Smartphone-based Assay Research Articles

Smartphone-Based Colourimetric Detection of Methyl Red, Co(II), Uric Acid, and Topotecan after Pre-concentration onto a Hectorite Clay-Hydroxyethylcellulose Hybrid

Objective:: This paper describes a new, digital image colourimetry-based format for the quantification of analytes in an aqueous solution. Method:: The proposed method is based on analyte pre-concentration by adsorption onto Bentone LT. Bentone LT pellet isolation comes after adsorption, followed by in-situ application of an analyteselective chromogenic reaction. The resulting pellet colouration is captured by the phone’s integrated camera and assessed using the free open-source image processing software, ImageJ. Responses are calibrated and quantified. Results:: We tested the applicability of the proposed methodology for the quantification of specific model analytes which are of concern in environmental matrices (methyl red, Co(II), uric acid, topotecan). The smartphone-based assay was proven reliable in quantifying the model analytes (standard recovery of 82-116%), alone or in mixture, from dilute aqueous solutions and was found to depict accurately the adsorption behaviour followed photometrically in solution. Lower limit of linearity was calculated at 0.05, 0.11, 0.85 and 0.20 μg/mL for methyl red, Co(II), uric acid, and topotecan, respectively. The proposed format was found superior when compared to alternative published photometric/ colourimetric assays in terms of the lower limit of linearity. In the presence of possible adsorption interferents, the lower limit of linear response was shifted to slightly higher concentrations for topotecan i.e. from 0.2 μg/mL to 0.5 μg/mL. Conclusion:: We here demonstrate the extended applicability of the proposed methodology for the smartphone-based quantification of the specific model analytes. The applicability of this analysis format likely extends to other analytes, where analyte-specific colour formation is feasible.

Point-of-care blood tests using a smartphone-based colorimetric analyzer for health check-up.

A microscale colorimetric assay was designed and implemented for the simultaneous determination of clinical chemistry tests measuring six parameters, including glucose (GLU), total protein (TP), human serum albumin (HSA), uric acid (UA), total cholesterol (TC), and triglycerides (TGs) in plasma samples. The test kit was fabricated using chromogenic reagents, comprising specific enzymes and binding dyes. Multiple colors that appeared on the reaction well when it was exposed to each analyte were captured by a smartphone and processed by the homemade Check6 application, which was designed as a colorimetric analyzer and simultaneously generated a report that assessed test results against gender-dependent reference ranges. Six blood checkup parameters for four plasma samples were conducted within 12min on one capture picture. The assay achieved wide working concentration ranges of 10.45-600 mg dL-1 GLU, 1.39-10.0g dL-1 TP, 1.85-8.0g dL-1 HSA, 0.86-40.0 mg dL-1 UA, 11.28-600 mg dL-1 TC, and 11.93-400 mg dL-1 TGs. The smartphone-based assay was accurate with recoveries of 93-108% GLU, 93-107% TP, 92-107% HSA, 93-107% UA, 92-107% TC, and 99-113% TGs. The coefficient of variation for intra-assay and inter-assay precision ranged from 3.2-5.2% GLU, 4.6-5.3% TP, 4.3-5.3% HSA, 2.8-6.6% UA, 2.7-6.5% TC, and 1.1-3.9% TGs. This assay demonstrated remarkable accuracy in quantifying the concentration-dependent color intensity of the plasma, even in the presence of other suspected interferences commonly present in serum. The results of the proposed method correlated well with results determined by the microplate spectrophotometer (R2 > 0.95). Measurement of these six clinical chemistry parameters in plasma using a microscale colorimetric test kit coupled with the Check6 smartphone application showed potential for real-time point-of-care analysis, providing cost-effective and rapid assays for health checkup testing.

Strand displacement-triggered FRET nanoprobe tracking TK1 mRNA in living cells for ratiometric fluorimetry of nucleic acid biomarker.

Aprecisely designed dual-color biosensor has realized a visual assessment of thymidine kinase 1 (TK1) mRNA in both living cells and cell lysates. The oligonucleotide probe is constructed by hybridizing the antisense strand of the target and two recognition sequences, in which FAM serves as the donor and TAMRA as the acceptor. Once interacting with the target, two recognition strands are replaced, and then the antisense complementary sequence forms a more stable double-stranded structure. Due to the increasing spatial distance between two dyes, the FRET is attenuated, leading to a rapid recovery of FAM fluorescence and a reduction of TAMRA fluorescence. A discernible color response from orange to green could be observed by the naked eye, with a limit of detection (LOD) of 0.38 nM and 5.22 nM for spectrometer- and smartphone-based assays, respectively. The proposed ratiometric method transcends previous reports in its capacities in visualizing TK1 expression toward reliable nucleic acid biomarker analysis, which might establish a general strategy for ratiometric biosensing via strand displacement.

