Abstract
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.
Highlights
Biomineralization is a natural process of global significance that involves the deposition of mineral ions under the control of biological organisms [1,2,3,4,5,6,7]
Using a standard microfluidic surface acoustic wave (SAW) biosensor system equipped with commercially available COO−/ H3O+-selfassembled monolayer (SAM) (COOH-SAM, in the following is termed COOSAM) sensor chips, we monitored the phase and amplitude signals as a function of time
The influence of the concentration of calcium carbonate relative to the solubility equilibrium and the flow rate on the SAW biosensor phase and amplitude signals was investigated in real-time
Summary
Biomineralization is a natural process of global significance that involves the deposition of mineral ions under the control of biological organisms [1,2,3,4,5,6,7]. The interaction of proteins with minerals is one of the key regulatory elements in biomineralization processes, and many proteins involved in biomineralization exhibit molecular features that make them attractive models for materials science and nanotechnology [8,9,10]. Gations report that the differences between the assemblies of shell proteins from one species to another species can be tremendous [14,15,16]. This observation suggests that multiple interactions between the proteins are fine-tuned in relationship to the forming mineral phases [17,18,19,20]
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