Polyadenine-mediated Immobilization of Aptamers on a Gold Substrate for the Direct Detection of Bacterial Pathogens

Abstract

Nucleic acid aptamers have been widely used as synthetic probes for bioanalytical applications. Herein, we carried out a detailed study on the immobilization of a series of aptamers ranging from 37 to 88 bases, which are specific to either Escherichia coli (E. coli) or Staphylococcus aureus (S. aureus), on a planar gold substrate via a polyadenine-mediated immobilization method. The resultant surfaces were characterized by both surface plasmon resonance spectroscopy (SPR) and X-ray photoelectron spectroscopy. The results clearly show that the aptamer solution at a lower ionic strength gives rise to a higher lateral density of the aptamer when compared to that at a higher ionic strength. The SPR aptasensors are then employed for detecting their corresponding bacteria (i.e., E. coli and S. aureus, respectively). The data indicate that the SPR aptasensor with a higher density of aptamer exhibits a better capture of target bacteria.

Strategies for Surface Design in Surface Plasmon Resonance (SPR) Sensing

“…Another approach is the direct attachment of a biomolecule of already modified thiol group at one end to the gold chip. Wang et al [ 27 ] studied the direct attachment of a specific aptamer for detecting Escherichia coli ( E. coli ) and Staphylococcus aureus ( S. aureus ). They studied the thickness of the immobilized short-chain aptamer in the presence of different concentrations of NaCl and observed that at a lower concentration, the aptamer thickness increased.…”

Recent Advancements in Aptamer-Based Surface Plasmon Resonance Biosensing Strategies

“…Notably most small molecules bind aptamers only with the one-site binding configuration because there is no room for the aptamer to interact with a second molecule [60]. Therefore, many SPR aptasensors have been developed based on this direct strategy [61][62][63][64][65]. For example Wu et al and Ashley et al immobilized a biotin-modified aptamer probe on an avidin modified chip through streptavidin-biotin interaction for the detection of aflatoxin in vin egar and lysozyme in milk [66,67].…”

Aptasensors for Staphylococcus aureus Risk Assessment in Food

“…Wang’s group assembled aptamers on a gold substrate mediated by polyadenine. The designed aptasensors can only show an SPR signal at concentrations of S. aureus greater than 1 × 10 6 CFU/ml ( Wang et al, 2019 ). The aptamer was applied to detect S. aureus in milk by resonance combination with localized surface plasmon resonance (LSPR).…”