Disposable label-free electrochemical immunosensor based on gold nanoparticles-Prussian blue for neutrophil gelatinase-associated lipocalin detection in urine samples.

Neutrophil gelatinase-associated lipocalin (NGAL) is a remarkable biomarker for assessing acute kidney injury. In this study, we developed a novel label-free NGAL electrochemical immunosensor based on gold nanoparticles (AuNPs) and Prussian blue (PB) without an external mediator. The AuNPs-PB based immunosensor was fabricated on a custom gold-electrode (AuE)-based polypropylene (PP) substrate. We systematically assessed and optimized key experimental parameters, including the process of AuNPs-PB electrodeposition, antibody concentration, and incubation time. The immunosensor response toward NGAL was determined using differential pulse voltammetry, where the decrease in the oxidation current response of the PB redox probe correlating with the increase in NGAL concentration. Our results demonstrated that the synergistic benefits of both AuNPs and PB significantly improved electrochemical activity for NGAL detection and provided a highly stable sensor across a range of pH values. The label-free immunosensor exhibited two linear ranges: 0.10-1.40 ng mL-1 and 1.40-25.0 ng mL-1, with a low detection limit of 0.094 ng mL-1. The developed NGAL immunosensor displayed high selectivity and excellent reproducibility. Furthermore, NGAL detection was completed within 30 min and the immunosensor exhibited storage stability for six weeks. Notably, NGAL levels determined in human urine samples using this developed label-free immunosensor showed good agreement with the results obtained from the enzyme-linked immunosorbent assay. This novel label-free NGAL immunosensor provides great potential in developing NGAL point-of-care testing applications.

Disposable Polyaniline/m-Phenylenediamine-Based Electrochemical Lactate Biosensor for Early Sepsis Diagnosis.

Lactate serves as a crucial biomarker that indicates sepsis assessment in critically ill patients. A rapid, accurate, and portable analytical device for lactate detection is required. This work developed a stepwise polyurethane-polyaniline-m-phenylenediamine via a layer-by-layer based electrochemical biosensor, using a screen-printed gold electrode for lactate determination in blood samples. The developed lactate biosensor was electrochemically fabricated with layers of m-phenylenediamine, polyaniline, a crosslinking of a small amount of lactate oxidase via glutaraldehyde, and polyurethane as an outer membrane. The lactate determination using amperometry revealed the biosensor's performance with a wide linear range of 0.20-5.0 mmol L-1, a sensitivity of 12.17 ± 0.02 µA·mmol-1·L·cm-2, and a detection limit of 7.9 µmol L-1. The developed biosensor exhibited a fast response time of 5 s, high selectivity, excellent long-term storage stability over 10 weeks, and good reproducibility with 3.74% RSD. Additionally, the determination of lactate in human blood plasma using the developed lactate biosensor was examined. The results were in agreement with the enzymatic colorimetric gold standard method (p > 0.05). Our developed biosensor provides efficiency, reliability, and is a great potential tool for advancing lactate point-of-care testing applications in the early diagnosis of sepsis.

Comparison of In-House Microfluidic Device and Centrifuge-Based Method Efficacy in Sperm Preparation for Assisted Reproductive Technology.

Background: Sperm DNA fragmentation can affect reproductive outcomes in assisted reproductive techniques (ART), and it is a concern in density gradient centrifugation (DGC). By contrast, microfluidic approaches allow the selection of highly motile sperm with low DNA fragmentation index (DFI). The purpose of current study, was to compare the efficacy of a microfluidic device designed in-house in comparison with DGC. Methods: Nineteen healthy men with normal semen profiles were included in the study. Semen samples were individually aliquoted for three sperm preparation analyses (crude and processed with to either DGC or the microfluidic method). Sperm parameters of the samples were evaluated along with DNA fragmentation using the terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) method. Results: Sperm processed using the microfluidic method showed a significantly lower DFI than those obtained using DGC and in crude semen, with DFI of 1.1%, 3.5%, and 4.9%, respectively. Although the microfluidic method yielded significantly lower sperm concentrations than DGC, no significant differences were observed in total motility, progressive motility, curvilinear velocity, straight-line velocity, or normal morphology. Conclusion: Using the in-house microfluidic device, sperm with lower DFI was effectively isolated when compared with DGC. The motility and normal morphology rates were comparable among the samples.

