Browsing by Subject "Fluorescence imaging"
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Item Assembly of colloidal nanocrystals into phospholipid structures and photothermal materials(2012-08) Rasch, Michael; Korgel, Brian Allan, 1969-There has been growing interest in developing colloidal metal and semiconductor nanocrystals as biomedical imaging contrast agents and therapeutics, since light excitation can cause the nanocrystals to fluoresce or heat up. Recent advances in synthetic chemistry produced fluorescent 2-4 nm diameter silicon and 1-2 nm diaemeter CuInSSe nanocrystals, as well as 16 nm diameter copper selenide (Cu₂₋[subscript x]Se) nanocrystals exhibiting strong absorbance of near infrared light suitable for biomedical applications. However, the syntheses yield nanocrystals that are stabilized by an adsorbed layer of hydrocarbons, making the nanocrystals hydrophobic and non-dispersible in aqueous solution. Encapsulating these nanocrystals in amphiphilic polymer micelles enables the nanocrystals to disperse in water. Subsequently, the Si nanocrystals were injected into tissue to demonstrate fluorescence imaging, the photothermal transduction efficiency of copper selenide nanocrystals was characterized in water, and the copper selenide nanocrystals were used enhance the photothermal destruction of cancer cells in vitro. The polymer-encapsulated copper selenide nanocrystals were found to have higher photothermal transduction efficiency than 140 nm diameter Au nanoshells, which have been widely investigated for photothermal therapy. Combining the optical properties of metal and semiconductor nanocrystals with the drug-carrying capability of lipid vesicles has received attention lately since it may create a nanomaterial capable of performing simultaneous drug delivery, optical contrast enhancement, and photo-induced therapy. Hydrophobic, dodecanethiol-coated Au nanocrystals were dispersed in water with phosphatidylcholine lipids and characterized using cryo transmission electron microscopy. 1.8 nm diameter Au nanocrystals completely load the bilayer of unsaturated lipid vesicles when the vesicles contain residual chloroform, and without chloroform the nanocrystals do not incorporate into the vesicle bilayer. 1.8 nm Au nanocrystals dispersed in water with saturated lipids to form lipid-coated nanocrystal agglomerates, which sometimes adhered to vesicles, and the shape of the agglomerates varied from linear nanocrystal chains, to flat sheets, to spherical clusters as the lipid fatty acid length was increased from 12 to 18 carbons. Including squalene formed lipid-stabilized emulsion droplets which were fully loaded with the Au nanocrystals. Results with 4.1 nm Au and 2-3 nm diameter Si nanocrystals were similar, but these nanocrystals could not completely load the bilayers of unsaturated lipids.Item Fluorescence Imaging for Nuclear Arms Control Verification(2014-08-14) Feener, Jessica SNuclear disarmament is a highly debated subject. Proponents argue that political conditions for nuclear disarmament are ripe. Opponents reason that dismantlement could create instability leading to a higher probability of nuclear war or large-scale conventional war. Verification of disarmament can help alleviate instabilities and as nuclear arsenals decrease, verifying actual warheads and not just delivery vehicles will become more important. Current techniques that could be used in warhead verification have the ability to reveal sensitive information about the warhead and thus require an information barrier. This research developed a proof-of-principle concept for a new technique to address the need of nuclear warhead verification for arms control treaties. Specifically, this technique uses fluorescence imaging to determine fissile material attributes in verifying, during the dismantlement process, an uncanned nuclear warhead or warhead component without revealing sensitive information. This could potentially reduce the need for an information barrier. Experiments were performed using a Princeton Instruments PIXIS: 1024B/BUV back-illuminated CCD camera to image the fluorescence produced by the decay of nuclear material. The Monte Carlo simulation tool GEANT4 was used to model the experimental setups and to compare with the experimental results. The results verified the proof-of-concept of fluorescence imaging for use in nuclear arms control treaty verification. Fluorescence imaging would be most beneficial for assessing the fissile material attributes of U enrichment (greater than a threshold) and symmetry. It also contributes valuable data for verifying the presence of fissile material, presence of Pu, presence of U, mass greater than a threshold, Pu age, and 239Pu to 240Pu ratio greater than a threshold. Fluorescence imaging may also be beneficial to the ?absence of oxide? attribute, but additional experiments are needed to confirm this assumption. Additionally, it was concluded that the only potential for revealing presumably sensitive information is the ability to provide too much image detail on external surfaces of Pu components. However, simple steps could be taken to prevent the imaging system from acquiring too much detail and thus eliminate the need for an information barrier.Item Optical and structural property mapping of soft tissues using spatial frequency domain imaging(2015-08) Yang, Bin, Ph. D.; Tunnell, James W.; Krishnan, Sunil; Reichenberg, Jason S; Yeh, Hsin-Chih; Sacks, MichaelTissue optical properties, absorption, scattering and fluorescence, reveal important information about health, and holds the potential for non-invasive diagnosis and therefore earlier treatment for many diseases. On the other hand, tissue structure determines its function. Studying tissue structural properties helps us better understand structure-function relationship. Optical imaging is an ideal tool to study these tissue properties. However, conventional optical imaging techniques have limitations, such as not being able to quantitatively evaluate tissue absorption and scattering properties and only providing volumetrically averaged quantities with no depth control capability. To better study tissue properties, we integrated spatial frequency domain imaging (SFDI) with conventional reflectance imaging modalities. SFDI is a non-invasive, non-contact wide-field imaging technique which utilizes structured illumination to probe tissues. SFDI imaging is able to accurately quantify tissue optical properties. By adjusting spatial frequency, the imaging depth can be tuned which allows for depth controlled imaging. Especially at high spatial frequency, SFDI reflectance image is more sensitive to tissue scattering property than absorption property. The imaging capability of SFDI allows for studying tissue properties from a whole new perspective. In our study, we developed both benchtop and handheld SFDI imaging systems to accommodate different applications. By evaluating tissue optical properties, we corrected attenuation in fluorescence imaging using an analytical model; and we quantified optical and physical properties of skin diseases. By imaging at high spatial frequency, we demonstrated that absorption in fluorescence imaging can also be reduced because of a reduced imaging depth. This correction can be performed in real-time at 19 frames/second. Furthermore, fibrous structures orientation from the superficial layer can be accurately quantified in a multi-layered sample by limiting imaging depth. Finally, we color rendered SFDI reflectance image at high spatial frequency to reveal structural changes in skin lesions.