(Invited) Lab-in-a-Tube Design Enables a Rapid Diagnosis of Infectious Disease

Disease diagnosis increasingly relies on molecular tests that are often limited by infrastructure constraints. For example, tuberculosis (TB) remains a leading cause of death from infectious disease, but an estimated 4.2 million (39.6%) new TB cases were not diagnosed in 2021 and only 57% were confirmed by gold-standard sputum culture or PCR-based tests, partially due to limited accessibility. New point-of-care tests are thus urgently needed to address coverage disparities for chronic, malignant, and infectious diseases.We have developed two smartphone-based assays that can address two diagnostic shortfalls: an on-chip interferon-gamma release assay (IGRA) that detects a T-cell activation response induced by pathogen antigens in fingerstick blood samples, and a lab-in-tube assay that employs CRISPR to sensitively detect pathogen DNA in sputum. Both approaches translate current diagnostic approaches to point-of-care devices that require minimal equipment, user expertise, and time.Results from our on-chip IGRA also correlated with clinical IGRA results when we employed two proteins associated with TNF-alpha receptor signaling (4-1BB and OX-40) to analyze T-cell activation, indicating this approach could detect infections in individuals with compromised interferon-gamma responses; as observed in HIV patients, who are at increased risk for TB. On-chip IGRA results from a SARS-CoV-2-specific assay also corresponded with both infection and vaccination history, suggesting this data could be employed as a high-throughput, high-capacity test to evaluate the effect of vaccination or previous infection to confer a protective immune response, evaluate its change over time, and predict the response to new variant strains to guide healthcare decisions. Mitogen-induced results could also guide immunotherapy decisions, as reduced IGRA values in patients receiving immune checkpoint inhibitors predict poor treatment response, reduced progression-free survival, and increased risk for interstitial pneumonia, while their change after adoptive T-cell therapy can be an independent predictor for overall survival. Results from our lab-in-tube TB DNA assay also had robust diagnostic performance when compared to gold-standard clinical assays but lacked their more extensive personnel, workflow, and infrastructure requirements and were performed in a closed-tube system that protected user from exposure to infectious material. This lab-in-tube approach also permits parallel multiplex analyses to be performed in a single tube, and thus can be employed to detect mutations associated with drug-resistance to guide treatment decisions. For example, we found that an assay with an optimized guide RNA accurately detected a single-nucleotide polymorphism (rpoB S450L) responsible for the majority of rifampin-resistant TB cases.Both these self-contained handheld devices can employ lyophilized reagents to limit cold-chain concerns, can be readily adapted to diagnose other disease conditions by substituting other disease-specific antibodies or guide RNAs, use rechargeable batteries to avoid infrastructure limitations, and can directly transmit results to central sites to improve disease control efforts.

Chromogenic, specific cascade detection of fluoride and alkaline earth metal ions

A salen-based colorimetric chemosensor (MM) has been designed and synthesized to selectively recognize F− and alkaline earth metal ions in solution and solid phase, respectively. A ratiometric UV–visible absorption spectral change with a colorimetric visualization from yellow to pink is observed in the presence of F− ions. The detection of F− ions is fully reversible in alkaline earth metal ions. The limit of detection (LOD) of F− ions by our as-prepared MM could be possible down to the μM range. A paper strips-based test kit has been fabricated to detect F− ions selectively by the naked eye. A smartphone-based assay analysis is also successfully performed to identify F− ions in the non-aqueous media. Such a dual ions sensing system with excellent reversibility and repeatability prompted us to consider probe MM a viable choice for fabricating molecular logic circuits and set-reset memorized molecular devices.

Construction of Metal Organic Framework-Derived Fe-N-C Oxidase Nanozyme for Rapid and Sensitive Detection of Alkaline Phosphatase.

