Development and characterization of mucoadhesive PHEA-TGA microspheres

The mucoadhesive polymers can assure an intimate and prolonged contact of drug delivery systems to the absorbing mucosa by weak non-covalent bonding (traditional polymers) or by covalent bonding to the mucus layer via thiol-disulfide exchange reactions with cysteine-rich mucin glycoproteins (thiomers). In this study the preparation of drug-loaded microparticles made of PHEA-thioglycolic acid conjugate (PHEA-TGA), a new thiomer of polyaspartamide type, has been studied. Empty microspheres and physical mixtures were also prepared for comparison. The microspheres were produced by spray-drying technique and characterized in terms of morphology, drug content, particle size, thermal behavior and bioadhesive properties. In vitro drug release studies were performed in simulated nasal fluid, pH 6.4. The dissolution rate of loratadine was strongly improved by incorporation in microparticles in respect to pure loratadine and corresponding loratadine/PHEA-TGA physical mixtures. Tensile studies showed that mucoadhesive properties of drug-loaded microparticles were comparable to empty microspheres.