Liquid Metal-Assisted High-Efficiency Exfoliation of Boron Nitride for Electrically Insulating Heat-Spreader Film.

Boron nitride nanosheets (BNNSs) are regarded as promising two-dimensional materials in thermally conductive yet electrically insulating applications. Attributed to the strong interlayer "lip-lip" interactions in bulk hexagonal boron nitride (h-BN), high-efficiency exfoliation and scalable fabrication of BNNSs via the top-down strategies remain formidable challenges. Herein, an interesting observation is manifested that gallium-based liquid metal (LM) forming robust coordination interactions with h-BN helps reduce the lip-lip interlayer interactions and thus facilitates successful exfoliation under intense shearing force. For example, employing the ball-milling technique, the BNNS yield can increase to 41.21% with the assistance of LM at only 2 h milling time. Its exfoliation efficiency (yield/time) reaches as high as 26.72%/h, more than 2-fold that of other previously reported methods, including sonication and other ball-milling methods. Moreover, the exfoliated BNNSs are still found to be highly electrically insulating with a band gap of 4.65 eV, showing prospective potential in thermally conductive yet electrical insulating applications. As a proof of concept, a microwave-transparent heat spreader (cellulose nanofiber/BNNSs) is fabricated and verified for applications in high-frequency thermal-management fields.

Oscillating Magnetic Field Regulates Cell Adherence and Endothelialization Based on Magnetic Nanoparticle-Modified Bacterial Cellulose.

Despite the widely explored biomaterial scaffolds in vascular tissue engineering applications lately, no ideal platform has been provided for small diameter synthetic vascular grafts mainly due to the thrombosis issue. Endothelium is the only known completely non-thrombogenic material; so, functional endothelialization onto vascular biomaterials is critical in maintaining the patency of vascular networks. Bacterial cellulose (BC) is a natural biomaterial with superior biocompatibility and appropriate hydrophilicity as potential vascular grafts. In previous studies, surface modification of active peptides such as Arg-Gly-Asp (RGD) sequences onto biomaterials has been proven to achieve accelerated and selective endothelial cell (EC) adhesion. In our study, we demonstrated a new strategy to remotely regulate the adhesion of endothelial cells based on an oscillating magnetic field and achieve successful endothelialization on the modified BC membranes. In details, we synthesized bacterial cellulose (BC), magnetic BC (MBC), and RGD peptide-grafted magnetic BC (RMBC), modified with the HOOC-PEG-COOH-coated iron oxide nanoparticles (PEG-IONs). The endothelial cells were cultured on the three materials under different frequencies of an oscillating magnetic field, including "stationary" (0 Hz), "slow" (0.1 Hz), and "fast" (2 Hz) groups. Compared to BC and MBC membranes, the cells on RMBC membranes generally show better adhesion and proliferation. Meanwhile, the "slow" frequency of a magnetic field promotes this phenomenon on RMBC and achieves endothelialization after culture for 4 days, whereas "fast" inhibits the cellular attachment. Overall, we demonstrate a non-invasive and convenient method to regulate the endothelialization process, with promising applications in vascular tissue engineering.

Visible-light driven degradation of tetracycline hydrochloride and 2,4-dichlorophenol by film-like N-carbon@N-ZnO catalyst with three-dimensional interconnected nanofibrous structure.

The emergence of more and more persistent organic molecules as contaminants in water simulates research towards the development of more advanced technologies, among which photocatalysis is a feasible choice. However, it is still challenging to design a photocatalyst that fulfills all the requirements for industrial application, i.e., active under visible-light irradiation, shape with handy convenience, highly uniform distribution of active sites, substrate with excellent electronic properties, etc. In this study, we report an attempt to solve these issues at once by designing a film-like photocatalyst with uniform distribution of nitrogen-doped ZnO nanoparticles along nitrogen-doped carbon ultrafine nanofibers with three-dimensional interconnected structure. Under visible-light irradiation, the product exhibited remarkable reactivity for the degradation of two model pollutants tetracycline hydrochloride and 2,4-dichlorophenol within 100 min. The cyclic experiments demonstrated only a slight loss (ca. 5 %) of reactivity after five consecutive photocatalytic reactions. We also investigated the detailed relationship between the structural features and the superior properties of this product, as well as the degradation mechanisms. The convenient shape of the product with excellent performances for the treatment of real polluted water increases its suitability for larger scale application. Our work provides a rational design of photocatalysts for environmental remediation.

In situ structural modification of bacterial cellulose by sodium fluoride.

