Expression and cytosolic assembly of the S-layer fusion protein mSbsC-EGFP in eukaryotic cells

3D printing/electrospinning of a bilayered composite patch with antibacterial and antiadhesive properties for repairing abdominal wall defects

The application of patch methods for repairing abdominal wall wounds presents a variety of challenges, such as adhesion and limited mobility due to inadequate mechanical strength and nonabsorbable materials. Among these complications, postoperative visceral adhesion and wound infection are particularly serious. In this study, a bilayered composite patch with a gelatin methacryloyl (GelMA)/sodium alginate (SA)-vancomycin (Van)@polycaprolactone (PCL) (GelMA/SA-Van@PCL) antibacterial layer was prepared via coaxial 3D printing and a polycaprolactone (PCL)-silicon dioxide (SiO2) antiadhesive layer (PCL-SiO2) was prepared via electrospinning and electrostatic spray for hernia repair. The evaluation of the physicochemical properties revealed that the composite patch had outstanding tensile properties (16 N cm-1), excellent swelling (swelling rate of 243.81 ± 12.52%) and degradation (degradation rate of 53.14 ± 3.02%) properties. Furthermore, the composite patch containing the antibiotic Van exhibited good antibacterial and long-term drug release properties. Both in vivo and in vitro experiments indicated that the composite patch displayed outstanding biocompatibility and antiadhesive properties and could prevent postoperative infections. In summary, the bilayered composite patch can effectively prevent postoperative complications while promoting tissue growth and repair and holds significant application potential in hernia repair.

Porous protein crystals: synthesis and applications

Large-pore protein crystals (LPCs) are an emerging class of biomaterials. The inherent diversity of proteins translates to a diversity of crystal lattice structures, many of which display large pores and solvent channels. These pores can, in turn, be functionalized via directed evolution and rational redesign based on the known crystal structures. LPCs possess extremely high solvent content, as well as extremely high surface area to volume ratios. Because of these characteristics, LPCs continue to be explored in diverse applications including catalysis, targeted therapeutic delivery, templating of nanostructures, structural biology. This Feature review article will describe several of the existing platforms in detail, with particular focus on LPC synthesis approaches and reported applications.

Production, secretion, and cell surface display of recombinant Sporosarcina ureae S-layer fusion proteins in Bacillus megaterium

Monomolecular crystalline bacterial cell surface layers (S-layers) have broad application potential in nanobiotechnology due to their ability to generate functional supramolecular structures. Here, we report that Bacillus megaterium is an excellent host organism for the heterologous expression and efficient secretion of hemagglutinin (HA) epitope-tagged versions of the S-layer protein SslA from Sporosarcina ureae ATCC 13881. Three chimeric proteins were constructed, comprising the precursor, C-terminally truncated, and N- and C-terminally truncated forms of the S-layer SslA protein tagged with the human influenza hemagglutinin epitope. For secretion of fusion proteins, the open reading frames were cloned into the Escherichia coli-Bacillus megaterium shuttle vector pHIS1525. After transformation of the respective plasmids into Bacillus megaterium protoplasts, the recombinant genes were successfully expressed and the proteins were secreted into the growth medium. The isolated S-layer proteins are able to assemble in vitro into highly ordered, crystalline, sheetlike structures with the fused HA tag accessible to antibody. We further show by fluorescent labeling that the secreted S-layer fusion proteins are also clustered on the cell envelope of Bacillus megaterium, indicating that the cell surface can serve in vivo as a nucleation point for crystallization. Thus, this system can be used as a display system that allows the dense and periodic presentation of S-layer proteins or the fused tags.

Calcium dependent formation of tubular assemblies by recombinant S-layer proteins in vivo and in vitro

Surface layer proteins have the appealing property to self-assemble in nanosized arrays in solution and on solid substrates. In this work, we characterize the formation of assembly structures of the recombinant surface layer protein SbsC of Geobacillus stearothermophilus ATTC 12980, which was tagged with enhanced green fluorescent protein and expressed in the yeast Saccharomyces cerevisiae. The tubular structures formed by the protein in vivo are retained upon bursting the cells by osmotic shock; however, their average length is decreased. During dialysis, monomers obtained by treatment with chaotropic chemicals recrystallize again to form tube-like structures. This process is strictly dependent on calcium (Ca(2+)) ions, with an optimal concentration of 10 mM. Further increase of the Ca(2+) concentration results in multiple non-productive nucleation points. We further show that the lengths of the S-layer assemblies increase with time and can be controlled by pH. After 48 h, the average length at pH 9.0 is 4.13 µm compared to 2.69 µm at pH 5.5. Successful chemical deposition of platinum indicates the potential of recrystallized mSbsC-eGFP structures for nanobiotechnological applications.

Carrier-free immobilized enzymes for biocatalysis

Methods for the preparation of carrier-free insoluble enzymes are reviewed. The technology of cross-linked enzyme aggregates has now been applied to a range of synthetically useful activities. Fusion proteins are also gaining momentum because they allow a relatively selective aggregation or even a specific self-assembly of the desired enzyme activity into insoluble particles in the absence of potentially denaturing chemicals required for precipitation and cross-linking. Recycling of insoluble protein particles for multiple rounds of batchwise reaction has been demonstrated in selected biotransformations. However, for application in a fully continuous biocatalytic process, low resistance to mechanical stress and high compressibility are issues for consideration on carrier-free enzyme particles.