Controlled assembly of rodlike viruses with polymers

Polymer-templated supramolecular co-assemblies of proteins and metal oxide clusters as versatile platform for chemo-enzymatic catalysis

The hybridization of enzymes and inorganics in controlled manner is challenging, however, critical for the development of chemo-enzymatic cascade catalyst with high efficiency and selectivity. Here, proteins and metal oxide clusters can be facilely co-assembled on the surface of colloid of poly(4-vinylpyridine) (P4VP) via hydrogen bonding, due to their enriched surface hydrogen bonding donors. The co-assembly method can be generally applied for preparing chemo-enzymatic catalyst within the selected database of various proteins and metal oxide clusters while the assembly units retain their structures and activities. Typically, a 2.5 nm metal oxide cluster {Mo₇₂Fe₃₀}, with peroxidase-like activity, are complexed with glucose oxidase (GOX) on P4VP for the catalysis against the oxidization of o-dianisidine (ODA) with the existence of glucose. Due to the synergistic effects of chemical and enzymatic catalysis, the co-assemblies show even higher ODA oxidation activity compared to GOX/catalase bi-enzymatic system, confirming the effectiveness of the co-assembly protocol for cascade catalysis and enabling its applications in rapid glucose detection and biomass conversion.

Synthesis and Advanced Characterization of Polymer–Protein Core–Shell Nanoparticles

Enzyme immobilization techniques are widely researched due to their wide range of applications. Polymer–protein core–shell nanoparticles (CSNPs) have emerged as a promising technique for enzyme/protein immobilization via a self-assembly process. Based on the desired application, different sizes and distribution of the polymer–protein CSNPs may be required. This work systematically studies the assembly process of poly(4-vinyl pyridine) and bovine serum albumin CSNPs. Average particle size was controlled by varying the concentrations of each reagent. Particle size and size distributions were monitored by dynamic light scattering, ultra-small-angle X-ray scattering, small-angle X-ray scattering and transmission electron microscopy. Results showed a wide range of CSNPs could be assembled ranging from an average radius as small as 52.3 nm, to particles above 1 µm by adjusting reagent concentrations. In situ X-ray scattering techniques monitored particle assembly as a function of time showing the initial particle growth followed by a decrease in particle size as they reach equilibrium. The results outline a general strategy that can be applied to other CSNP systems to better control particle size and distribution for various applications.

Protein-coated corrole nanoparticles for the treatment of prostate cancer cells

Development of novel therapeutic strategies to eradicate malignant tumors is of paramount importance in cancer research. In a recent study, we have introduced a facile protocol for the preparation of corrole-protein nanoparticles (NPs). These NPs consist of a corrole-core coated with protein. We now report that a novel lipophilic corrole, (2)Ga, delivered as human serum albumin (HSA)-coated NPs, displayed antineoplastic activity towards human prostate cancer DU-145 cells. Cryo-TEM analysis of these NPs revealed an average diameter of 50.2 ± 8.1 nm with a spherical architecture exhibiting low polydispersity. In vitro cellular uptake of (2)Ga/albumin NPs was attributable to rapid internalization of the corrole through ligand binding-dependent extracellular release and intercalation of the corrole cargo into the lipid bilayer of the plasma membrane. This finding is in contrast with a previously reported study on corrole-protein NPs that displayed cellular uptake via endocytosis. Investigation of the non-light-induced mechanism of action of (2)Ga suggested the induction of necrosis through plasma membrane destabilization, impairment of calcium homeostasis, lysosomal stress and rupture, as well as formation of reactive oxygen species (ROS). (2)Ga also exhibited potent light-induced cytotoxicity through ROS generation. These findings demonstrate a rapid cellular uptake of (2)Ga/protein NPs along with targeted induction of tumor cell necrosis.

