Recognition Of Biomolecules Research Articles

Structural properties and binding mechanism of DNA aptamers sensing saliva melatonin for diagnosis and monitoring of circadian clock and sleep disorders

Circadian desynchrony with the external light-dark cycle influences the rhythmic secretion of melatonin which is among the first signs of circadian rhythm sleep disorders. An accurate dim light melatonin onset (established indicator of circadian rhythm sleep disorders) measurement requires lengthy assays, and antibody affinities alterations, especially in patients with circadian rhythm disorders whose melatonin salivary levels vary significantly, making antibodies detection mostly inadequate. In contrast, aptamers with their numerous advantages (e.g., target selectivity, structural flexibility in tuning binding affinities, small size, etc.) can become preferable biorecognition molecules for salivary melatonin detection with high sensitivity and specificity. This study thoroughly characterizes the structural property and binding mechanism of a single-stranded DNA aptamer full sequence (MLT-C-1) and its truncated versions (MLT-A-2, MLT-A-4) to decipher its optimal characteristics for saliva melatonin detection. We use circular dichroism spectroscopy to determine aptamers’ conformational changes under different ionic strengths and showed that aptamers display a hairpin loop structure where few base pairs in the stem play a significant role in melatonin binding and formation of aptamer stabilized structure. Through microscale thermophoresis, aptamers demonstrated a high binding affinity in saliva samples (MLT-C-1F Kd = 12.5 ± 1.7 nM; MLT-A-4F Kd = 11.2 ± 1.6 nM; MLT-A-2F Kd = 2.4 ± 2.8 nM; limit-of-detection achieved in pM, highest sensitivity attained for MLT-A-2F aptamer with the lowest detection limit of 1.35 pM). Our data suggest that aptamers are promising as biorecognition molecules and provide the baseline parameters for the development of an aptamer-based point-of-care diagnostic system for melatonin detection and accurate profiling of its fluctuations in saliva.

Computational approaches screening DNA aptamers against conserved outer membrane protein W of Vibrio cholerae O1- an investigation expanding the potential for point-of-care detection with aptasensors

Foodborne outbreaks urge public health domain to upgrade diagnosis by means of simpler, quicker, and more affordable pathogen detection methods. A molecular recognition probe against an analyte of interest makes up a biosensor, along with a method for turning the recognition event into a quantifiable signal. Single-stranded DNA or RNA aptamers are promising bio-recognition molecules for a range of targets, including a wide range of non-nucleic acid targets with which they are highly specific and affine. In the proposed study, 40 DNA aptamers were screened and analyzed interactions using in-silico SELEX procedures, which can selectively interact with active sites at the extracellular region of the Outer membrane Protein W (OmpW) of Vibrio Cholerae. Multiple modeling techniques, like protein structural prediction with I-TASSER, aptamer structural modeling using M-fold, RNA composer, protein-DNA docking using HADDOCK, and large-scale (500 ns) molecular dynamics simulations through GROMACS have been employed. Out of 40, six aptamers having lowest free energy were docked against the predicted active site at the extracellular region of OmpW. VBAPT4-OmpW and VBAPT17-OmpW, the two highest-scoring Aptamer-Protein complexes, were chosen for molecular dynamics simulations. VBAPT4-OmpW is quite unable to attain its structural local minima after 500 ns. But VBAPT17-OmpW is showing great stability and is not destructive even after 500 ns. RMSF, DSSP, PCA, and Essential Dynamics all provided additional confirmation. Current findings, combined with the fabrication of biosensor devices, could pave the way for an innovative pathogen detection platform with high sensitivity, along with an effective and low-impact curative strategy for corresponding diseases.Communicated by Ramaswamy H. Sarma

A split-type photoelectrochemical immunosensor based on a high-performance In2O3/BiVO4 photoelectrode modulated by a ZIF-8 protective layer

