The HS-β-cyclodextrin/gold nanoparticles/hollow carbon microspheres (HS-β-CD/AuNPs/HCMS) hybrids were successfully synthesized and characterized via scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), Fourier transform infrared spectroscopy (FT-IR), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). A simple and reliable chiral sensing platform constructed from the prepared hybrids was used for enantioselective recognition of ascorbic acid (AA) and isoascorbic acid (IAA). Moreover, the stereoselectivity of HS-β-CD/AuNPs/HCMS to AA or IAA was investigated via differential pulse voltammetry (DPV). The results showed obvious differences in the peak currents of AA and IAA, demonstrating that this strategy could be employed to enantioselectively recognize AA and IAA. Under the optimum conditions, the chiral sensor exhibited an acceptable linear response to AA or IAA in the linear range of 1.0 × 10−4 to 5.0 × 10−3 M with a limit of detection of 1.7 × 10−5 M (S/N = 3). This approach provided a new available sensing interface to recognize and determine AA or IAA by electrochemical technology.

The nanocomposite (Au@BSA) which was synthesized using gold nanoparticles (AuNPs) and bovine serum albumin (BSA) was used as an electrochemical sensing layer for chiral recognition of propranolol (PRO). Scanning electron microscopy (SEM), energy dispersive X-ray (EDX) spectroscopy, transmission electron microscopy (TEM), ultraviolet-visible (UV-vis) spectroscopy and amperometric testing technique were employed to characterize the Au@BSA nanocomposite. Differential pulse voltammetry (DPV) and atomic force microscopy (AFM) were used to assess the enantioselective performance of the fabricated interface, and the optimal experimental conditions, such as acidity and incubation time were also discussed. The results showed that after the modified interface interacted with PRO enantiomers larger discrepancy was obtained from S-PRO, and linear electrochemical responses to PRO enantiomers were obtained from 1.0 × 10−5 to 5.0 × 10−3 mol L−1 with a detection limit of 3.3 × 10−6 mol L−1 (S/N = 3). To gain more information on the role of gold nanoparticles (AuNPs) and bovine serum albumin (BSA) in the chiral recognition of PRO enantiomers, the interface fabricated using AuNPs or BSA was also allowed to interact with PRO enantiomers, and no obvious signal discrepancy was obtained. The results suggested that only Au@BSA could be employed for the enantioselective recognition of PRO enantiomers.

•Electrochemiluminescent method was used to recognize penicillamine enantiomers.•Graphite-like carbon nitride nanosheets were applied in chiral recognition.•The strategy had acceptable sensitivity, stereoselectivity and stability.A new stable and stereo-selective electrochemiluminescence (ECL) interface has been designed for specific recognition of penicillamine (Pen) enantiomers by using hemoglobin (Hb) and gold nanoparticles functionalized graphite-like carbon nitride nanosheets composite (Au-g-C3N4 NHs) modified glassy carbon electrodes (Hb/Au-g-C3N4/GCE). The advantages of Hb as chiral selector and Au-g-C3N4 NHs as luminophore were perfectly displayed in this novel interface. The obviously different ECL intensity was exhibited after l-Pen and d-Pen adsorbed on Hb/Au-g-C3N4/GCE, and a larger response was observed on d-Pen/Hb/Au-g-C3N4/GCE. Under the optimum conditions, the developed ECL chiral sensor showed excellent analytical property for detection of Pen enantiomers in a linear range of 1.0 × 10−4 M to 5.0 × 10−3 M, and the detection limits of l-Pen and d-Pen were 3.1 × 10−5 M and 3.3 × 10−5 M (S/N = 3) respectively. This work with high selectivity, stability and reproducibility may open a new door based on ECL to discriminate Pen enantiomers.Illustration of the designed ECL chiral sensor based on hemoglobin and gold nanoparticles functionalized graphite-like carbon nitride nanosheets modified electrodes for discrimination of penicillamine enantiomers.

