Thermosensitive Microgel For Injectable 3d Cell Scaffolds

In present work,two kinds of thermosensitive hydrogel scaffold materials have been faricated:1. Injectable 3D cell scaffold built with thermal microgels In this work we try to develop a new thermal gelling injectable scaffold for 3D cell culture. Instead of using linear, branched, or grafted macromolecules, thermosensitive microgel particles or microspheres are used as building blocks for the construction of the macroscopic hydrogel scaffold. As a proof of concept, thermosensitive poly(N-isopropylacrylamide-co-2-hydroxyethylmethacrylate) (P(NIPAM-HEMA)) microgel particles were synthesized, which present a volume phase transition temperature (VPTT) at about 29 C. Rheological test shows that the concentrated P(NIPAM-HEMA) microgel dispersion is colloidally stable when heated above its VPTT, indicating hydrophobic interaction alone can not induce thermal gelation of the dispersion. In the presence of a low concentration of CaC12, however, with the introduction of additional ionic cross-linking, the microgel dispersion gelates and forms macroscopic hydrogel. Gelation temperature of the microgel dispersion decreases with increasing ionic strength. SEM observation reveals that the resultant bulky gel has an interconnected porous microstructure.293T cells, a human cell line, were encapsulated inside the hydrogel by simple mixing with the microgel dispersion at room temperature and heating to 37℃. MTT assays reveal that the cells are viable and proliferate inside the 3D scaffold.2. Syneresis effect of thermal gelable injectable 3D cell caffold shrinkage phenomonen is popular in PNIPAM hydrogels.in this work,we try to fabricate a scaffold which would not shrink or less shrinkage.we propose to introduce acrylic acid group (AAc) into the PNIPAM chains, acrylic acid group is hydrophilic and biocompatible.the hydrophilic property of AAc can weaken the hydrophobic effect of the thermal microgels,thereby leads to the weakening of syneresis effect of the micro-gel. To study shrinkage behavior of the formed bulk gel,a serie of thermal sensitive P (NIPAM-AAc) copolymeric microgels were prepaerd with various content of acrylic acid,the microgels were then heated at 37 C to formed physical network in situ. Rheologic experiments indicate that, the induced AAc group can change the phase transition behavior of P(NIPAM-AAc) microgels. P (NIPAM-AAc) copolymeric microspheres with different AAc content were then used to form injectable 3D cell scaffold with HepG2 cells by mixed together and heated at 37℃. Through systematic observation, we found that morphology and number of the cells in the cell scaffold with different AAc content are different,the cell number in the scaffold with a content AAc%=1% is the most one,indicating that P(NIPAM-AAc) with a AAc content of 1% is most suitable one for cell proliferation.