Application of smartphone-based spectroscopy to biosample analysis: A review

A smartphone serves as a data logger for a fully automated lab-constructed microfluidic system

Fluorescence is an innovative technique that has captivated scholars in recent years due to its superior sensitivity and selectivity. The development of microfluidic components has added to its appeal, particularly given the technology ability to control fluid using very small quantities (microliter range) and achieve high liquid throughput. We have combined these two technologies to develop a lab-constructed simple system for measuring fluorescence, notable for the following features:•The device constructed entirely in our lab and programmed for measuring the fluorescence of liquids using microfluidic technology, delivered excellent results. The regression coefficient R² (0.9995) was obtained five points between 0.001-0.01µg .ml-1. Moreover, the reproducibility standard deviation (%) of 0.008 µg .ml-1 fluorescein dye remained at zero, for ten repeated experiments.•The device was full automated using a smartphone as a data logger, and lab-constructed programs.•The results were satisfactory with a detection limit of 1 × 10-4 µg.ml-1. This proposed system can measure over 200 samples per hour making it highly efficient and eco-friendly due to the reduced use of reagents and lower waste production. The fully automated system can effectively be used to determine fluorescein dye concentrations. Another application (micro pump view) manages all actions required in this microfluidic system, such as operating the two lab-constructed peristaltic pumps.

A practical chromogenic and fluorogenic dual-mode sensing platform for rapid quantification of sulfite in food

Sulfur dioxide (SO2) and its derivatives (HSO3- and SO32-) are widely used in food-processing. Whereas excessive consumption of sulfur dioxide and its derivatives (>0.70 mg·kg-1day-1) severely endangers human health. In this work, we rationally constructed a practical dual-mode probe (dicyanomethylene)-1-methyl-1,4-dihydroquinolin-2-yl)vinyl)-1-methylquinolinium (QMN), which underwent a specific 1, 4-Michael addition with sulfite to afford a noticeable color change from pale yellow to red along with a high-contrast fluorescence turn-on response at 598 nm. QMN has the advantages of rapid response, high signal-to-noise ratio, excellent selectivity, good water-solubility, large Stokes shift and low detection limit (LOD = 31.9 nM). QMN has been successfully used to on-site visually determine sulfite in a diversity of foods with satisfactory recoveries (91.33-111.33 %) and high accuracy (93.74-98.71 %). Furthermore, a portable smartphone-based fluorescence sensing platform was fabricated for on-site determination of sulfite in food with good performance.

Emerging trends in sensors based on molecular imprinting technology: Harnessing smartphones for portable detection and recognition

Molecular imprinting technology (MIT) has become a promising recognition technology in various fields due to its specificity, high efficiency, stability and eco-friendliness in the recognition of target. Molecularly imprinted polymers (MIPs), known as 'artificial receptors', are shown similar properties to natural receptors as a biomimetic material. The selectivity of recognition for targets can be greatly improved when MIPs are introduced into sensors, as known that MIPs, are suitable for the pretreatment and analysis of trace substances in complex matrix samples. At present, various sensors has been developed by the combination with MIPs for detecting and identifying trace compounds, biological macromolecules or other substances, such as optical, electrochemical and piezoelectric sensors. Smart phones, with their built-in sensors and powerful digital imaging capabilities, provide a unique platform for the needs of portability and instant detection. MIP sensors based on smart phones are expected to become a new research direction in the future. This review discusses the latest applications of MIP sensors in the field of detection and recognition in recent years, summarizes the frontier progress of MIP sensor research based on smart phones in the past two years, and points out the challenges, limitations and future development prospects.

A colorimetric assay for H2O2 and glucose based on the morphology transformation of Au/Ag nanocages to nanoboxes

Herein, we introduced a sensitive colorimetric platform for hydrogen peroxide (H2O2) assay based on gold/silver (Au/Ag) nanocages with porous structure. In the presence of H2O2, the morphology of hollow Au/Ag nanocages was converted to closed nanoboxes, altering their localized surface plasmon resonance (LSPR) peak position and the solution color from light blue to deep blue. The morphology transformation and LSPR peak position of Au/Ag nanocages were proportional to H2O2 concentration at the range of 0.1 to 50 µM. The limit of detection (LOD) was obtained to be 0.02 µM, and the relative standard deviation (RSD, for 0.2, 2.0, and 20 µM) was 2.7, 2.3, and 2.9%, respectively. Moreover, a smartphone-based colorimetric sensor was developed for H2O2 assay at the concentration range of 0.25-4.0 µM, with LOD of 0.2 µM and RSD of 3.2, 2.5, and 2.9% (for 0.5, 1.0, and 3.0 µM, respectively). We exploited the established sensor for glucose assay by measuring the generated H2O2 from the enzymatic reaction between glucose and glucose oxidase. There was a linear relationship between LSPR peak wavelength variations and the amount of glucose from 1.0 to 50 µM, with LOD of 0.4 µM and RSD of 3.2, 3.1, and 3.8% (for 2.0, 10, and 30 µM, respectively). The sensor was successfully applied to determine H2O2 and glucose in food and human serum samples, respectively.

On-site quantitation of xanthine in fish and serum using a smartphone-based spectrophotometer integrated with a dual-readout nanosensing assay

Rapid and quantitative biochemical analysis at points-of-need is imperative for food safety inspection. This work reports on: 1) a stand-alone smartphone-based "two-in-one" spectrophotometer (the SAFS) installed with a self-developed application (the SAFS-App) which can precisely collect both absorption spectra and fluorescence spectra in a reproducible manner within 5 s; and 2) a straightforward protocol for xanthine detection using fluorescent carbon nanodots and silver nanoparticles. The assay performed with the SAFS demonstrates high specificity towards xanthine, and a linear range of 1-60 μM with LODs of 0.38 and 0.58 μM for colorimetric and fluorometric readouts, respectively. The reliability and robustness of the SAFS are validated by on-site quantitation of xanthine in fish and serum samples, with comparable accuracy to HPLC method. More importantly, the SAFS presents itself as an appealing device which is accessible to everyone through the Internet of Things and can be tailored for diverse point-of-care testing applications.

