Bimetallic Fe/Co-MOF dispersed in a PVA/chitosan multi-matrix hydrogel as a flexible sensor for the detection of lactic acid in sweat samples.

A novel bimetallic Fe/Co-metal-organic framework (MOF) hydrogel-based wearable sweat sensor was developed. Morphological and structural analysis of the hydrogel shows uniformly sized spines and spindle-shaped particles of the Fe/Co-MOF, and it has a high surface area (132.306 m2 g-1) and porosity (0.059 cm3 g-1) as confirmed by Brunauer-Emmett-Teller (BET) studies. The integration of the bimetallic MOF into a polyvinyl alcohol/chitosan (PVA/CS)-mixed matrix resulted in a multiple network hydrogel. The optimisation study investigated  the effects of different pH of the PBS electrolyte, scan rates, and accumulation time in voltammetry. The electrochemical methods such as cyclic voltammetry (CV), square wave voltammetry (SWV), and electrochemical impedance spectroscopy (EIS) provided information on the redox behaviour, electrochemical stability, and catalytic activity of the hydrogel. The sensor demonstrates a wide linear detection range from 0.05 µM to 100 mM, a superior sensitivity of 0.02 mA mM-1 cm-2, and a lower limit of detection of 0.01 µM . Active sites distributed over the hydrogel surface, specifically Fe2+ and Co2+ within the MOF structure, catalyse the oxidation of L-lactic acid, resulting in electron transfer and the formation of pyruvic acid. Notably, the fabricated sensor exhibits high selectivity, effectively discriminating against interfering species such as uric acid, ascorbic acid, glucose, urea, dopamine, NaCl, and CaCl2. Real-time analysis conducted in a simulated sweat sample via the standard addition method resulted in good recovery percentages of a minimum of 98%. The work presented here is a versatile and simple platform for point-of-care testing, especially for athletes and military personnel.

Rapid electrochemical detection of L-lactate in Baijiu affecting serotonin and dopamine secretion in mice.

Baijiu, a traditional Chinese alcoholic beverage, carries China's rich historical and cultural heritage. Consumers experience varying levels of relaxation and pleasure after consuming different types of Baijiu, with the biological basis of delectation influenced by serotonin and dopamine. In this study, we prepared carbon fiber electrodes modified with surface decorated gold nanoparticles to directly measure the electrochemical response signals in the serum of mice before and after gavage with different types of Baijiu. It was observed that the serum signal change in mice after consuming Baijiu sample 1 (J1) was higher than that of the other two types of Baijiu. Consequently, trace flavor compounds in the Baijiu samples were detected using gas chromatography-mass spectrometry (GC-MS) and liquid chromatography-mass spectrometry (LC-MS), revealing the highest content of L-lactic acid in J1. Mice were intraperitoneally injected with 200 mg kg-1 of L-lactic acid. The changes in dopamine and serotonin in the serum of the injected mice were monitored using a biosensor, and the results were compared with the results of high performance liquid chromatography-triple quadrupole mass spectrometry (HPLC-MS). The findings confirmed that L-lactic acid could indeed stimulate the secretion of both neurotransmitters in mice, suggesting that the trace components in J1 may even exhibit synergistic effects. This study contributes to a deeper understanding of the effects of Baijiu on the body and provides a scientific basis for the production and consumption of Baijiu.

A wearable nanozyme-enzyme electrochemical biosensor for sweat lactate monitoring.

In this study, we developed a wearable nanozyme-enzyme electrochemical biosensor that enablies sweat lactate monitoring. The biosensor comprises a flexible electrode system prepared on a polyimide (PI) film and the Janus textile for unidirectional sweat transport. We obtained favorable electrochemical activities for hydrogen peroxide reduction by modifying the laser-scribed graphene (LSG) electrode with cerium dioxide (CeO2)-molybdenum disulphide (MoS2) nanozyme and gold nanoparticles (AuNPs). By further immobilisation of lactate oxidase (LOx), the proposed biosensor achieves chronoamperometric lactate detection in artificial sweat within a range of 0.1-50.0 mM, a high sensitivity of 25.58 µA mM-1cm-2 and a limit of detection (LoD) down to 0.135 mM, which fully meets the requirements of clinical diagnostics. We demonstrated accurate lactate measurements in spiked artificial sweat, which is consistent with standard ELISA results. To monitor the sweat produced by volunteers while exercising, we conducted on-body tests, showcasing the wearable biosensor's ability to provide clinical sweat lactate diagnosis for medical treatment and sports management.

