**5. Microbes inspire chemistry: biomimetic synthesis of artificial nanoparticles**

Understanding MB is key not only for the in-depth learning of microbial physiological phenomena, but it can teach us valuable insights for the fabrication of technological materials. Magnetic nanoparticles have emerged as functional materials since the 1940s, when iron oxide powders, with crystals ranging from 60 nm to 1 μm, were used to impregnate recording tapes [72]. In that media, recorded information was engraved through changes in magnetization of the impregnated nanoparticles. Similarly, the biogenic magnetosomes can carry paleomagnetic signals, which can be detected, for instance, through the measurement of their magnetic properties in marine sediments [73]. The roles of bacterial magnetite as magnetofossils is only possible due to their stable single magnetic domain, caused by their controlled size range (20–100 nm) [73, 74]. This magnetic property also permits the utilization of biogenic nanomagnets in research on anticancer and antimicrobial therapy—as drug carriers, contrast agents, and hyperthermal agents—, enzyme immobilization—as recyclable supports—, cell labeling and other applications [11].

Biological materials are precisely arranged at the nanoscale. Hence, biomimetics, which is the art of imitating biological process to architecture novel materials, is proving profitable for nanotechnology industries [75]. One of the foundations of biomimetics is the biodiscovery and bioengineering of surface-binding proteins and peptides [76]. The regular structures present in such biomolecules enables the recognition and the interaction with atomic patterns on the surface of synthetic polymers, semiconductors, and metal oxide crystals [76]. In the case of metal oxides, these interactions occur basically via non-covalent weak bindings like hydrogen bonds and electrostatic dipoles.

In chemical syntheses, the shape- and size-controlled nanoparticles generally are obtained with high temperatures and organic solvents [74]. These consumptions are related to high production costs and environmental impacts during the life cycle of the nanoparticles [74]. One of the simplest and widely utilized techniques for making iron oxide nanoparticles is coprecipitation [74]. In this technique, ferrous and ferric salts are dissolved, and the cations are precipitated in an alkaline aqueous medium. For the synthesis of magnetite, a fixed molar proportion of 2:1 (Fe3+/Fe2+), is precipitated, following the stoichiometry:

3+ 2+ - 2Fe +Fe +8OH Fe O + 4H O → 34 2

**27**

*Biomineralization of Magnetosomes: Billion-Year Evolution Shaping Modern Nanotools*

in it ferrous form before being oxidized to ferric ion by magnetochromes—oxidizing domains of MamP, MamX, MamT and MamE [77]. This is an example of naturally occurring partial oxidation of ferrous ion. Partial oxidation is also used to obtain artificial, biomimetic magnetite [78]. In this case, the ferrous cation is precipitated to form ferrous hydroxide (Fe(OH)2). After that, a strong oxidizing agent, usually nitrate, partially transform Fe2+ to Fe3+, leading to magnetite:

> ( ) 2+ - <sup>2</sup> Fe +2OH Fe OH →

( ) - - 3Fe OH +NO Fe O +3H O+NO <sup>2</sup> 3 34 2 2 →

While coprecipitation leads to nanoparticles of an irregular shape, partial oxidation magnetite has a well-defined faceted morphology and a larger size [78]. Due to its low solubility, Fe(OH)2 tends to form larger precipitates. This is not the case for the coprecipitation of Fe3+ and Fe2+, which tends to form multiple, smaller

Complementary to oxidation control, the surface interaction of the forming magnetic crystal with biomolecules is the main strategy for synthesizing magnetosome-like nanoparticles. A summary of biomolecule-supplemented chemical

MamC protein from *Magnetococcus marinus* strain MC-1 has an effect of enlarging magnetite precipitates [79, 84]. Due to its effect over synthesis, this protein has been expressed for use in different biomimetics studies (**Figure 5**). Different coprecipitation experiments have shown an increase from ~10-25 nm, in control synthesis, to ~30-40 nm, when recombinant MamC from strain MC-1 is added in

