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Self-Assembly behavior of amphiphilic janus dendrimers in water: a combined experimental and coarse-grained molecular dynamics simulation approach(Instituto Tecnológico y de Estudios Superiores de Monterrey, 2018-05-14)Amphiphilic Janus dendrimers (JDs) are repetitively branched molecules with hydrophilic and hydrophobic components that self-assemble in water to form a variety of morphologies, including vesicles analogous to liposomes with potential pharmaceutical and medical application. To date, the self-assembly of JDs has not been fully investigated thus it is important to gain insight into its mechanism and dependence on JDs’ molecular structure. In this study, a series of amphiphilic JDs with variations in their core and branching pattern was synthesized and its aggregation behavior in water was evaluated using experimental and computational methods. JDs were obtained from 2,2-bis(hydroxymethyl)propionic acid, myristic acid and different glycols. Dispersions of JDs in water were carried out using the thin-film hydration, solvent injection methods and by microfluidics, using double emulsion drops with ultrathin shells as templates. Furthermore, a coarse-grained molecular dynamics (CG-MD) simulation was performed to study the mechanism of JDs aggregation. The resulting assemblies were characterized by optical microscopy, dynamic light scattering, confocal microscopy, and atomic force microscopy. The obtaining of assemblies in water with no interdigitated bilayers was confirmed by the experimental characterization and CG-MD simulation for one of the dendrimers. Assemblies with dendrimersome characteristics were obtained using the solvent injection method. Also, monodisperse nanometric assemblies were obtained by this method. The use of microfluidics enables the production of giant dendrimersomes from highly hydrophobic JDs, even when the dendrimers did not form vesicles using the thin-film hydration method. The results of this study establish a relationship between the molecular structure of the JDs and the properties of its aggregates in water. These results could be relevant for the design of novel JDs with tailored assemblies suitable for drug delivery systems. In addition, this study offers an approach to produce dendrimersomes in a more controlled way.
OntoOAI : modelo semántico para el descubrimiento selectivo de conocimiento sobre contenidos estructurados con OAI-PMHEl principio fundamental en la Web es la comunidad abierta: cualquiera puede contribuir sus ideas al todo. Esta apertura a la colaboración, su flexibilidad y tolerancia son factores que le han permitido convertirse en un recurso universal. Sin embargo, la masa creciente, dinámica y muchas veces poco estructurada de información en la Web impone retos importantes, uno de ellos: el descubrimiento de conocimiento. El descubrimiento de conocimiento, uno de los productos finales más interesantes de la computación, resulta particularmente relevante en la tarea de un investigador, profesor o alwnno, que usan la información científica para su quehacer profesional. Entre los esfuerzos que se han dado para organizar y estructurar la masa de datos, se ubica el Protocolo para Cosecha de Metadatos de la Iniciativa de Archivos Abiertos (OAIPMH ), estándar para los repositorios de información científica y académica.
Application of ultrasonic micro injection molding for manufacturing of UHMWPE microparts(2017-12-05)Ultrasonic micro injection molding was confirmed to be an efficient processing technique for the fabrication of a well-filled miniaturized dog-bone shaped specimen of ultra-high molecular weight polyethylene (UHMWPE). The influence of parameters such as mold temperature, plunger velocity profile, vibrational amplitude, shape of raw material, is analyzed using techniques such as the Design of Experiments, and a methodological proposal. The influence of four process parameters on the filling phase of the reduced-size cavity was then analyzed . It was established that it is possible to fabricate well-defined specimens when the highest ultrasonic amplitude is applied intermittently at specific intervals during the ultrasonic process to small compacted irregularly shaped UHMWPE samples and the mold temperature is set to 100 °C. GPC results showed a decrease in the molecular weight, which was the greatest when 100% of the ultrasonic amplitude was applied. The degree of crystallinity of the processed sample was increased because the reduction of the molecular weight. TGA showed that the thermal stability of UHMWPE fabricated by ultrasonic processing was not significantly influenced by the decrease in the molecular weight. FTIR spectra indicated oxidative degradation in three different regions of the processed UHMWPE specimen. Additionally, the band identified at the wavenumber 910 cm-1 indicated a chain scission phenomenon the polymer experienced during the ultrasonic processing
Development of SERS substrates for the characterization of cellular systems and the determination of molecules of interest(2017-12-04)Raman spectroscopy is a powerful vibrational spectroscopy technique that provides useful information regarding the chemical composition of a sample. It is a label-free technique that can be successfully applied for both single analyte detection and the analysis of complex matrices. The only main limitation of Raman spectroscopy is the inherent low scattering efficiency. Surface Enhanced Raman Spectroscopy (SERS) is employed to overcome this limitation. SERS active structures are typically in the form of colloidal solutions, or as solid substrates with metallic nanostructures on the surface. The work included in this dissertation explores the development of SERS substrates for (a) the detection of a single molecule of interest, and (b) the analysis of cellular systems. For the detection of molecules of interest, two studies were carried out: In the first study, the ideal synthesis conditions of colloidal silver nanoparticles that rendered the highest SERS enhancement was explored via principal component analysis (PCA). The selected silver nanoparticles were used for the ultrasensitive detection of phenolic compounds in solution. The second work focused on the development of solid substrates, where gold nanoparticles were synthesized and immobilized on a carbon nanofibers matrix and enhancement capacity of the SERS substrate was evaluated with Rhodamine 110. The use of SERS for the analysis of biological systems was also explored. First, the effect of an oxidative agent (CdTe quantum dots) on the freshwater microalgae H. pluvialis was studied with SERS via colloidal gold nanoparticles. Mammalian cell lines were also analyzed; Colloidal concave gold nanocubes were synthesized and immobilized onto a solid substrate for SERS enhancement of HeLa cells, showing that solid SERS substrates are also suitable for cell analysis. Finally, radiation resistant and radiation sensitive murine leukemia sublines were characterized for the first time by normal Raman spectroscopy and SERS, with the aim of contributing the development of predictive radiosensitivity assays. SERS substrates in colloidal and solid form were developed, and successfully used for the label-free detection of analytes in solution and complex biological samples, showing the versatility of SERS and contributing to this growing multidisciplinary field.