This critical review introduces a discussion on the influence of preparative procedures (nanofabrication) of nanostructured hybrids and biohybrids, comparing their structural and textural characteristics that determine the properties of the resulting materials. Selected examples of silicate-based hybrids of analogous compositions prepared by both molecular and blocks-assembly bottom–up strategies are discussed to show advantages and inconveniences of each methodology (341 references).

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Hybrid and biohybrid silicate based materials: molecular vs. block-assembling bottom–up processes

A high sensitive visible light-driven photoelectrochemical aptasensor for shrimp allergen tropomyosin detection using graphitic carbon nitride-TiO2 nanocomposite.

Cytokine sensing is challenging due to their typically low abundances in physiological conditions Nanomaterial fabricated interfaces demonstrated unique advantages in ultrasensitive sensing Here, we demonstrate an amperometric sensing device based on graphene oxide (GO) and structure-switching aptamers for long-term detection of cytokines in a living organism The device incorporates a single layer of GO acting as a signal amplifier on glassy carbon electrodes The hairpin aptamers specific to interferon-γ (IFN-γ), which were loaded with redox probes, are covalently attached to GO to serve as biorecognition moieties IFN-γ was able to trigger the configuration change of aptamers while releasing the trapped redox probes to introduce the electrochemical signal This in vivo device was capable of quantitatively and dynamically detecting IFN-γ down to 13 pg mL–1 secreted by immune cells in cell culture medium with no baseline drift even at a high concentration of other nonspecific proteins The biocompatib

Graphene Oxide Based Recyclable in Vivo Device for Amperometric Monitoring of Interferon-γ in Inflammatory Mice.

We report a first principles density functional theoretical (DFT) investigation of guanine (G) adsorption onto SiO2 clusters, viz., Si2O4, Si3O6, Si4O8 and Si5O10 in terms of geometry, binding energy (EB), binding site, energy gap (Eg), and electronic and spectral properties. Guanine entrapped within a Si9O18 cluster was also studied in terms of geometry, energy gap (Eg), electronic and spectral properties. We observed that the most stable forms of the cluster were Si5O10 and Si9O18. Guanine adsorbed onto SiO2 (G–SiO2) and guanine entrapped within SiO2 (GE–SiO2) were analyzed by the B3LYP/LanL2DZ method. The HOMO–LUMO energies illustrate that charge transfer from ligand to metal (L → M) occurs in G–SiO2 clusters as guanine to SiO2. The composite of guanine with nanostructured silica material was prepared by simple precipitation and chemical sol–gel processes. The prepared G–SiO2 and GE–SiO2 composites were characterized by FT-IR and FE-SEM with EDX analysis. The resulting experimental evidence is included for better understanding the guanine adsorption and entrapment. The adsorption and entrapping of G–SiO2 and GE–SiO2 was also confirmed by UV-vis spectroscopy. Experimental results are compared with the DFT results. Furthermore, the sol–gel silicate material used to protect the DNA base (guanine) from UVA-irradiation has been highlighted.

Experimental and first-principles investigation of the adsorption and entrapping of guanine with SiO2 clusters of sol–gel silicate material for understanding DNA photodamage

