Medically relevant assays with a simple smartphone and tablet based fluorescence detection system

On the Possibility of Fluorescent Capture Immunoassays on a Contact Lens

Blood samples and testing are routine in healthcare. Presently, there is a growing interest in using tear samples in place of blood. Tear samples can be obtained non-invasively and collection does not require the skills of a trained phlebotomist. Red blood cells and other cells are not present in tears, which avoids centrifugation. Importantly, basal tear samples contain most of the biomarkers present in blood. The difficulty is the small volume of basal tears, which is about 7 μL in each eye. Any contact with the eye results in additional reflex tears with a different chemical composition. The small tear samples are collected with capillary tubes and then sent out for amplified assays, such as enzyme-linked immunosorbent assay (ELISA) or polymerase chain reaction (PCR). The results are not available for several days or a week and, therefore, are less useful in an ophthalmology office. We propose the use of a contact lens that contains bound antibodies for fluorescence immunoassays. The lenses could be removed from the patient for point-of-care measurements at the bedside. To prove that this concept is possible, we performed a three-layer protein capture assay that mimics an immunoassay. For convenience, we used lysozyme (Lys), which spontaneously coats silicon hydrogel (SiHG) contact lenses (CL). Anti-lysozyme IgG was the second layer captured, with anti-lysozyme considered to be the target biomarker. The third layer was rhodamine or Alexa Fluor-labeled Ab against the IgG Fc region, considered to be the detection antibody. The multiple protein layers were stable and did not wash off the SiHG lenses. These results strongly suggest the contact lens can be used for capture immunoassays for a wide variety of biomarkers.

Salivary potassium measured by genetically encoded potassium ion indicators as a surrogate for plasma potassium levels in hemodialysis patients-a proof-of-concept study

BACKGROUND

Hyperkalemia is a common complication in cardiorenal patients treated with agents interfering with renal potassium (K+) excretion. It frequently leads to discontinuation of potentially life-saving medication, which has increased the importance of K+ monitoring. Non-invasive means to detect hyperkalemia are currently unavailable, but would be of potential use for therapy guidance. The aim of the present study was to assess the analytical performance of genetically encoded potassium-ion indicators (GEPIIs) in measuring salivary [K+] ([K+]Saliva) and to determine whether changes of [K+]Saliva depict those of [K+]Plasma.

METHODS

We conducted this proof-of-concept study: saliva samples from 20 healthy volunteers as well as plasma and saliva from 29 patients on hemodialysis (HD) before and after three consecutive HD treatments were collected. We compared [K+]Saliva as assessed by the gold standard ion-selective electrode (ISE) with GEPII measurements.

RESULTS

The Bland-Altmann analysis showed a strong agreement (bias 0.71; 95% limits of agreement from -2.79 to 4.40) between GEPII and ISE. Before treatment, patients on HD showed significantly higher [K+]Saliva compared with healthy controls [median 37.7 (30.85; 48.46) vs 23.8 (21.63; 25.23) mmol/L; P < .05]. [K+]Plasma in HD patients decreased significantly after dialysis. This was paralleled by a significant decrease in [K+]Saliva, and both parameters increased until the subsequent HD session. Despite similar kinetics, we found weak or no correlation between [K+]Plasma and [K+]Saliva.

CONCLUSION

GEPIIs have shown an excellent performance in determining [K+]Saliva. [K+]Plasma and [K+]Saliva exhibited similar kinetics. To determine whether saliva could be a suitable sample type to monitor [K+]Plasma, further testing in future studies are required.

Computational Portable Microscopes for Point-of-Care-Test and Tele-Diagnosis

In bio-medical mobile workstations, e.g., the prevention of epidemic viruses/bacteria, outdoor field medical treatment and bio-chemical pollution monitoring, the conventional bench-top microscopic imaging equipment is limited. The comprehensive multi-mode (bright/dark field imaging, fluorescence excitation imaging, polarized light imaging, and differential interference microscopy imaging, etc.) biomedical microscopy imaging systems are generally large in size and expensive. They also require professional operation, which means high labor-cost, money-cost and time-cost. These characteristics prevent them from being applied in bio-medical mobile workstations. The bio-medical mobile workstations need microscopy systems which are inexpensive and able to handle fast, timely and large-scale deployment. The development of lightweight, low-cost and portable microscopic imaging devices can meet these demands. Presently, for the increasing needs of point-of-care-test and tele-diagnosis, high-performance computational portable microscopes are widely developed. Bluetooth modules, WLAN modules and 3G/4G/5G modules generally feature very small sizes and low prices. And industrial imaging lens, microscopy objective lens, and CMOS/CCD photoelectric image sensors are also available in small sizes and at low prices. Here we review and discuss these typical computational, portable and low-cost microscopes by refined specifications and schematics, from the aspect of optics, electronic, algorithms principle and typical bio-medical applications.

