SOS Signal Research Articles

“SafeSteps” A Flutter -Based Application to Provide Security to Women’s

With women’s safety being one of the most serious and pressing issues worldwide, rapid technological advancements have created new opportunities to enhance personal security. This paper presents an improved mobile application that prioritizes women’s safety through a SIM card-based location tracking approach instead of relying on GPS services that require an internet connection. This feature ensures consistent and reliable location tracking even in areas with weak or no internet access. Inspired by existing platforms like bSafe and My Safetipin, the app includes an emergency alert system that allows users to trigger SOS signals to authorities and nearby registered users by pressing the power button, volume button, or using specific gestures. The involvement of nearby users aims to provide immediate assistance before law enforcement arrives, potentially preventing harm or saving lives. The paper features a survey and technical analysis detailing the app’s architecture, usability, and the benefits of SIM based tracking for improved response times during emergencies. Key Words: Women’s safety, SIM card location tracking, emergency alert system, SOS message, offline tracking, mobile safety app, user assistance network.

Delivery of functional Cas:DNA nucleoprotein complexes into recipient bacteria through a type IV secretion system

CRISPR-associated (Cas) endonucleases and their derivatives are widespread tools for the targeted genetic modification of both prokaryotic and eukaryotic genomes. A critical step of all CRISPR-Cas technologies is the delivery of the Cas endonuclease to the target cell. Here, we investigate the possibility of using bacterial conjugation to translocate Cas proteins into recipient bacteria. Conjugative relaxases are translocated through a type IV secretion system into the recipient cell, covalently attached to the transferred DNA strand. We fused relaxase R388-TrwC with the endonuclease Cas12a and confirmed that it can be transported through a T4SS. The fusion protein maintained its activity upon translocation by conjugation into the recipient cell, as evidenced by the induction of the SOS signal resulting from DNA breaks produced by the endonuclease in the recipient cell, and the detection of mutations at the target position. We further show how a template DNA provided on the transferred DNA can be used to introduce specific mutations. The guide RNA can also be encoded by the transferred DNA, enabling its production in the recipient cells where it can form a complex with the Cas nuclease transferred as a protein. This self-contained setup enables to target wild-type bacterial cells. Finally, we extended this strategy to the delivery of relaxases fused to base editors. Using TrwC and MobA relaxases as drivers, we achieved precise editing of transconjugants. Thus, conjugation provides a delivery system for Cas-derived editing tools, bypassing the need to deliver and express a cas gene in the target cells.

Simultaneous Triboelectric and Mechanoluminescence Sensing Toward Self‐Powered Applications

AbstractSimultaneous phenomena of triboelectricity and mechanoluminescence (ML) acquire vital insights into the mechanics of charge separation and recombination, as well as the relationship between mechanical stress and light emission. In the present work, polydimethylsiloxane (PDMS) and ZnS:Cu particle‐based composites are fabricated, which have good ML characteristics and can generate electricity via contact electrification. ML, in conjunction with a triboelectric nanogenerator (TENG), contributes by producing power from mechanical operations while also giving vital visual input in the form of light emission. This dual capability improves user awareness and efficiency in a variety of applications, making mechanical systems and wearable devices easier to monitor and optimize. To accomplish this, a single‐electrode mode silver (Ag) nanowires embedded PDMS‐ZnS: Cu‐based TENG device is developed and achieved an electrical output of 60 V, 395 nA, and 15 nC by using a linear motor. Furthermore, the combined ML and TENG device is employed in various cases of safety monitoring. This integration provides self‐powered devices that detect mechanical stress, delivering real‐time warnings and illumination signals for increased safety and communication in demanding conditions such as SOS signaling, underwater driving, deep mining, and sports.

