Extracellular Matrix Based,Photo-thermal Composite Films And Their Cellular Responses

Extracellular matrix(ECM)is a natural biological material secreted by cells,which is rich in large molecules such as structural proteins,functional proteins,proteoglycans.ECM has excellent biocompatibility that can mimic the cell microenvironment and regulate cell behaviors like adhesion,proliferation and differentiation.Thus ECM is an ideal tissue engineering materials.Bone marrow mesenchymal stem cells(BMSCs)are first choice of seed cells of tissue engineering for bone defect repair.Factors that affect BMSCs osteogenesis are important to be considered when preparing innovative scaffold materials suitable for cell/tissue growth.Mild thermal stimulation has gradually been extensively studied due to its ability to induce osteogenic differentiation of BMSCs.If the thermal stimulation can be led to the target area to avoid damage to surrounding normal tissue cells,it will definitely promote the application of thermal stimulation to induce bone formation.Therefore,based on the extracellular matrix,this article combined ECM with polydopamine(PDA)or graphene(Gr)to prepare composite film with photothermal effect.The main research results obtained in this paper are as follows:(1)Preparation of PDA/ECM composite film and the response of cells on it under photothermal stimulationThe PDA film was deposited on the surface of the substrate by deposition.ECM was obtained by culturing mouse embryonic fibroblasts(NIH 3T3)at high density and freezing and thawing cycles for decellularization.Due to the high affinity of the PDA,ECM could be attached to substrate deposited with PDA,and the combination of PDA/ECM as a modified coating with the substrate was very strong.The hydrophilicity and biocompatibility of the substrate were greatly improved.At the same time,the photothermal effect allowed the surface BMSCs to sense the thermal stimulation and differentiate into osteoblasts under low intensity,short term visible light,specifically manifested as alkaline phosphatase(ALP)activity and calcium mineralization deposition were increased.(2)Preparation of Gr/ECM composite film and the response of cells on it under photothermal stimulationECM were obtained by culturing NIH 3T3 at high density and freezing and thawing cycles for decellularization.During the cultivation,different volumes of nanographene aqueous solution were added to prepare Gr/ECM composite films in different concentration of graphene.The composite film had superior photothermal effect,and the higher concentration of graphene in the film,the higher temperature of the film surface under light.Although the biocompatibility of the composite film was reduced compared to ECM,it could effectively induce osteogenic differentiation of BMSCs through the regulation of photothermal stimulation(time and frequency).What's more,the BMSCs on composite with low degree of graphene showed significantly better osteogenic differentiation ability than pure ECM under low intensity,low frequency and short-time visible light.Heat shock protein 70(HSP70)expression was up-regulated under photothermal stimulation.We speculated that HSP70 up-regulated to a certain extent was involved in activating p-ERK expression to induce BMSCs to osteogenic differentiation.But excessive light and heat stimulation caused cell damage,cell growth and differentiation are inhibited,even though HSP70 expression wass still up-regulated.