Terminal supraparticle assemblies from similarly charged protein molecules and nanoparticles

Protein-nanoparticle co-assembly supraparticles for drug delivery: Ultrahigh drug loading and colloidal stability, and instant and complete lysosomal drug release

Two frequent problems hindering clinical translation of nanomedicine are low drug loading and low colloidal stability. Previous efforts to achieve ultrahigh drug loading (>30 %) introduce new hurdles, including lower colloidal stability and others, for clinical translation. Herein, we report a new class of drug nano-carriers based on our recent finding in protein-nanoparticle co-assembly supraparticle (PNCAS), with both ultrahigh drug loading (58 % for doxorubicin, i.e., DOX) and ultrahigh colloidal stability (no significant change in hydrodynamic size after one year). We further show that our PNCAS-based drug nano-carrier possesses a built-in environment-responsive drug release feature: once in lysosomes, the loaded drug molecules are released instantly (<1 min) and completely (∼100 %). Our PNCAS-based drug delivery system is spontaneously formed by simple mixing of hydrophobic nanoparticles, albumin and drugs. Several issues related to industrial production are studied. The ultrahigh drug loading and stability of DOX-loaded PNCAS enabled the delivery of an exceptionally high dose of DOX into a mouse model of breast cancer, yielding high efficacy and no observed toxicity. With further developments, our PNCAS-based delivery systems could serve as a platform technology to meet the multiple requirements of clinical translation of nanomedicines.

Tapered chiral nanoparticles as broad-spectrum thermally stable antivirals for SARS-CoV-2 variants

The incessant mutations of viruses, variable immune responses, and likely emergence of new viral threats necessitate multiple approaches to novel antiviral therapeutics. Furthermore, the new antiviral agents should have broad-spectrum activity and be environmentally stable. Here, we show that biocompatible tapered CuS nanoparticles (NPs) efficiently agglutinate coronaviruses with binding affinity dependent on the chirality of surface ligands and particle shape. L-penicillamine-stabilized NPs with left-handed curved apexes display half-maximal inhibitory concentrations (IC50) as low as 0.66 pM (1.4 ng/mL) and 0.57 pM (1.2 ng/mL) for pseudo-type SARS-CoV-2 viruses and wild-type Wuhan-1 SARS-CoV-2 viruses, respectively, which are about 1,100 times lower than those for antibodies (0.73 nM). Benefiting from strong NPs-protein interactions, the same particles are also effective against other strains of coronaviruses, such as HCoV-HKU1, HCoV-OC43, HCoV-NL63, and SARS-CoV-2 Omicron variants with IC50 values below 10 pM (21.8 ng/mL). Considering rapid response to outbreaks, exposure to elevated temperatures causes no change in the antiviral activity of NPs while antibodies are completely deactivated. Testing in mice indicates that the chirality-optimized NPs can serve as thermally stable analogs of antiviral biologics complementing the current spectrum of treatments.

Self-Assembly of Core-Shell Hybrid Nanoparticles by Directional Crystallization of Grafted Polymers

Nanoparticle self-assembly is an efficient bottom-up strategy for the creation of nanostructures. In a typical approach, ligands are grafted onto the surfaces of nanoparticles to improve the dispersion stability and control interparticle interactions. Ligands then remain secondary and usually are not expected to order significantly during superstructure formation. Here, we investigate how ligands can play a more decisive role in the formation of anisotropic inorganic-organic hybrid materials. We graft poly(2-iso-propyl-2-oxazoline) (PiPrOx) as a crystallizable shell onto SiO2 nanoparticles. By varying the PiPrOx grafting density, both solution stability and nanoparticle aggregation behavior can be controlled. Upon prolonged heating, anisotropic nanostructures form in conjunction with the crystallization of the ligands. Self-assembly of hybrid PiPrOx@SiO2 (shell@core) nanoparticles proceeds in two steps: First, the rapid formation of amorphous aggregates occurs via gelation, mediated by the interaction between nanoparticles through grafted polymer chains. As a second step, slow radial growth of fibers was observed via directional crystallization, governed by the incorporation of crystalline ribbons formed from free polymeric ligands in combination with crystallization of the covalently attached ligand shell. Our work reveals how crystallization-driven self-assembly of ligands can create intricate hybrid nanostructures.

Self-Organization of Iron Sulfide Nanoparticles into Complex Multicompartment Supraparticles

Self-assembled compartments from nanoscale components are found in all life forms. Their characteristic dimensions are in 50-1000 nm scale, typically assembled from a variety of bioorganic "building blocks". Among the various functions that these mesoscale compartments carry out, protection of the content from the environment is central. Finding synthetic pathways to similarly complex and functional particles from technologically friendly inorganic nanoparticles (NPs) is needed for a multitude of biomedical, biochemical, and biotechnological processes. Here, it is shown that FeS2 NPs stabilized by l-cysteine self-assemble into multicompartment supraparticles (mSPs). The NPs initially produce ≈55 nm concave assemblies that reconfigure into ≈75 nm closed mSPs with ≈340 interconnected compartments with an average size of ≈5 nm. The intercompartmental partitions and mSP surface are formed primarily from FeS2 and Fe2 O3 NPs, respectively. The intermediate formation of cup-like particles enables encapsulation of biological cargo. This capability is demonstrated by loading mSPs with DNA and subsequent transfection of mammalian cells. Also it is found that the temperature stability of the DNA cargo is enhanced compared to the traditional delivery vehicles. These findings demonstrate that biomimetic compartmentalized particles can be used to successfully encapsulate and enhance temperature stability of the nucleic acid cargo for a variety of bioapplications.

