Colorimetric Response Research Articles

Tetraphenylethylene-Derived Tetracarboxylate Featuring AIE Properties for Dual Ion Sensing and Mechanochromic Self-Erasable Writing.

The integration of multiple functions within a single fluorescent molecule provides a promising platform for developing versatile, efficient, and cost-effective materials with enhanced performance across diverse applications. In this study, we introduce TPEC, an aggregation-induced emission (AIE) molecule derived from tetraphenylethylene-based tetracarboxylate, which demonstrates multifunctional capabilities, including metal ion sensing and self-erasable writing. TPEC exhibits amphiphilicity in water, self-assembling into single-layer nanosheets with robust blue fluorescence. Notably, the aqueous solution of TPEC displays a fluorescence colorimetric response to Al3+ ions and fluorescence quenching in the presence of Fe³⁺ ions. Additionally, TPEC powders undergo fluorescence colorimetric changes under mechanical stimulation, enabling self-erasable writing on prepared paper. This study presents a straightforward strategy for the development of multifunctional luminescent materials based on the self-assembly of a single-component fluorophore.

Rapid and Specific Detection of Bacillus cereus Using Phage Protein-Based Lateral Flow Assays.

Rapid and precise diagnostic techniques are essential for identifying foodborne pathogens, including Bacillus cereus (B. cereus), which poses significant challenges to food safety. Traditional detection methods are limited by long incubation times and high costs. In this context, gold nanoparticle (AuNP)-based lateral flow assays (LFAs) are emerging as valuable tools for rapid screening. However, the use of antibodies in LFAs faces challenges, including complex production processes, ethical concerns, or variability. Here, we address these challenges by proposing an innovative approach using bacteriophage-derived proteins for pathogen detection on LFAs. We used the engineered endolysin cell-wall-binding domain (CBD) and distal tail proteins (Dit) from bacteriophages that specifically target B. cereus. The protein-binding properties, essential for the formation of efficient capture and detection biointerfaces in LFAs, were extensively characterized from the microstructural to the LFA device level. Machine-learning models leverage knowledge of the protein sequence to predict advantageous protein orientations on the nitrocellulose membrane and AuNPs. The study of the biointerface binding quantified the degree of attachment of AuNPs to bacteria, providing, for the first time, a microscopic model of the number of AuNPs binding to bacteria. It highlighted the binding of up to one hundred 40 nm AuNPs per bacterium in conditions mimicking LFAs. Eventually, phage proteins were demonstrated as efficient bioreceptors in a straightforward LFA prototype combining the two proteins, providing a rapid colorimetric response within 15 min upon the detection of 105 B. cereus cells. Recombinantly produced phage binding proteins present an opportunity to generate a customizable library of proteins with precise binding capabilities, offering a cost-effective and ethical alternative to antibodies. This study enhances our understanding of phage protein biointerfaces, laying the groundwork for their utilization as efficient bioreceptors in LFAs and rapid point-of-care diagnostic assays, thus potentially strengthening public health measures.

A paper-based analytical device for the on-site multiplexed monitoring of soil nutrients extracted with a cafetière

