NBD-based colorimetric and ratiometric fluorescent probe in NIR for bisulfite

This work presented a FRET-ICT based fluorescent probe (named NTC) composed of coumarin-benzothiazole as the acceptor and 4-nitrobenzo[c][1,2,5] oxadiazole (NBD) as the donor for the detection of SO2 derivatives in NIR. Probe NTC possessed superior performance including selectivity, quickly response toward SO32-/HSO3- and high energy transfer efficiency (94 %). The test strips provided a simple and effective tool in detecting the presence of bisulfite. Besides, NTC was applied to test the sulfur dioxide derivatives in food samples and cells.

A Novel DNBS-based Fluorescent Probe for the Detection of H2S in Cells and on Test Strips

Hydrogen sulfide (H2S) plays a key role in the physiology and pathology of organisms, and H2S in the environment is easily absorbed and harmful to health. It is of great significance to develop a probe with good selectivity, high sensitivity and good stability that can detect hydrogen sulfide inside and outside organisms. In this work, we designed a novel "turn-on" fluorescent probe CIM-SDB for the detection of H2S. The probe CIM-SDB used indene-carbazole as the fluorophore and 2,4-dinitrobenzenesulfonyl as the recognition site. The probe CIM-SDB exhibited high selectivity and sensitivity to H2S (detection limit as low as 123 nM). Moreover, the probe CIM-SDB was successfully applied to the detection of intracellular exogenous and endogenous H2S, and the test strips prepared by the probe CIM-SDB could realize the convenient and rapid detection of H2S.

A FRET-based ratiometric fluorescent probe for sensing bisulfite/sulfite and viscosity and its applications in food, water samples and test strips

A FRET-based ratiometric dual-response fluorescent probe, CQI, constructed by combining quinolinium-indole as the acceptor and coumarin as the donor, was developed for sensing HSO3-/SO32- and viscosity. After the interaction of probe CQI with the analyte, we achieved a green channel for the response to HSO3-/SO32- and an orange channel for the response to viscosity. We comprehensively evaluated the ability of CQI to detect SO2 derivatives and viscosity using fluorescence spectroscopy. Probe CQI exhibited a large Stokes shift (196 nm), a high energy transfer efficiency (99.6 %) and a wide detection range (0-250 μM). The fluorescence intensity of the probe increased up to 14-fold with increasing viscosity, and CQI could detect the viscosity of food thickeners. More importantly, probe CQI could not only successfully monitor SO2 derivatives in various food and water samples, but also be prepared as bisulfite test strips.

Microfluidic-assisted integrated nucleic acid test strips for POCT

Numerous diseases have posed significant threats to public health, notably the global pandemic of COVID-19, resulting in widespread devastation due to its high infectivity and severity. The nucleic acid lateral flow assay (NALFA) addresses challenges of complexity, cost, and time associated with traditional assays, offering a reliable platform for rapid and precise nucleic acid target detection. NALFA is gaining prominence as a point-of-care testing (POCT) technique, thanks to its user-friendly operation and rapid results. Nevertheless, conventional NALFA relies on specialized technicians and involves labor-intensive steps like DNA extraction and PCR processes, impeding its efficiency. To overcome these limitations, integrating NALFA with microfluidic technology, widely employed in rapid field detection, holds promise. This review comprehensively outlines prevailing strategies for integrating NALFA, encompassing both research initiatives and commercial applications. Addressing the bottleneck of nucleic acid amplification as a rate-limiting step, the review delves into progress in amplification-free NALFA and highlights prevalent signal amplification techniques. Ultimately, the review outlines the future prospect of integrated NALFA development, capturing the technology's evolution and providing valuable insights for academic and commercial endeavors.

Rational development of a peptide-based probe for fluorescence and colorimetric dual-mode detection of Cu2+ and S2- ions: Real application in cell imaging and test strips

A new dual-mode probe FAM-SSH with fluorescence and colorimetric properties was developed by solid-phase peptide synthesis, comprising 5-carboxy fluorescein (5-FAM) as a fluorophore, and tripeptide (Ser-Ser-His) as a recognition group. FAM-SSH not only displayed highly selective detection of Cu2+ based on fluorescence quenching mode, but also achieved colorimetric recognition of Cu2+ in solution, wherein a color change was observable to the naked eye. Additionally, the FAM-SSH-Cu2+ ensemble was highly selective for S2- over a wide pH range (7.0-12.0), characterized by a fluorescence enhanced response and colorimetric recognition, which was caused by the release of FAM-SSH and the precipitation of CuS. Moreover, the limit of detection (LOD) values for Cu2+ and S2- were 55.5 nM and 31.1 nM, respectively. Results of sample analyses and cell imaging experiments indicated that FAM-SSH has exciting field practicability and good cell permeability, and would be further useful for detection and imaging in environmental systems and living cells. Finally, test strips were produced by immersing them in FAM-SSH solution, thereby creating a method for portable visual detection. More importantly, a smartphone-assisted visual sensing platform was also developed for semi-quantitative Cu2+ and S2- detection with LOD values of 0.48 μM and 1.22 μM, respectively.

