Routes to Potentially Safer T1 Magnetic Resonance Imaging Contrast in a Compact Plasmonic Nanoparticle with Enhanced Fluorescence

Detection of tetanus toxoid with iron magnetic nanobioprobe

Diagnosis of diseases with low facilities, speed, accuracy and sensitivity is an important matter in treatment. Bioprobes based on iron oxide nanoparticles are a good candidate for early detection of deadly and infectious diseases such as tetanus due to their high reactivity, biocompatibility, low production cost and sample separation under a magnetic field. In this study, silane groups were coated on surface of iron oxide nanoparticles using tetraethoxysilane (TEOS) hydrolysis. Also, NH2groups were generated on the surface of silanized nanoparticles using 3-aminopropyl triethoxy silane (APTES). Antibody was immobilized on the surface of silanized nanoparticles using TCT trichlorothriazine as activator. Silanization and stabilized antibody were investigated by using of FT-IR, EDX, VSM, SRB technique. UV/vis spectroscopy, fluorescence, agglutination test and ELISA were used for biosensor performance and specificity. The results of FT-IR spectroscopy showed that Si-O-Si and Si-O-Fe bonds and TCT chlorine and amine groups of tetanus anti-toxoid antibodies were formed on the surface of iron oxide nanoparticles. The presence of Si, N and C elements in EDX analysis confirms the silanization of iron oxide nanoparticles. VSM results showed that the amount of magnetic nanoparticles after conjugation is sufficient for biological applications. Antibody stabilization on nanoparticles increased the adsorption intensity in the uv/vis spectrometer. The fluorescence intensity of nano bioprobe increased in the presence of 10 ng ml-1. Nanobio probes were observed as agglomerates in the presence of tetanus toxoid antigen. The presence of tetanus antigen caused the formation of antigen-nanobioprobe antigen complex. Identification of this complex by HRP-bound antibody confirmed the specificity of nanobioprobe. Tetanus magnetic nanobioprobe with a diagnostic limit of 10 ng ml-1of tetanus antigen in a short time can be a good tool in LOC devices and microfluidic chips.

Construction of nanoparticle-on-mirror nanocavities and their applications in plasmon-enhanced spectroscopy

Plasmonic nanocavities exhibit exceptional capabilities in visualizing the internal structure of a single molecule at sub-nanometer resolution. Among these, an easily manufacturable nanoparticle-on-mirror (NPoM) nanocavity is a successful and powerful platform for demonstrating various optical phenomena. Exciting advances in surface-enhanced spectroscopy using NPoM nanocavities have been developed and explored, including enhanced Raman, fluorescence, phosphorescence, upconversion, etc. This perspective emphasizes the construction of NPoM nanocavities and their applications in achieving higher enhancement capabilities or spatial resolution in dark-field scattering spectroscopy and plasmon-enhanced spectroscopy. We describe a systematic framework that elucidates how to meet the requirements for studying light-matter interactions through the creation of well-designed NPoM nanocavities. Additionally, it provides an outlook on the challenges, future development directions, and practical applications in the field of plasmon-enhanced spectroscopy.

Coating influence on inner shell water exchange: An underinvestigated major contributor to SPIONs relaxation properties

Superparamagnetic iron oxide nanoparticles (SPIONs) are heavily studied as potential MRI contrast enhancing agents. Every year, novel coatings are reported which yield large increases in relaxivity compared to similar particles. However, the reason for the increased performance is not always well understood mechanistically. In this review, we attempt to relate these advances back to fundamental models of relaxivity, developed for chelated metal ions, primarily gadolinium. We focus most closely on the three-shell model which considers the relaxation of surface-bound, entrained, and bulk water molecules as three distinct contributions to total relaxation. Because SPIONs are larger, more complex, and entrain significantly more water than gadolinium-based contrast agents, we consider how to adapt the application of classical models to SPIONs in a predictive manner. By carefully considering models and previous results, a qualitative model of entrained water interactions emerges, based primarily on the contributions of core size, coating thickness, density, and hydrophilicity.

