Portable Detection Platform Research Articles

A dual-reaction sites fluorescent probe for accurate detection of benzoyl peroxide in food

Benzoyl peroxide (BPO) is widely used as a whitening agent in flour, but excessive intake of BPO will severely endanger human health. To quickly and accurately detect BPO on-site, we have rationally designed a novel fluorescent probe PTPY-BE with dual-reaction sites. PTPY-BE underwent a specific cascade reaction with BPO to achieve high-contrast fluorescence turn-on response along with significant achromic reaction. The probe has high sensitivity, excellent selectivity, strong anti-interference ability and low detection limit (LOD = 0.83 mg·kg−1) for BPO. Furthermore, a portable detection platform was fabricated, which offers the portability and color visualization of traditional test strips and the color recognition of a smart device, enabling on-site visualization and quantitative detection of BPO. This platform has been successfully used to determine BPO in real food samples with good recoveries (93.59% - 107.13%). Therefore, this platform possessed great prospect and potential application for the determination of BPO in food.

Rapid, sensitive, and visual detection of pseudorabies virus with an RPA-CRISPR/EsCas13d-based dual-readout portable platform

Pseudorabies viruses (PRV) pose a major threat to the global pig industry and public health. Rapid, intuitive, affordable, and accurate diagnostic testing is critical for controlling and eradicating infectious diseases. In this study, a portable detection platform based on RPA-CRISPR/EsCas13d was developed. The platform exhibits high sensitivity (1 copy/μL), good specificity, and no cross-reactivity with common pathogens. The platform uses rapid preamplification technology to provide visualization results (lateral flow assays or visual fluorescence) within 1 h. Fifty pig samples (including tissues, oral fluids, and serum) were tested using this platform and real-time quantitative polymerase chain reaction (qPCR), showing 34.0 % (17 of 50) PRV positivity with the portable CRISPR/EsCas13d dual-readout platform, consistent with the qPCR results. These results highlight the stability, sensitivity, efficiency, and low equipment requirements of the portable platform. Additionally, a novel point-of-care test is being developed for clinical use in remote rural and resource-limited areas, which could be a prospective measure for monitoring the progression of pseudorabies and other infectious diseases worldwide.

Specific detection of gut pathogens for one-pot chip based on RPA-CRISPR/Cas12a

BackgroundThere are billions of bacteria in the intestine, most of which are harmless and play important roles in humans. Although only a very small number of bacteria can cause diseases, once the pathogenic bacteria are ingested into the body and multiply in large quantities, it can lead to inflammatory diseases in the intestines and even other organs. Although polymerase chain reaction can specifically detect bacterial nucleic acid. However, the demand for temperature cycling limits its portability. Therefore, it is hoped to establish a high-throughput, highly specific and portable detection platform for directly detecting nucleic acid of intestinal pathogens. ResultsHerein, a one-pot chip based on RPA-CRCISPR/Cas12a platform was developed. The chip is the same size as a glass slide and allows detection at the same temperature. Multiple samples could be detected simultaneously on the one chip, achieved high-throughput detection and improved the integration of detection. The specific recognition of CRISPR/Cas12a avoided the influence of non-specific amplification of RPA and enhanced the specificity of the analysis. At the same time, the one-pot chip avoided secondary contamination when the lid was opened during the analysis process. And the bacterial concentration showed good linearity at 102-108 cfu mL−1. The limit of detection could be as low as 0.43 cfu mL−1. This method has been successfully used to detect pollution samples. It can provide a reliable platform for early screening of gastrointestinal and other inflammatory diseases. SignificanceThe one-pot chip based on the RPA-CRISPR/Cas12a platform established can directly detect the nucleic acid of intestinal pathogens, with portability and specificity. It is worth noting that the platform has good programmability, can be used for other target detection by changing crRNA and RPA primers, it can achieve multi sample detection on the one chip.

