A novel MWCNT-encapsulated (2-aminoethyl)piperazine-decorated zinc(II) phthalocyanine composite: development of an electrochemical sensor for detecting the antipsychotic drug promazine in environmental samples.

A nanocomposite of (2-aminoethyl)piperazine ligand substituted with zinc(II) tetra carboxylic acid phthalocyanine (ZnTEPZCAPC) and MWCNTs was constructed and employed to develop an electrochemical sensor with outstanding sensitivity and a low detection limit. The macrocyclic complex ZnTEPZCAPC was first synthesized and then employed for the electrochemical determination of the antipsychotic drug promazine (PMZ). The as-prepared ZnTEPZCAPC and MWCNT nanocomposite was characterized using different techniques, such as Fourier-transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), UV-visible spectroscopy (UV-Vis), field emission scanning electron microscopy (FE-SEM), and thermogravimetric analysis (TGA). Further, the prepared ZnTEPZCAPC@MWCNT nanocomposites were modified on a glassy carbon electrode (GCE) surface, and the electrochemical activity was investigated using cyclic voltammetry (CV), differential pulse voltammetry (DPV), and chronoamperometry (CA) tests in pH 7.0 phosphate buffer solution (PBS) in the potential window of 0.0-1 V. The ZnTEPZCAPC@MWCNTs displayed a superior electrochemical performance because of their high electrochemical active surface area (0.453 cm2), good conductivity, and a synergetic effect. The developed electrochemical sensor exhibited a broad linear range of 0.05-635 µM and the lowest detection limit of 0.0125 nM, as well as excellent sensitivity, repeatability, and reproducibility. Finally, the fabricated sensor was successively used for the real-time detection of PMZ in environmental and biological samples and displayed feasible recoveries.

Unique development of a new dual application probe for selective detection of antiparallel G-quadruplex sequences.

G-Quadruplex (G4) structures play vital roles in many biological processes; consequently, they have been implicated in various human diseases like cancer, Alzheimer's disease etc. The selective detection of G4 DNA structures is of great interest for understanding their roles and biological functions. Hence, development of multifunctional fluorescent probes is indeed essential. In this investigation, we have synthesized a quinolinium based dual application probe (QnMF) that presents molecular rotor properties. This dual application molecular rotor is able to detect selectively antiparallel G4 sequences (22AG in 100 mM NaCl) through a turn-on response over other G4 topologies. The QnMF also contains a distinct fluorine-19 that undergoes a significant chemical shift in response to microenvironmental changes around the molecule when bound to G4 structures. The probe QnMF exhibits significantly brighter fluorescence emissions in glycerol (ε × Ï• = 2800 cm-1 M-1) and relatively less brighter fluorescence emissions in methanol (ε × Ï• = 40.5 cm-1 M-1). The restricted rotation inherent property of the QnMF molecular rotor is responsible for brighter fluorescence and leads to enhancement in the fluorescence upon binding to the G4 structure. Overall, the probe's dual detection method makes it useful for monitoring the G4 structures that are abundant and plays a vital role in living organisms.

Surface-modified CuO nanoparticles for photocatalysis and highly efficient energy storage devices.

Herein we report multifunctional surface-modified CuO nanomaterials were used to fulfill escalating needs in the electrochemical energy storage system and to achieve efficient photocatalysts for the degradation of AR88 organic dye. Due to the atom economy, ease of synthesis, high capacitance, observable electrochemical responsiveness, and low bandgap in CuO-based nanomaterials, its active surface was modified through cationic surfactant CTAB. Surface-modified nanoparticles were characterized using various characterization techniques such as XRD, DRS, FESEM, and TEM. Intriguingly the synthesized materials demonstrated a capacitance of 133 F/g with a long-term charge-discharge cycle of 2000 cycles. In addition, at pH 11, the material also exhibited a superior dye degradation performance under the UV lamp by showing 94.8% AR88 degradation at a catalyst concentration of 1.0 g/L. Hence, we believe this concept would provide novel insights into the preparation of the simplest and cheaper multifunctional materials for next-generation energy storage and photocatalytic applications.

