Self-assembling functionalised peptides into decellularised materials for application in small diameter vascular grafts

There is a clear clinical need for small diameter blood vessel grafts. Previous studies have shown that decellularised porcine arteries have potential for future development and clinical translation. However, in order to overcome the problems of thrombogenesis and encourage endothelialisation in small diameter applications, it will be necessary to devise innovative approaches. In this study it was hypothesised that a bioactive peptide could be self-assembled within the decellularised tissue to overcome the problems of thrombogenesis and to aid and enhance re-endothelialisation. A method for self-assembling the tape forming peptide, P11-4 within decellularised tissues was developed. The study then went on to explore the P11 series of peptides as materials for tissue engineering by examining biocompatibility and haemocompatibility and demonstrated the use of self-assembled peptide coatings to prevent thrombus formation and enhance re-endothelialisation. The self-assembly of peptide P11-4 within decellularised porcine internal carotid artery was assessed using a range of microscopic and spectroscopic techniques. Fluorescent microscopy was used to show the penetration of the peptide throughout the decellularised conduit. Self-assembly of the peptide was assessed by FTIR spectroscopy. Using CLSM and MPLSM it was shown that the peptide self-assembled around the extracellular matrix of the acellular tissue. Fluorescent microscopy was used in conjunction with a specially designed flow cell to show that the peptide coating remained in the decellularised vessel for over 14 days under model flow conditions. The biocompatibility and haemocompatibility of a library of 43 peptides was assessed to identify ideal candidate peptides for use and to develop design characteristics for the application of self-assembling peptides in biomedical settings. Testing was carried out using cytotoxicity testing, the Chandler loop thrombosis model, a haemolysis assay and a complement inhibition assay. The results showed that large poly-cationic peptides were non-bio or haemo compatible, large neutral peptides enhanced thrombosis formation and that poly-anionic peptides with hydrophobic cores inhibited the complement system. Peptide coatings of P11-4, P11-8 and P11-12 were shown to decrease, and in the case of P11-12 prevent, thrombus formation; showing potential for application in small diameter acellular blood vessels. Peptide P11-4, functionalised with cyclic RGD, was shown to enhance the attachment and retention of ovine endothelial cells on the decellularised vessel, demonstrating the potential of functionalised peptide to enhance re-endothelialisation. In conclusion, this study has demonstrated the potential of self assembling peptide technology for improving the function of acellular porcine arteries in vitro.