Hollow Silica Microparticles Based on Amphiphilic Polyphosphazenes.

Hollow microparticles are important materials, offering a larger surface area and lower density than their solid counterparts. Furthermore, their inner void space can be exploited for the encapsulation and release of guest species in a variety of applications. Herein, we present phosphazene-based silica hollow microparticles prepared via a surfactant-free sol-gel process through self-assembly of the alkoxysilyl-containing polymer in water-ethanol solution. Solely, a silane-derived polyphosphazene was used as the precursor for the microparticle formation, without additional classical silica sources. These novel hollow silica-based microparticles were prepared without surfactant, using a designed amphiphilic polyphosphazene for the particle formation made by two components, a hydrophilic unit consisting of 3-mercaptopropyl(trimethoxysilane), and a hydrophobic unit (dodecanethiol) attached to the double bonds from the poly(allylamine)phosphazene backbone via a thiol-ene photoreaction. Due to these two functionalities, a "vesicle"-like self-assembled structure was formed in the reaction medium, which could be then utilized for the microparticle preparation. The influence of NaOH during the synthesis was shown to affect the size and the wall thickness of the microparticles. This effect may enhance the possibilities to tailor such microparticles for drug delivery purposes or for future controlled release of other substances, such as drugs, fragrances, or anticorrosive pigments.

Reversible Speed Regulation of Self-Propelled Janus Micromotors via Thermoresponsive Bottle-Brush Polymers.

This work reports a reversible braking system for micromotors that can be controlled by small temperature changes (≈5 °C). To achieve this, gated-mesoporous organosilica microparticles are internally loaded with metal catalysts (to form the motor) and the exterior (partially) grafted with thermosensitive bottle-brush polyphosphazenes to form Janus particles. When placed in an aqueous solution of H2 O2 (the fuel), rapid forward propulsion of the motors ensues due to decomposition of the fuel. Conformational changes of the polymers at defined temperatures regulate the bubble formation rate and thus act as brakes with considerable deceleration/acceleration observed. As the components can be easily varied, this represents a versatile, modular platform for the exogenous velocity control of micromotors.

Dual stimuli-responsive polyphosphazene-based molecular gates for controlled drug delivery in lung cancer cells.

A switchable silane derived stimuli-responsive bottle-brush polyphosphazene (PPz) was prepared and attached to the surface of mesoporous silica nanoparticles (MSNs). The hybrid polymer with PEG-like Jeffamine® M-2005 side-arms undergo conformational changes in response to both pH and temperature due to its amphiphilic substituents and protonatable main-chain, hence were investigated as a gatekeeper. Safranin O as control fluorophore or the anticancer drug camptothecin (CPT) were encapsulated in the PPz-coated MSNs. At temperatures below the lower critical solution temperature (LCST), the swollen conformation of PPz efficiently blocked the cargo within the pores. However, above the LCST, the PPz collapsed, allowing release of the payload. Additionally, protonation of the polymer backbone at lower pH values was observed to enhance opening of the pores from the surface of the MSNs and therefore the release of the dye. In vitro studies demonstrated the ability of these nanoparticles loaded with the drug camptothecin to be endocytosed in both models of tumor (A549) and healthy epithelial (BEAS-2B) lung cells. Their accumulation and the release of the chemotherapeutic drug, co-localized within lysosomes, was faster and higher for tumor than for healthy cells, further, the biocompatibility of PPz-gated nanosystem without drug was demonstrated. Tailored dual responsive polyphosphazenes thus represent novel and promising candidates in the construction of future gated mesoporous silica nanocarriers designs for lung cancer-directed treatment.

Mesoporous Silica Micromotors with a Reversible Temperature Regulated On-Off Polyphosphazene Switch.

