Smartphone Readout Research Articles

Photonic hydrogel for continuous glucose monitoring using smartphone readout

Diabetes has become one of the leading deaths causes worldwide. Developing low-cost, rapid, and reusable sensors can provide a solution for continuous glucose monitoring to reduce the diabetic complications that could be fatal. Here, Phenylboronic acid (PBA)-based hydrogel sensors with embedded photonic nanostructures were developed for rapid and continuous glucose quantification within the physiological range. The photonic nanostructures were imprinted on the PBA-based hydrogel using simple and rapid process. Three different sensors: free-standing (FS), stand-alone (SA), and optical fiber (OF) were fabricated and tested in the glucose concentration range of 0–50 mM. A sensitivity of 6, 3, and 1.2 µW/mM was documented for FS, SA, and OF sensors, respectively. A rapid response time of 20 s and saturation time of 3 min were recorded along with a limit of detection of 1 mM. The sensing capabilities of these sensors were examined in both transmission and reflection configurations. Practicality of the sensors was tested using smartphone readout. The optical power was measured using a smartphone exploiting its photodiode and the power changes were correlated with glucose concentrations. These developed sensors may have applications in remote, continuous, and real-time glucose monitoring systems.

Polyoxometalate-cyclodextrin supramolecular entities for real-time in situ monitoring of dopamine released from neuroblastoma cells

Optimized and sensitive biomarker detection has recently been shown to have a critical impact on quality of diagnosis and medical care options. In this research study, polyoxometalate-γ-cyclodextrin metal-organic framework (POM-γCD MOF) was utilized as an electrocatalyst to fabricate highly selective sensors to detect in-situ released dopamine. The POM-γCD MOF produced multiple modes of signals for dopamine including electrochemical, colorimetric, and smartphone read-outs. Real-time quantitative monitoring of SH-SY5Y neuroblastoma cellular dopamine production was successfully demonstrated under various stimuli at different time intervals. The POM-CD MOF sensor and linear regression model were used to develop a smartphone read-out platform, which converts dopamine visual signals to digital signals within a few seconds. Ultimately, POM-γCD MOFs can play a significant role in the diagnosis and treatment of various diseases that involve dopamine as a significant biomarker.

Paper-based multiplex colorimetric vertical flow assay with smartphone readout for point-of-care detection of acute kidney injury biomarkers

Acute kidney injury (AKI) is a serious renal emergency that is often underdiagnosed and associated with high mortality rates. Early diagnosis of AKI is crucial to improve patient prognosis and reduce healthcare costs. In this study, a paper-based colloidal gold multiplex vertical flow assay was developed for rapid detection of three AKI biomarkers, namely, NGAL, CysC, and RBP4, in a single test kit. In this system, specific capture antibodies were pre-immobilized on the sensing membrane at four spatially isolated immunoreactive sites. Gold nanoparticles were conjugated with detection antibodies as the colorimetrical labels. The resultant images could be read out qualitatively by the naked eyes or quantitatively by a smartphone-based readout device. Three AKI biomarkers could be simultaneously detected in 10–15 min. The detection sensitivity and specificity for clinical serum samples collected from 25 patients with AKI and 25 healthy individuals were determined as 92% and 88%. This vertical flow assay platform is easy to use, rapid, and low cost. It is a promising diagnostic tool for multiplex detection of disease biomarkers at point of care.

A label-free colorimetric 3D paper-based device for ochratoxin A detection using G-quadruplex/hemin DNAzyme with a smartphone readout

The colorimetric sensor usually depends on enzyme-mediated signal amplification to achieve trace analysis of ochratoxin A (OTA) residues in food samples. However, the enzyme labeling and manual addition of reagents steps increased assay time and operation complexity, restricting their application in point-of-care testing (POCT). Herein, we report a label-free colorimetric device integrating a 3D paper-based analytical device and a smartphone as handheld readout for rapid and sensitive detection of OTA. Using vertical-flow design, the paper-based analytical device enables the specific recognition of target and self-assembly of G-quadruplex (G4)/hemin DNAzyme to be performed, then employs DNAzyme for transducing the OTA binding event signal into a colorimetric signal. The design of independent functional units, including biorecognition unit, self-assembly unit and colorimetric units, which can address crowding and disorder of biosensing interfaces and improve the recognition efficiency of aptamer (apta). In addition, we eliminated signal losses and nonuniform coloring by introducing carboxymethyl chitosan (CMCS) to obtain perfectly focused signals on colorimetric unit. On the basis of parameter optimization, the device exhibited a detection range of 0.1–500 ng/mL and a detection limit of 41.9 pg/mL for OTA. Importantly, good results were obtained in spiked real samples, indicating applicability and reliability of developed device.