High spin Fe(III)-doped nanostructures as T1 MR imaging probes

Magnetic Resonance Imaging (MRI) T₁ contrast agents based on Fe(III) as an alternative to Gd-based compounds have been under intense scrutiny in the last 6-8 years and a number of nanostructures have been designed and proposed for in vivo diagnostic and theranostic applications. Excluding the large family of superparamagnetic iron oxides widely used as T₂ -MR imaging agents that will not be covered by this review, a considerable number and type of nanoparticles (NPs) have been employed, ranging from amphiphilic polymer-based NPs, NPs containing polyphenolic binding units such as melanin-like or polycatechols, mixed metals such as Fe/Gd or Fe/Au NPs and perfluorocarbon nanoemulsions. Iron(III) exhibits several favorable magnetic properties, high biocompatibility and improved toxicity profile that place it as the paramagnetic ion of choice for the next generation of nanosized MRI and theranostic contrast agents. An analysis of the examples reported in the last decade will show the opportunities for relaxivity and MR-contrast enhancement optimization that could bring Fe(III)-doped NPs to really compete with Gd(III)-based nanosystems. This article is categorized under: Diagnostic Tools > In Vivo Nanodiagnostics and Imaging Diagnostic Tools > Diagnostic Nanodevices Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease.

Plasmonic gadolinium oxide nanomatryoshkas: bifunctional magnetic resonance imaging enhancers for photothermal cancer therapy

Nanoparticle-assisted laser-induced photothermal therapy (PTT) is a promising method for cancer treatment; yet, visualization of nanoparticle uptake and photothermal response remain a critical challenge. Here, we report a magnetic resonance imaging-active nanomatryoshka (Gd₂O₃-NM), a multilayered (Au core/Gd₂O₃ shell/Au shell) sub-100 nm nanoparticle capable of combining T₁ MRI contrast with PTT. This bifunctional nanoparticle demonstrates an r₁ of 1.28 × 10⁸ mM^-1 s^-1, an MRI contrast enhancement per nanoparticle sufficient for T₁ imaging in addition to tumor ablation. Gd₂O₃-NM also shows excellent stability in an acidic environment, retaining 99% of the internal Gd(3). This report details the synthesis and characterization of a promising system for combined theranostic nanoparticle tracking and PTT.

Emerging nanobiotechnology-encoded relaxation tuning establishes new MRI modes to localize, monitor and predict diseases

Magnetic resonance imaging (MRI) is one of the most important techniques in the diagnosis of many diseases including cancers, where contrast agents (CAs) are usually necessary to improve its precision and sensitivity. Previous MRI CAs are confined to the signal-to-noise ratio (SNR) elevation of lesions for precisely localizing lesions. As nanobiotechnology advances, some new MRI CAs or nanobiotechnology-enabled MRI modes have been established to vary the longitudinal or transverse relaxation of CAs, which are harnessed to detect lesion targets, monitor disease evolution, predict or evaluate curative effect, etc. These distinct cases provide unexpected insights into the correlation of the design principles of these nanobiotechnologies and corresponding MRI CAs with their potential applications. In this review, first, we briefly present the principles, classifications and applications of conventional MRI CAs, and then elucidate the recent advances in relaxation tuning via the development of various nanobiotechnologies with emphasis on the design strategies of nanobiotechnology and the corresponding MRI CAs to target the tumor microenvironment (TME) and biological targets or activities in tumors or other diseases. In addition, we exemplified the advantages of these strategies in disease theranostics and explored their potential application fields. Finally, we analyzed the present limitations, potential solutions and future development direction of MRI after its combination with nanobiotechnology.

NIR-I Dye-Based Probe: A New Window for Bimodal Tumor Theranostics

Near-infrared (NIR, 650-1700 nm) bioimaging has emerged as a powerful strategy in tumor diagnosis. In particular, NIR-I fluorescence imaging (650-950 nm) has drawn more attention, benefiting from the high quantum yield and good biocompatibility. Since their biomedical applications are slightly limited by their relatively low penetration depth, NIR-I fluorescence imaging probes have been under extensive development in recent years. This review summarizes the particular application of the NIR-I fluorescent dye-contained bimodal probes, with emphasis on related nanoprobes. These probes have enabled us to overcome the drawbacks of individual imaging modalities as well as achieve synergistic imaging. Meanwhile, the application of these NIR-I fluorescence-based bimodal probes for cancer theranostics is highlighted.

