Abstract

The fabrication of low-cost, stable, sensitive and selective biosensors for herbicides has gained considerable attention in recent years as modern agriculture makes massive use of pesticides that are known to be harmful for human health. The use of photosynthetic proteins for herbicide detection is the most straightforward strategy for this aim, as these are the natural target of this class of chemicals. Among the possible biosensor devices, the most successful that have led to commercial products are based on amperometric detection. In particular, in this type of biosensors, the monitored photocurrent is progressively attenuated in the presence of increasing amount of analyte, minimizing the mathematical treatment of the data. In the present work, we show the functionalization of screen-printed electrodes with an ordered film of photoactive biological material, by means of laser induced forward transfer (LIFT) technique, in order to fabricate a biohybrid device for energy conversion and/or biosensing. LIFT is an advanced tool for achieving the direct immobilization of biosystems [1] with high spatial resolution, due to the high impact pressure of the transferred droplets, at the receiver substrate. As a result, it enhances physical adsorption onto the electrode surface and high photocurrents can be attained by using extremely low quantities of deposited samples. The biomaterial used is the photosynthetic reaction center (RC) from the bacterium Rhodobacter (Rb.) sphaeroides. Cathodic or anodic photocurrents are detected depending on the potential applied to the working electrode: in particular, cathodic photocurrents are detected at the donor side under reducing potentials and anodic ones at the acceptor side under oxidizing potentials. Rb. sphaeroides RC is classified as Q-type and resembles the more evolved photosystem II (PSII) found in plants, algae and cyanobacteria, sharing the sensitivity to the same class of herbicides. However, bacterial RC has a simpler architecture, is more stable and is more selective to a particular class of herbicides, the triazinic ones, while PSII is sensitive to different classes of pesticides [2]. In the present case, thanks to the intimate contact between the RC and the electrode, we could detect cathodic photocurrents in the absence of any mediator at both acceptor and donor side, bringing about several advantages: simpler biosensor architecture, ideal square-wave shape of the photocurrents, and independence on the mediator concentration. Most importantly, the absence of quinone, often used as mediator at the acceptor side makes the biosensor particularly sensitive to the herbicide tested, due to the competitive nature of the binding reaction. We tested the herbicide terbutryn which, although is no longer permitted in the EU, has the strongest binding affinity to the RC and is more suitable to show the potentiality of the final device. A limit of detection for the terbutryn was found in the range 8-30 nM w

Autore Pugliese

• Milano Francesco , Trotta Massimo

Tutti gli autori

• L. Giotta; M. Chatzipetrou; D. Chirizzi; M. Trotta; M. Massaouti; M.R. Guascito; F. Milano; I. Zergioti

Titolo volume/Rivista

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Anno di pubblicazione

2015

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Numero di citazioni Wos

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Settori ERC

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