Smartphone-based low-cost and rapid quantitative detection of urinary creatinine with the Tyndall effect

This research aims to develop a robust and quantitative method for measuring creatinine levels by harnessing the enhanced Tyndall effect (TE) phenomenon. The envisioned sensing assay is designed for practical deployment in resource-limited settings or homes, where access to advanced laboratory facilities is limited. Its primary objective is to enable regular and convenient monitoring of renal healthcare, particularly in cases involving elevated creatinine levels. The creatinine sensing strategy is achieved based on the aggregation of gold nanoparticles (AuNPs) triggered via the direct crosslinking reaction between creatinine and AuNPs, where an inexpensive laser pointer was used as a handheld light source and a smartphone as a portable device to record the TE phenomenon enhanced by the creatinine-induced aggregation of AuNPs. After evaluation and optimization of parameters such as AuNP concentrations and TE measurement time, the subsequent proof-of-concept experiments demonstrated that the average gray value change of TE images was linearly related to the logarithm of creatinine concentrations in the range of 1-50 μM, with a limit of detection of 0.084 μM. Meanwhile, our proposed creatinine sensing platform exhibited highly selective detection in complex matrix environments. Our approach offers a straightforward, cost-effective, and portable means of creatinine detection, presenting an encouraging signal readout mechanism suitable for point-of-care (POC) applications. The utilization of this assay as a POC solution exhibits potential for expediting timely interventions and enhancing healthcare outcomes among individuals with renal health issues.

Intelligent Electrochemical Point-of-Care Test Method with Interface Control Based on DNA Pyramids: Aflatoxin B1 Detection in Food and the Environment

Sensitive, intelligent point-of-care test (iPOCT) methods for small molecules like aflatoxin B1 (AFB1) are urgently needed for food and the environment. The challenge remains of surface control in iPOCT. Herein, we developed an electrochemical sensor based on the DNA pyramid (DNP), combining a smartphone, app, and mobile electrochemical workstations to detect AFB1. The DNP's structure can reduce local overcrowding and entanglement between neighboring probes, control the density and orientation of recognition probes (antibodies), produce uniform and orientational surface assemblies, and improve antigen-antibody-specific recognition and binding efficiency. Simultaneously, the hollow structure of the DNP enhances the electron transfer capacity and increases the sensitivity of electrochemical detection. In this work, the biosensor based on DNP was first combined with electrochemical (Ec) iPOCT to simultaneously achieve ordered interface modulation of recognition probes and intelligent detection of AFB1. Under optimal conditions, we found a detection limit of 3 pg/mL and a linear range of 0.006-30 ng/mL (R2 = 0.995). Further, using peanut, soybean, corn, and lake water as complex matrices, it recorded recoveries of 82.15-100.53%, excellent selectivity, acceptable stability, and good reproducibility. Finally, this Ec iPOCT provides consistent results compared to the high-performance liquid chromatography-tandem mass spectrometry method.

Smartphone as a fluorescence detector for high-performance liquid chromatography

BACKGROUND

Fluorescence detection is employed in high-performance liquid chromatography (HPLC) due to its high specificity and sensitivity. However, it is often limited by expensive components and bulkiness. Recently, advances in technology and electronics have led to the development of smartphones that can serve as portable recording, analysis, and monitoring tools. Smartphone-based detection provides advantages of cost effectiveness, rapid signal/data processing, and the display of results on a handhold monitor. The combination of smartphone-based detection with HPLC can offer unique features that are beneficial in overcoming limitations of commercial fluorescence detectors. (90) RESULTS: A miniaturized and low-cost HPLC fluorescence detector based on a smartphone is introduced for the detection of six fluorescent molecules. The smartphone is able to capture emitted fluorescence in video format while MATLAB code is used for data processing to provide chromatograms based on different detection channels. A custom designed double-channel flow cell was utilized to enable simultaneous detection of fluorescent compounds with different excitation wavelengths. The detector consists of a lab-made flow cell, monochromatic LEDs as the light source, 3D printed housing and connector box, fiber optic cables, and a smartphone. The effects of flow cell geometry, channel width and light slit diameter, as well as a comparison of different flow cell manufacturing techniques, are studied and discussed. The validated system was successfully applied to samples from diverse water sources, yielding spiking recoveries within the range of 91.7% and 109.7%. (141) SIGNIFICANCE: This study introduces the first smartphone-based fluorescence detector for HPLC with cost-effective and customizable flow cells, allowing for the simultaneous detection of fluorescent compounds with different excitation wavelengths and offering a potential solution for the analysis of co-eluting compounds. Beyond its user-friendly interface and low-cost, smartphone detection in HPLC provides tremendous opportunities in further miniaturizing chromatographic instrumentation while offering high sensitivity and can be expanded to other mechanisms of detection. (70).

A molecularly imprinted ratiometric fluorescence sensor based on blue/red carbon quantum dots for the visual determination of thiamethoxam

Neonicotinoids such as thiamethoxam (TMX) were widely used in agricultural production and tended to accumulate in the environment, potentially harming human and ecosystem health. To enable widespread monitoring of TMX residues, it was essential to design a reliable and sensitive detection method. Here, we developed a novel smartphone-enablled molecularly imprinted ratiometric fluorescence sensing system for selective on-site detection of TMX. It was based on blue-emission carbon dots (CDs) wrapped with a molecularly imprinted layer (B-CDs@MIPs), which provided the response signal, while red-emission CDs (R-CDs) served as an internal reference. The fluorescence signal ratio of the sensor increased with the TMX concentration, resulting in an obvious fluorescence color change from red to blue. The sensor exhibited a satisfactory limit of detection (LOD) of 13.5 nM in fluorescence analysis while LOD of 70.1 nM in visual determination. In addition, the sensing system was validated using food and environment samples, exhibiting recoveries from 91.40% to 105.7%, indicating excellent reliability for TMX detection in actual samples. Thus, the sensing system developed in this study offered promising prospects for visual detection of pesticide residues in complex environmental samples.

Smartphone-Based Chemiluminescence Glucose Biosensor Employing a Peroxidase-Mimicking, Guanosine-Based Self-Assembled Hydrogel

Chemiluminescence is widely used for hydrogen peroxide detection, mainly exploiting the highly sensitive peroxidase-luminol-H₂O₂ system. Hydrogen peroxide plays an important role in several physiological and pathological processes and is produced by oxidases, thus providing a straightforward way to quantify these enzymes and their substrates. Recently, biomolecular self-assembled materials obtained by guanosine and its derivatives and displaying peroxidase enzyme-like catalytic activity have received great interest for hydrogen peroxide biosensing. These soft materials are highly biocompatible and can incorporate foreign substances while preserving a benign environment for biosensing events. In this work, a self-assembled guanosine-derived hydrogel containing a chemiluminescent reagent (luminol) and a catalytic cofactor (hemin) was used as a H₂O₂-responsive material displaying peroxidase-like activity. Once loaded with glucose oxidase, the hydrogel provided increased enzyme stability and catalytic activity even in alkaline and oxidizing conditions. By exploiting 3D printing technology, a smartphone-based portable chemiluminescence biosensor for glucose was developed. The biosensor allowed the accurate measurement of glucose in serum, including both hypo- and hyperglycemic samples, with a limit of detection of 120 µmol L^-1. This approach could be applied for other oxidases, thus enabling the development of bioassays to quantify biomarkers of clinical interest at the point of care.

