Construction Of Biomimetic Polyurethane In Liquid Crystal State And Primary Research On Promoting Osteogenic Differentiation Of Stem Cells

The main innovation of this research is to simulate the morphology of human cell membranes and construct a three-dimensional(3D)composite material in liquid crystal(LC)state.To study the cytotoxicity of synthetic LCs and the feasibility of constructing a composite material with 3D structure in the LC state,and to explore its effect on cell function,paying particular attention to the osteogenic differentiation function of stem cells.The specific research contents and results are as follows:Small-molecule LCs are synthesized by an acid chloride esterification method between cholesterol chloroformate as raw material and triethylene glycol(tetraethylene glycol)and acrylic acid chloride(undecenoyl chloride),six compounds srepresenting triethylene glycol cholesterol carbonate,tetraethylene glycol cholesterol carbonate,acryloyloxy-triethylene glycol cholesterol carbonate,undecylenyloxy-triethylene glycol cholesterol carbonate,acryloyloxy-tetraethylene glycol cholesterol carbonate,and undecylenyloxy-tetraethylene glycol cholesterol carbonate,respectively.Then,a series of new polymer LCs are prepared by hydrosilylation reaction between polymethylhydrogen siloxane and the above monomers.Molecular structure,LC properties,and viscoelastic behavior of polymers are obtained using fourier transform infrared spectroscopy(FT-IR),proton nuclear magnetic resonance(~1H-NMR),polarized optial microscope(POM),differential scanning calorimetry(DSC),and X-ray diffraction(XRD),etc.The results show that the synthetic polymers are cholesteric LC,and the LC phase temperature is in the range of normal human body temperature(37°C);The flexible backbone and long flexible spacer branch are beneficial to form a temperature range close to the human body temperature.To introduce a bioactive cholesteric LC into the PU,a casting film-forming technology is directly used to prepare LC composite film.The research results show that the PU/LC bionic composite film exhibits a more uniform LC state when the LC content is about 30%;The introduction of LC not only improves the hydrophilicity of the surface of the PU film,but reduces the elastic modulus and increases the breaking energy;Small-molecule LCs with double bond at end are toxic to cells,but polymer LCs have good affinity for cells;Compared with PU,polymer LC bionic composite film has better cell adhesion,proliferation,and growth,showing good cell compatibility;In addition,the introduction of LCs effectively promoted the growth and crystallinity of HA,and the type of LCs had little effect on the mineralization.In this study,3D printing technology and soaking-swelling blending technology are used to construct a 3D PU/LC composite scaffold in LC state and the mechanism of the influence of LC states on the differentiation of stem cells into osteoblasts were discussed.The research results show that the introduction of LC does not change the volume or shape of the scaffold,but reduces the compression performance and hardness;Cell experiments proved that the 3D scaffold in LC state has better cell affinity,showing good cell adhesion ability,and it has specific positive effects on the proliferation and differentiation of h MSCs(including ALP secretion,calcium deposition,and osteogenesis-related genes and protein expression),which provides preliminary theoretical basis and experimental evidence for the application of 3D LC scaffolds in the field of tissue engineering.