Real time monitoring of glucose in whole blood by smartphone

Paper-based sensors: affordable, versatile, and emerging analyte detection platforms

Paper-based sensors, often referred to as paper-based analytical devices (PADs), stand as a transformative technology in the field of analytical chemistry. They offer an affordable, versatile, and accessible solution for diverse analyte detection. These sensors harness the unique properties of paper substrates to provide a cost-effective and adaptable platform for rapid analyte detection, spanning chemical species, biomolecules, and pathogens. This review highlights the key attributes that make paper-based sensors an attractive choice for analyte detection. PADs demonstrate their versatility by accommodating a wide range of analytes, from ions and gases to proteins, nucleic acids, and more, with customizable designs for specific applications. Their user-friendly operation and minimal infrastructure requirements suit point-of-care diagnostics, environmental monitoring, food safety, and more. This review also explores various fabrication methods such as inkjet printing, wax printing, screen printing, dip coating, and photolithography. Incorporating nanomaterials and biorecognition elements promises even more sophisticated and sensitive applications.

Photothermal biosensing integrated with microfluidic paper-based analytical device for sensitive quantification of sarcosine

This article presents the development of a photothermal biosensing integrated with microfluidic paper-based analytical device (PT-μPAD) as a quantitative biosensor method for monitoring sarcosine in human control urine, plasma, and serum samples. The device utilizes gold nanoparticles (AuNPs) as both a peroxidase-like nanozyme and a photothermal substrate to enable sarcosine detection. In our PT-μPAD, hydrogen peroxide (H2O2) is generated through the oxidation of sarcosine by a sarcosine oxidase (SOx) enzyme. Subsequently, the H2O2 flows through the paper microchannels to the detection zone, where it etches the pre-deposited AuNPs, inducing a temperature change upon exposure by a 532 nm laser. The temperature variation is then measured using a portable and inexpensive infrared thermometer. Under optimized conditions, we obtained a linear range between 10.0 and 40.0 nmol L-1 (R2 = 0.9954) and a detection limit (LOD) of 32.0 pmol L-1. These values fall within the clinical range for sarcosine monitoring in prostate cancer diagnostics in humans. Moreover, our approach exhibits high selectivity without interfering effects. Recovery studies in various human control samples demonstrated a range of 99.05-102.11 % with the highest RSD of 2.25 %. The PT-μPAD was further validated for sarcosine determination in human control urine and compared with a commercial ELISA assay, revealing no significant difference between these two methods at a 95 % confidence level. Overall, our proposed sarcosine biosensor is well-suited for prostate cancer monitoring, given its affordability, sensitivity, and user-friendliness, even for unskilled individuals. Moreover, this strategy has promising prospects for broader applications, potentially detecting various biomarkers as a point-of-care (POC) diagnostic tool.

Using a cotton thread-based colorimetric sensor modified by carboxymethylcellulose and cuprizone with smartphone detection for quantification of copper

In the present work, we report the development of a novel cotton thread-based colorimetric sensor modified by carboxymethylcellulose (CMC) and cuprizone (CPZ) with smartphone detection and its application for the quantitative determination of cupric ions in water and cachaça. The cotton thread/smartphone detection-based colorimetric method is an easily affordable, low-cost technique which allows one to perform real-time and on-field determination analyses, especially with limited financial resources. The method involves the complexation of Cu(II) with CPZ, which causes a change in the coloration of the cotton thread from a shade of white to blue in the detection zone of the colorimetric sensor. The immobilization of CPZ on CMC in the cotton thread leads to the pre-concentration of Cu(II) via a complexation mechanism with colorimetric reaction. The application of the colorimetric sensor allows the quantification of copper in the range from 1 to 12 mg L-1, with a low limit of detection of 0.21 mg L-1. In addition, the recovery assays conducted in samples of water and cachaça resulted in recovery percentages ranging from 84.9% to 107%, which is indicative of a precise method. To validate the precision of the proposed colorimetric method, the values obtained from the quantification analysis were compared with those of the flame atomic absorption spectrometry and a good agreement at the 95% confidence level was obtained.

