Detection Limit For Glucose Research Articles

Coral-like Ti3C2Tx/PANI Binary Nanocomposite Wearable Enzyme Electrochemical Biosensor for Continuous Monitoring of Human Sweat Glucose

With the continuous advancement of contemporary medical technology, an increasing number of individuals are inclined towards self-monitoring their physiological health information, specifically focusing on monitoring blood glucose levels. However, as an emerging flexible sensing technique, continuous and non-invasive monitoring of glucose in sweat offers a promising alternative to conventional invasive blood tests for measuring blood glucose levels, reducing the risk of infection associated with blood testing. In this study, we fabricated a flexible and wearable electrochemical enzyme sensor based on a two-dimensional Ti3C2Tx MXene nanosheets and coral-like polyaniline (PANI) binary nanocomposite (denoted as Ti3C2Tx/PANI) for continuous, non-invasive, real-time monitoring of sweat glucose. The exceptional conductivity of Ti3C2Tx MXene nanosheets, in conjunction with the mutual doping effect facilitated by coral-like PANI, significantly enhances electrical conductivity and specific surface areas of Ti3C2Tx/PANI. Consequently, the fabricated sensor exhibits remarkable sensitivity (25.16 μA·mM−1·cm−2), a low detection limit of glucose (26 μM), and an extensive detection range (0.05 mM ~ 1.0 mM) in sweat. Due to the dense coral-like structure of Ti3C2Tx/PANI binary nanocomposite, a larger effective area is obtained to offer more active sites for enzyme immobilization and enhancing enzymatic catalytic activity. Moreover, the sensor demonstrates exceptional mechanical performance, enabling a 60° bend in practical applications, thus satisfying the rigorous demands of human sweat detection applications. The results obtained from continuous 60 min in vitro monitoring of sweat glucose levels demonstrate a robust correlation with the data of blood glucose levels collected by a commercial glucose meter. Furthermore, the fabricated Ti3C2Tx/PANI/GOx sensor demonstrated agreement with HPLC findings regarding the actual concentration of added glucose. This study presents an efficient and practical approach for the development of a highly reliable MXene glucose biosensor, enabling stable and long-term monitoring of glucose levels in human sweat.

Fabrication of natural enzyme-covered / amino-modified Pd-Pt bimetallic-doped zeolitic imidazolate framework for ultrasensitive detection of metabolites.

The present article introduced an natural enzyme-covered/amino-modified Pd-Pt bimetallic-doped zeolitic imidazolate framework (NAPPZ) for ultrasensitive and specific detection of glucose. The dodecahedral nanomaterial zeolitic imidazolate framework (ZIF-8)-loaded Pd-Pt bimetallic nanoparticles endowed the composite with peroxidase-like activity. The modification with glucose oxidase (GOx) facilitated the rapid access of H2O2 produced through glucose oxidation to the Pd-Pt nanoparticles vicinity reducing diffusion. GOx specifically catalyzes the transformation of glucose into H2O2, which then H2O2 rapidly migrates to the Pd-Pt nanoparticles, catalyzing the oxidation of colorless o-phenylenediamine into the orange-yellow product 2,3-diaminophenazine. Based on the aforementioned cascade reaction, the NAPPZ and NAPPZ based on ChOx were utilized for detecting glucose in human urine samples and cholesterol in milk, respectively. The NAPPZ strategy presented a broad detection range (20-1100μmol L-1) and a low detection limit (15.9μmol L-1) for glucose, and the NAPPZ based on ChOx strategy approach offered a broad detection range (10-500μmol L-1) and low detection limit (6.4μmol L-1) for cholesterol. Therefore, this novel method holds significant potential in the areas of clinical diagnostics and food safety.

Development of a 3D Hydrogel SERS Chip for Noninvasive, Real-Time pH and Glucose Monitoring in Sweat.

