A direct and selective electrochemical hydrogen sulfide sensor

Construction of an effective near-infrared fluorescence "turn-on" probe for hydrogen sulfide detection and imaging in living inflammatory cell and zebrafish models

Hydrogen sulfide (H2S) can act as a gaseous signaling mediator closely associated with inflammation development. In this work, we designed a fluorescence turn-on near-infrared (NIR) fluorescent probe CIT-H2S based on Intermolecular Charge Transfer (ICT) for the detection of H2S in living inflammatory cells and zebrafish. On this basis, a dicyanoisophorone fluorophore was chosen as the fluorescence signal reporting group of CIT-H2S, and an azide group was constructed as the recognition group of H2S. CIT-H2S is characterized by high selectivity and sensitivity for H2S over other interference species. The fluorescence intensity at 661 nm showed good linearity in the range of H2S concentration from 0 to 10 μM, with an excellent limit of detection (LOD) as low as 81.52 nM. Impressively, CIT-H2S has been visualized for detecting H2S in drug-induced inflammatory cell and zebrafish models, thus indicating that CIT-H2S is a robust tool with the ability to study the occurrence and development of hydrogen sulfide and inflammation.

Sensitive detection of H2S based on Ce doped ZnCo2O4 hollow microspheres at low working temperature

In order to develop a highly efficient H2S gas sensor at low working temperature, in this work, a kind of novel Ce-doped ZnCo2O4 hollow microspheres (Ce/ZnCo2O4 HMSs) were successfully synthesized using a template-free one-pot method, showing a sensitive response toward H2S. The microstructure and morphology of the material were characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The gas-sensing performance of the composite was investigated, showing that the ZnCo2O4 doped with 6 mol% Ce had the highest response to 20 ppm H2S at a low operating temperature of 160 °C with a response value of 67.42, which was about 2 times higher than that of original ZnCo2O4. The prepared Ce/ZnCo2O4 HMS sensor in response to H2S exhibited a linear range of 0.1-200 ppm with a low detection limit of 0.1 ppm under the conditions of ambient humidity of 45% and ambient temperature of 20 °C. Meanwhile, it also possessed good selectivity, repeatability and reproducibility. The response value of the sensor decreased by 5.32% after 7 months of continuous monitoring of H2S in an atmospheric environment of a pig farm, indicating that the sensor had a long-term stability and continuous service life with important application prospects.

Electrochemical Detection of Gasotransmitters: Status and Roadmap

Gasotransmitters, including nitric oxide (NO), carbon monoxide (CO), and hydrogen sulfide (H2S), are a class of gaseous, endogenous signaling molecules that interact with one another in the regulation of critical cardiovascular, immune, and neurological processes. The development of analytical sensing mechanisms for gasotransmitters, especially multianalyte mechanisms, holds vast importance and constitutes a growing area of study. This review provides an overview of electrochemical sensing mechanisms with an emphasis on opportunities in multianalyte sensing. Electrochemical methods demonstrate good sensitivity, adequate selectivity, and the most well-developed potential for the multianalyte detection of gasotransmitters. Future research will likely address challenges with sensor stability and biocompatibility (i.e., sensor lifetime and cytotoxicity), sensor miniaturization, and multianalyte detection in biological settings.

Iron oxide-supported gold nanoparticle electrode for simultaneous detection of arsenic and sulfide on-site

The environmental behavior of arsenic (As) has garnered significant attention due to its hazardous nature. The fate of As often couples with sulfide, thus co-detecting arsenic and sulfide on-site is crucial for comprehending their geochemical interactions. While electrochemical methods are suitable for on-site chemical analysis, there currently exists no electrode capable of simultaneously detecting both arsenic and sulfide. To address this, we developed a dual-metal electrode consisting of iron oxide-encased carbon cloth loaded with gold nanoparticles (Au/FeOx/CC) using the electrochemical deposition method. This electrode enables square wave stripping voltammetry (SWASV) binary detection of As and sulfide. Comparison experiments reveal that the reaction sites for sulfide primarily reside on FeOx, while the interface synergy of iron oxide and gold nanoparticles enhances the response to arsenite (AsIII). Arsenate (AsV) is directly reduced to As0 on Fe0, obviating the need for an external reducing agent. The electrode achieves detection limits of 1.5 μg/L for AsV, 0.25 μg/L for AsIII, and 11.6 μg/L for sulfide at mild conditions (pH 7.8). Field validation was conducted in the Tengchong geothermal hot spring region, where the electrochemical method exhibited good correlation with the standard methods: Total As (r = 0.978 vs. ICP-MS), AsIII (r = 0.895 vs. HPLC-ICP-MS), and sulfide (r = 0.983 vs. colorimetric method). Principal component analysis and correlation analysis suggest that thioarsenic, could potentially be positive interferents for AsIII. However, this interference can be anticipated and mitigated by monitoring the abundance of sulfide. The study provides new insights and problems for the electrochemical detection of coexisted As and sulfide.

