Enhancement Of Chemiluminescence Research Articles

Long-lasting chemiluminescence of lucigenin/p-aminophenol system for detection of p-aminophenol in environmental water

Long-lasting chemiluminescence of lucigenin/p-aminophenol (4-AP) system is explored for the first time and possible chemiluminescence enhancement mechanism is also proposed in this work. 4-AP can enhance chemiluminescence of lucigenin nearly 150 times and is stable for nearly 5 min, which overcomes the need of flow syringe pump. While o-aminophenol (2-AP) slightly enhances chemiluminescence of lucigenin and m-aminophenol (3-AP) does not. Thus, it can be applied in discrimination of three aminophenol isomers. More importantly, cyclic voltammetry proves the lowest oxidation peak for 4-AP at 115 mV, which is speculated to be the main reason for 4-AP induced chemiluminescence enhancement. It has been applied in chemiluminescence enhancement detection of 4-AP and p-nitrophenol (4-NP) from 80 nM to 60 μM, from 0.5 μM to 60 μM with limit of detection (LOD) of 26 nM and 0.17 μM, respectively. It shows high selectivity and anti-interference in chemiluminescence enhancment detection of 4-AP and 4-NP towards other organic compounds and metal ions. It also exhibits high accuracy in chemiluminescence enhancment detection of 4-AP and 4-NP in lake water with recoveries from 98.7% to 101.5% for and recoveries from 98.7% to 102.2%, respectively. It expands the study of long-lasting lucigenin chemiluminescence system and chemiluminescence method utilized in discrimination of aminophenols isomers.

A novel ultrasensitive chemiluminescence enzyme immunoassay by employment of a signal enhancement of horseradish peroxidase-luminol-hydrogen peroxide reaction for the quantitation of atezolizumab, a monoclonal antibody used for cancer immunotherapy.

This study describes, for the first time, the development and validation of a novel ultrasensitive chemiluminescence enzyme immunoassay (CLEIA) for the quantification of atezolizumab (ATZ), a monoclonal antibody approved by the FDA for treatment of different types of cancer. The assay involved the non-competitive binding of ATZ to its specific antigen (PD-L1 protein). The immune complex of PD-L1/ATZ formed on the internal surface of the plate wells was quantified by a novel chemiluminescence (CL)-producing horseradish peroxidase (HRP) reaction. The reaction employed a highly efficient CL enhancer for the HRP-luminol-hydrogen peroxide reaction which was 4-(imidazol-1-yl)phenol. The conditions of the CLEIA and its detection system were refined, and the optimum procedures were established. The CLEIA was validated in accordance with the guidelines of immunoassay validation for bioanalysis, and all the validation criteria were acceptable. The assay's limit of detection and limit of quantitation were 12.5 and 37.5 pg mL-1, respectively, with a working dynamic range of 25-800 pg mL-1. The assay enables the accurate and precise quantitation of ATZ in human plasma samples without any interferences from endogenous substances and/or the plasma matrix. The results of the proposed CLEIA were favourably comparable with those of a pre-validated enzyme-linked immunosorbent assay using a colorimetric detection system. The CLEIA is characterized by simple and high throughput features. The CLEIA is superior to the existing analytical methodologies for ATZ. The proposed CLEIA has a great value in the quantitation of ATZ in clinical settings for assessment of its pharmacokinetics, therapeutic drug monitoring, and refining the safety profile.

Synergistic enhancement of potassium permanganate-induced chemiluminescence by nitrogen and silver carbon dots and formaldehyde for selective detection of tannin

In this study, nitrogen and silver doped carbon dots (NAg-CDs) were synthesized via a simple and environmentally friendly hydrothermal one-pot method and were utilized in combination with formaldehyde to enhance potassium permanganate-induced chemiluminescence (CL). Remarkably, a chemiluminescent enhancement of approximately 448-fold was observed in the NAg-CDs-KMnO4-HCHO system than in the KMnO4-HCHO system. The enhanced CL intensity of the NAg-CDs-KMnO4-HCHO system can be significantly quenched by tannin. On this basis, we developed a simple, rapid, sensitive, and selective flow injection CL method for the detection of tannin, featuring a linear range of 0.4–10.0 μM and a detection limit of 43.0 nM. Furthermore, we effectively applied this method to the detection of tannin in red wine and tea samples, and the standard recoveries were 98.6 %104.9 %.

