Gd(III)-Dithiolane Gold Nanoparticles for T1-Weighted Magnetic Resonance Imaging of the Pancreas

Prospect of Gold Nanoparticles in Pancreatic Cancer

Pancreatic cancer (PC) is characterized by its notably poor prognosis and high mortality rate, underscoring the critical need for advancements in its diagnosis and therapy. Gold nanoparticles (AuNPs), with their distinctive physicochemical characteristics, demonstrate significant application potential in cancer therapy. For example, upon exposure to lasers of certain wavelengths, they facilitate localized heating, rendering them extremely effective in photothermal therapy. Additionally, their extensive surface area enables the conjugation of therapeutic agents or targeting molecules, increasing the accuracy of drug delivery systems. Moreover, AuNPs can serve as radiosensitizers, enhancing the efficacy of radiotherapy by boosting the radiation absorption in tumor cells. Here, we systematically reviewed the application and future directions of AuNPs in the diagnosis and treatment of PC. Although AuNPs have advantages in improving diagnostic and therapeutic efficacy, as well as minimizing damage to normal tissues, concerns about their potential toxicity and safety need to be comprehensively evaluated.

Influence of SPION Surface Coating on Magnetic Properties and Theranostic Profile

This study aimed to develop multifunctional nanoplatforms for both cancer imaging and therapy using superparamagnetic iron oxide nanoparticles (SPIONs). Two distinct synthetic methods, reduction-precipitation (MR/P) and co-precipitation at controlled pH (MpH), were explored, including the assessment of the coating's influence, namely dextran and gold, on their magnetic properties. These SPIONs were further functionalized with gadolinium to act as dual T1/T2 contrast agents for magnetic resonance imaging (MRI). Parameters such as size, stability, morphology, and magnetic behavior were evaluated by a detailed characterization analysis. To assess their efficacy in imaging and therapy, relaxivity and hyperthermia experiments were performed, respectively. The results revealed that both synthetic methods lead to SPIONs with similar average size, 9 nm. Mössbauer spectroscopy indicated that samples obtained from MR/P consist of approximately 11-13% of Fe present in magnetite, while samples obtained from MpH have higher contents of 33-45%. Despite coating and functionalization, all samples exhibited superparamagnetic behavior at room temperature. Hyperthermia experiments showed increased SAR values with higher magnetic field intensity and frequency. Moreover, the relaxivity studies suggested potential dual T1/T2 contrast agent capabilities for the coated SPpH-Dx-Au-Gd sample, thus demonstrating its potential in cancer diagnosis.

Gold Polymer Nanomaterials: A Promising Approach for Enhanced Biomolecular Imaging

Gold nanoparticles (AuNPs) possess unique optical properties, making them highly attractive nanomaterials for biomedical research. By exploiting the diverse optical characteristics of various gold nanostructures, significant enhancements can be achieved in biosensing and biomedical imaging fields. The potential of AuNPs can be enhanced by creating hybrid nanocomposites with polymers, which offer supplementary functionalities, responsiveness, and enhanced biocompatibility. Moreover, polymers can modify the surface charges of AuNPs, thereby improving or controlling the efficiency of cellular uptake and the distribution of these nanoparticles within the body. Polymer modification using AuNPs offers a wide array of benefits, including improved sensitivity, specificity, speed, contrast, resolution, and penetration depth. By incorporating AuNPs into the polymer matrix, these enhancements synergistically enhance the overall performance of various applications. This versatile approach opens promising possibilities in fields such as biomedicine, nanotechnology, and sensor development, providing a powerful platform for advanced research and technological innovations. In this review, the recent advancements in polymer-AuNPs synthesis and their applications in bioimaging will be covered. Prospects and challenges associated with polymer-AuNPs-based bioimaging agents in preclinical and clinical investigations will be discussed.

Microenvironment of pancreatic inflammation: calling for nanotechnology for diagnosis and treatment

Acute pancreatitis (AP) is a common and life-threatening digestive disorder. However, its diagnosis and treatment are still impeded by our limited understanding of its etiology, pathogenesis, and clinical manifestations, as well as by the available detection methods. Fortunately, the progress of microenvironment-targeted nanoplatforms has shown their remarkable potential to change the status quo. The pancreatic inflammatory microenvironment is typically characterized by low pH, abundant reactive oxygen species (ROS) and enzymes, overproduction of inflammatory cells, and hypoxia, which exacerbate the pathological development of AP but also provide potential targeting sites for nanoagents to achieve early diagnosis and treatment. This review elaborates the various potential targets of the inflammatory microenvironment of AP and summarizes in detail the prospects for the development and application of functional nanomaterials for specific targets. Additionally, it presents the challenges and future trends to develop multifunctional targeted nanomaterials for the early diagnosis and effective treatment of AP, providing a valuable reference for future research.

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.