Kanamycin (Kana) is widely used as a veterinary medicine and its abuse causes a serious threat to human health, raising the urgent demand for detection of residual Kana in animal-derived food with high specificity and sensitivity. Here, we developed a photoelectrochemical (PEC) biosensor for rapid quantification of Kana, with lead sulfide quantum dots/titanium dioxide nanoparticles (PbS QDs/TiO2 NPs) as a photosensitive composite, a Kana-specific DNA aptamer as a functional sensor, and ruthenium(III) hexaammine (Ru(NH3)63+) as a signal booster. To prepare the PEC aptasensor, TiO2 NPs, PbS QDs, and polyethyleneimine (PEI) were respectively used to modify the indium tin oxide electrode, and then the amine-terminated aptamer probe was connected to the PEI via glutaraldehyde. Finally, Ru(NH3)63+ was attached on the surface of the aptamer to increase the photocurrent intensity. When Kana binds competitively with Ru(NH3)63+ to the aptamer immobilized on the surface of the aptasensor, Ru(NH3)63+ will be released from the aptamer, resulting in a decrease of the photocurrent signal. This PEC aptasensor exhibits a good linear relationship between the photocurrent shift and the logarithm of Kana concentration within the range of 1.0-300.0 nmol L-1, and the detection limit is 0.161 nmol L-1. Importantly, the PEC aptasensor presented good detection selectivity owing to specific interaction with Kana and was successfully implemented to quantify Kana in honey and milk, suggesting that the PEC aptasensor has the potential of rapid detection of residual Kana in animal-derived foods.

Photoelectrochemical Aptasensors Constructed with Photosensitive PbS Quantum Dots/TiO2 Nanoparticles for Detection of Kanamycin.

The interactions between DNA purines (guanine and adenine) and the ruthenium complex Ru(NO)(NO3)3 were studied within nanostructured silica matrices prepared by a two-step sol−gel process. By infra...

Encapsulation of ruthenium nitrosylnitrate and DNA purines in nanostructured sol-gel silica matrices.

The interactions between DNA purines (guanine and adenine) and three ruthenium ammine complexes (hexaammineruthenium(III) chloride, hexaammineruthenium(II) chloride, and ruthenium-red) were studied in a confined environment, within sol−gel silica matrixes Two encapsulation methods were rehearsed (differing in temperature and condensation pH), in order to analyze the effects of the sol−gel processes on the purines and on the Ru complexes separately The extent of decomposition of the Ru complexes, as well as the interactions established with the purine bases, proved to be determined by the coencapsulation method Combined results by diffuse reflectance UV−vis and infrared spectroscopies showed that, when coencapsulation is carried out at 60 °C, specific H bonding interactions are established between the amine group of Ade and the ammine groups of the Ru complex or the hydroxo group of an early decomposition product These are responsible for the important role of the purine in inhibiting the oxidation rea

Interactions between DNA purines and ruthenium ammine complexes within nanostructured sol-gel silica matrixes.

The stability of the antitumor Ru(III) complex (H(2)trz)[trans-RuCl(4)(N(2)-Htrz)(2)] within a tailored sol-gel silica matrix was studied, combining the information from UV-vis and infrared spectroscopies. The matrix was synthesized by a one-step sol-gel process catalyzed by hydrofluoric acid, resulting extremely light, hydrophobic and fluorinated. It is shown that upon encapsulation, the complex undergoes a series of processes, starting with the increase in charge density on the metal center, followed by hydrolysis reactions. The modified complex interacts with the matrix through hydrogen bonds between the aquo/hydroxo ligands and the fluorine atoms. Its interactions with DNA purines (guanine and adenine) were probed within the confined medium defined by the same silica matrix. It is found that coencapsulated guanine does not interfere with the complex aquation processes, while coencapsulated adenine has a delaying effect. No covalent bonding between the complex and the purines is detected, but interactions between the triazole ligands and the imidazole ring of guanine and the imidazole and pyrimidine rings of adenine are observed. Hydrogen bonding is established between the carbonyl and the ammine groups of guanine and the aquo/hydroxo ligands of the complex. For adenine, those interactions involve mostly the N9H of the purine and the NH groups of the triazole ligands, in addition to π-π interactions.

Luís M. F. Lopes

Papers

Encapsulation of ruthenium nitrosylnitrate and DNA purines in nanostructured sol-gel silica matrices.

Interactions between DNA purines and ruthenium ammine complexes within nanostructured sol-gel silica matrixes.

Reactivity of the antitumor complex (H2trz)[trans-RuCl4(N2-Htrz)2] in the presence of DNA purines within a fluorinated silica matrix.