Oxidation Of Lactic Acid Research Articles

Quantification of lactic acid in wines using an amperometric biosensor

The objective of this study was to develop an analytical method that allows for the rapid and cost-effective detection and quantification of lactic acid in wines. The analysis of lactic acid is a time-consuming and costly process in the food industry. Therefore, the use of an enzymatic amperometric sensor that employs lactate oxidase (LacOx) immobilized on an oxygen electrode enabled the determination of lactic acid in wine. This study utilizes a voltage of −500mV and recorded the amperometric signal was obtained during oxygen consumption while lactic acid oxidation occurred in the sensor reactor. The detection time was at 10 s. A positive linear relationship was obtained between oxygen consumed as a function of time (mg O2/L x s−1). The lactic acid concentration ranged from 1 to 7 mM with a coefficient R2 = 0.994. The sensor exhibited good specificity KM = 0.675. The immobilized enzyme retained over 85% activity for 60 days, allowing for the reuse of the previously modified membrane up to 22 times. In comparison to other methods documented in the literature, the results demonstrate a favourable analytical quality. Furthermore, other aspects, such as the low residual formation, also exhibit a positive outcome. The analysis of lactic acid showed good correlation when compared to HPLC methodology, which occupies the same linear range. This validates the use of the sensor as an alternative method for quantifying lactic acid in wine. The value of this study lies in its presentation of a technique that is more straightforward to implement than traditional methods for quantifying lactic acid in grape wines.

Показатели крови перепелов при скармливании муки из высушенных личинок Lucilia Caesar

The aim of the research was to study the effect of compound feed with the addition of flour from dried larvae of the Lucilia Caesar fly on the morphological and biochemical parameters of the blood of young quails. The experiment was conducted on 160 Phoenix quail at the age of 10 days, of which two groups were formed according to the principle of balanced groups. The results of the tests showed that all the studied blood parameters of the experimental bird were within the physiological norm. When feeding compound feed with a protein supplement from flour of the Lucilia Caesar larva, the content of albumins in the blood serum of quails of the second group decreased by 2.0 g/l (p≤0.05)., globulins - by 1.0 g/l (p≤0.05), urea - by 0.24 mmol/l (p≤0.01). Probably, a decrease in albumins and urea in the blood of quails of the second group indicates that they are involved in protein synthesis. Gamma-glutamyltransferase (GGT) is an enzyme involved in amino acid metabolism. Catalyzes the transfer of a gamma - glutamyl residue from a gamma-glutamyl peptide to an amino acid, another peptide, or, during hydrolysis, to water. The activity of the enzyme in the blood increases in liver diseases. In our experiment, a decrease in the GGT content by 2.66 u/l in the blood of a bird receiving flour from the larvae of the Lucilia Caesar fly probably indicates an activation of amino acid synthesis in the body, which is quite consistent with the data of the average daily increments of the experimental bird. Lactate dehydrogenase (LDH) in the blood is an enzyme localized inside cells. The composition necessarily includes zinc ions. The main function is to catalyze the oxidation of lactic acid to pyruvate. In diseases accompanied by tissue damage and cell destruction, LDH activity in the blood increases. In this regard, it is an important marker of tissue destruction. According to our data, LDH levels in the blood of the experimental bird of the second group significantly decreased by 2909.75 mmol/l (p≤0.05), which indicates an improvement in the functional activity of the liver.

Показатели крови перепелов при скармливании муки из высушенных личинок Lucilia Caesar