Herein, a split-type photoelectrochemical (PEC) immunosensor is designed to detect neuron-specific enolase (NSE), which is a tumor marker for small cell lung cancer present in nerve and neuroendocrine tissues. In this study, a heterogeneous In2O3/BiVO4 structure is developed with coral-like BiVO4 films adsorbed onto In2O3 based on simplified successive ionic layer adsorption and reaction (s-SILAR). Moreover, immune recognition occurs in a 96-well plate in the split-type PEC immunosensor, thus effectively avoiding interference with the recognition of biomolecules. However, the sensitivity of zeolitic imidazolate framework (ZIF)− 8 molecules to pH varies, and most of the degradation of ZIF-8 molecules can be achieved by a reaction at a pH of 5.5–6.5 for > 30 min. Therefore, SiO2-glucose oxidase is selected as a regulatory switch to act on ZIF-8 molecules by catalyzing the conversion of glucose to gluconic acid, whereas In2O3/BiVO4 is selected as the photoactive substrate and ZIF-8 protective layer as the signal switch. By constructing a split-type PEC immunosensor, gluconic acid of different concentrations is released in the 96-well plate through the change of NSE concentration to regulate the degradation of the ZIF-8 protective layer and achieve the sensitive detection of NSE. The constructed PEC sensor exhibits an excellent photocurrent response between 0.1 pg mL–1 and 100 ng mL–1, with a detection limit of 0.03 pg mL–1. Simultaneously, the accuracy, specificity, stability, and reproducibility of this split-type PEC sensing platform predict its promising application in the future in the field of biomolecules.

Progress and Trends of Optical Microfiber-Based Biosensors.

Biosensors are central to diagnostic and medicinal applications, especially in terms of monitoring, managing illness, and public health. Microfiber-based biosensors are known to be capable of measuring both the presence and behavior of biological molecules in a highly sensitive manner. In addition, the flexibility of microfiber in supporting a variety of sensing layer designs and the integration of nanomaterials with biorecognition molecules brings immense opportunity for specificity enhancement. This review paper aims to discuss and explore different microfiber configurations by highlighting their fundamental concepts, fabrication processes, and performance as biosensors.

Recent Advances on Peptide-Based Biosensors and Electronic Noses for Foodborne Pathogen Detection

Foodborne pathogens present a serious issue around the world due to the remarkably high number of illnesses they cause every year. In an effort to narrow the gap between monitoring needs and currently implemented classical detection methodologies, the last decades have seen an increased development of highly accurate and reliable biosensors. Peptides as recognition biomolecules have been explored to develop biosensors that combine simple sample preparation and enhanced detection of bacterial pathogens in food. This review first focuses on the selection strategies for the design and screening of sensitive peptide bioreceptors, such as the isolation of natural antimicrobial peptides (AMPs) from living organisms, the screening of peptides by phage display and the use of in silico tools. Subsequently, an overview on the state-of-the-art techniques in the development of peptide-based biosensors for foodborne pathogen detection based on various transduction systems was given. Additionally, limitations in classical detection strategies have led to the development of innovative approaches for food monitoring, such as electronic noses, as promising alternatives. The use of peptide receptors in electronic noses is a growing field and the recent advances of such systems for foodborne pathogen detection are presented. All these biosensors and electronic noses are promising alternatives for the pathogen detection with high sensitivity, low cost and rapid response, and some of them are potential portable devices for on-site analyses.

Single‐Molecule Electronic Biosensors: Principles and Applications

AbstractSingle‐biomolecule electronic sensing techniques are of great importance in many fields, from medical diagnosis to disease surveillance. As the physiological changes of single biomolecules can be converted into measurable electrical signals, single‐molecule electronic biosensors can realize real‐time, highly sensitive, and high‐bandwidth detection of individual intra‐ or inter‐molecular interactions. These powerful single‐molecule sensing devices have demonstrated key advantages in precisely providing rare and detailed intermediate information along reaction pathways and revealing unique properties hidden in ensemble measurements. This review summarizes significant advances in single‐molecule electronic biosensors, emphasizing biomolecule recognition, interaction, and reaction dynamics at the single‐molecule level. Sensor configurations, sensing mechanisms, and representative applications are also discussed. Furthermore, a perspective on the use of photoelectric integrated systems for synchronous sensing of the electrical and optical signals of single biomolecules is provided.