Photo-induced metal-oxide biosensor for analysis of biofluids.

Determining the concentration of biomarkers offers insights into the health condition and performance of the body. The majority of the biosensors applied to measuring biomarkers in biological fluids are electrochemical bases; however, these biosensors suffer from several key drawbacks. These include utilizing complex sensing materials to obtain desirable analytical performance, which prevents their practical application; and operation at a relatively high potential, which leads to inaccurate measurements due to the undesired oxidation of non-target molecules. A novel photo-induced chemiresistive biosensor is introduced here that addresses these challenges. A UV-induced ZnO nanorod (NR) chemiresistive biosensor is developed and applied to monitoring lactate and glucose, as model biomarkers in sweat. The detection mechanism of lactate based on its interaction with ZnO NRs is proposed. Furthermore, the effect of the electrode design and operating parameters, including irradiance, radiation wavelength, and applied potential, are evaluated. The highest response, the shortest response time, and complete recovery are obtained at 5.6 mW/cm2 irradiance of 365 nm and 0.1 V potential. The results indicate that the developed transduction platform utilizing a simple sensing layer is a promising technique with excellent analytical performance for detecting different biomarkers, thereby paving the way toward the emergence of photo-induced chemiresistive biosensors for real-life applications.

A single-microbe living bioelectronic sensor for intracellular amperometric analysis.

Subcellularly amperometric analysis in situ is crucial for understanding intracellular redox biochemistry and subcellular heterogeneity. Unfortunately, the ultra-small size and complex microenvironment inside the cell pose a great challenge to achieve this goal. To address the challenge, a minimized living microbial sensor has been fabricated in this work for amperometric analysis. Here, by fabricating the dimidiate microelectrode as the working electrode, while fitting a living electroactive bacterium (EAB) as the transducer, outward extracellular electron transfer (EET) of the sensory EAB is correlated with the concentration of lactic acid, which is electrochemically recorded and thus displays an electrical signal output for detection. In specific, the S. oneidensis modified dimidiate microelectrode (S.O.@GNE-NPE) acts as an integrated electroanalytical device to generate the electrical signal in situ. The established microcircuit provides unprecedented precision and sensitivity, contributing to subcellular amperometric measurement. The microbial sensor shows a linear response in the concentration range of 0-60 mM, with a limit of detection (LOD) at 0.3 mM. The microsensor also demonstrates good selectivity against interferences. Additionally, intracellular analysis of lactic acid provides direct evidence of enhanced lactic metabolism in cancer cells as a result of "Warburg Effect". This work shows an example of nano-, bio- and electric technologies that have been integrated on the EAB-modified dimidiate microelectrode, and achieves intracellular biosensing application through such integration. It may give a new strategy on the combination of micro/nanotechnologies with sensory EAB for the necessary development of bioelectronic devices.

Fully integrated microneedle biosensor array for wearable multiplexed fitness biomarkers monitoring.

Fitness monitoring has become increasingly important in modern lifestyles; the current fitness monitoring always relies on physical sensors, making it challenging to detect pertinent issues at a deeper level when exercising. Here, we report a fully integrated wearable microneedle sensor that simultaneously measures fitness related biomarkers (e.g., glucose, lactate, and alcohol) during physical exercise. Such a sensor integrates a biocompatible 3D-printed microneedle array that can comfortably access skin interstitial fluid and a small circuit for signal processing and calibration, and wireless communication. The microneedle array features good biocompatibility and highly sensitive biochemical sensors that can detect even the slightest variations within the biomarkers of this fluid. On-body experimental results indicate that such a sensor can monitor fitness-related biomarkers across multiple subjects and support multi-day monitoring, with results showing a good correlation with commercial devices. The data was transmitted to a smartphone via Bluetooth and uploaded to cloud platforms for further health assessment. This study has the potential to boost intelligent wearable devices in sports health.

Sweat lactate sensor for detecting anaerobic threshold in heart failure: a prospective clinical trial (LacS-001).

