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Polarized hydroxyapatite (p-HAp), a calcium phosphate catalyst obtained at high temperature under intense electric field, has been used for the synthesis of ammonium starting from N2 and liquid water at low pressure (

The synthesis of hydroxyapatite (HAp) with different shapes and sizes has attracted increasing attention because the applicability of this ceramic material depends on structure-properties relationships (i.e., the dimensions and morphology of HAp crystals determine properties such as the bioactivity and mechanical strength). Although different synthetic routes based on the addition of surfactants, organic modifiers, or dispersants have been proposed to control the growth of HAp crystals, many efforts are being devoted to simplify the whole process using simple parameters such as pH. However, the control of the morphology is still poor and shows low reproducibility. In this work, a new additive-free synthetic route, which is based on the hydrothermal method and the utilization of nonaqueous solvents, is proposed. The influence of the synthesis parameters such as pH, concentration of starting solutions, and the solvent on relevant features such as phase purity, crystallinity, crystallite size, and morphology has been examined using spectroscopic techniques, X-ray diffraction, and scanning electron microscopy. As a consequence, this work presents an easy and robust method based only on the use of organic solvent and the control of the pH that produces pure and crystalline HAp with a controlled shape and size. This method has been used to elucidate some of the key aspects of the crystal growth mechanism and to synthesize HAp crystals with different and well-defined shapes (e.g., belts, rods, flakes needle-like, or polymorph) and sizes, in a reproducible way.

The design of catalysts with controlled selectivity at will, also known as catalytic plasticity, is a very attractive approach for the recycling of carbon dioxide (CO2). In this work, we study how catalytically active hydroxyapatite (HAp) and brushite (Bru) interact synergistically, allowing the production of formic acid or acetic acid depending on the HAp/Bru ratio in the catalyst. Raman, wide angle X-ray scattering, X-ray photoelectron spectroscopy, scanning electron microscopy and electrochemical impedance spectroscopy studies, combined with an exhaustive revision of the crystalline structure of the catalyst at the atomic level, allowed to discern how the Bru phase can be generated and stabilized at high temperatures. Results clearly indicate that the presence of OH– groups to maintain the crystalline structural integrity in conjunction with Ca2+ ions less bonded to the lattice fixate carbon into C1, C2 and C3 molecules from CO2 and allow the evolution from formic to acetic acid and acetone. In this way, the plasticity of the HAp-Bru system is demonstrated, representing a promising green alternative to the conventional metal-based electrocatalysts used for CO2 fixation. Thus, the fact that no electric voltage is necessary for the CO2 reduction has a very favorable impact in the final energetic net balance of the carbon fixation reaction.

The insertion of an implant in the body of a patient raises the risk of a posterior infection and formation of a biofilm, which can have critical consequences on the patient's health and be associated with a high sanitary cost. While antibacterial agents can be used to prevent the infection, such a strategy is time-limited and causes bacteria resistance. As an alternative to biochemical approaches, we propose here to use light-induced local hyperthermia with plasmonic nanoparticles. This strategy is implemented on surgical meshes, extensively used in the context of hernia repairing, one of the most common general surgeries. Surgical meshes were homogeneously coated with gold nanorods designed to efficiently convert near-infrared light into heat. The modified mesh was exposed to a biofilm of Staphylococcus aureus ( S. aureus) bacteria before being treated with a train of light pulses. We systematically study how the illumination parameters, namely fluence, peak intensity and pulse length, influence the elimination of attached bacteria. Additionally, fluorescence confocal microscopy provides us some insight on the mechanism involved in the degradation of the biofilm. This proof-of-principle study opens a new set of opportunities for the development of novel disinfection approaches combining light and nanotechnology.

Conversion of CO2 into valuable chemicals is not only a very challenging topic but also a socially demanding issue. In this work, permanently polarized hydroxyapatite obtained using a thermal stimulated polarization process is proposed as a highly selective catalyst for green production of ethanol starting from CO2 and CH4.

