Synthesis and Characterization of Fluorescent Quantum Dots as Probes to Study Radiation Induced ds-DNA Damage

Abstract

DNA is primarily a vital biomolecule that could be ambushed by both exogenous and endogenous sources of damage. Both exogenous and endogenous threats could provoke more than 105 DNA lesions spontaneously in human cells every day. The former sources come in a number of ways including, among others, ionizing radiations, ultraviolet (UV) light, thermal or hydrolysis disruption, environmental and industrial chemicals. Damages occurred by endogenous sources may come from several internal cellular processes like epigenetic modifications, hydrolysis, alkylation, nucleobase oxidation, adduct formations in bulk and errors in DNA replication by mismatch in nucleobases. Therefore, conservation of genome integrity is critical for traits inheritance to offspring and survival of any organism. Development of a rapid, sensitive and simple tool for the screening of DNA damage is the need of time. Fluorescence method is applied in a number of ways for the recognition of specific sequences of Deoxyribonucleic acid (DNA) along with Ribonucleic acid (RNA). QDS which are semiconductor nanoparticles, possess many unique structural and functional features such as nanoscale size, suitable fixity, narrow emission spectra, versatile surface modification and high specific surface area. Owing to these exceptional characteristics, these particles are used as markers, fluorescent probes and biosensors in numerous fields. The monolayered MoS2 owing small lateral size could offer novel optical properties due to their quantum confinement effect and it could act as a promising material for the development of novel optical sensors and optoelectronic devices. A highly fluorescent MoS2 QDs based FL emission sensor was formulated to study the radiation induced ds-DNA damage. The ds-DNA solution was exposed to UV radiation and ultra-sonic waves for definite period of time to induce the ds-DNA lesions. The FL emission spectra of MoS2 QDs with different concentrations of damaged ds-DNA was observed. A significant quenching in FL intensity of highly fluorescent MoS2 QDs indicated the presence of active sites in damaged ds-DNA which formed interactions with QDs and reduced the FL activity of fluorescent QDs. The excitation wavelength (260 nm) and concentration (200 µl) for QDs was optimized and used throughout the experiment process.