PENAFLOR TANIA

Apatite nanoparticles are biocompatible nanomaterials, so their film formation on biodevices is expected to provide effective bonding with living organisms. However, the biodevice-apatite interfaces have not yet been elucidated because there is little experimental evaluation and discussion on the nanoscale interactions, as well as the apatite surface reactivities. Our group has demonstrated the biomolecular adsorption properties on a quartz crystal microbalance with dissipation (QCM-D) sensor coated with apatite nanoparticles, demonstrating the applicability of apatite nanoparticle films on devices. Therefore, it is important to clarify the biodevice-apatite nanointerfaces by characterizing their physicochemical properties. This research aims to control the apatite nanoparticle surfaces using different types of pH adjusters as well as to investigate biodevice-apatite interfaces. In this study, tetramethylammonium hydroxide, sodium hydroxide, and potassium hydroxide were used to adjust the pH during the synthesis of apatite nanoparticles. As a result, it was found that the ratio of Ca-deficient hydroxyapatite phase to B-type carbonate ion-substituted hydroxyapatite phase could be controlled by adjusting the OH- concentration and that the formation of B-type carbonate ion substituted hydroxyapatite phase was demonstrated in terms of the charge compensation because hydrogen phosphate ion in the non-apatitic layer would be diffused and substituted inside the apatite core structure by the replacement of carbonate ion. By contrast, the phosphate ions in the core structure were moved and contained in the non-apatitic layer, and the proportion of phosphate ions in the non-apatitic layer increased. The surface changes of the nanoparticles provide an effective biodevice surface coating. It was observed that the thickness of the electrophoretically deposited nanoparticles clearly increased with the proportion of phosphate ions in the non-apatitic layer. Furthermore, the formation of the hydration layer with immersion in biological fluid was evaluated. It was inferred that the water molecules in the hydration layer interacted with the substituted ions and remained as nonfreezing water layer on the top surface of the nanoparticles, while the abundant phosphate ions newly interacted with the water molecules in the non-apatitic layer, thus increasing the proportion of intermediate water. These results indicated that the hydrogen phosphate and phosphate ions were retained in the non-apatitic layer on the top surfaces of apatite nanoparticles, so that the thickness of the electrophoretically deposited film and the weight fraction of the hydrated layer can be controlled by the component ratio of phosphate ions in the non-apatitic layer. It is expected that surface coating technology using apatite nanoparticles will be applied for biodevices.

Biological hydroxyapatite (HA) contains the different minor ions which favour its bio-reactivity in vivo. In this study, the preparation of HA particles containing both silicate and carbonate ions under the presence of sodium silicate was investigated, and the physicochemical properties were evaluated according to the contents and states of silicate and carbonate ions. The increment in the silicate ion reduced the crystallinity and expanded the crystalline size along with a-axis. Solid-state29 Si–NMR spectra indicated the increase in the adsorption of oligomeric silicate species on the HA particle surfaces in addition to the substitution state of silicate ions, suggesting the occurrence of the surface coating of silicates on the surfaces. The possible states of carbonate and silicate ions at the HA surfaces will provide the bioactivity.

Alpha-tricalcium phosphate (α-TCP), which can be converted to calcium-deficient hydroxyapatite (HA) by hydrolysis reaction, has been researched as a bone filling. Although the composites of α-TCP with various organic molecules can exhibit a novel functionality, the reaction based on the addition of the interactive organic molecules has not been understood. Investigation of the hydrolysis conversion process under various conditions can lead to the elucidation of the biomineralization process. In this study, we investigated the hydrolysis conversion of α-TCP to HA in the presence of orotic acid (Ort). As a result, the conversion rate from α-TCP to HA at the reaction time of 3 h was improved to be more than five times as compared to that in the absence of Ort. Moreover, the addition of Ort promoted the crystal growth and suppressed the crystal growth in the m-plane direction. Furthermore, the mechanism for promoting HA formation is assumed to be related to the molecular structure of Ort, which is capable of forming the interactions between carboxylate and Ca2+ ions.

