Insights into the Mechanism of Quantum Dot-Sensitized Singlet Oxygen Production for Photodynamic Therapy

Abstract

Semiconductor nanoparticles or quantum dots (QDs) have been proposed as potential vehicles for photodynamic therapy (PDT) since 2003. Some studies using cadmium-based QDs have shown promising results when coupled to molecular photosensitizers. However, the toxicity of such QDs and the low overall efficiency of these hybrids are still problematic. We have coupled two types (sizes) of less-toxic InP/ZnS QDs to the photosensitizer chlorin e6. The spectroscopic properties of these hybrids have been studied in detail. Spectroscopic methods have been applied to elucidate the energy transfer pathways and kinetics and the rate of singlet oxygen production of all components. Additionally, the PDT efficacy of the QD/chlorin e6 hybrids has been assessed against a breast cancer (MDA-MB-231) cell line using a colorimetric 3-(4,5 dimethylthiazol-2yl)-2,5-diphenyltetrazolium bromide (MTT) assay. We have found that the energy transfer between QDs and the molecular photosensitizer is the rate-determining step for the production of singlet oxygen and that the cell viabilities of the hybrid and free photosensitizer are comparable. These systematic findings show that the energy transfer between QDs and photosensitizers is a “bottleneck”, which suggests that a better chemical design of the QD/photosensitizer hybrids in future embodiments is essential.

Energy Transfer with Semiconductor Quantum Dot Bioconjugates: A Versatile Platform for Biosensing, Energy Harvesting, and Other Developing Applications

“…944 Under their preparation conditions, it was estimated that five to 20 Ce6 molecules were covalently coupled via NHS-EDC chemistry to each silicacoated InP/ZnS QD. Using optical spectroscopy, the kinetic rates of the various steps of the complex were systematically examined.…”

Quantum Dot‐Based Nanotools for Bioimaging, Diagnostics, and Drug Delivery

“…[23] In al ater study with animal models, they discovered at endency for silicon QDst oa ccumulate in mouse organs, anda dverse effects on the liver were detected three months after treatment. [118] QDs can transfer www.chembiochem.org 2016 Wiley-VCH Verlag GmbH &Co. KGaA, Weinheim energy to some intracellular molecules, and form reactive oxygen species (ROS). [117] Size, charge, and surface material also affect the toxicity of nanomaterials, because cellular uptake, interaction with the immune system, and elimination from the body depend on the properties of nanocarriers.…”

Emerging nanotechnological research for future pathways of biomedicine

“…Some researchers have also developed photosensitised QDs for production of radicals upon absorption of visible light; this approach is suitable to treat superficial tumours, whereas ionising radiation (X-rays and gamma rays) penetrates much deeper and offers a huge advantage in treating patients with tumours in internal organs (Juzenas et al, 2008 andcf. also Cheng andBurda, 2011;Paszko et al, 2011;Fowley et al, 2012;Charron et al, 2012).…”