Cationic Gold Research Articles

Spectral Response of Interfacial Water at Different Lipid Monolayer Interfaces upon Interaction with Charged Gold Nanoparticles

Understanding the interactions of nanoparticles with cell membranes is crucial for designing materials for biomedical applications. In this paper, through the combination of vibrational sum frequency generation (VSFG) and molecular dynamics simulation techniques, the spectral responses of the interfacial water molecules due to interaction of anionic gold nanoparticles (AGNPs) and cationic gold nanoparticles (CGNPs) with three differently charged model cell membranes, namely, 1,2-dipalmitoyl-sn-glycero-3-phosphoglycerol (DPPG, negatively charged), 1,2-dipalmitoyl-3-trimethylammonium-propane (DPTAP, positively charged), and zwitterionic 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC, neutral), have been investigated. The interfacial water intensity at the DPPG–water interface decreases abruptly in the presence of CGNPs because of the significant change in Stern layer configuration, whereas it does not show any noticeable change in the presence of AGNPs, resulting in an unperturbed stern layer configuration. However, in the case of DPTAP and DPPC interfaces, the Stern layer is significantly perturbed in the presence of both the charged GNPs, resulting in a substantial change in the interfacial water intensity. This is attributed to the change in orientation and structure of interfacial water molecules in the presence of both charged GNPs. These results provide valuable insights into the solvation structure and dynamics of water molecules to exploit for designing and optimizing the delivery system for biomedical applications.

Gold Clusters: From the Dispute on a Gold Chair to the Golden Future of Nanostructures.

The present work opens with an acknowledgement to the research activity performed by Luciana Naldini while affiliated at the Università degli Studi di Sassari (Italy), in particular towards gold complexes and clusters, as a tribute to her outstanding figure in a time and a society where being a woman in science was rather difficult, hoping her achievements could be of inspiration to young female chemists in pursuing their careers against the many hurdles they may encounter. Naldini’s findings will be a key to introduce the most recent results in this field, showing how the chemistry of gold compounds has changed throughout the years, to reach levels of complexity and elegance that were once unimagined. The study of gold complexes and clusters with various phosphine ligands was Naldini’s main field of research because of the potential application of these species in diverse research areas including electronics, catalysis, and medicine. As the conclusion of a vital period of study, here we report Naldini’s last results on a hexanuclear cationic gold cluster, [(PPh3)6Au6(OH)2]2+, having a chair conformation, and on the assumption, supported by experimental data, that it comprises two hydroxyl groups. This contribution, within the fascinating field of inorganic chemistry, provides the intuition of how a simple electron counting may lead to predictable species of yet unknown molecular architectures and formulation, nowadays suggesting interesting opportunities to tune the electronic structures of similar and higher nuclearity species thanks to new spectroscopic and analytical approaches and software facilities. After several decades since Naldini’s exceptional work, the chemistry of the gold cluster has reached a considerable degree of complexity, dealing with new, single-atom precise, materials possessing interesting physico-chemical properties, such as luminescence, chirality, or paramagnetic behavior. Here we will describe some of the most significant contributions.

Increasing Antibiotic Susceptibility: The Use of Cationic Gold Nanoparticles in Gram-Negative Bacterial Membrane Models.

Antibiotic resistance will be one of the most prominent challenges to health-care systems in the coming decades, with the OECD predicting that up to 2.4 million deaths will be caused between 2015 and 2050 by drug-resistant bacterial infections in first-world countries alone, with infections costing health-care systems billions of dollars each year. Developing new methods to increase bacterial susceptibility toward drugs is an important step in treating resistant infections. Here, the synergistic effects of gold nanoparticles and the antibiotic drug colistin sulfate have been examined. A tethered lipid bilayer membrane was used to mimic a Gram-negative bacterial cell membrane. Exposing the membrane to gold nanoparticles prior to adding the antibiotic significantly increased the effect of the antibiotic on the membrane. Cationic gold nanoparticles could thus be used to enhance bacterial susceptibility to antibiotics, leading to a more potent treatment.

