Electrochemical sensor for enzymatic lactate detection based on laser-scribed graphitic carbon modified with platinum, chitosan and lactate oxidase

Semiconducting polymer dots based l-lactate sensor by enzymatic cascade reaction system

BACKGROUND

l-lactate detection is important for not only assessing exercise intensity, optimizing training regimens, and identifying the lactate threshold in athletes, but also for diagnosing conditions like L-lactateosis, monitoring tissue hypoxia, and guiding critical care decisions. Moreover, l-lactate has been utilized as a biomarker to represent the state of human health. However, the sensitivity of the present l-lactate detection technique is inadequate.

RESULTS

Here, we reported a sensitive ratiometric fluorescent probe for l-lactate detection based on platinum octaethylporphyrin (PtOEP) doped semiconducting polymer dots (Pdots-Pt) with enzymatic cascade reaction. With the help of an enzyme cascade reaction, the l-lactate was continuously oxidized to pyruvic and then reduced back to l-lactate for the next cycle. During this process, oxygen and NADH were continuously consumed, which increased the red fluorescence of Pdots-Pt that responded to the changes of oxygen concentration and decreased the blue fluorescence of NADH at the same time. By comparing the fluorescence intensities at these two different wavelengths, the concentration of l-lactate was accurately measured. With the optimal conditions, the probes showed two linear detection ranges from 0.5 nM to 5.0 μM and 5.0 μM-50.0 μM for l-lactate detection. The limit of detection was calculated to be 0.18 nM by 3σ/slope method. Finally, the method shows good detection performance of l-lactate in both bovine serum and artificial serum samples, indicating its potential usage for the selective analysis of l-lactate for health monitoring and disease diagnosis.

SIGNIFICANCE

The successful application of the sensing system in the complex biological sample (bovine serum and artificial serum samples) demonstrated that this method could be used for sensitive l-lactate detection in practical clinical applications. This detection system provided an extremely low detection limit, which was several orders of magnitude lower than methods proposed in other literatures.

L-Lactate Electrochemical Biosensor Based on an Integrated Supramolecular Architecture of Multiwalled Carbon Nanotubes Functionalized with Avidin and a Recombinant Biotinylated Lactate Oxidase

L-Lactate is an important bioanalyte in the food industry, biotechnology, and human healthcare. In this work, we report the development of a new L-lactate electrochemical biosensor based on the use of multiwalled carbon nanotubes non-covalently functionalized with avidin (MWCNT-Av) deposited at glassy carbon electrodes (GCEs) as anchoring sites for the bioaffinity-based immobilization of a new recombinant biotinylated lactate oxidase (bLOx) produced in Escherichia coli through in vivo biotinylation. The specific binding of MWCNT-Av to bLOx was characterized by amperometry, surface plasmon resonance (SPR), and electrochemical impedance spectroscopy (EIS). The amperometric detection of L-lactate was performed at -0.100 V, with a linear range between 100 and 700 µM, a detection limit of 33 µM, and a quantification limit of 100 µM. The proposed biosensor (GCE/MWCNT-Av/bLOx) showed a reproducibility of 6.0% and it was successfully used for determining L-lactate in food and enriched serum samples.

Smartphone-based wearable microfluidic electrochemical sensor for on-site monitoring of copper ions in sweat without external driving

The directional movement of liquid without exogenous drive can show great potential in portable electrochemical platforms. Herein, we developed a portable electrochemical platform that drove electrolyte flow by surface tension gradient, which can realize collection of electrolyte, flow preconcentration and electrochemical detection of Cu2+. The induced graphene electrodes (LIG) was fabricated using laser direct writing, and flower cluster shaped ZnO nanorods (FC-ZnONRs) were prepared and modified on LIG, which provided a large amount of space for electrolyte to shuttled between the holes of LIG and ZnO, and increased the electrochemical active sites and electrons transport ability. The effect of surface tension gradients driving fluid flow could accelerate preconcentration, shorten detection time (save 300 s of preconcentration time) and enhance electrochemical responses in synergy with the 3D FC-ZnONRs/LIG. The microfluidic system possessed excellent performance for detection of Cu2+ ranged from 1 μg L-1 to 2100 μg L-1 with a low detection limit (LOD) of 0.0368 μg L-1 and high sensitivity of 0.414 μA (μg L-1)-1 cm-2. Additionally, this portable microfluidic system was successfully worn on the skin for analysing Cu2+ in human sweat, and the results showed good consistency with inductively coupled plasma-mass spectrometry (ICP-MS). This novel sensing system provides a sample collection, rapid detection, low cost and easy-to-operate strategy for heavy metal ions analysis in real samples and shows huge application prospects in point-of-care testing.

