Protein-supported transition metal catalysts: Preparation, catalytic applications, and prospects

The immobilization of transition metal catalysts onto supports enables their easier recycling and improves catalytic performance. Protein supports not only support and stabilize transition metal catalysts but also enable the incorporation of biocompatibility and enzymatic catalysis into these catalysts. Consequently, the engineering of protein-supported transition metal catalysts (PTMCs) has emerged as an effective approach to improving their catalytic performance and widening their catalytic applications. Here, we review the recent development of the preparation and applications of PTMCs. The preparation of PTMCs will be summarized and discussed in terms of the types of protein supports, including proteins, protein assemblies, protein-polymer conjugates, and cross-linked proteins. Then, their catalytic applications including organic synthesis, photocatalysis, polymerization, and biomedicine, will be surveyed and compared. Meanwhile, the established catalytic structures-function relationships will be summarized. Lastly, the remaining issues and prospects will be discussed. By surveying a wide range of PTMCs, we believe that this review will attract a broad readership and stimulate the development of PTMCs.

Protein encapsulation of nanocatalysts: A feasible approach to facilitate catalytic theranostics

Enzyme-mimicking nanocatalysts, also termed nanozymes, have attracted much attention in recent years. They are considered potential alternatives to natural enzymes due to their multiple catalytic activities and high stability. However, concerns regarding the colloidal stability, catalytic specificity, efficiency and biosafety of nanomaterials in biomedical applications still need to be addressed. Proteins are biodegradable macromolecules that exhibit superior biocompatibility and inherent bioactivities; hence, the protein modification of nanocatalysts is expected to improve their bioavailability to match clinical needs. The diversity of amino acid residues in proteins provides abundant functional groups for the conjugation or encapsulation of nanocatalysts. Moreover, protein encapsulation can not only improve the overall performance of nanocatalysts in biological systems, but also bestow materials with new features, such as targeting and retention in pathological sites. This review aims to report the recent developments and perspectives of protein-encapsulated catalysts in their functional improvements, modification methods and applications in biomedicine.

Proanthocyanin-Capped Biogenic TiO2 Nanoparticles with Enhanced Penetration, Antibacterial and ROS Mediated Inhibition of Bacteria Proliferation and Biofilm Formation: A Comparative Approach

Biofunctionalized TiO₂ nanoparticles with a size range of 18.42±1.3 nm were synthesized in a single-step approach employing Grape seed extract (GSE) proanthocyanin (PAC) polyphenols. The effect of PACs rich GSE corona was examined with respect to 1) the stability and dispersity of as-synthesized GSE-TiO₂ -NPs, 2) their antiproliferative and antibiofilm efficacy, and 3) their propensity for internalization and reactive oxygen species (ROS) generation in urinary tract infections (UTIs) causing Gram-negative Pseudomonas aeruginosa and Gram-positive Staphylococcus saprophyticus strains. State-of-the-art techniques were used to validate GSE-TiO₂ -NPs formation. Comparative Fourier transformed infrared (FTIR) spectral analysis demonstrated that PACs linked functional -OH groups likely play a central role in Ti⁴⁺ reduction and nucleation to GSE-TiO₂ -NPs, while forming a thin, soft corona around nascent NPs to attribute significantly enhanced stability and dispersity. Transmission electron microscopic (TEM) and inductively coupled plasma mass-spectroscopy (ICP-MS) analyses confirmed there was significantly (p<0.05) enhanced intracellular uptake of GSE-TiO₂ -NPs in both Gram-negative and -positive test uropathogens as compared to bare TiO₂ -NPs. Correspondingly, compared to bare NPs, GSE-TiO₂ -NPs induced intracellular ROS formation that corresponded well with dose-dependent inhibitory patterns of cell proliferation and biofilm formation in both the tested strains. Overall, this study demonstrates that -OH rich PACs of GSE corona on biogenic TiO₂ -NPs maximized the functional stability, dispersity and propensity of penetration into planktonic cells and biofilm matrices. Such unique merits warrant the use of GSE-TiO₂ -NPs as a novel, functionally stable and efficient antibacterial nano-formulation to combat the menace of UTIs in clinical settings.

