Oxide Formation on Biological Nanostructures via a Structure-Directing Agent: Towards an Understanding of Precise Structural Transcription

Investigations on the Impact of a Series of Alkoxysilane Precursors on the Structure, Morphology and Wettability of an Established Zirconium-Modified Hybrid Anticorrosion Sol-Gel Coating

The current study reports on the impact of a series of functional alkoxysilanes on the wettability and structure of a well-established silicon/zirconium hybrid anticorrosion sol-gel coating. The selected functional alkoxysilanes comprise tetra ethylorthosilicate (TEOS), 3-glycidyloxypropyltrimethoxysilane (GPTMS), 3-aminopropyltriethoxysilane (APTES) and vinyltriethoxysilane (VTES) and are incorporated at various concentrations (1, 5, 10 and 20%) within the silicon/zirconium sol-gel material. The prepared materials are successfully processed as coatings and cured at different temperatures in the range of 100-150 °C. The characterisation of the structures and surfaces is performed by dynamic light scattering (DLS), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), silicon nuclear magnetic resonance spectroscopy (29Si-NMR), atomic force microscopy (AFM) and static water contact angle (WCA). Structural characterisations (DLS, FTIR,29Si-NMR) show that the functional alkoxysilanes effectively bind at the surface of the reference sol-gel material, resulting in the formation of functional core-shell nanoparticles. WCA results show that the hydrophobic properties of all materials decrease with curing temperature, and AFM analysis demonstrated that this behaviour is associated with a decrease in roughness. The physico-chemical processes taking place are critically assigned and discussed.

Virus-Like Particle-Templated Silica-Adjuvanted Nanovaccines with Enhanced Humoral and Cellular Immunity

Virus-like particles (VLPs) are self-assembled viral proteins that represent a superior form of antigens in vaccine formulations. To enhance immunogenicity, adjuvants, especially the aluminum salts (Alum), are essentially formulated in VLP vaccines. However, Alum only induce biased humoral immune responses that limits further applications of VLP-based vaccines. To stimulate more balanced immunity, we, herein, develop a one-step strategy of using VLPs as the biotemplates to synthesize raspberry-like silica-adjuvanted VLP@Silica nanovaccines. Hepatitis B surface antigen (HBsAg) VLPs and human papillomavirus type 18 (HPV 18) VLPs are selected as model templates. Circular dichroism (CD) and affinity analyses demonstrate that HBsAg VLPs in the nanovaccines maintain their secondary structure and immunogenicity, respectively. VLP@Silica promote silica dissolution-induced lysosomal escape and cytosolic delivery of antigens, and enhance the secretion of both Th1 and Th2 type cytokines in murine bone marrow-derived dendritic cells (BMDCs). Additionally, they could improve antigen trafficking and mediate DC activation in draining lymph nodes (DLNs). Vaccination study demonstrate that both HBsAg VLP@Silica and HPV 18 VLP@Silica nanovaccines induce enhanced antigen-specific antibody productions and T-cell mediated adaptive immune responses. This design strategy can utilize VLPs derived from a diversity of viruses or their variants as templates to construct both prophylactic and therapeutic vaccines with improved immunogenicity.

Surface functionalization of anticoagulation and anti-nonspecific adsorption with recombinant hirudin modification

Surface functionalization to improve the blood compatibility is pivotal for the application of biomaterials. In this article, the surface of silicon was first functionalized with chemical groups, such as amino, quinone and phenol groups by the self-polymerization of dopamine, which were used to immobilize anticoagulant drugs hirudin. The detailed analysis and discussion about the grafting groups, morphology, wettability, the dynamic adsorption of proteins, the cytological property and the blood compatibility on the surfaces were carried on by the technology of contact angle, X-ray photoelectron spectroscopy, quartz crystal microbalance, endothelial cells culture and anticoagulant blood test in vivo. The surface with hirudin modification exhibited hydrophilic property and significantly inhibited the nonspecific adsorption of albumin, while it was more approachable to fibronectin. In vitro study displayed that the surface loaded with hirudin could promote the proliferation of endothelial cells. The evaluation of anticoagulant showed good anti-adhesion effect on platelets and the hemolysis rate decreased significantly to less than 0.4%. Activated partial thromboplastin time (APTT) of the silicon wafer loaded with hirudin can exceed 38 s, and the APTT prolongs as the hirudin concentration rises. This study suggested that such simple but effective surface functionalization technique, combining excellent anticoagulant activity together with reendothelialization potential due to the preferable fibronectin adsorption, provide great practical significance to the application of cardiovascular materials.