Self-Assembled Peptidyl Aggregates for the Fluorogenic Recognition of Mitochondrial DNA G-Quadruplexes.

The selective monitoring of G-quadruplex (G4) structures in living cells is important to elucidate their functions and reveal their value as diagnostic or therapeutic targets. Here we report a fluorogenic probe (CV2) able to selectively light-up parallel G4 DNA over antiparallel topologies. CV2 was constructed by conjugating the excimer-forming CV dye with a peptide sequence (l-Arg-l-Gly-glutaric acid) that specifically recognizes G4s. CV2 forms self-assembled, red excimer-emitting nanoaggregates in aqueous media, but specific binding to G4s triggers its disassembly into rigidified monomeric dyes, leading to a dramatic fluorescence enhancement. Moreover, selective permeation of CV2 stains G4s in mitochondria over the nucleus. CV2 was employed for tracking the folding and unfolding of G4s in living cells, and for monitoring mitochondrial DNA (mtDNA) damage. These properties make CV2 appealing to investigate the possible roles of mtDNA G4s in diseases that involve mitochondrial dysfunction.

Surfactant-induced excimer emission: A versatile platform for the design of fluorogenic probes.

We report that the electrostatic association between a cyanovinylene (CV)-based cationic dye (CV-N+) and anionic surfactants rapidly induced the formation of self-assembled aggregates of CV-N+ molecules in an aqueous solution, displaying a red-shifted (Δλ = 100 nm), broad excimer emission at 650 nm. The anionic-surfactant-mediated excimer-forming properties of CV-N+ were further exploited as a versatile platform for the design of simple fluorescent "light-up" sensing systems for the specific and efficient detection of enzymatic activity (i.e., phospholipase D) and small molecules (i.e., bisulfite ions), respectively, without the complicated functionalization of fluorophores with suitable recognition groups. In these systems, which can be ensembled using various substrates, the cationic CV-N+ dye interacts with an anionic surfactant, which is the product of an analyte-induced specific reaction, thus triggering the formation of emissive aggregates.

A fluorescent molecular rotor for the selective detection of the hybrid-conformation 22AG G-Quadruplex.

G-quadruplex (G4) DNA plays a vital role in myriad biological process and is linked to several human diseases, including Alzheimer's disease. Probing G4s with fluorescent probes can provide a better understanding their mechanisms of action and of their roles in Nature. In this study we developed a quinolinium-vinylaniline molecular rotor probe, featuring a diethylaminosalicylaldehyde unit that could discriminate the hybrid-22AG G4 sequence selectively amongst other G4 sequences. This probe underwent a significant red-shift upon binding to the target G4 (broad 575 nm â†’ sharp 630 nm) with enhanced fluorescence (up to 14-fold). We suspect that the vinylaniline unit of the molecular rotor, when bound to the hybrid-22 A G4, experienced restricted rotation, thereby undergoing enhanced intramolecular charge transfer. The presence of the diethylaminosalicylaldehyde moiety appeared to play a major role in the enhanced selectivity toward the 22AG G4.

A Short Review Comparing Carbon-Based Electrochemical Platforms With Other Materials For Biosensing SARS-Cov-2.

Due to the 2019 SARS-CoV-2 outbreak, low-cost, fast, and user-friendly diagnostic kits for biosensing SARS-CoV-2 in real samples employing multiple working electrodes are in high demand. Choosing SARS-CoV-2 detecting electrodes is difficult because each has advantages and limitations. Carbon-based electrochemical sensing applications have attracted attention from the electrochemical sensing community because carbon and carbon-based materials have been a godsend for testing utilizing an electrochemical platform. Carbon working electrode electrochemical platforms are cost-effective and fast. Covid-sensors use carbon-based materials because they can be easily changed (with inorganic and organic functionalities), have quick response kinetics, and are chemically resistant. Covid-19 sensing materials include graphene and graphite. This review explains how carbon materials have been employed in N and S protein electrochemical detection. Here, we discussed a carbon-based technology for SARS-CoV-2 biosensing. We've compared carbon-based electrochemical sensing to different electrodes.