On-nanoparticle monolayers as a solute-specific, solvent-like phase

In addition to modifying surface properties, self-assembled monolayers, SAMs, on nanoparticles can selectively incorporate small molecules from the surrounding solution. This selectivity has been used in the design of substrate-specific catalytic systems but its degree has not been quantified. This work uses catalytic centers embedded in on-nanoparticle hydrophobic SAMs to monitor and quantify the partitioning of molecules between the bulk solvent and these monolayers. A combination of experiments and theory allows us to relate the logarithm of the incorporation-into-SAM constant to the "bulk" log P values, characterizing the incoming substrates. These results are in line with classic, semi-empirical linear free energy relationships between partitioning solvent systems; in this way, they substantiate the view of nanoscopic on-particle SAMs acting akin to a bulk solvent phase.

Turning chiral peptides into a racemic supraparticle to induce the self-degradation of MDM2

INTRODUCTION

Chirality is immanent in nature, and chiral molecules can achieve their pharmacological action through chiral matching with biomolecules and molecular conformation recognition.

OBJECTIVES

Clinical translation of chiral therapeutics, particularly chiral peptide molecules, has been hampered by their unsatisfactory pharmaceutical properties.

METHODS

A mild and simple self-assembly strategy was developed here for the construction of peptide-derived chiral supramolecular nanomedicine with suitable pharmaceutical properties. In this proof-of-concept study, we design a D-peptide as MDM2 Self-Degradation catalysts (MSDc) to induce the self-degradation of a carcinogenic E3 Ubiquitin ligase termed MDM2. Exploiting a metal coordination between mercaptan in peptides and trivalent gold ion, chiral MSDc was self-assembled into a racemic supraparticle (MSDNc) that eliminated the consume from the T-lymphocyte/macrophage phagocytose in circulation.

RESULTS

Expectedly, MSDNc down-regulated MDM2 in more action than its L-enantiomer termed ^CtrlMSDNc. More importantly, MSDNc preponderantly suppressed the tumor progression and synergized the tumor immunotherapy in allograft model of melanoma through p53 restoration in comparison to ^CtrlMSDNc.

CONCLUSION

Collectively, this work not only developed a secure and efficient therapeutic agent targeting MDM2 with the potential of clinical translation, but also provided a feasible and biocompatible strategy for the construction of peptide supraparticle and expanded the application of chiral therapeutic and homo-PROTAC to peptide-derived chiral supramolecular nanomedicine.

Electric, magnetic, and shear field-directed assembly of inorganic nanoparticles

Ordered assemblies of inorganic nanoparticles (NPs) have shown tremendous potential for wide applications due to their unique collective properties, which differ from those of individual NPs. Various assembly methods, such as external field-directed assembly, interfacial assembly, template assembly, biomolecular recognition-mediated assembly, confined assembly, and others, have been employed to generate ordered inorganic NP assemblies with hierarchical structures. Among them, the external field-directed assembly method is particularly fascinating, as it can remotely assemble NPs into well-ordered superstructures. Moreover, external fields (e.g., electric, magnetic, and shear fields) can introduce a local and/or global field intensity gradient, resulting in an additional force on NPs to drive their rotation and/or translation. Therefore, the external field-directed assembly of NPs becomes a robust method to fabricate well-defined functional materials with the desired optical, electronic, and magnetic properties, which have various applications in catalysis, sensing, disease diagnosis, energy conversion/storage, photonics, nano-floating-gate memory, and others. In this review, the effects of an electric field, magnetic field, and shear field on the organization of inorganic NPs are highlighted. The methods for controlling the well-ordered organization of inorganic NPs at different scales and their advantages are reviewed. Finally, future challenges and perspectives in this field are discussed.

Chiral-engineered supraparticles: Emerging tools for drug delivery

The handedness of chiral-engineered supraparticles (CE-SPs) influences their interactions with cells and proteins, as evidenced by the increased penetration of breast, cervical, and myeloma cell membranes by d-chirality-coordinated SPs. Quartz crystal dissipation and isothermal titration calorimetry have been used to investigate such chiral-specific interactions. d-SPs are more thermodynamically stable compared with l-SPs in terms of their adhesion. Proteases and other endogenous proteins can be shielded by the opposite chirality of d-SPs, resulting in longer half-lives. Incorporating nanosystems with d-chirality increases uptake by cancer cells and prolongs in vivo stability, demonstrating the importance of chirality in biomaterials. Thus, as we discuss here, chiral nanosystems could enhance drug delivery systems, tumor markers, and biosensors, among other biomaterial-based technologies, by allowing for better control over their features.

Hierarchical Materials from High Information Content Macromolecular Building Blocks: Construction, Dynamic Interventions, and Prediction

Hierarchical materials that exhibit order over multiple length scales are ubiquitous in nature. Because hierarchy gives rise to unique properties and functions, many have sought inspiration from nature when designing and fabricating hierarchical matter. More and more, however, nature's own high-information content building blocks, proteins, peptides, and peptidomimetics, are being coopted to build hierarchy because the information that determines structure, function, and interfacial interactions can be readily encoded in these versatile macromolecules. Here, we take stock of recent progress in the rational design and characterization of hierarchical materials produced from high-information content blocks with a focus on stimuli-responsive and "smart" architectures. We also review advances in the use of computational simulations and data-driven predictions to shed light on how the side chain chemistry and conformational flexibility of macromolecular blocks drive the emergence of order and the acquisition of hierarchy and also on how ionic, solvent, and surface effects influence the outcomes of assembly. Continued progress in the above areas will ultimately usher in an era where an understanding of designed interactions, surface effects, and solution conditions can be harnessed to achieve predictive materials synthesis across scale and drive emergent phenomena in the self-assembly and reconfiguration of high-information content building blocks.

