Multifunctional theranostic gold nanoparticles for targeted CT imaging and photothermal therapy

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/102652/1/cmmi1563.pd

Assessing Longitudinal Impacts of Mentor Role on Student Outcomes

Most youth form relationships with extra-familial adults, sometimes called natural mentoring relationships, and these connections appear to benefit youth in several ways. Previous research demonstrates that the presence of a mentor can positively impact student outcomes including educational expectation, educational attainment, and social success. However, little research has considered how the impact of a natural mentorship may differ based upon the role of the adult in the youth’s life. Using data from three waves of the National Longitudinal Study of Adolescent Health, this study investigates if the role of a mentor (i.e. teacher, coach, religious leader) influences the types of benefits that adolescents gain from mentors. I used the Bayesian Additive Regression Trees (BART) model to predict domain specific outcomes in educational expectations, educational attainment, athleticism, and religiosity from the type of mentor and other covariates (e.g., base rates of academic success, fitness, religious beliefs, demographic composition). Findings indicate that the presence of an academic mentor during adolescence predicts increased educational attainment during young adulthood. Other types of mentors, such as athletic mentors or religious mentors, did not have significant impacts in terms of increasing athleticism or religiosity in young adulthood. These results suggest that academic mentors may have more longitudinal impacts on student success than other types of mentors

Nonlinear Moment-Tensor Inversion of Repetitive Long-Periods Events Recorded at Pacaya Volcano, Guatemala

Detailed models of low-frequency seismicity at volcanoes provide insights into conduit structure and dynamics of magmatic systems. Many active volcanoes produce repetitive seismic events, but these are often too small to model on their own. Here we examine thousands of repetitive explosion-related long-period (LP) events from Pacaya volcano, Guatemala, that were recorded during a temporary installation of four broadband seismic stations from October to November 2013. As most of the LP events are buried in background tremor, we used a matched filter from the higher signal-noise infrasound expression from these events. We derive a representative seismic signal from the phase-weighted stack of 8,587 of these events, and invert for a source moment tensor. To address the limitations posed by the number of stations of the local network, we employ a nonlinear waveform inversion that uses a grid search for source type to obtain a quantitative measure of the source mechanism reliability. With only four stations, Pacaya represents a case of limited observational data, where a quantitative description of moment-tensor uncertainty is needed before any interpretation is to be attempted. Results point to a shallow source mechanism somewhat like a tension crack, dipping ~40° to the east, consistent with the dominant E-W motion in the seismic records. The uncertainties determined from the nonlinear inversion are not insignificant, but clearly constrain the mechanism to be a source dominated by isotropic components. The N-S orientation of the modeled crack is parallel to surface features and the dominant dikes modeled in numerous geodetic studies, suggesting the conduit may be elongated N-S throughout most of its path through the edifice. Our study demonstrates that by stacking thousands of small LP events they can be modeled to build understanding about conduit structure

A brief account of nanoparticle contrast agents for photoacoustic imaging

Photoacoustic imaging (PAI) is a hybrid, nonionizing modality offering excellent spatial resolution, deep penetration, and high soft tissue contrast. In PAI, signal is generated based on the absorption of laser-generated optical energy by endogenous tissues or exogenous contrast agents leading to acoustic emissions detected by an ultrasound transducer. Research in this area over the years has shown that PAI has the ability to provide both physiological and molecular imaging, which can be viewed alone or used in a hybrid modality fashion to extend the anatomic and hemodynamic sensitivities of clinical ultrasound. PAI may be performed using inherent contrast afforded by light absorbing molecules such as hemoglobin, myoglobin, and melanin or exogenous small molecule contrast agent such as near infrared dyes and porphyrins. However, this review summarizes the potential of exogenous nanoparticle-based agents for PAI applications including contrast based on gold particles, carbon nanotubes, and encapsulated copper compounds

Cellular trafficking of Sn-2 phosphatidylcholine prodrugs studied with fluorescence lifetime imaging and super-resolution microscopy

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Rapid Synthesis of Near Infrared Polymeric Micelles for Real-Time Sentinel Lymph Node Imaging

In this manuscript a synthetic methodology for developing sub 20 nm sized polymeric micellar nanoparticles designed for extravascular imaging and therapy is revealed. A simple, one-pot method is followed, which involves a rapid co-self-assembly of an amphiphilic diblock copolymer (PS-b-PAA) and polyoxyethylene (80) sorbitan monooleate in water. Sorbitan monooleate imparts stability to the micelles and helps to drive down the particle size below 20 nm. The particles are incorporated with a water soluble dye ADS832WS, which absorbs in the near infrared range (λ_(ex) = 832 nm) for sensitive detection with optical and photoacoustic imaging techniques. A candidate lipophilic anti-angiogenic therapeutic agent fumagillin was also incorporated with high entrapment (>95%) efficiency. The effectiveness of this theranostic platform for real-time, high-resolution intraoperative photoacoustic imaging for facilitating direct assessment of the sentinel lymph nodes (SLN) in breast cancer staging is demonstrated. The technique offers huge potential providing faster resection of SLN and may minimize complications caused by axillary exploration due to mismarking with dyes or low-resolution imaging techniques. Finally, the biodistribution and organ accumulation of the intravenously and intradermally injected particles are studied in a rodent model by optical imaging. Data suggest that intraveneously injected NIR-polymeric nanoparticles follow a typical bio-distribution clearance path through the reticuloendothelial (RES) system. For the intradermally injected particles, a slower mechanism of clearance is noticed

A Facile Synthesis of Novel Self-Assembled Gold Nanorods Designed for Near-Infrared Imaging

Molecular imaging techniques now allow recognition of early biochemical, physiological, and anatomical changes before manifestation of gross pathological changes. Photoacoustic imaging represents a novel non-ionizing detection technique that combines the advantages of optical and ultrasound imaging. Noninvasive photoacoustic tomography (PAT) imaging in combination with nanoparticle-based contrast agents show promise in improved detection and diagnosis of cardiovascular and cancer related diseases. In this report, a novel strategy is introduced to achieve self-assembled colloidal gold nanorods, which are constrained to the vasculature. Gold nanorods (2–4 nm) were incorporated into the core of self-assembled lipid-encapsulated nanoparticles (sGNR) (∼130 nm), providing more than hundreds of gold atoms per nanoparticle of 20% colloid suspension. The physico-chemical characterization in solution and anhydrous state with analytical techniques demonstrated that the particles were spherical and highly mono dispersed. In addition to the synthesis and characterization, sensitive near-infrared photoacoustic detection was impressively demonstrated in vitro