Antimony Nanopolyhedrons with Tunable Localized Surface Plasmon Resonances for Highly Effective Photoacoustic-Imaging-Guided Synergistic Photothermal/Immunotherapy

NIR-IIb fluorescence antiangiogenesis copper nano-reaper for enhanced synergistic cancer therapy

The formation of blood vessel system under a relatively higher Cu2+ ion level is an indispensable precondition for tumor proliferation and migration, which was assisted in forming the tumor immune microenvironment. Herein, a copper ions nano-reaper (LMDFP) is rationally designed not only for chelating copper ions in tumors, but also for combination with photothermal therapy (PTT) to improve antitumor efficiency. Under 808 nm laser irradiation, the fabricated nano-reaper converts light energy into thermal energy to kill tumor cells and promotes the release of D-penicillamine (DPA) in LMDFP. Photothermal properties of LMDFP can cause tumor ablation in situ, which further induces immunogenic cell death (ICD) to promote systematic antitumor immunity. The released DPA exerts an anti-angiogenesis effect on the tumor through chelating copper ions, and inhibits the expression of programmed death ligand 1 (PD-L1), which synergizes with PTT to enhance antitumor immunity and inhibit tumor metastasis. Meanwhile, the nanoplatform can emit near-infrared-IIb (NIR-IIb) fluorescence under 980 nm excitation, which can be used to track the nano-reaper and determine the optimal time point for PTT. Thus, the fabricated nano-reaper shows powerful potential in inhibiting tumor growth and metastasis, and holds great promise for the application of copper nanochelator in precise tumor treatment.

PEI-Based Nanoparticles for Tumor Immunotherapy via In Situ Antigen-Capture Triggered by Photothermal Therapy

Activating a tumor antigen-specific immune response is key to the success of tumor immunotherapy and the development of personalized antitumor therapy. Nanocarriers can capture, enrich, and protect in situ produced tumor antigens due to immunogenic cell death (ICD), thus enhancing the tumor-specific immune response. Developing multifunctional nanocarriers that combine multiple antigen capturing mechanisms is crucial to the activation of tumor-specific immune responses. In this study, polyethylenimine (PEI) was employed as a main building block to construct a series of multifunctional indocyanine green (ICG)-loaded nanoparticles to capture antigens via multiple mechanisms: electrostatic interactions with PEI, hydrophobic interactions with the thermosensitive segment (POEGMA300), and covalent bonding with the pyridyl disulfide (PDS) groups, respectively. Their capacity of ICD induction, tumor antigen-capture, and antitumor immune responses were evaluated. Both the intrinsic toxicity of PEI and the ICG-mediated photothermal effect were responsible for inducing ICD. The positively charged PEI segment exhibited the best antigen-capturing ability via electrostatic interactions, promoted bone marrow-derived dendritic cell maturation and CD8+ T cell proliferation, and elicited antitumor immune responses in vivo. PDS groups bonded antigens covalently and significantly contributed to the suppression of distant tumor growth. Although the thermosensitive hydrophobic polymer segment did not contribute positively to antigen capture or tumor growth inhibition, NPs containing all of the functional modules prolonged the survival of tumor-bearing mice more than other treatments. This study provides more chemical insights into the design of polymer-based in situ nanovaccines against cancer.

Carbon-Encapsulated Magnetite Nanodoughnut as a NIR-II Responsive Nanozyme for Synergistic Chemodynamic-Photothermal Therapy

Magnetite-based nanozymes have attracted great interest for catalytic cancer therapy enabled by catalyzing hydrogen peroxide (H2 O2 ) to produce highly toxic hydroxyl radicals (•OH) to kill tumor cells. However, their therapeutic efficacies remain low due to insufficient •OH. Here, a light-responsive carbon-encapsulated magnetite nanodoughnuts (CEMNDs) with dual-catalytic activities for photothermal-enhanced chemodynamic therapy (CDT) is reported. The CEMNDs can accumulate in tumor and get into tumor cells and effectively act as peroxidase to convert H2 O2 to •OH that causes tumor cell death. The CEMNDs also possess intrinsic glutathione oxidase-like activity that which catalyzes the oxidation of reduced glutathione and produce lipid peroxidase for enhanced catalytic therapy. Furthermore, the CEMNDs can absorb 1064 nm light to elevate local temperature and increase release of Fe ions for photothermal therapy and enhanced CDT respectively. The in vivo experiments in an aggressive and drug-resistant metastatic mouse model of triple negative breast cancer model demonstrate excellent synergistic anti-tumor function and no measurable systemic toxicity of CEMNDs.

