Ultrasensitive sensor for detection of early stage chronic kidney disease in human

Ultrasensitive sensing urinary cystatin C via an interface-engineered graphene extended-gate field-effect transistor for non-invasive diagnosis of chronic kidney disease

Early chronic kidney disease (CKD) has strong concealment and lacks an efficient, non-invasive, and lable-free detection platform. Cystatin C (Cys C) in urine is closely related to the progress of CKD (especially at the early stage), which is an ideal endogenous marker to evaluate the impairment of renal function. Thus, the accurate detection of urinary Cys C (u-Cys C) is great significant for early prevention and treatment and delaying the course of the disease of CKD patients. Herein, we developed an extended-gate field-effect transistor (EG-FET) sensor for ultrasensitive detection of u-Cys C, which consists of a monolithic interface-engineered graphene EG electrode array and a commercially available MOSFET. Laser-induced graphene (LIG) loaded with sputtered Au NPs in the presence of adhesive Cr (Au NPs/Cr/LIG) boosts the electrical performance of the EG electrode. Meanwhile, Au NPs also serve as linkers to immobilize papain that can selectively form protein complexes with Cys C. Supported by the synergistic effect of multilevel interface-engineered graphene, our sensor exhibits a good linear correlation within the u-Cys C concentration range of 5 ag/μL to 50 ng/μL with low detection limit of 0.05 ag/μL. Our work makes accurate, specific and rapid detection of u-Cys C feasible and promising for early screening for CKD.

Phospholipid-functionalized gold electrode for cellular membrane interface studies - interactions between DMPC bilayer and human cystatin C

This work describes the electrochemical studies on the interactions between V57G mutant of human cystatin C (hCC V57G) and membrane bilayer immobilized on the surface of a gold electrode. The electrode was modified with 6-mercaptohexan-1-ol (MCH) and 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC). DMPC was used as a membrane mimetic for monitoring electrochemical changes resulting from the interactions between the functionalized electrode surface and human cystatin C. The interactions between the modified electrode and hCC V57G were investigated by cyclic voltammetry and electrochemical impedance spectroscopy in a phosphate buffered saline (PBS) containing Fe(CN)63-/4- as a redox probe. The electrochemical measurements confirm that fabricated electrode is sensitive to hCC V57G at the concentration of 1 × 10-14 M. The incubation studies carried out at higher concentrations resulted in insignificant changes observed in cyclic voltammetry and electrochemical impedance spectroscopy measurements. The calculated values of surface coverage θR confirm that the electrode is equally covered at higher concentrations of hCC V57G. Measurements of wettability and surface free energy made it possible to determine the influence of individual structural elements of the modified gold electrode on its properties, and thus allowed to understand the nature of the interactions. Contact angle values confirmed the results obtained during electrochemical measurements, indicating the sensitivity of the electrode towards hCC V57G at the concentration of 1 × 10-14 M. In addition, the XPS spectra confirmed the successful anchoring of hCC V57G to the DMPC-functionalized surface.

Design and development of opto-electrochemical biosensing devices for diagnosing chronic kidney disease

Chronic kidney disease (CKD) is emerging as one of the major causes of the increase in mortality rate and is expected to become 5th major cause by 2050. Many studies have shown that it is majorly related to various risk factors, and thus becoming one of the major health issues around the globe. Early detection of renal disease lowers the overall burden of disease by preventing individuals from developing kidney impairment. Therefore, diagnosis and prevention of CKD are becoming the major challenges, and in this situation, biosensors have emerged as one of the best possible solutions. Biosensors are becoming one of the preferred choices for various diseases diagnosis as they provide simpler, cost-effective and precise methods for onsite detection. In this review, we have tried to discuss the globally developed biosensors for the detection of CKD, focusing on their design, pattern, and applicability in real samples. Two major classifications of biosensors based on transduction systems, that is, optical and electrochemical, for kidney disease have been discussed in detail. Also, the major focus is given to clinical biomarkers such as albumin, creatinine, and others related to kidney dysfunction. Furthermore, the globally developed sensors for the detection of CKD are discussed in tabulated form comparing their analytical performance, response time, specificity as well as performance in biological fluids.