The aim of the research was to study the effect of compound feed with the addition of flour from dried larvae of the Lucilia Caesar fly on the morphological and biochemical parameters of the blood of young quails. The experiment was conducted on 160 Phoenix quail at the age of 10 days, of which two groups were formed according to the principle of balanced groups. The results of the tests showed that all the studied blood parameters of the experimental bird were within the physiological norm. When feeding compound feed with a protein supplement from flour of the Lucilia Caesar larva, the content of albumins in the blood serum of quails of the second group decreased by 2.0 g/l (p≤0.05)., globulins - by 1.0 g/l (p≤0.05), urea - by 0.24 mmol/l (p≤0.01). Probably, a decrease in albumins and urea in the blood of quails of the second group indicates that they are involved in protein synthesis. Gamma-glutamyltransferase (GGT) is an enzyme involved in amino acid metabolism. Catalyzes the transfer of a gamma - glutamyl residue from a gamma-glutamyl peptide to an amino acid, another peptide, or, during hydrolysis, to water. The activity of the enzyme in the blood increases in liver diseases. In our experiment, a decrease in the GGT content by 2.66 u/l in the blood of a bird receiving flour from the larvae of the Lucilia Caesar fly probably indicates an activation of amino acid synthesis in the body, which is quite consistent with the data of the average daily increments of the experimental bird. Lactate dehydrogenase (LDH) in the blood is an enzyme localized inside cells. The composition necessarily includes zinc ions. The main function is to catalyze the oxidation of lactic acid to pyruvate. In diseases accompanied by tissue damage and cell destruction, LDH activity in the blood increases. In this regard, it is an important marker of tissue destruction. According to our data, LDH levels in the blood of the experimental bird of the second group significantly decreased by 2909.75 mmol/l (p≤0.05), which indicates an improvement in the functional activity of the liver.

Efficient and selective upcycling of waste polylactic acid into acetate using nickel selenide

The conversion of waste polylactic acid (PLA) plastics into high-value-added chemicals through electrochemical methods is a promising and sustainable approach. However, developing efficient and highly selective catalysts for lactic acid oxidation reaction (LAOR) and understanding the reaction process are challenging. Here, we report the electrooxidation of waste PLA to acetate at a high current density of 100 mA cm−2 with high Faraday efficiency (∼95%) and excellent stability (>100 h) over a nickel selenide nanosheet catalyst. In addition, a total Faraday efficiency of up to 190% was achieved for carboxylic acids, including acetic acid and formic acid, by coupling with the cathodic CO2 reduction reaction. In situ experimental results and theoretical simulations revealed that the catalytic activity center of LAOR was dynamically formed NiOOH species, and the surface-adsorbed SeOx species accelerated the formation of Ni3+ species, thus promoting catalytic activity. The mechanism of lactic acid electrooxidation was further elucidated. Lactic acid was dehydrogenated to produce pyruvate first and then formed CH3CO due to preferential C–C bond cleavage, resulting in the presence of acetate. This work demonstrated a sustainable method for recycling waste PLA and CO2 into high-value-added products.

Sago Starch Modification by Combination of Lactic Acid Hydrolysis and Oxidation of Hydrogen Peroxide Under Ultraviolet Rotary Dryer Irradiation

Sago Starch Modification by Combination of Lactic Acid Hydrolysis and Oxidation of Hydrogen Peroxide Under Ultraviolet Rotary Dryer Irradiation

Effects of Passive Warm-up on Flexibility, Exercise Performance, and Lactate Oxidation Rate in Track and Field Athletes

PURPOSE This study sought to investigate the effects of passive warm-up on flexibility, exercise performance, and lactate oxidation rate in track and field athletes.METHODS A total of eight male athletes with more than three years of athlete experience were recruited as participants, and passive warm-up (PW) and active warm-up (AW) treatments were conducted in a single-group crossover study design. The participants performed thermal stimulation at 40°C for 20 minutes as a PW and performed a 60-70% HRmax cycle as an AW. Flexibility and exercise performance were measured after each treatment. Anaerobic power was measured using the Wingate test, and lactic acid concentration was measured.RESULTS Body temperature significantly increased in both PW and AW, and no significant difference was observed in exercise performance between treatments. Flexibility and lactic acid oxidation rate were significantly higher in PW than in AW.CONCLUSIONS In track and field sprinters, PW did not exhibit any significant difference in anaerobic power and exercise performance compared to AW even though no physical exercise was performed, and PW was effective in body temperature, lactic acid oxidation rate, and flexibility. PW suggests the possibility of replacing AW.

