Figure 1.
Schematic of µCPe. Glass or polystyrene dishes are coated with PDMS and then treated with oxygen plasma to form an oxygen-rich layer at the surface (i).
A stamp made of aluminum, copper, or silicon was brought into physical contact with the substrates (ii), and removed away to peel off the oxygen-rich layer at the places of the contact (iii). The substrates were then treated with Pluronic F-127 (iv) and ECM (in the present study, gelatin) (v). ECM and cells adhere selectively to the unpeeled regions (vi).
Figure 2.
Contact angles between the substrates and ultrapure water.
(a) Side views of a water droplet on bare PDMS, oxygen plasma-treated PDMS (PDMS + plasma), oxygen plasma-treated PDMS made contacted with an aluminum sheet (Peeling (Al)), oxygen plasma-treated PDMS made contacted with a copper sheet (Peeling (Cu)), or oxygen plasma-treated PDMS made contacted with a silicon wafer (Peeling (Si)). Representative data from n ≧ 3. Scale bar, 1 mm. (b) Quantified contact angles at each condition. Data are represented by mean ± SD.
Figure 3.
Transfer of the surface layer of PDMS onto an aluminum peeling stamp investigated by angle-resolved XPS.
(a) C1s, O1s, and Si2p spectra of an untreated PDMS. Representative data from n = 3. (b) High-resolution spectra of C1s, O1s, and Si2p obtained at the surface of oxygen plasma-treated PDMS before and after peel-off with the aluminum sheet. Representative pair from n = 3. (c) High-resolution spectra of C1s, O1s, Al2p, and Si2p obtained at the surface of the aluminum sheet before and after peel-off. Representative pair from n = 2. (d) Quantified changes in the elemental ratio. Data are represented by mean ± SD. The asterisks represent a significant difference in the compositional ratio of oxygen measured for n = 3 separate measurements.
Figure 4.
Representative images of spatially selective cell adhesions by µCPe.
(a) Cells adhere to unpeeled regions (left) but not to peeled regions (right) created by physical contact with an aluminum sheet. (b) Demonstration of the selective cell adhesion at a micro-scale using a copper EM grid with a square mesh length of 54 µm. Cells are restricted to spread within square islands. (c) A high magnification view of the cells on the square micropatterns. (d) Cells outside the micropatterns (allowed to spread freely) observed with the same magnification as that of c. (e) Coating with fluorescent fibrinogen visualizes square adhesive regions. (f) Intensity profile along the line A–B in e. Asterisks represent 54 µm. F-actin and nuclei are shown in green and blue, respectively. Scale bars, 200 µm (a and b); 25 µm (c and d); 200 µm (e).
Figure 5.
Repeatable use with identical silicon wafers.
(a) Cells adhere to unpeeled regions (left) but not to peeled regions (right) created by physical contact with a silicon wafer. 1st, 2nd, and 10th peelings represent selective cell adhesions using the same silicon stamp without ultrasonic cleaning, after 1st cleaning, and after 9th cleaning, respectively. F-actin and nuclei are shown in green and blue, respectively. Scale bar, 100 µm. (b) Contact angles for the same silicon wafers measured in sequence before the first peeling-off (Initial), after the first peeling-off (1st peeling), after the subsequent cleaning (1st cleaning), after the subsequent second peeling-off (2nd peeling), after the ninth cleaning (9th cleaning), after the tenth peeling-off (10th peeling), and after the tenth cleaning (10th cleaning). Data are represented by mean ± SD (n = 3).