Spontaneous assembly of viruses on multilayered polymer surfaces

Tailored Nucleation-Growth Strategy for Precise Self-Assembly of Block Copolymers

The self-assembly of block copolymers (BCPs) to form nanostructures of various morphologies and controllable dimensions has been a very promising research area in nanotechnology in recent decades. This concept mainly summarizes the recent advances in precise and controllable self-assembly of BCPs through a tailored nucleation-growth strategy to modulate the self-assembly behavior of the BCPs. These efforts have led to a better understanding of the self-assembly mechanisms and opened new possibilities for creating novel materials with designable properties. We hope that the concept is more than a periodical summary of previous research work and can provide valuable inspiration for the research field.

Synergistic impact of nano-supramolecular coordination polymer based on cadmium, ethyl nicotinate and thiocyanate ligands as efficient catalyst to remove harmful elements from wastewater

Under ultrasonication, cadmium nitrate tetrahydrates, ethyl nicotinate (EN), and potassium thiocyanate as connecting ligand self-assembled to form the nanosized supramolecular coordination polymer (NSCP1) and the crystalline supramolecular coordination polymer (SCP1) [Cd(EN)2(SCN)2]. Single crystal SCP1 X-ray diffraction (XRD) revealed that CdII has an octahedral shape. The network structure of SCP1 is composed of chair conformation cyclic [Cd2(SCN)2] n building blocks that form a one dimensional (1D) chain with bilaterally coordinated EN. The 1D-chain is joined to the other by extensive hydrogen bonds, which arrange the chains into a three-dimensional network. By stacking π-π, the strands are fluttering the three-dimensional (3D) network even more. Several structural characterization methods and spectral analyses were used to analyze SCP1 and NSCP1. The heterogeneous catalysts SCP1 and NSCP1 have been shown to display exceptionally strong catalytic activity against the breakdown of the designated contaminant, indigo carmine (IC) color in very short durations under ultraviolet (UV) or ultrasonic wave conditions. The photoluminescence probing approach was utilized to determine the reactive oxygen species and reaction process using the disodium salt of terephthalic acid.

Reprogramming Filamentous fd Viruses to Capture Copper Ions

C-terminal truncated variants (A, VA, NVA, ANVA, FANVA and GFANVA) of our recently identified Cu(II) specific peptide "HGFANVA" were displayed on filamentous fd phages. Wild type fd-tet and engineered virus variants were treated with 100 mM Cu(II) solution at a final phage concentration of 1011 vir/ml and 1012 vir/ml. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) imaging before Cu(II) exposure showed ≈6-8 nm thick filamentous virus layer formation. Cu(II) treatment resulted in aggregated bundle-like assemblies with mineral deposition. HGFANVA phage formed aggregates with an excessive mineral coverage. As the virus concentration was 10-fold decreased, nanowire-like assemblies were observed for shorter peptide variants A, NVA and ANVA. Wild type fd phages did not show any mineral formation. Energy dispersive X-ray spectroscopy (EDX) analyses revealed the presence of C and N peaks on phage organic material. Cu peak was only detected for engineered viruses. Metal ion binding of viruses was next investigated by enzyme-linked immunosorbent assay (ELISA) analyses. Engineered viruses were able to bind Cu(II) forming mineralized intertwined structures although no His (H) unit was displayed. Such genetically reprogrammed virus based biological materials can be further applied for bioremediation studies to achieve a circular economy.

Cholesteric Tactoids with Tunable Helical Pitch Assembled by Lysozyme Amyloid Fibrils

Amyloid fibrils are biological rod-like particles showing liquid-liquid crystalline phase separation into cholesteric phases through a complex behavior of nucleation, growth, and order-order transitions. Yet, controlling the self-assembly of amyloids into liquid crystals, and particularly the resulting helical periodicity, remains challenging. Here, a novel cholesteric system is introduced and characterized based on hen egg white lysozyme (HEWL) amyloid fibrils and the results rationalized via a combination of experiments and theoretical scaling arguments. Specifically, the transition behaviors are elucidated from homogenous nematic, bipolar nematic to cholesteric tactoids following the classic Onsager model and the free energy functional model from Frank-Oseen elasticity theory. Additionally, the critical effects of pH and ionic strength on these order-order-transitions, as well as on the shape and helical pitch of the cholesteric tactoids are demonstrated. It is found that a small increase in pH from 2.0 to 2.8 results in a 34% decrease in pitch, while, on the contrary, increasing ionic strength from 0 to 10 mm leads to a 39% increase in pitch. The present study provides an approach to obtain controllable chiral nematic structures from HEWL amyloid fibrils, and may contribute further to the application of protein-based liquid crystals in pitch-sensitive biosensors or biomimetic architectures.

Living Growth Kinetics of Polymeric Micelles on a Substrate

Living growth of micelles on the substrate is an intriguing phenomenon; however, little is known about its growth kinetics, especially from a theoretical viewpoint. Here, we examine the living growth kinetics of polymeric micelles on a hydrophobic substrate immersed in an aqueous solution. The block copolymers first assemble into short cylinder seeds anchored on the substrate. Then, the small aggregates of block copolymers in the solutions fuse onto the active ends of the anchored seeds, leading to micelle growth on the substrate. A theoretical model is proposed to interpret such living growth kinetics. It is revealed that the growth rate coefficient on the substrate is independent of the copolymer concentration and the multistep feedings; however, it is significantly affected by the surface hydrophobicity. Brownian dynamics simulations further support the proposed growth mechanism and the kinetic model. This work enriches living assembly systems and provides guidance for fabricating bioinspired surface nanostructures.

