Search

Polymer brushes, consisting of densely end-tethered polymers to a surface, can exhibit rapid and sharp conformational transitions due to specific stimuli, which offer intriguing possibilities for surface-based sensing of the stimuli. The key toward unlocking these possibilities is the development of methods to readily transduce signals from polymer conformational changes. Herein, we report on single-fluorophore integrated ultrathin (40 nm) polymer brush surfaces that exhibit changing fluorescence properties based on polymer conformation. The basis of our methods is the change in occupied volume as the polymer brush undergoes a collapse transition, which enhances the effective concentration and aggregation of the integrated fluorophores, leading to a self-quenching of the fluorophores' fluorescence and thereby reduced fluorescence lifetimes. By using fluorescence lifetime imaging microscopy, we reveal spatial details on polymer brush conformational transitions across complex interfaces, including at the air-water-solid interface and at the interface of immiscible liquids that solvate the surface. Furthermore, our method identifies the swelling of polymer brushes from outside of a direct droplet (

Glucose-responsive insulin-delivery platforms that are sensitive to dynamic glucose concentration fluctuations and provide both rapid and prolonged insulin release have great potential to control hyperglycemia and avoid hypoglycemia diabetes. Here, biodegradable and charge-switchable phytoglycogen nanoparticles capable of glucose-stimulated insulin release are engineered. The nanoparticles are “nanosugars” bearing glucose-sensitive phenylboronic acid groups and amine moieties that allow effective complexation with insulin (≈95% loading capacity) to form nanocomplexes. A single subcutaneous injection of nanocomplexes shows a rapid and efficient response to a glucose challenge in two distinct diabetic mouse models, resulting in optimal blood glucose levels (below 200 mg dL–1) for up to 13 h. The morphology of the nanocomplexes is found to be key to controlling rapid and extended glucoseregulated insulin delivery in vivo. These studies reveal that the injected nanocomplexes enabled efficient insulin release in the mouse, with optimal bioavailability, pharmacokinetics, and safety profiles. These results highlight a promising strategy for the development of a glucose-responsive insulin delivery system based on a natural and biodegradable nanosugar.

Deep eutectic solvents (DESs) are tuneable solvents with attractive properties for numerous applications. Their structure–property relationships are still under investigation, especially at the solid–liquid interface. Moreover, the influence of water on interfacial nanostructure must be understood for process optimization. Here, we employ a combination of atomic force microscopy and molecular dynamics simulations to determine the lateral and surface-normal nanostructure of the DES choline chloride:glycerol at the mica interface with different concentrations of water. For the neat DES system, the lateral nanostructure is driven by polar interactions. The surface adsorbed layer forms a distinct rhomboidal symmetry, with a repeat spacing of ~0.9 nm, comprising all DES species. The adsorbed nanostructure remains largely unchanged in 75 mol-% DES compared with pure DES, but at 50 mol-%, the structure is broken and there is a compromise between the native DES and pure water structure. By 25 mol-% DES, the water species dominates the adsorbed liquid layer, leaving very few DES species aggregates at the interface. In contrast, the near-surface surface-normal nanostructure, over a depth of ~3 nm from the surface, remains relatively unchanged down to 25 mol-% DES where the liquid arrangement changed. These results demonstrate not only the significant influence that water has on liquid nanostructure, but also show that there is an asymmetric effect whereby water disrupts the nanostructure to a greater degree closer to the surface. This work provides insight into the complex interactions between DES and water and may enhance their optimization for surface-based applications.

Mixtures of short-chain alcohols and water produce anomalous thermodynamic and structural quantities, including molecular segregation into water-rich and alcohol-rich components. Herein, we used molecular dynamics simulations with polarizable models to investigate interactions that could drive the self-association of water molecules in mixtures with methanol (MeOH). As water was diluted with MeOH, significant changes in the distribution of molecules and solvation properties occurred, where water exhibited a clear preference for self-association. When common structural quantities were analyzed, it was found that there was a clear reduction in water-water hydrogen bonding and tetrahedral order (both in terms of typical bulk behavior), contrary to the observed water self-association. However, when dipolar dispersion forces between all molecules as a function of system composition were analyzed, it was found that water-water dipolar interactions became significantly stronger with dilution (6-fold stronger interaction in 75% MeOH compared to 0% MeOH). This was only observed for water, where MeOH-MeOH interactions became weaker as the systems were more dilute in MeOH. These forces result from specific dipole orientations, likely occurring to adopt lower energy configurations (i.e., head-to-tail or antiparallel). For water, this may result from lost other interactions (e.g., hydrogen bonding), leading to more rotational freedom between the dipole moments. These intriguing changes in dipolar interactions, which directly result from structural changes, can therefore explain, in part, the driving force for water self-association in MeOH-water mixtures.

