Structural characterization of site-modified nanocapsid with monodispersed gold clusters

Advancing gastric cancer treatment: nanotechnology innovations and future prospects

Gastric cancer (GC) is the fifth most common cancer worldwide, particularly prevalent in Asia, especially in China, where both its incidence and mortality rates are significantly high. Meanwhile, nanotechnology has demonstrated great potential in the treatment of GC. In particular, nanodrug delivery systems have improved therapeutic efficacy and targeting through various functional modifications, such as targeting peptides, tumor microenvironment responsiveness, and instrument-based methods. For instance, silica (SiO2) has excellent biocompatibility and can be used as a drug carrier, with its porous structure enhancing drug loading capacity. Polymer nanoparticles regulate drug release rates and mechanisms by altering material composition and preparation methods. Lipid nanoparticles efficiently encapsulate hydrophilic drugs and promote cellular uptake, while carbon-based nanoparticles can be used in biosensors and drug delivery. Targets such as integrins, HER2 receptors, and the tumor microenvironment have been used to improve drug efficacy in GC treatment. Nanodrug delivery techniques not only enhance drug efficacy and delivery capabilities but also selectively target tumor cells. Currently, there is a lack of systematic summarization and synthesis regarding the relationship between nanodrug delivery systems and GC treatment, which to some extent hinders researchers and clinicians from efficiently searching for and referencing related studies, thereby reducing work efficiency. This study aims to systematically summarize the existing research on the relationship between nanodrug delivery systems and GC treatment, making it easier for professionals to search and reference, and thereby promoting further research on the role of nanodrug delivery systems and their clinical applications in GC. This review discusses the applications of functionalized nanocarriers in the treatment of GC in recent years, including surface modifications with targeted markers, the combination of phototherapy, chemotherapy, and immunotherapy, along with their advantages and challenges. It also examines the future prospects of targeted nanomaterials in GC treatment. The review particularly focuses on the combined application of nanocarriers in multiple treatment modalities, such as phototherapy, chemotherapy, and immunotherapy, demonstrating their potential in multimodal treatments. Furthermore, it thoroughly explores the specific challenges that nanocarriers face in GC treatment, such as biocompatibility, drug release control, and clinical translation issues, while providing a systematic outlook on future developments. Additionally, this study emphasizes the potential value and feasibility of nanocarriers in clinical applications, contrasting with most reviews that focus on basic research. Through these innovations, we offer new perspectives and directions for the development of nanotechnology in the treatment of GC.

When Metal Nanoclusters Meet Smart Synthesis

Atomically precise metal nanoclusters (MNCs) represent a fascinating class of ultrasmall nanoparticles with molecule-like properties, bridging conventional metal-ligand complexes and nanocrystals. Despite their potential for various applications, synthesis challenges such as a precise understanding of varied synthetic parameters and property-driven synthesis persist, hindering their full exploitation and wider application. Incorporating smart synthesis methodologies, including a closed-loop framework of automation, data interpretation, and feedback from AI, offers promising solutions to address these challenges. In this perspective, we summarize the closed-loop smart synthesis that has been demonstrated in various nanomaterials and explore the research frontiers of smart synthesis for MNCs. Moreover, the perspectives on the inherent challenges and opportunities of smart synthesis for MNCs are discussed, aiming to provide insights and directions for future advancements in this emerging field of AI for Science, while the integration of deep learning algorithms stands to substantially enrich research in smart synthesis by offering enhanced predictive capabilities, optimization strategies, and control mechanisms, thereby extending the potential of MNC synthesis.

Structural Elucidation of a Polypeptoid Chain in a Crystalline Lattice Reveals Key Morphology-Directing Role of the N-Terminus

The ability to engineer synthetic polymers with the same structural precision as biomacromolecules is crucial to enable the de novo design of robust nanomaterials with biomimetic function. Peptoids, poly(N-substituted) glycines, are a highly controllable bio-inspired polymer family that can assemble into a variety of functional, crystalline nanostructures over a wide range of sequences. Extensive investigation on the molecular packing in these lattices has been reported; however, many key atomic-level details of the molecular structure remain underexplored. Here, we use cryo-TEM 3D reconstruction to directly visualize the conformation of an individual polymer chain within a peptoid nanofiber lattice in real space at 3.6 Å resolution. The backbone in the N-decylglycine hydrophobic core is shown to clearly adopt an extended, all-cis-sigma strand conformation, as previously suggested in many peptoid lattice models. We also show that packing interactions (covalent and noncovalent) at the solvent-exposed N-termini have a dominant impact on the local chain ordering and hence the ability of the chains to pack into well-ordered lattices. Peptoids in pure water form fibers with limited growth in the a direction (<14 molecules in width), whereas in the presence of formamide, they grow to over microns in length in the a direction. This dependence points to the significant role of the chain terminus in determining the long-range order in the packing of peptoid lattices and provides an opportunity to modulate lattice stability and nanoscale morphology by the addition of exogenous small molecules. These findings help resolve a major challenge in the de novo structure-based design of sequence-defined biomimetic nanostructures based on crystalline domains and should accelerate the design of functional nanostructures.

