Co4+ in porous ZIF-67-derives intercalating-bridging adsorption of 2-reaction sites for simultaneous 2-electron transfer toward sensitive detection of uric acid.

Metal-organic frameworks (MOFs) have been used to detect uric acid (UA), but still very challenging to achieve a low detection limit due to the low inferior conductivity of MOFs. Herein, three different N-doped ZIF-67-derived carbons were synthesized for the first time by one-step co-pyrolysis of 2-methylimidazole with cobalt nitrate (CN), cobalt acetate (CA) or cobalt chloride (CC) toward UA sensing. Afterwards, the cobalt nitrate-derived Co particle (Co/CN) supported by N-doped ZIF-67-derived carbon displays extremely low detection limit and high sensitivity for UA, outperformed all reported MOFs-based UA sensors. More interestingly, it was discovered that the high valence Co4+ within the Co/CN sample produced in high-acidic environment can intercalate in the frame for a bridge adsorption between two reaction sites, which boosted simultaneous 2-electron transfer, while Co3+ only allows an end-adsorption structure for one-electron transfer being the rate determining step. Furthermore, the bridge adsorption mode of UA on Co4+ -based catalyst was also verified by theoretical DFT calculations and XPS experiment. This work holds great promise for a selective and sensitive UA sensor for practical bioscience and clinic diagnostic applications while shedding lights in fundamental research for innovative designs and developments of high-sensitive electrochemical sensors.

Mussel Adhesive Mimetic Silk Sericin Prepared by Enzymatic Oxidation for the Construction of Antibacterial Coatings.

With the rapid development and advancement in orthodontic and orthopedic technologies, the demand for biomedical-grade titanium (Ti) alloys is growing. The Ti-based implants are susceptible to bacterial infections, leading to poor healing and osteointegration, resulting in implant failure or repeated surgical intervention. Silk sericin (SS) is hydrophilic, biocompatible, and biodegradable and could induce a low immunological response in vivo. As a result, it would be intriguing to investigate the use of hydrophilic SS in surface modification. In this work, the tyrosine moiety in SS was oxidized by tyrosinase (or polyphenol oxidase) to the 3,4-dihydroxyphenylalanine (DOPA) form, generating the catechol moiety-containing SS (SSC). Inspired by the adhesion of mussel foot proteins, the SSC coatings could be directly deposited onto multiple surfaces in SS and tyrosinase mixed stock solutions to create active surfaces with catechol groups. Further, the SSC-coated Ti surfaces were hybridized with silver nanoparticles (Ag NPs) via in situ silver ion (Ag+) reduction. The antibacterial properties of the Ag NPs/SS-coated Ti surfaces are demonstrated, and they can prevent bacterial cell adhesion as well as early-stage biofilm formation. In addition, the developed Ag NPs/SSC-coated Ti surfaces exhibited a negligible level of cytotoxicity in L929 mouse fibroblast cells.

Simultaneous deposition of tannic acid and poly(ethylene glycol) to construct the antifouling polymeric coating on Titanium surface.

Titanium (Ti) and its alloys are primarily explored to produce biomedical implants owing to their improved mechanical stability, corrosion resistance, low density, and good biocompatibility. Despite, Ti substrate surfaces are easily contaminated by plasma proteins and bacteria. Herein, a simple one-step process for the simultaneous deposition of a polyphenol tannic acid (TA) and four-armed poly(ethylene glycol) (PEG10k-4-OH) on the Ti substrate (Ti-TA/PEG) surface was described. Additionally, a two-step process has been employed to fabricate the Ti-TA-PEG surface via successive deposition of TA and PEG10k-4-OH for comparison. The resultant Ti-TA/PEG surface prepared by simultaneous deposition of TA and PEG10k-4-OH exhibits higher coating thickness and better surface coverage than the Ti-TA-PEG surface. The Ti-TA/PEG and Ti-TA-PEG surfaces could actively inhibit the non-specific adsorption of proteins, suppress the bacterial and platelet adhesion, and prevents biofilm formation. Moreover, the Ti-TA/PEG surface displays a better antifouling performance than the Ti-TA-PEG surface. Thus, the present study demonstrates a simple and convenient approach for constructing polymeric coating with good anti-adhesive properties on the Ti substrate surface.

