Study On Electrochemiluminescencebased Biosensor For The Detection Of β-amyloid

Alzheimer disease（AD）is a neurodegenerative disease with clinical symptoms of memory impairment,impairment of executive functions,reduced language and orientation skills.In recent years,studies show thatβ-amyloid（Aβ）can be used as a marker for Alzheimer’s disease and that Aβinteracts with a variety of proteins and ions.The aggregation of Aβhas irreversible damage to AD patients,and it is particularly important to achieve early detection of Aβ.With the continuous development of biosensors,a variety of sensors have been applied to the detection of Aβ.In this paper,three electrochemiluminescence（ECL）-based biosensors were constructed to achieve quantitative detection of Aβthrough specific recognition of Aβaptamers with Aβ.The main elements are as follows:1.HSA/g-C₃N₄ as an electrochemiluminescent probe for the detection ofβ-amyloidIn this work,two-dimensional graphite-like carbon nitride（g-C₃N₄）,as an effective electrochemiluminescence（ECL）substrate,was prepared by one step calcination method.And human serum albumin（HSA）could bind to g-C₃N₄to form HSA/g-C₃N₄ complexes after g-C₃N₄ was activated by using 1-ethyl-3-（3-（dimethylamino）propyl）carbodiimide hydrochloride and N-hydroxysuccinimide.After incubating with amyloid-β（Aβ）,Aβwas bound with HSA to form Aβ/HSA/g-C₃N₄ complexes via HSA-Aβinteraction.Subsequently,the thiol-functionalized DNA aptamer,as the specific recognition element for Aβpeptide,was assembled on the gold electrode via Au-S interaction.The forming Aβ/HSA/g-C₃N₄ complexes were then anchored on the electrode through the specific recognition between the target Aβand the aptamer.Under the optimized conditions,the present ECL sensor reveals a good linear response to Aβpeptide ranging from 10 f M to 100 n M with a detection limit of7.2 f M.This biosensor also shows good sensitivity and selectivity.2.Ratiometric electrochemiluminescence sensor based on g-C₃N₄-heme for detection ofβ-amyloidA nitrogen carbide-heme chloride（g-C₃N₄-heme）complex was prepared by hydrothermal synthesis as the signal molecule,and luminol was used as the internal standard molecule.A ratiometric biosensor was constructed to achieve the quantitative detection of Aβowing to the interaction between heme and Aβand the specific binding of the aptamer to Aβ.Firstly,luminol was loaded on the electrode and electropolymerized polyaniline（PANI）film was used to improve its electrochemical properties and protect luminol from shedding.The sulfhydryl modified Aβaptamer was modified to the sensing interface by gold nanoparticles.And the g-C₃N₄-heme-Aβcomplex could be trapped to the sensing interface for the sensitive detection of Aβ.It was found that the ECL signal showed a good linear relationship with the concentration of Aβin the range of Aβconcentration from 10 f M to 10 n M,and the detection limit was as low as 4.2 f M.The biosensor has high sensitivity and excellent selectivity.3.ECL-RET-based antifouling electrochemiluminescent sensor forβ-amyloid detectionAn antifouling biosensor based on electrochemiluminescent resonance energy transfer（ECL-RET）was constructed.Due to the resonance energy transfer that can occur between g-C₃N₄ and cadmium sulfide quantum dots（Cd S QDs）,the enhanced ECL platform for target molecules was achieved.Specifically,g-C₃N₄ nanosheets were loaded on the electrodes,and PANI films were electrodeposited to protect the g-C₃N₄nanosheets and improve the electrochemical properties of the electrodes.The carboxyl-modified antifouling peptide with recognition of the Aβoligomer（KKLVFF）was bound to the sensing interface via amide bonding.Meanwhile,the amino-modified Aβaptamers were compounded with Cd S QDs with abundant carboxyl groups on the surface to form aptamer-Cd S QDs.Aptamer-Cd S QDs were trapped onto the electrode surface using peptide specific binding to Aβ,so achieving sensitive ECL detection of Aβ.It was shown experimentally that the logarithm of Aβconcentration showed a good linear relationship with ECL intensity in the range of 0.1 p M to 100 n M,with a detection limit as low as 16.1 f M.