Molecular Packing-Driven Manipulation of Aggregation Induced Emission in Gold Nanoclusters

A key limitation of supramolecular force-driven molecular assembly in aggregation-induced emission (AIE) materials is the need to precisely regulate molecular interactions within the assembly. Achieving such assemblies with in situ manipulable molecular arrangements could provide valuable insights into the role of molecular forces in AIE. Herein, by using glutathione-protected gold nanoclusters (AuNCs) as a model AIE material and a naturally occurring polyphenol, tannic acid (TA), as the assembling agent, we demonstrate that assemblies dominated by covalent bonds and hydrogen bonding show enhanced AIE, while those dominated by π-π stacking promote charge transfer, resulting in significant photoluminescence (PL) quenching. This phenomenon primarily stems from the oxidation of TA into smaller aromatic ring structures, leading to an increase in π-π interactions. The complete in situ oxidation of TA within the assembly induces a morphological transition from 3-D spherical to 2-D sheet-like structures due to the dominance of π-π interactions, consequently resulting in complete PL quenching of AuNCs. These findings highlight the critical role of molecular packing in modulating the AIE properties of AuNCs.

Enhanced vascularization and osseointegration under osteoporotic conditions through functional peptide coating on implant surfaces

Patients with osteoporosis face challenges such as decreased bone density, a sparse trabecular structure, weakened osteogenic ability, and impaired angiogenesis, leading to poor osseointegration and implant failure. Surface modification of implants with biologically active molecules possessing various functions is an effective strategy to improve osseointegration. In this study, we constructed a simple multifunctional coating interface that significantly improves osseointegration. In brief, a multifunctional coating interface was constructed by coupling the Rgd adhesive peptide, Ogp osteogenic peptide, and Ang angiogenic peptide to Lys6 (k6), which self-assembled layer by layer with TA to form the (TA-Rgd@ogp@ang)n composite membrane. This study characterized the surface morphology and biomechanical properties of the coating under both gas and liquid phases and monitored the deposition process and reaction rate of the two peptides with TA using a quartz crystal microbalance. Moreover, (TA-Rgd@ogp@ang)n exhibited a triple synergistic effect on cell migration and adhesion, osteogenic differentiation, and angiogenesis. It also ameliorated the high ROS environment characteristic of osteoporosis pathology, promoted angiogenic bone defect regeneration in osteoporosis, thereby avoiding poor osseointegration. This work provides a new approach for the prevention of implant failure in pathological environments by constructing multifunctional coatings on implants, with tremendous potential applications in the fields of orthopedics and dentistry.

Vesicle-like Nanocapsules Formed by Self-Assembly of Peptides with Oligoproline and -Leucine

Since drug carriers are envisaged to be used in a wide variety of situations and environments, nanocarriers with diverse properties, such as biocompatibility, biodegradability, nonimmunogenicity, adequate particle size, robustness, and cell permeability, are required. Here, we report the construction of novel nanocapsules with the above-mentioned features by the self-assembly of peptides composed of oligoproline and oligoleucine (i.e., H-Pro10Leu4-NH2 and H-Pro10Leu6-NH2). The peptides self-organized via hydrogen bonds and hydrophobic interactions between oligoleucine moieties to form vesicle-like nanocapsules with cationic oligoproline exposed on the surface. The guest encapsulation experiments revealed that the nanocapsules were capable of uptake of both water-soluble and insoluble compounds. Furthermore, positively charged and/or oligoproline-based peptides are known to improve cell permeability and cellular uptake, suggesting that the peptide nanocapsules are good candidates for nanocarriers to complement liposomes and polymer micelles.

Immobilizing c(RGDfc) on the surface of metal-phenolic networks by thiol-click reaction for accelerating osteointegration of implant

The limited osteointegration often leads to the failure of implant, which can be improved by fixing bioactive molecules onto the surface, such as arginyl-glycyl-aspartic acid (RGD): a cell adhesion motif. Metal-Phenolic Networks (MPNs) have garnered increasing attention from different disciplines in recent years due to their simple and rapid process for depositing on various substrates or particles with different shapes. However, the lack of cellular binding sites on MPNs greatly blocks its application in tissue engineering. In this study, we present a facile and efficient approach for producing PC/Fe@c(RGDfc) composite coatings through the conjugation of c(RGDfc) peptides onto the surface of PC/Fe-MPNs utilizing thiol-click reaction. By combined various techniques (ellipsometry, X-ray photoelectron spectroscopy, Liquid Chromatography-Mass Spectrometry, water contact angle, scanning electronic microscopy, atomic force microscopy) the physicochemical properties (composition, coating mechanism and process, modulus and hydrophilicity) of PC/Fe@c(RGDfc) surface were characterized in detail. In addition, the PC/Fe@c(RGDfc) coating exhibits the remarkable ability to positively modulate cellular attachment, proliferation, migration and promoted bone-implant integration in vivo, maintaining the inherent features of MPNs: anti-inflammatory, anti-oxidative properties, as well as multiple substrate deposition. This work contributes to engineering MPNs-based coatings with bioactive molecules by a facile and efficient thiol-click reaction, as an innovative perspective for future development of surface modification of implant materials.