Convoluted micellar morphological transitions driven by tailorable mesogenic ordering effect from discotic mesogen-containing block copolymer

Solution-state self-assemblies of block copolymers to form nanostructures are tremendously attractive for their tailorable morphologies and functionalities. While incorporating moieties with strong ordering effects may introduce highly orientational control over the molecular packing and dictate assembly behaviors, subtle and delicate driving forces can yield slower kinetics to reveal manifold metastable morphologies. Herein, we report the unusually convoluted self-assembly behaviors of a liquid crystalline block copolymer bearing triphenylene discotic mesogens. They undergo unusual multiple morphological transitions spontaneously, driven by their intrinsic subtle liquid crystalline ordering effect. Meanwhile, liquid crystalline orderedness can also be built very quickly by doping the mesogens with small-molecule dopants, and the morphological transitions are dramatically accelerated and various exotic micelles are produced. Surprisingly, with high doping levels, the self-assembly mechanism of this block copolymer is completely changed from intramolecular chain shuffling and rearrangement to nucleation-growth mode, based on which self-seeding experiments can be conducted to produce highly uniform fibrils.

M13KO7 bacteriophage enables Potato Virus Y detection

IMPORTANCE

In this study, we confirmed the binding of M13KO7 to Potato virus Y (PVY) using enzyme-linked immunosorbent assay. M13KO7 is a "bald" bacteriophage in which no recombinant antibody is displayed. M13KO7 is easy to propagate by using Escherichia coli, making this method more reasonable in economic perspective. Based on this study, we suggest that M13KO7 detection system has applicability as a novel biological tool for the detection of PVY.

Mechanisms of Biomolecular Self-Assembly Investigated Through In Situ Observations of Structures and Dynamics

Biomolecular self-assembly of hierarchical materials is a precise and adaptable bottom-up approach to synthesizing across scales with considerable energy, health, environment, sustainability, and information technology applications. To achieve desired functions in biomaterials, it is essential to directly observe assembly dynamics and structural evolutions that reflect the underlying energy landscape and the assembly mechanism. This review will summarize the current understanding of biomolecular assembly mechanisms based on in situ characterization and discuss the broader significance and achievements of newly gained insights. In addition, we will also introduce how emerging deep learning/machine learning-based approaches, multiparametric characterization, and high-throughput methods can boost the development of biomolecular self-assembly. The objective of this review is to accelerate the development of in situ characterization approaches for biomolecular self-assembly and to inspire the next generation of biomimetic materials.

Anti-Viral Surfaces in the Fight against the Spread of Coronaviruses

This review is conducted against the background of nanotechnology, which provides us with a chance to effectively combat the spread of coronaviruses, and which primarily concerns polyelectrolytes and their usability for obtaining protective function against viruses and as carriers for anti-viral agents, vaccine adjuvants, and, in particular, direct anti-viral activity. This review covers nanomembranes in the form of nano-coatings or nanoparticles built of natural or synthetic polyelectrolytes--either alone or else as nanocomposites for creating an interface with viruses. There are not a wide variety of polyelectrolytes with direct activity against SARS-CoV-2, but materials that are effective in virucidal evaluations against HIV, SARS-CoV, and MERS-CoV are taken into account as potentially active against SARS-CoV-2. Developing new approaches to materials as interfaces with viruses will continue to be relevant in the future.

Flow and assembly of cellulose nanocrystals (CNC): A bottom-up perspective - A review

Cellulosic sources, such as lignocellulose-rich biomass, can be mechanically or acid degraded to produce inclusions called cellulose nanocrystals (CNCs). They have several uses in the sectors of biomedicine, photonics, and material engineering because of their biodegradability, renewability, sustainability, and mechanical qualities. The processing and design of CNC-based products are inextricably linked to the rheological behaviour of CNC suspension or in combination with other chemicals, such as surfactants or polymers; in this context, rheology offers a significant link between microstructure and macro scale flow behaviour that is intricately linked to material response in applications. The flow behaviour of CNC items must be properly specified in order to produce goods with value-added characteristics. In this review article, we provide new research on the shear rheology of CNC dispersion and CNC-based hydrogels in the linear and nonlinear regime, with storage modulus values reported to range from ~10^-3 to 10³ Pa. Applications in technology and material science are also covered simultaneously. We carefully examined the effects of charge density, aspect ratio, concentration, persistence length, alignment, liquid crystal formation, the cause of chirality in CNCs, interfacial behaviour and interfacial rheology, linear and nonlinear viscoelasticity of CNC suspension in bulk and at the interface using the currently available literature.

Development and characterization of antibacterial coatings on surgical sutures based on sodium carboxymethyl cellulose/chitosan/chlorhexidine

The layer-by-layer assembly (LBL) method was used in this work to apply antibacterial coatings to the surface of sutures. The nanofilm was created using sodium carboxymethyl cellulose, chitosan, and chlorhexidine digluconate. Polyethylene terephthalate and polyamide surgical sutures were used as the substrate. At pH 5, thin, uniform coatings with the ideal number of biopolymers in the film (10 bilayers) are produced. The pH and the shape of the polyelectrolyte macromolecules determine the film's thickness and form. The morphology of the surface and the structure of the sutures after modification become homogeneous and smooth. Both treated and untreated sutures retain their mechanical strength, and there is no significant loss of tensile strength. Nanofilms obtained on the surface of the sutures showed high antimicrobial efficacy against microorganisms Staphylococcus aureus, Escherichia coli, Klebsiella pneumoniae, Staphylococcus epidermidis, and Streptococcus pneumoniae. Chlorhexidine incorporated into the multilayer membrane was found to have greater antimicrobial activity than sutures treated with chlorhexidine alone. Modified surgical sutures provide antibacterial qualities that last for up to 30 days in a stable, controlled manner. The results showed the prospects of applying nanofilms based on sodium carboxymethyl cellulose/chitosan/chlorhexidine to surgical sutures that can prevent the infectious consequences of surgical interventions.

