New Class of Crosslinker-Free Nanofiber Biomaterials from Hydra Nematocyst Proteins

Abstract

Nematocysts, the stinging organelles of cnidarians, have remarkable mechanical properties. Hydra nematocyst capsules undergo volume changes of 50% during their explosive exocytosis and withstand osmotic pressures of beyond 100 bar. Recently, two novel protein components building up the nematocyst capsule wall in Hydra were identified. The cnidarian proline-rich protein 1 (CPP-1) characterized by a “rigid” polyproline motif and the elastic Cnidoin possessing a silk-like domain were shown to be part of the capsule structure via short cysteine-rich domains that spontaneously crosslink the proteins via disulfide bonds. In this study, recombinant Cnidoin and CPP-1 are expressed in E. coli and the elastic modulus of spontaneously crosslinked bulk proteins is compared with that of isolated nematocysts. For the fabrication of uniform protein nanofibers by electrospinning, the preparative conditions are systematically optimized. Both fibers remain stable even after rigorous washing and immersion into bulk water owing to the simultaneous crosslinking of cysteine-rich domains. This makes our nanofibers clearly different from other protein nanofibers that are not stable without chemical crosslinkers. Following the quantitative assessment of mechanical properties, the potential of Cnidoin and CPP-1 nanofibers is examined towards the maintenance of human mesenchymal stem cells.

Wnt/β-catenin signaling induces axial elasticity patterns of Hydra extracellular matrix

“…Only one sample exhibited a random pattern, which could be attributed to artifacts from remaining nematocysts. 35

Figure 4 Three representative elasticity phenotypes of Hydra mesoglea (n = 38) (A) Type A is characterized by a uniform, soft mesoglea. (B) Type B shows higher elastic moduli in peduncle and budding regions compared to the head region.

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The Wnt-specific astacin proteinase HAS-7 restricts head organizer formation in Hydra

“…Animals were starved for 24 h prior to experiments, unless indicated otherwise. Whole mount immunocytochemistry using a CPP-1-specific antibody was performed as described previously [ 53 ].…”

Stimulus-Responsive, Gelatin-Containing Supramolecular Nanofibers as Switchable 3D Microenvironments for Cells

“…Figure 3 a shows a bright field microscopy image of the gelatin-βCD-Ad fibers in air after electrospinning. Continuous and uniform fibers were fabricated by adjusting the viscosity of the solution to approximately 0.8–1.0 Pas [ 9 , 37 ]. As shown in Figure 3 b, the fibers remained uniform after chemical crosslinking in the ethanol solution of [EDC] = [NHS] = 12.5 mM for 4 h. To ensure the stability of the fibers, the samples were rinsed with ethanol, dried in air, and soaked in PBS at 37 °C for 48 h before the imaging.…”

“…Polymer- and/or protein-based nanofibers are considered well-defined models of natural 3D ECMs [ 8 , 9 , 10 ]. Gelatin, a hydrolysate of collagen, has been widely applied as a biomaterial [ 11 ].…”