Biodegradable nanocarriers based on chitosan-modified mesoporous silica nanoparticles for delivery of methotrexate for application in breast cancer treatment

Nanocarriers have demonstrated great promise in the delivery of hydrophobic drugs particularly to tumor spaces by enhanced permeability and retention (EPR) effects. Mesoporous silica nanoparticles (MSNs) are the attractive nanocarrier system to reduce the drug's toxic side effects, enable controlled drug release, prevent drug degradation and provide a biocompatible and biodegradable high surface area carrier. Surface-modified MSNs have been applied to increase drug loading and efficiency. In this study, functionalized MSNs loaded with methotrexate (MTX) were designed for use as a cytotoxic agent. The MSNs were first modified with 3-triethoxysilylpropylamine (APTES) and then with chitosan through covalent coupling mediated by glutaraldehyde. The physicochemical properties of the nanoparticles were optimized for each step. The loading percentage (12.2%) and release profile of MTX as an anti-breast cancer drug, loaded at amine-modified MSNs, were measured via high performance liquid chromatography (HPLC). Moreover, the uptake profiles of fluorescein isothiocyanate (FITC)-labeled MSN-APTES-chitosan with or without MTX were monitored on MCF7 cancer cells via confocal microscopy. Following exposure of nanoparticles to body fluids, they were surrounded by specific proteins that may affect their cellular uptake. Hence, the adsorption profiles of protein corona on the surface of MSN, amine-modified MSN and MTX-loaded MSN-APTES-chitosan were analyzed. The cytotoxic potential for killing breast cancer cells was also studied. The MTX loaded MSN-APTES-chitosan showed a positive effect at a low dose (0.5 μM MTX). In this study, we introduce a new method to synthesize biodegradable MSNs with small and uniform particle size, achieve high MTX loading via covalent amine and chitosan-functionalization, monitor the cellular uptake and demonstrate the potential to decrease the viability of breast cancer cells at low dose.

Nanoparticle-Plant Interactions: Two-Way Traffic

In this Review, an effort is made to discuss the most recent progress and future trend in the two-way traffic of the interactions between plants and nanoparticles (NPs). One way is the use of plants to synthesize NPs in an environmentally benign manner with a focus on the mechanism and optimization of the synthesis. Another way is the effects of synthetic NPs on plant fate with a focus on the transport mechanisms of NPs within plants as well as NP-mediated seed germination and plant development. When NPs are in soil, they can be adsorbed at the root surface, followed by their uptake and inter/intracellular movement in the plant tissues. NPs may also be taken up by foliage under aerial deposition, largely through stomata, trichomes, and cuticles, but the exact mode of NP entry into plants is not well documented. The NP-plant interactions may lead to inhibitory or stimulatory effects on seed germination and plant development, depending on NP compositions, concentrations, and plant species. In numerous cases, radiation-absorbing efficiency, CO2 assimilation capacity, and delay of chloroplast aging have been reported in the plant response to NP treatments, although the mechanisms involved in these processes remain to be studied.

Purple heart plant leaves extract-mediated silver nanoparticle synthesis: Optimization by Box-Behnken design

The present research work describes a novel method for green synthesis of silver nanoparticles using purple heart plant leaves extract, which is recognized as frequently found in households as an ornamental plant. The aqueous methanolic extract of purple heart plant leaves was prepared and employed in the synthesis of stable silver nanoparticles via biological reduction method. The purple heart plant leaves extract-mediated synthesized silver nanoparticles were systematically optimized using Box-Behnken design considering the effect of various independent variables (factors) like concentration of AgNO₃, temperature and volume of purple heart plant leaves extract solution on the responses like particle size and polydispersity index of synthesized silver nanoparticles were optimized. Mathematical modelling was performed using quadratic polynomial model and response surface analysis was done to understand the factor-response relationship. The synthesized silver nanoparticles at optimum condition were found to be of spherical in shape under TEM with particle size of 98 nm and polydispersity index of 0.15. Optimized silver nanoparticles were further characterized through UV-VIS spectrophotometry, FTIR spectroscopy and TEM imaging studies. Also, the silver nanoparticles were evaluated for antibacterial activity on E. coli and S. aureus. In a nutshell, the studies construed successful synthesis of silver nanoparticles along with thorough understanding of the associated factors influencing their quality characteristics and significantly improved antibacterial activity as beneficial effect.

Can earthworms biosynthesize highly luminescent quantum dots?

