Stimuli-sensitive hydrogels: A novel ophthalmic drug delivery system

• Main Authors: Singh Vinod, Bushetti S, Appala Raju, Shareef Adil, Imam Syed, Singh Mamta
• Format: Article
• Language: English
• Published: Wolters Kluwer Medknow Publications 2010-01-01
• Series: Indian Journal of Ophthalmology
• Subjects: Polyacrylic acid; stimuli-sensitive hydrogels; timolol maleate; viscosity
• Online Access: http://www.ijo.in/article.asp?issn=0301-4738;year=2010;volume=58;issue=6;spage=477;epage=481;aulast=Singh
• ISSN: 0301-4738; 1998-3689

<b>Background:</b> Stimuli-sensitive hydrogels are three-dimensional, hydrophilic, polymeric networks capable of imbibing large amounts of water or biological fluids on stimulation, such as pH, temperature and ionic change. <b>Aim:</b> To develop hydrogels that are sensitive to stimuli, i.e. pH, in the cul-de-sac of the eye for providing a prolonged effect and increased bioavailability with reduction in frequency of administration. <b>Materials and Methods:</b> Hydrogels were formulated by using timolol maleate as the model drug, polyacrylic acid as the gelling agents, hydroxyl ethyl cellulose as the viscolizer and sodium chloride as the isotonic agent. Stirring of ingredients in pH 4 phosphate buffer at high speed was carried out. The dynamic dialysis technique was used for drug release studies. <i>In vivo</i> study for reduction in intraocular pressure was carried out by using albino rabbits. <b>Statistical Analysis:</b> Drug release studies data were used for statistical analysis in first-order plots, Higuchi plots and Peppas exponential plots. Student t-test was performed for <i>in vivo</i> study. <b>Results:</b> Viscosity of the hydrogel increases from 3.84 cps to 9.54 cps due to change in pH 4 to pH 7.4. The slope value of the Peppas equation was found to be 0.3081, 0.3743 and 0.2964. Up to 80&#x0025; of drug was released in an 8 h drug release study. Sterile hydrogels with no ocular irritation were obtained. <b>Conclusions:</b> Hydrogels show increase in viscosity due to change in pH. Hydrogels were therapeutically effacious, stable, non-irritant and showed Fickian diffusion. <i>In vivo</i> results clearly show a prolonged reduction in intraocular pressure, which was helpful for reduction in the frequency of administration.