In another study, *Ms. magneticum* strain AMB-1-derived Mms6 displays a negative effect on average particle size – 20 nm length down from 32 nm in the control experiment – in partial oxidation and coprecipitation-derived magnetite [80]. Instead, its addition to the reactional medium narrows size distribution regardless of the chemical route. The presence of recombinant Mms6 derived from strain AMB-1 imprints the cubo-octahedral morphology of the naturally occurring magnetosomes onto chemically precipitated crystals. From experiments using mutant clones of strain AMB-1, it has been demonstrated that the anionic residues Asp123, Glu124, and Glu125 effectively participate as key residues of Mms6 for defining crystal morphology are in the protein binding to magnetite [88]. The interactions between these C-terminal side-groups and the magnetite surface ultimately respond for the strong morphology and size controlling character of Mms6 either in

To modulate/improve magnetite chemical synthesis by the use MB proteins, magnetite-interacting components (MICs) of three magnetite-associated proteins (MamC, Mms6, and Mms7) have been subjected to NMR studies to investigate their affinity and binding to the ferrous ion during coprecipitation [81]. In all cases, it has been a clear role of aspartate and glutamate residues to the affinity to the cation [81]. The strong binding of ferrous cation to four anionic residues is related to confinement of iron by Mms6- and Mms7- MICs and, consequently, to the initiation of magnetite nucleation by these proteins. Besides ferrous ion, Mms6 glutamate residues positions 44, 50, and 55 at C-terminal region shows a strong binding affinity to ferric ion [90]. MamC-MIC, in turn, displays a weaker iron-binding but a stronger effect on magnetite size [81]. Thus, the ionotropic (i.e. iron-affinity) effect of MamC does not give sufficient ground for the role of this protein in

*DOI: http://dx.doi.org/10.5772/intechopen.94465*

syntheses of magnetic nanoparticles is in **Table 2**.

concentrations over 10 μg/mL [79, 84].

biologic or biomimetic mineralization [89].

precipitates [78].

This molar proportion is mandatory because it is the same ferrous/ferric ratio within magnetite [77]. In MTB, iron is accumulated inside the magnetosome vesicle *Biomineralization of Magnetosomes: Billion-Year Evolution Shaping Modern Nanotools DOI: http://dx.doi.org/10.5772/intechopen.94465*

in it ferrous form before being oxidized to ferric ion by magnetochromes—oxidizing domains of MamP, MamX, MamT and MamE [77]. This is an example of naturally occurring partial oxidation of ferrous ion. Partial oxidation is also used to obtain artificial, biomimetic magnetite [78]. In this case, the ferrous cation is precipitated to form ferrous hydroxide (Fe(OH)2). After that, a strong oxidizing agent, usually nitrate, partially transform Fe2+ to Fe3+, leading to magnetite:

> ( ) 2+ - <sup>2</sup> Fe +2OH Fe OH →

$$\text{\textbulletFe(OH)}\_{2} \text{\textbullet NO}\_{3}^{\cdot -} \rightarrow \text{Fe}\_{3}\text{O}\_{4} \text{\textbullet \textbullet NO}\_{2}^{\cdot -}$$

While coprecipitation leads to nanoparticles of an irregular shape, partial oxidation magnetite has a well-defined faceted morphology and a larger size [78]. Due to its low solubility, Fe(OH)2 tends to form larger precipitates. This is not the case for the coprecipitation of Fe3+ and Fe2+, which tends to form multiple, smaller precipitates [78].

Complementary to oxidation control, the surface interaction of the forming magnetic crystal with biomolecules is the main strategy for synthesizing magnetosome-like nanoparticles. A summary of biomolecule-supplemented chemical syntheses of magnetic nanoparticles is in **Table 2**.

MamC protein from *Magnetococcus marinus* strain MC-1 has an effect of enlarging magnetite precipitates [79, 84]. Due to its effect over synthesis, this protein has been expressed for use in different biomimetics studies (**Figure 5**). Different coprecipitation experiments have shown an increase from ~10-25 nm, in control synthesis, to ~30-40 nm, when recombinant MamC from strain MC-1 is added in concentrations over 10 μg/mL [79, 84].