Smartphone-Enabled Colorimetry

A smartphone is used as a colorimeter. The performance characterization for colorimetry is presented using both the built-in camera and a clip-on dispersive grating. Certified colorimetric samples provided by Labsphere^® are considered as test samples. Color measurements directly performed utilizing the smartphone camera only are obtained using the RGB Detector app, downloaded from the Google Play Store. More precise measurements are achieved using the commercially available GoSpectro grating and related app. In both cases, to quantify the reliability and sensitivity of smartphone-based color measurements, the CIELab color difference ΔE between the certified and smartphone-measured colors is calculated and is reported in this paper. In addition, as an example of a practical application of interest for the textile industry, several samples of cloth fabrics with a palette of the most common colors are measured, and the comparison with the certified color values is presented.

Smartphone-based on-site detection of hydrogen peroxide in milk by using a portable ratiometric fluorescent probe

The on-site detection of hydrogen peroxide (H₂O₂) is important for maintaining food safety as the ingestion of H₂O₂ can lead to serious pathological conditions. However, most reported fluorescent probes require a fluorometer to ensure readable signal output and reliable detection result. Consequently, the fluorescent detection of H₂O₂ can be realized only within a standard laboratory setting. Herein, we report a novel supramolecular strategy that can successfully convert the typical off-on response to H₂O₂ into a ratiometric response, which allows the on-site detection of H₂O₂ when used in conjunction with a smartphone-based 3D-printed miniaturized testing system. This method has acceptable sensitivity, good anti-interference ability, and desirable accuracy compared to a standard detection method. More importantly, this portable ratiometric method can be used to detect H₂O₂ residue in commercial milk samples with the simple testing apparatuses.

A smartphone-based fluorospectrophotometer and ratiometric fluorescence nanoprobe for on-site quantitation of pesticide residue

Cost-effective and user-friendly quantitation at points-of-need plays an important role in food safety inspection, environmental monitoring, and biomedical analysis. This study reports a stand-alone smartphone-based fluorospectrophotometer (the SBS) installed with a custom-designed application (the SBS-App) for on-site quantitation of pesticide using a ratiometric sensing scheme. The SBS can collect fluorescence emission spectra in the wavelength range of 380-760 nm within 5 s. A ratiometric fluorescence probe is facilely prepared by directly mixing the blue-emissive carbon nanodots (the Fe3+-specific fluorometric indicator) and red-emissive quantum dots (the internal standard) at a ratio of 11.6 (w/w). Based on the acetylcholinesterase/choline oxidase dual enzyme-mediated cascade catalytic reactions of Fe2+/Fe3+ transformation, a ratiometric fluorescence sensing scheme is developed. The practicability of the SBS is validated by on-site quantitation of chlorpyrifos in apple and cabbage with a comparable accuracy to the GC-MS method, offering a scalable solution to establish a cost-effective surveillance system for pesticide pollution.

Colorimetric Detection of Met Dimerization on Live Cells via Smartphone for High-Sensitivity Sensing of the HGF/Met Signaling Pathway

Membrane protein dimerization regulates numerous cellular biological processes; therefore, highly sensitive and facile detection of membrane protein dimerization are very crucial for clinical diagnosis and biomedical research. Herein, a colorimetric detection of Met dimerization on live cells via smartphone for high-sensitivity sensing of the HGF/Met signaling pathway was developed for the first time. The Met monomers on live cells were recognized by specific ligands (aptamers) first, and the Met dimerizations triggered the proximity-ligation-assisted catalytic hairpin assembly (CHA) reaction to generate large amounts of G-quadruplex (G4) fragments which can further combine hemin to form G4/hemin DNAzymes possessing the horseradish-peroxidase-like catalytic activity for catalyzing the oxidation of ABTS by H₂O₂ and producing the colorimetric signal (i.e., color change). The colorimetric detection of Met on live cells was then achieved by image acquisition and processing via a smartphone. As a proof-of-principle, the HGF/Met signaling pathway based on Met-Met dimerization was facile monitored, and the human gastric cancer cells MKN-45 with natural Met-Met dimers were sensitively tested and a wide linear working range from 2 to 1000 cells with a low detection limit of 1 cell was obtained. The colorimetric assay possesses a good specificity and high recovery rate of MKN-45 cells spiked in peripheral blood, which indicates that the proposed colorimetric detection of Met dimerization can be used for convenient observation of the HGF/Met signaling pathway and has extensive application prospects in point-of-care testing (POCT) of Met-dimerization-related tumor cells.

Dextran-Functionalized Super-nanoparticle Assemblies of Quantum Dots for Enhanced Cellular Immunolabeling and Imaging

Colloidal semiconductor quantum dots (QDs) are a popular material for applications in bioanalysis and imaging. Although individual QDs are bright, some applications benefit from the use of even brighter materials. One approach to achieve higher brightness is to form super-nanoparticle (super-NP) assemblies of many QDs. Here, we present the preparation, characterization, and utility of dextran-functionalized super-NP assemblies of QDs. Amphiphilic dextran was synthesized and used to encapsulate many hydrophobic QDs via a simple emulsion-based method. The resulting super-NP assemblies or "super-QDs" had hydrodynamic diameters of ca. 90-160 nm, were characterized at the ensemble and single-particle levels, had orders-of-magnitude superior brightness compared to individual QDs, and were non-blinking. Additionally, binary mixtures of red, green, and blue (RGB) colors of QDs were used to prepare super-QDs, including colors difficult to obtain from individual QDs (e.g., magenta). Tetrameric antibody complexes (TACs) enabled simple antibody conjugation for selective cellular immunolabeling and imaging with both an epifluorescence microscope and a smartphone-based platform. The technical limitations of the latter platform were overcome by the increased per-particle brightness of the super-QDs, and the super-QDs outperformed individual QDs in both cases. Overall, the super-QDs are a very promising material for bioanalysis and imaging applications where brightness is paramount.

