Fluorescent-based nanosensors for selective detection of a wide range of biological macromolecules: A comprehensive review

A contemporary overview on quantum dots-based fluorescent biosensors: Exploring synthesis techniques, sensing mechanism and applications

In the epoch of bioinformatics, pivotal biomedical scrutiny and clinical diagnosis hinge upon the unfolding of highly efficacious biosensors for intricate and targeted identification of specific biomolecules. In pursuit of developing robust biosensors endowed with superior sensitivity, precise selectivity, rapid performance, and operational simplicity, semiconductor QDs have been acknowledged as pivotal and advantageous entities. In this review, we present a comprehensive analysis of the latest unfolding within the domain of QDs used in fluorescent biosensors for the detection of diverse biomolecular entities, encompassing proteins, nucleic acids, and a range of small molecules, with an emphasis on the synthesis methodologies of QDs employed and mechanism behind sensing. Additionally, this review delves into several pivotal facets of QD-based fluorescent biosensors in detail, such as surface functionalization methodologies aimed at enhancing biocompatibility and improving target specificity. The challenges and future perspectives of QD-based fluorescent biosensors are also considered, emphasizing the necessity of ongoing multidisciplinary research to realize their full potential in enhancing personalized medicine and biomedical diagnostics.

Rapid identification of multiplexed pathogens via a two-step dual-channel fluorescence turn-on array

Bacterial infections have been an increasingly serious threat to human health. However, the rapid identification of multiplexed bacteria remains challenging due to their intricate composition. Herein, we developed a two-step, dual-channel fluorescence "turn-on" sensor array that sequentially amplifies signals via Indicator Displacement Analysis (IDA) and Aggregation-Induced Emission (AIE). Three weakly fluorescent, positively charged conjugated fluorophores (A1-A3) with AIE properties were designed to form electrostatic complexes (C1-C3) with negatively charged graphene oxide (GO). Upon addition of bacteria, fluorophores were released from the electrostatic complexes via IDA, resulting in fluorescence turn-on. These fluorophores then aggregated on the bacterial surface, further enhancing fluorescence. This array accurately differentiated among 10 distinct bacterial strains, achieving 98.3 % classification accuracy within 30 s. Finally, the approach facilitated semi-quantitative bacterial analysis, multiplex identification, and robust differentiation in artificial urine samples, presenting a promising method for early infectious disease diagnosis.

Small molecular fluorescent probes featuring protein-assisted functional amplification for improved biosensing and cancer therapeutics

In recent years, small molecular fluorescent probes have significantly advanced biosensing and cancer therapy, enabling applications such as target detection, cellular imaging, fluorescence-guided surgery, and phototherapy. However, conventional small molecular probes face limitations, including low biocompatibility, poor stability, and weak signal intensity. Protein-coordinated fluorescent probes have emerged as a promising solution, leveraging protein-assisted functional amplification to address these challenges. Mechanisms such as environmental shielding, conformational restriction, charge stabilization, and increased local concentration collectively enhance fluorescence emission and phototherapeutic efficacy. This article reviews recent progress (primarily within the last five years) in protein-coordinated fluorescent probes for biosensing and cancer therapy. It begins with a systematic summary of the interaction strategies between proteins and fluorescent probes and details key mechanisms behind protein-assisted functional amplification. Subsequently, the applications of these probes in biosensing and cancer therapy are comprehensively concluded. Finally, current challenges and future prospects are discussed in depth. This review aims to refine design strategies for protein-coordinated fluorescent probes and inspire innovative approaches in biosensing and cancer therapy.

The first example of white-light emission based on pyrimido[4',5':4,5]thieno[2,3-d]pyrimidine moiety: Synthesis, photophysical, and antimicrobial studies

A series of new AIE systems based on the pyrimidothienopyrimidine skeleton were efficiently synthesized and fully characterized. These compounds exhibited weak emission in solution but strong solid-state fluorescence with a red shift. Notably, compound 16 displayed unique white-light emission from a single-component system and tunable emission colors in DMF/water mixtures. This dual emission behavior, arising from AIE and excimer formation, is unprecedented for pyrimidothienopyrimidine derivatives. Although compounds 9a and 9b exhibited AIEE behavior, compounds 15c and 18 demonstrated AIE behavior, with significantly enhanced fluorescence intensity upon water addition. Moreover, most synthesized compounds exhibited moderate to strong antimicrobial activity against various bacterial and fungal strains, suggesting their potential for biological applications.

Detection of Cancer Biomarkers: Review of Methods and Applications Reported from Analytical Perspective

One in five deaths in developed countries is related to cancer. The cancer prevalence is likely to grow with aging population. The affordable and accurate early diagnostics of cancer based on detection of cancer biomarkers at low concentration during its early stages is one of the most efficient way to decrease mortality and human suffering from cancer. The data from 201 analytical papers are tabulated in 9 tables, illustrated in 8 figures and used for comparative analysis of methods applied for cancer biomarker detection, including polymerase chain reaction, Loop-mediated isothermal amplification (LAMP), mass spectrometry, enzyme-linked immunosorbent assay, electroanalytical methods, immunoassays, surface enhanced Raman scattering, Fourier Transform Infrared and others in terms of above-mentioned performance parameters. Median and/or average limit of detection (LOD) are calculated and compared between different analytical methods. We also described and compared LOD of the methods used for detection of three frequently detected cancer biomarkers: carcinoembryonic antigen, prostate-specific antigen and alpha-fetoprotein. Among those methods of detection, the reported electrochemical sensors often demonstrate relatively high sensitivity/low LOD while they often have a moderate instrumental cost and fast time to results. The review tabulates, compares and discusses analytical papers, which report LOD of cancer biomarkers and comprehensive quantitative comparison of various analytical methods is made. The discussion of those techniques applied for cancer biomarker detection included brief summary of pro and cons for each of those methods.

Water-Responsive Fluorescence and Room-Temperature Phosphorescence Carbon Dots for Trace Water Detection in Ethylene Glycol and Multimodal Anticounterfeiting

Identifying trace water in ethylene glycol is essential for maintaining stringent quality control in chemical processes and ensuring product purity. However, the development of highly sensitive detection methods for aqueous impurities within this viscous solvent presents significant challenges, primarily arising from the strong intermolecular hydrogen bonding network within ethylene glycol, which not only masks the presence of water but also interferes with conventional analytical techniques. This work introduces a novel fluorescence-based detection method that combines simplicity, efficiency, and rapid response by leveraging water-responsive carbon dots (CDs). Specifically, we synthesized water-responsive carbon dots (WCDs) that exhibit enhanced fluorescence in anhydrous ethylene glycol. Notably, the introduction of water induces a concentration-dependent fluorescence enhancement at 394 nm, establishing a linear correlation within the 0-0.284% (v/v) water content range (detection limit: 0.017%, 3σ/S) with a remarkably low. By exploiting the hydrogen bonding between WCDs and cellulose paper matrices, the triplet excited states are effectively stabilized, thereby enabling green room-temperature phosphorescence (RTP) emission. This enables precise modulation of the WCDs' aggregation-dispersion states through controlled water/ethanol addition, a mechanism that drives stimulus-responsive transitions between fluorescence and RTP. These tunable optical properties not only validate the detection mechanism but also create new opportunities for developing dual-mode dynamic anticounterfeiting technologies.

