BACKGROUND:The repair of large-scale bone defects is still facing serious challenges.It is of great significance to develop personalized,low-cost,and osteogenic-inducing tissue engineering scaffolds for bone repair. OBJECTIVE:To explore the process of 3D printing bone tissue engineering scaffold containing pearl composite material by low-temperature condensation deposition method,and further test the physicochemical properties and in vitro biological functions of the composite scaffold. METHODS:Pearl powder was prepared by grinding and sieving.The pearl powder of different qualities was added into the poly-L-lactic acid ink,so that the mass ratio of pearl powder to poly-L-lactic acid was 0,0.1,0.2,0.3,and 0.5,respectively.The 3D-printed poly-L-lactic acid/pearl powder scaffolds were prepared using the low-temperature condensation deposition method.The microstructure,compressive properties,water contact angle,cytocompatibility,and in vitro bone differentiation ability of the printed poly-L-lactic acid/pearl powder composite scaffolds were detected. RESULTS AND CONCLUSION:(1)Scanning electron microscopy showed that the five groups of scaffolds all had micropores with a diameter of 2 μm or even smaller,irregular shapes and interconnectivity.(2)All the five groups had good compressive properties.The compressive strength of the pearl powder 0.5 group was higher than that of the other four groups(P<0.05).The water contact angle of the pearl powder 0.2 group and the pearl powder 0.5 group was smaller than that of the pearl powder 0 group(P<0.01,P<0.001).(3)Bone marrow mesenchymal stem cells were co-cultured with five groups of scaffolds for 1,3,and 5 days,respectively.The cell proliferation in pearl powder 0.1,0.2,0.3,and 0.5 groups cultured for 3 and 5 days was faster than that in pearl powder 0 group(P<0.05).After 1 day of culture,live-dead staining exhibited that the number of cells on the scaffold was small,but all of them were living cells.(4)Bone marrow mesenchymal stem cells were inoculated on the scaffold surface of the pearl powder 0 group and pearl powder 0.1 group respectively for osteogenic differentiation.The alkaline phosphatase activity induced for 4 and 6 days in the pearl powder 0.1 group was higher than that in the pearl powder 0 group(P<0.05).(5)The results showed that the poly-L-lactic acid/pearl powder composite scaffold had good compressive strength,hydrophilicity,cytocompatibility,and osteogenic properties.

Objective To analyze the prevalence and genetic characteristics of influenza A(H3N2) viruses in the city of Xiangyang in 2022-2023, and to provide a scientific basis for predicting the epidemic and mutation of influenza virus. Methods Throat swab specimens of the influenza like cases were collected from national influenza monitoring sentinel hospitals in Xiangyang every week. RNA was extracted from the specimens for influenza diagnosing using real-time RT-PCR．Viruses were isolated from H3N2 positive specimens, and HA and NA genes were amplified and sequenced．3D modeling analyses were conducted. Results The gene phylogenetic tree showed that the H3N2 isolates in 2022-2023 belonged to 3C.2a1b.2a1 and 3C.2a1b.2a2 branches, respectively. The A(H3N2) influenza virus strains all had amino acid point mutation sites on important antigenic determinants of HA protein. The epitope mutations of the 2022 A(H3N2) strain mainly occurred in regions B, C, and D. The epitope mutations of the A(H3N2) strain in 2023 mainly occurred in regions C and D. Different glycosylation sites of HA gene were found in 2022-2023 strains. No variation was found in key amino acid sites associated with neuraminidase inhibitor resistance. The difference of overall structure was not obvious in the three-dimensional simulation structure diagram. Conclusion The A(H3N2) influenza strains isolated in this study have shown antigenic drift, especially the mutation of HA, which may affect the protective effect of the vaccine on the local population and lead to influenza epidemic. The variations of HA and NA suggest that close attention should be paid to the epidemic and genetic variation of H3N2 subtype influenza virus, to provide a scientific basis for the selection of influenza virus vaccine strains and the prevention and control of influenza.