A molecularly imprinted screen-printed carbon electrode for electrochemical epinephrine, lactate, and cortisol metabolites detection in human sweat

This study presents a novel approach to the detection of epinephrine, lactate, and cortisol biomarkers in human sweat using molecularly-imprinted polymers (MIP) embedded screen printed carbon electrode (SPCE) sensors. The epinephrine and lactate MIP SPCE sensors were fabricated by epinephrine or lactate-imprinted polyaniline co-polymerized with 3-aminophenylboronic acid and gold nanoparticles (PANI-co-PBA/AuNP) selective membrane on a commercial SPCE. The cortisol sensor was comprised of a cortisol-imprinted poly(glycidyl methacryate-co-ethylene glycol dimethacrylate) (poly (GMA-co-EGDMA)@AuNP selective membrane deposited on a SPCE. Both cyclic voltammetry (CV) and differential pulse voltammetry (DPV) were used as modes of analysis for the MIP SPCE sensors. All sensors exhibited a rapid (∼1 min) and selective response to the epinephrine, lactate, and cortisol target analytes, with excellent precision between scans for both CV and DPV analysis modes. For CV, the LOD for epinephrine, lactate, and cortisol was 8.2 nM, 13 mM, and 0.042 μM, respectively. The LOD for DPV were 0.60 nM, 2.2 mM, and 0.025 μM for epinephrine, lactate, and cortisol, respectively. The MIP SPCE sensor platforms were further validated through the successful quantification of epinephrine, lactate, and cortisol in human sweat.

Continuous monitoring of multiple biomarkers with an ultrasensitive 3D-structured wearable biosensor

Chronic diseases call for routine management of frequent monitoring of specific biomarkers. Traditional in vitro diagnostics technologies suffer from complex sampling processes and long detection intervals, which cannot meet the need of continuous monitoring. Wearable devices taking advantage of compact size, rapid detection process, and small sample consumption are promising to take the place of endpoint detection, providing more comprehensive information about human health. Here, we proposed a fully integrated wearable system with an ultrasensitive 3D-structured biosensor for real-time monitoring of multiple metabolites. The 3D-structured biosensor shows wide linear ranges of 400-1,400 μM and 0.1-8 mM and high sensitivities of 460.5 and 283.09 μA/(mM·cm2) for lactate and glucose detection, respectively. We have conducted in vivo animal experiments, and the proposed wearable biosensor demonstrated high consistency with established methods. We envision that this system could provide a real-time wearable detection platform for multiple biomarker detection.

Direct Laser Writing of Chitosan-Borax Composites: Toward Sustainable Electrochemical Sensors

In this study, the laser-induced graphitization process of sustainable chitosan-based formulations was investigated. In particular, optimal lasing conditions were investigated alongside the effect of borax concentration in the chitosan matrix. In all cases, it was found that the obtained formulations were graphitizable with a CO2 laser. This process gave rise to the formation of high surface area, porous, and electrically conductive laser-induced graphene (LIG) structures. It was found that borax, as a cross-linker of chitosan, enabled the graphitization process when its content was ≥30 wt % in the chitosan matrix, allowing the formation of an LIG phase with a significant content of graphite-like structures. The graphitization process was investigated by thermogravimetric analysis (TGA), Raman, X-ray photoemission (XPS), and Fourier transform infrared (FTIR) spectroscopies. LIG electrodes obtained from CS/40B formulations displayed a sheet resistance as low as 110 Ω/sq. Electrochemical characterization was performed after a 10 min electrode activation by cycling in 1 M KCl. A heterogeneous electron transfer rate, k0, of 4 × 10-3 cm s-1 was determined, indicating rapid electron transfer rates at the electrode surface. These results show promise for the introduction of a new class of sustainable composites for LIG electrochemical sensing platforms.