In another study, *Ms. magneticum* strain AMB-1-derived Mms6 displays a negative effect on average particle size – 20 nm length down from 32 nm in the control experiment – in partial oxidation and coprecipitation-derived magnetite [80]. Instead, its addition to the reactional medium narrows size distribution regardless of the chemical route. The presence of recombinant Mms6 derived from strain AMB-1 imprints the cubo-octahedral morphology of the naturally occurring magnetosomes onto chemically precipitated crystals. From experiments using mutant clones of strain AMB-1, it has been demonstrated that the anionic residues Asp123, Glu124, and Glu125 effectively participate as key residues of Mms6 for defining crystal morphology are in the protein binding to magnetite [88]. The interactions between these C-terminal side-groups and the magnetite surface ultimately respond for the strong morphology and size controlling character of Mms6 either in biologic or biomimetic mineralization [89].

To modulate/improve magnetite chemical synthesis by the use MB proteins, magnetite-interacting components (MICs) of three magnetite-associated proteins (MamC, Mms6, and Mms7) have been subjected to NMR studies to investigate their affinity and binding to the ferrous ion during coprecipitation [81]. In all cases, it has been a clear role of aspartate and glutamate residues to the affinity to the cation [81]. The strong binding of ferrous cation to four anionic residues is related to confinement of iron by Mms6- and Mms7- MICs and, consequently, to the initiation of magnetite nucleation by these proteins. Besides ferrous ion, Mms6 glutamate residues positions 44, 50, and 55 at C-terminal region shows a strong binding affinity to ferric ion [90]. MamC-MIC, in turn, displays a weaker iron-binding but a stronger effect on magnetite size [81]. Thus, the ionotropic (i.e. iron-affinity) effect of MamC does not give sufficient ground for the role of this protein in

*Materials at the Nanoscale*

**nanoparticles**

to 5.48 ± 1.3 in neutral condition.

nanoparticles with tunable properties.

potential of 0 mV (neutral condition) led to a crystal diameter of 31.5 ± 1.3 nm, which augmented to 37.2 ± 0.6 nm when the culture was carried out at -500 mV (reducing condition) [71]. The reducing condition also caused an increase in the total magnetite mass per cell as 9.1 ± 1.9 magnetosomes were observed per μm (cell length), in contrast

The evidence that characteristics of biogenic magnetite can be modified is of great interest for practical applications because certain purposes may require specific particle properties. Therefore, the knowledge of the interplay between environmental conditions and process regulation by biomolecules in biomineralization can help develop methods for the *in vitro* biomimetic preparation of magnetic

**5. Microbes inspire chemistry: biomimetic synthesis of artificial** 

recyclable supports—, cell labeling and other applications [11].

hydrogen bonds and electrostatic dipoles.

is precipitated, following the stoichiometry:

Understanding MB is key not only for the in-depth learning of microbial physiological phenomena, but it can teach us valuable insights for the fabrication of technological materials. Magnetic nanoparticles have emerged as functional materials since the 1940s, when iron oxide powders, with crystals ranging from 60 nm to 1 μm, were used to impregnate recording tapes [72]. In that media, recorded information was engraved through changes in magnetization of the impregnated nanoparticles. Similarly, the biogenic magnetosomes can carry paleomagnetic signals, which can be detected, for instance, through the measurement of their magnetic properties in marine sediments [73]. The roles of bacterial magnetite as magnetofossils is only possible due to their stable single magnetic domain, caused by their controlled size range (20–100 nm) [73, 74]. This magnetic property also permits the utilization of biogenic nanomagnets in research on anticancer and antimicrobial therapy—as drug carriers, contrast agents, and hyperthermal agents—, enzyme immobilization—as

