Role of Molecular Interactions in Supramolecular Polypeptide-Polyphenol Networks for Engineering Functional Materials.

Supramolecular assembly affords the development of a wide range of polypeptide-based biomaterials for drug delivery and nanomedicine. However, there remains a need to develop a platform for the rapid synthesis and study of diverse polypeptide-based materials without the need for employing complex chemistries. Herein, we develop a versatile strategy for creating polypeptide-based materials using polyphenols that display multiple synergistic cross-linking interactions with different polypeptide side groups. We evaluated the diverse interactions operating within these polypeptide-polyphenol networks via binding affinity, thermodynamics, and molecular docking studies and found that positively charged polypeptides (Ka of ∼2 × 104 M-1) and polyproline (Ka of ∼2 × 106 M-1) exhibited stronger interactions with polyphenols than other amino acids (Ka of ∼2 × 103 M-1). Free-standing particles (capsules) were obtained from different homopolypeptides using a template-mediated strategy. The properties of the capsules varied with the homopolypeptide used, for example, positively charged polypeptides produced thicker shell walls (120 nm) with reduced permeability and involved multiple interactions (i.e., electrostatic and hydrogen), whereas uncharged polypeptides generated thinner (10 nm) and more permeable shell walls due to the dominant hydrophobic interactions. Polyarginine imparted cell penetration and endosomal escape properties to the polyarginine-tannic acid capsules, enabling enhanced delivery of the drug doxorubicin (2.5 times higher intracellular fluorescence after 24 h) and a corresponding higher cell death in vitro when compared with polyproline-tannic acid capsules. The ability to readily complex polyphenols with different types of polypeptides highlights that a wide range of functional materials can be generated for various applications.

Assembly of Bioactive Nanoparticles via Metal-Phenolic Complexation.

The integration of bioactive materials (e.g., proteins and genes) into nanoparticles holds promise in fields ranging from catalysis to biomedicine. However, it is challenging to develop a simple and broadly applicable nanoparticle platform that can readily incorporate distinct biomacromolecules without affecting their intrinsic activity. Herein, a metal-phenolic assembly approach is presented whereby diverse functional nanoparticles can be readily assembled in water by combining various synthetic and natural building blocks, including poly(ethylene glycol), phenolic ligands, metal ions, and bioactive macromolecules. The assembly process is primarily mediated by metal-phenolic complexes through coordination and hydrophobic interactions, which yields uniform and spherical nanoparticles (mostly <200 nm), while preserving the function of the incorporated biomacromolecules (siRNA and five different proteins used). The functionality of the assembled nanoparticles is demonstrated through cancer cell apoptosis, RNA degradation, catalysis, and gene downregulation studies. Furthermore, the resulting nanoparticles can be used as building blocks for the secondary engineering of superstructures via templating and cross-linking with metal ions. The bioactivity and versatility of the platform can potentially be used for the streamlined and rational design of future bioactive materials.

Luminescent Metal-Phenolic Networks for Multicolor Particle Labeling.

The development of fluorescence labeling techniques has attracted widespread interest in various fields, including biomedical science as it can facilitate high-resolution imaging and the spatiotemporal understanding of various biological processes. We report a supramolecular fluorescence labeling strategy using luminescent metal-phenolic networks (MPNs) constructed from metal ions, phenolic ligands, and common and commercially available dyes. The rapid labeling process (<5 min) produces ultrathin coatings (≈10 nm) on diverse particles (e.g., organic, inorganic, and biological entities) with customized luminescence (e.g., red, blue, multichromatic, and white light) simply through the selection of fluorophores. The fluorescent coatings are stable at pH values from 1 to 8 and in complex biological media owing to the dominant π interactions between the dyes and MPNs. These coatings exhibit negligible cytotoxicity and their strong fluorescence is retained even when internalized into intracellular compartments. This strategy is expected to provide a versatile approach for fluorescence labeling with potential in diverse fields across the physical and life sciences.

Robust and Versatile Coatings Engineered via Simultaneous Covalent and Noncovalent Interactions.