A molecularly imprinted electrochemical microneedle sensor for multiplexed metabolites detection in human sweat

This article demonstrates an array of inexpensive molecularly imprinted microneedle platforms for the multiplexed electrochemical detection of pH, epinephrine, dopamine, and lactate biomarkers in human sweat. The multiplexed sensors were fabricated via layer-by-layer (LbL) assembly on a polydimethylsiloxane (PDMS) microneedle platform coated with a conductive PDMS/carbon nanotube (CNT)/cellulose nanocrystal (CNC) composite (PDMS/CNT/CNC@PDMS). The pH sensor was comprised of a pH-responsive polyaniline (PANI)/CNT/CNC/silver nanoparticle (AgNP) composite layer. The epinephrine, dopamine, and lactate sensors consisted of an additional epinephrine, dopamine, or lactate-imprinted PANI-co-3-aminophenylboronic acid (PBA)/gold nanoparticle (AuNP) layer atop the PANI/CNT/CNC/AgNP composite layer. Each sensor rapidly (∼2 min) and selectively responded to their target analytes, with excellent precision between scans. The limits of detection (LOD) for the epinephrine, dopamine, and lactate sensors were 0.0007 ± 0.0002 μM, 2.11 ± 0.05 nM, and 0.07 ± 0.07 mM, respectively. The pH sensor accurately responded to a pH range of 4.25-10. The applicability of the sensor platforms were successfully verified through quantification of pH, epinephrine, dopamine, and lactate in a human sweat sample, showing promise for use as a wearable, point of need (PON) sensor for sweat analytics.

Fabrication of a Lactate-Specific Molecularly Imprinted Polymer toward Disease Detection

The development of sensitive and selective robust sensor materials for targeted biomarker detection aims to contribute to self-health monitoring and management. Molecularly imprinted polymeric (MIP) materials can perform as biomimetic recognition elements via tailored routes of synthesis for specific target analyte extraction and/or detection. In this work, a sensitive- and selective-lactate MIP has been developed utilizing methacrylic acid and ethylene glycol dimethacrylate as the functional monomer and cross-linker, respectively. The sensitivity of the as-synthesized imprinted species was evaluated by determining the target analyte retention, imprinting factor, and selectivity adsorption of up to 63.5%, 6.86, and 0.82, respectively. MIP selectivity elucidated the imprinting mechanism between the functional monomers and target analyte lactate, further experimentally evidenced by using structurally competitive analytes malic acid and sodium 2-hydroxybutyrate, where retentions of 22.6 and 25.2%, respectively, were observed. Understanding the specific intermolecular mechanisms of both the template analyte and structural interferents with the MIP enables experimentalists to make informed decisions regarding monomer-target and porogen selections and possible sites of interaction for improved molecular imprinting. This imprinting system highlights the potential to be further developed into artificial receptor sensor materials for the detection of disease.

Chitosan-based hemostatic sponges as new generation hemostatic materials for uncontrolled bleeding emergency: Modification, composition, and applications

The choice of hemostatic technique is a curial concern for surgery and as first-aid treatment in combat. To treat uncontrolled bleeding in complex wound environments, chitosan-based hemostatic sponges have attracted significant attention in recent years because of the excellent biocompatibility, degradability, hemostasis and antibacterial properties of chitosan and their unique sponge-like morphology for high fluid absorption rate and priority aggregation of blood cells/platelets to achieve rapid hemostasis. In this review, we provide a historical perspective on the use of chitosan hemostatic sponges as the new generation of hemostatic materials for uncontrolled bleeding emergencies in complex wounds. We summarize the modification of chitosan, review the current status of preparation protocols of chitosan sponges based on various composite systems, and highlight the recent achievements on the detailed breakdown of the existing chitosan sponges to present the relationship between their composition, physical properties, and hemostatic capacity. Finally, the future opportunities and challenges of chitosan hemostatic sponges are also proposed.

