Gold-Aryl nanoparticles coated with polyelectrolytes for adsorption and protection of DNA against nuclease degradation

Fluorescent Multifunctional Organic Nanoparticles for Drug Delivery and Bioimaging: A Tutorial Review

Fluorescent organic nanoparticles (FONs) are a large family of nanostructures constituted by organic components that emit light in different spectral regions upon excitation, due to the presence of organic fluorophores. FONs are of great interest for numerous biological and medical applications, due to their high tunability in terms of composition, morphology, surface functionalization, and optical properties. Multifunctional FONs combine several functionalities in a single nanostructure (emission of light, carriers for drug-delivery, functionalization with targeting ligands, etc.), opening the possibility of using the same nanoparticle for diagnosis and therapy. The preparation, characterization, and application of these multifunctional FONs require a multidisciplinary approach. In this review, we present FONs following a tutorial approach, with the aim of providing a general overview of the different aspects of the design, preparation, and characterization of FONs. The review encompasses the most common FONs developed to date, the description of the most important features of fluorophores that determine the optical properties of FONs, an overview of the preparation methods and of the optical characterization techniques, and the description of the theoretical approaches that are currently adopted for modeling FONs. The last part of the review is devoted to a non-exhaustive selection of some recent biomedical applications of FONs.

Gold Nanoparticle-Mediated Gene Therapy

Gold nanoparticles (AuNPs) have gained increasing attention as novel drug-delivery nanostructures for the treatment of cancers, infections, inflammations, and other diseases and disorders. They are versatile in design, synthesis, modification, and functionalization. This has many advantages in terms of gene editing and gene silencing, and their application in genetic illnesses. The development of several techniques such as CRISPR/Cas9, TALEN, and ZFNs has raised hopes for the treatment of genetic abnormalities, although more focused experimentation is still needed. AuNPs, however, have been much more effective in trending research on this subject. In this review, we highlight recently well-developed advancements that are relevant to cutting-edge gene therapies, namely gene editing and gene silencing in diseases caused by a single gene in humans by taking an edge of the unique properties of the AuNPs, which will be an important outlook for future research.

Single-Stranded DNA Recognition over Fluorescent Gold-Aryl Nanoparticles

Fluorescence labeling of gold-aryl nanoparticles, AuNPs-COOH, was achieved by the covalent derivatization with dansyl chloride (DNS-Cl) reagent (5-naphthalene-1-sulfonyl chloride) for potential ssDNA recognition. The fluorescent gold nanoparticles of AuNPs-C6H4-4-COO-dansyl (AuNPs-DNS) of spherical shape and a size of 19.3 ± 8.3 nm were synthesized in a carbonate-bicarbonate buffer (pH = 10.6) at 37 °C. The fluorescence emission at 475 nm was acquired using fluorescence spectroscopy and investigated using time-resolved photoluminescence. The conjugation of ssDNA to AuNPs-DNS using the freeze-thaw and salt-aging methods was confirmed by fluorescence emission quenching, gel electrophoresis separation, and lifetime decrease. Conjugated ssDNA to AuNPs-DNS using the freeze-thaw method was more efficient than the salt-aging method. The purity of ssDNA upon conjugation was measured with optical density, and the obtained A260/A280 ratio was in the range of 1.7–2.0. This research can be applied to other nucleotide recognition and theranostics.

Conceptual Developments of Aryldiazonium Salts as Modifiers for Gold Colloids and Surfaces

Modified colloids and flat surfaces occupy an important place in materials science research due to their widespread applications. Interest in the development of modifiers that adhere strongly to surfaces relates to the need for stability under ambient conditions in many applications. Diazonium salts have evolved as the primary choice for the modification of surfaces. The term "diazonics" has been introduced in the literature to describe "the science and technology of aryldiazonium salt-derived materials". The facile reduction of diazonium salts via chemical or electrochemical processes, irradiation stimuli, or spontaneously results in the efficient modification of gold surfaces. Robust gold-aryl nanoparticles, where gold is connected to the aryl ring through bonding to carbon and films modified by using diazonium salts, are critical in electronics, sensors, medical implants, and materials for power sources. Experimental and theoretical studies suggest that gold-carbon interactions constructed via chemical reactions with diazonium salts are stronger than nondiazonium surface modifiers. This invited feature article summarizes the conceptual development of recent studies of diazonium salts in our laboratories and others with a focus on the surface modification of gold nanostructures, flat surfaces and gratings, and their applications in nanomedicine engineering, sensors, energy, forensic science, and catalysis.

Diazonium Gold Salts as Novel Surface Modifiers: What Have We Learned So Far?

The challenges of diazonium salts stabilization have been overcome by their isolation as metal salts such as tetrachloroaurate(III). The cleavage of molecular nitrogen from diazonium salts even at very low potential or on reducing surfaces by fine tuning the substituents on the phenyl ring expanded their applications as surface modifiers in forensic science, nanomedicine engineering, catalysis and energy. The robustness of the metal–carbon bonding produced from diazonium salts reduction has already opened an era for further applications. The integration of experimental and calculations in this field catalyzed its speedy progress. This review provides a narrative of the progress in this chemistry with stress on our recent contribution, identifies potential applications, and highlights the needs in this emerging field. For these reasons, we hope that this review paper serves as motivation for others to enter this developing field of surface modification originating from diazonium salts.

Green and cytocompatible carboxyl modified gold-lysozyme nanoantibacterial for combating multidrug-resistant superbugs

The dissemination of multi-drug resistant (MDR) superbugs in hospital environments, communities and food animals and the very dynamic bacterial mutation frequency require the development of prolonged therapeutic strategies to gain mastery over antibiotic resistance. A AuNP-lysozyme nanoantibacterial was fabricated by the conjugation of AuNPs-C6H4-4-COOH with lysozyme via green reduction of aryldiazonium gold(iii) salt [HOOC-4-C6H4N[triple bond, length as m-dash]N]AuCl4. Results from molecular docking calculations aimed at revealing the binding mode of benzoic acid with the lysozyme structure clearly showed the lowest energy conformation with benzoic acid bound in the deep buried hydrophobic cavity of the protein active site through strong hydrogen bonding and hydrophobic interactions, thus validating the experimental outcomes of the current study which also exhibited the binding of -COOH functional groups in the interior of the protein structure. The superiority of the lysozyme bioconjugate against superbugs was demonstrated by the enhanced and broadened lysozyme antibacterial activities of 98-99% against extended spectrum beta lactamase (ESBL) producing Escherichia coli and imipenem-resistant Pseudomonas aeruginosa clinical isolates and a selection of Gram-negative and Gram-positive standard ATCC strains. Selective toxicity against bacteria was confirmed by the high viability of HeLa and fibroblast cell lines and the outstanding hemocompatibility at the minimum bacterial inhibitory concentrations (MICs). Turbidimetric enzyme kinetic assay showed the enhancement of the lysozyme hydrolytic activity by gold nanoparticles on the Micrococcus lysodeikticus bacterial substrate. Using gel electrophoresis, the induced cell wall breakdown was confirmed by detecting the leaked-out bacterial genomic DNA. The integrity and morphology changes of the E. coli bacteria were investigated using a scanning electron microscope after one hour of contact with the lysozyme-gold bioconjugate. The antibacterial functionalities showed little or no damage to healthy human cells and can be applied to wound dressings and medical devices.

Synthesis of water-soluble gold–aryl nanoparticles with distinct catalytic performance in the reduction of the environmental pollutant 4-nitrophenol

In-depth kinetic insight into the catalytic reduction of nitrophenol pollutant using gold–carbon nanoparticles is described.