200 nm polycarbonate membrane

P@R837 NPs were fabricated as previously reported 5 . Briefly, PLGA (25 mg/mL) was dissolved in CH2Cl2 with 200 μg R837 (in DMSO at 5 mg/mL), then 0.5 mL polyvinylpyrrolidone (PVP) solution (5 % w/v) was added into the PLGA mixture followed by tip-sonication (40 % power for 3 minutes, 3 seconds on and 1 second off). After that, 2.5 mL PVP solution (5% w/v) was added dropwise into the obtained solution under constant stirring overnight at room temperature. The P@R837 NPs were obtained after centrifugation at 3,500 g for 25 min. The naked PLGA NPs (denoted as P) were fabricated using the same protocol, without adding the R837. To prepare CCMP@R837, 4T1 cell membrane pellet was bath-sonicated and physically co-extruded with P@R837 through a 200 nm polycarbonate membrane (Avanti Lipids) by mini extruder (Avanti Lipids) for 11 passes. Fluorescence labelled P, P@R837 and CCMP@R837 were named as F#P, F#P@R837 and F#CCMP@R837. These NPs were prepared by adding coumarin 6 into the solution of PLGA.

Liposomes were prepared using a mixture of 1,2-dimyristoyl-sn-glycero-3-phosphorylcholine (DMPC) and dipalmitoyl phosphatidylcholine (DPPC) at a ratio of 2:3 (mol%) and a concentration of 5 mM in a final volume of 1 mL. They were prepared using thin-film hydration as described previously [43] . In brief, lipids were suspended in filtered PBS at 42 °C, and extruded 21 times through a 200 nm polycarbonate membrane (all material from Avanti Lipids).