Biological materials are precisely arranged at the nanoscale. Hence, biomimetics, which is the art of imitating biological process to architecture novel materials, is proving profitable for nanotechnology industries [75]. One of the foundations of biomimetics is the biodiscovery and bioengineering of surface-binding proteins and peptides [76]. The regular structures present in such biomolecules enables the recognition and the interaction with atomic patterns on the surface of synthetic polymers, semiconductors, and metal oxide crystals [76]. In the case of metal oxides, these interactions occur basically via non-covalent weak bindings like

In chemical syntheses, the shape- and size-controlled nanoparticles generally are obtained with high temperatures and organic solvents [74]. These consumptions are related to high production costs and environmental impacts during the life cycle of the nanoparticles [74]. One of the simplest and widely utilized techniques for making iron oxide nanoparticles is coprecipitation [74]. In this technique, ferrous and ferric salts are dissolved, and the cations are precipitated in an alkaline aqueous medium. For the synthesis of magnetite, a fixed molar proportion of 2:1 (Fe3+/Fe2+),

3+ 2+ - 2Fe +Fe +8OH Fe O + 4H O → 34 2

This molar proportion is mandatory because it is the same ferrous/ferric ratio within magnetite [77]. In MTB, iron is accumulated inside the magnetosome vesicle

**26**


*Ms = magnetization saturation at 300 K; CP = coprecipitation; PO = partial oxidation; MIC = magnetiteinteracting component.*

#### **Table 2.**

*Summary of methods for chemical synthesis of biomimetic magnetic nanoparticles.*

biomineralization [84, 91, 92]. MamC must exert a template effect in magnetite formation [84]. In the MM, MamC is constituted by two transmembrane domains connected by alpha-helical looping, which contacts the forming magnetite within the magnetosome vesicle lumen [92]. The distance between iron-interacting residues Glu66 and Asp70 of the alpha-helical looping matches the iron interatomic distance within the magnetite surface plane. The alpha-helical conformation of the MamC-MIC ensures the proper positioning of the points of interaction with iron [91]. The complementary roles of MamC and Mms6 can be combined in a biomimetic synthesis, yielding large magnetosomes (30 ± 10 nm) with well-defined crystal faces [84].

Other MM proteins are also good candidates for use in biomimetics. MamF controls the size monodispersity of nanocrystals. In aqueous solution, this protein forms a self-aggregative proteinosome of approximately 36 nm [82]. When used as an additive in coprecipitation, homogeneously sized nanocrystals are obtained. As in MamC, Mms13 and MmsF have their active loops located between the two transmembrane domains [83]. These active loops were expressed in a chimeric coiled-coil scaffold protein, which was called Mms13cc and MmsFcc. The MmsFcc construct regulated the cuboidal morphology of the produced nanocrystals.

**29**

**Figure 5.**

*uniform morphology.*

nucleation sites [86, 93].

*Biomineralization of Magnetosomes: Billion-Year Evolution Shaping Modern Nanotools*

Taking the inspiration of the interaction between anionic residues and nascent magnetite, the addition of acidic polypeptides is an alternative to recombinant proteins [78]. In the presence of poly-aspartate, partial oxidation synthesis resulted in narrower size distribution of nanocrystals [78]. Using a classical partial oxidation synthesis, 65% of magnetite nanoparticles assumed a facetted shape with a size distribution between 20 and 60 nm. When the synthesis was supplemented with poly-aspartate, a drastic change of the morphology occurred, with 85% of the nanoparticles showing a more rounded shape. However, the size distribution

*Biomimetic route for making size- and shape-controlled magnetite nanoparticles [79]. MamC is a 12.4 kDa magnetite-interacting transmembrane protein found in different species of MTB. The gene encoding this protein in Mc. marinus strain MC-1 (mamC) was cloned in a pTrcHis-TOPO plasmidial expression vector. It was, then, transformed into Escherichia coli TOP10. The transforming E. coli can be cultivated in a large-volume (1–10 L) bioreactor and express the recombinant MamC. After mass-cultivation, expressed MamC, which is found in intracellular inclusion bodies, is recovered and then purified. MamC can be used as an additive for the coprecipitation of iron to synthesize nanometric magnetite. In this synthesis, MamC binds and stabilizes crescent magnetite nuclei. This interaction ultimately results in nanocrystals of narrowly distributed size and* 

