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Bioactive polypeptides are susceptible to inactivation by proteolytic enzymes in body fluids. Instead of many injections, these polypeptides may be specially formulated to prolong their action in vivo to several months by entrapment in a polymer mixture. In a recent fundamental study on implant for drug delivery, it was found in this laboratory that a polymer support component was not mandatory and pharmacologically active macromolecules could be readily delivered on a sustained basis. Consequently, when 10% insulin (Zn) was admixed with cholesterol and then compressed, the hormone action was extended to about 20 days when tested subcutaneously in Wistar rats with streptozotocin-induced diabetes. Evaluation of other lipids has shown that with palmitic acid as the excipient, the 8-hr action of insulin can be extended to about 40 days. The same type of sustained delivery implant containing insulin or pituitary growth hormone can enhance growth in normal Wistar rats. Since no synthetic materials were used, biocompatibility problem is not expected. Further, the fatty acid excipient is gradually eroded in vivo, and explantation of the implant will not be necessary as well. This approach shall be particularly useful in special formulations of other pharmaceutical proteins such as the rDNA-produced somatotropin analog used in growth enhancement of farm animals raised for consumer food products.

Dextran and its crosslinked beads have many biomedical applications. If stirring to maintain the epichlorohydrin emulsion is stopped in about 7 minutes, crosslinked dextran gel sheets can be prepared. The elastic sheet obtained after washing in water, followed by treatment with propylene glycol containing 15% isopropanol is suitable as a covering on rodent skin wound. Antibacterial agents can be dispersed into the sheet or admixed in the paste form of the gel.In standard tests, a 4 cm × 4 cm surface wound on the back of a 400-g Wistar rat was covered with the dextran gel material. The evaporation loss was found to reduce immediately from 94 mg H20/cm2/hr to 1/2 of this value which became 12.5 mg H20/cm2hr in 18 hours. Such a covered wound healed in 10–17 days with 10–15% distortion, while the controls were delayed to 25 ± 7 days with >65% wound contraction.Another modification of the gel material involves the surface attachment of the positively charged 2-diethylaminoethyl function (DEAE). Although up to 2.41 mM DEAE groups/g gel can be introduced, only 3 to 2 × 105 cells/cm2. Therefore, the gel material may have potential as a substrate for dermal cells as well for later transfer.