Argon Adsorption on Cationic Gold Clusters Aun+ (n ≤ 20).

The interaction of Aun+ (n ≤ 20) clusters with Ar is investigated by combining mass spectrometric experiments and density functional theory calculations. We show that the inert Ar atom forms relatively strong bonds with Aun+. The strength of the bond strongly varies with the cluster size and is governed by a fine interplay between geometry and electronic structure. The chemical bond between Aun+ and Ar involves electron transfer from Ar to Au, and a stronger interaction is found when the Au adsorption site has a higher positive partial charge, which depends on the cluster geometry. Au15+ is a peculiar cluster size, which stands out for its much stronger interaction with Ar than its neighbors, signaled by a higher abundance in mass spectra and a larger Ar adsorption energy. This is shown to be a consequence of a low-coordinated Au adsorption site in Au15+, which possesses a large positive partial charge.

Single Au atom supported defect mediated boron nitride monolayer as an efficient catalyst for acetylene hydrochlorination: A first principles study

• Monovacancy defect (nitrogen and boron) in boron nitride effectively adjust the properties of single gold and create the different charge state of Au. • Defective sites are stable active site for Au adsorption compare to pristine one. Single gold anion shows good catalytic performance in reaction which is comparable with single gold cation. • An E-R like reaction mechanism is revealed which begins with C 2 H 2 adsorption followed by HCl activation. • A novel LH mechanism with comparatively lower energy barrier than ER mechanism observed for Au/hBN • Defective boron nitride supported single Au atom catalyst show excellent stability and good catalytic performance towards acetylene hydrochlorination reaction. Hexagonal boron nitride (hBN) with defects shows remarkable performance as catalyst support for single-atom stabilization in several catalytic reactions, such as CO oxidation, N 2 fixation, and ORR. However, the anchoring sites for single-atoms and their catalytic performance towards acetylene hydrochlorination still needs a comprehensive investigation. The boron and nitrogen-vacancy in hBN not only stabilizes Au but can also effectively tune its electronic structure. The single-atom Au has charged negatively and positively on hBN with the formation nitrogen (hBNv) and boron (hBvN) vacancy, respectively. The electronic structure analysis, MD simulations, phonon band structure, and migration barrier uncovered the stability of Au supported on hBN. The reaction proceeded either with Eley–Rideal (E-R) mechanism, starting with C 2 H 2 adsorption after that HCl activation, product formation, or with Langmuir–Hinshelwood (L-H) method, starting with co-adsorption of C 2 H 2 and HCl. The L-H mechanism results in a smaller reaction barrier of 0.90 and 1.15 eV compared to the counterpart E-R mechanism with a barrier of 1.14 and 1.25 eV for Au/hBNv and Au/hBvN respectively. Moreover, both Au in cation and anion state can efficiently catalyze acetylene hydrochlorination with a competing energy barrier. Overall, current research gives a comprehensive explanation of the catalytic properties of hBN-based single-atom Au catalyst. Defected boron nitride can tune the electronic structure of Au and both Au cation and anion shows comparable performance towards acetylene hydrochlorination.

Dictating Catalytic Preference and Activity of a Nanoparticle by Modulating Its Multivalent Engagement

Incorporating adaptive and dynamic behavior in a catalytic system is the foremost prerequisite to gain nature-like complex functionality in a synthetic chemical network. Herein, we report a self-assembled modular catalytic system based on the multivalent interaction between a cationic gold nanoparticle surface and nucleotides. It is shown that the catalytic preference and activity of the nanoparticle can be directed in a controllable manner toward either hydrazone formation or a proton transfer reaction only by creating a differential local microenvironment around the nanoparticle surface, simply by changing or converting the multivalent scaffold around it. The temporal control of the system in governing the reaction preference and catalytic activity will enable designing a system of higher complexity with a preprogrammed reaction networking property.

