Multiscale Photoacoustic Microscopy of Single-Walled Carbon Nanotube-Incorporated Tissue Engineering Scaffolds

Three-dimensional polymeric scaffolds provide structural support and function as substrates for cells and bioactive molecules necessary for tissue regeneration. Noninvasive real-time imaging of scaffolds and/or the process of tissue formation within the scaffold remains a challenge. Microcomputed tomography, the widely used technique to characterize polymeric scaffolds, shows poor contrast for scaffolds immersed in biological fluids, thereby limiting its utilities under physiological conditions. In this article, multiscale photoacoustic microscopy (PAM), consisting of both acoustic-resolution PAM (AR-PAM) and optical-resolution PAM (OR-PAM), was employed to image and characterize single-walled carbon-nanotube (SWNT)–incorporated poly(lactic-co-glycolic acid) polymer scaffolds immersed in biological buffer. SWNTs were incorporated to reinforce the mechanical properties of the scaffolds, and to enhance the photoacoustic signal from the scaffolds. By choosing excitation wavelengths of 570 and 638 nm, multiscale PAM could spectroscopically differentiate the photoacoustic signals generated from blood and from carbon-nanotube-incorporated scaffolds. OR-PAM, providing a fine lateral resolution of 2.6 μm with an adequate tissue penetration of 660 μm, successfully quantified the average porosity and pore size of the scaffolds to be 86.5%±1.2% and 153±15 μm in diameter, respectively. AR-PAM further extended the tissue penetration to 2 mm at the expense of lateral resolution (45 μm). Our results suggest that PAM is a promising tool for noninvasive real-time imaging and monitoring of tissue engineering scaffolds in vitro, and in vivo under physiological conditions

Effect of Cd isoelectronic substitution on thermoelectric properties of Zn0.995Na0.005Sb

AbstractZnSb as a kind of material with abundant resource and low cost has a low thermal conductivity and a high Seebeck coefficient, giving the potential of high thermoelectric properties. In this paper, Cd isoelectronic substitution was adopted to further improve the thermoelectric performance by reducing the lattice thermal conductivity of ZnSb. The results show that Cd substitution reduces the lattice thermal conductivity and increases the electrical conductivity. A high ZT value of 1.22 is achieved at 350 °C for Zn0.915Na0.005Cd0.08Sb

Chronic label-free volumetric photoacoustic microscopy of melanoma cells in scaffolds in vitro

Visualizing cells in three-dimensional (3D) scaffolds has been one of the major challenges in tissue engineering. Current imaging modalities have limitations. Microscopy, including confocal microscopy, cannot penetrate deeply (> 300 μm) into the scaffolds; X-ray micro-computed tomography (micro-CT) requires staining of the structure with a toxic agent such as osmium tetroxide. Here, we demonstrate photoacoustic microscopy (PAM) of the spatial distribution and temporal proliferation of melanoma cells inside three-dimensionally porous scaffolds with thicknesses over 1 mm. Melanoma cells have a strong intrinsic contrast which is easily imaged by label-free PAM with high sensitivity. Spatial distributions of the cells in the scaffold were well-resolved in PAM images. Moreover, we chronically imaged the same cell/scaffold constructs at different time points over 2 weeks. The number of cells in the scaffold was quantitatively measured from the PAM volumetric information. The cell proliferation profile obtained from PAM correlated well with that obtained using the traditional 3-(4,5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) assay. We believe that PAM will become a useful imaging modality for tissue engineering applications, especially when thick scaffold constructs are involved, and that this modality can also be extended to image other cell types labeled with contrast agents

In vivo quantitative evaluation of gold nanocages' kinetics in sentinel lymph nodes by photoacoustic tomography

As a new class of sentinel lymph node (SLN) tracers for photoacoustic (PA) imaging, Au nanocages offer the advantages of noninvasiveness, strong optical absorption in the near-infrared region (for deep penetration), and accumulation in higher concentrations than the initial injected solution. By monitoring the amplitude changes of PA signals in an animal model, we quantified the accumulations of nanocages in SLNs over time. Based on this method, we quantitatively evaluated the kinetics of gold nanocages in SLN in terms of concentration, size, and surface modification. We could detect the SLN at an Au nanocage injection concentration of 50 pM and a dose of 100 μL in vivo. This concentration is about 40 times less than the previously reported value. We also investigated the influence of nanocages' size (50 nm and 30 nm in edge length), and the effects of surface modification (with positive, or neutral, or negative surface charges). The results are helpful to develop this AuNC-based PA imaging system for noninvasive lymph node mapping, providing valuable information about metastatic cancer staging

A stream processing framework based on linked data for information collaborating of regional energy networks

