Figure 4.

Selected examples of direct signal immunosensors based on electroactive label conjugates. (A) Scheme representing the construction of an immunosensor based on ferrocene monocarboxylic acid-tagged anti-VEGF antibodies immobilized on carbon fibre microelectrodes using Jeffamine cross-linker (reprinted with permission from Prabhulkar et al. [50]). (B) Procedure of immunosensor fabrication based on a polyaniline-modified gold surface employing covalently-bound ferrocene-labelled antibodies (reprinted with permission from Dou et al. [51]. (C) Scheme of immunosensor based on a glassy carbon electrode modified with titania sol-gel and horseradish peroxidase (HRP)-labelled human serum chorionic gonadotrophin (HCG) antibody (reprinted with permission from Chen et al. [52]). (D) Schematic illustration of immunosensor array based on a biopolymer/sol-gel membrane and HRP-labelled antibody-modified gold nanoparticles (reprinted with permission from Wu et al. [53].