Recent progress in colloidal nanocarriers loaded in situ gel in ocular therapeutics

Colloidal nanocarriers and stimuli-responsive in situ gel (ISG) present an effective alternative to conventional eye drops. A combination of the two effective strategies can aid in overcoming drawbacks associated with an individual strategy. Colloidal nanocarriers improve the drug permeation and drug bioavailability at the ocular surface, however, suffer from poor precorneal retention. In situ gel offers improved precorneal retention at the ocular surface. The combination of these two pharmaceutical technologies can shift the paradigm of ocular therapeutics by overcoming the physiological and anatomical barriers in ocular therapeutics. Recent trends in ocular drug delivery show researchers exploring colloidal nanocarriers loaded ISG to overcome the drawbacks such as poor bioavailability, precorneal retention, and impaired permeation associated with the marketed eye drops. The combination approach also aids in minimizing the dose and dosing frequency, the major factor influencing poor patient compliance. Several preclinical studies have shown significant improvement in ocular bioavailability for the nanocarriers loaded ISG when compared to drug-loaded ISG/drug-loaded nanocarriers and marketed formulations. This review compiles the efforts undertaken by various researchers in investigating colloidal nanocarriers loaded ISG in ocular drug delivery. Further, the review also discusses patents on ocular in situ gel polymers and regulatory aspects of the ISG polymers explored in ocular delivery.