Stirring-Controlled Synthesis of Ultrastable, Fluorescent Silver Nanoclusters

This paper describes how macroscopic stirring of a reaction mixture can be used to produce nanostructures exhibiting properties not readily achievable via other protocols. In particular, it is shown that by simply adjusting the stirring rate, a standard glutathione-based method-to date, used to produce only marginally stable fluorescent silver nanoclusters, Ag NCs-can be boosted to yield nanoclusters retaining fluorescence for unprecedented periods of over 2 years. This enhancement derives not simply from increased homogenization of the reaction mixture but mainly from an appropriately timed delivery of oxygen from above the reaction mixture. In effect, oxygen serves as a reagent that dictates size, structure, stability, and functional properties of the growing nanoobjects.

Nanotechnology: A Promising Targeted Drug Delivery System for Brain Tumours and Alzheimer's Disease

Nanotechnology is the process of modulating shape and size at the nanoscale to design and manufacture structures, devices, and systems. Nanotechnology's prospective breakthroughs are incredible, and some cannot even be comprehended right now. The blood-brain barrier, which is a prominent physiological barrier in the brain, limits the adequate elimination of malignant cells by changing the concentration of therapeutic agents at the target tissue. Nanotechnology has sparked interest in recent years as a way to solve these issues and improve drug delivery. Inorganic and organic nanomaterials have been found to be beneficial for bioimaging approaches and controlled drug delivery systems. Brain cancer (BC) and Alzheimer's disease (AD) are two of the prominent disorders of the brain. Even though the pathophysiology and pathways for both disorders are different, nanotechnology with common features can deliver drugs over the BBB, advancing the treatment of both disorders. This innovative technology could provide a foundation for combining diagnostics, treatments, and delivery of targeted drugs to the tumour site, further supervising the response and designing and delivering materials by employing atomic and molecular elements. There is currently limited treatment for Alzheimer's disease, and reversing further progression is difficult. Recently, various nanocarriers have been investigated to improve the bioavailability and efficacy of many AD treatment drugs. Nanotechnology-assisted drugs can penetrate the BBB and reach the target tissue. However, further research is required in this field to ensure the safety and efficacy of drug-loaded nanoparticles. The application of nanotechnology in the diagnosis and treatment of brain tumours and Alzheimer's disease is briefly discussed in this review.

Potential of fluorescent nanoprobe in diagnosis and treatment of Alzheimer's disease

Alzheimer's disease (AD) is well known for its insidious nature, slow progression and high incidence as a neurodegenerative disease. In the past, diagnosis of AD mainly depended on analysis of a patient's cognitive ability and behavior. Without a unified standard for analysis methods, this is prone to produce incorrect diagnoses. Currently, definitive diagnosis mainly relies on histopathological examination. Because of the advantages of precision, noninvasiveness, low toxicity and high spatiotemporal resolution, fluorescent nanoprobes are suitable for the early diagnosis of AD. This review summarizes the research progress of different kinds of fluorescent nanoprobes for AD diagnosis and therapy in recent years and provides an outlook on the development prospects of fluorescent nanoprobes.

Title: Advances of Gold Nanoclusters for Bioimaging

Gold nanoclusters (AuNCs) have become a promising material for bioimaging detection because of their tunable photoluminescence, large Stokes shift, low photobleaching, and good biocompatibility. Last decade, great efforts have been made to develop AuNCs for enhanced imaging contrast and multimodal imaging. Herein, an updated overview of recent advances in AuNCs was present for visible fluorescence (FL) imaging, near-infrared fluorescence (NIR-FL) imaging, two-photon near-infrared fluorescence (TP-NIR-FL) imaging, computed tomography (CT) imaging, positron emission tomography (PET) imaging, magnetic resonance imaging (MRI), and photoacoustic (PA) imaging. The justification of AuNCs applied in bioimaging mentioned above applications was discussed, the performance location of different AuNCs were summarized and highlighted in an unified parameter coordinate system of corresponding bioimaging, and the current challenges, research frontiers, and prospects of AuNCs in bioimaging were discussed. This review will bring new insights into the future development of AuNCs in bio-diagnostic imaging.