Alkaline phosphatase (ALP) is a phosphomonoester hydrolase and serves as a biomarker in various diseases. However, current detection methods for ALP rely on bulky instruments, extended time, and complex operations, which are particularly challenging in resource-limited regions. Herein, we synthesized a MOF-derived Fe-N-C nanozyme to create biosensors for the coulometric and visual detection of ALP. Specifically, we found the Fe-N-C nanozyme can efficiently oxidize 3,3',5,5'-tetramethylbenzidine (TMB) to generate blue-colored tetramethyl benzidine (TMBox) without the need for H2O2. To construct the biosensor, we incorporated the ALP enzymatic catalytic reaction to inhibit the oxidation of TMB by Fe-N-C oxidase nanozyme. This biosensor showed rapid and highly sensitive detection of ALP in both buffer and clinical samples. The limit of detection (LOD) of our approach could be achieved at 3.38 U L-1, and the linear range was from 5 to 60 U L-1. Moreover, we also developed a visual detection for ALP by using a smartphone-based assay and facilitated practical and accessible point-and-care testing (POCT) in resource-limited areas. The visual detection method also achieved a similar LOD of 2.12 U L-1 and a linear range of 5-60 U L-1. Our approach presents potential applications for other biomarker detections by using ALP-based ELISA methods.

Smartphone-Based Portable Bio-Chemical Sensors: Exploring Recent Advancements

Traditionally, analytical chemistry and diagnosis relied on wet laboratories and skilled professionals utilizing sophisticated instruments for sample handling and analysis. However, with the development of novel materials and sensing techniques, there has been a significant shift towards the use of standalone sensors, allowing tests to be conducted on-site or even in real time, leading to cost- and time-efficiency. With their widespread adoption globally, smartphones have emerged as an ideal platform for such sensors, boasting extensive sensor capabilities, advanced processing power, and communication functionalities. Smartphone-based assays make use of optical and electrochemical sensors, utilizing built-in cameras, ambient light sensors, and other features for optical sensing, while the micro-USB port, Bluetooth, and wireless connection facilitate data transmission and analog voltage application for electrochemical sensing. Previous overview papers have explored smartphone-based sensing in specific domains; this review provides a comprehensive examination of recent advancements in smartphone-based sensors, encompassing both optical and electrochemical sensing methods. The review provides the fundamental principles of these sensors and their implementation using smartphones, showcases recent applications, and presents innovative designs that take advantage of the inherent functionalities and sensor capabilities of smartphones. The review concludes by offering an outlook on the prospects of smartphone-based sensing and includes a reflective section emphasizing the potential impact of sensors in chemical and biological analyses. This comprehensive resource aims to provide information to researchers and practitioners interested in using smartphones for cutting-edge analytical methodologies.

Fabrication of a re-usable benzoxazole-based colorimetric sensor for selective and sensitive recognition of sarin mimic, diethylchlorophosphate

This report introduces a colorimetric benzoxazole-scaffold molecule, BPDA, to recognize a toxic sarin gas mimic, diethylchlorophosphate (DCP), in both solution and gas phases, respectively. The yellow color of the BPDA solution is slowly transferred into a noticeable fuchsia-pink color for the gradual accumulation of DCP, which is visualized in the bare eye. The fuchsia-pink color of the BPDA-DCP solution is wholly reversed to the yellow color of free BPDA due to the steady addition of triethylamine (TEA). Our developed BPDA-based colorimetric sensor shows excellent selectivity towards DCP with a detection limit of 44.5 nM. Also, a paper strip and smartphone-based assay analysis have been demonstrated for the practical utility of our BPDA for immediate detection of DCP within the stockpiles of similar toxic analytes. Also, a dip-stick method has been employed to identify and quantify the DCP vapor selectively among the other analogous poisonous organophosphates.

Sample-to-answer platform for the clinical evaluation of COVID-19 using a deep learning-assisted smartphone-based assay

Since many lateral flow assays (LFA) are tested daily, the improvement in accuracy can greatly impact individual patient care and public health. However, current self-testing for COVID-19 detection suffers from low accuracy, mainly due to the LFA sensitivity and reading ambiguities. Here, we present deep learning-assisted smartphone-based LFA (SMARTAI-LFA) diagnostics to provide accurate decisions with higher sensitivity. Combining clinical data learning and two-step algorithms enables a cradle-free on-site assay with higher accuracy than the untrained individuals and human experts via blind tests of clinical data (n = 1500). We acquired 98% accuracy across 135 smartphone application-based clinical tests with different users/smartphones. Furthermore, with more low-titer tests, we observed that the accuracy of SMARTAI-LFA was maintained at over 99% while there was a significant decrease in human accuracy, indicating the reliable performance of SMARTAI-LFA. We envision a smartphone-based SMARTAI-LFA that allows continuously enhanced performance by adding clinical tests and satisfies the new criterion for digitalized real-time diagnostics.

