A PVDF-based colorimetric sensor array for noninvasive detection of multiple disease-related volatile organic compounds.

Detection of human-generated volatile organic compounds (VOCs) is a new pathway for assessing health. Herein, a polyvinylidene fluoride (PVDF)-based colorimetric sensor array was designed for detecting disease-related VOCs (DVOCs) within 15 min, using a complex of Cu metal-organic framework, graphene aerogel, and dyes as response materials. Fingermaps derived from 28 DVOCs were obtained for further data processing. Pattern recognition was successfully employed in the correct discrimination of 28 DVOCs in low (10 µM), medium (100 µM), and high (300 µM) concentrations. Importantly, the sensor array also presented excellent discrimination ability and application potential when detecting VOCs produced by human cancer and normal cells. In general, VOC acquisition is noninvasive and harmless, and the PVDF-based sensor arrays are simple and visual. Such advantages expand their further application potential.

Improvement of Lignocellulolytic Enzyme Production Mediated by Calcium Signaling in Bacillus subtilis Z2 under Graphene Oxide Stress.

An increase in exoenzyme production can be enhanced by environmental stresses such as graphene oxide (GO) stress, but the link between the two events is still unclear. In this work, the effect of GO as an environmental stress factor on exoenzyme (lignocellulolytic enzyme, amylase, peptidase, and protease) biosynthesis was investigated in Bacillus subtilis Z2, and a plausible mechanism by which cytosolic Ca2+ regulates lignocellulolytic enzyme production in B. subtilis Z2 subjected to GO stress was proposed. The filter paper-hydrolyzing (FPase [representing total cellulase]), carboxymethylcellulase (CMCase [representing endoglucanase]), and ß-glucosidase activities and extracellular protein concentration of the wild-type strain under 10 µg/mL GO stress were 1.37-, 1.64-, 1.24-, and 1.16-fold those of the control (without GO stress), respectively. Correspondingly, the transcription levels of lignocellulolytic enzyme genes, cytosolic Ca2+ level, and biomass concentration of B. subtilis were all increased. With lignocellulolytic enzyme from B. subtilis used to hydrolyze alkali-pretreated rice straw, the released reducing sugar concentration reached 265.53 mg/g, and the removal rates of cellulose, hemicellulose, and lignin were 52.4%, 30.1%, and 7.5%, respectively. Furthermore, transcriptome data revealed that intracellular Ca2+ homeostasis played a key role in regulating the levels of gene transcription related to the synthesis of lignocellulolytic enzymes and exoenzymes. Finally, the use of Ca2+ inhibitors (LaCl3 and EDTA) and deletion of spcF (a calmodulin-like protein gene) further demonstrated that the overexpression of those genes was regulated via calcium signaling in B. subtilis subjected to GO stress. IMPORTANCE To effectively convert lignocellulose into fermentable sugars, high lignocellulolytic enzyme loading is needed. Graphene oxide (GO) has been shown to promote exoenzyme (lignocellulolytic enzyme, amylase, peptidase, and protease) production in some microorganisms; however, the regulatory mechanism of the biosynthesis of lignocellulolytic enzymes under GO stress remains unclear. In this work, the lignocellulolytic enzyme production of B. subtilis under GO stress was investigated, and the potential mechanism by which B. subtilis enhanced lignocellulolytic enzyme production through the calcium signaling pathway under GO stress was proposed. This work revealed the role of calcium signaling in the production of enzymes under external environmental stress and provided a direction to facilitate lignocellulolytic enzyme production by B. subtilis.

Preparation of bimetal-polydopamine organic frameworks with core-shell structure and their application in HER2 detection.

Human epidermal growth factor receptor 2 (HER2) is one of the specific markers of breast cancer, which is of great significance to the early diagnosis and prognosis of breast cancer. Here, a fluorescence biosensor was established to detect HER2 based on the fluorescence resonance energy transfer (FRET) and photoinduced electron transfer (PET) occurring between the bimetal-polydopamine organic framework with core-shell structure Au@PDA@UiO-66 and the Cy5 fluorophore in HER2-Cy5-Apt. Au@PDA@UiO-66 owns high-efficiency fluorescence quenching ability due to its large specific surface area and strong adsorption of single-stranded DNA. When the target appears, the fluorescence recovery space mediated by the target is large, so the proposed biosensor has better sensitivity in theory. Under optimized conditions, the proposed fluorescent biosensor can detect HER2 in a range of 0.005 ng mL-1 to 15 ng mL-1, with an actual detection limit as low as 0.005 ng mL-1. Corresponding selective experiments, reproducible experiments, and spiked experiments performed well, showing its great potential in HER2 detection.

