Improved Sensitivity and Selectivity of Glutathione Detection through Target-Driven Electron Donor Generation in Photoelectrochemical Electrodes

Biocompatibility FeOOH QD@ATP-BODIPY nanocomposite for glutathione detection and intracellular imaging

Monitoring of glutathione has attracted considerable attention owing to its biological and clinical significance. An eco-friendly, economic, simple, biocompatible probe with excellent sensitivity and selectivity is very important. Herein, FeOOH QD@ATP-BODIPY nanocomposite was fabricated from one-step synthesized FeOOH quantum dots (FeOOH QD) and commercial boron-dipyrromethene-conjugated adenosine 5'-triphosphate (ATP-BODIPY) for glutathione (GSH) sensing in solutions and living cells. Three fascinate merits of FeOOH QD were confirmed: (a) as fluorescence quencher for ATP-BODIPY, (b) as selective recognizer of GSH and (c) with carrier effects and membrane permeability. The construction and response mechanism of the nanocomposite was based on the competitive coordination chemistry and redox reaction of FeOOH QD between GSH and phosphate group of ATP-BODIPY. Under the optimal conditions, the detection limit for GSH was as low as 68.8 nM. Excellent linear range of 0.2-400 μM was obtained. Furthermore, the chemical response of the nanocomposite exhibits high selectivity toward GSH over other electrolytes and biomolecules. It was successfully applied for GSH determination in human serum samples. The MTT assay exhibited FeOOH QD@ATP-BODIPY nanocomposite own good biocompatibility. FeOOH QD@ATP-BODIPY respond to GSH in living cells in situ was also proved via fluorescence imaging. These suggested that the FeOOH QD@ATP-BODIPY nanocomposite had potential application in biological and clinical applications.

Pd Nanoclusters-Sensitized MIL-125/TiO2 Nanochannel Arrays for Sensitive and Humidity-Resistant Formaldehyde Detection at Room Temperature

Among the various hazardous substances, formaldehyde (HCHO), produced worldwide from wood furniture, dyeing auxiliaries, or as a preservative in consumer products, is harmful to human health. In this study, a sensitive room-temperature HCHO sensor, MTiNCs/Pd, has been developed by integrating Pd nanoclusters (PdNCs) into mesoporous MIL-125(Ti)-decorated TiO2 nanochannel arrays (TiNCs). Thanks to the enrichment effect of the mesoporous structure of MIL-125 and the large surface area offered by TiNCs, the resulting gas sensor accesses significantly enhanced HCHO adsorption capacity. The sufficient energetic active defects formed on PdNCs further allow an electron-extracting effect, thus effectively separating the photogenerated electrons and holes at the interface. The resulting HCHO sensor exhibits a short response/recovery time (37 s/12 s) and excellent sensitivity with a low limit of detection (4.51 ppb) under ultraviolet (UV) irradiation. More importantly, the cyclic redox reactions of Pdδ+ in PdNCs facilitated the regeneration of O2-(ads), thus ensuring a stable and excellent gas sensing performance even under a high-humidity environment. As a proof-of-principle of this design, a wearable gas sensing band is developed for the real-time and on-site detection of HCHO in cigarette smoke, with the potential as an independent device for environmental monitoring and other smart sensing systems.

Liposome-embedded PtCu nanozymes for improved immunoassay of accurate myocardial infarction

Herein, we developed a platinum-copper nano-enzyme-linked immunosorbent assay (NLISA) based split diagnostic platform for the ultrasensitive detection of cardiac troponin I (cTnI). The PtCu nanozyme synthesized by one-pot synthesis exhibited ultra-high peroxidase-like activity (35.17 U mg-1), which was about 4.5 times higher than that of the unmodified Pt nanozyme (8.83 U mg-1). Due to the efficient peroxidase-like activity of the copper-platinum complexed nanozyme, transduction and sequential amplification of cTnI biological signals were achieved in combination with a liposome-embedded amplification strategy. The encapsulation efficiency was calculated by introducing a liposomal bilayer model, which showed that the introduction of a single liposomal molecule could amplify the signal up to 870-fold, thus promising a high sensitivity test. Notably, the dynamic response of cTnI was in the range of 0.1-5000 pg mL-1 with an ultra-low detection limit (0.048 pg mL-1). The developed NLISA analysis system provides a new way to discover efficient and sensitive alternatives to ELISA kits, which can meet the practical needs of community healthcare testing conditions and rapid testing in hospitals.