Artificial intelligence-assisted smartphone-based sensing for bioanalytical applications: A review

Artificial intelligence (AI) has received great attention since the concept was proposed, and it has developed rapidly in recent years with applications in many fields. Meanwhile, newer iterations of smartphone hardware technologies which have excellent data processing capabilities have leveraged on AI capabilities. Based on the desirability for portable detection, researchers have been investigating intelligent analysis by combining smartphones with AI algorithms. Various examples of the application of AI algorithm-based smartphone detection and analysis have been developed. In this review, we give an overview of this field, with a particular focus on bioanalytical detection applications. The applications are presented in terms of hardware design, software algorithms, and specific application areas. We also discuss the existing limitations of AI-based smartphone detection and analytical approaches, and their future prospects. The take-home message of our review is that the application of AI in the field of detection analysis is restricted by the limitations of the smartphone's hardware as well as the model building of AI for detection targets with insufficient data. Nevertheless, at this juncture, while bioanalytical diagnostics and health monitoring have set the pace for AI-based smartphone applicability, the future should see the technology making greater inroads into other fields. In relation to the latter, it is likely that the ordinary or average person will play a greater participatory role.

Inexpensive High-Throughput Multiplexed Biomarker Detection Using Enzymatic Metallization with Cellphone-Based Computer Vision

Multiplexed biomarker detection can play a critical role in reliable and comprehensive disease diagnosis and prediction of outcome. Enzyme-linked immunosorbent assay (ELISA) is the gold standard method for immunobinding-based biomarker detection. However, this is currently expensive, limited to centralized laboratories, and usually limited to the detection of a single biomarker at a time. We present a low-cost, smartphone-based portable biosensing platform for high-throughput, multiplexed, sensitive, and quantitative detection of biomarkers from single, low-volume drops (<1 μL) of clinical samples. Biomarker binding to spotted capture antigens is converted, via enzymatic metallization, to the localized surface deposition of amplified, dry-stable, silver metal spots whose darkness is proportional to biomarker concentration. A custom smartphone application is developed, which uses real-time computer vision to enable easy optical detection of the deposited metal spots and sensitive and reproducible quantification of the biomarkers. We demonstrate the use of this platform for high-throughput, multiplexed detection of multiple viral antigen-specific antibodies from convalescent COVID-19 patient serum as well as vaccine-elicited antibody responses from uninfected vaccine-recipient serum and show that distinct multiplexed antibody fingerprints are observed among them.

Smartphone-based hand-held polarized light microscope for on-site pharmaceutical crystallinity characterization

Polarized light microscopy (PLM) is a common but critical method for pharmaceutical crystallinity characterization, which has been widely introduced for research purposes or drug testing and is recommended by many pharmacopeias around the world. To date, crystallinity characterization of pharmaceutical solids is restricted to laboratories due to the relatively bulky design of the conventional PLM system, while little attention has been paid to on-site, portable, and low-cost applications. Herein, we developed a smartphone-based polarized microscope with an ultra-miniaturization design ("hand-held" scale) for these purposes. The compact system consists of an optical lens, two polarizers, and a tailor-made platform to hold the smartphone. Analytical performance parameters including resolution, imaging quality of interference color, and imaging reproducibility were measured. In a first approach, we illustrated the suitability of the device for pharmaceutical crystallinity characterization and obtained high-quality birefringence images comparable to a conventional PLM system, and we also showed the great promise of the device for on-site characterization with high flexibility. In a second approach, we employed the device as a proof of concept for a wider application ranging from liquid crystal to environmental pollutants or tissues from plants. As such, this smartphone-based hand-held polarized light microscope shows great potential in helping pharmacists both for research purposes and on-site drug testing, not to mention its broad application prospects in many other fields.

A Portable Smartphone-Based System for the Detection of Blood Calcium Using Ratiometric Fluorescent Probes

Hypocalcemia is a disease that adversely affects the production and reproduction of dairy cows. A portable device for rapid bovine blood calcium sensing has been growing in demand. Herein, we report a smartphone-based ratiometric fluorescence probe (SRFP) platform as a new way to detect and quantify calcium ions (Ca²⁺) in blood serum. Specifically, we employed a cost-effective and portable smartphone-based platform coupled with customized software that evaluates the response of Ca²⁺ ions to ratiometric fluorescence probe in bovine serum. The platform consists of a three-dimensional (3D) printed housing and low-cost optical components that excite fluorescent probe and selectively transmit fluorescence emissions to smartphones. The customized software is equipped with a calibration model to quantify the acquired fluorescence images and quantify the concentration of Ca²⁺ ions. The ratio of the green channel to the red channel bears a highly reproducible relationship with Ca²⁺ ions concentration from 10 μM to 40 μM in bovine serum. Our detection system has a limit of detection (LOD) of 1.8 μM in bovine serum samples and the recoveries of real samples ranged from 92.8% to 110.1%, with relative standard deviation (RSD) ranging from 1.72% to 4.89%. The low-cost SRFP platform has the potential to enable campesino to rapidly detect Ca²⁺ ions content in bovine serum on-demand in any environmental setting.

Semiquantitative Screening of THC Analogues by Silica Gel TLC with an Ag(I) Retention Zone and Chromogenic Smartphone Detection

With the ever-evolving cannabis industry, low-cost and high-throughput analytical methods for cannabinoids are urgently needed. Normally, (potentially) psychoactive cannabinoids, typically represented by Δ9-tetrahydrocannabinol (Δ9-THC), and nonpsychoactive cannabinoids with therapeutic benefits, typically represented by cannabidiol (CBD), are the target analytes. Structurally, the former (tetrahydrocannabinolic acid (THCA), cannabinol (CBN), and THC) have one olefinic double bond and the latter (cannabidiolic acid (CBDA), cannabigerol (CBG), and CBD) have two, which results in different affinities toward Ag(I) ions. Thus, a silica gel thin-layer chromatography (TLC) plate with the lower third impregnated with Ag(I) ions enabled within minutes a digital chromatographic separation of strongly retained CBD analogues and poorly retained THC analogues. The resolution (R_s) between the closest two spots from the two groups was 4.7, which is almost 8 times higher than the resolution on unmodified TLC. After applying Fast Blue BB as a chromogenic reagent, smartphone-based color analysis enabled semiquantification of the total percentage of THC analogues (with a limit of detection (LOD) of 11 ng for THC, 54 ng for CBN, and 50 ng for THCA when the loaded volume is 1.0 μL). The method was validated by analyzing mixed cannabis extracts and cannabis extracts. The results correlated with those of high-performance liquid chromatography with ultraviolet detection (HPLC-UV) (R² = 0.97), but the TLC approach had the advantages of multi-minute analysis time, high throughput, low solvent consumption, portability, and ease of interpretation. In a desiccator, Ag(I)-TLC plates can be stored for at least 3 months. Therefore, this method would allow rapid distinction between high and low THC varieties of cannabis, with the potential for on-site applicability.