Synthesis and Characterization of Bio-Active GFP-P4VP Core–Shell Nanoparticles

Bioactive core–shell nanoparticles (CSNPs) offer the unique ability for protein/enzyme functionality in non-native environments. For many decades, researchers have sought to develop synthetic materials which mimic the efficiency and catalytic power of bioactive macromolecules such as enzymes and proteins. This research studies a self-assembly method in which functionalized, polymer-core/protein-shell nanoparticles are prepared in mild conditions. Transmission electron microscopy (TEM) and dynamic light scattering (DLS) techniques were utilized to analyze the size and distribution of the CSNPs. The methods outlined in this research demonstrate a mild, green chemistry synthesis route for CSNPs which are highly tunable and allow for enzyme/protein functionality in non-native conditions.

Artificial Cellulosome Complex from the Self-Assembly of Ni-NTA-Functionalized Polymeric Micelles and Cellulases

Polymer-protein core-shell nanoparticles have been explored for enzyme immobilization. This work reports on the development of functional polymeric micelles for immobilizing His6 -tagged cellulases with controlled spatial orientation of enzymes, resulting in "artificial cellulosomes" for effective cellulose hydrolysis. Poly(styrene)-b-poly(styrene-alt-maleic anhydride) was prepared through one-pot reversible addition-fragmentation chain-transfer polymerization and modified with nitrilotriacetic acid (NTA) to afford an amphiphilic block copolymer. The self-assembled polymer was mixed with a solution of NiSO4 to form Ni-NTA-functionalized micelles, which could successfully capture His6 -tagged cellulases and form hierarchically structured core-shell nanoparticles with cellulases as the corona. Because the anchored enzymes are site-specifically oriented and in close proximity, synergistic catalysis that results in over twofold activity enhancement has been achieved.

Cell-Penetrating Protein/Corrole Nanoparticles

Recent work has highlighted the potential of metallocorroles as versatile platforms for the development of drugs and imaging agents, since the bioavailability, physicochemical properties and therapeutic activity can be dramatically altered by metal ion substitution and/or functional group replacement. Significant advances in cancer treatment and imaging have been reported based on work with a water-soluble bis-sulfonated gallium corrole in both cellular and rodent-based models. We now show that cytotoxicities increase in the order Ga < Fe < Al < Mn < Sb < Au for bis-sulfonated corroles; and, importantly, that they correlate with metallocorrole affinities for very low density lipoprotein (VLDL), the main carrier of lipophilic drugs. As chemotherapeutic potential is predicted to be enhanced by increased lipophilicity, we have developed a novel method for the preparation of cell-penetrating lipophilic metallocorrole/serum-protein nanoparticles (NPs). Cryo-TEM revealed an average core metallocorrole particle size of 32 nm, with protein tendrils extending from the core (conjugate size is ~100 nm). Optical imaging of DU-145 prostate cancer cells treated with corrole NPs (≤100 nM) revealed fast cellular uptake, very slow release, and distribution into the endoplasmic reticulum (ER) and lysosomes. The physical properties of corrole NPs prepared in combination with transferrin and albumin were alike, but the former were internalized to a greater extent by the transferrin-receptor-rich DU-145 cells. Our method of preparation of corrole/protein NPs may be generalizable to many bioactive hydrophobic molecules to enhance their bioavailability and target affinity.

Tobacco Mosaic Virus-Functionalized Mesoporous Silica Nanoparticles, a Wool-Ball-like Nanostructure for Drug Delivery

The design of versatile tools to improve cell targeting and drug delivery in medicine has become increasingly pertinent to nanobiotechnology. Biological and inorganic nanocarrier drug delivery systems are being explored, showing advantages and disadvantages in terms of cell targeting and specificity, cell internalization, efficient payload delivery, and safety profiles. Combining the properties of a biological coating on top of an inorganic nanocarrier, we hypothesize that this hybrid system would improve nanoparticle-cell interactions, resulting in enhanced cell targeting and uptake properties compared to the bare inorganic nanocarrier. Toward this goal, we engineered a hierarchical assembly featuring the functionalization of cargo-loaded mesoporous silica nanoparticles (MSNPs) with tobacco mosaic virus (TMV) as a biological coating. The MSNP functions as a delivery system because the porous structure enables high therapeutic payload capacity, and TMV serves as a biocompatible coating to enhance cell interactions. The resulting MSNP@TMV nanohybrids have a wool-ball-like appearance and demonstrate enhanced cell uptake, hence cargo delivery properties. The MSNP@TMV have potential for medical applications such as drug delivery, contrast agent imaging, and immunotherapy.

