Bioactive Glasses Modulate Anticancer Activity and Other Polyphenol-Related Properties of Polyphenol-Loaded PCL/Bioactive Glass Composites

Abstract

In this work, bioactive glass (BG) particles obtained by three different methods (melt-quenching, sol-gel, and sol-gel-EISA) were used as modifiers of polyphenol-loaded PCL-based composites. The composites were loaded with polyphenolic compounds (PPh) extracted from sage (Salvia officinalis L.). It was hypothesized that BG particles, due to their different textural properties (porosity, surface area) and surface chemistry (content of silanol groups), would act as an agent to control the release of polyphenols from PCL/BG composite films and other significant properties associated with and affected by the presence of PPh. The polyphenols improved the hydrophilicity, apatite-forming ability, and mechanical properties of the composites and provided antioxidant and anticancer activity. As the BG particles had different polyphenol-binding capacities, they modulated the kinetics of polyphenol release from the composites and the aforementioned properties to a great extent. Importantly, the PPh-loaded materials exhibited multifaceted and selective anticancer activity, including ROS-mediated cell cycle arrest and apoptosis of osteosarcoma (OS) cells (Saos-2) via Cdk2-, GADD45G-, and caspase-3/7-dependent pathways. The materials showed a cytotoxic and antiproliferative effect on cancerous osteoblasts but not on normal human osteoblasts. These results suggest that the composites have great potential as biomaterials for treating bone defects, particularly following surgical removal of OS tumors.

Keywords: anticancer activity; bioactive glass; bone substitute; composite; drug delivery; plant extract; polyphenols.

Figure 1

Static water contact angle (A) and total SE (B) with its dispersive and polar components of both surfaces (AS and GS) of the films. Statistically significant differences (p < 0.05) for AS and GS are indicated by subsequent lower and upper Latin letters, respectively. Different letters indicate statistically significant differences.

Figure 2

Young’s modulus (A), tensile strength (B), and elongation at maximum force (C) of the films. Statistically significant differences (p < 0.05) are indicated by subsequent lower Latin letters. Different letters indicate statistically significant differences.

Figure 3

Radical scavenging capacity (RSC) against the ABTS^·+ and DPPH^· radicals as well as ferric-reducing antioxidant potential (FRAP) of the films (A). Statistically significant differences (p < 0.05) are indicated by subsequent lower, upper Latin letters and Greek letters, respectively. Different letters indicate statistically significant differences. The release profiles of polyphenols presented as percentage of released PPh in reference to the initial content in the films (B).

Figure 4

SEM images and EDX spectra (averaged for the entire analyzed surface) of the AS and GS of the films before and after 3- and 14-day incubation in SBF.

Figure 5

ATR-FTIR spectra of AS and GS of the films before and after 3- and 14-day incubation in SBF.

Figure 6

Changes of Ca (A), P (B), and Si (C) concentrations in SBF during incubation of the films.

Figure 7

Adenylate kinase (AK) level in the lysate corresponding to the number of intact adherent cells (A) and AK level in the supernatant related to AK level in the lysate representing material cytotoxicity (B). Statistically significant differences (p < 0.05) between films and TCPS after 1-, 3-, and 5-day cell culture periods are indicated by subsequent lower, upper Latin letters and Greek letters, respectively. Different letters indicate statistically significant differences.

Figure 8

ROS production (A), GADD45G expression (B), phospho-CDK2 (Tyr15) level (C), and caspase-3/7 activity (D) normalized to the number of cells, presented as absolute values (first and second columns) and as fold changes from the material without PPh (third column). Statistically significant differences (p < 0.05) between films and TCPS after 1-, 3-, and 5-day cell culture periods are indicated by subsequent lower, upper Latin letters and Greek letters, respectively. Different letters indicate statistically significant differences.