Biomolecule classification by multiscale one-dimensional convolutional neural network.

Raman spectroscopy has been used as a powerful tool to identify biomolecules in various fundamental and clinical studies. In recent years, machine learning has been used in the spectroscopy field to extract the spectrum feature for biomolecule classification and recognition. However, few methods have been developed for the classification of non-preprocessed spectra of biomolecules. The main challenge to deal with the spectra is the weak signals, strong backgrounds, and high bio-complexity. In this study, we developed a method to classify the membrane protein behavior in a nanometer-thin bilayer after an activator was applied. First, we used data augmentation to solve the problem of the sparsity of our spectrum data. Second, we constructed a multiscale 1D-CNN model for the spectrum classification. The ability to capture spectral features at different scales with the multiscale 1D-CNN model can deal with the difficulty to classify spectra of the complex cell membrane system. Last, score-CAM was used for model visualization to explain which spectrum features were used for the classification. The results show that our proposed multiscale 1D-CNN can improve the model performance metrics of other conventional machine algorithms by 4% to 13%. In addition, the obtained heatmaps from score-CAM also provided reasonable interpretations for the classification results in the amide I and amide III spectrum regions. These results show that the method we developed can give a persuasive classification for target biomolecules and has the potential to be applied in the study of disease treatment and biochemical reactions.

Ag–ZnO Nanocomposites as a 3D Metal-Enhanced Fluorescence Substrate for the Fluorescence Detection of DNA

Fluorescence enhancement, including metal-enhanced fluorescence (MEF), has been widely explored in the field of biosensor technology. Two- and three-dimensional (2D and 3D) MEF substrate approaches have been developed for biosensors to detect target biomarkers such as genes and proteins. However, several issues remain, not least poor reproducibility caused by limited recognition and diffusion of biomolecules among target molecules, biological probes, and MEF substrates in aqueous environments. Here, an Ag–ZnO nanocomplex as a 3D MEF substrate was developed in two steps: hydrothermal synthesis of ZnO nanowire (NW) as a building block of Ag nanoparticles (NPs), and photochemical deposition of AgNPs on the ZnO NW. Fluorescence enhancement on Ag–ZnO nanocomposites (NCs) compared with the glass substrate was 14.8-, 16.9-, 11.4-, and 14.2-fold in the presence of 10, 20, 40, and 60 base pair (bp) double-stranded (ds) DNA, respectively. The MEF effects on glass, ZnO NW, and Ag–ZnO NCs were analyzed by measuring the fluorescence lifetime of fluorescein (FAM)-labeled dsDNA, and the average lifetimes were 9.76, 9.34, and 7.86 ns, respectively. Ag–ZnO NCs showed a 50-fold higher sensitivity for the detection of dsDNA than Ag nanoisland film (AgNIF) as a 2D MEF substrate. Therefore, Ag–ZnO NCs may have potential as a 3D MEF substrate. The MEF phenomenon might involve broad-range interactions between the surface of the metal nanostructure on Ag–ZnO NCs and fluorophores in various scenarios. Our Ag–ZnO NCs could facilitate the development of sensitive MEF-based biosensors for DNA detection.

Label-Free Microchannel Immunosensor Based on Antibody-Antigen Biorecognition-Induced Charge Quenching.