Dual-Color Fluorescent Hydrogel Microspheres Combined with Smartphones for Visual Detection of Lactate

Since it is difficult for human eyes to distinguish between two identical colors with only <15% variation in brightness, mono-color fluorescent hydrogel microspheres have some limitations in the detection of lactate. Herein, we prepared novel dual-color fluorescent hydrogel microspheres, which can achieve hue transformation. Microspheres were prepared by introducing a fluorescent nanoparticle as the reference signal while CdTe QDs were used as the response signal. We used smartphones with image processing software to collect and analyze data. In this way, the signal of lactate was converted to RGB (red, green, and blue) values, which can be quantitatively read. Within 10 to 1500 μM, the R/G values of the microspheres had a linear relationship with the logarithm of the lactate concentration. Moreover, color cards for lactate detection were prepared, from which the color change and concentration of lactate could be easily read by the naked eye. It is worth mentioning that this method was successfully applied to screen patients with hyperlactatemia.

Development of a versatile smartphone-based environmental analyzer (vSEA) and its application in on-site nutrient detection

The citizen-science-based environmental survey can benefit from the smartphone technology used in chemical and biological sensing of a wide range of analytes. Quantification by smartphone-based colorimetric assays is being increasingly reported, however, most of the quantification uses empirical formula or complex exhaustive methods. In this study, a versatile and robust algorithm is proposed to overcome these limitations. A model is established to simulate and analyze the conversion process from the camera's spectral information into RGB (Red, Green, Blue) color information. Moreover, the feasibility of the algorithm for the quantification of different analytes is also explored. Based on this algorithm, a versatile smartphone-based environmental analyzer (vSEA) is built and its reliability, versatility, and analytical performance are comprehensively optimized. The good linearity (R² ≥ 0.9954) and precision (relative standard deviations < 5.3%) indicates that the vSEA is accurate enough to quantify the nutrients in most natural waters. Furthermore, the vSEA is used for the field measurement of five important nutrients, and the results show no significant difference compared to conventional methods. The vSEA offers a simpler and easier method for the on-site measurement of nutrients in natural water bodies, which can aid in the emergency monitoring of aqueous ecosystems and the performance of citizen-science-based research.

Paper-based multicolor sensor for on-site quantitative detection of 2,4-dichlorophenoxyacetic acid based on alkaline phosphatase-mediated gold nanobipyramids growth and colorimeter-assisted method for quantifying color

On-site quantitative analysis of pesticides is important for food safety. Colorimetric gold nanobipyramids (AuNBPs) sensors are powerful methods for on-site detection. However, a single quantitative method and the instability of AuNBPs in solution limit the practicability of those sensors. Here, a paper-based multicolor AuNBPs sensor involved a colorimeter-assisted method for quantifying color was developed for quantitative detection of 2,4-dichlorophenoxyacetic acid (2,4-D), a common herbicide. The novelty of this study lies in developing a general paper-based quantitative on-site method (PQOM) for colorimetric AuNBPs sensors. Firstly, a paper-based analytical device (PAD) consisting of a nylon membrane, absorbent cotton layers, and two acrylic plates was fabricated to deposit AuNBPs. We demonstrated the PAD could improve the stability of AuNBPs and the detection sensitivity of AuNBPs sensors. Then, a handheld colorimeter was first used to quantify the color change of AuNBPs on the PAD based on the CIELab color space. Finally, as proof of concept, the PQOM was successfully employed to quantify 2,4-D by combining with an alkaline phosphatase-mediated AuNBPs growth method. In this method, 2,4-D specifically inhibited alkaline phosphatase activity to suppress the generation of l-ascorbic acid, thereby mediating AuNBPs growth. The developed sensor exhibited seven 2,4-D concentration-related colors and detected as low as 50 ng mL-1 2,4-D by naked-eye observation and 18 ng mL-1 2,4-D by a colorimeter. It was applied to detect 2,4-D in the spiked rice and apple samples with good recovery rates (91.8-112.0%) and a relative standard deviation (n = 5) < 5%. The success of this study provides a sensing platform for quantifying 2,4-D on site.

Smartphone-Based Techniques Using Carbon Dot Nanomaterials for Food Safety Analysis

The development of portable and efficient nanoprobes to realize the quantitative/qualitative onsite determination of food pollutants is of immense importance for safeguarding human health and food safety. With the advent of the smartphone, the digital imaging property causes it to be an ideal diagnostic substrate to point-of-care analysis probes. Besides, merging the versatility of carbon dots nanostructures and bioreceptor abilities has opened an innovative assortment of construction blocks to design advanced nanoprobes or improving those existing ones. On this ground, massive endeavors have been made to combine mobile phones with smart nanomaterials to produce portable (bio)sensors in a reliable, low cost, rapid, and even facile-to-implement area with inadequate resources. Herein, this work outlines the latest advancement of carbon dots nanostructures on smartphone for onsite detecting of agri-food pollutants. Particularly, we afford a summary of numerous approaches applied for target molecule diagnosis (pesticides, mycotoxins, pathogens, antibiotics, and metal ions), for instance microscopic imaging, fluorescence, colorimetric, and electrochemical techniques. Authors tried to list those scaffolds that are well-recognized in complex media or those using novel constructions/techniques. Lastly, we also point out some challenges and appealing prospects related to the enhancement of high-efficiency smartphone based carbon dots systems.