Multimodal Enzyme-Carrying Suprastructures for Rapid and Sensitive Biocatalytic Cascade Reactions

Colloidal assemblies of mesoporous suprastructures provide effective catalysis in an advantageous volume-confined environment. However, typical fabrication methods of colloidal suprastructures are carried out under toxic or harmful conditions for unstable biomolecules, such as, biocatalytic enzymes. For this reason, biocatalytic enzymes have rarely been used with suprastructures, even though biocatalytic cascade reactions in confined environments are more efficient than in open conditions. Here, multimodal enzyme- and photocatalyst-carrying superstructures with efficient cascade reactions for colorimetric glucose detection are demonstrated. The suprastructures consisting of various functional nanoparticles, including enzyme-carrying nanoparticles, are fabricated by surface-templated evaporation driven suprastructure synthesis on polydimethylsiloxane-grafted surfaces at ambient conditions. For the fabrication of suprastructures, no additional chemicals and reactions are required, which allows maintaining the enzyme activities. The multimodal enzymes (glucose oxidase and peroxidase)-carrying suprastructures exhibit rapid and highly sensitive glucose detection via two enzyme cascade reactions in confined geometry. Moreover, the combination of enzymatic and photocatalytic cascade reactions of glucose oxidase to titanium dioxide nanoparticles is successfully realized for the same assay. These results show promising abilities of multiple colloidal mixtures carrying suprastructures for effective enzymatic reactions and open a new door for advanced biological reactions and enzyme-related works.

Protein Assembly by Design

Proteins are nature's primary building blocks for the construction of sophisticated molecular machines and dynamic materials, ranging from protein complexes such as photosystem II and nitrogenase that drive biogeochemical cycles to cytoskeletal assemblies and muscle fibers for motion. Such natural systems have inspired extensive efforts in the rational design of artificial protein assemblies in the last two decades. As molecular building blocks, proteins are highly complex, in terms of both their three-dimensional structures and chemical compositions. To enable control over the self-assembly of such complex molecules, scientists have devised many creative strategies by combining tools and principles of experimental and computational biophysics, supramolecular chemistry, inorganic chemistry, materials science, and polymer chemistry, among others. Owing to these innovative strategies, what started as a purely structure-building exercise two decades ago has, in short order, led to artificial protein assemblies with unprecedented structures and functions and protein-based materials with unusual properties. Our goal in this review is to give an overview of this exciting and highly interdisciplinary area of research, first outlining the design strategies and tools that have been devised for controlling protein self-assembly, then describing the diverse structures of artificial protein assemblies, and finally highlighting the emergent properties and functions of these assemblies.

Probing the size-dependent polarizability of mesoscopic ionic clusters and their induced-dipole interactions

Mesoscopic clusters composed of oppositely charged particles are ubiquitous in synthetic and biological soft materials. The effective interaction between these clusters is influenced by their polarizability, that is, the ability of their constituent charges to re-arrange in response to an external electrical field. Here, using coarse-grained simulations, we show that the polarizability of electrically neutral ionic clusters decreases as the number of constituent charges increases and/or their Coulombic interaction strength increases for various ion valencies, ion densities, and degrees of cluster boundary hardness. For clusters of random ionomers and their counterions, their polarizability is shown to depend on the number of polymer chains. The variation of the cluster polarizability with the cluster size indicates that throughout the assembly, the induced-dipole interactions between the clusters may be reduced substantially as they acquire more charges while maintaining zero net charge. Under certain conditions, the induced-dipole interactions may become repulsive, as inferred from our simulations with a polarizable solvent. As a result, the dipole-induced related interactions can serve as a counterbalancing force that contributes to the self-limiting aggregation of charge-containing assemblies.

On the Metal-Aided Catalytic Mechanism for Phosphodiester Bond Cleavage Performed by Nanozymes

Recent studies have shown that gold nanoparticles (AuNPs) functionalized with Zn(II) complexes can cleave phosphate esters and nucleic acids. Remarkably, such synthetic nanonucleases appear to catalyze metal (Zn)-aided hydrolytic reactions of nucleic acids similar to metallonuclease enzymes. To clarify the reaction mechanism of these nanocatalysts, here we have comparatively analyzed two nanonucleases with a >10-fold difference in the catalytic efficiency for the hydrolysis of the 2-hydroxypropyl-4-nitrophenylphosphate (HPNP, a typical RNA model substrate). We have used microsecond-long atomistic simulations, integrated with NMR experiments, to investigate the structure and dynamics of the outer coating monolayer of these nanoparticles, either alone or in complex with HPNP, in solution. We show that the most efficient one is characterized by coating ligands that promote a well-organized monolayer structure, with the formation of solvated bimetallic catalytic sites. Importantly, we have found that these nanoparticles can mimic two-metal-ion enzymes for nucleic acid processing, with Zn ions that promote HPNP binding at the reaction center. Thus, the two-metal-ion-aided hydrolytic strategy of such nanonucleases helps in explaining their catalytic efficiency for substrate hydrolysis, in accordance with the experimental evidence. These mechanistic insights reinforce the parallelism between such functionalized AuNPs and proteins toward the rational design of more efficient catalysts.

Supraparticle Engineering for Highly Dense Microspheres: Yttria-Stabilized Zirconia with Adjustable Micromechanical Properties

Various supraparticles have been extensively studied owing to their excellent catalytic properties that are attributed to their inherent porous structure; however, their mechanical properties have not garnered attention owing to their less dense structure. We demonstrate a rational approach for fabricating assembled supraparticles and, subsequently, highly dense microspheres. In addition, 3 mol % yttria-stabilized zirconia (3YSZ) and alumina particles were selected as building blocks and assembled into higher-order architectures using a droplet-based template method (spray drying) for validation with proof-of-concept. Moreover, structural features such as density, size, sphericity, and morphology of supraparticles were controlled by adjusting the competing kinetics occurring between the assembly of building blocks and evaporation of the solvent in the droplets. The preparatory aqueous suspension and process parameters were optimized as well. A detailed understanding of the formation mechanism facilitated the yield of tailor-made supraparticles and, thereafter, highly dense microspheres (approximate relative density = 99%) with excellent sphericity (>98%) via heat treatment. The microspheres displayed highest hardness (26.77 GPa) and superior elastic modulus (210.19 GPa) compared with the mechanical properties of the 3YSZ samples reported to date. Ultimately, the proposed supraparticle engineering provided insight for controlling the structural features and resultant micromechanical properties, which widely extends the applicability of supraparticle-based functional materials for practical purposes that require materials with high density and excellent mechanical properties.