Co-digestion of solid-liquid waste from citrus agroindustrial: Effect of hydraulic retention time and organic loading rate on H2 production in a long-term continuous operation leach bed reactor

The Leach Bed Reactor (LBR) application is a promising alternative for the anaerobic digestion of solid waste and wastewater. In this study, the LBR was continuously operated for 160 days in four different phases, for co-fermentation of solid and liquid waste from the citrus agroindustry, at 37 °C, evaluating the effect of hydraulic retention time (HRT) and organic loading rate (OLR). The maximum volumetric hydrogen production (VHPR) was observed at an HRT of 12h (958.3 mLH2.L-1.d-1); however, the highest hydrogen yield (HY) was identified at an HRT of 24h (104.9 mLH2.g-1CHO). Based on the metabolic characteristics of microorganisms identified in higher relative abundance, by 16S rRNA sequencing, such as Lactobacillus, Caproicoproducens, Bifidobacterium, Olsenella, and Solobacterium, an occurrence of chain elongation pathways in the production of butyric and caproic acids was inferred, with hydrogen production resulting from the lactic acid oxidation. The maximum electricity production potential of 16.3 kWh.m-3 liquor was estimated.

Linker-Assisted Assembly of Ligand-Bridged CdS/MoS2 Heterostructures: Tunable Light-Harvesting Properties and Ligand-Dependent Control of Charge-Transfer Dynamics and Photocatalytic Hydrogen Evolution.

We used linker-assisted assembly (LAA) to tether CdS quantum dots (QDs) to MoS2 nanosheets via L-cysteine (cys) or mercaptoalkanoic acids (MAAs) of varying lengths, yielding ligand-bridged CdS/MoS2 heterostructures for redox photocatalysis. LAA afforded precise control over the light-harvesting properties of QDs within heterostructures. Photoexcited CdS QDs transferred electrons to molecularly linked MoS2 nanosheets from both band-edge and trap states; the electron-transfer dynamics was tunable with the properties of bridging ligands. Rate constants of electron transfer, estimated from time-correlated single photon counting (TCSPC) measurements, ranged from (9.8 ± 3.8) × 106 s-1 for the extraction of electrons from trap states within heterostructures incorporating the longest MAAs to >5 × 109 s-1 for the extraction of electrons from band-edge or trap states in heterostructures with cys or 3-mercaptopropionic acid (3MPA) linkers. Ultrafast transient absorption measurements revealed that electrons were transferred within 0.5-2 ps or less for CdS-cys-MoS2 and CdS-3MPA-MoS2 heterostructures, corresponding to rate constants ≥5 × 109 s-1. Photoinduced CdS-to-MoS2 electron transfer could be exploited in photocatalytic hydrogen evolution reaction (HER) via the reduction of H+ to H2 in concert with the oxidation of lactic acid. CdS-L-MoS2-functionalized FTO electrodes promoted HER under oxidative conditions wherein H2 was evolved at a Pt counter electrode with Faradaic efficiencies of 90% or higher and under reductive conditions wherein H2 was evolved at the CdS-L-MoS2-heterostructure-functionalized working electrode with Faradaic efficiencies of 25-40%. Dispersed CdS-L-MoS2 heterostructures promoted photocatalytic HER (15.1 μmol h-1) under white-light illumination, whereas free cys-capped CdS QDs produced threefold less H2 and unfunctionalized MoS2 nanosheets produced no measurable H2. Charge separation across the CdS/MoS2 interface is thus pivotal for redox photocatalysis. Our results reveal that LAA affords tunability of the properties of constituent CdS QDs and MoS2 nanosheets and precise, programmable, ligand-dependent control over the assembly, interfacial structure, charge-transfer dynamics, and photocatalytic reactivity of CdS-L-MoS2 heterostructures.