Novel H2S sensing mechanism derived from the formation of oligomeric sulfide capping the surface of gold nanourchins

A gold nanourchin (AuNU) probe with a novel sensing mechanism for monitoring H2S was developed as a feasible colorimetric sensor. In this study, AuNUs that are selectively responsive to H2S were fabricated in the presence of trisodium citrate and 1,4-hydroquinone using a seed-mediated approach. Upon exposure of the AuNU solution to H2S, the hydrosulfide ions (HS-) in the solution are converted into oligomeric sulfides by 1,4-hydroquinone used as a reducing agent during the synthesis of AuNUs. The oligomeric sulfides formed in the AuNU solution upon the addition of H2S were found to coat the surface of the AuNUs, introducing a blue shift in absorption accompanied by a color change in the solution from sky blue to light green. This colorimetric alteration by the capping of oligomeric sulfides on the surface of AuNUs is unique compared to well-known color change mechanisms, such as aggregation, etching, or growth of nanoparticles. The novel H2S sensing mechanism of the AuNUs was characterized using UV-Vis spectroscopy, high-resolution transmission microscopy, X-ray photoelectron spectroscopy, surface-enhanced Raman spectroscopy, secondary ion mass spectroscopy, liquid chromatography-tandem mass spectrometry, and atom probe tomography. H2S was reliably monitored with two calibration curves comprising two sections with different slopes according to the low (0.3-15 μM) and high (15.0-300 μM) concentration range using the optimized AuNU probe, and a detection limit of 0.29 μM was obtained in tap water.

Reactive Sulfur Species in Human Diseases

Significance: Reactive sulfur species (RSS) have been recently recognized as redox molecules no less important than reactive oxygen species or reactive nitrogen species. They possess regulatory and protective properties and are involved in various metabolic processes, thereby contributing to the maintenance of human health. It has been documented that many disorders, including neurological, cardiovascular, and respiratory diseases, diabetes mellitus (DM), and cancer, are related to the disruption of RSS homeostasis. Recent Advances: There is still a growing interest in the role of RSS in human diseases. Since a decrease in hydrogen sulfide or other RSS has been reported in many disorders, safe and efficient RSS donors have been developed and tested under in vitro conditions or on animal models. Critical Issues: Cardiovascular diseases and DM are currently the most common chronic diseases worldwide due to stressful and unhealthy lifestyles. In addition, because of high prevalence and aging of the population, neurological disorders including Parkinson's disease and Alzheimer's disease as well as respiratory diseases are a formidable challenge for health care systems. From this point of view, the knowledge of the role of RSS in these disorders and RSS modulation options are important and could be useful in therapeutic strategies. Future Directions: Improvement and standardization of analytical methods used for RSS estimation are crucial for the use of RSS as diagnostic biomarkers. Finding good, safe RSS donors applicable for therapeutic purposes could be useful as primary or adjunctive therapy in many common diseases. Antioxid. Redox Signal. 39, 1000-1023.

Portable instrument based on color sensor chip for on-site rapid detection of dissolved sulfides in environmental water samples

To ensure real-time validity of the detection of unstable toxic environmental pollutants, such as dissolved sulfides, we developed a portable on-site rapid analysis instrument. Through novel design of the color sensor chip-based core sensing components and the conversion between color signal and absorbance by Lambert's law, the instrument showed great performance for rapid (within 3 min) and sensitive on-site detection of sulfides in the environment. It is easy to achieve user-friendly, sample in-answer out, one-stop operation due to the touch-screen-integrated user interface of the instrument's data terminal. The detection limit of this method is 2.24 μg/L, the linear operation range is 0-1000 μg/L, and the coefficient of determination is 0.999. This instrument has been successfully applied to the on-site determination of sulfides in the Yellow River Delta and the Yantai Guangdang River in China. The portable instrument showed excellent anti-interference, good stability, and simple operation, which showed great prospects for the on-site rapid analysis of unstable targets in the environment.