CuO nanorod-decorated hemin-graphene with enhanced peroxidase-mimicking performance for the colorimetric and electrochemical determination of 4-aminophenol with a smartphone.

The detection of 4-aminophenol (4-AP) is of critical importance due to its high toxicity, and the development of accurate, sensitive, and portable methods for this purpose is essential. Here, a facile colorimetric and electrochemical dual-mode sensor based on a CuO nanorod-decorated hemin-functionalized graphene nanocomposite (CuO/H-Gr) is successfully constructed for the detection of 4-AP. CuO/H-Gr exhibited superior peroxidase-mimicking activity, catalyzing the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) by H2O2 and generating a colorimetric signal. The catalytic system was found to contain hydroxyl radicals, as revealed by reactive oxygen species trials. Meanwhile, TMB was found to be an electroactive indicator that could be oxidized on a glassy carbon electrode. In the presence of CuO/H-Gr and H2O2, an enhanced electrochemical signal of TMB was generated. Upon the addition of 4-AP, the catalytic performance of CuO/H-Gr in the oxidation of TMB was significantly reduced, leading to a decrease in colorimetric and electrochemical signals. Based on this, a dual-mode sensor for the detection of 4-AP was developed. The linear response ranges for colorimetric and electrochemical sensors are 1.00-200 μM and 0.0100-300 μM, with detection limits of 0.687 μM and 0.00756 μM, respectively. Real water samples were tested to estimate the feasibility of the dual-mode sensor, and the recoveries were found to be consistent with those obtained by high-performance liquid chromatography. In addition, a smartphone-based assay was used to evaluate the levels of 4-AP, which opened a new path for on-site detection.

A coffee-ring effect-based paper sensor chip for the determination of beta-lactoglobulin in foods via a smartphone

To determine allergen beta-lactoglobulin (β-LG) in foods, a method by a coffee-ring effect (CRE)-based paper sensor chip combined with a smartphone has been developed. The strategy was based on the principle of fluorescence quenching by the quantum dot-aptamer-graphene oxide (QD-Apt-GO) and where the degree of quenching was inversely proportional to the concentration of β-LG. First, the prepared β-LG solution was added to the QD-Apt fluorescent probe solution followed by an appropriate amount of GO. After the reaction, a certain amount of the mixture was dispensed onto the detection zone of the sensor chip, resulting in the spread of the analyte solution by evaporation-driven flow. The QD-Apt and the QD-Apt-β-LG in the mixed solution formed a visible fluorescent coffee-ring. For signal quantitation, an image of the coffee-ring was taken by a smartphone and imported into self-programmed software for analysis. The quantitative results for β-LG were acquired rapidly based on the magnitude of the generated fluorescent coffee-ring. The limit of detection (LOD) for β-LG was 0.048 mg L-1 and the linear range for the optimized assay was 0.39–1000 mg L-1. The method was validated for analysis of real food samples and the results were consistent with those of a commercial ELISA assay kit. The smartphone-based assay provides a simple, economic, compact, and visual detection platform for the determination of β-LG in foods.

Smartphone-Based Multiplexed Biosensing Tools for Health Monitoring.

Many emerging technologies have the potential to improve health care by providing more personalized approaches or early diagnostic methods. In this review, we cover smartphone-based multiplexed sensors as affordable and portable sensing platforms for point-of-care devices. Multiplexing has been gaining attention recently for clinical diagnosis considering certain diseases require analysis of complex biological networks instead of single-marker analysis. Smartphones offer tremendous possibilities for on-site detection analysis due to their portability, high accessibility, fast sample processing, and robust imaging capabilities. Straightforward digital analysis and convenient user interfaces support networked health care systems and individualized health monitoring. Detailed biomarker profiling provides fast and accurate analysis for disease diagnosis for limited sample volume collection. Here, multiplexed smartphone-based assays with optical and electrochemical components are covered. Possible wireless or wired communication actuators and portable and wearable sensing integration for various sensing applications are discussed. The crucial features and the weaknesses of these devices are critically evaluated.

