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This study introduces a novel fluorescence 'turn-on' chemosensor, FHDA, based on a trans-Ferulic acid Schiff-base derivative. FHDA stands out as a highly selective and sensitive tool for the fluorescent detection of Al3+ with the fluorescence 'turn-on' effect. FHDA exhibits a strong CHEF effect and ICT upon complexation with Al3+ in a 1:2 binding stoichiometry. The significant Stokes shift (Δλ = 108 nm, λex = 422 nm, λem = 530 nm), large binding constant (Ka = 4.2 × 104 M-1), ∼9.5-fold increase in the quantum yield (FHDA, Φ = 0.020; FHDA-Al3+ complex, Φ = 0.189), and a LOD of 134 nM, makes FHDA an excellent chemosensor for detecting Al3+ in solution; tests in live cells and environmental samples also showed excellent responses. FHDA offers substantial improvements over existing methods with its ease of use, limited expense, high specificity, and the ability to provide real-time, in-situ monitoring of Al3+ ions. The utility of FHDA is highlighted through applications in monitoring Al3+ ions in e.g. lung cancer cells (A549) and environmental water samples. We believe that applications of FHDA can potentially lead to a novel diagnostic and therapeutic strategy against diseases linked to aluminum dysregulation.

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The extensive use of insecticides, such as pyrethroids, and pharmaceutical drugs, such as doxorubicin (DOX) has significantly increased to meet the growing demand for food production and disease treatment. Among them, 3-phenoxybenzoic acid (3-PBA), a metabolite of pyrethroid insecticides, poses various health and environmental risks. Similarly, DOX is a well-known anticancer drug and has been continuously used for many years. The high demand and unregulated disposal of these substances raise concerns for both humans and the environment. To address this issue, there is a pressing need to monitor the presence of these analytes in wastewater to protect our ecosystems. This challenge has inspired us to develop an MOF-based fluorometric dual sensor capable of rapid and selective detection of these analytes in aqueous solutions. This work represents the first MOF-based dual probe for detecting these targeted analytes. There was a 98% fluorescence quenching upon the introduction of DOX whereas about a 11-fold increment of the probe's fluorescence intensity took place in the presence of 3-PBA. The sensitivity of the probe is notably high as limits of detection (LOD) are 8.7 nM for DOX and 1.2 nM for 3-PBA. Our designed probe has the highest KSV value for DOX which is 3.37 × 106 M-1. The MOF demonstrated remarkable rapid response time of just 5 and 10 s for DOX and 3-PBA, respectively. The MOF exhibited outstanding selectivity in detecting DOX and 3-PBA, even when other interfering substances were present. We tested the probe's sensing abilities in various environments, such as serum, urine, wastewater, and different pH levels. These findings underscore the sensor's practicality and usefulness in real-world applications. The underlying mechanisms driving the sensing processes were thoroughly investigated by using various modern analytical methods.

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Non-natural building blocks (BBs) present a vast reservoir of chemical diversity for molecular recognition and drug discovery. However, leveraging evolutionary principles to efficiently generate bioactive molecules with a larger number of diverse BBs poses challenges within current laboratory evolution systems. Here, we introduce programmable chemical evolution (PCEvo) by integrating chemoinformatic classification and high-throughput array synthesis/screening. PCEvo initiates evolution by constructing a diversely combinatorial library to create ancestral molecules, streamlines the molecular evolution process and identifies high-affinity binders within 2-4 cycles. By employing PCEvo with 108 BBs and exploring >10^17 chemical space, we identify bicyclic peptidomimetic binders against targets SAR-CoV-2 RBD and Claudin18.2, achieving nanomolar affinity. Remarkably, Claudin18.2 binders selectively stain gastric adenocarcinoma cell lines and patient samples. PCEvo achieves expedited evolution in a few rounds, marking a significant advance in utilizing non-natural building blocks for rapid chemical evolution applicable to targets with or without prior structural information and ligand preference.

