Two-Dimensional Nickel Porphyrinic Metal-Organic Framework-Modified Electrode for Electrochemical Sensing.

Due to their highly exposed active sites and high aspect ratio caused by their substantial lateral dimension and thin thickness, two-dimensional (2D) metal-organic framework (MOF) nanosheets are currently considered a potential hybrid material for electrochemical sensing. Herein, we present a nickel-based porphyrinic MOF nanosheet as a versatile and robust platform with an enhanced electrochemical detection performance. It is important to note that the nickel porphyrin ligand reacted with Cu(NO3)2·3H2O in a solvothermal process, with polyvinylpyrrolidone (PVP) acting as the surfactant to control the anisotropic development of creating a 2D Cu-TCPP(Ni) MOF nanosheet structure. To realize the exceptional selectivity, sensitivity, and stability of the synthesized 2D Cu-TCPP(Ni) MOF nanosheet, a laser-induced graphene electrode was modified with the MOF nanosheet and employed as a sensor for the detection of p-nitrophenol (p-NP). With a detection range of 0.5-200 µM for differential pulse voltammetry (DPV) and 0.9-300 µM for cyclic voltammetry (CV), the proposed sensor demonstrated enhanced electrochemical performance, with the limit of detection (LOD) for DPV and CV as 0.1 and 0.3 µM, respectively. The outstanding outcome of the sensor is attributed to the 2D Cu-TCPP(Ni) MOF nanosheet's substantial active surface area, innate catalytic activity, and superior adsorption capacity. Furthermore, it is anticipated that the proposed electrode sensor will make it possible to create high-performance electrochemical sensors for environmental point-of-care testing since it successfully detected p-NP in real sample analysis.

Microfluidized hemp protein isolate: an effective stabilizer for high-internal-phase emulsions with improved oxidative stability.

BACKGROUND: Hemp protein isolates (HPIs), which provide a well-balanced profile of essential amino acids comparable to other high-quality proteins, have recently garnered significant attention. However, the underutilized functional attributes of HPIs have constrained their potential commercial applications within the food and agriculture field. This study advocates the utilization of dynamic-high-pressure-microfluidization (DHPM) for the production of stable high-internal-phase emulsions (HIPEs), offering an efficient approach to fully exploit the potential of HPI resources. RESULTS: The findings underscore the effectiveness of DHPM in producing HPI as a stabilizing agent for HIPEs with augmented antioxidant activity. Microfluidized HPI exhibited consistent adsorption and anchoring at the oil-water interface, resulting in the formation of a dense and compact layer. Concurrently, the compression of droplets within HIPEs gave rise to a polyhedral framework, conferring viscoelastic properties and a quasi-solid behavior to the emulsion. Remarkably, HIPEs stabilized by microfluidized HPI demonstrated superior oxidative and storage stability, attributable to the establishment of an antioxidative barrier by microfluidized HPI particles. CONCLUSION: This study presents an appealing approach for transforming liquid oils into solid-like fats using HPI particles, all without the need for surfactants. HIPEs stabilized by microfluidized HPI particles hold promise as emerging food ingredients for the development of emulsion-based formulations with enhanced oxidative stability, thereby finding application in the food and agricultural industries. © 2023 Society of Chemical Industry.

MOF-On-MOF Dual Enzyme-Mimic Nanozyme with Enhanced Cascade Catalysis for Colorimetric/Chemiluminescent Dual-Mode Aptasensing.

