Boron nitride-based nanocomposite hydrogels: preparation, properties and applications

Boron nitride microfiber reinforced polyacrylic acid hydrogels with excellent self-adhesion, fast pH response, and strain sensitivity

Hydrogels are widely utilized in the sensor field, but their inadequate adhesion presents a significant obstacle. Herein, a new multifunctional BNMFs/PAA composite hydrogel was prepared via the incorporation of one-dimensional porous boron nitride microfibers (BNMFs) and polyacrylic acid (PAA) hydrogels. BNMFs, as a reinforcing filler, play a very important role in enhancing the properties of the composite hydrogels. In particular, the porous micrometer structure plays a unique role in improving the adhesion properties of PAA hydrogels. The steric hindrance and the rich hydroxyl functional groups coming from BNMFs are key factors for the excellent adhesion of the composite hydrogels. The composite hydrogels show strong adhesion to various substrate materials. For iron plates and biological tissues, the adhesion energy can reach 1377 J m-2 and 317 J m-2, respectively. In addition, the developed BNMFs/PAA composite hydrogels exhibit excellent mechanical properties. The fracture strain of the composite hydrogels is increased by 2.4 times compared to pure PAA hydrogels. The hydrogen bonds formed between BNMFs and PAA are conducive to the mechanical properties of the BNMFs/PAA composite hydrogels. Meanwhile, BNMFs as fillers play a role in carrying and dissipating force. Furthermore, the BNMFs/PAA composite hydrogels have excellent strain and pH response characteristics. This is because the crosslinking network of the composite hydrogels becomes loose after the addition of BNMFs, resulting in rapid ion transport pathways. Therefore, the developed BNMFs/PAA composite hydrogels will have broad application prospects in the fields of motion monitoring, intelligent skin and biological adhesives.

Thermal Transport Phenomena in PEGDA-Based Nanocomposite Hydrogels Using Atomistic and Experimental Techniques

Poly(ethylene glycol) diacrylate (PEGDA) hydrogel is a very peculiar, fascinating material with good chemical stability and biocompatibility. However, the poor thermal transport phenomenon in PEGDA, limits its performance in cartilage replacement and developing therapies for treating burns. In this article, a combined experimental and atomistic approach was adopted to investigate the thermal transport phenomena in PEGDA hydrogel with different weight concentrations of boron nitride nanoplatelets as a function of water content. The incorporation of boron nitride nanofillers helps in enhancing the thermal conductivity of PEGDA hydrogels, and the reinforcement effect was more dominating at lower water content. Experimental investigation was complemented with molecular dynamics-based studies to capture the effect of defective (bicrystalline) boron nitride nanosheets on the interfacial thermal conductance in PEGDA hydrogels. It can be concluded from the simulations that defective nanosheets are superior reinforcement for enhancing the thermal transport in PEGDA hydrogels, and this is independent of the water content. These biocompatible boron nitride nanoparticle (BNNP)-incorporated PEGDA hydrogels with enhanced thermal conductivity are promising materials in addressing locally overheating tissues such as cartilage replacement. They may have comprehensive utility for biomedical applications such as tissue engineering, drug delivery, biosensors, and burn therapy.

Dispersing boron nitride nanosheets with carboxymethylated cellulose nanofibrils for strong and thermally conductive nanocomposite films with improved water-resistance

BNNS (boron nitride nanosheets)-CNF (cellulose nanofibrils) nanocomposite films have attracted increasing attention for advanced thermal management applications. However, the nanocomposite films reported so far generally suffer from unsatisfactory overall performance, especially for thermal conductivity and tensile strength. In this work, a nanocomposite film with excellent overall performance was prepared by using CCNF1.2 (carboxymethylated CNF with 1.2 mmol·g-1 carboxyl content) simultaneously as effective dispersant and reinforcement matrix for BNNS. The high aspect ratio of CCNF1.2 is primarily responsible for its excellent dispersion capability for BNNS, which provides strong steric hindrance repulsion force. Meanwhile, CCNF1.2 manifests the strongest hydrophobic-hydrophobic interactions with BNNS, and its carboxyl groups completely interact with the -OH of BNNS by hydrogen bonding. As a result, the BNNS-CCNF1.2 film (50 wt% BNNS) exhibits compacted aligned structure and superior comprehensive performance (125.0 MPa tensile strength, 17.3 W·m-1·K-1 in-plane thermal conductivity, and improved water resistance). This work demonstrates the effectiveness of CCNF in improving the overall performance of BNNS-CNF films and paves the way for their practical application in the advanced thermal management of next-generation electronic devices.