© 2005-2012 IEEE. Coordinating of energy networks to form a city-level multidimensional integrated energy system becomes a new trend in Energy Internet (EI). The collaborating in the information layer is a core issue to achieve smart integration. However, the heterogeneity of multiagent data, the volatility of components, and the real-time analysis requirement in EI bring significant challenges. To solve these problems, in this article we propose a stream processing framework based on linked data for information collaboration among multiple energy networks. The framework provides a universal data representation based on linked data and semantic relation discovery approach to model and semantically fuse heterogeneous data. Semantics-based information transmission contracts and channels are automatically generated to adapt to structural changes in EI. A multimodel-based dynamic adjusting stream processing is implemented using data semantics. A real-world case study is implemented to demonstrate the adaptability, feasibility, and flexibility of the proposed framework

Silencing of c-Ski augments TGF-b1-induced epithelial-mesenchymal transition in cardiomyocyte H9C2 cells

Background: The shRNA lentiviral vector was constructed to silence c-Ski expression in cardiac mus-  cle cells, with the aim of exploring the role of c-Ski in transforming growth factor b1 (TGF-b1)-induced epithelial-mesenchymal transitions (EMT) in H9C2 cells. Methods: Real-time polymerase chain reaction (RT-PCR) and western blot were used to detect c-Ski ex- pression at protein and messenger ribonucleic acid (mRNA) levels in 5 different cell lines. Then, lentiviral vector was constructed to silence or overexpress c-Ski in H9C2 cells. MTT and/or soft agar assay and tran- swell assay were used to detect cell proliferation and migration, respectively. The expression levels of c-Ski under different concentrations of TGF-b1 stimulation were detected by RT-qPCR and immunocytochemi- cal analysis. In the presence or absence of TGF-b1 stimulation, the proteins’ expression levels of a-SMA, FN and E-cadherin, which are closely correlated with the process of EMT, were measured by western blot after c-Ski silencing or overexpression. Meanwhile, the effect of c-Ski on Samd3 phosphorylation with TGF-b1 stimulation was investigated.  Results: There is a high expression of c-Ski at protein and mRNA levels in H9C2 cell line, which first demonstrated the presence of c-Ski expression in H9C2 cells. Overexpression of c-Ski significantly increased H9C2 cell proliferation. The ability of c-Ski gene silencing to suppress cell proliferation was gradually enhanced, and inhibition efficiency was the highest after 6 to 7 d of transfection. Moreover, H9C2 cells with c-Ski knockdown gained significantly aggressive invasive potential when compared with the control group. TGF-b1 stimulation could dose-independently reduce c-Ski expression in H9C2 cells and lead to obvious down-regulated expression of E-cadherin. Interestingly, c-Ski could restore E-cadherin expression while suppressing a-SMA and/or FN expression stimulated by TGF-b1. How- ever, shRNA-induced c-Ski knockdown aggravated only the TGF-b1-induced EMT. Moreover, c-Ski- -shRNA also promoted the phosphorylation of Samd3 induced by TGF-b1.  Conclusions: c-Ski expression in cardiac muscle cells could be down-regulated by TGF-b1. Silencing of c-Ski gene was accompanied by down-regulation of E-cadherin, up-regulation of a-SMA and/or FN and Smad3 phosphorylation induced by TGF-b1, promoting EMT process. Therefore, c-Ski may be closely associated with TGF-b1-induced EMT and play an important role in cardiac fibrosis develop- ment and progression.

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

Non-Invasive and In Situ Characterization of the Degradation of Biomaterial Scaffolds by Volumetric Photoacoustic Microscopy

Degradation is among the most important properties of biomaterial scaffolds, which are indispensable for regenerative medicine. The currently used method relies on the measurement of mass loss across different samples and cannot track the degradation of an individual scaffold in situ. Here we report, for the first time, the use of multiscale photoacoustic microscopy to non-invasively monitor the degradation of an individual scaffold. We could observe alterations to the morphology and structure of a scaffold at high spatial resolution and deep penetration, and more significantly, quantify the degradation of an individual scaffold as a function of time, both in vitro and in vivo. In addition, the remodeling of vasculature inside a scaffold can be visualized simultaneously using a dual-wavelength scanning mode in a label-free manner. This optoacoustic method can be used to monitor the degradation of individual scaffolds, offering a new approach to non-invasively analyze and quantify biomaterial–tissue interactions in conjunction with the assessment of in vivo vascular parameters

Quantitative Analysis of the Fate of Gold Nanocages In Vitro and In Vivo after Uptake by U87-MG Tumor Cells

Not always equal: When a mother cell that contains Au nanocages divides, the nanoparticles are unequally distributed between the two daughter cells. This unequal distribution of nanoparticles as well as their clearance from the cells (see picture) is quantitatively analyzed both in vitro and in vivo using two-photon microscopy and photoacoustic microscopy, respectively