Engineering of 2D artificial nanozyme-based blocking effect-triggered colorimetric sensor for onsite visual assay of residual tetracycline in milk

Accurate and low-cost onsite assay of residual antibiotics in food and agriculture-related matrixes (e.g., milk) is of significant importance for evaluating and controlling food pollution risk. Herein, we employed hybrid Cu-doped-g-C₃N₄ nanozyme to engineer smartphone-assisted onsite visual sensor for reliable and precise reporting the levels of tetracycline (TC) residues in milk through π-π stacking-triggered blocking effect. Benefiting from the synergetic effects of Cu²⁺ and g-C₃N₄ nanosheet, Cu-doped-g-C₃N₄ nanocomposite exhibited an improved peroxidase-like activity, which could effectively catalyze H₂O₂ to oxidate colorless TMB into steel-blue product oxTMB. Interestingly, owing to the blocking effect caused by the π-π stacking interaction between TC tetraphenyl skeleton and Cu-doped-g-C₃N₄ nanozyme, the affinity of Cu-doped-g-C₃N₄ nanocomposite toward the catalytic substrates was remarkably blocked, resulting in a TC concentration-dependent fading of solution color. Using smartphone-assisted detection a simple, low-cost, reliable, and sensitive portable colorimetric sensor-based nanozyme for onsite visual monitoring the residual TC in milk was successfully developed with a detection limit of 86.27 nM. Of particular mention is that this detection limit is comparable to most other reported colorimetric methods and below most official allowable residue thresholds in milk matrixes. This work gave a novel insight to integrate two-dimensional (2D) artificial nanozymes-based π-π stacking-triggered blocking effect with smartphone-assisted detection for developing efficient and low-cost colorimetric point-of-care testing of the risk factors in food and agriculture-related matrixes.

Development of a Smartphone-Integrated Reflective Scatterometer for Bacterial Identification

We present a smartphone-based bacterial colony phenotyping instrument using a reflective elastic light scattering (ELS) pattern and the resolving power of the new instrument. The reflectance-type device can acquire ELS patterns of colonies on highly opaque media as well as optically dense colonies. The novel instrument was built using a smartphone interface and a 532 nm diode laser, and these essential optical components made it a cost-effective and portable device. When a coherent and collimated light source illuminated a bacterial colony, a reflective ELS pattern was created on the screen and captured by the smartphone camera. The collected patterns whose shapes were determined by the colony morphology were then processed and analyzed to extract distinctive features for bacterial identification. For validation purposes, the reflective ELS patterns of five bacteria grown on opaque growth media were measured with the proposed instrument and utilized for the classification. Cross-validation was performed to evaluate the classification, and the result showed an accuracy above 94% for differentiating colonies of E. coli, K. pneumoniae, L. innocua, S. enteritidis, and S. aureus.

A ZnFe2O4-catalyzed segment imprinted polymer on a three-dimensional origami paper-based microfluidic chip for the detection of microcystin

Microcystin has been causing serious environmental pollution; however, the recognition of such compounds is still challenging because of low abundance and coexisting interfering species. In this contribution, we develop a novel microfluidic paper-based colorimetric sensor by exploiting molecular imprinting technology and Fenton reaction for on-site microcystin-RR determination in complex water samples using a smartphone.

Portable FRET-Based Biosensor Device for On-Site Lead Detection

Most methods for measuring environmental lead (Pb) content are time consuming, expensive, hazardous, and restricted to specific analytical systems. To provide a facile, safe tool to detect Pb, we created pMet-lead, a portable fluorescence resonance energy transfer (FRET)-based Pb-biosensor. The pMet-lead device comprises a 3D-printed frame housing a 405-nm laser diode-an excitation source for fluorescence emission images (YFP and CFP)-accompanied by optical filters, a customized sample holder with a Met-lead 1.44 M1 (the most recent version)-embedded biochip, and an optical lens aligned for smartphone compatibility. Measuring the emission ratios (Y/C) of the FRET components enabled Pb detection with a dynamic range of nearly 2 (1.96), a pMet-lead/Pb dissociation constant (K_d) 45.62 nM, and a limit of detection 24 nM (0.474 μg/dL, 4.74 ppb). To mitigate earlier problems with a lack of selectivity for Pb vs. zinc, we preincubated samples with tricine, a low-affinity zinc chelator. We validated the pMet-lead measurements of the characterized laboratory samples and unknown samples from six regions in Taiwan by inductively coupled plasma mass spectrometry (ICP-MS). Notably, two unknown samples had Y/C ratios significantly higher than that of the control (3.48 ± 0.08 and 3.74 ± 0.12 vs. 2.79 ± 0.02), along with Pb concentrations (10.6 ppb and 15.24 ppb) above the WHO-permitted level of 10 ppb in tap water, while the remaining four unknowns showed no detectable Pb upon ICP-MS. These results demonstrate that pMet-lead provides a rapid, sensitive means for on-site Pb detection in water from the environment and in living/drinking supply systems to prevent potential Pb poisoning.

A portable smartphone-assisted ratiometric fluorescence sensor for intelligent and visual detection of malachite green

Developing intelligent, sensitive, and visual methods for rapidly detecting veterinary drug residues is essential for ensuring food quality and safety. A portable smartphone-assisted ratiometric fluorescent sensor was successfully designed using fluorescent Al-MOF nanosheet and rhodamine B (RhB) as fluorescent probes to adjust to the requirement of malachite green (MG) detection. The developed ratiometric fluorescent sensor allowed sensitive and selective detection of MG with good linear relationships in a wide range of 0.5-200 μg/mL. The Quantitative linearrange is 5.3 μg/mL to 200 μg/mL. The limit of detection (LOD) and limit of quantification (LOQ) were calculated to be 1.6 μg/mL and 5.3 μg/mL respectively. The practicability of the proposed method was verified using high performance liquid chromatography (HPLC) in spiked fish tissues with satisfying recoveries and RSD. Moreover, portable smartphone-assisted fluorescent test papers were fabricated for the intelligent detection of MG. This integration of smartphones and fluorescent test papers was economical and saved time, providing an alternative strategy for the qualitative discernment and semi-quantitative analysis of MG on-site.

A Dual-Channel Intelligent Point-of-Care Testing System for Soluble Programmed Death-1 and Programmed Death-Ligand 1 Detection Based on Folding Paper-Based Immunosensors

Both programmed death-1 (PD-1) and programmed death-ligand 1 (PD-L1) are important proteins in cancer immunotherapy. Soluble forms (sPD-1 and sPD-L1) have potential for determining treatment and prognosis monitoring. However, there is a lack of detection methods for point-of-care testing (POCT) of these two proteins, so a low-cost rapid detection platform is urgently needed. To solve this problem, a dual-channel electrochemical platform, including a folding paper-based immunosensor and a POCT system for rapid simultaneous detection of these two proteins was designed and fabricated. The immunosensor consists of a three-electrode system and a reaction cell. The surface of the working electrode was modified with nanocomposites synthesized from amine-functionalized single-walled carbon nanotubes, new methylene blue, and gold nanoparticles. Antibodies to sPD-1 and sPD-L1 were also immobilized on the working electrode surface. A differential pulse voltammetry electrochemical method was adopted. The immunosensor was able to detect sPD-1 and sPD-L1 in the ranges of 50 pg/mL to 50 ng/mL and 5 pg/mL to 5 ng/mL, respectively. The limits of detection were 10 and 5 pg/mL. Using this detection platform, sPD-1 and sPD-L1 in plasma were detected by both enzyme-linked immunosorbent assay and the immunosensor, which has good application potential.