Bacterial cellulose could be produced in any shape due to its high moldability during fermentation process, but structural modification often requires the inclusion of templates or other polymeric materials. In this work, sodium fluoride was introduced in bacterial cultivation process to modify the microstructure. Under static conditions, the final pH, BC yield, morphology, structure and properties of the obtained BC were investigated. Because of the stronger hydrogen bonding formed between fluoride and hydroxyl groups, majority of cellulose chains were no longer restricted and could not aggregate into wider cellulose ribbons. After the removal of fluoride, the cellulose chains undergo random rearrangement into bulky ribbon due to inter-fibril hydrogen bonding of hydroxyl groups, of which the crystallinity can remain as high as ∼60 % in dry state. The treatment of sodium fluoride led to different mechanical properties. The modification of BC structure can be easily achieved in situ by controlling NaF concentrations.

A Dual-Crosslinked and Anisotropic Regenerated Cellulose/Boron Nitride Nanosheets Film With High Thermal Conductivity, Mechanical Strength, and Toughness.

The highly thermo-conductive but electrically insulating film, with desirable mechanical performances, is extremely demanded for thermal management of portable and wearable electronics. The integration of boron nitride nanosheets (BNNSs) with regenerated cellulose (RC) is a sustainable strategy to satisfy these requirements, while its practical application is still restricted by the brittle fracture and loss of toughness of the composite films especially at the high BNNS addition. Herein, a dual-crosslinked strategy accompanied with uniaxial pre-stretching treatment was introduced to engineer the artificial RC/BNNS film, in which partial chemical bonding interactions enable the effective interfiber slippage and prevent any mechanical fracture, while non-covalent hydrogen bonding interactions serve as the sacrifice bonds to dissipate the stress energy, resulting in a simultaneous high mechanical strength (103.4 MPa) and toughness (10.2 MJ/m3) at the BNNS content of 45 wt%. More importantly, attributed to the highly anisotropic configuration of BNNS, the RC/BNNS composite film also behaves as an extraordinary in-plane thermal conductivity of 15.2 W/m·K. Along with additional favorable water resistance and bending tolerance, this tactfully engineered film ensures promised applications for heat dissipation in powerful electronic devices.

Three-dimensional bacterial cellulose/polydopamine/TiO2 nanocomposite membrane with enhanced adsorption and photocatalytic degradation for dyes under ultraviolet-visible irradiation.

Cleaner production of photocatalyst with efficient property and stable reusability is of great importance for the elimination of organic pollutants in wastewater. Herein, we present a bacterial cellulose (BC)-based nanocomposite membrane with enhanced adsorption and photocatalytic degradation for dyes under UV radiation, by using BC nanofibers as a three-dimensional soft template, coated with the polydoamine (PDA) as a functional layer and a protective agent for immobilization of titanium dioxide (TiO2) nanoparticles. Compared with commercial P25, the as-prepared BC/PDA/TiO2 composite presented higher adsorption capacity for methyl orange, Rhodamine B and methylene blue, and the photocatalytic properties within 30 min after irradiation were further improved. BC/PDA/TiO2 also showed good stability, proved by the 5.5% reduction in photocatalytic capability after five cyclic tests. We expect our design could provide a facile and green approach with excellent photo-degradation performance for organic pollutants, providing further applications for photocatalysis and wastewater treatment.

Bacterial cellulose/attapulgite magnetic composites as an efficient adsorbent for heavy metal ions and dye treatment.

In recent decades, increased industrial activities have led to the release of various pollutants, such as toxic heavy metals, inorganic anions, and organics. It is imperative but challenging to develop an eco-friendly treatment technology with easy operation, low cost, and high efficiency. Here, we describe a design of magnetic purifier, which has biomass-based structure by blending attapulgite/chitosan (ATP/CS) composite with bacterial cellulose nanofibrils (BCNs). Compared to similar materials reported previously, our product exhibited efficient adsorption capacities towards various metal ions including Pb2+, Cu2+, and Cr6+, and anionic organic dyes including Congo red. The adsorption process could be well fitted by Langmuir isotherm and pseudo-second order equation. Additionally, the adsorption capacity only decreased less than 8% after five adsorption-desorption cycles. We expect our design will inspire more efforts to build a multifunctional water purifier with simple operation, and hopefully effectively remove pollutants from wastewater in future practical applications.

Axial-to-Central Chirality Transfer for Construction of Quaternary Stereocenters via Dearomatization of BINOLs.

All-carbon quaternary stereocenters are versatile building blocks, and their asymmetric construction has attracted much attention. Herein, we disclose an axial-to-central chirality transfer strategy for the synthesis of chiral quaternary stereocenters via dearomatization of (S)-BINOLs. The reaction proceeded smoothly with a wide range of propargyl carbonates to afford chiral spiro-compounds in high yields with excellent enantioselectivities. In addition, the strategy was extended to kinetic resolution of rac-BINOLs albeit with moderate s value.

Macroporous bacterial cellulose grafted by oligopeptides induces biomimetic mineralization via interfacial wettability.

