J. Manríquez

Applications of dendrimers in drug delivery agents, diagnosis, therapy, and detection

In recent years, the application of dendrimers in biomedicine attracted much attention from scientists. Dendrimers are interesting for biomedical applications because of their characteristics, including: a hyperbranching, well-defined globular structures, excellent structural uniformity, multivalency, variable chemical composition, and high biological compatibility. In particular, the three-dimensional architecture of dendrimers can incorporate a variety of biologically active agents to form biologically active conjugates. This review of dendrimers focuses on their use as protein mimics, drug delivery agents, anticancer and antiviral therapeutics, and in biomedical diagnostic applications such as chemically modified electrodes.

Electrochemical Characterization of TiO2 Films Formed by Cathodic EPD in Aqueous Media

The present work studies the influence of applied electric field on the cathodic electrophoretic formation of TiO 2 films in an aqueous medium. The growth of the film was followed by measuring current density, deposited mass, and thickness under imposed electric field (ϕ). In scanning electronic microscopy images of the TiO 2 films formed under different electric fields, three regions can be seen: (i) formation of nuclei that are converted into agglomerates, (ii) uniform and one-sided growth, and (iii) growth by the formation of agglomerates on the TiO 2 surface. The characterization of semiconductor properties showed that increased ϕ for film growth leads to an increase in the density of donors and to a displacement of the flatband potential toward less negative values. The photoelectrochemical characterization of the oxide films revealed that the photoelectrochemical performance of the TiO 2 films decreases as a function of the electric field used to carry out the electrophoretic deposition (EPD) process. The electrochemical behavior observed for these films seems closely related to the content of Ti 3+ doping sites electrogenerated in situ during the EPD, which act as electron traps negatively affecting the electron transport toward the indium tin oxide collector, also making their photoelectrochemical activity inefficient.

Design, self-assembly, and photophysical properties of pentameric metallomacrocycles: [M5(N-hexyl[1,2-bis(2,2':6',2''-terpyridin-4-yl)]carbazole)5][M = Fe(II), Ru(II), and Zn(II)].

A novel family of metallopentacycles was constructed by the facile self-assembly of a bis(terpyridine)-carbazole monomer utilizing terpyridine-metal(II)-terpyridine connectivity; its photophysical properties were investigated.

Synthesis of a water-soluble hexameric metallomacrocycle and its oxidized single-wall carbon nanotube composite

Polycationic water-soluble metallomacrocycles possessing 12 positive charges that facilitate ionic coordination with the carboxylate moieties of Oxi-SWNTs form a nanotube composite en route to tailored electronic properties. The multiple ionic pair interactions between the positively charged metallohexamers and carboxylate modified SWNT are evidenced by TEM and AFM images.

Glassy carbon electrodes sequentially modified by cysteamine-capped gold nanoparticles and poly(amidoamine) dendrimers generation 4.5 for detecting uric acid in human serum without ascorbic acid interference

Glassy carbon electrodes (GCE) were sequentially modified by cysteamine-capped gold nanoparticles (AuNp@cysteamine) and PAMAM dendrimers generation 4.5 bearing 128-COOH peripheral groups (GCE/AuNp@cysteamine/PAMAM), in order to explore their capabilities as electrochemical detectors of uric acid (UA) in human serum samples at pH 2. The results showed that concentrations of UA detected by cyclic voltammetry with GCE/AuNp@cysteamine/PAMAM were comparable (deviation <±10%; limits of detection (LOD) and quantification (LOQ) were 1.7×10(-4) and 5.8×10(-4) mg dL(-1), respectively) to those concentrations obtained using the uricase-based enzymatic-colorimetric method. It was also observed that the presence of dendrimers in the GCE/AuNp@cysteamine/PAMAM system minimizes ascorbic acid (AA) interference during UA oxidation, thus improving the electrocatalytic activity of the gold nanoparticles.

Ni(II)1,4,8,11-tetraazacyclotetradecane electrocatalytic films prepared on top of surface anchored PAMAM dendrimer layers. A new type of electrocatalytic material for the electrochemical oxidation of methanol

Gold electrodes, previously prepared with surface anchored PAMAM dendrimers, were further modified with a Ni-containing tetraazamacrocycle resulting in a novel electrocatalytic material which proved to be particularly efficient for the electrochemical oxidation of methanol in basic aqueous medium.

Influence of Surface Confined PAMAM Dendrimers on the Electrochemistry and Electrochromic Efficiency of Prussian Blue Films

In this work, results on a preliminary study of the influence of surface confined poly(amidoamine) (PAMAM) dendrimers (DMs) in the electrochromic properties of iron hexacyanoferrate [Prussian blue, (PB)] films, are presented. The results show that the DM-modified surfaces promote not only larger PB surface coverage values but also a significant increase in the electrochromic efficiency when compared to surfaces constructed in the absence of PAMAM DMs. A complementary electrochemical study also showed that the underlying DM structure induces chemical proportions of Fe(III)/[Fe(CN) 6 ] 4- in the PB film that are closer to those expected for the perfectly structured PB species.

Electrophoretically-Assisted Deposition of Mesoporphyrin IX on Nanoparticulate TiO2 Films for Constructing Efficient Dye-Sensitized Solar Cells

The successful fabrication of efficient dye-sensitized solar cells containing electrophoretically-deposited mesoporphyrin IX in semiconductor films based on sintered TiO 2 nanoparticles is presented in this work. For comparison purposes, photocells utilizing mesoporphyrin IX-sensitized TiO 2 electrodes were also constructed following the traditional dip-coating deposition technique. Electrochemical responses obtained from these modified surfaces revealed that the electrophoretic methodology generated perpendicularly-arranged porphyrin layers on the sintered oxide nanoparticles, while the dip-coating deposition technique resulted in parallel layers of porphyrin. It was demonstrated that the photovoltaic performance of cells containing electrophoretically-dyed TiO 2 films was three times higher than that of devices having photoelectrodes constructed according to the dip-coating protocol. To better understand this behavior, both types of solar cells were further investigated by means of photoelectrochemical impedance spectroscopy.

5,10,15,20-Tetrakis[4′-(terpyridinyl)phenyl]porphyrin and its RuII complexes: Synthesis, photovoltaic properties, and self-assembled morphology

A novel tetrakis(terpyridinyl)porphyrin derivative and its Ru(II) complexes were efficiently synthesized using microwave enhanced synthesis and shown to possess photovoltaic properties. Transmission electron microscopy and selected area electron diffraction were used to investigate its nanowire self-assembly.

Generación de estados superficiales durante la formación electroforética catódica de películas de TiO2 sobre ito

In the present work TiO2 films were formed over Indium Tin Oxide (ITO) employing cathodic electrophoretic deposition (Cathodic-EPD) and Dr. Blade Technique. The films were characterized by electrochemical techniques in order to compare their electronic properties; as well as, their photoelectrochemical behavior. The electrochemical performance showed by the films, allowed to relate the modification occurring during the Cathodic-EPD, with the partial reduction of TiO2 nanoparticles, generating Ti3+ defects. These trapping states are modifying the electronic properties of the film, and diminishing the transport of the photoelectrogenerated electrons toward ITO.