Ultrasensitive Silicon Nanowire Biosensor with Modulated Threshold Voltages and Ultra-Small Diameter for Early Kidney Failure Biomarker Cystatin C

Acute kidney injury (AKI) is a frequently occurring severe disease with high mortality. Cystatin C (Cys-C), as a biomarker of early kidney failure, can be used to detect and prevent acute renal injury. In this paper, a biosensor based on a silicon nanowire field-effect transistor (SiNW FET) was studied for the quantitative detection of Cys-C. Based on the spacer image transfer (SIT) processes and channel doping optimization for higher sensitivity, a wafer-scale, highly controllable SiNW FET was designed and fabricated with a 13.5 nm SiNW. In order to improve the specificity, Cys-C antibodies were modified on the oxide layer of the SiNW surface by oxygen plasma treatment and silanization. Furthermore, a polydimethylsiloxane (PDMS) microchannel was involved in improving the effectiveness and stability of detection. The experimental results show that the SiNW FET sensors realize the lower limit of detection (LOD) of 0.25 ag/mL and have a good linear correlation in the range of Cys-C concentration from 1 ag/mL to 10 pg/mL, exhibiting its great potential in the future real-time application.

A Non-Immunized and BSA-Template Aggregation-Induced Emission Sensor for Noninvasive Detection of Cystatin C in the Clinical Diagnosis of Diabetes Nephropathy

Diabetes nephropathy (DN) is one of the main causes of death in patients with diabetes. Cystatin C (Cys C) is a reliable indicator of glomerular filtration function. Therefore, it is urgent and meaningful to obtain early warning of DN by noninvasive measurement of Cys C. In this investigation, a novel fluorescence sensor (BSA-AIEgen sensor) was synthesized by cross-linking the aggregation-induced emission (AIE) characteristics of 2-(4-bromophenyl)-3-(4-(4-(diphenylamino) styryl) phenyl) fumaronitrile (TPABDFN) and bovine serum albumin (BSA), which exhibited the "On" state owing to the restriction of the intramolecular motions (RIM) phenomenon of TPABDFN. Intriguingly, a decrease in fluorescence of BSA-AIEgen sensors could be found owing to BSA on the surface of BSA-AIEgen sensor hydrolyzed by papain, but a reverse phenomenon emerged with the increase of Cys C content as the inhibitor of papain. Hence, Cys C was successfully detected by employing the fluorescent differential display and the linear range was from 12.5 ng/mL to 800 ng/mL (R² = 0.994) with the limit of detection (LOD) of 7.10 ng/mL (S/N = 3). Further, the developed BSA-AIEgen sensor successfully differentiates patients with diabetes nephropathy from volunteers with the advantages of high specificity, low cost, and simple operation. Accordingly, it is expected to become a non-immunized method to monitor Cys C for the early warning, noninvasive diagnosis, and drug efficacy evaluation of diabetes nephropathy.

Highly Specific Detection of Oxytocin in Saliva

Oxytocin is a peptide neurophysin hormone made up of nine amino acids and is used in induction of one in four births worldwide (more than 13 percent in the United States). Herein, we have developed an antibody alternative aptamer-based electrochemical assay for real-time and point-of-care detection of oxytocin in non-invasive saliva samples. This assay approach is rapid, highly sensitive, specific, and cost-effective. Our aptamer-based electrochemical assay can detect as little as 1 pg/mL of oxytocin in less than 2 min in commercially available pooled saliva samples. Additionally, we did not observe any false positive or false negative signals. This electrochemical assay has the potential to be utilized as a point-of-care monitor for rapid and real-time oxytocin detection in various biological samples such as saliva, blood, and hair extracts.

A novel biosensor for ultrasensitive detection of fungal genes

Fungal infections are a rapidly increasing public health problem due to their high morbidity and mortality rates, especially in populations with compromised immune systems. Rapid and accurate diagnosis of these diseases is, therefore, necessary to improve the prognosis of afflicted patients. Unfortunately, current clinical chemistry practice relies on lengthy culturing methods that are insufficient to meet the fast turnaround requirements. Here we present a cost-effective and robust nucleic acid sensor that can identify the presence of histoplasmosis causing fungal genes, in whole blood or bronchoalveolar lavage (BAL) samples, far earlier than current methods. Our novel assay involves the hybridization of target gene sequences with immobilized nucleic acid probes, allowing direct, label-free detection of Hcp100, CBP1, and M antigen genes through electrochemical analysis. The resultant current is attributed to the presence of fungal targets in the sample solution. The assay provides ultra-sensitive detection of DNA molecules with a limit of detection (LOD) values down to 100 aM, sufficient to meet the clinical diagnostic need. In addition, the turnaround time for the sample to result is less than 90 min compared to the current clinical procedure's turnaround time of 3-4 weeks.