A simple method for determining the anaerobic threshold in patients with heart failure (HF) is needed. This prospective clinical trial (LacS-001) aimed to investigate the safety of a sweat lactate-monitoring sensor and the correlation between lactate threshold in sweat (sLT) and ventilatory threshold (VT). To this end, we recruited 50 patients with HF and New York Heart Association functional classification I-II (mean age: 63.5 years, interquartile range: 58.0-72.0). Incremental exercise tests were conducted while monitoring sweat lactate levels using our sensor. sLT was defined as the first steep increase in lactate levels from baseline. Primary outcome measures were a correlation coefficient of ≥ 0.6 between sLT and VT, similarities as assessed by the Bland-Altman analysis, and standard deviation of the difference within 15 W. A correlation coefficient of 0.651 (95% confidence interval, 0.391-0.815) was achieved in 32/50 cases. The difference between sLT and VT was -4.9 ± 15.0 W. No comparative error was noted in the Bland-Altman plot. No device-related adverse events were reported among the registered patients. Our sweat lactate sensor is safe and accurate for detecting VT in patients with HF in clinical settings, thereby offering valuable additional information for treatment.

A sensor platform based on SERS detection/janus textile for sweat glucose and lactate analysis toward portable monitoring of wellness status.

Herein we report a wearable sweat sensor of a Janus fabric based on surface enhanced Raman scattering (SERS) technology, mainly detecting the two important metabolites glucose and lactate. Janus fabric is composed of electrospinning PU on a piece of medical gauze (cotton), working as the unidirectional moisture transport component (R = 1305%) to collect and transfer sweat efficiently. SERS tags with different structures act as the probe to recognize and detect the glucose and lactate in high sensitivity. Core-shell structured gold nanorods with DTNB inside (AuNRs@DTNB@Au) are used to detect lactate, while gold nanorods with MPBA (AuNRs@MPBA) are used to detect glucose. Through the characteristic SERS information, two calibration functions were established for the concentration determination of glucose and lactate. The concentrations of glucose and lactate in sweat of a 23 years volunteer during three-stage interval running are tested to be 95.5, 53.2, 30.5 µM and 4.9, 13.9, 10.8 mM, indicating the glucose (energy) consumption during exercise and the rapid accumulation of lactate at the early stage accompanied by the subsequent relief. As expected, this sensing system is able to provide a novel strategy for effective acquisition and rapid detection of essential biomarkers in sweat.

Lactate threshold evaluation in swimming using a sweat lactate sensor: A prospective study.

Since assessing aerobic capacity is key to enhancing swimming performance, a simple and widely applicable technology should be developed. Therefore, we aimed to noninvasively visualize real-time changes in sweat lactate (sLA) levels during swimming and investigate the relationship between lactate thresholds in sweat (sLT) and blood (bLT). This prospective study included 24 university swimmers (age: 20.7 s ± 1.8 years, 58% male) who underwent exercise tests at incremental speeds with or without breaks in a swimming flume to measure heart rate (HR), bLT, and sLT based on sLA levels using a waterproof wearable lactate sensor attached to the dorsal upper arm on two different days. The correlation coefficient and Bland-Altman methods were used to verify the similarities of the sLT with bLT and personal performance. In all tests, dynamic changes in sLA levels were continuously measured and projected onto the wearable device without delay, artifacts, or contamination. Following an initial minimal current response, with increasing speed the sLA levels increased substantially, coinciding with a continuous rise in HR. The speed at sLT strongly correlated with that at bLT (p < 0.01 and r = 0.824). The Bland-Altman plot showed a strong agreement (mean difference: 0.08 ± 0.1 m/s). This prospective study achieved real-time sLA monitoring during swimming, even with vigorous movement. The sLT closely approximated bLT; both were subsequently validated for their relevance to performance.

Effects of sodium lactate injection on meat quality and lactate content in broiler chickens: emphasis on injection method and dosage.