Bioconjugation of Au25 Nanocluster to Monoclonal Antibody at Tryptophan

We report the first bioconjugation of Au₂₅ nanocluster to a monoclonal antibody at scarcely exposed tryptophan (Trp) residues toward the development of high-resolution probes for cryogenic electron microscopy (cryo-EM) and tomography (cryo-ET). To achieve this, we improved the Trp-selective bioconjugation using hydroxylamine (ABNOH) reagents instead of previously developed N-oxyl radicals (ABNO). This new protocol allowed for the application of Trp-selective bioconjugation to acid-sensitive proteins such as antibodies. We found that a two-step procedure utilizing first Trp-selective bioconjugation for the introduction of azide groups to the protein and then strain-promoted azide-alkyne cycloaddition (SPAAC) to attach a bicyclononyne (BCN)-presenting redox-sensitive Au₂₅ nanocluster was essential for a scalable procedure. Covalent labeling of the antibody with gold nanoclusters was confirmed by various analytical methods, including cryo-EM analysis of the Au₂₅ nanocluster conjugates.

Virus-like nanoparticles as a theranostic platform for cancer

Virus-like nanoparticles (VLPs) are natural polymer-based nanomaterials that mimic viral structures through the hierarchical assembly of viral coat proteins, while lacking viral genomes. VLPs have received enormous attention in a wide range of nanotechnology-based medical diagnostics and therapies, including cancer therapy, imaging, and theranostics. VLPs are biocompatible and biodegradable and have a uniform structure and controllable assembly. They can encapsulate a wide range of therapeutic and diagnostic agents, and can be genetically or chemically modified. These properties have led to sophisticated multifunctional theranostic platforms. This article reviews the current progress in developing and applying engineered VLPs for molecular imaging, drug delivery, and multifunctional theranostics in cancer research.

High-Resolution Cryo-Electron Microscopy Reveals the Unique Striated Hollow Structure of Photocatalytic Macrocyclic Polydiacetylene Nanotubes

High-resolution structures are crucial for understanding the functional properties of nanomaterials. We applied single-particle cryo-electron microscopy (cryo-EM), a method traditionally used for structure determination of biological macromolecules, to obtain high-resolution structures of synthetic non-biological filaments formed by photopolymerization of macrocyclic diacetylene (MDA) amphiphilic monomers. Tomographic analysis showed that the MDA monomers self-assemble into hollow nanotubes upon dispersion in water. Single-particle analysis revealed tubes consisting of six pairs of covalently bonded filaments held together by hydrophobic interactions, where each filament is composed of macrocyclic rings stacked in parallel "chair" conformations. The hollow MDA nanotube structures we found may account for the efficient scavenging of amphiphilic pollutants in water and subsequent photodegradation of the guest species.

Covalent and non-covalent coupling of a Au102 nanocluster with a fluorophore: energy transfer, quenching and intracellular pH sensing

Interactions between an atomically precise gold nanocluster Au₁₀₂(p-MBA)₄₄ (p-MBA = para mercaptobenzoic acid) and a fluorescent organic dye molecule (KU, azadioxatriangulenium) are studied. In solution, the constituents form spontaneously a weakly bound complex leading to quenching of fluorescence of the KU dye via energy transfer. The KU can be separated from the complex by lowering pH, leading to recovery of fluorescence, which forms a basis for an optical reversible pH sensor. However, the sensor is not a stable entity, which could be delivered inside cells. For this purpose, a covalently bound hybrid is synthesized by linking the KU dye to the ligand layer of the cluster via an ester bond. Covalent linking facilitates entry of the cluster-dye hybrids into cells via endocytosis. Inside cells, the hybrids accumulate in endosomes where Au₁₀₂ releases its cargo via hydrolysis of the ester bond. Changes of the local pH inside endosomes regulate reversible fluorescence due to variations in the interactions between the Au₁₀₂ cluster and the dye. This work presents a concept for delivering reporter molecules into cells by using atomically precise gold nanoclusters as carriers and paves the way for future developments of cluster-reporter sensors for in vivo measurements of e.g. absolute pH values or ion concentrations.

