An anti-poisoning nanosensor for in situ monitoring of intracellular endogenous hydrogen sulfide

Development of a Photoelectrochemical Microelectrode Using an Organic Probe for Monitoring Hydrogen Sulfide in Living Brains

Hydrogen sulfide (H2S) is an important bioactive molecule that plays a significant role in various functions, particularly in the living brain, where it is closely linked to cognition, memory, and several neurological diseases. Consequently, developing effective detection methods for H2S is essential for studying brain functions and the underlying mechanisms of these diseases. This study aims to construct a novel photoelectrochemical (PEC) microelectrode Ti/TiO2@HSP for the quantitative monitoring of H2S levels in the living brain. The PEC microelectrode Ti/TiO2@HSP is formed by covalently bonding a specifically designed organic PEC probe HSP, which possesses a D-π-A structure, to the surface of TiO2 nanotubes generated via in situ anodic oxidation of titanium wire. The PEC probe HSP can effectively react with H2S and generate significant photocurrent response under long-wavelength excitation light (560 nm), thereby achieving quantitative detection of H2S. The sensor demonstrates high sensitivity and good selectivity. In vivo experiments utilizing the PEC microelectrode Ti/TiO2@HSP enable the monitoring of dynamic changes in H2S levels across various regions of the mouse brain. The findings reveal that in normal mice, the concentration of H2S in the hippocampus is significantly higher than in the striatum and cerebral cortex. Additionally, following propargylglycine drug stimulation, H2S concentrations in different brain regions were observed to decrease, with the most substantial reduction noted in the hippocampus. This suggests that cystathionine γ-lyase (CSE) is the primary enzyme responsible for H2S production in this area, while the striatum exhibits a less pronounced decrease in H2S concentration, indicating a reliance on alternative enzymatic pathways for H2S production. Therefore, this study not only successfully develops a high-performance H2S detection sensor but also provides new experimental tools and theoretical foundations for further exploring the roles of H2S in neurophysiological and pathological processes.

Electroactive polymer tag modified nanosensors for enhanced intracellular ATP detection

ATP plays a crucial role in cell energy supply, so the quantification of intracellular ATP levels is particularly important for understanding many physio-pathological processes. The intracellular quantification of this non-electroactive molecule can be realized using aptamer-modified nanoelectrodes, but is hindered by the limited quantity of modification and electroactive tags on the nanosized electrodes. Herein, we developed a simple but effective electrochemical signal amplification strategy for intracellular ATP detection, which replaces the regular ATP aptamer-linked ferrocene monomer with a polymer, thus greatly magnifying the amounts of electrochemical reporters linked to one chain of the aptamer and enhancing the signals. This ferrocene polymer-ATP aptamer was further immobilized onto Au nanowire electrodes (SiC@C@Au NWEs) to achieve accurate quantification of intracellular ATP in single cells, presenting high electrochemical signal output and high specificity. This work not only provides a powerful tool for quantifying intracellular ATP but also offers a simple and versatile strategy for electrochemical signal amplification in the detection of broader non-electroactive molecules involved in different kinds of intracellular physiological processes.

A novel fluorescent sensor with an overtone peak reference for highly sensitive detection of mercury (II) ions and hydrogen sulfide: Mechanisms and applications in environmental monitoring and bioanalysis

The present study introduces a novel fluorescent sensor with an overtone peak reference designed for the detection of mercury (Ⅱ) ions (Hg2+) and hydrogen sulfide (H2S). The study proposes two novel response mechanisms that hinges on the synergistic effect of cation exchange dissociation (CED) and photo-induced electron transfer (PET). This sensor exhibits a remarkable detection limit of 2.9 nM for Hg2+. Additionally, the sensor reacts with H2S to generate nickel sulfide (NiS) semiconductor nanoparticles, which amplify the fluorescence signal and enable a detection limit of 3.1 nM for H2S. The detection limit for H2S is further improved to 29.1 pM through the surface functionalization of the nanomaterial with pyridine groups (increasing reactivity) and chelation of gold nanoparticles (AuNPs), which enhances the sensor's specificity. This improvement is primarily due to the surface plasmon resonance (SPR) of AuNPs and their affinity for H2S. The single-emission strategy can yield skewed results due to environmental changes, whereas the overtone peak reference strategy enhances result accuracy and reliability by detecting environmental interference through reference emission peaks. In another observation, the low-toxicity dihydropyrene-bipyridine nanorods (TPP-BPY) has been successfully utilized for both endogenous and exogenous H2S detection in vivo using a mouse model. The successful development of TPP-BPY is expected to provide an effective tool for studying the role of H2S in biomedical systems.

Application and outlook of electrochemical technology in single-cell analysis

Cellular heterogeneity, especially in some important diseased cells like tumor cells, acts as an invisible driver for disease development like cancer progression in the tumor ecosystem, contributing to differences in the macroscopic and microscopic detection of disease lesions like tumors. Traditional analysis techniques choose group information masked by the mean as the analysis sample, making it difficult to achieve precise diagnosis and target treatment, on which could be shed light via the single-cell level determination/bioanalysis. Hence, in this article we have reviewed the special characteristic differences among various kinds of typical single-cell bioanalysis strategies and electrochemical techniques, and then focused on the recent advance and special bio-applications of electrochemiluminescence and micro-nano electrochemical sensing mediated in single-cell bioimaging & bioanalysis. Especially, we have summarized the relevant research exploration of the possibility to establish the in-situ single-cell electrochemical methods to detect cell heterogeneity through determination of specific biomolecules and bioimaging of some important biological processes. Eventually, this review has explored some important advances of electrochemical single-cell detection techniques for the real-time cellular bioimaging and diagnostics of some disease lesions like tumors. It raises the possibility to provide the specific in-situ platform to exploit the versatile, sensitive, and high-resolution electrochemical single-cell analysis for the promising biomedical applications like rapid tracing of some disease lesions or in vivo bioimaging for precise cancer theranostics.