Developing New Methodologies for Crosslinked Polymeric Nanostructure Syntheses, Chemoselective Modifications, and Applications as Imaging and Delivery Agents

The overall emphasis of this dissertation research includes the syntheses of amphiphilic block copolymers bearing functional groups through controlled radical polymerization techniques, followed by the aqueous assembly of these block copolymer precursors to construct polymeric nanostructures with different sizes and morphologies. Further chemical modification of the nanostructures afforded functional crosslinked nano-objects with reporting probes for imaging and biocompatible stealth materials for tuning the in vivo fate of nanostructures. Amphiphilic block copolymers poly(acrylic acid)-block-polystyrene: PAA-b-PS) with well-defined structures were prepared through nitroxide-mediated radical polymerization: NMP). Using novel pre-functionalization strategies, these block copolymer precursors were functionalized with DOTA for chelating 64Cu and were then assembled into micelles and crosslinked throughout the micelle shell domain to afford the shell crosslinked nanoparticles: SCKs), containing large numbers of effective DOTAs per particle for 64Cu radiolabeling These 64Cu-complexed nanoparticles showed impressive specific activities: ca. 400 μCi μg-1), which suggest that they will serve as highly sensitive in vivo positron emission tomography: PET) tracers at low administering doses. The pre-grafting strategy was further extended to accomplish SCKs with variable biodistributions. PAA-b-PS amphiphilic block copolymers were modified with varying numbers of poly(ethylene oxide): PEO) chains, together with DOTA, before assembling into block copolymer micelles and crosslinking throughout the micellar shell regions. After chelation of 64Cu tracers, the in vivo fate of PEGylated SCKs was evaluated by means of biodistribution experiments and PET imaging. The blood retention of PEGylated-SCKs exhibited tunabilities, depending on the mPEG grafting density and the nanoparticle surface properties. Various bi-functional pyrazine-based chromophores were used as crosslinkers to probe directly their incorporation efficiencies into the shells of block copolymer micelles, which further determined the actual crosslinking extents ─ a critical factor for developing SCKs as PET imaging agents. The micelles were made to carry poly(N-acryloxysuccinimide): PNAS) as pre-installed amine-reactive functionalities along amphiphilic triblock copolymer precursors: PEO-b-PNAS-b-PS) prepared through reversible addition-fragmentation chain transfer: RAFT) radical polymerizations. The incorporation/crosslinking efficiencies were dependent upon the type of crosslinker and the applied stoichiometries. The intrinsic reactivity of aldehyde motivated the developments of well-defined polymers having reactive carbonyl side chain substituents. Amphiphilic block copolymers bearing poly(4-vinyl benzaldehyde): PVBA) block segments with controlled molecular weights and low polydispersities were obtained through RAFT polymerizations and assembled into polymeric vesicles and micelles. The vesicles were crosslinked and functionalized with fluorescent molecules through chemoselectively-reductive amination and were shown to display interesting in vitro cell association behaviors. The micelles were modified with near-infrared fluorescent dyes and crosslinked with diamino crosslinkers, each via reductive amination, to prepare robust nanoparticles with optimized luminescent characteristics for in vivo optical imaging

Progressive multi-atlas label fusion by dictionary evolution

AbstractAccurate segmentation of anatomical structures in medical images is important in recent imaging based studies. In the past years, multi-atlas patch-based label fusion methods have achieved a great success in medical image segmentation. In these methods, the appearance of each input image patch is first represented by an atlas patch dictionary (in the image domain), and then the latent label of the input image patch is predicted by applying the estimated representation coefficients to the corresponding anatomical labels of the atlas patches in the atlas label dictionary (in the label domain). However, due to the generally large gap between the patch appearance in the image domain and the patch structure in the label domain, the estimated (patch) representation coefficients from the image domain may not be optimal for the final label fusion, thus reducing the labeling accuracy. To address this issue, we propose a novel label fusion framework to seek for the suitable label fusion weights by progressively constructing a dynamic dictionary in a layer-by-layer manner, where the intermediate dictionaries act as a sequence of guidance to steer the transition of (patch) representation coefficients from the image domain to the label domain. Our proposed multi-layer label fusion framework is flexible enough to be applied to the existing labeling methods for improving their label fusion performance, i.e., by extending their single-layer static dictionary to the multi-layer dynamic dictionary. The experimental results show that our proposed progressive label fusion method achieves more accurate hippocampal segmentation results for the ADNI dataset, compared to the counterpart methods using only the single-layer static dictionary

A theoretical study on the mechanism of the addition reaction between cyclopropenylidene and ethylene

