In situ-forming gels for ophthalmic drug delivery

Area of Science:

• Polymer Science
• Materials Science
• Ophthalmology

Background:

• Ophthalmic drug delivery faces challenges with poor bioavailability due to dilution and drainage.
• In situ-forming systems utilizing polymers with reversible phase transitions offer a solution.
• Previous work demonstrated gelation in response to multiple physical parameter variations.

Purpose of the Study:

• To characterize the rheological properties of a Carbopol (C) and methyl cellulose (MC) based in situ-forming ophthalmic drug delivery system.
• To evaluate the effect of pH and temperature variations on the system's viscosity and gelation.
• To identify an optimal formulation for enhanced ocular drug delivery.

Main Methods:

• Rheological characterization using rotational cone and plate viscometry.
• Testing at varying pH (4.0 and 7.4) and temperatures (25 and 37°C).
• Analysis of shear stress vs. shear rate flow curves to determine pseudoplastic behavior and yield point.

Main Results:

• The polymer solutions exhibited pseudoplastic behavior with a yield point.
• Increased pH and temperature led to higher viscosity, shear stress, and yield point.
• Simultaneous changes in pH and temperature had the most significant impact on rheological properties.
• A formulation of 1.5% MC and 0.3% C showed low initial viscosity and formed a strong gel under physiological conditions.

Conclusions:

• The Carbopol-methyl cellulose system demonstrates tunable rheological properties responsive to environmental changes.
• The optimized formulation effectively transitions from liquid to gel at physiological conditions.
• This in situ-forming system has the potential to improve ocular drug bioavailability by increasing precorneal residence time.