Figure 1.

(A) Scheme to show main types of biosensors to highlight aptasensor, classification of aptasensors based on its major components to highlight Gold Nanoparticles (AuNPs) based colorimetric aptasensors. (B) Generalized depiction of an aptamer library folding to form secondary structure in order to bind with high affinity target molecule to finally make aptamer-target complex. (C). Properties of Gold nanoparticles and calorimetry. (D) A generalized illustration on working principle of colorimetric aptasensor when bio-recognition element (BRE) combines with signal transduction element (STE) to make a colorimetric aptasensor to detect small molecular targets.