Biomimetic Magnetoliposomes as Oxaliplatin Nanocarriers: In Vitro Study for Potential Application in Colon Cancer

Current chemotherapy for colorectal cancer (CRC) includes the use of oxaliplatin (Oxa), a first-line cytotoxic drug which, in combination with irinotecan/5-fluorouracil or biologic agents, increases the survival rate of patients. However, the administration of this drug induces side effects that limit its application in patients, making it necessary to develop new tools for targeted chemotherapy. MamC-mediated biomimetic magnetic nanoparticles coupled with Oxa (Oxa-BMNPs) have been previously demonstrated to efficiently reduce the IC₅₀ compared to that of soluble Oxa. However, their strong interaction with the macrophages revealed toxicity and possibility of aggregation. In this scenario, a further improvement of this nanoassembly was necessary. In the present study, Oxa-BMNPs nanoassemblies were enveloped in phosphatidylcholine unilamellar liposomes (both pegylated and non-pegylated). Our results demonstrate that the addition of both a lipid cover and further pegylation improves the biocompatibility and cellular uptake of the Oxa-BMNPs nanoassemblies without significantly reducing their cytotoxic activity in colon cancer cells. In particular, with the pegylated magnetoliposome nanoformulation (a) hemolysis was reduced from 5% to 2%, being now hematocompatibles, (b) red blood cell agglutination was reduced, (c) toxicity in white blood cells was eliminated. This study represents a truly stepforward in this area as describes the production of one of the very few existing nanoformulations that could be used for a local chemotherapy to treat CRC.

Bioprospecting solid binding polypeptides for lithium ion battery cathode materials

Biotemplating presents a promising approach to improve the performance of inorganic materials via specific control over morphology, crystal structure, and the size of particles during synthesis and assembly. Among other biotemplates, solid binding polypeptides (SBPs) isolated for the material of interest provide high binding affinity and selectivity due to distinct combinations of functional groups found in amino acids. Nanomaterials assembled and synthesized with SBPs have found widespread applications from drug delivery to catalysis and energy storage due to their improved properties. In this study, the authors describe the identification of SBPs for binding to Li-ion battery cathode materials LiCoPO₄, LiMn_1.5Ni_0.5O₄, and LiMn₂O₄, which all have potential for improvement toward their theoretical values. The binding affinity of isolated peptides was assessed via phage binding assays and confirmed with electron microscopy in order to select for potential biotemplates. The authors demonstrate ten binding peptides for each material and analyze the sequences for enrichment in specific amino acids toward each structure (olivine and spinel oxide), as well as the test for specificity of selected sequences. In further studies, the authors believe that the isolated SBPs will serve as a template for synthesis and aid in assembly of cathode materials resulting in improved electrochemical properties for Li-ion batteries.

Hydroxyapatite Formation on Self-Assembling Peptides with Differing Secondary Structures and Their Selective Adsorption for Proteins

Self-assembling peptides have been employed as biotemplates for biomineralization, as the morphologies and sizes of the inorganic materials can be easily controlled. We synthesized two types of highly ordered self-assembling peptides with different secondary structures and investigated the effects of secondary structures on hydroxyapatite (HAp) biomineralization of peptide templates. All as-synthesized HAp-peptides have a selective protein adsorption capacity for basic protein (e.g., cytochrome c and lysozyme). Moreover, the selectivity was improved as peptide amounts increased. In particular, peptide-HAp templated on β-sheet peptides adsorbed more cytochrome c than peptide-HAp with α-helix structures, due to the greater than 2-times carboxyl group density at their surfaces. It can be expected that self-assembled peptide-templated HAp may be used as carriers for protein immobilization in biosensing and bioseparation applications and as enzyme-stabilizing agents.

Tuning properties of biomimetic magnetic nanoparticles by combining magnetosome associated proteins

The role of magnetosome associated proteins on the in vitro synthesis of magnetite nanoparticles has gained interest, both to obtain a better understanding of the magnetosome biomineralization process and to be able to produce novel magnetosome-like biomimetic nanoparticles. Up to now, only one recombinant protein has been used at the time to in vitro form biomimetic magnetite precipitates, being that a scenario far enough from what probably occurs in the magnetosome. In the present study, both Mms6 and MamC from Magnetococcus marinus MC-1 have been used to in vitro form biomimetic magnetites. Our results show that MamC and Mms6 have different, but complementary, effects on in vitro magnetite nucleation and growth. MamC seems to control the kinetics of magnetite nucleation while Mms6 seems to preferably control the kinetics for crystal growth. Our results from the present study also indicate that it is possible to combine both proteins to tune the properties of the resulting biomimetic magnetites. In particular, by changing the relative ratio of these proteins, better faceted and/or larger magnetite crystals with, consequently, different magnetic moment per particle could be obtained. This study provides with tools to obtain new biomimetic nanoparticles with a potential utility for biotechnological applications.