Carbon Vacancy-Enhanced Activity of Fe-N-C Single Atom Catalysts toward Luminol Chemiluminescence in the Absence of H2O2.

The classic luminol-H2O2 chemiluminescence (CL) systems suffer from easy self-decomposition of H2O2 at room temperature, hindering the practical applications of the luminol-H2O2 CL system. In this work, unexpectedly, we found that the carbon vacancy-modified Fe-N-C single atom catalysts (VC-Fe-N-C SACs) can directly trigger a luminol solution to generate strong CL emission in the absence of H2O2. The Fe-based SACs were prepared through the conventional pyrolysis of zeolitic imidazolate frameworks. The massive carbon vacancies were readily introduced into Fe-N-C SACs through a tannic acid-etching process. Carbon vacancy significantly enhanced the catalytic activity of Fe-N-C SACs on the CL reaction of luminol-dissolved oxygen. The VC-Fe-N-C SACs performed a 13.4-fold CL enhancement compared with the classic luminol-Fe2+ system. It was found that the introduction of a carbon vacancy could efficiently promote dissolved oxygen to convert to reactive oxygen species. As a proof of concept, the developed CL system was applied to detect alkaline phosphatase with a linear range of 0.005-1 U/L as well as a detection limit of 0.003 U/L. This work demonstrated that VC-Fe-N-C SAC is a highly efficient CL catalyst that can promote the analytic application of the luminol CL system.

Preparation of Co dual atomic site catalysts loaded on defect-engineered MOFs material with superb chemiluminescent enhancement effect for sensitive detection of bacteria

BackgroundDual atomic site catalysts (DASCs) have aroused extensive interest in analytical chemistry on account of the superb catalytic activity caused by the highly-exposed active centers and synergistic effect of adjacent active centers. The reported protocols for preparing DASCs usually involve harsh conditions such as acid/base etching and high-temperature calcination, leading to unfavorable water dispersity and restricted application. It is crucial to develop DASCs with satisfactory water dispersity, improved stability, and mild preparation procedures to facilitate their application as signal probes in analytical chemistry. Results: Formic acid was adopted as a modulator for preparing MOF-808 with abundant defective sites, which was used as the carrier for implanting Co atoms. Co DASCs with a special coordination structure of Co2–O10 and a high loading efficiency of 11.1 wt% were prepared with a mild solvothermal protocol. The resultant Co DASCs can significantly accelerate decay of H2O2 for forming numerous reactive oxygen radicals and boost chemiluminescent (CL) signal. Co DASCs at 1.0 μg mL−1 can enhance the CL signal of luminol-H2O2 system by about 5800 times. Thanks to their satisfactory water dispersity and excellent CL enhancement performance, they were used as ultra-sensitive CL signal probes for monitoring methicillin-resistant Staphylococcus aureus. The method shows a detection range of 102–107 CFU mL−1 and a detection limit of 47 CFU mL−1. Antibiotic susceptibility test was performed with the established CL method to prove its practicality. Significance: The water dispersible Co DASCs prepared with facile and mild solvothermal protocol exhibit prominent peroxidase-like activity and can promote the production of reactive oxygen radicals for boosting CL signal. Therefore, this study paves an avenue for implanting DASCs in defect-engineered carrier to prepare signal probes suitable for development of ultra-sensitive CL analytical methods.

Ultrabright chemiluminescent scaffold for portable visualizing organophosphorus compounds

Chemiluminescence (CL) has been recognized as one of the most powerful tools in analytical assays with high signal-to-noise ratio. Ultrabright chemiluminophores are highly desired in CL-based analytical approaches, imaging, for example, although the design of CL scaffold with ultra-brightness remains a challenge. We report a feasible strategy for constructing an ultrabright chemiluminophore, BTCL-Cl, by grafting benzothiazole moiety to the dioxetane center of Schaap’s adamantylidene-dioxetane. Compared with the classical undecorated chemiluminophores, the CL quantum yield of BTCL-Cl has improved by 2.4-folds to 17.6% with a short half-life due to deprotonation under alkaline conditions. Probe CL-HMPC, the thiol-recognizer-decorated BTCL-Cl, has demonstrated ultrahigh sensitivity (detection limit is 6.0 ng/mL) in monitoring organophosphorus compounds (OPs) by immediate releasing of thiols after the alkaline hydrolysis of OPs. The OPs-triggered remarkable CL enhancement has ensured quantitively visualization of OPs in the naked eye by imaging with a smartphone in situ. Using the versatile and ultrasensitive CL platform, we succeeded in feasibly visualizing the concentration of OPs on cabbage leaves on farmland by portable setups. The simple and promising approach for analyzing pesticides and potentially other targets brings tremendous imagination in related areas.

