DNA detection using commercial mobile phones

Critical importance of RGB color space specificity for colorimetric bio/chemical sensing: A comprehensive study

The use of the RGB color model in colorimetric chemical sensing via imaging techniques is widely prevalent in the literature. However, the lack of specificity in the selection of RGB color space during capture and analysis presents a significant challenge in creating standardised methods for this field and possible discrepancies. In this study, we conducted a comprehensive comparison and contrast of a total of 68 RGB color spaces to evaluate their respective impacts on colorimetric bio/chemical sensing. We explore the impact of dynamic range, sensitivity, and limit of detection, and show that the lack of specificity in RGB color space selection can significantly impact colorimetric chemical sensing by 42-77%. We also explore the impact of underlying RGB comparisons and demonstrate a further 18.3% discrepancy between RGB color spaces. By emphasising the importance of proper RGB color space selection and handling, our findings contribute to a better understanding of this critical area and present valuable opportunities for future research. We further provide valuable insights for creating standardised methods in this field, which can be utilised to avoid discrepancies and ensure accurate and reliable analysis in colorimetric bio/chemical sensing.

Smartphone-based platforms implementing microfluidic detection with image-based artificial intelligence

The frequent outbreak of global infectious diseases has prompted the development of rapid and effective diagnostic tools for the early screening of potential patients in point-of-care testing scenarios. With advances in mobile computing power and microfluidic technology, the smartphone-based mobile health platform has drawn significant attention from researchers developing point-of-care testing devices that integrate microfluidic optical detection with artificial intelligence analysis. In this article, we summarize recent progress in these mobile health platforms, including the aspects of microfluidic chips, imaging modalities, supporting components, and the development of software algorithms. We document the application of mobile health platforms in terms of the detection objects, including molecules, viruses, cells, and parasites. Finally, we discuss the prospects for future development of mobile health platforms.

Development of a double monitoring system for the determination of Cr(VI) in different water matrices by HPLC-UV and digital image-based colorimetric detection method with the help of a metal sieve-linked double syringe system in complexation

This study reports a cheap, efficient, sensitive, and simple double monitoring analytical method for trace determination of Cr(VI), which is toxic and harmful even at very low concentrations. A metal sieve-linked double syringe (MSLDS) system was used to help the formation of chromium complex (Cr-diphenyl carbazide, DPC) subsequently determined by high-performance liquid chromatography-ultraviolet (HPLC-UV) and digital image-based colorimetry (DIC) systems. The metal complex was eluted through a Phenomenex-Aqua C18 with a mobile phase comprising of 50 mM ammonium formate solution (pH 4.0):acetonitrile (78:22, v/v) and detected by the UV detector at the wavelength of 581 nm. Under their optimum conditions, the HPLC-UV and DIC systems exhibited good linearity in ranges of 10-500 µg L^-1 and 100-1000 µg L^-1, respectively. The percent relative standard deviations (RSD%s) calculated for the lowest concentrations of both systems fell below 10%, and this confirmed good repeatability for replicate measurements. The accuracy of the proposed methods was evaluated by performing spike recovery experiments on wastewater, river water, and tap water samples. The calculated recovery results were in the range of 81.5-105.5% for HPLC-UV system and 93.8-111.1% for the DIC system. These results indicate that the proposed methods are suitable for routine Cr(VI) determination in terms of their rapidness, simplicity, good repeatability, and low cost.