Development of a smartphone integrated 3D-printed point of care platform for sensitive detection of bilirubin

Strategic design and development of nanomaterials-based detection platforms specific to critical biomarkers like bilirubin holds immense promise for revolutionizing early disease detection. Bilirubin (BR) plays a pivotal role as a biomarker for liver function, making accurate and timely detection of BR crucial for diagnosing and monitoring of liver diseases. In this work, we synthesized blue light emitting graphene quantum dots (GQDs) via a single step pyrolysis method, which exhibited excellent photostability and biocompatibility. Under optimal conditions, the fluorescence of GQDs was significantly quenched with the successive addition of BR achieving an ultra-low detection limit (38.96 nM) over a concentration range of 0.18 μM-14.29 μM with high selectivity, and rapid response towards free BR. The sensing mechanism was identified as the inner filter effect after extensive investigations. Thereafter, the sensor system was directly applied to human serum and urine samples and was further compared with the conventional Jendrassik and Grof method, yielding satisfactory recoveries. To demonstrate the sensor system's potential for real world applications, we designed and fabricated a prototype point-of-care device (POC) through 3D printing, incorporating paper microfluidic devices and fluorescence image analysis-based android application through smartphone. The compact 3D-printed POC device achieved a detection limit of 114.66 nM for BR detection, proving to be a promising platform for affordable, efficient and rapid BR detection.

Application of metal stable isotopes labeling and elemental mass spectrometry for biomacromolecule profiling

Biomacromolecules including proteins and nucleic acids are widely recognized for their pivotal and irreplaceable role in maintaining the normal functions of biological systems. By combining metal stable isotope labeling with elemental mass spectrometry, researchers can quantify the amount and track the spatial distribution of specific biomacromolecules in complex biological systems. In this review, the probes classification and metal stable isotope labeling strategies are initially summarized. Secondly, the technical characteristics and working principle of the elemental mass spectrometry techniques including inductively coupled plasma mass spectrometry and secondary ion mass spectrometry are introduced to achieve highly sensitive detection of multiple biomacromolecules at molecular, cellular and tissue levels. Lastly, we underline the advantages and limitations of elemental mass spectrometry combined with metal stable isotope labeling strategies, and propose the perspectives for future developments.

Latest advancements and trends in biomedical polymers for disease prevention, diagnosis, treatment, and clinical application

Biomedical polymers are at the forefront of medical advancements, offering innovative solutions in disease prevention, diagnosis, treatment, and clinical use due to their exceptional physicochemical properties. This review delves into the characteristics, classification, and preparation methods of these polymers, highlighting their diverse applications in drug delivery, medical imaging, tissue engineering, and regenerative medicine. We present a thorough analysis of the recent advancements in biomedical polymer research and their clinical applications, acknowledging the challenges that remain, such as immune response management, controlled degradation rates, and mechanical property optimization. Addressing these issues, we explore future directions, including personalization and the integration of nanotechnology, which hold significant potential for further advancing the field. This comprehensive review aims to provide a deep understanding of biomedical polymers and serve as a valuable resource for the development of innovative polymer materials in both fundamental research and clinical practice.

Advances in mercury ion sensing using BODIPY-based compounds: a sexennial update

Pollution from mercury ions (Hg2+) continues to pose a significant threat to the environment and public health because of its extreme toxicity and bioaccumulative nature. BODIPY-based compounds are emerging as strong candidates for creating selective and sensitive chemosensors for mercury ion detection. Their structural tunability facilitates the introduction of various functional groups, improving their binding affinity and specificity toward mercury ions. This review elucidates various sensing mechanisms and provides comprehensive insights into the performance of these sensors, particularly with regard to selectivity, sensitivity, and detection limits. The synthetic routes for synthesizing the chemosensors are mentioned in detail. Given their reliability and flexibility, BODIPY-based sensors are poised to make significant contributions in the fields of both sensors and analytical chemistry.

Development of Fluorescence-Based Method for Dopamine Determination Using o-Phthaldialdehyde and 3-Mercaptopropyltriethoxysilane

Nanomaterials and sensors play an important role in modern technologies, including medical diagnostics and biochemical research. This work presents the possibility of using o-Phthaldialdehyde (OPA) in combination with 3-mercaptopropyltriethoxysilane (MPTES) to develop a dopamine-responsive sensor. During the experiment, these materials were used at different pH and ratios to determine the optimal parameters for obtaining high fluorescence intensity of the reaction product. The data obtained demonstrate a linear relationship between the fluorescence response (λex/λem = 340/460 nm) of OPA/MPTES and dopamine concentration in the range of 0.1-3.0 µM at a pH of 8, and the detection limit was 8.7 nM. The obtained results confirm the potential of OPA/MPTES as a sensing component for the detection of dopamine.

Establishing Detection Methods for Okadaic Acid Aptamer-Target Interactions: Insights from Computational and Experimental Approaches

The binding interactions between okadaic acid (OA) aptamers and OA molecules are crucial for developing effective detection methods. This study aims to identify the recognition site and establish a reliable detection protocol through computational simulations and experimental validations. After determining the target sequence (OA-2), molecular docking simulations using Sybyl-X and H-dock were conducted to predict the binding affinity and interaction sites of OA aptamers with their targets. These predictions were subsequently validated through experiments based on the Förster resonance energy transfer (FRET) principle. The combined approach not only confirmed the computational predictions, identifying the "major region" as the recognition basis of OA-2, but also provided deeper insights into the binding mechanisms. Subsequently, a classical AuNPs-aptamer colorimetric detection method was established based on the OA-2 sequence and applied to the detection of real shellfish samples, achieving a limit of quantification (LOQ) of 5.0 μg kg-1. The recoveries of OA in spiked samples ranged from 79.0% to 122.9%, with a relative standard deviation (RSD) of less than 14.7%. The results of this study contribute to the development of robust detection methods for OA aptamer-target interactions, enhancing the potential for practical applications in toxin detection and monitoring.

Applications of Functionalized Carbon-Based Quantum Dots in Fluorescence Sensing of Iron(III)

Iron, an essential trace element exhibits detrimental effects on human health when present at higher or lower concentration than the required. Therefore, there is a pressing demand for sensitive and selective detection of Fe3+ in water, food etc. Unfortunately, in several instances, the traditional approaches suffer from a number of shortcomings like complicated procedures, limited sensitivity, poor selectivity and more expensive and time consuming. The scope of optical tuning and excellent photophysical properties of carbon- based nanomaterials like carbon dots (C-dots) and graphene dots (g-dots) have made them promising optical sensors of metal ions. Moreover, high surface area, superior stability of such materials contributes towards the fruitful development of sensors. The present review offered critical information on the fabrication and fluorimetric applications of these functional nanomaterials for sensitive and selective detection of Fe3+. An in-depth discussion on fluorescent C-dots made from naturally occurring materials and chemical techniques were presented. Effect of doping in C-dots was also highlighted in terms of improved fluorescence response and selectivity. In a similar approach g-dots were also discussed. Many of these sensors exhibited great selectivity, superior sensitivity, high quantum yield, robust chemical and photochemical stability and real-time applicability. Further improvement in these factors can be targeted to develop new sensors.