Quantitative colorimetric sensing of heavy metal ions via analyte-promoted growth of Au nanoparticles with timer or smartphone readout.

This work describes two new colorimetric nanosensors for label-free, equipment-free quantitative detection of nanomolar copper (II) (Cu2+) and mercury (II) (Hg2+) ions. Both are based on the analyte-promoted growth of Au nanoparticles (AuNPs) from the reduction of chloroauric acid by 4-morpholineethanesulfonic acid. For the Cu2+ nanosensor, the analyte can accelerate such aredox system to rapidly form a red solution containing dispersed, uniform, spherical AuNPs that is related to these particles' surface plasmon resonance property. For the Hg2+ nanosensor, on the other hand, a blue mixture consisting of aggregated, ill-defined AuNPs with various sizes can be created, showing a significantly enhanced Tyndall effect (TE) signal (in comparison with that produced in the red solution of AuNPs). By using a timer and a smartphone to quantitatively measure the time of producing the red solution and the TE intensity (i.e., the average gray value of the corresponding image) of the blue mixture, respectively, the developed nanosensors are well demonstrated to achieve linear ranges of 6.4nM to 100μM and 6.1nM to 1.56μM for Cu2+ and Hg2+, respectively, with detection limits down to 3.5 and 0.1nM, respectively. The acceptable recovery results obtained from the analysis of the two analytes in the complex real water samples including drinking water, tap water, and pond water ranged from 90.43 to 111.56%.

Near Infrared-II Photothermal and Colorimetric Synergistic Sensing for Intelligent Onsite Dietary Myrosinase Profiling.

Myrosinase (Myr) is a type of critical β-thioglucosidase enzyme activator essential for sustaining many functional foods to perform their health-promoting functions. An accurate and reliable Myr test is meaningful for food quality and dietary nutrition assessments, whereas the currently reported methods do not guarantee specificity and have high reliance on instrumentation, which are not suitable for rapid and onsite Myr screening especially in complex systems from various sources. Herein, we present a unique NIR-II absorption-based photothermal-responsive colorimetric biosensor for anti-interference onsite Myr determination and realization of rapid visualized outputs with the aid of smartphone calculation. Typically, assisted by glucose oxidase (GOx), Myr specifically converts the sinigrin substrate into hydrogen peroxide (H2O2) that can oxidize 3,3',5,5'-tetramethylbenzidine (TMB) catalyzed by AuNPs to form a charge transfer complex (CTC) with NIR-II absorption and photothermal characters. Delightfully, such a proposed method is able to determine Myr within a wide range of 0 to 172.5 mU/mL with a detection limit down to 2.96 mU/mL. Moreover, simple, rapid, and real-time visual Myr identification in actual food-sourced samples could also be readily achieved by smartphone readout processing, with the promising advantages of anti-interference, high accuracy, and low cost as well as labor-saving and intelligence engagement, thus providing great feasibility for precise measurement in complex and dynamic dietary sample analysis. Overall, our proposed method presents a novel technology for onsite dietary Myr enzyme profiling, which is promising to be applied in the food industry for nutritional composition profiles, freshness evaluation, and quality assessment.

Red cabbage extract-mediated colorimetric sensor for swift, sensitive and economic detection of urease-positive bacteria by naked eye and Smartphone platform

