Putting gold nanocages to work for optical imaging, controlled release and cancer theranostics

A review of recent advances in the use of complex metal nanostructures for biomedical applications from diagnosis to treatment

Complex metal nanostructures represent an exceptional category of materials characterized by distinct morphologies and physicochemical properties. Nanostructures with shape anisotropies, such as nanorods, nanostars, nanocages, and nanoprisms, are particularly appealing due to their tunable surface plasmon resonances, controllable surface chemistries, and effective targeting capabilities. These complex nanostructures can absorb light in the near-infrared, enabling noteworthy applications in nanomedicine, molecular imaging, and biology. The engineering of targeting abilities through surface modifications involving ligands, antibodies, peptides, and other agents potentiates their effects. Recent years have witnessed the development of innovative structures with diverse compositions, expanding their applications in biomedicine. These applications encompass targeted imaging, surface-enhanced Raman spectroscopy, near-infrared II imaging, catalytic therapy, photothermal therapy, and cancer treatment. This review seeks to provide the nanomedicine community with a thorough and informative overview of the evolving landscape of complex metal nanoparticle research, with a specific emphasis on their roles in imaging, cancer therapy, infectious diseases, and biofilm treatment. This article is categorized under: Diagnostic Tools > In Vivo Nanodiagnostics and Imaging Therapeutic Approaches and Drug Discovery > Nanomedicine for Infectious Disease Diagnostic Tools > Diagnostic Nanodevices.

Ultra-sensitive fluorescent detection of strychnine based on carbon dot self-assembled gold nanocage sensing probe

The ultra-sensitive detection of strychnine is crucial to provide powerful evidence in strychnine poisoning cases. In this study, a novel fluorescent carbon dots (CDs) self-assembled gold nanocage (AuNCs) composite is synthesized for the ultra-sensitive detection of strychnine using molecularly imprinted polymer sensing technology (MIPs-CDs@AuNCs). With strong loading and delivery capability of AuNCs, the CDs could be loaded into AuNCs, where the anisotropy of CDs could significantly decrease and the fluorescence of the MIPs-CDs@AuNCs probe gained lower relative standard deviation (RSD). Moreover, the fluorescence response of MIPs-CDs@AuNCs to target strychnine was observed to be more significant than MIPs-CDs without gold nanocages. Under optimal conditions, the developed MIPs-CDs@AuNCs fluorescence strategy showed good linear relationship at the concentration of strychnine from 3 ng mL-1 to 200 ng mL-1 with the limit of detection as low as 1 ng mL-1. Besides, real blood samples were analyzed without complex pre-preparation procedure to investigate the performance of the proposed molecularly imprinted fluorescence probe, and satisfactory results were obtained with absolute deviations between -1.16 ng mL-1 and 1.28 ng mL-1, which exhibited a great potential for the detection of strychnine in health care work.

Revolutionizing cancer treatment: nanotechnology-enabled photodynamic therapy and immunotherapy with advanced photosensitizers

Nanotechnology-enhanced photodynamic therapy (PDT) and immunotherapy are emerging as exciting cancer therapeutic methods with significant potential for improving patient outcomes. By combining these approaches, synergistic effects have been observed in preclinical studies, resulting in enhanced immune responses to cancer and the capacity to conquer the immunosuppressive tumor microenvironment (TME). Despite challenges such as addressing treatment limitations and developing personalized cancer treatment strategies, the integration of nanotechnology-enabled PDT and immunotherapy, along with advanced photosensitizers (PSs), represents an exciting new avenue in cancer treatment. Continued research, development, and collaboration among researchers, clinicians, and regulatory agencies are crucial for further advancements and the successful implementation of these promising therapies, ultimately benefiting cancer patients worldwide.

Gold Nanobipyramids for Near-Infrared Fluorescence-Enhanced Imaging and Treatment of Triple-Negative Breast Cancer

There is an imminent need for novel strategies for the diagnosis and treatment of aggressive triple-negative breast cancer (TNBC). Cell-targeted multifunctional nanomaterials hold great potential, as they can combine precise early-stage diagnosis with local therapeutic delivery to specific cell types. In this study, we used mesoporous silica (MS)-coated gold nanobipyramids (MS-AuNBPs) for fluorescence imaging in the near-infrared (NIR) biological window, along with targeted TNBC treatment. Our MS-AuNBPs, acting partly as light amplification components, allow considerable metal-enhanced fluorescence for a NIR dye conjugated to their surfaces compared to the free dye. Fluorescence analysis confirms a significant increase in the dye's modified quantum yield, indicating that MS-AuNBPs can considerably increase the brightness of low-quantum-yield NIR dyes. Meanwhile, we tested the chemotherapeutic efficacy of MS-AuNBPs in TNBC following the loading of doxorubicin within the MS pores and functionalization to target folate receptor alpha (FRα)-positive cells. We show that functionalized particles target FRα-positive cells with significant specificity and have a higher potency than free doxorubicin. Finally, we demonstrate that FRα-targeted particles induce stronger antitumor effects and prolong overall survival compared to the clinically applied non-targeted nanotherapy, Doxil. Together with their excellent biocompatibility measured in vitro, this study shows that MS-AuNBPs are promising tools to detect and treat TNBCs.

Red Blood Cell Membrane-coated Functionalized Au Nanocage as a Biomimetic Platform for Improved MicroRNA Delivery in Hepatocellular Carcinoma

Dysregulation of microRNAs (miRNAs) expression is closely related to cancers and managing miRNA expression holds great promise for cancer therapy. However, their wide clinical application has been hampered by their poor stability, short half-life and non-specific biodistribution in vivo. Herein, a novel biomimetic platform designated as RHAuNCs-miRNA for improved miRNA delivery was prepared through wrapping miRNA-loaded functionalized Au nanocages (AuNCs) with red blood cell (RBC) membrane. RHAuNCs-miRNA not only successfully loaded miRNAs but also effectively protected them from enzymatic degradation. With good stability, RHAuNCs-miRNA had the characteristics of photothermal conversion and sustained release. Cellular uptake of RHAuNCs-miRNA by SMMC-7721 cells was in a time-dependent manner via clathrin- and caveolin-mediated endocytosis. The uptake of RHAuNCs-miRNAs was affected by cell types and improved by mild near infrared (NIR) laser irradiation. More importantly, RHAuNCs-miRNA exhibited a prolonged circulation time without the occurrence of accelerated blood clearance (ABC) in vivo, resulting in efficient delivery to tumor tissues. This study may demonstrate the great potential of RHAuNCs-miRNA for improved miRNAs delivery.