Portable detection platform integrated with smartphone-assisted ratiometric fluorescence sensor for visual on-site detection of lead(Ⅱ) in aquatic products

Lead ion (Pb2+) pollution seriously threatens the quality of aquatic products. In this study, a ratiometric fluorescence sensor consisting of tangerine fluorescent Mn:ZnS QDs (T-QDs) and blue fluorescent Fe-MOF (B-MOF) was developed for selective recognition of Pb2+. Upon exposure to Pb2+, the fluorescence of T-QDs was quenched while the fluorescence of B-QDs was slightly changed, causing the changes of fluorescence colors from tangerine to blue with a detection limit (LOD) of 3.79 nmol/L. The sensor also had the strengths of low cost, easy to operate, excellent sensitivity and selectivity. Significantly, a portable detection platform integrated with the sensor was constructed to achieve on-site visual detection. As expected, the detection platform was successfully applied for testing Pb2+ with the LOD of 7.78 nmol/L. The strategy may not only provide a great capacity for on-site monitoring of Pb2+ in aquatic products but also expand application in environmental pollution detection.

Catalytic Hairpin Assembly-Based Self-Ratiometric Gel Electrophoresis Detection Platform for Reliable Nucleic Acid Analysis.

The development of gel electrophoresis-based biodetection assays for point-of-care analysis are highly demanding. In this work, we proposed a ratiometric gel electrophoresis-based biosensing platform by employing catalytic hairpin assembly (CHA) process functions as both the signal output and the signal amplification module. Two types of nucleic acids, DNA and miRNA, are chosen for demonstration. The proposed strategy indeed provides a new paradigm for the design of a portable detection platform and may hold great potential for sensitive diagnoses.

Ferrous Ions Modulated Copper Nanocluster as a Fluorescent and Colorimetric Switch for the Detection of L–DOPA

AbstractL‐3,4‐dihydroxyphenylalanine (levodopa or L–DOPA) a precursor of neurotransmitter dopamine, has been universally prescribed as a gold standard for treatment of Parkinson's Disease (PD). However, direct administration of L–DOPA has risky adverse effects which makes it challenging in the treatment of PD. Hence developing simple detection platform for sensing of L–DOPA is significant. In this work, we have developed cysteine stabilized copper nanocluster quenched with Fe2+ (Fe2+@cys@CuNC) and used as both fluorescent and colorimetric probe for detection of L–DOPA. L–DOPA attributed a fluorescence quenching effect on developed probe. Fe2+@cys@CuNC detected L–DOPA within a linear range from 0.06 mM to 1.31 mM with a low limit of detection (LoD) of 6.57 nM. The probe also exhibited high selectivity for L–DOPA over other biomolecules and neurotransmitters. Furthermore, the capability of this probe was validated by sensing L–DOPA from human serum with excellent recovery rates of 85.75 % to 115.07 %. A low‐cost paper strip‐based portable detection platform was also developed for visual detection of L–DOPA.

Cucurbit[8]uril-Based Supramolecular Probe for the Detection of 3-Nitrotyrosine in Human Serum and Plasma.

The biomarker 3-nitrotyrosine (3-NT) is widely recognized as an indicator of renal oxidative stress injury, making its detection crucial for the early identification of renal insufficiency. This study presents the design and synthesis of a tetraphenylstyrene imidazole derivative (TIPE-MI), which is utilized to create a supramolecular probe in conjunction with cucurbit[8]uril (Q[8]) through host-guest interactions. The resulting supramolecular self-assembly exhibits excellent optical properties and has been employed for the specific detection of 3-NT through fluorescence quenching. The introduction of 3-NT resulted in a decreased fluorescence intensity of the yellow fluorescent probe, which gradually transitioned from bright yellow to light yellow and then became colorless as the 3-NT concentration was increased. A portable detection platform was devised to augment the efficiency of detection. In order to facilitate biological applications, we have substantiated the probe's exceptional precision in detecting 3-NT in biological samples, encompassing human serum and plasma. The probe also exhibited negligible cytotoxicity. The accumulation of the probe in renal cells elicited a fluorescence signal, thereby indicating the prospective viability of this system for visual detection with renal cytocompatibility.

