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Real-time monitoring of calcium carbonate and cationic peptide deposition on carboxylate-SAM using a microfluidic SAW biosensor
A microfluidic biosensor with surface acoustic wave technology was used in this study to monitor the interaction of calcium carbonate with standard carboxylate self-assembled monolayer sensor chips. Different fluids, with and without biomolecular components, were investigated. The pH-dependent surface interactions of two bio-inspired cationic peptides, AS8 and ES9, which are similar to an extracellular domain of the chitin synthase involved in mollusc shell formation, were also investigated in a biological buffer system. A range of experimental conditions are described that are suitable to study non-covalent molecular interactions in the presence of ionic substances, such as, mineral precursors below the solubility equilibrium. The peptide ES9, equal to the mollusc chitin synthase epitope, is less sensitive to changes in pH than its counterpart AS8 with a penta-lysine core, which lacks the flanking acidic residues. This study demonstrates the extraordinary potential of microfluidic surface acoustic wave biosensors to significantly expand our experimental capabilities for studying the principles underlying biomineralization in vitro.
Structure-property relationships in mechanically stimulated Sorghum bicolor stalks
Mechanical properties of plants and underlying structure-property relationships are important for agricultural purposes as well as for biomimetic concepts. In this study, the effect of mechanical stimulation on morphology and bending properties of the stalk was investigated for Sorghum bicolor (Poaceae), a widely used drought-tolerant biomass grass. An experimental set-up allowing for defined growth and mechanical perturbation (flexing) during a defined growth period was designed. Mechanical properties of individual internodes of the stalk were determined by three-point bending tests. We found that the three investigated lines showed differences in their general bending strength in the non-stimulated condition. However, similar high range of bending strength values was measured for all plant lines after they underwent the mechanical stimulation procedure. The anatomy of internode cross-sections was examined to evaluate structure-property relationships. An increased thickness of the outer sclerenchymatous tissue was observed for internodes with higher bending strength values. Dried internodes fail under lower strains but showed higher bending strength. These findings show that mechanosensitivity in sorghum is dependent on genetic as well as environmental factors. The experimental system presented here offers new straight-forward possibilities for S. bicolor line selection for applications requiring mechanical strength of the stalk.