Evaluation of a class of polyurethane materials for intraocular lens manufacturing

A promising 'single' and 'dual' drug-nanocomposite enriched contact lens for the management of glaucoma in response to the tear fluid enzyme

Glaucoma is a neurodegenerative condition that results in the damage of retinal ganglion cells due to elevated intraocular pressure (IOP). To curtail the limitations associated with conventional treatments such as eye drops and ocular suspensions, we have developed 'single' and 'dual' drug delivery contact lenses (CLs), that is, latanoprost (LP) and latanoprost-timolol (LP-TM) deliverable CLs, in response to lysozyme (Lyz), which is abundant in the lacrimal fluid. Since chitosan (CS) can entrap more of the drug and also undergo hydrolysis in the presence of Lyz, we have employed CS for the composite preparation. The CL fabrication was performed by free radical copolymerization of poly(2-hydroxyethyl methacrylate) (pHEMA) in the presence of the drug-loaded nanocomposite with UV-curing initiators using the pre-drug loading strategy. The surface morphological, optical and mechanical investigations confirmed the presence of the drugs, ≥80% transparency, the adequate flexibility and biocompatibility of both the CLs. The in vitro release experiments showed the release of 95.86% LP from LP-CL, and 83.87% LP and 86.70% TM from LP-TM-CL in the presence of 1.5 mg mL-1 of Lyz in 72 h. In vitro biocompatibility assay against human corneal epithelial (HCE) cells and ex vivo experiments on HET-CAM confirmed that the fabricated LP-CL and LP-TM-CL are well tolerated. Moreover, in vivo safety evaluations of CLs on New Zealand white rabbit eyes suggest no sign of irritation to the ocular tissues within 72 h of observation. Hence, the study suggests that the 'single' and 'dual' drug-loaded CLs could open a new avenue to manage glaucoma by maintaining mean diurnal IOP.

Pharmaceutical-loaded contact lenses as an ocular drug delivery system: A review of critical lens characterization methodologies with reference to ISO standards

Therapeutic contact lenses for ocular drug delivery have received considerable interest as they can potentially enhance ocular bioavailability, increase patient compliance, and reduce side effects. Along with the successful in vitro and in vivo studies on sustained drug delivery through contact lenses, lens critical properties such as water content, optical transparency and modulus have also been investigated. Aside from issues such as drug stability or burst release, the potential for the commercialization of pharmaceutical-loaded lenses can be limited by the alteration of lens physical and chemical properties upon the incorporation of therapeutic or non-therapeutic components. This review outlines advances in the use of pharmaceutical-loaded contact lenses and their relevant characterization methodologies as a potential ocular drug delivery system from 2010 to 2020, while summarizing current gaps and challenges in this field. A key reference point for this review is the relevant ISO standards on contact lenses, relating to the associated characterization methodologies. The content of this review is categorized based on the chemical, physical and mechanical properties of the loaded lens with the shortcomings of such analytical technologies examined.

Preparation of ordered mesoporous and macroporous thermoplastic polyurethane surfaces for potential medical applications

Thermoplastic polyurethanes are widely used in medical devices. In order to limit some of their shortfalls, like microbial attachment, surfaces modifications can be required. In this work, a two-step replication method was used to create ordered macroporous and mesoporous thermoplastic polyurethane surfaces using anodic aluminum oxide as master template. The intermediate mould materials that were tested were polystyrene and a polyacrylate resin with inorganic filler. All obtained surfaces were characterized by scanning electron microscopy. The initial anodic aluminum oxide surfaces possessed macro or mesopores, function of anodization conditions. The intermediate mould structure correctly replicated the pattern, but the polystyrene surface structures (pillars) were less resistant than the polyacrylate resin ones. The thermoplastic polyurethane pattern possessed macropores or mesopores of about 130 nm or 46 nm diameter and of about 300 nm or 99 nm interpore distances, respectively, in accordance with the initial pattern. Thermoplastic polyurethanes pore depth was however less than initial anodic aluminum oxide pore depth, linked to an incomplete replication during intermediate mould preparation (60 to 90% depth replication). The correct replication of the original pattern confirms that this novel fabrication method is a promising route for surface patterning of thermoplastic polyurethanes that could be used for medical applications.