Highly Efficient versus Null Electrochemical Enantioselective Recognition Controlled by Achiral Colinkers in Homochiral Metal-Organic Frameworks

Chiral materials capable of electrochemical enantiomeric recognition are highly desirable for many applications, but it is still very challenging to achieve high recognition efficiency for lack of the knowledge of structure-property relationships. Here, we report the completely distinct enantiomeric recognition related to slightly different achiral colinkers in isomorphic homochiral metal-organic frameworks with the same chiral linker. Cu-TBPBe, for which the achiral colinker has two pyridyl rings connected by ─CH═CH─, shows excellent enantioselectivity and sensitivity for electrochemical recognition of l-tryptophan (Trp) with a detection limit of 3.16 nM. The l-to-d ratio of differential pulse voltammetric (DPV) currents reaches 53, which is much higher than the values (2-14) reported for previous electrochemical sensors. By contrast, Cu-TBPBa, in which the achiral colinker has -CH₂-CH₂- between pyridyl rings, is incapable of discrimination between l-Trp and d-Trp. Structural and spectral analyses suggest that the achiral conjugated colinker and the chiral moieties around it cooperate to produce a chiral pocket in favor of enantioselective adsorption through multiple hydrogen-bonding and π-π stacking interactions. The work demonstrated that Cu-TBPBe can be used to fabricate reliable electrochemical sensors for ultrasensitive quantification of Trp enantiomers in racemic mixtures and in complex biological systems such as urine. The work also highlights that an achiral coligand can be of vital importance in determining enantiomeric discrimination, opening up a new avenue for the design of chiral sensing materials.

Using nanostructured carbon black-based electrochemical (bio)sensors for pharmaceutical and biomedical analyses: A comprehensive review

The outstanding electronic properties of carbon black (CB) and its economic advantages have fueled its application as nanostructured electrode material for the development of new electrochemical sensors and biosensors. CB-based electrochemical sensing devices have been found to exhibit high surface area, fast charge transfer kinetics, and excellent functionalization. In the present work, we set forth a comprehensive review of the recent advances made in the development and application of CB-based electrochemical devices for pharmaceutical and biomedical analyses - from quantitative monitoring of drug formulations to clinical diagnoses - and the underlying challenges and constraints that need to be overcome. We also present a thorough discussion about the strategies and techniques employed in the development of new electrochemical sensing platforms and in the enhancement of their analytical properties and biocompatibility for anchoring active biomolecules, as well as the combination of these sensing devices with other materials aiming at boosting the performance and efficiency of the sensors.

Electrochemical sensing of dobutamine, paracetamol, amlodipine, and daclatasvir in serum based on thiourea SAMs over nano-gold particles-CNTs composite

We report in this work a one-step approach for the formation of self-assembled monolayers (SAMs) from thiourea (TU) over gold nanoparticles dispersed in carbon nanotubes (CNTs-Aunano). The fabrication of the...

Green synthesis of nonprecious metal-doped copper hydroxide nanoparticles for construction of a dopamine sensor

Background: Copper oxide nanoparticles doped with nonprecious metal species (Ni and Mn) were synthesized. Method: A glassy carbon electrode (GCE) was modified by drop-casting of nanostructure suspensions, constructing Ni:Cu(OH)₂/GCE, Mn:Cu(OH)₂/GCE and Cu(OH)₂/GCE. Results: The voltammetric oxidation of dopamine (DA) by the constructed electrodes confirmed that the electrocatalytic oxidation of DA is a reversible, pH-dependent, diffusion-controlled process; the best response was obtained by Mn:Cu(OH)₂/GCE. A sensitive calibration graph (0.664 μA/μM) was produced for DA in the concentration range of 0.3-10.0 μM, with a detection limit of 79 nM using Mn:Cu(OH)₂/GCE. Conclusion: The Mn:Cu(OH)₂/GCE possessed an accurate response toward DA with an acceptable selectivity, stability and antifouling effect, revealing the applicability of the Mn:Cu(OH)₂/GCE for DA analysis in biological samples.

Facile Synthesis of Hollow Carbon Nanospheres by Using Microwave Radiation

Carbon-based nanomaterials have attracted much research interest in recent years due to their excellent chemical and physiological properties such as chemical stability, low cytotoxicity, and biocompatibility. The traditional methods to prepare hollow carbon nanospheres require complicated instrumentation and harsh chemicals, including high-temperature furnace, gas inlets, and hydrogen fluoride etching. Herein, we propose a new strategy to prepare hollow carbon nanospheres in a simple and fast manner by using microwave radiation. Polypyrrole-coated silica core-shell nanoparticles (SiO2@PPy NPs) were firstly prepared and subsequently processed by microwave radiation and aqueous alkaline solution to obtain the hollow carbon nanospheres. This facile method has potent potential to be utilized in the preparation of different types of hollow carbon nanospheres with various microstructure and elemental composition.

Design and fabrication of an electrochemical aptasensor using Au nanoparticles/carbon nanoparticles/cellulose nanofibers nanocomposite for rapid and sensitive detection of Staphylococcus aureus

Since that pathogenic bacteria are major threats to human health, this paper describes the fabrication of an effective and durable sensing platform based on gold nanoparticles/carbon nanoparticles/cellulose nanofibers nanocomposite (AuNPs/CNPs/CNFs) at the surface of glassy carbon electrode for sensitive and selective detection of Staphylococcus aureus (S. aureus). The AuNPs/CNPs/CNFs nanocomposite with the high surface area, excellent conductivity, and good biocompatibility was used for self-assembled of the thiolated specific S. aureus aptamer as a sensing element. The surface morphology of AuNPs/CNPs/CNFs nanocomposite was characterized with field emission scanning electron microscopy (FESEM), energy dispersive spectroscopy (EDS), dynamic light scattering (DLS) and ultraviolet-visible (UV-Vis) spectrophotometric methods. Each aptasensor modification step was monitored with cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) techniques. The fabricated aptasensor exhibited a wide linear dynamic range (1.2 × 10¹ to 1.2 × 10⁸) CFU mL^-1 with a LOD of 1 CFU mL^-1 and was be capable to accurate detection and determination of Staphylococcus aureus in human blood serum as a clinical sample with a complex matrix.