Spatiotemporal tracking of gold nanorods after intranasal administration for brain targeting

Intranasal administration is becoming increasingly more attractive as a fast delivery route to the brain for therapeutics circumventing the blood-brain barrier (BBB). Gold nanorods (AuNRs) demonstrate unique optical and biological properties compared to other gold nanostructures due to their high aspect ratio. In this study, we investigated for the first time the brain region-specific distribution of AuNRs and their potential as a drug delivery platform for central nervous system (CNS) therapy following intranasal administration to mice using a battery of analytical and imaging techniques. AuNRs were functionalized with a fluorescent dye (Cyanine5, Cy5) or a metal chelator (diethylenetriaminepentaacetic dianhydride, DTPA anhydride) to complex with Indium-111 via a PEG spacer for optical and nuclear imaging, respectively. Direct quantification of gold was achieved by inductively coupled plasma mass spectrometry. Rapid AuNRs uptake in mice brains was observed within 10 min following intranasal administration which gradually reduced over time. This was confirmed by the 3 imaging/analytical techniques. Autoradiography of sagittal brain sections suggested entry to the brain via the olfactory bulb followed by diffusion to other brain regions within 1 h of administration. The presence of AuNR in glioblastoma (GBM) tumors following intranasal administration was also proven which opens doors for AuNRs applications, as nose-to-brain drug delivery carriers, for treatment of a range of CNS diseases.

Engineered Nonviral Protein Cages Modified for MR Imaging

Diagnostic medical imaging utilizes magnetic resonance (MR) to provide anatomical, functional, and molecular information in a single scan. Nanoparticles are often labeled with Gd(III) complexes to amplify the MR signal of contrast agents (CAs) with large payloads and high proton relaxation efficiencies (relaxivity, r1). This study examined the MR performance of two structurally unique cages, AaLS-13 and OP, labeled with Gd(III). The cages have characteristics relevant for the development of theranostic platforms, including (i) well-defined structure, symmetry, and size; (ii) the amenability to extensive engineering; (iii) the adjustable loading of therapeutically relevant cargo molecules; (iv) high physical stability; and (v) facile manufacturing by microbial fermentation. The resulting conjugates showed significantly enhanced proton relaxivity (r1 = 11-18 mM-1 s-1 at 1.4 T) compared to the Gd(III) complex alone (r1 = 4 mM-1 s-1). Serum phantom images revealed 107% and 57% contrast enhancements for Gd(III)-labeled AaLS-13 and OP cages, respectively. Moreover, proton nuclear magnetic relaxation dispersion (1H NMRD) profiles showed maximum relaxivity values of 50 mM-1 s-1. Best-fit analyses of the 1H NMRD profiles attributed the high relaxivity of the Gd(III)-labeled cages to the slow molecular tumbling of the conjugates and restricted local motion of the conjugated Gd(III) complex.

Application of nanotechnology in the diagnosis and treatment of acute pancreatitis

Acute pancreatitis (AP) is a common digestive system disease. The severity of AP ranges from mild edema in the pancreas to severe systemic inflammatory responses leading to peripancreatic/pancreatic necrosis, multi-organ failure and death. Improving the sensitivity of AP diagnosis and developing alternatives to traditional methods to treat AP have gained the attention of researchers. With the continuous rise of nanotechnology, it is being widely used in daily life, biomedicine, chemical energy and many other fields. Studies have demonstrated the effectiveness of nanotechnology in the diagnosis and treatment of AP. Nanotechnology has the advantages of simplicity, rapidity and sensitivity in detecting biomarkers of AP, as well as enhancing imaging, which helps in the early diagnosis of AP. On the other hand, nanoparticles (NPs) have oxidative stress inhibiting and anti-inflammatory effects, and can also be loaded with drugs as well as being used in anti-infection therapy, providing a new approach for the treatment of AP. In this article, we elaborate and summarize on the potential of nanoparticles for diagnostic and therapeutic applications in AP from the current reported literature and experimental results to provide useful guidelines for further research on the application of nanotechnology.

Recent progress in the applications of gold-based nanoparticles towards tumor-targeted imaging and therapy

Cancer death rate remains high all over the world, scientists are paying increasing attention to meet the requirements for precise diagnosis and therapy. Therefore, early diagnosis and active treatment can effectively improve the five-year survival rate of patients. In recent years, gold-based nanomaterials have received increasing attention in medical fields due to their excellent biocompatibility, low toxicity and unique properties. In addition, because of the inherent nature of gold nanomaterials including for computed tomography (CT), fluorescence/optical imaging (FI/OI), surface enhanced Raman spectroscopy imaging (SERS), photoacoustic imaging (PAI) and photothermal therapy (PTT), various gold nanomaterials were developed as theranostic nanoplatforms. In this review, we summarized the latest developments of nanomaterials in imaging and combined therapy, and the prospects for the future application of gold-based theranostic nanoplatforms were also proposed.

We summarize the latest developments of gold nanomaterials in imaging and combined therapy as well as prospects for the future application of gold-based theranostic nanoplatforms.

Ultra-small bimetallic phosphide for dual-modal MRI imaging guided photothermal ablation of tumor

Metal phosphides have been proved to be the potential theranostic agents of tumor. However, the limitation of single-modal imaging or treatment effect of such materials need to be further improved....