Smartphone-integrated paper-based sensing platform for the visualization and quantitative detection of pymetrozine

Pymetrozine (PYM) is an effective pyridine insecticide for controlling aphids, while its residues pose a serious threat to human health. Herein, a europium complex (Eu-DBPA, DBPA represents deprotonated 2,5-dibromoterephthalic acid ligand) probe was prepared for the detection of PYM via fluorescence quenching. The detection process has the advantages of short response time (2 min), wide linear range (0–4 and 4–45 mg/kg) and low detection limit (2.2 μg/kg). Furthermore, a portable detection platform was designed by integrating Eu-DBPA-based paper strip with smartphone and applied for the visual detection of PYM in real cucumber, tomato, cabbage and apple samples, obtaining satisfactory recovery (99.00 %–107.00 %) and low standard deviation (RSD < 3.4 %). In addition, a logic gate device was designed to simplify the detection process. The smartphone-integrated paper-based probe detection platform provides a new strategy for intelligent and online identification of hazards in environmental and biological samples.

A smartphone-assisted portable strategy based on maple leaf-like Au/Cu2S/MoS2 composite for photothermal and colorimetric sensing of cortisol

Herein, we describe a first-time synthesis of a maple leaf-like Au/Cu2S/MoS2 composite (denoted as ACM throughout this paper) with both photothermal and peroxidase (POD) activities. Based on the ACM, we developed a smartphone-assisted portable detection platform for the photothermal and colorimetric dual-mode sensing of cortisol in human saliva. Because of complementary base pairing, the “Y”-type signal-probe (formed by the coincubation of ACM-DNA1 and ACM-DNA2) is fixed on cortisol-specific aptamer-functionalized magnetic beads (MB–Aptcortisol). ​In the presence of target cortisol, MB-Aptcortisol is more likely to combine with cortisol, “Y”-type signal-probes are released, which can oxidize 3,3′,5,5′-tetramethylbenzidine (TMB) to blue oxTMB in the existence of H2O2. Notably, the oxTMB exhibits a distinct photothermal response which, in combination with the photothermal properties of the ACM, achieves transduction and signal amplification of cortisol through a cascade enzyme reaction. The photothermal and colorimetric signals increase with increasing target concentrations. This portable dual-signal sensing platform enables the detection of cortisol in the range of 5–10000 ng/mL, with detection limits of 0.11 and 0.25 ng/mL for photothermal and colorimetric signals, respectively (The reference concentration of cortisol in saliva of healthy people is 1–12 ng/mL in the morning and 0.1–3 ng/mL at night). It is inexpensive, user-friendly, and allows for rapid analysis, rendering it suitable for clinical applications.

An all-in-one portable colorimetric detection platform for sensitive detection of bisphenol A based on target-mediated CeO2@ZIF-8/Apt biocomposites

BPA aptamers functionalized cerium oxide nanoparticles encapsulated in zeolitic imidazolate framework-8 (CeO2@ZIF-8/Apt) were developed to fabricate an all-in-one portable platform for on-site quantitative detection of BPA. By combining biocomposites with a 3,3′,5,5′-tetramethylbenzidine (TMB)-based sodium alginate (SA) hydrogel and smartphone-based RGB analysis, highly sensitive and convenient monitoring of BPA was achieved. CeO2@ZIF-8 composites were constructed using a novel surfactant-modified concentration-controlled synthesis strategy. After being functionalized with BPA aptamers, CeO2@ZIF-8/Apt biocomposites were used as target-response colorimetric probes for target recognition and signal transduction. The oxidase-like activity of CeO2@ZIF-8 was effectively sealed by BPA aptamers and controllably released in a concentration-dependent manner through aptamer-BPA reactions. Utilizing SA hydrogels containing TMB in the caps, a one-step sample addition and one-pot detection can be conveniently achieved and reliably quantified by smartphone-based RGB analysis in an instrument-free way. The detection range of this portable detection platform is 50 pg/mL to 500 ng/mL with limit of detection calculated as 34.88 pg/mL, comparable to that of conventional detection in the solution system (4.57 pg/mL). The recoveries in tap water, apple juice, and milk ranged from 91.02 % and 106.75 %. This work contributes new insights into the design of all-in-one detection platforms for contaminants monitoring in resource-constrained regions.