Polymer-Protein Core-Shell Nanoparticles for Enhanced Antigen Immunogenicity

Nanoengineered vaccine platforms can be modeled after viruses and other pathogens with highly organized and repetitive structures that trigger the host immune system. Here we demonstrated a pyridine-grafted poly(ε-caprolactone)-based polymer-protein core-shell nanoparticles (PPCS-NPs) platform can effectively trigger the host immune system and lead to significantly higher antibody titers.

Combining Protein Cages and Polymers: from Understanding Self-Assembly to Functional Materials

Protein cages, such as viruses, are well-defined biological nanostructures which are highly symmetrical and monodisperse. They are found in various shapes and sizes and can encapsulate or template non-native materials. Furthermore, the proteins can be chemically or genetically modified giving them new properties. For these reasons, these protein structures have received increasing attention in the field of polymer-protein hybrid materials over the past years, however, advances are still to be made. This Viewpoint highlights the different ways polymers and protein cages or their subunits have been combined to understand self-assembly and create functional materials.

Small Angle X-ray Scattering for Nanoparticle Research

X-ray scattering is a structural characterization tool that has impacted diverse fields of study. It is unique in its ability to examine materials in real time and under realistic sample environments, enabling researchers to understand morphology at nanometer and angstrom length scales using complementary small and wide angle X-ray scattering (SAXS, WAXS), respectively. Herein, we focus on the use of SAXS to examine nanoscale particulate systems. We provide a theoretical foundation for X-ray scattering, considering both form factor and structure factor, as well as the use of correlation functions, which may be used to determine a particle's size, size distribution, shape, and organization into hierarchical structures. The theory is expanded upon with contemporary use cases. Both transmission and reflection (grazing incidence) geometries are addressed, as well as the combination of SAXS with other X-ray and non-X-ray characterization tools. We conclude with an examination of several key areas of research where X-ray scattering has played a pivotal role, including in situ nanoparticle synthesis, nanoparticle assembly, and operando studies of catalysts and energy storage materials. Throughout this review we highlight the unique capabilities of X-ray scattering for structural characterization of materials in their native environment.

Viral nano-hybrids for innovative energy conversion and storage schemes

Typical rod-like viruses (the Tobacco Mosaic Virus (TMV) and the Bacteriophage M13) are biological nanostructures that couple a 1D mono-dispersed morphology with a precisely defined topology of surface spaced and orthogonal reactive domains. These biogenic scaffolds offer a unique alternative to synthetic nano-platforms for the assembly of functional molecules and materials. Spatially resolved 1D arrays of inorganic-organic hybrid domains can thus be obtained on viral nano-templates resulting in the functional arrangement of photo-triggers and catalytic sites with applications in light energy conversion and storage. Different synthetic strategies are herein highlighted depending on the building blocks and with a particular emphasis on the molecular design of viral-templated nano-interfaces holding great potential for the dream-goal of artificial photosynthesis.

Functionalized protein nanoemulsions by incorporation of chemically modified BSA

BSA-bioconjugates were synthesized for production of functionalized protein-based nanoemulsions using high pressure homogenization. These PEGylated nanoemulsions are designed for intravenous administration and drug delivery.

Enhanced therapeutic efficacy and cytotoxicity of doxorubicin-loaded vitamin E – Pluronic micelles against liver cancer

In this study, a new polymeric micelle delivery system was developed to increase the therapeutic efficacy of doxorubicin (DOX) and to reduce its associated side effects.

