Copper- and Cobalt-Codoped CeO₂ Nanospheres with Abundant Oxygen Vacancies as Highly Efficient Electrocatalysts for Dual-Mode Electrochemical Sensing of MicroRNA

Abstract

Oxide materials with redox properties have aroused growing interest in many applications. Introducing dopants into crystal lattices provides an effective way to optimize the catalytic activities of the oxides as well as their redox properties. Herein, CeO 2 nanospheres codoped with Cu and Co (CuCo−CeO 2 NSs) were first synthesized and exploited as efficient electrocatalysts for dual-mode electrochemical sensing of microRNA (miRNA). With the doping of Cu and Co into the CeO 2 lattice, large amounts of extra oxygen vacancies were generated, remarkably enhancing the redox and electrocatalytic properties of the CeO 2 material. The abundant oxygen vacancies of the CuCo−CeO 2 NSs were further identified by X-ray photoelectron spectroscopy (XPS), H 2 temperature-programmed reduction (H 2 -TPR), and electron-energy-loss spectroscopy (EELS). Moreover, Mg 2+induced DNAzyme-assisted target recycling was introduced for ultrasensitive determination. The dual-mode sensing with generality was conducted as follows: First, the CuCo−CeO 2 NSs acted as a direct redox mediator to generate a differentialpulse-voltammetry (DPV) signal, which was then greatly amplified by the efficient electrocatalysis of CuCo−CeO 2 NSs toward H 2 O 2 decomposition. Second, under the electrocatalysis of CuCo−CeO 2 NSs, 3,3-diaminobenzidine (DAB) was oxidized to form nonconductive insoluble precipitates (IPs), leading to great amplification of the electrochemical-impedimetricspectroscopy (EIS) signal. The dual-mode electrochemical sensor showed a wide linear range (0.1 fM to 10 nM) with a low detection limit (33 aM), paving a new way for constructing ultrasensitive electrochemical sensors.

New trends in the development of electrochemical biosensors for the quantification of microRNAs

“…Hairpins, molecular beacons, locked nucleic acids, and G-quadruplexes have been also used for the development of miRNAs bioanalytical platforms, taking advantage of the particular properties of each structure. Xue et al [34] described J o u r n a l P r e -p r o o f the voltammetric and impedimetric attomolar quantification of miRNA-141 using a GCE modified with AuNPs and a hairpin-locked DNAzyme which was opened in the presence of miRNA-141, yielding the "active" DNAzyme that, after cleavage by Mg 2+ , releases the target and generates successive activation cycles. The remaining fragment on the electrode surface collects numerous CuCo−CeO2signaling DNA bioconjugates and, in this way, the biosensing platform offers the great advantage of having two analytical signals, the voltammetric response of the hydrogen peroxide reduction and the charge transfer resistance due to the nonsoluble nature of 3,3-diaminobenzidine (DAB) oxidation product.…”

Avenues Toward microRNA Detection In Vitro: A Review of Technical Advances and Challenges

“…An increasing number of reports have indicated that functional nanomaterials can be an effective alternative strategy for enhancing the sensitivity and specificity of biosensors due to their electrocatalytic activity [93], such as metal oxide nanomaterials [94], platinum nanoparticle (PtNPs) [95] and magnetic nanoparticles [96]. For instance, a miRNA sensing scheme was developed based on the electrocatalytic properties of PtNPs and DSNSA, in which PtNPs are modified with complementary ssDNA probes at first, then with the progress of DSNSA, some of the PtNPs surfaces are exposed, reactivating the PtNPs-based electrocatalytic amplification [95].…”

“…For instance, a miRNA sensing scheme was developed based on the electrocatalytic properties of PtNPs and DSNSA, in which PtNPs are modified with complementary ssDNA probes at first, then with the progress of DSNSA, some of the PtNPs surfaces are exposed, reactivating the PtNPs-based electrocatalytic amplification [95]. Moreover, a dual-mode electrochemical platform was proposed by using CeO 2 nanospheres codoped with Cu and Co (CuCo−CeO 2 NSs) as an efficient electrocatalyst [94]. In this assay, Cu and Co are doped into the CeO 2 lattice, to generate large amounts of extra oxygen vacancies, and then remarkably enhance the redox and electrocatalytic properties of the CeO 2 material [94].…”

“…Moreover, a dual-mode electrochemical platform was proposed by using CeO 2 nanospheres codoped with Cu and Co (CuCo−CeO 2 NSs) as an efficient electrocatalyst [94]. In this assay, Cu and Co are doped into the CeO 2 lattice, to generate large amounts of extra oxygen vacancies, and then remarkably enhance the redox and electrocatalytic properties of the CeO 2 material [94]. In more recent years, increasing interest in the nanomaterial-based signal amplification strategies has led to the development of many novel composite nanomaterials, which have more superior characteristics than the monometallic frameworks counterparts.…”

Rapid evaluation of oxygen vacancies-enhanced photogeneration of the superoxide radical in nano-TiO2 suspensions

“…However, oxygen vacancies are elusive species, and are also oen highly diluted and therefore difficult to detect. 27,29 The presence of oxygen vacancies can be demonstrated by changing the spectral response (e.g., the Raman spectrum) as a function of the number of oxygen vacancies in the sample, [30][31][32][33][34] or by several complex techniques such as X-ray photoelectron spectroscopy (XPS), 27,35 electron spin resonance (ESR), 22 and high-resolution transmission electron microscopy (HRTEM). 20,26,30 Density functional theory (DFT) calculations have also been carried out to detect oxygen vacancies.…”