Biological characterization of a novel hybrid copolymer carrier system based on glycogen

Abstract

The effective drug delivery systems for cancer treatment are currently on high demand. In this paper, biological behavior of the novel hybrid copolymers based on polysaccharide glycogen were characterized. The copolymers were modified by fluorescent dyes for flow cytometry, confocal microscopy, and in vivo fluorescence imaging. Moreover, the effect of oxazoline grafts on degradation rate was examined. Intracellular localization, cytotoxicity, and internalization route of the modified copolymers were examined on HepG2 cell line. Biodistribution of copolymers was addressed by in vivo fluorescence imaging in C57BL/6 mice. Our results indicate biocompatibility, biodegradability, and non-toxicity of the glycogen-based hybrid copolymers. Copolymers were endocyted into the cytoplasm, most probably via caveolae-mediated endocytosis. Higher content of oxazoline in polymers slowed down cellular uptake. No strong colocalization of the glycogen-based probe with lysosomes was observed; thus, it seems that the modified externally administered glycogen is degraded in the same way as an endogenous glycogen. In vivo experiment showed relatively fast biodistribution and biodegradation. In conclusion, this novel nanoprobe offers unique chemical and biological attributes for its use as a novel drug delivery system that might serve as an efficient carrier for cancer therapeutics with multimodal imaging properties.

Glycogen as an advantageous polymer carrier in cancer theranostics: Straightforward in vivo evidence

“…Moreover, in our model, we found no pathological changes in organs, confirmed by histological and biochemical analysis of blood proteins. Given our glycogen-based conjugates were uptaken by cells via endocytosis and intracellularly degraded into D-glucose units 46 , we assume they degraded to form water and carbon dioxide in tumour tissue. Similar to commercial clinically approved Gd-based MR contrast agents, we hypothesise the released chelate (DOTA) and fluorescent dye were then cleared from the body by the kidneys or liver.…”

“…Two polymer conjugate variants were prepared: glycogen-based conjugates modified with POx (GOX) and glycogen-based conjugates without POx (GG). Glycogen conjugates grafted and non-grafted with GOX were synthesised as previously described 46 .…”

“…Most studies of polysaccharide drug delivery systems use alginate 34 , dextran 35,36 , chitosan 37,38 , pectin [39][40][41][42] , starch 43 or hyaluronic acid 44,45 . However, only a few studies have explored the potential of glycogen 32,46 . Glycogen is a natural hyperbranched polymer of suitable size for the EPR effect (hydrodynamic diameter ≈ 50 nm, molecular weight ≈ 10 MDa) and above the renal threshold, it is degraded into D-glucose by intracellular enzymes and further metabolized by normal physiological glycolysis 46 .…”

“…However, only a few studies have explored the potential of glycogen 32,46 . Glycogen is a natural hyperbranched polymer of suitable size for the EPR effect (hydrodynamic diameter ≈ 50 nm, molecular weight ≈ 10 MDa) and above the renal threshold, it is degraded into D-glucose by intracellular enzymes and further metabolized by normal physiological glycolysis 46 . Moreover, it is biocompatible, biodegradable 47 , widely available as a natural renewable resource (oysters, plants) 48,49 , and can be easily modified with drugs or diagnostic moieties, what makes glycogen ideally suited for use in the construction of a multimodal drug delivery system 32,46,50 . In the absence of evidence to indicate glycogen is efficient as a nanocarrier in a clinically relevant model such as a tumour-bearing animal, we performed a detailed characterisation of a modified glycogen carrier under in vivo conditions on an animal tumor model of hepatocellular carcinoma (HUH7 human cancer cell line).…”

Fluorine-Containing Block and Gradient Copoly(2-oxazoline)s Based on 2-(3,3,3-Trifluoropropyl)-2-oxazoline: A Quest for the Optimal Self-Assembled Structure for 19F Imaging

“…Moreover, polymer nanoparticle-based CAs show prolonged blood circulation time, leading to enhanced contrast signal and, thus, early detection and diagnosis of a tumor. 16,17 Due to their small size (10−50 nm), nanoparticles benefit from enhanced permeability and retention (EPR) effects in both tumors and infection sites. Another valuable advantage of polymeric materials is their ability to adjust their affinity to specific cells or tissues, which allows for an increase in the precision of the diagnostics and a minimization of side effects.…”