Category: Micro- and Nanotechnologies
Microfluidic paper analytical devices (µPADs) are a new class of low cost, user-friendly, portable and very simple analytical systems. µPADs can be used for water quality assessment, disaster vigilance and health diagnosis, especially in developing countries. Recently, microbial fuel cells were proposed as simple electrochemical devices able to perform as biosensors, and useful for several analytical applications such as water quality and toxicity monitoring, microbial activity and quantification, life sensors, among others. Then, the merge of MFCs and µPADs technologies can provide several advantages for the design of complete analytical systems that can be fabricated, used and disposed easily. Multiple applications can be envisioned for such an analytical device in both, environmental and clinical chemistry.
In this work we report an environmentally sustainable design for a microfluidic paper-based microbial fuel cell biosensor (µPAD-MFC). The µPAD-MFC was constructed with low cost, renewable materials such as paper, paper-based carbon nanotube/chitosan (CNT/CS) electrodes and biodegradable poly(vinyl alcohol)/chitosan (PVA/CS) membranes. Basically the device integrate filter paper (Whatman N° 1) anode and cathode reservoirs, glucose and lyophilized cells disposed into the anodic compartment, and ferricyanide adsorbed into the cathodic compartment. Paper compartments were partially overlapped and separated with a thin polymeric membrane (PVA/CS) between them, and resemble in some aspects a lateral flow test strip. This lateral flow type design was optimized to maximize the proton transport across the membrane.
The µPAD-MFC can be activated with a small sample volume (16 µl) that is transported onto one of the compartments (anode) with the assistance of paper capillary forces. The sample instantly hydrates the lyophilized microbial cells and then metabolic activity rapidly starts (glucose oxidation). Some of the electrons that move through the microbial catalytic pathway can reach the anode of the MFC, by means of the used redox mediator (methylene blue, MB).
Scanning electron microscopy (SEM) was used to investigate the cellular adherence on the electrodes and the paper fibers .Maximum power density of 6.3 ± 1.9 mW/m2 was achieved with P. putida KT2440 (3.0 × 108 CFU/ml). Simulated “toxic” water samples containing 10 mg/L of 3,5 DCP (3,5-dichlorophenol), 0.1% of formaldehyde or 10 mg/L of Zn2+ produced 36%, 42%, 25% signal decay, respectively, in comparison with the non-toxic (control sample) after 25 min incubation. This optimal analysis time (25 min) after the beginning of the test was determined by taking into account the inhibition rates and the low RSD values obtained. In conclusion, we show a novel µPAD-MFC device, lightweight, economic, easy to use and made with fully sustainable materials and process.
María González– PhD student at Biosensors and Bioanalysis Group, Universidad de Buenos Aires, Buenos Aires Capital, Ciudad Autonoma de Buenos Aires, Argentina
PhD student at Biosensors and Bioanalysis Group
Universidad de Buenos Aires
Buenos Aires Capital, Ciudad Autonoma de Buenos Aires, Argentina
María J. González. Environmental and sanitation engineer with a MSc. in Molecular Microbiology. Now I am PhD student at the biosensors and bio-analysis laboratory (University of Buenos Aires) with graduate fellowship funded by CONICET (2015 - 2020). I have experience of working with evaluation and environmental monitoring companies. Along my PhD, I have gained skills and experience studying alternative materials for microbial fuel cells applications (biosensor and energy production) such as carbon cloth electrode modification with nickel for hydrogen production; poly(vinyl alcohol)/chitosan based polymer exchange membranes as alternative membrane to Nafion; CNT- ink for flexible paper-based electrodes to be used in a MFC; microfluidic design on paper and polymethylmethacrylate for easy handle and disposal sensing devices, and finally computational tool design for biological systems modeling.