This study aims to develop an experimental model of high lactate levels in broilers to mimic the condition of birds under stress or diseases and evaluate its consequent effects on meat quality. The injection sites and dosage effects were compared separately in 2 experiments. Experiment 1 includes 3 injection sites: intraperitoneal injection, intramuscular injection, and subcutaneous injection. Experiment 2 was a dosage experiment based on the results of Experiment 1: sodium lactate intraperitoneal injection group with 1.5, 3, 6 mM concentration. The results showed that injecting sodium lactate intraperitoneally, intramuscularly, or subcutaneously all significantly decreased body weight and breast muscle weight while elevating lactic acid levels in both the blood and breast muscle of broilers. Moreover, all 3 injection methods caused a significant reduction in pH24h and an increase in the shear force value of breast muscle. In addition, dose-response experiments of intraperitoneal injection showed that a concentration of 3 mM and 6 mM were significantly decreased body weight and breast muscle weight in broiler chickens, accompanied by a notable increase in breast muscle lactate content. Compared to the control group, intraperitoneal injections of 1.5 mM, 3 mM, and 6 mM sodium lactate treatments significantly reduced the yellowness values of the breast muscle. As the dose of sodium lactate increased, the shear force value of the breast meat exhibited linear and quadratic increments, while the drip loss decreased linearly. Intraperitoneal injection of 3 mM sodium lactate also significantly reduced the pH24h of broiler breast muscle. In addition, an increased dose of lactate injections up-regulated the glycolytic pathway responsible for endogenous lactate production in the breast muscle by upregulating the expression of phosphofructokinase, pyruvate kinase and lactate dehydrogenase A. In conclusion, intraperitoneal injection of sodium lactate at 3 mM directly increased breast muscle lactate levels, providing a valuable method for establishing a high-level lactate model in poultry.

Kimchi Lactic Acid Bacteria Starter Culture: Impact on Fermented Malt Beverage Volatile Profile, Sensory Analysis, and Physicochemical Traits.

Starter cultures used during the fermentation of malt wort can increase the sensory characteristics of the resulting beverages. This study aimed to explore the aroma composition and flavor recognition of malt wort beverages fermented with lactic acid bacteria (Levilactobacillus brevis WiKim0194) isolated from kimchi, using metabolomic profiling and electronic tongue and nose technologies. Four sugars and five organic acids were detected using high-performance liquid chromatography, with maltose and lactic acid present in the highest amounts. Additionally, e-tongue measurements showed a significant increase in the sourness (AHS), sweetness (ANS), and umami (NMS) sensors, whereas bitterness (SCS) significantly decreased. Furthermore, 20 key aroma compounds were identified using gas chromatography-mass spectrometry and 15 key aroma flavors were detected using an electronic nose. Vanillin, citronellol, and ß-damascenone exhibited significant differences in the flavor profile of the beverage fermented by WiKim0194, which correlated with floral, fruity, and sweet notes. Therefore, we suggest that an appropriate starter culture can improve sensory characteristics and predict flavor development in malt wort beverages.

Validation of field-based running tests to determine maximal aerobic speed in professional rugby league.

Practitioners place importance on high-speed running (HSR) to monitor training practice and match-play demands, whilst attempting to maximise fitness and minimize the risk of injury occurrence. Practitioners apply various methods to quantify HSR, such as absolute thresholds, percentage of maximum sprint speed and maximal aerobic speed (MAS). A recent survey demonstrates the 5-minute run and 1200m shuttle test (ST) to be implemented among rugby league practitioners to quantify HSR by incorporating MAS. However, it is unclear as to how valid these methods are to accurately quantify MAS. Therefore, the aim of this study was to assess the validity of the 5-minute run and 1200m ST when compared to a gold standard measure for MAS. Twenty 1st team professional rugby league players competing in the European Super League participated in this study. Players were required to complete an incremental treadmill test, 5-minute run and 1200m ST over a two-week period in pre-season. MAS, peak heart rate (HRmax), peak lactate (Lapeak) and rating of perceived exertion (RPE) where collected upon completion of each test. Results demonstrated the 1200m ST to have a higher correlation for MAS than the 5-minute run (1200m ST: r = 0.73, 5-minute run: r = 0.64). However, when assessing validity using the level of agreement between data, the 5-minute run underreported MAS by 0.45 m·s-1 whereas the 1200m ST underreported MAS by 0.77 m·s-1. Ultimately, both field-based tests used in this study underreport MAS when compared to an incremental treadmill test, although the 5-minute run provides a closer agreement and therefore a more valid measurement for MAS than the 1200m ST.

A dried sweat spot paper (DSSP) method based on novel mass spectrometry probe labeling for detection and resolution of DL-lactate enantiomers as potential biomarkers for diabetes mellitus.

