Drug release from cation exchange membrane in rabbit eye

Area of Science:

• Ophthalmic Drug Delivery
• Biomaterials Science
• Polymer Chemistry

Background:

• Poly(acrylic acid) (PAA) grafted poly(vinylidene fluoride) (PVDF) membranes function as cation exchange membranes.
• Understanding cation release from these membranes is crucial for ocular drug delivery applications.
• The influence of ionic strength on drug release kinetics from ocular membranes requires investigation.

Purpose of the Study:

• To evaluate the effect of ionic strength on the release of model cations (propranolol and timolol) from PAA-PVDF membranes in an ocular environment.
• To assess the in vivo performance and tolerability of these drug-loaded membranes in rabbit eyes.

Main Methods:

• Cation exchange membranes were prepared by grafting PAA onto PVDF.
• Propranolol and timolol were adsorbed onto the membranes from solutions of varying ionic strengths (0.018–0.40 M) at pH 7.0.
• Drug-loaded membranes were implanted in the conjunctival sac of pigmented rabbits and retrieved at set time intervals to determine remaining drug content.

Main Results:

• The PAA-PVDF membranes were well tolerated and retained effectively in the rabbit eye.
• Release rates of both propranolol and timolol from the membranes decreased as the ionic strength of the adsorption medium increased.
• This suggests that ionic strength significantly modulates cation release from the membrane.

Conclusions:

• Increasing ionic strength of the adsorption medium effectively reduces the release rate of cations from PAA-PVDF membranes.
• The observed effect is attributed to the cation exchange properties and swelling behavior of the membrane.
• These findings have implications for designing controlled ocular drug delivery systems utilizing cation exchange membranes.