Screen printed carbon electrode modified with WS2 nanosheet incorporated with cobalt oxide for non-enzymatic detection of lactic acid

Lactic acid is an essential organic chemical in food, clinical, chemical, and bioprocessing industries. The non-enzymatic sensor also possesses satisfactory stability and repeatability. Herein we report the WS2/CO3O4 Composite has been prepared via facile cost-effective solid state & hydrothermal method. X-ray diffraction (XRD), Fourier- transform infrared spectroscopy (FT-IR), and Field emission scanning electron microscopy (FE-SEM) have been used to examine the facets, oxidation states and morphology respectively. The electrochemical activity of WS2/Co3O4 was investigated by cyclic voltammetry and amperometric measurement in 0.1 M NaOH. The high electrochemical activity towards the oxidation of lactic acid in a 0.1 M NaOH solution with fast response time of 5 s has been obtained using WS2/CO3O4. As well, EIS of WS2/CO3O4 shows the low charge transfer resistance compared to WS2 and Co3O4. The proposed non-enzymatic sensor shows a linear range of 50–1000 µM with a low detection limit of 6 µM for lactic acid detection. Moreover, the sensor shows excellent selectivity in the presence of interfering species such uric acid (UA), ascorbic acid (AA), dopamine (DA), Mg2+, and Ca2+ and lactic acid (LA). These molecules did not produce a remarkable current response. The real word application of as prepared WS2/Co3O4 sensor is tested in urine sample with an acceptable recovery of 97.01–100.03%.

Highly Selective Photocatalytic Conversion of Glucose on Holo-Symmetrically Spherical Three-Dimensionally Ordered Macroporous Heterojunction Photonic Crystal

Highly Selective Photocatalytic Conversion of Glucose on Holo-Symmetrically Spherical Three-Dimensionally Ordered Macroporous Heterojunction Photonic Crystal

A Bifunctional CdS/MoO2/MoS2 Catalyst Enhances Photocatalytic H2 Evolution and Pyruvic Acid Synthesis

AbstractThe best use of photogenerated electrons and holes is crucial to boosting photocatalytic activity. Herein, a bifunctional dual‐cocatalyst‐modified photocatalyst is constructed based on CdS/MoO2/MoS2 hollow spheres for hydrogen evolution coupled with selective pyruvic acid (PA) production from lactic acid (LA) oxidation. MoS2 and MoO2 are simultaneously obtained from the conversion of CdMoO4 in one step. In a photocatalytic process, the MoS2 and MoO2 function as the reduction and oxidation centers on which photogenerated electrons and holes accumulate and are used for hydrogen evolution reaction (HER) and PA synthesis, respectively. By monitoring the intermediates, a two‐step single‐electron route for PA production is proposed, initiated by the cleavage of the α‐C(sp3)−H bond in the LA. The conversion of LA and the selectivity of PA can reach ca. 29 % and 95 % after a five‐hour reaction, respectively.

A Bifunctional CdS/MoO2/MoS2 Catalyst Enhances Photocatalytic H2 Evolution and Pyruvic Acid Synthesis

The best use of photogenerated electrons and holes is crucial to boosting photocatalytic activity. Herein, a bifunctional dual-cocatalyst-modified photocatalyst is constructed based on CdS/MoO2 /MoS2 hollow spheres for hydrogen evolution coupled with selective pyruvic acid (PA) production from lactic acid (LA) oxidation. MoS2 and MoO2 are simultaneously obtained from the conversion of CdMoO4 in one step. In a photocatalytic process, the MoS2 and MoO2 function as the reduction and oxidation centers on which photogenerated electrons and holes accumulate and are used for hydrogen evolution reaction (HER) and PA synthesis, respectively. By monitoring the intermediates, a two-step single-electron route for PA production is proposed, initiated by the cleavage of the α-C(sp3 )-H bond in the LA. The conversion of LA and the selectivity of PA can reach ca. 29 % and 95 % after a five-hour reaction, respectively.

