Polymer solutions were prepared by dissolving Poly(lactic-co-glycolic acid) (PLGA, ratio 75:25, Mw: 66-107kDa, Sigma-Aldrich Chemical Company Ltd., Dorset, UK) into 1,1,1,3,3,3-hexafluoroisopropanol (HFIP, Apollo Scientific Limited, Cheshire, UK) at a concentration of 15% (weight to volume ratio).