BC@DNA-Mn3(PO4)2 Nanozyme for Real-Time Detection of Superoxide from Living Cells.

Electrochemical in situ sensing of small signal molecules released from living cells has an increasing significance in early diagnosis, pathological analyses, and drug discovery. Here, a living cell-fixed sensing platform was built using the BC@DNA-Mn3(PO4)2 nanozyme, in which a highly biocompatible bacterial cellulose riveted with very tiny Mn3(PO4)2; it not only delivers high catalytic activity toward superoxide anions but possesses excellent biocompatibility for cell adsorption and growth. Additionally, the experimental results suggested that fixing the living cells on the surface of the sensing platform facilitates tiny Mn3(PO4)2 activity centers to capture and detect O2•- very quickly and simultaneously has great potential in miniaturization, cost reduction, and real-time monitoring.

Cellulose Aerogel Derived Hierarchical Porous Carbon for Enhancing Flavin-Based Interfacial Electron Transfer in Microbial Fuel Cells.

The flavin-based indirect electron transfer process between electroactive bacteria and solid electrode is crucial for microbial fuel cells (MFCs). Here, a cellulose-NaOH-urea mixture aerogel derived hierarchical porous carbon (CPC) is developed to promote the flavin based interfacial electron transfer. The porous structure of the CPC can be tailored via adjusting the ratio of urea in the cellulose aerogel precursor to obtain CPCs with different type of dominant pores. According to the electrocatalytic performance of different CPC electrodes, the CPCs with higher meso- and macropore area exhibit greatly improved flavin redox reaction. While, the CPC-9 with appropriate porous structure achieves highest power density in Shewanella putrefaciens CN32 MFC due to larger active surface for flavin mediated interfacial electron transfer and higher biofilm loading. Considering that the CPC is just obtained from the pyrolysis of the cellulose-NaOH-urea aerogel, this work also provides a facile approach for porous carbon preparation.

Amino-containing tannic acid derivative-mediated universal coatings for multifunctional surface modification.

The development of a universal coating strategy for the construction of functional surfaces and modulation of surface properties is of great research interest. Tannic acid (TA) could serve as a sole precursor for the deposition of colorless coatings on substrate surfaces. However, the deposition of TA requires a high salt concentration (0.6 M), which may limit its practical application. Herein, primary amine moieties were introduced on the gallic acid groups in TA. The resultant amine-containing TA derivative (TAA) can self-polymerize under mild conditions (10 mM, Tris buffer), and form uniform and colorless coatings in a material-independent manner. In comparison with the TA coating under the same preparation conditions, the TAA coating exhibits an increased thickness as measured by ellipsometry. The TAA coating is adapted for secondary surface functionalization. The hydrophilic mPEG brushes can be grafted on the TAA coating to inhibit non-specific protein adsorption. A biotin probe can be immobilized on the TAA coating to promote specific binding with avidin. In addition, the TAA coating can be utilized for in situ reduction of silver ions to AgNPs. The resulting AgNP-loaded TAA coating can inhibit bacterial adhesion and prevent biofilm formation.

On-chip RT-LAMP and colorimetric detection of the prostate cancer 3 biomarker with an integrated thermal and imaging box.