Signal amplification strategies in photoelectrochemical sensing of carcinoembryonic antigen

Early detection of cancer markers is critical for cancer diagnosis and cancer therapy since these markers may indicate cancer risk, incidence, and disease prognosis. Carcinoembryonic antigen (CEA) is a type of non-specific and broad-spectrum cancer biomarker commonly utilized for early cancer diagnosis. Moreover, it serves as an essential tool to assess the efficacy of cancer treatment and monitor tumor recurrence as well as metastasis, thus garnering significant attention for precise and sensitive CEA detection. In recent years, photoelectrochemical (PEC) techniques have emerged as prominent methods in CEA detection due to the advantages of PEC, such as simple equipment requirements, cost-effectiveness, high sensitivity, low interference from background signals, and easy of instrument miniaturization. Different signal amplification methods have been reported in PEC sensors for CEA analysis. Based on these, this article reviews PEC sensors based on various signal amplification strategies for detection of CEA during the last five years. The advantages and drawbacks of these sensors were discussed, as well as future challenges.

Based on Fe and Ni prepared organic colloidal materials as efficient oxide nanozymes for chemiluminescence detection of GSH and Hg(II) ions

Metal-organic gels (MOGs) are a type of metal-organic colloid material with a large specific surface area, loose porous structure, and open metal active sites. In this work, FeNi-MOGs were synthesized by the simple one-step static method, using Fe(III) and Ni(II) as the central metal ions and terephthalic acid as the organic ligand. The prepared FeNi-MOGs could effectively catalyze the chemiluminescence of luminol without the involvement of H2O2, which exhibited good catalytic activity. Then, the multifunctional detected platform was constructed for the detection of GSH and Hg2+, based on the antioxidant capacity of GSH, and the strong affinity between mercury ion (Hg2+) and GSH which inactivated the antioxidant capacity of GSH. The experimental limits of detection (LOD) for GSH and Hg2+ were 76 nM and 210 nM, and the detection ranges were 2-100 μM and 8-4000 μM, respectively. The as-proposed sensor had good performance in both detection limit and detection range of GSH and Hg2+, which fully met the needs of daily life. Surprisingly, the sensor had low detection limits and an extremely wide detection range for Hg2+, spanning five orders of magnitude. Furthermore, the detection of mercury ions in actual lake water and GSH in human serum showed good results, with recovery rates ranging from 90.10 % to 105.37 %, which proved that the method was accurate and reliable. The as-proposed sensor had great potential as the platform for GSH and Hg2+ detection applications.

A Novel Ratiometric Photoelectrochemical Biosensor Based on Front and Back Illumination for Sensitive and Accurate Glutathione Sensing

The ratiometric detection method has a strong attraction for photoelectrochemical bioanalysis due to its high reliability and real-time calibration. However, its implementation typically depends on the spatial resolution of equipment and the pairing of wavelength/potential with photoactive materials. In this paper, a novel ratiometric photoelectrochemical biosensor based on front and back illumination was prepared for the detection of glutathione (GSH). Unlike traditional ratio methods, this ratiometric biosensor does not require voltage and wavelength modulation, thereby avoiding potential crosstalk caused by voltage and wavelength modulation. Additionally, the formation of a heterojunction between mTiO2 and Ag2S is conducive to enhancing light absorption and promoting charge separation, thereby boosting the photocurrent signal. Apart from forming a heterojunction with TiO2, Ag2S also shows a specific affinity towards GSH, thus enhancing the selectivity of the mTiO2/Ag2S ratiometric photoelectrochemical biosensor. The results demonstrate that the ratiometric photoelectrochemical biosensor exhibits a good detection range and a low detection limit for GSH, while also possessing significant interference elimination capability. The GSH detection range is 0.01-10 mmol L-1 with a detection limit of 6.39 × 10-3 mmol·L-1. The relative standard deviation of 20 repeated detections is 0.664%. Impressively, the proposed novel ratiometric PEC biosensor demonstrates enviable universality, providing new insights for the design and construction of PEC ratiometric sensing platforms.