The relativistic effects on the methane activation by gold(I) cations.

The reactivity of gold has been investigated for a long time. Here, we performed an in-depth analysis of relativistic effects over the chemical kinetic properties of elementary reactions associated with methane activation by gold(I) cations, CH4 + Au+ ↔ AuCH2 + + H2. The global reaction is modeled as a two-step process, CH4 + Au+ ↔ HAuCH3 + ↔ AuCH2 + + H2. Moreover, the barrierless dissociation of the initial adduct between reactants, AuCH4 +, is discussed as well. Higher-order relativistic treatments are used to provide corrections beyond the commonly considered scalar effects of relativistic effective core potentials (RECPs). Although the scalar relativistic contributions predominate, lowering the forward barrier heights by 48.4 and 36.1kcal mol-1, the spin-orbit coupling effect can still provide additional reductions of these forward barrier heights by as much as 9% (1.0 and 2.2kcal mol-1). The global reaction proceeds rapidly at low temperatures to the intermediate attained after the first hydrogen transfer, HAuCH3 +. The relativistic corrections beyond the ones from RECPs are still able to double the rate constant of the CH4 + Au+ → HAuCH3 + process at 300K, while the reverse reaction becomes five times slower. The formation of global products from this intermediate only becomes significant at much higher temperatures (∼1500K upward). The scalar relativistic contributions decrease the dissociation energy of the initial adduct, AuCH4 +, into the global products by 105.8kcal mol-1, while the spin-orbit effect provides an extra lowering of 1.8kcal mol-1.

Highly conductive and transparent graphene: Synergy of covalent and non-covalent co-doping

The three values of transparency, conductivity and flexibility make graphene a valid alternative to replace traditional electrode materials such as indium tin oxide in electrical and optical devices. In recent years, research efforts have been addressed to investigate doping methodologies for reducing further the sheet resistance while maintaining high transparency.In this contribution, we explore the possibility to integrate both the covalent and non-covalent doping in order to increase the carrier charge density without affecting their mobility significantly. We present a new graphene doping methodology that combines the effect of SOCl2 covalent p-doping with a synergic p-doping effect of cationic gold nanoparticles activated by the same SOCl2 chemistry. We demonstrate that this original co-doping strategy can provide CVD graphene multilayers with record sheet resistance Rs performances, which meet the technical target required by several industrial applications.

Kinetics and Mechanism of the Gold-Catalyzed Hydroamination of 1,1-Dimethylallene with N-Methylaniline.

The mechanism of the intermolecular hydroamination of 3-methylbuta-1,2-diene (1) with N-methylaniline (2) catalyzed by (IPr)AuOTf has been studied by employing a combination of kinetic analysis, deuterium labelling studies, and in situ spectral analysis of catalytically active mixtures. The results of these and additional experiments are consistent with a mechanism for hydroamination involving reversible, endergonic displacement of N-methylaniline from [(IPr)Au(NHMePh)]+ (4) by allene to form the cationic gold π-C1,C2-allene complex [(IPr)Au(η2 -H2 C=C=CMe2 )]+ (I), which is in rapid, endergonic equilibrium with the regioisomeric π-C2,C3-allene complex [(IPr)Au(η2 -Me2 C=C=CH2 )]+ (I'). Rapid and reversible outer-sphere addition of 2 to the terminal allene carbon atom of I' to form gold vinyl complex (IPr)Au[C(=CH2 )CMe2 NMePh] (II) is superimposed on the slower addition of 2 to the terminal allene carbon atom of I to form gold vinyl complex (IPr)Au[C(=CMe2 )CH2 NMePh] (III). Selective protodeauration of III releases N-methyl-N-(3-methylbut-2-en-1-yl)aniline (3 a) with regeneration of 4. At high conversion, gold vinyl complex II is competitively trapped by an (IPr)Au+ fragment to form the cationic bis(gold) vinyl complex {[(IPr)Au]2 [C(=CH2 )CMe2 NMePh]}+ (6).

