Qiao Xia

Chiral recognition of penicillamine enantiomers using hemoglobin and gold nanoparticles functionalized graphite-like carbon nitride nanosheets via electrochemiluminescence.

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 1.0×10-4M to 5.0×10-3M, and the detection limits of l-Pen and d-Pen were 3.1×10-5M and 3.3×10-5M (S/N=3) respectively. This work with high selectivity, stability and reproducibility may open a new door based on ECL to discriminate Pen enantiomers.

A biosensing interface based on Au@BSA nanocomposite for chiral recognition of propranolol

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.

Enantioselective recognition of ascorbic acid and isoascorbic acid on HS-β-cyclodextrin/gold nanoparticles/hollow carbon microspheres hybrid modified electrodes

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.

Chiral glutamic acid functionalized graphene: preparation and application

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 highly sensitive glutamic acid biosensor based on the determination of NADH enzymically generated by l -glutamic dehydrogenase

In this article, a sensitive and stereo-selective biosensor for L-glutamic acid (L-Glu) based on the electrochemiluminescence (ECL) of Ru(bpy)32+ has been designed by applying L-glutamic dehydrogenase (GLDH) for enzymatic generation of NADH in situ. The novel ECL Glu biosensor was prepared by immobilizing GLDH on the modified electrodes with Ru(bpy)32+–platinum nanoparticles (Ru–PtNPs) and reduced graphene oxide–multiwall carbon nanotubes–Nafion (rGO–MWCNT–Nf). Fourier transform infrared spectroscopy (FT-IR), electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM) and cyclic voltammetry (CV) were employed to investigate the characteristics of different materials. In addition, the ECL technology was adopted to explore the interactions between the prepared Glu biosensor and L- or D-Glu. A remarkable difference of ECL intensity was observed when the proposed biosensor interacted with L- and D-Glu, respectively, and good responses were obtained from L-Glu in a range from 1.0 × 10−7 M to 5.0 × 10−3 M with a low detection limit of 3.3 × 10−8 M (S/N = 3). The developed ECL biosensor showed satisfying sensitivity, selectivity, reproducibility and stability, therefore, it might provide a new perspective for the recognition and detection of L-Glu.

An ultrasensitive electrochemiluminescent D-alanine biosensor based on the synergetic catalysis of a hemin-functionalized composite and gold–platinum nanowires

Herein, an ultrasensitive and stereo-selective electrochemiluminescent (ECL) biosensor based on ECL signal amplification of luminol by the synergetic catalysis of a hemin-functionalized composite and gold–platinum nanowires (Au-PtNWs) has been designed for the detection of D-alanine (D-Ala). In the sensor design, D-amino acid oxidase (DAAO) was used to generate the ECL co-reactant (H2O2) for luminol in situ. The reduced graphene oxide-hemin-cysteine (rGO-H-Cys) composite and Au-PtNWs acted not only as amplification labels to amplify signals via synergetic catalysis, but also as an ideal nanocarrier to accelerate electron transfer. A great difference in ECL intensities toward D-Ala and L-Ala was obtained, and an obviously higher intensity was seen for D-Ala. Under optimal conditions, the ECL intensity had a linear relationship with the logarithm of the D-Ala concentration in the range from 1.0 × 10−9 to 5.0 × 10−3 M with a detection limit of 3.3 × 10−10 M (S/N = 3). This study provides a new method for the determination of D-Ala in food with high sensitivity, excellent selectivity, and good stability and reproducibility.