Common materials, extraordinary behavior: An ultrasensitive and enantioselective strategy for D-Tryptophan recognition based on electrochemical Au@p-L-cysteine chiral interface

Construction of CS/BSA multilayers for electrochemical recognition of tryptophan enantiomers

Electrochemical chiral sensor for recognition of amino acid enantiomers with cyclodextrin-based microporous organic networks

The paper reported that a simple chiral selective interface constructed by (1R, 2R)-2-amino-1, 2-diphenyl ethanol had been developed to discriminate tryptophan enantiomers. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were used for the characteristic analysis of the electrode. The results indicated that the interface showed stable and sensitive property to determine the tryptophan enantiomers. Moreover, it exhibited the better stereoselectivity for L-tryptophan than that for D-tryptophan. The discrimination characteristics of the chiral selective interface for discriminating tryptophan enantiomers, including the response time, the effect of tryptophan enantiomers concentration, and the stability, were investigated in detail. In addition, the chiral selective interface was used to determine the enantiomeric composition of L- and D-tryptophan enantiomer mixtures by measuring the relative change of the peak current as well as in pure enantiomeric solutions. These results suggested that the chiral selective interface has the potential for enantiomeric discrimination of tryptophan enantiomers.

Electrochemical recognition of tryptophan enantiomers based on the self-assembly of polyethyleneimine and chiral peptides

A sensitive electrochemical method was explored for chiral recognition of 3,4-dihydroxyphenylalanine (DOPA) enantiomers based on immobilization of β-cyclodextrin (β-CD) onto the nanocomposite comprising multiwalled carbon nanotubes (MWCNTs) and ionic liquid (IL) 1-butyl-3-methylimidazolium hexafluorophosphate (BIMIMPF6) modified glassy carbon electrode (β-CD/MWCNTs-IL/GCE). The combination of ionic liquid and carbon nanotubes could create unique nanomaterials which facilitated the electron transfer. In addition, β-CD was brought in to act as the chiral selector for DOPA enantiomers recognition. The immobilization process of β-CD/MWCNTs-IL/GCE was monitored by cyclic voltammetry, electrochemical impedance spectroscopy, and scanning electron microscopy. The chiral interface (β-CD/MWCNTs-IL/GCE) was employed to discriminate DOPA enantiomers via differential pulse voltammetry. The results indicated that the proposed sensor exhibited a stronger electrochemical response toward D-DOPA over the linear range from 4.0 × 10−3 to 4.0 × 10−9 mol L−1 and the detection limit was 1.2 × 10−9 mol L−1 (S/N = 3). This work provided an available platform for enantioselective recognition of DOPA enantiomers based on the nanocomposite.

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 (Fe3O4@PDA/Cu xO) as electrode units. d-Cys-Cu2+-d-Cys formed in the presence of cysteine exhibits strong stability and a shielding effect on the redox current of indicator Cu2+, 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-1 cm-2 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.

A composite chiral interface (BSA-MB-MWCNTs) was prepared from bovine serum albumin (BSA), methylene blue (MB), and multi-walled carbon nanotubes (MWCNTs) for chiral recognition of amine enantiomers (1S, 2S)-N,N'-dimethyl-1,2-cyclohexanediamine and (1R, 2R)-N,N'-dimethyl-1,2-cyclohexanediamine. The BSA-based composite was characterized by field emission scanning electron microscopy (FESEM) and ultraviolet-visible spectroscopy (UV-Vis). The electrochemical responses towards the two enantiomers were analyzed via cyclic voltammetry (CV), electrochemical AC impedance method (EIS), and differential-pulse voltammetry (DPV). The experimental results showed that the combination of MWCNTs and BSA could effectively improve the overall identification efficiency, and the peak current displayed by the S-enantiomer is larger, indicating that the prepared chiral surface has stronger interaction with the R-enantiomer. Under optimized condition, the current value of the oxidation peak of the chiral modified electrode showed a good linear relationship towards the amine concentration in the range of 5.0 × 10-3 to 5.0 × 10-5 mmol·L-1 . The proposed electrochemical chiral interface is easy to handle and provides a promising electrochemical sensing platform that can be used to identify chiral amine enantiomers.