The reaction mechanism between cyclopropenylidene and ethylene has been systematically investigated employing the MP2/6-311+G* level of theory to better understand the cyclopropenylidene reactivity with unsaturated hydrocarbons. Geometry optimization, vibrational analysis, and energy property for the involved stationary points on the potential energy surface have been calculated. Energies of all the species are also further refined by the CCSD(T)/6-311+G* single-point calculations. Firstly, one important reaction intermediate (INTa) has been located via a transition state (TSa). After that, the common intermediate (INTb) for the two pathways (1) and (2) has been formed via TSb. At last, two different products possessing three- and four-membered ring characters have been obtained through two reaction pathways. In the reaction pathway (1), a three-membered ring alkyne compound has been obtained. As for the reaction pathway (2), a four-membered ring conjugated diene compound has been formed, which is the most favorable reaction to occur from the kinetic and thermodynamic viewpoints

Gold nanocages covered with thermally-responsive polymers for controlled release by high-intensity focused ultrasound

This paper describes the use of Au nanocages covered with smart, thermally-responsive polymers for controlled release with high-intensity focused ultrasound (HIFU). HIFU is a highly precise medical procedure that uses focused ultrasound to heat and destroy pathogenic tissue rapidly and locally in a non-invasive or minimally invasive manner. The released dosage could be remotely controlled by manipulating the power of HIFU and/or the duration of exposure. We demonstrated localized release within the focal volume of HIFU by using gelatin phantom samples containing dye-loaded Au nanocages. By placing chicken breast tissues on top of the phantoms, we further demonstrated the feasibility of this system for controlled release at depths up to 30 mm. Because it can penetrate more deeply into soft tissues than near-infrared light, HIFU is a potentially more effective external stimulus for rapid, on-demand drug release

Gold nanocages covered with thermally-responsive polymers for controlled release by high-intensity focused ultrasound

This paper describes the use of Au nanocages covered with smart, thermally-responsive polymers for controlled release with high-intensity focused ultrasound (HIFU). HIFU is a highly precise medical procedure that uses focused ultrasound to heat and destroy pathogenic tissue rapidly and locally in a non-invasive or minimally invasive manner. The released dosage could be remotely controlled by manipulating the power of HIFU and/or the duration of exposure. We demonstrated localized release within the focal volume of HIFU by using gelatin phantom samples containing dye-loaded Au nanocages. By placing chicken breast tissues on top of the phantoms, we further demonstrated the feasibility of this system for controlled release at depths up to 30 mm. Because it can penetrate more deeply into soft tissues than near-infrared light, HIFU is a potentially more effective external stimulus for rapid, on-demand drug release

Dietary chitosan enhances hepatic CYP7A1 activity and reduces plasma and liver cholesterol concentrations in diet-induced hypercholesterolemia in rats

The present study was performed to elucidate the hypocholesterolemic action of chitosan on the diet-induced hypercholesterolemia in rats. Male Sprague-Dawley rats (n=24) were fed with chitosan-free diet (Control), diets containing 2% or 5% chitosan for 4 weeks. Hypercholesterolemia was induced by adding 1% cholesterol and 0.5% cholic acid to all diets. Body weight gain and food intake of rats did not differ among the groups. The chitosan treated groups showed significant improvement in the plasma concentration of total cholesterol and LDL-cholesterol compared to the control group (p<0.05). Also, the chitosan treated groups decreased the liver concentration of total lipid and total cholesterol compared to the control group (p<0.05). The activity of hepatic cholesterol 7α-hydroxylase (CYP7A1), the rate-limiting enzyme in the conversion of cholesterol to bile acids, was increased by 123% and 165% for the 2% or 5% chitosan diets, respectively. These findings suggest that enhancement of hepatic CYP7A1 activity may be a mechanism, which can partially account for the hypocholesterolemic effect of dietary chitosan in cholesterol metabolism

Single cell transcriptome profiling reveals cutaneous immune microenvironment remodeling by photodynamic therapy in photoaged skin

BackgroundThe immune microenvironment plays a critical role in maintaining skin homeostasis, which is closely related to the dysfunction in photoaged skin such as autoimmunity and tumorigenesis. Several recent studies have demonstrated the efficacy of 5-aminolevulinic acid photodynamic therapy (ALA-PDT) in alleviating photoaging and skin cancer. However, the underlying immune mechanisms and the immune microenvironment change by ALA-PDT remain largely unknown.MethodsTo illustrate the effects of ALA-PDT on immune microenvironment in photoaged skin, single cell RNA sequencing (scRNA-seq) analysis of photoaged skin on the extensor side of the human forearm before and after ALA-PDT was performed. R-packages of Seurat, clusterProfiler, Monocle, CellChat were used for cell clustering, differentially expressed genes analysis, functional annotation, pseudotime analysis and cell-cell communication analysis. The gene sets related to specific functions were extracted from the MSigDB database, which were used to score the functions of immune cells in different states. We also compared our result with published scRNA-seq data of photoaged skin of the eyelids.ResultsThe increase score of cellular senescence, hypoxia and reactive oxygen species pathway in immune cells and the decrease of immune receptor activity function and proportion of naive T cells were found in skin photoaging. Moreover, the function of T cell ribosomal synthesis was also impaired or down regulated and function of G2M checkpoint was up regulated. However, ALA-PDT showed promising results in reversing these effects, as it improved the above functions of T cells. The ratio of M1/M2 and percentage of Langerhans cells also decreased with photoaging and increased after ALA-PDT. Additionally, ALA-PDT restored the antigen presentation and migration function of dendritic cells and enhanced cell-cell communication among immune cells. These effects were observed to last for 6 months.ConclusionALA-PDT has potential to rejuvenate immune cells, partially reversed immunosenescence and improved the immunosuppressive state, ultimately remodelling the immune microenvironment in photoaged skin. These results provide an important immunological basis for further exploring strategies to reverse skin photoaging, chronological aging and potentially systemic aging

