(680g) Synthesis and Characterization of Novel Thermoresponsive Hydrogel for Drug Delivery Applications

Synthesis and Characterization of Novel Thermoresponsive Hydrogel for Drug Delivery Applications

Swetha Ainampudi, John O’Haver, Adam Smith

Department of Chemical Engineering, University of Mississippi

Purpose:

The purpose of this research is to synthesize a novel thermoresponsive triblock copolymer containing poly (DEGMEA-b-OEGMA-b- DEGMEA) hydrogel for drug delivery applications.

Methods:

Triblock copolymer consisting of poly (DEGMEA-b-OEGMA-b- DEGMEA) was synthesized using Reversible Addition-Fragmentation chain Transfer polymerization. S,S’-Bis (α, α’-dimethyl- α’-acetic acid)-trithiocarbonate  was used as a chain transfer agent (CTA)  and Azobisisobutyronitrile was used as polymerization initiator. Several ratios of monomer to CTA and CTA to initiator were evaluated. The lower critical solution temperature (LCST) of the triblock copolymer was altered by varying the OEGMA block ratio in the final copolymer. The molecular weight distribution and polydispersity index (PDI) of the resultant triblock copolymer were determined using gel permeation chromatography. Solid-state characterization was performed using Differential scanning calorimetry (DSC) and Thermogravimetric Analysis. Polymer swelling ratio was determined to characterize the water holding capability of the swollen hydrogel system. The sol-gel phase transition was determined using dynamic light scattering as well as DSC. The effect of hydrophobic/hydrophilic balance of triblock copolymers on the phase transition temperature was investigated. Gel network of the swollen hydrogel was investigated using scanning electron microscopy. In order to investigate the potential use of the hydrogel system for ocular drug delivery applications, diffusion studies were performed across cellulose membrane using vertical Franz diffusion cells. Diclofenac sodium served as the model drug.

Results:

200:1 ratio of monomer to CTA & CTA to initiator ratio of 15:1 gave better polymerization. The GPC results confirmed the successful formation of the triblock copolymer with a molecular weight of 80K Dalton and a PDI of 1.06. The phase transition temperature was confirmed by dynamic light scattering and DSC thermogram. Varying concentrations of the OEGMA block in the formed triblock copolymer gave varying LCST temperatures in the range of 24-40^oC. Two triblock copolymers were optimized for drug delivery purposes which have LCST temperatures of 32^oC and 37^oC. SEM images also confirmed the phase transition behavior of the triblock copolymer below and above the LCST. The polymer had a swelling ratio of 222% and was able to hold water up to four times its own weight. The drug release was effectively controlled by the hydrogel and a cumulative release of 45% was observes at the end of 6 hours.

Conclusion:

The results point to a potential thermoresponsive triblock copolymer of poly (DEGMEA-b-OEGMA-b- DEGMEA) for the use in drug delivery applications.