Nanodiamond (ND) interactions with primary rat alveolar epithelial cell monolayers (RAECM)

Abstract

We investigated interactions of positively and negatively charged 5 nm ND (zeta potentials of 50 and −60 mV, respectively; provided by Carbodeon, Vantaa, Finland) with RAECM. Transepithelial resistance (Rt) and equivalent short circuit current (Ieq) of RAECM in the presence and absence of ND in apical fluid for up to 24 h did not change. We estimated cellular uptake and transepithelial trafficking of ND across RAECM over 24h spectrofluorometrically with excitation/emission wavelengths at 275/555 nm. Cell uptake of positively charged ND was ~3 times greater than that (~9 pg/μg cell protein) of negatively charged ND, while transepithelial trafficking of positively and negatively charged ND was about the same at ~20 pg/cm2/s. Trafficking of ND is ~10‐fold faster than that of negatively or positively charged quantum dots (core diameter 5 nm) and negatively charged polystyrene nanoparticles (PNP, 20 nm), but ~2‐fold slower than that of positively charged PNP (20 nm). These data indicate that positively or negatively charged ND do not affect barrier function of alveolar epithelium and suggest that ND surface charge affects accumulation in but not translocation across alveolar epithelium. Mechanisms underlying ND entry into/egress from alveolar epithelial cells remain to be determined.(Funded by NIH and Hastings & Whittier Fdns.)