A novel electrochemical immunosensor for ultrasensitive detection of tumor necrosis factor a based on polystyrene - PAMAM dendritic polymer blend nanofibers

A simple, rapid, and highly sensitive label-free immunosensor based on polystyrene (PS)-polyamidoamine (PAMAM) dendritic polymer nanofibers (NFs) for detection of tumor necrosis factor-alpha (TNF-alpha) cytokine was developed. The choice of PAMAM was due to the possibility of designing the surface of NFs to create a novel interface with the high control ability of the density of amine groups at the surface by which capture antibody (anti-TNF-alpha) could be covalently attached to the surface of NFs through glutaraldehyde (GA) coupling chemistry. Evaluation of the electrode surface using cyclic voltammetry (CV) proved the electrode manufacturing stages were successful by decreasing the peak current values due to the blockage of electron transfer by the biomolecule layer on the surface of NFs, as well as the ability to precisely control the current peak by changing the diameter of the NFs and the concentration of dendrimer. Electrochemical impedance spectroscopy (EIS) was used to test the detection capability of the immunosensors and compare the role of the amount of PAMAM presented on the surface of NFs on their analytical performance. Increasing the concentration of dendrimer greatly increased the sensitivity of immunosensors due to the higher stabilization of the antibody on the nanofiber surface. The immunosensor had a very high affinity for TNF-alpha cytokines, with a linear response ranging from 10 to 200 pg/mL and a low limit of detection (LOD) of 669 fg/mL. Interference results with Interleukin-10 (IL-10) cytokine showed that the immunosensor was extremely specific and may be utilized to detect cytokines in clinical diagnosis.