Use of Quantum Dots as Nanotheranostic Agents: Emerging Applications in Rare Genetic Diseases

Rare genetic diseases (RGDs) affect a small percentage of the global population but collectively have a substantial impact due to their diverse manifestations. Although the precise reasons behind these diseases remain unclear, roughly 80% of cases are genetically linked. Recent efforts focus on understanding pathology and developing new diagnostic and therapeutic approaches for RGDs. However, there persists a gap between fundamental research and clinical therapeutic approaches, where advancements in nanotechnology offer promising improvements. In this context, nanosized light-emitting quantum dots (QDs), ranging from 2-10 nm, are promising materials for diverse applications. Their size-tunable light emission, high quantum yield, and photostability allow for precise tracking of cargo. Additionally, QDs can be functionalized with therapeutic agents, antibodies, or peptides to target specific cellular pathways, enhancing treatment efficacy while minimizing side effects. By combining diagnostic and therapeutic capabilities in a single platform, QDs thus offer a versatile and powerful approach to tackle rare genetic disorders. Despite several reviews on various therapeutic applications of QDs, their utilization in the specific domain of RGDs is not well documented. This review highlight QDs' potential in diagnosing and treating certain RGDs and addresses the challenges limiting their application.

Exploring the frontiers of emerging sensing of silver nanoprisms: recent progress and challenges

In recent years, the development and use of nanomaterials have transformed numerous aspects of biomedical science. Nanomaterials have played a pivotal role in advancing disease diagnosis and treatment across a wide range of applications. Within this scope, silver nanoprisms (AgNPrs) stand out due to their remarkable properties, such as extensive surface area, chemical robustness, and tunable electrical conductivity, making them excellent candidates for biomedical purposes. By tailoring these nanomaterials through functionalization or coating surface, their multifunctionality can be enhanced, unlocking new opportunities for their application in areas such as diagnosis, imaging, and therapeutic intervention. This review begins with an overview of AgNPrs' synthesis techniques and their unique physicochemical characteristics. Recent advancements in analytical methods utilizing AgNPrs, categorized by sensing mechanisms such as optical and electrochemical approaches, are highlighted in the context of diagnostics. Lastly, the challenges and future prospects of bringing AgNPr-based technologies to commercialization and integrating them into disease diagnostics and medical treatment are explored. The integration of AgNPrs in disease therapy holds promise for the development of advanced chemotherapy agents that effectively address the challenges of efficient cancer treatment looking ahead, the ongoing advancement of nanocarrier systems comprising AgNPrs-based molecules holds great promise for improving the quality of life for patients worldwide.

An Optoelectronic Sensing Real-Time Glucose Detection Film Using Photonic Crystal Enhanced Rare Earth Fluorescence and Additive Manufacturing

In this research, a novel detection method employing rare-earth upconversion nanoparticle (UCNP) as the core, coated with MnO2 nanosheets is designed, which formed a color and fluorescence dual-responsive UCNP composite material, MnO2-modified NaYF4:Yb,Tm@NaYF4. By enabling both colorimetric and fluorescence methods simultaneously, this composite material allows for the detection of glucose concentration under different conditions, while exhibiting strong resistance to environmental interference, chemical stability, and accuracy. To further enhance the sensitivity of the detection method, a photonic crystals (PCs)-PDMS array where polymethyl methacrylate PCs are deposited onto a substrate composed of PDMS-glass slice with hydrophobic surfaces is developed. This array can serve as a substrate that specifically reflected blue light while allowing other colors of light to pass through, which effectively reduced background signal interference and improved detection sensitivity (1.2 µm) with a wider linear range (20-800 µm). Finally, a portable fluorescence intensity detection device is designed to enhance the portability of the platform. Numerous experimental results demonstrated that this research significantly improved the sensitivity of glucose detection, providing new research directions for the field of fluid biomarker detectio.

Optical Bionanosensors for Sepsis Diagnostics

Sepsis is a global health challenge, characterized by a dysregulated immune response, leading to organ dysfunction and death. Despite advances in medical care, sepsis continues to claim a significant toll on human lives, with mortality rates from 10-25% for sepsis and 30-50% for septic shock, making it a leading cause of death worldwide. Current diagnostic methods rely on clinical signs, laboratory parameters, or microbial cultures and suffer from delays and inaccuracies. Therefore, there is a pressing need for novel diagnostic tools that can rapidly and accurately identify sepsis. This review highlights advances in biosensor development that could ultimately lead to faster and more accurate sepsis diagnostics. The focus is on nanomaterial-based optical approaches that promise rapid diagnostics without the need for large equipment or trained personnel. An overview of sepsis is provided, highlighting potential molecular targets and the challenges they present for assay development. The requirements for an ideal point-of-care test (POC) are discussed, including speed, simplicity, and cost-effectiveness. Different nanomaterials suitable for various optical detection methods are reviewed and innovative nanosensors are discussed for sepsis diagnostics, focusing on chemical design and approaches to increase selectivity by multiplexing.

A ratiometric fluorescent sensor based on dual-emitting carbon dots for the rapid detection of sulfite

Sulfur dioxide (SO2) derivatives are typically employed as antioxidants in food and pharmaceutical processing. However, excessive sulfite intake could trigger serious health problems. Hence, it is urgent to establish a rapid and effective system for monitoring SO2. This study adopted a one-step hydrothermal method to synthesize dual-emitting nitrogen-doped carbon quantum dots (CECDs) and developed a ratiometric sensor for sulfite using CECDs-Cr (VI) composites. The emission intensity ratio (I440/I500) of the CECDs-Cr (VI) composites increased considerably with the addition of HSO3-. A method based on the ratiometric sensor was established for SO2 derivatives with advanced efficiency and excellent linearity over a broad concentration range of 0-500 μM (R2 = 0.9946). Four medicine-food homology materials (MFHMs) fumigated with sulfur have been accurately detected using this approach. Furthermore, a portable test tube was prepared to achieve rapid and semi-quantitative detection of SO2 residues and applied to real samples. This work presents an effective approach to develop a rapid on-site detection platform for sulfite residues in food and pharmaceuticals.

An activatable "AIE + ESIPT" fluorescent probe for dual-imaging of lipid droplets and hydrogen peroxide in drug-induced liver injury model

BACKGROUND

Drug-induced liver injury (DILI) is one of the most common liver diseases. The crucial role of lipid droplets (LDs) and hydrogen peroxide (H2O2), two important biomarkers in the pathophysiology of DILI, has spurred considerable efforts to accurately visualize H2O2 and LDs for elucidating their functions in the progression of DILI. However, construction of a single fluorescent probe that is able to simultaneously image H2O2 and LDs dynamics remains to be a challenging task. Therefore, it is of great demand to develop a novel fluorescent probe for tracking the LDs status and H2O2 fluctuation in drug-induced liver injury.

