Endocytic uptake of a large array of HPMA copolymers: Elucidation into the dependence on the physicochemical characteristics

Abstract

Endocytic uptake and subcellular trafficking of a large array of HPMA (N-(2-hydroxypropyl) methacrylamide) based copolymers possessing positively or negatively charged residues, or hydrophobic groups were evaluated by flow cytometry and living cell confocal microscopy in cultured prostate cancer cells. The degrees of cellular uptake of various copolymer fractions with narrow polydispersities were quantified. The copolymer charge was the predominant physicochemical feature in terms of cellular uptake. Fast and efficient uptake occurred in positively charged copolymers due to non-specific adsorptive endocytosis, whereas slow uptake of negatively charged copolymers was observed. The uptake of copolymers was also molecular weight dependent. The copolymers were internalized into the cells through multiple endocytic pathways: positively charged copolymers robustly engaged clathrin-mediated endocytosis, macropinocytosis and dynamin-dependent endocytosis, while weakly negatively charged copolymers weakly employed these pathways; strongly negatively charged copolymers only mobilized macropinocytosis. HPMA copolymer possessing 4 mol% of moderately hydrophobic functional groups did not show preferential uptake. All copolymers ultimately localized in late endosomes/lysosomes via early endosomes; with varying kinetics among the copolymers. This study indicates that cell entry and subsequent intracellular trafficking of polymeric drug carriers are strongly dependent on the physicochemical characteristics of the nanocarrier, such as charge and molecular weight.

Endocytotic uptake of HPMA-based polymers by different cancer cells: impact of extracellular acidosis and hypoxia

“…42 A predominant factor for selecting different endocytotic routes seems to be the surface charge. Liu et al 25 analyzed the uptake of p(HPMA) polymer containing various positively or negatively charged groups as well as hydrophobic side chains. They demonstrated that positively charged copolymers were taken up by CME, micropinocytosis as well as dynamin-dependent endocytosis.…”

“…[22][23][24] On the other hand, studies revealed that the chemical structure of polymers may also play a role for their endocytotic uptake. Liu et al 25 demonstrated that HPMA-based polymers containing alkaline side chains, eg, 2-(N,N-dimethylamino) ethyl methacrylate (positive ζ potential), were taken up by cells much stronger than polymers containing acidic adducts, eg, methacrylic acid (negative ζ potential). This mechanism could be of importance in particular in an acidic extracellular environment.…”

“…It has been shown that the ζ potential of polymers plays a role for their cellular uptake. 25 In an acidic environment, the negative surface charge will be reduced, which then may alter endocytosis. However, Figure 2 shows that the uptake increased in random copolymer, whereas it reduced in homopolymer and block copolymer, which also had slightly negatively surface charge.…”

Enzyme/pH-sensitive dendritic polymer-DOX conjugate for cancer treatment

“…The higher level of internalization of free DOX than dendritic conjugate might be attributed to diffusion due to concentration gradients [30]. While multiple endocytosis ways were involved with cellular uptake of dendritic conjugate by 4T1 cells, and the uptake rate was much slower than free diffusion [42,43].…”

Polycaprolactone/maltodextrin nanocarrier for intracellular drug delivery: formulation, uptake mechanism, internalization kinetics, and subcellular localization

“…5,6 However, there seems to be a lack of in-depth understanding of how to effectively optimize intracellular delivery because cellular uptake mechanisms and rates vary widely with the type, size, charge, and surface properties of the nanoparticles employed, and more importantly, with the cell type under study. [6][7][8][9] This, hence, makes it implausible for broad generalizations to be made, and there is therefore the need to treat each nanocarrier and cell type specifically on a case-to-case basis. In addition, the rate of cellular uptake varies with cell population density, 10,11 further making it very challenging to draw general conclusions for the enhancement of particle cellular uptake.…”