DDR2 signaling and mechanosensing orchestrate neuroblastoma cell fate through different transcriptome mechanisms.

The extracellular matrix (ECM) regulates carcinogenesis by interacting with cancer cells via cell surface receptors. Discoidin Domain Receptor 2 (DDR2) is a collagen-activated receptor implicated in cell survival, growth, and differentiation. Dysregulated DDR2 expression has been identified in various cancer types, making it as a promising therapeutic target. Additionally, cancer cells exhibit mechanosensing abilities, detecting changes in ECM stiffness, which is particularly important for carcinogenesis given the observed ECM stiffening in numerous cancer types. Despite these, whether collagen-activated DDR2 signaling and ECM stiffness-induced mechanosensing exert similar effects on cancer cell behavior and whether they operate through analogous mechanisms remain elusive. To address these questions, we performed bulk RNA sequencing (RNA-seq) on human SH-SY5Y neuroblastoma cells cultured on collagen-coated substrates. Our results show that DDR2 downregulation induces significant changes in the cell transcriptome, with changes in expression of 15% of the genome, specifically affecting the genes associated with cell division and differentiation. We validated the RNA-seq results by showing that DDR2 knockdown redirects the cell fate from proliferation to senescence. Like DDR2 knockdown, increasing substrate stiffness diminishes cell proliferation. Surprisingly, RNA-seq indicates that substrate stiffness has no detectable effect on the transcriptome. Furthermore, DDR2 knockdown influences cellular responses to substrate stiffness changes, highlighting a crosstalk between these two ECM-induced signaling pathways. Based on our results, we propose that the ECM could activate DDR2 signaling and mechanosensing in cancer cells to orchestrate their cell fate through distinct mechanisms, with or without involving gene expression, thus providing novel mechanistic insights into cancer progression.

Advancing Biosensors with Machine Learning.

Chemometrics play a critical role in biosensors-based detection, analysis, and diagnosis. Nowadays, as a branch of artificial intelligence (AI), machine learning (ML) have achieved impressive advances. However, novel advanced ML methods, especially deep learning, which is famous for image analysis, facial recognition, and speech recognition, has remained relatively elusive to the biosensor community. Herein, how ML can be beneficial to biosensors is systematically discussed. The advantages and drawbacks of most popular ML algorithms are summarized on the basis of sensing data analysis. Specially, deep learning methods such as convolutional neural network (CNN) and recurrent neural network (RNN) are emphasized. Diverse ML-assisted electrochemical biosensors, wearable electronics, SERS and other spectra-based biosensors, fluorescence biosensors and colorimetric biosensors are comprehensively discussed. Furthermore, biosensor networks and multibiosensor data fusion are introduced. This review will nicely bridge ML with biosensors, and greatly expand chemometrics for detection, analysis, and diagnosis.

Batch fabrication of electrochemical sensors on a glycol-modified polyethylene terephthalate-based microfluidic device.

Developing low-cost methods for the fabrication of electrochemical microfluidic devices is urgently needed for transferring such devices from fundamental research to daily-life technology. Herein, glycol-modified polyethylene terephthalate (PETG)-based microfluidic devices with embedded channels and gold film electrode (GFE) are developed by a one-step, low-cost, straightforward, and mass-producible method, and are sealed by a reversible hydrophilic tape-based mechanism. Easily accessible poly (methyl methacrylate) (PMMA), polyethylene terephthalate (polyester, PET), and PETG are explored as substrate options for fabricating electrochemical sensors. The results demonstrated that PETG can be an excellent substrate for fabricating the electrode. The electrochemical stability and morphology of the device are investigated. Both redox ions ([Fe(CN)6]3-/4-) and redox organic compounds (dopamine) are used as model analytes to prove the electrochemical performance of the device. The PETG-based microfluidic devices integrated with electrochemical sensors can be used as alternative electrochemical devices for the detection of biological and chemical analytes. Meanwhile, batch-fabricated flexible electrochemical sensors based on PETG film and their electrochemical performance are reported.

Diagnostic methods and potential portable biosensors for coronavirus disease 2019.

