The wide array of periodontal tissue engineering applications has demonstrated the need for appropriate biodegradable materials. Porous chitosan/collagen – a natural derivative composite – scaffolds could be a candidate. In this study, differently proportioned porous chitosan/collagen scaffolds were prepared by controlled freezing and lyophylization of corresponding composite solutions. The scaffolds were investigated via aperture, porosity, swelling behavior and cell-mediated contraction testing. The morphology and distribution of human periodontal ligament cells (PDLCs) on these threedimensional scaffolds were investigated by SEM and CLSM. Compared to a single component scaffold, the addition of collagen to chitosan decreased the mean aperture, increased the swelling ability and the addition of chitosan to collagen decreased the contraction. The adherence and growth of PDLCs cultured within the chitosan/collagen scaffolds were better than on single chitosan or collagen scaffolds. It appears that chitosan/collagen composites are promising scaffold materials for periodontal tissue engineering.

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Defects in adaptive immune system, including reduced T cells and B cells, were frequently observed in non-severe COVID-19 patients with persistent SARS-CoV-2 shedding. Assessment of immune system could be clinically relevant for discharge management. AbstractBackground: COVID-19 has been widely spreading. We aim to examine adaptive immune cells in non-severe patients with persistent SARS-CoV-2 shedding.Methods 37 non-severe patients with persistent SARS-CoV-2 presence transferred to Zhongnan hospital of Wuhan University were retrospectively recruited to PP (persistently positive) group, which was further allocated to PPP group (n=19) and PPN group (n=18), according to their testing results after 7 days (N=negative).Epidemiological, demographic, clinical and laboratory data were collected and analyzed. Data from ageand sex-matched non-severe patients at disease onset (PA [positive on admission] patients, n=37), and lymphocyte subpopulation measurements from matched 54 healthy subjects were extracted for comparison. ResultsCompared with PA patients, PP patients had much improved laboratory findings, including WBCs, neutrophils, lymphocytes, neutrophil-to-lymphocyte ratio, albumin, AST, CRP, SAA, and IL-6. The absolute numbers of CD3 + T cells, CD4 + T cells, and NK cells were significantly higher in PP group than that in PA group, and were comparable to that in healthy controls. PPP subgroup had markedly reduced B cells and T cells compared to PPN group and healthy subjects. Finally, paired results of these lymphocyte subpopulations from 10 PPN patients demonstrated that the number of T cells and B cells significantly increased when the SARS-CoV-2 tests turned negative. ConclusionPersistent SARS-CoV-2 presence in non-severe COVID-19 patients is associated with reduced numbers of adaptive immune cells. Monitoring lymphocyte subpopulations could be clinically meaningful in 3 All rights reserved. No reuse allowed without permission.