Multiplex optical bioassays for food safety analysis: Toward on-site detection

Food safety analysis plays a significant role in controlling food contamination and supervision. In recent years, multiplex optical bioassays (MOBAs) have been widely applied to analyze multiple hazards due to their efficiency and low cost. However, due to the challenges such as multiplexing capacity, poor sensitivity, and bulky instrumentation, the further application of traditional MOBAs in food screening has been limited. In this review, effective strategies regarding food safety MOBAs are summarized, such as spatial-resolution modes performed in multi-T lines/dots strips or arrays of strip/microplate/microfluidic chip/SPR chip and signal-resolution modes employing distinguishable colorimetric/luminescence/fluorescence/surface plasma resonance/surface-enhanced Raman spectrum as signal tags. Following this, new trends on how to design engineered sensor architecture and exploit distinguishable signal reporters, how to improve both multiplexing capacity and sensitivity, and how to integrate these formats into smartphones so as to be mobile are summarized systematically. Typically, in the case of enhancing multiplexing capacity and detection throughput, microfluidic array chips with multichannel architecture would be a favorable approach to overcome the spatial and physical limitations of immunochromatographic assay (ICA) test strips. Moreover, noble metal nanoparticles and single-excitation, multiple-emission luminescence nanomaterials hold great potential in developing ultrasensitive MOBAs. Finally, the exploitation of innovative multiplexing strategy hybridized with powerful and widely available smartphones opens new perspectives to MOBAs. In future, the MOBAs should be more sensitive, have higher multiplexing capacity, and easier instrumentation.

Innovations in Prospective Perinatal Research as a Result Of the COVID-19 Pandemic

In 2020, in‐person research activities were stopped because of the spread of the novel coronavirus, severe acute respiratory syndrome coronavirus 2, and the resulting disease, coronavirus disease 2019. Our collaborative team of nurse and midwife scientists at universities across the United States adapted research activities to continue prospective perinatal research during the pandemic. These adaptations included development of new research techniques and the implementation of previously developed, but underused, strategies to conduct research from a distance. These strategies included online recruitment, virtual enrollment and consent, qualitative data collection via video conferencing, new applications of smart phone technology, wearable biological measurement, and participant self‐collection of biological samples. In addition to allowing research to continue during the pandemic, these innovative strategies may increase access to research for low‐income, rural, and racially diverse pregnant and postpartum populations. Decreased travel requirements, flexible scheduling, wearable devices, and the capacity to self‐collect biologic samples may improve recruitment and the experience of research participation. The rapid implementation of these research strategies has advanced innovation toward wider, more inclusive and increasingly diverse perinatal research access, and many of these strategies will continue to be used and refined.

Label-Free Physical Techniques and Methodologies for Proteins Detection in Microfluidic Biosensor Structures

Proteins in biological fluids (blood, urine, cerebrospinal fluid) are important biomarkers of various pathological conditions. Protein biomarkers detection and quantification have been proven to be an indispensable diagnostic tool in clinical practice. There is a growing tendency towards using portable diagnostic biosensor devices for point-of-care (POC) analysis based on microfluidic technology as an alternative to conventional laboratory protein assays. In contrast to universally accepted analytical methods involving protein labeling, label-free approaches often allow the development of biosensors with minimal requirements for sample preparation by omitting expensive labelling reagents. The aim of the present work is to review the variety of physical label-free techniques of protein detection and characterization which are suitable for application in micro-fluidic structures and analyze the technological and material aspects of label-free biosensors that implement these methods. The most widely used optical and impedance spectroscopy techniques: absorption, fluorescence, surface plasmon resonance, Raman scattering, and interferometry, as well as new trends in photonics are reviewed. The challenges of materials selection, surfaces tailoring in microfluidic structures, and enhancement of the sensitivity and miniaturization of biosensor systems are discussed. The review provides an overview for current advances and future trends in microfluidics integrated technologies for label-free protein biomarkers detection and discusses existing challenges and a way towards novel solutions.

Wash-free operation of smartphone-integrated optical immunosensor using retroreflective microparticles

Herein, we introduce a smartphone-integrated immunosensor based on non-spectroscopic optical detection. Sedimentation of the retroreflector and gentle inversion of the microfluidic chip was chosen as biosensing principles to ensure minimal human involvement. To realize this, wash-free immunosensing was implemented on a polymeric microfluidic chip device fabricated for light signal penetration in retroreflection signal acquisition. Applying a transparent chip and passive modulation of retroreflectors enabled the minimization of human error during sensing. In addition, a retroreflection-detectable optical gadget was constructed for integration with the commercial smartphone. The gadget had an optical chamber that induced retroreflection by integration with a smartphone. When the micro-sized reflector, named the retroreflective Janus microparticle, reacted on the sensing surface, the incident light was retroreflected towards the image sensor and quantified by a smartphone-installed Android application package. The developed application package features include time-lapse image capture performed by manipulating LED flash and camera modules, and quantification of retroreflected signal counts by image processing of time-lapse images. With this platform, the user could independently commence optical signal processing without a complicated optical setup and running software on a PC, and sensitive and reproducible immunosensing results could be obtained. The applicability test for creatine kinase-myocardial band detection from the buffer to serum was conducted and presented a calibration curve of 0-1000 ng/mL within 1 h. With the developed system, we believe that the applicability of the platform in bioanalytical detection can be expanded.

A redox-mediator pathway for enhanced multi-colour electrochemiluminescence in aqueous solution

The classic and most widely used co-reactant electrochemiluminescence (ECL) reaction of tris(2,2'-bipyridine)ruthenium(ii) ([Ru(bpy)3]2+) and tri-n-propylamine is enhanced by an order of magnitude by fac-[Ir(sppy)3]3- (where sppy = 5'-sulfo-2-phenylpyridinato-C 2,N), through a novel 'redox mediator' pathway. Moreover, the concomitant green emission of [Ir(sppy)3]3-* enables internal standardisation of the co-reactant ECL of [Ru(bpy)3]2+. This can be applied using a digital camera as the photodetector by exploiting the ratio of R and B values of the RGB colour data, providing superior sensitivity and precision for the development of low-cost, portable ECL-based analytical devices.