Deep-sea in situ determination of sulfide using a sensitized chemiluminescent terbium complex.

A new chemiluminescence (CL) method based on the chemiluminescent reaction between sulfide and an acidic permanganate solution was used to quantify sulfide in seawater. A terbium-pipemidic acid complex was used as CL enhancer. The method was used to determine sulfide in the concentration range of 1-30μmol/L in artificial seawater samples. The limit of detection of the method was 21nmol/L sulfide. The sensitivity of the CL method was eight times higher than that of the CL method reported previously. Br- ions, which are conservative ions, interfered with sulfide. We investigated the effects of salinity, water temperature, and interfering chemicals,such asheavy-metal ions and organic matter, on the performance of the CL method. In addition, sulfite-spiked natural seawater samples were analyzed. The results demonstrate that the CL method can be used to develop a deep-sea sulfide analyzer.

Strong enhancement of the chemiluminescence of cerium (IV)-Na2S system by mono-dispersed N-CDs generated in situ

In this study, nitrogen-doped carbon dots (N-CDs) was observed to strongly amplify the chemiluminescence (CL) intensity of Ce (IV)-Na2S system with an enhancement factor around 55. Possible mechanism was explored and discussed on account of results of free radical scavenger experiments, CL spectra and X-ray photoelectron spectroscopy (XPS), etc. During the CL process, mono-dispersed N-CDs generated in situ catalyzed the production of more 1O2 on its surface and the CL enhancement mainly attributed to the chemiluminescence resonance energy transfer (CRET) between (1O2)2*/Ce (III)* and N-CDs. The new CL system was then developed as a convenient and sensitive platform for H2S detection. The linear range was 20–200 nM and the limit of detection (LOD) was 0.32 nM. The applications in different water samples were proved to have good recovery rate (tap water: 100.46%-109.22%; pool water: 99.91%-102.87%) with satisfactory results.

Defective Site Modulation Strategy for Preparing Single Atom-Dispersed Catalysts as Superior Chemiluminescent Signal Probes

Single atom-dispersed catalysts (SADCs) with highly exposed active sites can be used as sensitive signal probes because of their superior catalytic efficiency. However, the dispersed atoms tend to aggregate, restricting the loading capacity of metal atoms. Herein, the defective sites on Zr-oxo clusters of metal-organic frameworks (MOFs) UiO-66-NH2 were modulated by excessive acetic acid and utilized for confining metal atoms with high loading capacity. To verify the feasibility of the designed strategy, the Co element was loaded onto MOFs UiO-66-NH2 to prepare SADCs with desirable Fenton-like activity. The prepared Co SADCs at a low concentration of 1.0 μg mL-1 are found to boost chemiluminescent (CL) emission for 3700 times due to the significantly improved Co content of 5.55 wt %. The superior CL enhancement efficiency is ascribed to reactive oxygen species generated by the accelerated decay of H2O2. To verify the application potential in CL assay, they were used as signal probes to establish an immunoassay method for carbendazim with a dynamic range of 1.0 pg mL-1 to 25 ng mL-1 and a limit of detection of 0.33 pg mL-1. This defective site modulation strategy paves an avenue for preparing SADCs with a high CL response by improving the loading capacity of metal atoms.

Chemiluminescent Cucurbit[n]uril-Based Chemosensor for the Detection of Drugs in Biofluids.

Chemiluminescence-based detection methods offer a superior signal-to-noise ratio and are commonly adopted for biosensors. This work presents the design and implementation of a supramolecular assay based on a chemiluminescent chemosensor. Specifically, an indicator displacement assay (IDA) with the supramolecular host-guest complex of chemiluminescent phenoxy 1,2-dioxetane and cucurbit[8]uril enables the low-micromolar detection of drugs in human urine and human serum samples. Cucurbit[8]uril thereby acts as a non-surfactant chemiluminescence enhancer and a synthetic receptor. Additionally, we show that adding an equimolar amount of cucurbit[8]uril to a commercially available dioxetane used in standard enzymatic chemiluminescence immunoassays enhances the chemiluminescence by more than 15 times. Finally, we demonstrate that a chemiluminescence resonance energy transfer between a unimolecular macrocyclic cucurbit[7]uril-dye conjugate and a phenoxy 1,2-dioxetane can be utilized to detect the herbicide paraquat at a micromolar concentration in aqueous media.