Costing analysis of a point-of-care drug checking program in Rhode Island

BACKGROUND

Drug checking is a harm reduction strategy that provides greater awareness and information about the drug supply to the community. While fentanyl test strips are low-cost and available in most parts of the U.S., community-based organizations are considering using more sophisticated technologies, such as Fourier-transform infrared (FTIR) spectroscopy to test drugs. FTIR can detect multiple substances in a non-destructive manner that can be rapidly communicated to the program client by a trained technician, however implementation costs in community-based settings have not been assessed.

METHODS

We conducted a costing analysis of a new pilot drug checking service that employed an FTIR spectrometer, fentanyl test strips and confirmatory testing in Rhode Island from January 2023-May 2023. We used microcosting methods to determine the overall cost during this period and cost per drug checked, reflecting realistic service capacity.

RESULTS

Among 101 drug samples that were voluntarily submitted and tested, 53% tested positive for fentanyl, 39% for cocaine, 9% for methamphetamine and 13% for xylazine, a powerful sedative. The total cost during this period was $71,044 and the cost per drug checked was $474, though sensitivity analyses indicated that the cost would rise to $78,058 - $83,058 or $544 - $593 for programs needing to pay for specialized training.

CONCLUSIONS

These findings demonstrate feasibility and inform the resources needed to scale-up drug checking services to reduce overdose risk.

BODIPY-based fluorescent probe for cysteine detection and its applications in food analysis, test strips and biological imaging

Cysteine, as one of semi-essential amino acids, which is absorbed from protein-rich foods and acts considerable role in various physiological processes. Here, we designed and synthesized a BODIPY-based turn-on fluorescent probe BDP-S for detecting Cys. The probe displayed short reaction time (10 min), distinct color response (from blue to pink), large signal noise ratio (3150-fold), high selectivity and sensitivity (LOD = 11.2 nM) toward Cys. Moreover, BDP-S could not only be used for quantitative determination of Cys in food samples, but also be conveniently deposited on the test strips for qualitative detection of Cys. Notably, BDP-S was successfully used for imaging Cys in living cells and in vivo. Consequently, this work provided a hopefully powerful tool for detecting Cys in food samples and complex biological systems.

Colorimetric chemosensors for the selective detection of arsenite over arsenate anions in aqueous medium: Application in environmental water samples and DFT studies

Novel organic receptors N3R1- N3R3 were developed for the selective colorimetric recognition of arsenite ions in the organo-aqueous media. In the 50% aq. acetonitrile media and 70% aq. DMSO media, receptors N3R2 and N3R3 showed specific sensitivity and selectivity towards arsenite anions over arsenate anions. Receptor N3R1 showed discriminating recognition of arsenite in the 40% aq. DMSO medium. All three receptors formed a 1:1 complex with arsenite and stable for a pH range of 6-12. The receptors N3R2 and N3R3 achieved a detection limit of 0.008 ppm (8 ppb) and 0.0246 ppm, respectively, for arsenite. Initial hydrogen bonding on binding with the arsenite followed by the deprotonation mechanism was well supported by the UV-Vis titration, ¹H- NMR titration, electrochemical studies, and the DFT studies. Colorimetric test strips were fabricated using N3R1- N3R3 for the on-site detection of arsenite anion. The receptors are also employed for sensing arsenite ions in various environmental water samples with high accuracy.

Fluorescent detection of tartrazine based on the supramolecular self-assembly of cationic perylene diimide

A cationic perylene probe was designed and synthesized for sensitive determination of tartrazine. In the presence of tartrazine, the fluorescence of the perylene probe was quenched by efficient supramolecular self-assembly of the perylene derivate. The quenching is caused by the synergistic effect of noncovalent interactions including static electricity, π-π stacking, and hydrophobic interaction. Benefiting from these advantages, the probe exhibited excellent sensing performance to tartrazine within 2 min. The detection and quantification limit of tartrazine are as low as 2.42 and 8.07 nmol L-1, respectively, with a wide linear operation range from 15 to 500 nmol L-1. Most importantly, due to the high binding affinity (3.22 × 107 mol L-1) between the perylene probe and tartrazine, the sensing system shows great anti-interference capacity. Subsequently, the visualization application of the approach was evaluated by portable device, and the limits of detection for visual detection for test strip, membrane, and hydrogel were 0.5, 0.5, and 5 μmol L-1, respectively. The approach has been applied to monitor tartrazine in various food condiments with recoveries in the range 91.29-108.83%. As far as we know, this is the first report of using perylene-based probe for tartrazine determination, offering a promising strategy for the construction of perylene-based detection system in the field of food safety.

Comparison of two commercial methods with a UHPLC-MS/MS method for the determination of multiple mycotoxins in cereals

Immunoassay-based techniques are important on-site screening tools for the detection of mycotoxins in cereals. This study aims to evaluate the trueness, precision, repeatability and cross-reactivity of commercially available test strips, ELISA kits and UHPLC-MS/MS on analyzing zearalenone, ochratoxin A, deoxynivalenol, T-2 toxin and fumonisin B₁. The results showed that false negative rate (25.7 %-37.4 %) of all tested mycotoxins by test strips was higher than the false positive rate (0 %-31.0 %). The repeatability of ELISA kits at the declared LOD dispersed from -85.7 % to +98.4 %. ELISA kits were more accurate at 50 % of the maximum residue limit (MRL) of mycotoxins than 150 % and 200 %. All the tested deoxynivalenol/zearalenone derivatives had cross-reactivity with different level, and sample matrix could reinforce this overestimation of target mycotoxin. This study emphasized that higher-quality antibody screening and more analytical performance investigations are need to address for on-site detection of mycotoxins in the future.