Metal-Bridged Graphene-Protein Supraparticles for Analog and Digital Nitric Oxide Sensing

Self-limited nanoassemblies, such as supraparticles (SPs), can be made from virtually any nanoscale components, but SPs from nanocarbons including graphene quantum dots (GQDs), are hardly known because of the weak van der Waals attraction between them. Here it is shown that highly uniform SPs from GQDs can be successfully assembled when the components are bridged by Tb3+ ions supplementing van der Waals interactions. Furthermore, they can be coassembled with superoxide dismutase, which also has weak attraction to GQDs. Tight structural integration of multilevel components into SPs enables efficient transfer of excitonic energy from GQDs and protein to Tb3+ . This mechanism is activated when Cu2+ is reduced to Cu1+ by nitric oxide (NO)-an important biomarker for viral pulmonary infections and Alzheimer's disease. Due to multipronged fluorescence enhancement, the limit of NO detection improves 200 times reaching 10 × 10-12 m. Furthermore, the uniform size of SPs enables digitization of the NO detection using the single particle detection format resulting in confident registration of as few as 600 molecules mL-1 . The practicality of the SP-based assay is demonstrated by the successful monitoring of NO in human breath. The biocompatible SPs combining proteins, carbonaceous nanostructures, and ionic components provide a general path for engineering uniquely sensitive assays for noninvasive tracking of infections and other diseases.

Nanosized non-proteinaceous complexes III and IV mimicking electron transfer of mitochondrial respiratory chain

Synthetic biology pursues the understanding of biological processes and their possible mimicry with artificial bioinspired materials. A number of materials have already been used to mimic the active site of simple redox proteins, including nanosized iron oxides due to their redox properties. However, the mimicry of membrane redox protein complexes is still a challenge. Herein, magnetic iron oxide nanoparticles (NPs), incorporated as non-proteinaceous complexes III and IV in a mitochondrial model membrane, catalyze electron transfer (ET) similarly to the natural complexes towards cytochrome c. The associated molecular mechanism is experimentally proven in solution and in a Langmuir-Blodgett film. A direct and entropy-driven ET, with rate constant of 2.63 ± 0.05Lmol^-1 at 25 °C, occurs between the iron sites of the NPs and the cytochrome c heme group, not affecting the protein secondary and tertiary structures. This process requires an activation energy of 40.2 ± 1.5 kJ mol^-1 resulting in an overall Gibbs free energy of -55.3 kJ mol^-1. Furthermore, the protein-NP system is governed by electrostatic and non-polar forces that contribute to an associative mechanism in the transition state. Finally, the incorporated NPs in a model membrane were able to catalyze ET, such as the natural complexes in respiratory chain. This work presents an experimental approach demonstrating that inorganic nanostructured systems may behave as embedded proteins in the eukaryotic cells membrane, opening the way for more sophisticated and robust mimicry of membrane protein complexes.

Self-limiting self-assembly of supraparticles for potential biological applications

Nanotechnology has largely spurred the development of biological systems by taking advantage of the unique chemical, physical, optical, magnetic, and electrical properties of nanostructures. Self-limiting self-assembly of supraparticles produce new nanostructures and display great potential to create biomimicking nanostructures with desired functionalities. In this minireview, we summarize the recent developments and outstanding achievements of colloidal supraparticles, such as the driving forces for self-limiting self-assembly of supraparticles and properties of constructed supraparticles. Their application values in biological systems have also been illustrated.

Confined space design by nanoparticle self-assembly

Nanoparticle (NP) self-assembly has led to the fabrication of an array of functional nanoscale systems, having diverse architectures and functionalities. In this perspective, we discuss the design and application of NP suprastructures (SPs) characterized by nanoconfined compartments in their self-assembled framework, providing an overview about SP synthetic strategies reported to date and the role of their confined nanocavities in applications in several high-end fields. We also set to give our contribution towards the formation of more advanced nanocompartmentalized SPs able to work in dynamic manners, discussing the opportunities of further advances in NP self-assembly and SP research.

Fabrication of Hierarchical Indium Vanadate Materials for Supercapacitor Application

Transition metal orthovanadates are emerging 2D materials for promising electrochemical energy storage applications. Facile hydrothermal method for nanocrystalline indium vanadate (InVO4) semiconducting materials' fabrication is economical because of its direct chemical synthesis. X-ray diffraction studies, field emission scanning electron microscope (SEM) images, transmission electron microscopy (TEM), and photoelectron X-ray spectrum are used to describe the semiconductor materials as synthesized. InVO4 microspheres have attracted a lot of attention in the energy and environmental sector. These microsphere-derived semiconductor materials are recognized to offer the advantages of their large surface area, tunable pore sizes, enhanced light absorption, efficient carrier (electron-hole) separation, superior electronic and optical behavior, and high durability. From the results of SEM and TEM, InVO4 shows a microsphere construction with a mixture of nanosized particles. Diffuse reflectance UV-visible measurements are used to determine the bandgap, and it is found to be 2.1 eV for InVO4. The electrochemical analysis reveals a superior performance of the pseudocapacitor with hydrothermally derived microspheres of InVO4. Alongside an improved pseudocapacity, developed after 4000 cycles, it has excellent cycling stability with a retention of ≈94% of its original specific capacitance efficiency.

