Researchers Develop Ultrasensitive Analysis Method for Environmental Contaminants

Fluoroquinolone antibiotic residues are environmental contaminants. As these chemicals are not easily biodegradable, the development of rapid and cost-effective methods for their detection is a growing concern in the forensic industry. In a study published in Chemical analysis, Researchers have designed a microfluidic photoelectrochemical aptasensor (PEC) using photoactive AgBr/CuBi₂HI₄ (ACO) composites for rapid and ultrasensitive detection of environmental contaminants.

Study: AgBr/CuBi2O4 Photocathode Direct Z Schematic for Ultrasensitive Detection of Ciprofloxacin and Ofloxacin by Controlling Luminol Release in a Self-Powered Microfluidic Photoelectrochemical Aptasensor. Image Credit: Sonis Photography/Shutterstock.com

Fluoroquinolone antibiotics, such as ofloxacin (OFL) and ciprofloxacin (CIP), pollute the environment by suppressing the activity and growth of microorganisms.

This study explores a novel approach to detect ofloxacin and ciprofloxacin by controlling the release of luminol in a self-powered microfluidic photoelectrochemical aptasensor.

How Do Fluoroquinolone Antibiotics Become Environmental Contaminants?

Fluoroquinolone (FA) antibiotics treat bacterial infections in humans and animals. They are effective against a broad spectrum of gram-negative and gram-positive pathogenic bacteria.

However, these antibiotic residues have emerged as possible contaminants. The presence of antibiotics in surface waters and animals can harm human health through the food chain. Fluoroquinolone antibiotics, including ofloxacin, ciprofloxacin, norfloxacin, enrofloxacin, and lomefloxacin, coexist in the environment, making their detection more challenging.

Limitations of Traditional Detection Techniques

Enzyme-linked immunosorbent assays, immunoassays, high-performance liquid chromatography, and capillary electrophoresis have been used to detect fluoroquinolone antibiotics.

However, various disadvantages such as time consuming, extensive pretreatment and high equipment costs limit the application of this technique. Therefore, a simple, robust and cost-effective analytical technique is needed.

Advantages of Using PEC Sensors

Photoelectrochemical sensors are innovative and rapidly developing analytical tools based on photoelectrochemical processes and the introduction of biological or chemical probes.

It outperforms standard optical and electrochemical sensors due to complete isolation from optical sources and electrochemical signals.

Self-powered photoelectrochemical sensors convert optical signals into electrical signals without external power. This sensor has a simple structure compared to the redundant three-electrode system. The sensors feature a wide dynamic range and outstanding sensitivity in pesticide residue detection, biological testing, and food analysis.

Although the performance of PEC sensors has reached acceptable levels, multi-target quantitative analysis remains a hurdle. Developing a portable and compact PEC sensor for ultrasensitive examination is one of the most important demands in the forensic industry.

Using a Microfluidic Photoelectrochemical Aptasensor to Detect Contaminants

An analytical framework that integrates a PEC sensor with a microfluidic device for the ultrasensitive detection of ciprofloxacin and ofloxacin has been explored.

A self-powered microfluidic PEC aptasensor designed using a direct Z-scheme ZnIn₂S₄/CdS as photoanode and AgBr/CuBiO₄ as a photocathode to achieve multi-target quantitative detection of ofloxacin and ciprofloxacin.

The luminol molecules are embedded in the porous structure of the silicon dioxide (PSiO .) nanosphere₂) by electrostatic adsorption between PSiO₂ and an aptamer (OFL) to enhance the cathodic photocurrent signal.

Instead of using platinum counter electrodes to supply electrons, CdS nanorod arrays (CZIS) were coated with ZnIn₂S₄ used as a photoanode.

Detection of CIP signal-off measured via aptamer_(CIP) and recognition of specific targets at the photoanode. Scanning electron microscopy (SEM) helps analyze the microstructure and morphology of AgBr/CuBi₂HI₄ composite.

X-ray photoelectron spectroscopy (XPS) experiments were carried out with a 2000 XPS system with a charge neutralizer and a monochromatic AlK source. Energy dispersive spectrometer (EDS) data and electron microscope images were analyzed using emission scanning electron microscopy (ESEM).

Key Findings from the Study

A standalone PEC aptasensor made by incorporating ZnIn. direct Z-scheme₂S₄/CdS photoanode with AgBr/CuBi2O4 photocathode into microfluidic device successfully detects ciprofloxacin and ofloxacin.

Matched band structure of AgBr and CuBi₂HI₄ very helpful in charge transfer and separation. ZnIn₂S₄The /CdS composite with a stable photocurrent signal supplies many electron carriers to the PEC system.

CuBi . pure₂HI₄ the sample has homogeneous nanocuboids on its surface with an average diameter of 34 m. In ACO composites, the development of direct Z-scheme heterojunctions significantly facilitates electron/hole pair separation.

Luminol is released through special recognition between OFL and aptamer_(OFL) react with O₂, and emits chemiluminescence, leading to a signal-on state. The steric barrier effect on the photoanode caused by the combination of CIP and aptamer_(CIP) creates a successful CIP signal-off detection.

The microfluidic PEC aptasensor features high stability, repeatability and selectivity for OFL and CIP detection based on an “on-off-on” signaling mechanism. High linearity for OFL and CIP was established, with detection limits of 0.022 and 0.06 pg/mL, respectively.

Microfluidic PEC sensing technology demonstrates the capability for multi-target quantitative analysis of two different types of fluoroquinolone antibiotics in real milk and water samples.

The proposed analytical method has the potential to be a strong competitor for the analysis of ultrasensitive fluoroquinolone antibiotics in various environmental samples.

Reference

Wu, T., Du, Y., Dai, L., Li, J., Song, X., Feng, J., Xueying Wang, Qin W., & Huangxian, J. (2022) Direct Z Schematic of AgBr Photocathodes /CuBi2O4 for Ultrasensitive Detection of Ciprofloxacin and Ofloxacin by Controlling Luminol Release in Self Powered Microfluidic Photoelectrochemical Aptasensors. ACS Publications. https://pubs.acs.org/doi/10.1021/acs.analchem.2c00889

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