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

9980795 Gower这个工程微系统：“XYZ”on a Chip项目的目标是将快速原型技术与仿生加工相结合，制造包含生物成分的工程微系统。目前，PI正在开发一种名为聚合物诱导液体前体(PILP)的仿生处理技术，用于在低温和水基条件下沉积矿物薄膜。这些良性的加工条件应该服从于加入热敏感成分，这将在拟议的方法中得到利用。PILP工艺的新奇之处在于，酸性聚电解质(聚天冬氨酸)通过隔离离子和诱导矿物前体的相分离，将传统的溶液结晶过程转变为固化过程。这种前驱体是中等粘度的液体，可以通过隔室进行模塑和成型。生物矿化的特征是生物体能够在泡腔内塑造无机晶体，因此推测这一PILP过程可能在钙质生物矿物的形态发生中发挥基础作用。因此，这项工作的第一个目标是利用微细加工技术来演示方解石的微成型。无机相的图案化将通过以下两种方法来研究：1)软光刻PILP前驱体的微成型，或2)通过温度诱导成型(TIF)过程产生的陶瓷前驱体的固体自由形式制造。图案化的无机层的通道随后将通过聚合第二相来填充，以使层平坦化(选择聚肉桂酸作为试验床)。然后，将使用快速原型来顺序地沉积大量薄层，以构建受控建筑的三维组合结构，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；因此，计算机辅助设计(CAD)允许对连续沉积进行空间控制，这是通过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支架结构中，并以空间统一和受控的方式。尿素酶-尿素酶系统将用于试验床，以确定该过程是否使蛋白质变性。蛋白质的空间分布将通过蛋白质的荧光标记和免疫金标记法进行检测。本文提出的工作将证明这种方法的可行性，并开始获得为各种应用开发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：生物成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-一种生物可降解矿物相，具有最佳的生物兼容性，用于缓慢释放包裹在矿物相中的药物。细胞和组织工程的微胶囊：含有骨形态发生蛋白的生物可降解相的多孔骨架，用于骨诱导骨移植替代物，或用于包埋体外硬组织工程(或其他组织)的骨祖细胞。同样，多孔框架可以为胰岛细胞提供一个笼子，能够通过生理介质的流动和用于治疗糖尿病的胰岛素的生物控制释放，同时隔离外来细胞以防止免疫原性反应。生物分离：三维框架的结构将使特定尺寸的分离和层析的孔隙率和孔隙率梯度能够受控，与生物成分的结合能力将特别有利于生物分离。生物催化：利用良性的生物仿生过程，酶可以被结合到框架中以制造多孔催化介质，并可能通过与框架的表面相互作用来控制蛋白质的取向，以实现催化部位的最佳呈现。

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.