Engineered Living Bacteriophage-Enabled Self-Adjuvanting Hydrogel for Remodeling Tumor Microenvironment and Cancer Therapy

Due to the complexity and heterogeneity in the tumor microenvironment, the efficacy of breast cancer treatment has been significantly impeded. Here, we established a living system using an engineered M13 bacteriophage through chemical cross-linking and biomineralization to remodel the tumor microenvironment. Chemically cross-linking of the engineered bacteriophage gel (M13 Gel) could in situ synthesize photothermal palladium nanoparticles (PdNPs) on the pVIII capsid protein to obtain M13@Pd Gel. In addition, NLG919 was further loaded into a gel to form (M13@Pd/NLG gel) for down-regulating the expression of tryptophan metabolic enzyme indoleamine 2,3-dioxygenase 1 (IDO1). Both in vitro and in vivo studies showed that the M13 bacteriophage served not only as a cargo-loaded device but also as a self-immune adjuvant, which induced the immunogenic death of tumor cells effectively and down-regulated IDO1 expression. Such a bioactive gel system constructed by natural living materials could reverse immunosuppression and significantly improve the anti-breast cancer response.

A decade of developing applications exploiting the properties of polyelectrolyte multilayer capsules

Transferring the layer-by-layer (LbL) coating approach from planar surfaces to spherical templates and subsequently dissolving these templates leads to the fabrication of polyelectrolyte multilayer capsules. The versatility of the coatings of capsules and their flexibility upon bringing in virtually any material into the coatings has quickly drawn substantial attention. Here, we provide an overview of the main developments in this field, highlighting the trends in the last decade. In the beginning, various methods of encapsulation and release are discussed followed by a broad range of applications, which were developed and explored. We also outline the current trends, where the range of applications is continuing to grow, including addition of whole new and different application areas.

Biotechnology Approach to Mineral Separation via Phage Flotation Collectors

A long-standing challenge in the mining industry is the separation of mineral particles that have similar surface characteristics for which surfactant-based flotation collectors cannot discriminate. In Florida phosphate mining, this problem occurs in the separation of dolomite [CaMg(CO₃)₂] contaminants from the desired francolite mineral {a fluorapatite [Ca₅(PO₄)₃(F,OH)]}. In this study, phage display techniques were used to select phage clones with specific binding affinity to francolite, which were then tested in a benchtop bubbler flotation apparatus for their ability to selectively float francolite particles from mixtures containing dolomite. Contact angles measured with the captive bubble technique were used to examine changes in the surface character of the mineral particles upon adsorption of the phage, which showed that the most selective phage led to an increase in the contact angle from 16 to 50°. Although this is below the level considered hydrophobic, the correlation between contact angles and increased flotation recovery suggests that the phage coat proteins are behaving as efficient bioamphiphiles for the attachment of the particles to air bubbles, demonstrating a new and environmentally friendly type of biocollector system. The chemical and physical characteristics of the phage "tail" peptides were evaluated to offer an explanation for the specificity of phage binding. We conclude with a discussion of the potential benefits of this biotechnology approach, even for commodity industries such as mining or other particle separation systems, when costs and sustainability are considered.

Layer-by-layer assembly methods and their biomedical applications

Various biomedical applications arising due to the development of different LbL assembly methods with unique process properties.

DNA Nanostructure-Programmed Cell Entry via Corner Angle-Mediated Molecular Interaction with Membrane Receptors

Despite its polyanionic nature, DNA can cross the negatively charged membrane to enter living cells by assembling into specific nanostructures, establishing various opportunities for biomedical applications. Mechanistic studies to explain how the geometrical parameters of DNA nanostructures impact the cell entry are critical but elusive. Here, we use experimentation and simulation to study the interaction between cells and three typical framework nucleic acids (FNAs), including tetrahedron, triangular prism, and cube. Different cellular uptake efficiency was observed among these FNAs, and similar distinction consistently existed in multiple cell lines. Scavenger receptors (SRs) were demonstrated to be essential in mediating the uptake process. Molecular docking simulations revealed that the SR binding predominantly depended on the corner angle of FNAs, determining cellular internalization frequency. This study clearly explains how FNAs interact with the membrane to initiate cell entry, offering new clues for the design of theranostic nanocarriers and the study of virus invasion.

Bacteriophage Capsid Modification by Genetic and Chemical Methods

Bacteriophages are viruses whose ubiquity in nature and remarkable specificity to their host bacteria enable an impressive and growing field of tunable biotechnologies in agriculture and public health. Bacteriophage capsids, which house and protect their nucleic acids, have been modified with a range of functionalities (e.g., fluorophores, nanoparticles, antigens, drugs) to suit their final application. Functional groups naturally present on bacteriophage capsids can be used for electrostatic adsorption or bioconjugation, but their impermanence and poor specificity can lead to inconsistencies in coverage and function. To overcome these limitations, researchers have explored both genetic and chemical modifications to enable strong, specific bonds between phage capsids and their target conjugates. Genetic modification methods involve introducing genes for alternative amino acids, peptides, or protein sequences into either the bacteriophage genomes or capsid genes on host plasmids to facilitate recombinant phage generation. Chemical modification methods rely on reacting functional groups present on the capsid with activated conjugates under the appropriate solution pH and salt conditions. This review surveys the current state-of-the-art in both genetic and chemical bacteriophage capsid modification methodologies, identifies major strengths and weaknesses of methods, and discusses areas of research needed to propel bacteriophage technology in development of biosensors, vaccines, therapeutics, and nanocarriers.

Filamentous Phages as Building Blocks for Bioactive Hydrogels

Filamentous bacteriophages (bacterial viruses) are semiflexible proteinous nanofilaments with high aspect ratios for which the surface chemistry can be controlled with atomic precision via genetic engineering. That, in addition to their ability to self-propagate and replicate a nearly monodisperse batch of biologically and chemically identical nanofilaments, makes these bionanofilaments superior to most synthetic nanoparticles and thus a powerful tool in the bioengineers' toolbox. Furthermore, filamentous phages form liquid crystalline structures at high concentrations; these ordered assemblies create hierarchically ordered macro-, micro-, and nanostructures that, once cross-linked, can form hierarchically ordered hydrogels, hydrated soft material with a variety of physical and chemical properties suitable for biomedical applications (e.g., wound dressings and tissue engineering scaffolds) as well as biosensing, diagnostic assays. We provide a critical review of these hydrogels of filamentous phage, and their physical, mechanical, chemical, and biological properties and current applications, as well as an overview of limitations and challenges and outlook for future applications. In addition, we present a list of design parameters for filamentous phage hydrogels to serve as a guide for the (bio)engineer and (bio)chemist interested in utilizing these powerful bionanofilaments for designing smart, bioactive materials and devices.

