Introduction: Biomaterials for implant interact with the body via proteins adsorbed on their surface. Therefore, the proteins highly affect biocompatibility of biomaterials. We have already identified eight proteins as candidates of the marker for blood compatibility by comprehensive analysis of protein adsorption on biomaterials with various blood compatibility. Here, we validate the predictivity of the candidates by analyzing their adsorption on the surface of metal materials for stents.
Materials and Methods: In addition to three normal metals: Co-Cr alloy (Co-Cr), Ni-Ti alloy (Ni-Ti), and stainless steel (SUS), three diamond-like carbon (DLC)-coated metals which were made with support by innovation promotion project from NEDO: DLC-coated SUS (SUS/DLC), Si-incorporated SUS/DLC (SUS/Si-DLC), and F-doped SUS/DLC (SUS/F/DLC), were incubated in human plasma for 1 h at 37°C. These materials were washed, and proteins adsorbed on them were collected. Obtained proteins were refined, and the comprehensive multivariate proteomic analysis was performed by shotgun LC-MS/MS followed by database search with Proteome Discoverer software using the Mascot search engine and the UniProtKB/Swiss-Prot database.
Results and Discussion: Five of eight marker candidates: complement C1r subcomponent (C1r), complement C1s subcomponent (C1s), complement C3, fibronectin, and vitronectin, were detected in this assay. Compared to SUS, C1s and C1r adsorption was decreased less than half and one fifth or less in SUS/Si-DLC and SUS/DLC, respectively. Adsorption for all of the five proteins was decreased one fifth or less in SUS/F/DLC, Co-Cr, and Ni-Ti compared to SUS. In addition, adsorption of other blood coagulation proteins was dramatically decreased in SUS/F/DLC and Ni-Ti. Taken together, we conclude that the blood compatibility of these materials in view of protein adsorption is SUS/F/DLC = Ni-Ti > Co-Cr > SUS/DLC > SUS/Si-DLC > SUS. F-doped DLC is reported to decrease platelet adhesion compared to SUS or DLC in human blood[1], and F-doped DLC-coated stents are reported to decrease the restenosis rate compared to conventional stents in miniature pigs[2]. DLC-coated stents are reported not to decrease the restenosis rate compared to conventional stents in clinical use[3][4], although their antithrombotic effect is reported by in vitro assay[5]. Thus, our results correlate to these reports. On the other hand, Ni-Ti stents are reported to induce more restenosis than DLC-coated stents in dogs[6]. The blood compatibility of biomaterials is determined from not only protein adsorption but also metal ion release from the materials, which may be the reason for this contradictory result with our observation
Conclusion: Our results suggest that the strategy utilizing these marker proteins adsorbed on biomaterials as blood compatibility marker is useful. We are now trying to develop testing method which easily measure these protein markers for general use.
References:
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