Selective biotemplated synthesis of TiO2 inside a protein cage

Advancements in Functional Nanomaterials Inspired by Viral Particles

Virus-like particles (VLPs) are nanostructures composed of one or more structural proteins, exhibiting stable and symmetrical structures. Their precise compositions and dimensions provide versatile opportunities for modifications, enhancing their functionality. Consequently, VLP-based nanomaterials have gained widespread adoption across diverse domains. This review focuses on three key aspects: the mechanisms of viral capsid protein self-assembly into VLPs, design methods for constructing multifunctional VLPs, and strategies for synthesizing multidimensional nanomaterials using VLPs. It provides a comprehensive overview of the advancements in virus-inspired functional nanomaterials, encompassing VLP assembly, functionalization, and the synthesis of multidimensional nanomaterials. Additionally, this review explores future directions, opportunities, and challenges in the field of VLP-based nanomaterials, aiming to shed light on potential advancements and prospects in this exciting area of research.

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.

Controlling Mineralization with Protein-Functionalized Peptoid Nanotubes

Sequence-defined foldamers that self-assemble into well-defined architectures are promising scaffolds to template inorganic mineralization. However, it has been challenging to achieve robust control of nucleation and growth without sequence redesign or extensive experimentation. Here, peptoid nanotubes functionalized with a panel of solid-binding proteins are used to mineralize homogeneously distributed and monodisperse anatase nanocrystals from the water-soluble TiBALDH precursor. Crystallite size is systematically tuned between 1.4 and 4.4 nm by changing protein coverage and the identity and valency of the genetically engineered solid-binding segments. The approach is extended to the synthesis of gold nanoparticles and, using a protein encoding both material-binding specificities, to the fabrication of titania/gold nanocomposites capable of photocatalysis under visible-light illumination. Beyond uncovering critical roles for hierarchical organization and denticity on solid-binding protein mineralization outcomes, the strategy described herein should prove valuable for the fabrication of hierarchical hybrid materials incorporating a broad range of inorganic components.

Multilayered Ordered Protein Arrays Self-Assembled from a Mixed Population of Virus-like Particles

Biology shows many examples of spatially controlled assembly of cells and biomacromolecules into hierarchically organized structures, to which many of the complex biological functions are attributed. While such biological structures have inspired the design of synthetic materials, it is still a great challenge to control the spatial arrangement of individual building blocks when assembling multiple types of components into bulk materials. Here, we report self-assembly of multilayered, ordered protein arrays from mixed populations of virus-like particles (VLPs). We systematically tuned the magnitude of the surface charge of the VLPs via mutagenesis to prepare four different types of VLPs for mixing. A mixture of up to four types of VLPs selectively assembled into higher-order structures in the presence of oppositely charged dendrimers during a gradual lowering of the ionic strength of the solution. The assembly resulted in the formation of three-dimensional ordered VLP arrays with up to four distinct layers including a central core, with each layer comprising a single type of VLP. A coarse-grained computational model was developed and simulated using molecular dynamics to probe the formation of the multilayered, core-shell structure. Our findings establish a simple and versatile bottom-up strategy to synthesize multilayered, ordered materials by controlling the spatial arrangement of multiple types of nanoscale building blocks in a one-pot fabrication.

Protein Cages: From Fundamentals to Advanced Applications

Proteins that self-assemble into polyhedral shell-like structures are useful molecular containers both in nature and in the laboratory. Here we review efforts to repurpose diverse protein cages, including viral capsids, ferritins, bacterial microcompartments, and designed capsules, as vaccines, drug delivery vehicles, targeted imaging agents, nanoreactors, templates for controlled materials synthesis, building blocks for higher-order architectures, and more. A deep understanding of the principles underlying the construction, function, and evolution of natural systems has been key to tailoring selective cargo encapsulation and interactions with both biological systems and synthetic materials through protein engineering and directed evolution. The ability to adapt and design increasingly sophisticated capsid structures and functions stands to benefit the fields of catalysis, materials science, and medicine.