Alkaline n-gqds fluorescent probe for the ultrasensitive detection of creatinine

Creatinine (Crn) is an important excretory product of the human body. Medical laboratory technology has improved over years and brought many advancements in clinical diagnostics equipment, and testing techniques and made the tests more efficient. Yet, the quantitative analysis of Crn is still carried out by the classical Jaffe's reaction (using Picric acid (PA) with NaOH) method. Since PA is hazardous to human health, alternative solutions such as; nanoparticles and surface-modified nanoparticles can be used. Exploring the optoelectronic properties of carbon-based quantum dots for biomolecule sensing is of current interest among researchers. Nitrogen functionalized graphene quantum dots (Alk-NGQDs) measured featured Crn easier and reduced the time taken for the test carried out in laboratories. The synthesized Alk-NGQDs optical, structural, morphological properties, surface and compositions are studied through XPS, HRTEM, XRD, FTIR, and spectroscopic techniques. Alk-NGQDs at alkaline conditions (pH 9.5) form a stable complex with Crn through intermolecular charge transfer (ICT). The fluorescence titration method is used to sense Crn in commercial Crn samples and human blood serum. To understand the efficacy of sensing creatinine using Alk-NGQDs, working concentration, fluorescence quantum yield, the limit of detection, and quenching constant are calculated using the Stern-Volmer plot. The emission property of Alk-NGQDs is aimed to bring an alternative to the traditional colorimetric Jaffe's reaction.

SPR-Based Sensor for the Early Detection or Monitoring of Kidney Problems

SPR-based technology has emerged as one of the most versatile optical tools for analyzing the binding mechanism of molecular interaction due to its inherent advantages in sensing applications, such as real-time, label-free, and high sensitivity characteristics. SPR is widely used in various fields, including healthcare, environmental management, and food-borne illness analysis. Meanwhile, kidney disease has grown to be one of the world's most serious public health problems in recent decades, resulting in physical degeneration and even death. As a result, several studies have published their findings regarding developing of reliable sensor technology based on the SPR phenomenon. However, an integrated and comprehensive discussion regarding the application of SPR-based sensors for detecting of kidney disease has not yet been found. Therefore, this review will discuss the recent advancements in the development of SPR-based sensors for monitoring kidney-related diseases. Numerous SPR configurations will be discussed, including Kretschmann, Otto, optical fiber-based SPR, and LSPR, which are all used to detect analytes associated with kidney disease, including urea, creatinine, glucose, uric acid, and dopamine. This review aims to show the broad application of SPR sensors which encouraged the development of SPR sensors for kidney problems monitoring.

Microneedle patches integrated with lateral flow cassettes for blood-free chronic kidney disease point-of-care testing during a pandemic

Chronic kidney disease (CKD) is the most neglected chronic disease affecting over 750 million persons in the world. Currently, many patients with cancers or other chronic diseases (i.e., CKD) struggle to receive clinical treatment or examination due to hospitals cancelling or delaying in the COVID-19 pandemic, which may increase the risk of death. Cystatin C (Cys C) has been proposed as a potential glomerular filtration rate (GFR) marker for the early detection of acute kidney injury and CKD. However, most traditional methods for Cys C detection are immunoassays using serum as a sample and are tedious to perform and economically burdensome. To diagnose the disease in the early stage and carry out daily management during the current pandemic, we developed an integration of hydrogel microneedle patch (HMNP) and lateral flow cassette (LFC) to rapidly detect Cys C in skin interstitial fluid (ISF) in 25 min for blood-free CKD management anytime and anywhere by the naked eye that can reduce the impact of an individual's quality of life and life expectancy. Conceivably, this strategy presents a wide scope in the application of numerous other diseases if corresponding analytes are available in skin ISF.