RESULTS

We developed an "AIE + ESIPT" fluorescent probe TPEHBT for dual-imaging of LDs and H2O2 during DILI process. TPEHBT displayed greatly enhanced fluorescent response to H2O2 by generating an excited state intramolecular proton transfer (ESIPT) fluorophore TPEHBT-OH with aggregation induced emission (AIE) properties. TPEHBT exhibits high selectivity, sensitivity (LOD = 4.73 nM) and large Stokes shift (320 nm) to H2O2. Interestingly, TPEHBT can light up LDs with high specificity. The probe was favorably applied in the detection of endogenous and exogenous H2O2 in living cells, and notably in the simultaneous real-time visualization of H2O2 generation and LDs accumulation during DILI process. Moreover, TPEHBT was able to image H2O2 generation in zebrafish animal model with APAP-induced liver injury.

SIGNIFICANCE

For the first time, probe TPEHBT was applied in the dual-imaging of H2O2 fluctuation and LDs status in APAP-induced liver injury model in vitro and in vivo. The present findings strongly suggest that TPEHBT is a promising tool for monitoring H2O2 and LDs dynamics in DILI progression.

Translocation mechanism of anticancer drugs through membrane with the assistance of graphene quantum dot

In recent years, as a new type of quasi-zero-dimensional nanomaterials, graphene quantum dots (GQDs) have shown excellent performance in advanced drug targeted delivery and controlled release. In this work, the delivery process of model drugs translocating into POPC lipid membrane with the assistance of GQDs was investigated via molecular dynamics (MD) simulation. Our simulation results demonstrated that a single doxorubicin (DOX) or deoxyadenine (DA) molecule is difficult to penetrate into the cell membrane. GQD7 could form sandwich-like structure with DOX and assist DOX to enter into the POPC membrane. However, due to the weak interaction with DA, both GQD7 and GQD19 can not assist DA translocating the POPC membrane in the limited MD simulation time. The drug delivery process for DOX could be divided into two steps: 1. GQDs and DOX aggregated into a cluster; 2. the aggregates enter into the POPC membrane. In all our simulation systems, if GQDs loaded with model drugs and entered the cell membrane, it had little effect on the cell membrane structure, and the cell membrane could maintain high integrity and stability. These results may promote the molecular design and application of GQD-based drug delivery systems.

Multiplexed bacterial recognition based on "All-in-One" semiconducting polymer dots sensor and machine learning

The accurate discrimination of bacterial infection is imperative for precise clinical diagnosis and treatment. Here, this work presents a simplified sensor array utilizing "All-in-One" Pdots for efficient discrimination of diverse bacterial samples. The "All-in-One" Pdots sensor (AOPS) were synthesized using three components that exhibit fluorescence resonance energy transfer (FRET) effect, facilitating the efficient integration of multiple discrimination channels to generate specific fluorescence response patterns through a single detection under single-wavelength excitation. Additionally, machine learning techniques were employed to visually represent the fluorescence response patterns of AOPS upon exposure to bacterial metabolites derived from diverse bacterial species. The as-prepared sensor platform demonstrated excellent performance in analyzing eight common bacteria, drug-resistant strains, mixed bacterial samples, bacterial biofilms and real samples, presenting significant potential in the identification of complex samples for bacterial analysis.

A clenbuterol detection method based on magnetic separation up-conversion fluorescent probe

In this study, a fluorescence detection method combining aptamer-modified up-conversion nanoparticles (UCNPs) and magnetic nanoparticles (MNPs) was developed for detection of Clenbuterol (CLB). The aptamer-modified magnetic NPs captured CLB, which reacted with the aptamer-modified UCNPs and generated a sandwich complex. The aptamer-modified UCNPs acted as a fluorescence source. The MNP-CLB-UCNP complex was retrieved from the solution using an magnetic field, and the fluorescence intensity was detected by fluorescence spectrophotometry with excitation and emission spectra at 980 nm and in the 400-800 nm region, respectively. The results showed that the fluorescence intensity gradually increased with increasing concentrations of CLB with a good specify. The method was highly sensitive for the quantification of CLB, with a limit of detection of 0.304 ng mL-1. The recovery rate of CLB from pork samples ranged from 84 % to 94.87 %. This fluorescence method enables the sensitive, precise, and accurate quantification of CLB residues in pork samples.

Synthesis and applications of luminescent metal organic frameworks (MOFs) for sensing dipicolinic acid in biological and water samples: a review

The detection of trace quantities of 2,6-dipicolinic acid (DPA) in real-world samples is crucial for early disease diagnosis and routine health monitoring. Metal-organic frameworks (MOFs), recognized for their diverse structural architectures, have emerged as advanced multifunctional hybrid materials. One of the most notable properties of MOFs is their luminescence (L), which can arise from structural ligands, guest molecules, and emissive metal ions. Luminescent MOFs have shown significant promise as platforms for sensor design. This review highlights the application of luminescent MOFs in the detection of DPA in biological and aqueous environments. It provides a comprehensive discussion of the various detection strategies employed in luminescent MOF-based DPA sensors. Additionally, it explores the origins of L in MOFs, their synthesis, and the mechanisms underlying their sensing capabilities. The article also addresses key challenges and limitations in this field, offering practical insights for the development of efficient luminescent MOFs for DPA detection.

Carbon quantum dots in N,N'-Dicyclohexylcarbodiimide assisted cellulose: A fluorescence sensitive approach for ex vivo glucose monitoring in human serum

Bioactive functional materials have been focused recently because of their superior properties due to structural orientations. Herein, carbon quantum dots (CQDs) encapsulated chemically modified carboxymethyl cellulose (CMC) nanocomposites are designed for non-enzymatic ex vivo glucose sensing by a low-cost green technique. The N,N'-Dicyclohexylcarbodiimide (DCC) assisted Steglich esterification between CMC and glucose is responsible for the fluorescence "Turn ON-OFF" mechanism behind glucose detection. The in vitro sensing study derived a limit of detection (LOD) of 7 nM for glucose covering two linear ranges from 0 to 0.06 mM (R2 = 0.9346) and 1.28 to 61.44 mM (R2 = 0.9704). The sensing system maintained excellent stability under extreme ionic strength and pH conditions and the high selectivity is successfully studied against interferents such as homologous sugars, amino acids, cations, and anions. Clinical potential of the proposed sensor is validated through direct testing in human blood samples against commercial glucometer. The sensor proved its reliability with recovery rates of 100 ± 5 % confirming its promising application in glucose monitoring towards effective diabetes management.

Carbon nanomaterial-based aptasensors for rapid detection of foodborne pathogenic bacteria

Each year, millions of people suffer from foodborne illness due to the consumption of food contaminated with pathogenic bacteria, which severely challenges global health. Therefore, it is essential to recognize foodborne pathogens swiftly and correctly. However, conventional detection techniques for bacterial pathogens are labor-intensive, low selectivity, and time-consuming, highlighting a notable knowledge gap. A novel approach, aptamer-based biosensors (aptasensors) linked to carbon nanomaterials (CNs), has shown the potential to overcome these limitations and provide a more reliable method for detecting bacterial pathogens. Aptamers, short single-stranded DNA (ssDNA)/RNA molecules, serve as bio-recognition elements (BRE) due to their exceptionally high affinity and specificity in identifying foodborne pathogens such as Salmonella spp., Escherichia coli (E. coli), Listeria monocytogenes, Campylobacter jejuni, and other relevant pathogens commonly associated with foodborne illnesses. Carbon nanomaterials' high surface area-to-volume ratio contributes unique characteristics crucial for bacterial sensing, as it improves the binding capacity and signal amplification in the design of aptasensors. Furthermore, aptamers can bind to CNs and create aptasensors with improved signal specificity and sensitivity. Hence, this review intends to critically review the current literature on developing aptamer functionalized CN-based biosensors by transducer optical and electrochemical for detecting foodborne pathogens and explore the advantages and challenges associated with these biosensors. Aptasensors conjugated with CNs offers an efficient tool for identifying foodborne pathogenic bacteria that is both precise and sensitive to potentially replacing complex current techniques that are time-consuming.