Quantitative isothermal amplification on paper membranes using amplification nucleation site analysis

Quantitative nucleic acid amplification tests (qNAATs) are critical in treating infectious diseases, such as in HIV viral load monitoring or SARS-CoV-2 testing, in which viral load indicates viral suppression or infectivity. Quantitative PCR is the gold standard tool for qNAATs; however, there is a need to develop point-of-care (POC) qNAATs to manage infectious diseases in outpatient clinics, low- and middle-income countries, and the home. Isothermal amplification methods are an emerging tool for POC NAATs as an alternative to traditional PCR-based workflows. Previous works have focused on relating isothermal amplification bulk fluorescence signals to input copies of target nucleic acids for sample quantification with limited success. In this work, we show that recombinase polymerase amplification (RPA) reactions on paper membranes exhibit discrete fluorescent amplification nucleation sites. We demonstrate that the number of nucleation sites can be used to quantify HIV-1 DNA and viral RNA in less than 20 minutes. An image-analysis algorithm quantifies nucleation sites and determines the input nucleic acid copies in the range of 67-3000 copies per reaction. We demonstrate a mobile phone-based system for image capture and onboard processing, illustrating that this method may be used at the point-of-care for qNAATs with minimal instrumentation.

Quantitative Isothermal Amplification on Paper Membranes using Amplification Nucleation Site Analysis

Quantitative nucleic acid amplification tests (qNAATs) are critical in treating infectious diseases, such as in HIV viral load monitoring or SARS-CoV-2 testing, in which viral load indicates viral suppression or infectivity. Quantitative PCR is the gold standard tool for qNAATs; however, there is a need to develop point-of-care (POC) qNAATs to manage infectious diseases in outpatient clinics, low- and middle-income countries, and the home. Isothermal amplification methods are an emerging tool for POC NAATs as an alternative to traditional PCR-based workflows. Previous works have focused on relating isothermal amplification bulk fluorescence signals to input copies of target nucleic acids for sample quantification with limited success. In this work, we show that recombinase polymerase amplification (RPA) reactions on paper membranes exhibit discrete fluorescent amplification nucleation sites. We demonstrate that the number of nucleation sites can be used to quantify HIV-1 DNA and RNA in less than 20 minutes. An image-analysis algorithm quantifies nucleation sites and determines the input nucleic acid copies in the range of 67-3,000 copies per reaction. We demonstrate a mobile phone-based system for image capture and onboard processing, illustrating that this method may be used at the point-of-care for qNAATs with minimal instrumentation.

Portable on-chip colorimetric biosensing platform integrated with a smartphone for label/PCR-free detection of Cryptosporidium RNA

Cryptosporidium, a protozoan pathogen, is a leading threat to public health and the economy. Herein, we report the development of a portable, colorimetric biosensing platform for the sensitive, selective and label/PCR-free detection of Cryptosporidium RNA using oligonucleotides modified gold nanoparticles (AuNPs). A pair of specific thiolated oligonucleotides, complementary to adjacent sequences on Cryptosporidium RNA, were attached to AuNPs. The need for expensive laboratory-based equipment was eliminated by performing the colorimetric assay on a micro-fabricated chip in a 3D-printed holder assembly. A smartphone camera was used to capture an image of the color change for quantitative analysis. The detection was based on the aggregation of the gold nanoparticles due to the hybridization between the complementary Cryptosporidium RNA and the oligonucleotides immobilized on the AuNPs surface. In the complementary RNA's presence, a distinctive color change of the AuNPs (from red to blue) was observed by the naked eye. However, in the presence of non-complementary RNA, no color change was observed. The sensing platform showed wide linear responses between 5 and 100 µM with a low detection limit of 5 µM of Cryptosporidium RNA. Additionally, the sensor developed here can provide information about different Cryptosporidium species present in water resources. This cost-effective, easy-to-use, portable and smartphone integrated on-chip colorimetric biosensor has great potential to be used for real-time and portable POC pathogen monitoring and molecular diagnostics.

Smartphone-based optical analysis systems

During the past few decades, there has been a growing trend towards the use of smartphone-based analysis systems. This is mainly due to its ubiquity, its increasing computing capacity, its relatively low cost and the ability to acquire and process data at the same time. Furthermore, there are many sensors integrated into a smartphone, for example a complementary metal-oxide semiconductor (CMOS) sensor. A CMOS sensor enables optical analysis for example by using it as a colorimeter, photometer or spectrometer. This review explores the current state-of-the-art smartphone-based optical analysis systems in various areas of application. It is organized into three sections, each of which investigates one class of smartphone-based devices: (i) smartphone-based colorimeters (ii) smartphone-based photo- and spectrometers and (iii) smartphone-based fluorimeters.

