Homogeneous silver nanoparticle loaded polydopamine/polyethyleneimine-coated bacterial cellulose nanofibers for wound dressing.

Utilizing mussel-inspired chemistry is an advanced strategy for surface modification, because dopamine (DA) can form a material-independent adhesive coating and further functionalization can be achieved, including the production of silver nanoparticles (AgNPs). Nevertheless, DA easily aggregates in the nanofiber network structure of bacterial cellulose (BC), which not only blocks the pores in the BC structure but also leads to the formation of large silver particles and the burst release of highly cytotoxic silver ions. Herein, a homogeneous AgNP-loaded polydopamine (PDA)/polyethyleneimine (PEI) coated BC was constructed via a Michael reaction between PDA and PEI. Under the action of PEI, the PDA/PEI coating was uniformly attached to the BC fiber surface with a thickness of approximately 4 nm, and homogeneous AgNPs were produced on the uniform PDA/PEI/BC (PPBC) fiber surface. The sustained release of silver ions was better from AgNPs@PPBC than from AgNPs@PDA/BC. The obtained AgNPs@PPBC exhibited excellent antibacterial activities and cytocompatibility. The results of the in vivo assay indicated that the AgNPs@PPBC dressing could inhibit S. aureus infection and inflammation, promote hair follicle growth, enhance collagen deposition, and accelerate wound healing within 12 days compared with BC. These results illustrate that the homogeneous AgNPs@PPBC dressing has great potential for treating infected wounds.

Hierarchical porous bacterial cellulose scaffolds with natural biomimetic nanofibrous structure and a cartilage tissue-specific microenvironment for cartilage regeneration and repair.

The limited three-dimensional (3D) nano-scale pore structure and lack of biological function hamper the application of bacterial cellulose (BC) in cartilage tissue engineering. To address this challenge, 3D hierarchical porous BC/decellularized cartilage extracellular matrix (DCECM) scaffolds with structurally and biochemically biomimetic cartilage regeneration microenvironment were fabricated by freeze-drying technique after EDC/NHS chemical crosslinking. The BC/DCECM scaffolds exhibited excellent mechanical properties, water superabsorbency and shape-memory properties. Compared with the BC control, the BC/DCECM scaffolds exhibited enhanced cell adhesion and proliferation. Cartilage regeneration in vitro and in vivo indicated that the BC/DCECM scaffolds achieved satisfactory neocartilage tissue regeneration with superior original shape fidelity, exterior natural cartilage-like appearance and histologically cartilage-specific lacuna formation and ECM deposition. Furthermore, the BC/DCECM scaffolds achieved superior repair outcomes, as hyaline cartilage-like tissue formed within the defect sites. The present study constitutes a strong step toward the further application of BC in cartilage tissue engineering.

Fabrication of Robust, Shape Recoverable, Macroporous Bacterial Cellulose Scaffolds for Cartilage Tissue Engineering.

Recently, the fabricating of three-dimensional (3D) macroporous bacterial cellulose (MP-BC) scaffolds with mechanically disintegrated BC fragments has attracted considerable attention. However, the successful implementation of these materials depends mainly on their mechanical stability and robustness. Here, a non-toxic crosslinker, 1-ethyl-3-(-3-dimethylaminopropyl) carbodiimide hydrochloride/N-hydroxysuccinimide (EDC/NHS), is employed to induce crosslinking reactions between BC fragments. In addition to their large pore sizes, the EDC/NHS-crosslinked MP-BC scaffolds exhibit excellent compression properties and shape recovery ability, owing to the EDC/NHS-induced crosslinking on the BC nanofibers. The results of in vitro studies reveal that the biocompatibility of MP-BC scaffolds is better than that of pristine BC scaffolds because the former provided more space for cell proliferation. The results of in vivo studies show that the neocartilage tissue with native cartilage appearance and abundant cartilage-specific extracellular matrix deposition is successfully regenerated in nude mice. The findings reveal the immense application potential of mechanically robust BC scaffolds with controllable pore sizes and shape-recoverable properties in tissue engineering.

Ultrathin, Strong, and Highly Flexible Ti3C2Tx MXene/Bacterial Cellulose Composite Films for High-Performance Electromagnetic Interference Shielding.

The fabrication of ultrathin films that are electrically conductive and mechanically strong for electromagnetic interference (EMI) shielding applications is challenging. Herein, ultrathin, strong, and highly flexible Ti3C2Tx MXene/bacterial cellulose (BC) composite films are fabricated by a scalable in situ biosynthesis method. The Ti3C2Tx MXene nanosheets are uniformly dispersed in the three-dimensional BC network to form a mechanically entangled structure that endows the MXene/BC composite films with excellent mechanical properties (tensile strength of 297.5 MPa at 25.7 wt % Ti3C2Tx) and flexibility. Importantly, a 4 µm thick Ti3C2Tx/BC composite film with 76.9 wt % Ti3C2Tx content demonstrates a specific EMI shielding efficiency of 29141 dB cm2 g-1, which surpasses those of most previously reported MXene-based polymer composites with similar MXene contents and carbon-based polymer composites. Our findings show that the facile, environmentally friendly, and scalable fabrication method is a promising strategy for producing ultrathin, strong, and highly flexible EMI shielding materials such as the freestanding Ti3C2Tx/BC composite films for efficient EMI shielding to address EMI problems of a fast-developing modern society.

Three-Dimensional Porous Scaffolds with Biomimetic Microarchitecture and Bioactivity for Cartilage Tissue Engineering.

Ideal tissue-engineering cartilage scaffolds should possess the same nanofibrous structure as the microstructure of native cartilage as well as the same biological function provided by the microenvironment for neocartilage regeneration. In the present study, three-dimensional composite biomimetic scaffolds with different concentration ratios of electrospun gelatin-polycaprolactone (gelatin-PCL) nanofibers and decellularized cartilage extracellular matrix (DCECM) were fabricated. The nanofibers with the biomimetic microarchitecture of native cartilage served as a skeleton with excellent mechanical properties, and the DCECM served as a biological functionalization platform for the induction of cell response and the promotion of cartilage regeneration. Experimental results showed that the composite nanofiber/DCECM (NF/DCECM) scaffolds had stronger mechanical properties and structural stability in wet state compared with those of DCECM scaffolds. In vitro experiments demonstrated that all scaffolds had good biocompatibility, but the chondrocyte proliferation rate of the composite NF/DCECM scaffolds was higher than that of the NF scaffolds. In vitro and in vivo cartilage regeneration results indicated that the DCECM component of the composite scaffolds facilitated early maturation of the cartilage lacuna and the secretion of collagen and glycosaminoglycan. The macroscopic and histological results at 12 weeks postsurgery exhibited that the composite NF/DCECM scaffolds yielded better cartilage repair outcomes than those of the nontreated group and NF scaffolds group. Overall, the present study demonstrated that the structurally and functionally biomimetic NF/DCECM scaffold is a promising tissue engineering scaffold for cartilage regeneration and cartilage defect repair.