High-Performance Nonvolatile Organic Photonic Transistor Memory Devices using Conjugated Rod-Coil Materials as a Floating Gate

A novel approach for using conjugated rod-coil materials as a floating gate in the fabrication of nonvolatile photonic transistor memory devices, consisting of n-type Sol-PDI and p-type C10-DNTT, is presented. Sol-PDI and C10-DNTT are used as dual functions of charge-trapping (conjugated rod) and tunneling (insulating coil), while n-type BPE-PDI and p-type DNTT are employed as the corresponding transporting layers. By using the same conjugated rod in the memory layer and transporting channel with a self-assembled structure, both n-type and p-type memory devices exhibit a fast response, a high current contrast between "Photo-On" and "Electrical-Off" bistable states over 10⁵ , and an extremely low programing driving force of 0.1 V. The fabricated photon-driven memory devices exhibit a quick response to different wavelengths of light and a broadband light response that highlight their promising potential for light-recorder and synaptic device applications.

Structure-tunable supraparticle assemblies of hollow cupric oxide sheathed with nanographenes

Self-assembled supraparticles (SPs), a secondary structure of clustered nanoparticles, have attracted considerable interest owing to their highly tunable structure, composition, and morphology from their primary nanoparticle constituents. In this study, hierarchically assembled hollow Cu2O SPs were prepared using a cationic polyelectrolyte poly(diallyl dimethylammonium chloride) (PDDA) during the formation of Cu2O nanoparticles. The concentration-dependent structural transformation of PDDA from linear chains to assembled droplets plays a crucial role in forming a hollow colloidal template, affording the self-assembly of Cu2O nanoparticles as a secondary surfactant. The use of the positively charged PDDA also affords negatively charged nanoscale graphene oxide (NGO), an electrical and mechanical supporter to uniformly coat the surface of the hollow Cu2O SPs. Subsequent thermal treatment to enhance the electrical conductivity of NGO within the NGO/Cu2O SPs allows for the concomitant phase transformation of Cu2O to CuO, affording reduced NGO/CuO (RNGO/CuO) SPs. The uniquely structured hollow RNGO/CuO SPs achieve improved electrochemical properties by providing enhanced electrical conductivity and electroactive surface area.

Influence of Structured Water Layers on Protein Adsorption Process: A Case Study of Cytochrome c and Carbon Nanotube Interactions and Its Implications

Cytochrome c, an essential protein of the electron transport chain, is known to be capable of amplifying the toxicity of carbon nanomaterials via free-radical generation. To understand their interaction, as well as the more general protein-nanoparticle interaction at molecular levels, we investigate the adsorptions between cytochrome c and carbon nanotubes (CNTs) in dynamic and thermodynamic ways using molecular dynamics simulations. The results reveal a well-defined three-phase process separated by two transition points: the diffusion phase where the protein diffuses in the water box, the lockdown phase I where the protein inserts into the surface-bound water layers and rearranges its conformation to fit to the surface of the CNT, and the lockdown phase II where cytochrome c repels the water molecules standing in its way to the surface of CNT and reaches stable adsorption states. The structured water layers affect the movement of atoms by electrostatic forces. In lockdown phase I, the conformation adjustment of the protein dominates the adsorption process. The most thermally favorable adsorption conformation is determined. It shows that except for the deformation of short β sheets and some portions of α helixes, most of the secondary structures of cytochrome c remain unchanged, implying that most of the functions of cytochrome c are preserved. During these processes, the energy contributions of the hydrophilic residues of cytochrome c are much larger than those of hydrophobic residues. Interestingly, the structured water layers at the CNT surface allow more hydrophilic residues such as Lys to get into close contact with the CNT, which plays a significant role during the anchoring process of adsorption. Our results demonstrate that the heme group is in close contact with the CNT in some of the adsorbed states, which hence provides a way for electron transfer from cytochrome c to the CNT surface.

Chiral Supraparticles for Controllable Nanomedicine

Chirality is ubiquitous in nature and hard-wired into every biological system. Despite the prevalence of chirality in biological systems, controlling biomaterial chirality to influence interactions with cells has only recently been explored. Chiral-engineered supraparticles (SPs) that interact differentially with cells and proteins depending on their handedness are presented. SPs coordinated with d-chirality demonstrate greater than threefold enhanced cell membrane penetration in breast, cervical, and multiple myeloma cancer cells. Quartz crystal microbalance with dissipation and isothermal titration calorimetry measurements reveal the mechanism of these chiral-specific interactions. Thermodynamically, d-SPs show more stable adhesion to lipid layers composed of phospholipids and cholesterol compared to l-SPs. In vivo, d-SPs exhibit superior stability and longer biological half-lives likely due to opposite chirality and thus protection from endogenous proteins including proteases. This work shows that incorporating d-chirality into nanosystems enhances uptake by cancer cells and prolonged in vivo stability in circulation, providing support for the importance of chirality in biomaterials. Thus, chiral nanosystems may have the potential to provide a new level of control for drug delivery systems, tumor detection markers, biosensors, and other biomaterial-based devices.

Polymer-guided assembly of inorganic nanoparticles

The self-assembly of inorganic nanoparticles is of great importance in realizing their enormous potentials for broad applications due to the advanced collective properties of nanoparticle ensembles. Various molecular ligands (e.g., small molecules, DNAs, proteins, and polymers) have been used to assist the organization of inorganic nanoparticles into functional structures at different hierarchical levels. Among others, polymers are particularly attractive for use in nanoparticle assembly, because of the complex architectures and rich functionalities of assembled structures enabled by polymers. Polymer-guided assembly of nanoparticles has emerged as a powerful route to fabricate functional materials with desired mechanical, optical, electronic or magnetic properties for a broad range of applications such as sensing, nanomedicine, catalysis, energy storage/conversion, data storage, electronics and photonics. In this review article, we summarize recent advances in the polymer-guided self-assembly of inorganic nanoparticles in both bulk thin films and solution, with an emphasis on the role of polymers in the assembly process and functions of resulting nanostructures. Precise control over the location/arrangement, interparticle interaction, and packing of inorganic nanoparticles at various scales are highlighted.