Cancer Immunotherapy Elicited by Immunogenic Cell Death Based on Smart Nanomaterials

Cancer immunotherapy has been a revolutionary cancer treatment modality because it can not only eliminate primary tumors but also prevent metastases and recurrent tumors. Immunogenic cell death (ICD) induced by various treatment modalities, including chemotherapy, phototherapy, and radiotherapy, converts dead cancer cells into therapeutic vaccines, eliciting a systemic antigen-specific antitumor. However, the outcome effect of cancer immunotherapy induced by ICD has been limited due to the low accumulation efficiency of ICD inducers in the tumor site and concomitant damage to normal tissues. The boom in smart nanomaterials is conducive to overcoming these hurdles owing to their virtues of good stability, targeted lesion site, high bioavailability, on-demand release, and good biocompatibility. Herein, the design of targeted nanomaterials, various ICD inducers, and the applications of nanomaterials responsive to different stimuli, including pH, enzymes, reactive oxygen species, or dual responses are summarized. Furthermore, the prospect and challenges are briefly outlined to provide reference and inspiration for designing novel smart nanomaterials for immunotherapy induced by ICD.

Recent Advances in Photoacoustic Agents for Theranostic Applications

Photoacoustic agents are widely used in various theranostic applications. By evaluating the biodistribution obtained from photoacoustic images, the effectiveness of theranostic agents in terms of their delivery efficiency and treatment responses can be analyzed. Through this study, we evaluate and summarize the recent advances in photoacoustic-guided phototherapy, particularly in photothermal and photodynamic therapy. This overview can guide the future directions for theranostic development. Because of the recent applications of photoacoustic imaging in clinical trials, theranostic agents with photoacoustic monitoring have the potential to be translated into the clinical world.

Review on Metal-Based Theranostic Nanoparticles for Cancer Therapy and Imaging

Theranostic agents are promising due to their ability to diagnose, treat and monitor different types of cancer using a variety of imaging modalities. The advantage specifically of nanoparticles is that they can accumulate easily at the tumor site due to the large gaps in blood vessels near tumors. Such high concentration of theranostic agents at the target site can lead to enhancement in both imaging and therapy. This article provides an overview of nanoparticles that have been used for cancer theranostics, and the different imaging, treatment options and signaling pathways that are important when using nanoparticles for cancer theranostics. In particular, nanoparticles made of metal elements are emphasized due to their wide applications in cancer theranostics. One important aspect discussed is the ability to combine different types of metals in one nanoplatform for use as multimodal imaging and therapeutic agents for cancer.

Multimodality imaging of nanoparticle-based vaccines: Shedding light on immunology

In recent years, there have been significant innovations in the development of nanoparticle-based vaccines and vaccine delivery systems. For the purposes of both design and evaluation, these nanovaccines are imaged using the wealth of understanding established around medical imaging of nanomaterials. An important insight to the advancement of the field of nanovaccines can be given by an analysis of the design rationale of an imaging platform, as well as the significance of the information provided by imaging. Nanovaccine imaging strategies can be categorized by the imaging modality leveraged, but it is also worth understanding the superiority or convenience of a given modality over others in a given context of a particular nanovaccine. The most important imaging modalities in this endeavor are optical imaging including near-infrared fluorescence imaging (NIRF), emission tomography methods such as positron emission tomography (PET) and single photon emission computed tomography (SPECT) with or without computed tomography (CT) or magnetic resonance (MR), the emerging magnetic particle imaging (MPI), and finally, multimodal applications of imaging which include molecular imaging with magnetic resonance imaging (MRI) and photoacoustic (PA) imaging. One finds that each of these modalities has strengths and weaknesses, but optical and PET imaging tend, in this context, to be currently the most accessible, convenient, and informative modalities. Nevertheless, an important principle is that there is not a one-size-fits-all solution, and that the specific nanovaccine in question must be compatible with a particular imaging modality. This article is categorized under: Nanotechnology Approaches to Biology > Nanoscale Systems in Biology Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease Therapeutic Approaches and Drug Discovery > Nanomedicine for Infectious Disease.

Stimuli-Responsive Gold Nanocages for Cancer Diagnosis and Treatment

With advances in nanotechnology, various new drug delivery systems (DDSs) have emerged and played a key role in the diagnosis and treatment of cancers. Over the last two decades, gold nanocages (AuNCs) have been attracting considerable attention because of their outstanding properties. This review summarizes current advancements in endogenous, exogenous, and dual/multi-stimuli responsive AuNCs in drug delivery. This review focuses on the properties, clinical translation potential, and limitations of stimuli-responsive AuNCs for cancer diagnosis and treatment.

Functionalization of Nanomaterials for Skin Cancer Theranostics

Skin cancer has drawn attention for the increasing incident rates and high morbidity worldwide. Timely diagnosis and efficient treatment are of paramount importance for prompt and effective therapy. Thus, the development of novel skin cancer diagnosis and treatment strategies is of great significance for both fundamental research and clinical practice. Recently, the emerging field of nanotechnology has profoundly impact on early diagnosis and better treatment planning of skin cancer. In this review, we will discuss the current encouraging advances in functional nanomaterials for skin cancer theranostics. Challenges in the field and safety concerns of nanomaterials will also be discussed.

