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1. Advanced Analysis of Clay Microporosity Using High-Resolution N2-Ar Adsorption Isotherms Coupled with the Derivative Isotherm Summation Method

Author

Anwar El Azrak, Denys I. Grekov, Laurent Truche, and Pascaline Pré

Subjects
clay, cation exchange, DIS method, microporosity, t-plot, Organic chemistry, QD241-441
Abstract

The textural properties of synthetic and natural clays in the sodium form and exchanged with tetramethylammonium cations (TMA+) were characterized using N2 and Ar physisorption isotherms at cryogenic temperatures. Specific surface areas and micro/mesoporous volumes were determined using the BET and the t-plot models. The t-plot analysis requires the use of reference isotherms measured at the same temperature on the surface of non-porous materials with an identical chemical composition. In order to better assess the effects of chemical heterogeneities in the clay particles, reference isotherms representative of silica surfaces were taken into account in the analysis of the t-curve and corrected to account for variations in curvature at the interface of the film adsorbed in the micropores. In addition, high-resolution Ar adsorption isotherms at 87 K were analyzed using the Derivative Isotherm Summation (DIS) method to quantify the energy contributions of adsorption sites and determine the fractions of basal and lateral surfaces of clay particles. The high-energy adsorption sites, identified in the low-pressure range, were attributed to intra-particle microporosity due to stacking defects and/or open inter-layer spaces. These sites were differentiated from those on the lateral and basal surfaces of the particles. A modification of the DIS method was proposed to measure these contributions and improve the fit with the experimental data. The results show that TMA+ cation exchange significantly increases the microporosity of clays compared to their sodic form, which can be attributed to the increased contribution of intra-particle adsorption sites due to interlayer expansion.

Published
2024
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2. Effect of Washing Treatment on the Textural Properties and Bioactivity of Silica/Chitosan/TCP Xerogels for Bone Regeneration

Author

Antonio Perez-Moreno, Gonzalo Pinaglia-Tobaruela, José Ignacio Vilches-Pérez, Nicolás de la Rosa-Fox, María V. Reyes-Peces, M. Piñero, Mercedes Salido, Rafael Fernandez-Montesinos, Anatomía Patológica, Biología Celular, Histología, Historia de la Ciencia, Medicina Legal y Forense y Toxicología, Física de la Materia Condensada, Materno-Infantil y Radiología, [Pérez-Moreno,A, Vilches-Pérez,JI, Fernández-Montesinos,R, Pinaglia-Tobaruela,G, Salido,M] Instituto de Investigación e Innovación Biomédica de Cádiz (INIBICA), Cádiz, Spain. [Pérez-Moreno,A, Reyes-Peces,MV, de la Rosa-Fox,N, Piñero,M] Department of Condensed Matter Physics, Faculty of Science, University of Cadiz, Puerto Real, Spain. [Reyes-Peces,MV, Piñero,M] Instituto de Microscopía Electrónica y Materiales (IMEYMAT), University of Cadiz, Cádiz, Spain. [Vilches-Pérez,JI, Salido,M] Department of Histology, SCIBM, Faculty of Medicine, University of Cadiz, Cádiz, Spain., and This research was 80% supported by Andalucía FEDER/ITI 2014-2020 Grant for PI 013/017 and Junta de Andalucía TEP115 and CTS 253 PAIDI research groups (Spain). The work has also been co-financed by the 2014–2020 ERDF Operational Programme and by the Department of Economy, Knowledge, Business and University of the Regional Government of Andalusia. Project reference: FEDER-UCA18_106598.

