PENAFLOR TANIA

The Zn−substituted HAp NPs were successfully synthesized at the initial molar ratios of (Ca+Zn)/P at 1.67 and 2.00, providing the stoichiometric Zn:HAp and carbonate Zn:CHAp NPs and the maximum Zn ion substitution in the structure is ca. 5 mol% by the XRF analysis. The 10.0−Zn:HAp and 10.0−Zn:CHAp NPs contain 0.76 and 0.68 wt% of Zn at the maxima, respectively, which is safety for cells in the animal body. The increase in the Zn ion concentration significantly induced the carbonate ion including. The crystalline size decreased with the increasing Zn ion substitution, indicating the suppression of the crystal growth by the Zn ion addition to resultantly increase the specific surface area. TEM observation clearly indicated that the needle-like shape nanoparticles were changed to the particulate shapes with increasing the Zn ion substitution to form aggregation form with the mesostructures. Thus, the morphological control by the Zn−substitution in stoichiometric and carbonate HAp NPs was successfully achieved. The Zn:HAp and Zn:CHAp NPs were deposited on the Ti-PDMS by an EPD technique obtaining an uniform and transparent Zn:HAp and Zn:CHAp NPs. The fibroblasts on the Zn−substituted HAp NP films exhibited good adhesion/spreading. In particular, the Zn:CHAp NP films are very cytocompatible. By the antibacterial test, the viable E. coli DH5α reduction was significantly observed in the films with the higher Zn amounts. Resultantly, the 5.0 and 10−Zn:CHAp NP films. Furthermore, all the nanoparticle films electrically plated on a Ti-PDMS substrate give no cytotoxicity, and the Zn:CHAp NP films significantly provided the bioactive properties for fibroblast ingrowth, suggesting the effect of Zn and carbonate ions on the cytocompatibility. Summarizing, The Zn:HAp and Zn:CHAp NP films with the optimized cytocompatible and antibacterial properties were successfully prepared as the Ti-PDMS surface modification technique.[Doctoral thesis] Doctoral supervisor: Dr. Motohiro Tagaya

Development of a methodology to synthesize the PDMS/TiO2/HAp composite with osteoconductive properties

The presence of fluorides in aqueous effluents can be due to natural effects or anthropogenic activities, and represents a serious contamination problem that directly affects the quality of water for human consumption. In this work, the synthesis of Al/Mg X= 0.20 double laminar hydroxides and activated alumina prepared from the precursor pseudo-boehmite was carried out. These materials were synthesized by a hydrolysis precipitation method based on the slow addition of the solutions prepared from the industrial grade reagents and then the obtained materials were calcined at 550 °C. The concentration of fluoride in a solution of known concentration (10 mg/L) prepared for a standard was analyzed, in addition, two water samples from two communities where high levels of fluoride contamination have been reported in the state of Guanajuato were also analyzed by a potentiometric method using a fluoride selective electrode. The elemental chemical composition on the surfaces of the alumina and the mixture of oxides was determined by IR spectroscopy and for the determination of amorphous or crystalline structures the XRD equipment was used, resulting Al-Mg X=0.20 a material of crystalline character and γ-Al2O3 an amorphous material. By means of concentration decay curves, γ-Al2O3 presented a higher adsorption capacity of [F-], an expected result due to the characteristics of the material.

In this study, the synthesis, characterization, and evaluation of hydroxyapatite were performed for several applications. Not only the biocompatible properties of hydroxyapatite were investigated, but also its adsorption abilities for radioactive elements like sodium radioactive. The hydroxyapatite`s adsorption abilities were studied in a collaborative project with the National Institute for Nuclear Investigations of Mexico. [Master thesis] Master's supervisor: Dr. Merced Martínez Rosales