The bacterial pathogens have caused various serious infectious diseases in the human body, and even some threats to human life by leading to deaths. Enterobacteriaceae species especially urease positive ones, Proteus mirabilis (P. mirabilis) and Klebsiella pneumoniae (K. pneumoniae), show resistance to antibiotics and cause respiratory and urinary tract infections. We have developed natural indicator-incorporated colorimetric urease tests with a naked eye and smartphone readout to rapidly, sensitively and economically detect P. mirabilis and K. pneumoniae. We utilized anthocyanin found as a predominant component in red cabbage (Brassica oleracea) extract as a natural pH indicator instead of toxic and synthetic indicators. As a mechanistic explanation for the detection of P. mirabilis and K. pneumoniae, urease enzymes secreted from the P. mirabilis and K. pneumoniae hydrolyze urea to produce ammonia (NH3), which increases the pH value of the reaction environment and leads to deprotonation from anthocyanins. The changes in the molecular structure and electronic structure of anthocyanins are responsible for revealing many different colors. We demonstrated how some reaction parameters including the concentration of the bacteria (colony-forming unit, CFU), the concentration of anthocyanin in the tests, initial color and pH values (pHs) of the tests influence their detection performance. We further developed a 3D-printed smartphone platform with smartphone based digital image processing software to improve the detection limit and shorten the detection time. We claim that natural indicator-incorporated rapid urease tests providing colorimetric readout evaluated by the human eye and smartphone imaging processing has great potential in practical use and they can be implemented in clinics.

Fluorescence immunoassay based on magnetic separation and ZnCdSe/ZnS quantum dots as a signal marker for intelligent detection of sesame allergen in foods

To detect sesame allergens, a novel fluorescent immunoassay incorporating a magnetic separation step has been developed via two measurement devices: a fluorescence spectrophotometer and a smartphone equipped with a color reader. Sesame allergen monoclonal antibody (Ab) was covalently bonded with quantum dots (QDs) to act as a signal probe. The capture probes were synthesized as sesame allergen (SA) modified carboxyl-functional magnetic polystyrene microspheres (MPMs). Analytical variables such as the amount of modified SA, the reaction volume of the QDs-Ab, the ionic strength, the pH, and the incubation time of the reaction were optimized. The analytical range and the limit of detection (LOD) of the spectrophotometer-based assay were 80–640 μg/L and 12.75 μg/L, respectively. The analytical range and the LOD with smartphone read-out were 80–640 μg/L and 10.15 μg/L, respectively. Furthermore, the developed assay using the fluorescence spectrophotometer and the smartphone read-out was successfully applied to field testing of SA in solution extracts of biscuits, bread, almond beverage, and energy bars with acceptable results. The recovery rates were in the range 89–108%. It was concluded that the new assay may be used for rapid sesame allergen testing in the laboratory and in the field.

Color-selective labyrinth-like quantum dot nanobeads enable point-of-care dual assay of Mycotoxins

Complex nanoparticles with hybrid forms of quantum dots and nano-scale templates are highly interesting due to various functionalities and broad applications in point-of-care testing (POCT). High sensitivity and throughput are significant for POCT in clinical applications and food safety, especially for determining multiple targets in complex matrices. Here, we developed the labyrinth-like quantum dot nanobeads (LQDBs) with controlled size, enhanced loading capacity and an intelligent mobile detection format. We reported a smartphone readout using color-selective LQDBs as fluorescent labels for POCT of dual targets in paper-test format. The labyrinth-like nanobeads assembled with QDs provided high colloidal stability, facile functionalization, and a rough surface for more binding sites to monoclonal antibodies enabled by a thin silica layer coating. Using LQDB, the POCT of dual targets was developed assisted with an in-house application on a smartphone. This assay detected aflatoxin B1 (AFB1) and zearalenone (ZEN) within 10 min using a competitive immunoassay. The LODs for urine and agricultural products were recorded as 0.002 and 0.02 ng/mL for AFB1 and ZEN, respectively. Reasonable specificity, repeatability, reproducibility, and validation results were recorded in real samples. This biosensing platform can be widely suitable in clinical healthcare and food safety applications.

Sensitive microRNA detection based on bimetallic label photothermal lateral flow locked nucleic acid biosensor with smartphone readout

Fast, convenient, and highly sensitive detection of microRNA (miRNA) is vital for the early diagnosis of diseases. Lateral flow biosensor (LFB) as microdevice has been used in rapid detection, however, the sensitivity is not satisfied for low-abundant miRNA detection, and short length of the miRNA requires high affinity detection probe. To address these issues, herein, we synthesized palladium-gold (Pd-Au) bimetallic nanoplates with high photothermal effect combined locked nucleic acid (LNA) detection probe to develop a photothermal lateral flow locked nucleic acid biosensor (P-LFLNAB) for miRNA detection. The P-LFLNAB enables sensitive and selective miRNA-21 detection with detection limit down to 0.094 pM using a smartphone with external thermal imager, which is 639.5 times lower than that of the conventional gold nanoparticles based colorimetric LFB and the most sensitive enzyme-free LFB for miRNA detection. Besides, the P-LFLNAB achieved single-base mismatch discrimination and can quantify signals in various cell lysates. This highly sensitive, selective and portable P-LFLNAB with smartphone readout has great potential in point-of-care test of miRNAs-related biomedical application.