Generalized van der Waals theory for phase behavior of two-dimensional nematic liquid crystals. II. Phase coexistence and adsorption

Adsorption of asymmetric particles or molecules into monolayers is important for many biological and technologically relevant physical systems. In-plane ordering can drastically affect adsorption and phase behavior. In this work, a generalized van der Waals theory previously developed [M. V. Zonta and E. R. Soulé, Phys. Rev. E 100, 062703 (2019)10.1103/PhysRevE.100.062703] is used to calculated phase behavior and adsorption isotherms in a system of hard-core rodlike particles with in-plane nematic order, as a function of the model parameters (aspect ratio L/B, isotropic and anisotropic interaction parameters χ and ν, and adsorption constant K_{ads}). For small L/B, isotropic-nematic and/or (depending on χ) isotropic liquid-gas coexistence is observed; as L/B increases, coexistence between two different nematic phases appears at low temperature, and liquid-gas equilibrium ceases to be observed for large enough L/B; this is understood considering that as aspect ratio increases, the range of stability of the nematic phase becomes larger. Adsorption isotherms are found to significantly deviate from Langmuir behavior, and are strongly affected by ordering and interactions (surface density in the adsorbed layer increases as interaction parameters and ordering increase). Phase coexistence is observed as discontinuous transitions in adsorption isotherms, where adsorption-desorption hysteresis cycles are possible.

Fabrication of 3D Ordered Structures with Multiple Materials via Macroscopic Supramolecular Assembly

Integration of diverse materials into 3D ordered structures is urgently required for advanced manufacture owing to increase in demand for high-performance products. Most additive manufacturing techniques mainly focus on simply combining different equipment, while interfacial binding of distinctive materials remains a fundamental problem. Increasing studies on macroscopic supramolecular assembly (MSA) have revealed efficient interfacial interactions based on multivalency of supramolecular interactions facilitated by a "flexible spacing coating." To demonstrate facile fabrication of 3D heterogeneous ordered structures, the combination of MSA and magnetic field-assisted alignment has been developed as a new methodology for in situ integration of a wide range of materials, including elastomer, resin, plastics, metal, and quartz glass, with modulus ranging from tens of MPa to over 70 GPa. Assembly of single material, coassembly of two to four distinctive materials, and 3D alignment of "bridge-like" and "cross-stacked" heterogeneous structures are demonstrated. This methodology has provided a new solution to mild and efficient assembly of multiple materials at the macroscopic scale, which holds promise for advanced fabrication in fields of tissue engineering, electronic devices, and actuators.

Ordering of adsorbed rigid rods mediated by the Boussinesq interaction on a soft substrate

Orientational ordering driven by mechanical distortion of soft substrates plays a major role in material transformation processes such as elastocapillarity and surface anchoring. We present a theoretical model of the orientational response of anisotropic rods deposited onto a surface of a soft, elastic substrate of finite thickness. We show that anisotropic rods exhibit a continuous isotropic-nematic phase transition, driven by orientational interactions between surface deposited rods. This interaction is mediated by the deformation of the underlying elastic substrate and is quantified by the Boussinesq solution adapted to the case of slender, surface deposited rods. From the microscopic rod-rod interactions, we derive the appropriate Maier-Saupe mean-field description, which includes the Boussinesq elastic free energy contribution due to the substrate elasticity, derive the conditions for the existence of a continuous orientational ordering transition, and discuss the implication of results in the soft (bio)system context.

Application of Bacteriophages in Nanotechnology

Bacteriophages (phages for short) are viruses, which have bacteria as hosts. The single phage body virion, is a colloidal particle, often possessing a dipole moment. As such, phages were used as perfectly monodisperse systems to study various physicochemical phenomena (e.g., transport or sedimentation in complex fluids), or in the material science (e.g., as scaffolds). Nevertheless, phages also execute the life cycle to multiply and produce progeny virions. Upon completion of the life cycle of phages, the host cells are usually destroyed. Natural abilities to bind to and kill bacteria were a starting point for utilizing phages in phage therapies (i.e., medical treatments that use phages to fight bacterial infections) and for bacteria detection. Numerous applications of phages became possible thanks to phage display-a method connecting the phenotype and genotype, which allows for selecting specific peptides or proteins with affinity to a given target. Here, we review the application of bacteriophages in nanoscience, emphasizing bio-related applications, material science, soft matter research, and physical chemistry.

Weak polyelectrolyte-based multilayers via layer-by-layer assembly: Approaches, properties, and applications

Layer-by-layer (LbL) assembly is a nanoscale technique with great versatility, simplicity and molecular-level processing of various nanoscopic materials. Weak polyelectrolytes have been used as major building blocks for LbL assembly providing a fundamental and versatile tool to study the underlying mechanisms and practical applications of LbL assembly due to its pH-responsive charge density and molecular conformation. Because of high-density uncompensated charges and high-chain mobility, weak polyelectrolyte exponential multilayer growth is considered one of the fastest developing areas for organized molecular films. In this article, we systematically review the current status and developments of weak polyelectrolyte-based multilayers including all-weak-polyelectrolyte multilayers, weak polyelectrolytes/other components (e.g. strong polyelectrolytes, neutral polymers, and nanoparticles) multilayers, and exponentially grown weak polyelectrolyte multilayers. Several key aspects of weak polyelectrolytes are highlighted including the pH-controllable properties, the responsiveness to environmental pH, and synergetic functions obtained from weak polyelectrolyte/other component multilayers. Throughout this review, useful applications of weak polyelectrolyte-based multilayers in drug delivery, tunable biointerfaces, nanoreactors for synthesis of nanostructures, solid state electrolytes, membrane separation, and sensors are highlighted, and promising future directions in the area of weak polyelectrolyte-based multilayer assembly such as fabrication of multi-responsive materials, adoption of unique building blocks, investigation of internal molecular-level structure and mechanism of exponentially grown multilayers, and exploration of novel biomedical and energy applications are proposed.

