Engineering of Nebulized Metal-Phenolic Capsules for Controlled Pulmonary Deposition.

Particle-based pulmonary delivery has great potential for delivering inhalable therapeutics for local or systemic applications. The design of particles with enhanced aerodynamic properties can improve lung distribution and deposition, and hence the efficacy of encapsulated inhaled drugs. This study describes the nanoengineering and nebulization of metal-phenolic capsules as pulmonary carriers of small molecule drugs and macromolecular drugs in lung cell lines, a human lung model, and mice. Tuning the aerodynamic diameter by increasing the capsule shell thickness (from ≈100 to 200 nm in increments of ≈50 nm) through repeated film deposition on a sacrificial template allows precise control of capsule deposition in a human lung model, corresponding to a shift from the alveolar region to the bronchi as aerodynamic diameter increases. The capsules are biocompatible and biodegradable, as assessed following intratracheal administration in mice, showing >85% of the capsules in the lung after 20 h, but <4% remaining after 30 days without causing lung inflammation or toxicity. Single-cell analysis from lung digests using mass cytometry shows association primarily with alveolar macrophages, with >90% of capsules remaining nonassociated with cells. The amenability to nebulization, capacity for loading, tunable aerodynamic properties, high biocompatibility, and biodegradability make these capsules attractive for controlled pulmonary delivery.

Modular Assembly of Host-Guest Metal-Phenolic Networks Using Macrocyclic Building Blocks.

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°).

Coatings super-repellent to ultralow surface tension liquids.

High-performance coatings that durably and fully repel liquids are of interest for fundamental research and practical applications. Such coatings should allow for droplet beading, roll off and bouncing, which is difficult to achieve for ultralow surface tension liquids. Here we report a bottom-up approach to prepare super-repellent coatings using a mixture of fluorosilanes and cyanoacrylate. On application to surfaces, the coatings assemble into thin films of locally multi-re-entrant hierarchical structures with very low surface energies. The resulting materials are super-repellent to solvents, acids and bases, polymer solutions and ultralow surface tension liquids, characterized by ultrahigh liquid contact angles (>150°) and negligible roll-off angles (~0°). Furthermore, the coatings are transparent, durable and demonstrate universal liquid bouncing, tailored responsiveness and anti-freezing properties, and are thus a promising alternative to existing synthetic super-repellent coatings.

Electrochemical Behavior and Redox-Dependent Disassembly of Gallic Acid/FeIII Metal-Phenolic Networks.

Metal-phenolic networks (MPNs) are a versatile class of organic-inorganic hybrid systems that are generating interest for applications in catalysis, bioimaging, and drug delivery. These self-assembled MPNs possess metal-coordinated structures and may potentially serve as redox-responsive platforms for triggered disassembly or drug release. Therefore, a comprehensive study of the reduction and oxidation behavior of MPNs for evaluating their redox responsiveness, specific conditions required for their disassembly, and the kinetics of metal ion release, is necessary. Using a representative MPN gallic acid-iron (GA/FeIII) system, we conducted electrochemical studies to provide fundamental insights into the redox behavior of these MPNs. We demonstrate that GA/FeIII is redox active, and evaluate its electrochemical reversibility, identify the oxidation state of the redox-active species, and provide information regarding the stability of the networks toward reductive stimuli and specific redox conditions required for the "on-off" or continuous release of FeIII. Overall, through studying the redox properties of GA/FeIII films, we advance the understanding of multifunctional iron-containing MPN platforms that may have practical significance for biologically relevant applications.

Particle Targeting in Complex Biological Media.

Over the past few decades, nanoengineered particles have gained increasing interest for applications in the biomedical realm, including diagnosis, imaging, and therapy. When functionalized with targeting ligands, these particles have the potential to interact with specific cells and tissues, and accumulate at desired target sites, reducing side effects and improve overall efficacy in applications such as vaccination and drug delivery. However, when targeted particles enter a complex biological environment, the adsorption of biomolecules and the formation of a surface coating (e.g., a protein corona) changes the properties of the carriers and can render their behavior unpredictable. For this reason, it is of importance to consider the potential challenges imposed by the biological environment at the early stages of particle design. This review describes parameters that affect the targeting ability of particulate drug carriers, with an emphasis on the effect of the protein corona. We highlight strategies for exploiting the protein corona to improve the targeting ability of particles. Finally, we provide suggestions for complementing current in vitro assays used for the evaluation of targeting and carrier efficacy with new and emerging techniques (e.g., 3D models and flow-based technologies) to advance fundamental understanding in bio-nano science and to accelerate the development of targeted particles for biomedical applications.

Multiligand Metal-Phenolic Assembly from Green Tea Infusions.