Harnessing the Immunogenic Potential of Gold Nanoparticle-Based Platforms as a Therapeutic Strategy in Breast Cancer Immunotherapy: A Mini Review

Breast cancer remains the most common malignancy among women worldwide. Although the implementation of mammography has dramatically increased the early detection rate, conventional treatments like chemotherapy, radiation therapy, and surgery, have significantly improved the prognosis for breast cancer patients. However, about a third of treated breast cancer patients are known to suffer from disease recurrences and progression to metastasis. Immunotherapy has recently gained traction due to its ability to establish long-term immune surveillance, and response for the prevention of disease recurrence and extension of patient survival. Current research findings have revealed that gold nanoparticles can enhance the safety and efficacy of cancer immunotherapy, through their unique intrinsic properties of good biocompatibility, durability, convenient surface modification, as well as enhanced permeability and retention effect. Gold nanoparticles are also able to induce innate immune responses through the process of immunogenic cell death, which can lead to the establishment of lasting adaptive immunity. As such gold nanoparticles are considered as good candidates for next generation immunotherapeutic strategies. This mini review gives an overview of gold nanoparticles and their potential applications in breast cancer immunotherapeutic strategies.

Nanocluster-Based Drug Delivery and Theranostic Systems: Towards Cancer Therapy

Over the last decades, the global life expectancy of the population has increased, and so, consequently, has the risk of cancer development. Despite the improvement in cancer therapies (e.g., drug delivery systems (DDS) and theranostics), in many cases recurrence continues to be a challenging issue. In this matter, the development of nanotechnology has led to an array of possibilities for cancer treatment. One of the most promising therapies focuses on the assembly of hierarchical structures in the form of nanoclusters, as this approach involves preparing individual building blocks while avoiding handling toxic chemicals in the presence of biomolecules. This review aims at presenting an overview of the major advances made in developing nanoclusters based on polymeric nanoparticles (PNPs) and/or inorganic NPs. The preparation methods and the features of the NPs used in the construction of the nanoclusters were described. Afterwards, the design, fabrication and properties of the two main classes of nanoclusters, namely noble-metal nanoclusters and hybrid (i.e., hetero) nanoclusters and their mode of action in cancer therapy, were summarized.

Photothermal and Photodynamic Therapy of Tumors with Plasmonic Nanoparticles: Challenges and Prospects

Cancer remains one of the leading causes of death in the world. For a number of neoplasms, the efficiency of conventional chemo- and radiation therapies is insufficient because of drug resistance and marked toxicity. Plasmonic photothermal therapy (PPT) using local hyperthermia induced by gold nanoparticles (AuNPs) has recently been extensively explored in tumor treatment. However, despite attractive promises, the current PPT status is limited by laboratory experiments, academic papers, and only a few preclinical studies. Unfortunately, most nanoformulations still share a similar fate: great laboratory promises and fair preclinical trials. This review discusses the current challenges and prospects of plasmonic nanomedicine based on PPT and photodynamic therapy (PDT). We start with consideration of the fundamental principles underlying plasmonic properties of AuNPs to tune their plasmon resonance for the desired NIR-I, NIR-2, and SWIR optical windows. The basic principles for simulation of optical cross-sections and plasmonic heating under CW and pulsed irradiation are discussed. Then, we consider the state-of-the-art methods for wet chemical synthesis of the most popular PPPT AuNPs such as silica/gold nanoshells, Au nanostars, nanorods, and nanocages. The photothermal efficiencies of these nanoparticles are compared, and their applications to current nanomedicine are shortly discussed. In a separate section, we discuss the fabrication of gold and other nanoparticles by the pulsed laser ablation in liquid method. The second part of the review is devoted to our recent experimental results on laser-activated interaction of AuNPs with tumor and healthy tissues and current achievements of other research groups in this application area. The unresolved issues of PPT are the significant accumulation of AuNPs in the organs of the mononuclear phagocyte system, causing potential toxic effects of nanoparticles, and the possibility of tumor recurrence due to the presence of survived tumor cells. The prospective ways of solving these problems are discussed, including developing combined antitumor therapy based on combined PPT and PDT. In the conclusion section, we summarize the most urgent needs of current PPT-based nanomedicine.

Reactive oxygen species / photothermal therapy dual-triggered biomimetic gold nanocages nanoplatform for combination cancer therapy via ferroptosis and tumor-associated macrophage repolarization mechanism

With the continuous development of cancer nanotechnology, an important trend in the research is to combine the broad application prospects of functional nanomaterials with recent biological discoveries and technological advances. Herein, a cancer cell membrane-camouflaged gold nanocage loading doxorubicin (DOX) and l-buthionine sulfoximine (BSO) (denoted as m@Au-D/B NCs) was constructed as an innovative nanoplatform to confer promising cancer combination therapy by evoking effective ferroptosis and immune responses. Briefly, the loading of BSO and DOX could induce ferroptosis through simultaneous effective glutathione (GSH) consumption and reactive oxygen species (ROS) accumulation. Gold nanocages (AuNCs) with distinct anti-tumor application performance was utilized as ideal nanocarrier for drug loading, evoking photothermal effects and photochemical catalysis to generate more ROS under near-infrared (NIR) irradiation. Moreover, m@Au-D/B NCs-mediated photothermal therapy (PTT) combined with ROS production could repolarize the tumor-associated macrophages (TAMs) from pro-tumor (M2) phenotype to anti-tumor (M1) phenotype, thus improving tumor-suppressive immune environment and then promoting the activation of effector cells and release of pro-inflammatory cytokines, in which the antitumor responses were evoked robustly in a methodical approach. The anti-tumor effects in vivo implied that m@Au-D/B NCs could significantly inhibit tumor growth without severe toxicity. Hence, this homotypic targeting nanosystem could offer an auspicious anticancer access by triggering combination cancer therapy via ferroptosis and tumor-associated macrophage repolarization mechanism.

Recent advances in nanomedicines for photodynamic therapy (PDT)-driven cancer immunotherapy

Cancer immunotherapy has made tremendous clinical progress in advanced-stage malignancies. However, patients with various tumors exhibit a low response rate to immunotherapy because of a powerful immunosuppressive tumor microenvironment (TME) and insufficient immunogenicity of tumors. Photodynamic therapy (PDT) can not only directly kill tumor cells, but also elicit immunogenic cell death (ICD), providing antitumor immunity. Unfortunately, limitations from the inherent nature and complex TME significantly reduce the efficiency of PDT. Recently, smart nanomedicine-based strategies could subtly modulate the pharmacokinetics of therapeutic compounds and the TME to optimize both PDT and immunotherapy, resulting in an improved antitumor effect. Here, the emerging nanomedicines for PDT-driven cancer immunotherapy are reviewed, including hypoxia-reversed nanomedicines, nanosized metal-organic frameworks, and subcellular targeted nanoparticles (NPs). Moreover, we highlight the synergistic nanotherapeutics used to amplify immune responses combined with immunotherapy against tumors. Lastly, the challenges and future expectations in the field of PDT-driven cancer immunotherapy are discussed.