Engineered Protein Photo-Thermal Hydrogels for Outstanding In Situ Tongue Cancer Therapy

Surgical excision is the main choice for tongue cancer treatment. However, the physiological functions of oral and maxillofacial regions might be severely impaired and high risk of tongue tumor recurrence cannot be avoided. It is thus becoming urgently important to develop alternative strategies for tongue cancer therapy. In this regard, a new class of near-infrared (NIR) light-responsive and peritumoral injectable hydrogel is fabricated with extraordinary photothermal therapy (PTT) for in situ tongue tumors. The as-prepared soft material exhibits good biocompatibility and ultra-strong photothermal effect due to the formed network by negatively charged proteins, chitosan molecules, and Ag₃ AuS₂ nanoparticles (NPs). In a well-constructed in situ tongue tumor model, tumors can be efficiently eradicated by one-time PTT treatment. Importantly, there are no side effects on surrounding normal tissues and potential tumor recurrence is inhibited. In stark contrast to traditional surgical excision, such biomaterials hold great potential for clinical treatment of oral cancers.

Advanced Nanomaterials-Assisted Cell Cryopreservation: A Mini Review

Cell cryopreservation is of vital significance both for transporting and storing cells before experimental/clinical use. Cryoprotectants (CPAs) are necessary additives in the preserving medium in cryopreservation, preventing cells from freeze-thaw injuries. Traditional organic solvents have been widely used in cell cryopreservation for decades. Given the obvious damage to cells due to their undesirable cytotoxicity and the burdensome post-thaw washing cycles before use, traditional CPAs are more and more likely to be replaced by modern ones with lower toxicity, less processing, and higher efficiency. As materials science thrives, nanomaterials are emerging to serve as potent vehicles for delivering nontoxic CPAs or inherent CPAs comparable to or even superior to conventional ones. This review will introduce some advanced nanomaterials (e.g., organic/inorganic nanoCPAs, nanodelivery systems) utilized for cell cryopreservation, providing broader insights into this developing field.

Recent Development of Gold Nanoparticles as Contrast Agents for Cancer Diagnosis

Simple Summary

The development of nanotechnology has brought revolution to the diagnosis and therapy of diseases, with a high precision and efficacy. Because nanoparticles can integrate multifunctions together including imaging, targeting, and therapeutics, they are more efficient than the standalone diagnostic or therapeutic entities. Among which, gold nanoparticles are most extensively investigated due to their excellent biocompatibility, versatility and ease of functionalization. Excepting the using of gold nanoparticles as vehicles for therapeutics delivery, they are also good candidates as contrast agents for imaging diagnosis, from magnetic resonance imaging, CT and nuclear imaging, fluorescence imaging, photoacoustic imaging to X-ray fluorescence imaging. We summarize their recent applications in these imaging modalities and challenges for their clinical translation.

Abstract

The last decade has witnessed the booming of preclinical studies of gold nanoparticles (AuNPs) in biomedical applications, from therapeutics delivery, imaging diagnostics, to cancer therapies. The synthetic versatility, unique optical and electronic properties, and ease of functionalization make AuNPs an excellent platform for cancer theranostics. This review summarizes the development of AuNPs as contrast agents to image cancers. First, we briefly describe the AuNP synthesis, their physical characteristics, surface functionalization and related biomedical uses. Then we focus on the performances of AuNPs as contrast agents to diagnose cancers, from magnetic resonance imaging, CT and nuclear imaging, fluorescence imaging, photoacoustic imaging to X-ray fluorescence imaging. We compare these imaging modalities and highlight the roles of AuNPs as contrast agents in cancer diagnosis accordingly, and address the challenges for their clinical translation.

Tailor-Made Nanomaterials for Diagnosis and Therapy of Pancreatic Ductal Adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is one of the deadliest cancers worldwide due to its aggressiveness and the challenge to early diagnosis and treatment. In recent decades, nanomaterials have received increasing attention for diagnosis and therapy of PDAC. However, these designs are mainly focused on the macroscopic tumor therapeutic effect, while the crucial nano-bio interactions in the heterogeneous microenvironment of PDAC remain poorly understood. As a result, the majority of potent nanomedicines show limited performance in ameliorating PDAC in clinical translation. Therefore, exploiting the unique nature of the PDAC by detecting potential biomarkers together with a deep understanding of nano-bio interactions that occur in the tumor microenvironment is pivotal to the design of PDAC-tailored effective nanomedicine. This review will introduce tailor-made nanomaterials-enabled laboratory tests and advanced noninvasive imaging technologies for early and accurate diagnosis of PDAC. Moreover, the fabrication of a myriad of tailor-made nanomaterials for various PDAC therapeutic modalities will be reviewed. Furthermore, much preferred theranostic multifunctional nanomaterials for imaging-guided therapies of PDAC will be elaborated. Lastly, the prospects of these nanomaterials in terms of clinical translation and potential breakthroughs will be briefly discussed.

