br The preparation of BPNs were performed
The preparation of BPNs were performed via liquid exfoliation of bulk BP. During the course of liquid exfoliation, the transformation of bulk BP structure was characterized by Raman spectrum and X-ray diffraction (XRD). As shown in Fig. S1, peaks with similar Raman shift were observed at 362, 437, and 467 cm−1 of bulk BP and BPNs, which Chemical Engineering Journal 370 (2019) 387–399
correspond to Ag1 mode, B2g mode, and Ag2 mode of BP, suggesting the obtained BPNs kept the structure of bulk counterpart during the ex-foliation. The slight shift towards high wavenumber was observed in the Raman spectrum of BPNs compared with bulk BP due to the ul-trathin thickness of the nanosheets . Besides, the main peaks in the XRD patterns of BPNs correspond with the bulk BP, suggesting that the nanosheets maintains the same crystal structure as bulk BP (Fig. S2). Moreover, the extra XRD peaks which of BPNs suggesting the random distribution of BPNs without preferential orientation during the pre-paration process . The transmission Cucurbitacin I microscopy (TEM) image of BPNs (Fig. 1a) indicated the sample were free-standing na-nosheets with diameter of several hundred nanometers. Compared with the TEM image of BPNs, a much rougher surface could be observed in BPNs-PDA, BPNs-PDA-PEG and BPNs-PDA-PEG-PEITC (Fig. 1b–d), be-cause the PDA layer was deposited onto the surface of BPNs. After loading with DOX, the morphology of BPNs-PDA-PEG-PEITC/DOX had no obvious change compared with BPNs-PDA-PEG-PEITC (Fig. S3). Atomic force microscopy (AFM) image (Fig. S4) show the thickness of the samples. BPNs with about 2.1 nm height was in line with the thickness of four-layer individual BP. For BPNSs-PDA-PEG-PEITC, the height increased to 3.2 nm due to the deposition of PDA on the BPNs surface. The size distribution of BPNs-PDA-PEG-PEITC measured (Fig. 1e) by dynamic light scattering (DLS) revealed that the hydro-dynamic size was 288 nm and the hydrodynamic size of BPNs-PDA-PEG-PEITC/DOX was 312 nm (Fig. S5). When the size of nanomaterials was between 60 nm and 400 nm, tumor tissue will exhibit the enhanced permeability retention (EPR) effect, which realize the accumulation of BPNs-PDA-PEG-PEITC/DOX to the tumor areas . In order to estimate the stability of BPNs-PDA-PEG-PEITC and BPNs-PDA-PEG-PEITC/DOX, the hydrodynamic size changes of BPNs-PDA-PEG-PEITC and BPNs-PDA-PEG-PEITC/DOX in PBS and FBS was measured last one week (Figs. S6 and S7). The size had no significant change indicating that the prepared nanomaterials both have good stability. The Fourier transform infrared (FT-IR) spectra of BPNs, BPNs-PDA, BPNs-PDA-PEG, and BPNs-PDA-PEG-PEITC was shown in Fig. 1f. All of the spectra showed the absorption peaks at 988 cm−1, 1189 cm−1 and 1622 cm−1 in spectra which were attributed to the PeO stretching vibration, PePeO linear stretching vibration and P]O stretching vibration, respectively . After the deposition of PDA layer, the new absorption peaks appeared at 1283 cm−1 (CeO stretching vibration), 1401 cm−1 (benzene skeleton vibration) and 1512 cm−1 (NeH shearing vibration) indicates the polymerization of PDA onto the BPNs [7,53]. After reaction with PEG-NH2, the intensity of peak at 2917 cm−1 (CeH vibration) was increased compared with BPNs-PDA which confirmed the functionalization of PEG-NH2 . The spectra of BPNs-PDA-PEG-PEITC with new peaks at 2109 and 2189 cm−1 was due to the N]C]S symmetric and asym-metric stretches of PEITC . Energy-dispersive X-ray (EDS) mapping and Xray photoelectron spectroscopy (XPS) of BPNSs-PDA-PEG-PEITC (Fig. 1g and h) were also used to characterize the functionalization of BPNs. Fig. 1g shows a uniform elemental distribution (P, N and S). The N element mapping was derived from the PDA layer and the S element mapping suggested the existence of PEITC. The XPS spectrum (Fig. 1h) indicated that the existence of N and S elements in the prepared ma-terials. All TEM, FT-IR, AFM, EDS-mapping and XPS data demonstrated the successful preparation of BPNs-PDA-PEG-PEITC.
2.2. Photothermal performances of BPNs-PDA-PEG-PETIC.
The UV–vis-NIR spectroscopy of BPNs-PDA-PEG-PEITC solutions with different concentrations was shown in Fig. 2a. An obvious ab-sorption at NIR wavelength indicating the potential application in tumor PTT. BPNs-PDA-PEG-PEITC with different concentrations (0, 25, 50, 100 μg/mL) were irradiated with 808 nm NIR laser (1.2 W/cm2) for 5 min. During the process of exposure, the concentration-dependent temperature increase was shown in Fig. 2b and corresponding thermal images of temperature variation were shown in Fig. 2c. The
Scheme 1. Schematic illustration of the preparation process of BPNs-PDA-PEG-PEITC-Mn/DOX and bioimaging-guided resistant cancer multimodal therapy.