Currently, gold nanoparticles have found applications in engineering and medical sciences, taking advantage from their properties and characteristics. Surface plasmon resonance, for instance, is one of the main features for optical applications and other physical properties, like high density, that represents the key for cellular uptake. Among other applications, in the medical field, some diseases may be treated by using gene therapy, including monogenetic or polygenetic disorders and infections. Gene adding, suppression, or substitution is one of the many options for genetic manipulation. This work explores an alternative non-viral method for gene transfer by using gold nanoparticles functionalized with organic polymers; two routes of synthesis were used: one of them with sodium borohydride as reducing agent and the other one with chitosan oligosaccharide as reducing and stabilizing agent. Gold nanoparticles conjugated with chitosan, acylated chitosan and chitosan oligosaccharide, were used to evaluate transfection efficiency of plasmid DNA into cell culture (HEK-293). Physical and chemical properties of gold nanocomposites were characterized by using UV-Vis Spectroscopy, ξ-potential, and transmission electron microscopy. Furthermore, the interaction between gold nanoparticles and plasmid DNA was demonstrated by using agarose gel electrophoresis. Transfection tests were performed and evaluated by β-galactosidase activity and green fluorescence protein expression. The percentage of transfection obtained with chitosan, acylated chitosan, and chitosan oligosaccharide were of 27%, 33%, and 60% respectively.

As nanoparticles are increasingly incorporated into consumer products and specialized areas, the need to study their toxicity and the importance of caution in their use are becoming more evident. The use of these novel materials in the automotive industry is causing increased nanoparticle emissions into the atmosphere, sparking concerns due to recent toxicology reports. Detecting and characterizing nanostructured atmospheric pollutants represent a complex task that alternative methods like genotoxic bioindicators may overcome. Ricinus communis was selected as a model plant to describe the genotoxic effect of air-dispersed nanostructured materials, using comet assay to evaluate the DNA damage by exposure to ZnO and CuO nanoparticles (ZnO-NPs, CuO-NPs), and total chlorophyll was determined to correlate the results. The plants were exposed for 1.25 h by nebulizing dispersions of the nanoparticles, and their effects were evaluated at 24 h and 5 days after exposure. Time was essential in demonstrating the DNA damage induced by lower levels of CuO-NPs and ZnO-NPs, which showed more significant damage after 5 days than bulk materials. In both compounds (CuO and ZnO), significant differences were observed in the comparison of their nanoscale and their bulk form, which confirms that the lower size of the nanoparticles presents a more significant genotoxic potential. In the scanning electron microscopy (SEM) micrographs, the accumulation of nanoparticles was observed near the stomata. The study demonstrated the viability of the comet assay as a sensitive tool both to assess DNA damage from ZnO-NPs and CuO-NPs on R. communis as a bioindicator and to investigate the potential risks of emerging nanomaterials, emphasizing the need for caution in their use.

We present an experimental procedure for determining the diameter of spherical gold nanoparticles (AuNPs) using a basic bright-field microscopy apparatus. We achieved high-contrast imaging by constructing a bright-field microscopy system with ultrabright LEDs (incorporating low-cost components), employing Köhler illumination near the coherence limit, and using digital processing to perform image averaging and background subtraction. Our system allows for the detection of 80 nm, 150 nm, and 300 nm diameter AuNPs immobilized on functionalized glass substrates. Through-focus images of the particles show characteristic contrast inversion, from where we find a nearly linear relationship between the minimum intensity contrast and particle diameter (as determined from scanning electron microscopy) for the three sizes studied and for three different illumination wavelengths covering the corresponding AuNP plasmon band (λ = 460 nm, 520 nm, and 620 nm). This behavior was found to be consistent with the corresponding scattering and absorption cross-sections of the AuNPs under the illumination wavelengths considered.