Cell-Derived Biogenetic Gold Nanoparticles for Sensitizing Radiotherapy and Boosting Immune Response against Cancer

The biosynthesis of nanomedicine has gained enormous attention and exhibited promising prospects, while the underlying mechanism and advantage remain not fully understood. Here, a cell-reactor based on tumor cells is developed to obtain biogenetic gold nanoparticles (Au@MC38) for sensitizing radiotherapy and boosting immune responses. It demonstrates that the intracellular biomineralization and exocytosis process of Au@MC38 can be regulated by the cellular metabolites level and other factors, such as glutathione and reactive oxygen species (ROS), autophagy, and UV irradiation. The elucidation of mechanisms may promote the understanding of interaction principles between nanoparticles and biosystems in the process of biosynthesis. Combined with radiotherapy, Au@MC38 strengthens the radiation-induced DNA damage and ROS generation, thus aggravating cell apoptosis and necrosis. Benefiting from homologous targeting and transcytosis effect, Au@MC38 demonstrates good tumor distribution. Local radiation-induced immunogenic cell death initiates an effective immune response. Especially, CD8a⁺ dendritic cells are significantly increased in mice that received combinatorial treatment. This radio-sensitization strategy has demonstrated the effective inhibition on primary and metastatic tumors, and achieved satisfactory survival benefit in combinatorial with immune checkpoint blockade. Thus, this bio-inspired synthetic strategy may impulse the development of biosynthesis and its therapeutic applications, contributing to a non-invasive and efficient modality for nanomedicine exploitation.

Green nanomedicine: the path to the next generation of nanomaterials for diagnosing brain tumors and therapeutics?

Introduction: Current brain cancer treatments, based on radiotherapy and chemotherapy, are sometimes successful, but they are not free of drawbacks.Areas covered: Traditional methods for the treatment of brain tumors are discussed here with new solutions presented, among which the application of nanotechnology has demonstrated promising results over the past decade. The traditional synthesis of nanostructures, which relies on the use of physicochemical methodologies are discussed, and their associated concerns in terms of environmental and health impact due to the production of toxic by-products, need for toxic catalysts, and their lack of biocompatibility are presented. An overview of the current situation for treating brain tumors using nanotechnological-based approaches is introduced, and some of the latest advances in the application of green nanomaterials (NMs) for the effective targeting of brain tumors are presented.Expert opinion: Green nanotechnology is introduced as a potential solution to toxic NMs through the application of environmentally friendly and cost-effective protocols using living organisms and biomolecules. The current status of this field, such as those involving clinical trials, is included, and the possible limitations of green-NMs and potential ways to avoid those limitations are discussed so that the field can potentially evolve.

Plasmonic Nanoparticles as Optical Sensing Probes for the Detection of Alzheimer's Disease

Alzheimer's disease (AD), considered a common type of dementia, is mainly characterized by a progressive loss of memory and cognitive functions. Although its cause is multifactorial, it has been associated with the accumulation of toxic aggregates of the amyloid-β peptide (Aβ) and neurofibrillary tangles (NFTs) of tau protein. At present, the development of highly sensitive, high cost-effective, and non-invasive diagnostic tools for AD remains a challenge. In the last decades, nanomaterials have emerged as an interesting and useful tool in nanomedicine for diagnostics and therapy. In particular, plasmonic nanoparticles are well-known to display unique optical properties derived from their localized surface plasmon resonance (LSPR), allowing their use as transducers in various sensing configurations and enhancing detection sensitivity. Herein, this review focuses on current advances in in vitro sensing techniques such as Surface-enhanced Raman scattering (SERS), Surface-enhanced fluorescence (SEF), colorimetric, and LSPR using plasmonic nanoparticles for improving the sensitivity in the detection of main biomarkers related to AD in body fluids. Additionally, we refer to the use of plasmonic nanoparticles for in vivo imaging studies in AD.