A sensitive, stable and stereoselective electrochemiluminescence (ECL) sensor has been designed to enantioselectively discriminate proline enantiomers by immobilizing Ru(bpy)32+–gold nanoparticles (Ru–AuNPs) and β-cyclodextrin–reduced graphene oxide (β-CD–rGO) on glassy carbon electrode. More Ru(bpy)32+ could be immobilized on the surface of electrode stably via preparing Ru–AuNPs and better stereoselectivity could be introduced to the sensor via the synthesis of β-CD–rGO. When the developed sensor interacted with proline enantiomers, obvious difference of ECL intensities towards L- and D-proline was observed, and a larger intensity was obtained from D-proline. As a result, ECL technique might act as a promising method to chiral recognition of amino acids enantiomers or chiral drugs.

A new nanocomposite of L-tryptophan functionalized graphene-supported platinum nanoparticles (L-Trp-rGO@PtNPs) was synthesized utilizing a facile ultrasonic method via π–π conjugate action between graphene-supported platinum nanoparticles and L-tryptophan (L-Trp) molecules. The prepared nanomaterial, which dispersed well in water and presented excellent conductivity, was modified on a glassy carbon electrode (L-Trp-rGO@PtNPs/GCE) for the chiral sensing of DOPA enantiomers. The immobilization process of L-Trp-rGO@PtNPs/GCE was characterized by cyclic voltammetry, electrochemical impedance spectroscopy, scanning electron microscopy, ultraviolet-visible (UV-vis) spectrometry and Raman spectroscopy. The electrochemical reactions of DOPA enantiomers were investigated via differential pulse voltammetry. The proposed electrochemical method showed excellent enantiospecificity for DOPA enantiomers and exhibited a stronger enantiospecificity for D-DOPA. In addition, the experimental parameters such as the concentration, the amount of L-Trp-rGO@PtNPs and the pH values were optimized. Under optimum conditions, the linear response ranges for the discrimination of DOPA were from 5.0 × 10−8 to 5.0 × 10−3 mol L−1 with a detection limit of 1.7 × 10−8 mol L−1 (S/N = 3).

Through the amide group of glutamic acid enantiomer and oxygen-containing groups in graphene oxide, chiral functionalized graphene nanosheets were synthesized, which showed good enantioselective recognition of 3,4-dihydroxyphenylalanine enantiomers. These chiral graphene hybrids should be novel promising materials for biological and pharmacological applications.

A simple and reliable chiral sensing platform for enantioselective recognition of lysine (Lys) enantiomers based on a nanostructured composite (NC) via the electrochemical impedance spectroscopy (EIS) technique was described. The NC has been successfully synthesized through covalent linkage among the semiconductor 3,4,9,10-perylenetetracarboxylic acid (PTCA), thionine (Thi) and chiral selector L-N-tert-butoxycarbonyl-O-benzylserine (L-BBSer). The stepwise synthesis process of the NC was characterized by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and EIS. The enantioselective interaction assay between NC modified glassy carbon electrode and lysine enantiomers relied on EIS technology. As a prototype example, good recognition results were obtained from the difference of electron transfer resistance (ΔRet), where ΔRetD was larger than ΔRetL and linear responses in ΔRet were found for Lys enantiomers ranging from 100 nM to 10 mM with a detection limit of 33 nM (S/N = 3). In addition, the results of analyzing another four amino acids revealed the specificity of the proposed sensor. The developed sensor with the advantages of simple preparation, long-term stability, good sensitivity and commendable selectivity, holds great potential application for the nanostructured composite adulterated with a chiral selector in chiral bio-electroanalysis.

