XYZ on a Chip: Incorporation of Biological Components into Microsystems via Biomimetic Processing

9980795 gower这个工程微系统：“XYZ”芯片项目的目标是将快速原型技术与仿生加工相结合，以制造含有生物成分的工程微系统。这种被称为聚合物诱导液体前驱体（PILP）工艺的仿生加工技术目前正在由PI开发，用于在低温和水基条件下沉积矿物薄膜。这些良好的加工条件应符合热敏成分的掺入，这将在拟议的方法中加以利用。PILP工艺的新颖之处在于，一种酸性聚电解质（聚天冬氨酸）通过隔离离子和诱导矿物前驱体的相分离，将传统的溶液结晶过程转变为凝固过程。该前体以中等粘性液体的形式存在，并且可以通过隔室进行模制和成型。生物矿化的标志是生物体在囊泡腔内“塑造”无机晶体的能力，因此假设这种PILP过程可能在钙质生物矿物质的形态发生中起着根本作用。因此，提出的工作的第一个目标是利用微加工技术演示方解石的“微成型”。无机相的图案将通过以下两种方法进行研究：1)软光刻“微成型”的PILP前驱体，或2)由温度诱导成形（TIF）工艺产生的固体自由形态陶瓷前驱体。图案化无机层的通道随后将通过二级相的聚合填充，以使层平面化（选择聚肉桂酸作为测试平台）。然后将使用快速原型技术依次沉积许多薄层，以构建受控建筑的三维复合结构，这是该项目的第二个目标。在许多方面，这种逐层制造方案类似于生物矿化中自然发生的过程；计算机辅助设计（CAD）允许对序列沉积进行空间控制，这是由生物系统中的细胞过程完成的。该项目的第三个目标是展示将生物成分结合到脚手架结构中，并以空间统一和可控的方式进行。脲酶-尿素酶系统将用作测试平台，以确定该过程是否使蛋白质变性。通过荧光和免疫金标记检测蛋白质的空间分布。本文提出的工作将证明该方法的可行性，并开始获得开发用于各种应用的定制复合材料的通用方法所需的工具，例如：生物受体微系统：生物组分的高度空间调节将是未来微电子与生物受体物种杂交的必要特征。药物递送-具有最佳生物相容性的可生物降解矿物相，可缓慢释放包封在矿物相内的药物。细胞微胶囊化和组织工程：一种含有骨形态发生蛋白的可生物降解相多孔框架，用于骨诱导骨移植替代品，或用于体外硬组织工程（或其他组织）中骨祖细胞的包封。同样，多孔框架可以为胰岛细胞提供一个笼子，通过生理介质的流动和生物控制胰岛素的释放来治疗糖尿病，同时隔离外来细胞以防止免疫原性反应。生物分离：框架的三维结构将能够控制孔隙度和孔隙度梯度，用于特定尺寸的分离和色谱，以及结合生物成分的能力，将特别适用于生物分离。生物催化：利用良性的仿生过程，酶可以加入到框架中来制造多孔的催化介质，并且可能通过与框架的表面相互作用来控制蛋白质的取向，以实现催化位点的最佳呈现。

9980795GowerThe goal of this Engineering Microsystems: "XYZ" on a Chip project is to combine rapid prototyping techniques with biomimetic processing for the fabrication of engineered microsystems that contain biological components. The biomimetic processing technique, called the Polymer-Induced Liquid-Precursor (PILP) process, is currently being developed by the PI for the deposition of mineral films under low-temperature and aqueous-based conditions. These benign processing conditions should be amenable to the incorporation of thermally sensitive ingredients, which will be capitalized on in the proposed methodology. The novelty of the PILP process is that an acidic polyelectrolyte (polyaspartic acid) transforms a traditional solution crystallization process into a solidification process by sequestering ions and inducing phase separation of a mineral precursor. This precursor is in the form of a moderately viscous liquid, and can be molded and shaped by a compartment. The hallmark of biomineralization is the ability of organisms to "mold" inorganic crystals within vesicular compartments, thus it is hypothesized that this PILP process may play a fundamental role in the morphogenesis of calcitic biominerals. Therefore, the first goal of the proposed work is to demonstrate "micromolding" of calcite using microfabrication techniques.Patterning of the inorganic phase will be investigated by the following two approaches: 1) soft lithography" micromolding of a PILP precursor, or 2) solid freeform fabrication of ceramic precursor generated by a Temperature Induced Forming (TIF) process. The channels of the patterned inorganic layer will subsequently be filled in by polymerization of a secondary phase for planarization of the layer (polycinnamic acid is chosen as the testbed). Rapid prototyping will then be used to sequentially deposit numerous thin layers, in order to construct a three-dimensional composite structure of controlled architecture, the second goal of the project. In many ways, this layer-by-layer fabrication scheme is similar to the processes that occur naturally in biomineralization; whereby computer-aided design (CAD) allows for the spatial control of the sequential depositions, which is accomplished by cellular processes in biological systems.A third goal of the project is to demonstrate the incorporation of biological components into scaffolding structures, and in a spatially uniform and controlled fashion. The Urease-urea enzyme system will be used for a testbed, in order to determine if the process denatures the protein. The spatial distribution of the protein will be examined by fluorescent and immunogold labeling of protein. The work proposed herein will demonstrate feasibility of the approach, and begin to acquire the tools necessary for developing a generalized methodology for customized composites for a variety of applications, such as the following:Bio receptor Microsystems: a high degree of spatial regulation of biological components will be a necessary feature for the future of hybridization of microelectronics with bioreceptor species.Drug Delivery- a biodegradable mineral phase with optimal biocompatibility for the slow release of agents encapsulated within the mineral phase.Microencapsulation of Cells and Tissue Engineering: a porous framework of a biodegradable phase containing bone morphogenetic proteins for application as osteoinductive bone-graft substitutes, or for encapsulation of osteoprogenitor cells for in vitro hard-tissue engineering (or other tissues). Likewise, a porous framework could provide a cage for Islet cells, enabling through flow of physiological media and biologically-controlled release of insulin for treatment of diabetes, while isolating the foreign cells to prevent immunogenic response.Bioseparations: structuring of the framework in three-dimensions will enable controlled porosity and porosity gradients for size-specific separations and chromatography, that along with the capability of incorporation of bioconstituents, will be particularly amenable to bioseparations.Biocatalysis: Using the benign biomimetic process, enzymes could be incorporated into the framework to fabricate a porous catalytic media, and possibly with controlled orientation of the protein through surface interactions with framework for optimal presentation of catalytic site.