Quantum Dots Mediated Imaging and Phototherapy in Cancer Spheroid Models: State of the Art and Perspectives

Abstract

Quantum Dots (QDs) are fluorescent nanoparticles known for their exceptional optical properties, i.e., high fluorescence emission, photostability, narrow emission spectrum, and broad excitation wavelength. These properties make QDs an exciting choice for bioimaging applications, notably in cancer imaging. Challenges lie in their ability to specifically label targeted cells. Numerous studies have been carried out with QDs coupled to various ligands like peptides, antibodies, aptamers, etc., to achieve efficient targeting. Most studies were conducted in vitro with two-dimensional cell monolayers (n = 8902) before evolving towards more sophisticated models. Three-dimensional multicellular tumor models better recapitulate in vivo conditions by mimicking cell-to-cell and cell-matrix interactions. To date, only few studies (n = 34) were conducted in 3D in vitro models such as spheroids, whereas these models could better represent QDs behavior in tumors compared to monolayers. Thus, the purpose of this review is to present a state of the art on the studies conducted with Quantum Dots on spheroid models for imaging and phototherapy purposes.

Green synthesis of glyco-CuInS2 QDs with visible/NIR dual emission for 3D multicellular tumor spheroid and in vivo imaging

“…In general, positively-charged QDs cannot reach the necrotic zone since they can be absorbed by the proliferating cells of the spheroid. While the negatively-charged QDs can diffuse more quickly, allowing them to penetrate deeply into the tissues [ 56 , 60 ]. Thus, our results are in excellent agreement with the experimental results reported in the previous study.…”

Carbon Dots: Opportunities and Challenges in Cancer Therapy

“…They are protected from the immune system, have a higher water solubility, and are less likely to aggregate when coated with polymer chains like PEG. However, the Enhanced Permeability and Retention (EPR) effect can cause these NPs to assemble in the tumor in specific situations, such as cancer imaging [ 113 ]. With a leaky and chaotic vascular network and little to no lymphatic drainage, this condition happens in solid tumors.…”

“…Additionally, due to a decreased absorption coefficient from skin and fatty tissue, as well as from oxygenated and deoxygenated blood, tissue autofluorescence is decreased in the NIR window, particularly between 650 and 950 nm. NIR QDs are therefore very intriguing for bioimaging, particularly for imaging malignancy during surgical treatment [ 113 ]. Researchers are now studying 3D spheroid cancer models for a better understanding of QD penetration compared to NP nanotheranostics.…”

Interplay of Oxidative Stress, Inflammation, and Autophagy in RAW 264.7 Murine Macrophage Cell Line Challenged with Si/SiO2 Quantum Dots

“…The emerging field of QDs use in biomedical imaging has shown promising results; however, their translation into clinical applications in humans is still in the early stages, in part due to partially explored safety ramifications [ 5 ]. Most studies involving QDs have been conducted in preclinical settings using in vitro experiments or animal models, and QDs use as therapeutic agents, drug carriers, or in medical imaging is still in the early stages of investigation [ 6 , 7 , 8 , 9 , 10 ]. Efforts to reduce nanoparticle toxicity due to their composition have included encapsulation in silicon shells, which has the added benefit of chemical flexibility and also makes the surface suitable for functionalization.…”