Fluorescence Sensing Platforms for Epinephrine Detection Based on Low Temperature Cofired Ceramics

Functional Group-Assisted Fluorescence Sensing Platform for Nanomolar-Level Detection of an Antineoplastic Drug and a Neurotransmitter from Environmental Water and Human Biofluids

A fast, sensitive, selective, and biocompatible dual sensor of an antineoplastic medication (methotrexate) and a neurotransmitter (adrenaline) is still being searched by present-day scientists. To overcome this issue, we have designed a functionalized, robust, bio-friendly luminescent MOF for the sensitive, selective, and rapid monitoring of methotrexate and adrenaline. This probe is the first ever reported MOF-based fluorescence sensor of methotrexate and second only for adrenaline. This fluorescence probe has a very low limit of detection (LOD) of 0.34 and 11.2 nM for adrenaline and methotrexate, respectively. The sensor can detect both the targeted analytes rapidly within 5 s. It can also detect adrenaline and methotrexate from human blood serum and urine accurately and precisely. This reusable sensor is equally efficient in detecting methotrexate from environmental water specimens. Biocompatible, user-friendly, and inexpensive chitosan@MOF@cotton composites were fabricated for the detection of adrenaline and methotrexate from the nanomolar to the micromolar range by the naked eye under a fluorescence lamp. This probe displayed high reproducibility, precision, and accuracy in sensing methotrexate and adrenaline. Fluorescence resonance energy transfer (FRET) and the inner filter effect (IFE) are the possible mechanisms for adrenaline and methotrexate sensing, respectively. The possible mechanism was supported by using required instrumental techniques and theoretical simulations.

Fluorescent-Based Neurotransmitter Sensors: Present and Future Perspectives

Neurotransmitters (NTs) are endogenous low-molecular-weight chemical compounds that transmit synaptic signals in the central nervous system. These NTs play a crucial role in facilitating signal communication, motor control, and processes related to memory and learning. Abnormalities in the levels of NTs lead to chronic mental health disorders and heart diseases. Therefore, detecting imbalances in the levels of NTs is important for diagnosing early stages of diseases associated with NTs. Sensing technologies detect NTs rapidly, specifically, and selectively, overcoming the limitations of conventional diagnostic methods. In this review, we focus on the fluorescence-based biosensors that use nanomaterials such as metal clusters, carbon dots, and quantum dots. Additionally, we review biomaterial-based, including aptamer- and enzyme-based, and genetically encoded biosensors. Furthermore, we elaborate on the fluorescence mechanisms, including fluorescence resonance energy transfer, photon-induced electron transfer, intramolecular charge transfer, and excited-state intramolecular proton transfer, in the context of their applications for the detection of NTs. We also discuss the significance of NTs in human physiological functions, address the current challenges in designing fluorescence-based biosensors for the detection of NTs, and explore their future development.

Label-Free Detection of Epinephrine Using Flower-like Biomimetic CuS Antioxidant Nanozymes

A biosensor comprising crystalline CuS nanoparticles (NPs) was synthesized via a one-step simple coprecipitation route without involvement of a surfactant. The powder X-ray diffraction method has been used to evaluate the crystalline nature and different phases consist of the formation of CuS NPs. Mainly hexagonal unit cells consist of the formation of CuS NP unit cells. Most of the surfaces are covered with rhombohedral microparticles with a smooth exterior and surface clustering, examined by SEM images, and the shape of NPs was spherical, having an average size of 23 nm, as confirmed by TEM analysis. This study has focused on the peroxidase-mimicking activity, superoxide dismutase (SOD)-mimicking activity, and chemosensor-based colorimetric determination and detection of epinephrine (EP) neurotransmitters with excellent selectivity. The CuS NPs catalyzed the oxidation of the oxidase substrate 3, 3-5, 5 tetramethyl benzidine (TMB) with the help of supplementary H2O2 that followed Michaelis-Menten kinetics with excellent Km and Vmax values calculated by the Lineweaver-Burk plot. Taking advantage of the drop in absorbance upon introduction of EP for the CuS NPs-TMB/H2O2 system, a colorimetric route has been developed for selective and real-time detection of EP. The sensitivity of the new colorimetric probe was vibrant, having a linear range of 0-16 μM, and achieved a low limit of detection of 457 nM. Moreover, the present nanosystem exhibited appreciable SOD-mimicking activity which could effectively remove O2•- from commercial cigarette smoke, along with it acting as a potential radical scavenger as well. The new nanosystem effectively scavenged •OH, O2.-, and metal chelation which were investigated calorimetrically.

