Anisotropic microtopography surface of chitosan scaffold regulating skin precursor-derived Schwann cells towards repair phenotype promotes neural regeneration

For repairing peripheral nerve and spinal cord defects,biomaterial scaffoid-based cell-therapy was emerged as an effective strategy,requiring the positive response of seed cells to biomaterial substrate and environment signals.Previous work highlighted that the imposed surface properties of scaffold could provide important guidance cues to adhered cells for polarization.However,the insufficiency of native Schwann cells and unclear cellular response mechanisms remained to be addressed.Given that,this study aimed to illuminate the micropatterned chitosan-film action on the rat skin precursor-derived Schwann cells(SKP-SCs).Chitosanfilm with different ridge/groove size was fabricated and applied for the SKP-SCs induction.Results indicated that SKP-SCs cultured on 30μm size microgroove surface showed better oriented alignment phenotype.Induced SKP-sCs presented similar genic phenotype as repair Schwann cells,increasing expression of c-Jun,neural cell adhesion molecule,and neurotrophic receptor p75.Moreover,SKP-SC-secretome was subjected to cytokine array GS67 assay,data indicated the regulation of paracrine phenotype,a panel of cytokines was verifed up-regulated at secreted level and gene expression level in induced SKP-SCs.These up-regulated cytokines exhibit a series of promotive neural regeneration functions,including cell survival,cell migration,cell proliferation,angiogenesis,axon growth,and cellular organization etc.through bioinformatics analysis.Furthermore,the effectively polarized SKP-SCs-sourced secretome,promoted the proliferation and migration capacity of the primarily cultured native rat Schwann cells,and augmented neurites growth of the cultured motoneurons,as well as boosted axonal regrowth of the axotomy-injured motoneurons.Taken together,SKP-SCs obtained pro-neuroregeneration phenotype in adaptive response to the anisotropic topography surface of chitosan-film,displayed the oriented parallel growth,the transition towards repair Schwann cell genic phenotype,and the enhanced paracrine effect on neural regeneration.This study provided novel insights into the potency of anisotropic microtopography surface to Schwann-like cells phenotype regulation,that facilitating to provide promising engineered cell-scaffold in neural injury therapies.

Accuracy controlling and mechanical behaviors of precursor-derived ceramic SiOC microlattices by projection micro stereolithography(PμSL)3D printing

Precursor-derived ceramic SiOC(PDC-SiOC)microlattices exhibit excellent oxidation resistance,high-temperature stability,and superior mechanical properties.However,the printing accuracy of the PDC-SiOC microlattices by 3D printing is still limited,and mechanical properties of the PDC-SiOC microlattices have not been studied systematically.Here,PDC-SiOC octet microlattices were fabricated by projection micro stereolithography(PμSL)3D printing,and photoabsorber(Sudan III)’s effect on the accuracy was systematically analyzed.The results showed that the addition of Sudan III improved the printing accuracy significantly.Then,the ceramization process of the green body was analyzed in detail.The order of the green body decreased,and most of their chemical bonds were broken during pyrolysis.After that,the PDC-SiOC microlattices with different truss diameters in the range of 52–220μm were fabricated,and their mechanical properties were investigated.The PDC-SiOC microlattices with a truss diameter of 52μm exhibited higher compression strength(31 MPa)than those with bigger truss diameters.The size effect among the PDC-SiOC microlattices was analyzed.Our work provides a deeper insight into the manufacturing of PDC-SiOC micro-scaled architectures by 3D printing and paves a path to the research of the size effect in ceramic structures.

Digital Light Processing 3D-Printed Ceramic Metamaterials for Electromagnetic Wave Absorption

Combining 3D printing with precursor-derived ceramic for fabricating electromagnetic(EM) wave-absorbing metamaterials has attracted great attention. This study presents a novel ultraviolet-curable polysiloxane precursor for digital light processing(DLP) 3D printing to fabricate ceramic parts with complex geometry, no cracks and linear shrinkage. Guiding with the principles of impedance matching, attenuation, and effective-medium theory, we design a crosshelix-array metamaterial model based on the complex permittivity constant of precursor-derived ceramics. The corresponding ceramic metamaterials can be successfully prepared by DLP printing and subsequent pyrolysis process, achieving a low reflection coefficient and a wide effective absorption bandwidth in the X-band even under high temperature. This is a general method that can be extended to other bands, which can be realized by merely adjusting the unit structure of meta-materials. This strategy provides a novel and effective avenue to achieve “target-design-fabricating” ceramic metamaterials, and it exposes the downstream applications of highly efficient and broad EM wave-absorbing materials and structures with great potential applications.

Characterization of free carbon in the as-thermolyzed Si-B-C-N ceramic from a polyorganoborosilazane precursor

Polyorganoborosilazane((B[C_(2)H_(4)-Si(CH_(3))NH]_(3))n)was synthesized via monomer route from a single-source precursor and thermolyzed at 1300℃in argon atmosphere.The as-thermolyzed Si-B-C-N ceramic was characterized using X-ray diffraction(XRD)and Raman spectroscopy.The crystallization behavior of silicon carbide in the as-thermolyzed amorphous Si-B-C-N matrix was understood by XRD studies,and the crystallite size calculated using Scherrer equation was found to increase from 2 nm to 8 nm with increase in dwelling time.Concomitantly,Raman spectroscopy was used to characterize the free carbon present in the as-thermolyzed ceramic.The peak positions,intensities and full width at half maximum(FWHM)of D and G bands in the Raman spectra were used to study and understand the structural disorder of the free carbon.The G peak shift towards 1600 cm-1 indicated the decrease in cluster size of the free carbon.The cluster diameter of the free carbon calculated using TK(Tuinstra and Koenl)equation was found to decrease from 6.2 nm to 5.4 nm with increase in dwelling time,indicating increase in structural disorder.