In this study, the lateral flow assay (LFA) has been developed for the detection of bacterial infection (BI) by specific biomarker procalcitonin (PCT), without a need for complicated instrumentations and technical expertise. For the development of the assay, gold nanoparticles (AuNP) and their conjugates with antibodies specific to the model antigen PCT are assessed. Polyclonal antibody (pAb) labelled with gold nanoparticles (AuNP) to obtain the AuNP-pAb complex and the specific monoclonal antibody (mAb) have been dropped at the test zone. This complex is placed over the conjugate line of the LFA strip. In the absence of PCT or the presence of other biomarkers, the test line remained colourless, which revealed the specificity of assay towards PCT among a pool of various analytes. Herein, observations have been made through two different platforms for quantitative and qualitative analysis for the detection of PCT biomarker. The qualitative analysis has been performed on the basis of appearance red color in the test band, while for quantitative analysis, a novel approach has been adopted. Herein, the nitrocellulose membrane (paper strip) is cut out from the LFA strip and used for electrochemical studies under similar solution conditions. Different paper strips presented different cyclic voltammograms (CV) that could be correlated to varying PCT concentrations captured at the test line of the paper strip. The qualitative detection limit for PCT using this LFA was determined to be 2 ng/ml and the quantitative detection limit was 1 ng/ml. The electrochemical response studies of the paper strip by CV technique revealed the sensitivity value of 0.695 mA ng/ml.
The present study reports the fabrication of reduced graphene oxide (rGO)/gold nanoparticles (AuNP) nanocomposites modified cellulose fiber paper-based electrochemical biosensor for procalcitonin (PCT) biomarker detection. PCT is a biomarker specific for bacterial infection (BI) detection and has gained much attention as a potential solution to the problems associated with determining appropriate antibiotic use. In sepsis and other severe infections, serum PCT levels increase to values above 100 ng mL À 1 in response to pro-inflammatory stimulation. The structural and morphological characterization of the rGO-AuNP composite are investigated using UV-Vis spectroscopy, FTIR spectroscopy, X-ray diffraction, and scanning electron microscopy. Monoclonal antibodies specific to PCT were covalently immobilized onto the rGO-AuNP nanocomposite modified paper to fabricate an electrochemical biosensor. The fabricated biosensor exhibits linearity in the PCT concentration range 10 À 15 × 10 3 pg mL À 1 , with a low detection limit 10 pg mL À 1 . Furthermore, the proposed biosensor also exhibited good selectivity and could detect PCT biomarkers even in the presence of other interfering electroactive species such as glucose, oxalic acid, and urea. The proposed CF-based biosensor has been proven as an accelerated simple point-ofcare (POC) exploratory approach for early PCT diagnosis in inadequate areas with limited production facilities, computational techniques, and highly skilled experts.
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