Self-assembly Of Nanoparticles For DNA Detection And Application

Sensing DNA sequences is critical in modern-day biology and medicine, and is likely to continue toincrease in importance over the next10-20years. The current uses for identifying DNA sequences aremany and include identifying individuals in forensic applications, sequencing of genes and genomes,identification of microorganisms in food and environmental samples, identification of infectious organismsin foods, diagnosis of cancer and genetic prognosis of disease. In the future, there will be increasing focusin medicine on the genetically modified foods, and this will invoke greater demand to detect and identifyDNA sequences.Firstly ènew Au NPs synthesis strategy by using trisodium citrate to reduce hydrogentetrachloroaurate (III)(HAuCl4) in the presence of single-strand DNA (ssDNA) at37°C. Under theassistance of the ssDNA, the Au NPs can be prepared at physiological temperature and still maintain theuniform shape and dispersity. More importantly, the stability of the Au NPs against salt-inducedaggregation was improved greatly. Due to the FAM’s exciton energy is very close to the Au NPs’ plasmonenergy, the fluorescence of the FAM-DNA could be greatly enhanced by DNA functional goldnanoparticles due to the interaction of plasmon and exciton. A method for the detecting of DNA with thefluorescence enhancement was developed. The limit of detection was0.08nmol/L. With their high stabilityand in situ functionalized ssDNA, these Au NPs have great potential in physiological system and could beused for nanomedicine, nanoapparatus and nanosensor applications.Secondly èwe present a synthetic method for complex assemblies from NPs and nanorods (NRs)based on selective modification of NRs with DNA oligomers. Three types of assemblies denoted as End,Side, and Satellite isomers which display distinct elements of regiospecificity, were prepared with the yieldexceeding85%. Multiple experimental methods independently verify various structural features,uniformity, and stability of the prepared assemblies. The presence of interparticle gaps with finelycontrolled geometrical parameters and inherently small size comparable with those of cellular organellesfomented their study as intracellular probes. Against initial expectations SERS intensity for End, Side, andSatellite isomers was found to be dependent primarily on the number of the NPs in the superstructuresrationalized with the help of electrical field simulations. Incubation of the label-free NP-NR assemblieswith HeLa cells indicated sufficient field enhancement to detect structural lipids of mitochondria andprovided the first proof-of-concept data for the possibility of real-time probing of local organelleenvironment in live cells. Further studies should include structural optimization of the assemblies formultitarget monitoring of metabolic activity and further increase in complexity for applications intransformative optics.Finally èwe described preparation and biomedical functionalities of complex nanoparticle assemblieswith magnetoplasmonic properties suitable for simultaneous cancer therapy and diagnostics (theranostics).Most commonly magnetoplasmonic nanostructures are made by careful adaptation of metal reductionprotocols which is both tedious and restrictive. Here we apply the strategy of nanoscale assemblies toprepare such systems from individual building blocks. The prepared superstructures are based on magneticFe3O4nanoparticles encapsulated in silica shell representing the magnetic module. The cores aresurrounded in a corona-like fashion by gold nanoparticles representing the plasmonic module. Asadditional functionality they were also were also coated by poly(ethyleneglycole) chains as a cloakingagent to extend the blood circulation time. The preparation is exceptionally simple and allows one to varythe contribution of each function. Both modules can carry drugs and, in this study, they were loaded with anticancer drug curcumin. Comprehensive set of microscopy, spectroscopy and biochemical methods wereapplied to characterize both imaging and therapeutic function of the nanoparticle assemblies againstleukemia HL-60cells. High contrast magnetic resonance images and high apoptosis rates demonstrate thesuccess of assembly approach for the preparation of magnetoplasmonic nanoparticles.