Chitosan-GPTMS-Silica Hybrid Mesoporous Aerogels for Bone Tissue Engineering

Abstract

This study introduces a new synthesis route for obtaining homogeneous chitosan (CS)-silica hybrid aerogels with CS contents up to 10 wt%, using 3-glycidoxypropyl trimethoxysilane (GPTMS) as coupling agent, for tissue engineering applications. Aerogels were obtained using the sol-gel process followed by CO2 supercritical drying, resulting in samples with bulk densities ranging from 0.17 g/cm3 to 0.38 g/cm3. The textural analysis by N2-physisorption revealed an interconnected mesopore network with decreasing specific surface areas (1230–700 m2/g) and pore sizes (11.1–8.7 nm) by increasing GPTMS content (2–4 molar ratio GPTMS:CS monomer). In addition, samples exhibited extremely fast swelling by spontaneous capillary imbibition in PBS solution, presenting swelling capacities from 1.75 to 3.75. The formation of a covalent crosslinked hybrid structure was suggested by FTIR and confirmed by an increase of four hundred fold or more in the compressive strength up to 96 MPa. Instead, samples synthesized without GPTMS fractured at only 0.10–0.26 MPa, revealing a week structure consisted in interpenetrated polymer networks. The aerogels presented bioactivity in simulated body fluid (SBF), as confirmed by the in vitro formation of hydroxyapatite (HAp) layer with crystal size of approximately 2 µm size in diameter. In vitro studies revealed also non cytotoxic effect on HOB® osteoblasts and also a mechanosensitive response. Additionally, control cells grown on glass developed scarce or no stress fibers, while cells grown on hybrid samples showed a significant (p < 0.05) increase in well-developed stress fibers and mature focal adhesion complexes.

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

“…The calculated CS amount, in all cases, was lower than the expected nominal content, being undetectable in W30 xerogels. The same conduct has been previously reported elsewhere by us, even using a cross-linker in the process [44], and others [45]. These results indicate a considerable dissolution and release of CS, and as a consequence, the final composition of the hybrids did not match the nominal content.…”

“…When HOB ® cells were seeded on the xerogels, an initial polarization could be seen from the first 24 h, followed by cell adhesion and morphological changes identified as initial markers of osteoblast differentiation and due to the presence of the biomaterial as described previously by us and others [ 44 , 53 , 75 , 76 , 77 ]. Adhesion, attachment, cell growth, and morphological changes in osteoblasts appeared to be substantially better in silica–chitosan xerogels’ experimental samples, mainly in those including TCP, than in cells grown on the bare substrata and revealed a successful cell attachment with marked morphological changes, such as filopodial and lamellipodial emission and an improved cell spreading.…”

“…The composition of silica xerogels can be tuned so that they elicit bone bioactive characteristics [ 44 , 53 ]. As it is widely accepted, the bone-bonding ability of a biomaterial depends on ion release and exchange to develop a biological apatite layer when these materials are in the presence of body fluids.…”

Biomechanical Analysis of Non-Metallic Biomaterial in the Manufacture of a New Knee Prosthesis

“…After a 30-min incubation at room temperature, cells were observed under fluorescence microscopy. ImageJ software was used to analyze the intensity of the different fluorescences, and the relationship between both markers was estimated [38][39][40].…”

Silica/Protein and Silica/Polysaccharide Interactions and Their Contributions to the Functional Properties of Derived Hybrid Wound Dressing Hydrogels

“…e GPTMS is another alkoxysilane, in which the two electrophilic carbons on the epoxy ring are prone to the nucleophilic attack of primary amine groups on polysaccharides and proteins, forming secondary amines (Figure 5(b)). However, the chemical grafting depends on the polymer type, reactants concentration, pH, temperature, and addition of silica [79]. In the case of silica-chitosan scaffolds, the 13 C and 29 Si NMR show the nucleophilic addition is through the primary amine of chitosan pH 2-4 and 40 °C, accompanied by the epoxy ring-opening and diol formation.…”