Planar carbon electrodes for real-time quantification of hydrogen sulfide release from cells

A planar electrode system was developed to permit the real-time, selective detection of hydrogen sulfide (H₂S) from stimulated cells. Planar carbon electrodes were produced via stencil printing carbon ink through a laser cut vinyl mask. Electrodes were preconditioned using a constant potential amperometry methodology to prevent sensor drift resulting from elemental sulfur adsorption. Modification with a bilaminar coating (electropolymerized ortho-phenylenediamine and a fluorinated xerogel) facilitated high selectivity to H₂S. To demonstrate the biological application of this planar sensor system, H₂S released from 17β-estradiol-stimulated human umbilical vein endothelial cells (HUVECs) was quantified in situ in real-time. Stimulated HUVECs released sustained H₂S levels for hours before returning to baseline. Cellular viability assays demonstrated negligible cell cytotoxicity at the electrochemical potentials required for analysis.

Field application of cost-effective sensors for the monitoring of NH3, H2S, and TVOC in environmental treatment facilities and the estimation of odor intensity

Odor is usually a complex mixture of various compounds. In many countries, odor complaints have been addressed using the air dilution olfactory method (ADOM) to reduce their malodor complaint. In this study, continuous monitoring of ammonia, hydrogen sulfide, and total volatile organic compounds (TVOC) using sensors was conducted in facilities for municipal and livestock wastewater treatment (LWT), and for food waste composting (FWC). Odor intensity was modeled by multivariate linear regression using sensor monitoring data with air dilution measured by the ADOM. In testing the performance of sensors in the lab, all three sensors showed acceptable values for linearity, accuracy, repeatability, lowest detection limit, and response time, so the sensors were acceptable for application in the field. In on-site real-time monitoring, the three sensors functioned well in the three environmental facilities during the testing period. Average ammonia and hydrogen sulfide concentrations were high in the LWT facility, while TVOC showed the highest concentration in the FWC facility. A longer sampling time is necessary for ammonia monitoring. Odor intensity from individual sensor data correlated well to complex odor measured by the ADOM. Finally, we suggest a protocol for field application of sensor monitoring and odor data reproduction.Implications: We suggest a protocol for the field application of sensor monitoring and odor data estimation in this study. This study can be useful to a policy maker and field operator to reduce odor emission through the determination of a more effective treatment technology and removal pathway for individual odorants.

The Roadmap of Graphene-Based Sensors: Electrochemical Methods for Bioanalytical Applications

Graphene (GR) has engrossed immense research attention as an emerging carbon material owing to its enthralling electrochemical (EC) and physical properties. Herein, we debate the role of GR-based nanomaterials (NMs) in refining EC sensing performance toward bioanalytes detection. Following the introduction, we briefly discuss the GR fabrication, properties, application as electrode materials, the principle of EC sensing system, and the importance of bioanalytes detection in early disease diagnosis. Along with the brief description of GR-derivatives, simulation, and doping, classification of GR-based EC sensors such as cancer biomarkers, neurotransmitters, DNA sensors, immunosensors, and various other bioanalytes detection is provided. The working mechanism of topical GR-based EC sensors, advantages, and real-time analysis of these along with details of analytical merit of figures for EC sensors are discussed. Last, we have concluded the review by providing some suggestions to overcome the existing downsides of GR-based sensors and future outlook. The advancement of electrochemistry, nanotechnology, and point-of-care (POC) devices could offer the next generation of precise, sensitive, and reliable EC sensors.

An indirect detection strategy-assisted self-cleaning electrochemical platform for in-situ and pretreatment-free detection of endogenous H2S from sulfate-reducing bacteria (SRB)