Pursuing convenient operations and precise testing have become an urgent requirement in clinical diagnosis, treatment, and prognosis. Label-free detection is desirable for obviating the labeling process while maintaining high sensitivity and efficiency. Here, we used the dual properties of highly selective antibody-antigen recognition and potential signaling of biomolecules to construct a label-free electroosmotic flow-driven microchannel (LF-EMB) biosensor based on an antibody-antigen biorecognition-induced charge quenching theory proposed herein. The LF-EMB consists of a one-step immune-reaction, one-button portable device, and supporting microfluidic chip, providing a high-powered tool for rapid on-site testing. The LF-EMB quantified interleukin-6 and kanamycin levels down to 1 pg/mL and 5 pg/mL, respectively, with the whole analysis completed within 35 min. The outstanding sensitivity and detection speed of the constructed LF-EMB provide a convenient option for the quantitative detection of inflammatory markers and antibiotics.

Single-use biomimetic sensors for rapid and sensitive cortisol detection in blood

The detection of biomarkers in blood using portable point-of-care (POC) devices can provide immense benefits for disease diagnosis and healthcare management. Electrochemical biosensors with rapid response, accuracy, high sensitivity, miniaturization, and portability are particularly advantageous for such applications. Here, we report on a photolithographically micropatterned, biomimetic organic 3-electrode impedimetric sensor (O3ES) for the ultralow volume (single drop – 10 μL) detection of cortisol in whole blood. The O3ES comprising a soft conducting polymer (PEDOT:PSS) and silk protein matrix provides a stable electrochemical signal from whole blood with minimal biofouling interference. A water-based, ambient processing of the sensors allows the immobilization of antibodies in the working electrode which act as the specific biorecognition molecules for cortisol. The increase in charge transfer resistance due to cortisol-antibody binding at the electrode surface is monitored to obtain a calibration curve via electrochemical impedance spectroscopy. The O3ES displays a linear and specific sensitivity towards cortisol in whole blood in the range of 0.01–50 μg dL−1. The flexible O3ES strips are designed to be discarded after a single use. This work demonstrates the realization of low-cost, disposable, organic POC sensors capable of detecting steroid hormones using ultralow sample volumes.

Structure and Molecular Dynamics in Metal-Containing Polyamide 6 Microparticles

Polymer microparticles are used in additive manufacturing, separation and purification devices, biocatalysis, or for the recognition of biomolecules. This study reports on the effect of metal fillers on the structure and molecular dynamics of polyamide 6 (PA6) microparticles (MPs) containing up to 19 wt.% of Al, Cu, or Mg. These hybrid MPs are synthesized via reactive microencapsulation by anionic ring-opening polymerization in solution, in the presence of the metal filler. 13C high-resolution solid-state NMR (ssNMR) spectroscopy is employed as the primary characterization method using magic angle spinning (MAS) and cross-polarization (CP)/MAS. Depending on the metal filler, the ssNMR crystallinity index of the MP varies between 39–50%, as determined by deconvolution of the 13C MAS and CP/MAS spectra. These values correlate very well with the crystallinity derived from thermal or X-ray diffraction data. The molecular dynamics study on PA6 and Cu-containing MP shows similar mobility of carbon nuclei in the kHz, but not in the MHz frequency ranges. The paramagnetic Al and Mg have an observable effect on the relaxation; however, conclusions regarding the PA6 carbon motions cannot be unequivocally made. These results are useful in the preparation of hybrid microparticles with customized structures and magneto-electrical properties.

Stimuli-Responsible SNARF Derivatives as a Latent Ratiometric Fluorescent Probe.

Fluorescence imaging is a powerful technique for continuous observation of dynamic intracellular processes of living cells. Fluorescent probes bearing a fluorescence switching property associated with a specific recognition or reaction of target biomolecule, that is, stimuli-responsibility, are important for fluorescence imaging. Thus, fluorescent probes continue to be developed to support approaches with different design strategies. When compared with simple intensity-changing fluorescent probes, ratiometric fluorescent probes typically offer the advantage of less sensitivity to errors associated with probe concentration, photobleaching, and environmental effects. For intracellular usage, ratiometric fluorescent probes based on small molecules must be loaded into the cells. Thus, probes having intrinsic fluorescence may obscure a change in intracellular signal if the background fluorescence of the remaining extracellular probes is high. To overcome such disadvantages, it is necessary to minimize the extracellular background fluorescence of fluorescent probes. Here, the design strategy of the latent ratiometric fluorescent probe for wash-free ratiometric imaging using a xanthene dye seminapthorhodafluor (SNARF) as the scaffold of fluorophore is discussed.