A novel metal-organic framework (MOF)-on-MOF dual enzyme-mimic nanozyme was designed as enhanced cascade signal amplification for the colorimetric and chemiluminescent (CL) dual-mode aptasensing. The MOF-on-MOF hybrid is composed of MOF-818 with catechol oxidase-like activity and iron porphyrin MOF [PMOF(Fe)] with peroxidase-like activity, called MOF-818@PMOF(Fe). MOF-818 can catalyze the 3,5-di-tert-butylcatechol substrate and produce H2O2 in situ. Subsequently, PMOF(Fe) catalyzes H2O2 to produce reactive oxygen species, which oxidize 3,3',5,5'-tetramethylbenzidine or luminol to produce color or luminescence. Thanks to the nano-proximity effect and the confinement effect, the efficiency of the biomimetic cascade catalysis is greatly improved, which in turn generates enhanced colorimetric and CL signals. Taking the detection of chlopyrifos as an example, the prepared dual enzyme-mimic MOF nanozyme is combined with the aptamer with specific recognition ability to develop a colorimetric/CL dual-mode aptasensor for highly sensitive and selective detection of chlorpyrifos. The proposed MOF-on-MOF dual nanozyme-enhanced cascade system may provide a new pathway for the further development of a biomimetic cascade sensing platform.

Two-Site Enhanced Porphyrinic Metal-Organic Framework Nanozymes and Nano-/Bioenzyme Confined Catalysis for Colorimetric/Chemiluminescent Dual-Mode Visual Biosensing.

The rational design of efficient nanozymes and the immobilization of enzymes are of great significance for the construction of high-performance biosensors based on nano-/bioenzyme catalytic systems. Herein, a novel V-TCPP(Fe) metal-organic framework nanozyme with a two-dimensional nanosheet morphology is rationally designed by using V2CTx MXene as a metal source and iron tetrakis(4-carboxyphenyl)porphine (FeTCPP) ligand as an organic linker. It exhibits enhanced peroxidase- and catalase-like activities and luminol-H2O2 chemiluminescent (CL) behavior. Based on the experimental and theoretical results, these excellent enzyme-like activities are derived from the two-site synergistic effect between V nodes and FeTCPP ligands in V-TCPP(Fe). Furthermore, a confined catalytic system is developed by zeolitic imidazole framework (ZIF) coencapsulation of the V-TCPP(Fe) nanozyme and bioenzyme. Using the acetylcholinesterase (AChE) as a model, our constructed V-TCPP(Fe)/AChE@ZIF confined catalytic system was successfully used for the colorimetric/CL dual-mode visual biosensing of organophosphorus pesticides. This work is expected to provide new insights into the design of efficient nanozymes and confined catalytic systems, encouraging applications in catalysis and biosensing.

Saturated Coordination LuN6 Defect Sites for Highly Efficient Electroreduction of CO2.

Metal single-atom and internal structural defects typically coexist in M-N-C materials obtained through the existing basic pyrolysis processes. Identifying a correlation between them to understand the structure-activity relationship and achieve efficient catalytic performance is important, particularly for the rare-earth (RE) elements with rich electron orbitals and strong coordination capabilities. Herein, a novel single-atom catalyst based on the RE element lutetium is successfully synthesized on a N-C support. Structural and simulation analyses demonstrate that the formation of a LuN6 structural site with an individual defect because of pyrolysis is thermodynamically favorable in Lu-N-C. Using KHCO3 -based electrolytes facilitates the fall of the K+ cations into the defective sites of Lu-N-C, thus enabling improved CO2 capture and activation, which increases the catalyst conductivity for Lu-N-C. In this study, the catalyst exhibits a Faradaic efficiency of 95.1% for CO at a current density of 18.2 mA cm-2 during carbon dioxide reduction reaction. This study thus provides new insights into understanding RE-N-C materials for energy utilization.

Effects of quercetin on the gel properties of pork myofibrillar proteins and related changes in protein conformation.

