Vascular Cell Responses To PDMS Surfaces Grafted With Topographical Heparin-like Polymers

Heparin-like polymers are promising synthetic materials with similar biological functionalities as heparin,such as anticoagulant ability,growth factor binding to regulate cellular functions,and inflammation mediation.The biocompatibility of heparin-like polymers with well-defined chemical structures has inspired many researchers to design heparin-like surfaces to explore their biological applications.The concept of the recombination of functional heparin structural units(sulfonate-and glyco-containing units)was proven to be successful in designing heparin-mimicking surfaces.However,besides surface structural units,surface topography is also an important contributor to the biological activity.In this work,both surface structural units and surface topography were taken into account to investigate the vascular cell behaviors on the polydimethylsiloxane(PDMS)surfaces grafted with heparin-like polymers.Specifically,a facile method to produce bromine-containing PDMS surface(PDMS-Br)with topographical features(surface patterning and micro-/nanoscale surface topographies)was developed by a one-step multicomponent thermocuring procedure and replica molding.Different structural units of heparin-like polymers,i.e.homopolymer of sodium 4-vinylbenzenesulfonate(pSS,sulfonate-containing),homopolymer of 2-methacrylamido glucopyranose(pMAG,glyco-containing),and copolymers of MAG and SS(pSG)were then introduced on the topographical PDMS-Br surface by visible light-induced graft polymerization.The main study content is as follows.(1)Preparation and characterization of topographical PDMS surfaces grafted with different structural units of heparin-like polymers.PDMS-Br surfaces with nanopatterned structures and micro-/nanoscale surface topographies were prepared by a one-step multicomponent thermocuring procedure and replica molding using a nanohole-arrayed silicon template and fresh lotus leaf template,respectively.Different heparin-like monomers,like MAG and SS,were chosen to perform visible light-induced graft polymerization on the flat and topographical PDMS-Br surfaces.Data obtained from atomic force microscopy(AFM)and scanning electron microscopy(SEM)confirmed the surface topographies constructed on the PDMS-Br surface.Static water contact angle,Fourier transform infrared(FTIR)spectroscopy,X-ray photoelectron spectroscopy(XPS)were used to characterize the material surfaces grafted with different structural units of heparin-like polymers.(2)The influence of chemical structural units and surface topography on vascular cell behaviors on the surfaces grafted with heparin-like polymers.For the flat surfaces,compared with the PDMS-Br surface,pSS-grafted and pSG-grafted surfaces significantly increased cell densities of both human umbilical vein endothelial cells(HUVECs)and human umbilical vein smooth muscle cells(HUVSMCs),indicating that they are "vascular cell-friendly".In contrast,the pMAG-grafted surface showed decreased cell attachment of both HUVECs and HUVSMCs,indicating that the pMAG-grafted surface is "vascular cell-resistant".The introduction of different surface topographies on the modified surfaces caused different vascular cell responses.Surface topography with regular patterns enhanced the cell responses of the corresponding flat surfaces.That is to say,surface pattern can make the "vascular cell-friendly" surface(PDMS-pSS and PDMS-pSG)still friendly whereas"vascular cell-resistant" surface(PDMS-pMAG)much more resistant.In contrast,lotus leaf-like topography decreased HUVECs densities on all of the modified surfaces in different degree,indicating that the introduction of lotus leaf-like topography may inhibit adhesion and proliferation of HUVECs regardless of the surface structural units.In this respect,the endothelial cell behavior is dominated by lotus leaf-like topography whereas the influence of surface structural units is weak.In conclusion,the combination of surface structural units and surface topography shows promise to prepare new heparin-like surfaces with improved cell compatibility that is suitable for blood-compatible biomaterials.