Mucoadhesive Nanoparticles for Drug Delivery to the Anterior Eye

From Preformulative Design to in Vivo Tests: A Complex Path of Requisites and Studies for Nanoparticle Ocular Application. Part 2: In Vitro, Ex Vivo, and In Vivo Studies

The incidence of ocular pathologies is constantly increasing, as is the interest of the researchers in developing new strategies to ameliorate the treatment of these conditions. Nowadays, drug delivery systems are considered among the most relevant approaches due to their applicability in the treatment of a great variety of inner and outer eye pathologies through painless topical administrations. The design of such nanocarriers requires a deep study of many aspects related to the administration route but also a consideration of the authorities and pharmacopeial requirements, in order to achieve a clinical outcome. On such bases, the scope of this review is to describe the path of the analyses that could be performed on nanoparticles, along with the assessment of their applicability for ophthalmic treatments. Preformulation studies, physicochemical and technological characterization, and preliminary noncellular in vitro studies have been described in part 1 of this review. Herein, first the in vitro cellular assays are described; subsequently, nonocular organotypic tests and ex vivo studies are reported, as to present the various analyses to which the formulations can be subjected before in vivo studies, described in the last part. In each step, the models that could be used are presented and compared, highlighting the pros and cons. Moreover, their reliability and eventual acceptance by regulatory agencies are discussed. Hence, this review provides an overview of the most relevant assays applicable for nanocarriers intended for ophthalmic administration to guide researchers in the experimental decision process.

Effective Treatment of Haemophilus influenzae-Induced Bacterial Conjunctivitis by a Bioadhesive Nanoparticle Reticulate Structure

Ocular formulations should provide an effective antibiotic concentration at the site of infection to treat bacterial eye infections. However, tears and frequent blinking accelerate the drug clearance rate and limit drug residence time on the ocular surface. This study describes a biological adhesion reticulate structure (BNP/CA-PEG) consisting of antibiotic-loaded bioadhesion nanoparticles (BNP/CA), with an average 500-600 nm diameter, and eight-arm NH₂-PEG-NH₂ for local and extended ocular drug delivery. This retention-prolonging effect is a function of the Schiff base reaction between groups on the surface of BNP and amidogen on PEG. BNP/CA-PEG showed significantly higher adhesion properties and better treatment efficacy in an ocular rat model with conjunctivitis in comparison to non-adhesive nanoparticles, BNP, or free antibiotics. Both in vivo safety experiment and in vitro cytotoxicity test verified the biocompatibility and biosafety of the biological adhesion reticulate structure, indicating a promising translational prospect for further clinical use.

Considerations for Polymers Used in Ocular Drug Delivery

PURPOSE

Age-related eye diseases are becoming more prevalent. A notable increase has been seen in the most common causes including glaucoma, age-related macular degeneration (AMD), and cataract. Current clinical treatments vary from tissue replacement with polymers to topical eye drops and intravitreal injections. Research and development efforts have increased using polymers for sustained release to the eye to overcome treatment challenges, showing promise in improving drug release and delivery, patient experience, and treatment compliance. Polymers provide unique properties that allow for specific engineered devices to provide improved treatment options. Recent work has shown the utilization of synthetic and biopolymer derived biomaterials in various forms, with this review containing a focus on polymers Food and Drug Administration (FDA) approved for ocular use.

METHODS

This provides an overview of some prevalent synthetic polymers and biopolymers used in ocular delivery and their benefits, brief discussion of the various types and synthesis methods used, and administration techniques. Polymers approved by the FDA for different applications in the eye are listed and compared to new polymers being explored in the literature. This article summarizes research findings using polymers for ocular drug delivery from various stages: laboratory, preclinical studies, clinical trials, and currently approved. This review also focuses on some of the challenges to bringing these new innovations to the clinic, including limited selection of approved polymers.

RESULTS

Polymers help improve drug delivery by increasing solubility, controlling pharmacokinetics, and extending release. Several polymer classes including synthetic, biopolymer, and combinations were discussed along with the benefits and challenges of each class. The ways both polymer synthesis and processing techniques can influence drug release in the eye were discussed.

CONCLUSION

The use of biomaterials, specifically polymers, is a well-studied field for drug delivery, and polymers have been used as implants in the eye for over 75 years. Promising new ocular drug delivery systems are emerging using polymers an innovative option for treating ocular diseases because of their tunable properties. This review touches on important considerations and challenges of using polymers for sustained ocular drug delivery with the goal translating research to the clinic.

Novel Contact Lenses Embedded with Drug-Loaded Zwitterionic Nanogels for Extended Ophthalmic Drug Delivery

Therapeutic ophthalmic contact lenses with prolonged drug release and improved bioavailability have been developed to circumvent tedious eye drop instillation. In this work, zwitterionic nanogels based on poly(sulfobetaine methacrylate) (PSBMA) were easily fabricated by one-step reflux-precipitation polymerization, with the advantages of being surfactant-free and morphology controlled. Then, the ophthalmic drug levofloxacin (LEV) was encapsulated into the nanogels. A set of contact lenses with varied nanogel-loading content was fabricated by the cast molding method, with the drug-loaded nanogels dispersed in pre-monomer solutions composed of 2-hydroxyethyl methacrylate (HEMA) and N-vinyl-2-pyrrolidone (NVP). The structure, surface morphology, water contact angle (WCA), equilibrium water content (EWC), transmittance, and mechanical properties of the contact lenses were subsequently investigated, and in vitro drug release and biocompatibility were further evaluated. As a result, the optimized contact lens with nanogel-loading content of 8 wt% could sustainably deliver LEV for ten days, with critical lens properties within the range of recommended values for commercial contact lenses. Moreover, cell viability assays revealed that the prepared contact lenses were cytocompatible, suggesting their significant potential as an alternative to traditional eye drops or ointment formulations for long-term oculopathy treatment.