Preparation of hydrophobic and hydrophilic albumin microspheres and determination of surface carboxylic acid and amino residues

Albumin microspheres (MS) have been studied extensively as delivery systems for targeting drugs since they are biodegradable, non-toxic, relatively easy to prepare and their size range can be controlled. A method for albumin MS production was developed which was faster, processed larger quantities of starting material than previous methods, and had chemically reactive groupings on the MS surface to which ligands could be attached. Relatively hydrophobic, hydrophilic and also carboxymethylated MS were manufactured. The number of carboxylic acid residues was determined on the surface of these MS using C-14-glycine ethyl ester hydrochloride as a probe, and the number of amino groups was determined using C-14-sodium acetate as a probe. The number of carboxylic acid residues per unit surface area for the hydrophobic, hydrophilic and carboxymethylated MS was 2.1 x 10(4), 4.1 x 10(4) and 8.4 x 10(4), respectively, and the number of amino acid residues was 2.2 x 10(3), 5.0 x 10(2) and 5.0 x 10(2), respectively. (C) 1997 Elsevier Science B.V.