The goal of this paper is the valorisation of the Chondrus crispus (Rhodophyta) wastes generated during the industrial extraction of hybrid carrageenan using microwave technology of a temperature range from 140 to 200 °C, using water as a solvent. Mineral and phenolic content, antioxidant capacity and thermorheological features of the recovered hybrid carrageenans were determined. Results indicated the suitability for the recovery of high valuable compounds from these algae residues, after the optimization of the extraction conditions. At microwave processing conditions (160 °C, 5 min), it is still possible to recover around 10% of semi-refined hybrid carrageenan from the industrial raw material as well as to achieve the maximum value of total phenolic compounds of 12.8 mg GAE/g extract and antioxidant capacity of 51.70 mg Trolox/g extract. Extracted biopolymers exhibited thermomechanical features, in terms of viscoelastic moduli or gelling and melting temperatures, comparable to their commercial counterparts.

Label-free biosensing based on metallic nano-particles supporting localized surface plasmon resonances (LSPR) has recently received growing interest (Anker, J. N., et al. Nat. Mater. 2008, 7, 442-453). Besides its competitive sensitivity (Yonzon, C. R., et al. J. Am. Chem. Soc. 2004, 126, 12669-12676; Svendendahl, M., et al. Nano Lett. 2009, 9, 4428-4433) when compared to the surface plasmon resonance (SPR) approach based on extended metal films, LSPR biosensing features a high-end miniaturization potential and a significant reduction of the interrogation device bulkiness, positioning itself as a promising candidate for point-of-care diagnostic and field applications. Here, we present the first, paralleled LSPR lab-on-a-chip realization that goes well beyond the state-of-the-art, by uniting the latest advances in plasmonics, nanofabrication, microfluidics, and surface chemistry. Our system offers parallel, real-time inspection of 32 sensing sites distributed across 8 independent microfluidic channels with very high reproducibility/repeatability. This enables us to test various sensing strategies for the detection of biomolecules. In particular we demonstrate the fast detection of relevant cancer biomarkers (human alpha-feto-protein and prostate specific antigen) down to concentrations of 500 pg/mL in a complex matrix consisting of 50% human serum.

Single-walled carbon nanotubes (SWCNTs) have been identified as a transporter for anti-cancer drugs, as they are capable of penetrating mammalian cell membranes and allow for a high drug loading due to their nanoscale dimensions and high aspect ratio. In addition, they can assist the targeting of therapeutic agents to the desired site of action by conjugation to antibodies or ligands of cancer cell surface receptors, which increases the effectiveness of the treatment and reduces side effects. In this work, we present a method for the triple functionalisation of oxidised SWCNTs with the anti-cancer drug doxorubicin, a monoclonal antibody, and a fluorescent marker at non-competing binding sites. The proposed methodology allows for the targeted delivery of the anti-cancer drug to cancer cells and the visualisation of the cellular uptake of SWCNTs by confocal microscopy. We show that the complex is efficiently taken up by cancer cells with subsequent intracellular release of doxorubicin, which then translocates to the nucleus while the nanotubes remain in the cytoplasm.

In this paper an in depth study is presented of the use of the horseradish peroxidase (HRP) enzyme as a self-indicating biorecognition reagent in UV-vis molecular absorption spectrometry. The HRP/H2O2 reaction mechanism in the absence of an external substrate has been clarified, and the interaction between HRP and glucose oxidase (GOx) has been studied. It has been demonstrated that GOx can act as a substrate of HRP; in both cases the kinetic constants have been obtained and mathematical models have been developed. Second, the HRP/H2O2 reaction is used to follow a H2O2-producing enzymatic reaction, the glucose reaction with GOx being used as a model. As an application of this, two methodologies have been proposed for glucose determination: with or without previous incubation of glucose with GOx. In both cases mathematical models relating HRP absorbance changes to glucose concentration have been developed and tested; both methods have been optimized, analytically characterized, and tested for glucose determination in samples. The methodology described could be applied to other heme-proteins and to other H2O2-producing enzymatic reactions. The models permit the reaction constants to be calculated. From the analytical chemistry point of view the models allow the prediction of the method sensitivity for other analytes involved in this type of reaction if the kinetic constants are known and can be used in the design of optical sensors.

