The range of morphologies of the microspheres were characterised using scanning electron microscopy (SEM), with a ZEISS CrossBeam 540 instrument, equipped with a Gemini 2 column (Carl Zeiss Microscopy, Jena, Germany). For the shape and surface analysis, the lyophilised microspheres were sputter coated with gold using an Emitech 550 (Emitech Ltd., Ashford, UK). The samples were then examined under vacuum at an acceleration voltage of 1 kV, and imaged using secondary electrons via an Everhart-Thornley detector.