Subjects
Calcium Phosphates, Bone Regeneration, Biocompatible Materials, 02 engineering and technology, Chemicals and Drugs::Chemical Actions and Uses::Specialty Uses of Chemicals::Solvents [Medical Subject Headings], 01 natural sciences, biodegradation, Osteoblastos, Chitosan, Organisms::Eukaryota::Animals::Chordata::Vertebrates::Mammals::Primates::Haplorhini::Catarrhini::Hominidae::Humans [Medical Subject Headings], chemistry.chemical_compound, Phenomena and Processes::Musculoskeletal and Neural Physiological Phenomena::Musculoskeletal Physiological Phenomena::Musculoskeletal Physiological Processes::Bone Remodeling::Bone Regeneration [Medical Subject Headings], Anatomy::Fluids and Secretions::Body Fluids [Medical Subject Headings], Materials Testing, Biology (General), Huesos, bone tissue engineering, Spectroscopy, Adhesiones focales, Cells, Cultured, hybrid xerogels, osteoblasts, General Medicine, 021001 nanoscience & nanotechnology, Silicon Dioxide, focal adhesions, tricalcium phosphate, Computer Science Applications, Body Fluids, Solvent, Quitosano, Chemistry, Distilled water, N2 physisorption, Anatomy::Cells::Connective Tissue Cells::Osteoblasts [Medical Subject Headings], 0210 nano-technology, Chemicals and Drugs::Biomedical and Dental Materials::Biocompatible Materials [Medical Subject Headings], QH301-705.5, Simulated body fluid, engineering.material, 010402 general chemistry, Chemicals and Drugs::Inorganic Chemicals::Minerals::Silicon Dioxide [Medical Subject Headings], Catalysis, Article, Inorganic Chemistry, Fosfatos de calcio, Conductas terapéuticas, Chemicals and Drugs::Inorganic Chemicals::Calcium Compounds::Calcium Phosphates [Medical Subject Headings], Chemicals and Drugs::Complex Mixtures::Colloids::Gels [Medical Subject Headings], Humans, Physical and Theoretical Chemistry, Fourier transform infrared spectroscopy, Analytical, Diagnostic and Therapeutic Techniques and Equipment::Investigative Techniques::Materials Testing [Medical Subject Headings], t-plot, Bone regeneration, Molecular Biology, QD1-999, Chemicals and Drugs::Macromolecular Substances::Polymers::Biopolymers::Chitin::Chitosan [Medical Subject Headings], Osteoblasts, Organic Chemistry, Biodegradation, 0104 chemical sciences, chemistry, Chemical engineering, bioactivity, Anatomy::Cells::Cells, Cultured [Medical Subject Headings], engineering, Solvents, Biopolymer, Biodegradación ambiental, Ingeniería de tejidos, Technology and Food and Beverages::Technology, Industry, and Agriculture::Manufactured Materials::Biomedical and Dental Materials::Polymers [Medical Subject Headings], chitosan, Gels
Abstract

Silica (SiO2)/chitosan (CS) composite aerogels are bioactive when they are submerged in simulated body fluid (SBF), causing the formation of bone-like hydroxyapatite (HAp) layer. Silica-based hybrid aerogels improve the elastic behavior, and the combined CS modifies the network entanglement as a crosslinking biopolymer. Tetraethoxysilane (TEOS)/CS is used as network precursors by employing a sol-gel method assisted with high power ultrasound (600 W). Upon gelation and aging, gels are dried in supercritical CO2 to obtain monoliths. Thermograms provide information about the condensation of the remaining hydroxyl groups (400-700 degrees C). This step permits the evaluation of the hydroxyl group's content of 2 to 5 OH nm(-2). The formed Si-OH groups act as the inductor of apatite crystal nucleation in SBF. The N-2 physisorption isotherms show a hysteresis loop of type H3, characteristic to good interconnected porosity, which facilitates both the bioactivity and the adhesion of osteoblasts cells. After two weeks of immersion in SBF, a layer of HAp microcrystals develops on the surface with a stoichiometric Ca/P molar ratio of 1.67 with spherulite morphology and uniform sizes of 6 mu m. This fact asserts the bioactive behavior of these hybrid aerogels. Osteoblasts are cultured on the selected samples and immunolabeled for cytoskeletal and focal adhesion expression related to scaffold nanostructure and composition. The initial osteoconductive response observes points to a great potential of tissue engineering for the designed composite aerogels., This research was 80% supported by Andalucia FEDER/ITI 2014-2020 Grant for PI 013/017 and Junta de Andalucia TEP115 and CTS 253 PAIDI research groups (Spain). The work has also been co-financed by the 2014-2020 ERDF Operational Programme and by the Department of Economy, Knowledge, Business and University of the Regional Government of Andalusia. Project reference: FEDER-UCA18_106598.

Published
2021

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