Nanoengineered particles for enhanced intra-articular retention and delivery of proteins

Localized intra-articular delivery of anti-inflammatory proteins can reduce inflammation in osteoarthritis but poses a challenge because of raid clearance within few hours of injection. A new class of polymer is developed that forms self-assembled nanoparticles ranging from 300 to 900 nm and demonstrates particle size dependent prolonged retention in intra-articular joint spaces compared to bolus protein over a period of 14 d.

Facile co-assembly process to generate core-shell nanoparticles with functional protein corona

A simple and robust protocol to maintain the structural feature of polymer-protein core-shell nanoparticles (PPCS-NPs) is developed based on the synergistic interactions between proteins and functional polymers. Using the self-assembly method, a broad range of proteins can be assembled to the selective water-insoluble polymers containing pyridine groups. The detailed analysis of the PPCS-NPs structure was conducted using FESEM and thin-sectioned TEM. The results illustrated that the protein molecules are located on the corona of the PPCS-NPs. While proteins are displacing between water and polymer to minimize the interfacial energy, the polymer offers a unique microenvironment to maintain protein structure and conformation. The proposed mechanism is based on a fine balance between hydrophobicity and hydrophilicity, as well as hydrogen bonding between proteins and polymer. The PPCS-NPs can serve as a scaffold to incorporate both glucose oxidase (GOX) and horseradish peroxidase (HRP) onto a single particle. Such a GOX-HRP bienzymatic system showed a ~20% increase in activity in comparison to the mixed free enzymes. Our method therefore provides a unique platform to preserve protein structure and conformation and can be extended to a number of biomolecules.

Self-assembly of rodlike virus to superlattices

Rodlike tobacco mosaic virus (TMV) has been found to assemble into superlattices in aqueous solution using the polymer methylcellulose to induce depletion and free volume entropy-based attractive forces. Both transmission electron microscopy and small-angle X-ray scattering show that the superlattices form in both semidilute and concentrated regimes of polymer, where the free volume entropy and the depletion interaction are the dominant driving force, respectively. The superlattices are NaCl and temperature responsive. The rigidity of the rodlike nanoparticles also plays an important role for the formation of superlattices through the free volume entropy mechanism. Compared to the rigid TMV particle, flexible bacteriophage M13 particles are only responsive to the depletion force and thus only assemble in highly concentrated polymer solution, where depletion interaction is dominant.

Superlattice of rodlike virus particles formed in aqueous solution through like-charge attraction

Rodlike tobacco mosaic virus (TMV) has been found to assemble into a 2D superlattice in aqueous solution with hexagonally packed structures in the presence of Ba(2+) through like-charge attraction whereas lower-Z divalent ions such as Zn(2+), Cd(2+), Mg(2+), and Ca(2+) induce only liquidlike ordering. The molar ratio between Ba(2+) and TMV is a crucial parameter in the formation of the superlattice. There is a critical molar ratio of Ba(2+) to TMV at which TMV exhibits a transition from a nonordered colloidal state to an ordered crystalline state. It is also found that the superlattice is formed regardless of the pH and TMV concentration within the range studied.

Genetically designed Peptide-based molecular materials

With recent developments of nanoscale engineering in the physical and chemical sciences and advances in molecular biology, molecular biomimetics is combining genetic tools and evolutionary approaches with synthetic nanoscale constructs to create a new hybrid methodology: genetically designed peptide-based molecular materials. Following the fundamental principles of genome-based design, molecular recognition, and self-assembly in nature, we can now use recombinant DNA technologies to design single or multifunctional peptides and peptide-based molecular constructs that can interact with solids and synthetic systems. These solid-binding peptides have made significant impact as inorganic synthesizers, nanoparticle linkers, and molecular assemblers, or simply as molecular building blocks, in a wide range of fields from chemistry to materials science to medicine. As part of the programmatic theme, "Nanoscience: Challenges for the Future", the current developments, challenges, and future prospects of the field were presented during a symposium at the 237th ACS National Meeting held in March 2009. This Nano Focus article presents a synopsis of the work discussed there.