Targeted Radiosensitizers for MR-Guided Radiation Therapy of Prostate Cancer

Adjuvant radiotherapy is frequently prescribed to treat cancer. To minimize radiation-related damage to healthy tissue, it requires high precision in tumor localization and radiation dose delivery. This can be achieved by MR guidance and targeted amplification of radiation dose selectively to tumors by using radiosensitizers. Here, we demonstrate prostate cancer-targeted gold nanoparticles (AuNPs) for MR-guided radiotherapy to improve the targeting precision and efficacy. By conjugating Gd(III) complexes and prostate-specific membrane antigen (PSMA) targeting ligands to AuNP surfaces, we found enhanced uptake of AuNPs by PSMA-expressing cancer cells with excellent MR contrast and radiation therapy outcome in vitro and in vivo. The AuNPs binding affinity and r₁ relaxivity were dramatically improved and the combination of Au and Gd(III)provided better tumor suppression after radiation. The precise tumor localization by MR and selective tumor targeting of the PSMA-1-targeted AuNPs could enable precise radiotherapy, reduction in irradiating dose, and minimization of healthy tissue damage.

Maximizing Magnetic Resonance Contrast in Gd(III) Nanoconjugates: Investigation of Proton Relaxation in Zirconium Metal-Organic Frameworks

Gadolinium(III) nanoconjugate contrast agents (CAs) provide significant advantages over small-molecule complexes for magnetic resonance imaging (MRI), namely increased Gd(III) payload and enhanced proton relaxation efficiency (relaxivity, r₁). Previous research has demonstrated that both the structure and surface chemistry of the nanomaterial substantially influence contrast. We hypothesized that inserting Gd(III) complexes in the pores of a metal-organic framework (MOF) might offer a unique strategy to further explore the parameters of nanomaterial structure and composition, which influence relaxivity. Herein, we postsynthetically incorporate Gd(III) complexes into Zr-MOFs using solvent-assisted ligand incorporation (SALI). Through the study of Zr-based MOFs, NU-1000 (nano and micronsize particles) and NU-901, we investigated the impact of particle size and pore shape on proton relaxivity. The SALI-functionalized Gd nano NU-1000 hybrid material displayed the highest loading of the Gd(III) complex (1.9 ± 0.1 complexes per node) and exhibited the most enhanced proton relaxivity (r₁ of 26 ± 1 mM^-1 s^-1 at 1.4 T). Based on nuclear magnetic relaxation dispersion (NMRD) analysis, we can attribute the performance of Gd nano NU-1000 to the nanoscale size of the MOF particles and larger pore size that allows for rapid water exchange. We have demonstrated that SALI is a promising method for incorporating Gd(III) complexes into MOF materials and identified crucial design parameters for the preparation of next generation Gd(III)-functionalized MOF MRI contrast agents.

Combined Magnetic Resonance Imaging and Photodynamic Therapy Using Polyfunctionalised Nanoparticles Bearing Robust Gadolinium Surface Units

A robust dithiocarbamate tether allows novel gadolinium units based on DOTAGA (q=1) to be attached to the surface of gold nanoparticles (2.6-4.1 nm diameter) along with functional units offering biocompatibility, targeting and photodynamic therapy. A dramatic increase in relaxivity (r₁ ) per Gd unit from 5.01 mm^-1  s^-1 in unbound form to 31.68 mm^-1  s^-1 (10 MHz, 37 °C) is observed when immobilised on the surface due to restricted rotation and enhanced rigidity of the Gd complex on the nanoparticle surface. The single-step synthetic route provides a straightforward and versatile way of preparing multifunctional gold nanoparticles, including examples with conjugated zinc-tetraphenylporphyrin photosensitizers. The lack of toxicity of these materials (MTT assays) is transformed on irradiation of HeLa cells for 30 minutes (PDT), leading to 75 % cell death. In addition to passive targeting, the inclusion of units capable of actively targeting overexpressed folate receptors illustrates the potential of these assemblies as targeted theranostic agents.

Gd(iii)-Pt(iv) theranostic contrast agents for tandem MR imaging and chemotherapy

Pt(iv) prodrugs have emerged as versatile therapeutics for addressing issues regarding off-target toxicity and the chemoresistance of classic Pt(ii) drugs such as cisplatin and carboplatin. There is significant potential for Pt(iv) complexes to be used as theranostic agents, yet there are currently no reported examples of Gd(iii)–Pt(iv) agents for simultaneous MR imaging and chemotherapy. Here we report the synthesis, characterization, and in vitro efficacy of two Gd(iii)–Pt(iv) agents, GP1 and GP2. Both agents are water soluble and stable under extracellularly relevant conditions but are reduced under intracellular conditions. Both are cytotoxic in multiple cancer cell lines, cell permeable, and significantly enhance the T₁-weighted MR contrast of multiple cell lines. Thus, GP1 and GP2 are promising agents for tandem MR imaging and chemotherapy and provide a versatile platform through which future Gd(iii)–Pt(iv) agents can be developed.

The first example of Gd(iii)–Pt(iv) theranostic agents that are intracellularly reduced to provide MR contrast enhancement with simultaneous Pt(ii) chemotherapy.

