Role of the Probe Sequence/Structure in Developing an Ultra-Efficient Label-Free COVID-19 Detection Method Based on Competitive Dual-Emission Ratiometric DNA-Templated Silver Nanoclusters as Single Fluorescent Probes.

We report the development of a label-, antibody-, enzyme-, and amplification-free ratiometric fluorescent biosensor for low-cost and rapid (less than 12 min) diagnosis of COVID-19 from isolated RNA samples. The biosensor is designed on the basis of cytosine-modified antisense oligonucleotides specific for either N gene or RdRP gene that can form silver nanoclusters (AgNCs) with both green and red emission on an oligonucleotide via a one-step synthesis process. The presence of the target RNA sequence of SARS-CoV-2 causes a dual-emission ratiometric signal transduction, resulting in a limit of detection of 0.30 to 10.0 nM and appropriate linear ranges with no need for any further amplification, fluorophore, or design with a special DNA fragment. With this strategy, five different ratiometric fluorescent probes are designed, and how the T/C ratio, the length of the stem region, and the number of cytosines in the loop structure and at the 3' end of the cluster-stabilizing template can affect the biosensor sensitivity is investigated. Furthermore, the effect of graphene oxide (GO) on the ratiometric behavior of nanoclusters is demonstrated and the concentration-/time-dependent new competitive mechanism between aggregation-caused quenching (ACQ) and aggregation-induced emission enhancement (AIE) for the developed ssDNA-AgNCs/GO nanohybrids is proposed. Finally, the performance of the designed ratiometric biosensor has been validated using the RNA extract obtained from more than 150 clinical samples, and the results have been confirmed by the FDA-approved reverse transcription-polymerase chain reaction (RT-PCR) diagnostic method. The diagnostic sensitivity and specificity of the best probe is more than >90%, with an area under the receiver operating characteristic (ROC) curve of 0.978.

Author Correction: Impediometric Electrochemical Sensor Based on The Inspiration of Carnation Italian Ringspot Virus Structure to Detect an Attommolar of miR.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Impediometric Electrochemical Sensor Based on The Inspiration of Carnation Italian Ringspot Virus Structure to Detect an Attommolar of miR.

Electrochemical sensors are the tools to detect the accurate and sensitive miRs. There is the challenge to increase the power and sensitivity of the surface for the electrochemical sensor. We design a virus-like hallow structure of cuco2o4 that it holds the large amounts of p19 protein by mimicking of inherent virus (Carnation italian ringspot virus) to detect 21mir with the limit of detection (LOD = 1aM). The electrochemical measurements are performed between the potentials at -0.3 V and +0.3 V with 1 mM [Fe(CN)6] -3/-4. After dropping the cuco2o4 on the SCPE (screen carbon printed electrode), the sensor is turned on due to the high electrochemical properties. Then, p19 proteins move into the hallow structure and inhibit the exchange of electrochemical reactions between the shells and the sensor is turned off. Then, adding the duplexes of RNA/miRs cause to increase the electrochemical property of p19 due to the change of p19 conformation and the system is turned on, again. So, for the first time, a virus-like hallow structure has been used to detect the 21miR in the human serum, MCF-7, Hella cells, with high sensitivity, specificity, and reproducibility in few minutes.

Facile preparation of a novel biogenic silver-loaded Nanofilm with intrinsic anti-bacterial and oxidant scavenging activities for wound healing.

To eliminate the microbial infection from an injury site, various modalities have been developed such as dressings and human skin substitutes. However, the high amount of reactive oxygen species, microbial infection, and damaging extracellular matrix remain as the main challenges for the wound healing process. In this study, for the first time, green synthesized silver nanoparticles (AgNPs) using Teucrium polium extract were embedded in poly lactic acid/poly ethylene glycol (PLA/PEG) film to provide absorbable wound dressing, with antioxidant and antibacterial features. The physicochemical analysis demonstrated, production of AgNPs with size approximately 32.2 nm and confirmed the presence of phytoconstituents on their surface. The antibacterial assessments exhibited a concentration-dependent sensitivity of Staphylococcus aureus and Pseudomonas aeruginosa toward biosynthesized AgNPs, which showed a suitable safety profile in human macrophage cells. Furthermore, oxidant scavenging assays demonstrated exploitation of plant extract as a reducing agent, endows antioxidant activity to biogenic AgNPs. The formation of PLA/PEG nanofilm and entrapment of AgNPs into their matrix were clearly confirmed by scanning electron microscopy. More importantly, antibacterial examination demonstrated that the introduction of biogenic AgNPs into PLA/PEG nanofibers led to complete growth inhibition of P. aeruginosa and S. aureus. In summary, the simultaneous antioxidant activity and antimicrobial activity of the novel biogenic AgNPs/PLA/PEG nanofilm showed its potential for application as wound dressing.