Recent Advances in Inorganic Chiral Nanomaterials

Inorganic nanoparticles offer a multifunctional platform for biomedical applications in drug delivery, biosensing, bioimaging, disease diagnosis, screening, and therapies. Homochirality prevalently exists in biological systems composed of asymmetric biochemical activities and processes, so biomedical applications essentially favor the usage of inorganic chiral nanomaterials, which have been widely studied in the past two decades. Here, the latest investigations are summarized including the characterization of 3D stereochirality, the bionic fabrication of hierarchical chirality, extension of the compositional space to poly-elements, studying optical activities with the (sub-)single-particle resolution, and the experimental demonstration in biomedical applications. These advanced studies pave the way toward fully understanding the two important chiral effects (i.e., the chiroptical and enantioselective effects), and prospectively promote the flexible design and fabrication of inorganic chiral nanoparticles with engineerable functionalities to solve diverse practical problems closely associated with environment and public health.

Combining Nanotechnology and Gas Plasma as an Emerging Platform for Cancer Therapy: Mechanism and Therapeutic Implication

Nanomedicine and plasma medicine are innovative and multidisciplinary research fields aiming to employ nanotechnology and gas plasma to improve health-related treatments. Especially cancer treatment has been in the focus of both approaches because clinical response rates with traditional methods that remain improvable for many types of tumor entities. Here, we discuss the recent progress of nanotechnology and gas plasma independently as well as in the concomitant modality of nanoplasma as multimodal platforms with unique capabilities for addressing various therapeutic issues in oncological research. The main features, delivery vehicles, and nexus between reactivity and therapeutic outcomes of nanoparticles and the processes, efficacy, and mechanisms of gas plasma are examined. Especially that the unique feature of gas plasma technology, the local and temporally controlled deposition of a plethora of reactive oxygen, and nitrogen species released simultaneously might be a suitable additive treatment to the use of systemic nanotechnology therapy approaches. Finally, we focus on the convergence of plasma and nanotechnology to provide a suitable strategy that may lead to the required therapeutic outcomes.

Numerical Study on the Surface Plasmon Resonance Tunability of Spherical and Non-Spherical Core-Shell Dimer Nanostructures

The near-field enhancement and localized surface plasmon resonance (LSPR) on the core-shell noble metal nanostructure surfaces are widely studied for various biomedical applications. However, the study of the optical properties of new plasmonic non-spherical nanostructures is less explored. This numerical study quantifies the optical properties of spherical and non-spherical (prolate and oblate) dimer nanostructures by introducing finite element modelling in COMSOL Multiphysics. The surface plasmon resonance peaks of gold nanostructures should be understood and controlled for use in biological applications such as photothermal therapy and drug delivery. In this study, we find that non-spherical prolate and oblate gold dimers give excellent tunability in a wide range of biological windows. The electromagnetic field enhancement and surface plasmon resonance peak can be tuned by varying the aspect ratio of non-spherical nanostructures, the refractive index of the surrounding medium, shell thickness, and the distance of separation between nanostructures. The absorption spectra exhibit considerably greater dependency on the aspect ratio and refractive index than the shell thickness and separation distance. These results may be essential for applying the spherical and non-spherical nanostructures to various absorption-based applications.

Versatile template-directed synthesis of gold nanocages with a predefined number of windows

Highly symmetrical gold nanocages can be produced with a controllable number of circular windows of either 2, 3, 4, 6 or 12 via an original fabrication route. The synthetic pathway includes three main stages: the synthesis of silica/polystyrene multipod templates, the regioselective seeded growth of a gold shell on the unmasked part of the silica surface and the development of gold nanocages by dissolving/etching the templates. Electron microscopy and tomography provide evidence of the symmetrical features of the as-obtained nanostructures. The optical properties of nanocages with 4 and 12 windows were measured at the single particle level by spatial modulation spectroscopy and correlated with numerical simulations based on finite-element modeling. The new multi-step synthesis approach reported here also allows the synthesis of rattle-like nanostructures through filling of the nanocages with a guest nano-object. With the potential to adjust the chemical composition, size and geometry of both the guest particle and the host cage, it opens new routes towards the fabrication of hollow nanostructures of high interest for a variety of applications including sensing devices, catalytic reactors and biomedicine.

Nonspherical Metal-Based Nanoarchitectures: Synthesis and Impact of Size, Shape, and Composition on Their Biological Activity

Metal-based nanoentities, apart from being indispensable research tools, have found extensive use in the industrial and biomedical arena. Because their biological impacts are governed by factors such as size, shape, and composition, such issues must be taken into account when these materials are incorporated into multi-component ensembles for clinical applications. The size and shape (rods, wires, sheets, tubes, and cages) of metallic nanostructures influence cell viability by virtue of their varied geometry and physicochemical interactions with mammalian cell membranes. The anisotropic properties of nonspherical metal-based nanoarchitectures render them exciting candidates for biomedical applications. Here, the size-, shape-, and composition-dependent properties of nonspherical metal-based nanoarchitectures are reviewed in the context of their potential applications in cancer diagnostics and therapeutics, as well as, in regenerative medicine. Strategies for the synthesis of nonspherical metal-based nanoarchitectures and their cytotoxicity and immunological profiles are also comprehensively appraised.