N, S-co-doped carbon/Co1-xS nanocomposite with dual-enzyme activities for a smartphone-based colorimetric assay of total cholesterol in human serum

We fabricated a novel N,S-co-doped carbon/Co1-xS nanocomposite (NSC/Co1-xS) using a facile sol-gel approach, which featured a multiporous structure, abundant S vacancies and Co-S nanoparticles filling the carbon-layer pores. When the Co1-xS nanoparticles were anchored onto the surface of N,S-co-doped carbon, a synergistic catalysis action occurred. The NSC/Co1-xS nanocomposites possessed both peroxidase-like and oxidase-mimetic dual-enzyme activities, in which the oxidase-mimetic activity dominated. By scavenger capture tests, the nanozyme was demonstrated to catalyze H2O2 to produce h+, •OH and •O2−, among which the strongest and weakest signals were h+ and •OH, respectively. The multi-valence states of Co atoms in the NSC/Co1-xS structure facilitated electronic transfer that enhanced redox reactions, thereby improving the resultant color reaction. Based on the NSC/Co1-xS's enzyme-mimetic catalytic reaction, a visual colorimetric assay and Android “Thing Identify” application (app), installed on a smartphone, offered detection limits of 1.93 and 2.51 mg/dl, respectively, in human serum samples. The selectivity/interference experiments, using fortified macromolecules and metal ions, demonstrated that this sensor had high selectivity and low interference potential for cholesterol analysis. Compared to standard assay kits and previously reported visual detection, the Android smartphone-based assays provided higher accuracy (recoveries up to 93.6–104.1%), feasibility for trace-level detection, and more convenient on-site application for cholesterol assay due to the superior enzymatic activity of NSC/Co1-xS. These compelling performance metrics lead us to posit that the NSC/Co1-xS-based nanozymic sensor offers a promising methodology for several practical applications, such as point-of-care diagnosis and workplace health evaluations.

Improving the Quantification of Colorimetric Signals in Paper-Based Immunosensors with an Open-Source Reader.

Measuring the colorimetric signals produced by the biospecific accumulation of colorimetric probes and recording the results is a key feature for next-generation paper-based rapid tests. Manual processing of these tests is time-consuming and prone to a loss of accuracy when interpreting faint and patchy signals. Proprietary, closed-source readers and software companies offering automated smartphone-based assay readings have both been criticized for interoperability issues. Here, we introduce a minimal reader prototype composed of open-source hardware and open-source software that has the benefits of automatic assay quantification while avoiding the interoperability issues associated with closed-source readers. An image-processing algorithm was developed to automate the selection of an optimal region of interest and measure the average pixel intensity. When used to quantify signals produced by lateral flow immunoassays for detecting antibodies against SARS-CoV-2, results obtained with the proposed algorithm were comparable to those obtained with a manual method but with the advantage of improving the precision and accuracy when quantifying small spots or faint and patchy signals.

Assessment of a Smartphone-Based Loop-Mediated Isothermal Amplification Assay for Detection of SARS-CoV-2 and Influenza Viruses

