Dual Activities of Flower-Like Gold-Iron Oxide Nanozyme for Peroxidase-Mimicking and Glucose Detection.

Nanozymes, constituting of inorganic nanomaterials, are the sustainable and cost-effective alternatives of the naturally abundant enzymes. For more than a decade, nanozymes have shown astonishingly enhanced enzymatic activity as compared to its naturally occurring counterpart and emerged as a potential platform in biomedical science. The current study reports a novel flower shaped gold-iron oxide nanocomposite prepared via a facile and green solution phase redox mediated synthesis.

Dual role of arsenite in hydrolysis and post-hydrolysis fluorescence sensing of selective pH-dependent probes.

In comparison to the sensing activity, the reactivity of arsenite (AsO) is less explored. Herein, we focused on AsO reactivity studies based on its p and compared the study with other common anions. All three p values of arsenite are >9.

Fluorogenic response from DNA templated micrometer range self-assembled gold nanorod.

Plasmonic gold nanorod (AuNR) on a macromolecular matrix exhibits an end-to-end (ETE) long-range self-assembly (AuNR) with > 100. In the case of small molecules as a template, the pre-synthesized macromolecular matrix is missing and this brings a synthetic challenge in directed long-range assembly of AuNR. Self-assembly with thiol-modified small DNA and AuNR shows a much short-range ETE assembly with < 25 a simple evaporation technique on a solid surface.

Seed free synthesis of polyethylene glycol stabilized gold nanoprisms exploiting manganese metal at low pH.

Manganese powder with a suitable potential (, -1.19 V) has never been investigated for the reduction of Au (, 1.00 V).

Growth Reaction of Gold Nanorods in the Presence of Mutated Peptides and Amine-Modified Single-Stranded Nucleic Acids.

Conformation of biomolecules like DNA, peptides and amino acids play vital role during nanoparticle growth. Herein, we have experimentally explored the effect of different noncovalent interaction between a 5'-amine modified DNA sequence (NH -C H -5'-ACATCAGT-3', PMR) and arginine during the seed-mediated growth reaction of gold nanorods (GNRs). Amino acid-mediated growth reaction of GNRs results in a snowflake-like gold nanoarchitecture.

Methionine-Controlled Impediment of Secondary Nucleation Leading to Nonclassical Growth within Self-Assembled Gold Nanoparticles.

The conventional key steps for seed-mediated growth of noble metal nanostructures involve classical and nonclassical nucleation. Furthermore, the surface of the seed catalytically enhances the secondary nucleation involving Au to Au reduction, thus providing in-plane growth of the seed. In contrast to this well-established growth mechanism, herein, we report the unique case of a methionine (Met)-controlled seed-mediated growth reaction, which rather proceeds impeding secondary nucleation in the presence of citrate-stabilized gold nanoparticles (AuNPs).

Green Synthesis of Luminescent Gold-Zinc Oxide Nanocomposites: Cell Imaging and Visible Light-Induced Dye Degradation.

Green synthesis of gold-zinc oxide (Au-ZnO) nanocomposite was successfully attempted under organic solvent-free conditions at room temperature. Prolonged stirring of the reaction mixture introduced crystallinity in the ZnO phase of Au-ZnO nanocomposites. Luminescence properties were observed in these crystalline Au-ZnO nanocomposites due to embedding of gold nanoparticles (AuNP) of 5-6 nm diameter on the surface.

Selective Release of Doxorubicin from Cucurbit[8]uril Stabilized Gold Supra-Pyramid Host at pH of Small Intestine.

Gold supra-pyramid structures were obtained by the addition of acidic solution of cucurbit[8]uril (CB[8]) to an aqueous solution of citrate stabilized gold nanoparticles (AuNP). The reaction resulted in the precipitation of supra-pyramid from the solution after just 1 min of shaking. Microscopic images confirmed formation of the supra-pyramid.

Formation of Growth-Mediated Gold Nanoflowers: Roles of the Reducing Agent and Amine-Modified, Single-Strand DNA Sequences.

The formation of growth-mediated structures from gold nanoparticle seeds was studied in the presence of amine-modified single-strand DNA sequences and reducing agents such as hydroxylamine and hydroquinone. In the case of hydroxylamine, spherical gold nanoparticle seeds (0.45 nM) were incubated with amine-modified single-strand DNA probes PMR (amine-5'-ACATCAGT-3') and PML (amine-5'-GATAAGCT-3'), which resulted in gold nanoflowers and nanospheres, respectively.

Tryptophan-Stabilized Au-FeO Nanocomposites as Electrocatalysts for Oxygen Evolution Reaction.

Au-FeO nanocomposites with a variable gold-to-iron ratio were stabilized with l-tryptophan. The synthetic methodology is based on the facile redox reaction between Au(III) and Fe(0) in the presence of gold nanoparticle as a seed at room temperature in an aqueous medium. The synthesis results in the deposition of Au nanoparticles on the surface of iron oxide layers.

Gold Nanoflower for Selective Detection of Single Arginine Effect in α-Helix Conformational Change over Lysine in 3-Helix Peptide.