To achieve low-cost, compact, and portable nucleic acid testing, an integrated device containing a three-dimensional printing fabricated reverse transcription loop-mediated isothermal amplification (RT-LAMP) chip, a thermal module, and an imaging module was developed. Samples and RT-LAMP reagents were loaded on a sponge-like polyvinyl alcohol pad on a chip, whereas the colorimetric detection zone was a dry paper pre-loaded with Calcine. The sealed chip was incubated on the integrated thermal module, and the RT-LAMP products were pressed into the Calcine pre-loaded dry paper by a stick. Colorimetric changes could be visually observed by the naked eye or imaged with a smartphone camera through the imaging module. For detection of the prostate cancer antigen 3 (PCA3) biomarker, LAMP primers were designed and verified. The specificity of Calcine pre-loaded dry paper based on colorimetric detection of positive LAMP products was investigated. The reaction conditions for on-chip RT-LAMP such as amplification time, temperature, and volume were optimized. Finally, a detection limit of 0.34 fg/µL RNA was achieved with the proposed on-chip RT-LAMP and colorimetric detection method for PCA3. Since the thermal plate is powered by a 12-V battery and the color change can be imaged with a smartphone, the integrated platform can be operated on-site, highlighting its potential in point-of-care testing applications.

Multi-chamber petaloid root-growth chip for the non-destructive study of the development and physiology of the fibrous root system of Oryza sativa.

The root system of plants is a major component of their bodies in terms of both function and bulk. The investigation of root system development is greatly assisted by microfluidic devices, which improve the spatial and temporal resolution of observations without destroying tissue. In the present study, a multi-chamber petaloid root-growth chip was developed for studying the development and physiology of root systems that have thin branching structures (i.e., fibrous root systems). The petaloid root-growth chip includes a central seed germination chamber and five root-growth chambers for observing the development of fibrous roots. The proposed device was applied for investigating the root system development of Oryza sativa. The phenotype and growth kinetics of O. sativa root systems grown in the proposed device were compared with those obtained during growth in a conventional conical flask with agar-based medium, and the results indicated that cultivation in the miniaturized device did not delay root system growth in the early stage (≤2 weeks). In addition, the transparent device enabled the non-destructive observation of the developmental and microstructural characteristics of the roots, such as the root caps, root border cells, and root hairs. Moreover, the ability to control the microenvironment in each of the five root-growth chambers individually facilitated the investigation of specific adaptations in the fibrous root growth of single O. sativa seedlings to different drought stresses. Accordingly, five polyethylene glycol (PEG)6000-induced drought stress conditions were established in the five root-growth chambers to investigate the root development of a single O. sativa seedling in the central germination chamber. In situ observations demonstrated that the different PEG6000-induced conditions affected the root growth responses and root microstructural adaptations of the single seedlings in each root-growth chamber. Therefore, the petaloid root-growth microfluidic chip can eliminate the effects of variations in different plant seeds to reveal the responses of plants to different environmental conditions more objectively while concurrently allowing for non-destructive observations at very high spatial and temporal resolution.

Hydrothermal derived protoporphyrin IX nanoparticles for inactivation and imaging of bacteria strains.

Overuse and abuse of antibiotics greatly hasten the development of microbial drug resistance and substantially threat to global public health. Developing alternative methods for combating bacterial infections is urgently required. In this work, a simple hydrothermal approach was employed to prepare the protoporphyrin IX-polyethylenimine nanoparticles (PPIX-PEI NPs) containing abundant amine groups and PPIX moieties. The as-obtained PPIX-PEI NPs exhibit antibacterial properties against both Gram-positive and Gram-negative bacteria. The presence of PPIX in the PPIX-PEI NPs can generate reactive oxygen species (ROS) under 635 nm laser irradiation, which enhance the antibacterial properties of the PPIX-PEI NPs against Gram-positive bacteria. Thus, the PPIX-PEI NPs display a synergistic antibacterial activity against Gram-positive bacteria in the combination of antibacterial photodynamic therapy (PDT). In addition, emission of red fluorescence by the PPIX-PEI NPs can help to differentiate bacteria and observe the bacterial morphologies using a confocal laser scanning microscope (CLSM).

Deposition of catechol-functionalized chitosan and silver nanoparticles on biomedical titanium surfaces for antibacterial application.

