No single clinical imaging modality has the ability to provide both high resolution and high sensitivity at the
anatomical, functional and molecular level. Synergistically integrated detection techniques overcome these barriers
by combining the advantages of different imaging modalities while reducing their disadvantages. We report the
development of protein nanospheres optimized for enhancing MRI, CT and US contrast while also providing high
sensitivity optical detection. Transferrin protein nanospheres (TfpNS), silicon coated, doped rare earth oxide and
rhodamine B isothiocyanate nanoparticles, Si⊂Gd2O3:Eu,RBITC, (NP) and transferrin protein nanospheres
encapsulating Si⊂Gd2O3:Eu,RBITC nanoparticles (TfpNS-NP) were prepared in tissue-mimicking phantoms and imaged utilizing multiple cross-sectional imaging modalities. Preliminary results indicate a 1:1 NP to TfpNS ratio
in TfpNS-NP and improved sensitivity of detection for MRI, CT, US and fluorescence imaging relative to its
component parts and/or many commercially available contrast agents.
This paper presents preliminary results on the use of transferrin protein nanospheres (TfpNS) for targeting
cancer cells in vitro. Protein nanospheres represent an easily prepared and modifiable nanoplatform for
receptor-specific targeting, molecular imaging and gene delivery. Rhodamine B isothiocyanate
conjugated TfpNS (RBITC-TfpNS) show significantly enhanced uptake in vitro in SK-MEL-28 human
malignant melanoma cells known to overexpress transferrin receptors compared to controls. RBITCTfpNS
labeling of the cancer cells is due to transferrin receptor-mediated uptake, as demonstrated by
competitive inhibition with native transferrin. Initial fluorescence microscopy studies indicate GFP
plasmid can be transfected into melanoma cells via GFP plasmid encapsulated by TfpNS.
Dye-labeled protein microspheres, submicron in size and capable of producing thermoelastically generated ultrasound in response to laser stimulation, are presented as contrast agents for photoacoustic imaging. Incident laser energy absorbed by fluorescein isothiocyanate (FITC)-labeled elastin submicrospheres results in thermoelastically generated sound production. Plotted A-line graphs reveal a distinctive morphology and a greater than two orders of magnitude increase in signal amplitude subsequent to converting FITC elastin into submicrospheres (despite a four orders of magnitude decrease in concentration). Evidence of nonlinearity and enhancement of ultrasound backscatter indicate a potential use in contrast-enhanced harmonic imaging. Photoacoustic and ultrasound imaging of FITC-elastin submicrospheres in a water-filled phantom vessel shows enhanced contrast at low concentration and clear delineation of the phantom vessel wall.
Metallic nanoparticle clusters coupling strong surface plasmons with a Raman reporter molecule have been
developed for application in multiplexed optical imaging. Of interest to our work is the ability of the
agents to serve as surface-enhanced Raman spectroscopy (SERS) probes. We present the seed-mediated
synthesis and characterization of rhodamine B isothiocyante Au nanoparticle clusters (RhB-AuNPCs).
RhB-AuNPCs are anisotropic structures which contain the Raman reporter, RhB, embedded between a gold
aggregate core and gold surface layer. In contrast to typical SERS studies, the Raman signal originates
from the probe (RhB-AuNPCs) and not from RhB incubated with a noble metal colloid. Characterization
of the probes' optical properties is presented. The overall goal of our study is to prepare probes that may be
used for the identification and spectroscopic labeling of multiple molecular biomarkers utilizing SERS
imaging.
Protein nanospheres capable of frequency controlled oscillation in response to laser stimulation are presented as contrast
agents for photoacoustic imaging. Incident laser energy absorbed by dye-labeled protein nanospheres causes
thermoelastically generated sound production. Plotted A-line graphs reveal a distinctive morphology and greater than 2
orders of magnitude increase in signal amplitude subsequent to converting labeled proteins into nanospheres. Evidence
of nonlinearity and enhancement of ultrasound backscatter indicate a potential use in contrast-enhanced harmonic
imaging. Photoacoustic and ultrasound imaging of protein nanospheres in phantom vessels show enhanced contrast at
low concentration and clear delineation of the phantom vessel wall.
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