Micropatterning of Poly (N-isopropylacrylamide) (PNIPAAm) Hydrogels: Effects on Thermosensitivity and Cell Release Behavior

The thermally driven, reversible change in the surface properties of poly (N-isopropylacrylamide) (PNIPAAm) hydrogels from a hydrophilic (water-swollen) state to a hydrophobic (deswollen) state when heated above the volume phase transition temperature (VPTT, ~35 oC) makes them useful in inducing controlled cell release. To improve the kinetics of swelling and deswelling, we have prepared microstructured (i.e., micropillared) thermoresponsive surfaces comprising pure PNIPAAm hydrogel and nanocomposite PNIPAAm hydrogel embedded with polysiloxane colloidal nanoparticles (~220 nm diameter, 1 wt%) via photopolymerization. The thermosensitivity (i.e., degree and rate of swelling/deswelling) of these surfaces and how it can be regulated using different micropillar sizes and densities were characterized by measuring the dynamic size changes in micropillar dimensions in response to thermal activation. Our results show that the dynamic thermal response rate can be increased by more than twofold when the micropillar size is reduced from 200 to 100 μm. The temperature-controlled cell release behaviors of pure PNIPAAm and nanocomposite PNIPAAm micropatterned surfaces were successfully characterized using mesenchymal progenitor cells (10T1/2). This study demonstrates that the thermosensitivity of PNIPAAm surfaces can be regulated by introducing micropillars of different sizes and densities, while maintaining good temperature-controlled cell release behavior

SUSTRACCIÓN Y RESTITUCIÓN DE MENORES EN EL DERECHO INTERNACIONAL Y EN EL DERECHO CONSTITUCIONAL MEXICANO

El tema de la sustracción de menores, obliga a hacer referencia a la guarda y custodia, derivada de la figura de la patria potestad, la que vinculada a la organización de la familia, ha sufrido, como esta, importantes variaciones en las últimas décadas, ante lo vertiginoso de los desplazamientos de personas a lo largo y ancho del mundo, con fines laborales, profesionales, académicos, artísticos, financieros, turísticos, empresariales, energéticos, inclusive delincuenciales, -por ejemplo, los terroristas-, y un largo etcétera, provocando la creación de relaciones de todo tipo, en el ámbito familiar: conyugales, concubinarias, de filiación y parentesco, entre personas de diferente nacionalidad, con las consecuencias legales inherentesEl presente capítulo de libro titulado ¨SUSTRACCIÓN Y RESTITUCIÓN DE MENORES EN EL DERECHO INTERNACIONAL Y EN EL DERECHO CONSTITUCIONAL MEXICANO¨ desarrolla una explicación acerca de los menores, abarcando desde el momento en que adquieren la protección del orden jurídico, asi, como quienes lo protegerán en ese orden jurídico, es decir, los padres que ejercen la patria potestad, otorgando de estos últimos una descripción explicativa de la potestad jurídica que se les otorg

Bacteria and diatom resistance of silicones modified with PEO-silane amphiphiles

International audienceSilicone coatings with enhanced antifouling behavior towards bacteria, diatoms, and a diatom dominated slime were prepared by incorporating PEO-silane amphiphiles with varied siloxane tether lengths (a-c): -(EtO)(3)Si(CH2)(2)-oligodimethylsiloxane(n)-block-poly(ethylene oxide)(8)-OCH3 [n=0 (a), 4 (b), and 13 (c)]. Three modified silicone coatings (A-C) were prepared by the acid-catalyzed sol-gel cross-linking of a-c, respectively, each with a stoichiometric 2:3M ratio of , -bis(Si-OH)polydimethylsiloxane (M-n=3,000gmol(-1)). The coatings were exposed to the marine bacterium Bacillus sp.416 and the diatom (microalga) Cylindrotheca closterium, as well as a mixed community of Bacillus sp. and C. closterium. In addition, in situ microfouling was assessed by maintaining the coatings in the Atlantic Ocean. Under all test conditions, biofouling was reduced to the highest extent on coating C which was prepared with the PEO-silane amphiphile having the longest siloxane tether length (c)

Implant-based repair of osteochondral defects

The present invention is directed to a unique technology for preparing a growth-factor free, cylindrical, hydrogel implant that has multiple (three or more) longitudinal hydrogel zones with varying chemical and physical properties. The implant may be wholly made of hydrogels or the hydrogels may be associated with cells, such as mesenchymal stem cells (MSCs).U

Non-toxic, anti-fouling silicones with variable PEO–silane amphiphile content

International audienc

Implant-based repair of osteochondral defects

The present invention is directed to a unique technology for preparing a growth-factor free, cylindrical, hydrogel implant that has multiple (three or more) longitudinal hydrogel zones with varying chemical and physical properties. The implant may be wholly made of hydrogels or the hydrogels may be associated with cells, such as mesenchymal stem cells (MSCs).U

Shape memory polymer scaffolds for tissue defects

A method of making a shape memory polymer (SMP) tissue scaffold includes forming a salt template and adding a macromer solution to the salt template. The macromer solution may include a photoinitiator solution. The method includes drying the SMP scaffold and leaching salt from the SMP scaffold. A coating is then applied to the SMP scaffold. The coating may be applied either before or after heating the SMP scaffold.U

Self-Cleaning Membrane to Extend the Lifetime of an Implanted Glucose Biosensor

The lifetime and efficacy of a subcutaneously implanted glucose biosensor could be greatly improved by a self-cleaning membrane capable of periodic physical removal of adhered cells associated with the foreign body reaction. Previously, we reported a thermoresponsive double network nanocomposite (DNNC) membrane composed of poly­(<i>N</i>-isopropylacrylamide) (PNIPAAm) and embedded polysiloxane nanoparticles. When the membrane was thermally cycled above and below its volume phase transition temperature (VPTT, ∼33–35 °C), the associated deswelling and reswelling, respectively, led to in vitro cell release. Herein, this membrane design was tailored to meet the specific demands of a subcutaneously implanted glucose biosensor, and critical functional properties were assessed. First, <i>N</i>-vinylpyrrolidone (NVP) comonomer increased the VPTT to ∼38 °C so that the membrane would be swollen and thus more permeable to glucose in the “off-state” (i.e., no heating) while residing in the subcutaneous tissue (∼35 °C). Second, glucose diffusion kinetics though the DNNC membrane was experimentally measured in its deswollen and reswollen states. A cylindrical DNNC membrane with dimensions considered suitable for implantation (1.5 × 5 mm, diameter × length) was used to model the glucose diffusion lag time. In addition, the DNNC cylinder was used to observe dimensional changes associated with deswelling and reswelling. Noncytotoxicity was confirmed and self-cleaning was assessed in vitro in terms of thermally driven cell release to confirm the potential of the DNNC membrane to control biofouling

Investigating the Effect of an Antifouling Surface Modification on the Environmental Impact of a Pasteurization Process: An LCA Study

International audienc