Timely detection and diagnosis are urgently needed to guide epidemiological measures, infection control, antiviral treatment, and vaccine research. In this review, biomarkers/indicators for diagnosis of coronavirus disease 2019 (COVID-19) or detection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in the environment are summarized and discussed. It is concluded that the detection methods targeting antibodies are not suitable for screening of early and asymptomatic cases since most patients had an antibody response at about 10 days after onset of symptoms. However, antibody detection methods can be combined with quantitative real-time reverse transcriptase-polymerase chain reaction (RT-qPCR) to significantly improve the sensitivity and specificity of diagnosis, and boost vaccine research. Fast, sensitive and accurate detection methods targeting antigens need to be developed urgently. Various specimens for diagnosis or detection are compared and analyzed. Among them, deep throat saliva and induced sputum are desired for RT-qPCR test or other early detection technologies. Chest computerized tomography (CT) scan, RT-qPCR, lateral flow immunochromatographic strip (LFICS) for diagnosis of COVID-19 are summarized and compared. Specially, potential electrochemical (EC) biosensor, surface enhanced Raman scattering (SERS)-based biosensor, field-effect transistor (FET)-based biosensor, surface plasmon resonance (SPR)-based biosensor and artificial intelligence (AI) assisted diagnosis of COVID-19 are emphasized. Finally, some commercialized portable detection device, current challenges and future directions are discussed.

Molecularly Imprinted Polymers and Surface Imprinted Polymers Based Electrochemical Biosensor for Infectious Diseases.

Owing to their merits of simple, fast, sensitive, and low cost, electrochemical biosensors have been widely used for the diagnosis of infectious diseases. As a critical element, the receptor determines the selectivity, stability, and accuracy of the electrochemical biosensors. Molecularly imprinted polymers (MIPs) and surface imprinted polymers (SIPs) have great potential to be robust artificial receptors. Therefore, extensive studies have been reported to develop MIPs/SIPs for the detection of infectious diseases with high selectivity and reliability. In this review, we discuss mechanisms of recognition events between imprinted polymers with different biomarkers, such as signaling molecules, microbial toxins, viruses, and bacterial and fungal cells. Then, various preparation methods of MIPs/SIPs for electrochemical biosensors are summarized. Especially, the methods of electropolymerization and micro-contact imprinting are emphasized. Furthermore, applications of MIPs/SIPs based electrochemical biosensors for infectious disease detection are highlighted. At last, challenges and perspectives are discussed.

Single domain antibody coated gold nanoparticles as enhancer for Clostridium difficile toxin detection by electrochemical impedance immunosensors.

This work presents a sandwich-type electrochemical impedance immunosensor for detecting Clostridium difficile toxin A (TcdA) and toxin B (TcdB). Single domain antibody conjugated gold nanoparticles were applied to amplify the detection signal. Gold nanoparticles (Au NPs) were characterized by transmission electron microscopy and UV­vis spectra. The electron transfer resistance (Ret) of the working electrode surface was used as a parameter in the measurement of the biosensor. With the increase of the concentration of toxins from 1 pg/mL to 100 pg/mL, a linear relationship was observed between the relative electron transfer resistance and toxin concentration. In addition, the detection signal was enhanced due to the amplification effect. The limit of detection for TcdA and TcdB was found to be 0.61 pg/mL and 0.60 pg/mL respectively at a signal-to-noise ratio of 3 (S/N = 3). This method is simple, fast and ultrasensitive, thus possesses a great potential for clinical applications in the future.

Aqueous phase synthesis of highly luminescent, nitrogen-doped carbon dots and their application as bioimaging agents.

Carbon dots are promising scaffolds for multifunctional therapeutic systems because of their fluorescence property, good biocompatibility, and low toxicity. In this work, we prepared nitrogen-doped carbon dots through an aqueous phase strategy using folic acid as precursor. The carbon dots possess many attractive features including uniform dispersion with size about 9 nm, bright photoluminescence, high photoluminescence quantum yield of 23%, and low toxicity, making them excellent imaging probes for biomedical applications.

