SYNTHESIS AND CHARACTERIZATION OF pH SENSITIVE PHARMACEUTICAL POLYMERS FOR CONTROLLED DRUG DELIVERY SYSTEMS.

Abstract

The Pharmaceutical industry is evaluating modes of delivery for their prized therapeutics at every step of the design cycle. In recent years, pH dependent drug delivery systems have focused much for specific purposes. Synthesis of pH dependent polymer in different monomeric ratio were intended to be used for controlled drug delivery systems. Previously synthesized monomers i.e; ethyl methacrylate (EMA) and acrylic acid (AA)took in different monomeric ratio (in moles) as -  EMA:AA(0.7 : 0.3), EMA : AA (0.6 : 0.4), EMA : AA (0.5 : 0.5), EMA : AA (0.4 : 0.6) and EMA : AA (0.3 : 0.7) with solvent Tetrahyrdrofuran(THF) and Azobis-iso butyronitrile (AIBN) initiator, which under goes polymerization .Polymers were prepared by solution polymerization technique and free radical mechanism. Swelling behavior of different polymeric films (polymers) which have obtained from polymerization in different monomeric ratios, studied in different pH buffer solutions. The different pH buffer solutions were  Hydrochloric acid buffer pH 1.2, Hydrochloric acid buffer pH 2.0, Phosphate  buffer pH 6.0,  Phosphate buffer pH 7.4, Phosphate buffer pH 8.0.These different pH buffer solutions were prepared according to Indian Pharmacopoeia 2007.The changes in polymeric films in  phosphate buffer (pH 8.0, pH 7.4) after 15,30, 45,60,75,90,120 minutes were noted. In buffer (pH 6.0,  pH2.0, and pH 1.2) the changes were noted after 1 hour,2hours,2 days,3 days,4 days,5 days,6 days,7 days. Swelling ratio calculated by formula. For microencapsulation paracetamol drug was taken as a model drug.  Emulsification solvent evaporation method have used for micro encapsulation of model drug. The standard calibration curve of paracetamol obtained a straight line. The relation between drug concentration & absorbance measured at 249 nm found linear. The drug was estimated by UV spectrophotometer at 249 nm using a calibration curve based on standard solutions. The percentage of Paracetamol encapsulated with respect to total amount of Paracetamol encapsulation taken loading efficacy. In vitro dissolution release of Paracetamol from micro spheres was evaluated using paddle dissolution apparatus (Lab India Disso 2000 dissolution tester). Dissolution media was 900 ml phosphate buffer (pH 7.4) & to this media the microspheres containing 200 mg of Paracetamol were added. The system was stirred at 500 pm & temp at 37^oC± 0.5 ^oC  samples were drawn at specified time intervals (10 min, 20 min, 30 min, 40 min, 50 min & 60 min) filtered & assayed spectrophotometrically  at 249nm.  For swelling study, all the copolymers in different monomeric ratio did not show good swelling or dissolution characteristic in acidic pH (pH 1.2-pH6.0) ethylmethacrylate : acrylic acid with monomer ratio 3:7 completely dissolved within 2 hours.

Keywords: Polymers, Ethylmethacrylate, Acrylic acid, Ultraviolet Spectrophotometer, Dissolution apparatus.