Bacterial cellulose (BC) has a role in tissue repair and regenerative medicine, which has already attracted tremendous interest from researchers, especially those working in the field of hybrid materials. Herein, we designed BC-based macroporous functional materials by dialdehyde bacterial cellulose (DBC) cross-linking with oligopeptides under mild reactive conditions. The interfacial properties of the surface modified BC were examined by biomimetic mineralization. The results showed that a macroporous structure was achieved by using oligopeptides as chemical cross-linking agents with an interconnected macroporosity ranging from 20 µm to 80 µm. Their mechanical properties were barely altered compared to the pristine BC. Their enhanced surface charges stemmed from the carboxyl groups of the oligopeptides engaging in reactions with amine and aldehyde groups. The oligopeptides cross-linked DBC showed a faster initial induction towards minerals via interfacial wettability resulting in promotion of mineralization, the hybrid materials had excellent biocompatibility relative to the pristine BC. These findings are vital to the development of other biopolymers with essential macroporous structures as well as improved interfacial wettability, which enables their possible uses in tissue repair and regenerative medicine.

Magnetic Janus particles as a multifunctional drug delivery system for paclitaxel in efficient cancer treatment.

Paclitaxel is broad-spectrum anticancer drug which has been widely used in clinic. However, traditional drug delivery often suffers from the scarcity of resources and systemic toxic side effects caused by the localization to non-tumor areas, rendering cancer treatment extremely challenging. To address this problem, we developed a novel multifunctional drug delivery system of a poly(lactic-co-glycolic acid) (PLGA) drug-loaded magnetic Janus particles (DMJPs) using electrohydrodynamic (EDH) co-jetting. The DMJPs were loaded with three compartments each with distinct function, i.e. paclitaxel for killing cancer cell, Fe3O4 nanoparticles for target location, and rhodamine B for fluorescence tracing, respectively. The Janus structure of the DMJPs, as demonstrated by the loaded nano-quantum dots CdS/ZnS and CdSe/ZnS in different compartments, enhanced not only the drug loading and encapsulation efficiency but also the cumulative release rate of the loaded drugs from DMJPs in different media. More importantly, DMJPs exhibited specific and high toxicity only to human breast cancer cells (MDA-MB-231), but not to mouse embryonic fibroblasts (NIH-3 T3). Consistently, DMJPs induced the higher lethal effect on cancer cells than paclitaxel suspension of high concentrations. Under guidance of external magnetic field, DMJPs can readily target and accumulate on and inside cancer cells for cell elimination. The specific targetability, selectivity, and toxicity of DMJPs on cancer cells would greatly avoid any potential side effects and reduce the overdose of drugs for conventional drug delivery. This work hopefully provides a new drug delivery system for the development of anticancer drug systems for clinical and precision medicine treatment.

Neurogenic differentiation of adipose derived stem cells on graphene-based mat.

Adipose derived stem cells (ADSCs) have been proved as an abundant and accessible cell source with the ability to differentiate into neuron-like cells. However, the low differentiation efficiency puts forward an important challenge to practical applications in clinic. Considering of the good biocompatibility of graphene-based materials and the potential interaction between graphene and cells mentioned in previous studies, herein, we investigated the effect of graphene oxide (GO) and reduced graphene oxide (rGO) mats on neurogenic differentiation of the ADSCs. We demonstrated the excellent capabilities of graphene-based mats, especially GO to support the neural differentiation of ADSCs. By comparing the observation under an optical microscope and fluorescence microscope, the conversion rate of neuron-like cells reached about 90%. We consider that GO mat is better for promoting the differentiation of ADSCs into neuron-like cells, which compared to rGO based platforms. Meanwhile, we made an analysis of the mechanism by which graphene induced the differentiation of ADSCs to neuron-like cells. The data obtained here highlight the effect of GO mat on neurogenic differentiation of ADSCs and implicate the potential of graphene-based materials in application of neural tissue engineering for the limited self-repair capability of nerve cells.

Complete genome sequence of the cellulose-producing strain Komagataeibacter nataicola RZS01.

Komagataeibacter nataicola is an acetic acid bacterium (AAB) that can produce abundant bacterial cellulose and tolerate high concentrations of acetic acid. To globally understand its fermentation characteristics, we present a high-quality complete genome sequence of K. nataicola RZS01. The genome consists of a 3,485,191-bp chromosome and 6 plasmids, which encode 3,514 proteins and bear three cellulose synthase operons. Phylogenetic analysis at the genome level provides convincing evidence of the evolutionary position of K. nataicola with respect to related taxa. Genomic comparisons with other AAB revealed that RZS01 shares 36.1%~75.1% of sequence similarity with other AAB. The sequence data was also used for metabolic analysis of biotechnological substrates. Analysis of the resistance to acetic acid at the genomic level indicated a synergistic mechanism responsible for acetic acid tolerance. The genomic data provide a viable platform that can be used to understand and manipulate the phenotype of K. nataicola RZS01 to further improve bacterial cellulose production.