Wearable Point of Care Devices for eHealth

Dear Colleagues,

The development of eHealth diagnostic devices (eDiagnostics) for remote testing represent the first block toward a eHealth system, i.e. the use of information communication technologies (ICT) in support of health, that the World Health Organization has set as a top priority in 2005. Differently from tradition Point of Care (POC) instrumentations, eDiagnostics should be easy-to-use with minimal user involvement, be network-connected to
allow remote monitoring, be able to analyze untreated biological samples, and have low-to-moderate cost to be affordable for general population. So far, four main POC technologies have been identified as potential candidates for new eDiagnostics: wearables, organ-interfaced electronics, paper diagnostics, microcell-based sensing.

This Special Issue focuses on wearable devices that analyze fluids and that can be obtained minimally invasively at home by the patients themselves, like blood, urine, interstitial fluids, saliva, tears, sweat, and breath. Devices exploit various transduction methods, i.e. amperometric or potentiometric, colorimetric or fluorescent, optical or impedance spectrometry, and may assume the form of subcutaneous needles to access interstitial fluids, printed skin-like patches for the collection and analysis of sweat, printed smart contact lenses, tiny implants for blood screening and mouthguards or bands for the testing of saliva. The list of analytes includes metabolites (glucose, lactate, and creatine), pH, ions (K⁺, Na⁺, Ca²⁺, Cl⁻, and NH₄⁺), heavy metal ions (zinc, cadmium, lead, copper, mercury), proteins, and other biomarkers.

Despite the significant advances in wearable biosensors, there are still reliability, stability, reproducibility, and biocompatibility issues that should be addressed. For example, changes in pH or temperature of sweat may influence the results of analysis (due to the influence of these factors on several enzymatic reactions); therefore, advanced calibration methods may be needed to provide accurate results. Moreover, the concentration of several biomarkers in sweat, saliva, tears, and breath might be correlated to pathological conditions and diseases like cancer, HIV, intestinal infections, cystic fibrosis, and schizophrenia, etc., but normal and pathological levels have not been established yet. It is worth mentioning that out of thousands of devices that have been developed in academic laboratories for POC testing, a very small percentage of them have been used to detect analytes in untreated biological fluids using an analytical procedure that is suitable for home applications. Furthermore, there is a gap between proof-of-concept testing in a laboratory and a full-scale clinical trial that the developers should bridge by performing initial field trials of the devices.

This issue, hence, aims at collecting original research and reviews that can highlight some of the following topics:

• Wearable and wireless systems able to collect and analyze saliva, sweat, tears, breath or/and subcutaneous microneedles/implants for the testing of blood or interstitial fluids;
• New transduction mechanisms and devices concepts, including Ion Sensitive Field Effect Transistors (IS-FETs), passive colorimetric or fluorescent patches, optical or impedance spectrometry;
• Noble materials, like graphene, nanotubes or nanowires, for high-sensitive, low-volume electrochemical sensing;
• Signal processing for the reduction of noise and readout delay, and strategies for the prediction of diseases, i.e. hyperglycemia;
• Studies on the correlation of biomarkers in sweat, saliva, tears, and breath to pathological conditions and diseases like cancer, HIV, intestinal infections, cystic fibrosis, and schizophrenia;
• Studies on the reliability, stability, reproducibility, and biocompatibility of devices;
• Initial field trials or/and clinical studies of new or already commercialized wearable devices.

Dr. Giovanni Antonio Salvatore
Dr. Ahyeon Koh
Guest Editors

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• Electrochemical sensors
• wearable devices/systems
• IS-FETs
• nanowires/tubes
• 2D materials
• predictive algorithms
• signal processing
• biomarkers
• clinical studies
• reliability
• biocompatibility
• sweat/saliva/interstitial fluids/tears