Multiple signal amplification strategies for ultrasensitive label-free electrochemical immunoassay for carbohydrate antigen 24-2 based on redox hydrogel

Publication date: 15 May 2017
Source:Biosensors and Bioelectronics, Volume 91
Author(s): Zhongxue Tang, Yuanyuan Fu, Zhanfang Ma
In this work, multiple signal amplification strategies for ultrasensitive label-free electrochemical immunoassay for carbohydrate antigen 24-2 (CA242) were developed using redox sodium alginate-Pb²⁺-graphene oxide (SA-Pb²⁺-GO) hydrogel. The SA-Pb²⁺-GO hydrogel was synthesised by simply mixing SA, GO, and Pb²⁺ and then implemented as a novel redox species with a strong current signal at −0.46V (vs. Ag/AgCl). After the three-dimensional and porous SA-Pb²⁺-GO hydrogel was in situ generated on a glassy carbon electrode (GCE), chitosan was adsorbed on the obtained electrode to further enrich Pb²⁺. When chitosan-Pb²⁺/SA-Pb²⁺-GO/GCE was incubated with anti-CA242 using glutaraldehyde and blocked by bovine serum albumin, the immunoassay platform for CA242 was obtained. Owing to the addition of GO, the obtained conductive SA-GO/GCE was beneficial for signal amplification. After incubating SA-GO/GCE with excessive amounts of Pb²⁺, the resistance of SA-Pb²⁺-GO/GCE further decreased and a strong redox signal was obtained. The chitosan fixed by electrostatic adsorption resulted in further adsorption of Pb²⁺, behaving as further amplifying the signal and improving conductivity. In this case, multiple signal amplification strategies were involved in the proposed immunosensor for the ultrasensitive detection of CA242. Under the optimal conditions, the proposed immunosensor exhibited a wide linear range from 0.005UmL⁻¹ to 500UmL⁻¹ with an ultralow detection limit of 0.067mUmL⁻¹. In comparison to previous works, the sensitivity of this method was 32.98μA (log10CCA242)⁻¹, which was a five-fold increase from the previous works.



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