Acoustic droplet–hydrogel composites for spatial and temporal control of growth factor delivery and scaffold stiffness

Fabiilli M L , Wilson C G , Frédéric Padilla, et al. Acta Biomaterialia, 2013, 9(7):7399-7409.
DOI：10.1016/j.actbio.2013.03.027

Abstract:

Wound healing is regulated by temporally and spatially restricted patterns of growth factor signaling, but there are few delivery vehicles capable of the “on-demand” release necessary for recapitulating these patterns. Recently we described a perfluorocarbon double emulsion that selectively releases a protein payload upon exposure to ultrasound through a process known as acoustic droplet vaporization (ADV). In this study, we describe a delivery system composed of fibrin hydrogels doped with growth factor-loaded double emulsion for applications in tissue regeneration. Release of immunoreactive basic fibroblast growth factor (bFGF) from the composites increased up to 5-fold following ADV and delayed release was achieved by delaying exposure to ultrasound. Releasates of ultrasound-treated materials significantly increased the proliferation of endothelial cells compared to sham controls, indicating that the released bFGF was bioactive. ADV also triggered changes in the ultrastructure and mechanical properties of the fibrin as bubble formation and consolidation of the fibrin in ultrasound-treated composites were accompanied by up to a 22-fold increase in shear stiffness. ADV did not reduce the viability of cells suspended in composite scaffolds. These results demonstrate that an acoustic droplet–hydrogel composite could have broad utility in promoting wound healing through on-demand control of growth factor release and/or scaffold architecture.

供稿人：曾广智

总结： 伤口愈合受时间和空间的限制，在不同状况下调节生长因子信号传导模式，但很少有能够 “按需”释放这些生长因子的传递载体。最近，我们描述了一种全氟化碳乳液，其通过称为声学液滴蒸发（ADV） 的过程在暴露于超声波时选择性地释放蛋白质有效负载。在本研究中，研究者描述了由掺杂有生长因子的双重乳液的纤维蛋白水凝胶组成的递送系统以用于组织再生。释放免疫反应性碱性成纤维细胞ADV后，复合材料的生长因子（bFGF）增加至5倍，并且通过延迟暴露于超声波实现延迟释放。与对照相比，超声处理材料的释放显着增加了内皮细胞的增殖，表明释放的bFGF具有生物活性。ADV还引发了纤维蛋白的超微结构和机械性质的变化，因为气泡的形成，超声处理的复合材料中纤维蛋白的固结伴导致剪切刚度增加22倍。ADV没有降低悬浮在复合支架中的细胞的活力。这些结果表明声学液滴-水凝胶复合物可通过按需控制生长因子释放和/或支架结构而在促进伤口愈合方面具有广泛的用途。


Schematic representation of drug release by ADV in a hydrogel scaffold. Bottom: A water-in-PFC-in-water (W1/PFC/W2) double emulsion, containing a growth factor in the W1 phase, is encapsulated within the scaffold. Upon exposure to acoustic amplitudes greater than the ADV threshold of the emulsion, the PFC within the droplets is vaporized, thus releasing the W1 phase. Top left: confocal fluorescence image (fluorescein, shown in green) of a PFC double emulsion droplet (scale bar = 10 μm). Smaller aqueous droplets, containing a water-soluble payload such as fluorescein or bFGF, are enveloped by a larger PFC globule. Top right: visible image of a 10 mg ml−1 fibrin gel containing 5% (v/v) double emulsion after targeted exposure to ultrasound. The “block M” consists of gas bubbles generated by ADV. Scale bar = 4 mm.

优点：

研究的结果证明了声学液滴-水凝胶复合材料作为药物递送载体以及支架结构和机械性质的改性剂的潜力。通过聚焦超声的应用，可以在非侵入性和空间和时间受限制的情况下“按需”释放生长因子或其他再生因子。这种新型平台将在组织工程和再生方面具有巨大的实用性

缺点：

复合材料中液滴的体积分数会增加暴露于超声波后形成的气泡数量，虽不会影响ADV。，但在较高的液滴浓度下，ADV产生的气泡的可能会产生声学“阴影”，并阻碍远场中液滴的蒸发。超声波在某些情况下可以改变溶解蛋白质的结构和功能，从而影响到携带蛋白质生长因子的活性，虽然可以通过提高频率减弱这种效应，但也会带来超声波穿深深度不够的问题。

Direct Transmission of Digital Message via Programmable Coding Metasurface

Tie Jun Cui, Shuo Liu, Guo Dong Bai, and Qian Ma
DOI: 10.1155/2019/2584509

Abstract:

In modern wireless communications, digital information is firstly converted to analog signal by a digital-analog convertor, which is then mixed to high-frequency microwave to be transmitted through a series of devices including modulator, mixer, amplifier, filter, and antenna and is finally received by terminals via a reversed process. Although the wireless communication systems have evolved significantly over the past thirty years, the basic architecture has not been challenged. Here, we propose a method to transmit digital information directly via programmable coding metasurface. Since the coding metasurface is composed of ‘0’ and ‘1’ digital units with opposite phase responses, the digital information can be directly modulated to the metasurface with certain coding sequences and sent to space under the illumination of feeding antenna. The information, being modulated in radiation patterns of the metasurface, can be correctly received by multiple receivers distributed in different locations. This method provides a completely new architecture for wireless communications without using complicated digital-analog convertor and a series of active/passive microwave devices. We build up a prototype to validate the new architecture experimentally, which may find promising applications where information security is highly demanded.