Plant viral nanoparticles for packaging and in vivo delivery of bioactive cargos

Nanoparticles have unique capabilities and considerable promise for many different biological uses. One capability is delivering bioactive cargos to specific cells, tissues, or organisms. Depending on the task, there are multiple variables to consider including nanoparticle selection, targeting strategies, and incorporating cargo so it can be delivered in a biologically active form. One nanoparticle option, genetically controlled plant viral nanoparticles (PVNPs), is highly uniform within a given virus but quite variable between viruses with a broad range of useful properties. PVNPs are flexible and versatile tools for incorporating and delivering a wide range of small or large molecule cargos. Furthermore, PVNPs can be modified to create nanostructures that can solve problems in medical, environmental, and basic research. This review discusses the currently available techniques for delivering bioactive cargos with PVNPs and potential cargos that can be delivered with these strategies. This article is categorized under: Implantable Materials and Surgical Technologies > Nanomaterials and Implants Biology-Inspired Nanomaterials > Protein and Virus-Based Structures.

Fabrication of nanohybrids assisted by protein-based materials for catalytic applications

Protein units and architectures were applied as supports in the synthesis of metal and metal oxide nanoparticles for environmentally benign catalytic applications.

Changes in the stability and biomechanics of P22 bacteriophage capsid during maturation

The capsid of P22 bacteriophage undergoes a series of structural transitions during maturation that guide it from spherical to icosahedral morphology. The transitions include the release of scaffold proteins and capsid expansion. Although P22 maturation has been investigated for decades, a unified model that incorporates thermodynamic and biophysical analyses is not available. A general and specific model of icosahedral capsid maturation is of significant interest to theoreticians searching for fundamental principles as well as virologists and material scientists seeking to alter maturation to their advantage. To address this challenge, we have combined the results from orthogonal biophysical techniques including differential scanning fluorimetry, atomic force microscopy, circular dichroism, and hydrogen-deuterium exchange mass spectrometry. By integrating these results from single particle and population measurements, an energy landscape of P22 maturation from procapsid through expanded shell to wiffle ball emerged, highlighting the role of metastable structures and the thermodynamics guiding maturation. The propagation of weak quaternary interactions across symmetric elements of the capsid is a key component for stability in P22. A surprising finding is that the progression to wiffle ball, which lacks pentamers, shows that chemical and thermal stability can be uncoupled from mechanical rigidity, elegantly demonstrating the complexity inherent in capsid protein interactions and the emergent properties that can arise from icosahedral symmetry. On a broader scale, this work demonstrates the power of applying orthogonal biophysical techniques to elucidate assembly mechanisms for supramolecular complexes and provides a framework within which other viral systems can be compared.

Modular Self-Assembly of Protein Cage Lattices for Multistep Catalysis

The assembly of individual molecules into hierarchical structures is a promising strategy for developing three-dimensional materials with properties arising from interaction between the individual building blocks. Virus capsids are elegant examples of biomolecular nanostructures, which are themselves hierarchically assembled from a limited number of protein subunits. Here, we demonstrate the bio-inspired modular construction of materials with two levels of hierarchy: the formation of catalytically active individual virus-like particles (VLPs) through directed self-assembly of capsid subunits with enzyme encapsulation, and the assembly of these VLP building blocks into three-dimensional arrays. The structure of the assembled arrays was successfully altered from an amorphous aggregate to an ordered structure, with a face-centered cubic lattice, by modifying the exterior surface of the VLP without changing its overall morphology, to modulate interparticle interactions. The assembly behavior and resultant lattice structure was a consequence of interparticle interaction between exterior surfaces of individual particles and thus independent of the enzyme cargos encapsulated within the VLPs. These superlattice materials, composed of two populations of enzyme-packaged VLP modules, retained the coupled catalytic activity in a two-step reaction for isobutanol synthesis. This study demonstrates a significant step toward the bottom-up fabrication of functional superlattice materials using a self-assembly process across multiple length scales and exhibits properties and function that arise from the interaction between individual building blocks.