Smart quick response code for multianalyte determination

The extensive use of smartphones with point-of-care (POC) applications has boosted the development of what is commonly known as Healthcare 4.0. The ability to track biomarker parameters has become a critical part of monitoring the progression of certain diseases, with a potential application in a large population group. In this line, this work presents a multianalyte quick response (QR) colorimetric code for real-time measurement of glucose and lactate samples using smartphones. The colorimetric QR code contains both QR static data and dynamic information from sample analyses. Two correction methods are applied in order to compensate for the variation in the surrounding conditions during biomarker tracking. Glucose and lactate recovery between 91 and 117% was found in assays including sweat and serum samples through smartphone readout.

Nanozymatic magnetic nanomixers for enzyme immobilization and multiplexed detection of metabolic disease biomarkers

Nanozymes with enzyme-mimicking catalytic activity and unique functions have stimulated increasing interest in the biosensing field. Herein, we report a magnetic nanozyme (MNE) with integrated superior peroxidase-like activity and efficient mixing ability. This nanozymatic magnetic nanomixer is synthesized by depositing a Fe2+-doped polydopamine coating on the surface of well-aligned magnetic nanoparticles to form a rigid chain-like nanostructure. Polydopamine coating of the nanozymatic MNE allows for efficient immobilization of natural enzymes such as glucose oxidase, cholesterol oxidase or urate oxidase to produce a series of enzymes-immobilized MNE (MNE@enzymes) with intrinsic multienzyme cascade properties. These MNE@enzymes show synchronously rotating capability in spinning magnetic fields, which leads to an 80∼100% improvement in their overall catalytic efficiencies. In the on-chip detection of small molecular metabolites (i.e., glucose, cholesterol, and uric acid), the rotating MNE@enzymes lead to detection sensitivities 2.1∼4.3 times higher than those of the static ones. Importantly, the consistent performance of the rotating MNE@enzymes offers the possibility of integrating the detection of glucose, free cholesterol and uric acid into a single multiplexing microchip assay with smartphone readout, affording an improved sensitivity, good selectivity and reliability. The designed enzymes-loaded MNEs holds great promise in developing rapid and ultrasensitive measurements of diverse targets of healthcare concerns using portable devices.

Smartphone-Integrated Photoacoustic Analytical Device for Point-of-Care Testing of Food Contaminant Azodicarbonamide.

Azodicarbonamide (ADA) is widely used as a flour additive due to its oxidizing and bleaching properties, but it reacts with wet flour during heat processing and is easily decomposed into semicarbazide with genotoxicity and carcinogenicity. In order to improve the efficiency of food safety supervision and expand the scope of food safety control, it is of great significance to develop a facile method for point-of-care testing (POCT) of ADA. Herein, a field-portable and universal smartphone-based photoacoustic (PA) integration device is constructed for quantitative POCT of ADA in flour. The recognition probe Prussian blue with favorable stability is loaded on a flexible substrate for fabricating a portable test strip. In the presence of target ADA, the PA signal changes driven by a modulated 808 nm laser beam can be conveniently collected through the recording application (Audio Lab) of the smartphone. By combining the economic test strip and portable PA device with smartphone readout, it not only greatly simplifies the operation steps but also dramatically reduces the size and cost of the instrument. There is a favorable linear relationship between the PA signal and ADA concentration in the range of 10-200 μmol L-1 (R2 = 0.9928), and a detection limit of 5 μmol L-1 obtained is much lower than the maximum allowable ADA level in the extract of flour (388 μmol L-1). The present miniature PA device with strong POCT ability holds enormous public health significance and economic value in the field of food safety, especially in resource-limited settings.

