Biosensing with Paper-Based Miniaturized Printed Electrodes–A Modern Trend

Abstract

From the bench-mark work on microfluidics from the Whitesides’s group in 2007, paper technology has experienced significant growth, particularly regarding applications in biomedical research and clinical diagnostics. Besides the structural properties supporting microfluidics, other advantageous features of paper materials, including their versatility, disposability and low cost, show off the great potential for the development of advanced and eco-friendly analytical tools. Consequently, paper was quickly employed in the field of electrochemical sensors, being an ideal material for producing custom, tailored and miniaturized devices. Stencil-, inkjet-, or screen-printing are the preferential techniques for electrode manufacturing. Not surprisingly, we witnessed a rapid increase in the number of publications on paper based screen-printed sensors at the turn of the past decade. Among the sensing strategies, various biosensors, coupling electrochemical detectors with biomolecules, have been proposed. This work provides a critical review and a discussion on the future progress of paper technology in the context of miniaturized printed electrochemical biosensors.

Trends in Paper-based Electrochemical Biosensors: From Design to Application

“…The paper's popularity is due to the high alpha-cellulose content, smooth surface, structural uniformity and absence of additives, which guarantee its quality, reproducibility and uniformity. 15 Another significant advantage of using Whatman grade 1 chromatographic filter paper is its suitability for immobilization of enzymes, proteins and DNA due to its high degree of non-specific binding towards biomolecules. In Table 2, we have summarized various studies that utilized different fabrication techniques for the production of paper-based devices and detection of distinct targets, incorporating different electrochemical detection methods using Whatman grade 1 chromatographic filter paper.…”

“…The auxiliary and sample pads are then folded and stacked together in order to produce a 3D device. 15 Simultaneous detection of carcinoembryonic antigen (CEA) and alphafetoprotein (AFP) was reported using a 3D electrochemical PAD. 33 Hydrophobic barriers on the PAD were wax printed followed by baking, with the outer and inner circles measuring 15 and 8 mm in diameter, respectively.…”

“…15 Additionally, hydrophobic patterning prevents the back-flow or overflowing of solution from the paper sensor. 41 The specific area of hydrophobic and hydrophilic zones will vary depending on the volume of the solution required.…”

“…15 The selection of specific electrode material determines its conductivity and sensitivity, as well as the cost of the device and the possibility of adopting specific immobilization procedures.…”

“…The electrodes can be produced via methods such as screenprinting, inkjet printing, or pencil drawing onto hydrophilic areas. 15 Moreover, to further enhance the sensitivity and specificity of the PAD sensor, nanotechnology modifications on the surface of working electrodes have been shown to improve the signal.…”