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Development, rapid detection and quantification of anticancer drugs in biological samples are crucial for effective drug monitoring. The present work describes the design of a Hf(IV)-based metal-organic framework (MOF) (1) by the reaction between Hf(IV) ion and 2-(thiophene-2-carboxamido)terephthalic acid linker with the surface area of 571 m2 g-1. Desolvated MOF (1') displayed highly discriminative fluorescence sensing properties for the antineoplastic drug flutamide and biomolecule hemin in an aqueous medium in the presence of co-existing biomolecules and ions. The MOF's response time for sensing flutamide and hemin was less than 5 s with low detection limits of 1.5 and 0.08 nM, respectively. Additionally, 1' also demonstrated recyclability up to five cycles and maintained its sensing ability across different pH media, various water samples, and biological fluids. Experimental and theoretical analyses suggested photoinduced electron transfer and inner-filter effect in the presence of flutamide and Förster resonance energy transfer in the presence of hemin are most likely reasons behind the fluorescence quenching of MOF. Furthermore, the MOF demonstrated catalytic activity in Friedel-Crafts alkylation reactions, providing a 96 % yield with slight decay in its activity over four uses. The enhanced activity of 1' compared to Hf-BDC and Hf-BDC-NH2 (BDC: 1,4-benzenedicarboxylic acid) is due to the functionalized thiophene moieties through hydrogen bond donating sites, confirmed by a series of control experiments.

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The monitoring and precise determination of pesticides and pharmaceutical drugs and their residues have become increasingly important in the field of food safety and water contamination issues. Herein, a fluorescent aluminium MOF-based sensor (1) was developed for the selective recognition of neonicotinoid insecticide dinotefuran and anti-Parkinson's drug entacapone. Guest-free MOF 1' exhibited ultra-fast response (<5 s) and ultra-low detection limits of 2.3 and 7.6 nM for dinotefuran and entacapone, which are lower than the previously reported MOF-based sensors. In the presence of other competitive analytes, great selectivity was achieved towards both analytes. The probe was recyclable up to five cycles. The sensing ability was explored towards entacapone in human serum, urine and dinotefuran in real soil, rice, honey samples, different fruits, vegetables, real water specimens and a wide range of pH media. A low-cost, handy MOF-based polymer thin-film composite (1'@PVDF-PVP) was developed for the on-site detection of dinotefuran and entacapone. Mechanistic studies involving analytical techniques and theoretical calculations suggested that FRET and PET are the probable reasons for entacapone sensing whereas IFE is responsible for dinotefuran detection. The entire work presents a low cost, multi-use photoluminescent sensor of entacapone and dinotefuran to address the environmental pollution.

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Ascorbic acid plays a significant role in regulation of various bodily functions with high concentrations in immune cells and being involved in connective tissue maintenance. Commonly it is detected through various colorimetric methods. In this study, we propose a one-step simple method based on the inhibitory activity of ascorbic acid on horseradish peroxidase and hydrogen peroxide. The detection is observed by colorimetric changes to TMB (3,3',5,5' tetramethylbenzidine). The enzyme inhibition unit was optimized with a high level of linearity (r2 = 0.9999) and the level of detection and level of quantification were found to be 1.35 nM and 4.08 nM, respectively with higher sensitive compared to the HPLC method (11 µM). Both intra and inter-assays showed high correlations at different AA concentrations. (r2 > 0.9999). Similar results were also observed for vitamin C tablets, ascorbate salts, fruits, and market products (r2 = 0.999). There was negligible effect of interference by citric acid, lactic acid, tartaric acids, and glucose with high recoveries (>98%) at 1 mg/mL to 0.0078 mg/mL concentration ranges. The recovery error (RE%) was found to be less than 10%. Our detection method is distinguished by its simplicity, nano-level of detection, reproducibility, and potential application and adaptability as a point-of-use test.