Integrated calibration and serum iron in situ analysis into an array microfluidic paper-based analytical device with smartphone readout

In this work, a colorimetric microfluidic paper-based analytical device (μPAD) combined with a smartphone readout was proposed for the determination of serum iron (Fe3+), which is linked to transferrin. Firstly, Fe3+ was selectively isolated and preconcentrated from serum by using anti-transferrin immunomagnetic beads (anti-Tf-MBs). Secondly, Fe3+ is reduced to Fe2+ by a hydroxylamine solution (pH 4.8) and then measured in the μPAD, which contains the colorimetric reagent ferrozine. Finally, the intensity of the purple color formed in the μPAD was measured by a smartphone. The approach exhibited an excellent linear correlation (r = 0.996) and good limit of detection (0.3 μg mL−1). Moreover, a certified reference material (human serum) was analyzed by this approach, showing an excellent accuracy (Er < 4%) and inter-device reproducibility (RSD = 1%, n = 3).Interestingly, the μPAD array-design allowed the simultaneous analysis of different samples, improving the sample throughput (up to 5 samples in 130 min, using 100 μL each), and the integration of calibration and analysis into the same device, simplifying the analysis without losing accuracy or sensitivity, and avoiding inter-device variability, which constituted an added value to this approach.These disposable μPADs meet several requirements of point-of-care testing (POCT) because it is cheap, portable, easy-to-use, sensitive, and specific. Therefore, it may be an interesting way for measuring patients’ serum iron levels in situ with reliability, especially, in developing countries, where the prevalence of iron deficiency and iron-deficiency anemia is higher and there are lower health resources than in developed countries.

A smartphone readout device for portable and sensitive estimation of Hg2+ via coumarin-modified paper

The development of cost-effective sensing system for Hg2+ quantitation is highly demanded for environmental monitoring. In this work, we reported an on-site, rapid and portable smartphone-based Hg2+ sensing system integrating coumarin-modified paper as a probe and smartphone readout device as a processing platform. For fluorescent sensing of Hg2+, the modified paper was fabricated by chemically grafting a coumarin-based probe N-((7-hydroxy-coumarin-3-yl)carbamothioyl)acetamide (HCCA) onto paper, and its physicochemical properties and sensing performance were characterized by elemental analysis, FTIR, XPS, SEM, and fluorescence spectral analysis. The modified paper displayed high selectivity and sensitivity for Hg2+, accompanied with a distinct fluorescence color change. For portable detection of the fluorescent sensors, a smartphone readout device was designed, consisting of a removable 3D-printed hardware device and an application. Remarkably, the smartphone readout device in cooperation with the modified paper is highly selective and sensitive to Hg2+ with the limit of detection (LOD) of 0.46 ppb, which avoids the requirement of sophisticated equipment and complex operation. The cost-effective sensing system based on smartphone shows a great potential for monitoring of Hg2+ in environmental water.

Nano-gold mediated aptasensor for colorimetric monitoring of acrylamide: Smartphone readout strategy for on-site food control

A simple aptasensor is embedded in the internal surface of a micropipette tip as the aptasensor substrate for the label-free monitoring of acrylamide. The aptasensor is based on the formation of the triple-helix molecular switch (THMS) structure of the DNA strands that induces the salt-enforced aggregation of gold nanoparticles (AuNPs). A smartphone imaging readout-based strategy is applied to quantify acrylamide. The developed aptasensor is novel for the naked-eye monitoring of the target through the color change of the solution inside the micropipette tip. The colorimetric aptasensor detects acrylamide in the concentration range of 0.05–200 nmol L−1 and at the trace level of 0.038 nmol L−1 with the comparable selectivity. The aptasensor can successfully quantify acrylamide in the chips, coffee, and bread samples with recoveries range from 92 to 102 %. The designed aptasensor paves an efficient device for the portable, on-site, facile, and real-time target sensing, superior for food safety control.

A high-resolution colorimetric immunoassay for tyramine detection based on enzyme-enabled growth of gold nanostar coupled with smartphone readout

In this work, a specific monoclonal antibody against tyramine was produced based on a new hapten design. Then, we developed a high-resolution multicolor colorimetric immunoassay for tyramine based on this antibody by integrating enzyme-induced multicolor generation with smartphone-assistant signal readout. The multicolor generation is due to the shift of the local surface plasmon resonance band of gold nanostructure controlled by alkaline phosphatase-induced the growth of gold nanostars. Quantitative detection of tyramine was achieved via analyzing the red/blue channel values of assay solution’s image taken by a smartphone with the support of a color recognizer application. The limit of detection of this immunoassay for tyramine detection in beef, pork and yoghurt was 19.7 mg/kg or L. The average recoveries were between 83 % and 103 %., and the results were validated by high performance liquid chromatography to be reliable. Overall, this developed immunoassay provides a promising platform for on-site detection of tyramine.