Reversing the Chirality of Surface Ligands Can Improve the Biosafety and Pharmacokinetics of Cationic Gold Nanoclusters

Severe toxicity and rapid in vivo clearance of cationic nanomaterials seriously hinder their clinical translation. Present strategies to improve the biosafety and in vivo performance of cationic nanomaterials require neutralization of positive charge, which often compromises their efficacy. Herein, we report that substituting L-glutathione (L-GSH) on cationic gold nanoclusters (GNCs) with its D-counterpart can effectively improve the biosafety and pharmacokinetics. Compared with L-GNCs, D-GNCs do not exhibit cellular cytotoxicity, hemolysis, or acute damage to organs. Cationic D-GNCs show less cell internalization than L-GNCs, and do not induce cellular apoptosis. In vivo, the chirality of surface ligands distinctly affects the pharmacokinetics and tumor targeting abilities of D-/L-GNCs. D-GNCs show higher extended circulation time in blood plasma compared to similarly-sized and poly (ethylene glycol)-modified gold nanoparticles. This work demonstrates that the choice of chirality of surface ligands can determine toxicities and pharmacokinetics of cationic nanomaterials.

Reversing the Chirality of Surface Ligands Can Improve the Biosafety and Pharmacokinetics of Cationic Gold Nanoclusters

AbstractSevere toxicity and rapid in vivo clearance of cationic nanomaterials seriously hinder their clinical translation. Present strategies to improve the biosafety and in vivo performance of cationic nanomaterials require neutralization of positive charge, which often compromises their efficacy. Herein, we report that substituting L‐glutathione (L‐GSH) on cationic gold nanoclusters (GNCs) with its D‐counterpart can effectively improve the biosafety and pharmacokinetics. Compared with L‐GNCs, D‐GNCs do not exhibit cellular cytotoxicity, hemolysis, or acute damage to organs. Cationic D‐GNCs show less cell internalization than L‐GNCs, and do not induce cellular apoptosis. In vivo, the chirality of surface ligands distinctly affects the pharmacokinetics and tumor targeting abilities of D‐/L‐GNCs. D‐GNCs show higher extended circulation time in blood plasma compared to similarly‐sized and poly (ethylene glycol)‐modified gold nanoparticles. This work demonstrates that the choice of chirality of surface ligands can determine toxicities and pharmacokinetics of cationic nanomaterials.

Chiral Gold(III) Complexes: Synthesis, Structure, and Potential Applications.

Since the beginning of the 2000's, homogeneous gold catalysis has emerged as a powerful tool to promote the cyclization of unsaturated substrates with excellent regioselectivity allowing the synthesis of elaborated organic scaffolds. An important goal to achieve in gold catalysis is the possibility to induce enantioselective transformations by the assistance of chiral complexes. Unfortunately, the linear geometry of coordination for gold usually encountered in complexes at the +1 oxidation states renders this goal very challenging. In consequence, the interest toward the synthesis of chiral gold(III) complexes is steadily growing. Indeed, the square planar geometry of the gold(III) cation appears more suitable to promote chiral induction. Beside catalysis, gold(III) complexes have also shown promising potential in the field of pharmacology. Herein, syntheses and applications of well-defined gold(III) complexes reported over the last fifteen years are summarized.

A Hollow-shaped Caged Triarylphosphine: Synthesis, Characterization and Applications to Gold(I)-catalyzed 1,8-Enyne Cycloisomerization

A hollow-shaped caged triarylphosphine with three bulky triarylmethyl substituents at the positions meta to the P atom was synthesized. Its gold(I) complex was synthesized and characterized by NMR spectroscopy and X-ray diffraction analysis. A cationic gold(I) complex with this ligand was applied to 1,8-enyne cycloisomerization.

Theoretical Study on the Adhesion Interaction between Epoxy Resin Including Curing Agent and Plated Gold Surface.

