Correlation between biological responses in vitro and in vivo to Ca-doped sol-gel coatings assessed using proteomic analysis

Poor correlation between the results of in vitro testing and the subsequent in vivo experiments hinders the design of biomaterials. Thus, new characterisation methods are needed. This study used proteomic and histological techniques to analyse the effects of Ca-doped biomaterials in vitro and in vivo and verify the correlation between the two systems. The sol-gel route was employed to synthesise coatings functionalised with 0.5 and 5 wt% of CaCl2. Morphology of the coatings was examined using SEM; the Ca2+ ion release from the materials was analysed by means of ICP-AES spectroscopy. The osteogenic and inflammatory responses were inspected in vitro in human osteoblasts (HOb) and TPH-1 monocytes. The in vivo experiments used a rabbit model. The nLC-MS/MS-based proteomic methods were utilised to analyse the proteins adhering to the material samples incubated with human serum or examine protein expression in the tissues close to the implants. Ca-doped biomaterials caused a remarkable increase in the adsorption of coagulation-related proteins, both in vitro (PLMN, THRB, FIBA and VTNC) and in vivo (FBLN1, G1U978). Enhanced affinity to these materials was also observed for proteins involved in inflammation (CO5, C4BPA, IGHM and KV302 in vitro; CARD6, DDOST and CD14 in vivo) and osteogenic functions (TETN, PEDF in vitro; FBN1, AHSG, MYOC in vivo). The results obtained using different techniques were well matched, with a good correlation between the in vitro and in vivo experiments. Thus, the proteomic analysis of biological responses to biomaterials in vitro is a useful tool for predicting their impact in vivo.