Researchers said the method will enable the rapid detection and risk assessment of BPA with high sensitivity and selectivity.
Direct measurement is difficult because of the weak response by conventional electrochemical sensors and current optical analysis methods are susceptible to interfering substances.
The one-step method is based on graphene oxide (GO) and an anti-BPA aptamer labelled by FAM.
Aptamers are single-stranded DNA or RNA (ssDNA or ssRNA) molecules that can bind to pre-selected targets including proteins and peptides with high affinity and specificity, according to Base Pair Technologies.
In the presence of BPA, the chemical binds to the aptamer because of strong affinity effects, including the electrostatic effect, hydrogen bond and spatial matching which prevent the adsorption of GO.
In the absence of BPA, FAM-ssDNA can be adsorbed onto the GO surface, leading to fluorescence resonance energy transfer (FRET) between GO and FAM-ssDNA.
Signal intensity change
Under different concentrations of BPA, based on the target-induced conformational change of anti-BPA aptamer and interactions between the fluorescently modified anti-BPA aptamer (FAM-ssDNA) and GO, results show the intensity of the fluorescence signal was changed.
The graphene oxide can specifically adsorb and quench the fluorescence of fluorescently modified ssDNA probes.
BPA can combine with anti-BPA optamer and switch its configuration to prevent the aptamer adsorbing on the surface of GO.
A variety of techniques for detection of benzene and its derivatives, including UV spectrometry, CD spectrum analysis, fluorescence analysis, immunoassay-based methods, electrochemical sensors, and conventional instrument-based methods have been looked at.
However, samples must be pretreated to meet the requirements of such instrument-based methods and technicians performing analyses must be proficient.
Immunoassay-based methods depend largely on the quality of the prepared antibodies.
“A fluoresently modified anti-BPA aptamer was used to produce a detectable signal, and the added BPA competitively bound with the aptamer and prevented the adsorption of GO,” said the researchers.
“The corresponding peak exhibited a linear relationship with the concentration of added BPA. Qualitative and quantitative detection of BPA were successfully realized with a LOD of 0.05 ng/mL, which was obtained in the range of 0.1 to 10 ng/mL by fluorescence spectrum analysis.”
BPA published research
Meanwhile, researchers from the University of Missouri, Westminster College, the US Geological Survey and the Saint Louis Zoo have determined that BPA can alter a turtle's reproductive system and disrupts sexual differentiation.
They found when turtle eggs are exposed to environmental estrogens, their sex is no longer determined by temperature, but by the chemical to which they're exposed.
Cheryl Rosenfeld, associate professor of biomedical sciences in the MU College of Veterinary Medicine, a researcher in the MU Bond Life Sciences Center, said the doses tested were environmentally relevant.
"If BPA has negative impacts on turtles, then it most likely has implications for human health as well."
In a separate study, scientists exposed pregnant mice to levels of BPA equivalent to those considered safe in humans.
They found three generations of female mouse offspring experienced significant reproductive problems, including declines in fertility, sexual maturity and pregnancy success.
Jodi Flaws, University of Illinois comparative biosciences professor, who led the analysis, said: “We found that exposing them to levels of BPA which are below what the US Food and Drug Administration says is a safe dose causes reproductive problems in these mice."
Source: ACS Appl. Mater. Interfaces, 2015, 7 (14), pp 7492–7496
Online ahead of print, DOI: 10.1021/acsami.5b00199
“Building An Aptamer/Graphene Oxide FRET Biosensor for One-Step Detection of Bisphenol A”
Authors: Yingyue Zhu, Yilin Cai, Liguang Xu, Lixue Zheng, Limei Wang, Bin Qi, and Chuanlai Xu