Components of the Sensing Layer

Sensing layer Transduction approach Electrochemical Analyte technique Sample Comment Reference 

Au-BSA-Ag Ab-HRP Amperometry Clenbuterol in TMB/HjOj solution Livestock urine Competitive assay Sixteen electrodes [55] 

Au/CHIT/Fe3 04/ PAMAM/ AuNPs/Ag/HRP HRP- MWCNTs- Ab CV in H2O2 Salbutamol Competitive assay [52] 

Au/AuNPs- PAAD/BSA-Ag Ab-HRP DPV in o-PD Brevetoxins and H2O2 Molluscs Au-PAADs are generated by chemical reduction of HAuCl4-dendrimer (generation 4.0) Competitive assay [116] 

AU/DT2ATG Abj-HRP CV/EIS in Anti-tTG [Fe(CN)e]3- - amperome-try (TMB and HjOj) Blood serum samples of celiac patients DT2 and Ab by EDC/NHS chemistry DT2 is a long-chain, carE)oxylic-terminated bipodal alkanethiol PEG groups in alkanethiol chain were effective in eliminating MSB [123] 

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Not only the components of the sensing layer are important but also the strategies of integration between them and with the primary transducer are of paramount importance. Passive adsorption is one of the simplest and most frequently used immobilization techniques, based mainly on weak noncovalent bindings. However, random protein orientation can lead to the obstruction of functional binding sites and can result in the loss of affinity or activity. Thus, covalent attachment of a protein layer on a chemically functionalized surface produces a more stable layer with correct orientation. This influences sensitivity and specificity of the immunoassay as density of immobilized protein can be better controlled and nonspecific adsorption may be decreased [155]. On the other hand, covalent procedures are usually longer and more tedious and are less justified when disposable surfaces can be used. 

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