Evaluation and Characterization of PHEMA Sponges as Implantable Drug Delivery Systems

Thomas D. Dziubla¹, Marc C. Torjman², Jeffrey I. Joseph² and Anthony M. Lowman¹
 School of Biomedical Science Engineering and Health Systems

¹Drexel University
3141 Chestnut Street
Philadephia, PA  19104
td25@Drexel.edu
(215) 895-5831

²Thomas Jefferson University

Implantable drug delivery devices are being pursued as a means of long-term quick-delivery vehicle of bioactive substances to the body. The draw back to most implantable devices is the chronic-inflammatory response that results in the avascular fibrous encapsulation of the implant, which prevents the device from effectively administering the drug over a long period of time.  One method of overcoming this problem is the addition of an intermediate that prevents this capsule formation.

Biocompatible materials with interconnected pores greater than 10µm have been shown to support the ingrowth and maintenance of vascularized tissue. Implants coated in such a porous material would not be encapsulated but actually generate a direct route for fast systemic delivery as well as anchoring the implant to the surrounding soft tissue.

In this work, we synthesize and evaluate the use of poly (2-hydroxy ethyl methacrylate) (PHEMA) sponges as an intermediate for an implantable drug delivery system.  Here we use a catheter tip as the model system. Scanning electron microscopy (SEM) and mercury porosimetry are used to characterize the pore microstructure of the sponges.  Also, in vitro and in vivo insulin infusion studies are performed to evaluate the effect of the hydrogel sponges on release characteristics.