Sustained delivery of growth factors with high loading efficiency in a layer by layer assembly

Layer by layer (LBL) assembly has garnered considerable interest due to its ability to generate multifunctional films with high tunability and versatility in terms of substrates and polyelectrolytes, allowing the option to use complex devices and drugs. Polyelectrolytes, such as growth factors (GFs), are essential, but costly, delicate, biological molecules that have been used in various tissue regeneration applications. For this reason, the controlled drug delivery of efficiently loaded GFs via LBL assembly (GF-LBL) can contribute to the establishment of cost-effective biologically triggered biomedical applications. We have developed an LBL method to load GFs (specifically, transforming growth factor beta 1, platelet-derived growth factor ββ, and insulin growth factor 1), with up to 90% efficiency approximately, by gas plasma surface activation and tuning the pH to increase the ionic strength of polyelectrolytes. Poly(styrenesulfonate) (PSS) and poly(ethyleneimine) (PEI) have been used to provide the initial necessary charge for multilayer build-up. Heparin and dextran sulphate have been investigated as counter polyelectrolytes to enhance the activity of GFs by protecting their ligands, where heparin resulted in the highest achievable loading efficiency for all GFs. Oxygen gas plasma and acidic pH levels also resulted in a significant increase in GF loading efficiency. The three GFs were released by diffusion and erosion in a controlled manner over lengthy time scales and the bioactivity was maintained for up to 14 days. When tested as implants in vitro, GF-LBL constructs increased fibroblast proliferation, influenced cell morphology and migration, and enhanced myofibroblast differentiation, indicating that the biological functionalities of the GFs were preserved. In conclusion, this developed LBL assembly method can provide a simple drug delivery system, which may yield more effective applications for tissue regeneration as well as biomedical sciences at large.

Self-Reorganizing Multilayer to Release Free Proteins from Self-Assemblies

The deconstruction of self-assemblies based on proteins and polyelectrolytes (PEs) and the subsequent release of intact proteins require either a switch from attractive to repulsive mode or particular PE properties (degradability, responsiveness, or differential affinity). Here, an interfacial self-assembly made of three charged species, i.e., a strong polyacid complexed with a protein and a weak polybase, is shown to self-reorganize upon a shift in pH. When the pH takes a value that is one pH unit lower than the pK_a of the weak polybase, the two PEs associate, thereby releasing the protein. The disassembly thus relies on associative forces rather than on the alteration of the protein-PE coupling strength. Hence, it allows the release of a protein using two simple PEs. The method is illustrated for lysozyme, which recovered up to half of its initial bioactivity after release. In contrast, a control self-assembled film that could not reorganize maintained only about 21% of the protein bioactivity after disassembly. This versatile approach is valuable for drug delivery devices and biomaterials as it allows the release of large numbers of active protein molecules.

Genetically Engineered Flagella Form Collagen-like Ordered Structures for Inducing Stem Cell Differentiation

Bacteria use flagella, the protein nanofibers on their surface, as a molecular machine to swim. Flagella are polymerized from monomers, flagellins, which can display a peptide by genetic means. However, flagella as genetically modifiable nanofibers have not been used in building bone extracellular matrix-like structures for inducing stem cell differentiation in non-osteogenic medium. Here we discovered that interactions between Ca2+ ions and flagella (displaying a collagen-like peptide (GPP)8 on every flagellin) resulted in ordered bundle-like structures, which were further mineralized with hydroxyapatite to form ordered fibrous matrix. The resultant matrix significantly induced the osteogenic differentiation of stem cells, much more efficiently than wild-type flagella and type I collagen. This work shows that flagella can be used as protein building blocks in generating biomimetic materials.

Nanocomposite multifunctional polyelectrolyte thin films with copper nanoparticles as the antimicrobial coatings

The work presents the formation and physicochemical characterization of polyelectrolyte-copper nanocomposite coatings using: poly(diallyldimethylammonium chloride) (PDADMAC) as a polycation, poly(sodium 4-styrenesulfonate)(PSS) as a polyanion and negatively charged copper nanoparticles (CuNPs) to obtain biocompatible surfaces with an antibacterial functionality. The mass and thickness of composite films were investigated by the quartz crystal microbalance with dissipation monitoring (QCM-D) and the ellipsometry whereas, the structure and morphology of coatings were examined using scanning electron microscopy (SEM). The increase of the UV-Vis absorption confirmed the formation of the consecutive layers of the film. Antibacterial activity of the coatings was tested on a representative Gram-positive bacteria strain, Staphylococcus aureus. The microbiological tests were performed and bacteria visualized using fluorescent staining and microscopic technique. It was demonstrated that nanostructured films had antibacterial properties, which makes polyelectrolyte multilayer films containing copper an interesting material in biomedical applications area, e.g., for the prevention of microbial deposition on surfaces.