Encapsulation of Inorganic Nanomaterials inside Virus-Based Nanoparticles for Bioimaging

Virus-based nanoparticles (VNPs) can serve as containers for inorganic nanomaterials with excellent physical and chemical properties. Incorporation of nanomaterials inside the inner cavity of VNPs has opened up lots of possibilities for imaging applications in the field of biology and medicine. Encapsulation of inorganic nanoparticles (NPs) in VNPs can achieve the labeling of VNPs with nanoprobes and maintain the original outer surface features of VNPs at the same time. In return, VNPs enhance the stability and biocompatibility of the inorganic cargoes. This review briefly summarizes the current typical strategies to encapsulate inorganic nanomaterials in VNPs, i.e. mineralization and self-assembly, as well as the applications of these hybrid nanostructures in the field of bioimaging, including in vitro and in vivo fluorescence imaging, magnetic resonance imaging, and theranostics. Nanophotonic studies based on the VNP platform are also discussed. We anticipate that this field will continue to flourish, with new exciting opportunities stemming from advancements in the rational design of VNPs, the development of excellent inorganic nanomaterials, the integration of multiple functionalities, and the regulation of nano-bio interfacial interactions.

Pathways for Gold Nucleation and Growth over Protein Cages

Proteins are widely utilized as templates in biomimetic synthesis of gold nanocrystals. However, the role of proteins in mediating the pathways for gold nucleation and growth is not well understood, in part because of the lack of spatial resolution in probing the complicated biomimetic mineralization process. Self-assembled protein cages, with larger size and symmetry, can facilitate in the visualization of both biological and inorganic components. We have utilized bacteriophage P22 protein cages of ∼60 nm diameter for investigating the nucleation and growth of gold nanocrystals. By adding a gold precursor into the solution with preexisting protein cages and a reducing agent, gold nuclei/prenucleation clusters form in solution, which then locate and attach to specific binding sites on protein cages and further grow to form gold nanocrystals. By contrast, addition of the reducing agent into the solution with incubated gold precursor and protein cages leads to the formation of gold nuclei/prenucleation clusters both in solution and on the surface of protein cages that then grow into gold nanocrystals. Because of the presence of cysteine (Cys) with strong gold-binding affinity, gold nanocrystals tend to bind at specific sites of Cys, irrespective of the binding sites of gold ions. Analyzing the results obtained using these alternate routes provide important insights into the pathways of protein-mediated biomimetic nucleation of gold that challenge the importance of incubation, which is widely utilized in the biotemplated synthesis of inorganic nanocrystals.

Virus-like particles: Next-generation nanoparticles for targeted therapeutic delivery

Most drug therapies distribute the agents throughout the entire body, even though the drugs are typically only needed at specific tissues. This often limits dosage and causes discomfort and harmful side‐effects. Significant research has examined nanoparticles (NPs) for use as targeted delivery vehicles for therapeutic cargo, however, major clinical success has been limited. Current work focuses mainly on liposomal and polymer‐based NPs, but emerging research is exploring the engineering of viral capsids as noninfectious protein‐based NPs—termed virus‐like particles (VLPs). This review covers the research that has been performed thus far and outlines the potential for these VLPs to become highly effective delivery vehicles that overcome the many challenges encountered for targeted delivery of therapeutic cargo.

Construction of core-shell hybrid nanoparticles templated by virus-like particles

Catalytically active gold in silica core–shell nanoparticles are prepared by pH controlled templating on virus-like particles.

Contemplating a role for titanium in organisms

Titanium is the ninth most abundant element in the Earth's crust and some organisms sequester it avidly, though no essential biological role has yet been recognized. This Minireview addresses how the properties of titanium, especially in an oxic aqueous environment, might make a biological role difficult to recognize. It further considers how new -omic technologies might overcome the limitations of the past and help to reveal a specific role for this metal. While studies with well established model organisms have their rightful place, organisms that are known avid binders or sequesterers of titanium should be promising places to investigate a biological role.

Protein cages and synthetic polymers: a fruitful symbiosis for drug delivery applications, bionanotechnology and materials science

Protein cages have become essential tools in bionanotechnology due to their well-defined, monodisperse, capsule-like structure. Combining them with synthetic polymers greatly expands their application, giving rise to novel nanomaterials fore.g.drug-delivery, sensing, electronic devices and for uses as nanoreactors.