Rescuelink: SOS Alert System for Disaster Response and Management

This study highlights the importance of such a system, given the absence of an effective platform that enables citizens to send SOS signals to emergency responders, leaving individuals without any response. This system provides web and mobile applications for residents, enables registered residents to send incident or emergency reports and communicate with the rescue team through a mobile app, and reduces response delays of the rescue team by getting an accurate location of the incident or emergency. The study used descriptive developmental research since it involves designing and developing the RESCUELINK: SOS System for Disaster Response and Management. Furthermore, it aims also to determine the acceptability of the system as evaluated by five (5) IT experts through the use of ISO/IEC 25010 based on the following characteristics: functional suitability, reliability, usability, efficiency, maintainability, portability, compatibility, and security. The RESCUELINK SOS System for Disaster Response and Management exhibits excellent performance across all evaluated ISO/IEC 25010 software quality characteristics, with an overall grand mean score of 4.66. Implementing this system in Silay City is expected to improve the efficiency and effectiveness of the DRRM operations significantly.

The LexA-RecA* structure reveals a cryptic lock-and-key mechanism for SOS activation.

The bacterial SOS response plays a key role in adaptation to DNA damage, including genomic stress caused by antibiotics. SOS induction begins when activated RecA*, an oligomeric nucleoprotein filament that forms on single-stranded DNA, binds to and stimulates autoproteolysis of the repressor LexA. Here, we present the structure of the complete Escherichia coli SOS signal complex, constituting full-length LexA bound to RecA*. We uncover an extensive interface unexpectedly including the LexA DNA-binding domain, providing a new molecular rationale for ordered SOS gene induction. We further find that the interface involves three RecA subunits, with a single residue in the central engaged subunit acting as a molecular key, inserting into an allosteric binding pocket to induce LexA cleavage. Given the pro-mutagenic nature of SOS activation, our structural and mechanistic insights provide a foundation for developing new therapeutics to slow the evolution of antibiotic resistance.

Identification of core genes involved in the response of Apocynum venetum to salt stress based on transcriptome sequencing and WGCNA.

Apocynum venetum L. belongs to the Apocynaceae family and is a plant that is highly resistant to stress. It is important in the fields of ecology, feeding, industry and medicine. The molecular mechanism underlying salt tolerance has not been elucidated. In this study, RNA-seq based transcriptome sequencing of A. venetum leaves after 0, 2, 6, 12, 24 and 48 h of treatment with 300 mM NaCl was performed. We conducted a comprehensive analysis of the transcriptome expression profiles of A. venetum under salt stress using the WGCNA method and identified red, black, and brown as the core modules regulating the salt tolerance of A. venetum. A co-expression regulatory network was constructed to identify the core genes in the module according to the correlations between genes. The genes TRINITY_DN102_c0_g1 (serine carboxypeptidase), TRINITY_DN3073_c0_g1 (SOS signaling pathway) and TRINITY_DN6732_c0_g1 (heat shock transcription factor) in the red module were determined to be the core genes. Two core genes in the black module, TRINITY_DN9926_c0_g1 and TRINITY_DN7962_c0_g1, are pioneer candidate salt tolerance-associated genes in A. venetum. The genes in the brown module were mainly enriched in two pathways, namely photosynthesis and osmotic balance. Among them, the TRINITY_DN6321_c0_g2 and TRINITY_DN244_c0_g1 genes encode aquaporin, which is helpful for maintaining the cell water balance and plays a protective role in defending A. venetum under abiotic stress. Our findings contribute to the identification of core genes involved in the response of A. venetum to salt stress.