Fluorescent probe/hydrogel-based portable platform for ultrasensitive on-site detection of explosive particles containing nitrite

On-the-spot identification of solid or deposited explosive airborne particulates through luminescence techniques plays a vital role in homeland security, environmental analysis, and medicolegal diagnosis. However, integrating the rapid collection of solid explosive particles with fluorescent probe equipment and developing a direct and ultrasensitive detection technique for explosive particles on-site remain a formidable challenge in the fluorescence sensing field. In this study, we developed a portable detection platform based on a complex system using a combination of fluorescence probes/hydrogels and smartphone technology, which could not only quickly collect and capture explosive airborne particles but could also immediately synchronously realize ultrasensitive detection. The newly designed fluorescent probe 2-(5-chloro-1H-benzo [d] imidazol-2-yl) aniline (10-CBMA) exhibited superior recognition ability compared to two other probes, namely, BMA and 9,10-CBMA, for nitrite solution and solid conditions, with a low detection limit (8.558 × 10−8 M, solution), a quick detection time (2 mins, solid), and excellent specificity even in the presence of other interfering ions. In addition, by utilizing the robust photography capabilities of smartphones, nitrite particles could be quickly recognized on the spot. Overall, this portable platform based on fluorescence probes/hydrogels for ultrasensitive nitrite solid detection strategy provided in-depth insights into advancing explosive detection.

A novel paper-based colorimetric sensor using parylene C for Al (III) detection on a smartphone platform

The paper-based analytical platforms have been applied in biochemical detection and environmental monitoring due to their low cost and easy operation. Despite their advantages, the complexity of fabrication has limited their further application. Here, a simple and innovative approach using parylene C, a material commonly used in semiconductors, is reported to fabricate paper-based chips and construct a point-of-care testing (POCT) platform through smartphones. Parylene C is deposited on the filter paper through a polydimethylsiloxane (PDMS) clamp and forms a hydrophobic barrier. A three-channel paper-based chip was utilized to detect aluminum (Al) ions on a smartphone platform by the chromogenic method. The color change after Al3+ detection is represented with △E which was photographed and calculated by app on smartphone. The detection limit is 0.05 mg/L and the detection range is from 0.05 mg/L to 10 mg/L which indicates the application potential in the field of biochemical detection. This new paper-based sensing method and smartphone-based portable detection platform are simple, low-cost, fast, and highly sensitive, and provides a potential application for on-site, visual detection of ions and even other substances.

Novel and portable test strip platform for rapid and sensitive on-site detection of procymidone pesticide.

A novel and portable detection platform for procymidone (PRM) was developed by combining simple sample pretreatment, lateral flow test strips based on multi-branched gold nanoparticle (LFTS-MBGNP), and a smartphone. Based on the large surface area of MBGNPs, rapid detection of PRM was realized by simple naked eye observation. By utilizing a smartphone as a portable signal analyzer, ultrasensitive quantitative detection of PRM in red wine was realized with the limits of detection (LOD) of 1.60ng/mL, which was 3000 times lower than the US limit (5ppm). Moreover, rapid detection of four kinds of fruits and vegetables was achieved within 10min, with LODs of 4.34ng/g, 6.93ng/g, 8.99ng/g, and 5.03ng/g, respectively, which could meet the PRM limit of the European Union (10ng/g). Integrating the optimized QuEChERS pretreatment method, the developed platform realized a simple and sensitive on-site detection of PRM pesticide in foods and red wine within 45min. This platform provides a useful tool and new idea for rapid screening and detection of pesticide residues in food.

