Profiling High-Abundance Serum Proteins in the Corona of Nanodiamonds Using Mass Spectrometry

Nanodiamonds (NDs) are promising agents for various biomedical applications. Upon entering the body, NDs interact with proteins to form a "protein corona" (PC), which influences their biological fate and cytotoxicity. In this study, 100 nm NDs were incubated with human serum, and MALDI-TOF MS was used to identify the major proteins dominating the corona on oxidized detonation ND (oxDND) and high-pressure high-temperature ND (HPHT ND). The results show that PC formation depends on serum protein abundance, protein affinity, kinetics, and ND properties. At a serum protein concentration of 5.3 μg/mL, both NDs are predominantly coated with apolipoprotein A1 (APO A1; Mw = 28,000 Da). As serum protein concentration decreased to 1.6 μg/mL, oxDND becomes dominated by human serum albumin (HSA; Mw = 66,500 Da), while HPHT ND exhibits a mixed APO A1-HSA corona. Differences in pore structure also influence protein binding: the larger pores of oxDND (9.41 nm) allow access to larger proteins like HSA, whereas smaller HPHT ND pores (3.39 nm) favor low molecular weight (Mw) proteins. Hemolysis assays indicated good hemocompatibility for both NDs, while cell viability assays revealed higher cytotoxicity for HPHT ND with a mixed corona compared to oxDND with an HSA-dominant corona. These findings highlight the importance of profiling high-abundance proteins in ND coronas and demonstrate how protein binding preferences modulate ND cytotoxicity.