A sensing interface with porous cluster-like nanocomposite films has been fabricated by electrochemical polymerization of L-cysteine on the surface of multi-walled carbon nanotubes (PLC/MWCNTs), and it was characterized by scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The nanocomposite films have been used to interact with tryptophan enantiomers (D- and L-Trp), and an obvious difference was achieved in the oxidation peak currents between D-Trp and L-Trp, suggesting that the PLC/MWCNTs could be used as a chiral selector to discriminate the Trp enantiomers. Under the optimum conditions, D-Trp and L-Trp presented a detection limit of 33 μM (S/N = 3), with a linear range of 1.0 × 10−4 M to 1.0 × 10−3 M. The simple method with rapid recognition, excellent stability and reproducibility provided a new perspective to recognize and determine Trp enantiomers.

A novel chiral sensing platform, employing a biomolecule-based nanocomposite prepared by calf thymus double stranded DNA, methylene blue and multiwall carbon nanotubes (DNA–MB–MWNTs), was utilized for the discrimination of quinine (QN) and quinidine (QD). The DNA-based nanocomposite, which could be used as an electrochemical sensing unit and chiral probe, was characterized by transmission electron microscopy (TEM), ultraviolet-visible spectroscopy (UV-Vis) and cyclic voltammetry (CV). After the proposed sensing platform interacted with QN and QD, a larger electrochemical signal was obtained from QD. The comparative experiments indicated that the proposed strategy not only simplified the fabrication processes but also enhanced the enantioselective interaction in chiral analysis. In addition, experimental factors such as acidity, interaction time and the concentration of enantiomers were investigated in regards to the effect on enantioselective interaction.

Simple and sensitive chiral interfaces were constructed by assembling L- or D-N-isobutyryl-cysteine (NIBC) on a gold electrode surface through an Au–S bond, and the two chiral interfaces were utilized to interact with L-methotrexate (L-Mtx). The surface characteristics and the process of interaction were explored via cyclic voltammetry (CV). The difference in peak current after L- and D-NIBC interacted with L-Mtx reached 525.3 μA, and a larger current difference was obtained from the L-NIBC interface, suggesting a stereoselective effect between L-Mtx and NIBC enantiomers. Therefore, the chiral NIBC interfaces could not only enhance the electron transfer of L-Mtx, but could also discriminate between NIBC enantiomers.

•Chiral amino acid polymer sensor was designed for chiral recognition.•The chiral discrimination was fast.•Poly-l-lysine displayed better recognition to DOPA enantiomers than poly-d-lysine.A fast electrochemical sensing to recognize 3,4-dihydroxyphenylalanine (DOPA) enantiomers was proposed based on poly-lysine enantiomers films as matrixes, which were electrodeposited on the surface of glass carbon electrodes via cyclic voltammetry (CV). Differential pulse voltammetry (DPV) and CV were employed to investigate the stereospecific recognition of DOPA enantiomers. The concentration of l-lysine, electro-polymerization cycles, pH and the effect of the temperature on the chiral discrimination were investigated to obtain optimization of the experimental parameters, and the Gibbs’ free energy (ΔG) was also discussed. The results showed that not only DOPA enantiomers could be recognized by poly-lysine matrix with the tendency of heterochiral interaction between poly-lysine and DOPA enantiomers, but also the largest discrimination responses were resided in poly-l-lysine matrix (PLL) and d-DOPA with the measurement range of 5.0 × 10−7 M to 8.0 × 10−3 M. The detection limit was 0.17 μM (S/N = 3), and the detection time only spent 75 s. The simple method with rapid recognition, good sensitivity and high stability provided a new perspective to recognize and determine DOPA enantiomers with fast, stabile, selective characteristics.

A chiral interface has been designed for specific recognition of carboxylic acids using multilayer architectures of β-cyclodextrin (β-CD) and methylene blue/reduce-graphene (MB@rGO) on glassy carbon electrodes. The advantages of β-CD as a chiral selector and MB@rGO composite as an electrochemical indicator were perfectly presented in this novel interface. It displayed good redox signal for sensing chiral target with high sensitivity and conductivity. Enormous signal differences were obtained after adsorption of target L isomer, due to strong blocking of the electron transfer process of methylene blue. Meanwhile mandelic acid was found to be the best chiral guest and obtained more effective chiral recognition.