Novel Spectroscopic Studies of the Interaction of Three Different Types of Iron Oxide Nanoparticles with Albumin

In the present work, we studied the interactions of three types of iron oxide nanoparticles (IONPs) with human serum albumin (HSA) by fluorescence and UV-Vis spectroscopy. The determined binding parameters of the reactions and the thermodynamic parameters, including ΔHo, ΔSo, and ΔGo indicated that electrostatic forces play a major role in the interaction of IONPs with HSA. These measurements indicate a fluorescent quenching mechanism based on IONPs-HSA static complex formation. Our study shows that the interaction between HSA and IONPs depends on the nanoparticle structure. The interaction between IONPs and HSA was found to be spontaneous, exothermic, and entropy-driven. HSA was shown to interact moderately with IONPs obtained with plant extracts of Uncaria tomentosa L. (IONP@UT) and Clinopodium vulgare L. (IONP@CV), and firmly with IONPs prepared with Ganoderma lingzhi (Reishi) extract (IONP@GL), via ground-state association. Analysis by modified Stern-Volmer approximation indicates that the quenching mechanism is static. Our study significantly improves our understanding of the mechanisms of interaction, distribution, and transport involved in the interaction between proteins and IONPs. It provides crucial insights into the functional perturbations of albumin binding capacity and the effects of IONPs on the stability and structural modifications of plasma carrier proteins.

Carbon dot-graphene oxide-based luminescent nanosensor for creatinine detection in human urine

A fluorescence (FL)-based nanosensor has been devised for creatinine (CR) detection in human urine specimens. The proposed nanosensor utilized a nanocomposite (NC) of carbon dots (CDs) and graphene oxide (GO). The formation of CDs/GO NC reduced the CD FL emission (λexcitation = 390 nm, λemission = 461 nm) by ~ 75%. With the introduction of CR to the NC, the CD emission intensity was reinstated by approximately 70%. The linear detection range for CR was 10-5 to 0.1 mg dL-1 (R2 = 0.998), with a limit of detection of 4.3 × 10-2 mg dL-1. Additionally, CDs/GO NC exhibited outstanding consistency and specificity in recognizing CR within urine specimens from both healthy individuals and patients suffering from chronic kidney disease (CKD). The Bland-Altman assessment (utilizing 25 human urine specimens) displayed remarkable consensus (R2 = 0.995) among the FL approach and the benchmark Jaffe technique. This observation indicates the hands-on usefulness of the nanosensor for identifying CR in biological specimens.

Reductive carbon dots for reduction, ratiometric fluorescence determination, and intracellular imaging of Au3

Many studies show that ortho-phenylenediamine (OPD) produces an oxidized fluorescent product when exposed to an oxidizing agent that enables the direct or indirect fluorescence detection of a range chemical and biochemical analytes. However, there is no report on this unique optical behavior for other two isomers of phenylenediamine. This study demonstrates that a simple hydrothermal treatment of para-phenylenediamine (PPD) in the presence of sulfuric acid results in the formation of fluorescent N, S-doped carbon dots (CDs) with triple functionalities including the reduction of Au3+ into gold nanoparticles (AuNPs), the stabilization of the produced AuNPs, and the determination of Au3+ concentration through an intrinsic ratiometric fluorescence signal. In the presence of Au3+, the blue emission of CDs at 437 nm quenched, and a green emission at 540 nm emerged. The linear concentration range for the determination of Au3+ was 20 nM-16 µM with a detection limit of 16 nM. Additionally, the dual emissive CDs-AuNPs hybrid probe showed potential for the indirect fluorescence ratiometric determination of cysteine and sulfide ions. The linear concentration range for cysteine and sulfide ions were 0.25-8 μM and 0.1-6 μΜ, with detection limits of 0.095 μM and 0.041 μM, respectively. Accordingly, CDs were applied to detect Au3+ and S2- in real water samples. Moreover, the synthesized CDs showed no cytotoxicity for HeLa cells up to 300 µg mL-1, as determined by the MTT assay. Therefore, their potential for intracellular imaging of Au3+ in living cells was also investigated.

Influence of Drugs and Toxins on Decomposition Dynamics: Forensic Implications

Drug and toxin-related deaths are common worldwide, making it essential to detect the postmortem concentration of various toxic substances at different stages of decomposition in a corpse. Indeed, determining the postmortem interval (PMI) and cause of death in an advanced stage of decomposed corpses has been a significant challenge in forensic investigations. Notably, the presence of drugs or toxins can have a significant impact on the microbial profile, potentially altering the succession of microbial communities and subsequent production of volatile organic compounds (VOCs), which, in turn, affect insect colonization patterns. This review aims to highlight the importance of investigating the interactions between drugs or toxins, microbial succession, VOC profiles, and insect behavior, which can provide valuable insights into forensic investigations as well as the ecological consequences of toxins occurring in decomposition. Overall, the detection of drugs and other toxins at different stages of decomposition can yield more precise forensic evidence, thereby enhancing the accuracy of PMI estimation and determination of the cause of death in decomposed remains.

Application of gold nanoclusters in fluorescence sensing and biological detection

Gold nanoclusters (Au NCs) exhibit broad fluorescent spectra from visible to near-infrared regions and good enzyme-mimicking catalytic activities. Combined with excellent stability and exceptional biocompatibility, the Au NCs have been widely exploited in biomedicine such as biocatalysis and bioimaging. Especially, the long fluorescence lifetime and large Stokes shift attribute Au NCs to good probes for fluorescence sensing and biological detection. In this review, we systematically summarized the molecular structure and fluorescence properties of Au NCs and highlighted the advances in fluorescence sensing and biological detection. The Au NCs display high sensitivity and specificity in detecting iodine ions, metal ions, and reactive oxygen species, as well as certain diseases based on the fluorescence activities of Au NCs. We also proposed several points to improve the practicability and accelerate the clinical translation of the Au NCs.

Sensitive and Selective Determination of Benzidine by Synthesized tragacanth-poly (Acrylic acid-co-acrylamide-GQD) Hydrogel Nanocomposite as a Highly Stable Fluorescent Probe

Benzidine is known as a toxic and highly carcinogenic substance, so its determination is an essential issue. Until now, no effective and stable fluorescent probe based on hydrogel nanocomposite has been reported for the determination of this substance. In this work, for the first time, the synthesis and use of tragacanth-poly (acrylic acid-co-acrylamide-GQD) hydrogel nanocomposite (H-GQD) as a novel, high-stable, and selective fluorescence hydrogel nanocomposite for the identification of benzidine is reported. To achieve the maximum responsiveness of this hydrogel nanocomposite to determine benzidine, various parameters such as pH, ionic strength, hydrogel nanocomposite concentration, sensitivity, and selectivity were investigated. The results of the investigations showed that the synthesized H-GQD has excellent stability, selectivity, and linearity range of 0.3 - 12 ppm with a limit of detection of 0.098 ppm. The results of the investigation of real water samples showed that the H-GQD has excellent recovery in the range of 93.3 - 106.6%. Finally, we believe that this H-GQD as a new and highly stable fluorescent probe can be a starting point for its application in various fields and industries to identify benzidine in water samples.