Recent advancements and future submissions of silica core-shell nanoparticles

The core-shell silica-based nanoparticles (CSNPs) possess outstanding properties for developing next-generation therapeutics. CSNPs provide greater surface area owing to their mesoporous structure, which offers a high opportunity for surface modification. This review highlights the potential of core-shell silica-based nanoparticle (CSNP) based injectable nanotherapeutics (INT); its role in drug delivery, biomedical imaging, light-triggered phototherapy, Plasmonic enhancers, gene delivery, magnetic hyperthermia, immunotherapy, and potential as next-generation theragnostic. Specifically, the conceptual crosstalk on modern synthetic strategies, biodistribution profiles with a mechanistic view on the therapeutics loading and release modeling are dealt in detail. The manuscript also converses the challenges associated with CSNPs, regulatory hurdles, and their current market position.

Controlled Assembly of Plasmonic Nanoparticles: From Static to Dynamic Nanostructures

The spatial arrangement of plasmonic nanoparticles can dramatically affect their interaction with electromagnetic waves, which offers an effective approach to systematically control their optical properties and manifest new phenomena. To this end, significant efforts were made to develop methodologies by which the assembly structure of metal nanoparticles can be controlled with high precision. Herein, recent advances in bottom-up chemical strategies toward the well-controlled assembly of plasmonic nanoparticles, including multicomponent and multifunctional systems are reviewed. Further, it is discussed how the progress in this area has paved the way toward the construction of smart dynamic nanostructures capable of on-demand, reversible structural changes that alter their properties in a predictable and reproducible manner. Finally, this review provides insight into the challenges, future directions, and perspectives in the field of controlled plasmonic assemblies.

Fe3O4 assembly for tumor accurate diagnosis by endogenous GSH responsive T2/T1 magnetic relaxation conversion

Superparamagnetic iron oxide nanoparticles with high magnetization strength and good biological safety have been widely used as magnetic resonance imaging (MRI) contrast agents for tumors. However, the accuracy of tumor diagnosis is still low due to the lack of tumor targeting and the interference signals from normal tissues. Endogenous substances in tumor (such as high levels of GSH and pH) stimuli-responsive contrast agents could offer higher sensitivity for tumor diagnosis. Herein, based on the characteristic of overexpression of GSH in tumors, we propose an ultra-small Fe₃O₄ assembly as an endogenous GSH responsive MRI contrast agent. The ultra-small superparamagnetic Fe₃O₄ are bonded to the crosslinker cystamine to synthesize Fe₃O₄ nanoclusters, which exhibit a T₂ imaging effect. When the contrast agent reaches the tumor tissue, the disulfide bond in cystamine is induced by GSH to break, the Fe₃O₄ nanoclusters are disassembled into ultra-small Fe₃O₄ nanoparticles, and the relaxation signal changes from T₂ to T₁, which is helpful for accurate diagnosis of tumors. In vivo experiments have shown that Fe₃O₄ nanoclusters can rapidly respond to overexpressed GSH in tumor sites for T₂/T₁ switchable imaging. This work not only designed an endogenous GSH responsive platform through simple synthesis methods, but also improved the accuracy of tumor diagnosis through the transformation of T₂/T₁ MRI signals.

Dendrimer-modified gold nanorods as a platform for combinational gene therapy and photothermal therapy of tumors

Background

The exploitation of novel nanomaterials combining diagnostic and therapeutic functionalities within one single nanoplatform is challenging for tumor theranostics.

Methods

We synthesized dendrimer-modified gold nanorods for combinational gene therapy and photothermal therapy (PTT) of colon cancer. Poly(amidoamine) dendrimers (PAMAM, G3) grafted gold nanorods were modified with GX1 peptide (a cyclic 7-mer peptide, CGNSNPKSC). The obtained Au NR@PAMAM-GX1 are proposed as a gene delivery vector to gene (FAM172A, regulates the proliferation and apoptosis of colon cancer cells) for the combination of photothermal therapy (PTT) and gene therapy of Colon cancer cells (HCT-8 cells). In addition, the CT imaging function of Au NR can provide imaging evidence for the diagnosis of colon cancer.

