This work presents the evaluation of chitosan-functionalised poly(2-hydroxyethyl methacrylate) (CS/PHEMA) core-shell microgels as drug delivery carriers. CS/PHEMA microgels were prepared by emulsifier-free emulsion polymerisation with N,N '-methylenebisacrylamide (MBA) as a crosslinker. The study on drug loading, using salicylic acid (SA) as a model drug, was performed. The results showed that the encapsulation efficiency (EE) increased as drug-to-microgel ratio was increased. Higher EE can be achieved with the increase in degree of crosslinking, by increasing the amount of MBA from 0.01 g to 0.03 g. In addition, the highest EE (61.1%) was observed at pH 3. The highest release of SA (60%) was noticed at pH 2.4, while the lowest one (49.4%) was obtained at pH 7.4. Moreover, the highest release of SA was enhanced by the presence of 0.2 M NaCl. The pH- and ionic-sensitivity of CS/PHEMA could be useful as a sustained release delivery device, especially for oral delivery.

Core-shell hydrogel latexes, composed of a poly(2-hydroxyethyl methacrylate) (PHEMA) core chemically coated with chitosan (CS) shell, were synthesized via an emulsifier-free emulsion polymerization, free radically initiated by a redox couple of tertbutyl hydroperoxide and amine groups on CS itself. The variation of some polymerization parameters [e.g., polymerization time, CS/ 2-hydroxyethyl methacrylate (HEMA) weight ratio, and content of crosslinker] was systematically investigated in this study. We found that the weight ratios between CS and the HEMA monomer influenced the course of polymerization, which was traced by the change in percentage monomer conversions, and the colloidal stability of the PHEMA-CS hydrogel latexes obtained. Moreover, the polymerization time affected their particle sizes and surface charges. For the colloidally stable PHEMA-CS hydrogel latexes, their sizes and charges ranged from 600 to 689 nm and from 32 to 51 mV, respectively. N,N 0 -Methylene bisacrylamide was used as a crosslinking agent for the core component; this was found to be able to enhance the hydrogels' thermal stability and water uptake. Moreover, the 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide assay showed that 100% cell viability was achieved during the treatment of the PHEMA-CS latex (0.2-2.5 mg/mL) with Caco-2 cells.