Traditional diagnostic methods, such as blood tests, are invasive and time-consuming, while sweat biomarkers offer a rapid physiological assessment. Surface-enhanced Raman spectroscopy (SERS) has garnered significant attention in sweat analysis because of its high sensitivity, label-free nature, and nondestructive properties. However, challenges related to substrate reproducibility and interference from the biological matrix persist with SERS. This study developed a novel ratio-based 3D hydrogel SERS chip, providing a noninvasive solution for real-time monitoring of pH and glucose levels in sweat. Encapsulating the probe molecule (4-MBN) in nanoscale gaps to form gold nanoflower-like nanotags with internal standards and integrating them into an agarose hydrogel to create a 3D flexible SERS substrate significantly enhances the reproducibility and stability of sweat analysis. Gap-Au nanopetals modified with probe molecules are uniformly dispersed throughout the porous hydrogel structure, facilitating the effective detection of the pH and glucose in sweat. The 3D hydrogel SERS chip demonstrates a strong linear relationship in pH and glucose detection, with a pH response range of 5.5-8.0 and a glucose detection range of 0.01-5 mM, with R2 values of 0.9973 and 0.9923, respectively. In actual sweat samples, the maximum error in pH detection accuracy is only 1.13%, with a lower glucose detection limit of 0.25 mM. This study suggests that the ratio-based 3D hydrogel SERS chip provides convenient, reliable, and rapid detection capabilities with substantial application potential for analyzing body fluid pH and glucose.

A Simple and Sensitive Wearable SERS Sensor Utilizing Plasmonic-Active Gold Nanostars.

Wearable sweat sensors hold great potential for offering detailed health insights by monitoring various biomarkers present in sweat, such as glucose, lactate, uric acid, and urea, in real time. However, most previously reported sensors, primarily based on electrochemical technology, are limited to monitoring only a single analyte at a given time. This study introduces a simple, sensitive, wearable patch based on surface-enhanced Raman spectroscopy (SERS), integrated with highly plasmonically active sharp-branched gold nanostars (GNS) for the simultaneous detection of three sweat biomarkers: lactate, urea, and glucose. We have fabricated the GNS on commercially available adhesive tape, resulting in achieving a low-cost, flexible, and adhesive wearable SERS patch. The limits of detection for lactate, urea, and glucose were achieved at 0.7, 0.6, and 0.7 μM, respectively, which are significantly lower than the clinically relevant concentrations of these biomarkers in sweat. We further evaluated the performance of our wearable SERS patch during outdoor activities, including sitting, walking, and running. To evaluate its overall effectiveness, we simultaneously measured the concentrations of lactate, urea, and glucose during these activities. Overall, our simple, sensitive wearable SERS sensor represents a significant breakthrough by enabling the simultaneous detection of lactate, urea, and glucose present in sweat, marking a major step toward future applications in autonomous and noninvasive personalized healthcare monitoring at home.

Preparation of g-C3N4/NS-CQDs composites and their application in the detection of hydrogen peroxide and glucose

Based on the excellent properties of g-C3N4, co-doped carbon quantum dots (NS-CQDs) were selected to modify it in order to enhance its peroxidase-like activity, and the synthesized NS-CQDs/g-C3N4 nano-enzymes were applied to the detection of common small molecules, such as hydrogen peroxide and glucose, to provide theoretical basis for the construction of g-C3N4 nano-enzymes-based biosensors. FT-IR, SEM, TEM, and other characterization methods determined the composition and morphology of NS-CQDs/g-C3N4. This paper discusses the influence of different morphologies on composites’ catalytic activity. According to the fluorescence spectrum, thecatalytic mechanismfollowsthe hydroxyl radicalmechanism. Under the optimal experimental conditions, the prepared composites were used to detect glucose, and the resultant detection limit of glucose was 1.63 μΜ. The results showed that NS-CQDs/g-C3N4 outperforms most of the nanoenzymes of similar materials, which provides a new idea to broaden its application in nanoenzymes.

Fabrication and application of multifunctional conductive hydrogel film for wearable sensors via efficient freeze-thaw cycling and annealing process

Conductive hydrogel films, as integral elements of flexible sensors, hold promising applications across diverse fields. However, their cost-effective and straightforward production, ensuring both excellent mechanical properties and conductivity, remains a formidable challenge. In our research, we developed a multifunctional conductive hydrogel film using a freeze-thaw cycling-annealing method. That process applied freeze-thaw cycling to reorganize the hydrogel’s cross-linking structure and improve the polyvinyl alcohol molecules’ crystallinity through annealing. The thickness of the fabricated film was approximately 100 μm, and the limit of detection and sensitivity for glucose were 2.82 μM and 117.6 μA /mM*cm2 respectively, and the sensitivity factor during the bending process was 2.61, which demonstrated excellent biocompatibility, mechanical properties, and electrochemical properties. It also facilitates wireless, real-time electrophysiological signal monitoring and sweat glucose tracking in the human body. In summary, the freeze-thaw cycling/annealing approach simplified and accelerated hydrogel film preparation. This development is poised to resolve the intricacies of existing hydrogel film production methods and broaden the application scope of such films in wearable devices.