Metal-Phenolic-Mediated Assembly of Functional Small Molecules into Nanoparticles: Assembly and Bioapplications

Small molecules, including therapeutic drugs and tracer molecules, play a vital role in biological processing, disease treatment and diagnosis, and have inspired various nanobiotechnology approaches to realize their biological function, particularly in drug delivery. Desirable features of a delivery system for functional small molecules (FSMs) include high biocompatibility, high loading capacity, and simple manufacturing processes, without the need for chemical modification of the FSM itself. Herein, we report a simple and versatile approach, based on metal-phenolic-mediated assembly, for assembling FSMs into nanoparticles (i.e., FSM-MPN NPs) under aqueous and ambient conditions. We demonstrate loading of anticancer drugs, latency reversal agents, and fluorophores at up to ~80 % that is mostly facilitated by π and hydrophobic interactions between the FSM and nanoparticle components. Secondary nanoparticle engineering involving coating with a polyphenol-antibody thin film or sequential co-loading of multiple FSMs enables cancer cell targeting and combination delivery, respectively. Incorporating fluorophores into FSM-MPN NPs enables the visualization of biodistribution at different time points, revealing that most of these NPs are retained in the kidney and heart 24 h post intravenous administration. This work provides a viable pathway for the rational design of small molecule nanoparticle delivery platforms for diverse biological applications.

Gelatin-based dynamic response antioxidant, anti-inflammatory multifunctional hydrogel for enhanced diabetic wound repair

Diabetic wound therapy presents significant challenges in the clinical environment, where persistent bleeding, disturbed inflammatory regulation, impaired cellular proliferation, and impaired tissue remodeling are major features of diabetic wound healing. However, current treatment strategies need to be considered in the context of the dynamic and complex needs of chronic wound healing. Here, multifunctional dynamic boronic acid cross-linked hydrogels were prepared by the reaction of gelatin (Gel) inoculated with 5-carboxy 3-nitrophenylboronic acid (NPBA) and Epigallocatechin gallate (EGCG) to achieve rapid gelation at pH = 7.4, EGCG could interact electrostatically with cationic antimicrobial peptides (AMP) to achieve the effective loading of AMP in the hydrogels. This hydrogel can be injected and adhered to skin defects in diabetic patients to provide a barrier and rapid hemostasis. In a high glucose microenvironment, the rapid release of AMP effectively kills bacteria, while the responsive release of EGCG eliminates reactive oxygen species (ROS) and promotes macrophage M2 polarization. In addition, the hydrogel had excellent biocompatibility and degradability properties, degraded completely after 3 days of subcutaneous injection, and was non-toxic in H&E staining of major organs and serum liver function indices in mice. This multifunctional injectable hydrogel accelerates diabetic skin wound repair and is a promising dressing for the precise treatment of diabetic wounds.

Engineering poly(ethylene glycol) particles for targeted drug delivery

Poly(ethylene glycol) (PEG) is considered to be the "gold standard" among the stealth polymers employed for drug delivery. Using PEG to modify or engineer particles has thus gained increasing interest because of the ability to prolong blood circulation time and reduce nonspecific biodistribution of particles in vivo, owing to the low fouling and stealth properties of PEG. In addition, endowing PEG-based particles with targeting and drug-loading properties is essential to achieve enhanced drug accumulation at target sites in vivo. In this feature article, we focus on recent work on the synthesis of PEG particles, in which PEG is the main component in the particles. We highlight different synthesis methods used to generate PEG particles, the influence of the physiochemical properties of PEG particles on their stealth and targeting properties, and the application of PEG particles in targeted drug delivery.