The design, synthesis and application of metal-organic framework-based fluorescence sensors

Fluorescence-based chemical sensors have garnered significant attention due to their rapid response, high sensitivity, cost-effectiveness and ease of operation. Recently, metal-organic frameworks (MOFs) have been extensively utilized as platforms for constructing fluorescence sensors, owing to their ultra-high porosity, flexible tunability, and excellent luminescent properties. This feature article summarizes the progress made mainly by our research group in recent years in the construction strategies, principles, and types of MOF sensors, as well as their applications in quantitative sensing, qualitative identification analysis, and multimodal/multifunctional analysis. In addition, the challenges and an outlook on the future progression of MOF-based sensors are discussed, highlighting how these studies can contribute to addressing these issues. Hopefully, this feature article can provide some valuable guidance for the construction and application of MOFs in fluorescence sensing, thereby broadening their practical applications.

Supramolecular-platform-assisted selective recognition of uric acid with high sensitivity via microenvironment modulation of a self-assembled probe

This report demonstrates a unique route for translating a non-responsive fluorophore into a responsive one to optically recognize uric acid (UA) in physiological-mimicking conditions. The explicit 'turn ON-turn OFF' fluorescence switching upon sequential disaggregation-reaggregation of the self-aggregated 3,3'-bisindolyl(phenyl)methane molecules materializes a straightforward, trouble-free supramolecular UA sensing platform.

A Smartphone-Integrated Ratiometric Fluorescence Sensor for the Ultrasensitive and Selective Detection of 5-Heneicosylresorcinol in Whole Wheat Foods

Precise on-site monitoring of alkylresorcinols, a vital biomarker, is crucial for verifying whole wheat foods and accurately quantifying the whole wheat content in various consumer and industrial products. Herein, for the first time, we introduce a novel ratiometric fluorescence sensor (CDs@ZIF-8/CdTe@MIP) for ultrasensitive and selective detection of alkylresorcinols. 5-Heneicosylresorcinol (C21:0 AR), the primary alkylresorcinol homologue in whole wheat grains, was selected as the target analyte. This analyte was specifically and selectively recognized by the incorporation of a molecularly imprinted polymer (MIP) layer. Within this nanoreactor, blue-emitting carbon dots embedded in zeolitic imidazolate framework-8 (CDs@ZIF-8) and orange-emitting CdTe quantum dots served as the self-calibration signal and response signal, respectively. Exploiting a photoinduced electron transfer effect between CdTe and C21:0 AR, the established fluorescence sensor exhibited remarkable sensing performance, offering wide linear responses in 0.005-1 μg·mL-1 and 1-80 μg·mL-1 concentration ranges, and achieving a low detection limit of 1.14 ng·mL-1. The proposed assay effectively detected C21:0 AR in real samples, including 8 whole wheat foods and 19 whole wheat grains, demonstrating good recoveries and relative standard deviation. Furthermore, an intelligent sensing platform was established by integrating CDs@ZIF-8/CdTe@MIP with a smartphone-assisted device, thus validating the feasibility of visual and on-site monitoring of C21:0 AR. Because of its rapid response, portability, cost-effectiveness, superior sensitivity, and high selectivity, the proposed sensor serves as a reliable method for the analysis of C21:0 AR, thus having substantial potential for on-site monitoring of whole wheat foods.

Zn-MOF@rGO nanocomposite: a versatile tool for highly selective and sensitive detection of Pb2+ and Cu2+ ions in water

In this work, a hybrid nanocomposite material (PUC2@rGO) was prepared by integrating our previously developed Zn-MOF (PUC2) with reduced graphene oxide (rGO) through the wet impregnation method. The characterization of PUC2@rGO was performed using various analytical techniques, including FTIR, PXRD, FE-SEM, HR-TEM, XPS, zeta potential, and time-resolved FL spectroscopy. Our investigation primarily focused on assessing the composite's capability to detect water pollutants. Notably, PUC2@rGO demonstrated remarkable selectivity and sensitivity towards Pb2+ and Cu2+ ions via fluorescence quenching, exhibiting low detection limits and high quenching constant values. Spectroscopic analysis revealed that electron transfer from PUC2@rGO (donor) to the metal ions (acceptor) resulted in the observed quenching effect induced by Pb2+ and Cu2+ ions. Time-resolved fluorescence studies of PUC2@rGO before and after adding Pb2+ and Cu2+ ions confirmed dynamic quenching, further affirming strong interactions between PUC2@rGO and the targeted metal ions. These findings highlight PUC2@rGO's potential for efficiently detecting heavy metal pollutants in water.

Lanthanide metal-organic frameworks as ratiometric fluorescent probes for real-time monitoring of PFOA photocatalytic degradation process

The assessment of perfluorooctanoic acid (PFOA) photocatalytic degradation usually involves tedious pre-treatment and sophisticated instrumentation, making it impractical to evaluate the degradation process in real-time. Herein, we synthesized a series of lanthanide metal-organic frameworks (Ln-MOFs) with outstanding fluorescent sensing properties and applied them as luminescent probes in the photocatalytic degradation reaction of PFOA for real-time evaluation. As the catalytic reaction proceeds, the fluorescence color changes significantly from green to orange-red due to the different interaction mechanisms between the electron-deficient PFOA and smaller radius F- with the ratiometric fluorescent probe MOF-76 (Tb: Eu = 29:1). The limit of detection (LOD) was calculated to be 0.0127 mM for PFOA and 0.00746 mM for F-. In addition, the conversion rate of the catalytic reaction can be read directly based on the chromaticity value by establishing a three-dimensional relationship graph of G/R value-conversion rate-time (G/R indicates the ratio between green and red luminance values in the image.), allowing for real-time and rapid tracking of the PFOA degradation. The recoveries of PFOA and F- in the actual water samples were 99.3-102.7% (RSD = 2.2-4.4%) and 100.7-105.3% (RSD = 3.9-6.8%), respectively. Both theoretical calculations and experiments reveal that the detection mechanism was attributed to the photoinduced electron transfer and energy transfer between the analytes and the probe. This method simplifies the sample analysis process and avoids the use of bulky instruments, and thus has great potential on the design and development of quantitative time-resolved visualization methods to assess catalytic performance and reveal mechanisms.

