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Nitric oxide (NO) plays an important role in physiological processes and it has been confirmed some human diseases are related to its biological function. Electrochemical sensors provide an efficient way to explore the NO function in biological processes. This review details different kinds of electrochemical sensors used for NO concentration detection between 2008 and 2013 together with their application in biological samples. Four commonly used electrodes and different assisted analysis membranes used for contributions towards the development of the novel sensors were summarized. Electrochemical sensors employed to measure NO concentration in a single cell, cell culture, tissue homogenate, organ, in vivo, human being, as well as in plant were also detailed. The trends of developing novel NO sensors were outlooked in the last part. [ABSTRACT FROM AUTHOR]

Simultaneous detection of multiple biomarkers is benefit for reducing the detection cycles, avoiding the false-positive signals, and providing the cross validation, which provide the opportunity to understand the pathogenic mechanisms and achieve precise early diagnosis. Here, we demonstrate the mini-pillar-based individual electrochemical array for simultaneous detection of multiple biomarkers. On such platform, the mini-pillar could confine the microdroplet as individual and open-channel microreactor, which is extremely helpful for reducing reagent consumption and extracting internal information, and the electrodes array embedded in mini-pillar are integrated on one side to achieve multiple and simultaneous electrochemical sensing. The introduction of gold nanodendrites by electrodeposition has greatly enhanced sensitivity via improving probe-binding capacity and response signals. Sensitive and selective detection of multiple Alzheimer's biomarkers including Tau, ApoE4, Amyloid-β and miRNA-101 on such mini-pillar-based biosensor is also achieved. Such biosensor platform with the advantages of high-yield, high sensitivity, low-waste and multiple signals output shows great promise in sensing multiple biomolecules for disease diagnosis and health monitoring. • An integrated mini-pillar-based electrochemical sensor is designed. • The optimal gold nanodendrites electrode has the high sensitivity and stability toward electrochemical sensing. • Multiple Alzheimer's biomarkers have been simultaneously detected on such mini-pillar-based electrochemical sensor. [ABSTRACT FROM AUTHOR]

High throughput and high sensitivity are two important aspects in multiple biomarker recognition, drug discovery and relevant biochemical sensing. Here, we integrate mini-pillar microarray with the circuit components toward high-throughput individual electrochemical sensing in microdroplets. On such droplet-microarray-based electrochemical platform, the high adhesion of the mini-pillar can hold a microdroplet (hundreds nanoliter to a few microliter) regardless of rotation and deformation. Each pillar as a unit has a three-electrode to achieve individual electrochemical sensing, and electrodes are integrated on one side to achieve the sequential electrochemical read-out. Qualitative and quantitative electrochemical assessments of multiple glucose concentrations in individual microdroplets are also achieved. Such mini-pillar-based individual electrochemical platform shows great potential in high-throughput and high-sensitive biomolecular recognitions, provides an opportunity to develop miniaturized sensing platform for emerging biological and pathological applications. • A mini-pillar-array electrochemical sensor is designed. • The mini-pillar-based electrochemical sensor can anchor the microliter droplets for high throughput biosensing. • The mini-pillar-based platform can achieve sensing of multiple glucose concentrations in array microdroplets. [ABSTRACT FROM AUTHOR]

