Carmen Coll

Enzyme-mediated controlled release systems by anchoring peptide sequences on mesoporous silica supports.

We thank the Spanish Government (projects MAT2009-14564-C04, CB07/01/2012, and BIO2007 60066), the Generalitat Valencia (project PROMETEO/2009/016, PROMETEO/2010/005), and the CIBER-BBN for their support.

A Mesoporous 3D Hybrid Material with Dual Functionality for Hg2+ Detection and Adsorption

Dual-function hybrid material U1 was designed for simultaneous chromofluorogenic detection and removal of Hg(2+) in an aqueous environment. Mesoporous material UVM-7 (MCM41 type) with homogeneously distributed pores of about 2-3 nm in size, a large specific surface area exceeding 1000 m(2) g(-1), and nanoscale particles was used as an inorganic support. The mesoporous solid is decorated with thiol groups that were treated with squaraine dye III to give a 2,4-bis(4-dialkylaminophenyl)-3-hydroxy-4-alkylsulfanylcyclobut-2-enone (APC) derivative that is covalently anchored to the inorganic silica matrix. The solid was characterised by various techniques including X-ray diffraction, transmission electron microscopy, Raman spectroscopy, and nitrogen adsorption. This hybrid solid is the chemodosimeter for Hg(2+) detection. Hg(2+) reacts with the APC fragment in U1 with release of the squaraine dye into the solution, which turns deep blue and fluoresces strongly. Naked-eye Hg(2+) detection is thus accomplished in an easy-to-use procedure. In contrast, U1 remains silent in the presence of other thiophilic transition metal ions, alkali and alkaline earth metal ions, or anions ubiquitously present in water such as chloride, carbonate, sulfate, and phosphate. Material U1 acts not only as chemodosimeter that signals the presence of Hg(2+) down to parts-per-billion concentrations, but at the same time is also an excellent adsorbent for the removal of mercury cations from aqueous solutions. The amount of adsorbed mercury ranges from 0.7 to 1.7 mmol g(-1), depending on the degree of functionalisation. In addition, hybrid material U1 can be regenerated for both sensing and removal purposes. As far as we know, U1 is the first example of a promising new class of polyfunctional hybrid supports that can be used as both remediation and alarm systems by selective signalling and removal of target species of environmental importance. Model compounds based on silica gel (G1), fumed silica (F1), and micrometre-sized MCM-41 scaffolds (M1) were also prepared and studied for comparative purposes.

Controlled release of vitamin B2 using mesoporous materials functionalized with amine-bearing gate-like scaffoldings

A study on the controlled release of vitamin B(2) in pure water from mesoporous silica-based materials containing a pH- and anion-controlled nano-supramolecular gate-like ensembles built up by anchoring suitable polyamines on the external surface is reported (solid S1). This solid contains the vitamin (the delivered molecule) onto the pores, whereas the amine-based gate-like ensemble is anchored on the pore outlets. To obtain solid S1 the mesoporous MCM-41 support was first synthesized using tetraethyl orthosilicate (TEOS) as hydrolytic inorganic precursor and the surfactant hexadecyltrimethylammonium bromide (CTAB) as porogen species. Calcination of the mesostructured phase resulted in the starting solid. Then, first the vitamin and the latter an excess of 3-[2-(2-aminoethylamino)ethylamino]propyl-trimethoxysilane were added to the suspension containing the MCM-41 scaffolding and stirred. Solid S1 was characterized using standard solid state procedures. It was found that the functionalization process and the inclusion of the vitamin on the pores do not modify the mesoporous structure of the starting material. Delivery studies in water were carried out at pH 2 and 7. At pH 2 all the anions studied (sulfate, phosphate, GMP and ATP) strongly hinder vitamin release (C(anion)=1 x 10(-2) mol dm(-3)), whereas at pH 7 the delivery was observed for sulfate and GMP whereas the gate remained closed in the presence of ATP and phosphate. Selective delivery at neutral pH and no-liberation in acidic conditions can also be controlled with ATP and GMP using a suitable concentration of anion. The remarkable anion-controllable response of the gate-like ensemble at a certain pH can be explained in terms of anion complex formation with the tethered polyamines. Finally, selectivity patterns have been discussed in terms of kinetic rates of vitamin B(2) release. The pH-controlled gate-like scaffoldings on S1 might be a suitable prototype for the development of orally applicable delivery systems designed to have the particular ability to protect the cargo from the acidic conditions of the stomach (acid pH, gate closed) but will release the load at the intestine (basic pH, gate open).