In this study, the adhesive interaction between gold and epoxy resin is theoretically investigated. These materials make up crucial components of a wide range of electronic devices. The objectives of the study are (1) to elucidate the bonding mechanism between epoxy resin and a realistic gold surface, and (2) to obtain a device-design guideline for superior adhesion, thus reducing the bonding breakage that may potentially cause device failure. Die pad surfaces used in chip attachment methods for microelectronics are usually fabricated using an electrolytic plating technique. This technique involves ionic gold solutions like K[Au(CN)2]. The combined theoretical and experimental studies previously carried out by the authors have revealed that the CN- counteranion of the gold cation has a high affinity for gold and is likely to remain on the realistic gold surface generated by plating. However, the cyano group content on the surface of the plated gold is still unknown. Therefore, gold surfaces embedded with cyano groups with various coverages are constructed. The effect of the varying coverage of the cyano groups on the adhesion strength is inspected using first-principles density functional theory calculations. As the number of cyano groups on the surface increases, the direct interaction between the gold surface and the epoxy resin is hindered, but the hydroxy and amino groups in the epoxy resin and hardener form more hydrogen bonds with the cyano groups adsorbed on the surface. It is found that the surface with intermediate cyano coverage (about 33%) yields the highest adhesive strength.

Nano-based Masks, Disinfectants and Sanitizers Effectively Combat Covid-19

COVID-19 is an infectious viral disease caused by novel coronavirus to SARS-CoV-2 which emerged from Wuhan, China at the end of year 2019. The World Health Organization (WHO) declared COVID-19 a global pandemic due to highly contagious nature of SARS-CoV-2. Till date COVID-19 has infected and claimed lives of millions of people around the world. The virus is mainly transmitted through droplets from symptomatic patients; however, there are many cases of infection from asymptomatic people, wherein the virus is transmitted even before the symptoms appear. Therefore, it has been strategized to control the spread of virus from one person to another. Moreover, inadequate medical facilities, high cost of treatment and lack of effective medication against novel COVID-19, non-pharmacological interventions (NPIs) can help mitigate the transmission such as wearing face masks, face shields, protective clothing and practicing social distancing. However, these standard protective equipment (PE) are not effective in preventing the spread of coronavirus. Meanwhile, nano-based products are of huge help in effectively preventing COVID-19 outbreak.
 Face-mask is a cost effective first line of defense against COVID-19 as mask helps prevent the entry of small sized particles. However, commonly used facial masks are incapable of preventing the entry of small sized corona virus, which gets stuck in mask and can live on it for up to 9 days. Moreover, if such mask worn for longer period of time, virus can enter inside the body via mouth and nasal passage. Therefore, masks should be designed such that they are effective, antiviral and comfortable to use. Recently a research showed that nanoceutical N95 mask made with Zinc Oxide nanoflower cotton fabrics were comfortable, washable, porous and light-weight which solved the common problem of carbon dioxide rebreathing and prevented the spread of virus through the pores.
 Nanotechnology also offers a lot of opportunities for the development of more effective and promising disinfectant systems. In Prague, nano-polymer disinfectants were sprayed on few public vehicles to check its efficiency. It was found that Nano-polymer disinfectant can work for almost 21 days as compared to traditional disinfectants. Moreover, it was also found that copper nanoparticles incorporated disinfectants could be really effective against COVID-19. Coronavirus estimated half-life on stainless steel is 5.6h and on plastics 6.8h therefore copper can be used to inactivate virus. Additionally, the efficiency of hand sanitizers could also be enhanced by introducing nanoparticles like copper, silver, gold, and quaternary ammonium cations (QUATs) due to their antiviral properties. These metals and metal oxides can be used to create a surface coating to protect the body against the covid-19 because they possess the ability to stops the binding of viral proteins with human epithelial cells and leads to the viral protein denaturation. Scaling-up these for commercial use could help in effectively preventing COVID-19 spread. These various available nano-based products help equip people for combating COVID-19.
 Dr. Humera Kausar
 Associate Professor
 Kinnaird College for Women University
 Lahore, Pakistan

