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TRACK 6 TRACK 6 Technical Program

photoacoustic imaging. Many previously-reported ICG-containing nanofor- Introduction: The success of stem cell-based therapies is significantly hin-
mulations are prone to leakage, due to ICG’s moderate hydrophilicity; how- dered by a rapid decline in survival/function of implanted cells and limita-
ever, Dex-PCL micelles are expected to have much greater stability, due to tions in clinically relevant technologies for monitoring cell fate in vivo. The
crosslinking of the outer dextran layer. Altogether, these materials represent overall goal of this research is to integrate a therapeutic delivery system with
a promising alternative to PEG-based options in several important nanoim- a novel cell imaging system to address critical barriers in translating stem
aging applications. cell therapies. We have developed a multifunctional nanoparticle system
capable of 1) delivering nucleic acids to MSCs to direct their behavior, 2) en-
riching the population of engineered stem cells for in vivo implantation, and
A Porphyrin-PEG Polymer With Rapid Renal Clearance 3) providing multi-modal imaging of cells during and post-implantation, using
conventional MRI and emerging photoacoustic tomography (PAT), in order
Poster Presentation. NEMB2016-5960 to better understand their role in the regenerative process. PAT has great
potential for cell imaging, as it has greater temporal and spatial resolution
compared to MRI, with the cost and convenience of a hand-held scanner.
Haoyuan Huang, University of New York at Buffalo, Buffalo, NY, Therefore, unlike MRI, PAT could be used clinically at point-of-care to aid in
United States, Weibo Cai, Reinier Hernandez, University of Wis- the implantation of the stem cells as well as quantitative monitoring/tracking
consin-Madison, Madison, WI, United States, Jumin Geng, Haotian the cells over time. The objective of this study was to engineer the multi-
Sun, Wentao Song, University of New York at Buffalo, Buffalo, NY, functional NP system and demonstrate proof-of-principle for gene delivery
United States, Feng Chen, Stephen A. Graves, Robert J. Nickles, and PA imaging of MSCs.
University of WisconsinMadison, Madison, WI, United States, Chong
Cheng, Jonathan Lovell, University at Buffalo, Buffalo, NY, United Materials and Methods: Multifunctional NPs were formulated to take ad-
States vantage of the controlled release properties of poly(lactic-co-glycolic acid)
(PLGA) and the magnetic and imaging contrast properties (by MRI and PAT)
of iron oxide. PLGA NPs encapsulating iron oxide NPs (IONP) and plasmid
In the past decades, there was a volatile expansion of developing nanosized DNA (magPLGA-NPs) were formulated by a modified double emulsion
probes for in vivo imaging. More and more diseases can be diagnosed fast method. NPs were characterized for size and morphology, as well as DNA
and easily by a variety of imaging techniques. Porphyrins and tetra-pyrrolic loading and integrity. Cellular uptake of NPs and transfection with reporter
derivatives have long been used as theranostic agents. The inherent optical gene GFP were evaluated by fluorescence microscopy and flow cytometry,
properties make porphyrin and its derivatives hold great potential as probes while cytotoxicity was determined by MTS assay. Magnetic selection of cells
used in these imaging techniques. Besides the novel optical properties, the that have taken up NPs was performed with magnetic-activated cell sorting
high activities of the central two hydrogens of porphyrins, aromatic rings (MACS) separation column coupled to a custom external magnet array. PA
make them can be easily chelated with a lot of metals in smooth conditions. characterization of NPs and NP-loaded MSCs were performed with input
The chelation of metals improves the optical skills of porphyrins and the wavelengths (λ) of 532 or 720 nm and 1 MHz motorized immersion acoustic
derivatives, and makes metallo-porphyrins become optimal probes for dif- transducer.
ferent imaging techniques. Although the hydrophobicity of some porphyrins
limits their water solubility, it could be increased dramatically just simply by Results and Discussion: The magPLGA NPs were 350 nm in size, with IONPs
conjugating with hydrophilic polymer chains. According to these knowledge, uniformly distributed within the PLGA polymer matrix, and were responsive
in this presentation, we will introduce our newest finding of porphyrin-PEG to magnetic fields. The formulation technique resulted in 84% DNA loading
conjugation polymer working as probes for detecting renal system functions efficiency into the NPs, which was retained in supercoiled conformation, a
and diseases. Acute renal failure was chosen in this study, due to it caus- characteristic necessary for gene expression. Encapsulation of IONPs into
es around 1-2 per thousand people suffered from this disease around the PLGA did not alter their absorption coefficients, resulting in linear correlation
world. Current detection method is evaluating serum levels of endogenous between PA signal and NP concentration for both 532 nm and 720 nm input
biomolecules such as creatine, urea and cystatin C. These testing methods λ, with 532 nm producing stronger PA signal. MagPLGA-NPs were taken
usually require arduous blood sample and take long time for detection. So, up by MSCs without any cytotoxicity, and provided sustained expression
with these drawbacks of current ways, an efficient and fast detection method of the encapsulated plasmid DNA. Significantly, the NPs were taken up by
is required. In our work, tetracarboxylic porphyrins and polyethylene glycol MSCs at levels sufficient for magnetic selection of the cells at 86% efficiency,
(PEG) diamines were crosslinked in conditions that gave rise to a water-sol- which will enable the enrichment and use of only the engineered MSCs for
uble porphyrin polyamide. Using PEG linkers 2 kDa or larger prevented downstream applications and/or allow active targeting of MSCs to tissues of
fluorescence self-quenching. This networked porphyrin mesh was retained interest using external magnetic field. Loading NPs into MSCs enabled their
during dialysis with membranes with a 100 kDa pore size, yet passed through imaging by PAT with 200,000 readily imaged with 532 nm and 720nm input
the membrane when centrifugal filtration was applied. Following intravenous λs. Based on cellular uptake studies and PA signal from magPLGA-NPs, we
administration, the porphyrin mesh, but not the free porphyrin, was rapidly estimate a detection limit of 10000 cells and 3000 cells for 720 nm and 532
cleared via renal excretion. The process could be monitored by fluorescence nm input λs respectively.
analysis of collected urine, with minimal background due to the large Stokes
shift of the porphyrin (230 nm separating excitation and emission peaks). Conclusions: This multifunctional NP platform has the potential to advance
In a rhabdomyolysis mouse model of renal failure, porphyrin mesh urinary translation of stem cell-based therapies, by improving stem cell function and
clearance was significantly impaired. This led to slower accumulation in the consistency via sustained drug/gene delivery, and providing a promising
bladder, which could be visualized non-invasively via fluorescence imaging. new tool to monitor cells in a clinically relevant manner.
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Without further modification, the porphyrin mesh was chelated with Cu for
dynamic whole body positron emission tomography imaging of renal clear-
ance. Together, these data show that small porphyrin-PEG polymers can Imaging and quantitative analysis of the nanoscaled brain inter-
serve as effective multimodal markers of renal function.
stitial space
Multifunctional nanoparticles for improved stem cell function Poster Presentation. NEMB2016-6166
and photoacoustic tracking
Hongbin Han, Peking University, Beijing, Select State/Province, China
Poster Presentation. NEMB2016-6066
Brain interstitial space provides the accomodation of brain cells. It occupies
Isaac Adjei, Huabei Jiang, Carlos Rinaldi, Jon Dobson, Blanka 20% of the total brain volume and is in width of 20-60nm. The transport 71
process in the cortex has been widely explored and the communication be-
Sharma, University of Florida, Gainesville, FL, United States tween ISF and CSF in the superficial cortex was recognized. Functional lym-