A novel fluorescent probe based on a tripeptide-Cu(II) complex system for detection of histidine and its application on test strips and smartphone

Herein, we reported a novel peptide-based fluorescent probe DSSH for highly selective and sensitive detections of both Cu²⁺ and _l-histidine (_l-His). DSSH exhibited different color changes and fluorescence "on-off" response toward Cu²⁺ with a 2:1 binding stoichiometry, and the limit of detection (LOD) for Cu²⁺ was calculated to be 22.9 nM. The in situ formed DSSH-Cu²⁺ ensemble showed obvious fluorescence "off-on" response to _l-His based on replacement reaction with Cu²⁺, as well as the discernable color changes under 365 nm UV lamp irradiation with "naked eye". The specificity of Cu²⁺/_l-His interactions allowed _l-His to be determined without interference from other amino acids, and the detection limit of DSSH-Cu²⁺ ensemble response to _l-His was determined as 25.7 nM. Notably, DSSH was successfully applied for detecting Cu²⁺ and _l-His in RKO living cells owing to its remarkable fluorescence behavior and low cytotoxicity. Test strips experiments suggested that DSSH can recognize Cu²⁺ and _l-His together by a remarkable fluorescence change. More importantly, smartphone was combined with _l-His solutions of different concentrations and converted into digital values through RGB channels, which was successfully used for semi-quantitative identification of _l-His, and the limit of detection (LOD) was 0.97 μM.

Point-of-care community drug checking technologies: an insider look at the scientific principles and practical considerations

Drug checking is increasingly being explored outside of festivals and events to be an ongoing service within communities, frequently integrated within responses to illicit drug overdose. The choice of instrumentation is a common question, and the demands on these chemical analytical instruments can be challenging as illicit substances may be more complex and include highly potent ingredients at trace levels. The answer remains nuanced as the instruments themselves are not directly comparable nor are the local demands on the service, meaning implementation factors heavily influence the assessment and effectiveness of instruments. In this perspective, we provide a technical but accessible introduction to the background of a few common drug checking methods aimed at current and potential drug checking service providers. We discuss the following tools that have been used as part of the Vancouver Island Drug Checking Project in Victoria, Canada: immunoassay test strips, attenuated total reflection IR-absorption spectroscopy, Raman spectroscopy from powder samples, surface-enhanced Raman scattering in a solution of colloidal gold nanoparticles, and gas chromatography-mass spectrometry. Using four different drug mixtures received and tested at the service, we illustrate the strengths, limitations, and capabilities of such instruments, and expose the scientific theory to give further insight into their analytical results. Each case study provides a walk-through-style analysis for a practical comparison between data from several different instruments acquired on the same sample. Ideally, a single instrument would be able to achieve all of the objectives of drug checking. However, there is no clear instrument that ticks every box; low cost, portable, rapid, easy-to-use and provides highly sensitive identification and accurate quantification. Multi-instrument approaches to drug checking may be required to effectively respond to increasingly complex and highly potent substances demanding trace level detection and the potential for quantification.

Rational design of trimetallic AgPt-Fe3O4 nanozyme for catalyst poisoning-mediated CO colorimetric detection

Carbon monoxide (CO) is not only a highly poisonous gas that brings great health risk, but also a significant signaling molecule in body. However, it is still challengeable for development of alternative colorimetric probes to traditional organic chromophores for simple, sensitive and convenient CO sensing. Here, for the first time, we rationally design a novel hydrophilic AgPt-Fe₃O₄ nanozyme with a unique heterodimeric nanostructure for colorimetric sensing of CO based on the excellent peroxidase-like catalytic activity as well as highly poisonous effect of CO on the nanozyme's catalytic activity. Both experimental evidence and theoretical calculations reveal the trimetallic AgPt-Fe₃O₄ nanozyme is susceptible to poisoning with the strongest affinity towards CO compared to individual Fe₃O₄ or Ag-Fe₃O₄, which is attributed to the adequate exposure of the active metallic sites and efficient interfacial synergy of unique heterodimeric nanostructure. Accordingly, a novel nanozyme-based colorimetric strategy is developed for CO detection with a low detection limit of 5.6 ppb in solution. Furthermore, the probe can be prepared as very convenient test strips and integrated with the portable smartphone platforms for detecting CO gas samples with a low detection limit of 8.9 ppm. Overall, our work proposes guidelines for the rational design of metallic heterogeneous nanostructure to expand the analytical application of nanozyme.

A fluorescent probe based on triphenylamine with AIE and ICT characteristics for hydrazine detection

A fluorescent probe MAM based on triphenylamine scaffold was synthesized. The electron donating group 4-methoxyphenyl and the electron acceptor dicyanoethylene were introduced on the triphenylamine scaffold to form a D-π-A fluorescent probe. The probe MAM exhibited the typical aggregation-induced emission (AIE) and intramolecular charge transfer (ICT) characteristics with the bright orange-red fluorescent emission in high water fraction (f_w ≥ 50%) and negligible emission in low water fraction. The probe MAM could detect hydrazine (N₂H₄) in DMSO-tris-HCl (10 mM, pH7.4, v/v, 3:1) with high selectivity and sensitivity. The specific reaction between MAM and hydrazine and the formation of the hydrazone blocked the ICT process, and the system emitted the cyan fluorescence which could be easily observed by naked eyes. The limit of detection (LOD) was 0.196 μM (6.25 ppb), which is lower than the US Environmental Protection Agency standard (10 ppb). The test strips prepared by the probe MAM could realize the convenient and rapid detection of N₂H₄ solution and vapor. The application of MAM in actual water samples and cells was investigated, and the results showed that MAM could sense N₂H₄ in environmental and biological aspects with potential application prospects.