Plant/Bacterial Virus-Based Drug Discovery, Drug Delivery, and Therapeutics

Viruses have recently emerged as promising nanomaterials for biotechnological applications. One of the most important applications of viruses is phage display, which has already been employed to identify a broad range of potential therapeutic peptides and antibodies, as well as other biotechnologically relevant polypeptides (including protease inhibitors, minimizing proteins, and cell/organ targeting peptides). Additionally, their high stability, easily modifiable surface, and enormous diversity in shape and size, distinguish viruses from synthetic nanocarriers used for drug delivery. Indeed, several plant and bacterial viruses (e.g., phages) have been investigated and applied as drug carriers. The ability to remove the genetic material within the capsids of some plant viruses and phages produces empty viral-like particles that are replication-deficient and can be loaded with therapeutic agents. This review summarizes the current applications of plant viruses and phages in drug discovery and as drug delivery systems and includes a discussion of the present status of virus-based materials in clinical research, alongside the observed challenges and opportunities.

Complementary Design for Pairing between Two Types of Nanoparticles Mediated by a Bispecific Antibody: Bottom-Up Formation of Porous Materials from Nanoparticles

Recent advances in biotechnology have enabled the generation of antibodies with high affinity for the surfaces of specific inorganic materials. Herein, we report the synthesis of functional materials from multiple nanomaterials by using a small bispecific antibody recombinantly constructed from gold-binding and ZnO-binding antibody fragments. The bispecific antibody-mediated spontaneous linkage of gold and ZnO nanoparticles forms a binary gold-ZnO nanoparticle composite membrane. The relatively low melting point of the gold nanoparticles and the solubility of ZnO in dilute acidic solution then allowed for the bottom-up synthesis of a nanoporous gold membrane by means of a low-energy, low-environmental-load protocol. The nanoporous gold membrane showed high catalytic activity for the reduction of p-nitrophenol to p-aminophenol by sodium borohydride. Here, we show the potential utility of nanoparticle pairing mediated by bispecific antibodies for the bottom-up construction of nanostructured materials from multiple nanomaterials.

Interactions between Metal Oxides and Biomolecules: from Fundamental Understanding to Applications

Metallo-oxide (MO)-based bioinorganic nanocomposites promise unique structures, physicochemical properties, and novel biochemical functionalities, and within the past decade, investment in research on materials such as ZnO, TiO₂, SiO₂, and GeO₂ has significantly increased. Besides traditional approaches, the synthesis, shaping, structural patterning, and postprocessing chemical functionalization of the materials surface is inspired by strategies which mimic processes in nature. Would such materials deliver new technologies? Answering this question requires the merging of historical knowledge and current research from different fields of science. Practically, we need an effective defragmentation of the research area. From our perspective, the superficial accounting of material properties, chemistry of the surfaces, and the behavior of biomolecules next to such surfaces is a problem. This is particularly of concern when we wish to bridge between technologies in vitro and biotechnologies in vivo. Further, besides the potential practical technological efficiency and advantages such materials might exhibit, we have to consider the wider long-term implications of material stability and toxicity. In this contribution, we present a critical review of recent advances in the chemistry and engineering of MO-based biocomposites, highlighting the role of interactions at the interface and the techniques by which these can be studied. At the end of the article, we outline the challenges which hamper progress in research and extrapolate to developing and promising directions including additive manufacturing and synthetic biology that could benefit from molecular level understanding of interactions occurring between inanimate (abiotic) and living (biotic) materials.

