N. Blanchemain, T. Laurent, F. Chai, C Neut, S. Haulon, M. Morcellet, H.F Hildebrand, B. Martel (Lille, France)
PET vascular grafts are used to replace or bypass damaged arteries. To minimize the risk of infection during and after surgical interventions (6% of surgical acts), a vascular PET prosthesis was functionalised with cyclodextrins (CDs) in order to obtain an effect of in situ prolonged release of antibiotics (ABs).
Firstly, hydroxypropyl b-CD (HPb-CD) was fixed onto woven PET vascular grafts (PolytheseÆ, Laboratoires Pérouse, France). Curing parameters investigation allowed us to settle the optimal fixation temperature and time of curing for attaining 6.7%-wt functionalization rate. The presence of a HPb-CD polymer (poly-HPb-CD) coating the fibers was detected upon SEM observation. Mechanical tests showed that the finishing reaction did not affect the mechanical properties of the prosthesis. Moreover, the degradation of poly-HPb-CD coating was observed along several months in in vitro conditions (batch in water).
The in vitro release assessments of sorbed ABs from samples (vancomycin, ciprofloxacin and rifampicin) was then measured by UV-visible spectrophotometry titration. The prostheses treated with HPb-CD displayed larger amounts of sorbed antibiotics, in particular ciprofloxacin. Respectively a 1.3-, 1.4- and 5.1-fold improvement of the sorption of rifampicin, vancomycin and ciprofloxacin upon CD finishing prostheses was observed. These results were confirmed by the minimal inhibitory concentration (MIC) determination measured in the supernatant solutions issued from desorption tests of ABs from prostheses.
Biological evaluation confirmed the non-toxicity of poly-HPb-CD, HPb-CD and vancomycin at high concentration (400 mg/L) and the toxicity of ciprofloxacin and rifampicin at 35 and 22 mg/L (tested with L132 cells line). Proliferation tests revealed a low adaptation of endothelial cells (HPMEC) compared to virgin prostheses due to the fibrous structure of the prostheses and to the roughness of the surface of the poly-HPb-CD coating. The proliferation rate of HPMEC decreased with the presence of ciprofloxacin and rifampicin, due to their toxicity, but not with vancomycin.
Bacteriologic tests showed that vascular prostheses modified with HPb-CD exposed to plasma were active against Staphylococcus aureus during more than 72 hours with rifampicin and more than 24 hours with ciprofloxacin and vancomycin, whilst virgin prostheses displayed inferior performances. In vivo tests were performed by subcutaneous implantation of the grafts on rats. After 7 and 14 days, a macroscopic evaluation did not allow us to detect any degradation of the implant neither any abnormal local signs of irritation. Furthermore, the histopathological analysis displayed inflammatory reactions and tissue degeneration in a lesser extent than the control.
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