A Fluorescent Probe Based on the Hydrazone Schiff Base for the Detection of Zn(2+) and its Application on Test Strips

A novel fluorescent probe SHK for Zn²⁺ detection was designed based on the hydrazone Schiff base, successfully synthesized by Suzuki coupling and condensation reactions. The probe SHK in DMSO/H₂O showed extremely weak fluorescence. However, the solution exhibited an intensive yellow-green emission with the introduction of Zn²⁺. In contrast, negligible fluorescence change was observed when other metal ions were added, suggesting a high selectivity of SHK for Zn²⁺ detection. The Job's Plot analysis revealed that a 1:1 stoichiometric adduct SHK-Zn²⁺ formed during the Zn²⁺ sensing. The binding constant of the complex was determined to be 184 M^- 1, and the detection limit for Zn²⁺ was calculated to be 112 µM. Moreover, the probe SHK achieved selective fluorescence sensing for Zn²⁺ on test strips, which guaranteed its practical application prospect.

A new chromone functionalized isoqunoline derived chemosensor with fluorogenic switching effect for selective detection of Zn2+ in real water samples and living cells

In this work, a selective chemosensor, (E)-N'-((4-oxo-4H-chromen-3-yl)methylene)isoquinoline-1-carbohydrazide (ENO), was rationally developed for colorimetric and fluorogenic detection of Zn²⁺ ions. It was readily synthesized from 4-oxo-4H-chromene-3-carbaldehyde and isoquinoline-1-carbohydrazide via one-step Schiff reaction. ENO exhibited excellent fluorescent response performances toward Zn²⁺ over a wide pH range in EtOH/H₂O media, including a distinguished color change from colorless to gold, a low limit of detection (LOD) value (34 nM), strong complexation ability (1.36 × 10⁵ M^-1) and rapid identification (2 min). The sensing mechanism of ENO toward Zn²⁺ was proposed on the basis of the chelation-enhanced fluorescence (CHEF) process, which was further supported by IR studies and the density functional theory (DFT) calculation. Moreover, ENO presented here demonstrated outstanding capability in monitoring trace level of Zn²⁺ ions in real water samples, living cells as well as the on-site assay kit.

2D Co(3)O(4) modified by IrO(2) nanozyme for convenient detection of aqueous Fe(2+) and intercellular H(2)O(2)

A portable sensor for visual monitoring of Fe²⁺ and H₂O₂, two-dimensional Co₃O₄ modified by nano-IrO₂ (IrO₂@2D Co₃O₄) was prepared in this work, for the first time, with the help of microwave radiation at 140 °C, which was further stabilized onto common test strips. The present IrO₂@2D Co₃O₄ possessed superior dual-function enzyme-like activity with low toxicity and excellent biocompatibility. Especially, trace Fe²⁺ and H₂O₂ could exclusively alter their enzyme-like catalytic activity with discriminating hyperchromic or hypochromic effect, i.e., from blue to colorless or to dark blue for both IrO₂@2D Co₃O₄ dispersion and its functionalized test strips. The linear regression equations were A₆₅₂ = 0.5940 - 0.00041 c_Fe²⁺ (10^-8 M, R² = 0.9927) for Fe²⁺ and ∆A₆₅₂ = 0.0023 c_H2O2 + 0.00025 (10^-7 M, R² = 0.9982) for H₂O₂, respectively. When applied to visual monitoring of aqueous Fe²⁺ and intercellular H₂O₂, the recoveries were 101.2 ~ 102.5% and 95.8 ~ 103.7% with detection limits of 1.25 × 10^-8 mol/L and 1.02 × 10^-7 mol/L, respectively, far below the permitted values in drinking water set by the World Health Organization. The mechanisms for the enhancing enzyme-mimetic activity of IrO₂@2D Co₃O₄ and its selective responses to Fe²⁺ and H₂O₂ were investigated in detail.

An AIE based fluorescent chemosensor for ratiometric detection of hypochlorous acid and its application

Detecting and imaging intracellular hypochlorous acid (HClO) is of great importance owning to its prominent role in numerous pathological and physiological processes. In this contribution, a novel AIE-based fluorescent chemosensor has been developed by employing a benzothiazole derivative. The synthesized probe displayed remarkable ratiometric fluorescent response to HClO with a large emission shift (139 nm), resulting in naked-eye fluorescence changes from red to blue. Under the optimal conditions, this probe was capable of quantitatively detecting HClO within 10 s, and possessed good sensitivity and high selectivity toward HClO over other biologically relevant species. Moreover, it has been successfully utilized to image the exogenous and endogenous HClO in living cells through dual channels, and conveniently detect hypochlorous acid solution on test strips with better accuracy, demonstrating its potential for monitoring HClO in biological and environment fields.

