Amperometric sarcosine biosensor with strong anti-interference capabilities based on mesoporous organic-inorganic hybrid materials

A closed-loop catalytic nanoreactor system on a transistor

Precision chemistry demands miniaturized catalytic systems for sophisticated reactions with well-defined pathways. An ideal solution is to construct a nanoreactor system functioning as a chemistry laboratory to execute a full chemical process with molecular precision. However, existing nanoscale catalytic systems fail to in situ control reaction kinetics in a closed-loop manner, lacking the precision toward ultimate reaction efficiency. We find an inter-electrochemical gating effect when operating DNA framework-constructed enzyme cascade nanoreactors on a transistor, enabling in situ closed-loop reaction monitoring and modulation electrically. Therefore, a comprehensive system is developed, encapsulating nanoreactors, analyzers, and modulators, where the gate potential modulates enzyme activity and switches cascade reaction "ON" or "OFF." Such electric field-effect property enhances catalytic efficiency of enzyme by 343.4-fold and enables sensitive sarcosine assay for prostate cancer diagnoses, with a limit of detection five orders of magnitude lower than methodologies in clinical laboratory. By coupling with solid-state electronics, this work provides a perspective to construct intelligent nano-systems for precision chemistry.

Multiplexed detection of biomarkers using a microfluidic chip integrated with mass-producible micropillar array electrodes

Quantifying multiple biomarkers with high sensitivity in tiny biological samples is essential to meet the growing demand for point-of-care testing. This paper reports the development of a novel microfluidic device integrated with mass-producible micropillar array electrodes (μAEs) for multiple biomarker detections. The μAE are mass-fabricated by soft lithography and hot embossing technique. Pt-Pd bimetallic nanoclusters (BNC) are modified on the surface of μAEs by constant potential (CP)/multi-potential step (MPS) electrodeposition strategies to improve the electroanalytical performance. The experimental result displays that Pt-Pd BNC/μAEs have good sensitivity enhancement compared with bare planar electrodes and bare μAEs, the enhancement being 56.5 and 9.5 times respectively, from the results of the H₂O₂ detection. Furthermore, glucose, uric acid and sarcosine were used as model biomarkers to show the biosensing capability with high sensitivity. The linear range and LOD of the glucose, uric acid and sarcosine detection are 0.1 mM-12 mM, 10 μM-800 μM and 2.5 μM-100 μM, 58.5, 3.4 and 0.4 μM, respectively. In particular, biosensing chips show wide linear ranges covering required detection ranges of glucose, uric acid and sarcosine in human serum, indicating the developed device has great potential in self-health management and clinical requirements.

Amperometric Miniaturised Portable Enzymatic Nanobiosensor for the Ultrasensitive Analysis of a Prostate Cancer Biomarker

Screen-printing technology is a game changer in many fields including electrochemical biosensing. Two-dimensional nanomaterial MXene Ti3C2Tx was integrated as a nanoplatform to immobilise enzyme sarcosine oxidase (SOx) onto the interface of screen-printed carbon electrodes (SPCEs). A miniaturised, portable, and cost-effective nanobiosensor was constructed using chitosan as a biocompatible glue for the ultrasensitive detection of prostate cancer biomarker sarcosine. The fabricated device was characterised with energy-dispersive X-ray spectroscopy (EDX), electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). Sarcosine was detected indirectly via the amperometric detection of H2O2 formed during enzymatic reaction. The nanobiosensor could detect sarcosine down to 7.0 nM with a maximal peak current output at 4.10 ± 0.35 × 10−5 A using only 100 µL of a sample per measurement. The assay run in 100 μL of an electrolyte showed the first linear calibration curve in a concentration window of up to 5 μM with a slope of 2.86 μA·μM−1, and the second linear calibration curve in the range of 5–50 μM with a slope of 0.32 ± 0.01 μA·μM−1 (R2 = 0.992). The device provided a high recovery index of 92.5% when measuring an analyte spiked into artificial urine, and could be used for detection of sarcosine in urine for at least a period of 5 weeks after the preparation.