Interfacial modular assembly has emerged as an adaptable strategy for engineering the surface properties of substrates in biomedicine, photonics, and catalysis. Herein, we report a versatile and robust coating (pBDT-TA), self-assembled from tannic acid (TA) and a self-polymerizing aromatic dithiol (i.e., benzene-1,4-dithiol, BDT), that can be engineered on diverse substrates with a precisely tuned thickness (5-40 nm) by varying the concentration of BDT used. The pBDT-TA coating is stabilized by covalent (disulfide) bonds and supramolecular (π-π) interactions, endowing the coating with high stability in various harsh aqueous environments across ionic strength, pH, temperature (e.g., 100 mM NaCl, HCl (pH 1) or NaOH (pH 13), and water at 100 °C), as well as surfactant solution (e.g., 100 mM Triton X-100) and biological buffer (e.g., Dulbecco's phosphate-buffered saline), as validated by experiments and simulations. Moreover, the reported pBDT-TA coating enables secondary reactions on the coating for engineering hybrid adlayers (e.g., ZIF-8 shells) via phenolic-mediated adhesion, and the facile integration of aromatic fluorescent dyes (e.g., rhodamine B) via π interactions without requiring elaborate synthetic processes.

Development and Validation of a Three-Gene-Based Prognostic Model for Predicting the Overall Survival of Head and Neck Squamous Cell Carcinoma Through Bioinformatics Analysis.

Head and neck squamous cell carcinoma (HNSCC) is one of the most common cancer worldwide and seriously threats public health safety. Despite the improvement of diagnostic and treatment methods, the overall survival for advanced patients has not improved yet. This study aimed to sort out prognosis-related molecular biomarkers for HNSCC and establish a prognostic model to stratify the risk hazards and predicate the prognosis for these patients, providing a theoretical basis for the formulation of individual treatment plans. We firstly identified differentially expressed genes (DEGs) between HNSCC tissues and normal tissues via joint analysis based on GEO databases. Then a total of 11 hub genes were selected for single-gene prognostic analysis to identify the prognostic genes. Later, the clinical information and transcription information of HNSCC were downloaded from the TCGA database. With the application of least absolute shrinkage and selection operator (LASSO) algorithm analyses for the prognostic genes on the TCGA cohort, a prognostic model consisting of three genes (COL4A1, PLAU and ITGA5) was successfully established and the survival analyses showed that the prognostic model possessed a robust performance in the overall survival prediction. Afterward, the univariate and multivariate regression analysis indicated that the prognostic model could be an independent prognostic factor. Finally, the predicative efficiency of this model was well confirmed in an independent external HNSCC cohort.

Particle engineering enabled by polyphenol-mediated supramolecular networks.

We report a facile strategy for engineering diverse particles based on the supramolecular assembly of natural polyphenols and a self-polymerizable aromatic dithiol. In aqueous conditions, uniform and size-tunable supramolecular particles are assembled through π-π interactions as mediated by polyphenols. Owing to the high binding affinity of phenolic motifs present at the surface, these particles allow for the subsequent deposition of various materials (i.e., organic, inorganic, and hybrid components), producing a variety of monodisperse functional particles. Moreover, the solvent-dependent disassembly of the supramolecular networks enables their removal, generating a wide range of corresponding hollow structures including capsules and yolk-shell structures. The versatility of these supramolecular networks, combined with their negligible cytotoxicity provides a pathway for the rational design of a range of particle systems (including core-shell, hollow, and yolk-shell) with potential in biomedical and environmental applications.

Polyphenol-Based Nanoparticles for Intracellular Protein Delivery via Competing Supramolecular Interactions.

Intracellular delivery of proteins is a promising strategy for regulating cellular behavior and therefore has attracted interest for biomedical applications. Despite the emergence of various nanoparticle-based intracellular delivery approaches, it remains challenging to engineer a versatile delivery system capable of responding to various physiological triggers without the need for complex chemical synthesis of the delivery system. Herein, we develop a template-mediated supramolecular assembly strategy to synthesize protein-polyphenol nanoparticles (NPs) capable of endosomal escape and subsequent protein release in the cytosol. These NPs are stable in serum and undergo surface charge reversal from negative to positive in acidic environments, leading to spontaneous endosomal escape. In the cytosol, endogenous small peptides and amino acids with relatively high charge densities, such as glutathione, trigger NP disassembly through competitive supramolecular interactions, thereby releasing functional bioactive proteins, as validated using cytochrome C and ß-galactosidase. The versatility of the present strategy in terms of nanoparticle size, protein type, and functional protein delivery makes this a promising platform for potential application in the field of protein therapeutics.

