Bioactive monetite‐containing whisker‐like fibers reinforced chitosan scaffolds

Abstract

The aim of this work was to develop bioactive chitosan scaffolds reinforced with monetite-containing whisker-like fibers. The fibers synthesized by homogeneous precipitation were characterized as monetite/hydroxyapatite short fibers (MAFs), using XRD, FTIR and SEM. The pure chitosan and MAFs/chitosan composite scaffolds were produced by freeze-drying, and characterized with respect to porosity, pore size, swelling behavior, compressive strength and modulus, and in vitro bioactivity. The incorporation of MAFs in chitosan matrices led to increase the pore size, according to the evaluation by FE-SEM, and decrease the porosity of composite scaffolds. The swelling ratio decreased as MAFs content of scaffolds increased. The compressive strength and modulus of scaffolds were improved by an increase in MAFs content. The noncross-linked scaffolds with a chitosan:MAFs weight ratio of 1:1 (CW3) showed a porosity of 75.5%, and the strength and modulus of 259 kPa and 2.8 MPa in dry state, respectively. The crosslinking by glutaraldehyde resulted in improved mechanical properties. The strength and modulus of cross-linked CW3 scaffolds in wet state reached to 345 kPa and 1.8 MPa, respectively. The in vitro bioactivity of the reinforced scaffolds, evaluated by FE-SEM/EDS, XRD, and ATR-FTIR, was confirmed by the formation of a carbonated apatite layer on their surfaces when they soaked in simulated body fluid (SBF). The results of this initial study indicate that the monetite-containing whisker-like fibers may be an appropriate reinforcement of chitosan scaffolds.

Synthesis of Fiber-like Monetite without Organic Additives and Its Transformation to Hydroxyapatite

“…This is probably due to the high concentration of H + at low pH, which greatly reduces the adsorption of NH 4 + on the surface of the crystals. Urea, which has two −NH 2 groups, shows a similar effect in controlling the elongation of monetite crystals …”

“…The most common morphology of DCPA, similar to DCPD, is irregular micro-sized plate-like particles (Figures 2a,b and 3a). The control of morphology and size of DCPA crystals is challenging; therefore, many organic additives such as cetyltrimethylammonium bromide 23 and urea 29 have been used to regulate its crystal growth in the aqueous solutions. However, our study reveals that the fiber-like DCPA can be synthesized using the "purely inorganic" system under proper pH, temperature, initial Ca/P and in the presence of a high concentration of NH 4 + .…”

“…Urea, which has two −NH 2 groups, shows a similar effect in controlling the elongation of monetite crystals. 29 4.2. Transformation of Monetite to Hydroxyapatite under Various Conditions.…”

“…Other methods such as wet-chemical, − sol–gel method, ball-milling, and spray-drying method have been used to prepare DCPA with particular particle size and morphologies. Most of the reported synthesized DCPA particles are plate-like, and reports regarding the synthesis of fiber-like DCPA are rare. , Additionally, in all reported methods, surfactants such as polycationic poly­( l -lysine) block copolymers and potassium dodecyl phosphate or organic solvents are required to regulate the crystal growth of DCPA. These surfactants or organic solvents are not easy to completely remove, and the residual organic molecules have potential risks to the safety of the human body when applying DCPA as the biomaterial.…”

Strontium doped bioglass incorporated hydrogel-based scaffold for amplified bone tissue regeneration

“…In this study, incorporation of strontium in bioglass had no effect on the degradation and swelling profile of BG containing scaffolds. As a rule, water uptake ability, degradation ratio and porosity of scaffolds could also affect their mechanical strength 26 , 59 , 60 .…”