Stimuli-Responsive Boron-Based Materials in Drug Delivery

Drug delivery systems, which use components at the nanoscale level as diagnostic tools or to release therapeutic drugs to particular target areas in a regulated manner, are a fast-evolving field of science. The active pharmaceutical substance can be released via the drug delivery system to produce the desired therapeutic effect. The poor bioavailability and irregular plasma drug levels of conventional drug delivery systems (tablets, capsules, syrups, etc.) prevent them from achieving sustained delivery. The entire therapy process may be ineffective without a reliable delivery system. To achieve optimal safety and effectiveness, the drug must also be administered at a precision-controlled rate and the targeted spot. The issues with traditional drug delivery are overcome by the development of stimuli-responsive controlled drug release. Over the past decades, regulated drug delivery has evolved considerably, progressing from large- and nanoscale to smart-controlled drug delivery for several diseases. The current review provides an updated overview of recent developments in the field of stimuli-responsive boron-based materials in drug delivery for various diseases. Boron-containing compounds such as boron nitride, boronic acid, and boron dipyrromethene have been developed as a moving field of research in drug delivery. Due to their ability to achieve precise control over drug release through the response to particular stimuli (pH, light, glutathione, glucose or temperature), stimuli-responsive nanoscale drug delivery systems are attracting a lot of attention. The potential of developing their capabilities to a wide range of nanoscale systems, such as nanoparticles, nanosheets/nanospheres, nanotubes, nanocarriers, microneedles, nanocapsules, hydrogel, nanoassembly, etc., is also addressed and examined. This review also provides overall design principles to include stimuli-responsive boron nanomaterial-based drug delivery systems, which might inspire new concepts and applications.

Multifunctional Photoactive Hydrogels for Wound Healing Acceleration

Light is an attractive tool that has a profound impact on modern medicine. Particularly, light-based photothermal therapy (PTT) and photodynamic therapy (PDT) show great application prospects in the prevention of wound infection and promoting wound healing. In addition, hydrogels have shown attractive advantages in the field of wound dressings due to their excellent biochemical effects. Therefore, multifunctional photoresponsive hydrogels (MPRHs) that integrate the advantages of light and hydrogels are increasingly used in biomedicine, especially in the field of wound repair. However, a comprehensive review of MPRHs for wound regeneration is still lacking. This review first focuses on various types of MPRHs prepared by diverse photosensitizers, photothermal agents (PHTAs) including transition metal sulfide/oxides nanomaterials, metal nanostructure-based PHTAs, carbon-based PHTAs, conjugated polymer or complex-based PHTAs, and/or photodynamic agents (PHDAs) such as ZnO-based, black-phosphorus-based, TiO₂-based, and small organic molecule-based PHDAs. We also then discuss how PTT, PDT, and photothermal/photodynamic synergistic therapy can modulate the microenvironments of bacteria to inhibit infection. Overall, multifunctional hydrogels with both therapeutic and tissue regeneration capabilities have been discussed and existing challenges, as well as future research directions in the field of MPRHs and their application in wound management are argued.

Advances in Studies of Boron Nitride Nanosheets and Nanocomposites for Thermal Transport and Related Applications

Hexagonal boron nitride (h-BN) and exfoliated nanosheets (BNNs) not only resemble their carbon counterparts graphite and graphene nanosheets in structural configurations and many excellent materials characteristics, especially the ultra-high thermal conductivity, but also offer other unique properties such as being electrically insulating and extreme chemical stability and oxidation resistance even at elevated temperatures. In fact, BNNs as a special class of 2-D nanomaterials have been widely pursued for technological applications that are beyond the reach of their carbon counterparts. Highlighted in this article are significant recent advances in the development of more effective and efficient exfoliation techniques for high-quality BNNs, the understanding of their characteristic properties, and the use of BNNs in polymeric nanocomposites for thermally conductive yet electrically insulating materials and systems. Major challenges and opportunities for further advances in the relevant research field are also discussed.