The Use of Biodegradable Poly(b-amino ester) and Poly(b-amino amide) Microspheres as an Experimental Therapeutic Delivery Vector for Selective Cancer Cell Targeting

Abstract

The design, synthesis, and use of new biodegradable polymers for drug delivery applications is an area of ever increasing interest. Polymeric drug delivery systems have several advantages compared to conventional drug delivery methods such as liposomes and antibodies. Since liposomes are spherical vessels made of phosphorolipids, they are tiny particles which can be taken up by the macrophages. Antibodies, meanwhile, have the disadvantage that most receptor sites on tumor cells are also present on healthy cells. Several of these advantages include localized delivery, improved drug efficiency, and drug protection of certain medications which may degrade rapidly when inside the body.

Poly(b-amino esters) and Poly(b-amino amides) are ideal polymers for the encapsulation, delivery, and release of various therapeutic agents to cancer cells, which have an acidic extra cellular pH level, near 6.8. Poly(b-amino esters) and Poly(b-amino amides) are specifically designed to degrade by hydrolysis of the ester and amide bonds respectively, in the polymer backbone. Microspheres of Poly(b-amino ester) and Poly(b-amino amide) are formed via a double emulsion process using Rhodamine B-Isothiocyanate (RBITC) labeled Bovine Serum Albumin (BSA) as the encapsulate. The fluorescence intensity of the RBITC-BSA released from the polymer sphere was measured as a way of testing polymer backbone hydrolysis. The polymer microspheres were placed into different solutions of varying pH ranges. The pH range extended from pH 5.5 to pH 7.4. The hydrolyzed polymer byproducts were removed and the resulting supernatant tested for fluorescence intensity. The results showed polymer hydrolysis and release of labeled BSA at pH 6.8 and lower.