Bioinspired Silicification Reveals Structural Detail in Self-Assembled Peptide Cages

Understanding how molecules in self-assembled soft-matter nanostructures are organized is essential for improving the design of next-generation nanomaterials. Imaging these assemblies can be challenging and usually requires processing, e.g., staining or embedding, which can damage or obscure features. An alternative is to use bioinspired mineralization, mimicking how certain organisms use biomolecules to template mineral formation. Previously, we have reported the design and characterization of Self-Assembled peptide caGEs (SAGEs) formed from de novo peptide building blocks. In SAGEs, two complementary, 3-fold symmetric, peptide hubs combine to form a hexagonal lattice, which curves and closes to form SAGE nanoparticles. As hexagons alone cannot tile onto spheres, the network must also incorporate nonhexagonal shapes. While the hexagonal ultrastructure of the SAGEs has been imaged, these defects have not been observed. Here, we show that positively charged SAGEs biotemplate a thin, protective silica coating. Electron microscopy shows that these SiO2-SAGEs do not collapse, but maintain their 3D shape when dried. Atomic force microscopy reveals a network of hexagonal and irregular features on the SiO2-SAGE surface. The dimensions of these (7.2 nm ± 1.4 nm across, internal angles 119.8° ± 26.1°) are in accord with the designed SAGE network and with coarse-grained modeling of the SAGE assembly. The SiO2-SAGEs are permeable to small molecules (<2 nm), but not to larger biomolecules (>6 nm). Thus, bioinspired silicification offers a mild technique that preserves soft-matter nanoparticles for imaging, revealing structural details <10 nm in size, while also maintaining desirable properties, such as permeability to small molecules.

Visualization of stable ferritin complexes with palladium, rhodium and iridium nanoparticles detected by their catalytic activity in native polyacrylamide gels

The reductive discoloration of azo dye, Congo red, catalyzed by noble metal nanoparticles was used to visualize protein-metal complexes in native polyacrylamide gels after counterstaining with Coomassie blue. This technique was used to characterize the synthesis of palladium, rhodium and iridium nanoparticles encapsulated in Pyrococcus furiosus ferritin.

Controlled cobalt doping in the spinel structure of magnetosome magnetite: new evidences from element- and site-specific X-ray magnetic circular dichroism analyses

The biomineralization of magnetite nanocrystals (called magnetosomes) by magnetotactic bacteria (MTB) has attracted intense interest in biology, geology and materials science due to the precise morphology of the particles, the chain-like assembly and their unique magnetic properties. Great efforts have been recently made in producing transition metal-doped magnetosomes with modified magnetic properties for a range of applications. Despite some successful outcomes, the coordination chemistry and magnetism of such metal-doped magnetosomes still remain largely unknown. Here, we present new evidences from X-ray magnetic circular dichroism (XMCD) for element- and site-specific magnetic analyses that cobalt is incorporated in the spinel structure of the magnetosomes within Magnetospirillum magneticum AMB-1 through the replacement of Fe(2+) ions by Co(2+) ions in octahedral (Oh) sites of magnetite. Both XMCD at Fe and Co L2,3 edges, and energy-dispersive X-ray spectroscopy on transmission electron microscopy analyses reveal a heterogeneous distribution of cobalt occurring either in different particles or inside individual particles. Compared with non-doped one, cobalt-doped magnetosome sample has lower Verwey transition temperature and larger magnetic coercivity, related to the amount of doped cobalt. This study also demonstrates that the addition of trace cobalt in the growth medium can significantly improve both the cell growth and the magnetosome formation within M. magneticum AMB-1. Together with the cobalt occupancy within the spinel structure of magnetosomes, this study indicates that MTB may provide a promising biomimetic system for producing chains of metal-doped single-domain magnetite with an appropriate tuning of the magnetic properties for technological and biomedical applications.

Protein-Mediated Biotemplating on the Nanoscale

Purified proteins offer a homogeneous population of biological nanoparticles, equipped in many cases with specific binding sites enabling the directed self-assembly of envisaged one-, two- or three-dimensional arrays. These arrays may serve as nanoscale biotemplates for the preparation of novel functional composite materials, which exhibit potential applications, especially in the fields of nanoelectronics and optical devices. This review provides an overview of the field of protein-mediated biotemplating, focussing on achievements made throughout the past decade. It is comprised of seven sections designed according to the size and configuration of the protein-made biotemplate. Each section describes the design and size of the biotemplate, the resulting hybrid structures, the fabrication methodology, the analytical tools employed for the structural analysis of the hybrids obtained, and, finally, their claimed/intended applications and a feasibility demonstration (whenever available). In conclusion, a short assessment of the overall status of the achievements already made vs. the future challenges of this field is provided.