Improvement of Hydrogen Peroxide and Glucose Detection in Serum using Persistent Luminescent Nanoparticles: Impact of Synthesis Parameters and Particle Size

AbstractPersistent Luminescent Nanoparticles (PLNPs) emit prolonged light after excitation, allowing getting images with high signal‐to‐noise ratio, making them particularly beneficial for in vitro biodetection. In this study, we report the preparation of a library of gallium and zinc‐based Persistent Luminescent Nanoparticles doped with chromium (ZnGa2O4:Cr3+) through two distinct syntheses conducted at 120 °C for 12 hours or 24 hours, followed by a calcination at 500 °C or 750 °C. Using centrifugation, and starting from polydisperse samples, we demonstrated the ability to achieve different sizes in a monodisperse manner. Furthermore, our research revealed that ZnGa2O4:Cr3+ (ZGO) nanoparticles react differently with hydrogen peroxide (H2O2) based on their size, synthesis duration, and calcination temperature. We observed the most significant amplification of persistent luminescence for ZGO particles prepared at 120 °C for 12 hours and calcinated at 500 °C, with a size of approximately 100 nm, in the presence of 100 mM H2O2 (later named ZGO‐2). This study enabled the detection of H2O2 in serum without autofluorescence using the developed PLNPs, with a detection limit of up to 2.1 μM and a recovery rate of around 99 %. Additionally, we designed a glucose test for based on the responsiveness of ZGO PLNPs to H2O2. Using glucose oxidase, the glucose detection limit in serum was established around 0.13 μM, with a detection range between 0–5 μM. These findings could open new avenues to further control the size, synthesis, calcination temperature, and persistent luminescence of PLNPs, thus enhancing their utility in the development of new in vitro biosensors.

Construction of multi(iron)porphyrin array multilayers on quartz surface as peroxidase mimetics for H2O2 and glucose colorimetric, fluorometric and color-read detection

Multi(metallo)porphyrin arrays are important artificial biomimetics for mimicking the biological catalytic reactions in nature. Here, we report construction of multi(iron)porphyrin array ultrathin films on the quartz surface by coordination-driven layer-by-layer (LBL) assembling method with the Pd(II) ion as a connector and iron(III) tetrapyridylporphyrin (FeTPyP) as a linker. It is revealed that the (Pd-FeTPyP)n LBL multilayers can catalyze oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) in the presence of H2O2 with peroxidase-like activity, resulting in the formation of the blue-colored oxidized TMB (oxTMB). Coupled with glucose oxidase, three sensitive probes based on the colorimetric, fluorometric and color-read methods have been developed by using modified quartz plates as the heterogenous catalyst, with a glucose detection limit of about 0.89, 1.5 and 0.65 μM, respectively. Mechanism studies confirm an enhanced affinity between (Pd-FeTPyP)n and H2O2/TMB molecules and an improved catalytic performance, which are attributed to the reason that the FeTPyP macrocycles are well-dispersed and arranged on the two-dimensional quartz surface. Furthermore, owing to chemically anchored on the transparent quartz surface, the (Pd-FeTPyP)n films exhibit good stability with naked-eye observation of color change under moderate conditions, thus providing a potential candidate for developing colorimetric, fluorometric and color-read glucose biosensors.

Construction of Pt/Ni/NiFe2O4/C nanocomposite with one dimensional hollow structure for portable glucose sensing application.

