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Structure and Rheology of Microgel Monolayers at the Water/Oil Interface

Macromolecules - Wed, 2017-04-26 13:10

MacromoleculesDOI: 10.1021/acs.macromol.6b02779
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High-Toughness Polycation Cross-Linked Triblock Copolymer Hydrogels

Macromolecules - Wed, 2017-04-26 12:08

MacromoleculesDOI: 10.1021/acs.macromol.7b00304
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Synergistic Thermoresponsive Optical Properties of a Composite Self-Healing Hydrogel

Macromolecules - Wed, 2017-04-26 07:31

MacromoleculesDOI: 10.1021/acs.macromol.7b00355
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Acoustic tweezing cytometry enhances osteogenesis of human mesenchymal stem cells through cytoskeletal contractility and YAP activation

Biomaterials - Wed, 2017-04-26 07:10
Publication date: July 2017
Source:Biomaterials, Volume 134

Author(s): Xufeng Xue, Xiaowei Hong, Zida Li, Cheri X. Deng, Jianping Fu

Human mesenchymal stem cells (hMSCs) have great potential for cell-based therapies for treating degenerative bone diseases. It is known that mechanical cues in the cell microenvironment play an important role in regulating osteogenic (bone) differentiation of hMSCs. However, mechanoregulation of lineage commitment of hMSCs in conventional two-dimensional (2D) monocultures or bioengineered three-dimensional (3D) tissue constructs remains suboptimal due to complex biomaterial design criteria for hMSC culture. In this study, we demonstrate the feasibility of a novel cell mechanics and mechanobiology tool, acoustic tweezing cytometry (ATC), for mechanical stimulation of hMSCs. ATC utilizes ultrasound (US) pulses to actuate functionalized lipid microbubbles (MBs) which are covalently attached to hMSCs via integrin binding to exert forces to the cells. ATC stimulation increases cytoskeletal contractility of hMSCs regardless of the cell area. Furthermore, ATC application rescues osteogenic differentiation of hMSCs in culture conditions that are intrinsically repressive for hMSC osteogenesis (e.g., soft cell culture surfaces). ATC application activates transcriptional regulator YAP to enhance hMSC osteogenesis. Our data further show that F-actin, myosin II, and RhoA/ROCK signaling functions upstream of YAP activity in mediating ATC-stimulated hMSC osteogenesis. With the capability of applying controlled dynamic mechanical stimuli to cells, ATC provides a powerful tool for mechanoregulation of stem cell behaviors in tissue engineering and regenerative medicine applications.





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A magnetic droplet vaporization approach using perfluorohexane-encapsulated magnetic mesoporous particles for ultrasound imaging and tumor ablation

Biomaterials - Wed, 2017-04-26 07:10
Publication date: July 2017
Source:Biomaterials, Volume 134

Author(s): Zhaogang Teng, Ronghui Wang, Yang Zhou, Michael Kolios, Yanjie Wang, Nan Zhang, Zhigang Wang, Yuanyi Zheng, Guangming Lu

Phase change agents consisting of low boiling point perfluorocarbon (PFC) compounds have attracted increasing attention for ultrasound contrast-enhanced imaging and tumor therapy. However, the refraction, acoustic shadowing, reverberation, or limited penetration depth hamper their practical applications through previously reported acoustic droplet vaporization (ADV) or optical droplet vaporization (ODV) technique. Herein, we demonstrate a magnetic droplet vaporization (MDV) approach by loading perflurohexane (PFH) in magnetic mesoporous particles with a hollow space to carry out ultrasound imaging and tumor ablation. In vitro and in vivo magnetic thermal effects show that magnetic energy can be efficiently transformed into thermal energy by the PFH-encapsulated magnetic mesoporous particles, and then leading to vaporization of the loaded PFH. Owing to the generation of the PFH gas bubbles, the ultrasound signals are greatly improved in both harmonic mode and B mode. Simultaneously, anti-cancer experiments demonstrate that the tumor can be ablated after treating with the MDV method for 4 days, demonstrating highly efficient anti-cancer effects.