BACKGROUND: Human sweat can be collected non-invasively with low infectivity; however, its application as a determination method has been challenged due to the presence of trace amounts of chiral metabolites. Moreover, its application as a biological fluid for disease diagnosis has not been previously reported. In this study, the human dried sweat spot paper (DSSP) method was proposed for the derivatization of a novel mass spectrometric chiral probe, N-[1-Oxo-5-(triphenylphosphonium) pentyl]-(S)-3-aminopyrrolidine (OTPA), determination and resolution of DL-lactic acid (DL-LA) enantiomers in human elbow sweat. RESULTS: The methodological validation revealed the resolution (Rs) as 1.78, the limit of detection (S/N = 3) as 20.83 fmol, good linearity (R2 ≥ 0.9996), and the intra-day and intra-day stability with RSD ranging from 0.53 to 10.85 %, while the average recovery rate of D-LA and L-LA were 104.00 % ± 4.68 % and 107.41 % ± 8.34 %, respectively, with high accuracy. In addition, the method was applied for the determination of DL-LA in the sweat on elbow of 10 healthy volunteers and 30 diabetic patients. The results demonstrated that the D/L ratio and L/D ratio were significantly different (p < 0.0001). In addition, a moderate positive linear correlation between the D/L-LA ratio in human sweat and fasting blood glucose level (r = 0.7744, p < 0.0001) was observed, thereby suggesting that the D/L ratio of lactate in human sweat correlate the glucose level in human fasting blood. SIGNIFICANCE AND NOVELTY: The D/L lactate ratio in human sweat could be used as a potential biomarker for diabetes screening. The method can be used to screen for diabetes by providing a dry sweat paper to test equipment and has the potential to be a non-invasive early-warning diagnostic tool for diabetes.

Wireless implantable bioelectronics with a direct electron transfer lactate enzyme for detection of surgical site infection in orthopaedics.

Periprosthetic infection is one of the most devastating complications following orthopaedic surgery. Rapid detection of an infection can change the treatment pathway and improve outcomes for the patient. In here, we propose a miniaturized lactate biosensor developed on a flexible substrate and integrated on a small-form bone implant to detect infection. The methods for lactate biosensor fabrication and integration on a bone implant are fully described within this study. The system performance was comprehensively electrochemically characterised, including with L-lactate solutions prepared in phosphate-buffered saline and culture medium, and interferents such as acetaminophen and ascorbic acid. A proof-of-concept demonstration was then conducted with ex vivo ovine femoral heads incubated with and without exposure to Staphylococcus epidermidis. The sensitivity, current density and limit-of-detection levels achieved by the biosensor were 1.25 µA mM-1, 1.51 µA.M-1.mm-2 and 66 µM, respectively. The system was insensitive to acetaminophen, while sensitivity to ascorbic acid was half that of the sensitivity to L-lactate. In the ex vivo bone model, S. epidermidis infection was detected within 5 h of implantation, while the control sample led to no change in the sensor readings. This pioneering work demonstrates a pathway to improving orthopaedic outcomes by enabling early infection diagnosis.

Changes in microbial dynamics and fermentation characteristics of alfalfa silage: A potent approach to mitigate greenhouse gas emission through high-quality forage silage.

Feeding ruminants with high-quality forage can enhance digestibility and reduce methane production. Development of high-quality silage from leguminous plants with lactic acid bacteria can improve digestibility and it mitigate the greenhouse gas emissions. In this study, we developed a high-quality alfalfa silage with improved fermentation index and microbial dynamics using Levilactobacillus brevis-KCC-44 at low or high moisture (LM/HM) conditions and preserved it for 75 or 150 days. Alfalfa fermentation with L. brevis enhances acidification and fermentation characteristics primarily due to the dominance of lactic acid bacteria (LAB) L. brevis (>95%) compared to alfalfa fermented with epiphytic LAB. The inoculant L. brevis improved the anaerobic fermentation indexes resulting in a higher level of lactic acid in both high (10.0 ± 0.12 & 8.90 ± 0.31%DM) and low moisture (0.55 ± 0.08 & 0.39 ± 0.0 %DM) in 75 and 150 days respectively, compared to control silage. In addition, the marginal amount of acetic acid (range from 0.23 ± 0.07 to 2.04 ± 0.27 %DM) and a reduced level of butyric acid (range between 0.03 ± 0.0 to 0.13 ± 02 %DM) was noted in silage treated with LAB than the control. The LAB count and abundance of Levilactobacillus were higher in alfalfa silage fermented with L. brevis. Microbial richness and diversity were reduced in alfalfa silage treated with L. brevis which prompted lactic acid production at a higher level even for a prolonged period of time. Therefore, this L.brevis is an effective inoculant for producing high-quality alfalfa silage since it improves fermentation indexes and provides reproducible ensiling properties.

