Chemical and Biomedical Engineering - Research Publications
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ItemOrdered Mesoporous Metal-Phenolic Network Particles.(American Chemical Society, 2020-01-08)Mesoporous metal-organic networks have attracted widespread interest owing to their potential applications in diverse fields including gas storage, separations, catalysis, and drug delivery. Despite recent advances, the synthesis of metal-organic networks with large and ordered mesochannels (>20 nm), which are important for loading, separating, and releasing macromolecules, remains a challenge. Herein, we report a templating strategy using sacrificial double cubic network polymer cubosomes (Im3̅m) to synthesize ordered mesoporous metal-phenolic particles (meso-MPN particles) with a large-pore (∼40 nm) single cubic network (Pm3̅m). We demonstrate that the large-pore network and the phenolic groups in the meso-MPN particles enable high loadings of various proteins (e.g., horseradish peroxidase (HRP), bovine hemoglobin, immunoglobulin G, and glucose oxidase (GOx)), which have different shapes, charges, and sizes (i.e., molecular weights spanning 44-160 kDa). For example, GOx loading in the meso-MPN particles was 362 mg g-1, which is ∼6-fold higher than the amount loaded in commercially available SiO2 particles with an average pore size of 50 nm. Furthermore, we show that HRP, when loaded in the meso-MPN particles (486 mg g-1), retained ∼82% activity of free HRP in solution and can be recycled at least five times with a minimal (∼13%) decrease in HRP activity, which exceeds HRP performance in 50 nm pore SiO2 particles (∼36% retained activity and ∼30% activity loss when recycled five times). Considering the wide selection of naturally abundant polyphenols (>8000 species) and metal ions available, the present cubosome-enabled strategy is expected to provide new avenues for designing a range of meso-MPN particles for various applications.
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ItemExpanding the Toolbox of Metal-Phenolic Networks via Enzyme-Mediated Assembly(Wiley, 2020-01-01)Functional coatings are of considerable interest because of their fundamental implications for interfacial assembly and promise for numerous applications. Universally adherent materials have recently emerged as versatile functional coatings; however, such coatings are generally limited to catechol, (ortho‐diphenol)‐containing molecules, as building blocks. Here, we report a facile, biofriendly enzyme‐mediated strategy for assembling a wide range of molecules (e.g., 14 representative molecules in this study) that do not natively have catechol moieties, including small molecules, peptides, and proteins, on various surfaces, while preserving the molecule's inherent function, such as catalysis (≈80 % retention of enzymatic activity for trypsin). Assembly is achieved by in situ conversion of monophenols into catechols via tyrosinase, where films form on surfaces via covalent and coordination cross‐linking. The resulting coatings are robust, functional (e.g., in protective coatings, biological imaging, and enzymatic catalysis), and versatile for diverse secondary surface‐confined reactions (e.g., biomineralization, metal ion chelation, and N‐hydroxysuccinimide conjugation).
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ItemModular Assembly of Host-Guest Metal-Phenolic Networks Using Macrocyclic Building Blocks(Wiley, 2020-01-02)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°).
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ItemThe Biomolecular Corona in 2D and Reverse: Patterning Metal–Phenolic Networks on Proteins, Lipids, Nucleic Acids, Polysaccharides, and Fingerprints(Wiley, 2020-01-03)The adsorption of biomolecules onto nanomaterials can alter the performance of the nanomaterials in vitro and in vivo. Recent studies have primarily focused on the protein “corona”, formed upon adsorption of proteins onto nanoparticles in biological fluids, which can change the biological fate of the nanoparticles. Conversely, interactions between nanomaterials and other classes of biomolecules namely, lipids, nucleic acids, and polysaccharides have received less attention despite their important roles in biology. A possible reason is the challenge associated with investigating biomolecule interactions with nanomaterials using current technologies. Herein, a protocol is developed for studying bio–nano interactions by depositing four classes of biomolecules (proteins, lipids, nucleic acids, and polysaccharides) and complex biological media (blood) onto planar substrates, followed by exposure to metal–phenolic network (MPN) complexes. The MPNs preferentially interact with the biomolecule over the inorganic substrate (glass), highlighting that patterned biomolecules can be used to engineer patterned MPNs. Subsequent formation of silver nanoparticles on the MPN films maintains the patterns and endows the films with unique reflectance and fluorescence properties, enabling visualization of latent fingerprints (i.e., invisible residual biomolecule patterns). This study demonstrates the potential complexity of the biomolecule corona as all classes of biomolecules can adsorb onto MPN-based nanomaterials.
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ItemRicocheting Droplets Moving on Super-Repellent Surfaces(Wiley Open Access, 2019-09-12)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.
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ItemMetal-Phenolic Coatings as a Platform to Trigger Endosomal Escape of Nanoparticles.(American Chemical Society, 2019-10-22)The intracellular delivery of functional nanoparticles (NPs) and the release of therapeutic payloads at a target site are central issues for biomedical applications. However, the endosomal entrapment of NPs typically results in the degradation of active cargo, leading to poor therapeutic outcomes. Current advances to promote the endosomal escape of NPs largely involve the use of polycationic polymers and cell-penetrating peptides (CPPs), which both can suffer from potential toxicity and convoluted synthesis/conjugation processes. Herein, we report the use of metal-phenolic networks (MPNs) as versatile and nontoxic coatings to facilitate the escape of NPs from endo/lysosomal compartments. The MPNs, which were engineered from the polyphenol tannic acid and FeIII or AlIII, enabled the endosomal escape of both inorganic (mesoporous silica) and organic (polystyrene and melamine resin) NPs owing to the "proton-sponge effect" arising from the buffering capacity of MPNs. Postfunctionalization of the MPN-coated NPs with low-fouling polymers did not impair the endosomal escape, indicating the modular and generalizable nature of this approach. We envisage that the ease of fabrication, versatility, low cytotoxicity, and promising endosomal escape performance displayed by the MPN coatings offer opportunities for such coatings to be used for the efficient delivery of cytoplasm-targeted therapeutics using NPs.