Construction of efficient and convenient sensors for recognition of chiral enantiomers is of much significance in the field of electrochemistry and life sciences. Herein, we designed an effective chiral interface for the successful identification of tryptophan (Trp) enantiomers by electrodepositing l-cysteine on the surface of glass carbon electrode modified with carbon black. The structure and morphology of the prepared sensor was characterized by scanning electron microscopy (SEM) and electrochemical methods. Compared with l-tryptophan (L-Trp), the sensor exhibits favorable chiral recognition towards D-tryptophan (D-Trp) with a separation coefficient of 2.50. Compared with existing studies on electrochemical chiral recognition of Trp enantiomers, our designed chiral platform boasts of a wider linear range (1.0–1400.0 μM) and lower limits of detection thus, 0.33 μM and 0.45 μM for L-Trp and D-Trp respectively. In addition, the proposed sensor has the capacity to recognize chiral molecules in Trp isomers mixture and the potential for the identification of other amino acids.

Based on N-doped carbon dots/β-cyclodextrin nanocomposites modified glassy carbon electrodes (N-CDs/β-CD/GCE), an effective electrochemical sensor for enantioselective recognition of tryptophan (Trp) enantiomers was developed by differential pulse voltammograms (DPVs). Fluorescent N-CDs were synthesized through a hydrothermal method and characterized by spectroscopic approaches. The N-CDs/β-CD nanocomposites were efficiently electrodeposited on the surface of GCE through C–N bond formation between N-CDs and electrode. The obtained N-CDs/β-CD/GCE was characterized by multispectroscopic and electrochemical methods. Such N-CDs/β-CD/GCE generated a significantly lower Ip and more negative Ep in the presence of l-Trp in DPVs, which was used for the enantioselective recognition of Trp enantiomers. The N-CDs/β-CD nanocomposites showed different binding constants for tryptophan enantiomers, and they further selectively bonded with l-Trp to form inclusion complexes. This N-CDs/β-CD/GCE combined advantages of N-CDs with strong C–N binding ability and β-CD with specific recognition of Trp enantiomers to fabricate a novel sensing platform for enantioselective recognition of Trp enantiomers. This strategy provided the possibility of using a nanostructured sensor to discriminate the chiral molecules in bio-electroanalytical applications.

Highly enantioselective electrochemical sensing based on helicoid Au nanoparticles with intrinsic chirality

An electrochemical 3D platform using poly (alizarin red S) and magnetite nanoparticles for rapid recognition and determination of tryptophan enantiomers in whole blood samples

Determination of functionalized gold nanoparticles incorporated in hydrophilic and hydrophobic microenvironments by surface modification of quartz crystal microbalance

Poly(glutathione disulfide)-poly(L-lysine) (PGSSG-PLY) multilayer films prepared by electropolymerization via cyclic voltammetry were constructed as a new chiral interface for recognition of ascorbic acid (AA) and isoascorbic acid (IAA). The morphology of the films was characterized by scanning electron microscopy (SEM), the electrochemical behaviors of the films were studied via chemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). Meanwhile, differential pulse voltammetry (DPV) was used to study the interactions between PGSSG-PLY modified glassy carbon electrodes and AA or IAA. A strong interaction with AA was observed on the chiral interface. The results proved that PGSSG film could amplify eletrochemical signal, while PLY film could provide more recognition sites to discriminate AA and IAA enantiomers with satisfying recognition efficiency. The possible formation of the films on the electrode surface was described. And the influences of electropolymerization cycles and pH to the recognition process were explored. Under the optimum conditions, the method showed an acceptable linear response to AA and IAA in a range from 1.0 × 10−7 to 5.0 × 10−3 M with a low detection limit of 3.3 × 10−8 M (S/N = 3). The modified electrodes also displayed good stability and reproducibility.

A chiral sensing platform was constructed via adsorptive functionalization of ammonium persulfate doped polyaniline (APS-DPANI) with bovine serum albumin (BSA). The novelty of this work is the construction of such chiral interface with adsorption principle. The material has been characterized by scanning electron microscope, Fourier transform infrared and X-ray photoelectron spectroscopy, and thermogravimetric and water contact angle analyses. It displayed considerable stability in multi-run cyclic voltammetric scanning. Moreover, the superior conductivity of APS-DPANI and the decent binding ability of BSA endowed this sensing platform with an excellent recognition effect for tryptophan (Trp) enantiomers in the differential pulse voltammetry (DPV) test. The recognition was highly reproducible, and the detection limits for L- and D-isomer were 0.071 and 0.0478 mM, respectively.

Chiral recognition of tryptophan enantiomers using chitosan-capped silver nanoparticles: Scanometry and spectrophotometry approaches