Ce(III)-modulation over non-enzymatic Pt/CeO2/GO biosensor with outstanding sensitivity and stability for lactic acid detection

A series of non-enzymatic graphene functionalized biosensors was developed via deposition precipitation method for lactic acid (LA) detection, which were characterized by transmission electron microscopy (TEM), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), gas chromatography-mass spectrometry, liquid chromatography-mass spectrometry, and proton nuclear magnetic resonance (1H NMR). The electrochemical performances of the non-enzymatic biosensors were measured by means of the electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) method. The comprehensive analysis of structures shows that Pt, CeO2, and GO components interact with each other. During the storing and releasing oxygen, the valence ratio of Ce3+/Ce4+ and the number of oxygen vacancies in CeO2 change accordingly, which can be conducive to increasing electronic transmission capacity and finally leads to the improvement of electrocatalytic performance. Among them, the Pt/CeO2/GO biosensor containing 0.47 at% platinum exhibits an excellent electrochemical detection performance with high sensitivity of 12.3 µA·L/ (mmol·cm2) and a low limit of detection (LOD) of 5.12 μmol/L in a wide linear range from 10 to 900 μmol/L. In addition, the proposed biosensor possesses a promising anti-interference capability, as well as high stability and good reproducibility, which was assessed by testing the cyclic voltammogram in 0.1 mol/L lactic acid one year later. The underlying mechanism was proposed for electrochemical oxidation of LA to carbon dioxide and acetic acid with the synergistic effect among Pt, CeO2, and GO. Furthermore, the results of the standard addition method in real samples (human serum and urine samples) reveal that the lactic acid detection of the non-enzymatic Pt/CeO2/GO biosensor is accompanied by high reliability. Thus, it will be a valuable biosensor for in vitro detection of lactic acid level in clinical samples.

CdS nanodots adorned (020)-featured WO3·H2O nanoplates heterojunction with augmented photocatalytic hydrogen production under Z-scheme charge transfer mechanism

In this paper, controllable nucleation and growth of CdS nanodots on the (020)-featured WO3·H2O nanoplates has been successfully accomplished to prepare CdS-WO3·H2O heterojunction with high-quality interfacial contact through a slow release of Cd2+ and S2- from the gradual self-loop hydrolysis of cadmium acetate and thioacetamide. The chemical and structural characteristics of as-prepared samples before and after heat treatment are detailedly investigated by TG-DSC, XRD, Raman, XPS, FESEM and HRTEM, as well as their light absorption performance from UV-Vis DRS. The maximum average hydrogen production rate for CdS-WO3·H2O reaches 2.15 mmol·g−1·h−1 under 300 W Xe lamp irradiation (λ > 420 nm) using lactic acid as sacrificial reagent, which is 8.27 and 2.72 times as much as CdS and CdS-WO3, respectively. According to band alignment, CdS-WO3·H2O exhibits greater energy difference of Fermi level than CdS-WO3, and augmented photocatalytic performance should arise from efficient Z-scheme charge transfer mechanism under stronger built-in electric field, in which the conduction band electrons of WO3·H2O and valence band holes of CdS are expected to effectively recombine at their interfacial zones, while the conduction band electrons of CdS and valence band holes of WO3·H2O contribute to the reduction of H+ and oxidation of lactic acid.

Non-enzymatic lactic acid sensor based on AuPtNPs functionalized MoS2 nanosheet as electrode modified materials

Lactic acid (LA) is an energy product of anaerobic metabolism and also used as an important biomarker in clinical medical diagnosis. Herein, a facile and efficient non-enzymatic electrochemical sensor had been successfully developed to determine LA using gold platinum bimetallic nanoparticles modified molybdenum disulfide nanosheet (MoS 2 -AuPt) as a sensing platform. The presence of AuPtNPs not only increased the electron transfer rate but also could replace enzymes for electrochemical oxidation of LA. Thus, MoS 2 -AuPt could be acted as an efficient electrocatalyst for non-enzymatic LA detection. Finally, the non-enzymatic LA sensor was used to detect different concentrations of LA, its linear range was 0.005–3 mM, the detection limit was 0.00033 mM, and the response time was less than 15 s. Moreover, the developed LA sensor had been successfully applied to detect LA in human sweat, which provided a broad prospect for the analysis of LA in some other complicated samples.