A smartphone-based particle diffusometry platform for sub-attomolar detection of Vibrio cholerae in environmental water

Each year, 3.4 million people die from waterborne diseases worldwide. Development of a rapid and portable platform for detecting and monitoring waterborne pathogens would significantly aid in reducing the incidence and spread of infectious diseases. By combining optical methods and smartphone technology with molecular assays, the sensitivity required to detect exceedingly low concentrations of waterborne pathogens can readily be achieved. Here, we implement smartphone-based particle diffusometry (PD) detection of loop-mediated isothermal amplification (LAMP) targeting the waterborne pathogen Vibrio cholerae (V. cholerae). By measuring the diffusion of 400 nm streptavidin-coated fluorescent nanoparticles imaged at 68X magnification on a smartphone, we can detect as few as 6 V. cholerae cells per reaction (0.66 aM) in just 35 minutes. In a double-blinded study with 132 pond water samples, we establish a 91.8% sensitivity, 95.2% specificity, and 94.3% accuracy of the smartphone-based PD platform for detection of V. cholerae. Together, these results demonstrate the utility of this smartphone-based PD platform for rapid and sensitive detection of V. cholerae at the point of use.

Current progress on COVID-19 related to biosensing technologies: New opportunity for detection and monitoring of viruses

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COVID-19 infection poses a serious risk to human life by causing acute lung damage.

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Various techniques used to identify and quantify COVID-19 infection.

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Major challenges for containing the spread of COVID-19 is the ability to identify asymptomatic cases.

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Currently available diagnostic methods, biosensing technology developed during COVID-19 infection.

The technologies used for coronavirus testing consist of a pre-existing device developed to examine different pathologies, such as bacterial infections, or cancer biomarkers. However, for the 2019 pandemic, researchers knew that their technology could be modified to detect a low viral load at an early stage. Today, countries around the world are working to control the new coronavirus disease (n-SARS-CoV-2). From this perspective, laboratories, universities, and companies around the world have embarked on a race to develop and produce much-needed test kits. This review has been developed to provide an overview of current trends and strategies in n-SARS-CoV-2 diagnostics based on traditional and new emerging assessment technologies, to continuous innovation. It focuses on recent trends in biosensors to build a fast, reliable, more sensitive, accessible, user-friendly system and easily adaptable technology n-SARS-CoV-2 detection and monitoring. On the whole, we have addressed and identified research evidence supporting the use of biosensors on the premise that screening people for n-SARS-CoV-2 is the best way to contain its spread.

Smartphone technology facilitates point-of-care nucleic acid diagnosis: a beginner's guide

The reliable detection of nucleic acids at low concentrations in clinical samples like blood, urine and saliva, and in food can be achieved by nucleic acid amplification methods. Several portable and hand-held devices have been developed to translate these laboratory-based methods to point-of-care (POC) settings. POC diagnostic devices could potentially play an important role in environmental monitoring, health, and food safety. Use of a smartphone for nucleic acid testing has shown promising progress in endpoint as well as real-time analysis of various disease conditions. The emergence of smartphone-based POC devices together with paper-based sensors, microfluidic chips and digital droplet assays are used currently in many situations to provide quantitative detection of nucleic acid targets. State-of-the-art portable devices are commercially available and rapidly emerging smartphone-based POC devices that allow the performance of laboratory-quality colorimetric, fluorescent and electrochemical detection are described in this review. We present a comprehensive review of smartphone-based POC sensing applications, specifically on microbial diagnostics, assess their performance and propose recommendations for the future.