Designing portable electrochemical sensors combined with highly efficient glucose oxidation electrodes offers a significant opportunity for convenient glucose detection. In this report, we present the design and preparation of platinum deposited Ni/NiFe2O4/Carbon composite (Pt/Ni/NiFe2O4/C) derived from Ni/Fe metal-organic frameworks (MOFs) followed by Pt deposition. Energy-dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and electron microscopy (EM) were utilized to analyze the crystal structure, morphology, and chemical composition of the resulting materials. The glucose sensing capabilities of the optimal Pt/Ni/NiFe2O4/C-3 were assessed using amperometry methods on a smartphone-based portable device. Acting as a nonenzymatic glucose sensor, the Pt/Ni/NiFe2O4/C-3 electrode demonstrated notable sensitivity and a low limit of detection for glucose. The portable sensor exhibits high sensitivities of 131.88μM mM cm-2 at low glucose concentration (3-500μM) and 29.52 μA mM cm-2 at high glucose concentration (700-4000μM), achieving a low detection limit of 1.1μM (S/N = 3). The sensor also demonstrates enhanced selectivity and stability for detecting glucose. Furthermore, the portable sensor exhibits a clear step-ampere response in the detection of serum samples with satisfactory recovery ranging from 99.30 to 101.32%. This suggests the significant potential of portable glucose sensing applications.

Urine Test Strip Quantitative Assay with a Smartphone Camera.

Urine test strips for urinalysis are a common diagnostic tool with minimal costs and are used in various situations including homecare and hospitalization. The coloration scaled by the naked eye is simple, but it is suitable for semiquantitative analysis only. In this paper, a colorimetric assay is developed based on a smartphone digital camera and urine test strips. Assays of pH, albumin, glucose, and lipase activity were performed as a tool for the diagnosis of aciduria, alkaluria, glycosuria, proteinuria, and leukocyturia. The RGB color channels were analyzed in the colorimetric assay, and the assay exerted good sensitivity, and all the particular diagnoses proved to be reliable. The limits of detection for glucose (0.11 mmol/L), albumin (0.15 g/L), and lipase (2.50 U/μL) were low enough to cover the expected physiological concentration, and the range for pH was also satisfactory. The urine test strips with a camera as an output detector proved applicability to spiked urine samples, and the results were also well in comparison to the standard assays which confirms the practical relevance of the presented findings.

Visual detection of H2O2 and glucose by HBcAb-HRP fluorescence-enhanced CdTe QDs/CDs ratiometric fluorescence sensing platform

This study presents the development of a sensitive and simple enhanced ratiometric fluorescence sensing platform in the consist of CdTe quantum dots (QDs), carbon dots (CDs), and hepatitis B core antibody labeled with horseradish peroxidase (HBcAb-HRP) for the visual analysis of H2O2 and glucose. The sulfur atoms in HBcAb-HRP have a strong affinity for Cd(II), which effectively enhances the fluorescence intensity of the CdTe QDs due to the generation of more radiative centers at the CdTe/Cd-SR complex. In the presence of H2O2, the Cd-S bonds are oxidized to form disulfide products and results in linear fluorescence quenching, while CDs maintain stable. Becasue glucose can be converted into H2O2 with the aid of glucose oxidase, this sensing platform can also be used for analyzing glucose. The detection limits for H2O2 and glucose are 2.9 μmol L−1 with RSD of 2.6% and 1.6 μmol L−1 with RSD of 2.4% respectively. In addition, under UV lamp irradiation, the orange-yellow CdTe QDs gradually quench with increasing H2O2 and glucose, while the blue CDs remain unchanged. A color change from orange-yellow to blue enables a visual semi-quantitative determination of H2O2 in commercial contact lens solution and glucose in human serum without any pretreatment. Thus, this CdTe QDs/CDs ratiometric sensing platform has significant potential for the rapid analysis of H2O2 and glucose in actual application.

Wearable biosensors for human sweat glucose detection based on carbon black nanoparticles.

Wearable glucose biosensors enable noninvasive glucose monitoring, thereby enhancing blood glucose management. In this work, we present a wearable biosensor based on carbon black nanoparticles (CBNPs) for glucose detection in human sweat. The biosensor consists of CBNPs, Prussian blue (PB), glucose oxidase, chitosan, and Nafion. The fabricated biosensor has a linear range of 5 µM to 1250 µM, sensitivity of 14.64 µAmM-1cm-2, and a low detection potential (-0.05 V, vs. Ag/AgCl). The detection limit for glucose was calculated as 4.83 µM. This reusable biosensor has good selectivity and stability and exhibits a good response to glucose in real sweat. These results demonstrate the potential of our CBNP-based biosensor for monitoring blood glucose in human sweat.

