Preparation and Characterisation of Polymeric Nanoparticles Using Low Molecular Weight Poly(vinyl alcohol)

The use of low molecular weight (MW) poly(vinyl alcohol) (PVA) grades (defined herein as <= 12,000 Mw) as an excipient to facilitate effective drug delivery is attractive as these polymers benefit from excellent biocompatibility. The aim of this study was to synthesise several partially hydrolysed grades of PVA by controlled saponification of low MW poly(vinyl acetate) and assess whether this material could form a nanocarrier suitable for drug delivery. Four grades of low MW PVA were synthesised by direct saponification. The polymers were analysed by C-13 nuclear magnetic resonance spectroscopy (C-13-NMR) and differential scanning calorimetry (DSC). Reaction conditions designed to produce 30, 40, 50 and 60% hydroxylation produced polymers with only 24.5, 33.2, 35.2 and 38.4% alcohol groups, respectively. DSC and C-13-NMR results showed that the synthesised partially hydrolysed PVA contained large blocks of alcohol monomers; block character (eta) ranged from 0.40 to 0.51. PVA 33, 35 and 38% hydrolysed were used to fabricate nanoparticles using a solvent displacement method and photon correlation spectroscopy was used to determine the size of nanoparticles produced. All the low M,, partially hydrolysed PVA grades synthesised produced smaller nanoparticles (similar to 160 nm) compared to equivalent high MW grades reported previously (similar to 175 nm-220 nm).