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ItemLigand-Functionalized Poly(ethylene glycol) Particles for Tumor Targeting and Intracellular Uptake.(American Chemical Society, 2019)Drug carriers typically require both stealth and targeting properties to minimize nonspecific interactions with healthy cells and increase specific interaction with diseased cells. Herein, the assembly of targeted poly(ethylene glycol) (PEG) particles functionalized with cyclic peptides containing Arg-Gly-Asp (RGD) (ligand) using a mesoporous silica templating method is reported. The influence of PEG molecular weight, ligand-to-PEG molecule ratio, and particle size on cancer cell targeting to balance stealth and targeting of the engineered PEG particles is investigated. RGD-functionalized PEG particles (PEG-RGD particles) efficiently target U-87 MG cancer cells under static and flow conditions in vitro, whereas PEG and cyclic peptides containing Arg-Asp-Gly (RDG)-functionalized PEG (PEG-RDG) particles display negligible interaction with the same cells. Increasing the ligand-to-PEG molecule ratio improves cell targeting. In addition, the targeted PEG-RGD particles improve cell uptake via receptor-mediated endocytosis, which is desirable for intracellular drug delivery. The PEG-RGD particles show improved tumor targeting (14% ID g-1) when compared with the PEG (3% ID g-1) and PEG-RDG (7% ID g-1) particles in vivo, although the PEG-RGD particles show comparatively higher spleen and liver accumulation. The targeted PEG particles represent a platform for developing particles aimed at balancing nonspecific and specific interactions in biological systems.
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ItemOxidation-Mediated Kinetic Strategies for Engineering Metal-Phenolic Networks(Wiley - V C H Verlag GmbH & Co. KGaA, 2019-09-02)The tunable growth of metal–organic materials has implications for engineering particles and surfaces for diverse applications. Specifically, controlling the self‐assembly of metal–phenolic networks (MPNs), an emerging class of metal–organic materials, is challenging, as previous studies suggest that growth often terminates through kinetic trapping. Herein, kinetic strategies were used to temporally and spatially control MPN growth by promoting self‐correction of the coordinating building blocks through oxidation‐mediated MPN assembly. The formation and growth mechanisms were investigated and used to engineer films with microporous structures and continuous gradients. Moreover, reactive oxygen species generated by ultrasonication expedite oxidation and result in faster (ca. 30 times) film growth than that achieved by other MPN assembly methods. This study expands our understanding of metal–phenolic chemistry towards engineering metal–phenolic materials for various applications.
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ItemTuning the Mechanical Behavior of Metal-Phenolic Networks through Building Block Composition(AMER CHEMICAL SOC, 2019-02-13)Metal-phenolic networks (MPNs) are an emerging class of functional metal-organic materials with a high degree of modularity in terms of the choice of metal ion, phenolic ligand, and assembly method. Although various applications, including drug delivery, imaging, and catalysis, have been studied with MPNs, in the form of films and capsules, the influence of metals and organic building blocks on their mechanical properties is poorly understood. Herein, we demonstrate that the mechanical properties of MPNs can be tuned through choice of the metal ion and/or phenolic ligand. Specifically, the pH of the metal ion solution and/or size of phenolic ligand influence the Young's modulus ( EY) of MPNs (higher pHs and smaller ligands lead to higher EY). This study systematically investigates the roles of both metal ions and ligands on the mechanical properties of metal-organic materials and provides new insight into engineering the mechanical properties of coordination films.
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ItemProtein Adsorption and Coordination-Based End-Tethering of Functional Polymers on Metal-Phenolic Network Films(AMER CHEMICAL SOC, 2019-03)Metal-phenolic network (MPN) coatings have generated increasing interest owing to their biologically inspired nature, facile fabrication, and near-universal adherence, especially for biomedical applications. However, a key issue in biomedicine is protein fouling, and the adsorption of proteins on tannic acid-based MPNs remains to be comprehensively studied. Herein, we investigate the interaction of specific biomedically relevant proteins in solution (e.g., bovine serum albumin (BSA), immunoglobulin G (IgG), fibrinogen) and complex biological media (serum) using layer-by-layer-assembled tannic acid/FeIII MPN films. When FeIII was the outermost layer, galloyl-modified poly(2-ethyl-2-oxazoline) (P(EtOx)-Gal) could be grafted to the films through coordination bonds. Protein fouling and bacterial adhesion were greatly suppressed after functionalization with P(EtOx)-Gal and the mass of adsorbed protein was reduced by 79%. Interestingly, larger proteins adsorbed more on both the MPNs and P(EtOx)-functionalized MPNs. This study provides fundamental information on the interactions of MPNs with single proteins, mixtures of proteins as encountered in serum, and the noncovalent, coordination-based, functionalization of MPN films.