Mini-encyclopedia of mitochondria-relevant nutraceuticals protecting health in primary and secondary care—clinically relevant 3PM innovation

Despite their subordination in humans, to a great extent, mitochondria maintain their independent status but tightly cooperate with the “host” on protecting the joint life quality and minimizing health risks. Under oxidative stress conditions, healthy mitochondria promptly increase mitophagy level to remove damaged “fellows” rejuvenating the mitochondrial population and sending fragments of mtDNA as SOS signals to all systems in the human body. As long as metabolic pathways are under systemic control and well-concerted together, adaptive mechanisms become triggered increasing systemic protection, activating antioxidant defense and repair machinery. Contextually, all attributes of mitochondrial patho-/physiology are instrumental for predictive medical approach and cost-effective treatments tailored to individualized patient profiles in primary (to protect vulnerable individuals again the health-to-disease transition) and secondary (to protect affected individuals again disease progression) care. Nutraceuticals are naturally occurring bioactive compounds demonstrating health-promoting, illness-preventing, and other health-related benefits. Keeping in mind health-promoting properties of nutraceuticals along with their great therapeutic potential and safety profile, there is a permanently growing demand on the application of mitochondria-relevant nutraceuticals. Application of nutraceuticals is beneficial only if meeting needs at individual level. Therefore, health risk assessment and creation of individualized patient profiles are of pivotal importance followed by adapted nutraceutical sets meeting individual needs. Based on the scientific evidence available for mitochondria-relevant nutraceuticals, this article presents examples of frequent medical conditions, which require protective measures targeted on mitochondria as a holistic approach following advanced concepts of predictive, preventive, and personalized medicine (PPPM/3PM) in primary and secondary care.

Second-order scattering sensor based on the Zn0.97La0.03O compound for selective and stable detection of glycated albumin

Here, we presented a second-order scattering sensor based on the Zn0.97La0.03O compound (LaZnO) for selective and stable detection of glycated albumin (GA, glycemic long-term biomarker). The LaZnO sample was obtained through the co-precipitation method and then characterized using microscopic and spectroscopic techniques. Furthermore, the selectivity, molecular interference, temporal stability, and pH effects of the LaZnO SOS signal in the absence and presence of GA were investigated. The results indicate the stability of the SOS signal over more than 60 days. Assays conducted within the pH range of 5 to 8 indicate that the detection of GA remains unaffected under the given conditions. Selectivity studies show that the SOS signal of LaZnO is reduced only upon contact with GA, while interference studies show that detection is not affected by other chemical species. Additionally, the calibration curve test showed high sensitivity of the material, with a detection limit of 0.55 µg/ml. All the results suggest that LaZnO can deliver efficiency, selectivity, accuracy, and fast response as a GA biosensor, emphasizing LaZnO’s usefulness in detecting protein biomarkers.

Disaster Guard for Disaster Management

The "Disaster Guard" project presents a comprehensive disaster management mobile app designed to empower individuals and communities in navigating the challenges of disaster preparedness, response, and recovery. With a focus on fostering resilience, the app integrates cutting-edge features, including real-time disaster alerts, location-based services, and a user-friendly emergency services directory. The inclusion of SOS and distress signaling, coupled with two-way communication channels, ensures swift assistance during critical moments. Leveraging data prediction and early warning systems, the platform enables proactive planning, enhancing the overall preparedness for potential disasters.

Zirconium ion ligand Cross-Linked carbon nanotubes and leather collagen fibers for Flexible, Stable, and highly efficient underwater sensors

Flexible sensing materials have recently found widespread applications in integrating various underwater sensors. In this study, we adopted oil-tanned sheepskin as a “structural template” and harnessed its distinctive three-dimensional collagen fiber network. By leveraging the coordination complexation of zirconium ions (Zr4+), we brided collagen fibers with carbon nanotubes (CNTs) to enhance the bonding fastness of the two. We finally constructed a double cross-linked network to produce a new flexible conductive leather called CNTs@Zr@OTL. This material is the basis for preparing leather bio-based piezoresistive sensors （LBPS） and further developing leather biosensing systems (LBS). Experimental outcomes revealed that when CNTs were employed at a concentration of 8.5 %, CNTs@Zr@OTL exhibited an electrical resistivity of approximately 7.4 Ω·cm and a shrinkage temperature of around 74.5 °C. Furthermore, this material demonstrated remarkable characteristics, including 24-hour biodegradability, a broad sensing range (20 %-120 %), and high sensitivity (with response and recovery times of 300 ms and 100 ms, respectively). Based on multiple cross-linked networks, we propose for the first time the underwater sensing mechanism of “Submarine Tunnel” to achieve strong stability in the water environment. Finally, we simulated the LBPS's response to minor external stimuli, including rainwater exposure, multiangle reactions, and water depth sensitivity. By interfacing with wireless modules and mobile phones, the LBS enabled the execution of emergency SOS signals, highlighting its potential applications in underwater motion monitoring and urgent rescue operations.

