Dual Responsive poly(vinyl caprolactam)-Based Nanogels for Tunable Intracellular Doxorubicin Delivery in Cancer Cells

Abstract

In this work, doxorubicin (Dox)-encapsulated poly(vinyl caprolactam) (PVCL)-based three-dimensional nanogel networks were developed and were crosslinked with disulfide linkages. The nanogels degrade rapidly to low molecular weight chains in the presence of the typical intracellular concentration of glutathione. Doxorubicin (Dox) was successfully encapsulated into these nanogels. The nanogels have a high drug loading of 49% and can be tailored to 182 nm to deliver themselves to the targeted cells and release Dox under dual stimuli conditions, such as redox and temperature. By evaluating cell viability in the HepG2 cell line, we observed that Dox-loaded nanogels effectively killed the cancer cell. Fluorescence microscopy results show that the nanogels could easily be internalized with HepG2 cells. The results confirm that the nanogels destabilized in intracellular cytosol via degradation of disulfide bonds in nanogels networks and release of the Dox nearby the nucleus. These carriers could be promising for cancer drug delivery.

Keywords: cancer cells; drug release; dual responsive; intracellular triggered; nanogels; poly(vinyl caprolactam).

Scheme 1

Schematic representation of Dox-loaded Cys-BIS-P(VCL-HEA) nanogels and their functional group interactions and dual responsive behavior of nanogels loaded with Dox under external stimuli (temperature) and internal stimuli (glutathione).

Figure 1

(a) UV-Visible spectra of Dox before and after loading into Cys-BIS-P(VCL-HEA) nanogels; (b) XRD pattern of pure Dox; and (c) XRD patterns of pristine Cys-BIS-P(VCL-HEA) and Dox-loaded Cys-BIS-P(VCL-HEA) nanogels.

Figure 2

(a) DLS size distribution of nanogels; (b–d) TEM images of Cys-BIS-P(VCL-HEA) nanogels.

Figure 3

(a,b) DLS size distribution of Cys-BIS-P(VCL-HEA) nanogels with respect to various temperatures and its LCST calculation; TEM images of (c) 5 mM and (d) 10 mM DTT-treated nanogels incubated for 6 h; (e) DLS size distribution curves of nanogels treated with 5 mM DTT for 5 h and 24 h incubation.

Figure 4

In vitro Dox release from Cys-BIS-P(VCL-HEA) nanogels in response to external stimuli (temperature) and internal stimuli (DTT).

Figure 5

(a) In vitro cytotoxicity of pure nanogels treated with CCDK-normal skin fibroblasts cells with different concentrations (0–1000 μg/mL) for 72 h incubation. (b) In vitro cytotoxicity of Dox-loaded Cys-BIS-P(VCL-HEA) nanogels treated with HepG2 cancer cells. (c) Fluorescence microscopy images of samples treated with HepG2 cells for 3 h incubation (DAPI (blue) staining for nucleus and red fluorescence represent the Dox or Dox-loaded nanogels).