The use of non-viral vectors as delivery systems in gene therapy has been extensively studied recently owing to their advantages over viral vectors. Here, we propose a new gene delivery system based on the use of RNA-wrapped single-walled carbon nanotubes (SWCNTs) complexed with the cationic protein, protamine and the drug chloroquine. Protamine was selected as a cationic protein acting as bridge between negatively charged RNA-wrapped SWCNTs and plasmid DNA. Protamine also contains a nuclear localization signal which enhances the expression of the transfected gene. The drug chloroquine, a lysosomotropic compound which has been reported to increase the transfection efficiency, was attached to RNA-wrapped SWNTs by ionic interactions. The simultaneous delivery of the drug chloroquine with plasmid DNA clearly showed an enhanced gene delivery and expression. The levels of gene expression were quantified using the luciferase reporter gene as model. Optimal conditions for transfection and gene expression were obtained and cytoxicity of the carbon nanotube complexes measured. The optimal complexes were shown to efficiently deliver plasmid DNA for efficient gene expression and may thereby be useful as gene delivery systems for gene therapy.

The surface chemistry of gold nanoparticles (AuNPs) plays a critical role in the self-assembly of thiolated molecules and in retaining the biological function of the conjugated biomolecules. According to the well-established gold–thiol interaction the undefined ionic species on citrate-reduced gold nanoparticle surface can be replaced with a self-assembled monolayer of certain thiolate derivatives and other biomolecules. Understanding the effect of such derivatives in the functionalization of several types of biomolecules, such as PEGs, peptides or nucleic acids, has become a significant challenge. Here, an approach to attach specific biomolecules to the AuNPs (~14 nm) surface is presented together with a study of their effect in the functionalization with other specific derivatives. The effect of biofunctional spacers such as thiolated poly(ethylene glycol) (PEG) chains and a positive peptide, TAT, in dsRNA loading on AuNPs is reported. Based on the obtained data, we hypothesize that loading of oligonucleotides onto the AuNP surface may be controlled by ionic and weak interactions positioning the entry of the oligo through the PEG layer. We demonstrate that there is a synergistic effect of the TAT peptide and PEG chains with specific functional groups on the enhancement of dsRNA loading onto AuNPs.

An in-depth study of a novel functionalization of carbon nanotubes for their application as protein and DNA carriers is presented. First, the optimum conditions for the dispersion of singlewalled carbon nanotubes (SWCNTs) with amphiphilic polypeptides were obtained, and the SWCNT–polypeptide complexes were characterized by different techniques (UV–Vis-NIR, CD, and AFM). Based on the properties of the SWCNT–polypeptide complexes, a model that characterizes the adsorption of natural proteins onto SWCNT was described for the first time. This model predicts the adsorption of natural proteins on SWCNTs based on the protein structure and composition, and therefore, allows the design of methods for the preparation of SWCNT–protein complexes. Besides, the use of cationic-designed amphiphilic polypeptides to disperse SWCNTs is applied for subsequent and efficient binding of DNA to carbon nanotubes by a bilayer approach. Therefore, in this article, we develop procedures for the use of SWCNTs as protein and DNA carriers. The systems were delivered into cells showing that the efficiency of delivery is affected by the charge of the complexes, which has important implications in the use of SWCNT as platforms for protein and DNA binding and subsequent use as delivery systems.

The use of carbon nanotubes as a gene delivery system has been extensively studied in recent years owing to its potential advantages over viral vectors. To achieve this goal, carbon nanotubes have to be functionalized to become compatible with aqueous media and to bind the genetic material. To establish the best conditions for plasmid DNA binding, we compare the dispersion properties of single-, double- and multi-walled carbon nanotubes (SWCNTs, DWCNTs and MWCNTs, respectively) functionalized with a variety of surfactants by non-covalent attachment. The DNA binding properties of the functionalized carbon nanotubes were studied and compared by electrophoresis. Furthermore, a bilayer functionalization method for DNA binding on SWCNTs was developed that utilized RNA-wrapping to solubilize the nanotubes and cationic polymers as a bridge between nanotubes and DNA.