Green synthesis of luminescent nitrogen-doped carbon dots from milk and its imaging application.

In the present work, a completely green synthetic method for producing fluorescent nitrogen-doped carbon dots by using milk is introduced. The process is environmentally friendly, simple, and efficient. By hydrothermal heating of milk, we produced monodispersed, highly fluorescent carbon dots with a size of about 3 nm. Imaging of U87 cells, a human brain glioma cancer cell line, can be easily achieved with high resolution using the prepared carbon dots as probes and validates their use in imaging applications.

Magnetite nanoparticles doped photoresist derived carbon as a suitable substratum for nerve cell culture.

A method which alters the substrate's physical and electrochemical properties by doping photoresist derived carbon with magnetite nanoparticles has been developed to enhance the existing substrate's ability to foster cell growth. Cyclic voltammetry, scanning electron microscopy and atomic force microscopy are used to evaluate the characters of the prepared film. And then, the magnetite nanoparticles doped carbon film is used as substrate for the growth of nerve cell. Here, rat pheochromocytoma cells are used for culture to test substrate-cell interactions. The results showed an increase in cell concentration and average neurite length with the increase of nanoparticle concentration on the surface. Importantly, the nerve cells can be grown on the magnetite nanoparticles doped carbon even in the absence of nerve growth factor. This finding will potentially provide a new material for nerve regeneration.

Recovery of nickel from aqueous solutions by complexation-ultrafiltration process with sodium polyacrylate and polyethylenimine.

The recovery of nickel from aqueous dilute solutions by complexation-ultrafiltration process with sodium polyacrylate (PAAS) and polyethylenimine (PEI) was studied. Experiments were performed as a function of aqueous pH, polymer/Ni(2+) ratio and background electrolyte concentration. At optimum experimental conditions, the nickel removal rate reaches 99.5% using PAAS and 93.0% using PEI as the complexation agent. The nickel removal rate was found to decrease as the adding salt NaCl concentration increases for both complexation agents. A series of experiments implied that the mechanism could be the compressing electric double layer other than the competitive complexation. Diafiltration technique was further performed to regenerate complexation agents and recover nickel. The nickel removal rates were found to be close to those obtained with the original PEI and PAAS. Finally, Langmuir-type binding isotherm equation was employed to evaluate the extent of nickel bound to PAAS and PEI. The overall results from the two-step process of complexation-UF and decomplexation-UF separation showed that it could be a promising method for nickel removal and recovery from aqueous solutions.

Highly sensitive and selective colorimetric detection of cartap residue in agricultural products.

The residue of pesticide has posed a serious threat to human health. Fast, broad-spectrum detection methods are necessary for on-site screening of various types of pesticides. With citrate-coated Au nanoparticles (Au NPs) as colorimetric probes, a visual and spectrophotometric method for rapid assay of cartap, which is one of the most important pesticides in agriculture, is reported for the first time. Based on the color change of Au colloid solution from wine-red to blue resulting from the aggregation of Au NPs, cartap could be detected in the concentration range of 0.05-0.6 mg/kg with a low detection limit of 0.04 mg/kg, which is much lower than the strictest cartap safety requirement of 0.1 mg/kg. Due to the limited research on the rapid detection of cartap based on Au NPs, the performance of the present method was evaluated through aggregation kinetics, interference influence, and sample pretreatment. To further demonstrate the selectivity and applicability of the method, cartap detection is realized in cabbage and tea with excellent analyte concentration recovery. These results demonstrate that the present method provides an easy and effective way to analyze pesticide residue in common products, which is of benefit for the rapid risk evaluation and on-site screening of pesticide residue.

Fe3O4 nanoparticles-enhanced SPR sensing for ultrasensitive sandwich bio-assay.