Aminophenylboronic acid-modified nitrogen-doped graphene quantum dots and their applications in lysine sensing based on interplaying fluorescent mechanisms

Using nitrogen-doped graphene quantum dots (N-GQDs) and 3-aminophenylboronic acid (APBA), a novel fluorescence nanosensor was developed. This nanosensor exhibits high selectivity and sensitivity for lysine detection. Its sensing mechanism involves the suppression of electron transfer from APBA to the N-GQDs unit, thereby inhibiting photoinduced electron transfer and initiating internal charge transfer. At an optimal pH of 7, the protonated α-amine and ε-amine groups of lysine interact with the amide and boronic acid moieties, respectively. This interaction results in a redshift of fluorescence, substantially enhancing the response signal. A linear response was observed within a concentration range 0.40-3.01 μM, with the detection limit being 0.005 μM. A similar linear range was also achieved for the determination of lysine in human serum. Density functional theory calculations correlating molecular orbits and geometries support UV-vis and fluorescence findings. Additionally, the nanosensor was successfully applied to detect lysine in living cells and real samples, including milk and honey. For practical application, we construct a lysine-specific sensing platform using a commercial chip (TCS34725) that collects red, blue, and green signals, thereby facilitating the convenient use of the nanosensor. Overall, this study offers new perspectives on the development and application of fluorescent nanosensors for detecting individual amino acids.

Fluorescent solid-state strips based on SiO2 shell-stabilized perovskite nanocrystals applying for magnetic aptasensing detection of aflatoxin B1 toxin in food

In this work, the perovskite fluorescent nanocrystals (CsPbBr3) were successfully synthesized and wrapped with SiO2 shell, utilized for the assembly of solid-state detection strip capable of conveniently and specifically detection of aflatoxin B1 (AFB1). The SiO2 coating aimed to enhance the stability of CsPbBr3 nanocrystals. The resulting CsPbBr3@SiO2 material exhibited remarkable fluorescence properties, and further self-assembled onto solid-state plate, generating AFB1-specific quenched fluorescence at a specific wavelength of 515 nm. When combined with the capture of AFB1 by magnetic nanoparticles conjugated with aptamers (MNPs-Apt), it was achieved the good separation and specific detection of AFB1 toxin in food matrices. The constructed fluorescent solid-state detection strip based on CsPbBr3@SiO2 exhibited good response to AFB1 toxin within a linear range of 0.1-100 ng mL-1 and an impressive detection limit as low as 0.053 ng mL-1. This presents a new strategy for the rapid screening and convenient detection of highly toxic AFB1.

Enhanced molecular first hyperpolarizabilities with Reichardt's type of zwitterions: a computational study on roles of various monocyclic aromatic bridges

CONTEXT

This work reports structure-property correlations of 27 zwitterions Reichardt's types of zwitterions. Focuses are twofold, to see the (1) impacts of metamerism with Reichardt's vs Brooker's types of zwitterions and (2) impacts of monocyclic aromatic rings as bridges. All the molecules considered here have pyridinium (common acceptor: A) and p-phenylene-dicyanomethanide (common donor: D). Fundamental molecular properties like dipole moments (μ), polarizabilities (α), hyperpolarizabilities (β), and adiabatic absorptions were computed only for the Reichardt types and compared with the literature reported respective Brooker's types of zwitterions. As an impact of metamerism, in general 2-3 times enhanced hyperpolarizabilities (β) were observed for Reichardt's compared to Brooker's types. Exceptions were observed with some triazine bridges and furan bridge, where Brooker's types were found to be more efficient. As impacts of aromatic bridges, in general, 6-sevenfold enhanced β compared to well-known traditional bridges and enhanced β were observed compared to D-A directly connected zwitterion (benzene bridge: sixfold enhanced β). Current findings show that the aromatic bridge control with Reichardt's types of zwitterions is more efficient and thus may be employed as an effective strategy for the designing of functional molecular chromophores for various other fundamental areas.

METHODS

All computations were performed with Gaussian 09. Geometry optimizations and computations of fundamental properties were carried out with HF, B3LYP, CAM-B3LYP, and ωB97xD methodologies, with 6-31G(d,p) and aug-cc-pVDZ basis sets. For adiabatic excitations, computations were carried out using TDDFT and TDHF approaches. For the computations of the response properties (like the nonlinear optical responses), CPHF approach was used.

Biotin-functionalized nanoparticles: an overview of recent trends in cancer detection

Electrochemical bio-sensing is a potent and efficient method for converting various biological recognition events into voltage, current, and impedance electrical signals. Biochemical sensors are now a common part of medical applications, such as detecting blood glucose levels, detecting food pathogens, and detecting specific cancers. As an exciting feature, bio-affinity couples, such as proteins with aptamers, ligands, paired nucleotides, and antibodies with antigens, are commonly used as bio-sensitive elements in electrochemical biosensors. Biotin-avidin interactions have been utilized for various purposes in recent years, such as targeting drugs, diagnosing clinically, labeling immunologically, biotechnology, biomedical engineering, and separating or purifying biomolecular compounds. The interaction between biotin and avidin is widely regarded as one of the most robust and reliable noncovalent interactions due to its high bi-affinity and ability to remain selective and accurate under various reaction conditions and bio-molecular attachments. More recently, there have been numerous attempts to develop electrochemical sensors to sense circulating cancer cells and the measurement of intracellular levels of protein thiols, formaldehyde, vitamin-targeted polymers, huwentoxin-I, anti-human antibodies, and a variety of tumor markers (including alpha-fetoprotein, epidermal growth factor receptor, prostate-specific Ag, carcinoembryonic Ag, cancer antigen 125, cancer antigen 15-3, etc.). Still, the non-specific binding of biotin to endogenous biotin-binding proteins present in biological samples can result in false-positive signals and hinder the accurate detection of cancer biomarkers. This review summarizes various categories of biotin-functional nanoparticles designed to detect such biomarkers and highlights some challenges in using them as diagnostic tools.

Selective Excitation of the 1Lα State of Tryptophan in Collagen-like Peptides Can Reveal the Formation of a Heterotrimer

Fluorescence emission from tryptophan residues has been often used to probe the protein structure due to its transition dipole moment sensitivity to the local environment. We report the fluorescence study of a collagen-like peptide heterotrimer modified with the tryptophan in the X position (X-Y-Gly) n that shows the diminished fluorescence in a homotrimer versus a heterotrimer when the 1Lα state is selectively excited. This behavior is only observed in folded peptides, below the helix-to-coil transition temperature, and can be explained by long-range interactions between the tryptophans located on different strands within the triple helix, not by the change in the local environment. Our results suggest that tryptophan homotransfer is possible at distances much longer than the R 0 (0.5-0.7 nm) previously estimated. These observations imply that the energy transfer between the 1Lα states of proximal tryptophans can be facilitated by constraining their rotation by the helix and, thus, can be employed as a reporter of heterotrimer formation in biosensors.

Chiral Nanostructured Glycerohydrogel Sol-Gel Plates of Chitosan L- and D-Aspartate: Supramolecular Ordering and Optical Properties

A comprehensive study was performed on the supramolecular ordering and optical properties of thin nanostructured glycerohydrogel sol-gel plates based on chitosan L- and D-aspartate and their individual components in the X-ray, UV, visible, and IR ranges. Our comparative analysis of chiroptical characteristics, optical collimated transmittance, the average cosine of the scattering angle, microrelief and surface asymmetry, and the level of structuring shows a significant influence of the wavelength range of electromagnetic radiation and the enantiomeric form of aspartic acid on the functional characteristics of the sol-gel materials. At the macrolevel of the supramolecular organization, a complex topography of the surface layer and a dense amorphous-crystalline ordering of polymeric substances were revealed, while at the nanolevel, there were two forms of voluminous scattering domains: nanospheres with diameters of 60-120 nm (L-) and 45-55 nm (D-), anisometric particles of lengths within ~100-160 (L-) and ~85-125 nm (D-), and widths within ~10-20 (L-) and ~20-30 nm (D-). The effect of optical clearing on glass coated with a thin layer of chitosan L-(D-)aspartate in the near-UV region was discovered (observed for the first time for chitosan-based materials). The resulting nanocomposite shape-stable glycerohydrogels seem promising for sensorics and photonics.

