Polyaniline-Coated U-Bent Optical Fiber Aptasensor for Detection of Arsenic in Environmental Matrices

Arsenic-contaminated groundwater has been a serious environmental issue for many decades. Currently, millions of people still live in elevated arsenic contamination areas. Cost-effective methods for trace arsenic detection promote routine analysis capabilities. This study explored a novel and synergistic combination of aptamers and polyaniline-coated U-bent optical fiber probes. The evanescent wave absorbance-based sensing provides high sensitivity. The selectivity of the aptamer in the developed sensor was achieved by optimizing the folding buffer. Furthermore, instead of a protein-based blocker, 1-Aminohexane was introduced as a blocking agent for the first time on optical fiber-based biosensors to eliminate any unwanted interference from unknown sources in real matrices. The developed sensing scheme resulted in the detection of as low as <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1~\mu $ </tex-math></inline-formula>g/L (or 1 ppb) of arsenic in spiked real samples, which is well under the permissible limits set by the World Health Organization (WHO) and other international environmental agencies. The developed aptasensor had a linear range of operation from 1 ppb up to 1 ppm (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${R} ^{{2}} \gt 0.99$ </tex-math></inline-formula>). The sensing scheme was tested in environmental waterbodies. The sensing scheme was also tested for cross-selectivity from other frequently occurring common interfering species, even at elevated concentrations in environmental water matrices. The recovery studies in the matrices resulted from 99.4% to 118.4% and the matrix factor was between 0.89 and 0.99, both within accepted limits.