Surface chemistry is a major factor that determines the wettability of materials, and devising broadly applicable coating strategies that afford tunable and selective surface properties required for next-generation materials remains a challenge. Herein, we report fluorinated metal-organic coatings that display water-wetting and oil-repelling characteristics, a wetting phenomenon different from responsive wetting induced by external stimuli. We demonstrate this selective wettability with a library of metal-organic coatings using catechol-based coordination and silanization (both fluorinated and fluorine-free), enabling sensing through interfacial reconfigurations in both gaseous and liquid environments, and establish a correlation between the coating wettability and polarity of the liquids. This selective wetting performance is substrate-independent, spontaneous, durable, and reversible and occurs over a range of polar and nonpolar liquids (60 studied). These results provide insight into advanced liquid-solid interactions and a pathway toward tuning interfacial affinities and realizing robust, selective superwettability according to the surrounding conditions.

Polymer brush surfaces that alter their physical properties in response to chemical stimuli have the capacity to be used as new surface‐based sensing materials. For such surfaces, detecting the polymer conformation is key to their sensing capabilities. Herein, we report on FRET‐integrated ultrathin (, FRET chemistry was integrated within stimuli‐responsive polymer brush layers on planar substrates for spatial sensing of changing polymer conformations. Sensing was demonstrated for a variety of liquid mixture compositions, including high‐resolution observation of lateral differences in polymer conformation at immiscible liquid interfaces (see picture), thus offering great potential to be leveraged for new surface‐based sensing devices.

Poly(ethylene glycol) (PEG) is well known to endow nanoparticles (NPs) with low-fouling and stealth-like properties that can reduce immune system clearance in vivo, making PEG-based NPs (particularly sub-100 nm) of interest for diverse biomedical applications. However, the preparation of sub-100 nm PEG NPs with controllable size and morphology is challenging. Herein, we report a strategy based on the noncovalent coordination between PEG-polyphenolic ligands (PEG-gallol) and transition metal ions using a water-in-oil microemulsion phase to synthesize sub-100 nm PEG NPs with tunable size and morphology. The metal-phenolic coordination drives the self-assembly of the PEG-gallol/metal NPs: complexation between MnII and PEG-gallol within the microemulsions yields a series of metal-stabilized PEG NPs, including 30-50 nm solid and hollow NPs, depending on the MnII/gallol feed ratio. Variations in size and morphology are attributed to the changes in hydrophobicity of the PEG-gallol/MnII complexes at varying MnII/gallol ratios based on contact angle measurements. Small-angle X-ray scattering analysis, which is used to monitor the particle size and intermolecular interactions during NP evolution, reveals that ionic interactions are the dominant driving force in the formation of the PEG-gallol/MnII NPs. pH and cytotoxicity studies, and the low-fouling properties of the PEG-gallol/MnII NPs confirm their high biocompatibility and functionality, suggesting that PEG polyphenol-metal NPs are promising systems for biomedical applications.

Developing facile methods for inducing phase transformation between metallic and semiconducting 2D transition metal dichalcogenide (TMDC) materials is crucial toward leveraging their use in cutting-edge energy devices. Herein, 2H-to-1T' phase transformations in chemically exfoliated Tungsten Disulfide (WS

Deep Eutectic Solvents (DESs) are complex solutions that present unique challenges compared to traditional solvents. Unlike most aqueous electrolytes and ionic liquids, DESs have delicate hydrogen bond networks that are responsible for their highly sensitive compositional dependence on the melting point. Prior work has demonstrated a unique nanoscale structure both experimentally and theoretically that brings both challenges and opportunities to their adoption in traditional electrochemical processes. In this study, we use in situ sample-rotated ultra-small angle x-ray scattering to resolve the near-interface solvent structure after electrodepositing Pd nanoparticles onto a glassy carbon electrode in choline chloride:urea and choline chloride:ethylene glycol DESs. Our results indicate that a hierarchical solvent structure can be observed on the meso-scale in the choline chloride:urea and choline chloride:ethylene glycol systems. Importantly, this extended solvent structure increases between −0.3 V and −0.5 V (vs Ag/AgCl) and remains high until −0.9 V (vs Ag/AgCl). Experimentally, the nature of this structure is more pronounced in the ethylene glycol system, as evidenced by both the x-ray scattering and the electrochemical impedance spectroscopy. Molecular dynamics simulations and dipolar orientation analysis reveal that chloride delocalization near the Pd interface and long-range interactions between the choline and each hydrogen bond donor (HBD) are very different and qualitatively consistent with the experimental data. These results show how the long-range solvent–deposit interactions can be tuned by changing the HBD in the DES and the applied potential.