Sustainable agricultural production has the aim to maximise the yield and quality of harvests. For that, farmers need to monitor nutrient levels within soils to apply fertilizers accordingly and to prevent land degradation and soil exhaustion. Current methods involve time-consuming sampling and transport to a laboratory; and most farmers do not have the resources to measure frequently at multiple locations, limiting their sustainable production. In order to address this challenge, a paper-based analytical device (PAD) for the multiplexed detection of soil nutrients, i.e. phosphate, nitrate and pH, extracted with a cafetière-based method, is developed in this work. The compact and easy-to-use platform enables an accurate soil analysis in less than 20min; 3min for extraction and 15min for readout. Two detection channels for nitrate and phosphate analysis, and one circular detection area for pH, including the selective reagents to each analyte, are defined within the PAD. Upon contact with the specific nutrients, the platform produces a colorimetric response that is easily readable by naked eye and smartphone camera. The detection reactions were optimized in the range 1 − 22.5mgL-1, 10 −100mgL-1 and 5.0 – 8.5 for phosphate, nitrate and pH, respectively, in agreement with the relevant levels in soils. The volume of water, the number of pushes of the plunger, the extraction time and the mass of soil were also optimized for the nutrient extraction method with the cafetière. The optimal workflow was validated with commercial soils and compared with the conventional UV-Vis method and the labels from the soil package, showing excellent agreement. This paper-based platform provides the possibility of a cheap, sensitive and specific monitoring of soil nutrients by minimally trained operators, such as farmers, enabling in-the-field analyses of multiple key soil nutrients in resource-limited settings and therefore addressing the challenge of routine monitoring for sustainable agriculture.

Bidirectional "Win-Win": Asymmetrical Nanobowl-Coupled Aggregation-Induced Emissive Nanosilicon-Enhanced Immunochromatographic Strips for the Ultrasensitive Detection of Salmonella typhimurium.

The lack of nanoprobes with an efficient signal response and overlook of cooperation between nanoprobes can be responsible for the unsatisfactory analytical performance of immunochromatographic strips (ITSs). Herein, asymmetrical nanobowl-confined innumerable gold nanoparticles (AuNPs) (AuNPs@AFRNBs) to enhance the light absorption are developed for quenching the fluorescence of aggregation-induced emissive (AIE) nanosilicons, which is used for the construction of a bidirectional complementary-enhanced ITS (BC-ITS) to ultrasensitively detect Salmonella typhimurium (S. typhimurium). Briefly, density functional theory-screened AIEgens with highly fluorescent brightness are confined in nanosilicons, and the nanoconfinement has improved the fluorescent brightness by 6.78-fold compared to the free AIEgens. Moreover, the substituent group effect has also enhanced the fluorescence of the prepared fluorescent nanosilicon by 10,000-fold in ITSs. By virtue of the superior light absorption of AuNPs@AFRNBs, the BC-ITS exhibits a bidirectional "win-win" performance for the sensitive monitoring of S. typhimurium: a "turn-on" mode with a high-brightness colorimetric response and an inverse "turn-off" fluorescence response, whose limits of detection are 364 and 302 CFU mL-1, respectively, which is approximately 100-fold more sensitive than the traditional AuNPs-ITS. Furthermore, the BC-ITS can be successfully used to identify S. typhimurium in milk, illustrating the superiority of the developed BC-ITS in point-of-care diagnosis.

Assessing Wear Characteristics of Sprayable, Diacetylene-Containing Sensor Formulations.

This work extends recent developments in diacetylene-based, sprayable sensors by identification and assessment of formulations which facilitate their use for wearable sensing. Diacetylene-based spray-on sensors have the potential to be a widely deployed sensing technology, as they require no power and can be applied as thin coatings onto surfaces to provide a colorimetric response to target exposure. In responding to radiation, liquid-phase targets, or gas-phase targets specifically determined by the formulation of the sprayable sensor used, this technology is amenable to wearable sensors for measuring exposure to different environmental risks. Here, we provide the means to improve wear resistance, reduce false-positive signals due to wetting, and enhance color fastness for coatings of sprayable, diacetylene-based sensor formulations on cotton fabric. These sensor formulations possess polymethyl methacrylate (PMMA), which enhances the coating stability to only 8% color loss due to wear compared to 18-25% without PMMA, while maintaining the inherent ability of diacetylene-component formulations to detect radiation as well as gas or liquid phase analytes. This represents a significant step toward the use of diacetylene-based sensing formulations for wearable sensing. In the future, the form of spray-on sensor materials demonstrated here may find use in wearable sensing applications for detection of cumulative exposure to UV radiation, hydrogen peroxide vapors, or solvent exposure. We expect trends toward applications toward other wearable sensors for environmental monitoring given the well-known customizability in target response of diacetylene-containing monomers by modifying their headgroup chemistry.

