Biomimetic Magnetite Formation: From Biocombinatorial Approaches to Mineralization Effects

Abstract

Biological materials typically display complex morphologies and hierarchical architectures, properties that are hardly matched by synthetic materials. Understanding the biological control of mineral properties will enable the development of new synthetic approaches toward biomimetic functional materials. Here, we combine biocombinatorial approaches with a proteome homology search and in vitro mineralization assays to assess the role of biological determinants in biomimetic magnetite mineralization. Our results suggest that the identified proteins and biomimetic polypeptides influence nucleation in vitro. Even though the in vivo role cannot be directly determined from our experiments, we can rationalize the following design principles: proteins, larger complexes, or membrane components that promote nucleation in vivo are likely to expose positively charged residues to a negatively charged crystal surface. In turn, components with acidic (negatively charged) functionality are nucleation inhibitors, which stabilize an amorphous structure through the coordination of iron.

Genetic and biochemical investigations of the role of MamP in redox control of iron biomineralization inMagnetospirillum magneticum

“…Further studies with Mms7ct indicate that it and other Mms proteins may play a more significant role in controlling magnetite mineral structure than previously hypothesized. Beyond simple control of size and shape of magnetite (29,30), they may also template the crystal lattice of the mineral itself similar to what has been observed with calcium biomineralization, where unstable crystal forms and phases of the mineral are stabilized by interaction with peptides and other macromolecules (1,2). In the specific case of iron minerals, lattice stabilization could also affect the redox potential of individual Fe atoms within the mineral.…”

“…In addition to redox partners that are necessary to generate both Fe(II) and Fe(III), there also exist small magnetosome proteins proposed to template mineralization by direct binding to the material (28) analogous to the more wellunderstood mineralization of calcium. These Mms proteins were identified by their tight association with the magnetite nanoparticles isolated from magnetotactic bacteria and have been shown experimentally to be able to control mineral shape in vitro through their highly acidic C-terminal sequences (29,30). Similar to other magnetotactic bacteria, the MAI of AMB-1 contains multiple mms genes, mms5 (mamG), mms6, and mms7 (mamD), which have been previously shown to possess overlapping genetic function as all genes must be deleted to observe the resulting biomineralization defect (12).…”

Single crystalline superstructured stable single domain magnetite nanoparticles

“…While such processes lead to the formation of SSD particles, imaging by transmission electron microscopy (TEM) has shown the particles to be widely dispersed in size due to aggregation20. The use of additives was reported to control the mechanism of magnetite formation and possibly the resulting nanoparticle dimensions2122232425. Here, we show that the addition of polyarginine mostly leads to the formation of 40 nm monodisperse magnetite particles that are made from 10 nm sub-domains, yet possess true SSD properties.…”

A Bioinspired Coprecipitation Method for the Controlled Synthesis of Magnetite Nanoparticles

“…21 VSM showed that the saturation magnetization (M s ) was 77 Am 2 /kg and that the coercivity (H c ) was 8 mT (Figure 7c), which reflect the decrease in the average crystal size as compared to the control (Figure 3e). The same Table 1, entry (a) 4, (b) 1, (c) 5, (d) 2, (e) 8, (f) 7 and (g) 3, which demonstrate that all crystal sizes between ∼15 nm and ∼60 nm are accessible through the manipulation of the experimental conditions.…”