Using association mapping and local interval haplotype association analysis to improve the cotton drought stress response

Drought stress has a serious impact on the growth and development of cotton. To explore the relevant molecular mechanism of the drought stress response in cotton, gene mapping based on the QTL interval mapped by simplified genome BSA-seq of the drought-resistance-related RIL population was performed. A QTL region spanning 2.02 Mb on chromosome D07 was selected, and 201 resource materials were genotyped using 9 KASP markers in the interval. After local interval haplotype association analysis, the overlap of the 110 kb peak region confirmed the reliability of this region, and at the same time, the role of GhGF14–30, the only gene in the overlapping region, was modeled in the response of cotton to drought stress. qRTPCR analysis of the materials and population parents proved that this gene plays a role in the drought stress response in cotton. Virus-induced gene silencing proved the importance of this gene in drought-sensitive materials, and drought-resistance-related marker genes also proved that the GhGF14–30 gene may play an important role in the ABA and SOS signaling pathways. This study provides a basis for mining drought stress response functional genes in cotton and lays the foundation for the molecular mechanism of the GhGF14–30 gene in response to drought stress in cotton.

Enhancement of cucumber resistance under salt stress by 2, 4-epibrassinolide lactones.

This study investigated the effects of exogenous 2, 4-epibrassinolide lactone (EBR) on the growth, photosynthetic pigments, antioxidant defense system, ion homeostasis, MAPK cascade and key genes of SOS signaling pathway of cucumber seedlings under salt stress using cucumber "Xinchun 4" as the test material. The experiment was set up with four treatments: foliar spraying of distilled water (CK), 50 mmol.L-1 NaCl (NaCl), 50 mmol.L-1 NaCl+foliar spray of 0.02 μmol.L-1 EBR (EBR+NaCl), and 50 mmol.L-1 NaCl+foliar spray of 24 μmol.L-1 Brassinazole (BRZ) (BRZ+NaCl). The results showed that EBR+NaCl treatment significantly increased plant height, above-ground fresh weight, total root length, total root surface area, average rhizome and photosynthetic pigment content compared to NaCl treatment. Meanwhile, compared with NaCl treatment, EBR+NaCl treatment significantly increased superoxide dismutase, catalase and ascorbate peroxidase (SOD, CAT and APX) activities, significantly promoted the accumulation of osmoregulatory substances (soluble sugars and proline), and thus effectively reduced malondialdehyde (MDA) content and relative electrical conductivity of cucumber leaves. Exogenous spraying of EBR also significantly reduced Na+/K+ under NaCl stress, effectively alleviating the toxic effects of Na+ ions. In addition, exogenous EBR induced the up-regulated expression of CsMAPK3, CsMAPK4, CsMAPK6 and CsMAPK9 genes in the MAPK cascade signaling pathway and CsSOS1, CsSOS2 and CsSOS3 genes in the SOS signaling pathway to enhance salt tolerance in cucumber under NaCl stress. Therefore, exogenous spraying EBR may effectively reduce the damage of salt stress on cucumber seedlings by improving antioxidant capacity, maintaining ion homeostasis and activating salt-tolerant related signaling pathways, which might promote the growth of cucumber seedlings and the establishment of root system morphology. This study provides a reference for EBR to improve the salt tolerance of cucumber.

Tobacco leaf tissue rapidly detoxifies direct salt loads without activation of calcium and SOS signaling.