Safe and effective antimicrobials are needed to combat emerging antibiotic-resistant bacteria. Structurally nanoengineered antimicrobial peptide polymers (termed SNAPPs) interact with bacterial cell membranes to potently kill bacteria but may also interact at some level with human cell membranes. We studied the association of four different SNAPPs with six different white blood cells within fresh whole human blood by flow cytometry. In whole human blood, SNAPPs had detectable association with phagocytic cells and B cells, but not natural killer and T cells. However, without plasma proteins and therefore no protein corona on the SNAPPs, a greater marked association of SNAPPs with all white blood cell types was detected, resulting in cytotoxicity against most blood cell components. Thus, the formation of a protein corona around the SNAPPs reduced the association and prevented human blood cell cytotoxicity of the SNAPPs. Understanding the bio-nano interactions of these SNAPPs will be crucial to ensuring that the design of next-generation SNAPPs and other promising antimicrobial nanomaterials continues to display high efficacy toward antibiotic-resistant bacteria while maintaining a low toxicity to primary human cells.

Water is a unique solvent that is ubiquitous in biology and present in a variety of solutions, mixtures, and materials settings. It therefore forms the basis for all molecular dynamics simulations of biological phenomena, as well as for many chemical, industrial, and materials investigations. Over the years, many water models have been developed, and it remains a challenge to find a single water model that accurately reproduces all experimental properties of water simultaneously. Here, we report a comprehensive comparison of structural and dynamic properties of 30 commonly used 3-point, 4-point, 5-point, and polarizable water models simulated using consistent settings and analysis methods. For the properties of density, coordination number, surface tension, dielectric constant, self-diffusion coefficient, and solvation free energy of methane, models published within the past two decades consistently show better agreement with experimental values compared to models published earlier, albeit with some notable exceptions. However, no single model reproduced all experimental values exactly, highlighting the need to carefully choose a water model for a particular study, depending on the phenomena of interest. Finally, machine learning algorithms quantified the relationship between the water model force field parameters and the resulting bulk properties, providing insight into the parameter-property relationship and illustrating the challenges of developing a water model that can accurately reproduce all properties of water simultaneously.

Water is a unique solvent that is ubiquitous in biology and present in a variety of solutions, mixtures, and materials settings. It therefore forms the basis for all molecular dynamics simulations of biological phenomena, as well as for many chemical, industrial, and materials investigations. Over the years, many water models have been developed, and it remains a challenge to find a single water model that accurately reproduces all experimental properties of water simultaneously. Here, we report a comprehensive comparison of structural and dynamic properties of 30 commonly used 3-point, 4-point, 5-point, and polarizable water models simulated using consistent settings and analysis methods. For the properties of density, coordination number, surface tension, dielectric constant, self-diffusion coefficient, and solvation free energy of methane, models published within the past two decades consistently show better agreement with experimental values compared to models published earlier, albeit with some notable exceptions. However, no single model reproduced all experimental values exactly, highlighting the need to carefully choose a water model for a particular study, depending on the phenomena of interest. Finally, machine learning algorithms quantified the relationship between the water model force field parameters and the resulting bulk properties, providing insight into the parameter-property relationship and illustrating the challenges of developing a water model that can accurately reproduce all properties of water simultaneously.

Selective self-assembly in multicomponent mixtures offers a method for isolating desired components from complex systems for the rapid production of functional materials. Developing approaches capable of selective assembly of "target" components into intended three-dimensional structures is challenging because of the intrinsically high complexity of multicomponent systems. Herein, we report the selective coordination-driven self-assembly of metal-phenolic networks (MPNs) from a series of complex multicomponent systems (including crude plant extracts) into thin films via metal chelation with phenolic ligands. The metal (FeIII) selectively assembles low abundant phenolic components (e.g., myricetrin and quercetrin) from plant extracts into thin films. This selective metal-phenolic assembly is independent of the substrate properties (e.g., size, surface charge, and shape). Moreover, the high selectivity is consistent across different target phenolic ligands in model mixtures, even though each individual component can form thin films from single-component systems. A computational simulation of film formation suggests that the driving force for the selective behavior stems from differences in the number of chelating sites in the phenolic structures. The MPN films are shown to demonstrate improved antioxidant properties compared with the corresponding phenolic compounds in their free form, therefore exhibiting potential as free-standing antioxidant films.

