Light-Up Nonthiolated Aptasensor for Low-Mass, Soluble Amyloid-β₄₀ Oligomers at High Salt Concentrations

Abstract

Herein, a light-up nonthiolated aptasensor was developed for low-mass, soluble amyloid-β oligomers (LS-Aβ). Au nanoparticles (AuNP) were employed as colorimetric probes, and the nonthiolated aptamers (Apt) were adsorbed on AuNP surfaces, acting as binding elements for LS-Aβ. The aggregation of AuNPs was induced when Apt-modified AuNPs (Apt@AuNPs) were under high-salt conditions. However, upon the addition of LS-Aβ into the Apt@AuNP solution, the salt tolerance of the AuNPs was greatly enhanced. Further studies confirmed that the formed LS-Aβ-Apt complex attached onto the AuNP surfaces via interactions between LS-Aβ and Au, which led to electrostatic and steric stabilization of the AuNPs under high-salt conditions. On the basis of this outcome, a sensitive light-up nonthiolated aptasensor for LS-Aβ was achieved with a detection limit of 10.0 nM and a linear range from 35.0 to 700 nM in a 175 mM NaCl solution. Cerebrospinal-fluid (CSF) samples from healthy persons and Alzheimer's disease (AD) patients were successfully distinguished by using this proposed method. The concentrations of LS-Aβ in the CSF of AD patients were of nanomolar grade, but there was no detectable LS-Aβ in those of the healthy persons. This work provides a new insight into the interaction between Apt@AuNPs and Aβ and also develops a simple, rapid, highly selective and sensitive, and applicable method for LS-Aβ detection in real CSF samples, which is significant for the diagnosis of AD.

Practical aptamer-based assay of heavy metal mercury ion in contaminated environmental samples: convenience and sensitivity

“…So, the results show that the sensitivity is smaller when using a single wavelength and the sensitivity of using absorbance ratio to detect mercury ions is higher. In fact, many similar colorimetric analyses based on spectral shift change mostly use the absorbance ratio to quantify the target to be measured probably because of this [13,17,20]. Moreover, the experimental results (Fig.…”

“…In 2014, a sensitive method for visual chiral recognition of tryptophan was suggested based on the inherent chirality of AuNPs to distinguish Dand L-tryptophan [19]. In 2018 [20], the aptasensor was developed for amyloid-β40 oligomers (LS-Aβ40-O) detection and the aggregation of aptamer-modified AuNPs were regulated based on the interactions between LS-Aβ40-O and Au under high-salt conditions. Because of high molar absorption coefficient and simple preparation of AuNPs, the colorimetric analysis based on AuNPs shows certain sensitivity and simplicity.…”

“…Clearly, the unlabeled manner is welcomed. Unfortunately, in unlabeled aptamer-based AuNPs colorimetric assays, the target response to AuNPs must be induced by high concentration of salt [13,20]. The induction of high concentration salt means that the response of the target to the signal probe is not direct, but indirect.…”

Addressing Cu2+ interference for accurate aptamer-based biomarker determinations of Alzheimer’s disease

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