Cary 60 spectrophotometer

Methotrexate was loaded by soaking 60 mg of MIL-100 NPs in 40 mL of an aqueous solution of MTX (1 mg·mL⁻¹) under constant stirring at 37 °C overnight. The suspension was then centrifuged (14,000 rpm, 10 min) and the supernatant was removed. The solid was washed two times with water, recovered by centrifugation (14,000 rpm, 10 min) and dried under vacuum overnight. The drug in the supernatant was measured in triplicate by UV–Vis spectroscopy (Cary 60 Spectrophotometer; Agilent, Australia) at 306 nm. The entrapment efficiency (EE%) was calculated according to Equation (1).
$$\mathrm{Entrapment} \mathrm{efficiency} \left(\mathrm{EE}\%\right)=\frac{\mathrm{weight} \mathrm{of} \mathrm{drug} \mathrm{in} \mathrm{MIL}-100 \mathrm{nanoparticles}}{\mathrm{weight} \mathrm{of} \mathrm{drug} \mathrm{fed} \mathrm{initially}} \times 100$$
The MTX release profiles were obtained by using simulated physiological media (phosphate buffered saline (PBS) solution 0.1 M) at pH 5.0 and pH 7.4, representing the cancer environment and the physiological pH, respectively. MTX@MIL-100(Fe) NPs and MTX@MIL-100 capsules (10 mg) were suspended in PBS solution (10 mL) and incubated at 37 °C under constant stirring, prepared in triplicate. Samples were removed after 0.5, 1, 2, 3, 4, 6, 7, 8, 12, 24 and 48 h, and an identical volume of fresh PBS was immediately replaced, keeping up the MTX concentration far from saturation.
The release of MTX was quantified in triplicate by UV–Vis spectroscopy (Cary 60 Spectrophotometer; Agilent, Sidney, Australia) at 306 nm.

GC-MS was performed on a Thermo Fisher Trace 1300s-ISQ LT instrument (Thermo Fisher, Waltham, MA, USA) with electron ionization (EI) mass spectrometry. NMR spectra were recorded at 500 MHz with Bruker Avance III HD instrument (Bruker, Billerica, MA, USA) using CDCl₃ as the solvent with tetramethylsilane (TMS) as the internal standard.
The FT-IR spectra were recorded within a 4000–500 cm⁻¹ region on a Thermo Fisher Nicolet iN10 MX & iS10 infrared spectrometer (Thermo Fisher, Waltham, MA, USA) using KBr pellets.
The UV–vis spectra was recorded within a 200–800 nm region on an Agilent Cary 60 spectrophotometer (Agilent, Palo Alto, CA, USA) with quartz cells at room temperature.
XPS measurements were performed on a Thermo Fisher ESCALAB 250Xi spectrometer (Thermo Fisher, Waltham, MA, USA).
The situ ATR-IR spectra were recorded within a 3000–600 cm⁻¹ region on a Mettler Toledo React IR15 spectrometer (Mettler Toledo, Zurich, Switzerland) equipped with a liquid-nitrogen-cooled MCT (mercury cadmium telluride) detector and a diamond probe. The typical experiments were carried out in a closed flask. The IR probe was immersed in liquid phase reaction mixture or gas phase.