A new colorimetric lactate biosensor based on CUPRAC reagent using binary enzyme (lactate-pyruvate oxidases)-immobilized silanized magnetite nanoparticles.

A novel optical lactate biosensor is presented that utilizes a colorimetric interaction between H2O2 liberated by a binary enzymatic reaction and bis(neocuproine)copper(II) complex ([Cu(Nc)2]2+) known as CUPRAC (cupric reducing antioxidant capacity) reagent. In the first step, lactate oxidase (LOx) and pyruvate oxidase (POx) were separately immobilized on silanized magnetite nanoparticles (SiO2@Fe3O4 NPs), and thus, 2 mol of H2O2 was released per 1 mol of the substrate due to a sequential enzymatic reaction of the mixture of LOx-SiO2@Fe3O4 and POx-SiO2@Fe3O4 NPs with lactate and pyruvate, respectively. In the second step, the absorbance at 450 nm of the yellow-orange [Cu(Nc)2]+ complex formed through the color reaction of enzymatically produced H2O2 with [Cu(Nc)2]2+ was recorded. The results indicate that the developed colorimetric binary enzymatic biosensor exhibits a broad linear range of response between 0.5 and 50.0 µM for lactate under optimal conditions with a detection limit of 0.17 µM. The fabricated biosensor did not respond to other saccharides, while the positive interferences of certain reducing compounds such as dopamine, ascorbic acid, and uric acid were minimized through their oxidative removal with a pre-oxidant (NaBiO3) before enzymatic and colorimetric reactions. The fabricated optical biosensor was applied to various samples such as artificial blood, artificial/real sweat, and cow milk. The high recovery values (close to 100%) achieved for lactate-spiked samples indicate an acceptable accuracy of this colorimetric biosensor in the determination of lactate in real samples. Due to the increase in H2O2 production with the bienzymatic lactate sensor, the proposed method displays double-fold sensitivity relative to monoenzymatic biosensors and involves a neat color reaction with cupric-neocuproine having a clear stoichiometry as opposed to the rather indefinite stoichiometry of analogous redox dye methods.

Different modeling approaches for inline biochemical monitoring over the VLP-making upstream stages using Raman spectroscopy.

This work aimed to set inline Raman spectroscopy models to monitor biochemically (viable cell density, cell viability, glucose, lactate, glutamine, glutamate, and ammonium) all upstream stages of a virus-like particle-making process. Linear (Partial least squares, PLS; Principal components regression, PCR) and nonlinear (Artificial neural networks, ANN; supported vector machine, SVM) modeling approaches were assessed. The nonlinear models, ANN and SVM, were the more suitable models with the lowest absolute errors. The mean absolute error of the best models within the assessed parameter ranges for viable cell density (0.01-8.83 × 106 cells/mL), cell viability (1.3-100.0 %), glucose (5.22-10.93 g/L), lactate (18.6-152.7 mg/L), glutamine (158-1761 mg/L), glutamate (807.6-2159.7 mg/L), and ammonium (62.8-117.8 mg/L) were 1.55 ± 1.37 × 106 cells/mL (ANN), 5.01 ± 4.93 % (ANN), 0.27 ± 0.22 g/L (SVM), 4.7 ± 2.6 mg/L (SVM), 51 ± 49 mg/L (ANN), 57 ± 39 mg/L (SVM) and 2.0 ± 1.8 mg/L (ANN), respectively. The errors achieved, and best-fitted models were like those for the same bioprocess using offline data and others, which utilized inline spectra for mammalian cell lines as a host.

The Fluorescent Detection of Glucose and Lactic Acid Based on Fluorescent Iron Nanoclusters.