Biosourced nanoparticles have a range of desirable properties for therapeutic applications, including biodegradability and low immunogenicity. Glycogen, a natural polysaccharide nanoparticle, has garnered much interest as a component of advanced therapeutic materials. However, functionalizing glycogen for use as a therapeutic material typically involves synthetic approaches that can negatively affect the intrinsic physiological properties of glycogen. Herein, the protein component of glycogen is examined as an anchor point for the photopolymerization of functional poly(N-isopropylacrylamide) (PNIPAM) polymers. Oyster glycogen (OG) nanoparticles partially degrade to smaller spherical particles in the presence of protease enzymes, reflecting a population of surface-bound proteins on the polysaccharide. The grafting of PNIPAM to the native protein component of OG produces OG-PNIPAM nanoparticles of ∼45 nm in diameter and 6.2 MDa in molecular weight. PNIPAM endows the nanoparticles with temperature-responsive aggregation properties that are controllable and reversible and that can be removed by the biodegradation of the protein. The OG-PNIPAM nanoparticles retain the native biodegradability of glycogen. Whole blood incubation assays revealed that the OG-PNIPAM nanoparticles have a low cell association and inflammatory response similar to that of OG. The reported strategy provides functionalized glycogen nanomaterials that retain their inherent biodegradability and low immune cell association.

Structural forces within aqueous water at a solid interface can significantly change surface reactivity and the affinity of solutes toward it. We show using molecular dynamics simulations how hydrophilic and hydrophobic quartz surfaces perturb the orientational structure of aqueous water, ultimately strengthening dipolar forces between molecules in proximity to the interface. When derived as a function of distance from each surface, it was found that both surfaces indirectly enhance the long-range dipolar attraction of water for itself toward the interfacial region. This was found to be longer-ranged for water molecules solvating the hydrophobic surface than those solvating the hydrophilic surface, with a range of up to 2.5 nm from the hydrophobic surface. Our results give direct quantification of surface-induced changes in solvent-solvent attraction, ultimately providing a counterintuitive addition to the balance of hydrophobic forces at aqueous-solid interfaces.

In recent years, spider silk-based materials have attracted attention because of their biocompatibility, processability, and biodegradability. For their potential use in biomaterial applications, i.e., as drug delivery systems and implant coatings for tissue regeneration, it is vital to understand the interactions between the silk biomaterial surface and the biological environment. Like most polymeric carrier systems, spider silk material surfaces can adsorb proteins when in contact with blood, resulting in the formation of a biomolecular corona. Here, we assessed the effect of surface net charge of materials made of recombinant spider silk on the biomolecular corona composition. In-depth proteomic analysis of the biomolecular corona revealed that positively charged spider silk materials surfaces interacted predominantly with fibrinogen-based proteins. This fibrinogen enrichment correlated with blood clotting observed for both positively charged spider silk films and particles. In contrast, negative surface charges prevented blood clotting. Genetic engineering allows the fine-tuning of surface properties of the spider silk particles providing a whole set of recombinant spider silk proteins with different charges or peptide tags to be used for, for example, drug delivery or cell docking, and several of these were analyzed concerning the composition of their biomolecular corona. Taken together this study demonstrates how the surface net charge of recombinant spider silk surfaces affects the composition of the biomolecular corona, which in turn affects macroscopic effects such as fibrin formation and blood clotting.

The manipulation of interfacial properties has broad implications for the development of high-performance coatings. Metal-phenolic networks (MPNs) are an emerging class of responsive, adherent materials. Herein, host-guest chemistry is integrated with MPNs to modulate their surface chemistry and interfacial properties. Macrocyclic cyclodextrins (host) are conjugated to catechol or galloyl groups and subsequently used as components for the assembly of functional MPNs. The assembled cyclodextrin-based MPNs are highly permeable (even to high molecular weight polymers: 250-500 kDa), yet they specifically and noncovalently interact with various functional guests (including small molecules, polymers, and carbon nanomaterials), allowing for modular and reversible control over interfacial properties. Specifically, by using either hydrophobic or hydrophilic guest molecules, the wettability of the MPNs can be readily tuned between superrepellency (>150°) and superwetting (ca. 0°).