An aptamer-gated silica mesoporous material for thrombin detection

An aptamer-capped mesoporous material for the selective and sensitive detection of α-thrombin in human plasma and serum has been prepared and characterised.

Nanoscopic hybrid systems with a polarity-controlled gate-like scaffolding for the colorimetric signalling of long-chain carboxylates

Hybrid mesoporous systems containing a gate-like ensemble functionalised with imidazolium groups and a dye are used for the selective colorimetric sensing of long-chain carboxylates.

Structural properties of positive linear time-invariant difference-algebraic equations☆

In this paper we analyze positive difference-algebraic equations. Conditions regarding some of the matrices involved in the solution of this kind of systems are described. Geometrical conditions are used to characterize positive structural properties.

Dual Enzyme-Triggered Controlled Release on Capped Nanometric Silica Mesoporous Supports

The development of nanoscopic hybrid materials equipped with “molecular gates” showing the ability of releasing target entrapped guests upon the application of an external trigger has attracted great attention and has been extensively explored during recent years.1 These nanodevices are composed of two subunits, namely, a suitable support and certain capping entities grafted on the surface of the scaffolding.2 The support is used as a suitable reservoir in which certain chemicals can be stored whereas the molecules grafted in the outer surface act as a “gate” and can control the release of the entrapped molecules at will. Both components are carefully selected and arranged in order to achieve a wide range of required functionalities.

Design of enzyme-mediated controlled release systems based on silica mesoporous supports capped with ester-glycol groups

An ethylene glycol-capped hybrid material for the controlled release of molecules in the presence of esterase enzyme has been prepared. The final organic-inorganic hybrid solid S1 was synthesized by a two-step procedure. In the first step, the pores of an inorganic MCM-41 support (in the form of nanoparticles) were loaded with [Ru(bipy)(3)]Cl(2) complex, and then, in the second step, the pore outlets were functionalized with ester glycol moieties that acted as molecular caps. In the absence of an enzyme, release of the complex from aqueous suspensions of S1 at pH 8.0 is inhibited due to the steric hindrance imposed by the bulky ester glycol moieties. Upon addition of esterase enzyme, delivery of the ruthenium complex was observed due to enzymatic hydrolysis of the ester bond in the anchored ester glycol derivative, inducing the release of oligo(ethylene glycol) fragments. Hydrolysis of the ester bond results in size reduction of the appended group, therefore allowing delivery of the entrapped cargo. The S1 nanoparticles were not toxic for cells, as demonstrated by cell viability assays with HeLa and MCF-7 cell lines, and were found to be associated with lysosomes, as shown by confocal microscopy. However, when S1 nanoparticles were filled with the cytotoxic drug camptothecin (S1-CPT), S1-CPT-treated cells undergo cell death as a result of S1-CPT cell internalization and subsequent cellular enzyme-mediated hydrolysis and aperture of the molecular gate that induced the release of the camptothecin cargo. These findings point to a possible therapeutic application of these nanoparticles.

Positive solutions of a discrete-time descriptor system

Discrete-time linear descriptor systems with restrictions over their trajectory are considered. In this work, some conditions required to achieve nonnegative output-response are studied. State–feedback and dynamic compensators are constructed to achieve the desired property. Finally, some applications to the Leontief economic model are given.

Positive N-periodic descriptor control systems ☆

This paper establishes the relationship between the positive N-periodic descriptor system in discrete-time and its associated invariant systems. Reachability and controllability properties of these kinds of systems are analyzed. Transmission of structural properties from the N-periodic system to their associated invariant systems is studied. Finally, some comments on the stability property are made.