Microspheres for Use in a Novel Electromagnetic Bioadhesion Testing System

Abstract

A new Electromagnetic Force Transducer (EMFT) has been developed to quantify the bioadhesive interactions between polymer microsphere drug delivery systems and living tissue. The EMFT uses a calibrated electromagnet to detach a magnetic-loaded polymer microsphere from a tissue sample, and consequently the adhesive force experienced between the tissue and polymer is proportional to the current through the electromagnet. Various microsphere manufacturing techniques were evaluated for their ability to predictably and consistently produce ferro- and ferrimagnetic microspheres for use with the EMFT. Solvent-Evaporation techniques were used to produce single-walled microspheres from poly(styrene) (PS), poly-(caprolactone) (PCL), poly(L-lactic acid) (PLA), and poly(L-lactide-co-glycolide) (PLGA) with 0-50% w/w loadings of ferrimagnetic iron oxide powder. A modified solvent-evaporation process was used to manufacture double-walled microspheres with alternating layers of PS and PLA. It has been demonstrated that ferrimagnetic iron oxide powder can be loaded exclusively in either of the polymers, and that polymer can be made to form either the outer layer or core of the microspheres. A modified Dip Inversion technique was used with moderate success to coat 50 μm glass spheres with PCL in hope of developing a suitable process to coat ferromagnetic metal microspheres in the future. Microspheres were characterized with electron and optical microscopy.