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Chitosan degradation products facilitate peripheral nerve regeneration by improving macrophage-constructed microenvironments

Biomaterials - Wed, 2017-04-26 07:10
Publication date: July 2017
Source:Biomaterials, Volume 134

Author(s): Yahong Zhao, Yongjun Wang, Jiahuan Gong, Liu Yang, Changmei Niu, Xuejun Ni, Yaling Wang, Su Peng, Xiaosong Gu, Cheng Sun, Yumin Yang

Chitosan-based artificial nerve grafts have been widely employed to repair peripheral nerve defects. Our previous study has shown that chitosan constructed nerve graft not only provides suitable scaffolds for nerve regeneration, its degradation products, chitooligosaccharides (COS), also promote nerve repair. However, the involved mechanisms are still not fully elucidated. In the present study, we observed that pro-inflammatory cytokines, as well as macrophage infiltration, were transiently up-regulated in the injured sciatic nerves which were bridged with silicon tubes filled with COS. Based upon transcriptome analysis, the axis of miR-327/CCL2 in Schwann cells (SCs) was identified as a potential target of COS. The following experiments have confirmed that COS stimulate CCL2 expression by down-regulating miR-327 in SCs. Consequently, the resulting CCL2 induces macrophage migration at injury sites to re-construct microenvironments and thus facilitates nerve regeneration. Collectively, our data provide a theoretical basis for the clinical application of chitosan-based grafts in peripheral nerve regeneration.





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Molecular imaging of activated platelets via antibody-targeted ultra-small iron oxide nanoparticles displaying unique dual MRI contrast

Biomaterials - Wed, 2017-04-26 07:10
Publication date: July 2017
Source:Biomaterials, Volume 134

Author(s): Hang T. Ta, Zhen Li, Christoph E. Hagemeyer, Gary Cowin, Shaohua Zhang, Jathushan Palasubramaniam, Karen Alt, Xiaowei Wang, Karlheinz Peter, Andrew K. Whittaker

Magnetic resonance imaging (MRI) is a powerful and indispensable tool in medical research, clinical diagnosis, and patient care due to its high spatial resolution and non-limited penetration depth. The simultaneous use of positive and negative MRI imaging that employs the same contrast agents will significantly improve detection accuracy. Here we report the development of functional multimodal iron oxide nanoparticles for targeted MRI of atherothrombosis using a combination of chemical and biological conjugation techniques. Monodisperse, water-soluble and biocompatible ultra-small magnetic dual contrast iron oxide nanoparticles (DCIONs) were generated using a high-temperature co-precipitation route and appeared to be efficient positive and negative dual contrast agents for magnetic resonance imaging. Using a unique chemo-enzymatic approach involving copper-free click chemistry and Staphylococcus aureus sortase A enzyme conjugation, DCIONs were functionalized with single-chain antibodies (scFv) directed against activated platelets for targeting purposes. The DCIONs were also labelled with fluorescent molecules to allow for optical imaging. The antigen binding activity of the scFv was retained and resulted in the successful targeting of contrast agents to thrombosis as demonstrated in a range of in vitro and in vivo experiments. T1- and T2-weighted MRI of thrombi was recorded and demonstrated the great potential of dual T1/T2 contrast iron oxide particles in imaging of cardiovascular disease.
Graphical abstract




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Local delivery of chondroitinase ABC with or without stromal cell-derived factor 1α promotes functional repair in the injured rat spinal cord

Biomaterials - Wed, 2017-04-26 07:10
Publication date: July 2017
Source:Biomaterials, Volume 134