The titanium (Ti) and its alloys have been widely used for dental and orthopedic implants. However, the Ti-based implants may suffer from bacterial infection, which would result in insufficient healing, implant failure and repeated surgical intervention. It is of great interest to inhibit the bacterial adhesion and colonization on the Ti-based implants by introducing proper surface coatings. In this work, a simple method was employed to synthesize the water-soluble catechol-containing chitosan (CACS). The CACS coatings can be deposited onto various substrate surfaces and exhibit substrate-independent behavior. The CACS-coated Ti surfaces were further deposited with silver nanoparticles (Ag NPs) via in-situ reduction of Ag+ ions using catechol moieties as the reducing agents. The resulting AgNPs/CACS-coated Ti surfaces exhibit antibacterial properties and can prevent the surface adhesion of bacterial cells, as evidenced by the inhibition zone test, live/dead bacterial staining assay and spread plate method. In addition, they show negligible cytotoxicity to L929 mouse fibroblast cells.

Spontaneous formation of tumor spheroid on a hydrophilic filter paper for cancer stem cell enrichment.

Emerging evidence has demonstrated that cancer stem cells (CSCs) play critical roles in tumor invasion, metastasis and recurrence. The specific targeting capability on CSCs is of high importance for the development of effective anti-tumor therapeutics. However, isolation, enrichment and cultivation of these special and rare groups of tumor cells for in vitro analyses is a nontrivial job and requires particular culture medium and environmental control. Herein, we established a low-cost and efficient method for CSC enrichment by culturing prostate cancer cells on a hydrophilic filter paper. We found that tumor spheroids could form spontaneously on a pristine filter paper solely with regular cell culture medium. The paper-grown cells had elevated expression of putative CSC markers, indicating increased stemness of the cancer cells. Moreover, increased resistance of the chemotherapeutic drug doxorubicin was observed on the formed CSC spheroids compared to regular culture. The properties of the filter paper were characterized to investigate the underlying mechanism behind the promoted tumor spheroid formation. The obtained results suggested that the excellent hydrophilicity of the cellulose fibers retarded the hydrophobic interaction-mediated cell anchoring on the cellulose fibers, while the limited space/niche between fibers promoted the aggregation of cells. In addition, biocompatible paper-based materials are able to realize convenient assembly of tissue-like structures for developing in vitro disease models or organs-on-paper applications. Therefore, hydrophilic filter papers could be a low-cost material for construction of various assay platforms for isolating and enriching CSCs, screening anti-tumor drugs, and constructing tumor models in vitro.

Electroacupuncture improves microcirculation and neuronal morphology in the spinal cord of a rat model of intervertebral disc extrusion.

Most studies on spinal cord neuronal injury have focused on spinal cord tissue histology and the expression of nerve cell damage and repair-related genes. The importance of the microcirculation is often ignored in spinal cord injury and repair research. Therefore, in this study, we established a rat model of intervertebral disc extrusion by inserting a silica gel pad into the left ventral surface of T13. Electroacupuncture was used to stimulate the bilateral Zusanli point (ST36) and Neiting point (ST44) for 14 days. Compared with control animals, blood flow in the first lumbar vertebra (L1) was noticeably increased in rats given electroacupuncture. Microvessel density in the T13 segment of the spinal cord was increased significantly as well. The number of normal neurons was higher in the ventral horn of the spinal cord. In addition, vacuolation in the white matter was lessened. No obvious glial cell proliferation was visible. Furthermore, hindlimb motor function was improved significantly. Collectively, our results suggest that electroacupuncture can improve neuronal morphology and microcirculation, and promote the recovery of neurological functions in a rat model of intervertebral disc extrusion.

Solution-prepared hybrid-nanoparticle dielectrics for high-performance low-voltage organic thin-film transistors.

