Biodegradable poly(D,L-lactide) coating of implants for continuous release of growth factors.
Local application of growth factors like insulin like growth factor-I (IGF-I) and transforming growth factor-beta 1 (TGF-beta1) from a biodegradable thin layer of poly(D,L-lactide) (PDLLA) coated implants could stimulate fracture healing. A new "cold coating technique" for metallic implants was established to produce a biodegradable coating with a high mechanical stability that provides a continuous release of incorporated growth factors. The properties of this bioactive coating were investigated in vitro and in vivo. Scanning electron microscope analysis revealed a coating thickness of in average 14.8 microm on titanium and 10.7 microm on steel wires. Intramedullary implantation and extraction experiments depicted a loss of PDLLA coating from titanium and steel implants of less than 5%. After explantation of the implants, the coating displayed a complete and regular layer without any defects of PDLLA uncovering the metallic surface. Smear tests demonstrate that the coating can be performed under sterile conditions. The PDLLA depicted a reduction of about 8% within 6 weeks in vitro and in vivo. The growth factors were incorporated in a stable form and demonstrated a loss of stability of less than 3% within 42 days and less than 5% within one year. In an elution experiment, 54% IGF-I and 48% TGF-beta1 were released within the first 48 h. After 42 days, 76% of IGF-I and 71% of TGF-beta1 were detected in the elution fluid by ELISA. Comparable results were obtained in the in vivo experiments after 42 days.
Schmidmaier
G
G
Dept. of Trauma and Reconstructive Surgery, Charité, Humboldt-University of Berlin, Berlin, Germany. gerhard.schmidmaier@charite.de
Wildemann
B
B
Stemberger
A
A
Haas
N P
NP
Raschke
M
M
D000818:Animals; D018786:Bone Substitutes; D016503:Drug Delivery Systems; D017102:Fracture Healing; D007334:Insulin-Like Growth Factor I / Q000008:administration & dosage; D011091:Polyesters; D019736:Prostheses and Implants; D051381:Rats; D016212:Transforming Growth Factor beta / Q000008:administration & dosage
D018786:Bone Substitutes; D011091:Polyesters; D016212:Transforming Growth Factor beta; C033616:poly(lactide); D007334:Insulin-Like Growth Factor I