Validation of a smartphone-compatible MIP-based sensor for bisphenol A determination in wastewater samples.

A handheld smartphone-compatible molecularly imprinted polymer (MIP)-based sensor was developed for the analysis of bisphenol A (BPA) in wastewater samples. Sensing elements based on ethylene glycol methacrylate phosphate (EGMP)-containing MIP films were designed and optimized using molecular dynamics simulations. The highly porous MIP films were synthesized via in situ polymerization, employing a fragment-based approach. The colorimetric response was based on the 4-aminoantipyrine method, while the MIP films were further utilized to detect BPA with a smartphone. The proposed sensor exhibited a wide linear range from 5 to 250μM, with a limit of detection (LOD) of 5μM (S/N = 3). Furthermore, the designed analytical system demonstrated excellent analytical performance in terms of selectivity, stability, and reproducibility. During sensor validation, real wastewater samples were successfully tested for BPA, showcasing the feasibility of the smartphone-compatible MIP-based sensor. Recovery values of 87.1-114.6% underscored the efficacy and reliability of the developed sensor system.

A promising platform for the rapid and sensitive sensing of mercury ion and its applications in biological and environmental system

Mercury ion (Hg2+) is one of harmful heavy metal ions that can accumulate inside the human organism and cause some health problems. Herein, a novel NBD derivative, 1-(2-((7-nitrobenzo[c] [1,2,5] oxadiazol-4-yl) amino) ethyl)-3-phenylthiourea (NBD-SCN), has been reasonably designed, which was simply synthesized by introducing NBD moiety as the fluorophore, phenyl-isothionitrate as the reaction site and ethylenediamine as a linker group, resulting in intense fluorescence emission with high fluorescence quantum yields. Intriguingly, probe NBD-SCN provides a dual-mode colorimetric and fluorescence response pattern for the sensing of mercury ion with great limit of detections (3.6 nM) and rapid response time (4 s). The strong combination of mercury ions and sulfur atoms leads to intramolecular cyclization, causing the color of probe solution changed from orange to pale yellow as well as a complete vanishing of fluorescence intensity. The proposed reaction mechanism was verified by fluorescence and UV titration, 1H NMR, FTIR, HRMS analyses and DFT studies. Motivated by an impressive chromatic variation, test strip sensing platform are facilely constructed for real-time and on-site measurement of Hg2+ levels. Furthermore, confocal imaging experiments verify that this probe can be used for monitoring mercury ion in living mung bean sprouts and in biological systems in real time.

Visual signal transduction for environmental stewardship: A novel biosensing approach to identify and quantify chlorpyrifos-related residues in aquatic environments

The pervasive presence of organophosphate pesticides (OPs), such as chlorpyrifos (CPF), in aquatic ecosystems underscores the urgent need for sensitive and reliable detection methods to safeguard environmental and public health. This study addressed the critical need for a novel biosensor capable of detecting CPF and its toxic metabolite, 3,5,6-trichloro-2-pyridinol (TCP), with high sensitivity and selectivity, suitable for field applications in environmental monitoring. The study engineered a whole-cell biosensor based on E. coli strains that utilize the ChpR transcriptional regulator and the vioABCE gene cluster, providing a distinct visual and colorimetric response to CPF and TCP. The biosensor's performance was optimized and evaluated across various water matrices, including freshwater, seawater, and soil leachate. The biosensor demonstrated high sensitivity with a broad linear detection range, achieving limits of detection (LODs) at 0.8 μM for CPF and 7.813 nM for TCP. The linear regression concentration ranges were 1.6–12.5 μM for CPF and 15.6–125 nM for TCP, aligning with environmental standard limits and ensuring the biosensor's effectiveness in real-world scenarios. This innovative biosensing approach offers a robust, user-friendly tool for on-site environmental monitoring, significantly mitigating OPs contamination and advancing current detection technologies to meet environmental protection standards.

