Fabrication Of Thermoresponsive Polymer Brushes And Their Applications In Modulating Adhesion And Orientation Of Different Cell Types

The cell adhesion is essential in ubiquitous physiological and pathological processes,including wound healing,tissue development and regeneration,embryogenesis,and cancer metastasis.In particular,cell-substrate adhesion also plays key roles in the fabrication of cell-seeded?scaffolds for many biological and medical applications in tissue engineering,regenerative medicine,drug screening,and biosensors.In Chapter 2,the thermoresponsive poly(N-isopropylacrylamide)(PNIPAAm)brushes were grafted onto the substrate of glass slides via surface-initiated atom transfer radical polymerization(SI-ATRP).With elegant control of the NIPAAm monomer concentrations in ATRP reaction,the thickness of the PNIPAAm brushes can be precisely controlled to modulate the adhesion of different types of cells.The polymer brushes were characterized by proton nuclear magnetic(1H NMR),X-ray electron spectroscopy analysis(XPS),water contact angle(WCA)and atomic force microscopy(AFM),respectively.Five types of cells,4T1,HEK293,H9C2,HUVEC and L929,were seeded on the PNIPAAm surfaces with different thicknesses.The morphologies of the cells were characterized by using phase-contrast microscopy,confocal laser scanning microscope(CLSM)and scanning electron microscopy(SEM).The results showed that different cell types exhibited different adhesion behaviors with different thicknesses of PNIPAAm.The mechanism was studied by immunofluorescence staining of F-actin,vinculin and fibronectin,respectively.In Chapter 3,strip micropattems of PNIPAAm/PEG-silane with different widths were prepared by soft lithography and selective O2 plasma etching and characterized by fluorescence microscopy and atomic force microscopy(AFM).The culturing of L929 and H9C2 on the top of the micropatterned surfaces revealed that L929 cells selectively attached onto the PNIPAAm strips,while the H9C2 cells selectively attached onto PEG-silane stripsTaking together,these studies revealed the action mechanisms in modulating selective adhesion of different cell types on thermoresponsive surfaces,which shed light on the fabrication of Patterned cells for tissue engineering and regenerative medicine.