Flower-like Gold Nanoparticles for In Situ Tailoring Luminescent Molecules for Synergistic Enhanced Chemiluminescence.

In recent years, gold nanoparticles (AuNPs) have attracted much attention due to their ease of surface modification, excellent biocompatibility, and extraordinary optoelectronic and catalytic activities. Herein, based on a AuNP-catalyzed reaction, a strategy for tailoring luminescent molecules in situ is proposed to trigger an ultrastrong chemiluminescence (CL). In the strategy, flower-like AuNPs are prepared using CL molecular probes (Probe-OH for NaClO/ONOO-) via one-pot synthesis and subsequently act as a tailor for Probe-OH to generate novel CL molecules, allowing a synergistic CL enhancement about 4 times that of initial Probe-OH. Furthermore, by modification with poly(vinylpyrrolidone) (PVP) on the surface, the CL signals (only for NaClO) are amplified by 100 times based on an intermolecular chemically initiated electron exchange luminescence (CIEEL) mechanism. Given the improved sensitivity and selectivity over Probe-OH, the thus-formed CIEEL nanoplatform (PVP-Au) is successfully developed for detecting NaClO in a wide range of 2.5-100 μM, and the detection limit is 10.68 nM. This work provides unprecedented perspectives for expanding this facile and effective strategy for CL amplification based on AuNP catalysis.

CRISPR/Cas12a-Triggered Chemiluminescence Enhancement Biosensor for Sensitive Detection of Nucleic Acids by Introducing a Tyramide Signal Amplification Strategy.

CRISPR-based biosensors have attracted increasing attention in accurate and sensitive nucleic acid detection. In this work, we report a CRISPR/Cas12a-triggered chemiluminescence enhancement biosensor for the ultrasensitive detection of nucleic acids by introducing tyramide signal amplification for the first time (termed CRICED). The hybrid chain DNA (crDNA) formed by NH2-capture DNA (capDNA) and biotin-recognition DNA (recDNA) was preferentially attached to the magnetic beads (MBs), and the streptavidin-HRP was subsequently introduced to obtain MB@HRP-crDNA. In the presence of the DNA target, the activated CRISPR/Cas12a is capable of randomly cutting initiator DNA (intDNA) into vast short products, and thus the fractured intDNA could not trigger the toehold-mediated DNA-strand displacement reaction (TSDR) event with MB@HRP-crDNA. After the addition of tyramine-AP and H2O2, abundant HRP-tyramine-AP emerges through the covalent attachment of HRP-tyramine, exhibiting enhanced chemiluminescence (CL) signals or visual image readouts. By virtue of this biosensor, we achieved high sensitivity of synthetic DNA target and amplified DNA plasmid using recombinase polymerase amplification (RPA) as low as 17 pM and single-copy detection, respectively. Our proposed CRICED was further evaluated to test 20 HPV clinical samples, showing a superior sensitivity of 87.50% and specificity of 100.00%. Consequently, the CRICED platform could be an attractive means for ultrasensitive and imaging detection of nucleic acids and holds a promising strategy for the practical application of CRISPR-based diagnostics.

Enhanced chemiluminescence imaging sensor for ultrasensitive detection of nucleic acids based on HCR-CRISPR/Cas12a