Quercetin-Ameliorated, Multi-Walled Carbon Nanotubes-Induced Immunotoxic, Inflammatory, and Oxidative Effects in Mice

The expanding uses of carbon nanotubes (CNTs) in industry and medicine have raised concerns about their toxicity on human and animal health. CNTs, including multi-walled nanotubes (MWCNTs), have been reported to induce immunotoxic, inflammatory, and oxidative effects. Quercetin is a natural flavonoid present in many vegetables and fruits and has immunomodulatory, anti-inflammatory, and antioxidant properties. Herein, we investigated the protective effects of quercetin on pristine MWCNTs-induced immunotoxicity in mice. In comparison with two doses of MWCNTs, high doses [0.5 mg/kg body weight (BW), once intraperitoneally (IP)] caused higher immunotoxic, inflammatory, and oxidative effects than low doses (0.25 mg/kg BW, once IP). Administration of quercetin (30 mg/kg BW, IP for 2 weeks) relieved these deleterious effects as evidenced by (1) reduced spleen weight, (2) increased number of total leukocytes, lymphocytes, and neutrophils, (3) elevated serum levels of IgM, IgG, and IgA, (4) decreased lipid peroxide malondialdehyde levels and increased levels of antioxidant markers reduced glutathione, superoxide dismutase, and catalase in the spleen, (5) decreased concentrations and mRNA levels of inflammatory markers tumor necrosis factor-alpha (TNFα), interleukin 1 beta (IL1ß), and IL6 in the spleen, (6) downregulated expression of immunomodulatory genes transforming growth factor-beta (TGFß), cyclooxygenase2 (COX2), and IL10, and (7) regenerative histological changes as indicated by decreased mononuclear cell infiltration, minimized degenerative changes and restored lymphocytes depletion in the spleen. These results infer that quercetin can ameliorate MWCNTs-induced immunotoxic, inflammatory, and oxidative effects.

Advances in Biosensor Technologies for Acute Kidney Injury

Acute kidney injury (AKI) is one of the most prevalent and complex clinical syndromes with high morbidity and mortality. The traditional diagnosis parameters are insufficient regarding specificity and sensitivity, and therefore, novel biomarkers and their facile and rapid applications are being sought to improve the diagnostic procedures. The biosensors, which are employed on the basis of electrochemistry, plasmonics, molecular probes, and nanoparticles, are the prominent ways of developing point-of-care devices, along with the mutual integration of efficient surface chemistry strategies. In this manner, biosensing platforms hold pivotal significance in detecting and quantifying novel AKI biomarkers to improve diagnostic interventions, potentially accelerating clinical management to control the injury in a timely manner. In this review, novel diagnostic platforms and their manufacturing processes are presented comprehensively. Furthermore, strategies to boost their effectiveness are also indicated with several applications. To maximize these efforts, we also review various biosensing approaches with a number of biorecognition elements (e.g., antibodies, aptamers, and molecular imprinting molecules), as well as benchmark their features such as robustness, stability, and specificity of these platforms.

Conventional and nanotechnology based sensors for creatinine (A kidney biomarker) detection: A consolidated review

There is an increasing demand for developing the novel methods for the detection of clinically important metabolites. One among those metabolites is creatinine (2-amino-1-methyl-5H-imidazol-4-one), a waste product, produced by the catabolism of phosphocreatine from muscle and protein metabolism, finally excreted by the kidney. It is very important to measure the creatinine level in human blood and urine because it reflects the muscular and thyroid functions. Importantly, the elevated level of creatinine is considered to be as impairment of the kidney. There are numerous methods existed to measure the concentration of creatinine in blood and urine. In this review, we consolidated the different conventional methods (chromatography, spectroscopy, immune sensor and enzyme-based detections) and their shortcomings. On other hand, we also dissertated the various nanomaterials (chemiluminescence, voltametric, amperometric, conductometric, potentiometric, impedimetric and nano polymer) based creatinine detection methods and their advantages. Finally, we also focussed on the point-of-care detection methods of creatinine determination. This review can conclude the low cost, more efficient and reliable new sensors have been developed with upgraded nanotechnology for the detection of creatinine.

