Patterned and switchable surfaces for biomaterial applications

Chapter 1 - Introductionof understanding phenomena like embryo development and wound healing and forthe improvement of implant compatibility. Significantly, substrates with alignedgrooves have been shown to orient cell growth parallel to the direction of the grooveswhilst also improving cell attachment as compared with flat surfaces [57-59],enabling the formation of patterned cell growth. Of interest are studies thatdemonstrate the ability of micro- and nanostructures on surfaces that are smaller thanthe typical cell dimensions (≈ 20 m) to influence the behaviour of cells [57, 58].Use of cliffs, pillars and islands on surfaces have also been shown to influence celloutgrowth [60]. The mechanism behind this effect is not fully understood. In somecases, improved attachment may be due to the increased surface area of the surface.Recently, Wan et al., [63] investigated cell attachment of osteoblast-like cells (OCT-1) on microfabricated PS and PLA surfaces with hemispherical bump and pit surfacefeatures. These features had a bimodal distribution of sizes with an average diameterof 2.2 and 0.45 m. The behaviour of the OCT-1 cells on the pit-patterned PS surfacewas most notable (Figure 1.2). Three interesting behavioural characteristics of cellswere observed; first, cells showed the ability to be able to stride over both the 2.2 mpits (Figure 1.2A) and the 0.45 m pits (Figure 1.2B). Second, the more flexiblepseudopods of the cells were able to enter into and grow along the walls of the 2.2m pits but not the 0.45 m pits, which were evidently too small. Third, the filopodiaof cells tended to grow along the ridge at the wall of the pits and as a result instigateda morphological change that allowed them to follow the curvature of the ridge(Figure 1.2C). This contact guidance phenomenon has also been observed in manyother studies [57-59].1-14