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 - [Formula: see text]/dL, sensitivity of 0.00049 a.u/[Formula: see text]/dL, coefficient of variation (CV) of 10.5%, and an estimated detection limit of [Formula: see text]/dL These analytical specifications are useful for predicting iron deficiency and overloads. The optimized reference method has a sensitivity of 0.00093 a.u/[Formula: see text]/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.

Free convective PCR: From principle study to commercial applications-A critical review

Polymerase chain reaction (PCR) is an extremely important tool for molecular diagnosis, as it can specifically amplify nucleic acid templates for sensitive detection. As another division of PCR, free convective PCR was invented in 2001, which can be performed in a capillary tube pseudo-isothermally within a significantly short time. Convective PCR thermal cycling is implemented by inducing thermal convection inside the capillary tube, which stratifies the reaction into spatially separate and stable melting, annealing, and extension zones created by the temperature gradient. Convective PCR is a promising tool that can be used for nucleic acid diagnosis as a point-of-care test (POCT) due to the significantly simplified heating strategy, reduced cost, and shortened detection time without sacrificing sensitivity and accuracy. Here, we review the history of free convective PCR from its invention to development and its commercial applications.

Smartphone-based clinical diagnostics: towards democratization of evidence-based health care

Recent advancements in bioanalytical techniques have led to the development of novel and robust diagnostic approaches that hold promise for providing optimal patient treatment, guiding prevention programs and widening the scope of personalized medicine. However, these advanced diagnostic techniques are still complex, expensive and limited to centralized healthcare facilities or research laboratories. This significantly hinders the use of evidence-based diagnostics for resource-limited settings and the primary care, thus creating a gap between healthcare providers and patients, leaving these populations without access to precision and quality medicine. Smartphone-based imaging and sensing platforms are emerging as promising alternatives for bridging this gap and decentralizing diagnostic tests offering practical features such as portability, cost-effectiveness and connectivity. Moreover, towards simplifying and automating bioanalytical techniques, biosensors and lab-on-a-chip technologies have become essential to interface and integrate these assays, bringing together the high precision and sensitivity of diagnostic techniques with the connectivity and computational power of smartphones. Here, we provide an overview of the emerging field of clinical smartphone diagnostics and its contributing technologies, as well as their wide range of areas of application, which span from haematology to digital pathology and rapid infectious disease diagnostics.

A smartphone-based on-site nucleic acid testing platform at point-of-care settings

We developed a smartphone-based on-site nucleic acid testing (NAT) platform that can image and analyze lateral flow nucleic acid assays at point-of-care settings. An inexpensive add-on was devised to run lateral flow assays while providing homogeneous ambient light for imaging. In addition, an Android app with a user-friendly interface was developed for the result analysis and management. Linear color calibration is implemented inside the app to minimize the colorimetric reaction difference between smartphones. A relationship function between nucleic acid concentration and colorimetric reaction was established and evaluated by leave-one-out cross validation. The predicted concentration and true concentration showed a good agreement with an R-squared value of 0.96. This smartphone-based NAT platform can be used to diagnose infectious diseases and monitor disease progression, and assess treatment efficacy, especially for resource-limited settings.

A fishhook probe-based rolling circle amplification (FP-RCA) assay for efficient isolation and detection of microRNA without total RNA extraction

MicroRNA (miRNA) analysis has vital significance as a potential biomarker in clinical diagnosis and cancer research. In this study, a simple and practical technique was proposed for the detection of microRNAs from cell lysates based on fishhook probe-mediated rolling circle amplification (RCA) and fluorescence imaging with a smartphone. Compared with reported methods related to miRNA detection, this method mainly focused on simplicity, low cost and portability. Fishhook probes were designed and immobilized on the surface of streptavidin-coated magnetic beads for effectively recognizing and capturing target miRNAs, thus achieving simple and selective separation from the sample matrix. Moreover, the captured miRNAs initiated and transferred RCA reaction into solution, thus making the heterogeneous separation and homogeneous amplification reactions compatible. Excess circular probes as well as other nucleic acids were removed by two-step magnetic separation, minimizing nonspecific amplification and background signal. Using magnetic separation, high specificity was obtained even for one base mismatch strand. Moreover, the detection of miR-21 in cell lysates was performed without total RNA extraction. The fishhook probe-based rolling circle amplification (FP-RCA) assay integrated isolation and detection of miRNAs into a compact process, which was simple and effective without the need for bulky and expensive equipment such as centrifuge, thermal cycler and fluorescent microscope except for a blue light source device and a smartphone camera. Our study may provide a low-cost and reliable platform for miRNA detection and related research.