Results

The results display that Au NR@PAMAM-GX1 can specifically deliver FAM172A to cancer cells with excellent transfection efficiency. The HCT-8 cells treated with the Au NR@PAMAM-GX1/FAM172A under laser irradiation have a viability of 20.45%, which is much lower than the survival rate of other single-mode PTT treatment or single-mode gene therapy. Furthermore, animal experiment results confirm that Au NR@PAMAM-GX1/FAM172A complexes can achieve tumor thermal imaging, targeted CT imaging, PTT and gene therapy after tail vein injection.

Conclusion

Our findings demonstrate that the synthesized Au NR@PAMAM-GX1 offer a facile platform to exert antitumor and improve the diagnostic level of tumor.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13046-021-02105-3.

Synthesis of a Thermal-Responsive Dual-Modal Supramolecular Probe for Magnetic Resonance Imaging and Fluorescence Imaging

Dual-modal imaging can integrate the advantages of different imaging technologies, which could improve the accuracy and efficiency of clinical diagnosis. Herein, a novel amphiphilic thermal-responsive copolymer obtained from three types of monomers, N-isopropyl acrylamide, 2-(acetoacetoxy) ethyl methacrylate, and propargyl methacrylate, by RAFT copolymerization, is reported. It can be grafted with β-cyclodextrin and aggregation-induced emission (AIE) luminogens tetraphenylethylene by click chemistry and Biginelli reaction. The multifunctional supramolecular polymer (P4) can be constructed by host-guest inclusion between the copolymer and the Gd-based contrast agent (CA) modified by adamantane [Ad-(DOTA-Gd)]. And it can form vesicles with a bilayer structure in aqueous which will enhance the AIE and magnetic resonance imaging effects. As fluorescent thermometer, P4 can enter HeLa cells for intracellular fluorescence imaging (FI) and is sensitive to temperature with detection limit value of 1.5 °C. As magnetic resonance CA, P4 exhibits higher relaxation compared to Magnevist, which can prolong the circulation time in vivo. In addition, Gd³⁺ in the polymer can be quickly released from the body by disassembly that reduced the biological toxicity. This work introduces new synthetic ideas for dual-modal probe, which has great potential for clinical diagnostic applications in bioimaging.

Optical Imaging and High-Accuracy Quantification of Intracellular Iron Contents

Precise quantification of intracellular iron contents is important to biomedical applications of magnetic nanoparticles. Current approaches for iron quantification rely on specialized instruments while most only yield iron quantities averaged over plenty of cells. Here, a simple and robust approach, combining digital optical microscopy with the Beer-Lambert's law, that allows for imaging stainable iron distribution in individual cells and the quantification of stainable iron contents with an unprecedented accuracy of femtogram per pixel, is presented. It is further shown that this approach enables studying of the internalization and reduction dynamics of super-paramagnetic iron oxide nanoparticles (SPIONs) by stem cells in single cell level.

A step towards gadolinium-free bioresponsive MRI contrast agent

The last 30 years of gadolinium-based "static" MRI contrast agents motivated to investigate bioresponsive agents with endogenous paramagnets. Iron(III) chelated by N,O-aminophenol skeleton of high versatility, and tuning potential was studied. The two-step convenient route of the ligand is characterized by high selectivity and allows for building a tunable chelate system. Functionalization with galactose endows a bioresponsive character sensitive to the enzyme activity. Direct relaxometric measurements of the resulting complexes revealed extremely high relaxivity of 5.62 mmol/dm³·s^-1 comparable to classic gadolinium complexes. Enzymatic hydrolysis leads to relaxivity change by over 80%. Phantom MRI studies prove the bioresponsive character by contras percentage change within the range 40-275%. Cytotoxicity studies showed 70-90% viability of HeLa cells of the iron complexes. Proposed iron-based chelates with galactosidase-sensitive fragment express unequivocal relaxivity and MRI contras change and good biocompatibility. Therefore, these complexes are a promising step towards modern, bioresponsive MRI contrast agents with a "human-friendly" metal.

