Paper biosensors: towards eco-friendly diagnosis

Biosensors for diagnosis

Home-based biosensors have changed the way society thinks about healthcare diagnostics. Biosensors are integrated analytical devices that are able to translate the biological recognition of a target analyte into a quantitative signal via a transducer. The design of a biosensor is to enable rapid, simple testing at the point of care using single-use, disposable test strips. Besides biomedical diagnosis, biosensors are nowadays applied to many other areas such as agriculture, drug discovery, forensics, environmental control and food safety. Within the healthcare sector, biosensors are applied not only to diagnostics but also to patient monitoring. Perhaps the most well-known example is the blood glucose biosensor, which is used by thousands of diabetic patients all over the world. The first commercial biosensor (YSI glucose biosensor) was introduced in the mid-70s but it was not until 1987 that fully-printed glucose biosensor strips (similar to those we know nowadays) were available on the market (Exactech, Medisense). A user-friendly tool for remote monitoring of blood glucose certainly was key for the management of diabetes, facilitating patients everyday life. The success of this application has almost been responsible for the exponential growth of the biosensor market, which is set to reach 27.06 Billion USD by 2022. In parallel to the achievement of the glucose biosensor, there has been progress in other technological fields, e.g. microfabrication, material sciences, microfluidics, electronics and Internet of Things (IoT). The combination of biosensing technologies with these advancements has aided the realisation of devices with enhanced capabilities used for wider applications.

Advancement vs pollution

The rise in production of single-use or short-lifetime electronic devices, such as biosensors, has resulted in the generation of an ever increasing volume of electronic waste. This is becoming of huge environmental concern for the developed world. According to a United Nations report published in 2017, more than 40 million tonnes of electronic waste was generated worldwide in 2016 and only 20% was correctly recycled. Although 66% of the world’s population is covered by electronic waste legislation, more must be done to encourage the rest of countries to establish policies.

Concerns surrounding global warming and pollution drive the need to look for alternative solutions. Due to its high recyclability, paper arises as an ecological alternative to traditional plastic biosensors. Technically, paper offers many inherent advantages; its internal composition, based on cellulose fibres, allows for manipulation in order to deliver electrical conduction, hydrophilicity/hydrophobicity and the sustenance of high temperatures without burning. Thus, paper as an active biosensing platform is emerging as a promising approach to develop eco-friendly diagnostics. Paper-based solutions will reduce the environmental impact of electronics by reducing carbon footprint, toxicity, and supporting waste management, and thus contributing to the targets set by the 2020 EU Climate Action.

Gravure printing of electronic structures on paper. Credit: CC-BY-SA 3.0 by Bystrikt

Paper as an eco-friendly alternative – where are we?

The area of paper-based biosensors is in its infancy; thus, a gap remains between the advanced research undergone at academia and clinical applications. This is mainly due to challenges such as substrate fragility, mass production, sample preparation and system integration. There are some successful paper-based biosensors that have reached the market, such as the pregnancy test. But they mainly provide qualitative or semi-quantitative yes/no responses, limiting its range of application. Currently, there is a huge amount of research ongoing in order to solve these issues, which is reflected in the peer-reviewed literature with 693 articles on paper biosensors published in 2017 (this figure was 126 articles in 1990). Within Europe, there are numerous collaborative research efforts in the race to close this gap and develop eco-friendly electronics. Examples are projects such as GREENSENSE, IMPETUS and INNPAPER which all aim to exploit the use of wood-derived materials (e.g. nano cellulose and paper) to develop PoC sensing systems.

Credit: Greensense project, grant agreement n° 761000
INNPAPER project brochure. Credit : INNPAPER

Along with the technological challenges, there are several issues regarding the commercial and societal aspects of paper-based biosensors that need to be solved. These include its combination with other biodegradable materials, regulation for disposal and proof of cost competitiveness as an alternative to plastic devices. These issues will be addressed as the technology is nearer to the market and proves its feasibility for daily acceptance and application.

Niamh T Brannelly and Laura Gonzalez-Macia

Niamh T. Brannelly is a PhD in Chemistry and a researcher at OSASEN SENSORES SL.

Laura Gonzalez-Macia is a PhD in Chemistry and a Marie Skłodowska-Curie Fellow at OSASEN SENSORES SL.

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