Predicting Diagnostic Potential of Cathepsin in Epithelial Ovarian Cancer: A Design Validated by Computational, Biophysical and Electrochemical Data

Background: Epithelial ovarian cancer remains one of the leading variants of gynecological cancer with a high mortality rate. Feasibility and technical competence for screening and detection of epithelial ovarian cancer remain a major obstacle and the development of point of care diagnostics (POCD) may offer a simple solution for monitoring its progression. Cathepsins have been implicated as biomarkers for cancer progression and metastasis; being a protease, it has an inherent tendency to interact with Cystatin C, a cysteine protease inhibitor. This interaction was assessed for designing a POCD module. Methods: A combinatorial approach encompassing computational, biophysical and electron-transfer kinetics has been used to assess this protease-inhibitor interaction. Results: Calculations predicted two cathepsin candidates, Cathepsin K and Cathepsin L based on their binding energies and structural alignment and both predictions were confirmed experimentally. Differential pulse voltammetry was used to verify the potency of Cathepsin K and Cathepsin L interaction with Cystatin C and assess the selectivity and sensitivity of their electrochemical interactions. Electrochemical measurements indicated selectivity for both the ligands, but with increasing concentrations, there was a marked difference in the sensitivity of the detection. Conclusions: This work validated the utility of dry-lab integration in the wet-lab technique to generate leads for the design of electrochemical diagnostics for epithelial ovarian cancer.

Current molecular diagnostics assays for SARS-CoV-2 and emerging variants

Since the SARS-CoV-2 virus triggered the beginning of the COVID-19 pandemic, scientists, government officials, and healthcare professionals around the world recognized the need for accessible, affordable, and accurate testing to predict and contain the spread of COVID-19. In the months that followed, research teams designed, tested, and rolled out hundreds of diagnostic assays, each with different sampling methods, diagnostic technologies, and sensitivity levels. However, the contagious virus continued to spread; SARS-CoV-2 travelled through airborne particles and spread rapidly, despite the widening use of diagnostic assays. As the pandemic continued, hundreds of millions of people contracted COVID-19 and millions died worldwide. With so many infections, SARS-CoV-2 received many opportunities to replicate and mutate, and from these mutations emerged more contagious, deadly, and difficult-to-diagnose viral mutants. Each change to the viral genome presented potential added challenges to containing the virus, and as such, researchers have continued developing and improving testing methods to keep up with COVID-19. In this chapter, we examine several SARS-CoV-2 variants that have emerged during the pandemic. Additionally, we discuss a few major COVID-19 diagnostic technique categories, including those involving real-time PCR, serology, CRISPR, and electronic biosensors. Finally, we address SARS-CoV-2 variants and diagnostic assays in the age of COVID-19 vaccines.

Trend in creatinine determining methods: Conventional methods to molecular‐based methods

Renal failure (RF) disease is ranked as one of the most prevalent diseases with severe morbidity and mortality. Early diagnosis of RF leads to subsequent control of disease to reduce the poor prognosis. The level of sera creatinine is considered as a significant biomarker for kidney biofunction, which is routinely detected by the Jaffe reaction. The normal range for creatinine in the blood may be 0.84‐1.21 mg/dL. Low accuracy, insufficient sensitivity, explosive and toxicity of picric acid, and pseudo‐interaction with nonspecific elements such as ammonium ions in the Jaffe method lead to the development of various techniques for precise detection of creatinine such as spectroscopic, electrochemical, and chromatography approaches and sensors based on enzymes, molecular imprinted polymer and nanoparticles, etc. Based on previously established results, they are trying to construct sensors with high accuracy, optimum sensitivity, acceptable linear/calibration range, and limit of detection, which are small in size and applicable by the patient him/herself (point‐of‐care testing). By comparing the results of research, a molecularly imprinted electrochemiluminescence‐based sensor with linear/calibration range of 5‐1 mMconcentration of creatinine and the detection limit of 0.5 nM has the best detectable resolution with 2 million measurable points. In this paper, we will review the recently developed methods for measuring creatinine concentration and renal biofunction.

