Disclosed is a dry powder of polymeric nanoparticles prepared by an emulsion polymerisation method which comprises: a) polymerizing an effective amount of one or more monomers, at least one of which is a 2-alkenoic acid, a hydroxy-alkyl 2-alkenoate, a dihydroxy-alkyl 2-alkenoate, a hydroxy-alkoxy-alkyl 2-alkenoate, a alkoxy-alkoxy-alkyl 2-alkenoate or a vicinyl epoxy-alkyl 2-alkenoate (such as acrylic acid, methacrylic acid, 2-hydroxyethyl acrylate, 2-hydroxyethylmethacrylate, diethyleneglycol monoacrylate, diethyleneglycol monomethacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methyacrylate, 3-hydroxypropyl acrylate, 3-hydroxypropyl methacrylate, dipropylene glycol monoacrylate, dipropylene glycol monomethacrylate, 2,3-dihydroxypropyl methacrylate, glycidyl acrylate or glycidyl methacrylate), in a polar solvent such as water, and from about 0.01 weight percent to about 0.1 weight percent of a surfactant to produce a suspension of a plurality of polymeric nanoparticles wherein the polymeric nanoparticles have an average diameter of less than 1 micron and b) drying / removing the liquid(s) from the suspension such that the amount of liquid(s) remaining in the dry powder is less than 10% by weight (such as by spray drying or lyophilization techniques), wherein the percentage is based on the total weight of the dry powder.
