2.4. Characterization

The morphologies of Np₀, Np₁, Np₂, and Np₃ were evaluated with the Scanning Electron Microscope (SEM) (JEOL JSM-7800F, Pleasanton, CA, USA) at 3.0 kV. The samples were diluted 1 to 15 before deposition on the film. The size distribution of NpFe₃O₄, Np₀, Np₁, Np₂, and Np₃ samples was determined by DLS using a Zetasizer-Nano ZS (Malvern Instruments, Malvern, UK), with a laser of wavelength = 633 nm (He–Ne, 4.0 mW). The ζ-potential of all samples was determined using a sizer-nano ZS (Malvern Instruments, Malvern, UK). The samples’ magnetization properties were carried out at 300 K using a Physical Property Measurement System vibrating Sample Magnetometer (PPMS-VSM, Quantum Design, San Diego, CA, USA); the samples were previously lyophilized. The vincristine sulfate load and release in Fe₃O₄@PNIPAM-CS were measured by indirect quantification using a Perkin Elmer UV-Vis spectrometer (lambda 850, Perkin Elmer Inc., Waltham, MA, USA); the absorbance was fixed at 310 nm. FTIR spectra were collected from a Spectrum (Perkin Elmer, Inc., Waltham, MA, USA) spectrometer equipped with a single diamond attenuated total reflectance (ATR) with a range of 8300–350 cm⁻¹ variable IR beam with diameter from 2 to 11 mm. The IR spectra were collected 16 times (spectral resolution 4 cm⁻¹).