Microsecond-resolved smartphone time-gated luminescence spectroscopy

Time-gated luminescence spectra are usually measured by laboratory instruments equipped with high-speed excitation sources and spectrometers, which are always bulky and expensive. To reduce the reliance on expensive laboratory instruments, we demonstrate the first, to the best of our knowledge, use of a smartphone for the detection of time-gated luminescence spectra. A mechanical chopper is used as the detection shutter and an optical switch is placed at the edge of the wheel to convert the chopping signal into a transistor-transistor logic (TTL) signal which is used to control the excitation source and achieve synchronization. The time-gated luminescence spectra at different delay times of Eu(TTA)₃ powder and the solutions of Eu-tetracycline complex are successfully detected with a temporal resolution of tens of microseconds by the proposed approach. We believe our approach offers a route toward portable instruments for the measurement of luminescence spectra and lifetimes.

Fluorescence Polarization-Based Bioassays: New Horizons

Fluorescence polarization holds considerable promise for bioanalytical systems because it allows the detection of selective interactions in real time and a choice of fluorophores, the detection of which the biosample matrix does not influence; thus, their choice simplifies and accelerates the preparation of samples. For decades, these possibilities were successfully applied in fluorescence polarization immunoassays based on differences in the polarization of fluorophore emissions excited by plane-polarized light, whether in a free state or as part of an immune complex. However, the results of recent studies demonstrate the efficacy of fluorescence polarization as a detected signal in many bioanalytical methods. This review summarizes and comparatively characterizes these developments. It considers the integration of fluorescence polarization with the use of alternative receptor molecules and various fluorophores; different schemes for the formation of detectable complexes and the amplification of the signals generated by them. New techniques for the detection of metal ions, nucleic acids, and enzymatic reactions based on fluorescence polarization are also considered.

Precision nutrition - review of methods for point-of-care assessment of nutritional status

Precision nutrition encompasses prevention and treatment strategies for optimizing health that consider individual variability in diet, lifestyle, environment and genes by accurately determining an individual's nutritional status. This is particularly important as malnutrition now affects a third of the global population, with most of those affected or their care providers having limited means of determining their nutritional status. Similarly, program implementers often have no way of determining the impact or success of their interventions, thus hindering their scale-up. Exciting new developments in the area of point-of-care diagnostics promise to provide improved access to nutritional status assessment, as a first step towards enabling precision nutrition and tailored interventions at both the individual and community levels. In this review, we focus on the current advances in developing portable diagnostics for assessment of nutritional status at point-of-care, along with the numerous design challenges in this process and potential solutions.

Ultra-portable, wireless smartphone spectrometer for rapid, non-destructive testing of fruit ripeness

We demonstrate a smartphone based spectrometer design that is standalone and supported on a wireless platform. The device is inherently low-cost and the power consumption is minimal making it portable to carry out a range of studies in the field. All essential components of the device like the light source, spectrometer, filters, microcontroller and wireless circuits have been assembled in a housing of dimensions 88 mm × 37 mm × 22 mm and the entire device weighs 48 g. The resolution of the spectrometer is 15 nm, delivering accurate and repeatable measurements. The device has a dedicated app interface on the smartphone to communicate, receive, plot and analyze spectral data. The performance of the smartphone spectrometer is comparable to existing bench-top spectrometers in terms of stability and wavelength resolution. Validations of the device were carried out by demonstrating non-destructive ripeness testing in fruit samples. Ultra-Violet (UV) fluorescence from Chlorophyll present in the skin was measured across various apple varieties during the ripening process and correlated with destructive firmness tests. A satisfactory agreement was observed between ripeness and fluorescence signals. This demonstration is a step towards possible consumer, bio-sensing and diagnostic applications that can be carried out in a rapid manner.