Domain-Limited Sub-Nanometer Co Nanoclusters in Defective Nitrogen Doped Carbon Structures for Non-Invasive Drug Monitoring

In this work, sub-nanometer Co clusters anchored on porous nitrogen-doped carbon (C─N─Co NCs) are successfully prepared by high-temperature annealing and pre-fabricated template strategies for non-invasive sensing of clozapine (CLZ) as an efficient substrate adsorption and electrocatalyst. The introduction of Co sub-nanoclusters (Co NCs) provides enhanced electrochemical performance and better substrate adsorption potential compared to porous and nitrogen-doped carbon structures. Combined with ab initio calculations, it is found that the favorable CLZ catalytic performance with C─N─Co NCs is mainly attributed to possessing a more stable CLZ adsorption structure and lower conversion barriers of CLZ to oxidized state CLZ. An electrochemical sensor for CLZ detection is conceptualized with a wide operating range and high sensitivity, with monitoring capabilities validated in a variety of body fluid environments. Based on the developed CLZ sensing system, the CLZ correlation between blood and saliva and the accuracy of the sensor are investigated by the gold standard method and the rat model of drug administration, paving the way for non-invasive drug monitoring. This work provides new insights into the development of efficient electrocatalysts to enable drug therapy and administration monitoring in personalized healthcare systems.

Thioredoxin Reductase-Mediated Reaction Evokes In Situ Surface Polarization Effect on BiOIO3: Toward a New Sensing Strategy for Cathodic Photoelectrochemistry

We have witnessed the fast progress of cathodic photoelectrochemistry over the past decades, though its signal transduction tactic still lacks diversity. Exploring new sensing strategies for cathodic photoelectrochemistry is extremely demanding yet hugely challenging. This article puts forward a unique idea to incorporate an enzymatic reaction-invoked surface polarization effect (SPE) on the surface of BiOIO3 to implement an innovative cathodic photoelectrochemical (PEC) bioanalysis. Specifically, the thioredoxin reductase (TrxR)-mediated reaction produced the polar glutathione (GSH), which spontaneously coordinated to the surface of BiOIO3 and induced SPE by forming a polarized electric field, resulting in improved electron (e-) and hole (h+) pair separation efficiency and an enhanced photocurrent output. Correlating this phenomenon with the detection of TrxR exhibited a high performance in terms of sensitivity and selectivity, achieving a linear range of 0.007-0.5 μM and a low detection limit of 2.0 nM (S/N = 3). This study brings refreshing inspiration for the cathodic PEC signal transduction tactic through enzyme-mediated in situ reaction to introduce SPE, which enriches the diversity of available signaling molecules. Moreover, this study unveils the potential of in situ generated SPE for extended and futuristic applications.

Fabrication and application of glutathione biosensing SPCE strips with gold nanoparticle modification

Glutathione (GSH) is a major antioxidant in organisms. An alteration in GSH concentration has been implicated in a number of pathological conditions. Therefore, GSH sensing has become a critical issue. In this study, a disposable strip used for tyrosinase-modified electrochemical testing was fabricated for the detection of GSH levels in vivo. The system is based on tyrosinase as a biorecognition element and a screen-printed carbon electrode (SPCE) as an amperometric transducer. On the tyrosinase-SPCE strips, the oxidation reaction from catechol to o-quinone was catalyzed by tyrosinase. The tyrosinase-SPCE strips were modified with gold nanoparticles (AuNPs). In the presence of AuNPs of 25 nm diameter, the cathodic peak current of cyclic voltammetry (CV) was significantly enhanced by 5.2 fold. Under optimized conditions (250 μM catechol, 50 mM phosphate buffer, and pH 6.5), the linear response of the tyrosinase-SPCE strips ranged from 31.25 to 500 μM GSH, with a detection limit of approximately 35 μM (S/N > 3). The tyrosinase-SPCE strips have been used to detect real samples of plasma and tissue homogenates in a mouse experiment. The mice were orally administrated with N-acetylcysteine (NAC) 100 mg kg-1 once a day for 7 days; the plasma GSH significantly enhanced 2.8 fold as compared with saline-treated mice (1123 vs. 480 μM μg-1 protein). NAC administration also could alleviate the adverse effect of GSH reduction in the mice treated with doxorubicin.