An Optical Au3+ Sensor Based on layer-by-layer PEI/PAA-Rho thin Films on ITO.

This study presents the development of a sensitive and selective gold ion (Au3+) sensor utilizing layer-by-layer (LbL) assembled thin films composed of polyethylenimine (PEI) and poly (acrylic acid) (PAA) conjugated with rhodamine (Rho). The first study revealed that the polymeric sensors (PAA-Rho) demonstrated significant selectivity and sensitivity in their colorimetric and fluorescence responses to Au3+ compared to other metal ions. In their spirolactam form, the polymeric sensors were non-fluorescent but could selectively transform into the fluorescent ring-opened amide form upon interaction with Au3+ ions, resulting in fluorescence enhancement and observable color changes. Common co-existing metal ions showed negligible interference in the detection of Au3+. The LbL sensor exhibited a linear increase in absorbance with the addition of bilayers, confirming successful film deposition. Surface morphology analysis using SEM, along with structural confirmation via ATR-FTIR and XRD, further validated the sensor's capability to detect cation. Results demonstrated that the LbL sensor exhibited selectivity for Au3+ ions within the range 1 × 10-6 to 1 × 10-3 M. This approach offers an easily understandable and intrinsically sensitive means for detecting Au3+ ions in both environmental and biological applications.

Fluorescence and colorimetric rapiddual-signal "on-off-on" switching detection of ascorbic acidbased on TSPP/DCIP.

Afluorescence and colorimetric dual-signal sensing system for the determination of ascorbic acid (AA) in complex media was developed by using 5,10,15, 20-tetrakis(4-sulfonyl) porphyrin (TSPP) as a sensing probe and sodium 2,6-dichloroindophenol (DCIP) as a bridge. A fluorescence resonance energy transfer (FRET) effect occurred when DCIP was added to the TSPP solution, resulting in the quenching of the fluorescence signal of TSPP and a change in the color of the solution from pink to blue. The DCIP in the system reacted with AA in a redoxreaction to produce colorless phenol imine, the color of the solution changed from blue to green causing an obvious colorimetric response, and the TSPP/DCIP sensing system's fluorescence signal restored owing to AA introduced. The fluorescence method for AAshowed good linearity in the ranges 0.08mM ~ 1mM and 1mM ~ 43.6mM with a detection limit of 6.4μM. And the colorimetric method for AAshowed excellent linearity in the range 0.46mM ~ 40.2mM with a detection limit of 76.0μM. Theconstructed "dual-signal" probe in the study has been successfully applied to the detection of AA in practical samples. The method proposed has great potential for practical applications and provides new ideas for the visual inspection of portable measurements.

Ultrafast detection of bisulfite by a unique quinolinium-based fluorescent probe and its applications in smartphone-assisted food detection and bioimaging

Sulfur dioxide (SO2) is one of the major pollutants in the atmosphere, which is highly susceptible to inhalation by the human body and is converted into its derivatives (HSO3−/SO32−), which is hazardous to both human health and the ecological environment. Therefore the detection of SO2 derivatives (HSO3−/SO32−) is very important. In this work, we have prepared ID-QL, a water-soluble fluorescent probe based on the intramolecular charge transfer (ICT) mechanism, it exhibits colorimetric and fluorescent dual-channel response to HSO3− with ultrafast, highly selective and sensitive detection. In particular, ID-QL can be used for quantitative detection of HSO3− in real food samples. We developed a portable test strip for ID-QL and successfully combined it with smartphone to achieve convenient, low-cost and portable detection of HSO3− in real samples. The probe displays good mitochondrial targeting ability and can be used for visual monitoring and imaging of sulfites in live cells and zebrafish.

