Fig. 1

Preparation and characterization of different sizes of MTX-TMPs. A A549 cells (1 × 10⁸) were exposed to a concentration gradient of MTX (1 mg/ml) under UV irradiation for the preparation of MTX-TMPs. MTX-TMPs were isolated by gradient centrifugation, and the concentration and particle size was analysed by nanoparticle tracking analysis (NTA). B Small microparticles (SMPs) and large microparticles (LMPs) were separated by size-exclusion chromatography. The size distribution was analysed by NTA. C Zeta potential of SMPs and LMPs, as measured by Dynamic light scattering (DLS). Data are presented as means ± s.d. (n = 3). D Morphology of SMPs and LMPs were analysed by transmission electron microscope. Scale bars, 200 nm. E The calibration curves showed good linearity over the concentration ranges of 1–50 µg/ml for MTX, Y = 1.940*X + 0.07887, R² = 0.9999. The concentration of MTX loaded in 1 × 10¹⁰ SMPs and LMPs was measured by HPLC. F The radio of the number of SMPs and LMPs containing 10 µg MTX (n = 3). G Verification of the storage stability of two groups of MTX-TMPs. The same number of SMPs and LMPs were stored at 4 and 37 °C, respectively, and the corresponding number was detected from Day 0 to Day 5 (n = 3). H SMPs and LMPs were stored at 4 °C, and the stability of the loaded MTX was detected by HPLC at 48 h (n = 3)