Interpenetrating polymer network (IPN) is generally considered to be one of the most effective methods for imparting high-strength mechanical properties to hydrogel materials. To broaden the application of alginate hydrogel in skeletal muscle or muscle tissue engineering, the interpenetrating network technology and layer-by-layer (LBL) electrostatic assembly were proposed to fabricate the homogeneous alginate/polyacrylamide-chitosangelatin (Alg/PAAM-CS-GT) composite hydrogel scaffolds, using the hydroxyapatite/D-glucono-δ-lactone (HAP/GDL) complex as the gelling system. The effects of different components of alginate/polyacrylamide (Alg/PAAM) on the morphology, mechanical properties, swelling, degradability, and cytocompatibility of the hydrogel scaffolds were comparatively characterized. Experimental results showed that the as-prepared Alg/PAAM-CS-GT composite hydrogel scaffolds exhibited sharp edges and regular 3D structures. Their pore structure could be regulated by changing the content of PAAM in Alg/PAAM-CS-GT composite hydrogel scaffolds. And the filling of PAAM reduced the pores and thickened the pore walls, which obviously enhanced the mechanical properties of Alg/PAAM-CS-GT composite hydrogel scaffolds. FT-IR and thermogravimetric analysis showed that O‧‧‧N hydrogen bonding between COOH of SA and NH 2 of PAAM could be helpful to improve the thermal stability of the composite hydrogel scaffolds. The swelling and biodegradation measurements indicated that the swelling and degradation of Alg/PAAM-CS-GT composite hydrogel scaffolds could be effectively regulated by changing the component content of the composite hydrogel. In addition, the in vitro cytocompatibility analysis showed that the Alg/PAAM-CS-GT composite hydrogel scaffolds could support the growth of MC3T3-E1 cells and promote cell proliferation and differentiation. According to the in vitro cytocompatibility test results, the optimum PAAM content for the Alg/PAAM-CS-GT composite hydrogel scaffolds was 60%. Because of good morphology, well-developed pores, excellent mechanical properties, and high

It is common knowledge that pure alginate hydrogel is more likely to have weak mechanical strength, a lack of cell recognition sites, extensive swelling and uncontrolled degradation, and thus be unable to satisfy the demands of the ideal scaffold. To address these problems, we attempted to fabricate alginate/bacterial cellulose nanocrystals-chitosan-gelatin (Alg/BCNs-CS-GT) composite scaffolds using the combined method involving the incorporation of BCNs in the alginate matrix, internal gelation through the hydroxyapatite-d-glucono-δ-lactone (HAP-GDL) complex, and layer-by-layer (LBL) electrostatic assembly of polyelectrolytes. Meanwhile, the effect of various contents of BCNs on the scaffold morphology, porosity, mechanical properties, and swelling and degradation behavior was investigated. The experimental results showed that the fabricated Alg/BCNs-CS-GT composite scaffolds exhibited regular 3D morphologies and well-developed pore structures. With the increase in BCNs content, the pore size of Alg/BCNs-CS-GT composite scaffolds was gradually reduced from 200 μm to 70 μm. Furthermore, BCNs were fully embedded in the alginate matrix through the intermolecular hydrogen bond with alginate. Moreover, the addition of BCNs could effectively control the swelling and biodegradation of the Alg/BCNs-CS-GT composite scaffolds. Furthermore, the in vitro cytotoxicity studies indicated that the porous fiber network of BCNs could fully mimic the extracellular matrix structure, which promoted the adhesion and spreading of MG63 cells and MC3T3-E1 cells on the Alg/BCNs-CS-GT composite scaffolds. In addition, these cells could grow in the 3D-porous structure of composite scaffolds, which exhibited good proliferative viability. Based on the effect of BCNs on the cytocompatibility of composite scaffolds, the optimum BCNs content for the Alg/BCNs-CS-GT composite scaffolds was 0.2% (w/v). On the basis of good merits, such as regular 3D morphology, well-developed pore structure, controlled swelling and biodegradation behavior, and good cytocompatibility, the Alg/BCNs-CS-GT composite scaffolds may exhibit great potential as the ideal scaffold in the bone tissue engineering field.

Background: The potato tuber moth (PTM), Phthorimaea operculella (Zeller), is a worldwide pest that feeds on both the leaves and tubers of potato plants. PTM larvae can digest leaves, or tubers, resulting in serious damage to potato plants in the field and potato tubers in storage. To understand how midgut bacterial diversity is influenced by the consumption of these two tissue types, the symbiotic bacteria in the potato-feeding PTM midgut and the endophytic bacteria of potato tissues were analyzed. Results: At the genus level, the bacterial community composition in the PTM midgut was influenced by the tissues consumed, owing to their different nutrient contents. Escherichia_Shigella and Enterobacter were the most dominant genera in the midgut of leaf-feeding and tuber-feeding PTMs, respectively. Interestingly, even though only present in low abundance in leaves and tubers, Escherichia_Shigella were dominantly distributed only in the midgut of leaffeeding PTMs, indicating that specific accumulation of these genera have occurred by feeding on leaves. Moreover, Enterobacter, the most dominant genus in the midgut of tuber-feeding PTMs, was undetectable in all potato tissues, indicating it is gut-specific origin and tuber feeding-specific accumulation. Both Escherichia_Shigella and Enterobacter abundances were positively correlated with the dominant contents of potato leaves and tubers, respectively. Conclusions: Enrichment of specific PTM midgut bacterial communities was related to different nutrient levels in different tissues consumed by the insect, which in turn influenced host utilization. We provide evidence that a portion of the intestinal microbes of PTMs may be derived from potato endophytic bacteria and improve the understanding of the relationship between potato endophytic bacteria and the gut microbiota of PTMs, which may offer support for integrated management of this worldwide pest.

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