As discussed, biomimetic synthesis of magnetite with recombinant magnetosome proteins involves electrostatic interaction between anionic aminoacids with iron cations. Nevertheless, the use of cationic polymers and aminoacids also has been proven successful in imitating characteristics of magnetosomes into artificial magnetite. In those cases, the one accepted chemical mechanism is the dipole stabilization of the negatively charged surface of magnetite crystals by positive side groups, namely amino and guanidine, present in alkaline aminoacids [85, 86]. This phenomenon is supported by the phosphatidylethanolamine composition of the magnetosome vesicle, which exposed positively charged amino groups to the

In one experiment performed at the Max Planck Institute of Colloids and Interfaces, Germany, a wide array of randomly-generated peptides was expressed in phage display and had their binding capacity tested against a magnetite powder [86]. The primary structure of magnetite adhering peptides was then compared to the proteomes of several MTB species, but no significant similarity was spotted.

became significantly narrower, with most particles ranging 15-30 nm.

*DOI: http://dx.doi.org/10.5772/intechopen.94465*

*Biomineralization of Magnetosomes: Billion-Year Evolution Shaping Modern Nanotools DOI: http://dx.doi.org/10.5772/intechopen.94465*

#### **Figure 5.**

*Materials at the Nanoscale*

Magnetosomal proteins

Aminoacids Lysine (0.1 to 10 mM)

Arginine (0.1 to 10 mM)

14-mer peptide (magnetitebinding domain + ovarian cancer target) + ginger extract

*interacting component.*

**Table 2.**

Polyaminoacids and polypeptides

**28**

biomineralization [84, 91, 92]. MamC must exert a template effect in magnetite formation [84]. In the MM, MamC is constituted by two transmembrane domains connected by alpha-helical looping, which contacts the forming magnetite within the magnetosome vesicle lumen [92]. The distance between iron-interacting residues Glu66 and Asp70 of the alpha-helical looping matches the iron interatomic distance within the magnetite surface plane. The alpha-helical conformation of the MamC-MIC ensures the proper positioning of the points of interaction with iron [91]. The complementary roles of MamC and Mms6 can be combined in a biomimetic synthesis, yielding large magnetosomes (30 ± 10 nm) with well-defined crystal faces [84]. Other MM proteins are also good candidates for use in biomimetics. MamF controls the size monodispersity of nanocrystals. In aqueous solution, this protein forms a self-aggregative proteinosome of approximately 36 nm [82]. When used as an additive in coprecipitation, homogeneously sized nanocrystals are obtained. As in MamC, Mms13 and MmsF have their active loops located between the two transmembrane domains [83]. These active loops were expressed in a chimeric coiled-coil scaffold protein, which was called Mms13cc and MmsFcc. The MmsFcc construct regulated the cuboidal morphology of the produced nanocrystals.

*Ms = magnetization saturation at 300 K; CP = coprecipitation; PO = partial oxidation; MIC = magnetite-*

*Summary of methods for chemical synthesis of biomimetic magnetic nanoparticles.*

**Additive(s) Synthesis Size (nm) Shape Ms (emu/g) References**

MamC CP 30–40 Rhomboid — [79]

MamC-MIC CP 26.1 ± 0.61 Cuboid — [81]

MmsF CP 36 Rounded 129 [82]

Active loop of MmsF CP 50 ± 13 Cuboidal 90 [83]

MamC + Mms6 CP 30 ± 10 Rhomboid — [84]

Polyarginine CP 35 ± 5 Irregular — [86] Polyaspartate PO 7.6 ± 1.5 Rounded 78 [78]