Magnetic nanoparticles (MNPs) have been receiving increasing attention because of its great potentials in bioseparation. However, the separation products are difficult to be detected by general method due to their extremely small size. Here, we demonstrate that MNPs can greatly enhance the signal of surface plasmon resonance spectroscopy (SPR). Features of MNPs-aptamer conjugates as a powerful amplification reagent for ultrasensitive immunoassay are reported in this work for the first time. In order to evaluate the sensing ability of MNPs-aptamer conjugates as an amplification reagent, a sandwich SPR sensor is constructed by using thrombin as model analyte. Thrombin, captured by immobilized anti-thrombin aptamer on SPR gold film, is sensitively detected by SPR spectroscopy with a lowest detection limit of 0.017 nM after MNPs-aptamer conjugates is used as amplification reagent. At the same time, the excellent selectivity of the present biosensor is also confirmed by using three kinds of proteins (BSA, human IgM and human IgE) as controls. These results confirm that MNPs is a powerful sandwich element and an excellent amplification reagent for SPR based sandwich immunoassay and SPR has a great potential for the detection of MNPs-based bioseparation products.

Magnetic nanoparticle enhanced surface plasmon resonance sensing and its application for the ultrasensitive detection of magnetic nanoparticle-enriched small molecules.

Magnetic nanoparticles (MNPs) have been frequently used in bioseparation, but their applicability in bioassays is limited due to their extremely small size so that sensitive detection is difficult to achieve using a general technique. Here, we present an amplification technique using MNPs for an enhanced surface plasmon resonance (SPR) bioassay. The amplification effect of carboxyl group modified Fe(3)O(4) MNPs of two sizes on SPR spectroscopy is first demonstrated by assembling MNPs on amino group modified SPR gold substrate. To further evaluate the feasibility of the use of Fe(3)O(4) MNPs in enhancing a SPR bioassay, a novel SPR sensor based on an indirect competitive inhibition assay (ICIA) is developed for detecting adenosine by employing Fe(3)O(4) MNP-antiadenosine aptamer conjugates as the amplification reagent. The results confirm that Fe(3)O(4) MNPs can be used as a powerful amplification agent to provide a sensitive approach to detect adenosine by SPR within the range of 10-10,000 nM, which is much superior to the detection result obtained by a general SPR sensor. Importantly, the present detection methodology could be easily extended to detect other biomolecules of interest by changing the corresponding aptamer in Fe(3)O(4) MNP-aptamer conjugates. This novel technique not only explores the possibility of the use of SPR spectroscopy in a highly sensitive detection of an MNP-based separation product but also offers a new direction in the use of Fe(3)O(4) MNPs as an amplification agent to design high performance SPR biosensors.

Aptamer-Au NPs conjugates-accumulated methylene blue for the sensitive electrochemical immunoassay of protein.

In this paper, we combine the advantages of aptamer, nanomaterial and antibody to design an electrochemical sandwich immunoassay for the ultrasensitive detection of human immunoglobulin E (IgE) by using methylene blue (MB) as electrochemical indicator. The sandwich structure is fabricated by using goat anti-human IgE as capturing probe. Aptamer-Au nanoparticles (NPs) conjugates are used both as a sandwich amplification element as well as an accumulation reagent of MB. Once the aptamer-Au NPs conjugates specifically bind to electrode surface, MB molecules are accumulated on its surface by the specific interaction of MB with G base of aptamer-Au NPs conjugates. Therefore, with the increase of human IgE concentration, more aptamer-Au-NPs conjugates are bound, and thus, more MB molecules are accumulated. A good linear relationship is obtained for the detection of human IgE over a range of 1-10,000 ng/ml with a lowest detection limit of 0.52 ng/ml. In addition, by using BSA, human IgA and human IgM as contrast, the excellent specificity of this sensing system for the detection of human IgE is also demonstrated.

Aptamer-Au NPs conjugates-enhanced SPR sensing for the ultrasensitive sandwich immunoassay.

