Abstract
Ocular in situ gels are a promising alternative to overcome drawbacks of conventional eye drops because they associate the advantages of solutions such as accuracy and reproducibility of dosing, or ease of administration with prolonged contact time of ointments. Chitosan is a natural polymer suitable for use in ophthalmic formulations due to its biocompatibility, biodegradability, mucoadhesive character, antibacterial and antifungal properties, permeation enhancement and corneal wound healing effects. The combination of chitosan, pH-sensitive polymer, with other stimuli-responsive polymers leads to increased mechanical strength of formulations and an improved therapeutic effect due to prolonged ocular contact time. This review describes in situ gelling systems resulting from the association of chitosan with various stimuli-responsive polymers with emphasis on the mechanism of gel formation and application in ophthalmology. It also comprises the main techniques for evaluation of chitosan in situ gels, along with requirements of safety and ocular tolerability.
Highlights
Topical instillation is the most commonly used ocular drug delivery method, but the bioavailability of the active substances is less than 5% [1]
Imam et al formulated an in situ gel based on a mixture of chitosan, gellan gum, and polyvinyl alcohol (PVA) for ocular release of besifloxacin
The gelling temperature was calculated as the measured value for t1 and t2 ± SD [89]. Another method for determining the gelation temperature was used by Varshosaz et al for an in situ gelling system based on poloxamer and chitosan
Summary
Topical instillation is the most commonly used ocular drug delivery method, but the bioavailability of the active substances is less than 5% [1]. A promising alternative are in situ gelling systems that undergo a phase transition in the eye, resulting a gel in response to environmental changes These systems associate in the same formulation the advantages of solutions such as accuracy and reproducibility of dosing, or ease of administration with the increased retention time of an ointment [5,6]. Incorporation of a therapeutic agent into a natural polymeric matrix protects the active compound from degradation, enhances absorption, improves the therapeutic effect, and decreases the frequency of administration. Mar. Drugs 2018, 16, 373 therapeutic agent into a natural polymeric matrix protects the active compound from degradation, enhances absorption, improves the therapeutic effect, and decreases the frequency of administration. Glucosamine and D-glucosamine linked by β-1,4-glycosidic bonds (Figure 1) [7]
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