Engineering Prodrug Nanomedicine for Cancer Immunotherapy

Immunotherapy has shifted the clinical paradigm of cancer management. However, despite promising initial progress, immunotherapeutic approaches to cancer still suffer from relatively low response rates and the possibility of severe side effects, likely due to the low inherent immunogenicity of tumor cells, the immunosuppressive tumor microenvironment, and significant inter- and intratumoral heterogeneity. Recently, nanoformulations of prodrugs have been explored as a means to enhance cancer immunotherapy by simultaneously eliciting antitumor immune responses and reversing local immunosuppression. Prodrug nanomedicines, which integrate engineering advances in chemistry, oncoimmunology, and material science, are rationally designed through chemically modifying small molecule drugs, peptides, or antibodies to yield increased bioavailability and spatiotemporal control of drug release and activation at the target sites. Such strategies can help reduce adverse effects and enable codelivery of multiple immune modulators to yield synergistic cancer immunotherapy. In this review article, recent advances and translational challenges facing prodrug nanomedicines for cancer immunotherapy are overviewed. Last, key considerations are outlined for future efforts to advance prodrug nanomedicines aimed to improve antitumor immune responses and combat immune tolerogenic microenvironments.

Multifunctional magnetic iron oxide nanoparticles: an advanced platform for cancer theranostics

Multifunctional magnetic nanoparticles and derivative nanocomposites have aroused great concern for multimode imaging and cancer synergistic therapies in recent years. Among the rest, functional magnetic iron oxide nanoparticles (Fe3O4 NPs) have shown great potential as an advanced platform because of their inherent magnetic resonance imaging (MRI), biocatalytic activity (nanozyme), magnetic hyperthermia treatment (MHT), photo-responsive therapy and drug delivery for chemotherapy and gene therapy. Magnetic Fe3O4 NPs can be synthesized through several methods and easily surface modified with biocompatible materials or active targeting moieties. The MRI capacity could be appropriately modulated to induce response between T1 and T2 modes by controlling the size distribution of Fe3O4 NPs. Besides, small-size nanoparticles are also desired due to the enhanced permeation and retention (EPR) effect, thus the imaging and therapeutic efficiency of Fe3O4 NP-based platforms can be further improved. Here, we firstly retrospect the typical synthesis and surface modification methods of magnetic Fe3O4 NPs. Then, the latest biomedical application including responsive MRI, multimodal imaging, nanozyme, MHT, photo-responsive therapy and drug delivery, the mechanism of corresponding treatments and cooperation therapeutics of multifunctional Fe3O4 NPs are also be explained. Finally, we also outline a brief discussion and perspective on the possibility of further clinical translations of these multifunctional nanomaterials. This review would provide a comprehensive reference for readers to understand the multifunctional Fe3O4 NPs in cancer diagnosis and treatment.

Quasi-amorphous and Hierarchical Fe2O3 Supraparticles: Active T1-Weighted Magnetic Resonance Imaging in Vivo and Renal Clearance

The exploration of magnetic resonance imaging (MRI) agents possessing excellent performances and high biosafety is of great importance for both fundamental science research and biomedical applications. In this study, we present that monodisperse Fe₂O₃ supraparticles (SPs) can act as T₁-weighted MRI agents, which not only possess a distinct off-on MRI switch in the tumor microenvironment but also are readily excreted from living bodies due to its quasi-amorphous structure and hierarchical topology design. First, the Fe₂O₃ SPs have a surface-to-volume ratio obviously smaller than that of their building blocks by means of self-assembly processes, which, on the one hand, causes a rather low r₁ relaxivity (0.19 mM^-1 s^-1) and, on the other hand, can effectively prevent their aggregation after intravenous injection. Second, the Fe₂O₃ SPs have a dramatic disassembly/degradation-induced active T₁-weighted signal readout (more than 6 times the r₁ value enhancement and about 20 times the r₂/r₁ ratio decrease) in the tumor microenvironment, resulting in a high signal-to-noise ratio for imaging performances. Therefore, they possess excellent in vivo imaging capacity, even with a tumor size as small as 5 mm³. Third, the disassembled/decomposed behaviors of the Fe₂O₃ SPs facilitate their timely clearance/excretion from living bodies. In particular, they exhibit distinct renal clearance behavior without any kidney damage with the right dosage. Fourth, the favorable biodegradability of the as-prepared Fe₂O₃ SPs can further relieve the concerns about the unclear biological effects, particularly on nanomaterials, in general.