Protein-based nanoplatform for detection of tumorigenic polyps in the colon via noninvasive mucosal routes

The use of nanoparticulate systems to diagnose and treat tumors has gained momentum with the rapid development of nanomedicine. Many nanotheranostics fail due to insufficient bioavailability and low accumulation at the tumor site, resulting in undesirable side effects. We describe the use of an engineered hepatitis E viral nanoparticle (HEVNP) with enhanced bioavailability, tissue retention and mucosal penetration capacities. HEVNP is a modular nanocapsule that can encapsulate heterologous nucleotides, proteins and inorganic metals, such as ferrite oxide nanoparticles. Additionally, the exterior protruding arms of HEVNP is composed of loops that are used for chemical coupling of targeting and therapeutic peptides. We propose the use of HEVNP to target colorectal cancer (i.e., polyps) with imaging-guided delivery using colonoscopy.

A new lateral flow plasmonic biosensor based on gold-viral biomineralized nanozyme for on-site intracellular glutathione detection to evaluate drug-resistance level

Temozolomide (TMZ)-resistant glioblastoma multiforme (GBM) cells would have abnormal redox status due to bio-thiols, like glutathione (GSH), which constitute the most crucial defense system that protects cells from therapeutic agents. Current strategies for GSH detection often require sophisticated instruments that may not be available in laboratories with fewer resources. Here, we circumvent this problem by introducing a lateral flow plasmonic biosensor (LFPB) based on gold-viral biomineralized nanoclusters (AuVCs) as nanozymes that enables the detection of a few molecules with the naked eye and quantified by an auto-analysis software. The GSH level controls the growth of gold nanoparticles (AuNPs) and generates coloured patterns with distinct tonality, which are then auto-analyzed to calculate the GSH concentrations by smartphone with an auto-analysis software. Under the optimized conditions, grayscale value plotted against GSH concentration exhibited a linear relationship within the range of 25-500 μM with a limit of detection (LoD) of 9.80 μM and highly positive correlation between detected GSH level and TMZ drug-resistance level in GBM cells. This excellent property allowed our approach to be used for on-site determination of GSH levels in a rapid (i.e., within 30 min), simple (i.e., auto-analysis software), and cost-effective process (i.e., instrument-free) for cancer precision therapy.

Atomic-level separation of thiolate-protected metal clusters

Fine metal clusters have attracted much attention from the viewpoints of both basic and applied science for many years because of their unique physical/chemical properties and functions, which differ from those of bulk metals. Among these materials, thiolate (SR)-protected gold clusters (Au_n(SR)_m clusters) have been the most studied metal clusters since 2000 because of their ease of synthesis and handling. However, in the early 2000s, it was not easy to isolate these metal clusters. Therefore, high-resolution separation methods were explored, and several atomic-level separation methods, including polyacrylamide gel electrophoresis (PAGE), high-performance liquid chromatography (HPLC), and thin-layer chromatography (TLC), were successively established. These techniques have made it possible to isolate a series of Au_n(SR)_m clusters, and much knowledge has been obtained on the correlation between the chemical composition and fundamental properties such as the stability, electronic structure, and physical properties of Au_n(SR)_m clusters. In addition, these high-resolution separation techniques are now also frequently used to evaluate the distribution of the product and to track the reaction process. In this way, high-resolution separation techniques have played an essential role in the study of Au_n(SR)_m clusters. However, only a few reviews have focused on this work. This review focuses on PAGE, HPLC, and TLC separation techniques, which offer high resolution and repeatability, and summarizes previous studies on the high-resolution separation of Au_n(SR)_m and related clusters with the purpose of promoting a better understanding of the features and the utility of these techniques.

Tissue targeted nanocapsids for oral insulin delivery via drink

For the past eight decades, subcutaneous injection has been the main route used for supplementing the suboptimal insulin secretion for administering insulin as a treatment for diabetes mellitus. Although this method is effective, subcutaneous injections are painful, inconvenient and carry a high risk of infections leading to poor patient compliance. The insulin-encapsulated hepatitis E virus nanoparticle, composed of the noninfectious hepatitis E viral capsid, is expected to deliver insulin from the GI tract to the liver after ingestion. Hepatitis E virus nanoparticle could be the answer to the long search of effective and efficient means to administer insulin orally and the most preferred route of drug delivery with highest patient compliance.