Band gap tunable cadmium selenide (CdSe) quantum dots (QDs) were synthesized within earthworms that emit in the middle of the visible spectrum. We demonstrated that this luminescence emission is a combination of the earthworm's protein and QD luminescence, such that the contribution of QDs in the luminescence was negligible. Eisenia fetida earthworms were used for QD biosynthesis and were exposed to different concentrations of CdCl₂ and Na₂ SeO₃ in standard soil for an adequate exposure time. The size of the CdSe QDs based on the effective mass model was in agreement with the size measured from the transmission electron microscopy analysis, with an average diameter of 7 nm. Ultraviolet-visible and photoluminescence analyses confirmed the synthesis of CdSe QDs with unique absorption and luminescence at 430 nm and 605 nm, respectively.

Inhibition of Bacteria Associated with Wound Infection by Biocompatible Green Synthesized Gold Nanoparticles from South African Plant Extracts

Unlike conventional physical and chemical methods, the biogenic synthesis of gold nanoparticles (GNPs) is considered a green and non-toxic approach to produce biocompatible GNPs that can be utilized in various biomedical applications. This can be achieved by using plant-derived phytochemicals to reduce gold salt into GNPs. Several green synthesized GNPs have been shown to have antibacterial effects, which can be applied in wound dressings to prevent wound infections. Therefore, the aim of this study is to synthesize biogenic GNPs from the South African Galenia africana and Hypoxis hemerocallidea plants extracts and evaluate their antibacterial activity, using the Alamar blue assay, against bacterial strains that are known to cause wound infections. Additionally, we investigated the toxicity of the biogenic GNPs to non-cancerous human fibroblast cells (KMST-6) using 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide (MTT) assay. In this paper, spherical GNPs, with particle sizes ranging from 9 to 27 nm, were synthesized and fully characterized. The GNPs from H. hemerocallidea exhibited antibacterial activity against all the tested bacterial strains, whereas GNPs produced from G. africana only exhibited antibacterial activity against Pseudomonas aeruginosa. The GNPs did not show any significant toxicity towards KMST-6 cells, which may suggest that these nanoparticles can be safely applied in wound dressings.

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.

Nucleation and Assembly of Silica into Protein-Based Nanocomposites as Effective Anticancer Drug Carriers Using Self-Assembled Silk Protein Nanostructures as Biotemplates

Bombyx mori (B. mori) silk fibroin and sericin can act as a great candidate in delivering drugs or other bioactive substances. Silica also has a great application in the field of drug delivery. To the best of our knowledge, there has been no report on the design of a nanocomposite made of silk protein and silica for drug delivery. Here, for the first time, we used B. mori silk fibroin (SF) and sericin (SS), self-assembled into nanospheres and nanofibers in situ in the aqueous solution, respectively, as a biotemplate to regulate the nucleation and self-assembly of silica for designing anticancer drug delivery. SF and SS mediated the nucleation and assembly of silica into monodispersed nanospheres (termed Si/SF) and nanofibers (termed Si/SS), respectively. The size and topography of the silica assemblies were dependent on the concentration of SF or SS as well as reaction conditions. Both Si/SF nanospheres and Si/SS nanofibers showed a high loading capability and sustained release profile of an anticancer drug, doxorubicin (DOX), in vitro. Si/SF nanospheres were found to be efficiently internalized in human cervical carcinoma (HeLa) cells and accumulate around the cell nuclei. Si/SS nanofibers could only adhere to the surface of the cancer cells. This indicates that DOX-loaded Si/SF nanospheres and Si/SS nanofibers are more effective in cancer therapy than free DOX. Our results suggest that the self-assembled Si/SF spheres and Si/SS nanofibers are potential effective anticancer drug carriers.

Water-Dispersible Silica-Coated Upconverting Liposomes: Can a Thin Silica Layer Protect TTA-UC against Oxygen Quenching?

Light upconversion by triplet-triplet annihilation (TTA-UC) in nanoparticles has received considerable attention for bioimaging and light activation of prodrugs. However, the mechanism of TTA-UC is inherently sensitive for quenching by molecular oxygen. A potential oxygen protection strategy is the coating of TTA-UC nanoparticles with a layer of oxygen-impermeable material. In this work, we explore if (organo)silica can fulfill this protecting role. Three synthesis routes are described for preparing water-dispersible (organo)silica-coated red-to-blue upconverting liposomes. Their upconversion properties are investigated in solution and in A549 lung carcinoma cells. Although it was found that the silica offered no protection from oxygen in solution and after uptake in A549 cancer cells, upon drying of the silica-coated liposome dispersion in an excess of (organo)silica precursor, interesting liposome-silica nanocomposite materials were obtained that were capable of generating blue light upon red light excitation in air.