We successfully synthesized the photofunctionalized octacalcium phosphate (OCP) with layered structures and high biosafety. Specifically, two systems of europium(III) ion (Eu3+)-doped OCP particles (OCP:Eu) and succinate (Suc)-modified OCP:Eu particles (Suc-OCP:Eu) were synthesized by substituting an Eu3+ ion with a Ca2+ ion of OCP while maintaining the layered structures. The OCP:Eu and Suc-OCP:Eu (crystal shape sizes: ca. 0.4-1.0 μm) exhibited the strong luminescence based on the f-f transition of the Eu3+ ion, and the luminescence intensity and quantum efficiency increased with increasing the initial Eu molar concentration to Ca+Eu up to 10 mol %, indicating the suppression of the concentration quenching by the layered structures. The intensity and efficiency of Suc-OCP:Eu were about 1.3 times as high as the OCP:Eu, indicating that the hybridization with Suc ions leads to the enhancement of the luminescent properties. The sustained release of the Suc ion from Suc-OCP:Eu in simulated body fluid (SBF) was achieved for more than 168 h, and the release rates at the immersion time of 168 h were 85, 60, and 20% for the Suc-OCP:Eu at the initial molar concentrations of Eu to Ca+Eu of 0, 5, and 10 mol %, respectively. Moreover, the intensity, efficiency, and layer structure of Suc-OCP:Eu were maintained by the immersion time of 168 h. Thus, the effect of the hybridization with Suc ions on the luminescence properties of the Eu3+ ion, and that of the doping on the release of the Suc ion in SBF was clarified. We achieved the synergistic functions of both photofunctions and organic molecules in the layered structure of the biocompatible OCP, and the sustained release of organic molecules in biological solution.

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

The synthesized elliptical hydroxyapatite (E-HAp) and needle-like HAp (N-HAp) nanoparticles (NPs) were electrophoretically deposited on a gold (Au) substrate. A comparative study of the hydration layers on E-HAp, N-HAp, and Au films was achieved to investigate the interfacial effect of the hydration layers on the conformation of the adsorbed fibrinogen (Fgn) and fibroblast adhesion properties. As a result, the ratios of three types of hydration layer states (free water, intermediate water, nonfreezing water) analyzed by a Fourier transform infrared (FT-IR) spectral deconvolution of the O-H stretching absorption band were investigated. The ratio of the bonding water state (i.e., intermediate and nonfreezing water molecules) is almost the same between two HAp films, and the E-HAp film with an elliptical shape and smaller particle size exhibited the smallest ratio of nonfreezing water, which can suppress the denaturation of the adsorbed protein. Subsequently, FT-IR spectral deconvolution results of the amide I band of the adsorbed Fgn on the E-HAp film indicated the higher proportion of α-helix and β-sheet structures as compared with those on the N-HAp and Au films, suggesting that the smaller proportion of nonfreezing waters would play a significant role in the stereoscopic Fgn conformation. In the culture of fibroblasts, FT-IR spectra of the adhered cells on the E-HAp, N-HAp, and Au films exhibited different absorbance intensities of the amide A, I, II, and III bands, suggesting a different amount of collagen-producing states by the cells, which were also supported by immunostaining results of the collagen type I. Therefore, the different hydration structures on the films clearly influenced the conformation of the adsorbed protein, and the preferential conformation was found at the interfaces between the fibroblasts and the underground E-HAp films.

The present study evaluated biodiesel production using Layered Double Hydroxides (LDHs) and derived mixed oxides as heterogeneous catalysts to analyse the relation between the physicochemical and textural properties of these materials with biodiesel yield. Experimental planning was conducted to evaluate the effect of different Mg/Al molar ratios, precipitating agents (Na2CO3 or NH3) and calcination effect on methyl ester yield. Materials were characterized by X-ray diffraction (XRD), N2-BET method, fourier-transform infrared spectra (FT-IR), point of zero charge (pHPZC) and scanning electron microscope (SEM). Biodiesel synthesis was further optimized through experimental planning considering the catalyst concentration and methanol:oil molar ratio at 4 periods of time as variables, using the material which exhibited the best performance. The material with best catalytic activity was a derived mixed oxide (calcined at 450 °C) with a Mg/Al ratio of x = 0.59, using Na2CO3 as precipitating agent. The optimized parameters for the chemical reaction were: 23:1 methanol:oil molar ratio, 3.5 wt% catalyst at 65 °C for 1 h, resulting in a maximum ester conversion of 98.59 wt%.