Stimulus-Responsive DNA Hydrogel Biosensors for Food Safety Detection

Food safety has always been a major global challenge to human health and the effective detection of harmful substances in food can reduce the risk to human health. However, the food industry has been plagued by a lack of effective and sensitive safety monitoring methods due to the tension between the cost and effectiveness of monitoring. DNA-based hydrogels combine the advantages of biocompatibility, programmability, the molecular recognition of DNA molecules, and the hydrophilicity of hydrogels, making them a hotspot in the research field of new nanomaterials. The stimulus response property greatly broadens the function and application range of DNA hydrogel. In recent years, DNA hydrogels based on stimulus-responsive mechanisms have been widely applied in the field of biosensing for the detection of a variety of target substances, including various food contaminants. In this review, we describe the recent advances in the preparation of stimuli-responsive DNA hydrogels, highlighting the progress of its application in food safety detection. Finally, we also discuss the challenges and future application of stimulus-responsive DNA hydrogels.

High-Throughput Microfluidic Production of Bimetallic Nanoparticles on MXene Nanosheets and Application in Hydrogen Peroxide Detection

Nanoparticle-functionalized transition-metal carbides and nitrides (MXenes) have attracted extensive attention in electrochemical detection owing to their excellent catalytic performance. However, the mainstream synthetic routes rely on the batch method requiring strict experimental conditions, generally leading to low yield and poor size tunability of particles. Herein, we report a high-throughput and continuous microfluidic platform for preparing a functional MXene (Ti₃C₂T_x) with bimetallic nanoparticles (Pt-Pd NPs) at room temperature. Two 3D micromixers with helical elements were integrated into the microfluidic platform to enhance the secondary flow for promoting transport and reaction in the synthesis process. The rapid mixing and strong vortices in these 3D micromixers prevent aggregation of NPs in the synthesis process, enabling a homogeneous distribution of Pt-Pd NPs. In this study, Pt-Pd NPs loaded on the MXene nanosheets were synthesized under various hydrodynamic conditions of 1-15 mL min^-1 with controlled sizes, densities, and compositions. The mean size of Pt-Pd NPs could be readily controlled within the range 2.4-9.3 nm with high production rates up to 13 mg min^-1. In addition, synthetic and electrochemical parameters were separately optimized to improve the electrochemical performance of Ti₃C₂T_x/Pt-Pd. Finally, the optimized Ti₃C₂T_x/Pt-Pd was used for hydrogen peroxide (H₂O₂) detection and shows excellent electrocatalytic activity. The electrode modified with Ti₃C₂T_x/Pt-Pd here presents a wide detection range for H₂O₂ from 1 to 12 000 μM with a limit of detection down to 0.3 μM and a sensitivity up to 300 μA mM^-1 cm^-2, superior to those prepared in the traditional batch method. The proposed microfluidic approach could greatly enhance the electrochemical performance of Ti₃C₂T_x/Pt-Pd, and sheds new light on the large-scale production and catalytic application of the functional nanocomposites.

A perylenediimide modified SiO2@TiO2 yolk-shell light-responsive nanozyme: Improved peroxidase-like activity for H2O2 and sarcosine sensing

Although light-responsive nanozyme have been widely used in colorimetric sensing, some limitations such as poor catalytic activity, low detection efficiency, and unclear structure-activity relationships remain unresolved. Herein, we prepared an excellent light-responsive peroxidase (POD) mimic, perylenediimide (PDI-OH) modified SiO₂ @TiO₂ yolk-shell spheres (SiO₂ @TiO₂/PDI-OH), based on DFT-assisted design. The experiment and DFT calculation revealed that the enhanced POD-like activity was mainly attributed to a suitable built-in electric field among adjacent PDI-OH molecules on the surface of the SiO₂ @TiO₂ and the unique yolk-shell structure with more reaction sites of SiO₂ @TiO₂. Consequently, the highly selective and ultrasensitive detection of H₂O₂ is achieved with a detection limit (LOD) of 7.6 × 10^-8M. Further, the selective detection of sarcosine with LOD of 1.2 × 10^-7 M was also achieved by introducing sarcosine oxidase (SOx). This colorimetric assay is successfully applied to selectively detect H₂O₂ and sarcosine levels in real samples. Controlled response time, anti-interference, and the robustness of the developed colorimetric sensor are the key advantages. And the present work firstly clarifies the effect of PDIs substituents on the POD-like activity of light-responsive nanozymes and provided new guidelines to develop high-performance nanozymes for hazardous substances detection.