BACKGROUND: To study the effects of quercetin on the functionality of myofibrillar proteins (MPs), various levels of quercetin (0, 10, 50, 100 and 200 µmol g-1 protein) were added to MP solution and the structure and gel properties of MPs were determined. RESULTS: Compared with the control MPs not treated with quercetin, adding 10, 50 and 100 µmol g-1 quercetin caused a significant (P < 0.05) loss of sulfhydryls; 10 and 50 µmol g-1 quercetin enhanced the surface hydrophobicity significantly (P < 0.05), and 50, 100 and 200 µmol g-1 quercetin reduced the fluorescence intensity of tryptophan. Additions of 50, 100 and 200 µmol g-1 quercetin resulted in a significant (P < 0.05) reduction in MP solubility. Adding 10, 50 and 100 µmol g-1 quercetin did not significantly (P > 0.05) change the gel strength and water-holding ability of MPs than control, but 200 µmol g-1 quercetin declined the gel properties significantly (P < 0.05). The microstructure and dynamic rheological properties confirmed the results of the gel properties of MPs affected by various levels of quercetin. CONCLUSION: The results obtained in the present study show that mildly high levels of quercetin can maintain the gel properties of MPs, which may be a result of the moderate MP cross-linkage and aggregation caused by the covalent and non-covalent interactions of MPs. © 2023 Society of Chemical Industry.

Fabrication of glycated yeast cell protein via Maillard reaction for delivery of curcumin: improved environmental stability, antioxidant activity, and bioaccessibility.

BACKGROUND: The application of curcumin (CUR) in the food industry is limited by its instability, hydrophobicity and low bioavailability. Yeast cell protein (YCP) is a by-product of spent brewer's yeast, which has the potential to deliver bioactive substances. However, the environmental stresses such as pH, salt and heat treatment has restricted its application in the food industry. Maillard reaction as a non-enzymatic browning reaction can improve protein stability under environmental stress. RESULTS: The CUR was successfully encapsulated into the hydrophobic core of YCP/glycated YCP (GYCP) and enhanced by hydrogen bonding, resulting in static fluorescence quenching of YCP/GYCP. The average diameter and dispersibility of GYPC-CUR nanocomplex were significantly improved after glucose glycation (121.40 nm versus 139.70 nm). Moreover, the encapsulation capacity of CUR was not influenced by glucose glycation. The oxidative stability and bioaccessibility of CUR in nanocomplexes were increased compared with free CUR, especially complexed with GYCP conjugates. CONCLUSION: Steric hindrance provided by glucose conjugation improved the enviriomental stability, oxidative activity and bioaccessibility of CUR in nanocomplexes. Thus, glucose-glycated YCP has potential application as a delivery carrier for hydrophobic compounds in functional foods. © 2022 Society of Chemical Industry.

Inhibition of circ_0081234 reduces prostate cancer tumor growth and metastasis via the miR-1/MAP 3 K1 axis.

INTRODUCTION: Circular RNAs (circRNAs) are crucial regulators of tumor occurrence and progression, and circRNAs are enriched and stable in exosomes. The present study aimed to explore the role and potential mechanism of cancer-derived exosomal circ_0081234 in prostate cancer (PCa). METHODS: Exosomes were extracted using the ExoQuick Precipitation Kit (System Biosciences, Mountain View, CA, USA). The levels of circ_0081234, miR-1 and mitogen-activated protein kinase kinase kinase 1 (MAP 3 K1) were examined using a quantitative real-time polymerase chain reaction or western blotting. Cell migration and invasion were evaluated via a transwell assay. The protein levels of N-cadherin, vimentin and E-cadherin were detected by western blotting. The interaction between miR-1 and circ_0081234 or MAP 3 K1 was verified via a dual-luciferase reporter assay and an RNA pull-down assay. RESULTS: The circ_0081234 level was increased in PCa tissues with spinal metastasis in comparison to primary PCa tissues without spinal metastasis. Exosomal circ_0081234 promoted the migration, invasion and epithelial-mesenchymal transition of PCa cells. Knockdown of circ_0081234 blocked PCa cell progression by regulating miR-1. In addition, miR-1 overexpression suppressed PCa cell progression by repressing MAP 3 K1. Moreover, circ_0081234 increased MAP 3 K1 level via sponging miR-1. Depletion of circ_0081234 inhibited tumor growth in vivo. CONCLUSIONS: Exosomal circ_0081234 promoted migration, invasion and epithelial-mesenchymal transition of PCa cells by regulating the miR-1/MAP 3 K1 axis.