Dual modes of fluorescence sensing and smartphone readout for sensitive and visual detection of mercury ions in Porphyra

A convenient and intuitive method for detecting trace heavy metal ions is vital for food safety and quality monitoring. Herein, a dual-emission ratiometric fluorescence probe based on Zr-based metal-organic frameworks (Zr-MOF) and silver nanoclusters (AgNCs) was assembled to sensitive and visual detect mercury ions (Hg2+). The sensor exhibits good sensitivity from 0.010 to 0.5 μg mL−1 with a low detection limit of 1.8 μg L−1 (corresponding to 0.72 μg kg−1 by weight). The proposed method was finally applied to determine Hg2+ in the Porphyra matrix with satisfactory outcomes, the analytical recoveries were in the range of 94.74%–101.1%, indicating the practicability of the developed method. Meanwhile, the smartphone-based colorimetric method was established by capturing the changes in fluorescence colors of the probes exposed to different Hg2+ concentrations, with a quick sample-to-answer monitoring time of 10 min. The fluorescence probe, with these merits of simplicity, rapid response, and high sensitivity, offered a promising means for evaluating the safety of food polluted with Hg2+.

Molecularly imprinted polymer integrated into paper-based analytical device for smartphone-based detection: Application for sulfamethoxazole

In this work, we developed a paper-based analytical device (PAD) that utilizes molecularly imprinted polymer (MIP) as the biomimetic receptor and a very simple colorimetric assay combined with a smartphone readout. Sulfamethoxazole was used as a model analyte to evaluate the feasibility of the developed MIP-PAD. After the synthesis of MIP, its adsorption properties (isotherm, kinetic and thermodynamic) were scrutinized. Thereafter, The MIP- PAD was fabricated through the vacuum-assisted deposition of MIP suspension onto porous paper forming a 7 mm diameter of MIP layer. The MIP-PAD was characterized by Fourier-transform infrared spectroscopy and scanning electron microscopy. The sulfamethoxazole transforms into azo dye through a colorimetric reaction. The smartphone was utilized for the read-out of results. The LOD was 0.21 ppm. The proposed MIP-PAD showed high long-term stability. The determination of SMX was carried out in spiked tap and river water samples to evaluate the applicability of the proposed analytical strategy in real-world applications. The developed MIP-PAD would provide a new platform for real-time, selective, rapid, user-friendly, low-cost, portable, and straightforward colorimetric assays in environmental monitoring, public health, and food control.

Kirigami paper-based colorimetric immunosensor integrating smartphone readout for determination of humoral autoantibody immune response

Ultrasensitive, rapid, and low-cost paper-based immunodevice integrating a smartphone platform to detect ultra-low concentrations of tumour-specific anti-p53 autoantibodies (anti-p53aAbs) in human serum samples was developed. The immunodevice was fabricated based on the principles of kirigami (paper cutting and pasting art). It consisted of hydrophilic paper discs sandwiched between a superhydrophobic paper basement and polyethylene terephthalate-ethylene vinyl acetate (PET-EVA) laminate to delineate the sensing discs. The human p53 antigen (p53Ag) was covalently immobilized onto the pre-functionalized paper disc and used as the biorecognition element to capture anti-p53aAbs in human serum samples. The Fe3O4@SiO2-prNH2-Au@Pd0.30NPs-anti-IgG immunonanoprobes were used as the catalytic label for substrate (TMB/H2O2) oxidation, which generates blue colourimetric spots on the paper sensor. A smartphone installed on a custom-made imaging photo box equipped with colour analysis software was used as a reader to capture and quantitatively analyze the images. The immunodevice exhibited a linear increase in the colour pixel intensity with increasing concentrations of anti-p53aAbs from 10 pg.mL−1 to 25.0 ng.mL−1, with a sensitivity of 1.05 pixel.mL.pg−1 and a detection limit of 3.1 pg.mL−1. The fabricated proof-of-concept immunodevice could provide a simple, affordable, and minimally invasive method for cancer diagnosis at point-of-care.