In vitro dose–response effects of poly(amidoamine) dendrimers [amino-terminated and surface-modified with N-(2-hydroxydodecyl) groups] and quantitative determination by a liquid chromatography–hybrid quadrupole/time-of-flight mass spectrometry based method

Abstract

This article presents a dose–response study of the effects of two types of third-generation (G3) and fourth-generation poly(amidoamine) (PAMAM) dendrimers on two cell lines (RTG-2 and H4IIE) by in vitro cytotoxicity assays with 3-(4,5-dimethylthizol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), neutral red uptake (NRU), and lactate dehydrogenase (LDH) assays. We particularly investigated the potential cytotoxic effect of positive surface charge, which a cationic amino-terminated PAMAM dendrimer can display, on the marked ability of PAMAM dendrimers to cross the cell membrane compared with PAMAM dendrimers functionalized with chains of N-(2-hydroxydodecyl). Quantification of dose–response effects was performed by use of mass spectrometry analysis. The analytical method using liquid chromatography–hybrid quadrupole/time-of-flight mass spectrometry that we developed allowed characterization of defective dendrimers instead of “ideal structures.” Identification was based on accurate mass measurement, assignment of elemental composition, and the fully resolved ¹³ C/¹² C isotopic clusters of the multiply charged ions of PAMAM dendrimers. Validation of the liquid chromatography–mass spectrometry method made possible reliable and reproducible quantification of the extracellular and intracellular concentration of dendrimers at a micromolar level (limits of detection from 0.14 to 1.34 μM and from 0.43 to 1.82 μM in standard and culture medium, respectively). A higher cytotoxicity was found with the H4IIE cell line for surface-modified PAMAM dendrimers. The LDH assay was significantly more sensitive than the MTT and NRU assays, with half-maximal inhibitory concentrations (IC₅₀) of 12.96 and 38.31 μg mL^-1 for surface-modified G3 and G4 dendrimers, respectively. No cytotoxic effects, in terms of IC₅₀, of amino-terminated PAMAM dendrimers were observed on both H4IIE and RTG-2 cells when the concentration was below 500 μg mL^-1 for G3 and G4 dendrimers.