Plasmonic molecular assays: Recent advances and applications for mobile health

Plasmonics-based biosensing assays have been extensively employed for biomedical applications. Significant advancements in use of plasmonic assays for the construction of point-of-care (POC) diagnostic methods have been made to provide effective and urgent health care of patients, especially in resourcelimited settings. This rapidly progressive research area, centered on the unique surface plasmon resonance (SPR) properties of metallic nanostructures with exceptional absorption and scattering abilities, has greatly facilitated the development of cost-effective, sensitive, and rapid strategies for disease diagnostics and improving patient healthcare in both developed and developing worlds. This review highlights the recent advances and applications of plasmonic technologies for highly sensitive protein and nucleic acid biomarker detection. In particular, we focus on the implementation and penetration of various plasmonic technologies in conventional molecular diagnostic assays, and discuss how such modification has resulted in simpler, faster, and more sensitive alternatives that are suited for point-of-use. Finally, integration of plasmonic molecular assays with various portable POC platforms for mobile health applications are highlighted.

Simple Approaches to Minimally-Instrumented, Microfluidic-Based Point-of-Care Nucleic Acid Amplification Tests

Designs and applications of microfluidics-based devices for molecular diagnostics (Nucleic Acid Amplification Tests, NAATs) in infectious disease testing are reviewed, with emphasis on minimally instrumented, point-of-care (POC) tests for resource-limited settings. Microfluidic cartridges ('chips') that combine solid-phase nucleic acid extraction; isothermal enzymatic nucleic acid amplification; pre-stored, paraffin-encapsulated lyophilized reagents; and real-time or endpoint optical detection are described. These chips can be used with a companion module for separating plasma from blood through a combined sedimentation-filtration effect. Three reporter types: Fluorescence, colorimetric dyes, and bioluminescence; and a new paradigm for end-point detection based on a diffusion-reaction column are compared. Multiplexing (parallel amplification and detection of multiple targets) is demonstrated. Low-cost detection and added functionality (data analysis, control, communication) can be realized using a cellphone platform with the chip. Some related and similar-purposed approaches by others are surveyed.

Ultrasensitive, rapid and inexpensive detection of DNA using paper based lateral flow assay

Sensitive, specific, rapid, inexpensive and easy-to-use nucleic acid tests for use at the point-of-need are critical for the emerging field of personalised medicine for which companion diagnostics are essential, as well as for application in low resource settings. Here we report on the development of a point-of-care nucleic acid lateral flow test for the direct detection of isothermally amplified DNA. The recombinase polymerase amplification method is modified slightly to use tailed primers, resulting in an amplicon with a duplex flanked by two single stranded DNA tails. This tailed amplicon facilitates detection via hybridisation to a surface immobilised oligonucleotide capture probe and a gold nanoparticle labelled reporter probe. A detection limit of 1 × 10^-11 M (190 amol), equivalent to 8.67 × 10⁵ copies of DNA was achieved, with the entire assay, both amplification and detection, being completed in less than 15 minutes at a constant temperature of 37 °C. The use of the tailed primers obviates the need for hapten labelling and consequent use of capture and reporter antibodies, whilst also avoiding the need for any post-amplification processing for the generation of single stranded DNA, thus presenting an assay that can facilely find application at the point of need.

