Agostino Romeo1 Paul Eduardo David Soto Rodriguez1 Ana Moya2 3 Gemma Gabriel2 3 Rosa Villa2 3 Rafael Artuch6 5 Samuel Sanchez1 4

1, Institute of Bioengineering of Catalonia, Barcelona, , Spain
2, National Centre of Microelectronics - Microelectronics Institute of Barcelona, Barcelona, , Spain
3, Research Networking Center in Bioengineering, Biomaterials and Nanomedicine (CIBER-BBN), Barcelona, , Spain
6, Laboratory of Hereditary Metabolic Diseases, Hospital Sant Joan de Déu, Barcelona, , Spain
5, CIBER-ER (Biomedical Network Research Center for Rare Diseases), Instituto de Salud Carlos III, Madrid, , Spain
4, Institucio Catalana de Recerca i Estudis Avancats (ICREA), Barcelona, , Spain

In the last few decades the quality of life has significantly improved due to the achievements of biomedical technology. Innovative healthcare solutions contributed to these advances by decreasing costs and making health assessment easier and more accessible. Versatile biochemical sensors targeted to health biomarkers and bioanalytes (metal ions, proteins, amino acids, glucose, lactate, etc.) can non-invasively monitor the health status of the user by analyzing external body fluids (sweat, saliva, tear fluid) alternative to blood.[1,2] On-demand biosensing is envisaged due to the versatility of sensing platforms that can adapt to specific needs in terms of target biomarkers and health issues to monitor. To this regard, several recognition systems, including antibodies, enzymes, and inorganic nanomaterials can be used to modify the sensors to achieve high selectivity towards target analytes. In this scenario, recent advances in microfabrication, sensor technologies and data transmission led to the developments of point-of-care (PoC) diagnostics.
Here we present few examples of biosensors for painless and on-demand self-assessment of health conditions. In particular, we describe a non-invasive electrochemical sensor for the non-enzymatic analysis of tear glucose.[3] Electrochemical sensing is chosen among other types of transduction because it is well suited for simple, rapid, and cost-effective personalized medicine devices. Electrodes are fabricated on soft and flexible materials using inkjet printing and then modified with CuO microparticles (CuO-µPs) to carry out non-enzymatic detection of glucose. This detection mechanism is based on the CuO-catalyzed electro-oxidation of glucose in alkaline environment, due to the electrochemical conversion of CuO into strong oxidizing Cu(III) species such as CuOOH or Cu(OH)4−. Glucose detection is achieved by CA, with an excellent linearity observed in the 3–700 µM range, matching typical glucose levels in tears. A sensitivity of 850 µA mM−1cm−2 and a limit of detection (LOD) of 2.99 µM are calculated. This sensor shows good selectivity, reproducibility, and life-time, resulting in a reliable tool for painless and non-invasive self-assessment of diabetes, as confirmed by tests on tear samples.
Personalized and non-invasive sensing technologies allow to easily and frequently monitor the health status of an individual as often as needed. This helps make early-stage detection simpler and more convenient, thus enhancing the efficacy of therapeutic treatments. Rapid and cheap PoC diagnostics also allows improving the life style of patients, by interfering in low or negligible extent to their daily activities.

[1] A. Romeo, et al. Lab Chip 16, 1957 (2016)
[2] D. Vilela, et al. Lab Chip 16, 402 (2016)
[3] A. Romeo, et al., Appl. Mat. Today 10, 133 (2018)