Endophthalmitis Prophylaxis Using a Single Drop of Thermoresponsive Controlled-Release Microspheres Loaded with Moxifloxacin in a Rabbit Model

Trans-corneal drug delivery strategies in the treatment of ocular diseases

The cornea is a remarkable tissue that possesses specialized structures designed to safeguard the eye against foreign objects. However, its unique properties also make it challenging to deliver drugs in a non-invasive manner. This review highlights recent advancements in achieving highly efficient drug transport across the cornea, focusing on nanomaterials. We have classified these strategies into three main categories based on their mechanisms and have analyzed their success and limitations in a systematic manner. The purpose of this review is to examine potential general principles that could improve drug penetration through the cornea and other natural barriers in the eye. We hope it will inspire the development of more effective drug delivery systems that can better treat ocular diseases.

Anti-Infective Treatment and Resistance Is Rarely Problematic with Eye Infections

The treatment of eye infections is very different than treating other body infections that require systemic anti-infectives. Endophthalmitis, keratitis, conjunctivitis, and other ocular infections are treated with direct injection and with topical drops directly to the infection site. There are no anti-infective susceptibility standards to interpret treatment success, but the systemic standards can be used to guide ocular therapy if the concentration of anti-infective in the ocular tissue is assumed to be higher than the concentration in the blood serum. This Perspective describes: (1) eye infections, (2) diagnostics of eye infections, (3) anti-infective treatment of eye infections, (4) anti-infective resistance of ocular pathogens, and (5) alternative anti-infective delivery and therapy. The data, based on years of clinical and laboratory research, support the premise that ocular infections are less problematic if etiologic agents are laboratory-diagnosed and if prompt, potent, anti-infective therapy is applied. Anti-infective susceptibility should be monitored to assure continued therapeutic success and the possibility of new-found resistance. New delivery systems and therapies may be helpful to better treat future ocular infections.

A sustained release cysteamine microsphere/thermoresponsive gel eyedrop for corneal cystinosis improves drug stability

Cystinosis is a rare, metabolic, recessive genetic disease in which the intralysosomal accumulation of cystine leads to system wide organ and tissue damage. In the eye, cystine accumulates in the cornea as corneal cystine crystals and severely impacts vision. Corneal cystine crystals are treated with cysteamine eyedrops when administrated 6 to 12 times day and used within 1 week. The strict dosing regimen and poor stability are inconvenient and add to the burden of therapy. To reduce the dosing frequency and improve the stability, we present reformulation of cysteamine into a novel controlled release eyedrop. In this work, we characterize and evaluate a topical drug delivery system comprised of encapsulated cysteamine in polymer microspheres with a thermoresponsive gel carrier. Spray-dried encapsulation of cysteamine was performed. In vitro cysteamine release, stability, and ocular irritation and corneal permeation were evaluated. The data suggest that encapsulated cysteamine improves the stability to 7 weeks when compared with 1-week aqueous cysteamine eyedrops. Release studies from one drop of our system show that cysteamine release was present for 24 h and above the minimum cysteamine eyedrop amount (6 drops). Cysteamine from our system also resulted in negligible irritation and enhanced permeation when compared with traditional cysteamine eyedrops. In vivo studies were implemented to support ease of administration, tolerability, and retention for 24 h. These studies suggest that our controlled release delivery system may provide stable cysteamine from a safe, once daily gel eyedrop.

Controlled release of ciprofloxacin and ceftriaxone from a single ototopical administration of antibiotic-loaded polymer microspheres and thermoresponsive gel

Acute otitis media (AOM) is the main indication for pediatric antibiotic prescriptions, accounting for 25% of prescriptions. While the use of topical drops can minimize the administered dose of antibiotic and adverse systemic effects compared to oral antibiotics, their use has limitations, partially due to low patient compliance, high dosing frequency, and difficulty of administration. Lack of proper treatment can lead to development of chronic OM, which may require invasive interventions. Previous studies have shown that gel-based drug delivery to the ear is possible with intratympanic injection or chemical permeation enhancers (CPEs). However, many patients are reluctant to accept invasive treatments and CPEs have demonstrated toxicity to the tympanic membrane (TM). We developed a novel method of delivering therapeutics to the TM and middle ear using a topical, thermoresponsive gel depot containing antibiotic-loaded poly(lactic-co-glycolic acid) microspheres. Our in vitro and ex vivo results suggest that the sustained presentation can safely allow therapeutically relevant drug concentrations to penetrate the TM to the middle ear for up to 14 days. Animal results indicate sufficient antibiotic released for treatment from topical administration 24h after bacterial inoculation. However, animals treated 72h after inoculation, a more clinically relevant treatment practice, displayed spontaneous clearance of infection as is also often observed in the clinic. Despite this variability in the disease model, data suggest the system can safely treat bacterial infection, with future studies necessary to optimize microsphere formulations for scaled up dosage of antibiotic as well as further investigation of the influence of spontaneous bacterial clearance and of biofilm formation on effectiveness of treatment. To our knowledge, this study represents the first truly topical drug delivery system to the middle ear without the use of CPEs.

Tuning of thermoresponsive pNIPAAm hydrogels for the topical retention of controlled release ocular therapeutics

Low patient compliance and poor bioavailability of ophthalmic medications are the main limitations of topical eye drops. A potential solution to these disadvantages could be provided by thermoresponsive hydrogels, which could be used as the basis for a gelling eye drop for long-term release of therapeutics. We previously reported such a system capable of being retained in the lower fornix of rabbits, continuously releasing an anti-glaucoma drug for one month. Here, we sought to improve the properties of the existing gels as most relevant to patient use without altering the drug release profile. Specifically, we optimized the sol-to-gel transition temperature and de-swelling kinetics of pNIPAAm gels to avoid risk of the gelled drop reverting to liquid during cold or windy weather, and ensure quick gelation upon administration. A reduction of the gel LCST, faster gelation kinetics, and suitable viscosity for the administration as an eye drop were successfully achieved through modification of the poly(ethylene glycol) content in the water phase and its molecular weight. Our data suggest that drug release is not affected by these changes, with representative drug concentration profiles of the previous and new formulations demonstrating comparable anti-glaucoma release kinetics.