Evidence of contact epitaxy in the self-assembly of HgSe nanocrystals formed at a liquid-liquid interface

The grazing incidence x-ray scattering results presented here show that the self-assembly process of HgSe nanocrystals formed at a liquid-liquid interface is quite different along the in-plane direction and across the interface. In situ x-ray reflectivity and ex situ microscopy measurements suggest quantized out-of-plane growth for HgSe nanoparticles of a size of about [Formula: see text] nm initially. Grazing incidence small-angle x-ray scattering measurements for films transferred from the water-toluene interface at various stages of reaction show that these nanoparticles first form random clusters with an average radius of 2.2 nm, giving rise to equally spaced rings of several orders. Finally, these clusters self-organize into face-centered cubic superstructures, giving sharp x-ray diffraction peaks oriented normal to the liquid-liquid interface with more than 100 nm-coherent domains. We also observed the x-ray diffraction pattern of the HgSe crystalline phase, with the superlattice peaks in these grazing incidence measurements of the transferred films. The electron microscopy and atomic force microscopy results support the x-ray observation of the self-organization of HgSe nanocrystals into close-packed superlattices. These results show that capillary wave fluctuation promotes the oriented attachment of clusters at the liquid-liquid interface, giving direct experimental evidence of contact epitaxy.

Phage as a Genetically Modifiable Supramacromolecule in Chemistry, Materials and Medicine

Filamentous bacteriophage (phage) is a genetically modifiable supramacromolecule. It can be pictured as a semiflexible nanofiber (∼900 nm long and ∼8 nm wide) made of a DNA core and a protein shell with the former genetically encoding the latter. Although phage bioengineering and phage display techniques were developed before the 1990s, these techniques have not been widely used for chemistry, materials, and biomedical research from the perspective of supramolecular chemistry until recently. Powered by our expertise in displaying a foreign peptide on its surface through engineering phage DNA, we have employed phage to identify target-specific peptides, construct novel organic-inorganic nanohybrids, develop biomaterials for disease treatment, and generate bioanalytical methods for disease diagnosis. Compared with conventional biomimetic chemistry, phage-based supramolecular chemistry represents a new frontier in chemistry, materials science, and medicine. In this Account, we introduce our recent successful efforts in phage-based supramolecular chemistry, by integrating the unique nanofiber-like phage structure and powerful peptide display techniques into the fields of chemistry, materials science, and medicine: (1) successfully synthesized and assembled silica, hydroxyapatite, and gold nanoparticles using phage templates to form novel functional materials; (2) chemically introduced azo units onto the phage to form photoresponsive functional azo-phage nanofibers via a diazotization reaction between aromatic amino groups and the tyrosine residues genetically displayed on phage surfaces; (3) assembled phage into 2D films for studying the effects of both biochemical (the peptide sequences displayed on the phages) and biophysical (the topographies of the phage films) cues on the proliferation and differentiation of mesenchymal stem cells (MSCs) and induced pluripotent stem cells (iPSCs) and identified peptides and topographies that can induce their osteogenic differentiation; (4) discovered that phage could induce angiogenesis and osteogenesis for MSC-based vascularized bone regeneration; (5) identified novel breast cancer cell-targeting and MSC-targeting peptides and used them to significantly improve the efficiency of targeted cancer therapy and MSC-based gene delivery, respectively; (6) employed engineered phage as a probe to achieve ultrasensitive detection of biomarkers from serum of human patients for disease diagnosis; and (7) constructed centimeter-scale 3D multilayered phage assemblies with the potential application as scaffolds for bone regeneration and functional device fabrication. Our findings demonstrated that phage is indeed a very powerful supramacromolecule suitable for not only developing novel nanostructures and biomaterials but also advancing important fields in biomedicine, including molecular targeting, cancer diagnosis and treatment, drug and gene delivery, stem cell fate direction, and tissue regeneration. Our successes in exploiting phage in chemistry, materials, and medicine suggest that phage itself is nontoxic at the cell level and can be safely used for detecting biomarkers in vitro. Moreover, although we have demonstrated successful in vivo tissue regeneration induced by phage, we believe future studies are needed to evaluate the in vivo biodistribution and potential risks of the phage-based biomaterials.