Dual Imaging Gold Nanoplatforms for Targeted Radiotheranostics

Gold nanoparticles (AuNPs) are interesting for the design of new cancer theranostic tools, mainly due to their biocompatibility, easy molecular vectorization, and good biological half-life. Herein, we report a gold nanoparticle platform as a bimodal imaging probe, capable of coordinating Gd³⁺ for Magnetic Resonance Imaging (MRI) and ⁶⁷Ga³⁺ for Single Photon Emission Computed Tomography (SPECT) imaging. Our AuNPs carry a bombesin analogue with affinity towards the gastrin releasing peptide receptor (GRPr), overexpressed in a variety of human cancer cells, namely PC3 prostate cancer cells. The potential of these multimodal imaging nanoconstructs was thoroughly investigated by the assessment of their magnetic properties, in vitro cellular uptake, biodistribution, and radiosensitisation assays. The relaxometric properties predict a potential T₁- and T₂- MRI application. The promising in vitro cellular uptake of ⁶⁷Ga/Gd-based bombesin containing particles was confirmed through biodistribution studies in tumor bearing mice, indicating their integrity and ability to target the GRPr. Radiosensitization studies revealed the therapeutic potential of the nanoparticles. Moreover, the DOTA chelating unit moiety versatility gives a high theranostic potential through the coordination of other therapeutically interesting radiometals. Altogether, our nanoparticles are interesting nanomaterial for theranostic application and as bimodal T₁- and T₂- MRI / SPECT imaging probes.

Gold nanomaterials functionalised with gadolinium chelates and their application in multimodal imaging and therapy

An overview of recent progress in the design of gadolinium-functionalised gold nanoparticles for use in MRI, multimodal imaging and theranostics.

Molecular Magnetic Resonance Imaging with Gd(III)-Based Contrast Agents: Challenges and Key Advances

In an era of personalized medicine, the clinical community has become increasingly focused on understanding diseases at the cellular and molecular levels. Magnetic resonance imaging (MRI) is a powerful imaging modality for acquiring anatomical and functional information. However, it has limited applications in the field of molecular imaging due to its low sensitivity. To expand the capability of MRI to encompass molecular imaging applications, we introduced bioresponsive Gd(III)-based magnetic resonance contrast agents (GBCAs) in 1997. Since that time, many research groups across the globe have developed new examples of bioresponsive GBCAs. These contrast agents have shown great promise for visualizing several biochemical processes, such as gene expression, neuronal signaling, and hormone secretion. They are designed to be conditionally retained, or activated, in vivo in response to specific biochemical events of interest. As a result, an observed MR signal change can serve as a read-out for molecular events. A significant challenge for these probes is how to utilize them for noninvasive diagnostic and theranostic applications. This Perspective focuses on the design strategies that underlie bioresponsive probes, and describes the key advances made in recent years that are facilitating their application in vivo and ultimately in clinical translation. While the field of bioresponsive agents is embryonic, it is clear that many solutions to the experimental and clinical radiologic problems of today will be overcome by the probes of tomorrow.

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.

Polyfunctionalised Nanoparticles Bearing Robust Gadolinium Surface Units for High Relaxivity Performance in MRI

The first example of an octadentate gadolinium unit based on DO3A (hydration number q=1) with a dithiocarbamate tether has been designed and attached to the surface of gold nanoparticles (around 4.4 nm in diameter). In addition to the superior robustness of this attachment, the restricted rotation of the Gd complex on the nanoparticle surface leads to a dramatic increase in relaxivity (r₁ ) from 4.0 mm^-1  s^-1 in unbound form to 34.3 mm^-1  s^-1 (at 10 MHz, 37 °C) and 22±2 mm^-1  s^-1 (at 63.87 MHz, 25 °C) when immobilised on the surface. The one-pot synthetic route provides a straightforward and versatile way of preparing a range of multifunctional gold nanoparticles. The incorporation of additional surface units for biocompatibility (PEG and thioglucose units) and targeting (folic acid) leads to little detrimental effect on the high relaxivity observed for these non-toxic multifunctional materials. In addition to the passive targeting attributed to gold nanoparticles, the inclusion of a unit capable of targeting the folate receptors overexpressed by cancer cells, such as HeLa cells, illustrates the potential of these assemblies.

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.

Zwitterionic Gadolinium(III)-Complexed Dendrimer-Entrapped Gold Nanoparticles for Enhanced Computed Tomography/Magnetic Resonance Imaging of Lung Cancer Metastasis

