Abstract
Introduction: Intraosseous Transcutaneous Amputation Prostheses (ITAP) could overcome the problems associated with conventional stump-socket prostheses for amputees (pressure sores, pain, infections and unnatural gait), by attaching the external prosthesis directly to the skeleton via a skin penetrating abutment. Despite this, the skin breach introduces a potential route for infection. For success, a biological seal at the skin-ITAP interface is essential.
The protein Laminin-5 (L-5) is a ‘biological glue’, which is integral to epitheial cell adhesion. Covalently bonding L-5 to the ITAP titanium alloy (Ti6Al4V), may enhance the strength of the skin-ITAP interface.
Silanisation, a chemical technique that covalently bonds proteins to metals, could be used to bond L-5 to Ti6Al4V. We have assessed the characteristics L-5 silanised Ti6Al4V as a potential substrate for ITAP.
Method: To determine the maximum quantity of L-5 that could be silanised to Ti6Al4V, and its relative stability when soaked in foetal calf serum (FCS) over time; polished Ti6Al4V discs were silanised by immersing in aminopropyltriethoxysilane followed by glutaraldehyde. Radiolabelled rat laminin-5-I125 was then added. Discs were immersed in FCS for 4 days (37 C) and analysed at 24 hour intervals in a liquid scintillation counter. Un-silanised discs were used as controls.
Results: L-5 was successfully covalently bound to Ti6Al4V. 10ng, 100ng, 250ng and 500ng droplets yielded significantly more silanised L-5 (p< 0.05), but no difference was observed between 750ng and 1000ng. Percentage L-5 covalently bound ranged from 33% and 65%.
A small decrease in bound L-5 occurred after 24 hours of FCS soaking (p< 0.05), but subsequent to this no significant reduction was observed for 4 days (p< 0.05). Controls showed a significantly larger reduction after 24 hours (p< 0.05).
Conclusion: Covalently bonding L-5 to Ti6Al4V by silanisation can be achieved with predictable results. Large enough quantities can be immobilised to influ-ence cellular function. L-5 silanised to Ti6Al4V remains stable in vitro over time and is not removed. Following the study of cellular interactions with silanised L-5, a stable skin seal may be achieved at the transcutaneous portion of the ITAP.
Correspondence should be addressed to Mr Carlos Wigderowitz, Senior Lecturer, University Department of Orthopaedic and Trauma Surgery, Ninewells Hospital and Medical School, Dundee DD1 9SY.
