Hydrophilic microspheres

Table 3 A Typical Recipe for the Synthesis of Uniform Hydrophilic Microspheres [66]...

Colvin, M., Smolka, A., Rembaum, A., and Chang, M. (1988) The Covalent Binding of Enzymes and Immunoglobulins to Hydrophilic Microspheres in Microspheres-. Medical and Biological Applications, pp. 1-13. CRC, Boca Raton, FL. 

A unique method of formulating delivery systems based on starch/ PLA systems was studied (138). In that approach, the goal was to provide a better matrix for delivery of high molecular weight hydrophilic molecules. A hydrophilic material, starch, was combined through graft polymerization to PLA. The carbolactic polymers were then used to entrap bovine serum albumin in microspheres. 

WE Longo, EP Goldberg. Hydrophilic albumin microspheres. In KJ Widder, R Green, eds. Methods in Enzymology Part A, Drug and Enzyme Targeting. Orlando Academic Press, 1985, pp 18-26. 

Walter, E Dreher, D Kok, M Thiele, L Kiama, S.G., Gehr, P and Merkle, H.P., Hydrophilic poly(dl-lactide-co-glycolide) microspheres for the delivery of DNA to human-derived macrophages and dendritic cells, Journal of Controlled Release, 2001, 76, 149-168. 

PVA must be cross-linked in order to be useful for a wide variety of applications. A hydrogel can be described as a hydrophilic, cross-linked polymer, which can sorbe a great amount of water by swelling, without being soluble in water. Other specific features of hydrogels are their soft elastic properties, and their good mechanical stability, independent of the shape (rods, membranes, microspheres, etc.). 

Several attempts were made to influence the biodistribution of microspheres. The site of embolization depends on the site of administration and on the diameter of the microspheres [335]. Block copolymers have been used to coat the microspheres with the aim to prevent the recognition by the RES [9, 336-338] or to target them to the bone marrow [339], Interesting results in changing the body distribution of coated microspheres have been obtained. However, it appears that covalent attachment of hydrophilic polymer chains, e.g., PEG chains, is the better way [340]. 

In order to construct functional microspheres by modification of the surface with adsorbed proteins, e.g., enzymes and antibodies, the conformation and orientation of adsorbed proteins must be controlled to keep them as active as free proteins. If hydrophilic particles are used as a carrier, they hardly suffer nonspecific adsorption, but even antibody cannot be adsorbed. In this case, antibody is immobilized on the particles by chemical reactions such as those mentioned in the previous section (9). 

Shameem, M., Lee, H., Burton, K., Thanoo, B.C., and Deluca, P.P. (1999). Effect of gamma-irradiation on peptide-containing hydrophilic poly (d,l-lactide-co-glycolide) microspheres. PDA J. Pharmaceut. Sci. Tech., 53, 309-313. 

Pradhan, R., and Vasavada, R. Formulation and in vitro release study of ply(DL-lactide) microspheres containing hydrophilic compounds, glycine and its homopeptides. J. Contr. Rel. 30 143-154, 1994. 

Wada, R., Hyon, S. H., and Ikada, Y. Lactic acid oligomer microspheres containing hydrophilic drugs. J. Pharm. Sci. 79(10) 919—924, 1990. 

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