An enantioselective membrane electrode based on vancomycin (Van) was proposed for the assay of penicillamine enantiomers. Cyclic voltammetry, electrochemical impedance spectroscopy, atomic force microscopy and UV-Vis spectra were employed to investigate the chiral recognition phenomenon. The results exhibited that the binding effect between D-penicillamine (D-Pen) and the proposed Van membrane electrode was obviously stronger than that of L-penicillamine (L-Pen). In addition, the amount of Van, the pH of the supporting electrolyte solution and the concentration of Pen enantiomers were systematically investigated and optimized. The association constant (K) was calculated to be 1.05 × 104 L mol−1 for D-Pen and 1.40 × 102 L mol−1 for L-Pen. The enantioselective concentration range of the proposed membrane electrode is 10−7 to 10−2 mol L−1. The results suggested that the chiral selective membrane has the potential to discriminate and determine chiral drugs in the pharmaceutical application of electrochemical analysis.

A reagentless method for the selective electrochemical discrimination of tryptophan (Trp) enantiomers has been developed by means of adsorbing human serum albumin (HSA) onto a methylene blue–multi-wall carbon nanotubes nanohybrid (MB–MWNTs) modified glassy carbon electrode (HSA/MB–MWNT/GCE). Cyclic voltammetry (CV) was employed to monitor the immobilization processes and the electrochemical behavior of the Trp enantiomers on the HSA/MB–MWNT/GCE. It was found that the newly developed electrode exhibited different interactions toward the Trp enantiomers, with a stronger binding effect obtained between HSA and L-Trp. The linear range of the biosensor was investigated from 1.0 × 10−1 to 1.0 × 10−8 mol L−1 with a detection limit of 3.3 × 10−9 mol L−1. In addition, the values of the enantioselectivity coefficient (α) and the association constant (k) were calculated. This work appears to provide a reference for the development of a reagentless electrochemical chiral biosensor and improves understanding of the high selectivity between biological molecules and chiral amino acids.

Chiral surfaces were obtained based on self-assembled monolayers of penicillamine enantiomers (L- or D-Pen) onto gold electrodes, and the enantioselective behavior was investigated by adsorbing hemoglobin (Hb) on the different chiral surfaces. Electrochemical methods, UV-vis and atomic force microscopy were adopted to monitor the protein adsorption. The properties of Hb adhesion on different chiral surfaces were further demonstrated by electrocatalytic responding to H2O2. The results showed that L-Pen had a higher dense adsorption to Hb than that of D-Pen. The Michaelis–Menten constants of the Hb/L-Pen/Au and Hb/D-Pen/Au sensors were first calculated to appeal to chiral recognition, the results showed that Hb/L-Pen/Au had a stronger catalytic ability, and further certified that Hb could adsorb on L-Pen assembled surfaces more easily. This work provided a promising reference for the investigation of chiral molecules.

As a natural chiral selector, bovine serum albumin (BSA) has been used to recognize penicillamine (Pen) enantiomers through electrochemical methods. The recognition and assay rely on the stereoselectivity of BSA embedded in ultrathin Al2O3 sol–gel film coated on the surface of glassy carbon electrode (BSA/GCE). The enantioselective interaction between Pen enantiomers and BSA was monitored by cyclic voltammetry and electrochemical impedance spectroscopy measurements, from which larger response signals were obtained from d-Pen. The factors influencing the performance of the modified biosensor were also investigated. The association constant (K) was calculated to be 1.93 × 104 L mol−1 for d-Pen and 1.20 × 103 L mol−1 for l-Pen. A good linear response was exhibited with the concentration of Pen enantiomers by BSA/GCE over the range of 1 × 10−8–1 × 10−1 mol L−1 with a detection limit of 3.31 × 10−9 mol L−1.

