Xflash 6160 detector

The composition of the sample mixture prior to loading in the DAC was analyzed by means of scanning electron microscopy using the JOEL JSM-IT500HR scanning electron microscope (JEOL USA, Inc., Peabody, MA, United States). The chemical composition was checked at 15 kV using energy-dispersive X-ray spectroscopy (EDS) of QUANTAX EDS System with XFlash 6160 detector (Bruker Nano GmbH, Berlin, Germany). No impurities or traces of any other elements were found. The detailed summary is shown in Supplementary Figure S1.

The falcon tubes containing glass slides of heart or lung cryo-sections were dried at room temperature before analysis without any pretreatment. The surface of the FE-SEM aluminum sample stage was covered with carbon conducting tape and the glass slide was attached onto it. A Hitachi S-4800 field emission scanning electron microscope (FE-SEM) equipped with Bruker Xflash 6160 detector was used for observation of heart or lung tissue sections of eight mice from dirty air and eight mice from filtered air, at acceleration voltage of 1.0 kV, and emission current of 10 µA. The vacuum level in the observation chamber was ~ 10⁻⁷ Pa. The observations were made at the working distance of 2.1 mm to 2.4 mm, and at the scan speed of 20 s for each figure, at 10 k, 20 k, 50 k, and 100 k magnifications.

Materials characterization consisted of imaging use both optical microscopy (OM) and scanning electron microscopy (SEM) at Queen’s University Department of Mechanical and Materials Engineering. An Olympus SZX7 stereo-microscope was used for OM. An FEI Nova NanoSEM 450™ with Bruker XFlash 6160 detector was operated at 20 kV for high magnification imaging and qualitative chemical analysis by energy-dispersive spectroscopy (EDS). All specimens were ultrasonically cleaned in ethanol for two minutes and hot air-dried before imaging in the SEM to enhance imaging conditions and minimize contamination in the microscope. All SEM images reported used secondary electron imaging (SEI) mode.