Schematic illustration of the working mechanism of the proposed DDM system.

供稿人：赵天宇

摘要：

在现代无线通信中，数字信息首先通过数模转换器转换为模拟信号，然后将其混合到高频微波中，通过包括调制器，混频器，放大器，滤波器和天线在内的一系列设备进行传输，最终由终端通过反向过程接收。虽然无线通信系统在过去三十年中已经有了很大的发展，但基本架构并未受到挑战。在这里，我们提出了一种通过可编程编码表面直接传输数字信息的方法。由于编码表面由具有相反相位响应的“0”和“1”数字单元组成，因此数字信息可以用某些编码序列直接调制到表面，并在馈电天线的照射下发送到空间。以超曲面的辐射图调制的信息可以由分布在不同位置的多个接收器正确地接收。该方法提供了一种全新的无线通信架构，无需使用复杂的数模转换器和一系列有源/无源微波器件。崔铁军团队构建了一个模型，以实验方式验证新架构。这一发现可能会应用在需要高度信息安全性的场景。

推荐理由：

  1. 首次提出将数字超表面用于无线信号传输，并且实验验证。
  2. 解读超表面反射出的信息需要在特定方向接收信号，保证了信息的安全性。
  3. 自适应调节算法解决传输信号被障碍物遮挡时传输受损的难题。

缺点：

  1. 文中没有讨论这种数字超表面传递信息的速度，即通信领域的带宽，并且缺少与传统手段的比较。
  2. 文中讨论的传输信号设备并没有给出信号在空间中的衰减。

Broadband and wide-angle negative reflection at a phononic crystal boundary

Degang Zhao, Yangtao Ye, Shengjun Xu, Xuefeng Zhu, and Lin Yi
DOI: 10.1063/1.4863691

Abstract:

We have theoretically and experimentally demonstrated the anomalous negative reflection at the boundary of a well-designed two-dimensional phononic crystal. This exotic phenomenon is attributed to the selective enhancement of −1st order diffraction mode with the zero-order diffraction mode being dramatically suppressed. After material and structural optimization, the negative reflection can be maintained in a broadband of frequencies and for a wide incident angle range. Our system can be employed to design Littrow configuration to realize perfect broadband and wide-angle blazing. The study gives a possibility to achieve greater flexibility and stronger effects in manipulating reflected acoustic waves, which has potential applications in underwater communication, medical ultrasonics, etc.

供稿人：胡洲

声子晶体边界上的宽频宽角度负反射

总结：

本文通过理论和实验证实了2D声子晶体界面上的负反射，即反射波与入射波位于界面法线的同侧。其机理是：由于声子晶体的边界为周期的波浪形边界，根据分层多重散射理论，可将其边界处的反射波 $P(r)$ 分解为多个平面波$P_n(r)$，其中$n$代表$n$阶衍射模态。在低频区，只有$0$阶衍射模态。随着频率的增加，$-1$阶衍射模态最先出现。当$k_{-1,x}<0$时，$-1$阶衍射模态将沿着$x$轴负方向传播，即产生负反射现象。因此，利用声子晶体的禁带特性，设计特殊的声子晶体，使其$-1$阶衍射模态增强，同时$0$阶衍射模态被抑制，则可实现负反射。
通过进一步优化背景介质的材料属性和散射体的体积分数，发现产生负反射的频率范围随入射角度的增大而增大。最后基于优化后声子晶体，实现了宽入射角度的完美$Littrow$结构，使其干涉角度不再受光栅表面构型的限制。

$P(r)=\sum_n{p_nexp(ik_n\cdot r)}, n=0,\pm1,\pm2,\cdots$

$k_n=(k_{nx},k_{ny}),k_{nx}=k_0 \sin \theta+n \frac{2\pi}{a},k_{ny}=\sqrt{k_0^2-k_{nx}^2}$


The schematic presentation of negative wave reflection at a phononic crystal boundary.

优点：

  1. 利用声子晶体的禁带属性，实现了宽频宽角度范围的负反射
  2. 实现了宽入射角度的完美$Littrow$结构，打破了传统光栅的发光角度依赖光栅表面构型的限制

不足：

  1. 产生负反射是基于声子晶体禁带，这限制了产生负反射的频率范围在高频区
  2. 宽入射角度范围能产生负反射对应的频率范围较窄
  3. 该工作只关注了$-1$阶衍射模态，更高阶衍射模态对负反射是否存在影响呢

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