Plastic Antibody of Polypyrrole/Multiwall Carbon Nanotubes on Screen-Printed Electrodes for Cystatin C Detection

This work reports the design of a novel plastic antibody for cystatin C (Cys-C), an acute kidney injury biomarker, and its application in point-of-care (PoC) testing. The synthetic antibody was obtained by tailoring a molecularly imprinted polymer (MIP) on a carbon screen-printed electrode (SPE). The MIP was obtained by electropolymerizing pyrrole (Py) with carboxylated Py (Py-COOH) in the presence of Cys-C and multiwall carbon nanotubes (MWCNTs). Cys-C was removed from the molecularly imprinted poly(Py) matrix (MPPy) by urea treatment. As a control, a non-imprinted poly(Py) matrix (NPPy) was obtained by the same procedure, but without Cys-C. The assembly of the MIP material was evaluated in situ by Raman spectroscopy and the binding ability of Cys-C was evaluated by the cyclic voltammetry (CV) and differential pulse voltammetry (DPV) electrochemical techniques. The MIP sensor responses were measured by the DPV anodic peaks obtained in the presence of ferro/ferricyanide. The peak currents decreased linearly from 0.5 to 20.0 ng/mL of Cys-C at each 20 min successive incubation and a limit of detection below 0.5 ng/mL was obtained at pH 6.0. The MPPy/SPE was used to analyze Cys-C in spiked serum samples, showing recoveries <3%. This device showed promising features in terms of simplicity, cost and sensitivity for acute kidney injury diagnosis at the point of care.

Development and Evaluation of a Quantitative Fluorescent Lateral Flow Immunoassay for Cystatin-C, a Renal Dysfunction Biomarker

The diagnosis, prognosis, and control of chronic kidney disease rely on an understanding of the glomerular filtration rate (GFR). The renal clearance of the cystatin-C is closely associated with the GFR. Cystatin-C is a more suitable GFR marker than the commonly used creatinine. General techniques for cystatin-C calculation, such as particle-enhanced turbidimetric and nephelometric assay, are time-consuming and tedious. Here, we propose a rapid, quantitative immunoassay for the detection of cystatin-C. A fluorescence-based lateral-flow kit was developed in a sandwich format by using a monoclonal antibody. A Linear calibration was obtained over the clinical diagnostic range of 0.023-32 µg/mL and the limit of detection (LOD) was 0.023 µg/mL and the limit of quantification (LOQ) was 0.029 µg/mL. Average recoveries from spiked urine samples ranged from 96-100% and the coefficient of variation was less than 4% for both intra and inter-day assays with excellent repeatability. With the comparison with an ELISA kit, the developed kit is highly sensitive, performs well over the detection range, provides repeatable results in a short time, and can easily be used at point-of-care (POC), making it an ideal candidate for rapid testing in early detection, community screening for renal function disorders.

Serum Creatinine Electrochemical Biosensor on Printed Electrodes Using Monoenzymatic Pathway to 1-Methylhydantoin Detection

The rising prevalence of Chronic Kidney Disease (CKD) has necessitated efforts towards the development of cost-effective and accurate biosensors for serum creatinine, which is a potent biomarker reflecting kidney function. This work presents a novel and cost-effective technique to estimate serum creatinine without any sample preprocessing. The technique involves the conversion of creatinine by a monoenzymatic pathway to 1-methylhydantoin. The concentration of 1-methylhydantoin is then quantified by utilizing its innate ability to form a complex with transition metals such as cobalt. The complex formation has been validated using optical spectroscopy and the transmittance at 290 nm wavelength is used to identify the optimum concentration of cobalt chloride in sensing chemistry. This chemical assay is shown to be robust against interference from serum albumin, the abundant plasma protein that can potentially influence the sensor response. The electrochemical biosensor developed using screen-printed electrodes thus provides highly selective creatinine estimation over the range of 0.2-4 mg/dL in a sample volume of 300 μL with no preprocessing and hence can be easily translated into a viable point-of-care (POC) device.

