin vehicles can potentially eliminate the risk of bovine spongiform encephalopathy. In the present work, to investigate whether it was appropriate for use as cell sheet delivery vehicles, 1-ethyl-3-(3-dimethyl aminopropyl) carbodiimide (EDC) cross-linked hyaluronic acid (HA) hydrogels were studied by determinations of morphological characteristic, mechanical and thermal property, water content, in vitro degradability and cytocompatibility. Glutaraldehyde (GTA) cross-linked HA samples were used for comparison. It was found that HA discs after cross-linking significantly increased its tensile stress but reduced its tensile strain, water uptake and enzymatic degradability. The results of differential scanning calorimetry demonstrated that cross-linking could lead to the alteration of polymer structure. In addition, the EDC-cross-linked HA discs had a smoother surface structure, a faster degradation rate and a relatively lower cytotoxicity as compared to the GTA cross-linked counterparts. It is concluded that EDC can be successfully applied for HA cross-linking to fabricate structurally stable, mechanically reinforced, readily deformable, transparent and cytocompatible HA hydrogel discs with the potential to be applied as delivery vehicles for corneal endothelial cell therapy.

Poly(2-hydroxyethyl methacrylate) film as a drug delivery system for pilocarpine

This work investigates pilocarpine trapped in a matrix diffusion-controlled drug delivery system using hydrophilic inserts of Poly(2-hydroxyethyl methacrylate) (pHEMA) to ensure an increased bioavailability of pilocarpine and prolong the length of time in which the medication remains in the eyes of the test subjects. The physical and chemical properties of pilocarpine were investigated to elucidate the mechanism of drug-polymer interaction and the effect on drug release behavior of controlled release polymeric devices. In vitro release studies indicated that pilocarpine continued to be released from the inserts for a 24 h period. The results of intraocular pressure tests performed on albino rabbits were consistent with the observed in vitro behavior. The pressure decrease was significant for a period longer than 48 h. It confirms that the inserts, as sustainable releasing devices, are promising carriers for ophthalmic drug delivery systems.

5-FU loaded pHEMA drainage implants for glaucoma-filtering surgery: device design and in vitro release kinetics

Implantable monolithic and reservoir-like water-swellable drainage devices were developed for the subconjunctival sustained release of 5-fluorouracil (5-FU) in glaucoma-filtering surgery. A water-swellable matrix was formed of a copolymer of 2-hydroxyethyl methacrylate (HEMA) with different amounts of ethylene glycol dimethacrylate (EGDMA). Drug incorporation was done before polymerization and cross-linking. Briefly, to prepare the monolithic device the monomer-drug mixture is compression moulded into a 10 mm cylinder of 1 mm length. Furthermore, reservoir-like devices were obtained by coating the monolithic devices with a highly cross-linked polymer of HEMA (pHEMA) composition. The pHEMA devices containing 5-FU or not were well characterized by means of dynamic swelling studies, structural and thermal analysis. The release of 5-FU from these implants was studied in vitro. The rate of drug release was controlled by changing the drug loading (i.e. 10 mg or 20 mg 5-FU per device), cross-linking density of polymer matrix and type of implantable device, i.e. monolithic or reservoir-like device. While monolithic devices are releasing total releasable 5-FU during the first 10 h, reservoir-like devices prolong 5-FU release for up to 120 h. The 5-FU diffusion coefficient in swollen devices (Ds,s) is in the order of 10(-8) cm2 s-1 (approximately 10 times smaller than Dw,g values) and it is dependent on the cross-linking density of polymeric matrix and device load. These preliminary results suggested that 20 mg 5-FU-loaded reservoir-like devices may be a potentially effective system to deliver 5-FU into the subconjunctiva.