The interface between forensic science and technology: how technology could cause a paradigm shift in the role of forensic institutes in the criminal justice system

In this paper, the importance of modern technology in forensic investigations is discussed. Recent technological developments are creating new possibilities to perform robust scientific measurements and studies outside the controlled laboratory environment. The benefits of real-time, on-site forensic investigations are manifold and such technology has the potential to strongly increase the speed and efficacy of the criminal justice system. However, such benefits are only realized when quality can be guaranteed at all times and findings can be used as forensic evidence in court. At the Netherlands Forensic Institute, innovation efforts are currently undertaken to develop integrated forensic platform solutions that allow for the forensic investigation of human biological traces, the chemical identification of illicit drugs and the study of large amounts of digital evidence. These platforms enable field investigations, yield robust and validated evidence and allow for forensic intelligence and targeted use of expert capacity at the forensic institutes. This technological revolution in forensic science could ultimately lead to a paradigm shift in which a new role of the forensic expert emerges as developer and custodian of integrated forensic platforms.

The Assessment of the Readiness of Molecular Biomarker-Based Mobile Health Technologies for Healthcare Applications

Mobile health technologies to detect physiological and simple-analyte biomarkers have been explored for the improvement and cost-reduction of healthcare services, some of which have been endorsed by the US FDA. Advancements in the investigations of non-invasive and minimally-invasive molecular biomarkers and biomarker candidates and the development of portable biomarker detection technologies have fuelled great interests in these new technologies for mhealth applications. But apart from the development of more portable biomarker detection technologies, key questions need to be answered and resolved regarding to the relevance, coverage, and performance of these technologies and the big data management issues arising from their wide spread applications. In this work, we analyzed the newly emerging portable biomarker detection technologies, the 664 non-invasive molecular biomarkers and the 592 potential minimally-invasive blood molecular biomarkers, focusing on their detection capability, affordability, relevance, and coverage. Our analysis suggests that a substantial percentage of these biomarkers together with the new technologies can be potentially used for a variety of disease conditions in mhealth applications. We further propose a new strategy for reducing the workload in the processing and analysis of the big data arising from widespread use of mhealth products, and discuss potential issues of implementing this strategy.

Smartphone-based fluorescence detector for mHealth

We describe here a compact smartphone-based fluorescence detector for mHealth. A key element to achieving high sensitivity using low sensitivity phone cameras is a capillary array, which increases sensitivity by 100×. The capillary array was combined with a white LED illumination system to enable wide spectra fluorescent excitation in the range of 450-740 nm. The detector utilizes an orthographic projection system to form parallel light projection images from the capillaries at a close distance via an object-space telecentric lens configuration that reduces the total lens-to-object distance while maintaining uniformity in measurement between capillaries. To further increase the limit of detection (LOD), a computational image processing approach was employed to decrease the level of noise. This enables an additional 5-10× decrease in LOD. This smartphone-based detector was used to measure serial dilutions of fluorescein with a LOD of 1 nM with image stacking and 10 nM without image stacking, similar to the LOD obtained with a commercial plate reader. Moreover, the capillary array required a sample volume of less than 10 μl, which is an order of magnitude less than the 100 μl required for the plate reader.As fluorescence detection is widely used in sensitive biomedical assays, the approach described here has the potential to increase mHealth clinical utility, especially for telemedicine and for resource-poor settings in global health applications.

Microfluidic devices for nucleic acid (NA) isolation, isothermal NA amplification, and real-time detection