Bio-fabricated silver nanoparticles preferentially targets Gram positive depending on cell surface charge

Recently bio-inspired experimental processes for synthesis of nanoparticles are receiving significant attention in nanobiotechnology. Silver nanoparticles (Ag NPs) have been used very frequently in recent times to the wounds, burns and bacterial infections caused by drug-resistant microorganisms. Though, the antibacterial effects of Ag NPs on some multi drug-resistant bacteria specially against Gram positive bacteria has been established, but further investigation is needed to elicit its effectiveness against Gram negatives and to identify the probable mechanism of action. Thus, the present study was conducted to synthesize Ag NPs using Andrographis paniculata leaf extract and to investigate its antibacterial efficacy. After synthesis process the biosynthesized nanoparticles were purified and characterized with the help of various physical measurement techniques which raveled their purity, stability and small size range. The antimicrobial activity of Ag NPs was determined against both Gram-positive Enterococcus faecalis and Gram-negative Proteus vulgaris. Results showed comparatively higher antibacterial efficacy of Ag NPs against Gram positive Enterococcus faecalis strains. It was found that greater difference in zeta potential values between Gram positive bacteria and Ag NPs triggers better internalization of the particles. Thus the cell surface charge played vital role in cell killing which was confirmed by surface zeta potential study. Finally it may be concluded that green synthesized Ag NPs using Andrographis paniculata leaf extract can be very useful against both multi drug resistant Gram-positive and Gram-negative bacteria.

Bioinspired synthesis of magnetite nanoparticles

Magnetite (Fe3O4) is a widespread magnetic iron oxide encountered in many biological and geological systems, and also in many technological applications. The magnetic properties of magnetite crystals depend strongly on the size and shape of its crystals. Hence, engineering magnetite nanoparticles with specific shapes and sizes allows tuning their properties to specific applications in a wide variety of fields, including catalysis, magnetic storage, targeted drug delivery, cancer diagnostics and magnetic resonance imaging (MRI). However, synthesis of magnetite with a specific size, shape and a narrow crystal size distribution is notoriously difficult without using high temperatures and non-aqueous media. Nevertheless, living organisms such as chitons and magnetotactic bacteria are able to form magnetite crystals with well controlled sizes and shapes under ambient conditions and in aqueous media. In these biomineralization processes the organisms use a twofold strategy to control magnetite formation: the mineral is formed from a poorly crystalline precursor phase, and nucleation and growth are controlled through the interaction of the mineral with biomolecular templates and additives. Taking inspiration from this biological strategy is a promising route to achieve control over the kinetics of magnetite crystallization under ambient conditions and in aqueous media. In this review we first summarize the main characteristics of magnetite and what is known about the mechanisms of magnetite biomineralization. We then describe the most common routes to synthesize magnetite and subsequently will introduce recent efforts in bioinspired magnetite synthesis. We describe how the use of poorly ordered, more soluble precursors such as ferrihydrite (FeH) or white rust (Fe(OH)2) can be employed to control the solution supersaturation, setting the conditions for continued growth. Further, we show how the use of various organic additives such as proteins, peptides and polymers allows for either the promotion or inhibition of magnetite nucleation and growth processes. At last we discuss how the formation of magnetite-based organic-inorganic hybrids leads to new functional nanomaterials.

Nano- and micro-patterning biotemplated magnetic CoPt arrays

Patterned thin-films of magnetic nanoparticles (MNPs) can be used to make: surfaces for manipulating and sorting cells, sensors, 2D spin-ices and high-density data storage devices. Conventional manufacture of patterned magnetic thin-films is not environmentally friendly because it uses high temperatures (hundreds of degrees Celsius) and high vacuum, which requires expensive specialised equipment. To tackle these issues, we have taken inspiration from nature to create environmentally friendly patterns of ferromagnetic CoPt using a biotemplating peptide under mild conditions and simple apparatus. Nano-patterning via interference lithography (IL) and micro-patterning using micro-contact printing (μCP) were used to create a peptide resistant mask onto a gold surface under ambient conditions. We redesigned a biotemplating peptide (CGSGKTHEIHSPLLHK) to self-assemble onto gold surfaces, and mineralised the patterns with CoPt at 18 °C in water. Ferromagnetic CoPt is biotemplated by the immobilised peptides, and the patterned MNPs maintain stable magnetic domains. This bioinspired study offers an ecological route towards developing biotemplated magnetic thin-films for use in applications such as sensing, cell manipulation and data storage.

