Hui-Rong Shen

Release of BSA from poly(ortho ester) extruded thin strands

A solventless procedure was used where powdered polymer and micronized protein were intimately mixed and then extruded into 1 mm strands that were cut to the desired length. The polymers used were poly(ortho esters) specifically designed to allow extrusion in the neighborhood of 70 degrees C. At these temperatures many proteins maintain activity in the dry state. In vitro erosion and BSA release results indicate that after a fairly long lag-time, BSA release and polymer erosion occur concomitantly indicating an erosion-controlled process. The lag-time could be eliminated by the addition to the mixture prior to extrusion between 1 and 5 wt% poly(ethylene glycol) or its methoxy derivatives. The lag-time could also be eliminated by using an AB-block copolymer where A is poly(ortho ester) and B is poly(ethylene glycol).

Development of poly(ortho esters) and their application for bovine serum albumin and bupivacaine delivery

The preparation of drug delivery devices using solventless fabrication procedures is of significant interest and two such procedures are described. In one such procedure, powdered polymer and micronized protein are intimately mixed and then extruded into 1 mm strands that are cut to the desired length. The polymers used were specifically designed to allow extrusion at temperatures where proteins maintain activity in the dry state. In vitro erosion and BSA release show that BSA release and polymer erosion occur concomitantly indicating an erosion-controlled process. There is a lag-time, but that can be eliminated by the addition to the mixture prior to extrusion small amounts of poly(ethylene glycol) or its methoxy derivatives. The lag-time could also be eliminated by using an AB-block copolymer where A is poly(ortho ester) and B is poly(ethylene glycol). Another means of using solventless fabrication methods is to use a semi-solid material into which drugs can be mixed at room temperature and the semi-solid injected. Data on BSA and bupivacaine release are presented.

Post surgical pain management with poly(ortho esters)

Poly(ortho esters), POE, are synthetic bioerodible polymers that can be prepared as solid materials, or as viscous, injectable polymers. These materials have evolved through a number of families, and the latest member of this family, POE IV, is particularly well suited to drug delivery since latent acid is integrated into the polymer backbone, thereby, modulating surface erosion. POE IV predominantly undergoes surface erosion and is able to moderate drug release over periods from days to many months. One indication in which the POE IV polymer is currently being investigated is in sustained post-surgical pain management. The local anesthetic agent, mepivacaine, has been incorporated into a viscous, injectable POE IV and its potential to provide longer-acting anesthesia has been explored in non-clinical models.

Protein release from poly(ortho ester) extruded rods

Poly(ortho ester) rods containing 15 wt% FITC-BSA were prepared by extruding an intimate mixture of finely powdered polymer and protein at a temperature where protein activity is retained. After an induction period, linear in vitro release kinetics were obtained with concomitant polymer weight loss.