4D-printed needle panel meters coupled with enzymatic derivatization for reading urea and glucose concentrations in biological samples

On-site analytical techniques continue being developed with advances in modern technology. To demonstrate the applicability of four-dimensional printing (4DP) technologies in the direct fabrication of stimuli-responsive analytical devices for on-site determination of urea and glucose, we used digital light processing three-dimensional printing (3DP) and 2-carboxyethyl acrylate (CEA)-incorporated photocurable resins to fabricate all-in-one needle panel meters. When adding a sample having a value of pH above the pKa of CEA (ca. 4.6-5.0) into the fabricated needle panel meter, the [H+]-responsive layer of the needle, printed using the CEA-incorporated photocurable resins, swelled as a result of electrostatic repulsion among the dissociated carboxyl groups of the copolymer, leading to [H+]-dependent bending of the needle. When coupled with a derivatization reaction (urease-mediated hydrolysis of urea to decrease [H+]; glucose oxidase-mediated oxidization of glucose to increase [H+]), the bending of the needle allowed reliable quantification of urea or glucose when referencing pre-calibrated concentration scales. After method optimization, the method's detection limits for urea and glucose were 4.9 and 7.0 μM, respectively, within a working concentration range from 0.1 to 10 mM. We verified the reliability of this analytical method by determining the concentrations of urea and glucose in samples of human urine, fetal bovine serum, and rat plasma with spike analyses and comparing the results with those obtained using commercial assay kits. Our results confirm that 4DP technologies can allow the direct fabrication of stimuli-responsive devices for quantitative chemical analysis, and that they can advance the development and applicability of 3DP-enabling analytical methods.

Paper-based optical sensors paired with smartphones for biomedical analysis

The traditional analytical methods used for biomedical analysis are expensive and not easy to handle and require sophisticated instruments, thus their application is limited in resource-limited settings. Due to their portability, low cost, and ability to be applied to different analytical techniques, paper-based analytical devices are becoming valuable tools for biomedical analysis. The integration of smartphones into analytical devices has provided the ability to build portable, cost-effective, straightforward analytical devices for biomedical analysis and mobile health. The key aim of this review is to emphasize the recent applications of PADs combined with a smartphone for the optical analysis of biomedical species. We started this review by highlighting the type of papers and their modifications with different materials to prepare the PADs. After that, this review presents various detection methods including colorimetry, fluorescence, and luminescence where the smartphone is used for read-out. In the end, we provided the recent applications of the analysis of different biomedical compounds such as cancer and cardiovascular biomarkers, metal ions, glucose, viruses, etc. We believe that the present review will attract a wide scientific community in the areas of analytical chemistry, sensors, and clinical testing.

Nanozyme-based colorimetric biosensor with a systemic quantification algorithm for noninvasive glucose monitoring

Diabetes mellitus accompanies an abnormally high glucose level in the bloodstream. Early diagnosis and proper glycemic management of blood glucose are essential to prevent further progression and complications. Biosensor-based colorimetric detection has progressed and shown potential in portable and inexpensive daily assessment of glucose levels because of its simplicity, low-cost, and convenient operation without sophisticated instrumentation. Colorimetric glucose biosensors commonly use natural enzymes that recognize glucose and chromophores that detect enzymatic reaction products. However, many natural enzymes have inherent defects, limiting their extensive application. Recently, nanozyme-based colorimetric detection has drawn attention due to its merits including high sensitivity, stability under strict reaction conditions, flexible structural design with low-cost materials, and adjustable catalytic activities. This review discusses various nanozyme materials, colorimetric analytic methods and mechanisms, recent machine learning based analytic methods, quantification systems, applications and future directions for monitoring and managing diabetes.

Fluorescent sensor based on pyrroloquinoline quinone (PQQ)-glucose dehydrogenase for glucose detection with smartphone-adapted signal analysis

A new nano-structured platform for fluorescent analysis using PQQ-dependent glucose dehydrogenase (PQQ-GDH) was developed, particularly using a smartphone for transduction and quantification of optical signals. The PQQ-GDH enzyme was immobilized on SiO₂ nanoparticles deposited on glass microfiber filter paper, providing a high load of the biocatalytic enzyme. The platform was tested and optimized for glucose determination using a wild type of the PQQ-GDH enzyme. The analysis was based on the fluorescence generated by the reduced form of phenazine methosulfate produced stoichiometrically to the glucose concentration. The fluorescent signals were generated at separate analytical spots on the paper support under wavelength (365 nm) UV excitation. The images of the analytical spots, dependent on the glucose concentration, were obtained using a photo camera of a standard smartphone. Then, the images were processed and quantified using software installed in a smartphone. The developed biocatalytic platform is the first step to assembling a large variety of biosensors using the same platform functionalized with artificial allosteric chimeric PQQ-dependent glucose dehydrogenase activated with different analytes. The future combination of the artificial enzymes, the presently developed analytical platform, and signal processing with a smartphone will lead to novel point-of-care and end-user biosensors applicable to virtually all possible analytes.