An ultrasensitive Cystatin C renal failure immunosensor based on a PPy/CNT electrochemical capacitor grafted on interdigitated electrode

An interdigitated immunosensor for Cystatin C detection based on polypyrrole/carbon nanotube electrochemical capacitor is described. Cystatin C (CysC) is powerful biomarker for early acute renal failure and one predictive for cardiovascular risk, sepsis, cancer and death. Recently, electrochemical immunosensors based on interdigitated electrodes (IDE) have been successfully focused on development of point-of-care testing, due to their miniaturization facilities and higher sensitivity as compared with the screen-printed electrochemical sensing. Herein, a polypyrrole/carbon nanotube nanoyhibrid film was grafted on two gold fingers by electropolymerization obtaining a supercapacitor. Anti-CysC antibodies were immobilized on the IDE by covalent entrapment via ethylenediamine bifunctional agent, followed by glycine blocking in acid and alkaline medium. Under low frequency, capacitive effect of antigen-antibody interaction were observed by double layer capacitance, and analytical responses of this IDE immunosensor to CysC serum were obtained by changes on phase angle a linear range up to 300 ng/mL. The cutoff was calculated for serum samples showing a total reducing of non-specific binding at approximately 28 ng/mL CysC. This immunosensor based on interdigitated electrode (IDE) is a potential tools as portable device,with possibility to use as a practical and rapid test for CysC diagnostic in samples of serum.

Development of peptide biosensor for the detection of dengue fever biomarker, nonstructural 1

Dengue virus (DENV) nonstructural 1 (NS1) protein is a specific and sensitive biomarker for the diagnosis of dengue. In this study, an efficient electrochemical biosensor that uses chemically modified affinity peptides was developed for the detection of dengue virus NS1. A series of amino acid-substituted synthetic peptides was rationally designed, chemically synthesized and covalently immobilized to a gold sensor surface. The sensor performance was monitored via square wave voltammetry (SWV) and electrochemical impedance spectroscopy (EIS). Potential affinity peptides specific for NS1 were chosen according to the dynamic current decrease in SWV experiments. Using circular dichroism, the molar ellipticity of peptides (DGV BP1–BP5) was determined, indicating that they had a mostly similar in random coil structure, not totally identical. Using SWV, DGV BP1 was selected as a promising recognition peptide and limit of detection for NS1 was found to be 1.49 μg/mL by the 3-sigma rule. DGV BP1 showed good specificity and stability for NS1, with low signal interference. The validation of the sensor to detect NS1 proteins was confirmed with four dengue virus culture broth (from serotype 1 to 4) as proof-of-concept. The detection performance of our sensor incorporating DGV BP1 peptides showed a statistically significant difference. These results indicate that this strategy can potentially be used to detect the dengue virus antigen, NS1, and to diagnosis dengue fever within a miniaturized portable device in point-of-care testing.

A Review: New Trends in Electrode Systems for Sensitive Drug and Biomolecule Analysis

Drug and biomolecule analysis with high precision, fast response, not expensive, and user-friendly methods have been very important for developing technology and clinical applications. Electrochemical methods are highly capable for assaying the concentration of electroactive drug or biomolecule and supply excellent knowledge concerning its physical and chemical properties such as electron transfer rates, diffusion coefficients, electron transfer number, and oxidation potential. Electrochemical methods have been widely applied because of their accuracy, sensitivity, cheapness, and can applied on-site determinations of various substances. The progress on electronics has allowed developing reliable, more sensitive and less expensive instrumentations, which have significant contribution in the area of drug development, drug and biomolecule analysis. The developing new sensors for electrochemical analysis of these compounds have growing interest in recent years. Screen-printed based electrodes have a great interest in electrochemical analysis of various drugs and biomolecules due to their easy manufacturing procedure of the electrode allow the transfer of electrochemical laboratory experiments for disposable on-site analysis of some compounds. Paper based electrodes are also fabricated by new technology. They can be preferred due to their easy, cheap, portable, disposable, and offering high sensitivity properties for many application field such as environmental monitoring, food quality control, clinical diagnosis, drug, and biomolecules analysis. In this review, the recent electrochemical drug and biomolecule (DNA, RNA, µRNA, Biomarkers, etc.) studies will be presented that involve new trend disposable electrodes.