Simultaneous detection of tyrosine and uric acid in sweat using CoWO4@CNT with a hydrogel modified electrochemical biosensor.

The levels of uric acid (UA) and tyrosine (Tyr) in sweat reflect a person's overall health. However, simultaneously identifying several components in sweat remains challenging. Here, we achieve simultaneous detection of UA and Tyr by synthesizing CoWO4@CNT in a single step using a hydrothermal method. CoWO4's high catalytic efficacy and large CNT reaction area allow the detection of 1-1000 µM UA (LOD = 0.14 µM) and 5-1000 µM Tyr (LOD = 4.2 µM). To increase sweat collection, we developed a polydopamine-polyacrylamide (PDA-PAM) hydrogel with a sweat absorption rate of up to 226%. Finally, by monitoring sweat at various times of day, our sensors can discriminate between UA and Tyr in real sweat, and the results are consistent with the individuals' activity levels. Overall, the effective electrocatalytically active materials and PDA-PAM hydrogel improve the detection of UA and Tyr. The remarkable performance of CoWO4@CNT in real samples shows that it has the potential to improve health detection and real-time sweat analysis.

Simultaneous detection of dihydroxybenzene isomers in the environment by a free-standing flexible ZnCo2O4 nanoplate arrays/carbon fiber cloth electrode.

The simultaneous determination of dihydroxybenzene isomers is highly valuable for early environmental monitoring, but it is still a challenge. In this work, a free-standing flexible electrode was prepared for the simultaneous detection of hydroquinone (HQ), catechol (CC), and resorcinol (RC). The bimetallic zinc/cobalt zeolitic imidazolate frameworks nanoplate arrays (Zn/Co-ZIF NPAs) grown in situ on the carbon fiber cloth (CFC) was fabricated by a facile static synthesis method, and the porous ternary ZnCo2O4 NPAs derived from Zn/Co-ZIF NPAs were formed by annealing in air. Due to the fast electron transmission, abundant active sites and excellent electrocatalytic properties with enzyme-like kinetic performance of the ZnCo2O4/CFC electrode, the as-proposed sensor showed a wilder linear response (2-500 µM), a lower detection limits (0.03 µM HQ, 0.06 µM CC and 0.15 µM RC) and a higher sensitivity (23.58 µA µM-1 cm-2 HQ, 17.72 µA µM-1 cm-2 CC, and 15.18 µA µM-1 cm-2 RC), respectively. More importantly, the proposed electrochemical sensor exhibited excellent detection performance in complex water samples, providing a strategy for the detection of other toxic substances in the ecological environment.

Synthesis of rare-earth metal-organic frameworks to construct high-resolution sensing array for multiplex anions detection, cell imaging and blood phosphorus monitoring.

Accurate detection and differentiation of multiple anions is still a difficult problem due to their wide variety, structural similarity, and mutual interference. Hence, four rare-earth metal-organic frameworks (RE-MOFs) including Dy-MOFs, Er-MOFs, Tb-MOFs and Y-MOFs are successfully prepared by using TCPP as the ligand and rare-earth ions as the metal center via coordination chelation. It is found that 7 anions can light up their fluorescence. Thus, a high-resolution sensing array based on RE-MOFs nanoprobes is employed to differentiate these anions from intricate analytes in real-time scenarios. The distinctive host-guest response promotes the RE-MOFs nanoprobes to selectively extract the target anions from the complex samples. By taking advantage of the cross-response between RE-MOFs nanoprobes and anions, it allows to create an array for detecting target analytes using pattern recognition. Additionally, RE-MOFs nanoprobes also facilitate the quantitative analysis of these anions (PO43-, H2PO4-, HPO42-, F-, S2-, CO32- and C2O42-). More importantly, the exceptional effectiveness of this method has been demonstrated through various successful applications, including quality monitoring of 8 toothpaste brands, intracellular phosphate imaging, and blood phosphorus detection in mice with vascular calcification. These findings provide robust evidence for the efficacy and reliability of the RE-MOFs nanoprobes array for anion recognition.