Halogen bond-assisted self-assembly of gold nanoparticles in solution and on a planar surface

Halogen bonding (XB) has been shown to be a powerful tool for promoting molecular self-assembly in different fields. The use of XB for noncovalent assembly of inorganic nanoparticles (NP) is, instead, quite limited, considering how extensively other interactions (i.e., electrostatic forces, hydrophobic effect, hydrogen bonding, etc.) have been exploited to modulate and program NP self-assembly. Here, we designed and synthesized XB-capable organic ligands that were efficiently used to functionalize the surface of gold NPs (AuNPs). XB-assisted AuNP self-assembly was attained in solution mixing AuNPs bearing XB-donor ligands with ditopic XB-acceptor molecules and AuNPs functionalized with XB-acceptor moieties. Likewise, a preliminary study of XB-driven adsorption of these AuNPs on surface was performed via Quartz Crystal Microbalance with Dissipation Monitoring (QCM-D), used as an in situ tool for measuring mass changes upon XB-driven self-assembly.

Spontaneous and instant formation of highly stable protein-nanoparticle supraparticle co-assemblies driven by hydrophobic interaction

Recently, supraparticle protein-nanoparticle co-assemblies (or 'supraparticle co-assemblies' for short) have attracted considerable interest due to their fundamental and technological value. However, it remains challenging to form supraparticle co-assemblies with high stability. Here, we show that using hydrophobic interaction, instead of the previously used electrostatic and van der Waals interactions, as the primary driving force can lead to instant formation of exceptionally stable supraparticle co-assemblies with minimal external energy input. Our formation method of supraparticle co-assemblies simply involves mixing globular proteins (e.g., bovine serum albumin) with hydrophobic nanoparticles (e.g., hydrophobic magnetic nanoparticles and hydrophobic quantum dots) without significant energy input (e.g., sonication or stirring). Upon mixing of hydrophobic nanoparticles and proteins, the formation of supraparticle co-assemblies only takes <1 minute. Further incubation of the mixture for several hours results in a gradual increase of the size uniformity of supraparticle co-assemblies. The formed supraparticle co-assemblies have been colloidally stable for 6 months and counting, and can withstand harsh environments such as basic and acidic pH, high temperature, high dilution, and serum. Co-encapsulation of different sizes/types of nanoparticles is found to be feasible and the co-encapsulation number ratio of different nanoparticles is well-controlled by the feeding ratio. Proof-of-concept studies show the potential of the supraparticle co-assemblies for biological imaging, delivery, and modulation. The combination of very rapid formation, minimal energy consumption, highly stable products, and inexpensive raw materials of this hydrophobic interaction-driven process meets many of the main goals of 'ideal' nano-manufacturing. Thus, this process could serve as the foundation of ideal manufacturing of supraparticle co-assemblies.

Producing protein-nanoparticle co-assembly supraparticles by the interfacial instability process

Originally discovered in fundamental research of nanomaterial-biomolecule interactions, protein-nanoparticle co-assembly supraparticles (PNCAS) have become an emerging class of nanomaterials with various biological applications. We apply the interfacial instability process, which was originally reported for forming nanoparticles-encapsulated polymeric micelles, to produce PNCAS. By doing so hydrophobic nanoparticles, which are often the product formed from the upstream nanoparticle synthesis step, can be directly used as the raw materials of the production process of PNCAS. On the other hand, we take advantage of the structural features of protein molecules, in comparison with amphiphilic block copolymers, to mitigate two common problems encountered in the original interfacial instability-mediated nanoparticle encapsulation process, namely (1) poor encapsulation number control and (2) inconvenience and high cost to vary the assembly size. Additionally, we achieve semi-continuous and scalable production of PNCAS by combining the electrospray process and the interfacial instability process. We also conduct proof-of-concept studies of biological applications of the PNCAS products.

Sub-micron sized cytochrome c particles adsorbing to solid surfaces: A comparison between solution phase and colloidal system

Present work reports on Cytochrome C (Cyt C) adsorption from solution and as sub-micron sized colloidal particles (pH 7.5) at fluid/solid interface. The colloidal particles from 2 methods ((method 1 freeze-thaw); (method 2-Decane/water interface)) have been characterized by UV-Visible spectroscopy, Static and Time resolved Fluorescence spectra and Circular dichroic spectroscopy. Morphology and size studies indicate that the colloids are solid and well-packed. Using Quartz crystal microbalance with dissipation, elastic compliance of the protein on quartz surface has been monitored. Properties of the protein from solution and as colloids assembled from method 2 are similar in elastic compliance (65.53 ± 1.2 and 73.5 ± 1.1 GPa^-1 respectively) due to polar/non-polar interactions at the solid surface. For particles from method 1, irregular desolvation of water on the particle surface results in higher compliance (104.3 ± 1.3 GPa^-1). Change in work of adhesion from contact angle profiles shows optimal adhesion for colloids from method 1 whereas the protein solution and as colloids from method 2, show subnormal adhesion. The work shows the role of extensive H-bonding with the hydrodynamically coupled water leading to a fluid like system in protein colloids from method 1 whereas those from method 2 behaved more like the pure protein adsorbing from solution.

