Quantum dots: Prospectives, toxicity, advances and applications

Quantum Dots are fluorescence type semiconductor nano sized particles. They are made up of either heavy metal or inorganic material with size range from 2 to 10 nm. The word quantum dots itself indicates its quantum confinement and optical properties. They contain same number of electrons and atoms, hence are called as artificial atom. Quantum dots consist of two free functional groups for binding with drug molecule. Surface modification of quantum dots through covalent and/or non-covalent binding affects and alters the properties of drug molecule. Their cellular delivery is mediated by passive transport, facilitated delivery and active transport. The outer shell of quantum dots is made of semiconductor material which provides the surface for bio-conjugation leading to improvement in aqueous solubility. This provides effective surface area for binding of drug with the targeting molecule. The unique feature being that the material of shell reduces the toxicity of core of quantum dots. Various functionalization and surface modification makes them suitable for application in pharmaceutical field such as biomedical imaging, drug delivery, drug release study and diagnosis. Toxicity of quantum dots depends upon the size, material used, dose, route of administration and capping material. The regulatory status of quantum dots is not yet clear; still they are regarded as safe to use. The first clinical trial of quantum-dot technology in humans was approved by USFDA in 2011. With the advances in technology; most of the chemotherapeutics and cytotoxic drugs are delivered as quantum dots for improved/enhanced pharmacological action.