Design of dual mode or multimode contrast agents or nanoplatforms with antifouling properties is crucial for improved cancer diagnosis since the antifouling materials are able to escape the clearance of the reticuloendothelial system with improved pharmacokinetics. Herein, we present the creation of zwitterionic gadolinium(III) (Gd(III))-complexed dendrimer-entrapped gold nanoparticles (Au DEN) for enhanced dual mode computed tomography (CT)/magnetic resonance (MR) imaging of lung cancer metastasis. In the present work, poly(amidoamine) (PAMAM) dendrimers of generation 5 were partially decorated with carboxybetanie acrylamide (CBAA), 2-methacryloyloxyethyl phosphorylcholine (MPC), and 1,3-propane sultone (1,3-PS), respectively at different degrees, then used to entrap Au NPs within their interiors, and finally acetylated to cover their remaining amine termini. Through protein resistance, macrophage cellular uptake, and pharmacokinetics assays, we show that zwitterionic Au DEN modified with 1,3-PS exhibit the best antifouling property with the longest half-decay time (37.07 h) when compared to the CBAA- and MPC-modified Au DEN. Furthermore, with the optimized zwitterion type, we then prepared zwitterionic Gd(III)-loaded Au DEN modified with arginine-glycine-aspartic acid peptide for targeted dual mode CT/MR imaging of a lung cancer metastasis model. We disclose that the designed multifunctional Au DEN having an Au core size of 2.7 nm and a surface potential of 7.6 ± 0.9 mV display a good X-ray attenuation property, relatively high r₁ relaxivity (13.17 mM s^-1), acceptable cytocompatibility, and targeting specificity to α_vβ₃ integrin-expressing cancer cells and enable effective dual mode CT/MR imaging of a lung cancer metastasis model in vivo. The developed multifunctional zwitterion-functionalized Au DEN may be potentially adopted as an effective nanoprobe for enhanced dual-modal CT/MR imaging of other cancer types.

Multifunctional Magnetic Gold Nanomaterials for Cancer

The integration of multiple imaging and therapeutic agents into a customizable nanoplatform for accurate identification and rapid prevention of cancer is attracting great attention. Among the available theranostic nanosystems, magnetic gold nanoparticles are particularly promising as they exhibit unique physicochemical properties that can support multiple functions, including cancer diagnosis by magnetic resonance imaging, X-ray computed tomography, Raman and photoacoustic imaging, drug delivery, and plasmonic photothermal and photodynamic therapies. This review gives an overview of recent advances in the fabrication of multifunctional gold nanohybrids with magnetic and optical properties and their successful demonstration in multimodal imaging and therapy of cancer. Concerns around toxicity of these nanomaterials are also discussed in view of an imminent transition to clinical practice.

Current multifunctional albumin-based nanoplatforms for cancer multi-mode therapy

Albumin has been widely applied for rational design of drug delivery complexes as natural carriers in cancer therapy due to its distinct advantages of biocompatibility, abundance, low toxicity and versatile property. Hence, various types of multifunctional albumin-based nanoplatforms (MAlb-NPs) that adopt multiple imaging and therapeutic techniques have been developed for cancer diagnosis and treatment. Stimuli-responsive release, including reduction-sensitive, pH-responsive, concentration-dependent and photodynamic-triggered, is important to achieve low-toxicity cancer therapy. Several types of imaging techniques can synergistically improve the effectiveness of cancer therapy. Therefore, combinational theranostic is considered to be a prospective strategy to improve treatment efficiency, minimize side effects and reduce drug resistance, which has received tremendous attentions in recent years. In this review, we highlight several stimuli-responsive albumin nanoplatforms for combinational theranostic.

Recent advances in nanomaterial-based synergistic combination cancer immunotherapy

This review aims to summarize various synergistic combination cancer immunotherapy strategies based on nanomaterials.

Dy-DOTA integrated mesoporous silica nanoparticles as promising ultrahigh field magnetic resonance imaging contrast agents

Integrating Dy-DOTA motifs into mesoporous silica nanoparticle scaffolds generates remarkable ultrahigh field T2 relaxivities for a well-defined and tailorable contrast agent, attributed to enhanced Curie outer-sphere contributions as supported by simulation.

A Markedly Improved Synthetic Approach for the Preparation of Multifunctional Au-DNA Nanoparticle Conjugates Modified with Optical and MR Imaging Probes

We describe a new, and vastly superior approach for labeling spherical nucleic acid conjugates (SNAs) with diagnostic probes. SNAs have been shown to provide the unique ability to traverse the cell membrane and deliver surface conjugated DNA into cells while preserving the DNA from nuclease degradation. Our previous work on preparing diagnostically labeled SNAs was labor intensive, relatively low yielding, and costly. Here, we describe a straightforward and facile preparation for labeling SNAs with optical and MR imaging probes with significantly improved physical properties. The synthesis of Gd(III) labeled DNA Au nanoparticle conjugates is achieved by sequential conjugation of 3'-thiol-modified oligonucleotides and cofunctionalization of the particle surface with the subsequent addition of 1,2 diothiolate modified chelates of Gd(III) (abbreviated: DNA-Gd^III@AuNP). This new generation of SNA conjugates has a 2-fold increase of DNA labeling and a 1.4-fold increase in Gd(III) loading compared to published constructs. Furthermore, the relaxivity ( r₁) is observed to increase 4.5-fold compared to the molecular dithiolane-Gd(III) complex, and 1.4-fold increase relative to previous particle constructs where the Gd(III) complexes were conjugated to the oligonucleotides rather than directly to the Au particle. Importantly, this simplified approach (2 steps) exploits the advantages of previous Gd(III) labeled SNA platforms; however, this new approach is scalable and eliminates modification of DNA for attaching the contrast agent, and the particles exhibit improved cell labeling.

A tunable one-pot three-component synthesis of an125I and Gd-labelled star polymer nanoparticle for hybrid imaging with MRI and nuclear medicine

Bimodal radioiodine/Gd labelled polymeric nanoparticles prepared using a versatile one-step three-component click reaction.

