The particle size and shape of the microsphere particles were characterised, for unlyophilised liquid samples and for lyophilised powder samples, using a Morphologi G3 instrument (Malvern Instruments Ltd., UK). Each unlyophilised liquid sample was dispersed in 1 mL of 5% aqueous PVA solution to allow for spatial separation of the particles and reduction of agglomerates. The lyophilised powder samples were prepared for measurement using a dry powder disperser. The instrument captured images of the individual particles and the morphological properties for each particle were determined from the images by image analysis (Morphologi G3 software).