Cu2O induced Au nanochains for highly sensitive dual-mode detection of hydrogen sulfide

Colorimetric and chemoresistive gas sensing methods have aroused great interest in H₂S monitoring due to their unique merits of naked-eye readout, and highly sensitive and rapid detection. However, combining these two methods for gas detection, especially utilizing one material as their common sensing material is a grand challenge because they are inconsistent in sensing mechanism. Taking advantage of the strong chemical affinity of Cu₂O for H₂S and the excellent performance of localized surface plasmon resonance (LSPR) of Au nanoparticles (NPs) in the visible regions and its ability as a noble metal to enhance gas sensing property, the Cu₂O-Au nanochains (NCs) were prepared for dual-mode detection of H₂S gas. The Cu₂O-Au chemoresistive gas sensor shows a 5-fold higher response than Cu₂O sensor at room temperature with a low detection limit of 10 ppb. Such good performance is attributed to the spillover effect and catalytic activity of Au NPs, and the enhanced H₂S adsorption after Au loading as revealed by density functional theory calculation. Test strips containing Cu₂O-Au produced for gaseous H₂S detection show superior color gradient changes (blue, yellow, and brown). Finally, the practicability of the method was validated by real-time monitoring H₂S released from cell culture.

Integration of quantum dots with Zn2GeO4 nanoellipsoids to expand the dynamic detection range of uranyl ions in fluorescent test strips

Fluorescent colorimetric test strips normally have a narrow dynamic detection-range due to the limited responsive range from single responsive materials, which cannot meet the wide detection requirement in practical applications. Herein, we developed an approach to detect uranyl ions (UO₂²⁺) with a broad detection range using the synthesized ZnS:Mn quantum dots (QDs) modified Zn₂GeO₄ nanoellipsoids (Zn₂GeO₄ @ZnS:Mn NEs), containing two responsive materials with the opposite signal responses at different UO₂²⁺ concentrations. Specifically, a red to chocolate color change was observed at low analyte concentrations (0.01-100 μM) resulting from the photoinduced electron transfer effect from ZnS:Mn QDs to UO₂²⁺. A sequentially olive drab to green color change has been observed when further increasing the UO₂²⁺ concentration (100-1000 μM) as a result of the antenna effect between Zn₂GeO₄ nanoellipsoids and UO₂²⁺. In addition, a low-cost and portable fluorescent test strip has been further fabricated through embedding Zn₂GeO₄ @ZnS:Mn NEs on a microporous structure membrane, demonstrating a facile yet effective colorimetric response to UO₂²⁺ in lab water, lake water, and seawater with a wide dynamic range. Therefore, it is potentially attractive for real-time and on-site detection of UO₂²⁺ in sudden-onset situations.

Peptide-based colorimetric and fluorescent dual-functional probe for sequential detection of copper(Ⅱ) and cyanide ions and its application in real water samples, test strips and living cells

A novel dual-functional peptide probe FLH based on fluorescent "on-off-on" strategy and colorimetric visualization method was designed and synthesized. This new probe exhibited highly selective and rapid detection of Cu²⁺ with significant fluorescent "turn-off" response, with a visible colorimetric change from yellow to orange. The combination ratio of FLH to Cu²⁺ (1:1) was determined using ESI-HRMS spectra and Job's plot. The fluorescent emission showed a good linear response (R² = 0.9986) with a low detection limit of 1.5 nM. In addition, the FLH-Cu²⁺ complex displayed colorimetric changes and a fluorescent "off-on" response toward CN^- over a wide pH range from 7 to 12. This detection behavior was observed within 20 s, with a limit of detection (LOD) for CN^- at 12.7 nM. Based on stability and accuracy, FLH was next developed as dual-functional test strips, and was also successfully applied to detect Cu²⁺ and CN^- in two actual water samples. More importantly, the cytotoxicity studies indicated that FLH had good biocompatibility and low toxicity, and was successfully utilized for monitoring Cu²⁺ and CN^- in living cells through fluorescence imaging.

Rapid and accurate etizolam detection using surface-enhanced Raman spectroscopy for community drug checking

BACKGROUND

In British Columbia, Canada, illicit opioids have been increasingly combined with etizolam, a benzodiazepine analog, that continues to challenge popular portable drug checking technologies as it is often present in low concentrations as a result of its high potency. An unknown combination of opioids and benzodiazepines may have dangerous consequences due to unpredictable dosing, increased respiratory depression, and complicated overdose response measures.

METHODS

Surface-enhanced Raman spectroscopy (SERS) using a portable Raman spectrometer is used to establish a univariate model for the detection of etizolam in opioid drug mixtures (n=100) obtained from the Vancouver Island Drug Checking Project, where the presence of etizolam has been determined using paper-spray mass spectrometry. Benzodiazepine immunoassay test strips are also performed on all samples for comparison.

RESULTS

SERS is shown to detect etizolam with high sensitivity (96%) and specificity (86%). In contrast, benzodiazepine test strips demonstrate a low sensitivity (8%) for the detection of etizolam of the same samples (n=100), with only small improvements when studied over a larger subset of samples (n=506, sensitivity = 29%).

CONCLUSION

We have demonstrated the potential of SERS for trace detection of etizolam within complex sample matrices. Since SERS is one of the few portable technologies capable of trace detection, further studies on its ability for quantification and discrimination of trace adulterants in street samples is of significant interest for point-of-care applications.