The low bio-affinity of medical catheters often causes bacterial infection through the permeation interspaces between catheters and skin tissues. Thus, the surface modification of the biomedical polymer (e.g., silicone resin) used as catheters is desired for improving the biocompatible and antibacterial properties. As the modification material, hydroxyapatite (Ca10(PO4)3(OH)2) (HAp), which is crystallographically and chemically similar to the components of human hard tissues, is a good candidate. Importantly, naturally-formed HAp is not absolutely pure and has some impurities of ions (Zn2+, Mg2+, K+, etc.), which provides biocompatibility as well as antibacterial properties. Thus, the substituted ions not only alter the space group of crystal structure, thermal stability, and mechanical properties of HAp but also play an important role in the biological behaviors. In this study, the synthesis of zinc-substituted HAp (Zn:HAp) nanocrystals and subsequent formation of the nanocrystalline film on the biomedical polymer without using chemical reagents for investigating their biocompatibility as well as antibacterial properties (“Chapter 1”). In “Chapter 2”, Zn:HAp nanocrystals were synthesized by a wet chemical method. In the method, the initial (Ca+Zn)/P ratio of 1.67 and 2.00 were adjusted from the reagents (CaCl2, ZnCl2, and K2HPO4) to resultantly from the stoichiometric and carbonate HAp nanocrystals, respectively. The initial ZnCl2 was changed as the dopant concentration of Zn/(Ca+Zn) = 0.0, 2.5, 5.0 and 10 mol%. The zinc-substitution significantly suppressed the crystal growth to obtain the optimized crystalline nano-sizes for the modification. In “Chapter 3”, an electrophoretic deposition at the optimized voltage of 100 V was used for the surface modification of biomedical polymers. As a result, the nanocrystalline Zn:HAp film formation on the surfaces was successfully achieved. Furthermore, the fibroblast compatibility, as well as antibacterial activity, was confirmed on the film surfaces. In particular, the films made from the Zn:HAp nanocrystals with (Ca+Zn)/P =2.00 and Zn/(Ca+Zn) =5 mol% is the best possibility for the surface modification. In “Chapter 4”, the nanocrystalline Zn:HAp films were summarized to provide good biocompatibility as well as antibacterial properties on biomedical polymer surfaces, suggesting a useful catheter surface modification technique. The percutaneous device applications are shown in Table 1.1 which has been grouped as blood and body cavity access devices, then conclude for power or signal transmission and internal prosthetic devices. [Master thesis] Master's supervisor: Dr. Motohiro Tagaya and Dr. Kobayashi Takaomi

Heterogeneous platinum catalysts supported on aluminosilicates obtained by coprecipitation process at basic pH are important for industrial processes due to a wide variety of applications such as hydrogenation, isomerization, oxidation, reforming, dehydrogenation and hydrosilylation. The starting materials for the synthesis of aluminosilicate were a technical grade aluminum salt-making that has low cost and alkoxide (TEOS) synthesized in the laboratory of Technology and Silicon Chemistry of the University of Guanajuato. The aluminosilicates have a large BET surface area, defined pore size distributions and pore volume, suitable which allow them to be used as supports. Based on these properties, in this study, we incorporated platinum particles on aluminosilicates by the incipient wet impregnation method. The Pt/AlSi was calcinated and subsequently reduced to obtain the catalyst. The characterization of the catalyst has been performed using X-ray diffraction (XRD), Infrared Spectroscopy (FT-IR), Thermal Analysis (TGA/DTA), Specific Surface Area (SBET) and acid-basic sites determination. The SBET results are between 200-300 m2/g. The activity of Pt/Al2O3SiO2 catalyst was proved in a hydrosilylation reaction between 1-alkyne and HSiR’3. The structural characterization of products (RCH=CHSiR’3 α, β-trans and β-cis) was performed by 1H-NMR and FT-IR. In order to compare the efficacy of synthesized catalysts were carried out simultaneous reactions between this and Karstedt´s catalyst. We analyzed the reaction times obtaining the same for both reactions. [Bachelor thesis] Bachelor's supervisor: Dr. Merced Martínez Rosales