Hydroxylamine-based growth reaction in the presence of natural l-amino acids (9 mM) and gold nanoparticle seed mostly produce aggregated or nonaggregated gold nanostructures except the cases of immediate precipitation with aspartic acid, glutamic acid, cysteine, and tyrosine. Among the other amino acids, arginine shows the control growth reaction to form gold nanoflower from gold nanoparticle seeds, which were preincubated with amine-modified DNA (NH-oln). The absorbance trend with NH-oln in the presence of arginine is similar to the aggregation behavior in the presence of histidine and methionine.

Regioisomeric cryptand stabilized gold supraspheres and elongated dodecahedron supraparticles for reversible host-guest chemistry.

Addition of bis-pyrazole based cryptand regioisomers (1 and 2) to citrate stabilized gold nanoparticles (AuNPs) led to gold supraspheres (AuSSL) and elongated dodecahedron (AuEDL) supraparticles, respectively. These supraparticles as heterogenous hosts show a high uptake of a small fluorophore SEA-SC1 in an aqueous medium and reversible release in organic solvents.

Highly selective tridentate fluorescent probes for visualizing intracellular Mg dynamics without interference from Ca fluctuation.

We developed highly selective fluorescent Mg probes based on a novel tridentate Mg-selective chelator. The superior selectivity for Mg over Ca enabled the detection of intracellular Mg concentration changes without any response to Ca influx. The new probes are potential keys to elucidating intracellular Mg dynamics under conditions of extremely sharp Ca fluctuation.

Fluorogen-free aggregation induced NIR emission from gold nanoparticles.

Controlled diluted aqua regia addition leads to NIR (near infrared) luminescence from aggregated gold nanoparticles at 916 nm. This turn-on luminescence has been observed for gold nanoparticles, regardless of reductants used in their preparation. These aggregated nanoparticles are nontoxic and have been used for bioimaging in human liver carcinoma cells.

Nucleic Acid Templated Chemical Reaction in a Live Vertebrate.

Nucleic acid templated reactions are enabled by the hybridization of probe-reagent conjugates resulting in high effective reagent concentration and fast chemical transformation. We have developed a reaction that harnesses cellular microRNA (miRNA) to yield the cleavage of a linker releasing fluorogenic rhodamine in a live vertebrate. The reaction is based on the catalytic photoreduction of an azide by a ruthenium complex.

In cellulo protein labelling with Ru-conjugate for luminescence imaging and bioorthogonal photocatalysis.

Labelling of proteins with a luminescent ruthenium complex enables the direct visualization and photocatalytic reduction of aryl azide in live cells. The confinement of catalysis to the labeled proteins was visualized using an azide-based immolative linker releasing a precipitating dye.

Detection of miRNA in live cells by using templated RuII-catalyzed unmasking of a fluorophore.

Reactions templated by cellular nucleic acids are attractive for nucleic acid sensing or responsive systems. Herein we report the use of a photocatalyzed reductive cleavage of an immolative linker to unmask a rhodamine fluorophore, and its application to miRNA imaging. The reaction was found to proceed with a very high turnover (>4000) and provided reliable detection down to 5 pM of template by using γ-serine-modified peptide nucleic acid (PNA) probes.

Nucleic acid-tagged peptides: encoding libraries and controlling dimerization and conformation.

Recent progress in the synthesis, screening, and self-assembly of nucleic acid-tagged peptidic libraries is reviewed.

Photoreductive uncaging of fluorophore in response to protein oligomers by templated reaction in vitro and in cellulo.

The photoreduction of azide-based immolative linker by Ru(II) conjugates to uncage rhodamine was achieved using different oligomeric protein templates. The generality of the approach was validated with three sets of ligand having varying affinity to their target (biotin, desthiobiotin and raloxifene). The reaction rates of the templated reaction was found to be at least 30-fold faster than the untemplated reaction providing a clear fluorescent signal in response to the protein oligomer within 30 min.

pH induced dual "OFF-ON-OFF" switch: influence of a suitably placed carboxylic acid.

The design and synthesis of molecular probes competent for pH signaling within or beyond a certain range is a complicated matter. Herein a new mechanism for ''OFF-ON-OFF'' absorbance and fluorescence intensities vs. pH behaviour is described.

Sequential ordering among multicolor fluorophores for protein labeling facility via aggregation-elimination based β-lactam probes.

Development of protein labeling techniques with small molecules is enthralling because this method brings promises for triumph over the limitations of fluorescent proteins in live cell imaging. This technology deals with the functionalization of proteins with small molecules and is anticipated to facilitate the expansion of various protein assay methods. A new straightforward aggregation and elimination-based technique for a protein labeling system has been developed with a versatile emissive range of fluorophores.

Cryptand derived fluorescence signaling systems for sensing Hg(II) ion: A comparative study.

Two laterally non-symmetric aza-oxa cryptands have been derivatized with the electron-withdrawing fluorophore, 7-nitrobenz-2-oxa-1,3-diazole to obtain the corresponding mono-, bis- and tris-products. In each case, no appreciable emission is observed when the fluorophore is excited due to an efficient photoinduced intramolecular electron transfer (PET) from the lone pair on nitrogen present in the bridges. In the presence of a number of transition and heavy metal ions, their emission characteristics change.