Addition of poly (oxyethylene)cholesteryl ether in the synthesis promoted the formation of the hydroxyapatite nanoparticles (HAp NPs) with the elliptical morphologies. The adsorption mechanism, interfacial interactions and conformation of the adsorbed fibrinogen (Fgn) on the HAp NP films were investigated. The Fgn adsorption behavior demonstrated the higher affinity of Fgn with the HAp NP films. At the lower temperature at 22 °C, Fgn was preferentially adsorbed on the gold though hydrophobic interactions with the larger Fgn adsorption amount. At the higher temperature at 37 °C or at the higher phosphate ion concentrations caused the structural changes of the adsorbed Fgn. Moreover, the temperature increment in PBS increased the Fgn adsorption amount with the rearrangement into the end-on orientation of the Fgn. Accordingly, HAp induced the electrostatic force and hydrogen bonding to be the stable Fgn-HAp NP film, minimizing the interactions among the water molecules. The HAp NP films with the preferentially elliptical crystalline shapes induced the Fgn steric conformation structures, and the secondary structural changes of the adsorbed Fgn by the increment of temperature were also supported by the Fourier transform infrared spectroscopy (FTIR) deconvolution results.

Bone is an organic-inorganic composite with the ability to regenerate itself. Thus, several studies based on artificial organic-inorganic interface sciences have been tried to develop capable materials for effective regenerative bone tissues. Hydroxyapatite nanoparticles (HAp NPs) have extensively been researched in bone tissue engineering due to the compositional and shape similarity to the mineral bone and excellent biocompatibility. However, HAp alone has low mechanical strength, which limits its applications. Therefore, HAp NPs have been deposited on the biocompatible polymer matrix, obtaining composites with the enhanced mechanical, thermal, and rheological properties and with higher biocompatibility and bioactivity. For developing new biomedical applications, polymer-HAp interfacial interactions that provide biofusion should be investigated. This paper reviewed common coating techniques for obtaining HAp NPs/polymer fusion interfaces as well as in vitro studies of interfacial interactions with proteins and cells, demonstrating better biocompatibility. Studies based on interfacial interactions between biomolecules and HAp NPs were highlighted, and how these interactions can be affected by specific protein preadsorption was also summarized.

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

The culture behavior of the osteoblast-like cells on the calcium phosphate (CP) films interacted with phospholipid vesicle (PV) were investigated. The different CP crystalline phases were prepared from the biological solutions such as simulated body fluid (SBF) and unique SBF, which were called as CP/PV and U-CP/PV films, respectively, and these were used after the sterilization. The protein adsorption amounts on the CP/PV films were higher than that of the PV film. The osteoblast-like cells cultured on the U-CP/PV film had the longest length along with the extension direction. The density of the osteoblast-like cells adhered on the CP/PV and U-CP/PV films were higher, suggesting the preferential adhesion on the surfaces. The differentiated osteoblasts on the films were visualized by the alkaline phosphatase and Alizarin-red-S staining methods. It was suggested that the osteoblasts cultured on the CP/PV and U-CP/PV films exhibited the possibility of the high osteogenic activities. Therefore, the PV-interacted CP films prepared from the biological solutions are useful for the osteoblast culture plates.

