Endocytosis Pathways of the Folate Tethered Star-Shaped PEG-PCL Micelles in Cancer Cell Lines

Abstract

This study reports on the cellular uptake of folate tethered micelles using a branched skeleton of poly(ethylene glycol) and poly(ε-caprolactone). The chemical structures of the copolymers were characterized by proton nuclear magnetic resonance spectroscopy, and Fourier transform infrared spectroscopy. Doxorubicin (DOX) was utilized as an anticancer drug. The highest drug loading efficiencies of DOX in the folate decorated micelle (DMCF) and folate-free micelle (DMC) were found to be 88.5% and 88.2%, respectively, depending on the segment length of the poly(ε-caprolactone) in the copolymers. A comparison of fluorescent microscopic images of the endocytosis pathway in two cell lines, human breast cancer cells (MCF-7) and human oral cavity carcinoma cells (KB), revealed that the micelles were engulfed by KB and MCF-7 cells following in vitro incubation for one hour. Flow cytometric analysis revealed that free folic acid can inhibit the uptake of DOX by 48%-57% and 26%-39% in KB cells and MCF-7 cells, respectively. These results prove that KB cells are relatively sensitive to folate-tethered micelles. Upon administering methyl-β-cyclodextrin, an inhibitor of the caveolae-mediated endocytosis pathway, the uptake of DOX by KB cells was reduced by 69% and that by MCF-7 cells was reduced by 56%. This finding suggests that DMCF enters cells via multiple pathways, OPEN ACCESSPolymers 2014, 6 635 thus implying that the folate receptor is not the only target of tumor therapeutics.

Soft structure formation and cancer cell transport mechanisms of a folic acid–dipeptide conjugate

“…Thus, it appears that different cell lines used different endocytic pathways for the transport of 3 particles . It must be mentioned that there are numerous reports for folate conjugates following multiple pathways for cellular entry, thus suggesting that entry via FR is not a unique pathway for cell uptake and monovalency or multivalency of folate conjugates has little effect on the rate of cell internalization, knowing that multivalent folate conjugates are possibly taken up via different endocytic pathways .…”

DOX-encapsulated intelligent PAA-g-PEG/PEG–Fa polymeric micelles for intensifying antitumor therapeutic effect via active-targeted tumor accumulation

“…Hsieh et al 43 reported that the folate tethered star-shaped PEG-PCL micelles show greater endocytosis into KB and MCF-7 cancer cells than DOX-loaded micelles without the folate ligand via folate receptor-mediated endocytosis and caveolae/lipid-raft mediated endocytosis. Zhao and his colleagues 42 prepared the folate-modified poly(2-ethyl-2oxazoline) polymeric micelles, the in vitro and in vivo study results clearly manifested that Fa modified micelles could increase the specific delivery to folate receptor-positive human HeLa, KB and MCF-7/ADR cells, while it did not apparently increase for folate receptor-negative A549 cells under the conditions of the same test.…”

Engineered pH‐responsive hydrazone‐carboxylate complexes‐encapsulated 2D matrices for cathepsin‐mediated apoptosis in cancer

“…Although the deviation in the charge of Dox molecules with varying pH is achieved, it is difficult to load them into the LDH matrices at these conditions via ion‐exchange, which may lead to deprived loading efficiency of Dox . Moreover, compared with the free drugs that are generally internalized into cells by a diffusion mechanism, the delivery of such drugs using nanoarchitectures has shown promising potential in anti‐cancer application due to their specific internalization process into cells via endocytosis pathway and others …”

“…17 Moreover, compared with the free drugs that are generally internalized into cells by a diffusion mechanism, the delivery of such drugs using nanoarchitectures has shown promising potential in anti-cancer application due to their specific internalization process into cells via endocytosis pathway and others. 18,19 Motivated by the facts behind the current advancements in engineering various intelligent nano-delivery systems, conjugation of drugs with the stimuli-responsive molecular switches has become one of the most efficient approaches in delivering a drug cargo in spatiotemporal controlled way, while experiencing the chemical or physical changes in regard to the biological stimuli. 9,20 Among the various external stimuli, pH of the surrounding microenvironment is the most efficient biological stimuli in delivering chemotherapeutic agents.…”