Tailored functionalization of poly(L-lactic acid) substrates at the nanoscale to enhance cell response

Poly(L-lactic) acid (PLLA) has been widely employed in tissue engineering due to its mechanical properties, biodegradability and biocompatibility. The layer-by-layer (LbL) technique was here proposed as a simple method to impart bioactivity to the surface of PLLA substrates. Aminolysis treatment was applied to introduce amino groups on the surface of PLLA solvent cast films. Then, PLLA films were coated with heparin (HE)/chitosan (CH) multilayer by the LbL technique. Each functionalization step was characterized through physico-chemical and morphological analyses. Aminolysis treatment increased film surface wettability (64.8° ± 2.4° against 74.6° ± 1.3° for untreated PLLA) due to the formation of surface amino groups, which were quantified by acid orange colorimetric assay (0.05 nmol/mm²). After the deposition of 9 layers, the static contact angle varied between values close to 40° C (HE-based layer) and 60 °C (CH-based layer), showing the typical alternate trend of LbL coating. The successful HE/CH deposition was confirmed by ATR-FTIR and X-ray photoelectron spectroscopy (XPS) analyses. Particularly, XPS spectra of coated samples showed the presence of nitrogen (indicative of HE and CH deposition), and sulfur (indicative of HE deposition). The amount of deposited HE was quantified by Taylor's Blue colorimetric method: after the deposition of 19 and 20 layers the HE concentration was around 33 µg/cm². Finally, in vitro studies performed using HaCaT immortalized human skin keratinocytes, C2C12 immortalized mouse myoblasts and human fibroblasts demonstrated that HE/CH multilayer-coated PLLA is a promising substrate for soft tissue engineering, as cell response may be modulated by changing the surface chemical properties.

Adsorption and Interfacial Layer Structure of Unmodified Nanocrystalline Cellulose at Air/Water Interfaces

Nanocrystalline cellulose (NCC) is a promising biological nanoparticle for the stabilization of fluid interfaces.  However, the adsorption and interfacial layer structure of NCC are poorly understood as it is currently unknown how to form  NCC interfacial layers. Herein, we present parameters for the adsorption of unmodified NCC at the air-water (A/W) interface. Initial NCC adsorption is limited by diffusion, followed by monolayer saturation and decrease in surface tension at the time scale of hours. These results confirm the current hypothesis of a Pickering stabilization. NCC interfacial performance can be modulated by salt-induced charge screening, enhancing adsorption kinetics, surface load, and interfacial viscoelasticity. Adsorbed NCC layers were visualized by atomic force microscopy at planar Langmuir films and curved air bubbles, whereat NCC coverage was higher at curved interfaces. Structural analysis by neutron reflectometry revealed that NCC forms a discontinuous monolayer with crystallites oriented in the interfacial plane at a contact angle < 90°, favoring NCC desorption upon area compression. This provides the fundamental framework on the formation and structure of NCC layers at the A/W interface, paving the way for exploiting NCC interfacial stabilization for tailored colloidal materials.

DNA Nanostructure-Programmed Like-Charge Attraction at the Cell-Membrane Interface

Cell entry of anionic nano-objects has been observed in various types of viruses and self-assembled DNA nanostructures. Nevertheless, the physical mechanism underlying the internalization of these anionic particles across the negatively charged cell membrane remains poorly understood. Here, we report the use of virus-mimicking designer DNA nanostructures with near-atomic resolution to program "like-charge attraction" at the interface of cytoplasmic membranes. Single-particle tracking shows that cellular internalization of tetrahedral DNA nanostructures (TDNs) depends primarily on the lipid-raft-mediated pathway, where caveolin plays a key role in providing the short-range attraction at the membrane interface. Both simulation and experimental data establish that TDNs approach the membrane primarily with their corners to minimize electrostatic repulsion, and that they induce uneven charge redistribution in the membrane under the short-distance confinement by caveolin. We expect that the nanoscale like-charge attraction mechanism provides new clues for viral entry and general rules for rational design of anionic carriers for therapeutics.

Integrating Proteins in Layer-by-Layer Assemblies Independently of their Electrical Charge

Layer-by-layer (LbL) assembly is an attractive method for protein immobilization at interfaces, a much wanted step for biotechnologies and biomedicine. Integrating proteins in LbL thin films is however very challenging due to their low conformational entropy, heterogeneous spatial distribution of charges, and polyampholyte nature. Protein-polyelectrolyte complexes (PPCs) are promising building blocks for LbL construction owing to their standardized charge and polyelectrolyte (PE) corona. In this work, lysozyme was complexed with poly(styrenesulfonate) (PSS) at different ionic strengths and pH values. The PPCs size and electrical properties were investigated, and the forces driving complexation were elucidated, in the light of computations of polyelectrolyte conformation, with a view to further unravel LbL construction mechanisms. Quartz crystal microbalance and atomic force microscopy were used to monitor the integration of PPCs compared to the one of bare protein molecules in LbL assemblies, and colorimetric assays were performed to determine the protein amount in the thin films. Layers built with PPCs show higher protein contents and hydration levels. Very importantly, the results also show that LbL construction with PPCs mainly relies on standard PE-PE interactions, independent of the charge state of the protein, in contrast to classical bare protein assembly with PEs. This considerably simplifies the incorporation of proteins in multilayers, which will be beneficial for biosensing, heterogeneous biocatalysis, biotechnologies, and medical applications that require active proteins at interfaces.

Fabrication of Nanoreaction Clusters with Dual-Functionalized Protein Cage Nanobuilding Blocks

Fabrication of functional nanostructures is a prominent issue in nanotechnology, because they often exhibit unique properties that are different from the individual building blocks. Protein cage nanoparticles are attractive nanobuilding blocks for constructing nanostructures due to their well-defined symmetric spherical structures, polyvalent nature, and functional plasticity. Here, a lumazine synthase protein cage nanoparticle is genetically modified to be used as a template to generate functional nanobuilding blocks and covalently display enzymes (β-lactamase) and protein ligands (FKBP12/FRB) on its surface, making dual-functional nanobuilding blocks. Nanoreaction clusters are subsequently created by ligand-mediated alternate deposition of two complementary building blocks using layer-by-layer (LbL) assemblies. 3D nanoreaction clusters provide enhanced enzymatic activity compared with monolayered building block arrays. The approaches described here may provide new opportunities for fabricating functional nanostructures and nanoreaction clusters, leading to the development of new protein nanoparticle-based nanostructured biosensor devices.