Spot tests: past and present

Microchemistry, i.e., the chemistry performed at the scale of a microgram or less, has its roots in the late eighteenth and early nineteenth centuries. In the first half of the twentieth century a wide range of spot tests have been developed. For didactic reasons, they are still part of the curriculum of chemistry students. However, they are even highly important for applied analyses in conservation of cultural heritage, food science, forensic science, clinical and pharmacological sciences, geochemistry, and environmental sciences. Modern pregnancy tests, virus tests, etc. are the most recent examples of sophisticated spot tests. The present ChemTexts contribution aims to provide an overview of the past and present of this analytical methodology.

Lighting up Individual Organelles With Fluorescent Carbon Dots

Cell organelles play crucial roles in the normal functioning of an organism, therefore the disruption of their operation is associated with diseases and in some cases death. Thus, the detection and monitoring of the activities within these organelles are of great importance. Several probes based on graphene oxide, small molecules, and other nanomaterials have been developed for targeting specific organelles. Among these materials, organelle-targeted fluorescent probes based on carbon dots have attracted substantial attention in recent years owing to their superior characteristics, which include facile synthesis, good photostability, low cytotoxicity, and high selectivity. The ability of these probes to target specific organelles enables researchers to obtain valuable information for understanding the processes involved in their functions and/or malfunctions and may also aid in effective targeted drug delivery. This review highlights recently reported organelle-specific fluorescent probes based on carbon dots. The precursors of these carbon dots are also discussed because studies have shown that many of the intrinsic properties of these probes originate from the precursor used. An overview of the functions of the discussed organelles, the types of probes used, and their advantages and limitations are also provided. Organelles such as the mitochondria, nucleus, lysosomes, and endoplasmic reticulum have been the central focus of research to date, whereas the Golgi body, centrosome, vesicles, and others have received comparatively little attention. It is therefore the hope of the authors that further studies will be conducted in an effort to design probes with the ability to localize within these less studied organelles so as to fully elucidate the mechanisms underlying their function.

Paper-based analytical devices for virus detection: Recent strategies for current and future pandemics

The importance of user-friendly, inexpensive, sensitive, and selective detection of viruses has been highlighted again due to the recent Coronavirus disease 2019 (COVID-19) pandemic. Among the analytical tools, paper-based devices (PADs) have become a leading alternative for point-of-care (POC) testing. In this review, we discuss the recent development strategies and applications in nucleic acid-based, antibody/antigen-based and other affinity-based PADs using optical and electrochemical detection methods for sensing viruses. In addition, advantages and drawbacks of presented PADs are identified. Current state and insights towards future perspectives are presented regarding developing POC diagnosis platform for COVID-19. This review considers state-of-the-art technologies for further development and improvement in PADs performance for virus detection.

Molecular Imprinting: Green Perspectives and Strategies

Advances in revolutionary technologies pose new challenges for human life; in response to them, global responsibility is pushing modern technologies toward greener pathways. Molecular imprinting technology (MIT) is a multidisciplinary mimic technology simulating the specific binding principle of enzymes to substrates or antigens to antibodies; along with its rapid progress and wide applications, MIT faces the challenge of complying with green sustainable development requirements. With the identification of environmental risks associated with unsustainable MIT, a new aspect of MIT, termed green MIT, has emerged and developed. However, so far, no clear definition has been provided to appraise green MIT. Herein, the implementation process of green chemistry in MIT is demonstrated and a mnemonic device in the form of an acronym, GREENIFICATION, is proposed to present the green MIT principles. The entire greenificated imprinting process is surveyed, including element choice, polymerization implementation, energy input, imprinting strategies, waste treatment, and recovery, as well as the impacts of these processes on operator health and the environment. Moreover, assistance of upgraded instrumentation in deploying greener goals is considered. Finally, future perspectives are presented to provide a more complete picture of the greenificated MIT road map and to pave the way for further development.

Smartphone-Enabled Personalized Diagnostics: Current Status and Future Prospects

Smartphones are becoming increasingly versatile thanks to the wide variety of sensor and actuator systems packed in them. Mobile devices today go well beyond their original purpose as communication devices, and this enables important new applications, ranging from augmented reality to the Internet of Things. Personalized diagnostics is one of the areas where mobile devices can have the greatest impact. Hitherto, the camera and communication abilities of these devices have been barely exploited for point of care (POC) purposes. This short review covers the recent evolution of mobile devices in the area of POC diagnostics and puts forward some ideas that may facilitate the development of more advanced applications and devices in the area of personalized diagnostics. With this purpose, the potential exploitation of wireless power and actuation of sensors and biosensors using near field communication (NFC), the use of the screen as a light source for actuation and spectroscopic analysis, using the haptic module to enhance mass transport in micro volumes, and the use of magnetic sensors are discussed.

Ultrasensitive On-Field Luminescence Detection Using a Low-Cost Silicon Photomultiplier Device

The availability of portable analytical devices for on-site monitoring and rapid detection of analytes of forensic, environmental, and clinical interest is vital. We report the development of a portable device for the detection of biochemiluminescence relying on silicon photomultiplier (SiPM) technology, called LuminoSiPM, which includes a 3D printed sample holder that can be adapted for both liquid samples and paper-based biosensing. We performed a comparison of analytical performance in terms of detectability with a benchtop luminometer, a portable cooled charge-coupled device (CCD sensor), and smartphone-integrated complementary metal oxide semiconductor (CMOS) sensors. As model systems, we used two luciferase/luciferin systems emitting at different wavelengths using purified protein solutions: the green-emitting P. pyralis mutant Ppy-GR-TS (λ_max 550 nm) and the blue-emitting NanoLuc (λ_max 460 nm). A limit of detection of 9 femtomoles was obtained for NanoLuc luciferase, about 2 and 3 orders of magnitude lower than that obtained with the portable CCD camera and with the smartphone, respectively. A proof-of-principle forensic application of LuminoSiPM is provided, exploiting an origami chemiluminescent paper-based sensor for acetylcholinesterase inhibitors, showing high potential for this portable low-cost device for on-site applications with adequate sensitivity for detecting low light intensities in critical fields.