We investigated the coating process of mesostructured triblock copolymer-tetraethoxysilane (P123-TEOS) and mesoporous silica (MPS) films on a bioinert poly(dimethylsiloxane) (PDMS) with the different cross-linker con-centrations through an oxygen-plasma treatment to evaluate the mesostructure formation and adsorption ability of proteins (albumin, fibrinogen, γ-globulin, fetal bovine serum). In the PDMS preparation, the cross-linker con-centration affected the polymer network formation and the siliceous layer was formed on the most-surfaces by the plasma treatment. The transparent siliceous films of P123-TEOS and MPS were successfully covered on the cross-linked PDMS without voiding and the coating film thicknesses were ca. 100 nm. The FT-IR spectra indicated that the change from P123-TEOS to MPS occurred with preserving the PDMS chemical bonds by the calcination. Especially, the XRD patterns and nitrogen adsorption and desorption isotherms of the MPS on PDMS indicated the mesostructured film formation with preserving the ordered nanopore structures (BJH pore sizes: 1.6{4.2 nm, BET surface areas: 394{602 m2/g). The hydrophobic PDMS surfaces became more wettable by the coating. The adsorption amounts of acidic proteins (albumin, fibrinogen) were changed by the coating. For the fibrinogen, the P123-TEOS on PDMS exhibited the most adsorption sites. Therefore, the bio-interactive properties of the PDMS surfaces were demonstrated based on the coating processes.

The cytocompatibility of the poly(dimethylsiloxane) (PDMS) surfaces can be improved by the coating with biomaterials. In this study, the methodology for the particulate titania (PT) coating on the PDMS film was investigated via the combined process of microfluidic synthesis system with spin-coating, leading to the one-step synthesis and coating. The PT was successfully deposited on the O2-plasma-treated PDMS films by mixing titanium tetraisopropoxide, isopropyl alcohol, water and octadecylamine in a microfluidic reactor and subsequently dropping. The rotation speed in the spin-coating plays an important role in the PT morphologies and deposition amounts on the PDMS films. Through the detailed investigation, the efficient condition for adhering PT to PDMS as well as inducing apatite formation from simulated body fluid was successfully discovered.

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.

Nanocrystalline zinc (Zn)-substituted hydroxyapatite (HAp) films were prepared and electrically-plated on a titanium-coated silicone to investigate the biological properties. The hydroxyapatite nanocrystals with the different initial molar (Zn + Ca)/P ratios (1.67 and 2.00) and Zn ion concentrations were synthesized and subsequently coated by an electrophoretic deposition method to successfully form homogenous thin films. The nanocrystalline films provided bioactive properties based on the fibroblast ingrowth as well as the reduction in the number of viable Escherichia coli. Therefore, the optimized cytocompatible and antibacterial properties of the films by the effective Zn ion substituted in the HAp will be useful as a silicone surface modification technique.

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

Hydroxyapatite (Ca10(PO4)3(OH)2) (HAp) is crystallographically and chemically similar to the human hard tissues and has been widely researched. The naturally formed HAp has some impurities of some ions, which provides the biocompatibility as well as the nanosized morphologies in the tissues. In this study, the morphosynthesis of zinc-substituted stoichiometric and carbonate hydroxyapatite (Zn:HAp and Zn:CAp) nanoparticles was investigated from the reagents of CaCl2, ZnCl2, and K2HPO4. The initial (Ca + Zn)/P ratios of 1.67 and 2.00 were adjusted by the initial ZnCl2 amount at the Zn/(Ca + Zn) concentration of 0.0-10 mol%. The crystalline sizes of the nanoparticles decreased with increasing the Zn ion amount, suggesting that the Zn substitution significantly suppressed the crystal growth. TEM images of the nanoparticles indicated that all the crystalline sizes are less than 100 nm and the needle-like shapes were significantly changed to spherical shapes with increasing the Zn ion substitution to resultantly exhibit the higher surface areas as well as the nanoparticle aggregation states. Furthermore, all the nanoparticle films electrically plated on a silicone substrate give no cytotoxicity, and the Zn:CAp nanoparticle films significantly provided the bioactive properties for fibroblast ingrowth, suggesting the effect of Zn and carbonate ions on the cytocompatibility.

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