The Influence of Size and Chemical Composition of Silver and Gold Nanoparticles on in vivo Toxicity with Potential Applications to Central Nervous System Diseases

The physicochemical and optical properties of silver nanoparticles (SNPs) and gold nanoparticles (GNPs) have allowed them to be employed for various biomedical applications, including delivery, therapy, imaging, and as theranostic agents. However, since they are foreign body systems, they are usually redistributed and accumulated in some vital organs, which can produce toxic effects; therefore, this a crucial issue that should be considered for potential clinical trials. This review aimed to summarize the reports from the past ten years that have used SNPs and GNPs for in vivo studies on the diagnosis and treatment of brain diseases and those related to the central nervous system, emphasizing their toxicity as a crucial topic address. The article focuses on the effect of the nanoparticle´s size and chemical composition as relevant parameters for in vivo toxicity. At the beginning of this review, the general toxicity and distribution studies are discussed separately for SNPs and GNPs. Subsequently, this manuscript analyzes the principal applications of both kinds of nanoparticles for glioma, neurodegenerative, and other brain diseases, and discusses the advances in clinical trials. Finally, we analyze research prospects towards clinical applications for both types of metallic nanoparticles.

Diphenylalanin nanofibers-inspired synthesis of fluorescent gold nanoclusters for screening of anti-amyloid drugs

Protein misfolding and aggregation into amyloid structures is linked with a number of pathophysiological disorders. In the past decade, significant progresses have been made in the drug discovery strategies against toxic aggregates. Although lack of specificity and high sensitivity for in vitro screening system still seen. Here we demonstrate a new targeting probe based on FF diphenylalanine peptide -protected gold nanoclusters (FF AuNCs). Diphenylalanine peptide has previously been shown to self-assemble into well-ordered fiber like the fibers that are observed in amyloid aggregates. We used of the self-assembly properties along with the ability of FF dipeptide in reduction of gold ions for synthesis of novel Au nanoclusters. We used FF AuNCs for monitoring of effectiveness of anti-amyloid drugs. Fluorescence was considerably diminished when drugs at different concentrations added, due to destruction of the amyloid fibers. Furthermore, the analysis of several components demonstrates significant selectivity against the amyloid disrupting molecules. Prepared FF AuNCs will gain possible strategy for in vitro screening of amyloid disrupting molecules.

Luminescent gold nanoclusters for bioimaging applications

Luminescent nanomaterials have emerged as attractive candidates for sensing, catalysis and bioimaging applications in recent years. For practical use in bioimaging, nanomaterials with high photoluminescence, quantum yield, photostability and large Stokes shifts are needed. While offering high photoluminescence and quantum yield, semiconductor quantum dots suffer from toxicity and are susceptible to oxidation. In this context, atomically precise gold nanoclusters protected by thiol monolayers have emerged as a new class of luminescent nanomaterials. Low toxicity, bioavailability, photostability as well as tunable size, composition, and optoelectronic properties make them suitable for bioimaging and biosensing applications. In this review, an overview of the sensing of pathogens, and of in vitro and in vivo bioimaging using luminescent gold nanoclusters along with the limitations with selected examples are discussed.

Optimal route of gold nanoclusters administration in mice targeting Parkinson’s disease

Aim: To explore the optimal route of gold nanoclusters (AuNCs) administration in mice targeting Parkinson’s disease. Materials & methods: Assessing the pharmacokinetic and bioavailability of AuNCs in mice administrated following intravenous, intraperitoneal, gavage and intranasal injection. Investigating the biodistribution of AuNCs in mice by atomic absorption spectrometry and transmission electron microscope. Toxicity assessments of AuNCs were carried out both in cells and in mice. Results: Administration of AuNCs via intraperitoneal injection showed the greatest bioavailability and the longest residence in brain. AuNCs could penetrate blood–brain barrier and be excreted mainly through kidney. No obvious toxicity of AuNCs found in cells and in mice. Conclusion: The optimal route of AuNCs administration in mice targeting Parkinson’s disease is intraperitoneal administration.