A critical need exists in low-income and middle-income countries for low-cost, low-tech, yet highly reliable and scalable testing for SARS-CoV-2 virus that is robust against circulating variants. To assess whether a smartphone-based assay is suitable for SARS-CoV-2 and influenza virus testing without requiring specialized equipment, accessory devices, or custom reagents. This cohort study enrolled 2 subgroups of participants (symptomatic and asymptomatic) at Santa Barbara Cottage Hospital. The symptomatic group consisted of 20 recruited patients who tested positive for SARS-CoV-2 with symptoms; 30 asymptomatic patients were recruited from the same community, through negative admission screening tests for SARS-CoV-2. The smartphone-based real-time loop-mediated isothermal amplification (smaRT-LAMP) was first optimized for analysis of human saliva samples spiked with either SARS-CoV-2 or influenza A or B virus; these results then were compared with those obtained by side-by-side analysis of spiked samples using the Centers for Disease Control and Prevention (CDC) criterion-standard reverse transcriptase-quantitative polymerase chain reaction (RT-qPCR) assay. Next, both assays were used to test for SARS-CoV-2 and influenza viruses present in blinded clinical saliva samples obtained from 50 hospitalized patients. Statistical analysis was performed from May to June 2021. Testing for SARS-CoV-2 and influenza A and B viruses. SARS-CoV-2 and influenza infection status and quantitative viral load were determined. Among the 50 eligible participants with no prior SARS-CoV-2 infection included in the study, 29 were men. The mean age was 57 years (range, 21 to 93 years). SmaRT-LAMP exhibited 100% concordance (50 of 50 patient samples) with the CDC criterion-standard diagnostic for SARS-CoV-2 sensitivity (20 of 20 positive and 30 of 30 negative) and for quantitative detection of viral load. This platform also met the CDC criterion standard for detection of clinically similar influenza A and B viruses in spiked saliva samples (n = 20), and in saliva samples from hospitalized patients (50 of 50 negative). The smartphone-based LAMP assay was rapid (25 minutes), sensitive (1000 copies/mL), low-cost (<$7/test), and scalable (96 samples/phone). In this cohort study of saliva samples from patients, the smartphone-based LAMP assay detected SARS-CoV-2 infection and exhibited concordance with RT-qPCR tests. These findings suggest that this tool could be adapted in response to novel CoV-2 variants and other pathogens with pandemic potential including influenza and may be useful in settings with limited resources.

Ion-Selective Optodes Integrated Paper-Based Device for Simultaneous Colorimetric Quantification of Salivary Na&lt;sup&gt;+&lt;/sup&gt;, K&lt;sup&gt;+&lt;/sup&gt; and Ca&lt;sup&gt;2+&lt;/sup&gt;

The quantification of electrolytes in biological fluids plays an important role for evaluating the human health condition. This work proposes a disposable and simple microfluidic paper-based analytical device (μPAD) for the quantitative colorimetric detection of salivary Na+, K+ and Ca2+, relying on ion-selective optodes (ISOs). Nanoscale ISOs composed of pluronic F-127 surfactant-based micelles were used as a colorimetric indicator system, reducing the assay time compared to the previously reported bulk membrane approach. Devices consist of three functionalized paper layers assembled by lamination, with the optical signal read out from the bottom layer. Saliva was chosen as the biological specimen because it is painlessly collected and easy-to-handle, which makes it suitable for POC assays. Simultaneous Na+, K+ and Ca2+ detection by a single μPAD was successfully confirmed by using aqueous metal ion samples with various concentrations of Na+, K+ and Ca2+ within the biologically relevant range. The simultaneous detection of the three cationic species enabled the correction of the three ion quantities by eliminating the interference from other ions using the calculated selectivity coefficients. For proof-of-concept, Na+ quantification in a human saliva sample was conducted by the developed μPADs. The calibration curve for this assay was prepared by applying artificial saliva to the μPADs. The concentrations of Na+ in spiked human saliva were also measured by the μPADs. The obtained recovery rates were 78-132 %, which indicates the quantification of the added Na+ in the real sample matrix. Finally, this μPAD was successfully integrated into a smartphone-based assay, which enables salivary electrolyte quantification in resource poor settings. The developed μPADs satisfy the criteria of low-cost (< $0.3/device), rapidity (< 5 min) and simple analytical procedure compared to the conventional ion-selective electrode (ISE) method.

Tandem reassembly of split luciferase-DNA chimeras for bioluminescent detection of attomolar circulating microRNAs using a smartphone

Detection of dysregulated circulating microRNAs (miRNAs) in human biofluids is a fundamental ability to determine tumor occurrence and metastasis in a minimally invasive fashion. However, the requirements for sophisticated instruments and professional personnel impede the translation of miRNA tests into routine clinical diagnostics, especially for resource-limited regions. Herein, we developed a DNA-guided bioluminescence strategy for the detection of circulating miRNAs. In this strategy, a pair of split luciferase-DNA chimeras was constructed and integrated into the miRNA-triggered rolling circle amplification (RCA) process. The tandem reassembly of split luciferase-DNA chimeras on the RCA products elicited a turn-on bioluminescence response with ultrahigh signal-to-background (S/B) ratio. This strategy enabled smartphone-based assays for different miRNAs with attomolar sensitivity and single-base specificity, as demonstrated here for miR-21. miR-148b, and cel-miR-39. Further application of our approach to the clinical serum samples realized identification of dysregulated miR-21 and miR-148b in the lung cancer patients, showing a satisfactory agreement with the control assays performed with quantitative reverse transcription polymerase chain reaction (qRT-PCR). Therefore, the developed method possesses the benefits of high performance and reliability, offering a potential tool for implementing miRNA-based diagnosis in point-of-care (POC) settings.

