2.5 Evaluation of photothermal effect and controlled E2 release from bilayer scaffolds
The encapsulation of PDA particles in PLGA/GelMA fibers would produce photothermal effect for the scaffolds. To study the photothermal effect, bilayer S+F-PDA scaffolds were exposed to a near-infrared (NIR) laser (808 nm wavelength) at different densities (0.5 W/cm2and 1.0 W/cm2). The temperature changes were revealed by thermal images which were recorded using an infrared camera (GUIDE® EasIR-9, AutoNavi, China). Additionally, to study the effect of NIR laser irradiation on E2 release, S+F-PDA@E2 scaffolds were exposed to different power densities (0, 0.5, and 1.0 W/cm2) of the NIR laser for 30min every 1 hour in PBS (pH 7.4) at 37 ℃. PBS was collected at each predetermined time point, and an equal amount of fresh PBS was added to the system. The amount of E2 released in PBS was determined using a UV-vis spectrophotometer (UV-2600, Shimadzu, Japan) at the wavelength of 280 nm, and cumulative release curves for E2 were then plotted.
Since human uterus has a dynamic pH environment, it is very important to investigate E2 release kinetics in solutions of different pH values. S+F-PDA@E2 scaffold samples were therefore immersed in different buffer solutions (at pH 4.5, pH 7.4, and pH 9.0) at 37 ℃. At each predetermined time point, a small amount of buffer solution was extracted from the release system and an equal amount of fresh buffer solution was supplemented. The amount of E2 released was determined using the UV-vis spectrophotometer. The cumulative amounts of E2 released in different buffer solutions were calculated, and E2 release curves were established.