Direct and selective metal-free N6-arylation of adenosine residues for simple fluorescence labeling of DNA and RNA.

We have developed an unprecedented transition metal-free approach for the direct fluorescence turn-on labeling of natural oligonucleotides through selective N6-arylation of adenosine moieties. This method allows the simple and direct fluorescence labeling of natural unmodified DNA and RNA, but is dependent on the secondary structure, favoring single-stranded structures.

Loop-mediated fluorescent probes for selective discrimination of parallel and antiparallel G-Quadruplexes.

Herein we report simple pyridinium (1-3) and quinolinium (4) salts for the selective recognition of G-quadruplexes (G4s). Among them, the probe 1, interestingly, selectively discriminated parallel (c-KIT-1, c-KIT-2, c-MYC) G4s from anti-parallel/hybrid (22AG, HRAS-1, BOM-17, TBA) G4s at pH 7.2, through a switch on response in the far-red window. Significant changes in the absorption (broad 575 nm â†’ sharp 505 nm) and emission of probe 1 at 620 nm, attributed to selective interaction with parallel G4s, resulted in complete disaggregation-induced monomer emission. Symmetrical push/pull molecular confinements across the styryl units in probe 1 enhanced the intramolecular charge transfer (ICT) by restricting the free rotation of CC units in the presence of sterically less hindered and highly accessible G4 surface/bottom tetrads in the parallel G4s, which is relatively lower extent in antiparallel/hybrid G4s. We confirm that the disaggregation of probe 1 was very effective in the presence of parallel G4-forming ODNs, due to the presence of highly available free surface area, resulting in additional π-stacking interactions. The selective sensing capabilities of probe 1 were analyzed using UV-Vis spectroscopy, fluorescence spectroscopy, molecular dynamics (MD)-based simulation studies, and 1H NMR spectroscopy. This study should afford insights for the future design of selective compounds targeting parallel G4s.

Highly fluorescent morpholine naphthalimide deoxyuridine nucleotide for the detection of miRNA 24-3P through rolling circle amplification.

In this study we synthesized the nucleotide dUrkTP, a highly fluorescent naphthalimide deoxyuridine triphosphate that undergoes aggregation-induced emission (AIE). We incorporated and extended dUrkTP during the primer extension of DNA mediated by DNA polymerase, and also in the rolling circle amplification of DNA mediated by Phi29 polymerase. Accordingly, we could use this fluorescent nucleotide for the detection of microRNA 24-3P, a biomarker of porcine reproductive and respiratory syndrome virus. The direct labeling system obtained during rolling circle DNA amplification exhibited increased fluorescence, due to AIE of the dUrkTP residue upon gel formation, thereby allowing the detection of miRNA 24-3P. This direct labeling system facilitated the simple and inexpensive detection of miRNA 24-3P with high sensitivity (limit of detection: 3.58 fM) and selectivity.

Propargylamine-selective dual fluorescence turn-on method for post-synthetic labeling of DNA.

We have developed a propargylamine-selective dual fluorescence turn-on system, using ylidenemalononitrile enamines, for post-synthetic DNA labeling, allowing the direct monitoring of DNA using dual emission in living cells.

Label-free sensing platform for miRNA-146a based on chromo-fluorogenic pyrophosphate recognition.

In this study we applied the dual-responsive chromo-fluorescent Cu2+ chelate 1C for the recognition of miRNA-146a through a pyrophosphate (PPi) sensing strategy in a rolling circle amplification (RCA) process. This approach for the recognition of miRNA-146a was highly robust, selective, and sensitive down to the attomolar (fluorogenic) and sub-micromolar (chromogenic) ranges under modified biochemical conditions at elevated temperature. Probe 1 selectively recognized Cu2+ and PPi ions in a sequential manner, as evidenced by colorless→pink→colorless transitions; the fluorescence emissions centered at 480 nm underwent a corresponding on-off-on sequence in the bluish-green region. We attribute this reversible switching upon the addition of Cu2+/PPi ions to effective chelation-induced ligand-to-metal charge/electron transfer that resulted in opening of the lactam ring upon complexation and closing of the lactam ring upon decomplexation. We also report a label-free approach for monitoring miRNA-146a amplification in an RCA process under modified T4 ligase and ϕ29 buffer conditions, using the Cu2+ ensemble 1C at pH 7.0 (4-(2-hydroxyethyl)piperazine-1-ethanesulfonic acid: HEPES, 10 mM MgCl2); the time required to perform this process (40-50 min) was relatively shorter than conventional RCA process. This ensemble 1C could recognize miRNA-146a colorimetrically (from pink to colorless) and fluorimetrically ("turn-on" mode) at concentrations within the highly sensitive atto-/nanomolar range under physiological conditions. This cost-effective label-free sensing strategy appears to be a universal method for detecting miRNAs according to the specified length of the template.