Anti-Biofilm Activity of Graphene Quantum Dots via Self-Assembly with Bacterial Amyloid Proteins

Bacterial biofilms represent an essential part of Earth's ecosystem that can cause multiple ecological, technological, and health problems. The environmental resilience and sophisticated organization of biofilms are enabled by the extracellular matrix that creates a protective network of biomolecules around the bacterial community. Current anti-biofilm agents can interfere with extracellular matrix production but, being based on small molecules, are degraded by bacteria and rapidly diffuse away from biofilms. Both factors severely reduce their efficacy, while their toxicity to higher organisms creates additional barriers to their practicality. In this paper, we report on the ability of graphene quantum dots to effectively disperse mature amyloid-rich Staphylococcus aureus biofilms, interfering with the self-assembly of amyloid fibers, a key structural component of the extracellular matrix. Mimicking peptide-binding biomolecules, graphene quantum dots form supramolecular complexes with phenol-soluble modulins, the peptide monomers of amyloid fibers. Experimental and computational results show that graphene quantum dots efficiently dock near the N-terminus of the peptide and change the secondary structure of phenol-soluble modulins, which disrupts their fibrillation and represents a strategy for mitigation of bacterial communities.

Lectin-Recognizable MOF Glyconanoparticles: Supramolecular Glycosylation of ZIF-8 Nanocrystals by Sugar-Based Surfactants

A strategy toward the integration of highly functional microporous materials, such as metal-organic frameworks (MOFs), in composites via biochemical recognition interactions is presented. Postsynthetic modification of zeolitic-imidazolate framework-8 MOF nanocrystals with a maltose-exposing biocompatible surfactant (the so-called "Glyco-MOFs") was performed to confer affinity toward lectin protein concanavalin A. The addition of small amounts of concanavalin A to the colloidal Glyco-MOF dispersion triggers the aggregation of these units into self-limited size supramolecular architectures directed by specific sugar-lectin binding interactions.

Supraparticles: Functionality from Uniform Structural Motifs

Under the right process conditions, nanoparticles can cluster together to form defined, dispersed structures, which can be termed supraparticles. Controlling the size, shape, and morphology of such entities is a central step in various fields of science and technology, ranging from colloid chemistry and soft matter physics to powder technology and pharmaceutical and food sciences. These diverse scientific communities have been investigating formation processes and structure/property relations of such supraparticles under completely different boundary conditions. On the fundamental side, the field is driven by the desire to gain maximum control of the assembly structures using very defined and tailored colloidal building blocks, whereas more applied disciplines focus on optimizing the functional properties from rather ill-defined starting materials. With this review article, we aim to provide a connecting perspective by outlining fundamental principles that govern the formation and functionality of supraparticles. We discuss the formation of supraparticles as a result of colloidal properties interplaying with external process parameters. We then outline how the structure of the supraparticles gives rise to diverse functional properties. They can be a result of the structure itself (emergent properties), of the colocalization of different, functional building blocks, or of coupling between individual particles in close proximity. Taken together, we aim to establish structure-property and process-structure relationships that provide unifying guidelines for the rational design of functional supraparticles with optimized properties. Finally, we aspire to connect the different disciplines by providing a categorized overview of the existing, diverging nomenclature of seemingly similar supraparticle structures.

Antibacterial Metal Oxide Nanoparticles: Challenges in Interpreting the Literature

Metal oxide nanoparticles (MO-NPs) are known to effectively inhibit the growth of a wide range of Gram-positive and Gram-negative bacteria. They have emerged as promising candidates to challenge the rising global issue of antimicrobial resistance. However, a comprehensive understanding of their mechanism of action and identifying the most promising NP materials for future clinical translation remain a major challenge due to variations in NP preparation and testing methods. With various types of MO-NPs being rapidly developed, a robust, standardized, in vitro assessment protocol for evaluating the antibacterial potency and efficiency of these NPs is needed. Calculating the number of NPs that actively interact with each bacterial cell is critical for assessing the dose response for toxicity. Here we discuss methods to evaluate MO-NPs antibacterial efficiency with focus on issues related to NPs in these assays. We also highlight sources of experimental variability including NP preparation, initial bacterial concentration, bacterial strains tested, culture microenvironment, and reported dose.

One-step fabrication of LSPR-tuneable reconfigurable assemblies of gold nanoparticles decorated with biotin-binding proteins

Assemblies of gold nanoparticles with chain-like morphologies and new near-infrared (NIR) localized surface plasmon resonance (LSPR) are obtained by adding the biotin-binding proteins avidin, neutravidin or streptavidin to citrate-capped nanoparticles. The key idea behind this one-step fabrication method is to destabilize the colloids by adding positively charged proteins and/or by making their zeta potential less negative. The extent of assembly, and therefore the NIR LSPR, can be fine-tuned by varying the concentration of proteins as well as by changing the pH of the solution. The resulting nanoparticle clusters can also reconfigure into smaller assemblies that absorb less NIR light by adding thiolated molecules or by increasing the pH of the solution. This, along with the observation that the proteins retain their biotin-binding properties in the assemblies, makes the proposed method promising for the development of new biosensors and drug delivery platforms capable of self-regulating their optical properties as a function of chemical signals in their environment.

Reversible Self-Assembly of Glutathione-Coated Gold Nanoparticle Clusters via pH-Tunable Interactions

Nanoparticle (NP) clusters with diameters ranging from 20 to 100 nm are reversibly assembled from 5 nm gold (Au) primary particles coated with glutathione (GSH) in aqueous solution as a function of pH in the range of 5.4 to 3.8. As the pH is lowered, the GSH surface ligands become partially zwitterionic and form interparticle hydrogen bonds that drive the self-limited assembly of metastable clusters in <1 min. Whereas clusters up to 20 nm in size are stable against cluster-cluster aggregation for up to 1 day, clusters up to 80 nm in size can be stabilized over this period via the addition of citrate to the solution in equal molarity with GSH molecules. The cluster diameter may be cycled reversibly by tuning pH to manipulate the colloidal interactions; however, modest background cluster-cluster aggregation occurs during cycling. Cluster sizes can be stabilized for at least 1 month via the addition of PEG-thiol as a grafted steric stabilizer, where PEG-grafted clusters dissociate back to starting primary NPs at pH 7 in fewer than 3 days. Whereas the presence of excess citrate has little effect on the initial size of the metastable clusters, it is necessary for both the cycling and dissociation to mediate the GSH-GSH hydrogen bonds. In summary, these metastable clusters exhibit significant characteristics of equilibrium self-limited assembly between primary particles and clusters on time scales where cluster-cluster aggregation is not present.