The endogenous hydrogen sulfide (H₂S) can be adopted as an indicator for the indirect detection of sulphate-reducing bacteria (SRB), which considered to be closely related to pipeline corrosion and human intestinal health. Unfortunately, the in-situ detection of endogenous H₂S from SRB in the complex culture medium still faces huge challenges. Besides nonspecific adsorption from the culture medium of SRB, the problem of electrode passivation by produced elemental sulfur during electrochemical detection processes of H₂S cannot be ignored. To address these challenges, herein a synergistic sensing platform based on self-cleaning electrode interface and indirect detection strategy (specific H₂S-induced chemical reaction) is developed. This indirect sensing strategy-assisted self-cleaning electrochemical platform showed a relatively good linear response toward H₂S in the range of 0.5 - 5 μM, and the corresponding limit of detection (LOD) was calculated to be 5.09 nM. More importantly, the satisfactory self-cleaning electrode interface in indirect detection system (with only a 4.10% decrease in signal over 50 electrochemical repeated cycles) showed the electrode surface not being disturbed by elemental sulfur. Furthermore, this good selectivity of the indirect detection strategy in combination with the reproducibility, stability, and antifouling activity of the self-cleaning interface, enabled a synergistic sensing platform to detect H₂S directly in the complex culture medium of SRB without time-consuming sample pretreatments. Moreover, this proposed construction strategy of synergetic sensing platform could be explored to other endogenous molecules in complex environment based on different antifouling materials and specific reactions.

Electrochemical detection of uric acid in undiluted human saliva using uricase paper integrated electrodes

In this study, we introduce a uricase-immobilized paper (UOx­-paper) integrated electrochemical sensor for detection of uric acid (UA) in saliva. The UOx was immobilized on the detection zone in the wax-patterned paper substrate. This UOx-paper was integrated with a Prussian blue­-modified, screen-printed carbon electrode after electropolymerization of o-phenylenediamine to construct an electrochemical cell for small-volume (20 μL) of samples. First, we optimized the fabrication conditions of UOx-paper. Next, the amperometric response of the UOx-paper-based electrochemical UA sensor was analyzed using a known concentration of UA standard solution in artificial saliva at an applied potential of − 0.1 V (versus Ag pseudo-reference electrode). The UOx-­paper based electrochemical UA sensor showed a sensitivity of 4.9 μA·mM⁻¹ in a linear range of 50 to 1000 μM (R² = 0.998), high selectivity and good reproducibility, as well as a limit of detection of 18.7 μM (0.31 mg/dL) UA. Finally, we quantified the UA levels in undiluted saliva samples of healthy controls (n = 20) and gout patients (n = 8). The levels were correlated with those measured with conventional salivary UA enzymatic assays as well as serum UA levels. The UOx-paper-based electrochemical UA sensor is a user-friendly and convenient tool to assess salivary UA levels.

Preparation of Highly Stable and Electrochemically Active Three-dimensional Interconnected Graphene Frameworks from Jute Sticks

Over the past few years, the environmentally friendly synthesis of nanomaterials, including graphene using green chemistry, has attracted tremendous attention due to its easy handling, low cost, and biocompatibility. Here we demonstrate a facile and efficient green synthesis route for producing highly stable and electrochemically active three-dimensional interconnected graphene frameworks (3DIGF) from jute sticks. Initially, jute sticks derived three-dimensional amorphous activated carbon nanosheets (3DAACNs) were prepared at low temperatures (i.e., 850 °C) in an inert environment. The resultant 3DAACNs were then heat treated at a high temperature (i.e., 2700 °C) under an inert environment, resulting in 3DIGF. The prepared carbonaceous materials were fully characterized, and various experimental techniques confirmed the preparation of 3DIGF. The prepared 3DIGF shows a highly stable nature in thermal and chemical environments and demonstrates a highly dynamic nature for the electrooxidation of sulfide. This study could be considered a vital contribution towards the economic and simple approach for preparing 3DIGF from biomass.

Gut microbiota reinforce host antioxidant capacity via the generation of reactive sulfur species

Gut microbiota act beyond the gastrointestinal tract to regulate the physiology of the host. However, their contribution to the antioxidant capacity of the host remains largely understudied. In this study, we observe that gut bacteria increase the steady-state plasma levels of high-antioxidant molecules, reactive sulfur species (RSS), such as hydrogen sulfide and cysteine persulfide (CysSSH), in the host. Moreover, gut bacteria utilize cystine as a substrate to enzymatically produce CysSSH. Administration of cystine to mice increases their plasma levels of RSS and suppresses the concanavalin-A-induced oxidative stress and liver damage in a gut-microbiota-dependent manner. We find that gut bacteria belonging to the Lachnospiraceae and Ruminococcaceae families have a high capacity to produce RSS, requiring pyridoxal 5'-phosphate for their enzymatic reactions. Collectively, our data demonstrate that gut microbiota enhance the antioxidant capacity of the host through the generation of RSS.