Aptamer-Based Fluorescent Biosensing of Adenosine Triphosphate and Cytochrome c via Aggregation-Induced Emission Enhancement on Novel Label-Free DNA-Capped Silver Nanoclusters/Graphene Oxide Nanohybrids.

Four fluorescent DNA-stabilized fluorescent silver nanoclusters (DNA-AgNCs) were designed and synthesized with differences in lengths of cytosine-rich DNA strand (as the stabilizing agent) and target-specific strand DNA aptamers for adenosine triphosphate (ATP) and cytochrome c (Cyt c). After their nanohybrid formation with graphene oxide (GO), it was unexpectedly found that, depending on the composition of the base and length of the strand DNA aptamer, the fluorescence intensity of three of the nanohybrids significantly enhanced. Our experimental observations and quantum mechanical calculations provided an insight into the mechanisms underlying the behavior of DNA-AgNCs/GO nanohybrids. The enhanced fluorescence was found to be attributed to the aggregation-induced emission enhancement (AIE) characteristic of the DNA-AgNCs adsorbed on the GO surface, as confirmed evidently by both fluorescence and transmission electron microscopies. The AIE is a result of hardness and oxidation properties of GO, which lead to enhanced argenophilic interaction and thus to increased Ag(I)-DNA complex shell aggregation. Consequently, two of the DNA-AgNCs/GO nanohybrids were successfully extended to construct highly selective, sensitive, label-free, and simple aptasensors for biosensing of ATP (LOD = 0.42 nM) and Cyt c (LOD = 2.3 nM) in lysed Escherichia coli DH5 α cells and mouse embryonic stem cells, respectively. These fundamental findings are expected to significantly influence the designing and engineering of new AgNCs/GO-based AIE biosensors.

MOF assistance synthesis of nanoporous double-shelled CuCo2O4 hollow spheres for hybrid supercapacitors.

Design of complex hollow nanostructures of two or more transition metal oxides seems to be necessary to answer the demand for novel energy storage electrodes owning outstanding performance for advanced developments of modern electronics. Herein, we develop a metal-organic frameworks (MOFs) assistance self-templated method for the synthesis of double-shell CuCo2O4 hollow spheres as battery-type electrode material with a large surface area of 93 m2 g-1. This electrode material reveals excellent electrochemical performance with an ultrahigh specific capacity of 701 C g-1 at 2 A g-1. Additionally, remarkably high cycling performance is exhibited with maintaining more than 93.6% of the initial capacity after 6000 cycles. The assembly of the double-shell hollow spheres electrode with reduced graphene oxide (rGO) electrode in an asymmetric cell results in a high-performance supercapacitor with an energy density of 38.4 Wh kg-1 and a power density of 16 kW kg-1, that is remarkably higher than that of conventional supercapacitors and comparable with Ni-MH batteries. Additionally, we display that assembling two asymmetric devices in series could effectively power blue, green, and red LED indicators. The excellent electrochemical performance of the ZCCO electrode shows its high potential for the production of advanced energy storage devices.

Self-templated synthesis of uniform nanoporous CuCo2O4 double-shelled hollow microspheres for high-performance asymmetric supercapacitors.

Multilevel interior nanoporous CuCo2O4 microspheres have been for the first time developed using a facile self-templated method. Electrochemical results in three- and two-electrode systems show that the double-shelled hollow microsphere electrode is a promising candidate for high-performance supercapacitors.

All-solid state, flexible, high-energy integrated hybrid micro-supercapacitors based on 3D LSG/CoNi2S4 nanosheets.

3D LSG/CoNi2S4//LSG interdigitated microelectrodes have been firstly developed by a facile, scalable and low cost process for all-solid-state, flexible integrated asymmetric micro-supercapacitors. These devices can achieve energy densities of up to 49 W h l-1 which is comparable to those of lead acid batteries.

Hierarchical CuCo2S4 hollow nanoneedle arrays as novel binder-free electrodes for high-performance asymmetric supercapacitors.

Hierarchical CuCo2S4 hollow nanoneedle arrays have been firstly synthesized on a Ni foam using a facile template-free hydrothermal method and applied as novel binder-free electrodes for high-performance asymmetric supercapacitors with ultrahigh specific capacitance, high energy density, excellent rate capability and outstanding long-term cycling stability.