Molecular Self-Assembly Strategy for Generating Catalytic Hybrid Polypeptides

Recently, catalytic peptides were introduced that mimicked protease activities and showed promising selectivity of products even in organic solvents where protease cannot perform well. However, their catalytic efficiency was extremely low compared to natural enzyme counterparts presumably due to the lack of stable tertiary fold. We hypothesized that assembling these peptides along with simple hydrophobic pockets, mimicking enzyme active sites, could enhance the catalytic activity. Here we fused the sequence of catalytic peptide CP4, capable of protease and esterase-like activities, into a short amyloidogenic peptide fragment of Aβ. When the fused CP4-Aβ construct assembled into antiparallel β-sheets and amyloid fibrils, a 4.0-fold increase in the hydrolysis rate of p-nitrophenyl acetate (p-NPA) compared to neat CP4 peptide was observed. The enhanced catalytic activity of CP4-Aβ assembly could be explained both by pre-organization of a catalytically competent Ser-His-acid triad and hydrophobic stabilization of a bound substrate between the triad and p-NPA, indicating that a design strategy for self-assembled peptides is important to accomplish the desired functionality.

Genetically Engineered Virus Nanofibers as an Efficient Vaccine for Preventing Fungal Infection

Candida albicans (CA) is a kind of fungus that can cause high morbidity and mortality in immunocompromised patients. However, preventing CA infection in these patients is still a daunting challenge. Herein, inspired from the fact that immunization with secreted aspartyl proteinases 2 (Sap2) can prevent the infection, it is proposed to use filamentous phage, a human-safe virus nanofiber specifically infecting bacteria (≈900 nm long and 7 nm wide), to display an epitope peptide of Sap2 (EPS, with a sequence of Val-Lys-Tyr-Thr-Ser) on its side wall and thus serve as a vaccine for preventing CA infection. The engineered virus nanofibers and recombinant Sap2 (rSap2) are then separately used to immunize mice. The humoral and cellular immune responses in the immunized mice are evaluated. Surprisingly, the virus nanofibers significantly induce mice to produce strong immune response as rSap2 and generate antibodies that can bind Sap2 and CA to inhibit the CA infection. Consequently, immunization with the virus nanofibers in mice dramatically increases the survival rate of CA-infected mice. All these results, along with the fact that the virus nanofibers can be mass-produced by infecting bacteria cost-effectively, suggest that virus nanofibers displaying EPS can be a vaccine candidate against fungal infection.

Shape matters when engineering mesoporous silica-based nanomedicines

This review introduces various fabrication methods for non-spherical mesoporous silica nanomaterials and the roles of particle shape in nanomedicine applications.

Green Synthesis of Metallic Nanoparticles via Biological Entities

Nanotechnology is the creation, manipulation and use of materials at the nanometre size scale (1 to 100 nm). At this size scale there are significant differences in many material properties that are normally not seen in the same materials at larger scales. Although nanoscale materials can be produced using a variety of traditional physical and chemical processes, it is now possible to biologically synthesize materials via environment-friendly green chemistry based techniques. In recent years, the convergence between nanotechnology and biology has created the new field of nanobiotechnology that incorporates the use of biological entities such as actinomycetes algae, bacteria, fungi, viruses, yeasts, and plants in a number of biochemical and biophysical processes. The biological synthesis via nanobiotechnology processes have a significant potential to boost nanoparticles production without the use of harsh, toxic, and expensive chemicals commonly used in conventional physical and chemical processes. The aim of this review is to provide an overview of recent trends in synthesizing nanoparticles via biological entities and their potential applications.

Phage-mediated counting by the naked eye of miRNA molecules at attomolar concentrations in a Petri dish

The ability to count biomolecules such as cancer-biomarker miRNAs with the naked eye is seemingly impossible in molecular diagnostics. Here, we show an ultrasensitive naked-eye-counting strategy for quantifying miRNAs by employing T7 phage-a bacteria-specific virus nanoparticle-as a surrogate. The phage is genetically engineered to become fluorescent and capable of binding a miRNA-capturing gold nanoparticle (GNP) in a one-to-one manner. Target miRNAs crosslink the resultant phage-GNP couple and miRNA-capturing magnetic microparticles, forming a sandwich complex containing equimolar phage and miRNA. The phage is then released from the complex and developed into one macroscopic fluorescent plaque in a Petri dish by plating it in a host bacterial medium. Counting the plaques by the naked eye enables the quantification of miRNAs with detection limits of ∼3 and ∼5 aM for single-target and two-target miRNAs, respectively. This approach offers ultrasensitive and convenient quantification of disease biomarkers by the naked eye.