MOF-Fabric Composites Based on a Multi-Functional MOF as Luminescent Sensors for a Neurotransmitter and an Anti-Cancer Drug

A biocompatible, reliable, fast, and nanomolar-level dual-functional sensor for a neurotransmitter (e.g., adrenaline) and an anti-cancer drug (e.g., 6-mercaptopurine (6-MP)) is still far away from the hand of modern-day researchers. To address this issue, we synthesized an aqua-stable, bio-friendly, thiourea-functionalized Zr(IV) metal-organic framework (MOF) for selective, rapid sensing of adrenaline and 6-MP with ultra-low limit of detection (LOD for adrenaline = 1.9 nM and LOD for 6-MP = 28 pM). This is the first MOF-based fluorescent sensor of both the targeted analytes. The sensor not only can detect adrenaline in HEPES buffer medium but also in different bio-fluids (e.g., human urine and blood serum) and pH media. It also exhibited 6-MP sensing ability in aqueous medium and in various wastewater specimens and pH solutions. For the quick and on-site detection of this neuro-messenger (adrenaline) and the drug (6-MP), cost-effective sensor-coated cotton fabric composites were fabricated. The MOF@cotton fabric composite is capable of detecting both the analytes up to the nanomolar level by the naked eye under UV light. The sensor can be recycled up to five times without significantly losing its efficiency. The Förster resonance energy transfer in the presence of adrenaline and inner-filter effect in the presence of 6-MP are the most likely reasons behind the quenching of the MOF's fluorescence intensity, which were proved with the help of appropriate instrumental techniques.

New Trends in Fluorescent Nanomaterials-Based Bio/Chemical Sensors for Neurohormones Detection-A Review

The study of neurotransmitters and stress hormones allows the determination of indicators of the current stress load in the body. These species also create a proper strategy of stress protection. Nowadays, stress is a general factor that affects the population, and it may cause a wide range of serious disorders. Abnormalities in the level of neurohormones, caused by chronic psychological stress, can occur in, for instance, corporate employees, health care workers, shift workers, policemen, or firefighters. Here we present a new nanomaterials-based sensors technology development for the determination of neurohormones. We focus on fluorescent sensors/biosensors that utilize nanomaterials, such as quantum dots or carbon nanomaterials. Nanomaterials, owing to their diversity in size and shape, have been attracting increasing attention in sensing or bioimaging. They possess unique properties, such as fluorescent, electronic, or photoluminescent features. In this Review, we summarize new trends in adopting nanomaterials for applications in fluorescent sensors for neurohormone monitoring.

'Laccase-like' properties of coral-like silver citrate micro-structures for the degradation and determination of phenolic pollutants and adrenaline

Laccases are multicopper containing oxidase enzymes that are highly important in environmental remediation and biotechnology. To date, complex Copper containing materials have been reported as laccase mimic, and the possibility of a non-Cu laccase mimic remained unknown. In this work, we report an exceptionally simple functional laccase mimic based on coral-like silver citrate (AgCit) microstructures. The AgCit was synthesized by a simple precipitation method and was found to possess excellent laccase-like activity capable of oxidizing phenolic substrates and the endocrine hormone adrenaline. Compared to the natural laccase enzyme, our reported laccase-mimic has a higher υ_max and lower K_m value using adrenaline as a substrate. In addition, the AgCit laccase mimic was observed to be stable at extreme pH, higher temperature, and suitable for long-term storage at room temperature. The laccase-like properties of the AgCit nanozyme were successfully applied for the quantification and degradation of various phenolic pollutants and the adrenaline hormone.