Rational Design of Magnetic Micronanoelectrodes for Recognition and Ultrasensitive Quantification of Cysteine Enantiomers

Abstract

Driven by the urgent need for recognition and quantification of trace amino acids enantiomers in various biologic samples, we demonstrate for the first time an ultrasensitive electrochemical chiral biosensor for cysteine (Cys) based on magnetic nanoparticles (FeO@PDA/Cu O) as electrode units. d-Cys-Cu-d-Cys formed in the presence of cysteine exhibits strong stability and a shielding effect on the redox current of indicator Cu, which can be used to quantify and recognize d-Cys by square wave voltammetry. Simultaneous detection of d-Cys and homocysteine (Hcy) is achieved in the presence of other amino acids, demonstrating an excellent selectivity of the sensor. Moreover, aided by the enrichment treatment effect of magnetic micronanoelectrodes, an ultrahigh sensitivity up to 102 μA μM cm was achieved, the detection limit is reduced to picomolar level (83 pM) for d-Cys and can be used for the recognition of cysteine enantiomers. The proposed method has been verified by real sample analysis with satisfactory results. The results highlight the feasibility of our proposed strategy for magnetic micronanoelectrode sensor, electrochemical recognition, and quantification of d-Cys, which can be more broadly applicable than that with traditional electrode structures and further advance the field of electrochemical sensors.

Electrochemical Amino Acid Sensing: A Review on Challenges and Achievements

“…This revealed that both the nature and structure of modifier should be wisely tuned to reach the optimum performance for this sensor. Iron compounds, after copper ones, are by far the most studied non-noble-metal-based modifiers in cysteine electroanalysis [ 56 , 78 , 112 , 113 , 114 , 115 , 116 , 117 , 118 , 119 , 120 , 121 , 122 ]. Duan et al [ 112 ] developed an outstanding sensor taking advantage of extreme stability, excellent electrocatalytic activity and the redox properties of Prussian blue (PB, Fe 4 [Fe(CN) 6 ] 3 ).…”

“…Though the preparation process of this sensor was rather complex ( Figure 6 A), the resultant sensor was extremely sensitive and selective. In another approach, Zhou et al [ 113 ] proposed a magnetic GCE modified with a Fe 2 O 3 /polydopamine/Cu 2 O composite to detect cysteine and reported an ultra-sensitive sensor with an outstanding LOD of 83.0 pM (83.0 × 10 −15 mol L −1 ). In contrast to the work of Duan et al [ 112 ], in this sensor, the iron oxide moiety is used, mainly because of its magnetic properties, and iron oxide is not directly involved in electrochemical signal production because Cu 2+ ions undertake this task.…”

Artificial Chiral Probes and Bioapplications

“…For d-Cys, the LOD was as low as 83 × 10 −12 m, and this strategy could be used to identify and detect d-Cys in clinical samples. [107] [101] Copyright 2010, Nature Publishing Group. D-G) Reproduced with permission.…”

“…Based on Fe 3 O 4 @polydopamine/Cu x O, Song et al developed an electrochemical chiral sensor for cysteine (Cys). For d ‐Cys, the LOD was as low as 83 × 10 −12 m , and this strategy could be used to identify and detect d ‐Cys in clinical samples . Zhang et al reported an electrochemical chiral sensing platform based on composites of AuNP‐methylene blue multiwalled carbon nanotubes (AuNP–MB–MWCNTs) and calf thymus double‐strand DNA (ctDNA) and used this platform to recognize enantiomers of propranolol (PRO).…”

Dual-Signal Electrochemical Enantiospecific Recognition System via Competitive Supramolecular Host–Guest Interactions: The Case of Phenylalanine

“…Recently, electrochemical chiral recognition has received considerable attention, due to the many advantages they offer, such as low cost, fast response, inexpensive instrument, and facile miniaturization. − For instance, Kong et al demonstrated that the self-assemblies composed of diphenylalanine and oxalic acid with different charging states possess quite different chiral recognition capabilities toward tryptophan isomers. In another interesting report, the researchers constructed an electrochemical chiral sensing platform for d -/ l -tryptophan, d -/ l 3,4-dihydroxyphenylalanine, and (R)-/(S)-propranolol by electrodepositing R/S-2′-hydroxymethyl-3,4-ethylenedioxythiophene on the electrode surface .…”