Nanostructure and Bioactivity of Hybrid Aerogels (original) (raw)
Related papers
Bioactive organic-inorganic hybrid aerogels
MRS Proceedings, 2004
ABSTRACTWe have prepared organic-inorganic hybrid materials (OIHM), incorporating an organic phase in the inorganic precursor sol, using high power ultrasound for assistance with agitation. A sono-ormosil results after gelation. Colloidal silica particles have been added to these hybrids to enable network porous volume and pore radius to be tailored to specific requirements. Finally, in vitro bioactivity of this material has been promoted by adding calcium to the initial sol. The structure and bioactivity of these materials have been subjected to preliminary study, including their mechanical behaviour. These materials have a very fine structure especially after colloidal silica particles have been included. When immersed in a solution simulating blood plasma, they are bioactive, and the sample with colloid particles presents a better behaviour in vitro
Structure of bioactive mixed polymer/colloid aerogels
Journal of Non-Crystalline Solids, 2005
The structure of polymer/colloid mixed silica sono-aerogels has been studied by SAXS, N 2 adsorption-desorption and Hg porosimetry. The system is described as a composite in which the polymeric phase (sonogel) is the matrix. The structure of this phase prepared with ultrasounds is very fine consisting in aggregates of $5 nm radius formed by elementary particles of 1 nm radius. Including Ca(II) into the silica atomic network causes enlarging the average size of the particle more than three times with respect to its size in its pure silica counterpart. The stiffness increases as well by 50%. The size of the particles and pores is also affected by the ultrasound dose applied; the higher for the larger the particles. On the other hand, a low dose produces a rough particle surface.
Mechanical Properties of Bioactive Hybrid Organic/Inorganic Aerogels
Key Engineering Materials, 2009
Hybrid silica-organic polymer aerogels based on tetraethoxysilane (TEOS) have been synthesized, polydimethylsiloxane (PDMS) and methyltriethoxysilane (MTES) have been used as organic phases. Synthetic wollastonite powder was added as bioactive phase. The composites were prepared by dispersing wollastonite powder in the sol with the assistance of high power ultrasounds to control the gelling time. Wet composites were dried under supercritical conditions of the solvent. The mechanical characterization was performed by uniaxial compression and by nanoindentation. Young`s modulus from uniaxial compression increase from 5 MPa to 100 MPa for increasing MTES content and also rupture modulus was enhanced from 0.85 MPa to about 50 MPa, so the incorporation of cross linkers in this kind of aerogels, was proven to enhance the mechanical resistance. However the inclusion of wollastonite powders provokes a dropping of the Young's modulus and hardness. All the composites showed bioactivity by the formation of an apatite layer when immersed in Simulated Body Fluid (SBF).
The effect of process variables on the properties of nanoporous silica aerogels
Silica aerogel, a nanoporous material, was produced by using rice husk ash via sol–gel method. The aim of the study is to examine effects of the acid type (acetic, hydrochloric, nitric, oxalic and sulfuric acid), dryer type (air, freeze, oven and vacuum) and the addition of tetraethyl orthosilicate on the structural and physical properties of aerogels produced from rice husk ash. In addition, this is the first study investigating the effect of vacuum oven drying on the structure of rice husk based silica aerogel. Specific surface area and pore size of obtained silica aerogels have been analyzed by the N2 adsorption and desorption measurements at 77 K via Brunauer–Emmett–Teller (BET) and Barrett–Joiner–Halenda (BJH) methods, respectively. Surface functional groups were determined with fourier transform infrared spectroscopy (FTIR). Surface morphology was examined with scanning electron microscopy (SEM). Moreover, density was calculated by tapping method. The results showed that all of the variables had remarkable effects on the final properties of the silica aerogel. The BET specific surface area of the silica aerogels increased with the addition of tetraethyl orthosilicate, while the tapping density decreased. The BET specific surface area and pore size of silica aerogels varied between 140.7–322.5 m2 g−1, and 5.38–12.05 nm, respectively. Silica aerogel which was obtained by using oxalic acid, tetraethyl orthosilicate addition and air dryer had the highest BET specific surface area (322.5 m2 g−1).