Smartphone-based photoelectrochemical immunoassay for carcinoembryonic antigen based on BiOCl/CuBi2O4 heterojunction

Photoelectrochemical (PEC) immunoassay has been widely developed for biomarker detection, but most include heavy and expensive instruments that are not suited for portable and on-site detection. In this work, the PEC immunoassay platform for mobile phones was reported for flexible, rapid, low-cost detection of carcinoembryonic antigen (CEA). The PEC detection platform was successfully composed of disposable screen-printed carbon electrodes, a micro-electrochemical workstation, a flashlight (the excitation light source), and a smartphone with a companion software with a micro-electrochemical workstation for rapid and on-site detection of target biomarkers. In this portable smartphone-based PEC system, the S-scheme heterojunction BiOCl/CuBi2O4 was effectively excited due to the efficient electron transfer rate and excellent photocurrent response under visible light. Specifically, the sandwich-type immunoreaction for capturing target biomarkers introduced alkaline phosphatase (ALP) labeled gold nanoparticles (Au NPs). The addition of CEA increased the ascorbic acid (AA) content and enhanced the photocurrent. The proposed immunoassay presented a good linear with the logarithm of CEA concentrations range within 0.01–40 ng mL−1, and the detection limit of 3.5 pg mL−1 (S/N = 3). Therefore, the portable detection platform offered an implementable approach to the development of miniaturized and portable photoelectrochemical detectors and on-site detection technology.

Laser induced graphene electrochemical aptasensor based on tetrahedral DNA for ultrasensitive on-site detection of microcystin-LR

The development of accurate and reliable sensor for on-site detection of microcystin-LR (MC-LR), one of hazardous environmental pollutants, is highly required. Herein, a laser induced graphene (LIG)-based electrochemical aptasensor for sensitive on-site detection of MC-LR was reported. LIG electrode, the substrate of aptasensor, was prepared via thermal transfer with ethylene-vinyl acetate copolymer, and LIG acted as quasi-reference electrode to replace conventional Ag/AgCl electrode for better operability and robustness. LIG electrode provided large surface area to assemble tetrahedral DNA to absorb methylene blue (MB) for the signal amplification. For detection, the specific recognition of MC-LR with aptamer led to the stripping of tetrahedral DNA complex and further the decreased redox current of MB (IMB). Consequently, the fabricated aptasensor offered high analytical performance for MC-LR detection with a linear range of 1 × 10-2-1 × 105 pM and a detection limit of 3 × 10-3 pM, which was successfully used for water sample analysis with comparable reliability and accuracy of standard method. Furthermore, a portable detection platform by coupling of LIG-based electrochemical aptasensor with electrochemical workstation was constructed for on-site detection of MC-LR. This work offers a novel method for the on-site monitoring of MC-LR, which promotes the investigation of LIG-based electrochemical biosensing in the field of environmental analysis.

Rapid, sensitive, and visual detection of Clonorchis sinensis with an RPA-CRISPR/Cas12a-based dual readout portable platform

Clonorchis sinensis is a food-borne parasite that parasitizes the liver and bile ducts of humans and many animals. This parasite exerts a high burden due to diverse hepatobiliary morbidities (e.g., cholangitis, cholecystitis, cholelithiasis, and cholangiocarcinoma), and an effective detection strategy is urgently needed. CRISPR/Cas12a exhibits nonspecific trans-cleavage activity upon binding to its specific target and has been widely used for nucleic acid detection. In this study, an RPA-CRISPR/Cas12a-based dual readout portable detection platform was established, which shows high sensitivity (one copy/μl) and specificity (no cross-reactivity with common pathogens) by rapid preamplification and combines lateral flow strips and visual fluorescence for visualization of results by the naked eye within 1 h. Moreover, 50 human fecal swabs and 50 fish flesh samples were detected by this platform and nested PCR. The CRISPR/Cas12a-based dual readout portable platform showed 10.0 % (5/50) C. sinensis-positive samples in human fecal swabs and 28.0 % (14/50) in fish flesh, which was consistent with the results of nested PCR. The results demonstrate that our portable platform has the advantages of stability, sensitivity, accuracy, and low equipment requirements. Furthermore, we provide novel point-of-care testing (POCT) for clinical use in remote rural and resource-constrained areas.