An immunochromatography strip with peroxidase-mimicking ferric oxyhydroxide nanorods-mediated signal amplification and readout

Immunochromatography testing strips (ICTs) promise to become the point-of-care test format for early diagnosis due to their convenience, low cost, and simplification. However, the insufficient signal intensity and limited sensitivity of this format hamper their application. Herein, we overcame these limitations by integrating rod-like ferric oxyhydroxide (β-FeOOH) nanoparticles with ICTs. By varying the concentration of PEI, a one-pot, mild-temperature hydrolysis method was adapted for the synthesis and morphology regulation of β-FeOOH nanorod. Due to the excellent enzyme-like catalytic activity toward peroxidase substrates (TMB) in the presence of hydrogen peroxide (H₂O₂), the β-FeOOH nanorod in ICTs served as a signal generator and the nanozyme for signal amplification. The proof-of-concept work was performed for the detection of human chorionic gonadotropin (hCG). A two fold improvement of detection sensitivity was achieved compared to the sensitivity of conventional Au NPs-based ICTs. These results show that β-FeOOH-based ICT has a potential application in POCT detection in clinical diagnostics.

Designed multifunctional ratiometric fluorescent probe for directly detecting fluoride ion/ dichromate and indirectly monitoring urea

UiO-66-NH₂@eosin Y composite was obtained by confining eosin Y (EY) into the cavities of Zr-MOF and could emit two fluorescence peaks at 453 and 543 nm at an excitation wavelength of 355 nm. This multi-responsive and multifunctional ratiometric fluorescent nanoprobe not only enable directly distinct detection of F^-/Cr₂O₇^2- with ultra-high selectivity and sensitivity, but also could indirectly monitor the concentration of urea based on unique enzymatic hydrolysis reaction. The multifunctional probe was utilized for fluorescence labeling F-/Cr₂O₇^2- in sweat latent fingerprint through an environmentally friendly powder strategy and exhibited obvious luminescence visualization changes. Notably, the corresponding portable on-line test strips of probe for detection of F^- and Cr₂O₇^2- were made for monitoring the levels of F^- and Cr₂O₇^2-. Furthermore, the probe was applied to evaluate the degrees of F^-/Cr₂O₇^2- in HepG-2 cell and urea in serum with superior results,which indicate the potential application of the as-synthesized UiO-66-NH₂@EY as multifunctional probe for the detection of F^-, Cr₂O₇^2- and urea in biological samples. Finally, in order to extend the device-based applications of probe, an AND-OR-coupled molecular logic gate was put on agenda.

Colorimetric cellulose-based test-strip for rapid detection of amyloid β-42

An innovative sensing assay is described for point-of-care (PoC) quantification of a biomarker of Alzheimer's disease, amyloid β-42 (Aβ-42). This device is based on a cellulose paper-dye test strip platform in which the corresponding detection layer is integrated by applying a molecularly imprinted polymer (MIP) to the cellulose paper surface. Briefly, the cellulose paper is chemically modified with a silane to subsequently apply the MIP detection layer. The imprinting process is confirmed by the parallel preparation of a control material, namely a non-imprinted polymer (NIP). The chemical changes of the surface were evaluated by Fourier transform infrared spectroscopy (FTIR), contact angle, and thermogravimetric analysis (TG). Proteins and peptides can be quantified by conventional staining methods. For this purpose, Coomassie blue (CB) was used as a staining dye for the detection and quantification of Aβ-42. Quantitative determination is made possible by taking a photograph and applying an appropriate mathematical treatment to the color coordinates provided by the ImageJ program. The MIP shows a linear range between 1.0 ng/mL and 10 μg/mL and a detection limit of 0.71 ng/mL. Overall, this cellulose-based assay is suitable for the detection of peptides or proteins in a sample by visual comparison of color change. The test strip provides a simple, instrument-free, and cost-effective method with high chemical stability, capable of detecting very small amounts of peptides or proteins in a sample, and can be used for the detection of any (bio)molecule of interest.

Construction of DCM-based NIR fluorescent probe for visualization detection of H2S in solution and nanofibrous film

Hydrogen sulfide (H₂S) played crucial roles in biological processes and daily life, and the abnormal level of H₂S was associated with many physiological processes. In this paper, we designed and developed a dicyanomethylene-4H-chromene (DCM)-based near-infrared (NIR) fluorescent probe DCM-NO guided by theoretical calculation. The probe displayed excellent selectivity towards H₂S with a fast response time (3 min) and low detection limit (fluorescence 25.3 nM/absorption 6.61 nM) in Hela cells and real water samples. Furthermore, the probe-doped solid sensing materials (test strips and nanofibrous films) exhibited specific visualization of H₂S under ambient light or hand-held UV lamp, providing great potential for on-site and real-time application in environmental and biological systems.