Natural polyphenols for drug delivery and tissue engineering construction: A review

Polyphenols, natural compounds rich in phenolic structures, are gaining prominence due to their antioxidant, anti-inflammatory, antibacterial, and anticancer properties, making them valuable in biomedical applications. Through covalent and noncovalent interactions, polyphenols can bind to biomaterials, enhancing their performance and compensating for their shortcomings. Such polyphenol-based biomaterials not only increase the efficacy of polyphenols but also improve drug stability, control release kinetics, and boost the therapeutic effects of drugs. They offer the potential for targeted drug delivery, reducing off-target impacts and enhancing therapeutic outcomes. In tissue engineering, polyphenols promote cell adhesion, proliferation, and differentiation, thus aiding in the formation of functional tissues. Additionally, they offer excellent biocompatibility and mechanical strength, essential in designing scaffolds. This review explores the significant roles of polyphenols in tissue engineering and drug delivery, emphasizing their potential in advancing biomedical research and healthcare.

Engineering tunable dual peptide hybrid coatings promote osseointegration of implants

Utilizing complementary bioactive peptides is a promising surface engineering strategy for bone regeneration on osteogenesis. In this study, we designed block peptides, (Lysine)6-capped RGD (K6-(linker-RGD)3) and OGP (K6-linker-(YGFGG)2), which were mildly grafted onto PC/Fe-MPNs through supramolecular interactions between K6 and PC residues on the MPNs surface to form a dual peptide coating, named PC/Fe@K6-RGD/OGP. The properties of the block peptides coating, including mechanics, hydrophilicity, chemical composition, etc., were detailly characterized by various techniques (ellipsometry, quartz crystal microbalance, X-ray photoelectron spectroscopy, water contact angle, scanning electronic microscopy and atomic force microscopy). Importantly, the RGD/OGP ratio can be well adjusted, which allowed optimizing the RGD/OGP ratio to endow significantly enhanced osteogenic activity of MC3T3-E1 cells through the Wnt/β-catenin pathway, while also promoting cell adhesion, immune regulation, inhibiting osteoclast differentiation and oxidative stress reduction. In vivo, the optimized RGD/OGP coatings promoted bone regeneration and osseointegration around implants in rats with bone defects. In conclusion, rationally designed PC/Fe@K6-RGD/OGP coating integrated RGD and OGP bioactivities, providing a convenient approach to enhance bioinert implant surfaces for bone regeneration.

Supramolecular self-assembly of EGCG-selenomethionine nanodrug for treating osteoarthritis

Osteoarthritis (OA) has emerged as a significant health concern among the elderly population, with increasing attention paid to ferroptosis-induced OA in recent years. However, the prolonged use of nonsteroidal anti-inflammatory drugs or corticosteroids can lead to a series of side effects and limited therapeutic efficacy. This study aimed to employ the Mannich condensation reaction between epigallocatechin-3-gallate (EGCG) and selenomethionine (SeMet) to efficiently synthesize polyphenol-based nanodrugs in aqueous media for treating OA. Molecular biology experiments demonstrated that EGCG-based nanodrugs (ES NDs) could effectively reduce glutathione peroxidase 4 (GPX4) inactivation, abnormal Fe2+ accumulation, and lipid peroxidation induced by oxidative stress, which ameliorated the metabolic disorder of chondrocytes and other multiple pathological processes triggered by ferroptosis. Moreover, imaging and histopathological analysis of the destabilization of the medial meniscus model in mice confirmed that ES NDs exhibiting significant therapeutic effects in relieving OA. The intra-articular delivery of ES NDs represents a promising approach for treating OA and other joint inflammatory diseases.

Recent Progress in Protein-Polyphenol Assemblies for Biomedical Applications

Nowadays, natural materials as smart building blocks for assembling functional materials have aroused extensive interest in the scientific community. Proteins and polyphenols are typical natural building blocks that are widely used. On the one hand, proteins are one of the most versatile classes of biomolecules, serving as catalysts, signaling molecules, transporters, receptors, scaffolds that maintain the integrity of cell and tissue, and more. On the other hand, the facile adhesion of naturally abundant polyphenols with other substances and their potential biomedical applications have been highly attractive for functional biomaterials fabrication. Additionally, there are a variety of interactions between the proteins and polyphenols, mainly hydrogen bonding, hydrophobic, and ionic interactions. These reversible dynamic interactions enable proteins and polyphenols to form stable protein-polyphenol assemblies and maintain their inherent structures and biological activities in the assemblies. Therefore, protein-polyphenol assemblies can be applied to design a variety of advanced functional materials for biomedical applications. Herein, recent progress in protein-polyphenol particles, capsules, coatings, and hydrogels is summarized, the preparation and application of these assemblies are introduced in detail, and the future of the field is prospected.