A smartphone-assisted paper-based ratio fluorescent probe for the rapid and on-site detection of tetracycline in food samples

Rapid, sensitive and portable analytical methods for on-site detection of tetracycline (TC) in food samples is of critical importance for food safety and public health. In this study, a dual-emission ratio fluorescent probe (Gd0.9@Eu0.1) was prepared and utilized for the detection of tetracycline (TC) by observing the fluorescence color change from blue to red. The detection process exhibits a wide linear range (0–52.0 μM), good selectivity and low detection limit (14 nM). A paper-based probe and a colorimetric card was constructed for the visual detection of TC. Furthermore, a novel and portable detection platform combining smartphone and test strip was exploited for the quantitative and on-site detection of TC in real pork sample. The developed method was validated through intra- (n = 5) and inter-day (n = 2) measurements, as well as comparison with a traditional HPLC method. These statistical result validate the reliability and accuracy of the developed method. This intelligent detection platform represents a promising approach for the rapid, sensitive and visual detection of TC in food samples.

Molecular-electromechanical system for unamplified detection of trace analytes in biofluids.

Biological research and diagnostic applications normally require analysis of trace analytes in biofluids. Although considerable advancements have been made in developing precise molecular assays, the trade-off between sensitivity and ability to resist non-specific adsorption remains a challenge. Here, we describe the implementation of a testing platform based on a molecular-electromechanical system (MolEMS) immobilized on graphene field-effect transistors. A MolEMS is a self-assembled DNA nanostructure, containing a stiff tetrahedral base and a flexible single-stranded DNA cantilever. Electromechanical actuation of the cantilever modulates sensing events close to the transistor channel, improving signal-transduction efficiency, while the stiff base prevents non-specific adsorption of background molecules present in biofluids. A MolEMS realizes unamplified detection of proteins, ions, small molecules and nucleic acids within minutes and has a limit of detection of several copies in 100 μl of testing solution, offering an assay methodology with wide-ranging applications. In this protocol, we provide step-by-step procedures for MolEMS design and assemblage, sensor manufacture and operation of a MolEMS in several applications. We also describe adaptations to construct a portable detection platform. It takes ~18 h to construct the device and ~4 min to finish the testing from sample addition to result.

Pd(II)-based coordination polymer nanosheets for ratiometric colorimetric and photothermal dual-mode assay of serum alkaline phosphatase

Fabrication of a multi-signal readout assay with high sensitivity and selectivity is highly desirable for clinical and biochemical analysis, but remains a challenge due to laborious procedures, large-scale instruments, and inadequate accuracy. Herein, a straightforward, rapid, and portable detection platform based on palladium(II) methylene blue (MB) coordination polymer nanosheets (PdMBCP NSs) was unveiled for the ratiometric dual-mode detection of alkaline phosphatase (ALP) with temperature and colorimetric signal readout properties. The sensing mechanism is the ALP-catalyzed generation of ascorbic acid for competitive binding and etching PdMBCP NSs to release free MB in a quantitive means for detection. Specifically, ALP addition led to the decrease of temperature signal readout from the decomposed PdMBCP NSs under 808 nm laser excitation, and simultaneous increase of the temperature from the generated MB with a 660 nm laser, together with the corresponding absorbance changes at both wavelengths. Notably, this ratiometric nanosensor exhibited a detection limit of 0.013 U/L (colorimetric) and 0.095 U/L (photothermal) within 10 min, respectively. The reliability and satisfactory sensing performance of the developed method were further confirmed by clinic serum samples. Therefore, this study provides a new insight for the development of dual-signal sensing platforms for convenient, universal, and accurate detection of ALP.

Simple method for visual detection of nitrite using fluorescence and colorimetry by poly (tannic acid) nanoparticles

The nitration reaction of nitrite and phenolic substances was first used to identify and detect NO2− by taking fluorescent poly (tannic acid) nanoparticles (FPTA NPs) as sensing platform. With the low cost, good biodegradable and convenient water-soluble FPTA NPs, a fluorescent and colorimetric dual modes detecting assay was realized. In fluorescent mode, the linear detection range of NO2− was 0–36 μM, the LOD was as low as 3.03 nM, and the response time was 90 s. In colorimetric mode, the linear detection range of NO2− was 0–46 μM, and the LOD was as low as 27 nM. Besides, a smartphone with FPTA NPs@ agarose hydrogel formed a portable detection platform to test the fluorescent and visible color changes of FPTA NPs for NO2− sensing as well as for accurate visualization and quantitative detection of NO2− in actual water and food samples.