Novel hierarchical CuNiAl LDH nanotubes with excellent peroxidase-like activity for wide-range detection of glucose

Rational synthesis of FeNiCo-LDH nanozyme for colorimetric detection of deferoxamine mesylate

The accurate surveillance and sensitive detection of deferoxamine mesylate (DFO) is of great significance to ensure the safety of thalassemia major patients. Herein, we report a new nanozyme-based colorimetric sensor platform for DFO detection. First, a metal-organic framework (ZIF-67) was used as a precursor for the synthesis of FeNiCo-LDH (Layered Double Hydroxide, LDH) via an ion exchange reaction stirring at room temperature. The results of electron microscopy and nitrogen adsorption-desorption showed that FeNiCo-LDH exhibited a 3D hollow and mesopores structure, which supplied more exposed active sites and faster transfer of mass. The as-prepared FeNiCo-LDH showed superior peroxidase-like activity with a low Km and high υmax. It can catalyze the decomposition of H2O2 to generate reactive oxygen species (ROS) and further react with 3,3',5,5'-tetramethylbenzidine (TMB) to form blue oxidized TMB (oxTMB), which has a characteristic absorption at 652 nm. Once DFO was introduced, it can complex with FeNiCo-LDH and inhibit the peroxidase-like activity of FeNiCo-LDH, making the color of oxTMB lighter. The quantitative range of DFO was 0.8-28 μM with a detection limit of 0.71 μM. This established method was applied to the detection of DFO content in urine samples of thalassemia patients, and the spiked recoveries were falling between 97.7% and 109.6%, with a relative standard deviation was less than 5%, providing a promising tool for the clinical medication of thalassemia patients.

Advances in layered double hydroxide based labels for signal amplification in ultrasensitive electrochemical and optical affinity biosensors of glucose

Since the development of enzyme electrodes, the research area of glucose biosensing has seen outstanding progress and improvement. Numerous sensing platforms have been developed based on different immobilization techniques and improved electron transfer between the enzyme and electrode. Interestingly, these platforms have consistently used innovative nanostructures and nanocomposites. In recent years, layered double hydroxides (LDHs) have become key tools in the field of analytical chemistry owing to their outstanding features and benefits, such as facile synthesis, cost-effectiveness, substantial surface area, excellent catalytic performance, and biocompatibility. LDHs are often synthesized as nanomaterial composites or manufactured with specific three-dimensional structures. The purpose of this review is to illustrate the biosensing prospects of LDH-based glucose sensors and the need for improvement. First, various clinical and conventional approaches for glucose determination are discussed. The definitions, types, and various synthetic methodologies of LDHs are then explained. Subsequently, we discuss the various research studies regarding LDH-based electrochemical and optical assays, focusing on modified systems, improved electron transfers pathways (through developments in surface science), and different sensing designs based on nanomaterials. Finally, a summary of the current limitations and future challenges in glucose analysis is described, which may facilitate further development and applications.

π-Conjugated Copper Phthalocyanine Nanoparticles as Highly Sensitive Sensor for Colorimetric Detection of Biomarkers

Though numerous nanomaterials with enzyme-like activities have been utilized as probes and sensors for detecting biological molecules, it is still challenging to construct highly sensitive detectors for biomarkers using polymeric materials. Benefiting from the π-d delocalization effect of electrons, excellent metal-chelating property, high electron transferability, and good chemical stability of π-conjugated phthalocyanine, the design of the copper phthalocyanine-based conjugated polymer nanoparticles (Cu-PcCP NPs) as a colorimetric sensor for a variety of biomarkers is reported. The Cu-PcCP NPs are synthesized through a simple microwave-assisted polymerization, and their chemical structures are thoroughly characterized. The colorimetric results of Cu-PcCP NPs demonstrate excellent peroxidase-like detecting activity and also great substrate selectivity than most of the reported Cu-based nanomaterials. The Cu-PcCP NPs can achieve a detection limit of 4.88 μM for the H₂ O₂ , 4.27 μM for the L-cysteine, and 21.10 μM for the glucose via a cascade catalytic system, which shows comparable detecting sensitivity as that of many earlier reported enzyme-like nanomaterials. Moreover, Cu-PcCP NPs present remarkable resistance to harsh conditions, including high temperature, low pH, and excessive salts. These highly specific π-conjugated copper-phthalocyanine nanoparticles not only overcome the current limitation of polymeric material-based sensors but also provide a new direction for designing next-generation enzyme-like nanomaterial-based colorimetric biosensors.

