Rong An,Muqiu Wu,Jing Li,Xiuhua Qiu,Faiz Ullah Shah,Jianliang Li
A strongly ‘pinned’ ionic liquid (IL, [BMIM][PF6]) film on a silicon (Si) surface via carbon capsuled Fe3O4 core–shell (Fe3O4@C) nanoparticles is achieved, revealing excellent friction-reducing ability at a high load. The adhesion force is measured to be ∼198 nN at the Fe3O4@C-Si interface by the Fe3O4@C colloidal AFM tip, which is stronger than that at both Fe3O4@C-Fe3O4@C (∼60 nN) and IL-Si (∼10 nN) interfaces, indicating a strong ‘normal pin-force’ towards the Si substrate. The resulting strengthened force enables the formation of lateral IL networks via the dipole–dipole attractions among Fe3O4 cores. The observed blue shift of the characteristic band related to the IL anion in the ATR-FTIR spectra confirmed the enhanced interaction. The N–Si, P–O chemical bonds formed as a result of the IL interactions with the Si substrate confirmed by XPS spectroscopy suggested that the IL lay on the Si plane. This orientation is favorable for Fe3O4@C nanoparticles to exert ‘normal pin-force’ and press the IL film strongly onto surfaces. The IL ions/clusters are thus anchored by these Fe3O4@C ‘pins’ onto the substrate to form a dense film, resulting in a smaller interaction size parameter, which is responsible for the reduced friction coefficient μ.
Manping Lin,Huaiyu Wang,Changshun Ruan,Juan Xing,Jinfeng Wang,Yan Li,Yuanliang Wang,Yanfeng Luo
The amount, type, and conformation of proteins adsorbed on an implanted biomaterial are believed to influence cell adhesion. Nevertheless, only a few research works have been dedicated to the contribution of protein adsorption force. To verify our hypothesis that the adsorption force of protein on biomaterial is another crucial mediator to cell adhesion, fibronectin (FN) adsorbed on self-assembled monolayers (SAMs) with terminal −OH, −CH3, and −NH2 was quantified for FN adsorption force (Fad) by utilizing a sphere/plane adsorption model and parallel plate flow chamber. As revealed, Fad on SAMs followed a chemistry-dependence of −NH2 > −CH3 ≫ −OH. It is further demonstrated that Fad together with FN conformation could regulate the late osteoblast adhesion and the consequent reorganization of the adsorbed FN and fibrillogenesis of the endogenous FN. Our study suggests that protein adsorption force plays a key role in cell adhesion and should be involved for better biomaterial design.
Manping Lin,Shilong Mao,Jinfeng Wang,Juan Xing,Yuanliang Wang,Kaiyong Cai,Yanfeng Luo
The transmission of cell traction force (CTF) to underlying biomaterials is essential for adhered cells to measure and respond to their mechanical microenvironment . Given that the protein layer adsorbed on materials lies between the cells and materials, we hypothesize that the interfacial strength of protein-material interfaces (i.e., the adsorption force of proteins, F ad ) should have an important role in regulating the transmission of CTF. To test this hypothesis, rat mesenchymal stem cells (rMSCs) were cultured on poly(dimethyl siloxane) (PDMS) substrates with different F ad of fibronectin (FN), and the transmission of CTF was observed by immunofluorescence staining of FN and deformation of PDMS. As revealed, FN on substrates with low F ad is more liable to be desorbed by CTF, which prevents the transmission of CTF to substrates. In contrast, high F ad facilitates the transmission of CTF from rMSCs to the FN layer and PDMS substrates so that rMSCs can perceive the mechanical properties of substrates. We further demonstrated that the divergent transmission of CTF on low and high F ad substrates regulates the lineage specifications of rMSCs. Our study confirms the important role of F ad in CTF transmission and provides a new perspective to gain insights into cell-material interactions and cell fates, which may help to guide the design of better biomaterials.
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