Nanostructured materials have potential as platforms for analytical assays and catalytic reactions. Herein, we report the synthesis of electrocatalytically active cobalt phosphate nanostructures (CPNs) using a simple, low-cost, and scalable preparation method. The electrocatalytic properties of CPNs toward the electrooxidation of glucose (Glu) were studied by cyclic voltammetry and chronoamperometry in relevant biological electrolytes, such as phosphate-buffered saline (PBS), at physiological pH (7.4). Using CPNs, Glu detection could be achieved over a wide range of biologically relevant concentrations, from 1 to 30 mM Glu in PBS, with a sensitivity of 7.90 nA/mM cm2 and a limit of detection of 0.3 mM, thus fulfilling the necessary requirements for human blood Glu detection. In addition, CPNs showed a high structural and functional stability over time at physiological pH. The CPN-coated electrodes could also be used for Glu detection in the presence of interfering agents (e.g., ascorbic acid and dopamine) and in human serum. Density functional theory calculations were performed to evaluate the interaction of Glu with different faceted cobalt phosphate surfaces; the results revealed that specific surface presentations of under-coordinated cobalt led to the strongest interaction with Glu, suggesting that enhanced detection of Glu by CPNs can be achieved by lowering the surface coordination of cobalt. Our results highlight the potential use of phosphate-based nanostructures as catalysts for electrochemical sensing of biochemical analytes.

The poor penetration of nanocarrier-siRNA constructs into tumor tissue is a major hurdle for the in vivo efficacy of siRNA therapeutics, where the ability of the constructs to permeate the 3D multicellular matrix is determined by their physicochemical properties. Herein, we optimized the use of soft glycogen nanoparticles for the engineering of glycogen-siRNA constructs that can efficiently penetrate multicellular tumor spheroids and exert a significant gene silencing effect. Glycogen nanoparticles from different bio-sources and with different structural features were investigated. We show that larger glycogen nanoparticles ranging from 50 to 80 nm are suboptimal systems for complexation of nucleic acids if fine control of the size of constructs is required. Our studies suggest that 20 nm glycogen nanoparticles are optimal for complexation and efficient delivery of siRNA. The chemical composition, surface charge, and size of glycogen-siRNA constructs were finely controlled to minimize interactions with serum proteins and allow penetration into 3D multicellular spheroids of human kidney epithelial cells and human prostate cancer cells. We introduced pH sensitive moieties within the construct to enhance early endosome escape and efficiently improve the silencing effect in vitro. Glycogen-siRNA constructs were found to mediate gene silencing in 3D multicellular spheroids causing ∼60% specific gene silencing. The optimized construct exhibited an in vivo circulation lifetime of 8 h in mice, with preferential accumulation in the liver. No accumulation in the kidney, lung, spleen, heart or brain, or signs of toxicity in mice were observed. Our results highlight the potential for screening siRNA nanocarriers in 3D cultured prostate tumor models, thereby improving the predictive therapeutic efficacy of glycogen-based platforms in human physiological conditions.

Using molecular dynamics simulations we probe the structure and interactions at the water liquid–vapor (LV) interface. In the interfacial region, strong ordering of dipole moments is observed, where water molecules exhibit “frustrated” orientations. By selectively analyzing the dipolar potential of mean force between these frustrated molecules and other molecules, we find a significant enhancement of dipolar interactions across the interfacial region. This interaction is derived in terms of a component of the surface tension, with a temperature-dependent magnitude of ∼−20 mN m–1, representing a stabilizing interaction at the interface. This stabilization has the same magnitude, but opposite sign, to the surface tension of alkanes and short-chain alcohols. Our results highlight a mechanism by which interfacial waters recover lost free energy from an absence of van der Waals interactions in the vapor region and likely explains the driving force for specific water structure at the LV interface.

The self-assembly of molecular building blocks into well-defined macroscopic materials is desirable for developing emergent functional materials. However, the self-assembly of molecules into macroscopic materials remains challenging, in part because of limitations in controlling the growth and robustness of the materials. Herein, we report the molecular self-assembly of nano- to macroscopic free-standing materials through the coordination of metals with natural phenolic molecules. Our method involves a simple and scalable solution-based template dipping process in precomplexed metal–phenolic solutions, enabling the fabrication of free-standing macroscopic materials of customized architectures (2D and 3D geometries), thickness (about 10 nm to 5 μm), and chemical composition (different metals and phenolic ligands). Our macroscopic free-standing materials can be physically folded and unfolded like origami, yet are selectively degradable. Furthermore, metal nanoparticles can be grown in the macroscopic free-s...

