In Vivo Distribution and Toxicity of PAMAM Dendrimers in the Central Nervous System Depend on Their Surface Chemistry

Abstract

Dendrimers have been described as one of the most tunable and therefore potentially applicable nanoparticles both for diagnostics and therapy. Recently, in order to realize drug delivery agents, most of the effort has been dedicated to the development of dendrimers that could internalize into the cells and target specific intracellular compartments in vitro and in vivo. Here, we describe cell internalization properties and diffusion of G4 and G4-C12 modified PAMAM dendrimers in primary neuronal cultures and in the CNS of live animals. Confocal imaging on primary neurons reveals that dendrimers are able to cross the cell membrane and reach intracellular localization following endocytosis. Moreover, functionalization of PAMAMs has a dramatic effect on their ability to diffuse in the CNS tissue in vivo and penetrate living neurons as shown by intraparenchymal or intraventricular injections. 100 nM G4-C12 PAMAM dendrimer already induces dramatic apoptotic cell death of neurons in vitro. On the contrary, G4 PAMAM does not induce apoptotic cell death of neural cells in the sub-micromolar range of concentration and induces low microglia activation in brain tissue after a week. Our detailed description of dendrimer distribution patterns in the CNS will facilitate the design of tailored nanomaterials in light of future clinical applications.

Different patterns of nuclear and mitochondrial penetration by the G3 PAMAM dendrimer and its biotin–pyridoxal bioconjugate BC-PAMAM in normal and cancer cells in vitro

“…22 The application of fluorescence imaging in living cells by confocal laser scanning microscopy and recently by two-photon imaging microscopy can monitor the dynamic aspects of cellular trafficking and colocalization of dendrimers with high spatial and temporal resolution. [23][24][25] The cellular internalization and trafficking of dendrimers depend on their size, shape, charge, and surface functionality as well as the cell type. 26,27 Many studies have revealed that cationic PAMAM dendrimers can cross cell membranes by various endocytic pathways, including clathrin-dependent pathways in Caco-2 cells, 28,29 clathrin-dependent and macropinocytosis pathways in HeLa cells, 30 and non-clathrin, non-caveolae, cholesterol-dependent pathways in A549 lung epithelial cells and B16F10 melanoma cells.…”

“…No entry of FITC-G4 PAMAM into human keratinocyte HaCaT cell nuclei was observed after 24 hours and 48 hours treatments by Pai et al, 59 or after 24 hours in primary neuronal cultures. 25 The localization of later generation G6 PAMAM dendrimers conjugated with estrogen was observed in the membrane and cytoplasm, but not in the nuclei of estrogen receptor-positive MCF-7 human breast cancer cells. 66 At the nondividing phase, the nuclear envelope acts as a molecular permeability barrier, enabling the free diffusion of small hydrophilic molecules (up to 9 nm size) through the nuclear pore complex.…”

Viologen-phosphorus dendrimers exhibit minor toxicity against a murine neuroblastoma cell line

“…In vitro studies have revealed that these nanoparticles possess the ability to inhibit the fibrillation and aggregation of proteins involved in neurodegenerative disorders [7][8][9]. Importantly, in vivo studies of polyamidoamine (PAMAM) dendrimers have been performed to determine their toxicity to the central nervous system [10], check their ability to localize in inflammatory cells in the brain [11], and show their potential in dendrimer-drug conjugates for the treatment of neuroinflammation [12,13]. Significant progress has been made in research on the interactions between dendrimers and living cells or organisms, resulting in commercially available products such as transfection agents (SuperFect from Qiagen and PrioFect from EMD-Merck), markers for rapid heart attack diagnosis (Stratus CS Acute Care from Siemens Healthcare), and anthrax-detecting agents (Alert Ticket from the US Army Research Laboratory) [3].…”

Multivalent Peptide–Nanoparticle Conjugates for Influenza‐Virus Inhibition

“…Polyamidoamine (PAMAM) dendrimers have also been used for multivalent display, for example, of siallyllactose21 showing in vitro inhibition at micromolar ligand concentrations as well as protection of mice from infection. However, depending on their structure multivalent PAMAM scaffolds may also be cytotoxic 17, 22, 23…”