The incorporation of an extraneous on-off braking system is necessary for the effective motion control of the next generation of micrometer-sized motors. Here, the design and synthesis of micromotors is reported based on mesoporous silica particles containing bipyridine groups, introduced by cocondensation, for entrapping catalytic cobalt(II) ions within the mesochannels, and functionalized on the surface with silane-derived temperature responsive bottle-brush polyphosphazene. Switching the polymers in a narrow temperature window of 25-30 °C between the swollen and collapsed state, allows the access for the fuel H2 O2 contained in the dispersion medium to cobalt(II) bipyridinato catalyst sites. The decomposition of hydrogen peroxide is monitored by optical microscopy, and effectively operated by reversibly closing or opening the pores by the grafted gate-like polyphosphazene, to control on demand the oxygen bubble generation. This design represents one of the few examples using temperature as a trigger for the reversible on-off external switching of mesoporous silica micromotors.

Biocompatible Phenylboronic-Acid-Capped ZnS Nanocrystals Designed As Caps in Mesoporous Silica Hybrid Materials for on-Demand pH-Triggered Release In Cancer Cells.

Biocompatible ZnS-based nanocrystals capped with 4-mercaptophenylboronic acid (ZnS@B) have been size-designed as excellent pH-responsive gatekeepers on mesoporous silica nanoparticles (MSNs), which encapsulate fluorophore safranin O (S2-Saf) or anticancer drug epirubicin hydrochloride (S2-Epi) for delivery applications in cancer cells. In this novel hybrid system, the gate mechanism consists of reversible pH-sensitive boronate ester moieties linking the nanocrystals directly to the alcohol groups from silica surface scaffold, avoiding tedious intermediate functionalization steps. The ∼3 nm size of the ZnS@B nanocrystals was tailored to allow efficient sealing of the pore voids and achieve a "zero premature cargo release" at neutral pH (7.4). The system selectively released the cargo in acidic conditions (pH 5.4 and 3.0) because of the hydrolysis of the boronate esters, which unblocked the pore voids. Delivery of the cargo by off-on cycles was demonstrated by changes in pH from 7.4 to 3.0, showing its potential pH-switching behavior. Cellular uptake of these nanocarriers within human cervix adenocarcinoma (HeLa) cells was achieved and the controlled release of the chemotherapeutic drug epirubicin was shown to occur within the endogenous endosomal/lysosomal acidified cancer cell microenvironment and further diffused into the cytosol. Cytotoxicity tests done on the mesoporous support without cargo and covalently linked with ZnS@B nanocrystals as caps were negative, suggesting that the proposed system is biocompatible and can be considered as a very promising drug nanocarrier.

Molecularly Imprinted Polymer Coated Quantum Dots for Multiplexed Cell Targeting and Imaging.

Advanced tools for cell imaging are of great interest for the detection, localization, and quantification of molecular biomarkers of cancer or infection. We describe a novel photopolymerization method to coat quantum dots (QDs) with polymer shells, in particular, molecularly imprinted polymers (MIPs), by using the visible light emitted from QDs excited by UV light. Fluorescent core-shell particles specifically recognizing glucuronic acid (GlcA) or N-acetylneuraminic acid (NANA) were prepared. Simultaneous multiplexed labeling of human keratinocytes with green QDs conjugated with MIP-GlcA and red QDs conjugated with MIP-NANA was demonstrated by fluorescence imaging. The specificity of binding was verified with a non-imprinted control polymer and by enzymatic cleavage of the terminal GlcA and NANA moieties. The coating strategy is potentially a generic method for the functionalization of QDs to address a much wider range of biocompatibility and biorecognition issues.

Smart Polymeric Nanoparticles as Emerging Tools for Imaging--The Parallel Evolution of Materials.

The field of imaging has developed considerably over the past decade and recent advances in the area of nanotechnology, in particular nanomaterials, have opened new opportunities. Polymeric nanoparticles are particularly interesting and a number of novel materials, characterized by stimuli-responsive characteristics and fluorescent tagging, have allowed visualization, intracellular labeling and real-time tracking. In some of the latest applications the nanoparticles have been used for imagining of tumor cells, both in vivo and ex vivo.