Redox-Mediated Gold Nanoparticles with Glucose Oxidase and Egg White Proteins for Printed Biosensors and Biofuel Cells.

Glucose oxidase (GOx)-based electrodes are important for bioelectronics, such as glucose sensors. It is challenging to effectively link GOx with nanomaterial-modified electrodes while preserving enzyme activity in a biocompatible environment. To date, no reports have used biocompatible food-based materials, such as egg white proteins, combined with GOx, redox molecules, and nanoparticles to create the biorecognition layer for biosensors and biofuel cells. This article demonstrates the interface of GOx integrated with egg white proteins on a 5 nm gold nanoparticle (AuNP) functionalized with a 1,4-naphthoquinone (NQ) and conjugated with a screen-printed flexible conductive carbon nanotube (CNT)-modified electrode. Egg white proteins containing ovalbumin can form three-dimensional scaffolds to accommodate immobilized enzymes and adjust the analytical performance. The structure of this biointerface prevents the escape of enzymes and provides a suitable microenvironment for the effective reaction. The bioelectrode's performance and kinetics were evaluated. Using redox-mediated molecules with the AuNPs and the three-dimensional matrix made of egg white proteins improves the transfer of electrons between the electrode and the redox center. By engineering the layer of egg white proteins on the GOx-NQ-AuNPs-mediated CNT-functionalized electrodes, we can modulate analytical performances such as sensitivity and linear range. The bioelectrodes demonstrate high sensitivity and can prolong the stability by more than 85% after 6 h of continuous operation. The use of food-based proteins with redox molecule-modified AuNPs and printed electrodes demonstrates advantages for biosensors and energy devices due to their small size, large surface area, and ease of modification. This concept holds a promise for creating biocompatible electrodes for biosensors and self-sustaining energy devices.

Tackling the challenges of developing microneedle-based electrochemical sensors.

Microneedles provide unique advantages in biomedical areas, particularly biosensing, because of their opportunities for minimally invasive and convenient detection. This review introduces concepts of electrochemical microneedle-based sensors for minimally invasive analysis together with insights into skin compartments for designing successful microneedles. We discuss requirements for developing microneedle-based biosensors, including electrical and electrochemical behaviors of materials (such as metals, nanomaterials, and conducting polymers) which are the key factors for sensitive biosensors. We further emphasize immobilization strategies to attach biorecognition elements to electrode materials. Moreover, we detail advanced techniques that require state-of-the-art fabrications and materials to realize porous, biodegradable, and antifouling materials to enhance biosensing performances. We also emphasize studies of cytotoxicity and damage to the skin to elucidate biocompatible potentials. Furthermore, we highlight the latest advances in microneedles published from 2019 to 2022. This review also includes an overview of key remaining obstacles and opportunities where developments will push the advances continuously. The conclusion and outlook on the status of laboratory and commercial availability are added. We prospect that microneedle sensors will be integrated into a closed-loop system biodevice for diverse applications, e.g., detection and therapy. This review discusses concepts of electrochemical microneedle-based sensors for minimally invasive monitoring. We discuss requirements including geometry, mechanical, electrical, electrochemical properties, and immobilization strategy. We illustrate advanced techniques and materials to enrich biosensor features, e.g., porosity, dissolvable ability, and anti-fouling capability. Concern of toxicity is highlighted. We also illustrate recent applications and outlooks of recently published study that exploits microneedle-based biosensors.

A Novel Microfluidic-Based OMC-PEDOT-PSS Composite Electrochemical Sensor for Continuous Dopamine Monitoring.