Nonenzymatic Glucose Sensor Using Bimetallic Catalysts.

Bimetallic glucose oxidation electrocatalysts were synthesized by two electrochemical reduction reactions carried out in series onto a titanium electrode. Nickel was deposited in the first synthesis stage followed by either silver or copper in the second stage to form Ag@Ni and Cu@Ni bimetallic structures. The chemical composition, crystal structure, and morphology of the resulting metal coating of the titanium electrode were investigated by X-ray diffraction, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and electron microscopy. The electrocatalytic performance of the coated titanium electrodes toward glucose oxidation was probed using cyclic voltammetry and amperometry. It was found that the unique high surface area bimetallic structures have superior electrocatalytic activity compared to nickel alone. The resulting catalyst-coated titanium electrode served as a nonenzymatic glucose sensor with high sensitivity and low limit of detection for glucose. The Cu@Ni catalyst enables accurate measurement of glucose over the concentration range of 0.2-12 mM, which includes the full normal human blood glucose range, with the maximum level extending high enough to encompass warning levels for prediabetic and diabetic conditions. The sensors were also found to perform well in the presence of several chemical compounds found in human blood known to interfere with nonenzymatic sensors.

Parallel Monitoring of Glucose, Free Amino Acids, and Vitamin C in Fruits Using a High-Throughput Paper-Based Sensor Modified with Poly(carboxybetaine acrylamide).

Herein, a cost-effective and portable microfluidic paper-based sensor is proposed for the simultaneous and rapid detection of glucose, free amino acids, and vitamin C in fruit. The device was constructed by embedding a poly(carboxybetaine acrylamide) (pCBAA)-modified cellulose paper chip within a hydrophobic acrylic plate. We successfully showcased the capabilities of a filter paper-based microfluidic sensor for the detection of fruit nutrients using three distinct colorimetric analyses. Within a single paper chip, we simultaneously detected glucose, free amino acids, and vitamin C in the vivid hues of cyan blue, purple, and Turnbull's blue, respectively, in three distinctive detection zones. Notably, we employed more stable silver nanoparticles for glucose detection, replacing the traditional peroxidase approach. The detection limits for glucose reached a low level of 0.049 mmol/L. Meanwhile, the detection limits for free amino acids and vitamin C were found to be 0.236 mmol/L and 0.125 mmol/L, respectively. The feasibility of the proposed sensor was validated in 13 different practical fruit samples using spectrophotometry. Cellulose paper utilizes capillary action to process trace fluids in tiny channels, and combined with pCBAA, which has superior hydrophilicity and anti-pollution properties, it greatly improves the sensitivity and practicality of paper-based sensors. Therefore, the paper-based colorimetric device is expected to provide technical support for the nutritional value assessment of fruits in the field of rapid detection.

Biohybrid tongue based on hypothalamic neuronal network-on-a-chip for real-time blood glucose sensing and assessment

The expression of sweet receptors in the hypothalamus has been implicated in energy homeostasis control and the pathogenesis of obesity and diabetes. However, the exact mechanism by which hypothalamic glucose-sensing neurons function remains unclear. Conventional detection methods, such as fiber photometry, optogenetics, brain-machine interfaces, patch clamp and calcium imaging, pose limitations for real-time glucose perception due to their complexity, cytotoxicity and so on. Therefore, this study proposes a biohybrid tongue based on hypothalamic neuronal network (HNN)-on-a-chip coupling with microelectrode array (MEA) for real-time glucose perception. Hypothalamic neuronal cultures were cultivated on a two-dimensional “brain-on-chip” device, enabling the formation of neuronal networks and electrophysiological signal detection. Additionally, we investigated the endogenous expression of sweet taste receptors (T1R2/T1R3) in hypothalamic neuronal cells, providing the basis for the biohybrid tongue based on HNN-on-a-chip's sweetness detection capabilities. The spike signal response to sucrose and glucose stimulation was detected, and concentration-dependent responses were explored with glucose concentrations ranging from 0.01 mM to 8 mM. MEAs allow for real-time recordings, enabling the observation of dynamic changes in neuronal responses to glucose fluctuations over time. The biohybrid tongue based on HNN-on-a-chip can measure various parameters, including spike frequency and amplitude, providing insights into neuronal firing patterns and excitability. Moreover, hypothalamic glucoregulatory neurons that sense and respond to changes in blood glucose was identified, including glucose-excited neurons (GE-Neurons) and glucose-inhibited neurons (GI-Neurons). The detection range for GE-Neurons spans from 0.4 to 6 mM, while GI-Neurons demonstrate sensitivity within the range of 1–8 mM. And the glucose detection limit was firmly established at 0.01 mM. Through non-linear regression analysis, the IC50 for GI-Neurons' spike firing was determined to be 4.18 mM. In conclusion, the biohybrid tongue based on HNN-on-a-chip offers a valuable in vitro tool for studying hypothalamic neurons, elucidating glucose sensing mechanisms, and understanding hypothalamic neuronal function.

