ABSTRACT
Indocyanine green (ICG) is a clinically approved dye that has shown great promise as a phototheranostic material with fluorescent, photoacoustic and photothermal responses in the near-infrared region. However, it has certain limitations, such as poor photostability and non-specific binding to serum proteins, subjected to rapid clearance and decreased theranostic efficacy in vivo. This study reports stable and biocompatible nanoparticles of ICG (ICG-Fe NPs) where ICG is electrostatically complexed with an endogenously abundant metal ion (Fe3+) and subsequently nanoformulated with a clinically approved polymer surfactant, Pluronic F127. Under near-infrared laser irradiation, ICG-Fe NPs were found to be more effective for photothermal temperature elevation than free ICG molecules owing to the improved photostability. In addition, ICG-Fe NPs showed the markedly enhanced tumor targeting and visualization with photoacoustic/fluorescent signaling upon intravenous injection, attributed to the stable metal complexation that prevents ICG-Fe NPs from releasing free ICG before tumor targeting. Under dual-modal imaging guidance, ICG-Fe NPs could successfully potentiate photothermal therapy of cancer by applying near-infrared laser irradiation, holding potential as a promising nanomedicine composed of all biocompatible ingredients for clinically relevant phototheranostics.
ABSTRACT
Obtaining molecular information on cells in real time has been a critical challenge in studying the interaction between molecules of interest and intracellular components. Fluorescence-based methods have long served as excellent tools to study such important interactions. In this paper, we introduce a Raman scattering-based method as a promising platform to achieve the real-time monitoring of subtle molecular changes occurring within cells. We found that the Raman scattering-based method enabled monitoring changes in the mitochondrial membrane potential at the single-cell level in rheumatoid arthritis synovial fibroblasts induced by tumor necrosis factor-alpha (TNF-α) protein, various chemicals (MgCl2, FCCP, and sodium pyruvate), and a non-chemical stimulus (i.e., light). The triphenylphosphine-modified gold nanoparticles were selectively localized in the mitochondria and showed the characteristic Raman spectrum of cytochrome C and other Raman spectra of molecular components inside the cell. The surface-enhanced Raman spectrum originating from mitochondria was sensitively changed over time when mitochondrial depolarization was induced by the addition of TNF-α, or chemicals known to induce mitochondrial depolarization. The Raman-based signal changes were well matched with results of the conventional fluorescence-based analysis. However, in contrast to the conventional approach, the Raman-based method enables monitoring such changes in real time and provides detailed molecular information in terms of the interaction of molecules. Therefore, these results highlight the possibility of surface-enhanced Raman scattering-based live cell analysis for future proteomics or drug-screening applications.
ABSTRACT
Obtaining molecular information from inside cells is an important topic to understand the outcome of molecular interactions between potential drug molecules and biomolecules inside cells. To envision this goal, we investigated the surface-enhanced Raman scattering-based single-cell spectroscopic method to monitor changes in intracellular molecular signatures during mitochondrially mediated apoptosis in real time. Triphenylphosphine-modified gold nanoparticles were localized successfully to the mitochondria and greatly enhanced to obtain the intrinsic Raman scattering spectrum of mitochondria and cytochrome c in the live cell. Photothermally induced apoptosis showed a moderate decrease in the disulfide bond and a sharp increase in ß-sheet structures depending on the input-laser power, along with morphological changes. However, chemical drug induced-apoptosis showed more subtle changes in the disulfide bond, as well as changes in Raman peaks corresponding to cytochrome c, and the appearance of a new peak at 1420 cm-1, which enabled us to study the molecular interactions within the mitochondria in real time from a single cell, following treatment with a novel pyruvate dehydrogenase kinase inhibitor.
