Research On The Bioink Of Cryogenic Bioprinting Based On GelMA

3D Bioprinting is an emerging technology which applies 3D printing in the field of biological engineering.Based on extruded 3D printing technology,this paper made extruded hydrogel 3D printer and freezing platform,and used GelMA biological ink to build a set of extruded biological 3D printing system.The extrusion performance of the whole system,the mechanical properties and biological properties of biological ink were initially explored and studied.Using 3D modeling and numerical simulation technology,the extrusion biological 3D printer and freezing platform were designed in the preliminary stage.The overall frame of the printer is built with aluminum profile and I3 frame.The injection pump is used to accurately control the flow of biological ink extrusion.The experimental results show that the printer can extrude and print hydrogel bio-ink after the whole assembly.Using the simulation software COMSOL,the cooling power of semiconductor ceramic sheet under theoretical conditions is simulated.According to the comparison of heat dissipation experimental data,the cooling platform adopts ice-water mixture for heat dissipation.Refrigeration temperature range: 0?—-20?;The table area is100mm*100mm;Temperature control accuracy: ±0.05?.Firstly,the effects of different violet coupling time on the cell survival rate in GelMA bio-ink and the elastic modulus of the hydrogel scaffold after cross-linking were investigated,as well as the surface morphology,swelling rate and degradation rate of the hydrogel scaffold after gelation.The experimental results showed that the cell survival rate was still about 99% when the 120 S crosslinking time was used,and the cell proliferation experiment had a good performance.Meanwhile,the elastic modulus of the hydrogel scaffold did not increase with the increasing of the time of the crosslinking.In order to improve the mechanical properties of GelMA bio-ink after gelation,sodium alginate(SA)was added into GelMA bio-ink.The rheological properties of GelMA + sodium alginate(SA)biological ink were investigated by flat plate rheometer.The mechanical properties of the hydrogel scaffold were tested by universal testing machine,and the surface morphology,swelling rate and degradation rate of the GelMA + sodium alginate(SA)hydrogel scaffold were tested.Through the experimental results concluded that 5% GelMA + 2% SA components of biological ink has good rheological properties and shear thinned,worth exploring the best printing process parameters,got behind in glue water gel stent excellent biological compatibility,biological toxicity,regardless of whether the cells grown in the group branch surface or internal stent,the growth of the cells are able to good proliferation.In order to further improve the mechanical properties and extrusion printing performance of the hydrogel scaffold prepared with biological ink,a certain mass fraction of hydroxyapatite(nHAP)was added into the 5%GelMA+2%SA biological ink.The mechanical experiment and biological cell experiment of GelMA + sodium alginate(SA)+ hydroxyapatite(nHAP)bio-ink were carried out.The experimental results show that the viscoelasticity of biological ink increases with the addition of nHAP,but the viscoelasticity of biological ink does not change much with the increase of the content of nHAP.Meanwhile,the elastic modulus of hydrogel scaffold increases with the increase of the concentration of nHAP after cross-linking.However,with the increase of hydroxyapatite(nHAP)concentration,the proliferation and growth of cells were inhibited more obviously.In conclusion,the extrusion experiment of GelMA + sodium alginate(SA)biological ink was carried out by using the above extruded 3D printer with biological ink concentration,ink extrusion speed,extrusion needle moving speed and printer needle inner diameter as variables.The experimental results show that the GelMA +sodium alginate(SA),ink viscosity is mainly depends on the concentration of sodium alginate(SA),higher biological ink viscosity is suitable for use needle diameter larger extruding needles,slow speed of extruding needles and larger extrusion speed,low viscosity biological ink suitable for selecting the needle diameter smaller extruding needles,faster speed of extruding needles and smaller extrusion speed.In GelMA biological ink on the basis of exploring the development of a can be used in cryogenic extrusion biological printing technology(Low-temperature extrusion bioprinting,LTEB)and be able to load cells are capable of long-term storage at Low temperature and frozen biological printing ink,a certain volume fraction is added in the biological ink GelMA glycol and a certain quality score trehalose/lactose/raffinose as a protectant cells cryopreserved,configure a to hybrid cells cryopreservation biological ink in Low temperature.The experimental results showed that the survival rate of GelMA biological ink cells was greatly improved after adding ethylene glycol and trehalose/lactose/raffinose,and the maximum survival rate of cells could reach about 73% after 15-day storage at-80?.