Bacteriophage-Based Biosensors: A Platform for Detection of Foodborne Bacterial Pathogens from Food and Environment.

Foodborne microorganisms are an important cause of human illness worldwide. Two-thirds of human foodborne diseases are caused by bacterial pathogens throughout the globe, especially in developing nations. Despite enormous developments in conventional foodborne pathogen detection methods, progress is limited by the assay complexity and a prolonged time-to-result. The specificity and sensitivity of assays for live pathogen detection may also depend on the nature of the samples being analyzed and the immunological or molecular reagents used. Bacteriophage-based biosensors offer several benefits, including specificity to their host organism, the detection of only live pathogens, and resistance to extreme environmental factors such as organic solvents, high temperatures, and a wide pH range. Phage-based biosensors are receiving increasing attention owing to their high degree of accuracy, specificity, and reduced assay times. These characteristics, coupled with their abundant supply, make phages a novel bio-recognition molecule in assay development, including biosensors for the detection of foodborne bacterial pathogens to ensure food safety. This review provides comprehensive information about the different types of phage-based biosensor platforms, such as magnetoelastic sensors, quartz crystal microbalance, and electrochemical and surface plasmon resonance for the detection of several foodborne bacterial pathogens from various representative food matrices and environmental samples.

Experimental Evaluation of Quantum Dots and Antibodies Conjugation by Surface Plasmon Resonance Spectroscopy.

The application of antibody-functionalized quantum dots (QDs) in different areas has been widely described in the literature. However, a standard routine method for obtaining information on the conjugation efficiency of QDs with antibodies in terms of the interaction of the functionalized QDs with a specific antigen is still lacking. Herein, surface plasmon resonance (SPR) spectroscopy is proposed for this purpose. Gold-coated SPR sensor disks were modified with a self-assembled monolayer of 11-mercaptoundecanoic acid, and carbodiimide cross-linker chemistry was used to covalently immobilize the CD44 biomarker on the premodified surface (Au/CD44). Meanwhile, QDs functionalized with amine-derivatized polyethylene glycol (PEG) (QDs-NH2) were chosen for conjugation with antibodies because of their low non-specific adsorption on the Au/CD44 surface. Prior to conjugation, the surface binding capacity (Bmax) and equilibrium dissociation constant (KD) of the specific antibodies against CD44 (anti-CD44) were found to be 263.32 ± 2.44 m° and 1.00 × 10−7 ± 2.29 × 10−9 M, respectively. QDs-NH2 and anti-CD44 were conjugated at their initial molar ratios of 1:3, 1:5, 1:10 and 1:12. SPR measurements showed that the conjugates (QDs-anti-CD44) prepared using 1:10 and 1:12 molar ratios interacted comparably with immobilized CD44 biomarkers. The equilibrium angles in the case of 10- and 12-fold concentrations of anti-CD44 were calculated to be 60.43 ± 4.51 and 61.36 ± 4.40 m°, respectively. This could be explained by the QDs-NH2 and anti-CD44 having a similar surface loading (about four molecules per QDs-NH2) and similar hydrodynamic diameters, which were 46.63 ± 3.86 and 42.42 ± 0.80 nm for the 1:10 and 1:12 ratios, respectively. An initial QDs-NH2: anti-CD44 molar ratio of 1:10 was chosen as being optimal. SPR spectroscopy proved to be the right choice for QDs-anti-CD44 conjugation optimization, and can be used for the evaluation of conjugation efficiency for other nanostructures with various bio-recognition molecules.