Characterization of atmospheric-pressure spark generated atomic silver and gold clusters by time-of-flight mass spectrometry

The potential of using atmospheric-pressure spark ablation for production of atomic clusters has been shown in the recent past. In this study we used this method to produce atomic clusters in Argon and investigated their chemical composition with an atmospheric pressure interface time-of-flight mass spectrometer (APi-TOF-MS). Both anionic and cationic silver and gold clusters were generated and characterised. The carrier gas was used directly from the gas cylinder without the application of any additional gas purification. As a result, the carrier gas stream contained trace impurities of N2, O2, and H2O, as well as radicals such as O, OH, and H and their ionized forms resulting from the plasma created by the sparks. The experimental results show that different reactivities towards oxygen and water traces can be observed depending on the number of metal atoms in the clusters, their polarity, as well as their compositions; e.g., Aun− shows less reactive behaviour towards oxygen and hydrogen compared to Agn−. The results also show that certain cluster types can be generated at large enough quantities by atmospheric-pressure spark ablation, which considering the low installation and operating cost of the technique can pave the way towards its exploitation for numerous technological applications.

Synthesis, Characterization, and Comparative Theoretical Investigation of Dinitrogen-Bridged Group 6-Gold Heterobimetallic Complexes.

We have prepared and characterized a series of unprecedented group 6–group 11, N2-bridged, heterobimetallic [ML4(η1-N2)(μ-η1:η1-N2)Au(NHC)]+ complexes (M = Mo, W, L2 = diphosphine) by treatment of trans-[ML4(N2)2] with a cationic gold(I) complex [Au(NHC)]+. The adducts are very labile in solution and in the solid, especially in the case of molybdenum, and decomposition pathways are likely initiated by electron transfers from the zerovalent group 6 atom to gold. Spectroscopic and structural parameters point to the fact that the gold adducts are very similar to Lewis pairs formed out of strong main-group Lewis acids (LA) and low-valent, end-on dinitrogen complexes, with a bent M–N–N–Au motif. To verify how far the analogy goes, we computed the electronic structures of [W(depe)2(η1-N2)(μ-η1:η1-N2)AuNHC]+ (10W+) and [W(depe)2(η1-N2)(μ-η1:η1-N2)B(C6F5)3] (11W). A careful analysis of the frontier orbitals of both compounds shows that a filled orbital resulting from the combination of the π* orbital of the bridging N2 with a d orbital of the group 6 metal overlaps in 10W+ with an empty sd hybrid orbital at gold, whereas in 11W with an sp3 hybrid orbital at boron. The bent N–N–LA arrangement maximizes these interactions, providing a similar level of N2 “push–pull” activation in the two compounds. In the gold case, the HOMO–2 orbital is further delocalized to the empty carbenic p orbital, and an NBO analysis suggests an important electrostatic component in the μ-N2–[Au(NHC)]+ bond.

Chemical Bonding in Homoleptic Carbonyl Cations [M{Fe(CO)5 }2 ]+ (M=Cu, Ag, Au).