Gold Nanoparticles Mediate Improved Detection of β-amyloid Aggregates by Fluorescence

The early detection of the amyloid beta peptide aggregates involved in Alzheimer’s disease is crucial to test new potential treatments. In this research, we improved the detection of amyloid beta peptide aggregates in vitro and ex vivo by fluorescence combining the use of CRANAD-2 and gold nanorods (GNRs) by the surface enhancement fluorescence effect. We synthetized GNRs and modified their surface with HS-PEG-OMe and HS-PEG-COOH and functionalized them with the D1 peptide, which has the capability to selectively bind to amyloid beta peptide. For an in vitro detection of amyloid beta peptide, we co-incubated amyloid beta peptide aggregates with the probe CRANAD-2 and GNR-PEG-D1 observing an increase in the intensity of the fluorescence signal attributed to surface enhancement fluorescence. Furthermore, the surface enhancement fluorescence effect was observed in brain slices of transgenic mice with Alzheimer´s disease co-incubated with CRANAD-2 and GNR-PEG-D1. An increase in the fluorescence signal was observed allowing the detection of aggregates that cannot be detected with the single use of CRANAD-2. Gold nanoparticles allowed an improvement in the detection of the amyloid aggregated by fluorescence in vitro and ex vivo.

Comparison of ferumoxytol- and gadolinium chelate-enhanced MRI for assessment of sarcomas in children and adolescents

OBJECTIVES

We compared the value of ferumoxytol (FMX)- and gadolinium (Gd)-enhanced MRI for assessment of sarcomas in paediatric/adolescent patients and hypothesised that tumour size and morphological features can be equally well assessed with both protocols.

METHODS

We conducted a retrospective study of paediatric/adolescent patients with newly diagnosed bone or soft tissue sarcomas and both pre-treatment FMX- and Gd-MRI scans, which were maximal 4 weeks apart. Both protocols included T1- and T2-weighted sequences. One reader assessed tumour volumes, signal-to-noise ratios (SNR) of the primary tumour and adjacent tissues and contrast-to-noise ratios (CNR) of FMX- and Gd-MRI scans. Additionally, four readers scored FMX- and Gd-MRI scans according to 15 diagnostic parameters, using a Likert scale. The results were pooled across readers and compared between FMX- and Gd-MRI scans. Statistical methods included multivariate analyses with different models.

RESULTS

Twenty-two patients met inclusion criteria (16 males, 6 females; mean age 15.3 ± 5.0). Tumour volume was not significantly different on T1-LAVA (p = 0.721), T1-SE (p = 0.290) and T2-FSE (p = 0.609) sequences. Compared to Gd-MRI, FMX-MRI demonstrated significantly lower tumour SNR on T1-LAVA (p < 0.001), equal tumour SNR on T1-SE (p = 0.104) and T2-FSE (p = 0.305), significantly higher tumour-to-marrow CNR (p < 0.001) on T2-FSE as well as significantly higher tumour-to-liver (p = 0.021) and tumour-to-vessel (p = 0.003) CNR on T1-LAVA images. Peritumoural and marrow oedema enhanced significantly more on Gd-MRI compared to FMX-MRI (p < 0.001/p = 0.002, respectively). Tumour thrombi and neurovascular bundle involvement were assessed with a significantly higher confidence on FMX-MRI (both p < 0.001).

CONCLUSIONS

FMX-MRI provides equal assessment of the extent of bone and soft tissue sarcomas compared to Gd-MRI with improved tumour delineation and improved evaluation of neurovascular involvement and tumour thrombi. Therefore, FMX-MRI is a possible alternative to Gd-MRI for tumour staging in paediatric/adolescent sarcoma patients.

KEY POINTS

• Ferumoxytol can be used as an alterative to gadolinium chelates for MRI staging ofpaediatric sarcomas. • Ferumoxytol-enhanced MRI provides equal assessment of tumour size and other diagnostic parameters compared to gadolinium chelate-enhanced MRI. • Ferumoxytol-enhanced MRI provides improved delineation of sarcomas from bone marrow, liver and vessels compared to gadolinium chelate-enhanced MRI.