Flexible carbon fiber cloth supports decorated with cerium metal- organic frameworks and multi-walled carbon nanotubes for simultaneous on-site detection of Cd2+ and Pb2+ in food and water samples.

The widespread heavy metal pollution endangers human health; hence, accurate on-site detection and quantification of heavy metal content in the surroundings is a vital step in reversing the harmful effect. Herein, an electrochemical sensor based on flexible cerium metal-organic framework@multi-walled carbon nanotubes/carbon cloth (CeMOF@MWCNTs/CC) was constructed for simultaneous on-site detection of Cd2+ and Pb2+ in food and water samples. The rich carboxyl groups of MWCNTs provided abundant sites for the adsorption of Cd2+ and Pb2+, and the mutual conversion of Ce3+ and Ce4+ in CeMOF facilitated the reduction and reoxidation of metal ions. The prepared electrode showed excellent performance in the simultaneous measurement of Cd2+ and Pb2+, with detection limits of 2.2 ppb and 0.64 ppb, respectively. More importantly, the sensing platform has been successfully used to detect simultaneously Cd2+ and Pb2+ in grain and water samples, and the detection results were consistent with the standard methods, showing great potential in environmental monitoring and food safety.

A novel electrochemical sensor for simultaneous detection of Cd2+ and Pb2+ by MXene aerogel-CuO/carbon cloth flexible electrode based on oxygen vacancy and bismuth film.

Herein, a novel MXene aerogel-CuO/carbon cloth (MXA-CuO/CC) electrochemical sensor was constructed, and the synergistic adsorption of heavy metal ions by oxygen vacancies and Bi (III) was investigated with Cd2+ and Pb2+ as detection targets. The oxygen vacancies of CuO have a strong affinity for heavy metal ions, which promoted the adsorption of Cd2+ and Pb2+ on the electrode surface. In addition, the introduced Bi (III) can form alloys with heavy metal ions, which effectively enhanced the adsorption capacity of sensing electrodes for Cd2+ and Pb2+. Differential pulse anodic stripping voltammetry (DPASV) was used to study the performance of MXA-CuO/CC sensitive electrode for the detection of Cd2+ and Pb2+ separately and simultaneously. The constructed sensing electrode has excellent detection performance, and can detect Cd2+ (4 µg L-1- 800 µg L-1) and Pb2+ (4 µg L-1- 1200 µg L-1) simultaneously with detection limits of 0.3 µg L-1 (Cd2+) and 0.2 µg L-1 (Pb2+), respectively. The proposed sensor electrode also has good anti-interference performance, excellent stability and reproducibility. It is worth mentioning that the proposed method can accurately detect Cd2+ and Pb2+ in food and water samples, which is consistent with the detection results of inductively coupled plasma mass spectrometry (ICP-MS) and atomic absorption spectroscopy (AAS).

Fabrication of a novel hydrogel-based microfluidic chip and its application in pathogen analysis.

Herein, we develop a novel hydrogel-based microfluidic chip, which can serve as a multifunctional analytical platform. The chip was fabricated through a newly developed hydrogel material, which shows satisfactory properties such as fast forming speed and good hydrophilicity. The chip mainly consists of two independent functional parts: a chromogenic layer and a microfluidic layer. The specially-designed toothed structure in the microfluidic layer can promote surface interactions and realize efficient enrichment of the target. The chromogenic layer contains chromogenic media, which can achieve rapid target identification through a simple visual readout. As a proof of concept, the proposed chip is employed for pathogen analysis. It shows satisfactory performance for efficient enrichment of Escherichia coli (E. coli) O157:H7. On the other hand, the visual detection limit of the chip for E. coli O157:H7 can reach 10 cfu mL-1. It is believed that this work could provide a valuable reference for chip material exploitation and application.