Polymers
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 °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 N2 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. ...
Safety and efficacy assessment of aerogels for biomedical applications
Biomedicine & Pharmacotherapy, 2021
The unique physicochemical properties of aerogels have made them an attractive class of materials for biomedical applications such as drug delivery, regenerative medicine, and wound healing. Their low density, high porosity, and ability to regulate the pore structure makes aerogels ideal nano/micro-structures for loading of drugs and active biomolecules. As a result of this, the number of in vitro and in vivo studies on the therapeutic efficacy of these porous materials has increased substantially in recent years and continues to be an area of great interest. However, data about their in vivo performance and safety is limited. Studies have shown that polymerbased, silica-based and some hybrid aerogels are generally regarded as safe but given that studies on the acute, subacute, and chronic toxicity for the majority of aerogel types is missing, more work is still needed. This review presents a comprehensive summary of different biomedical applications of aerogels proposed to date as well as new and innovative applications of aerogels in other areas such as decontamination. We have also reviewed their biological effect on cells and living organisms with a focus on therapeutic efficacy and overall safety (in vivo and in vitro).
An Opinion Paper on Aerogels for Biomedical and Environmental Applications
Molecules
Aerogels are a special class of nanostructured materials with very high porosity and tunable physicochemical properties. Although a few types of aerogels have already reached the market in construction materials, textiles and aerospace engineering, the full potential of aerogels is still to be assessed for other technology sectors. Based on current efforts to address the material supply chain by a circular economy approach and longevity as well as quality of life with biotechnological methods, environmental and life science applications are two emerging market opportunities where the use of aerogels needs to be further explored and evaluated in a multidisciplinary approach. In this opinion paper, the relevance of the topic is put into context and the corresponding current research efforts on aerogel technology are outlined. Furthermore, key challenges to be solved in order to create materials by design, reproducible process technology and society-centered solutions specifically for ...
Gels
We report the synthesis of mesoporous silica–gelatin hybrid aerogels with 15, 25, and 30 wt. % gelatin contents, using 3-glycidoxypropyl trimethoxysilane (GPTMS) as a coupling agent, for tissue-engineering applications. Aerogels were obtained using a one-step sol–gel process followed by CO2 supercritical drying, resulting in crack-free monolith samples with bulk densities ranging from 0.41 g cm−3 to 0.66 g cm−3. Nitrogen adsorption measurements revealed an interconnected mesopore network and a general decrease in the textural parameters: specific surface areas (651–361 m2 g−1), pore volume (1.98–0.89 cm3 g−1), and pore sizes (10.8–8.6 nm), by increasing gelatin content. Thermogravimetric analysis (TGA), Fourier-transform infrared (FTIR) spectroscopy and uniaxial compression experiments confirmed that the structure, thermal properties and mechanical behavior of these aerogels changed significantly when the concentration of gelatin reached 25 wt.%, suggesting that this composition cor...
MRS Proceedings, 2001
ABSTRACTNovel transition-metal containing hybrid biopolymer-silica aerogels have been synthesized as transparent monolithic structures. The compositions include Ru(III), Rh(III), Co(II), and Pd(II) species, silica and chitosan, and amine-group-containing biopolymer derived from chitin. Due to its aqueous solubility and hydrogen bonding properties, chitosan was homogeneously incorporated into the silica network. These aerogels have densities in the range of 0.25-0.30 g/cm3, BET surface areas in the range of 600-975 m2/g, and refractive indexes below 1.17 (at 632.8 nm). Infrared spectroscopy shows that chitosan is effectively introduced into the silica aerogels, and the transition metal ions can coordinate with the amine sites on chitosan. This combines the metal-ion interaction of chitosan with that of silica aerogels. Transmission electronic microscopy indicates that the particle sizes of silica are about 2 nm. Small angle neutron scattering (SANS) has been used to study the microst...