The synthesis of hybrid functional materials using the coordination-driven assembly of metal-phenolic networks (MPNs) is of interest in diverse areas of materials science. To date, MPN assembly has been explored as monoligand systems (i.e., containing a single type of phenolic ligand) where the phenolic components are primarily obtained from natural sources via extraction, isolation, and purification processes. Herein, we demonstrate the fabrication of MPNs from a readily available, crude phenolic source-green tea (GT) infusions. We employ our recently introduced rust-mediated continuous assembly strategy to prepare these GT MPN systems. The resulting hollow MPN capsules contain multiple phenolic ligands and have a shell thickness that can be controlled through the reaction time. These multiligand MPN systems have different properties compared to the analogous MPN systems reported previously. For example, the Young's modulus (as determined using colloidal-probe atomic force microscopy) of the GT MPN system presented herein is less than half that of MPN systems prepared using tannic acid and iron salt solutions, and the disassembly kinetics are faster (∼50%) than other, comparable MPN systems under identical disassembly conditions. Additionally, the use of rust-mediated assembly enables the formation of stable capsules under conditions where the conventional approach (i.e., using iron salt solutions) results in colloidally unstable dispersions. These differences highlight how the choice of phenolic ligand and its source, as well as the assembly protocol (e.g., using solution-based or solid-state iron sources), can be used to tune the properties of MPNs. The strategy presented herein expands the toolbox of MPN assembly while also providing new insights into the nature and robustness of metal-phenolic interfacial assembly when using solution-based or solid-state metal sources.

Exploring the Structural Space of the Galectin-1-Ligand Interaction.

Galectin-1 is a tumor-associated protein recognizing the Galß1-4GlcNAc motif of cell-surface glycoconjugates. Herein, we report the stepwise expansion of a multifunctional natural scaffold based on N-acetyllactosamine (LacNAc). We obtained a LacNAc mimetic equipped with an alkynyl function on the 3'-hydroxy group of the disaccharide facing towards a binding pocket adjacent to the carbohydrate-recognition domain. It served as an anchor motif for further expansion by the Sharpless-Huisgen-Meldal reaction, which resulted in ligands with a binding mode almost identical to that of the natural carbohydrate template. X-ray crystallography provided a structural understanding of the galectin-1-ligand interactions. The results of this study enable the development of bespoke ligands for members of the galectin target family.

Lactosylated Glycogen Nanoparticles for Targeting Prostate Cancer Cells.

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 ß-galactoside moieties, is termed galacto-glycogen (GG), and is found to interact strongly with peanut agglutinin (PNA), a ß-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.

Rust-Mediated Continuous Assembly of Metal-Phenolic Networks.

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.

Cell-Conditioned Protein Coronas on Engineered Particles Influence Immune Responses.

A protein corona, which forms on engineered particles as soon as they are introduced into biological environments, is known to provide particles with a "biological identity". Protein coronas derived from various biological environments have been demonstrated to alter the cell internalization mechanism, to diminish targeting ability and to induce nanoparticle aggregation. So far, most of these studies have challenged engineered particles with a static biological environment. However, the extracellular environment is highly dynamic due to the process termed "cell-conditioning", in which cells deplete and secrete biomolecules. In this work, we demonstrate that protein coronas formed on engineered particles from such cell-conditioned media affect the biophysical particle properties and protein adsorption differently to protein coronas derived from an unconditioned environment. When investigating particles with protein coronas formed in various biologically relevant environments for their interaction with immune cells, we observed differences in pro-inflammatory cytokine secretion and immune cell apoptosis. We found that the particles either increased or mitigated the secretion of a specific cytokine, depending on the environment where the protein corona was formed. Our study suggests that the use of protein coronas could be useful to engineer drug carriers for elongated circulation, enhanced biocompatibility, and lower toxicity by triggering a specific immune response.

Biofunctional metal-phenolic films from dietary flavonoids.

We assembled dietary, bioactive flavonoids into a metal coordinated network to form thin, surface-bound films and hollow capsules, overcoming the poor water solubility of free flavonoids. Films formed from quercetin, myricetin, luteolin and fisetin show radical scavenging activity, a renowned feature of their parent flavonoids, and can be reused over multiple cycles. These films are expected to have potential applications in the pharmaceutical and food industries.

Engineered Metal-Phenolic Capsules Show Tunable Targeted Delivery to Cancer Cells.

We engineered metal-phenolic capsules with both high targeting and low nonspecific cell binding properties. The capsules were prepared by coating phenolic-functionalized hyaluronic acid (HA) and poly(ethylene glycol) (PEG) on calcium carbonate templates, followed by cross-linking the phenolic groups with metal ions and removing the templates. The incorporation of HA significantly enhanced binding and association with a CD44 overexpressing (CD44+) cancer cell line, while the incorporation of PEG reduced nonspecific interactions with a CD44 minimal-expressing (CD44-) cell line. Moreover, high specific targeting to CD44+ cells can be balanced with low nonspecific binding to CD44- cells simply by using an optimized feed-ratio of HA and PEG to vary the content of HA and PEG incorporated into the capsules. Loading an anticancer drug (i.e., doxorubicin) into the obtained capsules resulted in significantly higher cytotoxicity to CD44+ cells but lower cytotoxicity to CD44- cells.

Super-resolution imaging of plasma membrane glycans.

Much of the physiology of cells is controlled by the spatial organization of the plasma membrane and the glycosylation patterns of its components, however, studying the distribution, size, and composition of these components remains challenging. A bioorthogonal chemical reporter strategy was used for the efficient and specific labeling of membrane-associated glycoconjugates with modified monosaccharide precursors and organic fluorophores. Super-resolution fluorescence imaging was used to visualize plasma membrane glycans with single-molecule sensitivity. Our results demonstrate a homogeneous distribution of N-acetylmannosamine (ManNAc)-, N-acetylgalactosamine (GalNAc)-, and O-linked N-acetylglucosamine (O-GlcNAc)-modified plasma membrane proteins in different cell lines with densities of several million glycans on each cell surface.