The enantioselective interaction between horseradish peroxidase (HRP) and arginine enantiomers was investigated by electrochemical methods through studying the electrocatalytic activity of H2O2 biosensor, which was obtained through l-arginine or d-arginine functionalized multi-walled carbon nanotubes (d-Arg-MWCNTs or l-Arg-MWCNTs) immobilizing horseradish peroxidase (HRP) on glassy carbon electrode. Cyclic voltammetric and chronoamperometry were used to characterize the properties of the biosensor. Under the optimal conditions, LAM-CS@HRP/dpAu/GCE biosensor showed better electrocatalytic activity to H2O2 compared to DAM-CS@HRP/dpAu/GCE and MWCNTs-CS@HRP/dpAu/GCE, implying that the different configurations of nanocomposites have different interactions with HRP. The currents of LAM-CS@HRP/dpAu/GCE biosensor had a linear relationship with the concentration of H2O2 in the range of 2.5 × 10− 6 to 2.9 × 10− 3 M with a detection limit of 8.3 × 10− 7 M (S/N = 3). For MWCNTs-CS-HRP/dpAu/GCE electrode, the calibration range of H2O2 was from 6.4 × 10− 4 to 2.9 × 10− 2 M and a detection limit of 2 × 10− 5 M (S/N = 3). For the case of DAM-CS@HRP/dpAu/GCE, there has a linear relationship with the concentration of H2O2 from 1.8 × 10− 5 to 2.6 × 10− 3 M and the detection limit is 6 × 10− 5 M (S/N = 3).Highlights► A new strategy is designed to enantioselectively recognize the chiral molecules. ► Chiral nanomaterials were used to construct hydrogen peroxide biosensors and good electrocatalytic response was achieved. ► This work provides a reference for the investigation of biocompatible materials.

A new strategy is established for detecting chiral amino acids based on the electron transfer from hemoglobin Fe(II) to Cu(II) in copper complexes of the amino acids. The sensor shows a highly selective recognition of arginine enantiomers.

Electrochemical reduction of tyrosine (Tyr) enantiomers on gold matrices in chlorhydric acid (HCl) solutions (0.01 M, pH 2.00) was performed. The characteristics of the Tyr reductive product adsorbed onto the electrode surface were studied using cycle voltammetry (CV). A significant redox peak of Tyr was observed from 0.70 to 1.60 V potential ranges. The compared investigation about electrocatalytic ability of Tyr enantiomers used gold matrices (bare gold electrode and electrodepositive gold nanoparticles modified glassy carbon electrode (AuNPs-GCE)). The Scanning Electron Microscope (SEM) images have been utilized to discuss the surface morphous. And the redox degree of l-Tyr on gold matrices was obviously much larger than that of d-Tyr. The mechanism for stereoselectivity in redox reactions of Tyr enantiomers on gold matrices had been analyzed. In addition, the AuNPs-GCE was used to determine Tyr enantiomers. Both l-Tyr and d-Tyr presented a sensitivity of 1.30 μM (S/N = 3), with two linear ranges from 4.00 μM up to 1.00 mM. This method proposed the possibility of using a nanostructured surface to discriminate and determine the chiral molecules in bio-electroanalytical application.

A new chiral biosensor has been fabricated by immobilizing γ-globulin on gold nanoparticles modified glassy carbon electrodes, which could recognize and detect mandelic acid (MA) enantiomers. Differential pulse voltammetry, quartz crystal microbalance, ultraviolet–visible spectroscopy, and atomic force microscopy were used to characterize the enantioselectivity. The results exhibited that γ-globulin modified electrode could enantioselectively recognize MA enantiomers, and larger response signals were obtained from R-MA. The factors influencing the performance of the resulting biosensor were investigated. The enantiomeric composition of R- and S-MA enantiomer mixtures could be determined by measuring the current responses of the sample. The developed electrodes have the advantages of simple preparation, good stability, and rapid detection.