An enzyme-free sensitive electrochemical microRNA-16 biosensor by applying a multiple signal amplification strategy based on Au/PPy-rGO nanocomposite as a substrate.

In present study, a sensitive and effective electrochemical microRNA (miRNA) sensing platform is successfully developed by integrating gold nanoparticles/polypyrrole-reduced graphene oxide (Au/PPy-rGO), catalyzed hairpin assembly (CHA) and hybridization chain reaction (HCR) multiple signal amplification strategy. Firstly, Au/PPy-rGO was employed onto a bare GCE by electrodeposition that can greatly enhanced conductivity and effectively immobilize probes. Then, the thiolated capture probes (SH-CP) were self-assembled on the Au/PPy-rGO modified GCE via Au-S bond. The target miRNA triggered the dynamic assembly of the two hairpin substrates (H1 and H2), leading to the cyclicality of the target miRNA and the formation of H1-H2 complexes without the assistance of enzyme. Subsequently, the newly emerging DNA fragment of H2 triggered the HCR when a mixture solution (hairpins H3 and H4) and produced dsDNA polymers. Finally, a substantial amount of methylene blue (MB) as signal indicator was intercalated into the minor groove of the long dsDNA polymers to achieve detected electrochemical signal. The fabricated sensor is able to detect miRNA-16 (model target) with concentration range from 10 fM to 5 nM with a low detection limit (LOD) of 1.57 fM (S/N = 3). Current research suggests that the developed multiple signal amplification platform has a great potential for the applications in the field of biomedical research and clinical analysis.

[Study on all-round evaluation of biocompatibility of biomaterial].

Biocompatibility has always been the focal point in the study of biomaterials applied to medical apparatus. But at present, the standard system hasn't formed completely to evaluate the biomaterials. In recent years scientists tend to use general standard of evaluation. In this article, based on the recalcification time, the adhesion of platelets as well as the total quantity of plasma protein and some other evidences, combining with the Analytic hierarchy process (AHP), the method of general evaluation on the biocompatibility of anticoagulant biomaterials was discussed.

[Characterization of anticoagulant biomaterial and its development].

Good anticoagulant biomaterials need good surface chemical properties, good mechanics performances and particularly good characteristics of biocompatibility, including tissue compatibility and hemocompatibility. In order to understand with greater clearness the anticoagulant biomaterial, we have to characterize them by different methods. In this paper, the approaches to assessing and displaying the characteristics of anticoagulant biomaterial are reviewed in three aspects, namely the surface chemical properties and structure, the mechanics performances the and the biocompatibility of anticoagulant biomaterial.

[Progress in the treatment of stained teeth].

The treatment of stained teeth has been one of the striking aspects of stomatology and esthetic dentistry. Based on detailed data and references, this article introduces the types of stained teeth and the main treatment methods including strong point, weakness, limitation of the usage, result, and the relevant mechanisms. It addresses the researches on problems in the treatment of stained teeth. Also in this paper is envisaged what will be done to treat the stained teeth in future.

Investigation on clotting and hemolysis characteristics of heparin-immobilized polyether sulfones biomembrane.

In this study, a novel heparin-immobilized polyethersulfone (PES) was synthesized. PES was initially sulfonated with chlorosulfonic acid and then 1,6-hexanediamine was grafted to the -SO(3)H groups of sulfonated PES, which subsequently reacted with heparin through a covalent bond by using (1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDAC) as catalyst. The hydrophobic/hydrophilic property was characterized by measuring the water contact angle. The data shows decline from 62.29 degrees +/- 1.2 degrees to 47.86 degrees +/- 0.3 degrees for water and 86.79 degrees +/- 0.8 degrees to 68.34 degrees +/- 1.0 degrees for glycerol, which indicates an enhancement of hydrophilicity. Plasma hemolysis assay shows a comparatively low hemolysis ratio of 1.04%, which is below permissible limit of 5%. A higher content of dissociated blood cells and Ca(2+) concentration was found in red blood cell counting and coagulation factor IV test in heparinized PES. Plasma recalcification time of 360 s also offers positive evidence that heparinized PES seems to have a good anticoagulation property. This new heparin-immobilized PES biomaterials may have the potential for biomedical applications.