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BACKGROUND: The fabrication of sensors capable of achieving rapid, sensitive, and highly selective detection of target molecules in complex fluids is key to realizing their real-world applications. For example, there is an urgent need in drugged driving roadside screening scenarios to develop a method that can be used for rapid drug detection and that avoids interference from the matrix in the sample. How to minimize the interference of complex matrices in biofluids at the electrode interface is the key to improve the sensitivity of the sensor. RESULTS: This work develops a facile and green method to prepare rough electrodes with a porous structure for constructing electrochemical aptamer-based (EAB) sensors for rapid, sensitive and accurate detection of Δ9-tetrahydrocannabinol (THC) in biofluids. The electroactive area of the rough electrode was 21 times of smooth electrode. And the antifouling performance of the rough electrode was much better than that of smooth electrode. Based on the unique advantages of the rough electrode, the developed EAB sensor achieves rapid nanomolar detection of THC in undiluted serum, undiluted urine and 50 % saliva with the detection limit of 5.0 nM, 10 nM and 10 nM, respectively. Moreover, our method possesses good reproducibility, accuracy and specificity. SIGNIFICANCE: The porous structure can effectively reduce the non-specific adsorption and enhance the stability of the signal, while the larger active area can modify more aptamers, thus improving the sensitivity. The detection limits of the EAB sensor were lower than the cutoff concentration of THC in drugged driving and the measuring process was completed within 60 s after target addition, which makes the present sensors capable for real-world applications.

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Fluorescent and colorimetric chemosensors for selective detection of various biologically important analytes have been widely applied in different areas such as biology, physiology, pharmacology, and environmental sciences. The research area based on fluorescent chemosensors has been in existence for about 150 years with the development of large number of fluorescent chemosensors for selective detection of cations as metal ions, anions, reactive species, neutral molecules and different gases etc. Despite the progress made in this field, several problems and challenges still exist. The most important part of sensing is limit of detection (LOD) which is the lowest concentration that can be measured (detected) with statistical significance by means of a given analytical procedure. Although there are so many reports available for detection of millimolar to micromolar range but the development of chemosensors for the detection of analytes in nanomolar range is still a challenging task. Therefore, in our current review we have focused the history and a general overview of the development in the research of fluorescent sensors for selective detection of various analytes at nanomolar level only. The basic principles involved in the design of chemosensors for specific analytes, binding mode, photophysical properties and various directions are also covered here. Summary of physiochemical properties, mechanistic view and type of different chemosensors has been demonstrated concisely in the tabular forms.

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The rising costs of pharmaceutical research are currently limiting the productivity of drug discovery and development, but can potentially be diminished via miniaturization of the synthesis and screening of new compounds. As droplet microarrays already present themselves as a versatile tool for highly miniaturized biological screening of various targets, their use for chemical synthesis is still limited. In this study, the influential palladium-catalyzed Suzuki-Miyaura reaction is successfully implemented at the nanoliter scale on droplet microarrays for the synthesis of an 800-compound library of biphenyls. Each reaction is carried out in individual 150 nL droplets. Remarkably, the synthesis of these 800 compounds requires a minimal amount of reagents, totaling 80 µmol, and a solvent volume of 400 µL. Furthermore, the cleavage kinetics and purity of the obtained biphenylic compounds are investigated. Via the solid-phase synthesis approach, the compounds could be purified from excess reactants and catalyst prior to the analysis and a UV-cleavable linker allows for fast and additive-free cleavage of each compound into the individual 100 nL droplet. This novel approach expands the toolbox of the droplet microarray for miniaturized high-throughput chemical synthesis and paves the way for future synthesis and screening of chemical compounds in a single platform.

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Identifying residues critical to protein-protein binding and efficient design of stable and specific protein binders are challenging tasks. Extending beyond the direct contacts in a protein-protein binding interface, our study employs computational modeling to reveal the essential network of residue interactions and dihedral angle correlations critical in protein-protein recognition. We hypothesized that mutating residues exhibiting highly correlated dynamic motion within the interaction network could efficiently optimize protein-protein interactions to create tight and selective protein binders. We tested this hypothesis using the ubiquitin (Ub) and MERS coronaviral papain-like protease (PLpro) complex, since Ub is a central player in multiple cellular functions and PLpro is an antiviral drug target. Our designed ubiquitin variant (UbV) hosting three mutated residues displayed a ∼3,500-fold increase in functional inhibition relative to wild-type Ub. Further optimization of two C-terminal residues within the Ub network resulted in a KD of 1.5 nM and IC50 of 9.7 nM for the five-point Ub mutant, eliciting 27,500-fold and 5,500-fold enhancements in affinity and potency, respectively, as well as improved selectivity, without destabilizing the UbV structure. Our study highlights residue correlation and interaction networks in protein-protein interactions, and introduces an effective approach to design high-affinity protein binders for cell biology research and future therapeutics.