Syntheses of the copper and gold complexes [Cu{Fe(CO)5}2][SbF6] and [Au{Fe(CO)5}2][HOB{3,5‐(CF3)2C6H3}3] containing the homoleptic carbonyl cations [M{Fe(CO)5}2]+ (M=Cu, Au) are reported. Structural data of the rare, trimetallic Cu2Fe, Ag2Fe and Au2Fe complexes [Cu{Fe(CO)5}2][SbF6], [Ag{Fe(CO)5}2][SbF6] and [Au{Fe(CO)5}2][HOB{3,5‐(CF3)2C6H3}3] are also given. The silver and gold cations [M{Fe(CO)5}2]+ (M=Ag, Au) possess a nearly linear Fe‐M‐Fe’ moiety but the Fe‐Cu‐Fe’ in [Cu{Fe(CO)5}2][SbF6] exhibits a significant bending angle of 147° due to the strong interaction with the [SbF6]− anion. The Fe(CO)5 ligands adopt a distorted square‐pyramidal geometry in the cations [M{Fe(CO)5}2]+, with the basal CO groups inclined towards M. The geometry optimization with DFT methods of the cations [M{Fe(CO)5}2]+ (M=Cu, Ag, Au) gives equilibrium structures with linear Fe‐M‐Fe’ fragments and D 2 symmetry for the copper and silver cations and D 4d symmetry for the gold cation. There is nearly free rotation of the Fe(CO)5 ligands around the Fe‐M‐Fe’ axis. The calculated bond dissociation energies for the loss of both Fe(CO)5 ligands from the cations [M{Fe(CO)5}2]+ show the order M=Au (D e=137.2 kcal mol−1)>Cu (D e=109.0 kcal mol−1)>Ag (D e=92.4 kcal mol−1). The QTAIM analysis shows bond paths and bond critical points for the M−Fe linkage but not between M and the CO ligands. The EDA‐NOCV calculations suggest that the [Fe(CO)5]→M+←[Fe(CO)5] donation is significantly stronger than the [Fe(CO)5]←M+→[Fe(CO)5] backdonation. Inspection of the pairwise orbital interactions identifies four contributions for the charge donation of the Fe(CO)5 ligands into the vacant (n)s and (n)p AOs of M+ and five components for the backdonation from the occupied (n‐1)d AOs of M+ into vacant ligand orbitals.

Nanoparticles Modified With Cationic Thiol Surfactant as Efficient Inhibitors for the Corrosion of Carbon Steel

In this work, we report synthesis, characterization and corrosion inhibition properties of cationic thiol surfactant-capped silver (SC-Ag-NPs) and gold (SC-Au-NPs) nanoparticles. SC-Ag-NPs and SC-Au-NPs were characterized using regular techniques include TEM. Corrosion study was carried out using carbon steel (CS) in 3.5% NaCl aqueous solution and characterized using multiple electrochemical techniques. Our results suggest that the paint containing SC-Ag-NPs and SC-Au-NPs endow efficient corrosion protection to the CS. Especially, SC-Au-NPs based paint form a stronger barrier between the metal and the corrosive ions, leading to better inhibition properties.

Photothermal-triggered system for oligonucleotides delivery from cationic gold nanorods surface: A molecular dynamic investigation

Bioconjugate gold-based nanostructures combining the plasmonic photothermal effect with photothermal-triggered DNA delivery are appealing materials for medical diagnostic and therapy for cell-based disease. In this study, we demonstrate the use of surface hybridization to prepare DNA-modified gold nanorods to be used as photo-delivery system for single stranded oligonucleotides. The as prepared DNA modified gold nanorods have strong absorption bands in the visible and near-infrared regions in which the absorbed light through photothermal effect, induces a surface temperature increasing up to the melting temperature with consequent DNA release. No evident DNA release was observed below the melting temperature.The experimental data were supported by molecular dynamic simulation investigation, showing the kinetics aspect of dsDNA de-hybridization at gold nanorods surface at temperature below (298 K) and above (333 K) the melting temperature of sequence investigated. We demonstrate that the cationic charges of surfactant, localized at nanorods surface, induce a remarkable de-hybridization of strands DNA, as confirmed by an increasing of hybridization enthalpy value of about 7 kcal/mol and by a faster de-hybridization process, respect the model of gold nanorods without positive charges. These data were corroborated by the increasing of the root mean square deviation value (about 4.4 Å, calculated at 333 K) indicating that the presence of cationic headgroup at gold surface induce separation of the double strand.This finding data paving the way for the development of nanostructured material for photothermal-triggered delivery systems of DNA for gene therapy application.