Recent Advances in Wearable Biosensors for Non-Invasive Detection of Human Lactate

Lactate, a crucial product of the anaerobic metabolism of carbohydrates in the human body, is of enormous significance in the diagnosis and treatment of diseases and scientific exercise management. The level of lactate in the bio-fluid is a crucial health indicator because it is related to diseases, such as hypoxia, metabolic disorders, renal failure, heart failure, and respiratory failure. For critically ill patients and those who need to regularly control lactate levels, it is vital to develop a non-invasive wearable sensor to detect lactate levels in matrices other than blood. Due to its high sensitivity, high selectivity, low detection limit, simplicity of use, and ability to identify target molecules in the presence of interfering chemicals, biosensing is a potential analytical approach for lactate detection that has received increasing attention. Various types of wearable lactate biosensors are reviewed in this paper, along with their preparation, key properties, and commonly used flexible substrate materials including polydimethylsiloxane (PDMS), polyethylene terephthalate (PET), paper, and textiles. Key performance indicators, including sensitivity, linear detection range, and detection limit, are also compared. The challenges for future development are also summarized, along with some recommendations for the future development of lactate biosensors.

Nanomaterial-Based Electrochemical Nanodiagnostics for Human and Gut Metabolites Diagnostics: Recent Advances and Challenges

Metabolites are the intermediatory products of metabolic processes catalyzed by numerous enzymes found inside the cells. Detecting clinically relevant metabolites is important to understand their physiological and biological functions along with the evolving medical diagnostics. Rapid advances in detecting the tiny metabolites such as biomarkers that signify disease hallmarks have an immense need for high-performance identifying techniques. Low concentrations are found in biological fluids because the metabolites are difficult to dissolve in an aqueous medium. Therefore, the selective and sensitive study of metabolites as biomarkers in biological fluids is problematic. The different non-electrochemical and conventional methods need a long time of analysis, long sampling, high maintenance costs, and costly instrumentation. Hence, employing electrochemical techniques in clinical examination could efficiently meet the requirements of fully automated, inexpensive, specific, and quick means of biomarker detection. The electrochemical methods are broadly utilized in several emerging and established technologies, and electrochemical biosensors are employed to detect different metabolites. This review describes the advancement in electrochemical sensors developed for clinically associated human metabolites, including glucose, lactose, uric acid, urea, cholesterol, etc., and gut metabolites such as TMAO, TMA, and indole derivatives. Different sensing techniques are evaluated for their potential to achieve relevant degrees of multiplexing, specificity, and sensitivity limits. Moreover, we have also focused on the opportunities and remaining challenges for integrating the electrochemical sensor into the point-of-care (POC) devices.

The Characteristics Analysis of a Microfluid-Based EGFET Biosensor with On-Chip Sensing Film for Lactic Acid Detection

In this research, a microfluid-based extended gate field-effect transistor (EGFET) biosensor with an on-chip sensing window (OCSW) was fabricated. The detection window was composed of six metal layers, and a ruthenium dioxide (RuO₂) film was spattered on the surface and functionalized with lactase to detect lactic acid (LA). To detect LA in a more diversified way, a microfluidic system was integrated with the biosensor. Moreover, a special package was used to seal the sensing window and microfluidic tube and insulate it from other parts to prevent water molecule invasion and chip damage. The sensitivity analysis of the EGFET biosensor was studied by a semiconductor parameter analyzer (SPA). The static and dynamic measurements of the EGFET with sensing windows on a chip were analyzed. The sensing characteristics of the EGFET biosensor were verified by the experimental results. The proposed biosensor is suitable for wearable applications due to the advantages of its low weight, low voltage, and simple manufacturing process.

Applications of Chitosan in Surgical and Post-Surgical Materials

The continuous advances in surgical procedures require continuous research regarding materials with surgical applications. Biopolymers are widely studied since they usually provide a biocompatible, biodegradable, and non-toxic material. Among them, chitosan is a promising material for the development of formulations and devices with surgical applications due to its intrinsic bacteriostatic, fungistatic, hemostatic, and analgesic properties. A wide range of products has been manufactured with this polymer, including scaffolds, sponges, hydrogels, meshes, membranes, sutures, fibers, and nanoparticles. The growing interest of researchers in the use of chitosan-based materials for tissue regeneration is obvious due to extensive research in the application of chitosan for the regeneration of bone, nervous tissue, cartilage, and soft tissues. Chitosan can serve as a substance for the administration of cell-growth promoters, as well as a support for cellular growth. Another interesting application of chitosan is hemostasis control, with remarkable results in studies comparing the use of chitosan-based dressings with traditional cotton gauzes. In addition, chitosan-based or chitosan-coated surgical materials provide the formulation with antimicrobial activity that has been highly appreciated not only in dressings but also for surgical sutures or meshes.