Stable gadolinium based nanoscale lyophilized injection for enhanced MR angiography with efficient renal clearance

There is a great demand to develop high-relaxivity nanoscale contrast agents for magnetic resonance (MR) angiography with high resolution. However, there should be more focus on stability, ion leakage and excretion pathway of the intravenously injected nanoparticles, which are closely related to their clinic potentials. Herein, uniform ultrasmall-sized NaGdF₄ nanocrystal (sub-10 nm) was synthesized using a facile high temperature organic solution method, and the nanocrystals were modified by a ligand-exchange approach using PEG-PAA di-block copolymer. The PEG-PAA modified NaGdF₄ nanocrystal (denoted as ppNaGdF₄ nanocrystal) exhibited a high r₁ relaxivity which was twice of commercially used gadopentetate dimeglumine (Gd-DTPA) injection. MR angiography on rabbit using ppNaGdF₄ nanocrystal at a low dose showed enhanced vascular details and long circulation time. Lyophilized powder of ppNaGdF₄ nanocrystals have been successfully prepared without aggregation or reduction of MR performance, indicating the stability and an effective way to store this nanoscale contrast agent. No haemolysis was induced by ppNaGdF₄ nanocrystal, and an extremely low leakage of gadolinium ions was confirmed. Furthermore, efficient renal excretion was one of the clearance pathways of ppNaGdF₄ nanocrystal according to both the time dependent distribution data in blood and tissues and MR images. The in vivo toxicity evaluation further validated the great potential as a clinical agent for blood pool imaging.

BSA-Bioinspired Gadolinium Hybrid-Functionalized Hollow Gold Nanoshells for NIRF/PA/CT/MR Quadmodal Diagnostic Imaging-Guided Photothermal/Photodynamic Cancer Therapy

Multimodal imaging-guided synergistic therapy promises a more accurate diagnosis and higher therapeutic efficiency than single imaging modality or their simple "mechanical" combination. In this research, we have constructed an innovative multifunctional drug delivery platform by gadolinium (Gd)-based bovine serum albumin (BSA) hybrid-coated hollow gold nanoshells (Au@BSA-Gd). The obtained nanoparticles exhibited excellent photothermal effect and computed tomography (CT)/photoacoustic (PA) activity. Besides, the BSA-bioinspired gadolinium complex endowed the nanoparticles with an excellent T₁ contrast agent for magnetic resonance imaging (MRI). In addition, the near-infrared (NIR) absorbing phototherapeutic agent [indocyanine green (ICG)] was loaded into the Au@BSA-Gd nanoparticles because of their unique, hollow, and porous structures, thus possessing photodynamic/photothermal property and near-infrared fluorescence (NIRF)/PA imaging capability. As a result, a combined cancer therapy containing the photothermal therapy of Au@BSA-Gd and the synchronous photodynamic/photothermal therapy of ICG was constructed. Furthermore, the well-designed nanocomposites with multiple integrated modalities enabled them to be an ideal nanotheranostic agent for NIRF/PA/CT/MR quadmodal imaging. Therefore, the ICG-loaded albumin-bioinspired gadolinium hybrid-functionalized hollow gold nanoshells (ICG-Au@BSA-Gd) hold great promise as a theranostic platform for simultaneous therapeutic monitoring and precise cancer therapy.

Hydrodenticity to enhance relaxivity of gadolinium-DTPA within crosslinked hyaluronic acid nanoparticles

AIM

The efficacy of gadolinium (Gd) chelates as contrast agents for magnetic resonance imaging remains limited owing to poor relaxivity and toxic effects. Here, the effect of the hydration of the hydrogel structure on the relaxometric properties of Gd-DTPA is explained for the first time and called Hydrodenticity.

RESULTS

The ability to tune the hydrogel structure is proved through a microfluidic flow-focusing approach able to produce crosslinked hyaluronic acid nanoparticles, analyzed regarding the crosslink density and mesh size, and connected to the characteristic correlation times of the Gd-DTPA.

CONCLUSION

Hydrodenticity explains the boosting (12-times) of the Gd-DTPA relaxivity by tuning hydrogel structural parameters, potentially enabling the reduction of the administration dosage as approved for clinical use. [Formula: see text].

Renal Clearable Peptide Functionalized NaGdF4 Nanodots for High-Efficiency Tracking Orthotopic Colorectal Tumor in Mouse

The effective delivery of bioimaging probes to a selected cancerous tissue has extensive significance for biological studies and clinical investigations. Herein, the peptide functionalized NaGdF₄ nanodots (termed as, pPeptide-NaGdF₄ nanodots) have been prepared for highly efficient magnetic resonance imaging (MRI) of tumor by formation of Gd-phosphonate coordinate bonds among hydrophobic NaGdF₄ nanodots (4.2 nm in diameter) with mixed phosphorylated peptide ligands including a tumor targeting phosphopeptide and a cell penetrating phosphopeptide. The tumor targeting pPeptide-NaGdF₄ nanodots have paramagnetic property with ultrasmall hydrodynamic diameter (HD, c.a., 7.3 nm) which greatly improves their MRI contrast ability of tumor and facilitates renal clearance. In detail, the capability of the pPeptide-NaGdF₄ nanodots as high efficient contrast agent for in vivo MRI is evaluated successfully through tracking small drug induced orthotopic colorectal tumor (c.a., 195 mm³ in volume) in mouse.