Polyphenol-Mediated Assembly of Proteins for Engineering Functional Materials.

Functional materials composed of proteins have attracted much interest owing to the inherent and diverse functionality of proteins. However, establishing general techniques for assembling proteins into nanomaterials is challenging owing to the complex physicochemical nature and potential denaturation of proteins. Here, a simple, versatile strategy is introduced to fabricate functional protein assemblies through the interfacial assembly of proteins and polyphenols (e.g., tannic acid) on various substrates (organic, inorganic, and biological). The dominant interactions (hydrogen-bonding, hydrophobic, and ionic) between the proteins and tannic acid were elucidated; most proteins undergo multiple noncovalent stabilizing interactions with polyphenols, which can be used to engineer responsiveness into the assemblies. The proteins retain their structure and function within the assemblies, thereby enabling their use in various applications (e.g., catalysis, fluorescence imaging, and cell targeting).

Ordered Mesoporous Metal-Phenolic Network Particles.

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.

Fluorescent Poly(glycerol-co-sebacate) Acrylate Nanoparticles for Stem Cell Labeling and Longitudinal Tracking.

The stable presence of fluorophores within the biocompatible and biodegradable elastomer poly(glycerol-co-sebacate) acrylate (PGSA) is critical for monitoring the transplantation, performance, and degradation of the polymers in vivo. However, current methods such as physically entrapping the fluorophores in the polymer matrix or providing a fluorescent coating suffer from rapid leakage of fluorophores. Covalent conjugation of fluorophores with the polymers and the subsequent core-cross-linking are proposed here to address this challenge. Taking rhodamine as the model dye and PGSA nanoparticles (NPs) as the model platform, we successfully showed that the synthesized rhodamine-conjugated PGSA (PGSAR) NPs only released less than 30% rhodamine at day 28, whereas complete release of dye occurred for rhodamine-encapsulated PGSA (PGSA-p-R) NPs at day 7 and 57.49% rhodamine was released out for the un-cross-linked PGSAR NPs at day 28. More excitingly, PGSAR NPs showed a strong quantum yield enhancement (26.24-fold) of the fluorophores, which was due to the hydrophobic environment within PGSAR NPs and the restricted rotation of (6-diethylamino-3H-xanthen-3-ylidene) diethyl group in rhodamine after the conjugation and core-cross-linking. The stable presence of dye in the NPs and enhanced fluorescence allowed a longitudinal tracking of stem cells both in vitro and in vivo for at least 28 days.

Cryomilling for the fabrication of doxorubicin-containing silica-nanoparticle/polycaprolactone nanocomposite films.

Bionanocomposites need to have a homogeneous distribution of nanomaterials in the polymeric matrix to achieve consistent mechanical and biological functions. However, a significant challenge lies in achieving the homogeneous distribution of nanomaterials, particularly through a solvent-free approach. This report introduces a technology to address this need. Specifically, cryomilling, a solvent-free, low-temperature processing method, was applied to generate a bionanocomposite film with well-dispersed nanoparticles. As a proof-of-concept, polycaprolactone (PCL) and doxorubicin-containing silica nanoparticles (Si-Dox) were processed through cryomilling and subsequently heat pressed to form the PCL/Si-Dox (cPCL/Si-Dox) film. Homogeneous distribution of Si-Dox was observed under both confocal imaging and atomic force microscopy imaging. The mechanical properties of cPCL/Si-Dox were comparable to those of the pure PCL film. Subsequent in vitro release profiles suggested that sustained release of Dox from the cPCL/Si-Dox film was achievable over 50 days. When human cervical cancer cells were seeded directly on these films, uptake of Dox was observed as early as day 1 and significant inhibition of cell growth was recorded on day 5.