Fluorination Effects in XPhos Gold(I) Fluorothiolates

Gold phosphine derivatives such as thiolates have been recently proposed as catalysts or catalyst precursors. The relevance of the supramolecular environment on the fine-tuning of the catalytical activity on these compounds incentivizes the use of tools that are convenient to characterize in detail the non-covalent landscape of the systems. Herein, we show the molecular and supramolecular diversity caused by the changes in the fluorination pattern in a family of new XPhos goldfluorothiolate derivatives. Furthermore, we studied the supramolecular interactions around the Au centers using quantum chemical topology tools, in particular the quantum theory of atoms in molecules (QTAIM) and the non-covalent interaction index. Our results give detailed insights into the fluorination effects on the strength of intramolecular and intermolecular interactions in these systems. We have also used QTAIM delocalization indexes to define a novel hapticity indicator. Finally, we assessed the trans influence of the fluorothiolates on the phosphine in terms of the change in the δ 31P-NMR. These results show the feasibility of the use of fluorination in the modulation of the electronic properties of Buchwald phosphine gold(I) compounds, and thereby its potential catalytic activity.

Microwave-triggered/HSP-targeted gold nano-system for triple-negative breast cancer photothermal therapy

Due to the lack of effective therapeutic targets and the passive delivery of a limited quantity of nanoparticles to the tumors, the photothermal conversion agents used in photothermal therapy (PTT) have not been effective in treating triple-negative breast cancer (TNBC). As a result, there is a need to improve the tumor-targeting ability of these photothermal conversion agents. To address this, a microwave-triggered heat shock protein (HSP)-targeted gold nano-system (cmHSP-AuNC), with a gold nanocage (AuNC) as a photothermal conversion agent and anti-HSP monoclonal antibody (cmHSP) as a targeting ligand, was fabricated. cmHSP-AuNC was characterized based on morphology, particle size, zeta potentials, absorption spectrum, and photothermal conversion ability. The expression of HSP70 in 4T1 cells after microwave irradiation was verified by western blotting, and the optimal treatment conditions to achieve the highest expression were determined. Both in vitro and in vivo results indicated that the induction through microwave irradiation could effectively activate the HSP70 overexpression in TNBC, thereby significantly improving the targeting ability, tumor accumulation and anti-tumor efficacy of cmHSP-AuNC. This study proposes a promising strategy for improving the targeting ability and therapeutic efficacy of PTT.

Dual-Wavelength Photosensitive Nano-in-Micro Scaffold Regulates Innate and Adaptive Immune Responses for Osteogenesis

The immune response of a biomaterial determines its osteoinductive effect. Although the mechanisms by which some immune cells promote regeneration have been revealed, the biomaterial-induced immune response is a dynamic process involving multiple cells. Currently, it is challenging to accurately regulate the innate and adaptive immune responses to promote osteoinduction in biomaterials. Herein, we investigated the roles of macrophages and dendritic cells (DCs) during the osteoinduction of biphasic calcium phosphate (BCP) scaffolds. We found that osteoinductive BCP directed M2 macrophage polarization and inhibited DC maturation, resulting in low T cell response and efficient osteogenesis. Accordingly, a dual-targeting nano-in-micro scaffold (BCP loaded with gold nanocage, BCP-GNC) was designed to regulate the immune responses of macrophages and DCs. Through a dual-wavelength photosensitive switch, BCP-GNC releases interleukin-4 in the early stage of osteoinduction to target M2 macrophages and then releases dexamethasone in the later stage to target immature DCs, creating a desirable inflammatory environment for osteogenesis. This study demonstrates that biomaterials developed to have specific regulatory capacities for immune cells can be used to control the early inflammatory responses of implanted materials and induce osteogenesis.

Absolute Templating of M(111) Cluster Surrogates by Galvanic Exchange

The precise preparation of monodisperse nanomaterials is among the most fundamental tasks in inorganic synthesis and materials science. Achieving this goal by galvanic exchange is hardly predictable and often results in major structural changes and polydisperse mixtures. Taking advantage of the enhanced stability imparted by ambiphilic carbenes, we report and rationalize the absolute templating, the complete exchange of metals in a template, of group 11 clusters across the entire coinage metal family by means of galvanic exchange. We further delineate that these species provide a molecular model for better understanding the reduction of CO₂ at M(111) coinage metal surfaces.

Smart gold nanocages for mild heat-triggered drug release and breaking chemoresistance

Chemotherapy is an important modality available for cancer treatment. However, the present chemotherapy is still far from being satisfactory mainly owing to the severe side effects of the chemotherapeutic agents and drug resistance of cancer cells. Thus, reversing drug resistance by constructing an ideal chemotherapeutic strategy with the least side effects and the best efficacy is greatly needed. Here, we designed a smart nanosystem of thermo-sensitive liposome coated gold nanocages with doxorubicin (DOX) loading (LAD) for near-infrared (NIR)-triggered drug release and chemo-photothermal combination therapy. The biocompatible liposomes coating facilitated the cellular uptake of LAD and meanwhile avoided drug leakage during the circulation. More importantly, LAD exhibited controllable photothermal conversion property and produced mild heat under NIR irradiation, which not only triggered DOX release and transferred DOX from lysosome to nucleus, but also elicited the mild heat cell killing effect to improve the curative efficiency. Further mechanism study revealed that mild heat could reverse drug resistance by down-regulation of the chemoresistance-related markers (e.g., HSF-1, p53, P-gp), and inhibited DOX export and increased drug sensitiveness, thereby prominently increased the anticancer efficiency. This versatile nanoplatform with enhanced curative efficacy and lower side effect is promising to apply in the field of drug controlled release and combination tumor therapy.

Noble Metal Nanostructured Materials for Chemical and Biosensing Systems

Nanomaterials with unique physical and chemical properties have attracted extensive attention of scientific research and will play an increasingly important role in the future development of science and technology. With the gradual deepening of research, noble metal nanomaterials have been applied in the fields of new energy materials, photoelectric information storage, and nano-enhanced catalysis due to their unique optical, electrical and catalytic properties. Nanostructured materials formed by noble metal elements (Au, Ag, etc.) exhibit remarkable photoelectric properties, good stability and low biotoxicity, which received extensive attention in chemical and biological sensing field and achieved significant research progress. In this paper, the research on the synthesis, modification and sensing application of the existing noble metal nanomaterials is reviewed in detail, which provides a theoretical guidance for further research on the functional properties of such nanostructured materials and their applications of other nanofields.

Gold nanocages for effective photothermal conversion and related applications

Gold nanocages are highly effective in converting light to heat, making them versatile for an array of photothermal applications.