Electrochemical enantioselective recognition of tryptophane (Trp) enantiomers in the presence of Cu(II) using l-cysteine (l-Cys) self-assembled gold electrode is described. The chiral recognition of Trp enantiomers was investigated via cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and quartz crystal microbalance (QCM). Time dependencies of the enantioselective interaction for the l-Cys modified electrodes with Trp enantiomers solutions in the presence of Cu(II) were also studied. The results showed that l-Cys had stronger interaction with d-Trp than l-Trp in the presence of Cu(II), and the discrimination was caused by the selective formation of Cu complexes with l-Cys and Trp enantiomers relying on the principle of chiral ligand exchange. The structure of the Cu complexes was optimized by the hybrid density functional theory (DFT) method. And the enantiomeric composition of l- and d-Trp was monitored by measuring the current responses of the sample.Graphical abstractThe electrochemical response before and after l-Cys-Au interacted with (A) l-Trp and (B) d-Trp in the presence of Cu(II).Highlights► A new strategy has been applied to chiral recognize tryptophane enantiomers. ► A larger difference of electrochemical response between l-Trp and d-Trp was observed. ► The structure of the putative Cu complex was optimized by the hybrid density functional theory (DFT) method. ► This work is expected to give interesting insight for the research of various chiral drugs.

A simple and fast strategy for stereospecific redox reaction is proposed using glutamic acid enantiomer electropolymerized films. The mechanism of enantioselectivity on the electropolymerized films has been explored.

An obviously enantioselective strategy for the recognition of mandelic acid (MA) enantiomers in the presence of Zn(II) ions on a l-cysteine (l-Cys) self-assembled gold electrode is described. The high recognition of MA was evaluated via electrochemical impedance spectroscopy and cyclic voltammetry. After the modified electrode interacted with R- or S-MA solution containing Zn(II) ions for 10 min, larger electrochemical response signals were observed for R-MA. Time dependencies of the enantioselective interaction for the modified electrode with the solitary Zn(II) solution and MA enantiomers solutions containing Zn(II) were also investigated. The results showed that the enantioselective recognition was caused by the selective formation of Zn complex with l-Cys and MA enantiomers. In addition, the enantiomeric composition of R- and S-MA enantiomer mixtures could be monitored by measuring the current responses of the sample.

•PTCA-MWCNTs achieved signal amplification and exhibited good dispersibility.•Large immobilization amount of DAAO has been achieved by PTCA-MWCNTs.•The designed sensor achieved high selectivity and sensitivity of d-alanine.With an excellent electron-transfer ability of 3,4,9,10-perylene tetracarboxylic acid functionalized multi-walled carbon nanotubes (PTCA-MWCNTs), and successful maintenance of d-amino acid oxidase (DAAO) activity by the protection of bovine serum albumin (BSA) and glycerol, a signal amplification biosensor for chiral recognition of d-alanine (d-Ala) has been designed. PTCA worked as redox probe due to its self-derived redox activity. The proposed biosensor was characterized by scanning electron microscopy (SEM), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). After the biosensor interacting with d-alanine and l-alanine respectively, a larger current response was obtained from d-alanine. The linear range of the biosensor under the optimum working conditions was investigated by current-time response in successive addition of d-Ala from 1.0 × 10−8 to 1.0 × 10−3 M with a lower detection limit of 3.3 × 10−9 M (S/N = 3). Possible explanations for substrate specificity of the biosensor were discussed. This method showed high sensitivity and selectivity for chiral recognition of d-alanine. It also exhibited good stability, repeatability and reproducibility. The proposed biosensor was applied for real sample measurement.Illustration of the proposed electrochemical biosensor based on the 3,4,9,10-perylene tetracarboxylic acid functionalized multi-walled carbon nanotubes and d-amino acid oxidase for chiral recognition of d-alanine.Download full-size image

Through the amide group of glutamic acid enantiomer and oxygen-containing groups in graphene oxide, chiral functionalized graphene nanosheets were synthesized, which showed good enantioselective recognition of 3,4-dihydroxyphenylalanine enantiomers. These chiral graphene hybrids should be novel promising materials for biological and pharmacological applications.