Molecular (nucleic acid)-based diagnostics tests have many advantages over immunoassays, particularly with regard to sensitivity and specificity. Most on-site diagnostic tests, however, are immunoassay-based because conventional nucleic acid-based tests (NATs) require extensive sample processing, trained operators, and specialized equipment. To make NATs more convenient, especially for point-of-care diagnostics and on-site testing, a simple plastic microfluidic cassette ("chip") has been developed for nucleic acid-based testing of blood, other clinical specimens, food, water, and environmental samples. The chip combines nucleic acid isolation by solid-phase extraction; isothermal enzymatic amplification such as LAMP (Loop-mediated AMPlification), NASBA (Nucleic Acid Sequence Based Amplification), and RPA (Recombinase Polymerase Amplification); and real-time optical detection of DNA or RNA analytes. The microfluidic cassette incorporates an embedded nucleic acid binding membrane in the amplification reaction chamber. Target nucleic acids extracted from a lysate are captured on the membrane and amplified at a constant incubation temperature. The amplification product, labeled with a fluorophore reporter, is excited with a LED light source and monitored in situ in real time with a photodiode or a CCD detector (such as available in a smartphone). For blood analysis, a companion filtration device that separates plasma from whole blood to provide cell-free samples for virus and bacterial lysis and nucleic acid testing in the microfluidic chip has also been developed. For HIV virus detection in blood, the microfluidic NAT chip achieves a sensitivity and specificity that are nearly comparable to conventional benchtop protocols using spin columns and thermal cyclers.

Transformation of personal computers and mobile phones into genetic diagnostic systems

Molecular diagnostics based on the polymerase chain reaction (PCR) offer rapid and sensitive means for detecting infectious disease, but prohibitive costs have impeded their use in resource-limited settings where such diseases are endemic. In this work, we report an innovative method for transforming a desktop computer and a mobile camera phone--devices that have become readily accessible in developing countries--into a highly sensitive DNA detection system. This transformation was achieved by converting a desktop computer into a de facto thermal cycler with software that controls the temperature of the central processing unit (CPU), allowing for highly efficient PCR. Next, we reconfigured the mobile phone into a fluorescence imager by adding a low-cost filter, which enabled us to quantitatively measure the resulting PCR amplicons. Our system is highly sensitive, achieving quantitative detection of as little as 9.6 attograms of target DNA, and we show that its performance is comparable to advanced laboratory instruments at approximately 1/500th of the cost. Finally, in order to demonstrate clinical utility, we have used our platform for the successful detection of genomic DNA from the parasite that causes Chagas disease, Trypanosoma cruzi, directly in whole, unprocessed human blood at concentrations 4-fold below the clinical titer of the parasite.

Thousand-fold fluorescent signal amplification for mHealth diagnostics

The low sensitivity of Mobile Health (mHealth) optical detectors, such as those found on mobile phones, is a limiting factor for many mHealth clinical applications. To improve sensitivity, we have combined two approaches for optical signal amplification: (1) a computational approach based on an image stacking algorithm to decrease the image noise and enhance weak signals, and (2) an optical signal amplifier utilizing a capillary tube array. These approaches were used in a detection system which includes multi-wavelength LEDs capable of exciting many fluorophores in multiple wavelengths, a mobile phone or a webcam as a detector, and capillary tube array configured with 36 capillary tubes for signal enhancement. The capillary array enables a ~100× increase in signal sensitivity for fluorescein, reducing the limit of detection (LOD) for mobile phones and webcams from 1000 nM to 10nM. Computational image stacking enables another ~10× increase in signal sensitivity, further reducing the LOD for webcam from 10nM to 1 nM. To demonstrate the feasibility of the device for the detection of disease-related biomarkers, adenovirus DNA labeled with SYBR green or fluorescein was analyzed by both our capillary array and a commercial plate reader. The LOD for the capillary array was 5 ug/mL, and that of the plate reader was 1 ug/mL. Similar results were obtained using DNA stained with fluorescein. The combination of the two signal amplification approaches enables a ~1000× increase in LOD for the webcam platform. This brings it into the range of a conventional plate reader while using a smaller sample volume (10 ul) than the plate reader requires (100 ul). This suggests that such a device could be suitable for biosensing applications where up to 10 fold smaller sample sizes are needed. The simple optical configuration for mHealth described in this paper employing the combined capillary and image processing signal amplification is capable of measuring weak fluorescent signals without the need of dedicated laboratories. It has the potential to be used to increase sensitivity of other optically based mHealth technologies, and may increase mHealth's clinical utility, especially for telemedicine and for resource-poor settings and global health applications.