Gold nanoclusters for biomedical applications: toward in vivo studies

In parallel with the rapidly growing and widespread use of nanomedicine in the clinic, we are also witnessing the development of so-called theranostic agents that combine diagnostic and therapeutic properties.

CLVFFA-Functionalized Gold Nanoclusters Inhibit Aβ40 Fibrillation, Fibrils' Prolongation, and Mature Fibrils' Disaggregation

The abnormal aggregation of amyloid beta (Aβ or A beta) from monomeric proteins into amyloid fibrils is an important pathological contact to Alzheimer's disease (AD). Amyloid beta 40 (Aβ40), the pivotal biomarker of AD, aggregates to form amyloid plaques. For this reason, inhibition of amyloid fibrillation had become a crucial prevention and therapeutic strategy. Usually, LVFFA is the central hydrophobic fragment of Aβ and can inhibit the aggregation of Aβ40. In this work, in order to improve the inhibitory ability of LVFFA, hexapeptide CLVFFA were conjugated at the surface of Au clusters (AuNCs) to manufacture a nanosized inhibitor, AuNCs-CLVFFA. Thioflavin T fluorescence and transmission electron microscope results showed that AuNCs-CLVFFA inhibited Aβ40 fibrillogenesis, fibrils' prolongation, and mature fibrils' disaggregation. Furthermore, AuNCs as the backbone of the inhibitor showed extraordinary inhibition ability for Aβ40 aggregation at a low AuNCs-CLVFFA concentration. Free hexapeptide CLVFFA, at the same concentration, showed almost no inhibition. Additionally, the inhibitor could maintain the optical properties of nanoclusters, and the cell viability demonstrated that the inhibitor had good biocompatibility and may potentially be applied into AD therapy or treatment.

X-ray crystal structure and doping mechanism of bimetallic nanocluster Au36−xCux(m-MBT)24(x= 1–3)

Combined experimental and theoretical methods have been used to explore the doping preference of Cu atoms in novel Au_36−xCu_x(m-MBT)₂₄(x= 1–3) nanoclusters.

Mammalian cells: a unique scaffold forin situbiosynthesis of metallic nanomaterials and biomedical applications

Nanoscale materials biosynthesis by using mammalian scaffold is green and highly biocompatible.

Recent advances in biomedical applications of fluorescent gold nanoclusters

Fluorescent gold nanoclusters (AuNCs) are emerging as novel fluorescent materials and have attracted more and more attention in the field of biolabeling, biosensing, bioimaging and targeted cancer treatment because of their unusual physicochemical properties, such as long fluorescence lifetime, ultrasmall size, large Stokes shift, strong photoluminescence, as well as excellent biocompatibility and photostability. Recently, significant efforts have been committed to the preparation, functionalization and biomedical application studies of fluorescent AuNCs. In this review, we have summarized the strategies for preparation and surface functionalization of fluorescent AuNCs in the past several years, and highlighted recent advances in the biomedical applications of the relevant fluorescent AuNCs. Based on these observations, we also give a discussion on the current problems and future developments of the fluorescent AuNCs for biomedical applications.

Fluorescent metal quantum clusters: an updated overview of the synthesis, properties, and biological applications

A brief history of metal quantum clusters, their synthesis methods, physical properties, and an updated overview of their applications is provided.

Early detection of Alzheimer's disease using a biosensor based on electrochemically-reduced graphene oxide and gold nanowires for the quantification of serum microRNA-137

Serum miR-137 is quantified for the early detection of Alzheimer's disease using a electrochemically reduced graphene oxide and gold nanowire modified electrode.

Lysozyme-stabilized Ag nanoclusters: synthesis of different compositions and fluorescent responses to sulfide ions with distinct modes

The effect of composition on the photoluminescence properties of lysozyme-stabilized Ag nanoclusters and their sensing modes for sulfide anions were studied.

In vivo target bio-imaging of cerebral ischemic stroke by real-time labeling of zinc

Through intravenous injection of zinc gluconate, we could readily realize in vivo fluorescence imaging by real-time labeling the relevant brain regions of CIS model mice based on the in situ biosynthesis of fluorescence zinc nanoclusters in target diseased sites.