Versatile bimetallic metal-organic framework with nanocutting channels tailored for efficient electrocatalytic water oxidation and glucose detection

Metal–organic frameworks (MOF) with outstanding properties have shown great potential for electrochemical water splitting, particularly for the oxygen evolution reaction (OER) and nonenzymatic glucose detection. In this study, a facile method was used to synthesize CoNiMOF (with 5-aminoisophthalic acid as the organic linker) as electrocatalyst for the OER and glucose oxidation reaction (GOR). In-depth structural and microstructural analyses confirmed the formation of the MOF via metal–ligand (electron donor–acceptor) coordination. Among the different CoNiMOFs, CoNi(1:3)MOF shown to have nanocutting channels along the edges of the microstructural sheets, exhibited good catalytic activity toward the OER and GOR. CoNi(1:3)MOF delivers the best electrocatalytic performance in 1 M KOH with an overpotential of 348 mV at 20 mA cm−2 for the OER, benefitting from the specific morphology and electronic control. Moreover, the electrocatalyst was remarkably stable after 5000 cyclic voltammetry cycles and chronopotentiometric (20 h) analysis. As glucose sensor, CoNi(1:3)MOF exhibits a remarkably low glucose detection limit (1.03 μΜ) and wide detection range (2–500 μΜ and 1–15 mM, respectively). In addition, CoNi(1:3)MOF performed efficiently in an interference study, which revealed the selectivity of the developed sensor. The active formation of bimetallic MOF structures and the synergistic effect between the two metals in the electrocatalyst is attributed to the efficient modulation of the electronic structure, which effectively influenced the OER and GOR performance.

4D-printed needle panel meters coupled with enzymatic derivatization for reading urea and glucose concentrations in biological samples

On-site analytical techniques continue being developed with advances in modern technology. To demonstrate the applicability of four-dimensional printing (4DP) technologies in the direct fabrication of stimuli-responsive analytical devices for on-site determination of urea and glucose, we used digital light processing three-dimensional printing (3DP) and 2-carboxyethyl acrylate (CEA)–incorporated photocurable resins to fabricate all-in-one needle panel meters. When adding a sample having a value of pH above the pKa of CEA (ca. 4.6–5.0) into the fabricated needle panel meter, the [H+]-responsive layer of the needle, printed using the CEA-incorporated photocurable resins, swelled as a result of electrostatic repulsion among the dissociated carboxyl groups of the copolymer, leading to [H+]-dependent bending of the needle. When coupled with a derivatization reaction (urease-mediated hydrolysis of urea to decrease [H+]; glucose oxidase-mediated oxidization of glucose to increase [H+]), the bending of the needle allowed reliable quantification of urea or glucose when referencing pre-calibrated concentration scales. After method optimization, the method's detection limits for urea and glucose were 4.9 and 7.0 μM, respectively, within a working concentration range from 0.1 to 10 mM. We verified the reliability of this analytical method by determining the concentrations of urea and glucose in samples of human urine, fetal bovine serum, and rat plasma with spike analyses and comparing the results with those obtained using commercial assay kits. Our results confirm that 4DP technologies can allow the direct fabrication of stimuli-responsive devices for quantitative chemical analysis, and that they can advance the development and applicability of 3DP-enabling analytical methods.