Size-Controlled Formation of Noble-Metal Nanoparticles in Aqueous Solution with a Thiol-Free Tripeptide

A combinatorial screening revealed the peptide H-His-d-Leu-d-Asp-NH2 (1) as an additive for the generation of monodisperse, water-soluble palladium nanoparticles with average diameters of 3 nm and stabilities of over 9 months. The tripeptide proved to be also applicable for the size-controlled formation of other noble-metal nanoparticles (Pt and Au). Studies with close analogues of peptide 1 revealed a specific role of each of the three amino acids for the formation and stabilization of the nanoparticles. These data combined with microscopic and spectroscopic analyses provided insight into the structure of the self-assembled peptidic monolayer around the metal core. The results open interesting prospects for the development of functionalized metal nanoparticles.

Advances in nanoscale alloys and intermetallics: low temperature solution chemistry synthesis and application in catalysis

Based on the bottom-up chemistry techniques, the size, shape, and composition controlled synthesis of nanoparticles can now be achieved uniformly, which is of great importance to the nanoscience community as well as in modern catalysis research. The low-temperature solution-phase synthesis approach represents one of the most attractive strategies and has been utilized to synthesize nanoscale metals, alloys and intermetallics, including a number of new metastable phases. This perspective will highlight the solution-based nanoparticle synthesis techniques, a low-temperature platform, for the synthesis of size and shape-tunable nanoscale transition metals, alloys, and intermetallics from the literature, keeping a focus on the utility of these nanomaterials in understanding the catalysis. For each solution-based nanoparticle synthesis technique, a comprehensive overview has been given for the reported nanoscale metals, alloys, and intermetallics, followed by critical comments. Finally, their enhanced catalytic activity and durability as novel catalysts have been discussed towards several hydrogenation/dehydrogenation reactions and also for different inorganic to organic reactions. Hence, the captivating advantages of this controllable low-temperature solution chemistry approach have several important implications and together with them this approach provides a promising route to the development of next-generation nanostructured metals, alloys, and intermetallics since they possess fascinating properties as well as outstanding catalytic activity.

Facile synthesis of a biocompatible silver nanoparticle derived tripeptide supramolecular hydrogel for antibacterial wound dressings

Through a mineralization process, Nap-FFC peptides produced transparent silver nanoparticle-based hydrogels (AgNPs@Nap-FFC) for antibacterial wound dressing.

Recent advances in noble metal based composite nanocatalysts: colloidal synthesis, properties, and catalytic applications

This Review article provides a report on progress in the synthesis, properties and catalytic applications of noble metal based composite nanomaterials. We begin with a brief discussion on the categories of various composite materials. We then present some important colloidal synthetic approaches to the composite nanostructures; here, major attention has been paid to bimetallic nanoparticles. We also introduce some important physiochemical properties that are beneficial from composite nanomaterials. Finally, we highlight the catalytic applications of such composite nanoparticles and conclude with remarks on prospective future directions.

Bio-inspired synthesis of metal nanomaterials and applications

This critical review focuses on recent advances in the bio-inspired synthesis of metal nanomaterials (MNMs) using microorganisms, viruses, plants, proteins and DNA molecules as well as their applications in various fields. Prospects in the design of bio-inspired MNMs for novel applications are also discussed.

Taking a hard line with biotemplating: cobalt-doped magnetite magnetic nanoparticle arrays

Rapid advancements made in technology, and the drive towards miniaturisation, means that we require reliable, sustainable and cost effective methods of manufacturing a wide range of nanomaterials. In this bioinspired study, we take advantage of millions of years of evolution, and adapt a biomineralisation protein for surface patterning of biotemplated magnetic nanoparticles (MNPs). We employ soft-lithographic micro-contact printing to pattern a recombinant version of the biomineralisation protein Mms6 (derived from the magnetotactic bacterium Magnetospirillum magneticum AMB-1). The Mms6 attaches to gold surfaces via a cysteine residue introduced into the N-terminal region. The surface bound protein biotemplates highly uniform MNPs of magnetite onto patterned surfaces during an aqueous mineralisation reaction (with a mean diameter of 90 ± 15 nm). The simple addition of 6% cobalt to the mineralisation reaction maintains the uniformity in grain size (with a mean diameter of 84 ± 14 nm), and results in the production of MNPs with a much higher coercivity (increased from ≈ 156 Oe to ≈ 377 Oe). Biotemplating magnetic nanoparticles on patterned surfaces could form a novel, environmentally friendly route for the production of bit-patterned media, potentially the next generation of ultra-high density magnetic data storage devices. This is a simple method to fine-tune the magnetic hardness of the surface biotemplated MNPs, and could easily be adapted to biotemplate a wide range of different nanomaterials on surfaces to create a range of biologically templated devices.