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Stimuli-responsive emission color modulation in fluorescent metal-organic frameworks (MOFs) promises luminescence-ink-based security application, while task-specific functionality-engineered pores can aid fast-responsive, discriminative, and ultralow detection of harmful organo-aromatics in the aqueous phase. Considering practical applicability, a self-calibrated fluoro-switch between encrypted and decrypted states is best suited for antiforgery measures, whereas image-based monitoring of organo-toxins by repetitive and handy methods over multiple platforms endorses in-field sensory potential. Herein, we constructed a mixed-ligand based chemically stable and bilayered-pillar MOF from -NH2-hooked pyridyl linker and tricarboxylate ligand that embraces negatively charged [Cd3(µ2-OH)(COO)6] node and shows pore-space-partitioning by nitrogen-rich flanked organic struts. Owing to the presence of a self-calibrating triazolylamine moiety-grafted auxiliary linker, this anionic MOF delineates reversible and multicyclic fluoro-swapping between protonated-encrypted and deprotonated-decrypted domains in the alternative presence of acid and base. Such pH-triggered, site-specific luminescence variation is utilized to construct highly regenerative anticounterfeiting labels for vivid acronym encryption. The intense fluorescence signature of the material is further harnessed in extremely selective and quick responsive sensing of harmful feed additive roxarsone (ROX) and dichloran (DCNA) pesticide in highly recyclable fashion with significant quenching and nanomolar limits of detection (ROX: 52 ppb; DCNA: 26.8 ppb). Notably, the ultrasensitive fluoro-detection of both these organo-toxins is successfully demonstrated via a handy paper-strip method as well as on the vegetable surface for real-time monitoring. Comprehensive density functional theory studies validate the electron transfer mechanism through redistribution of molecular orbital energy levels by each of the targeted analytes in this electron-rich framework besides evidencing MOF-analyte supramolecular interactions.

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A novel probe ITQ (9-(((E)-1 H-inden-1-ylidene)methyl)-8-(3-(((E)-1 H-inden-1-ylidene)methyl)phenoxy)-2,3,6,7-tetrahydro-1 H,5 H-pyrido[3,2,1ij]quinolone) was successfully designed and synthesized to detect amino acid lysine (Lys). The selective sensing behavior of the probe ITQ was observed using absorption and emission spectral results. Further, the probe ITQ exhibits a strong binding affinity for Lys [1.4 × 104 M- 1] and detects and quantifies Lys even in its nanomolar concentration. Moreover, the probe ITQ detects Lys at 1:2 binding stoichiometry with suitable biological pH [4-11]. Furthermore, the probe ITQ was also successfully utilized to detect Lys in tablets, real samples (avocado, soyabean and pork) and in live HeLa cells.

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Herein, we report an electrochemical scaffold consisting of functionalized multiwalled carbon nanotubes (COOH-fMWCNTs) and iron-doped zinc oxide nanoparticles (Fe-ZnO) for the detection of a hazardous textile dye safranin T (ST) and monitoring of its photocatalytic degradation. Prior to the detection and degradation analysis, Fe-ZnO NPs were synthesized by the sol-gel method and characterized by a number of structural and morphological techniques. The carboxyl moiety of COOH-fMWCNTs possessing a strong affinity for the amino functionality of ST led to significant enhancement of the current response at the designed electrochemical platform, whereas the electrocatalytic role, surface area enhancement, and the provision of binding sites of Fe-ZnO led to a further increase in the peak current intensity of ST. Electrochemical impedance spectroscopy showed that the sensing scaffold made of the glassy carbon electrode modified with COOH-fMWCNTs and Fe-ZnO efficiently transfers charge between the transducer and the redox probe. Under optimized conditions, the developed sensor showed a 2.3 nM limit of detection for ST. Moreover, recovery experiments and anti-interference tests qualified the sensing platform for practical applications. The dye was photocatalytically degraded using Fe-ZnO NPs up to 99% in 60 min with a rate constant of 0.068 min-1. The designed sensor was used to probe the degradation kinetics of the target dye, and the results were found consistent with the findings obtained from electronic absorption method. To the best of our knowledge, the present work is the first approach for the efficient detection and almost absolute degradation of ST.