A Portable Electrochemical Sensor Based on Manganese Porphyrin-Functionalized Carbon Cloth for Highly Sensitive Detection of Nitroaromatics and Gaseous Phenol.

Organic pollutants (OPs) have garnered a considerable amount of attention in recent times due to their extreme toxicity toward humans and the ecosystem. The need for an inexpensive yet robust, sensitive, selective, and easy-to-operate method for detecting OPs remains a challenge. Herein, a portable electrochemical sensor is proposed based on manganese porphyrin-functionalized carbon cloth (CC). To explain the electrochemical performance of the sensor, cyclic voltammetry (CV) and differential pulse voltammetry (DPV) were employed. The presence of manganese(III) ion in the center of the porphyrin ligand acted as an agent for the transfer of electrons and enhanced sensitivity toward analyte-specific redox catalysis. Moreover, it allowed for the concurrent detection of multiple analytes in a complex environment. The modified CC electrode can selectively detect nitroaromatic and phenolic compounds with accessible data collected through wireless means onto a smartphone device. The as-synthesized electrode demonstrated a higher sensitivity toward the detection of nitrobenzene (NB) and aqueous phenol with a limit of detection (LOD) found to be 5.9268 × 10-10 M and 4.0178 × 10-10 M, respectively. Additionally, our proposed portable electrochemical sensor demonstrates a high selectivity and reproducibility toward nitroaromatic and phenolic compounds, which can be employed in real complex water samples. With regard to the sensor's remarkable electrochemical performance, it is envisaged that such a sensor could pave the way for environmental point of care (POC) testing.

Magnetic zirconium-based Prussian blue analog nanozyme: enhanced peroxidase-mimicking activity and colorimetric sensing of phosphate ion.

A magnetic zirconium hexacyanoferrate-based Prussian blue analog (MB@ZrHCF) nanozyme was synthesized using dopamine (DA) reduction-assisted method and employed for colorimetric PO43- sensing. The MB@ZrHCF exhibits enhanced peroxidase-mimicking activity and ultrafast catalytic rate via the color reaction of 3,3',5,5'-tetramethylbenzidine (TMB) oxidized by hydrogen peroxide (H2O2). The catalytic reaction mechanism of MB@ZrHCF catalyzing H2O2 to produce hydroxyl radical (∙OH) was studied. Then, MB@ZrHCF was successfully applied to the detection of H2O2. Additionally, the catalytic activity of the nanocomposite is inhibited due to the steric hindrance effect from the coordination of PO43- and Zr(IV) node. Based on this, the MB@ZrHCF nanozyme can be used to detect PO43- in two linear ranges (10-100 µM and 100-200 µM) with a limit of detection of 2.25 µM. The proposed colorimetric sensor possesses excellent selectivity and reliability for PO43- sensing, which can be successfully applied to detect PO43- in sea and tap water samples.

Toward High-Performance Electrochromic Conjugated Polymers: Influence of Local Chemical Environment and Side-Chain Engineering.

Three homologous electrochromic conjugated polymers, each containing an asymmetric building block but decorated with distinct alkyl chains, were designed and synthesized using electrochemical polymerization in this study. The corresponding monomers, namely T610FBTT810, DT6FBT, and DT48FBT, comprise the same backbone structure, i.e., an asymmetric 5-fluorobenzo[c][1,2,5]thiadiazole unit substituted by two thiophene terminals, but were decorated with different types of alkyl chain (hexyl, 2-butyloctyl, 2-hexyldecyl, or 2-octyldecyl). The effects of the side-chain structure and asymmetric repeating unit on the optical absorption, electrochemistry, morphology, and electrochromic properties were investigated comparatively. It was found that the electrochromism conjugated polymer, originating from DT6FBT with the shortest and linear alkyl chain, exhibits the best electrochromic performance with a 25% optical contrast ratio and a 0.3 s response time. The flexible electrochromic device of PDT6FBT achieved reversible colors of navy and cyan between the neutral and oxidized states, consistent with the non-device phenomenon. These results demonstrate that subtle modification of the side chain is able to change the electrochromic properties of conjugated polymers.