Nanotechnology based therapeutic application in cancer diagnosis and therapy

Due to the lack of early diagnosis, cancer remains as one of the leading cause of human mortality. Inability to translate research into clinical trials and also inability of chemotherapeutics delivery to targeted tumor sites are major drawbacks in cancer therapeutics. With the emergence of nanomedicine, several nanoprobes (conjugated with targeting ligands and chemotherapeutic drugs) are developed. It can interact with biological system and thus sense and monitor the biological events with high efficiency and accuracy along with therapy application. Nanoparticles like gold and iron oxide are frequently used in the computed tomography and magnetic resonance imaging applications, respectively. Moreover, enzymatic activity of gold and iron oxide nanoparticles enables the visible colorimetric diagnostic of cancer cells, whereas, fluorescence property of quantum dots and upconversion nanoparticles helps in in vivo imaging application. Other than this, drug conjugation with nanoparticles also reduces the systemic toxic effect of chemotherapeutic drugs. Due to their several unique intrinsic properties, nanoparticles itself can also be employed as therapeutics in cancer treatment by photothermal therapy (PTT) and photodynamic therapy (PDT). Thus, the main focus of this review is to emphasize on current progress in diagnostic and therapeutic application of nanoprobes in cancer.

Chirality Transfer in Galvanic Replacement Reactions

Demand for the transfer of chirality from a pre-engineered nanoparticle to any other metal is of fundamental importance for developing a wide range of chirality-related applications. Herein, we show that binary alloy chiral nanoparticles (CNPs) with an engineerable composition can be formed from metallic CNPs with intrinsic structural chirality serving as sacrificial templates (STs), via a galvanic replacement reaction (GRR). This GRR-mediated chirality transfer is a general phenomenon and results in the formation of Cu-Ag CNPs with solid morphology and mesoporous CNPs made of Ag-Au, Ag-Pt, and Ag-Pd. Our study imposes a new component, i.e., structural chirality, on the GRR. The insights from our study improve our fundamental understanding of the GRR principle and devise a versatile method to generate mesoporous alloy CNPs for developing prominent chirality-related applications in asymmetric catalysis, enantiodifferentiation, enantioseparation, biodetection, and bioimaging.

Optical resonances of hollow nanocubes controlled with sub-particle structural morphologies

The structural details of nanoparticles at the sub-particle level are critical for our understanding of their functionalities and the basic mechanisms involved in their formation. In particular, the geometries of such features determine the particle's overall optical response. Hollow metallic nanoparticles (hollow-MNPs) that have cubic geometries, with varying morphologies on their walls and voids in their body, offer a platform to study the effects of such structural features on the properties of single nanoparticles and their ensemble. Here, we report the control over sub-particle pinholes and voids by modifying the dynamics of the galvanic reaction, and we connect these structures to the optical response of the hollow nanocubes. We observe that symmetry breakage in individual particles, caused by pinholes and voids, has a drastic effect on the plasmon-resonance peak positions in their UV-Vis-NIR spectra. Via electron microscopy imaging, statistical analyses, and electromagnetic simulations, we observe that enlargement in a pinhole's diameter and an increase in their number produce a redshift in the resonance absorption peak of the ensemble. Our results outline nanoparticle design avenues via sub-particle morphologies for several applications, including those operating in the biological window and those carrying chemical payloads in organisms.

A Gold Nanocage/Cluster Hybrid Structure for Whole-Body Multispectral Optoacoustic Tomography Imaging, EGFR Inhibitor Delivery, and Photothermal Therapy

Gold nanocages (AuNCs) and gold nanoclusters (AuClusters) are two classes of advantageous nanostructures with special optical properties, and many other attractive properties. Integrating them into one nanosystem may achieve greater and smarter performance. Herein, a hybrid gold nanostructure for fluorescent and optoacoustic tomography imaging, controlled release of drugs, and photothermal therapy (PTT) is demonstrated. For this nanodrug (EA-AB), an epidermal growth factor receptor (EGFR) inhibitor erlotinib (EB) is loaded into AuNCs, which are then capped and functionalized by biocompatible AuCluster@BSA (BSA = bovine serum albumin) conjugates via electrostatic interaction. Upon cell internalization, the lysosomal proteases and low pH cause the release of EB from EA-AB, and also induce fluorescence restoration of the AuCluster for imaging. Irradiation with near-infrared light further promotes the drug release and affords a PTT effect as well. The AuNC-based nanodrug is optoacoustically active, and its biodistribution and metabolic process have been successfully monitored by whole-body and 3D multispectral optoacoustic tomography imaging. Owing to the combined actions of PTT and EGFR pathway blockage, EA-AB exhibits marked tumor inhibition efficacy in vivo.

Oridonin-loaded and GPC1-targeted gold nanoparticles for multimodal imaging and therapy in pancreatic cancer

Purpose

Early diagnosis and therapy are critical to improve the prognosis of patients with pancreatic cancer. However, conventional imaging does not significantly increase the capability to detect early stage disease. In this study, we developed a multifunctional theranostic nanoplatform for accurate diagnosis and effective treatment of pancreatic cancer.

Methods

We developed a theranostic nanoparticle (NP) based on gold nanocages (AuNCs) modified with hyaluronic acid (HA) and conjugated with anti-Glypican-1 (anti-GPC1) antibody, oridonin (ORI), gadolinium (Gd), and Cy7 dye. We assessed the characteristics of GPC1-Gd-ORI@HAuNCs-Cy7 NPs (ORI-GPC1-NPs) including morphology, hydrodynamic size, stability, and surface chemicals. We measured the drug loading and release efficiency in vitro. Near-infrared fluorescence (NIRF)/magnetic resonance imaging (MRI) and therapeutic capabilities were tested in vitro and in vivo.

Results

ORI-GPC1-NPs demonstrated long-time stability and fluorescent/MRI properties. Bio-transmission electron microscopy (bio-TEM) imaging showed that ORI-GPC1-NPs were endocytosed into PANC-1 and BXPC-3 (overexpression GPC1) but not in 293 T cells (GPC1- negative). Compared with ORI and ORI-NPs, ORI-GPC1-NPs significantly inhibited the viability and enhanced the apoptosis of pancreatic cancer cells in vitro. Moreover, blood tests suggested that ORI-GPC1-NPs showed negligible toxicity. In vivo studies showed that ORI-GPC1-NPs enabled multimodal imaging and targeted therapy in pancreatic tumor xenografted mice.