CRISPR/Cas systems have ignited increasing attention in accurate and sensitive nucleic acids detection. In this work, we proposed the first CRISPR/Cas12a-based chemiluminescence enhancement biosensor by employing HCR amplifying strategy (CLE-CRISPR) for nucleic acids detection, which shows the advantages of high sensitivity and specificity, low-cost, visual imaging by comparison to reported biosensors. Upon the DNA target recognition, the activated CRISPR/Cas12a enabled randomly cutting initiator DNA (intDNA) into vast short products, which could not trigger the toehold-mediated DNA-strand displacement reaction (TSDR) with MB@crDNA. Thereby, the terminus of crDNA induced the hybridization chain reaction (HCR) with the coexistence of two hairpins (H1 and H2), forming a long double-stranded DNA framework. The attached streptavidin-AP yielded a conspicuous CL signal or visual imaging directly related to the DNA target concentration. The proposed CLE-CRISPR platform exhibited excellent sensitivity, with a relatively low detection limit at 3 pM for synthetic DNA target and single copy detection for plasmid by combining recombinase polymerase amplification (RPA) kit. We further validated the practical application of this platform using HPV clinical samples, achieving superior sensitivity and specificity of 88.89% and 100%, respectively. We believe that this work not only extends the application scope of CRISPR/Cas12a, but also devotes a new approach for clinical diagnosis.

Chemiluminescence Detection in the Study of Free-Radical Reactions. Part 2. Luminescent Additives That Increase the Chemiluminescence Quantum Yield.

The present review examines the use of chemiluminescence detection to evaluate the course of free radical reactions in biological model systems. The application of the method is analyzed by using luminescent additives that enhance the luminescence thanks to a triplet–singlet transfer of the electron excitation energy from radical reaction products and its emission in the form of light with a high quantum yield; these additives are called chemiluminescence enhancers or activators. Examples of these substances are provided; differences between the so-called chemical and physical enhancers are described; coumarin derivatives, as the most promising chemiluminescence enhancers for studying lipid peroxidation, are considered in detail. The main problems related to the use of coumarin derivatives are defined, and possible ways of solving these problems are presented. Intrinsic chemiluminescence and the mechanism of luminescence accompanying biomolecule peroxidation are discussed in the first part of the review.

A peroxyoxalate chemiluminescence recovery system based on the interaction of N-doped graphene oxide nanosheets and an oligopeptide for ultra-sensitive and selective copper(II) ion detection.

In this paper, a peroxyoxalate chemiluminescence (CL) recovery system based on the interaction of N-doped graphene oxide nanosheets (N-GONs) and an oligopeptide for copper(II) ion detection has been reported. N-GONs as an excellent CL enhancer are prepared by the hydrothermal method using citric acid and ammonia, and the morphology and structure are characterized in detail by TEM, XPS, FT-IR and UV/vis, etc. In the bis(2,4,6-trichlorophenyl)oxalate (TCPO) and hydrogen peroxide (TCPO + H2O2) CL reaction system, the addition of N-GONs gives a remarkable CL emission, which can be quenched by an oligopeptide composed of ten amino acid residues due to the interaction between the N-GON plane and the oligopeptide strand. While in the presence of copper(II) ion, the quenched CL is recovered gradually along with the addition of copper(II) ion in the system. Based on the above CL reactions, a TCPO + H2O2 + N-GONs + oligopeptide CL system is constructed, achieving an ultra-sensitive and selective detection of copper(II) ion in environmental water samples. The detection limit of this method is as low as 0.2 pmol L-1, which is at least three orders of magnitude lower than other CL methods. The N-GONs and oligopeptide involved in the CL system are environmentally friendly, making it possess potential in the detection of copper(II) ion in environmental water samples.

Emitter-Quencher Pair of Single Atomic Co Sites and Monolayer Titanium Carbide MXenes for Luminol Chemiluminescent Reactions.

A facile, one-step doping protocol was adopted to synthesize Co single atomic site catalysts (SASCs) in UiO-66 metal-organic frameworks. In view of highly uniform active sites of Co-O6 moieties, the SASCs specifically contribute to catalyzing the generation of a large amount of singlet oxygen instead of superoxide or hydroxyl radicals, which endows Co SASCs with a the remarkable enhancement effect (∼3775 times) on luminol chemiluminescent (CL) emission. Interestingly, monolayer titanium carbide MXenes can drastically quench the CL signal of the Co SASC-boosted luminol reaction by ∼94.6% as highly efficient luminescent absorbents. Furthermore, the emitter-quencher pair of Co SASCs and titanium carbide MXenes was successfully adopted to develop an immunoassay method for cardiac troponin I (cTnI) on an immunochromatographic test strip platform. With a sandwich immunoreaction mode, a titanium carbide MXene-labeled cTnI tracer antibody was captured on the test line of a test strip, which significantly inhibited the CL response of the Co SACs-boosted luminol system. The dynamic range for quantitating cTnI is 1.0-100 pg mL-1, with a detection limit of 0.33 pg mL-1 (3σ). The test strip was successfully used to detect cTnI in human serum samples collected from cardiopathy patients. This proof-of-principle work manifests both the CL enhancement of SASCs and the quenching behavior of MXenes, which shows the thrilling prospects of combinational usage of the two functionalized nanomaterials for tracking biological recognition events.

