Exploring Quantum Dots for Diagnosis and Treatment of CNS Disorders: Toxicity, Biodistribution, and Emerging Challenges

Researchers are in a continual quest for advanced nanotechnology-based delivery systems to revolutionize the field of brain targeting. Nanotechnology has special significance for drug candidates failing therapeutically due to their low solubility, permeability, and stability in different physiological environments. They provide the right platform for the enhancement of the bioavailability of drug molecules via controlled release and proper targeting. Recently, quantum dots, the nanoparticles composed of fluorescent semiconducting materials, are gaining much popularity among researchers because of their promising multipronged approach due to numerous unique characteristics such as high surface area owing to their nanosize, fluorescence intensity, photoluminescence, optical and electrical properties, targeting capabilities, high quantum yield, high drug encapsulation efficiencies, high biological membrane permeability capacities, and photostability. Quantum dots possess immense potential for targeting drugs and diagnostic molecules to the site of interest by permeating the blood-brain barrier (BBB), which is the main obstacle for brain delivery. Furthermore, the effectiveness of this nanosystem increases manyfold as compared to its existing counterparts due to its multifunctional approaches of maximizing drug targeting, imaging, and diagnosis to fulfill the purpose of BBB permeation, visualizing brain structures, and monitoring drug delivery patterns for effective treatment of brain disorders. This review focuses on the discussion of the blood-brain barrier as a major obstacle, quantum dots as emerging tools for imaging and targeting, and their recent developments with a special emphasis on toxicity aspects, their biodistribution, challenges, and future prospects.