Metal–phenolic networks (MPNs) are a versatile class of self-assembled materials that are able to form functional thin films on various substrates with potential applications in areas including drug delivery and catalysis. Different metal ions (e.g., FeIII, CuII) and phenols (e.g., tannic acid, gallic acid) have been investigated for MPN film assembly; however, a mechanistic understanding of the thermodynamics governing MPN formation remains largely unexplored. To date, MPNs have been deposited at low ionic strengths (

Glyconanoparticles that exhibit multivalent binding to lectins are desirable for molecular recognition and therapeutic applications. Herein we explore the use of glycogen nanoparticles as a biosourced glycoscaffold for engineering multivalent glyconanoparticles. Glycogen nanoparticles, a naturally occurring highly branched polymer of glucose, was functionalized with lactose, achieved through copper(I)-catalyzed alkyne-azide cycloaddition chemistry, for targeted interaction with lectins ex situ and on prostate cancer cells. The lactosylated glycogen, which contains terminal β-galactoside moieties, is termed galacto-glycogen (GG), and is found to interact strongly with peanut agglutinin (PNA), a β-galactoside-specific lectin, as observed by optical waveguide lightmode spectroscopy, dynamic light scattering, and quartz crystal microbalance measurements. The GG nanoparticles exhibit multivalent binding to PNA with an affinity constant of 3.4 × 105 M-1, and the GG-PNA complex cannot be displaced by lactose, demonstrating the competitive binding of GG to the lectin. These GG nanoparticles were tested for association with prostate cancer cell membranes in vitro, where the particles exhibited a high affinity for the membrane, as observed from flow cytometry and confocal microscopy. This is inferred to result from specific extracellular galectin-1 targeting. Furthermore, the GG nanoparticles induce aggregation between prostate cancer cells. Our results highlight a strategy for engineering a biosourced polysaccharide with surface moieties that exhibit strong multivalent interactions with lectins, and targeted interaction with prostate cancer cells.

Upon exposure to human blood, nanoengineered particles interact with a multitude of plasma components, resulting in the formation of a biomolecular corona. This corona modulates downstream biological responses, including recognition by and association with human immune cells. Considerable research effort has been directed toward the design of materials that can demonstrate a low affinity for various proteins (low-fouling materials) and materials that can exhibit low association with human immune cells (stealth materials). An implicit assumption common to bio-nano research is that nanoengineered particles that are low-fouling will also exhibit stealth. Herein, we investigated the link between the low-fouling properties of a particle and its propensity for stealth in whole human blood. High-fouling mesoporous silica (MS) particles and low-fouling zwitterionic poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC) particles were synthesized, and their interaction with blood components was assessed before and after precoating with serum albumin, immunoglobulin G, or complement protein C1q. We performed an in-depth proteomics characterization of the biomolecular corona that both identifies specific proteins and measures their relative abundance. This was compared with observations from a whole blood association assay that identified with which cell type each particle system associates. PMPC-based particles displayed reduced association both with cells and with serum proteins compared with MS-based particles. Furthermore, the enrichment of specific proteins within the biomolecular corona was found to correlate with association with specific cell types. This study demonstrates how the low-fouling properties of a material are indicative of its stealth with respect to immune cell association.

Metal-phenolic networks (MPNs) have received widespread interest owing to their modular incorporation of functional metal ions and phenolic ligands. However, the interaction between MPNs and biomolecules is still relatively unexplored. Herein, we studied the effects of MPN-coated gold nanoparticles on amyloid fibril formation (which is associated with Alzheimer's disease) as a function of the metal ion in the MPN systems. All coated particles examined inhibited amyloid formation, with cobalt(ii) MPN-coated particles exhibiting the highest inhibition activity (90%). Molecular dynamics simulations and quantum mechanics calculations suggested that the geometry of the exposed cobalt coordination site in the cobalt-tannic acid networks facilitates its interactions with histidine and methionine residues in the amyloid beta peptides. Furthermore, the unique structure of cobalt MPNs may enable a wider variety of biomedical applications.