Fast and precise analysis techniques using small sample volumes are required for next-generation clinical monitoring at the patient's bedside, so as to provide the clinician with relevant chemical data in real-time. The integration of an electrochemical sensor into a microfluidic chip allows for the achievement of real-time chemical monitoring due to the low consumption of analytes, short analysis time, low cost, and compact size. In this work, dopamine, used as a model, is an important neurotransmitter responsible for controlling various vital life functions. The aim is to develop a novel serpentine microfluidic-based electrochemical sensor, using a screen-printed electrode for continuous dopamine detection. The developed sensor employed the composite of ordered mesoporous carbon (OMC) and poly (3,4 ethylenedioxythiophene)-poly (styrene sulfonate) (PEDOT-PSS). The performance of a microfluidic, integrated with the sensor, was amperometrically evaluated using a computer-controlled microfluidic platform. The microfluidic-based dopamine sensor exhibited a sensitivity of 20.2 ± 0.6 µA µmol L-1, and a detection limit (LOD) of 21.6 ± 0.002 nmol L-1, with high selectivity. This microfluidic-based electrochemical sensor was successfully employed to determine dopamine continuously, which could overcome the problem of sensor fouling with more than 90% stability for over 24 h. This novel microfluidic sensor platform provides a powerful tool for the development of a continuous dopamine detection system for human clinical application.

Portable Microfluidic Biosensing System for Real-Time Analysis of Microdialysate in Transplant Kidneys.

Currently, there is a severe shortage of donor kidneys that are fit for transplantation, due in part to a lack of adequate viability assessment tools for transplant organs. This work presents the integration of a novel wireless two-channel amperometric potentiostat with microneedle-based glucose and lactate biosensors housed in a 3D printed chip to create a microfluidic biosensing system that is genuinely portable. The wireless potentiostat transmits data via Bluetooth to an Android app running on a tablet. The whole miniaturized system is fully enclosed and can be integrated with microdialysis to allow continuous monitoring of tissue metabolite levels in real time. We have also developed a wireless portable automated calibration platform so that biosensors can be calibrated away from the laboratory and in transit. As a proof of concept, we have demonstrated the use of this portable analysis system to monitor porcine kidneys for the first time from organ retrieval, through warm ischemia, transportation on ice, right through to cold preservation and reperfusion. The portable system is robust and reliable in the challenging conditions of the abattoir and during kidney transportation and can detect clear physiological changes in the organ associated with clinical interventions.

Clinical translation of microfluidic sensor devices: focus on calibration and analytical robustness.

We present approaches to facilitate the use of microfluidics outside of the laboratory, in our case within a clinical setting and monitoring from human subjects, where the complexity of microfluidic devices requires high skill and expertise and would otherwise limit translation. Microfluidic devices show great potential for converting complex laboratory protocols into on-chip processes. We demonstrate a flexible microfluidic platform can be coupled to microfluidic biosensors and used in conjunction with clinical microdialysis. The versatility is demonstrated through a series of examples of increasing complexity including analytical processes relevant to a clinical environment such as automatic calibration, standard addition, and more general processes including system optimisation, reagent addition and homogenous enzyme reactions. The precision and control offered by this set-up enables the use of microfluidics by non-experts in clinical settings, increasing uptake and usage in real-world scenarios. We demonstrate how this type of system is helpful in guiding physicians in real-time clinical decision-making.

Real-time detection of carboplatin using a microfluidic system.

A microfluidic sensor system based on a carbon nanotube-epoxy composite electrode was fabricated to allow detection of the presence of the anti-cancer drug carboplatin in healthy tissue in real time during chemotherapy. Detection of carboplatin was carried out by observing the effects of the drug on the differential pulse voltammetry of free purine bases using a novel carbon nanotube-epoxy composite electrode. In free solution these electrodes performed better than glassy carbon electrodes for oxidation of the free purine bases AMP and GMP, and than DNA-modified carbon nanotube-epoxy composite sensors for detection of carboplatin. On-line carboplatin detection was performed using a computer-controlled microfluidic platform. The methodology for on-line carboplatin detection was optimised in terms of the analysis time and to allow repeated carboplatin measurement using the same electrode. Microdialysis sampling and our microfluidic platform were combined to give a proof-of-concept system for real-time carboplatin detection with a limit of detection of 0.014 µM carboplatin in the sampled media. This paper is dedicated to Craig Lunte's pioneering work in analysis and microdialysis.