Paper-Based Enzymatic Electrochemical Sensors for Glucose Determination

The general objective of Analytical Chemistry, nowadays, is to obtain best-quality information in the shortest time to contribute to the resolution of real problems. In this regard, electrochemical biosensors are interesting alternatives to conventional methods thanks to their great characteristics, both those intrinsically analytical (precision, sensitivity, selectivity, etc.) and those more related to productivity (simplicity, low costs, and fast response, among others). For many years, the scientific community has made continuous progress in improving glucose biosensors, being this analyte the most important in the biosensor market, due to the large amount of people who suffer from diabetes mellitus. The sensitivity of the electrochemical techniques combined with the selectivity of the enzymatic methodologies have positioned electrochemical enzymatic sensors as the first option. This review, focusing on the electrochemical determination of glucose using paper-based analytical devices, shows recent approaches in the use of paper as a substrate for low-cost biosensing. General considerations on the principles of enzymatic detection and the design of paper-based analytical devices are given. Finally, the use of paper in enzymatic electrochemical biosensors for glucose detection, including analytical characteristics of the methodologies reported in relevant articles over the last years, is also covered.

Advancing pharmacy and healthcare with virtual digital technologies

Digitalisation of the healthcare sector promises to revolutionise patient healthcare globally. From the different technologies, virtual tools including artificial intelligence, blockchain, virtual, and augmented reality, to name but a few, are providing significant benefits to patients and the pharmaceutical sector alike, ranging from improving access to clinicians and medicines, as well as improving real-time diagnoses and treatments. Indeed, it is envisioned that such technologies will communicate together in real-time, as well as with their physical counterparts, to create a large-scale, cyber healthcare system. Despite the significant benefits that virtual-based digital health technologies can bring to patient care, a number of challenges still remain, ranging from data security to acceptance within the healthcare sector. This review provides a timely account of the benefits and challenges of virtual health interventions, as well an outlook on how such technologies can be transitioned from research-focused towards real-world healthcare and pharmaceutical applications to transform treatment pathways for patients worldwide.

Instant messaging client gives the opportunity to recognize gut microbiota and dysbiosis-related disease: An investigation study on WeChat APP

Objectives

Gut microbiota and dysbiosis are closely related to the occurrence and development of various diseases. It is necessary to popularize gut microbiota-related knowledge to the public. And the instant messaging client on smartphones supplies a perfect tool to achieve this goal. Hence, we will describe the current status of gut microbiota education spread by WeChat official accounts.

Methods

The keywords of “gut microbiota,” “fecal microbiota transplantation (FMT),” and “probiotics” were searched in the articles published from January 2015 to August 2020 on the WeChat official accounts. And the data were analyzed based on the 10 common gut dysbiosis-related diseases.

Results

A total of 3061 WeChat official accounts have published 11,239 articles on gut microbiota dysbiosis-related diseases, with a rising trend in the total article numbers and the total pageviews. The keywords of “gut microbiota” dominate 50.61%, and the articles on inflammatory bowel disease had the largest proportion. Additionally, articles on the keyword “gut microbiota” also included cancer and obesity, articles on the keyword “FMT” mainly consist of Clostridium difficile infection and psychological disease, and the keyword “probiotics” was mainly related to obesity and irritable bowel syndrome disease. The top three total pageviews were on inflammatory bowel disease, obesity, and cancer.

Conclusion

This study indicates the current research hotspots and public concerns on the gut microbiota, and WeChat as an instant messaging client plays an important role in promoting the scientific popularization of gut microbiota.