In biological fluids, proteins bind to particles, forming so-called protein coronas. Such adsorbed protein layers significantly influence the biological interactions of particles, both in vitro and in vivo. The adsorbed protein layer is generally described as a two-component system comprising "hard" and "soft" protein coronas. However, a comprehensive picture regarding the protein corona structure is lacking. Herein, we introduce an experimental approach that allows for in situ monitoring of protein adsorption onto silica microparticles. The technique, which mimics flow in vascularized tumors, combines confocal laser scanning microscopy with microfluidics and allows the study of the time-evolution of protein corona formation. Our results show that protein corona formation is kinetically divided into three different phases: phase 1, proteins irreversibly and directly bound (under physiologically relevant conditions) to the particle surface; phase 2, irreversibly bound proteins interacting with preadsorbed proteins, and phase 3, reversibly bound "soft" protein corona proteins. Additionally, we investigate particle-protein interactions on low-fouling zwitterionic-coated particles where the adsorption of irreversibly bound proteins does not occur, and on such particles, only a "soft" protein corona is formed. The reported approach offers the potential to define new state-of-the art procedures for kinetics and protein fouling experiments.

Light-driven directional motion is common in nature but remains a challenge for synthetic microparticles, particularly regarding collective motion on a macroscopic scale. Successfully engineering microparticles with light-driven collective motion could lead to breakthroughs in drug delivery, contaminant sensing, environmental remediation, and artificial life. Herein, metal-phenolic particle microswimmers capable of autonomously sensing and swimming toward an external light source are reported, with the speed regulated by the wavelength and intensity of illumination. These microswimmers can travel macroscopic distances (centimeters) and can remain illuminated for hours without degradation of motility. Experimental and theoretical analyses demonstrate that motion is generated through chemical transformations of the organic component of the metal-phenolic complex. Furthermore, cargos with specific spectral absorption profiles can be loaded into the particles and endow the particle microswimmers with activated motion corresponding to these spectral characteristics. The programmable nature of the light navigation, tunable size of the particles, and versatility of cargo loading demonstrate the versatility of these metal-phenolic particle microswimmers.

The Hofmeister effect describes how different ions make solutes more or less hydrophobic. The effect is thought to occur due to structural changes in the solvent induced by the ion's presence, particularly in water. In this study, the structural changes in water due to the presence of ions are investigated by molecular dynamics simulations of various monatomic ions in the SPC/E water model. Structural analyses reveal specific orientations of solvating waters around each of the ions studied. Using a new method, these orientations are quantified by a set of pair correlation functions that describe dipole-ion correlations in structure. These correlations are shown to contribute to the potential of mean force between waters and the ion of interest, and therefore to the free energy of the system. The magnitude of this free energy is found to result in a Hofmeister series for the various ions studied, therefore demonstrating a Hofmeister effect with respect to water's structure that is quantified by pair correlation functions. Most crucially, the pair correlations that lead to this Hofmeister effect also contribute to the hydrophobic effect (the entropy of hydrophobic solvation) [Liu et al., J. Chem. Phys., 2015, 142, 114117], and those which dominate the hydrophobic effect are modulated by an ion's presence, therefore demonstrating a mechanistic link between the two effects.

Interfacial self-assembly is a powerful organizational force for fabricating functional nanomaterials, including nanocarriers, for imaging and drug delivery. Herein, the interfacial self-assembly of pH-responsive metal-phenolic networks (MPNs) on the liquid-liquid interface of oil-in-water emulsions is reported. Oleic acid emulsions of 100-250 nm in diameter are generated by ultrasonication, to which poly(ethylene glycol) (PEG)-based polyphenolic ligands are assembled with simultaneous crosslinking by metal ions, thus forming an interfacial MPN. PEG provides a protective barrier on the emulsion phase and renders the emulsion low fouling. The MPN-coated emulsions have a similar size and dispersity, but an enhanced stability when compared with the uncoated emulsions, and exhibit a low cell association in vitro, a blood circulation half-life of ≈50 min in vivo, and are nontoxic to healthy mice. Furthermore, a model anticancer drug, doxorubicin, can be encapsulated within the emulsion phase at a high loading capacity (≈5 fg of doxorubicin per emulsion particle). The MPN coating imparts pH-responsiveness to the drug-loaded emulsions, leading to drug release at cell internalization pH and a potent cell cytotoxicity. The results highlight a straightforward strategy for the interfacial nanofabrication of pH-responsive emulsion-MPN systems with potential use in biomedical applications.