Ultraweak chemiluminescence enhanced on the surface of lanthanide metal–organic framework nanosheets synthesized by ultrasonic wave

In this paper, lanthanide metal–organic frameworks (Ln-MOFs, Ln = Ce, Gd, Ho) were facilely synthesized by ultrasonic method and applied in enhancing chemiluminescence (CL) emission of NaIO4-H2O2 system. The synthesized Ln-MOFs were characterized to be nanosheet-like shapes. Comparing with the NaIO4-H2O2 system without Ln-MOFs, the CL intensities of Ln-MOFs-NaIO4-H2O2 systems were enhanced 28, 32 and 67 times by Ce-MOFs, Gd-MOFs and Ho-MOFs, respectively. Catalytic properties of Ln-MOFs accounted for the improved performance in CL and increased the generation of some reactive oxygen species (ROS) (·O2−, 1O2 and ·OH) which induced CL enhancement. The large surface area of nanosheets and structural defects generated during the ultrasonic synthesis process could facilitate the exposure of catalytic active sites and ROS generation. This work gave insights into developing novel CL systems based on advanced materials with effective surfaces.

Relay Enhancement of Chemiluminescence in Studying the Kinetics of the Inhibited Oxidation of Olefins

Relay Enhancement of Chemiluminescence in Studying the Kinetics of the Inhibited Oxidation of Olefins

Next generation luminol derivative as powerful benchmark probe for chemiluminescence assays

Chemiluminescence (CL) provides outstanding analytical performance due to its independence from external light sources, background-free nature and exceptional sensitivity and selectivity. Yet, ultra-sensitive (bio)analysis is impeded by low hydrophilicity, poor quantum yields, fast kinetics or instability of most CL reagents such as luminol, acridinium esters, dioxetanes or peroxyoxalic derivatives. Photophysical studies show that m-carboxy luminol overcomes these limitations as its hydrophilic design provides a 5-fold increase in relative quantum yield resulting in superior performance in H2O2-dependent bioassays with 18-fold higher sensitivity for the quantification of its co-reactant H2O2, and 5-times lower detection limits for the luminophore. Studies with CL enhancers suggest its significance for mechanistic investigations in tandem with peroxidases. Finally, its integration into enzymatic and immunoassay applications demonstrates that m-carboxy luminol will provide signal enhancement, lower detection limits, and increased dynamic ranges for any other luminol-based CL assay, thus comprising the potential to replace luminol as benchmark probe.

On paper synthesis of metal-organic framework as a chemiluminescence enhancer for estimating the total phenolic content of food samples using a smartphone readout

Herein, a novel paper-based chemiluminescence (CL) assay is reported using a smartphone readout for on-site and reliable analytical applications. The CL system was based on the high-performance improving effect of cobalt-imidazole metal-organic framework (CoMOF) on luminol-hydrogen peroxide (H2O2) CL emission. The CoMOF was grown on paper and used as a support for the CL reaction, which led to an intense CL emission and good reproducibility. More importantly, the stability of luminol, as the CL reagent, was greatly improved in the presence of CoMOF. This high stability, along with the high-yield CL emission, makes the device highly suitable for commercialization. Furthermore, using a smartphone as the detector for the developed device made the process easier and more accessible for public usage. In this work, the new paper-based CL smartphone device was used for the detection of the total phenolic content of food samples. Phenolic compounds (PC) are hydroxyl radical scavengers that can effectively quench the CL emission of the luminol–H2O2–CoMOF system. After optimizing the reaction conditions, the system could detect PC at the μg mL−1 level. Detection limits of 0.12, 0.28, 0.46, 0.85, and 1.23 μg mL−1 were obtained for gallic acid, quercetin, catechin, kaempferol, and caffeic acid, respectively. This work is the first report on the practical application of smartphone CL assays for the estimation of PC. The proposed assay is an easy-to-use, low-cost, portable, and suitable assay for on-site screening purposes.