Cotton thread-based multi-channel photothermal biosensor for simultaneous detection of multiple microRNAs

The abnormal expression of microRNAs (miRNAs) is associated with various diseases. Developing simple and portable methods for sensitive, rapid and simultaneous detection of multiple miRNAs is critical to achieve accurate and timely diagnosis. Herein, a cotton thread-based multi-channel photothermal biosensor was proposed for simultaneous detection of three breast cancer-related miRNAs including miRNA-10b, miRNA-27a and miRNA-let-7a. Three cotton thread-based channels with one input were designed and the capture probes for detecting different miRNAs were immobilized on the test zones of the corresponding channels. Cu_2-xS nanostrings prepared on the basis of hybridization chain reaction (HCR) were taken as the photothermal agents for signal transduction and amplification. The formation of a sandwich structure among the capture probe, target miRNA, and Cu_2-xS nanostrings led to the accumulation of the Cu_2-xS nanostrings on the test zones and transformed the concentration of miRNA into temperature signal under 808 nm laser irradiation. The temperature changes were quantified by a portable thermal camera and directly reflected the concentration of miRNAs. Under the optimal conditions, the developed multi-channel photothermal biosensor showed excellent specificity and sensitivity with the detection limits of 37 pM, 38 pM and 38 pM for miRNA-10b, miRNA-27a and miRNA-let-7a, respectively. Furthermore, a simultaneous detection of the three miRNAs in cell lysates were achieved and the results were in accordance with that obtained by the quantitative reverse transcription polymerase chain reaction (qRT-PCR), indicating its excellent capacity for practical applications. The developed biosensor provided an important tool for analysis of multiple targets and showed great potential in clinical diagnosis.

Smartphone-based colorimetric detection systems for glucose monitoring in the diagnosis and management of diabetes

Diabetes is a group of metabolic conditions resulting in high blood sugar levels over prolonged periods that affects hundreds of millions of patients worldwide. Measuring glucose concentration enables patient-specific insulin therapy, and is essential to reduce the severity of the disease, potential complications, and related mortalities. Recent advances and developments in smartphone-based colorimetric glucose detection systems are discussed in this review. The importance of glucose monitoring, data collection, transfer, and analysis, via non-invasive/invasive methods is highlighted. The review also presents various approaches using 3D-printed materials, screen-printed electrodes, polymer templates, designs allowing multiple glucose analysis, bioanalytes and/or nanostructures for glucose detection. The positive effects of advances in improving the performance of smartphone-based platforms are introduced along with future directions and trends in the application of emerging technologies in smartphone-based diagnostics.

Optical glucose biosensor built-in disposable strips and wearable electronic devices

On-demand screening, real-time monitoring and rapid diagnosis of ubiquitous diseases, such as diabetes, at early stages are indispensable in personalised treatment. Emerging impacts of nano/microscale materials on optical and portable biosensor strips and devices have become increasingly important in the remarkable development of sensitive visualisation (i.e. visible inspection by the human eye) assays, low-cost analyses and personalised home testing of patients with diabetes. With the increasing public attention regarding the self-monitoring of diabetes, the development of visual readout, easy-to-use and wearable biosensors has gained considerable interest. Our comprehensive review bridges the practical assessment gap between optical bio-visualisation assays, disposable test strips, sensor array designs and full integration into flexible skin-based or contact lens devices with the on-site wireless signal transmission of glucose detection in physiological fluids. To date, the fully modulated integration of nano/microscale optical biosensors into wearable electronic devices, such as smartphones, is critical to prolong periods of indoor and outdoor clinical diagnostics. Focus should be given to the improvements of invasive, wireless and portable sensing technologies to improve the applicability and reliability of screen display, continuous monitoring, dynamic data visualisation, online acquisition and self and in-home healthcare management of patients with diabetes.

Digital image colorimetry detection of carbaryl in food samples based on liquid phase microextraction coupled with a microfluidic thread-based analytical device

This research used a digital image colorimetry (DIC) method to detect carbaryl in food samples using effervescence-assisted liquid phase microextraction based on solidification of switchable hydrophilicity solvent combined with a microfluidic thread-based analytical device (EA-LPME-SSHS-μTAD). 1-naphthol, the hydrolysate of carbaryl, was extracted into octanoic acid by the adjustment of pH values of the sample solution and separated through solidification in an ice bath. Then 1-naphthol contained in the extracted solution was coupled with 4-methoxybenzenediazonlum tetrafluoroborate (MBDF) fixed on the μTAD to produce tangerine compounds. The inherent colour variation was captured by a smartphone and processed to calculate the intensity (I). Under the optimal conditions, the limit of quantification was within 0.020-0.027 mg kg^-1. The recovery was varied in the range from 92.3% to 105.9% with a relative standard deviation (RSD) below 5%. The developed method provides an alternative strategy to extract and detect pesticides for food samples.

