0; (G) DOX confinement due to the PEM layer contraction at pH 8.0; and (H) DOX release in different media at pH 7.4 and

5.2. Polyelectrolyte multilayer coating PAH/PSS multilayer coating was deposited by alternately exposing the internal side of the micropillar sample to solutions of PAH and PSS (1 mg mL−1 in CaCl2 0.5 M) for 20 min each in an ultrasonic bath (E in Figure 1). After the deposition of each polyelectrolyte, the sample was thoroughly washed twice in Milli-Q water for 5 min each. This sequence was repeated until obtaining the desired number (4, 8 or 12) of PAH/PSS bilayers. Characterization instruments The morphology and structure of the macroporous silicon and subsequent silicon dioxide micropillars were characterized by scanning electron microscopy (SEM) using a FEI Quanta 600 environmental scanning see more electron click here microscope (FEI, Hillsboro, OR, USA) operating at an accelerating MM-102 price voltage between 15 and 25 kV. The micropillars were also morphologically characterized by transmission electron microscopy (TEM) using a JEOL 1011 (JEOL Ltd., Akishima-shi, Japan) operating in dark-field mode at 80 kV. Confocal laser scanning microscopy images

were taken using a Nikon Eclipse TE2000-E inverted microscope, equipped with a C1 laser confocal system (EZ-C1 software, Nikon, Tokyo, Japan). A 488-nm helium-neon laser was used as excitation source for DOX-loaded micropillars. The emission was collected through a 590 ± 30 bandpass emission filter

(red channel). All fluorescence images were captured using a 5-megapixel CCD. The concentrations of DOX were determined using a spectrofluorometer (PTI Quantamaster 40, Photon Technologies International, Edison, NJ, USA) Epothilone B (EPO906, Patupilone) at an exciting wavelength of 480 nm. DOX loading and pH-responsive drug release Doxorubicin was loaded inside the PEM-coated micropillar, as well as in bare SiO2 samples. To perform the drug loading, the micropillar samples were exposed to a solution of DOX 1 mg mL−1, adjusted to pH 2.0 with HCl 1 M, for 20 h in the dark (F in Figure 1). Then, DOX solution was adjusted to pH 8.0 with NaOH 0.1 M and further stirred for 2 h (G in Figure 1). The drug-loaded samples were washed three times in water at pH 8 for 10 min each. The amount of released DOX in solutions of pH 7.4 (phosphate buffer) and 5.2 (acetate buffer) was monitored over time (up to 24 h) at an exciting wavelength of 480 nm (H in Figure 1). Results and discussion Figure 2A shows a SEM image of SiO2 micropillars with a diameter of 1.8 μm, protruding out of the backside of the Si wafer. The micropillar arrays retain the same arrangement and dimensions as the preceding macropores.