Conclusion

ORI-GPC1-NP is a promising theranostic platform for the simultaneous diagnosis and effective treatment of pancreatic cancer.

Wulff in a cage gold nanoparticles as contrast agents for computed tomography and photoacoustic imaging

Nanostructures have potential for use in biomedical applications such as sensing, imaging, therapeutics, and drug delivery. Among nanomaterials, gold nanostructures are of considerable interest for biomedical research, owing to their bio-inertness, controllable surface chemistry, X-ray opacity, and optical properties. Gold nanocages are particularly attractive for imaging and therapeutic applications, because they strongly absorb light in the near infra-red region which has high light transmission in tissue. However, the X-ray attenuation of nanocages is relatively low due to their hollow structure. In this study, for the first time, we sought to combine the attractive optical properties of nanoshells with the high payloads of solid nanoparticles and investigated their biomedical applications. Here, we report the engineering of Wulff in a cage nanoparticles via converting gold Wulff-shaped seeds into gold-silver core-shell structures and then performing a galvanic replacement reaction. The structure of these nanoparticles was determined using transition electron microscopy. This morphological transformation of gold nanoparticles shaped as truncated octahedrons into a complex Wulff in a cage nanoparticles during the reaction resulted in extensive changes in their optical properties that made these unique structures a potential contrast agent for photoacoustic imaging. We found that the Wulff in a cage nanoparticles had no adverse effects on the viabilities of J774A.1, Renca, and HepG2 cells at any of the concentrations tested. In vitro and in vivo experiments showed robust signals in both photoacoustic imaging and computed tomography. To the best of our knowledge, this is the first report of Wulff in a cage nanoparticles serving as a platform for multiple imaging modalities. This unique multifunctional nanostructure, which integrates the competencies of both core and shell structures, allows their use as contrast agents for photoacoustic imaging, computed tomography and as a potential agent for photothermal therapy.

Controlled synthesis of noble metal nanomaterials: motivation, principles, and opportunities in nanocatalysis

This review describes some principles of the controlled synthesis of metal nanoparticles, focusing on how the fundamental understanding of their synthesis in the solution-phase can be put to tailor size, shape, composition, and architecture. The maneuvering over these parameters not only enable the tuning of properties, but also the maximization and optimization of performances for various applications. Herein, we start with a brief description of metallic nanoparticles, highlighting the motivation for achieving physicochemical control in their synthesis. After that, we turn our attention to some important definitions and classifications as well as their unique properties such as surface and quantum effects. Moreover, we discuss the strategies for the controlled synthesis of metal nanomaterials based on the top-down and bottom-up approaches, focusing our discussion on their formation mechanisms in liquid-phase in terms of both thermodynamic and kinetic control. Finally, we point out the promising applications of controlled nanomaterials in the field of nanocatalysis and plasmon-enhanced catalysis, describing some of the current challenges in these fields.

Morphological control of seedlessly-synthesized gold nanorods using binary surfactants

High purity gold nanorods (AuNRs) with tunable morphology have been synthesized through a binary-surfactant seedless method, which enables the formation of monocrystalline AuNRs with diameters between 7 and 35 nm. The protocol has high shape yield and monodispersity, demonstrating good reproducibility and scalability allowing synthesis of batches 0.5 l in volume. Morphological control has been achieved through the adjustment of the molar concentrations of cetyltrimethylammonium bromide and sodium oleate in the growth solution, providing fine tuning of the optical scattering and absorbance properties of the AuNRs across the visible and NIR spectrum. Sodium oleate was found to provide greatest control over the aspect ratio (and hence optical properties) with concentration changes between 10 and 23 mM leading to variation in the aspect ratio between 2.8 and 4.8. Changes in the geometry of the end-caps were also observed as a result of manipulating the two surfactant concentrations.

Synthesis and hydrogenation application of Pt-Pd bimetallic nanocatalysts stabilized by macrocycle-modified dendrimer

Different generations of poly(propylene imine) (G _n -PPI) terminated with N-containing 15-membered triolefinic macrocycle (G _n M) (n = 2, 3, 4, 5) were prepared. The bimetallic nanoparticle catalysts G _n M-(Pt _x /Pd_10-x ) (x = 0, 3, 5, 7, 10) were prepared by the synchronous ligand-exchange reaction between G _n M and the complexes of Pt(PPh₃)₄ and Pd(PPh₃)₄. The structure and catalytic properties of G _n M-(Pt _x /Pd_10-x ) were characterized via Fourier transform infrared spectroscopy, ¹H nuclear magnetic resonance spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, high-resolution transmission electron microscopy, energy-dispersive spectroscopy and inductively coupled plasma atomic emission spectroscopy. The novel bimetallic Pd-Pt nanoparticle catalysts stabilized by dendrimers (DSNs) present higher catalytic activities for the hydrogenation of dimeric acid (DA) than that of nitrile butadiene rubber (NBR). It can be concluded that bimetallic Pd-Pt DSNs possess alloying and synergistic electronic effects on account of the hydrogenation degree (HD) of DA and NBR. Furthermore, the HD of DA and NBR shows a remarkable decrease with the incremental generations (n) of G _n M-(Pt₃/Pd₇) (n = 2, 3, 4, 5).

Experimental Comparison of Photothermal Conversion Efficiency of Gold Nanotriangle and Nanorod in Laser Induced Thermal Therapy

An experimental comparison of the photothermal conversion efficiency (PCE) for gold nanotriangles (GNTs) and nanorods (GNRs) was carried out in the present work. The discrete dipole approximation method was applied to identify the spectral characteristic of GNTs and GNRs with different aspect ratios. On this basis, the PCE of GNTs and GNRs in photothermal therapy were compared theoretically. Afterwards, an in vitro experiment was adopted to investigate the thermal effect of porcine muscle induced by laser irradiation, with and without injected GNTs and GNRs. The influences of laser total power, nanoparticle concentration, and nanoparticle type were investigated. It was found that for the commonly-used wavelengths for photothermal therapy, the PCE of GNTs is higher than that of the GNRs. Furthermore, for GNRs loaded in tissue in vitro, high laser power and high concentration of nanoparticles leads to the degeneration and even carbonization of tissue. However, for the GNTs with the same situation (laser power, nanoparticle volume concentration, and heating time), it could lead to the tissue's evaporation instead of carbonization.

