Photosynthetic algae and cost-effective carbon black nanomaterial in a joint combination to develop miniaturised electrochemical sensor for a sustainable monitoring of herbicide in surface water.

Joint research project

Project leaders: Viviana Scognamiglio, Aziz Amine
Agreement: MAROCCO - CNRST - Centre National pour la Recherche Scientifique et Technique
Call: CNR/CNRST biennio 2018-2019 2018-2019
Department: Chemical sciences and materials technology
Thematic area: Chemical sciences and materials technology
Status of the project: New

Research proposal

Drinking water access represents a crucial issue to ensure geographic, socio-cultural, and economic equalities. In the Mediterranean region, water is a scarce and fragile resource, unequally distributed in space and time. This scarcity arise from different sources as rapid population growth, socio-economic development, mass tourism, human activities as agriculture, being responsible of spreading of tons of pesticides causing pollutions of ecosystems and human/animal poisonings (1). Among pesticides, atrazine continuous to be found as pervasive pollutant of watersheds and drinking water systems, despite banned in European Union and linked to harm to wildlife and humans (2). Several regulations have been stated to set the maximum level of atrazine concentration in different matrices, as drinking water and inland surface waters (EU Dir. 2013/39/EC).

This proposal intends to develop a sustainable, cost-effective, and sensitive biosensor for atrazine monitoring in water. This biosensor will be developed in joint combination between the Italian Partner IC-CNR and the Moroccan partner UH2C, which will share their common knowledge on:
i) Chlamydomonas reinhardtii (IC-CNR): a green photosynthetic algae well studied as a model organism, owing to its ease of culturing, the ability to manipulate its genetics, and the potential to recognise photosynthetic herbicides for biosensor development;
ii) carbon black (CB) modified screen-printed electrodes (SPEs) (UH2C): CB is a form of amorphous carbon with an extremely high surface area to volume ratio. Until 2010, few papers are reported in literature for analyte detection in solution.

Recently, IC-CNR and UH2C developed in joint cooperation biosensors for environmental analysis to detect toxins and chemical warfare agents (3, 4). Herein, for the first time:
i) the algae will be immobilised on CB modified SPEs
ii) the response of the algae will be quantified measuring the oxygen at CB nanomodified SPEs, since UH2C has demonstrated its suitability in oxygen reduction replacing the more expensive electrodes (platinum, carbon nanotubes modified electrode).

Indeed, photosynthetic herbicides as atrazine block the electron transport by competitive inhibiting the plastoquinone (QB) binding to the reaction centre D1 protein of the Photosystem II (PSII). Their interaction with D1 leads to a reduction of output currents in a concentration-dependent manner, due to oxygen reduction signal originated from the algal activity in response to light exposure (5).
The choice to immobilise C. reinhardtii on CB-SPEs relies on the amazing features of this material. Indeed, CB is able improving the electroanalytical performances of (bio)sensors by enhancing the electron transfer and augmenting the loading surfaces for biocomponent immobilisation. Recently the successful use of CB as modifier for screen-printed electrodes have been largely demonstrated (6). In particular, UH2C together with the analytical group of University of Rome "Tor Vergata" (UTV) is the pioneering in the use of CB as electrode modifier, indeed UH2C, described the fascinating electrochemical properties of CB in the ink/paste as well as in modifying electrodes by drop casting for the determination of several analytes including catechol, hydrogen peroxide, NADH, and thiocholine.
The results of UH2C have been corroborated by other outstanding groups, as Compton's group that reported the gain of using CB over the more specialized MWCNTs. Pumera's group has proved that CB is more convenient than the thermally reduced graphene oxide, and Fatibello-Filho's group as well as Evtugyn's group successfully used CB modified electrode to detect different analytes. UH2C has also demonstrated the suitability of CB to be combined with biocomponents.
In this project, we will investigate two novel aspects:
i) the combination of CB with whole cell (algae), never explored before;
ii) the use of CB-SPEs for oxygen detection; never reported in literature (our preliminary results have confirmed its suitability).

For this purpose, algae will be immobilized on SPEs modified by drop casting with CB dispersion. To preserve the algal photosynthetic functionality, C. reinhardtii cells will be immobilized on the working electrode surface of CB-SPEs using hydrogel entrapment, alginate gel entrapment, and crosslinking method using glutaraldehyde to finally choose the most effective in terms of stability. Cyclic voltammetry (CV) measurements will be performed to compare the performance of CB-SPEs with the most used electrodes. Electrochemical impedance spectroscopy will be performed to characterise the CB-SPEs to evaluate the electron transfer resistance. Thus, atrazine detection will be provided by amperometry by measuring the inhibition of the photosynthetic activity in the presence of herbicide as a decrease of oxygen production and current signal reductions.

Technological/scientific impacts
The proposed technologies based on the combination of algae and CB will:
- enhance the performance of SPEs exploiting a whole organism able sensing biotoxicity and alternative nanomaterials.
- provide innovative, sensitive, cheap, versatile biosensors for water analysis (ca. 5 EUR per analysis).

Socio/economic impacts
This biosensor will address crucial problems faced by developing countries being a robust technology for water management under the pressure of climate change. This will allow:
- manage the high incidence of water contamination and help restrain the elevated costs for water supply;
- enhance water access to a widen number of people, promote environmental protection, food safety and security;
- the technology transfer to mass production, improving SME technology and income.

1) http://www.who.int/bulletin/volumes/86/3/07-041814/en/
2) https://www.atsdr.cdc.gov/toxprofiles/tp153.pdf
3) Sensors, 15(2), 4353-4367
4) Talanta 150, 440-448
5) Sensors and Actuators B: Chemical, 185, 321-330
6) Electrochem. Commun. 12 (2010) 346-35

Research goals

Actually, a strong gap in monitoring environmental pollution emerges from the information reported to the Commission. Indeed, around 15% of surface water bodies in the EU are in unknown ecological status and 40% in unknown chemical status. In some Member States, ecological and chemical water status is unknown for more than 50% of the water bodies.
As a consequence, innovative and reliable tools for water monitoring and treatment is crucial, since the costs of monitoring/treatment of water resources is much lower than the cost of inappropriate decisions.

In this context, the main objectives of the proposal are:
o to develop an innovative analytical tool for the detection of atrazine in water bodies, to minimise pollution risks associated with water supply.
o to integrate different technologies for water resource management, including printed electrodes (PE), nanomaterials, electrochemical detection, and algae as green and versatile biocomponent;
o to increase the connection and cooperation between academics of different countries and share common knowledge, taking in account the critical role of the gender and the presence of non-EU countries;
o to develop joint technologies for water supply, food security, human and wildlife health, societal well-being and economic growth in developing countries.

Last update: 01/05/2024