The chemical characterization of individual nanoparticles (NPs) </= 100 nm in diameter is one of the current frontiers in analytical chemistry. We present here, a methodology for the characterization of individual NPs by obtaining molecular information from single massive cluster impacts. The clusters used in this secondary ion mass spectrometry (SIMS) technique are Au4004+ and C60+. The ionized ejecta from each impact are recorded individually which allows to identify ions emitted from a surface volume of ~10 nm in diameter and 5-10 nm in depth. The mode of analyzing ejecta individually from each single cluster impact gives insight into surface homogeneity, in our case NPs and their immediate surroundings. We show that when the NPs (50 nm Al) are larger than the size of the volume perturbed by the projectile, the secondary ion emission (SI) resembles that of a bulk surface. However, when the NP (5 nm Ag) is of the size range of the volume perturbed by projectile the SI emission is different from that of a bulk surface. As part of this sub-assay volume study, the influence of neighboring NP on the SI emission was examined by using a mixture of different types of NPs (5 nm Au and 5 nm Ag). The methodology of using cluster SIMS via a sequence of stochastic single impacts yield information on the surface coverage of the NPs, as well as the influence of the chemical environment on the type of SI emission. We also present a case of soft landing NPs for laser desorption ionization mass spectrometry. NPs enhance the SI emission in a manner that maintains the integrity of the spatial distribution of molecular species. The results indicate that the application can be extended to imaging mass spectrometry.

Natural IgM producing phagocytic B cells (NIMPABs) are a rare population of immune cells that can produce antibodies to broadly target and eliminate cancer cells via phosphatidylcholine (PtC)-specific phagocytosis. A novel, dual-labeled lipid-shelled superparamagnetic iron oxide nanoparticle (SPION)-based (SLNP) system was developed to trigger specific phagocytotic behavior in and subsequent enrichment of NIMPABs for a potential immunotherapy. Here we propose the design of an in vitro model to assess cell-SLNP interactions with J774A.1 monocyte cell line and the optimization of SLNP formulation. First, we developed and examined the morphology, size, concentration, purification, sterilization, and storage conditions of oleylamine-coated SPIONs and SLNPs using various microscopy methods, spectroscopy, dynamic light scattering, and zeta potential. Our data confirmed SPIONs are magnetic and 7-8 nm in diameter. SLNPs containing SPIONs retained the magnetic property, and are typically measured between 100-120 nm in diameter, and had a positive zeta potential. Fluorescence labeling of the SLNPs did not affect their properties. Second, we examined cytotoxicity and phagocytosis of SLNPs with J774A.1 cells. Our preliminary data showed that significant percentage of phagocytosis can be observed as early as 2 hours. However, longer than 2 hour incubation resulted in significant cytotoxic effects. The source of SLNP cytotoxicity was examined with transmission electron microscopy and characterization techniques, identifying high un-encapsulated free oleylamine-coated SPION content in SLNP samples contributing to a positive zeta potential for these samples. Simplified SLNPs with oleic acid-coated SPIONs were synthesized and resulting examined particles had a negative zeta potential, reduced free SPION content and improved SPION incorporation into SLNP cores. Based on these findings, SLNP criteria, characterization techniques, and cell assays were revised to establish a rigorous, standardized workflow essential for determining the optimal SLNP formulation. Future work must continue to modify SLNP formulation with information obtained from all characterization techniques and cellular assays outlined in the in vitro model. Once optimized, selective SLNP-mediated isolation of NIMPAB cells can be validated ex vivo with murine peritoneal cavity washout cells and then human peripheral blood samples. / 2024-08-26T00:00:00Z

Optical trapping is a method which uses focused laser light to manipulate small objects. This optical manipulation can be scaled below the diffraction limit by using interactions between light and apertures in a metal film to localize electric fields. This method can trap objects as small as several nanometers. The ability to determine the properties of a trapped nanoparticle is among the most pressing issues to the utilization of this method to a broader range of research and industrial applications. Presented here are two methods which demonstrate the ability to determine the properties of a trapped nanoparticle. The first method incorporates Raman spectroscopy into a trapping setup to obtain single particle identification. Raman spectroscopy provides a way to uniquely identify an object based on the light it scatters. Because Raman scattering is an intrinsically weak process, it has been difficult to obtain single particle sensitivity. Using localized electric fields at the trapping aperture, the Raman integrated trapping setup greatly enhances the optical interaction with the trapped particle enabling the required sensitivity. In this work, the trapping and identification of 20 nm titania and polystyrene nanoparticles is demonstrated. The second method uses an aperture assisted optical trap to detect the response of a magnetite nanoparticle to a varying applied magnetic field. This information is then used to determine the magnetic susceptibility, remanence, refractive index, and size distribution of the trapped particle. / Graduate / 0544 / 0752 / stevenjones3.14@gmail.com

Water utilities in Nova Scotia face numerous challenges treating low turbidity water and complying with stringent guidelines and treatment standards. Problems associated with the treatment of low-turbidity water are not confined to Nova Scotia; several other provinces, British Columbia, Manitoba and Ontario share similar water characteristics of drinking water sources. The treatment of low turbidity water is a challenge for these utilities as it requires maintaining the appropriate coagulant dosage that will ensure adequate particle and natural organic matter removal, while at the same time not enhancing the formation of disinfection by-products. Another concern associated with the treatment of such water is that when the particle content of the water is very low, charge neutralization will not be effective due to the weak contact between destabilized particles. Currently, nanoparticles are not regulated as water contaminants, and thus it is unclear whether the existing filtration treatment practices are capable of removing them from drinking water. Obtaining in-depth information on nanoparticle characteristics in drinking water sources will provide a valuable resource that can assist in the development of future treatment strategies. In this research, characteristics of four synthetic nanoparticles cerium dioxide (CeO2), ferric oxide (Fe2O3), silicon dioxide (SiO2) and titanium dioxide (TiO2) were investigated in Milli-Q water for particle size, surface area, and surface potential using different characterization techniques. Water samples from Pockwock Lake were also characterized for naturally occurring nanoparticles. After initial testing, titanium dioxide (TiO2) nanoparticles were selected to examine particle removal at bench-scale filtration experiments, under operating conditions similar to those practiced at the J.D. Kline Water Supply Plant, Halifax, NS, Canada. Filter performance for the deposition of TiO2 nanoparticles was evaluated through the calculation of its attachment efficiency and coefficient under various water chemistry conditions. The calculated filter efficiency was then applied to simulate natural nanoparticles removal from water. The results of the research indicate that the investigated nanoparticles behaved similar to natural particles and formed aggregates with larger particle sizes in Milli-Q water. Among the tested nanoparticles, only titanium dioxide could be coagulated with alum, as its negative surface charge and zero point of charge were closer to that of alum. Filtration experiments revealed that TiO2 nanoparticles, when present in water, could successfully be removed by an alum dose of 8 mg/L. Indeed, removal in excess of 99.5% was achieved under the study conditions. Under the investigated water chemistry conditions, very low attachment efficiencies (?) of 0.001, 0.002 and 0.01, and filter coefficients (?) of -0.003, -0.001 and -0.02 were determined for the filters. Based on the calculated attachment efficiencies, and under the studied conditions, natural nanoparticles remain dispersed in the water and would not likely to be removed by direct filtration. The overall research findings represent a major step forward in nanoparticle removal by direct filtration.

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