Optical Properties of Doxorubicin Hydrochloride Load and Release on Silica Nanoparticle Platform

Abstract

Silica nanoparticles (SiO₂ NPs) synthesized by the Stober method were used as drug delivery vehicles. Doxorubicin hydrochloride (DOX·HCl) is a chemo-drug absorbed onto the SiO₂ NPs surfaces. The DOX·HCl loading onto and release from the SiO₂ NPs was monitored via UV-VIS and fluorescence spectra. Alternatively, the zeta potential was also used to monitor and evaluate the DOX·HCl loading process. The results showed that nearly 98% of DOX·HCl was effectively loaded onto the SiO₂ NPs' surfaces by electrostatic interaction. The pH-dependence of the process wherein DOX·HCl release out of DOX·HCl-SiO₂ NPs was investigated as well. For comparison, both the free DOX·HCl molecules and DOX·HCl-SiO₂ NPs were used as the labels for cultured cancer cells. Confocal laser scanning microscopy images showed that the DOX·HCl-SiO₂ NPs were better delivered to cancer cells which are more acidic than healthy cells. We propose that engineered DOX·HCl-SiO₂ systems are good candidates for drug delivery and clinical applications.

Keywords: doxorubicin hydrochloride (DOX·HCl); drug delivery; silica nanoparticles (SiO2 NPs).

Figure 1

Absorption and fluorescence intensity spectra of free DOX in aqueous solution at 480 nm (a) and 595 nm (b) with the concentration in the range of 1.72 × 10⁻⁶ M to 1.72 × 10⁻⁵ M.

Figure 2

The absorption (a) and fluorescence (b) spectra of DOX·HCl in varying pH buffer solution from 3.0 to 8.0.

Figure 3

The SiO₂ NPs solutions before (A); freshly prepared and stay-for-some-time DOX·HCl-SiO₂ NPs (B,C).

Figure 4

TEM images of SiO₂·NPs at scale bare of 100 nm before (A) and after (B) absorbed DOX·HCl molecules.

Figure 5

The absorption spectra of SiO₂ NPs, 120 µg/mL DOX·HCl absorbing on SiO₂ NPs and residual DOX·HCl content in supernatant compared with those of free DOX·HCl at 60 µg/mL, and the residual DOX·HCl in the supernatant (a); the absorption of DOX·HCl in supernatant compared with those of free DOX·HCl at 2 µg/mL in aqueous solution (b); and the fluorescence spectra of three above solutions (c).

Figure 6

DOX·HCl release profiles from DOX·HCl-SiO₂ NPs in the different pH buffers varying from 3.0 to 8.0 in time.

Figure 7

CLSM images of MCF7 cells incubated with DOX·HCL molecule (on top), DOX·HCl–SiO₂ NPs system (bottom) at DOX·HCl concentration of 4 µM. Images were acquired after 2 and 6 h. (Nuclei of these cells incubated with DAPI molecules). Scale bar 50 μm.