Salt stress is a major abiotic stress, responsible for declining agricultural productivity. Roots are regarded as hubs for salt detoxification, however, leaf salt concentrations may exceed those of roots. How mature leaves manage acute sodium chloride (NaCl) stress is mostly unknown. To analyze the mechanisms for NaCl redistribution in leaves, salt was infiltrated into intact tobacco leaves. It initiated pronounced osmotically-driven leaf movements. Leaf downward movement caused by hydro-passive turgor loss reached a maximum within 2 h. Salt-driven cellular water release was accompanied by a transient change in membrane depolarization but not an increase in cytosolic calcium ion (Ca2+ ) level. Nonetheless, only half an hour later, the leaves had completely regained turgor. This recovery phase was characterized by an increase in mesophyll cell plasma membrane hydrogen ion (H+ ) pumping, a salt uptake-dependent cytosolic alkalization, and a return of the apoplast osmolality to pre-stress levels. Although, transcript numbers of abscisic acid- and Salt Overly Sensitive pathway elements remained unchanged, salt adaptation depended on the vacuolar H+ /Na+ -exchanger NHX1. Altogether, tobacco leaves can detoxify sodium ions (Na+ ) rapidly even under massive salt loads, based on pre-established posttranslational settings and NHX1 cation/H+ antiport activity. Unlike roots, signaling and processing of salt stress in tobacco leaves does not depend on Ca2+ signaling.

The microbiome-product colibactin hits unique cellular targets mediating host-microbe interaction.

The human microbiota produces molecules that are evolved to interact with the diverse cellular machinery of both the host and microbes, mediating health and diseases. One of the most puzzling microbiome molecules is colibactin, a genotoxin encoded in some commensal and extraintestinal microbes and is implicated in initiating colorectal cancer. The colibactin cluster was discovered more than 15 years ago, and most of the research studies have been focused on revealing the biosynthesis and precise structure of the cryptic encoded molecule(s) and the mechanism of carcinogenesis. In 2022, the Balskus group revealed that colibactin not only hits targets in the eukaryotic cell machinery but also in the prokaryotic cell. To that end, colibactin crosslinks the DNA resulting in activation of the SOS signaling pathway, leading to prophage induction from bacterial lysogens and modulation of virulence genes in pathogenic species. These unique activities of colibactin highlight its ecological role in shaping gut microbial communities and further consequences that impact human health. This review dives in-depth into the molecular mechanisms underpinning colibactin cellular targets in eukaryotic and prokaryotic cells, aiming to understand the fine details of the role of secreted microbiome chemistry in mediating host–microbe and microbe–microbe interactions. This understanding translates into a better realization of microbiome potential and how this could be advanced to future microbiome-based therapeutics or diagnostic biomarkers.

Abstract ND02: MRTX0902: A SOS1 inhibitor for therapeutic intervention of KRAS-driven cancers