Monitoring water quality through citizen science while teaching STEM undergraduate courses during a global pandemic

Due to the COVID-19 pandemic, many universities struggle to engage students while implementing a distance-based teaching/learning approach and to provide hands-on activities to students enrolled in STEM classes. Implementing service-focused activities that can be conducted by the students remotely can overcome these struggles. The goals of this study were to 1) implement citizen science activities focused on water quality using three commercially available low-cost test strips (2:1, 5:1, and 16:1) while teaching four undergraduate engineering courses at the University of Mississippi (UM) during a pandemic event, and 2) evaluate the acceptability and validate the results obtained. Eighty-five undergraduate students (citizen scientists) and five research scientists (control group) collected two water samples (with triplicates) after receiving detailed step-by-step written guidelines and video tutorials. One hundred twenty tap water samples were collected from private households across Lafayette County and its surrounding counties and multiple buildings on campus. Five laboratory fortified blank (LBF) samples were implemented to validate the results. While the academic background of the participants did not impact the results (p > 0.05), the results obtained using the different test strips were statistically different (p < 0.05). In fact, results obtained using the 2:1 and the 5:1 test strips were close to the LFBs, while, except for the higher concentration of Total Alkalinity (40 mg/L CaCO₃), results obtained using the 16:1 test strips were significantly different than the LFBs. Results (in terms of pH, Nitrate, and Total Chlorine) obtained by the citizen scientists using the 2:1 and 5:1 test strips were consistent with those reported in the annual drinking water quality reports from UM and municipalities included in the investigated region. Overall, this activity was well received by the students. Approximately 75% of them agreed that this hands-on activity was a positive experience while struggling to attend face-to-face classes.

Visual monitoring of trace water in organic solvents based on ecofriendly b/r-CDs ratiometric fluorescence test paper

Developing a green, non-toxic and easy to synthesize of fluorescence probe for fast and visual detecting trace water in various organic solvents was an important task. Here, a novel dual-emission fluorescence probe (b/r-CDs) was designed based on the red CDs (r-CDs) and blue CDs (b-CDs) to detect the trace water and enhance the visualization for naked-eye observation in different organic solvents. Among, the red fluorescence carbon dots (CDs) was found to have the capability to monitor trace amounts of water, which synthesized with green tea by facile ultrasonic method. Further, Such a dual-emission probe could fast monitor trace water in various organic solvents with high stability and fast response. Importantly, a synergistic mechanism of the dynamic process (b-CDs) and static quenching (r-CDs) was proved for the study of water detection. Moreover, the test paper was made for detecting trace water in different organic solvents, achieving convenient and effective detection.

A water-soluble fluorescent probe for the detection of thiophenols in water samples and in cells imaging

Water pollution is the main cause of death of aquatic organisms such as fish et al. Content of thiophenols in water samples is an important indicator for assessing the degree of water pollution. The development of fluorescent probes with high selectivity and high sensitivity to detect thiophenols in water samples is extremely important in both environmental and life sciences. Although several fluorescent probes for thiophenols detection have been reported in recent years, most of them required the assistance of organic solvents to remedy the restriction caused by the poor water solubility of the probe, which did not fully reflect the actual situation of thiophenols in actual water samples. To fully overcome this shortage, we modified the 1,8-naphthylimide moiety with carboxyl to obtain a water-soluble fluorescent probe which could react with thiophenols specifically through nucleophilic aromatic substitution reaction (S_NAr) reaction with turn-on fluorescent responses. The corresponding detection limit was 71 nM. Supported by the spectroscopic changes, test strips based on the probe could detect thiophenols quantificationally and conveniently. At the same time, the probe could detect thiophenols in water sample with quantitative recovery. Besides, cell imaging experiments demonstrated the possibility of the probe to detect thiophenols in living cells.

A highly sensitive fluorescent sensor for Cd2+ and Zn2+ based on diarylethene with a pyrene unit

A novel multifunctional diarylethene fluorescence sensor 1O containing pyrene unit was designed and synthesized. The photochromism and fluorescence photoswitching properties of this diarylethene were studied in detail by irradiation of UV/Vis lights and response of metal ions in acetonitrile solution. Diarylethene fluorescence sensor 1O has high selectivity and sensitivity for the detections of Cd²⁺ and Zn²⁺. The limit of detections (LODs) for Cd²⁺ and Zn²⁺ were determined to be 1.85 × 10^-9 mol L^-1 and 7.68 × 10^-9 mol L^-1, respectively. The binding constants (K_a) of 1O with Cd²⁺ and Zn²⁺ in acetonitrile solution were calculated to be 5.8 × 10⁴ mol^-1 L and 6.0 × 10⁴ mol^-1 L, respectively. The compound 1O responded to the metal ions (Cd²⁺/Zn²⁺) to form complexations with 1 : 1 stoichiometry which were verified by Job's plot and MS analysis, respectively. In addition, the fluorescence sensor 1O has been successfully applied to the detection of Cd²⁺ and Zn²⁺ in real water samples and processed into test strips for on-site analysis and testing.

Synthesis of methionine methyl ester-modified coumarin as the fluorescent-colorimetric chemosensor for selective detection Cu2+ with application in molecular logic gate

A methionine methyl ester-modified coumarin derivative was designed and synthesized, which could discriminate Cu²⁺ from other metal ions in HEPES buffer (10 mM, pH 7.4)/CH₃CN (40:60, V/V). The detection limit of WM toward Cu²⁺ was 1.84 × 10^-7 M, which was lower than the concentration of Cu²⁺ in drinking water suggested by WHO and EPA. And the proposed coordination mode exhibiting the interaction between WM and Cu²⁺ was studied by UV-Vis, fluorescence spectrum, ESI-MS and FT-IR. Based on the fluorescent reversibility of WM, WM was considered as a molecular logic gate and molecular keypad lock. In addition, the test strips and the silica gel plates prepared from the solution of WM also demonstrate the favorable selectivity toward Cu²⁺.

