Aila Jimenez-Ruiz

Covalent and Non‐Covalent DNA–Gold‐Nanoparticle Interactions: New Avenues of Research

The interactions of DNA, whether long, hundred base pair chains or short-chained oligonucleotides, with ligands play a key role in the field of structural biology. Its biological activity not only depends on the thermodynamic properties of DNA-ligand complexes, but can and often is conditioned by the formation kinetics of those complexes. On the other hand, gold nanoparticles have long been known to present excellent biocompatibility with biomolecules and are themselves remarkable for their structural, electronic, magnetic, optical and catalytic properties, radically different from those of their counterpart bulk materials, and which make them an important asset in multiple applications. Therefore, thermodynamic and kinetic studies of the interactions of DNA with nanoparticles acting as small ligands are key for a better understanding of those interactions to allow for their control and modulation and for the opening of new venues of research in nanomedicine, analytic and biologic fields. The interactions of gold nanoparticles with both DNA polymers and their smaller subunits; special focus is placed on those interactions taking place with nonfunctionalized gold nanoparticles are reviewed in the present work.

Nonfunctionalized Gold Nanoparticles: Synthetic Routes and Synthesis Condition Dependence

Since Faraday first described gold sol synthesis, synthetic routes to nanoparticles, as well as their applications, have experienced a huge growth. Variations in synthesis conditions such as pH, temperature, reduction, and the stabilizing agent used will determine the morphology, size, monodispersity, and stability of nanoparticles obtained, allowing for modulation of their physical and chemical properties. Although many studies have been made about the synthesis and characterization of individual nanosystems of interest, to our knowledge the common, general traits that all those synthesis share have not been previously compiled. In this review, we aim to offer a global vision of some of the most relevant synthetic procedures reported up to date, with a special focus on nonfunctionalized gold nanoparticle synthetic routes in aqueous media, and to display a broad overview of the influence that synthesis conditions have on the shape, stability, and reactivity of nanoparticle systems.

Electrochemiluminescent (ECL) [Ru(bpy)3]2+/PAMAM dendrimer reactions: coreactant effect and 5-fluorouracil/dendrimer complex formation

AbstractElectrogenerated chemiluminescence (ECL) reactions between tris(2,2′-bipyridine)ruthenium(II) and PAMAM dendrimers of the full (G1.0) and half (G1.5) generations were carried out in an aqueous medium at pH 6.1 and 10.0. In the absence of 5-fluoro-1H,3H-pyrimidine-2,4-dione (5-fluorouracil, 5-Fu) (coreactant effect study), the ECL efficiency trends as a function of [G1.0] and [G1.5] at pH 6.1 and 10.0 revealed that PAMAM dendrimers are about 100 (G1.5, pH 6.1), 60 (G1.5, pH 10.0), 26 (G1.0, pH 10.0) and 13 (G1.0, pH 6.1) times more efficient as ECL coreactants than oxalate anion is. Moreover, ECL reactions were done in the presence of several solutions of 5-Fu at a fixed concentration of the G1.0 and G1.5 dendrimers at pH 6.1 and 10.0 (binding study). The ECL efficiency trends as a function of [5-Fu] highlighted a dendrimer/5-Fu binding. Therefore, one of the most remarkable and novel findings of this work is the potential of PAMAM dendrimers to be used as both sensors and biosensors in an aqueous medium in the presence of a suitable sensitizer. Redox potentials of the [Ru(bpy)3]3+/2+ couple were also determined in the absence and presence of 5-Fu at both pHs. In the absence of 5-Fu the positive or negative shift of redox potentials showed the influence of the repulsive or attractive electrostatic long-range and short-range interactions between the charged dendrimer surface and the oxidized and reduced forms of the couple. In the presence of 5-Fu the trends of redox potentials highlighted the existence of a charged dendrimer/5-Fu species. Graphical AbstractECL emission for the [Ru(bpy)3]2+/ G1.0 dendrimer reaction in the presence of the 5-Fu at pH 6.1

Exploring Factors for the Design of Nanoparticles as Drug Delivery Vectors

To achieve optimal results when employing nanoparticles in biomedical fields, choosing the right type of nanoparticle and determining the correct procedure for drug loading are key factors. Each type of nanoparticle presents a determined set of characteristics that are, in some cases, unique. In general, their surface charge, geometry or hydrophilic character may be limiting factors, depending on what their intended application is. Once synthesized, additional factors, such as their interaction with biological systems and liberation mechanisms into the target cells, also need to be taken into account. Multiple advantages arise from the use of nanoparticles, such as the capability to solubilize hydrophobic compounds and an increased bioavailability. Those advantages justify the extensive and delicate study that should be undertaken in order to use them as drug delivery agents. One of the most important factors for the design of a drug delivery system with nanoparticles is achieving a high drug-to-nanoparticle ratio. In this Minireview, all of these key factors, both physicochemical and biological, are described, and special emphasis is placed on loading methods employed to introduce drugs into nanoparticles.

A colorimetric study of the interaction of cationic and anionic surfactants with anionic gold nanoparticles

The interactions of citrate-capped 10-nm gold nanoparticles with a cationic model surfactant, CTACl, and an anionic one, SDS, are explored. Results show that for CTACl, values of the c.m.c. close to those reported in the absence of nanoparticles can be obtained by simple colorimetric measurements. For SDS, its interaction with the same-charge nanoparticles is explored through the use of an indirect colorimetric method involving NaCl addition, and a surfactant-nanoparticle interaction model is postulated in this basis. C.m.c. measurements for SDS in the presence of AuNPs show that, despite both substrates being anionic, SDS micelle formation is actually promoted in the presence of gold nanoparticles.