Aug 18 2020
Researchers from the University of São Paulo (USP) in São Carlos, Brazil, have developed a wearable sensor printed on microbial nanocellulose, a naturally occurring polymer.
Applied to skin as a piece of sticking plaster, the device developed by Brazilian researchers can be used to monitor human metabolism and administer drugs. Image Credit: researcher’s archive.
They achieved this in collaboration with researchers from São Paulo State University (UNESP) in Araraquara, the University of Araraquara (UNIARA), the University of Campinas (UNICAMP), and the Brazilian National Nanotechnology Laboratory (LNNano).
The skin-adherent sensor is a better alternative for traditional sensors printed on plastic surfaces. It helps perform noninvasive detection and tracking of different substances present in sweat.
The research was headed by Osvaldo Novais de Oliveira Junior and funded by FAPESP through the projects “Development of analytical tools based on electronic tongues for simultaneous detection of bacterial threats,” “Design and fabrication of nanostructured flexible devices for biomarker detection,” “Printed and implantable biosensors made from biopolymers for long-term monitoring,” as well as a Multiuser Equipment grant.
The article titled “Microbial nanocellulose adherent to human skin used in electrochemical sensors to detect metal ions and biomarkers in sweat” has been published in the Talanta journal.
Microbial nanocellulose is a 100% natural polymer. It is produced by bacteria from sugar. Its main advantage over plastic is its far better interface with human skin. It’s been commercially available for some years for use in wound dressings, among other applications, but it had never before been studied as an electrochemical sensor substrate.
Robson Rosa da Silva, Study Co-First Author, University of São Paulo
In the case of wearable sensors developed on plastic substrates, one main problem is that perspiration tends to form a barrier between the sensor and skin, hampering the detection and leading to allergies. “Nanocellulose is totally breathable, enabling sweat to reach the electrode’s active layer,” added Silva.
The newly developed sensor resembles a small adhesive rectangle measuring 1.5 cm in length by 0.5 cm in width. It is as thin as a sheet of tissue paper and has the ability to detect a wide array of biomarkers such as uric acid, potassium, sodium, glucose, and lactic acid, among others.
These elements or substances circulate in the bloodstream and are also detectable in sweat. Therefore, diabetes monitoring is one possible application of the nanocellulose sensor. Another is hormone control in women via detection of the hormone estradiol. As proof of concept, we exposed the sensor to low levels of toxic metals such as lead and cadmium, and the result was positive.
Robson Rosa da Silva, Study Co-First Author, University of São Paulo
The device can also be utilized to detect the existence of atmospheric pollutants in organisms.
A semiautomatic screen printer and a paste containing a high concentration of carbon particles are used to print the detection units on the microbial nanocellulose substrate. Carbon has been chosen as it exhibits higher electrical conductivity.
Chemical oxidation-reduction reactions produce an electrical signal that measures the concentration of the metabolite of interest. The sensor is connected to a potentiostat that makes electrochemical measurements by means of variations in the electric current. The data obtained are transmitted to a computer and converted into standard curves.
Paulo Augusto Raymundo Pereira, Study Co-First Author, University of São Paulo
Pereira considers that it is easy to design the wireless communication between the sensor and a data measuring and reading device.
The team is currently analyzing the use of the sensor to administer drugs and has been making efforts to render it commercially viable.
The project’s first stage titled “Fabrication of screen printed electrodes on biodegradable substrates (nanocellulose and onion films Allium cepa L.) for medical, food and agroindustrial applications,” carried out by Biosmart Nanotechnology, was financially supported by FAPESP’s Innovative Research in Small Business (PIPE) Program.
Journal Reference:
Silva, R. R., et al. (2020) Microbial nanocellulose adherent to human skin used in electrochemical sensors to detect metal ions and biomarkers in sweat. Talanta. doi.org/10.1016/j.talanta.2020.121153.