Synthesis of 1D Silica Nanostructures with Controllable Sizes Based on Short Anionic Peptide Self-Assembly

Artificial synthesis of silica under benign conditions is usually achieved by using cationic organic matrices as templates while the anionic analogues have not received enough consideration, albeit they are also functioning in biosilica formation. In this work, we report the design and self-assembly of an anionic peptide amphiphile (I3E) and the use of its self-assemblies as templates to synthesize 1D silica nanostructures with tunable sizes. We show that short I3E readily formed long nanofibrils in aqueous solution via a hierarchical self-assembly process. By using APTES and TEOS as silica precursors, we found that the I3E nanofibrils templated the production of silica nanotubes with a wide size distribution, in which the silica size regulation was achieved by tuning the interactions among the peptide template and silicon species. These results clearly illustrate a facile method for generating silica nanomaterials based on anionic matrices.

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.

Preparation of single-handed helical carbonaceous nanotubes using 3-aminophenol-formaldehyde resin

Single-handed helical carbonaceous nanotubes with optical activity were prepared using 3-aminophenol-formaldehyde resin.

Stem cells loaded with nanoparticles as a drug carrier for in vivo breast cancer therapy

A novel anti-cancer drug carrier, mesenchymal stem cells (MSCs) encapsulating drug-loaded hollow silica nanoparticles, is used to carry a photosensitizer drug and deliver it to breast tumors, due to the natural high tumor affinity of the MSCs, and inhibit tumor growth by photo dynamic therapy. This new strategy for delivering a photo sensitizer to tumors by using tumor-affinitive MSCs addresses the challenge of the accumulation of photosensitizer drugs in tumors in photodynamic therapy.

Controlled alignment of filamentous supramolecular assemblies of biomolecules into centimeter-scale highly ordered patterns by using nature-inspired magnetic guidance

We took the advantage of the capability of magnetic nanoparticles (MNPs) being aligned along a magnetic field and reproducibly generated large scale bio-nanofiber assemblies with the orientation of the constituent bio-nanofibers defined by the applied magnetic field. When decorated by MNPs, bio-nanofibers could be guided by the external magnetic field to become oriented either horizontally or vertically, forming single- and multi-orientation layered assemblies.

Virus-based photo-responsive nanowires formed by linking site-directed mutagenesis and chemical reaction

Owing to the genetic flexibility and error-free bulk production, bio-nanostructures such as filamentous phage showed great potential in materials synthesis, however, their photo-responsive behaviour is neither explored nor unveiled. Here we show M13 phage genetically engineered with tyrosine residues precisely fused to the major coat protein is converted into a photo-responsive organic nanowire by a site-specific chemical reaction with an aromatic amine to form an azo dye structure on the surface. The resulting azo-M13-phage nanowire exhibits reversible photo-responsive properties due to the photo-switchable cis-trans isomerisation of the azo unit formed on the phage. This result shows that site-specific display of a peptide on bio-nanostructures through site-directed genetic mutagenesis can be translated into site-directed chemical reaction for developing advanced materials. The photo-responsive properties of the azo-M13-phage nanowires may open the door for the development of light controllable smart devices for use in non-linear optics, holography data storage, molecular antenna, and actuators.

Lighting up silica nanotubes transcribed from the submicron structure of a metal-peptide hybrid

Fluorescent silica nanotubes are attracting increasing interest because of their versatile applicability in a range of diverse fields. By using sol-gel transcription of tetraethylorthosilicate (TEOS) from various soft templates, silica nanotubes can be conveniently prepared. Metal-peptide hybrids with well-defined nanostructures and outstanding functionalities are very interesting candidates to serve as templates. Herein, we demonstrate that glutathione (GSH) can act as a building block for a bioinspired structure with dimensions down to the nanoscale, based on specific interactions between metal ions and the peptide. Congo red is able to selectively stain the nanofibres obtained, and appears apple-green in colour, implying that Congo red is promising to serve as an effective and convenient probe for determining the self-assembly of GSH and copper ions. Furthermore, silica nanotubes are synthesized using the nanofibres as a template in a very simple way. The silica nanotubes can be lit up by biomolecule-templated metal nanoparticles or nanoclusters and emit bright fluorescence. This work will certainly open up new opportunities in fabricating a broad range of nanostructured materials with versatile functionalities.