A FRET-based ratiometric two-photon fluorescent probe for superoxide anion detection and imaging in living cells and tissues.

The superoxide anion (O2˙-) plays a crucial role in several physiological processes and many human diseases. Developing new methods for O2˙- detection in biological systems is very important. A FRET-based two-photon (TP) fluorescent probe with a ratiometric signal, TFR-O, was developed. A naphthalene derivative based TP fluorescent group was selected as the energy donor group, and a rhodol fluorescent group was chosen as the energy acceptor; the trifluoromethanesulfonate group was chosen as the recognition moiety. After reacting with O2˙-, the recognition moiety was removed and the fluorophore was released, leading to a fluorescence intensity decrease at the wavelength of 425 nm and a significant enhancement of the fluorescence intensity at 550 nm. The fluorescence intensity ratio between 550 and 425 nm (I550/I425) varied from 0.15 to 6.72, with the O2˙- concentration increasing from 0 to 50 µM. The detection limit of the TFR-O was 83 nM. Moreover, TFR-O was applied for detecting and imaging O2˙- in cells and liver tissues.

High-Performance TPE-S Modified by a Flame-Retardant System Based on Black Phosphorus Nanosheets.

Few-layer black phosphorus nanosheets (BPs) combined with melamine cyanurate and poly(phenylene oxide) were used to prepare a flame-retardant thermoplastic elastomer based on polystyrene (TPE-S) for the first time. Compared with neat TPE-S, BP-modified TPE-S with a phosphorus content of 7.98% (TPE-S/BP-7.98) passed the UL-94 vertical burning V-0 rating, and the limiting oxygen index value increased to 24.0%. The peak heat release rate (PHRR), total heat release, and the average combustion effective heat of TPE-S/BP-7.98 were decreased by 61.8, 26.0, and 35.3%, respectively. The time to PHRR was increased from 90 s (neat TPE-S) to 170 s. Scanning electron microscopy of frozen fracture sections showed favorable compatibility and dispersibility of BPs in TPE-S. In addition, the introduction of BPs showed the most negligible effect on the mechanical properties of TPE-S compared with other flame retardants (aluminum hypophosphite and red phosphorus).

An enzyme-activated two-photon ratiometric fluorescent probe with lysosome targetability for imaging ß-glucuronidase in colon cancer cells and tissue.

Colon cancer is a malignant neoplasm with high mortality that has seriously threatened human life. Accumulating evidence reveals that the ß-glucuronidase (GLU), a lysosomal exoglycosidase enzyme, plays important roles in the pathological progression of colon cancer. Unfortunately, understanding the pathological roles of GLU remains a challenge due to the lack of effective detection methods for visualization the fluctuations of GLU in tissues. In this paper, based on hydrolysis function of GLU, an enzyme-activated ratiometric two-photon (TP) fluorescent probe (RN-GLU) was designed. RN-GLU was synthesized by introducing a glucopyranuronic acid methyl ester as the recognition group and 1, 8-naphthalimide as a TP fluorophore. In the presence of GLU, the trigger group was removed made an ICT process occurred induced enhancement of fluorescence ratio (I553 nm/I441 nm, 214-fold). Probe RN-GLU displayed low detection limit (1.2 × 10-2 µg/L) and rapid detection to GLU in vitro through a ratiometric response mode. Meanwhile, RN-GLU exhibited high selectivity for GLU and showed nearly no response to other relevant biological species. The imaging results demonstrated that RN-GLU could be applied for ratiometric monitoring of endogenous GLU levels in HCT116 cells with good lysosome targetable ability. Due to its two-photon excitation, RN-GLU could monitor GLU in colon cancer tumor tissue with good penetration ability (imaging depth of 200 µm). RN-GLU could be developed as a potential method for evaluating and confirming the functions of GLU in colon cancer diagnosis and complex biosystem.

Outstanding Bio-Tribological Performance Induced by the Synergistic Effect of 2D Diamond Nanosheet Coating and Silk Fibroin.

Due to their excellent biocompatibility, outstanding mechanical properties, high strength-to-weight ratio, and good corrosion resistance, titanium (Ti) alloys are extensively used as implant materials in artificial joints. However, Ti alloys suffer from poor wear resistance, resulting in a considerably short lifetime. In this study, we demonstrate that the chemical self-assembly of novel two-dimensional (2D) diamond nanosheet coatings on Ti alloys combined with natural silk fibroin used as a novel lubricating fluid synergistically results in excellent friction and wear performance. Linear-reciprocating sliding tests verify that the coefficient of friction and the wear rate of the diamond nanosheet coating under silk fibroin lubrication are reduced by 54 and 98%, respectively, compared to those of the uncoated Ti alloy under water lubrication. The lubricating mechanism of the newly designed system was revealed by a detailed analysis of the involved microstructural and chemical changes. The outstanding tribological behavior was attributed to the establishment of artificial joint lubrication induced by the cross binding between the diamond nanosheets and silk fibroin. Additionally, excellent biocompatibility of the lubricating system was verified by cell viability, which altogether paves the way for the application of diamond coatings in artificial Ti joint implants.

