Hydrophilic albumin microspheres.

Abstract

A method has been developed for preparing unique hydrophilic HSA/MS. Important aspects of this synthesis include addition of the cross-linking agent (glutaraldehyde) in the organic phase and use of concentrated polymer solutions as dispersion media. The polymer solutions afford excellent steric stabilization of aqueous albumin microdispersions for microsphere synthesis. Steric stabilization of dispersions by polymer solutions was shown to be a function of polymer concentration and molecular weight. The HSA/MS prepared by this method are hydrophilic and easily dispersed in a variety of aqueous media without surfactants. Chemical modifications are easily accomplished using available reactive aldehyde groups remaining after cross-linking. Although hydrophilicity of the microspheres is advantageous for many drug delivery applications, in some instances (such as the use of MS in adjuvant immunotherapy or vaccine preparations) some hydrophobicity may be desirable. For this purpose, surface modifications to produce controlled hydrophobicity is easily achieved by covalent coupling with appropriate reagents (e.g., fatty amines). Adriamycin was bound to HSA/MS by both physical association (to 18 wt%) and covalent binding (also to 18 wt%). In vitro release of drug was measured for the MS using a dynamic flow method. Two distinct release mechanisms could be achieved depending on the type of drug bonding used: slow by hydrolytic degradation of covalent bonds and fast by release of physically adsorbed drug. This new and versatile synthesis of hydrophilic HSA/MS opens up many new opportunities for producing chemically modified MS containing high concentrations of therapeutic agents. Use for immunodiagnostic and adjuvant compositions is also suggested.(ABSTRACT TRUNCATED AT 250 WORDS)