A smartphone-assisted colorimetric sensor based on Fe1-xS nanozyme for detection of glucose and ascorbic-acid in soft drinks

Due to their distinct enzyme-like catalytic activity, iron-based nanomaterials have attracted considerable attention from researchers in the field of biomolecular detection. However, the current literature predominantly focuses on iron oxide nanozymes, with limited attention given to iron sulfide (FexSy) nanozymes. In this work, a glutathione-modified Fe1-xS nanoparticles (Fe1-xS NPs) with a diameter of 4–6 nm was synthesized in one-pot aqueous solution at room temperature. The resulting Fe1-xS NPs exhibited superior peroxidase-like (POD) activity compared to natural horseradish peroxidase, indicating their potential as a promising alternative for POD applications. A sensor utilizing the POD activity of Fe1-xS NPs was developed for detecting glucose and ascorbic-acid (AA) in soft drinks. The detection limits for glucose and AA were determined to be 37 and 5.3 μM, respectively, with broader linear ranges of 200–700 and 10–500 μM. Moreover, Fe1-xS NPs demonstrated exceptional selectivity and anti-interference properties in detecting glucose and AA in soft drinks. Furthermore, this study proposed a smartphone-assisted colorimetric sensor based on Fe1-xS nanozymes for rapid and specific detection of glucose and AA. This technique has the potential to be utilized in the future for convenient and efficient detection of glucose and AA.

Amorphization-Modulated Metal Sulfides with Boosted Active Sites and Kinetics for Efficient Enzymatic Colorimetric Biodetection.

Colorimetric biosensing has become a popular sensing method for the portable detection of a variety of biomarkers. Artificial biocatalysts can replace traditional natural enzymes in the fields of enzymatic colorimetric biodetection; however, the exploration of new biocatalysts with efficient, stable, and specific biosensing reactions has remained challenging so far. Here, to enhance the active sites and overcome the sluggish kinetics of metal sulfides, the creation of an amorphous RuS2 (a-RuS2 ) biocatalytic system is reported, which can dramatically boost the peroxidase-mimetic activity of RuS2 for the enzymatic detection of diverse biomolecules. Due to the existence of abundant accessible active sites and mildly surface oxidation, the a-RuS2 biocatalyst displays a twofold Vmax value and much higher reaction kinetics/turnover number (1.63 × 10-2 s-1 ) compared to that of the crystallized RuS2 . Noticeably, the a-RuS2 -based biosensor shows an extremely low detection limit of H2 O2 (3.25× 10-6 m), l-cysteine (3.39× 10-6 m), and glucose (9.84× 10-6 m), respectively, thus showing superior detection sensitivity to many currently reported peroxidase-mimetic nanomaterials. This work offers a new path to create highly sensitive and specific colorimetric biosensors in detecting biomolecules and also provides valuable insights for engineering robust enzyme-like biocatalysts via amorphization-modulated design.

Silk fibroin based wearable electrochemical sensors with biomimetic enzyme-like activity constructed for durable and on-site health monitoring

Flexible biomimetic sensors have encountered a bottleneck of sensitivity and durability, as the sensors must directly work within complex body fluid with ultra-trace biomarkers. In this work, a wearable electrochemical sensor on a modified silk fibroin substrate is developed using gold nanoparticles hosted into N-doped porous carbonizated silk fibroin (AuNPs@CSF) as active materials. Taking advantage of the inherent biocompatibility and flexibility of CSF, and the high stability and enzyme-like catalytic activity of AuNPs, AuNPs@CSF-based sensor exhibits durable stability and superior sensitivity to monitor H2O2 released from cancer cell (4T1) and glucose in sweat. The detection limits for H2O2 and glucose are low to be 1.88 μM and 23 μM respectively, and the sensor can be applied in succession within 30 days at room temperature. Further, physical cross-linking of polyurethane (PU) with SF well matches with the skin tissue mechanically and provides a flexible, robust and stable electrode-tissue interface. AuNPs@CSF is applied successfully for wearable electrochemical monitoring of glucose in human sweat.The present AuNPs@CSF will possess a potential application in clinical diagnosing of H2O2- or glucose-related diseases in future.