We demonstrate self-folding of precisely patterned, optically transparent, all-polymeric containers and describe their utility in mammalian cell and microorganism encapsulation and culture. The polyhedral containers, with SU-8 faces and biodegradable polycaprolactone (PCL) hinges, spontaneously assembled on heating. Self-folding was driven by a minimization of surface area of the liquefying PCL hinges within lithographically patterned two-dimensional (2D) templates. The strategy allowed for the fabrication of containers with variable polyhedral shapes, sizes and precisely defined porosities in all three dimensions. We provide proof-of-concept for the use of these polymeric containers as encapsulants for beads, chemicals, mammalian cells and bacteria. We also compare accelerated hinge degradation rates in alkaline solutions of varying pH. These optically transparent containers resemble three-dimensional (3D) micro-Petri dishes and can be utilized to sustain, monitor and deliver living biological components.

We describe strategies to curve, rotate, align and bond precisely patterned two dimensional (2D) nanoscale panels using forces derived from a minimization of surface area of liquefying or coalescing metallic grains. We demonstrate the utility of this approach by discussing variations in template size, patterns and material composition. The strategy provides a solution path to overcome the limitation of inherently two dimensional lithographic processes by transforming 2D templates into mechanically robust and precisely patterned nanoscale curved structures and polyhedra with considerable versatility in material composition.

Biopolymer-forming proteins are integral in the development of customizable biomaterials, but recombinant expression of these proteins is challenging. In particular, biopolymer-forming proteins have repetitive, glycine-rich domains and, like many heterologously expressed proteins, are prone to incomplete translation, aggregation, and proteolytic degradation in the production host. This necessitates tailored purification processes to isolate each full-length protein of interest from the truncated forms as well as other contaminating proteins; owing to the repetitive nature of these proteins, the truncated polypeptides can have very similar chemistry to the full-length form and are difficult to separate from the full-length protein. We hypothesized that bacterial expression and secretion would be a promising alternative option for biomaterials-forming proteins, simplifying isolation of the full-length target protein. By using a selective secretion system, truncated forms of the protein are not secreted and thus are not found in the culture harvest. We show that a synthetically upregulated type III secretion system leads to a general increase in secretion titer for each protein that we tested. Moreover, we observe a substantial enhancement in the homogeneity of full-length forms of pro-resilin, tropo-elastin crosslinking domains, and silk proteins produced in this manner, as compared with proteins purified from the cytosol. Secretion via the type III apparatus limits co-purification of truncated forms of the target protein and increases protein purity without extensive purification steps. Demonstrating the utility of such a system, we introduce several modifications to resilin-based peptides and use an un-optimized, single-column process to purify these proteins. The resulting materials are of sufficiently high quantity and yield for the production of antimicrobial hydrogels with highly reproducible rheological properties. The ease of this process and its applicability to an array of engineered biomaterial-forming peptides lend support for the application of bacterial expression and secretion for other proteins that are traditionally difficult to express and isolate from the bacterial cytoplasm. Biotechnol. Bioeng. 2016;113: 2313-2320. © 2015 Wiley Periodicals, Inc.

The type III secretion system (T3SS) encoded at the Salmonella pathogenicity island 1 (SPI-1) locus secretes protein directly from the cytosol to the culture media in a concerted, one-step process, bypassing the periplasm. While this approach is attractive for heterologous protein production, product titers are too low for many applications. In addition, the expression of the SPI-1 gene cluster is subject to native regulation, which requires culturing conditions that are not ideal for high-density growth. We used transcriptional control to increase the amount of protein that is secreted into the extracellular space by the T3SS of Salmonella enterica. The controlled expression of the gene encoding SPI-1 transcription factor HilA circumvents the requirement of endogenous induction conditions and allows for synthetic induction of the secretion system. This strategy increases the number of cells that express SPI-1 genes, as measured by promoter activity. In addition, protein secretion titer is sensitive to the time of addition and the concentration of inducer for the protein to be secreted and SPI-1 gene cluster. Overexpression of hilA increases secreted protein titer by >10-fold and enables recovery of up to 28 ؎ 9 mg/liter of secreted protein from an 8-h culture. We also demonstrate that the protein beta-lactamase is able to adopt an active conformation after secretion, and the increase in secreted titer from hilA overexpression also correlates to increased enzyme activity in the culture supernatant.

The concept of self-assembly of a two-dimensional (2D) template to a three-dimensional (3D) structure has been suggested as a strategy to enable highly parallel fabrication of complex, patterned microstructures. We have previously studied the surface tension based self-assembly of patterned, microscale polyhedral containers (cubes, square pyramids and tetrahedral frusta). In this paper, we describe the observed hierarchical self-assembly of more complex, patterned polyhedral containers in the form of regular dodecahedra and octahedra. The hierarchical design methodology, combined with the use of self-correction mechanisms, was found to greatly reduce the propagation of selfassembly error that occurs in these more complex systems. It is a highly effective way to massproduce patterned, complex 3D structures on the microscale and could also facilitate encapsulation of cargo in a parallel and cost-effective manner. Furthermore, the behavior that we have observed may be useful in the assembly of complex systems with large numbers of components.