Abstract KRAS is the most frequently mutated oncogene in cancer and drives uncontrolled growth through hyperactivation of the MAPK pathway. Significant progress has been made in the past several years to directly target KRASG12C with the FDA approval of sotorasib and the reported clinical activity of adagrasib (MRTX849). Despite these remarkable breakthroughs, additional therapies that enhance the depth and duration of response to KRASG12C inhibitors provide the opportunity to build upon the initial progress. SOS proteins are guanine nucleotide exchange factors (GEFs) that transduce receptor tyrosine kinase (RTK) signaling from the cell surface and facilitate the activation of RAS family proteins. In addition, SOS1 is a target of negative feedback signaling following RAS-mediated activation of the RAF-MEK-ERK cascade. Thus, SOS proteins represent a significant therapeutic node that maintains RAS pathway equilibrium as well as oncogenic signaling dynamics. Here we highlight the discovery and preclinical evaluation of MRTX0902, a potent, selective, and orally bioavailable inhibitor of SOS1 presently in IND-enabling studies. A structure-based approach was used to identify a novel chemical series that disrupts the protein-protein interaction between SOS1 and KRAS, thereby preventing SOS1-mediated GTP-exchange on GDP-bound KRAS. Considering MRTX849 preferentially binds to inactive GDP-bound KRASG12C, targeting SOS1 in this genetic context increases the ability of MRTX849 to bind and inhibit KRASG12C. The combination of MRTX0902 with MRTX849 enhances the depth and durability of an anti-tumor response when compared to MRTX849 alone in pre-clinical KRASG12C tumor models. MRTX0902 augments additional targeted therapies across a variety of RAS-addicted tumors, indicating that SOS1 inhibition is effective against a broad spectrum of mutations within the MAPK pathway. Furthermore, drug-anchored CRISPR experiments with MRTX0902 and MRTX849 uncovered a previously underappreciated functional role of the SOS1 paralog, SOS2, in KRAS-addicted tumors. In addition to aiding in the understanding of SOS and RAS family signaling dynamics, these studies implicate SOS2 as a potential cancer drug target in the context of SOS1/KRASG12C inhibition. In summary, we have used a structure-based approach to discover a SOS1 inhibitor that augments the anti-tumor activity of MRTX849 and additional targeted MAPK pathway inhibitors. We anticipate our findings to translate into the clinic and make an impact in patients with RAS-addicted tumors. Citation Format: John M. Ketcham, Shilpi Khare, Niranjan Sudhakar, David M. Briere, Larry Yan, Jade Laguer, Laura Vegar, Darin Vanderpool, Jill Hallin, Lauren Hargis, Vickie Bowcut, David Lawson, Robin J. Gunn, Anthony Ivetac, Nicole C. Thomas, Barbara Saechao, Natalie Nguyen, Jeffrey Clarine, Lisa Rahbaek, Christopher R. Smith, Aaron C. Burns, Matthew A. Marx, James G. Christensen, Peter Olson, Jacob R. Haling. MRTX0902: A SOS1 inhibitor for therapeutic intervention of KRAS-driven cancers [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr ND02.

Signaling for Abiotic Stress Tolerance in Plants: A Review

Plants copiously rely on intense sensitivity recognition and acclimation mechanisms to cope against various environmental perturbations. Abiotic stresses such as water availability (drought or flooding), salinity, nutrient stress and metal stress aregrievous threatto the global agriculture as they hinder the crop plant to attain its whole genetic potential resulting in the notable yield loss. Signal transduction networks validate the plants in stress signal perception accompanied by transduction than finally inception of the response. Stress signal transduction and its perception is hugely decisive step to conquer these environmental obstacles for the better growth and survival of the crop plant. This review emphasizes on various pathways namely hormone signaling and their cross talk, ROS signaling, ABA signaling, Ion homeostasis, MAPK pathways, SOS signaling and transcriptional factors (TFs). Peculiarly, in future recent biotechnological innovations will help in understanding the gene function and ingress to whole genome sequences provide new guidance for crop refinement.

The Child and Women Safety with Wearable Devices

In today's environment, the safety of children and women is becoming increasingly crucial. Women's crime is rising day by day. To address this problem, a technology-driven solution based on the most recent technical advances can be devised. This is an IoT-based solution that will assist us in effectively combating the conditions. Camera, GPS, GSM, microphone, and voice recognition modules are all hidden inside. The voice command will send an SOS signal to the people on your contact list as well as local authorities. Authorities can rush to the scene of the occurrence and stop it from happening. Immediately when the instruction through voice is turned on, the camera begins recording, and uploading the data to cloud storage. The recordings from the camera will be utilized for finding the criminal.

Structure, Function, and Regulation of the Plasma Membrane Na+/H+ Antiporter Salt Overly Sensitive 1 in Plants.