Multicomponent Plasmonic Nanoparticles: From Heterostructured Nanoparticles to Colloidal Composite Nanostructures

Plasmonic nanostructures possessing unique and versatile optoelectronic properties have been vastly investigated over the past decade. However, the full potential of plasmonic nanostructure has not yet been fully exploited, particularly with single-component homogeneous structures with monotonic properties, and the addition of new components for making multicomponent nanoparticles may lead to new-yet-unexpected or improved properties. Here we define the term "multi-component nanoparticles" as hybrid structures composed of two or more condensed nanoscale domains with distinctive material compositions, shapes, or sizes. We reviewed and discussed the designing principles and synthetic strategies to efficiently combine multiple components to form hybrid nanoparticles with a new or improved plasmonic functionality. In particular, it has been quite challenging to precisely synthesize widely diverse multicomponent plasmonic structures, limiting realization of the full potential of plasmonic heterostructures. To address this challenge, several synthetic approaches have been reported to form a variety of different multicomponent plasmonic nanoparticles, mainly based on heterogeneous nucleation, atomic replacements, adsorption on supports, and biomolecule-mediated assemblies. In addition, the unique and synergistic features of multicomponent plasmonic nanoparticles, such as combination of pristine material properties, finely tuned plasmon resonance and coupling, enhanced light-matter interactions, geometry-induced polarization, and plasmon-induced energy and charge transfer across the heterointerface, were reported. In this review, we comprehensively summarize the latest advances on state-of-art synthetic strategies, unique properties, and promising applications of multicomponent plasmonic nanoparticles. These plasmonic nanoparticles including heterostructured nanoparticles and composite nanostructures are prepared by direct synthesis and physical force- or biomolecule-mediated assembly, which hold tremendous potential for plasmon-mediated energy transfer, magnetic plasmonics, metamolecules, and nanobiotechnology.

Gold nanomaterials as key suppliers in biological and chemical sensing, catalysis, and medicine

BACKGROUND

Gold nanoparticles (AuNPs) with unique physicochemical properties have received a great deal of interest in the field of biological, chemical and biomedical implementations. Despite the widespread use of AuNPs in chemical and biological sensing, catalysis, imaging and diagnosis, and more recently in therapy, no comprehensive summary has been provided to explain how AuNPs could aid in developing improved sensing and catalysts systems as well as medical settings.

SCOPE OF REVIEW

The chemistry of Au-based nanosystems was followed by reviewing different applications of Au nanomaterials in biological and chemical sensing, catalysis, imaging and diagnosis by a number of approaches, and finally synergistic combination therapy of different cancers. Afterwards, the clinical impacts of AuNPs, future application of AuNPs, and opportunities and challenges of AuNPs application were also discussed.

MAJOR CONCLUSIONS

AuNPs show exclusive colloidal stability and are considered as ideal candidates for colorimetric detection, catalysis, imaging, and photothermal transducers, because their physicochemical properties can be tuned by adjusting their structural dimensions achieved by the different manufacturing methods.

GENERAL SIGNIFICANCE

This review provides some details about using AuNPs in sensing and catalysis applications as well as promising theranostic nanoplatforms for cancer imaging and diagnosis, and sensitive, non-invasive, and synergistic methods for cancer treatment in an almost comprehensive manner.

Leveraging the interplay of nanotechnology and neuroscience: Designing new avenues for treating central nervous system disorders

Nanotechnology has the potential to open many novel diagnostic and treatment avenues for disorders of the central nervous system (CNS). In this review, we discuss recent developments in the applications of nanotechnology in CNS therapies, diagnosis and biology. Novel approaches for the diagnosis and treatment of neuroinflammation, brain dysfunction, psychiatric conditions, brain cancer, and nerve injury provide insights into the potential of nanomedicine. We also highlight nanotechnology-enabled neuroscience techniques such as electrophysiology and intracellular sampling to improve our understanding of the brain and its components. With nanotechnology integrally involved in the advancement of basic neuroscience and the development of novel treatments, combined diagnostic and therapeutic applications have begun to emerge. Nanotheranostics for the brain, able to achieve single-cell resolution, will hasten the rate in which we can diagnose, monitor, and treat diseases. Taken together, the recent advances highlighted in this review demonstrate the prospect for significant improvements to clinical diagnosis and treatment of a vast array of neurological diseases. However, it is apparent that a strong dialogue between the nanoscience and neuroscience communities will be critical for the development of successful nanotherapeutics that move to the clinic, benefit patients, and address unmet needs in CNS disorders.

