title: Modifying theophylline microparticle surfaces via the sequential deposition of poly(vinyl alcohol-co-vinyl acetate) copolymers.
abstract: The aim of this study was to investigate the manner in which amphiphilic poly(vinyl alcohol-co-vinyl acetate) copolymers (PVA-Ac) assembled on drug surfaces and use this information to generate a novel bi-layer polymer coating for a theophylline microparticle. Three grades of PVA-Ac, differing in hydrolysis degree and monomer distribution, were synthesised, characterised by nuclear magnetic resonance and shown to interact with theophylline when suspended in water. PVA-Ac deposition at the solid/liquid interface was driven by polymer hydrogen bond formation in a process that induced consequential structural changes in the macromolecule architecture. The most hydrophobic grades of the copolymer appeared to adsorb in a multistage process that passed through a series of equilibrium points. The PVA-Ac surface allowed two grades of the copolymer to be sequentially adsorbed and this resulted in the fabrication of a microparticle with desirable characteristics for pharmaceutical formulation production.
authors.affiliation: Tianjin Key Laboratory for Modern Drug Delivery & High Efficiency, School of Pharmaceutical Science & Technology, Tianjin University, Tianjin 300072, China.
authors.forename: Yanjun
authors.initials: Y
authors.lastname: Zhao
authors.affiliation: Institute of Pharmaceutical Science, King's College London, 150 Stamford Street, London SE1 9NH, UK.
authors.forename: Mannar A
authors.initials: MA
authors.lastname: Alas'ad
authors.affiliation: Institute of Pharmaceutical Science, King's College London, 150 Stamford Street, London SE1 9NH, UK. Electronic address: stuart.jones@kcl.ac.uk.
authors.forename: Stuart A
authors.initials: SA
authors.lastname: Jones
mesh_terms: D000327:Adsorption; D010316:Particle Size; D011145:Polyvinyls / Q000737:chemistry*; D017550:Spectroscopy, Fourier Transform Infrared; D013499:Surface Properties; D013806:Theophylline / Q000737:chemistry*
chemical_list: D011145:Polyvinyls; C487082:poly(vinyl alcohol-co-vinyl acetate); D013806:Theophylline
keywords: Adsorption; Microparticle; Polymer; Polyvinyl; Theophylline