Advancing bacterial 3D printing for the production of next-generation bio-materials

天然细菌和工程细菌具有非凡的生物合成能力。这些材料几乎可以用于任何可以想象的应用：从抗菌伤口敷料的功能化细菌纤维素贴片，到细菌自愈混凝土，或者使用细菌制造纳米复合材料。然而，利用这种巨大的制造潜力来定制具有明确三维形状和组成的设计的能力在很大程度上仍然是难以捉摸的。目前的3D细菌打印方法依赖于使用支架或传统的逐层增材制造策略来塑造其设计，通常导致结构简单，几何形状受限，物理化学和机械性能单调。相比之下，在不同性能之间无缝转换的单体异质复合材料（功能梯度复合材料）长期以来一直是设计师和工程师的圣杯。项目主管已经设计并正在开发一种新型的3D打印平台，用于从根本上增强性能和功能的新型生物材料。这种新的平台技术采用一系列cad编程的光线索，在特定的xyz坐标上“随意”激活工程细胞的基因表达，从而允许复合生物材料的空间组成无缝变化。工程细胞被方便地嵌入到半透明的、生物相容的基质中，这种基质提供了额外的功能，一旦打印过程完成，就可以很容易地移除。这种方法的最终成功不仅取决于克服使用光带来的光学挑战（即衍射，色散等），还取决于我们对该项目的许多生物学相关方面实现精确控制的能力。该项目将继续努力弥合合成生物学和3D打印技术之间的差距，并将重点进一步开发必要的生物工具，以有效地制造3D生物材料。在项目的初始阶段，将生成不那么复杂、简单的概念验证结构。这将有助于确定和划定生产更复杂复合材料的预期和意外挑战。下一步将包括但不限于工作底盘中生物合成途径的优化；寻找合适的照明系统以提高印刷效率；将生物分子反馈控制整合到基因设计中（例如，整合正反馈回路有助于提高打印效率）；开发有效的分泌系统和替代的“分泌”策略（例如，用于复合材料的一种或多种成分的细胞外生物合成的酶展示）；生物材料工程（例如，通过合并细菌淀粉样蛋白）和功能化（例如，银纳米颗粒）；将数学建模的光驱动基因表达系统集成到3D打印软件中，实现真正的计算机引导生物制造；等。最后，将分析下一代3D生物材料的物理化学和机械行为，并与现有生物材料进行比较。

Natural and engineered bacteria possess extraordinary biosynthetic capabilities. These can serve almost any application imaginable: from functionalised bacterial cellulose patches for antimicrobial wound dressing to bacterial self-healing concrete or the use of bacteria to make nacre-inspired composite materials. The ability to harness such great manufacturing potential into customised designs with defined three-dimensional shape and composition remains, however, largely elusive. Current 3D bacterial printing approaches rely on the use of scaffolds or conventional layer-by-layer additive manufacturing strategies to shape their designs, often resulting in unsophisticated structures with restricted geometries and monotonous physico-chemical and mechanical properties. In contrast, one-body yet heterogeneous composite materials with seamless transitions between disparate properties (functionally graded composite materials) have long been a holy grail for designers and engineers. The project supervisors have devised and are currently developing a novel enabling platform for the 3D printing of new classes of bio-materials with radically enhanced properties and functionalities. This new platform technology employs a series of CAD-programmed light cues to activate gene expression of engineered cells "at will" at specific xyz coordinates, which allows for seamless changes in the spatial composition of the composite bio-material. Engineered cells are conveniently embedded into a translucent, bio-compatible matrix that provides additional capabilities and that can be easily removed once the printing process is finished. The final success of this approach will depend not only on overcoming the optical challenges (i.e. diffraction, dispersion, etc.) posed by the use of light but also on our ability to achieve exquisite control over a number of biology-related aspects of the project. This project will build on ongoing efforts to bridge the gap between synthetic biology and 3D printing technology and will focus on further developing the necessary biological tools for the effective manufacturing of bio-materials in 3D. In the initial phases of the project, less-sophisticated, simple proof-of-concept structures will be generated. This will help identify and delimit expected and also unexpected challenges for the production of more complex composite materials. Next steps will include, but not be limited to, optimisation of biosynthetic pathways in the working chassis; finding appropriate illumination regimes to improve printing efficiencies; incorporation of biomolecular feedback control into genetic designs (e.g. incorporation of positive feedback loops could help improve printing efficiency); development of efficient secretion systems and alternative "secretion" strategies (e.g. enzyme display for extracellular biosynthesis of one or more constituents of the composite material); bio-material engineering (e.g. through incorporation of bacterial amyloids) and functionalisation (e.g. silver nanoparticles); integration of mathematically-modelled light-driven gene expression systems into 3D printing software for truly computer-guided bio-fabrication; etc. Finally, resultant next-generation 3D bio-materials will be analysed for their physico-chemical and mechanical behaviour and compared with existing bio-materials.