Nitroxide-Based Macromolecular Contrast Agents with Unprecedented Transverse Relaxivity and Stability for Magnetic Resonance Imaging of Tumors

Metal-free magnetic resonance imaging (MRI) agents could overcome the established toxicity associated with metal-based agents in some patient populations and enable new modes of functional MRI in vivo. Herein, we report nitroxide-functionalized brush-arm star polymer organic radical contrast agents (BASP-ORCAs) that overcome the low contrast and poor in vivo stability associated with nitroxide-based MRI contrast agents. As a consequence of their unique nanoarchitectures, BASP-ORCAs possess per-nitroxide transverse relaxivities up to ∼44-fold greater than common nitroxides, exceptional stability in highly reducing environments, and low toxicity. These features combine to provide for accumulation of a sufficient concentration of BASP-ORCA in murine subcutaneous tumors up to 20 h following systemic administration such that MRI contrast on par with metal-based agents is observed. BASP-ORCAs are, to our knowledge, the first nitroxide MRI contrast agents capable of tumor imaging over long time periods using clinical high-field 1H MRI techniques.

Guiding Brain-Tumor Surgery via Blood-Brain-Barrier-Permeable Gold Nanoprobes with Acid-Triggered MRI/SERRS Signals

Surgical resection is a mainstay in the treatment of malignant brain tumors. Surgeons, however, face great challenges in distinguishing tumor margins due to their infiltrated nature. Here, a pair of gold nanoprobes that enter a brain tumor by crossing the blood-brain barrier is developed. The acidic tumor environment triggers their assembly with the concomitant activation of both magnetic resonance (MR) and surface-enhanced resonance Raman spectroscopy (SERRS) signals. While the bulky aggregates continuously trap into the tumor interstitium, the intact nanoprobes in normal brain tissue can be transported back into the blood stream in a timely manner. Experimental results show that physiological acidity triggers nanoparticle assembly by forming 3D spherical nanoclusters with remarkable MR and SERRS signal enhancements. The nanoprobes not only preoperatively define orthotopic glioblastoma xenografts by magnetic resonance imaging (MRI) with high sensitivity and durability in vivo, but also intraoperatively guide tumor excision with the assistance of a handheld Raman scanner. Microscopy studies verify the precisely demarcated tumor margin marked by the assembled nanoprobes. Taking advantage of the nanoprobes' rapid excretion rate and the extracellular acidification as a hallmark of solid tumors, these nanoprobes are promising in improving brain-tumor surgical outcome with high specificity, safety, and universality.

Spherical Polyelectrolyte Brushes as a Novel Platform for Paramagnetic Relaxation Enhancement and Passive Tumor Targeting

A novel platform for the development of highly efficient magnetic resonance imaging (MRI) contrast agents has been demonstrated. New contrast agents are designed and produced through electrostatic self-assembly of cationic gadolinium(III) complexes onto anionic spherical polyelectrolyte brushes (SPB). The structurally well-defined SPB are composed of polystyrene core and polyacrylic acid brush layer, where numerous binding sites and confined microenvironments are available for the embedment of the gadolinium(III) contrast agents. Both in vitro and in vivo experiments show excellent biocompatibility and relaxometric performance of these SPB-based gadolinium hybrid materials. The enhanced relaxivity value is up to 86.2 mM^-1 s^-1 per Gd, a remarkably high record value at 1.5 T magnetic field. In vivo imaging displays a prolonged blood circulation time and massive accumulation of the contrast agents at the tumor region due to the enhanced permeability and retention effect. The SPB-based gadolinium hybrid materials not only broaden the horizons of new MRI contrast agents, but also have a great potential for tumor diagnosis.

Oxygen Vacancy Enables Markedly Enhanced Magnetic Resonance Imaging-Guided Photothermal Therapy of a Gd3+-Doped Contrast Agent

Gd³⁺-based contrast agents (CAs) are the most prevailing and widely used for enhanced magnetic resonance imaging (MRI). Numbers of approaches have been developed to regulate the key parameters in order to obtain high-relaxivity CAs, according to the classic Solomon-Bloembergen-Morgen theory. Herein, a method of controlling oxygen vacancies in inorganic nanosized CAs has been developed for largely accelerated proton relaxation to obtain a high r₁ value. Such a strategy is verified on oxygen-deficient PEG-Na_xGdWO₃ nanorods, which exhibit a remarkable r₁ value up to 80 mM^-1 s^-1 (at 0.7 T) and a high r₁ value of 32.1 mM^-1 s^-1 on a clinical 3.0 T scanner, offering an excellent blood pool MRI performance at a low dose. Meanwhile, free electrons and/or oxygen-vacancy-induced small polarons can endow PEG-Na_xGdWO₃ nanorods with significant photothermal conversion for MRI-guided photothermal therapy.