Levodopa (L -dopa) is an effective medication for Parkinson's disease. However, excess intake from overdose or the intake of natural sources of L -dopa can be dangerous, causing, for example, tardive dyskinesia. Therefore, in medicated individuals, it is important to monitor the levels of L -dopa in the body. In this paper, we report a simple, wearable, noninvasive, and portable metal−organic framework (MOF)-based electrochemical sensor with integrated enzymes for monitoring the concentration of levodopa in sweat, which can be used as a proxy for L -dopa levels in the body. Zeolitic imidazolate framework/graphene oxide (ZIF-8/GO) composites were prepared by the in-situ growth of ZIF-8 nanoparticles on the surface of GO, and, subsequently, tyrosinase was loaded onto the composite to yield the sensor. Integration with a wireless electronic circuit enabled communication between the sensor and a smartphone application for continuous analysis. The sensor was found to have a wide linear response range from 1 to 95 µM, a low limit of detection of 0.45 µM, satisfactory reproducibility, and excellent selectivity. In addition, the sensor showed high sensitivity and good stability as a result of the anchoring of the enzyme. Thus, the sensor shows promise for continuous, noninvasive point-of-care drug monitoring and management. • Noninvasive electrochemical sensor for levodopa determination in sweat developed. • Anchoring tyrosinase on ZIF-8/graphene oxide increases stability and active sites. • Linear electrochemical response over wide concentration range (1–95 µM). • Low limit of detection of 0.45 µM. • Continuous wireless monitoring of volunteers possible during exercise. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel colorimetric-electrochemical dual-mode smartphone sensor was developed. • MOF-818 possesses high peroxidase-like activity under 37 °C and acidic conditions and electrocatalytic activity to H 2 O 2. • H 2 S can coordinate with copper sites of MOF-818 and inhibit the catalytic activity. • The dual-mode sensor exhibited excellent selectivity and sensitivity toward H 2 O 2 and H 2 S. • The dual-mode sensor can be used to monitor H 2 O 2 and H 2 S released from living cells. Hydrogen peroxide (H 2 O 2) and hydrogen sulfide (H 2 S) play a key role in many cellular signaling pathways. The efficient and accurate in situ detection of H 2 O 2 and H 2 S released from living cells has attracted extensive research interests. Herein, we presented a portable colorimetric and electrochemical dual-mode sensor for detection of cellular secreted H 2 O 2 and H 2 S based on MOF-818 nanozyme. MOF-818 containing trinuclear copper centers not only possesses excellent peroxidase-like activity under 37 °C and acidic conditions, but also exhibits outstanding electrocatalytic reduction activity to H 2 O 2 (reduction peak potential at −0.08 V vs Ag/AgCl). Meanwhile, the copper sites of MOF-818 can be coordinated with sulfide, reducing the catalytic activity of MOF-818. As a result, the colorimetric and electrochemical sensing of H 2 O 2 and H 2 S were established based on "signal-on" and "signal-off" strategies, respectively. Additionally, the combination of a smartphone and a miniature electrochemical analyzer enables dual-mode colorimetric and electrochemical sensing platform for in situ detection of H 2 O 2 and H 2 S released from live cells. This portable dual-mode sensor based on MOF nanozyme not only opens a new path for point-of-care testing, but also has potential applications in the field of cell biology and clinical diagnosis. [ABSTRACT FROM AUTHOR]

The chemistry of the metal-organic frameworks (MOFs) coating may affect the biological functionality of the encapsulated biomacromolecules in harsh environment. Enzymes encapsulated in hydrophilic MAF-7 can retain high activity in harsh environment. We conducted this study to prepare a non-invasive wearable uircase@MAF-7-based electrochemical sensor that can achieve accurate and sensitive detection of UA levels in sweat by integrating a flexible microfluidic chip and wireless electronic readout device. The flexible microfluidic chip enabled an easy and effective collection of sweat samples. MAF-7 protected enzyme activity by encapsulating uricase. The uricase@MAF-7-based electrochemical sensor enabled the highly sensitive detection of UA in the concentration range of 2 μM–70 μM with a detection limit of as low as 0.34 μM. Additionally, we evaluated the utility of the sensor for monitoring UA levels in real sweat samples by means of a high purine dietary challenge. This personalized wearable sweat sensing device has a potential to be used for monitoring disease-related metabolites in daily life. [Display omitted] • The flexible microfluidic chip enabled an easy and effective collection of sweat. • We embedded uricase into hydrophilic MAF-7 using the one-pot strategy. • This wearable sweat sensing device can monitor disease-related metabolites. [ABSTRACT FROM AUTHOR]