A commercially available dye as a highly versatile colorimetric fluoride sensor

Reported herein is the successful use of the commercially available organic dye bromocresol green (compound 1) for high-performing and practical fluoride detection. This dye responds to fluoride anion with high selectivity (virtually no response to other halide anions), excellent sensitivity (limits of detection as low as 0.22 ppm) and rapid response times, and maintains functionality when it is adsorbed on filter paper. Mechanistic studies determined that the fluoride-induced colorimetric changes were due to intermolecular hydrogen bonding between compound 1 and fluoride. Finally, the broad applicability of this sensor was demonstrated through the colorimetric response of compound 1 – functionalized paper to fluoride in commercial mouthwash. These findings underscore compound 1’s potential as a practical and commercially viable fluoride sensor, in addition to compound 1’s better-known role as a colorimetric pH indicator.

Bimetallic nanocolloidal plasmonic array for polyphenol characterization and calibration-free antioxidant capacity evaluation.

Abimetallic plasmonic nanoparticles-based approach for the untargeted evaluation of phenolic compounds (PC)-pattern and antioxidant capacity (AoC) is proposed. The rationale relies on the PC's ability to drive the formation of bimetallic silver/gold nanocolloidal 'probes' with different conformations. Ag/Au bimetallic nanostructures, according to the PCs' amount and class, return characteristic plasmonic and colorimetric tags. Plasmonic indexes are proposed to assess the dominant PC classes, while the colorimetric response, analyzed simply by a smartphone, is employed to obtain an AoC score, withoutcalibration. The methods were tested with PCs belonging to different chemical classes, and challenged to classify different food samples.The proposed approach allows PC-dominant class identification and AoC-evaluation consistent with HPLC-MS/MS and conventional photometric assays.

Multifunctional performance of chitosan/soy protein isolation-based films impregnated carbon dots/anthocyanin derived from purple hull pistachio for tracking and extending the shelf life of fish

The present study aimed to develop a sustainable biopolymer film that exhibits active and intelligent properties. The chitosan/soy protein isolation (Cs/SPI) based film was prepared by blending purple hull pistachio anthocyanin (PHPA) with carbon dots (CDs), which were synthesized using a by-product from purple hull pistachio (PHP) extraction. PHPA and CDs were shown to be compatible with the Cs/SPI biopolymer films. The resulting matrix was a homogeneous film with improved physico-mechanical properties. The biopolymer films were characterized by their various desirable properties, including 100% UV protection, potent antibacterial activity against S.aureus and E. coli strains with inhibition zonoe about 22.1 ± 36±0.24 mm and 20.36 ± 0.21 mm, respectively, and strong antioxidant properties (DPPH; 82.3 ± 0.1 % and ABTS; 90.6 ± 0.1 %). The film was also found to exhibit distinguishable colorimetric responses to pH 2–12 buffers and volatile ammonia. The packaging test of CS/SPI/PHPA/PHP-CDs film in scenario one (intelligent assay) for evaluation through fish freshness monitoring showed that the film's color changed from light pink (fresh fish) to yellow/brownish (spoilage fish) during storage at 4 °C and 25 °C. Also, scenario two (active assay) at 4 °C showed the ability to increase the shelf life of fish up to 12 days. The study demonstrated that the biopolymer films have exhibited exceptional adaptability, making it a highly promising option for prompt and effective on-site detection of food quality. Furthermore, the film's capacity to prolong the shelf life of fish and reduce the rate of quality degradation during storage positions it as an outstanding contender for multifunctional film applications in the food industry.