Functionalized Gold Nanoparticles as Contrast Agents for Proton and Dual Proton/Fluorine MRI

Gold nanoparticles carrying fluorinated ligands in their monolayer are, by themselves, contrast agents for 19F magnetic resonance imaging displaying high sensitivity because of the high density of fluorine nuclei achievable by grafting suitable ligands on the gold core surface. Functionalization of these nanoparticles with Gd(III) chelates allows adding a further functional activity to these systems, developing materials also acting as contrast agents for proton magnetic resonance imaging. These dual mode contrast agents may allow capitalizing on the benefits of 1H and 19F magnetic resonance imaging in a single diagnostic session. In this work, we describe a proof of principle of this approach by studying these nanoparticles in a high field preclinical scanner. The Gd(III) centers within the nanoparticles monolayer shorten considerably the 19F T1 of the ligands but, nevertheless, these systems display strong and sharp NMR signals which allow recording good quality 19F MRI phantom images at nanoparticle concentration of 20 mg/mL after proper adjustment of the imaging sequence. The Gd(III) centers also influence the T1 relaxation time of the water protons and high quality 1H MRI images could be obtained. Gold nanoparticles protected by hydrogenated ligands and decorated with Gd(III) chelates are reported for comparison as 1H MRI contrast agents.

Fluorescence-enhanced covalent organic framework nanosystem for tumor imaging and photothermal therapy

Fluorescent dyes, as a key factor in fluorescence imaging, usually exhibit a low signal-to-noise ratio (SNR) due to the limited loading capacities of delivery systems (usually less than 10.0 wt%) and their uncontrolled release. Herein, we developed a type of pH-responsive nanoplatform (MnO2/ZnCOF@Au&BSA) based on a zinc porphyrin covalent organic framework (COF), in which the zinc porphyrin (ZnPor) loading rate is 22.5 wt%. At pH = 7.4, the interlinked ZnPor in the assembly state did not show a fluorescence signal ("off" state). Together with the pH-triggered disintegration of ZnCOF in tumor cells (pH = 5.5), the scattered ZnPor displayed an obvious fluorescence signal recovery ("on" state). Simultaneously, the shed BSA-coated gold nanoparticles ingeniously caused the fluorescence signal to be further amplified through the metal-enhanced fluorescence effect, which was about 3.0-fold higher in vivo than in the free ZnPor group. Combined with the excellent photothermal therapy effect by the nanoplatform itself with the tumor inhibition rate of 79.5%, this nanosystem effectively solves the problem of low loading capacities and imaging SNR by traditional delivery systems, and successfully develops the potential of COFs for fluorescence imaging, achieving the purpose of integration of diagnosis and treatment.

A Water Solvation Shell Can Transform Gold Metastable Nanoparticles in the Fluxional Regime

Solvated gold nanoparticles have been modeled in the fluxional regime by density functional theory including dispersion forces for an extensive set of conventional morphologies. The study of isolated adsorption of one water molecule shows that the most stable adsorption forms are similar (corners and edges) regardless of the nanoparticle shape and size, although the adsorption strength differs significantly (0.15 eV). When a complete and explicit water solvation shell interacts with gold nanoclusters, metastable in vacuum and presenting a predominance of (100) square facets (ino-decahedra Au₅₅ and Au₁₄₇), these nanoparticles are found unstable and transform into the closest morphologies exhibiting mainly (111) triangular facets and symmetries. The corresponding adsorption strength per water molecule becomes independent of shape and size and is enhanced by the formation of two hydrogen bonds on average. For applications in radiotherapy, this study suggests that the shapes of small gold nanoparticles should be homogenized by interacting with the biological environment.

Applications of nanoparticles in biomedical imaging

An urgent need for early detection and diagnosis of diseases continuously pushes the advancements of imaging modalities and contrast agents. Current challenges remain for fast and detailed imaging of tissue microstructures and lesion characterization that could be achieved via development of nontoxic contrast agents with longer circulation time. Nanoparticle technology offers this possibility. Here, we review nanoparticle-based contrast agents employed in most common biomedical imaging modalities, including fluorescence imaging, MRI, CT, US, PET and SPECT, addressing their structure related features, advantages and limitations. Furthermore, their applications in each imaging modality are also reviewed using commonly studied examples. Future research will investigate multifunctional nanoplatforms to address safety, efficacy and theranostic capabilities. Nanoparticles as imaging contrast agents have promise to greatly benefit clinical practice.