A highly sensitive fluorescent probe with different responses to Cu2+ and Zn2

We report a highly sensitive fluorescent probe based on p-dimethylaminobenzoyl derivatives (probe L) for the detection of Cu²⁺ and Zn²⁺. In this work, the probe L exhibited a fluorescent turn-on sensing model to Cu²⁺ and Zn²⁺ with a distinct fluorescent color change from colorless to green and yellow respectively. Probe L exhibited high selectivity as a fluorescent Cu²⁺/Zn²⁺ probe with a limit of detection (LOD) of 45 nM/17 nM. The results of ¹H NMR titrations revealed that the response of L to Cu²⁺ and Zn²⁺ was triggered by the interaction of the thiophene unit and the metal ion. Furthermore, the fluorescence titrations and Job's plot curves displayed the binding ratio of 1:2 for Cu²⁺ and 1:1 for Zn²⁺ metal-L complex formation respectively. Density functional theory calculation also demonstrated the possibility of molecular luminescence and the process of metal-L complex formation. Additionally, fluorescent test strips have been prepared for convenient detection of Cu²⁺ and Zn²⁺, which means the convenient and rapid assay in real samples can be achieved.

A cyclometalated iridium(III) complex-based fluorescence probe for hypochlorite detection and its application by test strips

A new cyclometalated iridium(III) complex-based fluorescence probe (IrCN) for hypochlorite (ClO^-) has been synthesized and characterized. The probe displayed nonfluorescent around 577 nm, while a 54-fold enhancement in fluorescence emission intensity was observed after the addition of ClO^- due to the removal of C=N isomerization effect. Such "turn-on" fluorescence probe worked excellently in wide pH range (5-12) with short response time (<20 s) and the detection limit was as low as 0.11 μM. In addition, IrCN exhibited high selectivity towards ClO^- even in the presence of other competing species. Furthermore, IrCN was successfully integrated in fluorescent test strips for real-time detection of ClO^-.

Highly selective and ratiometric fluorescent nanoprobe for the detection of cysteine and its application in test strips

Cysteine (Cys) is a bithiol that plays a vital role in many physiological processes. However, it is difficult to discriminate Cys from homocysteine (Hcy) and glutathione (GSH), due to their similar chemical structures and reactivity. Herein, we have developed a polymeric nanoprobe, nanoHFA, for ratiometric, highly selective, and sensitive detection of Cys based on 7-hydroxycoumarin-3-carboxylic acid (HC) and fluorescein isothiocyanate (FITC)-acrylate (FITC-A) group-functionalized lipopolymer DSPE-PEG. The probe nanoHFA showed a strong fluorescence emission peak centered at 450 nm attributed to HC and a weak fluorescence emission peak centered at 520 nm due to the photoinduced electron transfer (PET) process of FITC induced by acrylate group. In the presence of Cys, the fluorescence signal at 520 nm could be lit up and the ratio of F_520nm/F_450nm showed a good linear relationship in the range of 5-60 μM with a low detection limit of 0.37 μM. The probe also displayed excellent water solubility and high selectivity to Cys over other biothiols such as Hcy and GSH. Moreover, we further used probe nanoHFA to detect Cu²⁺ ions in the range of 100-550 nM with a detection limit of 77 nM. The nanoprobe was successfully applied for the quantitative detection of Cys in fetal bovine serum, and fluorescent strips were developed for facile and visual detection of Cys and Cu²⁺ ions. Graphical abstract ᅟ.

A highly selective colorimetric and "turn-on" fluorimetric chemosensor for detecting CN(-) based on unsymmetrical azine derivatives in aqueous media

A novel highly selective chemosensor S1 for cyanide based on unsymmetrical azine derivative was successfully designed and synthesized, which showed both colorimetric and fluorescence turn-on responses for cyanide ions in aqueous. This structurally simple chemosensor could detect CN(-) anion over other anions in aqueous solution DMSO/H2O (v/v=3:2) undergo deprotonation reaction. Results showed that the chemosensor S1 exhibited 50 fold enhancement in fluorescence at 530nm and showed an obvious change in color from colorless to yellow that could be detected by naked eye under the UV-lamp after the addition of CN(-) in aqueous solution. Moreover, the detection limit on fluorescence response of the sensor to CN(-) is down to 6.17×10(-8)M by titration method. Test strips based on S1 were obtain, which could be used as a convenient and efficient CN(-) test kit to detect CN(-) in aqueous solution.

Development of test strips for rapid buprenorphine detection in vitro

OBJECTIVES

Buprenorphine (BUP) is the primary treatment for narcotic addiction, but it is often abused by opioid-dependent patients in many countries. For timely and effective detection and controlling the amount of BUP used in therapy, a rapid and sensitive test is needed. In the present study, we describe the development of test strips using monoclonal antibodies (MAbs) for the detection of BUP.

DESIGN AND METHODS

The MAbs were generated from hybridomas, and purified MAbs were used to create colloidal gold-antibody conjugates that were placed in the test strips.

RESULTS

The BUP test strips had a limit of detection (LOD) of 12.5 ng/mL and did not cross-react with other drugs tested at physiological levels.

CONCLUSIONS

Therefore, this assay has sufficient sensitivity and specificity for BUP detection in urine specimens so that the dosage of BUP given to individuals being treated for opioid dependence can be monitored.