ELP-OPH/BSA/TiO₂ nanofibers/c-MWCNTs based biosensor for sensitive and selective determination of p-nitrophenyl substituted organophosphate pesticides in aqueous system

A novel biosensor for rapid, sensitive and selective monitoring of p-nitrophenyl substituted organophosphate pesticides (OPs) in aqueous system was developed using a functional nanocomposite which consists of elastin-like-polypeptide-organophosphate hydrolase (ELP-OPH), bovine serum albumin (BSA), titanium dioxide nanofibers (TiO₂NFs) and carboxylic acid functionalized multi-walled carbon nanotubes (c-MWCNTs). ELP-OPH was simply purified from genetically engineered Escherichia coli based on the unique phase transition of ELP and thus served as biocatalyst for OPs, while BSA was used to stabilize OPH activity in the nanocomposite. TiO₂NFs was employed to enrich organophosphates in the nanocomposite due to its strong affinity with phosphoric group in OPs, while c-MWCNTs was used to enhance the electron transfer in the amperometric detection as well as for covalent immobilization of ELP-OPH. ELP-OPH/BSA/TiO₂NFs/c-MWCNTs nanocomposite were systematically characterized using field emission scanning electron microscopy (SEM), Raman spectra, Fourier Transform infrared spectroscopy (FTIR) and X-ray Diffraction (XRD). Under the optimized operating conditions, the ELP-OPH/BSA/TiO₂NFs/c-MWCNTs based biosensor for OPs shows a wide linear range, a fast response (less than 5 s) and limits of detection (S/N=3) as low as 12 nM and 10 nM for methyl parathion and parathion, respectively. Such excellent sensing performance can be attributed to the synergistic effects of the individual components in the nanocomposite. Its further application for selectively monitoring OPs compounds spiked in lake water samples was also demonstrated with good accuracy. These features indicate that the developed nanocomposite offers an excellent biosensing platform for rapid, sensitive and selective detection of organophosphates compounds.