a method for forming microspheres containing bioactive material , comprising dissolving a polymer matrix , such as albumin or beta - cyclodextrin , in an aqueous medium in a first vessel ; contacting the dissolved polymer matrix with a crosslinking agent , such as glutaraldehyde , to crosslink the polymer matrix and the crosslinking agent ; neutralizing with sodium bisulfate any excess crosslinking agent remaining after crosslinking is substantially complete ; solubilizing in a second vessel a bioactive material in an aqueous solution ; mixing the solubilized bioactive material together with the neutralized crosslinked polymer matrix in solution to form a mixture ; and , spray drying the mixture to produce nanospheres , whereby substantial bioactivity of the biomaterial is retained upon cellular uptake .