Prevalence of Prenatal Brain Abnormalities in Fetuses with Congenital Heart Disease: Systematic Review.

OBJECTIVES: Studies have demonstrated an association between congenital heart defects (CHD) and postnatal brain abnormalities and neurodevelopmental delay. Recent evidence suggests that some of these brain abnormalities are present even before birth. The primary aim of this study was to perform a systematic review to quantify the prevalence of prenatal brain abnormalities in fetuses with CHD. METHODS: MEDLINE, EMBASE and The Cochrane Library were searched. Reference lists within each article were hand-searched for additional reports. The outcomes included structural brain abnormalities (MRI), changes in brain volume (MRI, 3-D volumetric MRI, 3-D ultrasound and Phase Contrast Magnetic Resonance), metabolism or maturation (Magnetic Resonance Spectroscopy and Phase Contrast Magnetic Resonance) and blood flow (Doppler ultrasound, Phase Contrast Magnetic Resonance and 3D Power Doppler ultrasound) in fetuses with CHD. Cohort and case-control studies were included. Cases of chromosomal or genetic abnormalities, case reports and editorials were excluded. Proportion meta-analysis was used for analysis. Between-study heterogeneity was assessed using the I(2) test (Registration number: CRD42015025546). RESULTS: The search yielded 1,943 citations; and 20 studies were included in the review (n = 1175 cases, 221 in the meta-analysis). Three studies reported data on structural brain abnormalities, while data on altered brain volume, metabolism and blood flow were reported in 7, 3 and 14 studies, respectively. The three studies reporting data on structural brain abnormalities were suitable for inclusion in a meta-analysis (221 cases). The prevalence of prenatal structural brain abnormalities in fetuses with CHD was 28% (95% CI 18%-40%), similar prevalence in fetuses with tetralogy of Fallot of 25% (95% CI 14%-39). These abnormalities included ventriculomegaly (commonest), agenesis of the corpus callosum, ventricular bleeding, increased extra-axial space, vermian hypoplasia, white matter abnormalities and delayed brain development. Fetuses with CHD were more likely, than those without CHD, to have reduced brain volume, delay in brain maturation and altered brain circulation, most commonly in the form of reduced middle cerebral artery pulsatility index and cerebroplacental ratio. These changes are usually evident in the third trimester, but some studies have reported them as early as the second trimester. CONCLUSIONS: In the absence of known major aneuploidy or genetic syndromes, fetuses with CHD are at increased risk of brain abnormalities, which are present antenatally

Neutrino Physics with JUNO

The Jiangmen Underground Neutrino Observatory (JUNO), a 20 kton multi-purposeunderground liquid scintillator detector, was proposed with the determinationof the neutrino mass hierarchy as a primary physics goal. It is also capable ofobserving neutrinos from terrestrial and extra-terrestrial sources, includingsupernova burst neutrinos, diffuse supernova neutrino background, geoneutrinos,atmospheric neutrinos, solar neutrinos, as well as exotic searches such asnucleon decays, dark matter, sterile neutrinos, etc. We present the physicsmotivations and the anticipated performance of the JUNO detector for variousproposed measurements. By detecting reactor antineutrinos from two power plantsat 53-km distance, JUNO will determine the neutrino mass hierarchy at a 3-4sigma significance with six years of running. The measurement of antineutrinospectrum will also lead to the precise determination of three out of the sixoscillation parameters to an accuracy of better than 1\%. Neutrino burst from atypical core-collapse supernova at 10 kpc would lead to ~5000inverse-beta-decay events and ~2000 all-flavor neutrino-proton elasticscattering events in JUNO. Detection of DSNB would provide valuable informationon the cosmic star-formation rate and the average core-collapsed neutrinoenergy spectrum. Geo-neutrinos can be detected in JUNO with a rate of ~400events per year, significantly improving the statistics of existing geoneutrinosamples. The JUNO detector is sensitive to several exotic searches, e.g. protondecay via the $p\to K^++\bar\nu$ decay channel. The JUNO detector will providea unique facility to address many outstanding crucial questions in particle andastrophysics. It holds the great potential for further advancing our quest tounderstanding the fundamental properties of neutrinos, one of the buildingblocks of our Universe