A biomimetic mussel-inspired photoelectrochemical biosensing chip for the sensitive detection of CD146

A universal biomimetic mussel-inspired photoelectrochemical biosensing chip was constructed by a polydopamine coating strategy.

Growth kinetics and mechanistic action of reactive oxygen species released by silver nanoparticles from Aspergillus niger on Escherichia coli

Silver Nanoparticles (AgNPs), the real silver bullet, are known to have good antibacterial properties against pathogenic microorganisms. In the present study AgNPs were prepared from extracellular filtrate of Aspergillus niger. Characterization of AgNPs by UV-Vis spectrum reveals specific surface plasmon resonance at peak 416 nm; TEM photographs revealed the size of the AgNPs to be 20–55 nm. Average diameter of the produced AgNPs was found to be 73 nm with a zeta potential that was −24 mV using Malvern Zetasizer. SEM micrographs showed AgNPs to be spherical with smooth morphology. EDS revealed the presence of pure metallic AgNPs along with carbon and oxygen signatures. Of the different concentrations (0, 2.5, 5, 10, and 15 μg/mL) used 10 μg/mL were sufficient to inhibit 10⁷ CFU/mL of E. coli. ROS production was measured using DCFH-DA method and the the free radical generation effect of AgNPs on bacterial growth inhibition was investigated by ESR spectroscopy. This paper not only deals with the damage inflicted on microorganisms by AgNPs but also induces cell death through the production of ROS released by AgNPs and also growth kinetics of E. coli supplemented with AgNPs produced by A. niger.

Protein-directed approaches to functional nanomaterials: a case study of lysozyme

Using lysozyme as a model, protein-directed approaches to functional nanomaterials were reviewed, making rational materials design possible in the future.

Biotemplating Magnetic Nanoparticles on Patterned Surfaces for Potential Use in Data Storage

Thin-films of magnetic nanoparticles (MNPs) with high coercivities are deposited onto surfaces for use in data storage applications. This usually requires specialist clean-room facilities, sputtering equipment and high temperatures to achieve the correct crystallographic phases. One possible cheaper and more environmentally friendly alternative could be to use biomolecules. Many biomineralization and biotemplating molecules have been identified that are able to template a wide range of technologically relevant materials using mild, aqueous chemistry under physiological reaction conditions. Here, we have designed a dual affinity peptide (DAP) sequence to template MNPs onto a surface. One end of the DAP has a high binding affinity for SiO2 and the other for MNPs of the L10 phase of CoPt, a high coercivity magnetic material. Images of the biomineralized substrates show that nanoparticles of CoPt are localized onto the areas that were functionalized with the biotemplating DAP. Magnetic force microscopy (MFM) plots of the biotemplated nanoparticles show that there is magnetic contrast on the patterned surface.

Formation of ferric oxyhydroxide nanoparticles mediated by peptides in anchovy (Engraulis japonicus) muscle protein hydrolysate

Nanosized iron fortificants appear to be promising and can be synthesized in a greener way using peptides as biotemplates. Anchovy is a huge underdeveloped source of muscle protein that enhances human nonheme iron absorption. This paper shows that peptides in anchovy ( Engraulis japonicus ) muscle protein hydrolysate (AMPH) mediate the formation of monodispersed ferric oxyhydroxide nanoparticles (FeONPs) with diameters of 20-40 nm above pH 3.0. Peptides in AMPH nucleate iron through carboxyl groups and crystal growth then occur as a result of condensation of carboxylate-ligated hydroxide iron centers, yielding Fe-O-Fe cross-link bonds. Monomers of FeONPs are formed after steric obstruction of further crystal growth by peptide backbones with certain lengths and further stabilized by surface-adsorbed peptides. The iron-loading capacity of peptides in AMPH is up to 27.5 mg iron/g peptide. Overall, the present study provides a greener alternative route to the synthesis of FeONPs.