Wireless Data Acquisition of Transient Signals for Mobile Spectrometry Applications

Wireless data acquisition using smartphones or handhelds offers increased mobility, it provides reduced size and weight, it has low electrical power requirements, and (in some cases) it has an ability to access the internet. Thus, it is well suited for mobile spectrometry applications using miniaturized, field-portable spectrometers, or detectors for chemical analysis in the field (i.e., on-site). There are four main wireless communications standards that can be used for wireless data acquisition, namely ZigBee, Bluetooth, Wi-Fi, and UWB (ultra-wide band). These are briefly reviewed and are evaluated for applicability to data acquisition of transient signals (i.e., time-domain) in the field (i.e., on-site) from a miniaturized, field-portable photomultiplier tube detector and from a photodiode array detector installed in a miniaturized, field-portable fiber optic spectrometer. These are two of the most widely used detectors for optical measurements in the ultraviolet-visible range of the spectrum. A miniaturized, 3D-printed, battery-operated microplasma-on-a-chip was used for generation of transient optical emission signals. Elemental analysis from liquid microsamples, a microplasma, and a handheld or a smartphone will be used as examples. Development and potential applicability of wireless data acquisition of transient optical emission signals for taking part of the lab to the sample types of mobile, field-portable spectrometry applications will be discussed. The examples presented are drawn from past and ongoing work in the authors' laboratory. A handheld or a smartphone were used as the mobile computing devices of choice.

Ultrasensitive Profiling of Metabolites Using Tyramine-Functionalized Graphene Quantum Dots

Graphene quantum dots (GQDs) are emerging fluorescence reporters attractive for optical sensing, owing to their high photostability, highly tunable photoluminescence, molecular size, atomically thin structure, biocompatibility, and ease of functionalization. Herein, we present a fluorometric sensing platform based on tyramine-functionalized GQDs, which is able to detect a spectrum of metabolites with high sensitivity and specificity. Furthermore, multiparametric blood analysis (glucose, cholesterol, L-lactate, and xanthine) is demonstrated. This convenient metabolite profiling technique could be instrumental for diagnosis, study, and management of metabolic disorders and associated diseases, such as diabetes, obesity, lactic acidosis, gout, and hypertension.

Flexible opto-electronics enabled microfluidics systems with cloud connectivity for point-of-care micronutrient analysis

In developing countries, the deployment of medical diagnostic technologies remains a challenge because of infrastructural limitations (e.g. refrigeration, electricity), and paucity of health professionals, distribution centers and transportation systems. Here we demonstrate the technical development and clinical testing of a novel electronics enabled microfluidic paper-based analytical device (EE-μPAD) for quantitative measurement of micronutrient concentrations in decentralized, resource-limited settings. The system performs immune-detection using paper-based microfluidics, instrumented with flexible electronics and optoelectronic sensors in a mechanically robust, ultrathin format comparable in size to a credit card. Autonomous self-calibration, plasma separation, flow monitoring, timing and data storage enable multiple devices to be run simultaneously. Measurements are wirelessly transferred to a mobile phone application that geo-tags the data and transmits it to a remote server for real time tracking of micronutrient deficiencies. Clinical tests of micronutrient levels from whole blood samples (n=95) show comparable sensitivity and specificity to ELISA-based tests. These results demonstrate instantaneous acquisition and global aggregation of diagnostics data using a fully integrated point of care system that will enable rapid and distributed surveillance of disease prevalence and geographical progression.

Design, Synthesis, and Characterization of Small-Molecule Reagents That Cooperatively Provide Dual Readouts for Triaging and, When Necessary, Quantifying Point-of-Need Enzyme Assays

A newly designed small molecule reagent provides both qualitative and quantitative readouts in assays that detect enzyme biomarkers. The qualitative readout enables rapid triaging of samples so that only samples that contain relevant concentrations of the target analyte must be quantified. The reagent is accessible in essentially three steps and 34% overall yield, is stable as a solid when heated to 44 °C for >1 month, and does not produce background signal when used in an assay. This paper describes the design and synthesis of the reagent, characterizes its response properties, and establishes the scope of its reactivity.