Buffering Adaptive Immunity by Hydrogen Sulfide

T cell-mediated adaptive immunity is designed to respond to non-self antigens and pathogens through the activation and proliferation of various T cell populations. T helper 1 (Th1), Th2, Th17 and Treg cells finely orchestrate cellular responses through a plethora of paracrine and autocrine stimuli that include cytokines, autacoids, and hormones. Hydrogen sulfide (H₂S) is one of these mediators able to induce/inhibit immunological responses, playing a role in inflammatory and autoimmune diseases, neurological disorders, asthma, acute pancreatitis, and sepsis. Both endogenous and exogenous H₂S modulate numerous important cell signaling pathways. In monocytes, polymorphonuclear, and T cells H₂S impacts on activation, survival, proliferation, polarization, adhesion pathways, and modulates cytokine production and sensitivity to chemokines. Here, we offer a comprehensive review on the role of H₂S as a natural buffer able to maintain over time a functional balance between Th1, Th2, Th17 and Treg immunological responses.

Biocompatible Electrochemical Sensor Based on Platinum-Nickel Alloy Nanoparticles for In Situ Monitoring of Hydrogen Sulfide in Breast Cancer Cells

Hydrogen sulfide (H₂S), an endogenous gasotransmitter, is produced in mammalian systems and is closely associated with pathological and physiological functions. Nevertheless, the complete conversion of H₂S is still unpredictable owing to the limited number of sensors for accurate and quantitative detection of H₂S in biological samples. In this study, we constructed a disposable electrochemical sensor based on PtNi alloy nanoparticles (PtNi NPs) for sensitive and specific in situ monitoring of H₂S released by human breast cancer cells. PtNi alloy NPs with an average size of 5.6 nm were prepared by a simple hydrothermal approach. The conversion of different forms of sulfides (e.g., H₂S, HS^-, and S^2-) under various physiological conditions hindered the direct detection of H₂S in live cells. PtNi NPs catalyze the electrochemical oxidation of H₂S in a neutral phosphate buffer (PB, pH 7.0). The PtNi-based sensing platform demonstrated a linear detection range of 0.013-1031 µM and the limit of detection was 0.004 µM (S/N = 3). Moreover, the PtNi sensor exhibited a sensitivity of 0.323 μA μM^-1 cm^-2. In addition, the stability, repeatability, reproducibility, and anti-interference ability of the PtNi sensor exhibited satisfactory results. The PtNi sensor was able to successfully quantify H₂S in pond water, urine, and saliva samples. Finally, the biocompatible PtNi electrode was effectively employed for the real-time quantification of H₂S released from breast cancer cells and mouse fibroblasts.

Growth of large-scale MoS2 nanosheets on double layered ZnCo2O4 for real-time in situ H2S monitoring in live cells

There is an urgent need to develop in situ sensors that monitor the continued release of H2S from biological systems to understand H2S-related pathology and pharmacology. For this purpose, we have developed a molybdenum disulfide supported double-layered zinc cobaltite modified carbon cloth electrode (MoS2-ZnCo2O4-ZnCo2O4) based electrocatalytic sensor. The results of our study suggest that the MoS2-ZnCo2O4-ZnCo2O4 electrode has excellent electrocatalytic ability to oxidize H2S at physiological pH, in a minimized overpotential (+0.20 vs. Ag/AgCl) with an amplified current signal. MoS2 grown on double-layered ZnCo2O4 showed relatively better surface properties and electrochemical properties than MoS2 grown on single-layered ZnCo2O4. The sensor delivered excellent analytical parameters, such as low detection limit (5 nM), wide linear range (10 nM-1000 μM), appreciable stability (94.3%) and high selectivity (2.5-fold). The practicality of the method was tested in several major biological fluids. The electrode monitors the dynamics of bacterial H2S in real-time for up to 5 h with good cell viability. Our research shows that MoS2-ZnCo2O4-ZnCo2O4/carbon cloth is a robust and sensitive electrode to understand how bacteria seek to adjust their defense strategies under exogenously induced stress conditions.

A spiropyran functionalized fluorescent probe for mitochondria targeting and imaging of endogenous hydrogen sulfide in living cells

A turn-on spiropyran functionalized fluorescein derivative (FMC) is developed for targeting HS- in mitochondria. FMC exhibits very weak fluorescence at 525 nm under the excitation of 470 nm in aqueous solution due to its colorless spiropyran form; upon addition of HS-, a strong fluorescence enhancement by 6.4-fold is observed with spirocycle-opened merocyanine form and rapid trapping kinetics for HS-. FMC has good biocompatibility and high selectivity towards HS- with a detection limit of 88.2 nM and is very sensitive among the reported H2S fluorescent probes. Moreover, the significant colocalization of FMC with Mito Tracker® Deep Red FM in human laryngeal epidermoid carcinoma (HEp-2) cells and the Pearson correlation coefficient of 0.87 together demonstrate that FMC can target and image the endogenous H2S in the mitochondria of living cells.