Using bimetallic Au/Cu nanoplatelets for construction of facile and label-free inner filter effect-based photoluminescence sensing platform for sarcosine detection

Herein, we report a facile and label-free method for sensitive and specific determination of prostate cancer biomarker sarcosine via using photoluminescent bimetallic Au/Cu nanoplatelets (AuCu NPs) to construct an inner filter effect (IFE)-based photoluminescence (PL) sensing platform. The AuCu NPs were formed by the cysteine-induced co-reduction reaction, which displayed bright PL with an emission peak at 560 nm. Meanwhile, the Cu(I) doping caused a maximum 25-fold enhancement of quantum yield (QY), compared with the native Au(I) complexes, i.e., from 0.85 to 21.5%. By integrating the AuCu NPs with p-phenylenediamine (PPD) oxidation reaction, an IFE-based sensor for sarcosine detection was constructed. In this method, sarcosine is oxidized under the catalysis of sarcosine oxidase (SOx) to yield H₂O₂. The latter further oxidizes PPD to form 2,5-diamino-N,N'-bis(p-aminophenyl)-l,4-benzoquinone di-imine (PPDox) in the presence of horseradish peroxidase (HRP). The UV-vis absorption spectrum of the PPDox can overlap well with the excitation and emission spectra of the AuCu NPs, resulting in the efficient quenching of the AuCu NPs via the IFE effect. Therefore, this IFE-based AuCu NPs/SOx/PPD/HRP sensing platform can be used for highly sensitive and specific sensing of sarcosine. The sensing platform showed two linear regions of the PL intensity of the AuCu NPs versus the concentration of sarcosine in the range of 0.5-5 μM and 5-100 μM with a detection limit (LOD) of 0.12 μM (S/N = 3). Furthermore, this IFE-based sensing platform could be developed into a paper-based biosensor for simple, instrument-free, and visual detection of sarcosine.

A low-cost and high-performance 3D micromixer over a wide working range and its application for high-sensitivity biomarker detection

Homogenous mixing in microfluidic devices is often required for efficient chemical and biological reactions.Passive micromixing without external energy input has attracted much research interest. We have developed a high-performance 3D...

Novel Prostate Cancer Biomarkers: Aetiology, Clinical Performance and Sensing Applications

The review initially provides a short introduction to prostate cancer (PCa) incidence, mortality, and diagnostics. Next, the need for novel biomarkers for PCa diagnostics is briefly discussed. The core of the review provides details about PCa aetiology, alternative biomarkers available for PCa diagnostics besides prostate specific antigen and their biosensing. In particular, low molecular mass biomolecules (ions and metabolites) and high molecular mass biomolecules (proteins, RNA, DNA, glycoproteins, enzymes) are discussed, along with clinical performance parameters.

Polymer-dispersed reduced graphene oxide nanosheets and Prussian blue modified biosensor for amperometric detection of sarcosine

A new disposable amperometric biosensor for sarcosine (Sar, a biomarker for prostate cancer) was designed based on screen-printed carbon electrodes, Prussian blue, polymer dispersed reduced graphene oxide (P-rGO) nanosheets, and sarcosine oxidase (SOx). Poly(sodium 4-styrenesulfonate-r-LAHEMA) denoted as PSSL was newly synthesized as dispersant for rGO. The P-rGO was utilized for SOx immobilization, the sulfonate and disulfide functionalities in PSSL enable physical adsorption of SOx and its bioactivity and stability properties were improved. The biosensor was optimized by various enzyme concentration, applied potential, and operating pH. Under the optimized conditions, the biosensor exhibited maximum current responses within 5 s at an applied potential of -0.1 V vs. integrated Ag/AgCl reference electrode. The biosensor had a dynamic linear range of 10-400 μM, with a sensitivity of 9.04 μA mM^-1 cm^-2 and a low detection limit of 0.66 μM (S/N = 3). Additionally, the biosensor possesses strong anti-interference capability, high reproducibility, and storage stability over 3 weeks. Furthermore, its clinical applicability was tested in urine samples from both prostate cancer patients and healthy control, and the analytical recoveries were satisfactory. Therefore, this biosensor has significant potential in the rapid and non-invasive point-of-care testing for prostate cancer diagnosis.

