Bacterial cellulose-based hydrogel with regulated rehydration and enhanced antibacterial activity for wound healing.

Bacterial cellulose (BC) hydrogels are promising medical biomaterials that have been widely used for tissue repair, wound healing and cartilage engineering. However, the high water content of BC hydrogels increases the difficulty of storage and transportation. Moreover, they will lose their original hydrogel structure after dehydration, which severely limits their practical applications. Introducing the bio-based polyelectrolytes is expected to solve this problem. Here, we modified BC and combined it with quaternized chitosan (QCS) via a chemical reaction to obtain a dehydrated dialdehyde bacterial cellulose/quaternized chitosan (DBC/QCS) hydrogel with repeated swelling behavior and good antibacterial properties. The hydrogel can recover the initial state on the macro scale with a swelling ratio over 1000 % and possesses excellent antimicrobial properties against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) with a killing rate of 80.8 % and 81.3 %, respectively. In addition, the hydrogel has excellent biocompatibility, which is conducive to the stretching of L929 cells. After 14 d of in vivo wound modeling in rats, it was found that the hydrogel loaded with pirfenidone (PFD) could promote collagen deposition and accelerate wound healing with scar prevention. This rehydratable hydrogel can be stored and transported under dry conditions, which is promising for practical applications.

Bacterial cellulose-based hydrogel with antibacterial activity and vascularization for wound healing.

Skin wounds need an appropriate wound dressing to help prevent bacterial infection and accelerate wound closure. Bacterial cellulose (BC) with a three-dimensional (3D) network structure is an important commercial dressing. However, how to effectively load antibacterial agents and balance the antibacterial activity is a lingering issue. Herein, this study aims to develop a functional BC hydrogel containing silver-loaded zeolitic imidazolate framework-8 (ZIF-8) antibacterial agent. The tensile strength of the prepared biopolymer dressing is >1 MPa, the swelling property is over 3000 %, the temperature can reach 50 °C in 5 min with near-infrared (NIR) and the release of Ag+ and Zn2+ is stable. In vitro investigation shows that the hydrogel displays enhanced antibacterial activity, and the bacteria survival ratios are only 0.85 % and 0.39 % against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). In vitro cell experiments present that BC/polydopamine/ZIF-8/Ag (BC/PDA/ZIF-8/Ag) shows satisfactory biocompatibility and promising angiogenic ability. In vivo study, the full-thickness skin defect on rats demonstrates remarkably wound healing ability and accelerated skin re-epithelialization. This work presents a competitive functional dressing with effective antibacterial properties and accelerative angiogenesis activities for wound repair.

Self-Stretchable Fiber Liquid Sensors Made with Bacterial Cellulose/Carbon Nanotubes for Smart Diapers.

Liquid sensors for detecting water and body fluids are crucial in daily water usage and health monitoring, but it is challenging to combine sensing performance with high tensile deformation and multifunctional applications. Here, a substrate-free, self-stretchable bacterial cellulose (BC)/carbon nanotube (CNT) helical fiber liquid sensor was prepared by the solution spinning and coiling process using BC as the water-sensitive matrix and CNTs as the active sensing materials. The BC/CNT (BCT) fiber sensor has a high stretch ratio of more than 1000% and a rapid response for a current change rate of 104% within 1 s, which is almost unaffected under washing and various stretching or knotting deformations. By combination of the BCT fiber, we can design smart diapers or water level detectors, which rapidly monitor the status of smart diapers or water level, and the monitoring result can be transferred on time through an alarm device or smartphone. In short, the scalable and continuous preparation of the self-stretchable BCT helical fiber will provide a capacious platform for the development of a wearable sensor applied in daily life (such as smart diapers, water level detection, etc.).

Anti-Fouling, Adhesive Polyzwitterionic Hydrogel Electrodes Toughened Using a Tannic Acid Nanoflower.

Conductive polyzwitterionic hydrogels with good adhesion properties show potential prospect in implantable electrodes and electronic devices. Adhesive property of polyzwitterionic hydrogels in humid environments can be improved by the introduction of catechol groups. However, common catechol modifiers can usually quench free radicals, resulting in a contradiction between long-term tissue adhesion and hydrogel toughness. By adding tannic acid (TA) to the dispersion of clay nanosheets and nanofibers, we designed TA-coated nanoflowers and nanofibers as the reinforcing phase to prepare polyzwitterionic hydrogels with adhesion properties. The hydrogel combines the mussel-like and zwitterionic co-adhesive mechanism to maintain long-term adhesion in underwater environments. In particular, the noncovalent cross-linking provided by the nanoflower structure effectively compensates for the defects caused by free-radical quenching so that the hydrogel obtained a high stretchability of over 2900% and a toughness of 1.16 J/m3. The hydrogel also has excellent anti-biofouling property and shows resistance to bacteria and cells. In addition, the hydrogel possesses a low modulus (<10 kPa) and ionic conductivity (0.25 S/m), making it an ideal material for the preparation of implantable electrodes.

Bacterial cellulose reinforced chitosan-based hydrogel with highly efficient self-healing and enhanced antibacterial activity for wound healing.

Biocompatible hydrogels with versatile functions are highly desired for demanding the complicated tissue issues, including irregular site and motional wound. Herein, a bio-based hydrogel with multifunctional properties is designed based on quaternized chitosan and dialdehyde bacterial cellulose. As a functional wound dressing, the hydrogel shows rapid self-healing performance and injectable behaviors due to dynamic Schiff-base interactions and presents superior antibacterial activity against E. coli (gram-negative) and S. aureus (gram-positive). The constructed 3D hydrogel also exhibits proper compressive property, desired water retention capacity. To be mentioned, the hydrogel could mimic the structure of natural extracellular matrix (ECM) in the presence of bacterial cellulose nanofibers. Thus, the biopolymer-based hydrogel shows good biocompatibility in terms of cell proliferation and cell spreading. The prepared chitosan-based hydrogel with self-healing, antibacterial, and low cost will become a promising biomaterial for wound healing.