Design and Preliminary Characterization of Sweet Potato Starch – Urea-Borate Polymer

Abstract

Background – Sweet potato (Ipomoea batatas) starch has been reported for its potential as a directly compressible and sustained- release polymer in its native and modified forms. Chemical modification by crosslinking with urea and borax to form starch urea-borate  will enhance its drug release-retarding properties.

Objective – To design starch-urea-borate (SUB) polymer using sweet potato starch to  produce a new, affordable biodegradable polymer, and carry out preliminary characterization of the polymer.

Method – Native starch  was extracted from sweet potato tubers and crosslinked with urea and borax to form starchurea borate (SUB) polymer. The native and  modified starches were characterized for morphology (SEM), FT-IR, DSC, pH, densities, swelling, flow properties and viscosity.

Results –  Modification yielded 96.66% w/w of SUB and disrupted the granular structure of the native starch, producing significantly larger (p<0.01)  granules with irregular shapes. FTIR spectrum revealed a peak at 3369.05 cm1 due to –NH2 confirming the presence of a secondary  amide resulting from the polymerization reaction between urea and starch in the presence of borate. A shift in the peak of DSC  endotherm was observed for SUB. Modification yielded lower particle density but higher bulk and tapped densities. The swelling index  increased significantly (p<0.01). Hausner’s ratio (1.06± 0.00), Carr’s index (6.33± 0.01%) and angle of repose (26.14±1.15º) showed good flow but reduction in compressibility of SUB. Viscosity revealed shear thickening or dilatant behaviour.

Conclusion- The material and  physicochemical properties of SUB polymer showed its potential for application in drug delivery systems, possibly as a release retarding  polymer.