Smartphone colorimetric assay of acid phosphatase based on a controlled iodine-mediated etching of gold nanorods.

A simple but efficient colorimetric assay was developed for the detection and quantification of acid phosphatase (ACP) using a smartphone. This strategy is based on target-controlled iodine-mediated etching of gold nanorods (AuNRs). Due to effective hydrolysis of the substrate pyrophosphate (PPi) by ACP, chelated Cu2+ with PPi was released, which promoted the redox reaction with an iodide ion (I-), leading to the formation of I3-. As the etching agent of AuNRs, I3- caused a blueshift of the localized surface plasmon resonance peak and, more importantly, an observable color change. The vivid colors were recorded with a smartphone camera and directly analyzed using an image-processing app. On the basis of the direct correlation between ACP concentration and the etching degree of AuNRs as well as color change, this smartphone nanocolorimetry technique showed a good linear response toward ACP over the range of 0-15.0U/L, with a detection limit of 0.97U/L. Using the standard addition method, the practical applicability of the proposed smartphone-based assay was successfully demonstrated by determining ACP in human serum samples, with results consistent with those obtained by UV-Vis spectrophotometry.

Total Iron Measurement in Human Serum With a Novel Smartphone-Based Assay.

Background: Abnormally low or high blood iron levels are common health conditions worldwide and can seriously affect an individual’s overall well-being. A low-cost point-of-care technology that measures blood iron markers with a goal of both preventing and treating iron-related disorders represents a significant advancement in medical care delivery systems. Methods: A novel assay equipped with an accurate, storable, and robust dry sensor strip, as well as a smartphone mount and (iPhone) app is used to measure total iron in human serum. The sensor strip has a vertical flow design and is based on an optimized chemical reaction. The reaction strips iron ions from blood-transport proteins, reduces Fe(III) to Fe(II), and chelates Fe(II) with ferene, with the change indicated by a blue color on the strip. The smartphone mount is robust and controls the light source of the color reading App, which is calibrated to obtain output iron concentration results. The real serum samples are then used to assess iron concentrations from the new assay, and validated through intra-laboratory and inter-laboratory experiments. The intra-laboratory validation uses an optimized iron detection assay with multi-well plate spectrophotometry. The inter-laboratory validation method is performed in a commercial testing facility (LabCorp). Results: The novel assay with the dry sensor strip and smartphone mount, and App is seen to be sensitive to iron detection with a dynamic range of 50 – n}{}300~mu text{g}n/dL, sensitivity of 0.00049 a.u/n}{}mu text{g}n/dL, coefficient of variation (CV) of 10.5%, and an estimated detection limit of n}{}sim 15~mu text{g}n/dL These analytical specifications are useful for predicting iron deficiency and overloads. The optimized reference method has a sensitivity of 0.00093 a.u/n}{}mu text{g}n/dL and CV of 2.2%. The correlation of serum iron concentrations (N = 20) between the optimized reference method and the novel assay renders a slope of 0.95, and a regression coefficient of 0.98, suggesting that the new assay is accurate. Last, a spectrophotometric study of the iron detection reaction kinetics is seen to reveal the reaction order for iron and chelating agent. Conclusion: The new assay is able to provide accurate results in intra- and inter- laboraty validations, and has promising features of both mobility and low-cost manufacturing suitable for global healthcare settings.

Automation of Optical Control of Metal Ions in Liquid Using a Smartphone

A new automated smartphone-based assay for metals ions determination based on the color reaction with organic ligands was developed. Quantification was performed by measuring the color of the polymer optode. This offers a smartphone-based alternative to the colorimeric method for signal treatment usually employed in automatic methods. The technique enabled linear calibration within the range 1–500 ppb of metals ions. The sampling time used for this concentration range was 15 min. The method was also tested for the quantification of metals ions in water samples, followed by digital image treatment of the optode. The automated detection metals ions approach was demonstrated by applying smartphone to the analysis of metals ions. Relative recoveries of the analytes ranged from 87 % to 105 %. The described procedure has the potential to be a fully automated online smartphone platform for the purpose of routine onsite water analysis.