Author(s): Malgosia M. Pakulska, Charles H. Tator, Molly S. Shoichet

Traumatic spinal cord injury (SCI) is a devastating event for which functional recovery remains elusive. Due to the complex nature of SCI pathology, a combination treatment strategy will likely be required for success. We hypothesized that tissue and functional repair would be achieved in a rat model of impact-compression SCI by combining degradation of the glial scar, using chondroitinase ABC (ChABC), with recruitment of endogenous neural precursor cells (NPCs), using stromal cell-derived factor 1α (SDF). To test this hypothesis, we designed a crosslinked methylcellulose hydrogel (XMC) for minimally invasive, localized, and sustained intrathecal drug delivery. ChABC was released from XMC using protein-peptide affinity interactions while SDF was delivered by electrostatic affinity interactions from polymeric nanoparticles embedded in XMC. Rats with SCI were treated acutely with a combination of SDF and ChABC, SDF alone, ChABC alone, or vehicle alone, and compared to injury only. Treatment with ChABC, both alone and in combination with SDF, resulted in faster and more sustained behavioural improvement over time than other groups. The significantly reduced chondroitin sulfate proteoglycan levels and greater distribution of NPCs throughout the spinal cord tissue with ChABC delivery, both alone and in combination with SDF, may explain the improved locomotor function. Treatment with SDF alone had no apparent effect on NPC number or distribution nor synergistic effect with ChABC delivery. Thus, in this model of SCI, tissue and functional repair is attributed to ChABC.





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A novel antigen delivery system induces strong humoral and CTL immune responses

Biomaterials - Wed, 2017-04-26 07:10
Publication date: July 2017
Source:Biomaterials, Volume 134

Author(s): Zishan Yang, Miaomiao Xu, Zhenghu Jia, Yuting Zhang, Li Wang, Hongru Zhang, Jingya Wang, Mei Song, Yapu Zhao, Zhenzhou Wu, Liqing Zhao, Zhinan Yin, Zhangyong Hong

New strategies with the ability to enhance both the humoral and cellular immune responses remain a priority for the development of future therapeutic cancer vaccines. In this study, we took advantage of β-glucan particles (GPs) derived from Saccharomyces cerevisiae baker's yeast and a novel reverse micro-emulsion method to prepare an antigen-loaded GP carrier system for dendritic cell (DC) specific antigen delivery, followed by careful evaluation of the immune functions of the prepared particles in initiating both the humoral and cellular immune responses through in vitro and in vivo experiments. The prepared particles greatly promoted DC activation and cytokine production and cross presented the antigen to CD8 cells, inducing very strong OVA specific humoral and cellular immune responses. Treatment with these particles significantly prevented the growth of implanted EG7-OVA tumors in a prophylactic and pre-established tumor model. These results suggest that our strategy may be able to be utilized as a promising platform for cancer immunotherapy.





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Diels–Alder Reversible Thermoset 3D Printing: Isotropic Thermoset Polymers via Fused Filament Fabrication

Advanced Functional Materials - Wed, 2017-04-26 06:16

This study presents a new 3D printing process, the Diels–Alder reversible thermoset (DART) process, and a first generation of printable DART resins, which exhibit thermoset properties at use temperatures, ultralow melt viscosity at print temperatures, smooth part surface finish, and as-printed isotropic mechanical properties. This study utilizes dynamic covalent chemistry based on reversible furan-maleimide Diels–Alder linkages in the polymers, which can be decrosslinked and melt-processed during printing between 90 and 150 °C, and recrosslinked at lower temperatures to their entropically favored state. This study compares the first generation of DART materials to commonly 3D printed high-toughness thermoplastics. Parts printed from typical fused filament fabrication compatible materials exhibit anisotropy of more than 50% and sometimes upward of 98% in toughness when deformed along the build direction, while the first generation of DART materials exhibit less than 4% toughness reduction when deformed along the build direction. At room temperature, the toughest DART materials exhibit baseline toughness of 18.59 ± 0.91 and 18.36 ± 0.57 MJ m−3 perpendicular and parallel to the build direction, respectively. DART printing will enable chemists, polymer engineers, materials scientists, and industrial designers to translate new robust materials possessing targeted thermomechanical properties, multiaxial toughness, smooth surface finish, and low anisotropy.

A new process called Diels–Alder reversible thermoset (DART) 3D printing, adapted from fused filament fabrication and based on dynamic, covalent chemistries, and a first generation of printable DART resins are demonstrated with thermoset properties at use temperatures up to 80 °C, superior surface finish, isotropism, and tough mechanical properties along the build direction of 18.36 ± 0.57 MJ m−3.

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Inhaled Nanoparticles Accumulate at Sites of Vascular Disease

ACS Nano - Wed, 2017-04-26 05:00

ACS NanoDOI: 10.1021/acsnano.6b08551
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