A new strategy is established for detecting chiral amino acids based on the electron transfer from hemoglobin Fe(II) to Cu(II) in copper complexes of the amino acids. The sensor shows a highly selective recognition of arginine enantiomers.

A reagentless method for the selective electrochemical discrimination of tryptophan (Trp) enantiomers has been developed by means of adsorbing human serum albumin (HSA) onto a methylene blue–multi-wall carbon nanotubes nanohybrid (MB–MWNTs) modified glassy carbon electrode (HSA/MB–MWNT/GCE). Cyclic voltammetry (CV) was employed to monitor the immobilization processes and the electrochemical behavior of the Trp enantiomers on the HSA/MB–MWNT/GCE. It was found that the newly developed electrode exhibited different interactions toward the Trp enantiomers, with a stronger binding effect obtained between HSA and L-Trp. The linear range of the biosensor was investigated from 1.0 × 10−1 to 1.0 × 10−8 mol L−1 with a detection limit of 3.3 × 10−9 mol L−1. In addition, the values of the enantioselectivity coefficient (α) and the association constant (k) were calculated. This work appears to provide a reference for the development of a reagentless electrochemical chiral biosensor and improves understanding of the high selectivity between biological molecules and chiral amino acids.

A simple and fast strategy for stereospecific redox reaction is proposed using glutamic acid enantiomer electropolymerized films. The mechanism of enantioselectivity on the electropolymerized films has been explored.

An enantioselective membrane electrode based on vancomycin (Van) was proposed for the assay of penicillamine enantiomers. Cyclic voltammetry, electrochemical impedance spectroscopy, atomic force microscopy and UV-Vis spectra were employed to investigate the chiral recognition phenomenon. The results exhibited that the binding effect between D-penicillamine (D-Pen) and the proposed Van membrane electrode was obviously stronger than that of L-penicillamine (L-Pen). In addition, the amount of Van, the pH of the supporting electrolyte solution and the concentration of Pen enantiomers were systematically investigated and optimized. The association constant (K) was calculated to be 1.05 × 104 L mol−1 for D-Pen and 1.40 × 102 L mol−1 for L-Pen. The enantioselective concentration range of the proposed membrane electrode is 10−7 to 10−2 mol L−1. The results suggested that the chiral selective membrane has the potential to discriminate and determine chiral drugs in the pharmaceutical application of electrochemical analysis.

Chiral surfaces were obtained based on self-assembled monolayers of penicillamine enantiomers (L- or D-Pen) onto gold electrodes, and the enantioselective behavior was investigated by adsorbing hemoglobin (Hb) on the different chiral surfaces. Electrochemical methods, UV-vis and atomic force microscopy were adopted to monitor the protein adsorption. The properties of Hb adhesion on different chiral surfaces were further demonstrated by electrocatalytic responding to H2O2. The results showed that L-Pen had a higher dense adsorption to Hb than that of D-Pen. The Michaelis–Menten constants of the Hb/L-Pen/Au and Hb/D-Pen/Au sensors were first calculated to appeal to chiral recognition, the results showed that Hb/L-Pen/Au had a stronger catalytic ability, and further certified that Hb could adsorb on L-Pen assembled surfaces more easily. This work provided a promising reference for the investigation of chiral molecules.

Simple and sensitive chiral interfaces were constructed by assembling L- or D-N-isobutyryl-cysteine (NIBC) on a gold electrode surface through an Au–S bond, and the two chiral interfaces were utilized to interact with L-methotrexate (L-Mtx). The surface characteristics and the process of interaction were explored via cyclic voltammetry (CV). The difference in peak current after L- and D-NIBC interacted with L-Mtx reached 525.3 μA, and a larger current difference was obtained from the L-NIBC interface, suggesting a stereoselective effect between L-Mtx and NIBC enantiomers. Therefore, the chiral NIBC interfaces could not only enhance the electron transfer of L-Mtx, but could also discriminate between NIBC enantiomers.