Construction of multifunctional coating with cationic amino acid-coupled peptides for osseointegration of implants

Osseointegration is an important indicator of implant success. This process can be improved by coating modified bioactive molecules with multiple functions on the surface of implants. Herein, a simple multifunctional coating that could effectively improve osseointegration was prepared through layer-by-layer self-assembly of cationic amino acids and tannic acid (TA), a negatively charged molecule. Osteogenic growth peptide (OGP) and the arginine-glycine-aspartic acid (RGD) functional polypeptides were coupled with Lys6 (K6), the two polypeptides then self-assembled with TA layer by layer to form a composite film, (TA-OGP@RGD)n. The surface morphology and biomechanical properties of the coating were analyzed in gas and liquid phases, and the deposition process and kinetics of the two peptides onto TA were monitored using a quartz crystal microbalance. In addition, the feeding consistency and adsorption ratios of the two peptides were explored by using fluorescence visualization and quantification. The (TA-OGP@RGD)n composite membrane mediated the early migration and adhesion of cells and significantly promoted osteogenic differentiation and mineralization of the extracellular matrix in vitro. Additionally, the bifunctional peptide exhibited excellent osteogenesis and osseointegration owing to the synergistic effect of the OGP and RGD peptides in vivo. Simultaneously, the (TA-OGP@RGD)n membrane regulated the balance of reactive oxygen species in the cell growth environment, thereby influencing the complex biological process of osseointegration. Thus, the results of this study provide a novel perspective for constructing multifunctional coatings for implants and has considerable application potential in orthopedics and dentistry.

Peptide-Based Coacervate Protocells with Cytoprotective Metal-Phenolic Network Membranes

Protocells have garnered considerable attention from cell biologists, materials scientists, and synthetic biologists. Phase-separating coacervate microdroplets have emerged as a promising cytomimetic model because they can internalize and concentrate components from dilute surrounding environments. However, the membrane-free nature of such coacervates leads to coalescence into a bulk phase, a phenomenon that is not representative of the cells they are designed to mimic. Herein, we develop a membranized peptide coacervate (PC) with oppositely charged oligopeptides as the molecularly crowded cytosol and a metal-phenolic network (MPN) coating as the membrane. The hybrid protocell efficiently internalizes various bioactive macromolecules (e.g., bovine serum albumin and immunoglobulin G) (>90%) while also resisting radicals due to the semipermeable cytoprotective membrane. Notably, the resultant PC@MPNs are capable of anabolic cascade reactions and remain in discrete protocellular populations without coalescence. Finally, we demonstrate that the MPN protocell membrane can be postfunctionalized with various functional molecules (e.g., folic acid and fluorescence dye) to more closely resemble actual cells with complex membranes, such as recognition molecules, which allows for drug delivery. This membrane-bound cytosolic protocell structure paves the way for innovative synthetic cells with structural and functional complexity.

Polyphenol-Based Nanosystems for Next-Generation Cancer Therapy: Multifunctionality, Design, and Challenges

With the continuous updating of cancer treatment methods and the rapid development of precision medicine in recent years, there are higher demands for advanced and versatile drug delivery systems. Scientists are committed to create greener and more effective nanomedicines where the carrier is no longer limited to a single function of drug delivery. Polyphenols, which can act as both active ingredients and fundamental building blocks, are being explored as potential multifunctional carriers that are efficient and safe for design purposes. Due to their intrinsic anticancer activity, phenolic compounds have shown surprising expressiveness in ablation of tumor cells, overcoming cancer multidrug resistance (MDR), and enhancing immunotherapeutic efficacy. This review provides an overview of recent advances in the design, synthesis, and application of versatile polyphenol-based nanosystems for cancer therapy in various modes. Moreover, the merits of polyphenols and the challenges for their clinical translation are also discussed, and it is pointed out that the novel polyphenol delivery system requires further optimization and validation.

Hierarchical Superstructure of Plant Polyphenol and Arginine Surfactant for Long-Lasting and Target-Selective Antimicrobial Application

Antimicrobial agents are massively used to disinfect the pathogen contaminated surfaces since the Corona Virus Disease 2019 (COVID-19) outbreak. However, their defects of poor durability, strong irritation, and high environmental accumulation are exposed. Herein, a convenient strategy is developed to fabricate long-lasting and target-selective antimicrobial agent with the special hierarchical structure through bottom-up assembly of natural gallic acid with arginine surfactant. The assembly starts from rodlike micelles, further stacking into hexagonal columns and finally interpenetrating into spherical assemblies, which avoid explosive release of antimicrobial units. The assemblies show anti-water washing and high adhesion on various surfaces; and thus, possess highly efficient and broad-spectrum antimicrobial activities even after using up to eleven cycles. Both in vitro and in vivo experiments prove that the assemblies are highly selective in killing pathogens without generating toxicity. The excellent antimicrobial virtues well satisfy the increasing anti-infection demands and the hierarchical assembly exhibits great potential as a clinical candidate.