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Herein, a Eugenol-derived fluorescence 'turn-on' probe FLHE was synthesized by condensing 2-((3-(trifluoromethyl)phenyl)amino)benzohydrazide with 5-allyl-2-hydroxy-3-methoxybenzaldehyde. FLHE demonstrated very low fluorescence in the studied organic solvents of varying polarities. However, upon titration with Zn2+ in HEPES buffer (pH = 7.4, 50% ACN, v/v), FLHE showed 40-fold higher fluorescence signals indicating the formation of the FLHE-Zn2+ complex. The fluorescence turn-on phenomenon upon FLHE-Zn2+ complex formation results from a chelation-enhanced fluorescence (CHEF) effect. The FLHE-Zn2+ complexation demonstrated a stokes shift of 156 nm (λex = 350 nm, λem = 506 nm) and an about 33-fold increase in the quantum yield (FLHE, Φ = 0.007; FLHE-Zn2+ complex, Φ = 0.23). The binding constant (Ka) determined by the Benesi-Hildebrand plot for interaction between FLHE and Zn2+ was 5.33 × 103 M-1. FLHE demonstrated a LOD of 31.8 nM for detecting Zn2+ in the environmental samples without interference from other cations and anions. FLHE-based paper strip (FLHE-PS) assay was developed to quantify the Zn2+ ions in water and the water content of organic solvent. FLHE-PS allows the detection of Zn2+ in aqueous solutions with a LOD of 63.2 nM and quantifying water in acetonitrile with a LOD of 0.14%. These results indicate that the FLHE has high applicability for detecting Zn2+ in living cells and environmental samples and detecting the presence of water in the organic solvents.

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Identifying critical residues in protein-protein binding and efficiently designing stable and specific protein binders to target another protein is challenging. In addition to direct contacts in a protein-protein binding interface, our study employs computation modeling to reveal the essential network of residue interaction and dihedral angle correlation critical in protein-protein recognition. We propose that mutating residues regions exhibited highly correlated motions within the interaction network can efficiently optimize protein-protein interactions to create tight and selective protein binders. We validated our strategy using ubiquitin (Ub) and MERS coronaviral papain-like protease (PLpro) complexes, where Ub is one central player in many cellular functions and PLpro is an antiviral drug target. Molecular dynamics simulations and experimental assays were used to predict and verify our designed Ub variant (UbV) binders. Our designed UbV with 3 mutated residues resulted in a ~3,500-fold increase in functional inhibition, compared with the wild-type Ub. Further optimization by incorporating 2 more residues within the network, the 5-point mutant achieved a KD of 1.5 nM and IC50 of 9.7 nM. The modification led to a 27,500-fold and 5,500-fold enhancements in affinity and potency, respectively, as well as improved selectivity, without destabilizing the UbV structure. Our study illustrates the importance of residue correlation and interaction networks in protein-protein interaction and introduces a new approach that can effectively design high affinity protein binder for cell biology studies and future therapeutic solution.

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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.