The goal of this work is to explore the amplification effect of aptamer-gold nanoparticles (Au NPs) conjugates for ultrasensitive detection of large biomolecules by surface plasmon resonance (SPR). A novel sandwich immunoassay is designed to demonstrate the amplification effect of aptamer-Au NPs conjugates by using human immunoglobulin E (IgE) as model analyte. Human IgE, captured by immobilized goat anti-human IgE on SPR gold film, is sensitively detected by SPR spectroscopy with a lowest detection limit of 1 ng/ml after anti-human IgE aptamer-Au NPs conjugates is used as amplification reagent. Meanwhile, the non-specific adsorption of aptamer-Au NPs conjugates on goat anti-human IgE is confirmed by SPR spectroscopy and then it is minimized by treating aptamer-Au NPs conjugates with 6-mercaptohexan-1-ol (MCH). These results confirm that aptamer-Au NPs conjugates is a powerful sandwich element and an excellent amplification reagent for SPR-based sandwich immunoassay.

Au NPs-aptamer conjugates as a powerful competitive reagent for ultrasensitive detection of small molecules by surface plasmon resonance spectroscopy.

Features of Au NPs-aptamer conjugates as a powerful competitive reagent to substitute antibody in enhancing surface plasmon resonance spectroscopy (SPR) signal for the detection of small molecule are explored for the first time. In order to evaluate the sensing ability of Au NPs-aptamer conjugates as a competitive reagent, a novel SPR sensor based on indirect competitive inhibition assay (ICIA) for the detection of adenosine is constructed by employing the competitive reaction between antiadenosine aptamer with adenosine and antiadenosine aptamer with its partial complementary ss-DNA. The partial complementary ss-DNA of antiadenosine aptamer is firstly immobilized on SPR gold film as sensing surface. When the Au NPs-antiadenosine aptamer conjugates solution is added to SPR cell in the absence of adenosine, Au NPs-antiadenosine aptamer conjugates is adsorbed to SPR sensor by the DNA hybridization reaction, and results in a large change of SPR signal. However, the change of SPR signal is decreased when the mixing solution of adenosine with Au NPs-antiadenosine aptamer conjugates is added. This is because adenosine reacts with antiadenosine aptamer in Au NPs-antiadenosine aptamer conjugates and changes its structure from ss-DNA to tertiary structure, which cannot hybridize with its partial complementary ss-DNA immobilized on SPR gold surface. Based on this principle, a SPR sensor for indirect detection of adenosine can be developed. The experimental results confirm that the SPR sensor possesses a good sensitivity and a high selectivity for adenosine, which indirectly confirms that Au NPs-aptamer conjugates is a powerful competitive reagent. More significantly, it can be used to develop other SPR sensors based on ICIA to detect different targets by changing the corresponding type of aptamer in Au NPs-aptamer conjugates.

Aptamer-based Au nanoparticles-enhanced surface plasmon resonance detection of small molecules.

Small molecules are difficult to detect by conventional SPR technique directly because the changes in the refractive index resulting from the binding processes of small biomolecules are often small. In order to extend the application of SPR biosensor in detecting a small molecule, we combine the advantage of aptamer technique with the amplifying effect of Au nanoparticles to design a sensitive SPR sensor for detecting small molecules. The principle of this sensor is based on surface inhibition detection. The aptamer is first immobilized on SPR gold film with its ss-DNA structure. The aptamer possessing this structure can be hybridized with Au nanoparticles-tagged complementary ss-DNA and result in a large change of SPR signal. However, the aptamer will change its structure from ss-DNA to tertiary structure after adenosine is added to the SPR cell. The aptamer possessing tertiary structure could not hybridize with Au nanoparticles-tagged complementary ss-DNA. Thus, the change of SPR signal resulted in the hybridization reaction between aptamer and Au nanoparticles-tagged complementary ss-DNA will decrease with the increase of the number of aptamers possessing tertiary structure, which is proportional to the concentration of the small molecule. Based on this principle, we choose a simple system (antiadenosine aptamer/adenosine) to detect the sensing ability of this SPR biosensor for a small molecule. The experimental results confirm that the SPR sensor we developed possesses a good sensitivity and a high selectivity for adenosine. The detection range for adenosine is from 1 x 10 (-9) to 1 x 10 (-6) M. More significantly, it is fairly easy to generalize this strategy to detect a spectrum of small molecules by SPR spectroscopy using different aptamers. Therefore, it is expected that this method may offer a new direction in designing high-performance SPR biosensors for sensitive and selective detection of a wide spectrum of small molecules.