Bioreducible Hydrophobin-Stabilized Supraparticles for Selective Intracellular Release

One of the main hurdles in nanomedicine is the low stability of drug-nanocarrier complexes as well as the drug delivery efficiency in the region-of-interest. Here, we describe the use of the film-forming protein hydrophobin HFBII to organize dodecanethiol-protected gold nanoparticles (NPs) into well-defined supraparticles (SPs). The obtained SPs are exceptionally stable in vivo and efficiently encapsulate hydrophobic drug molecules. The HFBII film prevents massive release of the encapsulated drug, which, instead, is activated by selective SP disassembly triggered intracellularly by glutathione reduction of the protein film. As a consequence, the therapeutic efficiency of an encapsulated anticancer drug is highly enhanced (2 orders of magnitude decrease in IC₅₀). Biodistribution and pharmacokinetics studies demonstrate the high stability of the loaded SPs in the bloodstream and the selective release of the payloads once taken up in the tissues. Overall, our results provide a rationale for the development of bioreducible and multifunctional nanomedicines.

Droplets, Evaporation and a Superhydrophobic Surface: Simple Tools for Guiding Colloidal Particles into Complex Materials

The formation of complexly structured and shaped supraparticles can be achieved by evaporation-induced self-assembly (EISA) starting from colloidal dispersions deposited on a solid surface; often a superhydrophobic one. This versatile and interesting approach allows for generating rather complex particles with corresponding functionality in a simple and scalable fashion. The versatility is based on the aspect that basically one can employ an endless number of combinations of components in the colloidal starting solution. In addition, the structure and properties of the prepared supraparticles may be modified by appropriately controlling the evaporation process, e.g., by external parameters. In this review, we focus on controlling the shape and internal structure of such supraparticles, as well as imparted functionalities, which for instance could be catalytic, optical or electronic properties. The catalytic properties can also result in self-propelling (supra-)particles. Quite a number of experimental investigations have been performed in this field, which are compared in this review and systematically explained.

Programmed Self-Assembly of Hierarchical Nanostructures through Protein-Nanoparticle Coengineering

Hierarchical organization of macromolecules through self-assembly is a prominent feature in biological systems. Synthetic fabrication of such structures provides materials with emergent functions. Here, we report the fabrication of self-assembled superstructures through coengineering of recombinant proteins and nanoparticles. These structures feature a highly sophisticated level of multilayered hierarchical organization of the components: individual proteins and nanoparticles coassemble to form discrete assemblies that collapse to form granules, which then further self-organize to generate superstructures with sizes of hundreds of nanometers. The components within these superstructures are dynamic and spatially reorganize in response to environmental influences. The precise control over the molecular organization of building blocks imparted by this protein-nanoparticle coengineering strategy provides a method for creating hierarchical hybrid materials.

Surface tension of a Yukawa fluid according to mean-field theory

Yukawa fluids consist of particles that interact through a repulsive or attractive Yukawa potential. A surface tension arises at the walls of the container that encloses the fluid or at the interface between two coexisting phases. We calculate that surface tension on the level of mean-field theory, thereby either ignoring the particle size (ideal Yukawa fluid) or accounting for a non-vanishing particle size through a nonideal contribution to the free energy, exemplified either on the level of a lattice gas (lattice Yukawa fluid) or based on the Carnahan-Starling equation of state (Carnahan-Starling Yukawa fluid). Our mean-field results, which do not rely on assuming small gradients of the particle concentrations, become exact in the limit of large temperature and large screening length. They are calculated numerically in the general case and analytically in the two limits of small particle concentration and close to the critical point for a phase-separating system. For a sufficiently small particle concentration, our predicted surface tension is accurate whereas for a phase boundary, we expect good agreement with exact calculations in the limit of a large screening length and if the mean-field model employs the Carnahan-Starling equation of state.

Self-emulsification of eugenol by modified rice proteins to design nano delivery systems for controlled release of caffeic acid phenethyl ester

O/W emulsions with varied structures were self-assembled as a result of protein-oil binding, which can be tailored for controlled release.

Colloidal Assembly of Hierarchically Structured Porous Supraparticles from Flower-Shaped Protein-Inorganic Hybrid Nanoparticles

Mimicry of biomineralization is an attractive strategy to fabricate nanostructured hybrid materials. While biomineralization involves processes that organize hybrid clusters into complex structures with hierarchy, arrangement of artificial components in biomimetic approaches has been challenging. Here, we demonstrate self-assembly of hierarchically structured porous supraparticles from protein-inorganic hybrid flower-shaped (FS) nanoparticle building blocks. In our strategy, the FS nanoparticles self-assemble via high valency interactions in combination with interfacial adsorption and compression. The flower-like shape directed robust assembly of the FS nanoparticles into chain-like clusters in solution, which were further assembled into spherical supraparticles during rotation of FS nanoparticle solution. Continuously expanding and contracting the air-water interface during rotation catalyzed assembly of FS nanoparticle clusters, indicating that adsorption and compression of the building blocks at the interface were critical. The resulting supraparticles contain hierarchical pores which are translated from the structural characteristics of individual FS nanoparticle building blocks. The protein-inorganic supraparticles are protein-compatible, have large surface area, and provide specific affinity recognition for robust protein immobilization. A variety of functional proteins could be immobilized to the porous supraparticles, making it a general platform that could provide benefits for many applications.