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Detecting megadalton matrix-assisted laser desorption/ionization (MALDI) ions in an ion trap mass spectrometer is a technical challenge. In this study, megadalton protein and polymer ions were successfully measured by MALDI linear ion trap mass spectrometer (LIT-MS) for the first time. The LIT-MS is comprised of a Thermo linear ion trap mass analyzer and a highly sensitive charge-sensing particle detector (CSPD). A newly designed radio frequency (rf) scan mode with dipolar resonance ejection techniques is proposed to extend the mass range of LIT-MS up to one million Thomson (Th). We analyze high mass ions with mass-to charge (m/z) ratios ranging from 100 kTh to 1 MTh, including thyroglobulin, alpha-2-macroglobulin, immunoglobulins (e.g., IgG and IgM), and polymer (∼ 940 kTh) ions. Besides, it is also very challenging for ion trap mass spectrometry to detect megadalton ions at low concentrations. By adopting high affinity carboxylated/oxidized detonation nanodiamonds (oxDNDs) to enrich IgM molecules and form antibody-nanodiamond conjugates, we have successfully reached âˆ¼ 5 nM (5 µg/mL) concentration which is better than that by the other techniques.

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Identifying critical residues in protein-protein binding and efficiently designing stable and specific protein binders is challenging. In addition to direct contacts in a protein-protein binding interface, our study employs computation modeling to reveal the essential network of residue interaction and dihedral angle correlation critical in protein-protein recognition. We propose that mutating residues regions exhibited highly correlated motions within the interaction network can efficiently optimize protein-protein interactions to create tight and selective protein binders. We validated our strategy using ubiquitin (Ub) and MERS coronaviral papain-like protease (PLpro) complexes, where Ub is one central player in many cellular functions and PLpro is an antiviral drug target. Our designed UbV with 3 mutated residues resulted in a ~3,500-fold increase in functional inhibition, compared with the wild-type Ub. Further optimization by incorporating 2 more residues within the network, the 5-point mutant achieved a KD of 1.5 nM and IC50 of 9.7 nM. The modification led to a 27,500-fold and 5,500-fold enhancements in affinity and potency, respectively, as well as improved selectivity, without destabilizing the UbV structure. Our study highlights residue correlation and interaction networks in protein-protein interaction, introduces an effective approach to design high affinity protein binders for cell biology and future therapeutics solutions.

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A cysteamine functionalized nanodiamond (NDC) was conjugated to gold nanoparticles (AuNPs) to deliver NDC@AuNPs and utilized in enhanced colorimetric detection of Cr3+ at pH 6 environment. The conjugation was validated using FTIR, TEM, PXRD, DLS, and zeta potential investigations. At pH 6, superior sensory response of NDC@AuNPs to Cr3+ than that of other ions was validated by UV-vis spectroscopy and colorimetric photographs. Results from UV-vis titrations displayed a linear regression from 0.01 to 0.4 µM with a LOD of 0.236 ± 0.005 nM. The particle aggregation, size variations, potential changes, and binding modes are investigated using TEM, DLS, and FTIR techniques to explore the underlying mechanisms. By adding the EDTA, sensory response is reversible up to 4 cycles. Finally, spiked real water experiments show improved sensing of Cr3+ at pH 6 via the observed recovery between 96 and 110 %, which is in good agreement with the ICP-mass data.

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With severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) as an emergent human virus since December 2019, the world population is susceptible to coronavirus disease 2019 (COVID-19). SARS-CoV-2 has higher transmissibility than the previous coronaviruses, associated by the ribonucleic acid (RNA) virus nature with high mutation rate, caused SARS-CoV-2 variants to arise while circulating worldwide. Neutralizing antibodies are identified as immediate and direct-acting therapeutic against COVID-19. Single-domain antibodies (sdAbs), as small biomolecules with non-complex structure and intrinsic stability, can acquire antigen-binding capabilities comparable to conventional antibodies, which serve as an attractive neutralizing solution. SARS-CoV-2 spike protein attaches to human angiotensin-converting enzyme 2 (ACE2) receptor on lung epithelial cells to initiate viral infection, serves as potential therapeutic target. sdAbs have shown broad neutralization towards SARS-CoV-2 with various mutations, effectively stop and prevent infection while efficiently block mutational escape. In addition, sdAbs can be developed into multivalent antibodies or inhaled biotherapeutics against COVID-19.