Self-Assembled Nanoporous Biofilms from Functionalized Nanofibrous M13 Bacteriophage

Highly periodic and uniform nanostructures, based on a genetically engineered M13 bacteriophage, displayed unique properties at the nanoscale that have the potential for a variety of applications. In this work, we report a multilayer biofilm with self-assembled nanoporous surfaces involving a nanofiber-like genetically engineered 4E-type M13 bacteriophage, which was fabricated using a simple pulling method. The nanoporous surfaces were effectively formed by using the networking-like structural layers of the M13 bacteriophage during self-assembly. Therefore, an external template was not required. The actual M13 bacteriophage-based fabricated multilayered biofilm with porous nanostructures agreed well with experimental and simulation results. Pores formed in the final layer had a diameter of about 150–500 nm and a depth of about 15–30 nm. We outline a filter application for this multilayered biofilm that enables selected ions to be extracted from a sodium chloride solution. Here, we describe a simple, environmentally friendly, and inexpensive fabrication approach with large-scale production potential. The technique and the multi-layered biofilms produced may be applied to sensor, filter, plasmonics, and bio-mimetic fields.

Protein cage assembly across multiple length scales

Within the materials science community, proteins with cage-like architectures are being developed as versatile nanoscale platforms for use in protein nanotechnology. Much effort has been focused on the functionalization of protein cages with biological and non-biological moieties to bring about new properties of not only individual protein cages, but collective bulk-scale assemblies of protein cages. In this review, we report on the current understanding of protein cage assembly, both of the cages themselves from individual subunits, and the assembly of the individual protein cages into higher order structures. We start by discussing the key properties of natural protein cages (for example: size, shape and structure) followed by a review of some of the mechanisms of protein cage assembly and the factors that influence it. We then explore the current approaches for functionalizing protein cages, on the interior or exterior surfaces of the capsids. Lastly, we explore the emerging area of higher order assemblies created from individual protein cages and their potential for new and exciting collective properties.

Restructuring of poly(2-ethyl-2-oxazoline)/tannic acid multilayers into fibers

H-Bonded, pH-responsive poly(2-ethyl-2-oxazoline) (PEOX) and tannic acid (TA) multilayers were prepared by layer-by-layer deposition. Free-floating PEOX/TA multilayers were shown to restructure in a pH3 phosphate buffer solution to H-bonded, pH-responsive PEOX/TA fibers. This restructuring was also evident during the growth of multilayers thicker than 15 bilayers (BL). The growth profile of 30 BL-thick films showed a significant decrease in the film thickness from 118 nm to 85 nm between 15 BL and 20 BL, after which the growth trend was regained with some small fluctuations. This decrease was associated with the detachment of film patches from the top surface of the film. The rinse solutions consisted of fibrous aggregates, which were formed by the restructuring of the detached multilayer patches. These fibers were characterized by TGA, XPS, FTIR and SEM measurements which showed that the fibers consisted of H-bonded PEOX and TA molecules. As such, the fibers were pH-responsive and disintegrated at pH > 8.5. Scanning electron microscopy images indicated that the fibers might have been formed by the curling of planar LbL film patches and the dried fibers looked like collapsed hollow tubes on solid substrates. These results contribute to our understanding of the stability of LbL films in various chemical conditions and the ways to modify the morphology of self-assembled structures. pH-responsive fibrous aggregates are important in a variety of biomedical applications, from controlled release to sensors.

Upregulation of osteogenesis of mesenchymal stem cells with virus-based thin films

A major aim of tissue engineering is to develop biomimetic scaffolding materials that can guide the proliferation, self-renewal and differentiation of multipotent stem cells into specific lineages. Cellular functions can be controlled by the interactions between cells and biomaterials. Therefore, the surface chemistry and topography of support materials play a pivotal role in modulating cell behaviors at many stages of cell growth and development. Due to their highly ordered structure and programmable surface chemistries, which provide unique topography as biomaterials, viral nanoparticles have been utilized as building blocks for targeted cell growth and differentiation. This review article discusses the fabrication of two-dimensional virus-based thin film on substrates and highlights the study of the effect of chemical and physical cues introduced by plant virus nanoparticle thin films on the promotion of osteogenic differentiation of BMSCs.

Nanomanufacture of Free-Standing, Porous, Janus-Type Films of Polymer-Plant Virus Nanoparticle Arrays

We present a facile method for preparing hierarchical assemblies of cowpea mosaic virus (CPMV) nanoparticles adsorbed onto patterned polypyrrole copolymer arrays, which can be released as a freely standing and microporous polymer-protein membrane with a Janus-type structure. The patterning protocol is based on colloidal sphere lithography wherein a sacrificial honeycomb pattern composed of colloidal polystyrene (PS) microspheres is assembled on an electrode. A thin layer of polypyrrole film is electropolymerized within the interstices of the template and monitored using an electrochemical quartz crystal microbalance with dissipation (EC-QCM-D) and microscopy. Dissolving the PS template reveals an inverse opaline pattern capable of electrostatically capturing the CPMV particles. Through an electrochemical trigger, the polypyrrole-CPMV delaminates from the surface producing a self-sustaining polymer-protein membrane that can potentially be used for sensing and nanocargo applications.

A New Label-Free Technique for Analysing Evaporation Induced Self-Assembly of Viral Nanoparticles Based on Enhanced Dark-Field Optical Imaging

Nanoparticle self-assembly is a complex phenomenon, the control of which is complicated by the lack of appropriate tools and techniques for monitoring the phenomenon with adequate resolution in real-time. In this work, a label-free technique based on dark-field microscopy was developed to investigate the self-assembly of nanoparticles. A bio-nanoparticle with complex shape (T4 bacteriophage) that self-assembles on glass substrates upon drying was developed. The fluid flow regime during the drying process, as well as the final self-assembled structures, were studied using dark-field microscopy, while phage diffusion was analysed by tracking of the phage nanoparticles in the bulk solutions. The concentrations of T4 phage nanoparticles and salt ions were identified as the main parameters influencing the fluid flow, particle motion and, consequently, the resulting self-assembled structure. This work demonstrates the utility of enhanced dark-field microscopy as a label-free technique for the observation of drying-induced self-assembly of bacteriophage T4. This technique provides the ability to track the nano-sized particles in different matrices and serves as a strong tool for monitoring self-assembled structures and bottom-up assembly of nano-sized building blocks in real-time.

