Unique Sensing Interface That Allows the Development of an Electrochemical Immunosensor for the Detection of Tumor Necrosis Factor α in Whole Blood

Electrochemical affinity biosensors that can operate in whole blood are a rarity because biofouling of electrode surfaces compromises the performance of the final device. The common anti-biofouling layers that can be applied to electrodes, poly(ethylene glycol) (PEG) or oligo(ethylene glycol) (OEG) layers, form a high impedance layer on the electrode, effectively passivating the electrode. In response to this issue, we have developed effective anti-biofouling chemistry, that employs short chain zwitterionic species, derived from aryl diazonium salts, that give low impedance layers compatible with amperometry. Herein, we demonstrate the application of this surface chemistry to mixed layers of phenyl phosphorylcholine (PPC) and phenyl butyric acid (PBA), to develop immunosensors that can be used in whole blood. The capability of these new modification layers is demonstrated with an immunosensor for detecting tumor necrosis factor alpha in whole blood. The immunosensor is shown to specifically and precisely detect TNF-alpha in whole blood samples with a minimum detection limit of 10 pg/mL with a wide linear range of 0.01 ng/mL to 500 ng/mL. The results are comparable with those from commercial ELISA kit, indicating the developed immunosensor has great potential for future clinic use.