Preparation of TiO2/MoSe2 heterostructure composites by a solvothermal method and their photocatalytic hydrogen production performance

TiO2/MoSe2 composite photocatalysts were prepared by a solvothermal method using different MoSe2 loadings on the surface of TiO2 to improve the catalytic activity. Upon increasing the MoSe2 loading, the fluorescence intensity of the catalyst gradually decreased, indicating that the MoSe2 loading increased the utilization of photogenerated carriers in TiO2 and improved the catalytic activity. The formic acid produced by the oxidation of lactic acid and methanol dissociated into oxygen-containing anions that were electrostatically adsorbed on the catalyst surfaces. During photocatalysis, the photogenerated electrons on TiO2 were transferred to MoSe2, which separated the photogenerated electrons and holes and increased the quantum efficiency. Therefore, the hydrogen production rate of the composite catalyst was higher than that of pure TiO2, with a quantum efficiency of about 36.8%.

Design of an enzyme-mimicking NiO@Au nanocomposite for the sensitive electrochemical detection of lactic acid in human serum and urine

Detection of lactic acid (LA) in biological systems is required for medical diagnostics and the management of numerous medical conditions due to its key active metabolic role in the production of glycogen in muscle. Herein, we report on the facile synthesis of a novel enzyme-free gold (Au) modified flower-structured nickel oxide (NiO@Au) nanocomposite through an electrochemical strategy, which resulted in the generation of a sensing electrode material with robust synergistic effects. This sensing platform contained highly porous structured NiO flowers, which provided an extensive surface area with the capacity to mimic enzymatic activity, akin to lactate dehydrogenase (LDH) and lactate oxidase (LOD), etc. for the oxidation of LA. The effective dispersion of Au on NiO further enhanced the electron transfer process at the electrode surface. The developed sensor demonstrated a low detection limit of 11.6 µM, high sensitivity of 8.0 µA/mM, a wide linear range between 100.0 µM and 0.5 M, exceptional selectivity against potential interferences such as cystamine, ascorbic acid, uric acid, and glucose, and excellent stability over repeated cycles. The developed sensor was further tested for the detection and determination of LA in human serum and urine samples, showing that this new NiO@Au nanocomposite has strong practical applicability. The present study established a novel strategy for the synthesis of a unique NiO@Au nanocomposite, while offering a powerful and reliable electrochemical platform for the sensitive detection of LA, which translates to broad applications in biomedical, food safety, and environmental monitoring.

Solar hydrogen generation from organic substance using earth abundant CuS–NiO heterojunction semiconductor photocatalyst

This work explores the critical role of NiO co-catalyst assembled on the surface of a CuS primary photocatalyst which effectively improves interface properties and enhances solar-to-hydrogen production by prolonging lifetime of photo-excitons generated at the CuS surface. The nanoscale CuS/NiO heterojunction is formulated using hydrothermal and wet impregnation methods. The resultant CuS/NiO composite shows optical absorbance between 380 and 780 nm region. The type-II energetic structure formed at CuS/NiO heterojunction facilitates rapid charge separation and as a result, the CuS/NiO composite exhibits 13 folds higher photocatalytic water splitting performance than CuO and NiO. The champion CuO/NiO photocatalyst is first identified by screening the catalysts using a preliminary water splitting test reaction under natural Sunlight irradiation. After the optimization of the catalyst, it was further explored for enhanced photocatalytic hydrogen production using different organic substances dispersed in water (alcohols, amine and organic acids). The champion CuS/NiO catalyst (CPN-2) exhibited the photocatalytic hydrogen production rate of 52.3 mmol h−1.g−1cat in the presence of lactic acid-based aqueous electrolyte and, it is superior than hydrogen production rate obtained in the presence of other organic substances (triethanolamine, glycerol, ethylene glycol, methanol) tested under identical experimental conditions. These results indicate that the energetic structure of CuS/NiO photocatalyst is favorable for photocatalytic oxidation or reforming of lactic acid. The oxidation of lactic acid contributes both protons and electrons for enhanced hydrogen generation as well as protects CuS from photocorrosion. The modification of surface property and energetic structure of CuS photocatalyst by the NiO co-catalyst improves photogenerated charge carrier separation and in turn enhances the solar-to-hydrogen generation efficiency. The recyclability tests showed the potential of CPN-2 photocatalyst for prolonged photocatalytic hydrogen production while continuous supply of lactic acid feedstock is available.