Achieving Controllable Thermochromic Fluorescence via Synergistic Intramolecular Charge Transfer and Molecular Packing

Thermochromic fluorescent materials (TFMs) have attracted significant attention due to their unique fluorescent colorimetric response to temperature. However, existing TFMs still suffer from weak stimulus responsiveness, broad temperature response ranges, uncontrollable emission color changes, and low quantum yields. In this study, we address these issues by designing and synthesizing three diketone‐boron complexes with distinct emission wavelengths (NWPU‐(2‐4)). Utilizing a molecular engineering strategy to manipulate intramolecular charge transfer transitions and molecular packing modes, our synthesized complexes exhibit efficient fluorescence emission in both solution and solid states. Moreover, their emission wavelengths are highly sensitive to environmental polarity. By incorporating these compounds into thermosensitive matrices of long‐chain alkanes, we produced TFMs with varied fluorescence emission peak variation ranges. Notably, the TFM based on NWPU‐4, owing to its strong charge transfer transitions and dense J‐aggregate packing configuration, not only exhibits intense fluorescence emission spanning the deep red to near‐infrared spectrum but also displays a remarkable 90 nm broad range of thermochromic properties. Ultimately, it was successfully applied to programmable, thermally controlled, multi‐level information encryption.

Achieving Controllable Thermochromic Fluorescence via Synergistic Intramolecular Charge Transfer and Molecular Packing.

Thermochromic fluorescent materials (TFMs) have attracted significant attention due to their unique fluorescent colorimetric response to temperature. However, existing TFMs still suffer from weak stimulus responsiveness, broad temperature response ranges, uncontrollable emission color changes, and low quantum yields. In this study, we address these issues by designing and synthesizing three diketone-boron complexes with distinct emission wavelengths (NWPU-(2-4)). Utilizing a molecular engineering strategy to manipulate intramolecular charge transfer transitions and molecular packing modes, our synthesized complexes exhibit efficient fluorescence emission in both solution and solid states. Moreover, their emission wavelengths are highly sensitive to environmental polarity. By incorporating these compounds into thermosensitive matrices of long-chain alkanes, we produced TFMs with varied fluorescence emission peak variation ranges. Notably, the TFM based on NWPU-4, owing to its strong charge transfer transitions and dense J-aggregate packing configuration, not only exhibits intense fluorescence emission spanning the deep red to near-infrared spectrum but also displays a remarkable 90 nm broad range of thermochromic properties. Ultimately, it was successfully applied to programmable, thermally controlled, multi-level information encryption.

A simple benzothiazolium-based sensor for cyanide detection: Applications in environmental analysis and bioimaging

A new sensor based on Ethylbenzothiazolium-2-hydroxynaphthaldehyde conjugate-based fluorescent sensor, (E)-3-ethyl-2-(2-(2-hydroxynaphthalen-1-yl) vinyl) benzo[d]thiazol-3-ium iodide (SU-1) was designed and synthesized. The structure of SU-1 was confirmed by 1H NMR, 13C NMR, HRMS, and single crystal XRD spectral analysis. SU-1 displayed a colorimetric and fluorometric response in a DMSO:H2O (1:1,v/v) matrix, changing color from pale yellow to colorless visible to the naked eye, accompanied by a ∼ 120 nm red-shift in the absorption spectra upon CN− addition. This shift, due to formation of deprotonation followed by the nucleophilic attack on the benzothiazolium ring’s double bond, disrupts π-conjugation, blocking intramolecular charge transfer within SU-1. However, competitive anions showed negligible interference while detecting CN−. The Limit of detection for CN− was determined to be 0.27 nM, significantly below the WHO’s permissible CN− concentration in drinking water (1.9 μM). Job’s plot analysis shows that the binding stoichiometry of SU-1 to CN− is a 1:1, with a stability constant (Ka) of 1.58 x 104 M−1. The sensor demonstrated practical applications in environmental water samples and fluorescence imaging of intracellular CN− in CAD cell line.

