title: Control of crystal polymorph in microfluidics using molluscan 28 kDa Ca²(+)-binding protein.
abstract: Biominerals produced by biological systems in physiologically relevant environments possess extraordinary properties that are often difficult to replicate under laboratory conditions. Understanding the mechanism that underlies the process of biomineralisation can lead to novel strategies in the development of advanced materials. Using microfluidics, we have demonstrated for the first time, that an extrapallial (EP) 28 kDa protein, located in the extrapallial compartment between mantle and shell of Mytilus edulis, can influence, at both micro- and nanoscopic levels, the morphology, structure and polymorph that is laid down in the shell ultrastructure. Crucially, this influence is predominantly dependent on the existence of an EP protein concentration gradient and its consecutive interaction with Ca²(+) ions. Novel lemon-shaped hollow vaterite structures with a clearly defined nanogranular assembly occur only where particular EP protein and Ca²(+) gradients co-exist. Computational fluid dynamics enabled the progress of the reaction to be mapped and the influence of concentration gradients across the device to be calculated. Importantly, these findings could not have been observed using conventional bulk mixing methods. Our findings not only provide direct experimental evidence of the potential influence of EP proteins in crystal formation, but also offer a new biomimetic strategy to develop functional biomaterials for applications such as encapsulation and drug delivery.
authors.affiliation: Department of Geographical & Earth Sciences, University of Glasgow, UK.
authors.forename: Bozhi
authors.initials: B
authors.lastname: Ji
authors.forename: Maggie
authors.initials: M
authors.lastname: Cusack
authors.forename: Andy
authors.initials: A
authors.lastname: Freer
authors.forename: Phil S
authors.initials: PS
authors.lastname: Dobson
authors.forename: Nikolaj
authors.initials: N
authors.lastname: Gadegaard
authors.forename: Huabing
authors.initials: H
authors.lastname: Yin
mesh_terms: D000818:Animals; D002021:Buffers; D002113:Calcification, Physiologic; D002119:Calcium Carbonate / Q000138:chemical synthesis / Q000737:chemistry; D002122:Calcium Chloride / Q000737:chemistry; D002135:Calcium-Binding Proteins / Q000737:chemistry*; D002254:Carbonates / Q000737:chemistry; D003460:Crystallization / Q000379:methods; D046210:Microfluidic Analytical Techniques / Q000379:methods; D044085:Microfluidics / Q000379:methods*; D008855:Microscopy, Electron, Scanning; D049880:Mytilus edulis / Q000737:chemistry; D064030:S100 Calcium Binding Protein G / Q000737:chemistry; D012710:Serum Albumin, Bovine / Q000737:chemistry; D013059:Spectrum Analysis, Raman
chemical_list: D002021:Buffers; D002135:Calcium-Binding Proteins; D002254:Carbonates; D064030:S100 Calcium Binding Protein G; D012710:Serum Albumin, Bovine; C005686:sodium carbonate; D002119:Calcium Carbonate; D002122:Calcium Chloride