Application of ultrasound on monitoring the evolution of the collagen fiber reinforced nHAC/CS composites in vivo

3D printing of human ear pinna using cartilage specific ink

Biofabrication of a complex structure such as ear pinna is not precise with currently available techniques. Auricular deformities (e.g. microtia) can cause physical, social as well as psychological impacts on a patient's wellbeing. Currently available surgical techniques and transplantation methods have many limitations that can be overcome with the help of 3D bioprinting technology. Printable bioink enriched with cartilage-specific extracellular matrix (ECM) synthesis was done by digesting goat ear pinna cartilage and polymerized by adding polyvinyl alcohol and gelatine. Rheological analysis and Fourier-transform infrared spectroscopy were used for the characterization of bioink to get desired viscosity and polymerization. Human ear pinna was printed using extrusion method and computer-aided design, stereolithography software which facilitated the automated printing in relatively less time without continuous monitoring. Thermal degradation of pinna was checked by thermal gravimetric analysis. Biodegradability and swelling of ear pinna were observed for understanding the nature of pinna and the impact of external factors. Reconstructed pinna's biocompatibility was proved byin ovoandin vivostudies. The occurrence of angiogenesis in the grafted ear manifested the capacity of proliferation and engraftment of cartilage cells. Histology and SEM analysis revealed the recellularization and the synthesis of ECM components such as glycosaminoglycan and collagen in transplanted 3D printed ear pinna. The expression of CD90+ which indicated newly synthesized cartilage in the transplanted 3D printed ear pinna. The absence expression of CD14+ also indicated acceptance of xenogenic transplanted 3D printed ear pinna. Transplantation of 3D ear pinna was successful in an animal model and can be utilized as tissue engineered ear bank.

[Chitosan-collagen polymer induced remineralization of tooth hard tissue through self-growing methods]

OBJECTIVE

To modify biomacromolecules, such as chitosan and collagen, to synthesize a mineralized template that will induce self-growing remineralization of tooth enamel.

METHODS

Natural polycation polysaccharide chitosan was modified through phosphorylation to synthesize the polyanion derivative ofphosphorylated chitosan. Parent hydrogels com- bined with chitosan and collagen I were built through peptide binding reaction using genipin as a crosslinker. The gels self- assembled on the tooth's inert surface, which was stimulated by ultraviolet radiation. The bionic saliva provided mineralized ion, and then the hydroxyapatite assembled and grew in situ on the tooth.

RESULTS

The functional group P04(3-) (3,446 cm(-1)) was grafted on chitosan as confirmed by the Fourier transform infrared spectroscopy. The porous polyelectrolyte complex hydrogel formed by the interaction between the polycation chitosan and the polyanion phosphorylated chitosan could induce hydroxyapatite crystal nucleation and growth on the hydrogel fiber surfaces. The neonatal crystal was hydroxyapatite as confirmed by X-ray diffraction and was tightly connected to the tooth. A continuous structure of column crystals with sizes ranging from 30 nm to 60 nm was observed. The structure was in parallel direction similar to the direction of the enamel rod, and its hardness was close to dentin.

CONCLUSION

The parent hydrogels that were easily obtained and controlled could mimic the template of the enamel mineralization and induce a self-growing hydroxyapatite, which is an important step in the structural bionics of enamel.