Efecto del proceso de extrusión del sorgo sobre el color de las harinas y tortillas a base de mezclas con harina de maíz / Effect of the extrusion process in the color of instant sorghum flours and its tortillas prepared with different levels of lime-treated corn flours

Fue estudiado el efecto del proceso de extrusión sobre el color de las harinas instántaneas de sorgo y sus respectivas tortillas elaboradas con diferentes niveles de substitución con harinas de maíz nixtamalizada. En el proceso de extrusión fueron utilizadas cuatro harinas obtenidas de dos genotipos de sorgo (integral y decorticado de cada genotipo). Estas harinas fueron procesadas en el extrusor de laboratorio Braberder GNF/2 de tornillo sin fin único. Para la elaboración de tortillas de sorgo y mezclas maíz-sorgo fueron seleccionadas 4 harinas del proceso de extrusión, 1) Cultivar CMSXS 9A: harina integral extrdida con 15% de humedad y con una velocidad de tornillo de 1.30 rpm y harina de sorgo decorticado con tamaños de particula menores de 0.420 mm extrudida con 15% de humedad y con una velocidad de tornillo de 1.30 rpm; 2) Cultivar CMSXS 145: harina integral extrudida con 18% de humedad y con una velocidad de tornillo de 170 epm y harina de sorgo decorticado extrudida con 15% de humedad y con una velocidad y con una de tornillo de 1.30 rpm. Las harinas instantáneas y tortillas obtenidas de sorgos decorticados (20%) presentaron colores más blancos (mayores valores de L) en relación con sus respectivas harinas integrales. La adición de niveles crecientes de harina de maíz nixtamalizada (10, 20, 30, 40 y 50%) a las harinas de sorgo instantáneas, mejoraron el color de las mezclas de harinas y su respectivas tortillas, principalmente en el caso de harinas integrales de sorgo. Los resultados obtenidos indicaron un cambio considerable en las características de color de las harinas, cuando fueron transformadas en tortillas, obteniéndose los mejores resultados con las tortillas elaboradas con harina de sorgo decorticado de ambos genotipos y en el caso de harinas integrales, las mezclas con harina de maíz mejoraron sensiblemente el color de las tortillas. Estos resultados indicaron que la separación de las capas externas del grano, posibilitó la obtención de tortillas con mejores características de color en relación a las tortillas elaboradas con harina de sorgo integral

Propiedades físicas, químicas y correlaciones de maíces híbridos precoces para valles altos / Physical and chemical properties and correlations of early corn kernels for high valleys

La evaluación de las propiedades físicas y químicas del grano de maíz permite caracterizar de manera integral las variedad4es experimentales que presentan buen rendimiento y características agronómicas favorables, los objetivos del presente estudio fueron: 1) clasificar 24 hibridos modernos de maíz tipo precoz; en base al tipo de endospermo y 2) determinar sus propiedades físico-químicas y su correlaciones. Los parámetros físicos fueron: peso hectolitrico (Peh), textura de endospermo (TE), índice de perlado (IP), peso de 1000 granos (P1000), reflectancia en el infrarrojo (NIR) y color (Ref), los químicos: proteína (Prt), lisina (Lis) y triptofano (trp). La clasificación en base al IP Permitió detectar 5 híbridos con endospermo suave, 12 intermedios y 7 duros. Los híbridos con endospermo duro presentaron el promedio Peh de 80.30 Kg/hl, Prt de 10.70%, Trip 0.082% y NIR de 0.35, que fueron estadísticamente mayores a aquellos de los híbridos con endospermo suave. El IP correlacionó negativamente con Prt. NIR y Peh y positivamente con Ref, lo cual significa que los maíces con endospermo suave o harinoso presentaron menor contenido de proteína, menor tamaño medio de partícula en la harina, mayor tamaño de grano y harina de color más claro. Se detectaron híbridos con rendimientos de 8.1 a 9.5 ton ha-1 con endospermo suave, intermedio o duro