Gd doped molybdenum selenide/carbon nanofibers: an excellent electrocatalyst for monitoring endogenous H2S

Design and synthesis of Gd doped molybdenum selenide/carbon nanofibers for monitoring H₂S.

Controlled-Potential-Based Electrochemical Sulfide Sensors: A Review

Due to their potential applications in industry and potent toxicity to the environment, sulfides and their detection have attracted the attention of researchers. To date, a large number of controlled-potential techniques for electrochemical sulfide sensors have been developed, thanks to their simplicity, reasonable limit of detection (LOD), and good selectivity. Different researchers have applied different strategies for developing selective and sensitive sulfide sensors. However, there has been no systematic review on controlled-potential techniques for sulfide sensing. In light of this absence, the main aim of this review article is to summarize various strategies for detecting sulfide in different media. The efficiencies of the developed sulfide sensors for detecting sulfide in its various forms are determined, and the essential parameters, including sensing strategies, working electrodes, detection media, pH, LOD, sensitivity, and linear detection range, are emphasized in particular. Future research in this area is also recommended. It is expected that this review will act as a basis for further research on the fabrication of sulfide sensors for practical applications.

Fluorescent detection of S2- based on ZnMOF-74 and CuMOF-74

The detection of S^2- is of great significance because excess S^2- can lead to a variety of serious physiological diseases. Here, two metal-organic frameworks (MOFs), ZnMOF-74 and CuMOF-74, were synthesized by using 2,5-dihydroxy terephthalic acid with strong fluorescence as organic ligand and Zn²⁺ or Cu²⁺ as central coordination ions for S^2- detection. Both as-prepared ZnMOF-74 and CuMOF-74 displayed nanospheres with a diameter of about 100 nm. Under the excitation of 353 nm, the ZnMOF-74 had a characteristic emission peak at 537 nm and the CuMOF-74 had a characteristic emission peak at 528 nm under excitation of 356 nm. The interaction of S^2- and Zn²⁺ weakened the fluorescence of ZnMOF-74 but the interaction of S^2- with Cu²⁺ to form CuS restored the fluorescence of CuMOF-74, so the ZnMOF-74 and CuMOF-74 were exploited as a fluorescent nanosensor for sensing S^2-. The ZnMOF-74 sensor has a good linear range of 19.6 nmol L^-1-90.0 μmol L^-1, and the limit of detection was as low as 6.53 nmol L^-1. The CuMOF-74 sensor has a good linear relationship with II₀ in the S^2- concentration range of 1.50 nmol L^-1-125 μmol L^-1, and the limit of detection was 1.50 nmol L^-1. The proposed ZnMOF-74 and CuMOF-74 sensor could also detect S^2- in actual samples.

Reactive Sulfur Species: A New Redox Player in Cardiovascular Pathophysiology

Hydrogen sulfide has emerged as an important gaseous signaling molecule and a regulator of critical biological processes. However, the physiological significance of hydrogen sulfide metabolites such as persulfides, polysulfides, and other reactive sulfur species (RSS) has only recently been appreciated. Emerging evidence suggests that these RSS molecules may have similar or divergent regulatory roles compared with hydrogen sulfide in various biological activities. However, the chemical nature of persulfides and polysulfides is complex and remains poorly understood within cardiovascular and other pathophysiological conditions. Recent reports suggest that RSS can be produced endogenously, with different forms having unique chemical properties and biological implications involving diverse cellular responses such as protein biosynthesis, cell-cell barrier functions, and mitochondrial bioenergetics. Enzymes of the transsulfuration pathway, CBS (cystathionine beta-synthase) and CSE (cystathionine gamma-lyase), may also produce RSS metabolites besides hydrogen sulfide. Moreover, CARSs (cysteinyl-tRNA synthetase) are also able to generate protein persulfides via cysteine persulfide (CysSSH) incorporation into nascently formed polypeptides suggesting a new biologically relevant amino acid. This brief review discusses the biochemical nature and potential roles of RSS, associated oxidative stress redox signaling, and future research opportunities in cardiovascular disease.