A facile synthesis of a novel polymer-based nanocomposite as colorimetric response sensor for fluoride ion detection in real-life complex mediums

The surface modification of Poly (acrylamide-co-methylenbisacrylamide-co-N-(4-(2-(phenylcarbamothioyl)hydrazineyl)phenyl)methacrylamide) as a sensor (AR) via titanium dioxide as a novel colorimetric nanocomposite sensor with high sensitivity and selectivity for determination of fluoride anion was described. The colorimetric response of the AR has been screened in dimethyl sulfoxide /Water with a volumetric ratio of 7:3 and acetonitrile in separate media with equal amounts of various anions. In the presence of the mentioned anionic solutions, only the solutions containing fluoride ions, made a significant change in color from pale yellow to orange-red via the –NH deprotonation mechanism, which could be detected with the naked eye. The Box-Behnken design, response surface methodology through UV-Vis spectroscopy techniques in various pH and temperatures and reaction times were tested to optimize the AR conditions. Also, a lateral flow assay test of the synthesized AR detected fluoride ions in real-life samples, including water, contrary to different sources such as toothpaste and mouthwash. Furthermore, according to the World Health Organization report on fluoride ion toxicity in water, the detection limit of the AR was lower than of the declared level.

Customizable OpenGUS immunoassay: A homogeneous detection system using β-glucuronidase switch and label-free antibody

We developed a customizable OpenGUS immunoassay that enables rapid and sensitive detection of analytes without requiring antibody modification. This immunoassay employs label-free whole antibodies, an antibody-binding Z domain (ZD) derived from Staphylococcal protein A, and a β-glucuronidase (GUS) switch mutant, allowing for easy replacement of antibodies to tailor the immunoassays for various targeted antigens. The working principle is that the OpenGUS probe, the fusion protein of ZD and a GUS switch, converts the antibody-antigen interaction into GUS activation in a one-pot reaction. To enhance the signal-to-background ratio of the immunoassay, a GUS switch mutant that exhibits reduced background activation was developed by screening several additional mutations at the diagonal interface residue H514. Moreover, we optimized the composition of the reaction buffer, including organic solvents, salt, and surfactant. Under optimal conditions, we customized OpenGUS immunoassays for Cry j 1, human C-reactive protein, and human lactoferrin, achieving around 10–20-fold maximum fluorescence (15 min) or colorimetric (2 h) responses with picomolar to low nanomolar level detection limit, simply by using commercially available IgGs. Additionally, the three analytes were successfully detected in complex matrices similar to those used in practical applications. We believe that this customizable OpenGUS immunoassay will pave the way for the prompt development of rapid and sensitive homogeneous immunoassays for point-of-care diagnostics, high-throughput testing, and onsite environmental assessments.

Development of MnO2 nanosheets nanozyme-based colorimetric and photothermal dual-signal platform for monitoring alkaline phosphatase activity

Herein, a dual-signal biosensing platform for monitoring alkaline phosphatase (ALP) activity was developed. This platform combined the oxidase-mimicking activity of MnO2 nanosheets (NS) with the colorimetric and photothermal properties of oxidized 3,3′,5,5′-tetramethylbenzidine (oxTMB). MnO2 NS effectively catalyzed the oxidation of TMB to oxTMB, resulting in a color change from colorless to blue and a significant light absorption band at 652 nm. Meanwhile, oxTMB demonstrated pronounced photothermal properties, with the solution exhibiting a notable increase in temperature upon irradiation with an 808 nm laser. In the presence of ALP, 2-Phospho-L-ascorbic acid trisodium salt (AAP) was converted into L-ascorbic acid (L-AA), which then reacted with MnO2 NS. Consequently, MnO2 NS was inhibited from oxidizing TMB to oxTMB. Based on this principle, a dual-readout assay that integrated both colorimetric and photothermal signals for ALP detection was developed. The detection limits were 0.08 mU/mL for the colorimetric method and 0.12 mU/mL for the photothermal method. Furthermore, the platform was successfully applied to human serum samples, demonstrating its effectiveness in detecting ALP in complex biological matrices. The combination of colorimetric and photothermal responses enhanced both the accuracy and reliability of ALP detection, making this platform a promising tool for biomedical applications.