Poly(N-isopropylacrylamide-co-acrylamide) (PNIAM-co-AM)grafted surfaces have been reported to promote cell adhesion and detachment by a hydrophobic-to-hydrophilic transition triggered by temperature change. However, the surface uniformity and cell detachment consistency are still an issue. In this study, PNIAM-co-AM is prepared with spin coating to control the grafting density and the thickness and to achieve better cell detachment. The atomic force microscopy results indicate that the surface becomes smoother as the spin speed increases. The attenuated total reflection Fourier transform infrared results show a grafting density from 1.68 to 2.03 μg/cm 2 . Ellipsometry suggests that the thickness of the spin-coated PNIAM-co-AM layer is 11−21 nm. The grafted surfaces were tested with mouse preosteoblast MC3T3-E1 cells, which grew successfully. The detachment reached 100 percent with the samples prepared with 1.5 and 2 h ultraviolet exposure times without the use of a poly(vinylidene difluoride) membrane. The detached sheet was in good condition, as indicated by Live/Dead stains.

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Cell sheet engineering, a scaffold-free approach to fabricate functional tissue constructs from several cell monolayers, has shown promise in tissue regeneration and wound healing. Unfortunately, these cell sheets are often too small to provide sufficient wound area coverage. In this study, we describe a process to enlarge cell sheets using MEEK micrografting, a technique extensively used to expand skin autografts for large burn treatments. Human dermal fibroblast cell sheets were placed on MEEK’s prefolded gauze without any use of adhesive, cut along the premarked lines and stretched out at various expansion ratios (1:3, 1:6 and 1:9), resulting in regular distribution of many square islands of fibroblasts at a much larger surface area. The cellular processes essential for wound healing, including reattachment, proliferation, and migration, of the fibroblasts on expanded MEEK gauze were superior to those on nylon dressing which served as a control. The optimal expansion ratio with the highest migration rate was 1:6, possibly due to the activation of chemical signals caused by mechanical stretching and an effective intercellular communication distance. Therefore, the combination of cell sheet engineering with the MEEK micrografting technique could provide high quality cells with a large coverage area, which would be particularly beneficial in wound care applications.

No abstract

One of many challenges in wound treatment is to provide sufficient wound area coverage to protect against pathogens and speed up the wound healing process. Recently, cell sheet engineering has shown promise in treating deep wounds. Unfortunately, the cell sheet size is too small for practical use. To overcome this limitation, the MEEK micrografting technique, currently being used in the treatment of extensive deep burns, was investigated. This technique was modified and applied to enlarge dermal fibroblast cell sheets, constructed using temperature-responsive PNIAM-co-AM graft copolymer, by transforming the intact cell sheets into small cell islands at expansion ratios of 1:3, 1:6 and 1:9. Afterwards, cell mechanisms essential for wound healing, including reattachment, proliferation, and migration were investigated. The fibroblast cells on MEEK gauzes possessed high cell viability, capable of reattachment and migration. The optimal expansion ratio having the highest migration rate was 1:6, possibly due to an effective intercellular communication distance. Therefore, the combination of cell sheet engineering with the MEEK micrografting technique could provide high quality cells with a large coverage area, which would be particularly beneficial in wound care applications.