Biological nanoparticles found in living systems possess distinct molecular architectures and diverse functions. Glycogen is a unique biological polysaccharide nanoparticle fabricated by nature through a bottom-up approach. The biocatalytic synthesis of glycogen has evolved over time to form a nanometer-sized dendrimer-like structure (20-150 nm) with a highly branched surface and a dense core. This makes glycogen markedly different from other natural linear or branched polysaccharides and particularly attractive as a platform for biomedical applications. Glycogen is inherently biodegradable, nontoxic, and can be functionalized with diverse surface and internal motifs for enhanced biofunctional properties. Recently, there has been growing interest in glycogen as a natural alternative to synthetic polymers and nanoparticles in a range of applications. Herein, the recent literature on glycogen in the material-based sciences, including its use as a constituent in biodegradable hydrogels and fibers, drug delivery vectors, tumor targeting and penetrating nanoparticles, immunomodulators, vaccine adjuvants, and contrast agents, is reviewed. The various methods of chemical functionalization and physical assembly of glycogen nanoparticles into multicomponent nanodevices, which advance glycogen toward a functional therapeutic nanoparticle from nature and back again, are discussed in detail.

Droplet bouncing on repellent solid surfaces (e.g., the lotus leaf effect) is a common phenomenon that has aroused interest in various fields. However, the scenario of a droplet bouncing off another droplet (either identical or distinct chemical composition) while moving on a solid material (i.e., ricocheting droplets, droplet billiards) is scarcely investigated, despite it having fundamental implications in applications including self‐cleaning, fluid transport, and heat and mass transfer. Here, the dynamics of bouncing collisions between liquid droplets are investigated using a friction‐free platform that ensures ultrahigh locomotion for a wide range of probing liquids. A general prediction on bouncing droplet–droplet contact time is elucidated and bouncing droplet–droplet collision is demonstrated to be an extreme case of droplet bouncing on surfaces. Moreover, the maximum deformation and contact time are highly dependent on the position where the collision occurs (i.e., head‐on or off‐center collisions), which can now be predicted using parameters (i.e., effective velocity, effective diameter) through the concept of an effective interaction region. The results have potential applications in fields ranging from microfluidics to repellent coatings., Droplets colliding and ricocheting on super‐repellent surfaces display dynamics consistent with droplet–surface collisions, but with tunable dynamics between bouncing droplets via control over the angle of incidence. Parameters introduced using the concept of an effective interaction region allow for a universal description and prediction of droplet bouncing dynamics, with implications for wetting characteristics of next‐generation surfaces.

The use of natural compounds for preparing hybrid molecular films-such as surface coatings made from metal-phenolic networks (MPNs)-is of interest in areas ranging from catalysis and separations to biomedicine. However, to date, the film growth of MPNs has been observed to proceed in discrete steps (≈10 nm per step) where the coordination-driven interfacial assembly ceases beyond a finite time (≈1 min). Here, it is demonstrated that the assembly process for MPNs can be modulated from discrete to continuous by utilizing solid-state reactants (i.e., rusted iron objects). Gallic acid etches iron from rust and produces chelate complexes in solution that continuously assemble at the interface of solid substrates dispersed in the system. The result is stable, continuous growth of MPN films. The presented double dynamic process-that is, etching and self-assembly-provides new insights into the chemistry of MPN assembly while enabling control over the MPN film thickness by simply varying the reaction time.

We report polymer capsule-based probes for quantifying the pressure exerted by cells during capsule internalisation (Pin). Poly(methacrylic acid) (PMA) capsules with tuneable mechanical properties were fabricated through layer-by-layer assembly. The Pin was quantified by correlating the cell-induced deformation with the ex situ osmotically induced deformation of the polymer capsules. Ultimately, we found that human monocyte-derived macrophage THP-1 cells exerted up to approximately 360 kPa on the capsules during internalisation.

Transmission electron micrographs of glycogen extracted from healthy mouse hearts reveal aggregate structures around 133 nm in diameter. These structures are similar to, but on average somewhat smaller than, the α-particles of glycogen found in mammalian liver. Like the larger liver glycogens, these new particles in cardiac tissue appear to be aggregates of β-particles. Free β-particles are also present in liver, and are the only type of particle seen in skeletal muscle. They have diameters from 20 to 50 nm. We discuss the number distributions of glycogen particle diameters and the implications for the structure-function relationship of glycogens in these tissues. We point out the possible implications for the study of glycogen storage diseases, and of non-insulin dependent diabetes mellitus.