Unprecedented green-emissive boranyl-hydrazone supramolecular assemblies and their in vitro diagnostic applications.

This paper describes a novel symmetric N,N'-diethylsalicylaldehyde boranyl hydrazone (1) and its in situ-generated assemblies displaying opto-analytical capabilities for the diagnosis of nucleic acids under physiological conditions. The sensing capabilities of these unprecedented supramolecular assemblies were characterized using UV-Vis spectroscopy, fluorescence spectroscopy, 1D and 2D NMR spectroscopy, dynamic light scattering, and zeta potential measurements. Model compounds lacking boranyl units (2, 3) were prepared to correlate and evaluate the sensing mechanism. The rationally designed probe 1 displays unusual aggregation-induced emissive (AIE) properties, with an average particle size of 1096 nm exhibiting green emission upon excitation at 377 nm in pH-7.2 TRIZMA buffer. A selective switch on response toward organic PO43- accompanied through specific nano-aggregations patterns and sizes, thereby causing a significant red-shift through AIE. Exploiting such switch on in green channel behavior has allowed the monitoring of DNase I activities and polymerase chain reactions.

Daphnetin: A novel blue-green photonic switch for disodium phosphates that allows monitoring of polymerase chain reactions.

This paper describes the very simple and robust ratiometric photonic switching properties of daphnetin (DP) toward HPO42- ions selectively in complex biological fluids, without any interference from other relevant anions under physiological conditions. The sensing ability of DP toward HPO42- ions was first demonstrated using UV-Vis and fluorescence spectroscopy, dynamic light scattering (DLS), and one- and two-dimensional NMR spectroscopy. DP can detect HPO42- ions at concentrations up to the sub-micromolar/nanomolar level very effectively, with a ratiometric response resulting from intramolecular charge transfer aided by aggregated-induced emission. The interactions between DP and HPO42- ions resulted in new bands appearing in the UV-Vis (at 385 nm) and emission (at 535 nm) spectra. The noncovalently held HPO42- ions induced pronounced specific aggregation of DP molecules, resulting in the new excimer band at 535 nm while retaining the monomer band centered at 445 nm. In contrast, reciprocal absorptivity changes were observed at 320 and 385 nm, with exponential decrements and increments, respectively. This probe could effectively monitor the consumption of dNTPs during various cycles of the polymerase chain reaction performed with relatively short oligonucleotides as well as genomic DNA from Agrobacterium tumefaciens (AcH5α strain).

A new fluorogenic sensing platform for salicylic acid derivatives based on π-π and NH-π interactions between electron-deficient and electron-rich aromatics.

A novel simple fluorescent probe was designed for the recognition of electron-rich salicylic acid derivatives (SAs). The imidazole-appended aminomethyl perylene probe 1 selectively differentiated between electron-rich amino-SAs and electron-deficient nitro-SAs in EtOH, exhibiting the highest selectivity and sensitivity toward 5-aminosalicylic acid (5-ASA) and showing strong 1:1 binding (Ka=1.37×107M-1). This high selectivity and sensitivity resulted from the synergistic multiple hydrogen bonding interactions of secondary amine and imidazole units and π-π interactions between electron-rich and electron-deficient rings, along with the unusual NH-π interactions between 5-ASA and the perylene moiety of 1. The limit of detection (LOD) for 5-ASA in EtOH was 0.012ppb.