In this paper, a novel fluorescent detection method for glucose and lactic acid was developed based on fluorescent iron nanoclusters (Fe NCs). The Fe NCs prepared using hemin as the main raw material exhibited excellent water solubility, bright red fluorescence, and super sensitive response to hydrogen peroxide (H2O2). This paper demonstrates that Fe NCs exhibit excellent peroxide-like activity, catalyzing H2O2 to produce hydroxyl radicals (•OH) that can quench the red fluorescence of Fe NCs. In this paper, a new type of glucose sensor was established by combining Fe NCs with glucose oxidase (GluOx). With the increase in glucose content, the fluorescence of Fe NCs decreases correspondingly, and the glucose content can be detected in the scope of 0-200 µmol·L-1 (µM). Similarly, the lactic acid sensor can also be established by combining Fe NCs with lactate oxidase (LacOx). With the increase in lactic acid concentration, the fluorescence of Fe NCs decreases correspondingly, and the lactic acid content can be detected in the range of 0-100 µM. Furthermore, Fe NCs were used in the preparation of gel test strip, which can be used to detect H2O2, glucose and lactic acid successfully by the changes of fluorescent intensity.

Impact of lactate/albumin ratio on prognostic outcomes in patients with concomitant heart failure and chronic kidney disease.

Previous studies have linked the lactate/albumin (L/A) ratio to poor outcomes in various conditions, but its connection to mortality in patients with both heart failure (HF) and chronic kidney disease (CKD) remains unclear. Using data from 1537 patients in MIMIC-IV, this study examined the relationship between L/A ratio and in-hospital and one-year mortality, employing Cox models, Kaplan-Meier (KM) analysis, and restricted cubic splines (RCS). The non-survivor group showed higher L/A ratios than survivors (1.04 ± 0.78 vs. 0.58 ± 0.29, p < 0.001), indicating a significant link between higher L/A ratios and mortality. Cox analysis identified the L/A ratio was significantly related to all-cause mortality both in-hospital (HR 2.033; 95% CI 1.576-2.624; p < 0.001) and one-year (HR 1.723; 95% CI 1.428-2.078; p < 0.001). The association between L/A ratio and mortality was non-linear and increasing. The KM survival curves demonstrated significantly poorer survival outcomes for the high L/A group compared to the low L/A group, a difference that was statistically validated by a significant log-rank test (log-rank p < 0.001). L/A ratio has a significant association with poor prognosis in patients with HF and CKD patients in a critical condition. This finding demonstrates that L/A ratio might be useful in identifying patients with HF and CKD at high risk of all-cause death. Further large-scale prospective studies are needed to verify these results and inform clinical decisions.

Intradermal Lactate Monitoring Based on a Microneedle Sensor Patch for Enhanced In Vivo Accuracy.

Lactate is an important diagnostic and prognostic biomarker of several human pathological conditions, such as sepsis, malaria, and dengue fever. Unfortunately, due to the lack of reliable analytical decentralized platforms, the determination of lactate yet relies on discrete blood-based assays, which are invasive and inefficient and may cause tension and pain in the patient. Herein, we demonstrate the potential of a fully integrated microneedle (MN) sensing system for the minimally invasive transdermal detection of lactate in an interstitial fluid (ISF). The originality of this analytical technology relies on: (i) a strategy to provide a uniform coating of a doped polymer-based membrane as a diffusion-limiting layer on the MN structure, optimized to perform full-range lactate detection in the ISF (linear range of response: 0.25-35 mM, 30 s assay time, 8 h operation), (ii) double validation of ex vivo and in vivo results based on ISF and blood measurements in rats, (iii) monitoring of lactate level fluctuations under the administration of anesthesia to mimic bedside clinical scenarios, and (iv) in-house design and fabrication of a fully integrated and portable sensing device in the form of a wearable patch including a custom application and user-friendly interface in a smartphone for the rapid, routine, continuous, and real-time lactate monitoring. The main analytical merits of the lactate MN sensor include appropriate selectivity, reversibility, stability, and durability by using a two-electrode amperometric readout. The ex-vivo testing of the MN patch of preconditioned rat skin pieces and euthanized rats successfully demonstrated the accuracy in measuring lactate levels. The in vivo measurements suggested the existence of a positive correlation between ISF and blood lactate when a lag time of 10 min is considered (Pearson's coefficient = 0.85, mean difference = 0.08 mM). The developed MN-based platform offers distinct advantages over noncontinuous blood sampling in a wide range of contexts, especially where access to laboratory services is limited or blood sampling is not suitable. Implementation of the wearable patch in healthcare could envision personalized medicine in a variety of clinical settings.