SPETS: Secure and Privacy-Preserving Energy Trading System in Microgrid.

Recently, the development of distributed renewable energy resources, smart devices, and smart grids empowers the emergence of peer-to-peer energy trading via local energy markets. However, due to security and privacy concerns in energy trading, sensitive information of energy traders could be leaked to an adversary. In addition, malicious users could perform attacks against the energy market, such as collusion, double spending, and repudiation attacks. Moreover, network attacks could be executed by external attackers against energy networks, such as eavesdropping, data spoofing, and tampering attacks. To tackle the abovementioned attacks, we propose a secure and privacy-preserving energy trading system (SPETS). First, a permissioned energy blockchain is presented to perform secure energy transactions between energy sellers and buyers. Second, a discrete-time double auction is proposed for energy allocation and pricing. Third, the concept of reputation scores is adopted to guarantee market reliability and trust. The proposed energy system is implemented using Hyperledger Fabric (HF) where the chaincode is utilized to control the energy market. Theoretical analysis proves that SPETS is resilient to several security attacks. Simulation results demonstrate the increase in sellers' and buyers' welfare by approximately 76.5% and 26%, respectively. The proposed system ensures trustfulness and guarantees efficient energy allocation. The benchmark analysis proves that SPETS consumes few resources in terms of memory and disk usage, CPU, and network utilization.

An Adaptive Unsupervised Feature Selection Algorithm Based on MDS for Tumor Gene Data Classification.

Identifying the key genes related to tumors from gene expression data with a large number of features is important for the accurate classification of tumors and to make special treatment decisions. In recent years, unsupervised feature selection algorithms have attracted considerable attention in the field of gene selection as they can find the most discriminating subsets of genes, namely the potential information in biological data. Recent research also shows that maintaining the important structure of data is necessary for gene selection. However, most current feature selection methods merely capture the local structure of the original data while ignoring the importance of the global structure of the original data. We believe that the global structure and local structure of the original data are equally important, and so the selected genes should maintain the essential structure of the original data as far as possible. In this paper, we propose a new, adaptive, unsupervised feature selection scheme which not only reconstructs high-dimensional data into a low-dimensional space with the constraint of feature distance invariance but also employs ℓ2,1-norm to enable a matrix with the ability to perform gene selection embedding into the local manifold structure-learning framework. Moreover, an effective algorithm is developed to solve the optimization problem based on the proposed scheme. Comparative experiments with some classical schemes on real tumor datasets demonstrate the effectiveness of the proposed method.

Impact of Extrusion Temperature on In Vitro Digestibility and Pasting Properties of Pea Flour.

Pea flour was extruded at 50, 70, and 90 °C. The in vitro digestibility and characteristics of native and extruded pea flour were investigated. The in vitro starch digestibility (IVSD) and in vitro protein digestibility (IVPD) of the extruded pea flour were higher than those of the native pea flour and increased with increasing extrusion temperature from 50 to 90 °C. The rapidly digestible starch increased to 28.34% at 90 °C, the highest slowly digestible starch (SDS) content was 22.70% at 50 °C, and resistant starch content decreased to 4.71% at 90 °C. The IVPD increased from 80.94% relative to the native pea flour to 90.21% at 90 °C. Improved swelling power enabled the extruded pea flour to exhibit better performance and higher breakdown viscosity and lower setback viscosity than the native pea flour demonstrated that extrusion reduced the thermal stability and retrogradation tendency. Increasing extrusion temperatures greatly reduced the relative crystallinity (based on X-ray diffraction analysis) from 32.69% relative to the native pea flour to 9.76% at 90 °C. Extrusion treatment also reduced ß-sheet content (based on Fourier transform infrared spectroscopy analysis) from 36.40% relative to the native pea flour to 31.79% at 90 °C. IVPD and IVSD improved, and the SDS content increased at 50 °C and 70 °C, thereby indicating that extruded pea flour can be applied to healthy food products.

