Tissue engineering has directed a lot of effort toward the development of devices with suitable biocompatibility and mechanical properties. Chitosan has been pointed as a valuable material to be applied in scaffolds due to its antimicrobial activity and biocompatibility. Nevertheless, the low mechanical resistance associated with the requirement of toxic crosslinkers has hampered translational application of chitosan hydrogel. Herein, the use of gold nanoparticles (AuNP) as crosslinker is reported as a great strategy to obtain chitosan hydrogel without using toxic reactants. In addition, the resultant chitosan hydrogel, crosslinked by AuNP of 30 nm (AuNP30), presented outstanding properties compared to chitosan hydrogel crosslinked by glutaraldehyde. Chitosan hydrogel crosslinked by AuNP30 presented lower porosity, which provided lower swelling degree and slower degradation rate. In addition, compressive strength was about two times higher than the chitosan hydrogel crosslinked by glutaraldehyde. The crosslink by AuNP30 also increased the biocompatibility of the hydrogel. Chitosan hydrogel crosslinked by AuNP30 did not show cytotoxicity against MEF cells, whereas cell viability of cells incubated with extract from chitosan hydrogel crosslinked by glutaraldehyde was only 41%. In conclusion, the results reported herein pointed that the use of AuNP30 as crosslinker agent provided to chitosan hydrogel enhanced properties that made it suitable to application in biomedical devices.
Nanodiamonds (NDs) are amongst the most investigated carbon-based nanostructures due to their chemical stability and favorable mechanical properties. Despite the number of works on methods for NDs production, one of the main challenges is to achieve their colloidal stability in aqueous suspension. Additionally, NDs are normally obtained by expensive, complex and time-consuming process. Herein, it was presented a facile method to obtain NDs in aqueous suspension by using columnar structure diamond from Hot-Filament Chemical Vapour Deposition reactor (HFCVD). CVD diamond leftover thick film from CVDVale Company was used. Therefore, this method has the advantage of being not only practical but also cost-effective since it brings a profitable use of CVD diamond leftover. The Diamond thick film was submitted to ultrasonic cavitation in the presence and absence of ZrO 2 microbeads in aqueous medium. The NDs hydrodynamic diameter and the stability in aqueous suspension were monitored by light scattering, size and morphology were analyzed by transmission electronic microscopy. Considering the wide application of NDs in biomedical devices, cytotoxicity of aqueous suspensions of NDs was evaluated against murine embryonic fibroblast cells. Furthermore, NDs were functionalized with hydrogen and carboxyl groups. NDs aqueous suspension of straight size distribution was obtained even in the absence of ZrO 2 beads, indicating that they may be dispensable in order to decrease NDs size. NDs of average hydrodynamic diameter of 22 nm and − 35 mV of Zeta-potential were obtained after ultrasonic cavitation followed by 2 h of centrifugation, not demonstrating cytotoxicity to cells at very low (0.05-0.5 μg/mL) nor at higher concentrations (116 μg/mL). Nevertheless, NDs showed a moderate cytotoxicity at intermediary concentration range (0.5-2.2 μg/mL). From our knowledge, this is the first work that reports on a facile method for providing NDs aqueous suspension with high colloidal stability from HFCVD diamond leftover.
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