A novel chemometric-amperometric biosensor for selective and ultra-sensitive determination of Streptococcus pneumoniae based on detection of a protein marker: A suitable and reliable alternative method

Abstract

In this work, a novel amperometric biosensor assisted by first-order calibration methods was fabricated based on detection of L-ascorbate 6-phosphate lactonase (AG) as a protein marker of Streptococcus pneumonia (SQP). Fabrication of the biosensor was based on modification of a rotating glassy carbon electrode (GCE) by multiwalled carbon nanotubes-graphene-ionic liquid (MWCNTs-Gr-IL) composite film. The MWCNTs-Gr-IL/GCE was modified by electrosynthesis of 4-amino-N,N,N-trimethylanilinium (ATA) and 4-aminobenzenesulfonate (ABS) on its surface. The aniline-modified S7 peptide which is an AG-binding peptide with the sequence of HHHHHHGGGGGENIMPVLGC (molecular weight = 2083.3 Da) was modified with phenylamine which was electrochemically synthesized onto the biosensor surface (SP/ATA-ABS/MWCNTs-GR-IL/GCE). Binding of the AG with the SP at the biosensor increased the steric hinderance at the biosensor surface which caused its response to electrochemical probe molecules to be decreased which was used for detection of the AG. The amperometric response of the biosensor was calibrated in an artificial human serum sample with the help of several first-order calibration algorithms including PLS, rPLS, RBF-PLS, BP-ANN, LS-SVM, and CPR, and it was validated in real human serum samples with the aim of exploiting first-order advantage for selective determination of the AG. Interestingly, performance of the biosensor assisted by BP-ANN in determination of the AG in real human serum samples, and detection of the SQP based on detection of the AG on its membrane were successful while the biosensor response to SQP mutans was insignificant due to the absence of AG on SQP mutans membrane.