Effect of pristine and functionalized multiwalled carbon nanotubes on rat renal cortex

The increasing application of carbon nanotubes (CNTs) within environmental, occupational and consumer settings has raised concerns regarding their biosafety and adverse effects on human health. The present study was designed to investigate the possible adverse effect of pristine and functionalized (amylated and polyethelene glycol coated) multi-walled (MW) CNTs on rat kidney with special concern to the histological alterations and the associated oxidative stress, apoptosis and inflammation. Healthy male albino rats (n = 40) were randomly divided into 4 groups: group I (control), group II (pristine MWCNTs), group III (amylated MWCNTs) and group IV [polyethelene glycol (PEG)-coated MWCNTs]. Animals of groups II, III and IV received a single dose of 1 mg/kg body weight of MWCNTs via intra-tracheal (IT) instillation at the beginning of the experiment and all rats were sacrificed after 30 days. Rats in groups II and III showed, nearly similar, renal tissue damage (evidenced by thin collapsed glomeruli, packed mesangial and endothelial cells as well as edematous hemorrhagic glomeruli with apoptotic changes) and functional disruptions (indicated by high serum levels of urea and creatinine) probably through induction of oxidative stress [revealed by high level of the lipid peroxidation marker malondialdehyde (MDA) and lower levels of the antioxidant enzymes superoxide dismutase (SOD) and glutathione peroxidase (GPx)], apoptosis (indicated by high caspase 3 activity), and inflammation (evidenced by high level of IL1β). However, PEG-coated MWCNTs-treated group (group IV) showed nearly normal renal structure and function. It could be concluded that pristine and functionalized amylated MWCNTs have nephrotoxic effect, while PEG-coated MWCNTs had lowest, or none, toxic effects making them safer for therapy and diagnosis of a variety of diseases.

Modern creatinine (Bio)sensing: Challenges of point-of-care platforms

The importance of knowing creatinine levels in the human body is related to the possible association with renal, muscular and thyroid dysfunction. Thus, the accurate detection of creatinine may indirectly provide information surrounding those functional processes, therefore contributing to the management of the health status of the individual and early diagnosis of acute diseases. The questions at this point are: to what extent is creatinine information clinically relevant?; and do modern creatinine (bio)sensing strategies fulfil the real needs of healthcare applications? The present review addresses these questions by means of a deep analysis of the creatinine sensors reported in the literature over the last five years. There is a wide range of techniques for detecting creatinine, most of them based on optical readouts (20 of the 33 papers collected in this review). However, the use of electrochemical techniques (13 of the 33 papers) is recently emerging in alignment with the search for a definitive and trustworthy creatinine detection at the point-of-care level. In this sense, biosensors (7 of the 33 papers) are being established as the most promising alternative over the years. While creatinine levels in the blood seem to provide better information about patient status, none of the reported sensors display adequate selectivity in such a complex matrix. In contrast, the analysis of other types of biological samples (e.g., saliva and urine) seems to be more viable in terms of simplicity, cross-selectivity and (bio)fouling, besides the fact that its extraction does not disturb individual's well-being. Consequently, simple tests may likely be used for the initial check of the individual in routine analysis, and then, more accurate blood detection of creatinine could be necessary to provide a more genuine diagnosis and/or support the corresponding decision-making by the physician. Herein, we provide a critical discussion of the advantages of current methods of (bio)sensing of creatinine, as well as an overview of the drawbacks that impede their definitive point-of-care establishment.

Machine Learning Approach to Enhance the Performance of MNP-Labeled Lateral Flow Immunoassay

The use of magnetic nanoparticle (MNP)-labeled immunochromatography test strips (ICTSs) is very important for point-of-care testing (POCT). However, common diagnostic methods cannot accurately analyze the weak magnetic signal from ICTSs, limiting the applications of POCT. In this study, an ultrasensitive multiplex biosensor was designed to overcome the limitations of capturing and normalization of the weak magnetic signal from MNPs on ICTSs. A machine learning model for sandwich assays was constructed and used to classify weakly positive and negative samples, which significantly enhanced the specificity and sensitivity. The potential clinical application was evaluated by detecting 50 human chorionic gonadotropin (HCG) samples and 59 myocardial infarction serum samples. The quantitative range for HCG was 1-1000 mIU mL^-1 and the ideal detection limit was 0.014 mIU mL^-1, which was well below the clinical threshold. Quantitative detection results of multiplex cardiac markers showed good linear correlations with standard values. The proposed multiplex assay can be readily adapted for identifying other biomolecules and also be used in other applications such as environmental monitoring, food analysis, and national security.