Unique three‐component co‐assembly among AIEgen, L‐GSH, and Ag+ for the formation of helical nanowires

AbstractNature has selected, produced, and evolved numerous molecular architectural motifs over billions of years for particular bio‐functions. During this process, molecular self‐assembly plays a critically important role. Inspired by these delicate assemblies, scientists devote themselves to developing various sophisticated complexes assembled by diverse and numerous structural motifs. By far, most of the examples focus on single‐molecule self‐assembly or co‐assembly between two molecules, seldom works report the co‐assembly among three building blocks due to the substantially increased complexity and decreased controllability. Here we report a novel three‐component co‐assembly among L‐glutathione (L‐GSH), AgNO3, and an aggregation‐induced emission luminogen (AIEgen), namely triphenylamine–pyridinium (abbreviated to TPA‐Py). TPA‐Py, L‐GSH, and Ag+ co‐assemble into numerous long and ordered nanowires with left‐handed helices, which show remarkable AIE properties that can be observed by naked eyes. This effect is only detected in this system, the replacement of TPA‐Py with other AIEgens, L‐GSH with other cysteine derivatives or anions, Ag+ with other metal ions, could not lead to the unique AIE effect, which endows this system with high specificity and controllability. This work provides new insight into the design of biomolecule recognition systems and discloses that ternary co‐assembly could become a facile route to build sophisticated nanobiomaterials.

PEGylated Ni Single-Atom Catalysts as Ultrasensitive Electrochemiluminescent Probes with Favorable Aqueous Dispersibility for Assaying Drug-Resistant Pathogens.

Ni single-atom catalysts (SACs) were synthesized by high-temperature calcination of nickel ions and 1,10-phenanthroline on carbon black as a carrier. Benefiting from the ultrahigh atom utilization efficiency, Ni SACs can significantly accelerate decay of dissolved oxygen to generate abundant reactive oxygen species through an oxygen reduction reaction occurring on cathodes. The generated reactive oxygen species can vastly enhance the electrochemiluminescent (ECL) signal of luminol without participation of exogenous co-reactants. To overcome the inherent unfavorable aqueous dispersibility of Ni SACs prepared by the calcination protocol, they were functionalized with highly hydrophilic PEG 2000. Thanks to the abundant carboxyl groups on PEG 2000, the PEGylated Ni SACs (Ni@PEG) can be used as ECL probes to tag biorecognition molecules. In this proof-of-principle work, an ECL biosensor for assaying methicillin-resistant Staphylococcus aureus was developed by using porcine IgG as capture molecule and phage cell-binding domain tagged with Ni@PEG as signal tracer. It shows a broad linear range of 73-7.3 × 106 CFU/mL and a low detection limit of 25 CFU/mL. The recovery values for assaying spiked samples are between 80.8 and 119.2%. It was also utilized to assess MRSA susceptibility to four antibiotics, with results consistent with those obtained by the standard broth microdilution technique. To the best of our knowledge, it is the first time to utilize aqueous dispersible SACs as highly sensitive ECL probes for developing biosensors.

Design principles of bioinspired interfaces for biomedical applications in therapeutics and imaging.

In the past two decades, we have witnessed rapid developments in nanotechnology, especially in biomedical applications such as drug delivery, biosensing, and bioimaging. The most commonly used nanomaterials in biomedical applications are nanoparticles, which serve as carriers for various therapeutic and contrast reagents. Since nanomaterials are in direct contact with biological samples, biocompatibility is one of the most important issues for the fabrication and synthesis of nanomaterials for biomedical applications. To achieve specific recognition of biomolecules for targeted delivery and biomolecular sensing, it is common practice to engineer the surfaces of nanomaterials with recognition moieties. This mini-review summarizes different approaches for engineering the interfaces of nanomaterials to improve their biocompatibility and specific recognition properties. We also focus on design strategies that mimic biological systems such as cell membranes of red blood cells, leukocytes, platelets, cancer cells, and bacteria.

Luminescent Aptamer-Based Bioassays for Sensitive Detection of Food Allergens.