Templated co-assembly into nanorods of polyanions and artificial virus capsid proteins

Recombinant triblock polypeptides C-S_n-B, where C is a 400 amino acid long hydrophilic random coil block, S_n is a multimer of the silk-like octapeptide S = (GAGAGAGQ), and B = K₁₂ is an oligolysine, have previously been shown to encapsulate double stranded DNA into rod-shaped, virus-like particles. In order to gain insight of the co-assembly process, and in order to be able to use these proteins for templating other types of nanorods, we here explore their co-assembly with a range of polyanionic templates: poly(acrylic acids) (PAA) of a wide range of lengths, poly(styrene sulphonate) (PSS) and the stiff anionic polysaccharide xanthan. The formation of the complexes was characterized using Dynamic Light Scattering (DLS), cryogenic Transmission Electronic Microscopy (Cryo-TEM) and Atomic Force Microscopy (AFM). Except at very high molar masses, we find that flexible anionic PAA and PSS lead to co-assembly of proteins with single polyanion chains into nanorods, with a packing factor as expected on the basis of charge stochiometry. Only for very long PAA templates (8 × 10⁵ Da) we find evidence for heterogeneous complexes with thin and thick sections. For the very stiff xanthan chains, we find that its stiffness precludes co-assembly with the artificial viral capsid proteins into condensed and regular nanorods. Given the simple and robust formation of rod-like structures with a range of polyanionic templates, we anticipate that the artificial virus proteins will be useful for preparing high-aspect ratio nanoparticles and scaffolds of precise size and find applications in nanotechnology and materials science for which currently natural rod-like viruses are being explored.

Layer-By-Layer Self-Assembly of Polyelectrolytic Block Copolymer Worms on a Planar Substrate

Cationic and anionic block copolymer worms are prepared by polymerization-induced self-assembly via reversible addition-fragmentation chain transfer (RAFT) aqueous dispersion copolymerization of 2-hydroxypropyl methacrylate and glycidyl methacrylate (GlyMA), using a binary mixture of a nonionic poly(ethylene oxide) macromolecular RAFT agent and either a cationic poly([2-(methacryloyloxy)ethyl]trimethylammonium chloride) or an anionic poly(potassium 3-sulfopropyl methacrylate) macromolecular RAFT agent. In each case, covalent stabilization of the worm cores was achieved via reaction of the epoxide groups on the GlyMA repeat units with 3-mercaptopropyltriethoxysilane. Aqueous electrophoresis studies indicated a pH-independent mean zeta potential of +40 mV and -39 mV for the cationic and anionic copolymer worms, respectively. These worms are expected to mimic the rigid rod behavior of water-soluble polyelectrolyte chains in the absence of added salt. The kinetics of adsorption of the cationic worms onto a planar anionic silicon wafer was examined at pH 5 and was found to be extremely fast at 1.0 w/w % copolymer concentration in the absence of added salt. Scanning electron microscopy (SEM) analysis indicated that a relatively constant worm surface coverage of 16% was achieved at 20 °C for adsorption times ranging from just 2 s up to 2 min. Furthermore, the successive layer-by-layer deposition of cationic and anionic copolymer worms onto planar surfaces was investigated using SEM, ellipsometry, and surface zeta potential measurements. These techniques confirmed that the deposition of oppositely charged worms resulted in a monotonic increase in the mean layer thickness, with a concomitant surface charge reversal occurring on addition of each new worm layer. Unexpectedly, two distinct linear regimes were observed when plotting the mean layer thickness against the total number of adsorbed worm layers, with a steeper gradient (corresponding to thicker layers) being observed after the deposition of six worm layers.

Shaping micro-clusters via inverse jamming and topographic close-packing of microbombs

Designing topographic clusters is of significant interest, yet it remains challenging as they often lack mobility or deformability. Here we exploit the huge volumetric expansion (up to 3000%) of a new type of building block, thermally expandable microbombs. They consist of a viscoelastic polymeric shell and a volatile gas core, which, within structural confinement, create micro-clusters via inverse jamming and topographical close-packing. Upon heating, microbombs anchored in rigid confinement underwent balloon-like blowing up, allowing for dense clusters via soft interplay between viscoelastic shells. Importantly, the confinement is unyielding against the internal pressure of the microbombs, thereby enabling self-assembled clusters, which can be coupled with topographic inscription to introduce structural hierarchy on the clusters. Our strategy provides densely packed yet ultralight clusters with a variety of complex shapes, cleavages, curvatures, and hierarchy. In turn, these clusters will enrich our ability to explore the assemblies of the ever-increasing range of microparticle systems.

Self-assembled systems are normally composed of incompressible building blocks, which constrain their space filling efficiency. Yu et al. show programmable, densely packed clusters using thermally expandable soft microparticles, whereby the self-assembling process is realized via a jamming transition.

Immobilization of bacteriophage in wound-dressing nanostructure

Opportunistic bacteria that cause life-threatening infections are still a central problem associated with a healthcare setting. Bacteriophage capsid immobilization on nanostructured polymers maximizes its tail exposure and looks promising in applications toward skin-infections as alternative to antibiotics standardly used. The main goal of this work was to investigate the covalent immobilization of vB_Pae_Kakheti25 bacteriophage capsid on polycaprolactone (PCL) nanofibers (non-woven textile), as a potential effective antimicrobial, laundry resistant and non-toxic dressing for biomedical use. Surface analyses showed that the immobilization of vB_Pae_Kakheti25 bacteriophage capsid on PCL nanofibres oriented bacteriophage tails to interact with bacteria. Furthermore, antimicrobial assays showed a very effective 6 log bacterial reduction, which was equivalent to 99.9999%, after immediate and 2 hours of contact, even following 25 washing cycles (due to covalent bond). The activity of PCL-vB_Pae_Kakheti25 against P. aeruginosa was immediate and its reduction was complete.