Imaging Laser-Triggered Drug Release from Gold Nanocages with Transient Absorption Lifetime Microscopy

Nanoparticles have shown promise in loading and delivering drugs for targeted therapy. Many progresses have been made in the design, synthesis, and modification of nanoparticles to fulfill such goals. However, realizing targeted intracellular delivery and controlled release of drugs remains challenging, partly because of the lack of reliable tools to detect the drug-releasing process. In this paper, we applied femtosecond laser pulses to trigger the explosion of gold nanocages (AuNCs) and control the intracellular release of loaded aluminum phthalocyanine (AlPcS) molecules for photodynamic therapy (PDT). AuNCs were found to enhance the encapsulation efficiency and suppress the PDT effect of AlPcS molecules until they were released. More importantly, we discovered that the excited-state lifetimes of the AlPcS-AuNC conjugate (∼3 ps) and free AlPcS (∼11 ps) differ significantly, which was utilized to image the released drug molecules using transient absorption lifetime microscopy with the same laser source. This technique extracts information similar to fluorescence lifetime imaging microscopy but is superior in imaging the molecules that hardly fluoresce or are prone to photobleaching. We further combined a dual-phase lock-in detection technique to show the potential of real-time imaging based on the change in transient optical behaviors. Our method may provide a new tool for investigating nanoparticle-assisted drug delivery and release.

Galectin-1-based tumour-targeting for gold nanostructure-mediated photothermal therapy

PURPOSE

To demonstrate delivery of Au nanocages to cells using the galectin-1 binding peptide anginex (Ax) and to demonstrate the value of this targeting for selective in vitro photothermal cell killing.

MATERIALS AND METHODS

Au nanocages were synthesised, coated with polydopamine (PDA), and conjugated with Ax. Tumour and endothelial cell viability was measured with and without laser irradiation. Photoacoustic (PA) mapping and PA flow cytometry were used to confirm cell targeting in vitro and in tissue slices ex vivo.

RESULTS

Cell viability was maintained at ≥50% at 100 pM suggesting low toxicity of the nanocage alone. Combining the targeted construct (25 pM) with low power 808 nm laser irradiation for 10-20 min (a duration previously shown to induce rapid and sustained heating of Au nanocages [AuNC] in solution), resulted in over 50% killing of endothelial and tumour cells. In contrast, the untargeted construct combined with laser irradiation resulted in negligible cell killing. We estimate approximately 6 × 10⁴ peptides were conjugated to each nanocage, which also resulted in inhibition of cell migration. Binding of the targeted nanocage reached a plateau after three hours, and cell association was 20-fold higher than non-targeted nanocages both in vitro and ex vivo on tumour tissue slices. A threefold increase in tumour accumulation was observed in preliminary in vivo studies.

CONCLUSIONS

These studies demonstrate Ax's potential as an effective targeting agent for Au-based theranostics to tumour and endothelial cells, enabling photothermal killing. This platform further suggests potential for multimodal in vivo therapy via next-generation drug-loaded nanocages.

Nanocaged platforms: modification, drug delivery and nanotoxicity. Opening synthetic cages to release the tiger

Nanocages (NCs) have emerged as a new class of drug-carriers, with a wide range of possibilities in multi-modality medical treatments and theranostics. Nanocages can overcome such limitations as high toxicity caused by anti-cancer chemotherapy or by the nanocarrier itself, due to their unique characteristics. These properties consist of: (1) a high loading-capacity (spacious interior); (2) a porous structure (analogous to openings between the bars of the cage); (3) enabling smart release (a key to unlock the cage); and (4) a low likelihood of unfavorable immune responses (the outside of the cage is safe). In this review, we cover different classes of NC structures such as virus-like particles (VLPs), protein NCs, DNA NCs, supramolecular nanosystems, hybrid metal-organic NCs, gold NCs, carbon-based NCs and silica NCs. Moreover, NC-assisted drug delivery including modification methods, drug immobilization, active targeting, and stimulus-responsive release mechanisms are discussed, highlighting the advantages, disadvantages and challenges. Finally, translation of NCs into clinical applications, and an up-to-date assessment of the nanotoxicology considerations of NCs are presented.

Galvanic replacement reaction: recent developments for engineering metal nanostructures towards catalytic applications

Recent developments to achieve further physicochemical control in metallic nanomaterials by galvanic replacement are discussed towards applications in catalysis.

Functional hollow nanostructures for imaging and phototherapy of tumors

Various types of inorganic and organic phototherapeutic hollow nanostructures for the imaging and treatment of tumors are reviewed.

Theoretical Comparison of Optical Properties of Near-Infrared Colloidal Plasmonic Nanoparticles

We study optical properties of near-infrared absorbing colloidal plasmonic nanostructures that are of interest for biomedical theranostic applications: SiO₂@Au core-shell particles, Au nanocages and Au nanorods. Full-wave field analysis is used to compare the absorption spectra and field enhancement of these structures as a function of their dimensions and orientation with respect to the incident field polarization. Absorption cross-sections of structures with the same volume and LSPR wavelength are compared to quantify differential performance for imaging, sensing and photothermal applications. The analysis shows that while the LSPR of each structure can be tuned to the NIR, particles with a high degree of rotational symmetry, i.e. the SiO₂@Au and nanocage particles, provide superior performance for photothermal applications because their absorption is less sensitive to their orientation, which is random in colloidal applications. The analysis also demonstrates that Au nanocages are advantaged with respect to other structures for imaging, sensing and drug delivery applications as they support abundant E field hot spots along their surface and within their open interior. The modeling approach presented here broadly applies to dilute colloidal plasmonic nanomaterials of arbitrary shapes, sizes and material constituents and is well suited for the rational design of novel plasmon-assisted theranostic applications.