Protein particles are prepared by causing or allowing protein molecules dispersed in a liquid medium at a concentration of 8 mg.mL−1 or greater to react in the presence of a zero-length crosslinker, so as to produce protein particles comprising protein molecules that are covalently bonded together. The protein particles may be produced with sizes in the sub-micron range with closely defined sizes and size distributions. The particles have applications in many fields, but are useful inter alia for the delivery of therapeutic agents and other agents, eg imaging contrast agents, to the body.