"Gingival Soft Tissue Integrative" Lithium Disilicate Glass-Ceramics with High Mechanical Properties and Sustained-Release Lithium Ions.

Due to their good mechanical performances and high biocompatibility, all-ceramic materials are widely applied in clinics, especially in orthopedic and dental areas. However, the "hard" property negatively affects its integration with "soft" tissue, which greatly limits its application in soft tissue-related areas. For example, dental implant all-ceramic abutments should be well integrated with the surrounding gingival soft tissue to prevent the invasion of bacteria. Mimicking the gingival soft tissue and dentine integration progress, we applied the modified ion-exchange technology to "activate" the biological capacity of lithium disilicate glass-ceramics, via introducing OH- to weaken the stability of Si-O bonds and release lithium ions to promote multi-reparative functions of gingival fibroblasts. The underlying mechanism was found to be closely related to the activation of mitochondrial activity and oxidative phosphorylation. In addition, during the ion-exchange process, the larger radius sodium ions (Na+) replaced the smaller radius lithium ions (Li+), so that the residual compressive stress was applied to the glass-ceramics surface to counteract the tensile stress, thus improving the mechanical properties. This successful case in simultaneous improvement of mechanical properties and biological activities proves the feasibility of developing "soft tissue integrative" all-ceramic materials with high mechanical properties. It proposes a new strategy to develop advanced bioactive and high strength all-ceramic materials by modified ion-exchange, which can pave the way for the extended applications of such all-ceramic materials in soft tissue-related areas.

Enhanced thermal transportation across an electrostatic self-assembly of black phosphorene and boron nitride nanosheets in flexible composite films.

For effective heat dissipation in portable electronics, there is a great demand for lightweight and flexible films with superior thermal transport properties. Despite extensive efforts, enhancing the intrinsic low thermal conductivity of polymers while simultaneously maintaining their flexibility is difficult to achieve due to the dilemma of quarrying appropriate filler loading. Herein, a cellulose nanofiber-based film with high in-plane thermal conductivity up to 72.53 W m-1 K-1 was obtained by harnessing the advantage of functionalized boron nitride nanosheets (f-BNNS) and black phosphorene (BP) via the vacuum filtration process. Besides, our unique design based on the electrostatic coupling of black phosphorene and functionalized boron nitride nanosheets significantly reduced the interfacial thermal resistance of the composite films. This work offers new insights into establishing a facile, yet efficient approach to preparing high thermal conductive heat spreaders.

Constructing a three-dimensional nano-crystalline diamond network within polymer composites for enhanced thermal conductivity.

In order to meet the requirement of thermal performance with the rapid development of high-performance electronic devices, constructing a three-dimensional thermal transport skeleton is an effective method for enhancing the thermal conductivity of polymer composites. In this work, a three-dimensional porous diamond framework was prepared by depositing nano-crystalline diamond on alumina foam which was impregnated with epoxy to obtain a nano-crystalline diamond@alumina foam/epoxy composite. The epoxy composite with nano-crystalline diamond@alumina foam demonstrated a thermal conductivity of 2.21 W m-1 K-1, which was increased by 1063% in comparison with pure epoxy. The thermal conductivity of the epoxy composite measured under various conditions and heat transport applications demonstrates that it possesses excellent thermal transportation and stability properties. This work provides a new idea to significantly enhance the thermal transportation properties of epoxy composites in the application of advanced packaging materials.

Enhanced Thermal Conductivity of Polymer Composite by Adding Fishbone-like Silicon Carbide.

The rapid development of chip technology has all put forward higher requirements for highly thermally conductive materials. In this work, a new type of material of Fishbone-like silicon carbide (SiC) material was used as the filler in a polyvinylidene fluoride (PVDF) matrix. The silicon carbide/polyvinylidene fluoride (SiC/PVDF) composites were successfully prepared with different loading by a simple mixing method. The thermal conductivity of SiC/PVDF composite reached 0.92 W m-1 K-1, which is 470% higher than that of pure polymer. The results show that using the filler with a new structure to construct thermal conductivity networks is an effective way to improve the thermal conductivity of PVDF. This work provides a new idea for the further application in the field of electronic packaging.