Characterisation of amine functionalised poly(3-hydroxybuturate-co-3-hydroxyvalerate) surfaces

There is an increasing acceptance of the importance of tailoring biomaterial surface properties. This study aimed to introduce and characterise amine functionalities onto the hydrophobic bacterial polymer poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV). Gamma irradiation induced simultaneous grafting of 2-aminoethyl methacrylate (AEMA) onto PHBV films was carried out using various concentrations of AEMA (2.5 or 4.5 w/v%) in either water or methanol and at two irradiation doses (4.5 or 9 kGy). Successful grafting was verified from XPS analysis, water contact angle and ATR-FTIR spectroscopy. Characterisation using DSC indicated that grafting had occurred predominantly in the amorphous region of the PHBV substrate. 1H NMR of the grafting solution post grafting showed that monomer conversion is incomplete in methanol. The use of gold nano-particles (AuNPs) as a simple tool to probe the presence of these functional groups was evaluated using a suspension of citrate functionalized AuNPs prepared by reduction of Au(III) with citric acid. These particles were found to be polydisperse (0.8-2 nm and 7-70 nm) and negatively charged (zeta potential of −33 ± 9 mV) and capable of interacting electrostatically with the amine groups on the PHBV surface and imaged using SEM.