Quantitative hematocrit measurement of whole blood in a point-of-care lateral flow device using a smartphone flow tracking app

We present a rapid and quantitative point-of-care (PoC) system based on a smartphone application that is capable of accurately tracking the flow of red blood cells (RBCs) through a no-reaction lateral flow assay (nrLFA) device. Utilizing only the camera feed from the smartphone and built-in image processing, the nrLFA is identified and RBC fluid flow distances and rates are recorded in parallel with the test without the need of any custom hardware or enclosure. We demonstrated the application by first measuring and then calculating hematocrit (Hct) values of whole blood samples with nominal content of 28%, 35%, 40%, and 45% Hct on the nrLFA platform. The PoC system was able to accurately measure (to within 1% Hct of nominal values) whole blood Hct in ~10-20 s after sample dispensing.

Modulating the mixed potential for developing biosensors: Direct potentiometric determination of glucose in whole, undiluted blood

The growing demand for tools to generate chemical information in decentralized settings is creating a vast range of opportunities for potentiometric sensors, since their combination of robustness, simplicity of operation and cost can hardly be rivalled by any other technique. In previous works, we have shown that the mixed potential of a Pt electrode can be controlled with analytical purposes using a coating of Nafion, thus providing a way to develop a potentiometric biosensor for glucose. Unfortunately, the linear range of this device did not match the relevant clinical range for glucose in blood. This work presents a novel strategy to control the mixed potential that allows the development of a potentiometric biosensor for the direct detection of glucose in whole, undiluted blood without any sample pretreatment. By changing the ionomer, the analytical response can be tuned, shifting the linear range while keeping the sensitivity. Aquivion, a polyelectrolyte from the same family as Nafion, is used to stabilize the mixed potential of a platinized paper-based electrode, to entrap the enzyme and to reduce the interference from negatively charged species. Factors affecting the generation of the signal and the principle of detection are discussed. Optimization of the biosensor composition was achieved with particular focus on the characterization of the linear range and sensitivity. The accurate measurement of blood sugar levels in a single drop of whole blood with excellent recovery is presented.

Bioactive microfluidic paper device for pesticide determination in waters

This work presents a new optical microfluidic paper biosensor for the detection of organophosphate pesticides and carbamate pesticides. The assay strip is composed of a paper support (1 × 17.6 mm) onto which acetylcholine esterase (AChE) and acetylcholine chloride (AChCl) are deposited, in such a way that there is a small hole between them that ensures that they only come into contact in the reaction zone when they are carried by a solution of the sample by lateral flow to the reaction zone containing bromocresol purple (BCP) as the pH indicator, immobilized by sol-gel. The sensor operates at room temperature and the rate of the inhibited reaction serves as an analytical signal, which is measured using a camera by quantifying the appropriate colour coordinate. Calibration curves were obtained for chlorpyrifos and carbaryl, with a useful concentration range from 0.24 to 20 μg L^-1 for carbaryl and from 2.00 to 45 μg L^-1 for chlorpyrifos. The detection limits were 0.24 and 2.00 μg L^-1, respectively, and with reproducibility around 4.2-5.5%. The method was applied to the determination of pesticides in different water samples, with no sample preparation.

Electro-kinetically driven route for highly sensitive blood pathology on a paper-based device

Enhancing the sensitivity of colorimetric detection in paper-devices is a quintessential step in achieving frugal diagnosis. Here, we demonstrate an effective way of improving the detection sensitivity of paper-based devices, as mediated by electro-kinetic mechanisms. By directly employing blood plasma, we investigate the electro-kinetic clustering of glucose, a neutral molecule in paper devices. Under the influence of uniform electric field, dispersed glucose gets accumulated in the paper strips. Due to the combination of EOF and electrophoretic migration, we achieve twofold increase in the colour intensity for both normal and diabetic samples. This approach is robust and possesses better sensitivity than conventional colorimetric assays and can be easily extended to other body fluid based diagnosis. These results may turn out to be of profound importance in improving the quality of pathological diagnosis in low-cost paper-based point-of-care devices deployed in resource-limited settings.