Nicolet continuum xl microscope

Spectra of single cells were recorded at the ID21 beamline synchrotron (European Synchrotron Radiation Facility),34 using the bending and edge radiations from a bending magnet. Spectra were recorded on a Nicolet Continuum XL microscope (Thermo Fisher Scientific, Waltham, MA, USA) equipped with a 50 mm liquid nitrogen-cooled mercury cadmium telluride “A” detector, a 32X/NA0.65 Schwarzschild objective, a motorized knife-edge aperture, and an XYZ motorized stage and coupled with a Nicolet 5700 spectrometer (Thermo Fisher). Spectra of a minimum of about five individual cells were recorded in transmission between 800 and 4,000 cm⁻¹, with 128 scans at 4 cm⁻¹ resolution, 15×15 μm aperture dimension. At least three cells for each condition were mapped with an 8×8 μm aperture dimension and 6×6 μm step size.
Chemical maps were created and analyzed with the Omnic software (Thermo Fisher) by measuring and plotting the intensity of the specific bands of the second derivative of the spectra: PLGA, 1,770–1,740 cm^−1;35 amide I, 1,670–1,625 cm⁻¹; lipids, 2,970–2,950 cm⁻¹. PyMCA (European Synchrotron Radiation Facility) and Origin 8.0 (OriginLab, Northampton, MA, USA) were used for data analysis.