Construction of a binder-free non-enzymatic glucose sensor based on Cu@Ni core-shell nanoparticles anchored on 3D chiral carbon nanocoils-nickel foam hierarchical scaffold

Bimetallic nanostructures composited with carbonaceous materials are the potential contenders for quantitative glucose measurement owing to their unique nanostructures, high biomimetic activity, synergistic effects, good conductivity and chemical stability. In the present work, chemical vapors deposition technique has been employed to grow 3D carbon nanocoils (CNCs) with a chiral morphology on hierarchical macroporous nickel foam (NF) to get a CNCs/NF scaffold. Following, bimetallic Cu@Ni core-shell nanoparticles (CSNPs) are effectively coupled with this scaffold through a facile solvothermal route in order to fabricate a binder-free novel Cu@Ni CSNPs/CNCs/NF hybrid nanostructure. The constructed free-standing 3D hierarchical composite electrode guarantees highly efficient glucose redox activity due to core-shell synergistic effects, enhanced electrochemical active surface area, excellent electrochemical stability, improved conductivity with better ion diffusivity and accelerated reaction kinetics. Being a non-enzymatic glucose sensor, this electrode achieves highly swift response time of 0.1 s, ultra-high sensitivity of 6905 μA mM^-1 cm^-2, low limit of detection of 0.03 μM along with potential selectivity and good storage stability. Moreover, the proposed sensor is also tested successfully for the determination of glucose concentration in human serum samples under good recovery ranging from 96.6 to 102.1 %. The 3D Cu@Ni CSNPs/CNCs/NF composite electrode with unprecedented catalytic performance can be utilized as an ideal biomimetic catalyst in the field of non-enzymatic glucose sensing.

Copper Aluminum Layered Double Hydroxides with Different Compositions and Morphologies as Electrocatalysts for the Carbon Dioxide Reduction Reaction

Electrochemical CO₂ reduction (CO₂ RR) is a key technology to convert greenhouse gas CO₂ to value-added products, such as CO and formic acid (HCOOH). In the present study, two-dimensional Cu- and Al-based layered double hydroxides (Cu-Al/LDHs) were applied as CO₂ RR catalysts. The catalysts were synthesized using a simple co-precipitation method employing sodium carbonate solutions with different pH and synthesis temperatures. The elemental ratio of Cu and Al, and sheet size were controlled. The most active Cu-Al/LDH showed a faradaic efficiency for CO generation of 42 % and one for formate generation of 22 % at the current density of 50 mA using a gas diffusion electrode system under galvanostatic conditions. Our result indicates that the sheet size of the LDH sheet is a critical parameter for determining CO₂ RR activity.

A facile strategy for synthesis of porous Cu2O nanospheres and application as nanozymes in colorimetric biosensing

Due to the unique advantages, developing a rapid, simple and economical synthetic strategy for porous nanomaterials is of great interest. In this work, for the first time, using sodium hypochlorite as a green oxidant, urea was oxidized to CO2 as a carbon source to prepare the fine-particle crosslinked Cu-precursors, which could be further reduced by sodium ascorbate into pure Cu2O nanospheres (NPs) with a porous morphology at room temperature. Interestingly, our study reveals that introduction of an appropriate amount of MgCl2 into the raw materials can tune the pore sizes and surface area, but has no influence on the phase purity of the resulting Cu2O NPs. Significantly, all the synthesized Cu2O NPs exhibited intrinsic peroxidase-like activity with higher affinity towards both 3,3,5,5-tetramethylbenzidine (TMB) and H2O2 than horseradish peroxidase (HRP) due to the highly porous morphology and the electrostatic attraction towards TMB. The colorimetric detection of glucose based on the resulting porous Cu2O NPs presented a limit of detection (LOD) of 2.19 μM with a broad linear range from 1-1000 μM, much better than many recently reported composite-based nanozymes. Meanwhile, this nanozyme system was utilized to detect l-cysteine, exhibiting a LOD value as low as 0.81 μM within a linear range from 0 to 10 μM. More interesting, this sensing system shows high sensitivity and excellent selectivity in determining glucose and l-cysteine, which is suitable for detecting serum samples with reliable results. Therefore, the present study not only develops a simple strategy to prepare Cu2O NPs with controllable porous structure, but also indicates its promising applications in bioscience and disease diagnosis.