Orthographic projection capillary array fluorescent sensor for mHealth

To overcome the limited sensitivity of phone cameras for mobile health (mHealth) fluorescent detection, we have previously developed a capillary array which enables a ∼100 × increase in detection sensitivity. However, for an effective detection platform, the optical configuration must allow for uniform measurement sensitivity between channels when using such a capillary array sensor. This is a challenge due to the parallax inherent in imaging long parallel capillary tubes with typical lens configurations. To enable effective detection, we have developed an orthographic projection system in this work which forms parallel light projection images from the capillaries using an object-space telecentric lens configuration. This optical configuration results in a significantly higher degree of uniformity in measurement between channels, as well as a significantly reduced focal distance, which enables a more compact sensor. A plano-convex lens (f=150 mm) was shown to produce a uniform orthographic projection when properly combined with the phone camera's built in lens (f=4mm), enabling measurements of long capillaries (125 mm) to be made from a distance of 160 mm. The number of parallel measurements which can be made is determined by the size of the secondary lens. Based on these results, a more compact configuration with shorter 32 mm capillaries and a plano-convex lens with a shorter focal length (f=10mm) was constructed. This optical system was used to measure serial dilutions of fluorescein with a limit of detection (LOD) of 10nM, similar to the LOD of a commercial plate reader. However, many plate readers based on standard 96 well plate requires sample volumes of 100 μl for measurement, while the capillary array requires a sample volume of less than 10 μl. This optical configuration allows for a device to make use of the ∼100 × increase in fluorescent detection sensitivity produced by capillary amplification while maintaining a compact size and capability to analyze extremely small sample volumes. Such a device based on a phone or other optical mHealth technology will have the sensitivity of a conventional plate reader but have greater mHealth clinical utility, especially for telemedicine and for resource-poor settings and global health applications.

Capillary Array Waveguide Amplified Fluorescence Detector for mHealth

Mobile Health (mHealth) analytical technologies are potentially useful for carrying out modern medical diagnostics in resource-poor settings. Effective mHealth devices for underserved populations need to be simple, low cost, and portable. Although cell phone cameras have been used for biodetection, their sensitivity is a limiting factor because currently it is too low to be effective for many mHealth applications, which depend on detection of weak fluorescent signals. To improve the sensitivity of portable phones, a capillary tube array was developed to amplify fluorescence signals using their waveguide properties. An array configured with 36 capillary tubes was demonstrated to have a ~100X increase in sensitivity, lowering the limit of detection (LOD) of mobile phones from 1000 nM to 10 nM for fluorescein. To confirm that the amplification was due to waveguide behavior, we coated the external surfaces of the capillaries with silver. The silver coating interfered with the waveguide behavior and diminished the fluorescence signal, thereby proving that the waveguide behavior was the main mechanism for enhancing optical sensitivity. The optical configuration described here is novel in several ways. First, the use of capillaries waveguide properties to improve detection of weak florescence signal is new. Second we describe here a three dimensional illumination system, while conventional angular laser waveguide illumination is spot (or line), which is functionally one-dimensional illumination, can illuminate only a single capillary or a single column (when a line generator is used) of capillaries and thus inherently limits the multiplexing capability of detection. The planar illumination demonstrated in this work enables illumination of a two dimensional capillary array (e.g. x columns and y rows of capillaries). In addition, the waveguide light propagation via the capillary wall provides a third dimension for illumination along the axis of the capillaries. Such an array can potentially be used for sensitive analysis of multiple fluorescent detection assays simultaneously. The simple phone based capillary array approach presented in this paper is capable of amplifying weak fluorescent signals thereby improving the sensitivity of optical detectors based on mobile phones. This may allow sensitive biological assays to be measured with low sensitivity detectors and may make mHealth practical for many diagnostics applications, especially in resource-poor and global health settings.