Zirconium-Metalloporphyrin Frameworks-Luminol Competitive Electrochemiluminescence for Ratiometric Detection of Polynucleotide Kinase Activity.

We propose a novel competitive mechanism involving the dissolved oxygen (O2) between zirconium-based porphyrinic metal-organic framework nanoparticles (NMOFs) and luminol into a ratiometric electrochemiluminescence (ECL) biosensing interface. Zinc tetrakis(carboxyphenyl)-porphyrin (ZnTCPP) in NMOFs as electron media reduce O2 into reactive oxygen species (ROS) and produce singlet oxygen (1O2), resulting in cathodic ECL. Meanwhile, ROS also react with the luminol anion radical and amplify the anodic ECL emission. Based on the competitive-mechanism-driven ECL process, taking the detection of polynucleotide kinase (PNK) as example, with assembling DNA-functionalized NMOFs on the sensing interface, a lower detection limit of 6.5 × 10-5 U mL-1 and broader linear relationship range from 0.0002 to 10 U mL-1 were obtained compared with that of single-signal-driven ECL sensors. This proposed MOFs-luminol competitive ECL mechanism involving dissolved O2 may provide a new pathway for further research of a green and highly sensitive ECL biosensing system.

DNA-Mediated Nanoscale Metal-Organic Frameworks for Ultrasensitive Photoelectrochemical Enzyme-Free Immunoassay.

A novel enzyme-free photoelectrochemical (PEC) immunoassay was developed for the ultrasensitive detection of prostate specific antigen (PSA) based on the DNA-mediated nanoscale zirconium-porphyrin MOFs (NMOFs). By virtue of the intrinsic coordination between unsaturated zirconium sites of the NMOFs frameworks and phosphonate groups, the 5'-phosphorylared ss-DNA-tagged antibody (Ab-DNA) conjugate with a consecutive stretch of guanines as a spacer could be loaded on the NMOFs easily, obtaining a novel type of Ab-DNA-functionalized NMOFs complex. Additionally, as a photocathode PEC active nanomaterial, NMOFs exhibited a significant enhanced photocurrent response with the presence of dopamine under oxygen-containing aqueous media at -0.3 V (vs Ag/AgCl). Furthermore, with the aid of the electrochemical grafting of polyamidoamine (PAMAM) dendrimers functionalized interface, the novel type of Ab-DNA-NMOFs further served as a PEC signal nanoprobe for the ultrasensitive PSA immunoassay. Under optimal conditions, the corresponding immunosensor possessed a wide calibration range of 1 pg mL-1 to 10 ng mL-1 and a limit of detection (LOD) of 0.2 pg mL-1. This present work demonstrated the promising application of DNA-mediated NMOFs in developing highly sensitive, environmentally friendly, and cost-effective PEC biosensors.

Zirconium-Based Porphyrinic Metal-Organic Framework (PCN-222): Enhanced Photoelectrochemical Response and Its Application for Label-Free Phosphoprotein Detection.

A simple and rapid photoelectrochemical (PEC) sensor was developed for the label-free detection of a phosphoprotein (α-casein) based on a zirconium based porphyrinic metal-organic framework (MOF), PCN-222, which exhibited an enhanced photocurrent response toward dopamine under the O2-saturated aqueous media. In this work, in terms of PEC measurements and cyclic voltammetry, the PEC behaviors of PCN-222 in aqueous media were thoroughly investigated for the first time. Additionally, in the virtue of the steric hindrance effect from the coordination of the phosphate groups and inorganic Zr-O clusters as binding sites in PCN-222, this biosensor showed high sensitivity for detecting α-casein and the limit of detection (LOD) was estimated to be 0.13 µg mL-1. Moreover, the proposed method provides a promising platform for clinic diagnostic and therapeutics.