The presence of hidden allergens in food products, often due to unintended contamination along the food supply chain (production, transformation, processing, and transport), has raised the urgent need for rapid and reliable analytical methods for detecting trace levels of such species in food products. Indeed, food allergens represent a high-risk factor for allergic subjects due to potentially life-threatening adverse reactions. Portable biosensors based on immunoassays have already been developed as rapid, sensitive, selective, and low-cost analytical platforms that can replace analyses with traditional bench-top instrumentation. Recently, aptamers have attracted great interest as alternative biorecognition molecules for bioassays, since they can bind a variety of targets with high specificity and selectivity, and they enable the development of assays exploiting a variety of transduction and detection technologies. In particular, aptasensors based on luminescence detection have been proposed, taking advantage of the development of ultrasensitive tracers and enhancers. This review aims to summarize and discuss recent efforts in the field of food allergen analysis using aptamer-based bioassays with luminescence detection.

One-step high-throughput detection of low-abundance biomarker BDNF using a biolayer interferometry-based 3D aptasensor

Although biosensors for signal monitoring have been extensively developed, their application in one-step high-throughput detection of low-abundance disease biomarkers remains challenging. This study presents a 3D aptasensor based on a biolayer interferometry (BLI) technique, followed by the sensitive and rapid detection of the specific biomarker brain-derived neurotrophic factor (BDNF) for early screening of glaucoma, an irreversible disease that causes blindness. The developed 3D aptasensor enabled one-step batch conversion of the low-abundance biomarker BDNF binding into optical interference signal, which was mainly attributed to the following factors: (1) A dimeric aptamer with extremely high targeting affinity was constructed as a biorecognition molecule, (2) highly sensitive 3D matrix sensors were integrated as signal transduction elements, and (3) the BLI Octet system with automated, high-throughput, and real-time online monitoring capabilities was used for reporting. The 3D aptasensor exhibited a broad detection window from 0.41 to 250 ng/mL BDNF, with a limit of detection of 0.2 ng/mL. Furthermore, detection of BDNF in glaucoma patient serum using the aptasensor showed good agreement with ELISA findings as well as the clinical diagnosis of the patient, demonstrating the feasibility of the system as a screening tool for glaucoma. This one-step high-throughput screening approach provides a valuable solution for the early diagnosis of glaucoma and may reduce the risk of blindness in visually impaired people.

Label-free detection of glypican-3 using reduced graphene oxide /polyetherimide/gold nanoparticles enhanced aptamer specific sensing interface on light-addressable potentiometric sensor

Glypican-3 (GPC3) protein is considered as an effective and specific biomarker for the accurate diagnosis of hepatocellular carcinoma (HCC), and there is a critical demand to construct strategies with shorter time, lower cost noise and higher sensitivity. In this study, a biosensor for label-free detection of GPC3 was prepared by modifying GPC3 aptamer (GPC3Apt) on the surface of Si-based light addressable potentiometric sensor (LAPS) chip modified by reduced graphene oxide/polyetherimide/gold nanoparticles (rGO/PEI/AuNPs). Among them, GPC3Apt with a low equilibrium dissociation constant was used as a biorecognition molecule to recognize and capture GPC3. The rGO/PEI/AuNPs decorated on the LAPS surface could enlarge the surface area for GPC3Apt immobilization and provide more active sites for GPC3Apt to bind effectively with the target GPC3. When a bias voltage was provided to the LAPS system, the forming GPC3-GPC3Apt complexs on the sensing interface of LAPS would cause the potential of the sensitive membrane surface to change and generate a corresponding offset response in photocurrent-voltage (I-V) curves. The potential shift and GPC3 concentration showed a good linear range from 0.1 to 100.0 μg/mL with a detection limit of 40.0 ng/mL (S/N = 3) and a sensitivity of 1.33638 mV/μg/mL. In addition, the LAPS detection system also has good specificity and stability, which can be used for the detection of GPC3 in spiked serum samples.