CP 21 ± 7 to 29 ± 7 Rhomboid 67 (for

16 ± 7 to 19 ± 6 — 36 (for

CP 7.35 ± 3.7 Irregular 48.9 [87]

octahedral

— [80]

10 mM Lys)

10 mM Arg)

[85]

Mms6 PO 20.2 ± 4.0 Cubo-

Mms6-MIC 19.9 ± 0.36 Rhomboid — Mms7-MIC 18.54 ± 0.29 Cuboid —

MamF 25 Irregular 44

Active loop of Mms13 34 ± 12 Irregular 93

*Biomimetic route for making size- and shape-controlled magnetite nanoparticles [79]. MamC is a 12.4 kDa magnetite-interacting transmembrane protein found in different species of MTB. The gene encoding this protein in Mc. marinus strain MC-1 (mamC) was cloned in a pTrcHis-TOPO plasmidial expression vector. It was, then, transformed into Escherichia coli TOP10. The transforming E. coli can be cultivated in a large-volume (1–10 L) bioreactor and express the recombinant MamC. After mass-cultivation, expressed MamC, which is found in intracellular inclusion bodies, is recovered and then purified. MamC can be used as an additive for the coprecipitation of iron to synthesize nanometric magnetite. In this synthesis, MamC binds and stabilizes crescent magnetite nuclei. This interaction ultimately results in nanocrystals of narrowly distributed size and uniform morphology.*

Taking the inspiration of the interaction between anionic residues and nascent magnetite, the addition of acidic polypeptides is an alternative to recombinant proteins [78]. In the presence of poly-aspartate, partial oxidation synthesis resulted in narrower size distribution of nanocrystals [78]. Using a classical partial oxidation synthesis, 65% of magnetite nanoparticles assumed a facetted shape with a size distribution between 20 and 60 nm. When the synthesis was supplemented with poly-aspartate, a drastic change of the morphology occurred, with 85% of the nanoparticles showing a more rounded shape. However, the size distribution became significantly narrower, with most particles ranging 15-30 nm.

As discussed, biomimetic synthesis of magnetite with recombinant magnetosome proteins involves electrostatic interaction between anionic aminoacids with iron cations. Nevertheless, the use of cationic polymers and aminoacids also has been proven successful in imitating characteristics of magnetosomes into artificial magnetite. In those cases, the one accepted chemical mechanism is the dipole stabilization of the negatively charged surface of magnetite crystals by positive side groups, namely amino and guanidine, present in alkaline aminoacids [85, 86]. This phenomenon is supported by the phosphatidylethanolamine composition of the magnetosome vesicle, which exposed positively charged amino groups to the nucleation sites [86, 93].

In one experiment performed at the Max Planck Institute of Colloids and Interfaces, Germany, a wide array of randomly-generated peptides was expressed in phage display and had their binding capacity tested against a magnetite powder [86]. The primary structure of magnetite adhering peptides was then compared to the proteomes of several MTB species, but no significant similarity was spotted.

However, of the five magnetite-interacting peptides identified in that study, three had arginine as half the residues in the sequence. The cationic poly-arginine was used as an additive to the iron precipitation. The resulting nanoparticles possessed a fine size distribution (30-40 nm), reproducible – despite irregular – morphologies and colloidal stability. These characteristics were not achieved in the control of conventional precipitation. Poly-arginine also improves the tuneability of the biomimetic synthesis. In the presence of the additive, the average diameters of the magnetite precipitates could be adjusted from 10 to 40 nm when the reaction occurred in pHs from 9 to 11, respectively [94].

As polyaminoacids, single aminoacids can promote control over magnetic nanoparticle syntheses [85]. When arginine and lysine were tested for that purpose, the latter was able to control the particle size according to its concentration (**Table 2**) [85]. The side-chain amino group in lysine can perform a steadier stabilization of the anionic oxyhydroxide precursor of magnetite. Then, further growth of lysine-stabilized nuclei enables a larger crystal size with a better-defined hexahedral shape. The control over size and shape also reflects in the magnetic properties of the nanomaterial. The obtained nanoparticles displayed a superparamagnetic behavior, with a large magnetic moment and magnetization saturation (67 emu/g).

