Biological approaches to artificial photosynthesis: general discussion

Metals in Catalysis, Biomimetics & Inorganic Material

Synthetic approaches to artificial photosynthesis: general discussion

Metals in Catalysis, Biomimetics & Inorganic Material

Microbial amperometric biosensor for online herbicide detection : photocurrent inhibition of Anabaena variabilis

A microbial biosensor based on the cyanobacteria Anabaena variabilis was developed for online herbicide detection through inhibition of generated photocurrent. Specifically, atrazine and diuron were employed as model photosynthesis-inhibiting herbicides. To fabricate the biosensor, bacterial cells were immobilized on a carbon felt electrode using alginate as an entrapping polymer and p-benzoquinone (BQ) as the redox mediator to sustain the electron transfer. The current generated by the photo-bioelectrocatalytic oxidation of water was evaluated. During the calibration, an immediate concentration-dependent decrease of the photocurrent was observed after the injection of the tested herbicides. The biosensor showed a sensitivity of 1224.6 \u3bcA \u3bcM 121 cm 122 towards atrazine up to 0.56 \u3bcM. As diuron is a much stronger photosynthesis inhibitor, the biosensor allows only turn on/turn off detection for this compound. In order to avoid the release of the mediator in solution, the encapsulation of BQ in the polymer was tested. Addition of activated carbon was necessary to create a conductive network inside the alginate matrix, enabling to achieve a sensitivity of 127.7 \u3bcA \u3bcM 121 cm 122 towards atrazine up to 131 \u3bcM (lower limit of detection 64 nM). Therefore, not only the entrapment prevented the release of BQ in solution, but improved the operating range of the sensor, with a limited decrease of sensitivity that does not hinder its application. These characteristics make the biosensor suitable for environmental analysis, opening for the on-line monitoring of herbicides

Rechargeable membraneless glucose biobattery: Towards solid-state cathodes for implantable enzymatic devices.

Enzymatic biobatteries can be implanted in living organisms to exploit the chemical energy stored in physiological fluids. Generally, commonly-used electron donors (such as sugars) are ubiquitous in physiological environments, while electron acceptors such as oxygen are limited due to many factors including solubility, temperature, and pressure. The wide range of solid-state cathodes, however, may replace the need for oxygen breathing electrodes and serve in enzymatic biobatteries for implantable devices. Here, we have fabricated a glucose biobattery suitable for in vivo applications employing a glucose oxidase (GOx) anode coupled to a solid-state Prussian Blue (PB) thin-film cathode. PB is a non-toxic material and its electrochemistry enables fast regeneration if used in a secondary cell. This novel biobattery can effectively operate in a membraneless architecture as PB can reduce the peroxide produced by some oxidase enzymes. The resulting biobattery delivers a maximum power and current density of 44 μW cm−2 and 0.9 mA cm−2, respectively, which is ca. 37% and 180% higher than an equivalent enzymatic fuel cell equipped with a bilirubin oxidase cathode. Moreover, the biobattery demonstrated a stable performance over 20 cycles of charging and discharging periods with only ca. 3% loss of operating voltage

A Self-Powered Minimalistic Glucometer: A Lean Approach to Sustainable Single-Use Point-of-Care Devices

In this work, a novel glucose quantification strategy is presented in a self-powered biosensing device. The analyte in the sample is oxidized in an enzymatic fuel cell and the generated charge is transferred to a capacitor. The built-up capacitor voltage at a specific time can be directly correlated with the concentration of analyte. An electro-fluidic switch placed on a paper-based microfluidic channel connects a minimalistic electronic circuit to the fuel cell. The circuit modules discriminate the built-up capacitor voltage, which corresponds to a particular glucose range. The digital semi-quantitative result is visualized vía electrochromic displays. As a practical application of this working principle, the self-powered single-use device has been designed to perform screening of gestational diabetes mellitus. The device discriminates between healthy (7.8 mm), and diabetes (>11.1 mm) condition providing a reliable result. This single use, printable, and disposable self-powered glucose biosensing device is autonomous and fully powered by the glucose contained in a 3.5 µL sample. It offers an energy-saving, environmentally friendly, and low-cost solution for Point-of-Care testing. By replacing the selective enzyme in the fuel cell, this strategy can be used for measuring other health parameters such as creatinine, cholesterol, or uric acid, among others

‘Plug-and-Power’ Point-of-Care diagnostics: A novel approach for self-powered electronic reader-based portable analytical devices

This paper presents an innovative approach in the portable Point-of-Care diagnostics field, the Plug-and-Power concept. In this new disposable sensor and plug-and-play reader paradigm, the energy required to perform a measurement is always available within the disposable test component. The reader unit contains all the required electronic modules to run the test, process data and display the result, but does not include any battery or power source. Instead, the disposable part acts as both the sensor and the power source. Additionally, this approach provides environmental benefits related to battery usage and disposal, as the paper-based power source has non-toxic redox chemistry that makes it eco-friendly and safe to follow the same waste stream as disposable test strips. The feasibility of this Plug-and-Power approach is demonstrated in this work with the development of a self-powered portable glucometer consisting of two parts: a test strip including a paper-based power source and a paper-based biofuel cell as a glucose sensor; and an application-specific battery-less electronic reader designed to extract the energy from the test strip, process the signal provided and show the glucose concentration on a display. The device was tested with human serum samples with glucose concentrations between 5 and 30 mM, providing quantitative results in good agreement with commercial measuring instruments. The advantages of the present approach can be extended to any kind of biosensors measuring different analytes and biological matrices, and in this way, strengthen the goals of Point-of-Care diagnostics towards laboratory decentralization, personalized medicine and improving patient compliance