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.
Highlights
A new generation of bio-based aerogels has been attracted much attention research during the last two decades, in emerging areas associated to environmental and biomedical sciences [1,2,3,4,5].Thanks to their unique and tuneable properties, as well as ease of functionalization, a widespread rangePolymers 2020, 12, 2723; doi:10.3390/polym12112723 www.mdpi.com/journal/polymersPolymers 2020, 12, 2723 of applications has been proposed and developed for silica-based biopolymer aerogels [6]
High resolution imaging HRTEM was performed with TEM TALOS FX200 (Thermo Scientific, Waltham, MA, USA) and selected-area electron diffraction (SAED) patterns were obtained in microprobe mode, in order to identify the crystalline nature of possible nanocrystalline phases
CS-SiO2 and CS-glycidoxypropyl trimethoxysilane (GPTMS)-SiO2 monolithic hybrid aerogels were here synthesized by sol-gel techniques
Summary
A new generation of bio-based aerogels has been attracted much attention research during the last two decades, in emerging areas associated to environmental and biomedical sciences [1,2,3,4,5]. After a thorough investigation of the topic, CS-silica aerogels were proposed for different applications and here we will take special consideration of biomaterials for biomedical purposes [1,2,20,26,35,36] To this end, many research studies presented in the literature about the synthesis of chitosan-silica hybrids proposed the use of crosslinking agents, to create strong interactions at nanoscale with creation of covalent bonds between chitosan and silica network [37]. Two types of alkoxysilanes: TEOS, as silica inorganic precursor, properties To this end, we synthesized monolithic hybrid aerogels by sol-gel followed by and GPTMS, CO as crosslinker agent,on used in different molar ratios. Addition this investigates the in vitro of the hybrid materials in simulated body fluid (SBF), as well as the osteoblast cell response of the hybrids by in vitro culture methods
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