Biomedical applications of graphene-based nanomaterials: recent progress, challenges, and prospects in highly sensitive biosensors

Graphene-based nanomaterials (graphene, graphene oxide, reduced graphene oxide, graphene quantum dots, graphene-based nanocomposites, etc.) are emerging as an extremely important class of nanomaterials primarily because of their unique and advantageous physical, chemical, biological, and optoelectronic aspects. These features have resulted in uses across diverse areas of scientific research. Among all other applications, they are found to be particularly useful in designing highly sensitive biosensors. Numerous studies have established their efficacy in sensing pathogens and other biomolecules allowing for the rapid diagnosis of various diseases. Considering the growing importance and popularity of graphene-based materials for biosensing applications, this review aims to provide the readers with a summary of the recent progress in the concerned domain and highlights the challenges associated with the synthesis and application of these multifunctional materials.

Advancing mass spectrometry-based chemical imaging: A noncontact continuous flow surface probe in mass spectrometry for enhanced signal detection and spatial resolution

A new method has been developed for mass spectrometric imaging of small molecules and proteins on tissue or in thinly sliced materials. A laser desorption Venturi electrospray ionization-mass spectrometer was developed for molecular imaging. This method combines laser desorption (LD) and electrospray ionization (ESI) systems before a mass spectrometer (MS). To carry out laser desorption, samples are excited with a laser from the back side of a glass substrate. The desorbed molecules or particles are then captured by a solvent flow. In the ESI system, these desorbed particles and molecules are ionized. The spray part of the solvent system consists of two capillaries: one delivers solvent to the sample plate sides to capture desorbed molecules and particles, and the other carries the solution to the mass spectrometry side using the Venturi effect. A 2D stage facilitates sampling. The system is designed to minimize the sample size after desorption using a 355 nm diode laser, and it is optimized for molecules of various sizes, including organic molecules, amino acids, and proteins. Despite challenging atmospheric conditions for protein desorption, this specialized design enables the collection of protein spectra. The amino acids and other small molecules showed high sensitivity in the MSI measurements. This innovative MS imaging system can be directly applied to real tissue systems and other plant samples to visualize the molecular level distributions.

Nanosensor based approaches for quantitative detection of heparin

Heparin, being a widely employed anticoagulant in numerus clinical complications, requires strict quantification and qualitative screening to ensure the safety of patients from potential threat of thrombocytopenia. However, the intricacy of heparin's chemical structures and low abundance hinders the precise monitoring of its level and quality in clinical settings. Conventional laboratory assays have limitations in sensitivity and specificity, necessitating the development of innovative approaches. In this context, nanosensors emerged as a promising solution due to enhanced sensitivity, selectivity, and ability to detect heparin even at low concentrations. This review delves into a range of sensing approaches including colorimetric, fluorometric, surface-enhanced Raman spectroscopy, and electrochemical techniques using different types of nanomaterials, thus providing insights of its principles, capabilities, and limitations. Moreover, integration of smart-phone with nanosensors for point of care diagnostics has also been explored. Additionally, recent advances in nanopore technologies, artificial intelligence (AI) and machine learning (ML) have been discussed offering specificity against contaminants present in heparin to ensure its quality. By consolidating current knowledge and highlighting the potential of nanosensors, this review aims to contribute to the advancement of efficient, reliable, and economical heparin detection methods providing improved patient care.

Semiconducting polymer dots for multifunctional integrated nanomedicine carriers

The expansion applications of semiconducting polymer dots (Pdots) among optical nanomaterial field have long posed a challenge for researchers, promoting their intelligent application in multifunctional nano-imaging systems and integrated nanomedicine carriers for diagnosis and treatment. Despite notable progress, several inadequacies still persist in the field of Pdots, including the development of simplified near-infrared (NIR) optical nanoprobes, elucidation of their inherent biological behavior, and integration of information processing and nanotechnology into biomedical applications. This review aims to comprehensively elucidate the current status of Pdots as a classical nanophotonic material by discussing its advantages and limitations in terms of biocompatibility, adaptability to microenvironments in vivo, etc. Multifunctional integration and surface chemistry play crucial roles in realizing the intelligent application of Pdots. Information visualization based on their optical and physicochemical properties is pivotal for achieving detection, sensing, and labeling probes. Therefore, we have refined the underlying mechanisms and constructed multiple comprehensive original mechanism summaries to establish a benchmark. Additionally, we have explored the cross-linking interactions between Pdots and nanomedicine, potential yet complete biological metabolic pathways, future research directions, and innovative solutions for integrating diagnosis and treatment strategies. This review presents the possible expectations and valuable insights for advancing Pdots, specifically from chemical, medical, and photophysical practitioners' standpoints.

Ultrasensitive NIR fluorometric assay for inorganic pyrophosphatase detection via Cu2+-PPi interaction using bimetallic Au-Ag nanoclusters

BACKGROUND

Inorganic pyrophosphatase (PPase) is key enzyme playing a key role in biochemical transformations such as biosynthesis of DNA and RNA, bone formation, metabolic pathways associated with lipid, carbohydrate and phosphorous. It has been reported that lung adenocarcinomas, colorectal cancer, and hyperthyroidism disorders can result from abnormal level of PPase. Therefore, it is of notable significance to develop simple and effective real time assay for PPase enzyme activity monitoring for screening of many metabolic pathways as well as for early disease diagnosis.

RESULT

The fluorometric detection of PPase enzyme in near infrared region-1 (NIR-1) has been carried out using bimetallic nanoclusters (LA@AuAg NCs). The developed sensing strategy was based on quenching of fluorescence intensity of LA@AuAg NCs upon interaction with copper (Cu2+) ions. The off state of LA@AuAg_Cu2+ ensemble was turned on upon addition of pyrophosphate anion (PPi) due to strong binding interaction between PPi and Cu2+. The catalytic conversion of PPi into phosphate anion (Pi) in the presence of PPase led to liberation of Cu2+ ions, and again quenched off state was retrieved due to interaction of free Cu2+ with LA@AuAg NCs. The ultrasensitive detection of PPase was observed in the linear range of 0.06-250 mU/mL with LOD as 0.0025 mU/mL. The designed scheme showed good selectivity towards PPase enzyme in comparison to other bio-substrates, along with good percentage recovery for PPase detection in real human serum samples.

SIGNIFICANCE

The developed NIR based assay is ultrasensitive, highly selective and robust for PPase enzyme and can be safely employed for other enzymes detection. This highly sensitive nature of biosensor was result of involvement of fluorescence-based technique and synergistic effect of dual metal in NIR based bimetallic NCs. Moreover, owing to the emission in NIR domain, in future, these nanoclusters can be safely employed for many biomedical applications for In vivo studies.