Rheological characterization of bioadhesive binary polymeric systems designed as platforms for drug delivery implants

This study describes the formulation and characterization of binary interactive polymeric systems, designed as platforms for improved drug delivery to mucosal sites. Binary interactive systems were manufactured containing hydroxyethylcellulose (HEC; 1-5% w/w) and polycarbophil (PC; 1-5% w/w) at pH 7, and their rheological (flow and dynamic), mechanical, and mucoadhesive properties were characterized, both before and after dilution with phosphate buffered saline (designed to mimic dilution by biological fluids). Physical interactions between HEC and PC were confirmed by the observed rheological synergy. Within the binary interactive systems increasing polymer concentration increased the storage modulus (G'), loss modulus (G' '), dynamic viscosity (eta'), hardness, compressibility, consistency, and mucoadhesion yet decreased the loss tangent. This was attributed to enhanced entanglements and interactions between adjacent polymer chains. Dilution with PBS altered the above properties; however, the binary interactive systems, particularly those containing higher concentrations of HEC, still exhibited predominantly elastic properties (high G', low tan delta). In light of this, it is suggested that the rheological and mucoadhesive properties of binary interactive systems composed of HEC (5% w/w) and PC (1-3% w/w) offered particular promise as platforms for topical mucosal drug delivery systems.