Ultra-fine nickel sulfide nanoclusters @ nickel sulfide microsphere as enzyme-free electrode materials for sensitive detection of lactic acid

Abstract A new facile fabrication of ultrafine nanoclusters of nickel-sulfides with an average diameter of ~3.4 nm on NiS microsphere (NiS-NC@NiS-MS) on bare nickel foam (NiF) substrate (designated as NiS-NC@NiS-MS/NiF) using one-step electrochemical strategy for the direct electrochemical oxidation and sensing of lactic acid (LA) is demonstrated. The dimension, surface morphology, crystalline nature, chemical composition, and electrochemical characteristics of the NiS Nanoclusters @ NiS Microsphere are systematically studied with field-emission scanning electron microscope (FE-SEM), high-resolution transmission electron microscope (HR-TEM), X-ray diffraction, X-ray photoelectron spectroscopy (XPS), and cyclic voltammetric measurements. The developed NiS-NC@NiS-MS/NiF electrode exhibits an excellent enzyme-mimic electrocatalytic activity towards the lactic acid oxidation at the less positive potential of ~0.45 V (vs Ag/AgCl)) and high catalytic anodic current of ~1.7 mA. The present enzyme-mimic NiS-NC@NiS-MS catalyst based sensor presents an experimental lowest detection limit of 0.5 μM, high sensitivity of 0.39 μA μM−1 with a rapid sensing response, and a linear range from 0.5 μM to 85.5 μM. Owing to the uniform and high dispersion of small NiS nanoclusters, abundant electrochemical active sites, and improved mass-transfer kinetics, the NiS-NC@NiS-MS/NiF electrode delivers a high performance lactic acid sensing. The developed non-enzymatic lactic acid biosensor based on NiS nanoclusters shows an outstanding anti-interference ability in the presence of various potential interferences (uric acid (UA), ascorbic acid (AA), paracetamol (PA), Mg2+, Na+ and Ca2+), good reproducibility, and long-term durability. Moreover, the present sensor is successfully tested the lactic acid sensing in practical human urine samples.

Hollow sphere nickel sulfide nanostructures–based enzyme mimic electrochemical sensor platform for lactic acid in human urine

An enzyme-free electrochemical sensor platform is reportedbased on hollow sphere structured nickel sulfide (HS-NiS) nanomaterials for the sensitive lactic acid (LA) detection in human urine. Hollow sphere nickel sulfide nanostructures directly grow on the nickel foam (NiF) substrate by using facile and one-step electrochemical deposition strategy towards the electrocatalytic lactic acid oxidation and sensing for the first time. The as-developed nickel sulfide nanostructured electrode (NiF/HS-NiS) has beensuccessfully employed as the enzyme mimic electrode towards the enhanced electrocatalytic oxidation and detection of lactic acid. The NiF/HS-NiS electrode exhibits an excellent electrocatalytic activity and sensing ability with low positive potential (~ 0.52V vs Ag/AgCl), catalytic current density (~ 1.34mA), limit of detection (LOD) (0.023μM), linear range from 0.5 to 88.5μM with a correlation coefficient of R2 = 0.98, sensitivity (0.655μAμM-1cm-2), and selectivity towards the lactic acid owing to the ascription of high inherent electrical conductivity, large electrochemical active surface area (ECASA), high electrochemical active sites, and strong adsorption ability. The sensors developed in this work demonstrate the selectivity against potential interferences, including uric acid (UA), ascorbic acid (AA), paracetamol (PA), Mg2+, Na+, and Ca2+. Furthermore, the developed sensors show practicability by sensing lactic acid in human urine samples, suggesting thatthe HS-NiS nanostructures device haspromising clinical diagnosticpotential. Graphical abstract.