Development of micropillar array electrodes for highly sensitive detection of biomarkers

Micropillar array electrodes (μAEs) have been widely applied in electrochemical detection owing to their advantages of increased mass transport, lower detection limit, and potential to be miniaturized. This paper reports the fabrication, simulation, surface modification, and characterization of PDMS-based μAEs coated with gold films. The μAEs consist of 9 × 10 micropillars with a height of either 100 μm, 300 μm, or 500 μm in a 0.09 cm2 region. Numerical simulation was employed to study the influence of geometrical parameters on the current density. The μAEs were fabricated by soft lithography and characterized using both SEM and cyclic voltammetry. Experiments revealed that high pillars enabled enhanced voltammetric current density regardless of the scan rates. The platinum-palladium/multi-walled carbon nanotubes (Pt-Pd/MWCNTs) were coated on the μAEs to improve their electrochemical detection capability. The μAEs demonstrated 1.5 times larger sensitivity compared with the planar electrode when hydrogen peroxide was detected. Furthermore, μAE500 with Pt-Pd/MWCNTs was employed to detect sarcosine, a potential biomarker for prostate cancer. The linear range and limit of detection for sarcosine were from 5 to 60 μM and 1.28 μM, respectively. This detection range covers the concentration of sarcosine in human tissues (0-60 μM). These results suggest that the μAEs have better detection performance in comparison to planar electrodes due to their large surface area and pillar height. This paper provides essential guidelines for the application of μAEs in high sensitivity electrochemical detection of low abundance analytes.

Electrochemical aptasensor using boron-carbon nanorods decorated by nickel nanoparticles for detection of E. coli O157:H7

The development of a label-free impedimetric aptasensor is reported for rapid and sensitive detection of Escherichia coli O157:H7 employing boron-carbon nanorods decorated by nickel nanoparticles (BC-Ni) nanostructured platform. These highly electroactive BC-Ni nanorods were synthesized to increase the sensitivity of the sensor surface and subsequently functionalized with a specific anti-E. coli O157:H7 aptamer (K_d = 69 nM) as bio-recognition moiety. This fully characterized high-affinity DNA aptamer against the bacteria was selected using a facile microtiter plate-based cell-SELEX methodology. The fabricated electrochemical aptasensor is demonstrated to detect E. coli O157:H7 selectively with a detection limit of 10 cfu and a dynamic detection range of 10⁰ to 10⁵ cfu in water, juice, and fecal samples. Graphical abstract.

Metal Oxides-Based Semiconductors for Biosensors Applications

The present mini review contains a concessive overview on the recent achievement regarding the implementation of a metal oxide semiconductor (MOS) in biosensors used in biological and environmental systems. The paper explores the pathway of enhancing the sensing characteristics of metal oxides by optimizing various parameters such as synthesis methods, morphology, composition, and structure. Four representative metal oxides (TiO₂, ZnO, SnO₂, and WO₃) are presented based on several aspects: synthesis method, morphology, functionalizing molecules, detection target, and limit of detection (LOD).

Ultrasensitive Ti3C2TX MXene/Chitosan Nanocomposite-Based Amperometric Biosensor for Detection of Potential Prostate Cancer Marker in Urine Samples

Two-dimensional layered nanomaterial Ti₃C₂T_X (a member of the MXene family) was used to immobilise enzyme sarcosine oxidase to fabricate a nanostructured biosensor. The device was applied for detection of sarcosine, a potential prostate cancer biomarker, in urine for the first time. The morphology and structures of MXene have been characterised by atomic force microscopy (AFM) and scanning electron microscopy (SEM). Electrochemical measurements, SEM and AFM analysis revealed that MXene interfaced with chitosan is an excellent support for enzyme immobilisation to fabricate a sensitive biosensor exhibiting a low detection limit of 18 nM and a linear range up to 7.8 µM. The proposed biosensing method also provides a short response time of 2 s and high recovery index of 102.6% for detection of sarcosine spiked into urine sample in a clinically relevant range.