Physiological studies have confirmed that export of Na+ to improve salt tolerance in plants is regulated by the combined activities of a complex transport system. In the Na+ transport system, the Na+/H+ antiporter salt overly sensitive 1 (SOS1) is the main protein that functions to excrete Na+ out of plant cells. In this paper, we review the structure and function of the Na+/H+ antiporter and the physiological process of Na+ transport in SOS signaling pathway, and discuss the regulation of SOS1 during phosphorylation activation by protein kinase and the balance mechanism of inhibiting SOS1 antiporter at molecular and protein levels. In addition, we carried out phylogenetic tree analysis of SOS1 proteins reported so far in plants, which implied the specificity of salt tolerance mechanism from model plants to higher crops under salt stress. Finally, the high complexity of the regulatory network of adaptation to salt tolerance, and the feasibility of coping strategies in the process of genetic improvement of salt tolerance quality of higher crops were reviewed.

Multipurposed Intelligent ID Card for Social Distancing & Safety Emergency alert systems

Abstract: This proposed invention is related with multipurpose device which is intelligent id card provided to the employee will help track and trace by connecting to the respective corporate server network. This server acts as a central intelligence and provides a dashboard that will help set up and get data and insights. These constantly monitor the smart cards and transmit their position to the central system. Many important multi-tasking tasks can be performed using this smart ID card which has the ability to provide real-time location information and also automatically identify if the person is where they should be. Accidents, such as a person walking into a danger zone, can be easily reported. In the event of a fire, you can quickly find the total people count along with the latest positions. The crowding of places such as offices, shops, workplaces, bathrooms, canteens, etc. it can be reported in real-time in order to avoid any infections. The temperature measurement alone is useless if the readings are not associated with the employee and are recorded to analyses trends. The proposed ID card will keep track of the number of times the employee has washed their hands. If not, a social notification will be raised. With real-time monitoring, you can easily provide daily attendance data to HR for payroll calculation and contract work invoice review. The employee's Bluetooth tag will help track time spent within the authorized area and will sound an alarm if the person enters a danger zone, all in real-time. The employee tag will allow the employee to send an SOS signal in case of any danger or panic situation. It will not be necessary to keep an attendance register. The tag will automatically record the time of entry and exit. A body sensor attached to the ID card will detect if the card is moved away from the body and kept aside. Hence, there is no possibility of cheating. The battery inside the card would last 5 to 10 years. IP 65, therefore resistant to water and rain. No maintenance is required. Keywords: Covid-19 study, Safety Device, Health Tracking, Social distancing, smart id.

An optical sensing system with ratiometric and turn-off dual-mode of CDs@MnO2 nanosheets for the determination of H2O2 and glucose based on a combination of first-order scattering, fluorescence, and second-order scattering

The optical sensor with ratiometric and turn-off dual modes is constructed to detect H2O2 and glucose based on blue fluorescent carbon dots (CDs) and MnO2 nanosheets with great ability of fluorescence quenching and scattering. Employing CDs@MnO2 nanosheets nanocomposite as the probe, H2O2 is detected by simultaneously collecting first-order scattering (FOS, 353.5 nm), fluorescence (440 nm), and second-order scattering (SOS, 710 nm) under the excitation of 350 nm. H2O2 with strong oxidation property can etch the lamellar structure of MnO2 nanosheets into nano-fragments, which made the fluorescence of CDs in the system recover and the scattering intensity (FOS and SOS) of the system decrease significantly. Therefore, the optical sensor combined FOS and fluorescence signals in ratiometric mode, and SOS signal in turn-off mode to realize sensitive determination of H2O2. The linear ranges of ratiometric mode and turn-off mode for H2O2 detection were 0.2–40 and 0.2–15 μM, respectively. And the limits of detection (LODs) of two modes were 73 and 104 nM, respectively. Furthermore, the sensor was also successfully applied to the detection of glucose which can react to produce H2O2. Satisfactorily, the LODs of this sensor for glucose detection were 95 and 113 nM for ratiometric mode and turn-off mode, respectively. This work not only provides a new method for the accurate detection of H2O2 and glucose, but also extends a new idea for the study of the combination of scattering and fluorescence.