Nanocellulose/bioactive glass cryogels as scaffolds for bone regeneration

A major challenge exists in the preparation of scaffolds for bone regeneration, namely, achieving simultaneously bioactivity, biocompatibility, mechanical performance and simple manufacturing. Here, cellulose nanofibrils (CNF) are introduced for the preparation of scaffolds taking advantage of their biocompatibility and ability to form strong 3D porous networks from aqueous suspensions. CNF are made bioactive for bone formation through a simple and scalable strategy that achieves highly interconnected 3D networks. The resultant materials optimally combine morphological and mechanical features and facilitate hydroxyapatite formation while releasing essential ions for in vivo bone repair. The porosity and roughness of the scaffolds favor several cell functions while the ions act in the expression of genes associated with cell differentiation. Ion release is found critical to enhance the production of the bone morphogenetic protein 2 (BMP-2) from cells within the fractured area, thus accelerating the in vivo bone repair. Systemic biocompatibility indicates no negative effects on vital organs such as the liver and kidneys. The results pave the way towards a facile preparation of advanced, high performance CNF-based scaffolds for bone tissue engineering

Ultra-thin electrospun nanofibers for development of damage-tolerant composite laminates

The present article overcomes existing challenges in inter-laminar toughening of novel multifunctional fiber-reinforced polymer composites via development and embedment of highly stretched, ultra-thin electrospun thermoplastic nanofibers made of polyamide 6.6. The nanofibers exhibit significant enhancement of the composite laminate's structural integrity with almost zero weight penalty via ensuring a smooth stress transfer throughout the plies and serving tailoring mechanical properties in desired directions, with no interference with geometric features, e.g., thickness. The findings for 1.5 g per square meter electrospun nanofibers have demonstrated, on test coupon specimens, improvements up to 85% and 43% in peak load and crack opening displacement, respectively, with significant improvement (>25%) and no sacrifice of fracture toughness at both initiation and propagation phases. The initial stiffness for the modified specimens was improved by nearly 150%. The enhancement is mainly due to nanofibers contributing to the stiffness of the resin-rich area at the crack tip adjacent to the polytetrafluoroethylene (PTFE) film. Glass fiber-reinforced woven phenolic pre-impregnated composite plies have been modified with the nanofibers (each layer having an average thickness of 2.0 gsm) degrades the adhesion properties (chemical bonding) between glass fibers and the phenolic matrix. The density of nanofibers increases, so does the likelihood of forming a physical barrier between the plies resulting in the loss of resin flow and poor adhesion. Such an effect was evident from microscopic investigations and reduction in fracture toughness data at the initiation and propagation phases

Bioinspired and osteopromotive polydopamine nanoparticle-incorporated fibrous membranes for robust bone regeneration

Due to their inherent hydrophobic and bioinert nature, synthetic degradable polymer-based membranes show inferior stem cell attachment, proliferation, and even differentiation. To overcome these limitations, bioinspired and osteopromotive polydopamine nanoparticle-incorporated fibrous membranes are developed via a two-step route: pH-induced polymerization of dopamine and co-electrospinning of polycaprolactone (PCL) with polydopamine nanoparticles (PDA NPs). Hybrid membranes with optimized PDA NP content exhibit high quantities of apatite deposition and prominent cytocompatibility (cell attachment, spreading and reproduction) and osteo-differentiation potential (alkaline phosphatase activity, calcium mineralization, and osteogenesis-related genes and protein expression) of human mesenchymal stem cells cultured without any growth factors. Importantly, in vivo assessments using a mouse calvarial critical-sized defect demonstrate that the engineered fibrous membranes remarkably boost bone reconstruction and regeneration. Accordingly, our bioinspired PCL-based hybrid fibrous membranes with robust osteoinductive ability can potentially be utilized as a clinically applicable candidate in guided tissue regeneration applications