Not only is the size dispersity and morphology better controlled in biomimetic synthesis, but the colloidal stability of bioinspired nanomagnets is generally improved. The magnetic core of bare nanomagnets exerts an attractive force, possibly leading to instability to the colloidal suspension [78, 85]. When peptides are added to the precipitation media, functional groups of the same charge become exposed on the nanoparticle surface and counterbalance the attractive force with electrostatic repulsion [78, 85]. Due to the interaction of cationic amino groups with magnetite, carboxyl groups become exposed during coprecipitation with lysine [85]. Thus, the zeta-potential of those nanoparticles was -31 mV at physiological pH, while the control nanoparticles showed a 0 value. The synthesis of magnetite supplemented with poly-aspartate led to nanoparticles with surface-exposed carboxyl groups [78]. Therefore, the measured zeta potential was approximately -30 mV. Because suspension stability in aqueous media is crucial for biomedical applications, the colloidal stability obtained in biomimetic nanoparticles is a fundamental property.

The knowledge gained from biomimetic approaches was used to construct a double-stimuli-responsive nanoformulation consisting of a nanomagnet bound to the antiproliferative drug oxaliplatin [95]. The nanocrystal was synthesized by co-precipitation of iron ions in the presence of recombinant MamC. The magnetiteoxaliplatin bond was stable at pH 7.2. In acidic pH, the release of oxaliplatin was triggered. This release was further boosted by the application of an alternating magnetic field and the cytotoxicity against colorectal cancer cells was improved [95]. The responsive to alternating magnetic fields also enables MamC-derived magnetic nanoparticles to be used in hyperthermia treatments [96]. A 25 mg/mL suspension of the biomimetic nanoparticles exposed to an alternating field of 226 Oe at a 280 kHz frequency can cause a temperature increase of 16.7 °C (specific absorption rate = 47 W/g).

Another functional magnetic nanoparticle was coprecipitated in the presence of a bifunctional polypeptide and ginger extract [87]. The fourteen-residue-long polypeptide was designed from two heptapeptides: a magnetite binding domain and a cell-targeting domain with specificity to ovarian carcinoma cells. The metalreducing and chelating activity of the ginger extract leads to nanoparticles averaging 10 nm in length and 48.9 emu/g of magnetization saturation. When different cell lines – A2780 (ovarian carcinoma) and L929 (mouse fibroblast) – were treated with the functional nanoparticle, the first group exhibited a particle uptake almost 5 times more intense.

**31**

**Author details**

and Fernanda de Avila Abreu\*

provided the original work is properly cited.

*Biomineralization of Magnetosomes: Billion-Year Evolution Shaping Modern Nanotools*

In this chapter, we have summarized how the basic-science knowledge gained through molecular biology, phylogenetics, and metagenomics of MTB can be translated into tools of technological interest. Although the authors had not the pretentiousness of gathering extensive information available on the topic, the chapter evidences how cross-disciplinary research is crucial for understanding and applying such a complex biological phenomenon. This is especially true in a field in

We thank Unidade de Microscopia Multiusuário Souto-Padrón & Lins

This research was funded by Brazilian agencies CNPq, CAPES and FAPERJ.

(UniMicro, UFRJ, Brazil) for the use of their microscopy facility.

Tarcisio Nascimento Correa, Igor Nunes Taveira, Rogerio Presciliano de Souza Filho

© 2020 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium,

Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil

\*Address all correspondence to: fernandaaabreu@micro.ufrj.br

*DOI: http://dx.doi.org/10.5772/intechopen.94465*

which intriguing discoveries are made at a fast pace.

The authors declare no conflicts of interest.

**6. Conclusion**

**Acknowledgements**

**Conflict of interest**

*Biomineralization of Magnetosomes: Billion-Year Evolution Shaping Modern Nanotools DOI: http://dx.doi.org/10.5772/intechopen.94465*