Oleic acid capped barium strontium titanate (OA-BST) nanoparticles were synthesized for solution-prepared dielectrics in organic thin-film transistors (OTFTs). The as-synthesized nanoparticles were well-dispersed in organic solvents to deposit very homogeneous dielectric films by direct spin coating. Bottom-gate pentacene TFTs fabricated using these nanoparticle dielectric films showed high mobilities of 1-2 cm(2) V(-1) s(-1) with on/off ratios of 10(3) under a low driven voltage of -2.5 V. Top-gate poly(3,3'''-didodecylquaterthiophene) (PQT-12) TFTs with nanoparticle dielectrics also exhibited a low-voltage operation (-5 V) performance with mobilities of 0.01-0.1 cm(2) V(-1) s(-1) and on/off ratios of 10(3)-10(4). Detailed studies on the gate voltage-dependent mobility of the devices showed that only a low gate electric field needed to achieve the saturated mobility for the OA-BST-based pentacene OTFTs could be attributed to the low trapped-state densities (<3.9 x 10(11) cm(-2)) at the dielectric/semiconductor interfaces for these devices.

Bottom-contact poly(3,3'''-didodecylquaterthiophene) thin-film transistors with gold source-drain electrodes modified by alkanethiol monolayers.

A series of alkanethiol monolayers (CH 3(CH 2) n-1 SH, n = 4, 6, 8, 10, 12, 14, 16) were used to modify gold source-drain electrode surfaces for bottom-contact poly(3,3'''-didodecylquaterthiophene) (PQT-12) thin-film transistors (TFTs). The device mobilities of TFTs were significantly increased from approximately 0.015 cm (2) V (-1) s (-1) for bare electrode TFTs to a maximum of approximately 0.1 cm (2) V (-1) s (-1) for the n = 8 monolayer devices. The mobilities of devices with alkanethiol-modified Au electrodes varied parabolically with alkyl length with values of 0.06, 0.1, and 0.04 cm (2) V (-1) s (-1) at n = 4, 8, and 16, respectively. Atomic force microscopy investigations reveal that alkanethiol electrode surface modifications promote polycrystalline PQT-12 morphologies at electrode/PQT-12 contacts, which probably increase the density of states of the PQT-12 semiconductor at the interfaces. The contact resistance of TFTs is strongly modulated by the surface modification and strongly varies with the alkanethiol chain length. The surface modifications of electrodes appear to significantly improve the charge injection, with consequent substantial improvement in device performance.

Nanostructured polyaniline/titanium dioxide composite anode for microbial fuel cells.

A unique nanostructured polyaniline (PANI)/mesoporous TiO(2) composite was synthesized and explored as an anode in Escherichia coli microbial fuel cells (MFCs). The results of X-ray diffraction, morphology, and nitrogen adsorption-desorption studies demonstrate a networked nanostructure with uniform nanopore distribution and high specific surface area of the composite. The composite MFC anode was fabricated and its catalytic behavior investigated. Optimization of the anode shows that the composite with 30 wt % PANI gives the best bio- and electrocatalytic performance. A possible mechanism to explain the excellent performance is proposed. In comparison to previously reported work with E. coli MFCs, the composite anode delivers 2-fold higher power density (1495 mW/m(2)). Thus, it has great potential to be used as the anode for a high-power MFC and may also provide a new universal approach for improving different types of MFCs.

[Study on the formaldehyde-induced DNA damage with comet assay].

Formaldehyde is known as a genotoxic substance. Numerous studies have shown that formaldehyde could induce DNA-DNA and DNA-protein crosslinks. However, scholars have disagreed with each other on the formaldehyde-induced DNA strand breaks. We chose buccal cells as materials to evaluate the genotoxicity of formaldehyde with comet assay--especially for DNA strand breaks. The results showed that formaldehyde of low concentration induced DNA strand breaks, while formaldehyde of high concentration induced DNA-DNA and DNA-protein crosslinks. According to our experimental results, we proposed the concept of the "peak point of break" at which formaldehyde induced DNA strand breaks most.