Magnetic zirconium hexacyanoferrate(II) nanoparticle as tracing tag for electrochemical DNA assay.

Novel multifunctional magnetic zirconium hexacyanoferrate nanoparticles (ZrHCF MNPs) were prepared, which consisted of magnetic beads (MBs) inner core and zirconium hexacyanoferrate(II) (ZrHCF) outer shell. As an artificial peroxidase, the ZrHCF MNPs exhibited remarkable electrocatalytic properties in the reduction of H2O2 at 0.2 V vs saturated calomel electrode (SCE). On the basis of the bonding interaction between Zr (IV) of the shell ZrHCF framework and phosphonate groups, the 5'-phosphorylated ssDNA probes with a consecutive stretch of guanines as a spacer could be incorporated in ZrHCF MNPs easily. Thus, DNA-grafted ZrHCF MNPs could be simply obtained by magnetic separation. The prepared nanoelectrocatalyst was further used as signal nanoprobe for the ultrasensitive electrochemical DNA assay. Under optimal conditions, the proposed biosensor presents high sensitivity for detecting target DNA with a linear range from 1.0 fM to 1.0 nM and a low detection limit of 0.43 fM. Moreover, it exhibits good performance with excellent selectivity, high stability, and acceptable fabrication reproducibility.

Biosensing platform based on graphene oxide via self-assembly induced by synergic interactions.

A novel self-assembled glucose biosensor based on graphene oxide (GO) was constructed by using 1-pyrenebutyric acid-N-hydroxysuccinimide ester (PANHS) as linking molecular. The stepwise self-assembly process was performed for PANHS anchoring in N,N-dimethylformamide (DMF) solvent and the further glucose oxidase (GOD) binding in aqueous solution, respectively. The molecular interactions and the morphologic properties were characterized by Fourier transform infrared spectroscopy (FTIR), field emission scanning electronic microscopy (FESEM), and atomic force microscopy (AFM). In addition, the quantitative loadings of anchored PANHS and GOD were well elucidated by surface plasmon resonance (SPR) measurements. The obtained novel glucose sensor exhibited satisfactory analytical performance to glucose: wide linear range (4.0×10(-6) to 4.4×10(-3) M), fast response (10s), high sensitivity (40.5±0.4 mA M(-1) cm(-2)), and low detection limit (2 µM, S/N=3). Furthermore, the biosensor exhibited excellent long-term stability and satisfactory reproducibility.

Integrin activation and internalization on soft ECM as a mechanism of induction of stem cell differentiation by ECM elasticity.

The mechanism by which ECM elasticity induces lineage specification of stem cells has not been clearly understood. Integrins are well-documented mechanosensors that are positioned at the beginning of the sensing pathway. By using an antibody specifically recognizing the active conformation of ß1 integrin, we observed that ß1 integrin activation in bone marrow mesenchymal stem cells (BMMSCs) was induced by soft substrate to a significantly greater degree than by stiff substrate. In contrast, however, the level of cell surface integrin on soft substrate was significantly lower than that on stiff substrate. Soft substrate markedly enhanced the internalization of integrin, and this internalization was mediated mainly through caveolae/raft-dependent endocytosis. The inhibition of integrin internalization blocked the neural lineage specification of BMMSCs on soft substrate. Furthermore, soft substrate also repressed the bone morphogenetic protein (BMP)/Smad pathway at least partially through integrin-regulated BMP receptor endocytosis. A theoretical analysis based on atomic force microscopy (AFM) data indicated that integrin-ligand complexes are more easily ruptured on soft substrate; this outcome may contribute to the enhancement of integrin internalization on soft substrate. Taken together, our results suggest that ECM elasticity affects integrin activity and trafficking to modulate integrin BMP receptor internalization, thus contributing to stem cell lineage specification.