Cu3P/1-MT Nanocomposites Potentiated Photothermal-Immunotherapy

Purpose

Photothermal therapy (PTT) is a promising anticancer treatment that involves inducing thermal ablation and enhancing antitumor immune responses. However, it is difficult to completely eradicate tumor foci through thermal ablation alone. Additionally, the PTT elicited antitumor immune responses are often insufficient to prevent tumor recurrence or metastasis, due to the presence of an immunosuppressive microenvironment. Therefore, combining photothermal and immunotherapy is believed to be a more effective treatment approach as it can modulate the immune microenvironment and amplify the post-ablation immune response.

Methods

Herein, the indoleamine 2, 3-dioxygenase-1 inhibitors (1-MT) loaded copper (I) phosphide nanocomposites (Cu₃P/1-MT NPs) are prepared for PTT and immunotherapy. The thermal variations of the Cu₃P/1-MT NPs solution under different conditions were measured. The cellular cytotoxicity and immunogenic cell death (ICD) induction efficiency of Cu₃P/1-MT NPs were analyzed by cell counting kit-8 assay and flow cytometry in 4T1 cells. And the immune response and antitumor therapeutic efficacy of Cu₃P/1-MT NPs were evaluated in 4T1-tumor bearing mice.

Results

Even at low energy of laser irradiation, Cu₃P/1-MT NPs remarkably enhanced PTT efficacy and induced immunogenic tumor cell death. Particularly, the tumor-associated antigens (TAAs) could help promote the maturation of dendritic cells (DCs) and antigen presentation, which further activates infiltration of CD8⁺ T cells through synergistically inhibiting the indoleamine 2, 3-dioxygenase-1. Additionally, Cu₃P/1-MT NPs decreased the suppressive immune cells such as regulatory T cells (Tregs) and M2 macrophages, indicating an immune suppression modulation effect.

Conclusion

Cu₃P/1-MT nanocomposites with excellent photothermal conversion efficiency and immunomodulatory properties were prepared. In addition to enhanced the PTT efficacy and induced immunogenic tumor cell death, it also modulated the immunosuppressive microenvironment. Thereby, this study is expected to offer a practical and convenient approach to amplify the antitumor therapeutic efficiency with photothermal-immunotherapy.

Second Near-Infrared (NIR-II) Window for Imaging-Navigated Modulation of Brain Structure and Function

For a long time, optical imaging of the deep brain with high resolution has been a challenge. Recently, with the advance in second near-infrared (NIR-II) bioimaging techniques and imaging contrast agents, NIR-II window bioimaging has attracted great attention to monitoring deeper biological or pathophysiological processes with high signal-to-noise ratio (SNR) and spatiotemporal resolution. Assisted with NIR-II bioimaging, the modulation of structure and function of brain is promising to be noninvasive and more precise. Herein, in this review, first the advantage of NIR-II light in brain imaging from the interaction between NIR-II and tissue is elaborated. Then, several specific NIR-II bioimaging technologies are introduced, including NIR-II fluorescence imaging, multiphoton fluorescence imaging, and photoacoustic imaging. Furthermore, the corresponding contrast agents are summarized. Next, the application of various NIR-II bioimaging technologies in visualizing the characteristics of cerebrovascular network and monitoring the changes of the pathology signals will be presented. After that, the modulation of brain structure and function based on NIR-II bioimaging will be discussed, including treatment of glioblastoma, guidance of cell transplantation, and neuromodulation. In the end, future perspectives that would help improve the clinical translation of NIR-II light are proposed.

Inorganic Nanomaterials Used in Anti-Cancer Therapies:Further Developments

In this article, we provide an overview of the progress of scientists working to improve the quality of life of cancer patients. Among the known methods, cancer treatment methods focusing on the synergistic action of nanoparticles and nanocomposites have been proposed and described. The application of composite systems will allow precise delivery of therapeutic agents to cancer cells without systemic toxicity. The nanosystems described could be used as a high-efficiency photothermal therapy system by exploiting the properties of the individual nanoparticle components, including their magnetic, photothermal, complex, and bioactive properties. By combining the advantages of the individual components, it is possible to obtain a product that would be effective in cancer treatment. The use of nanomaterials to produce both drug carriers and those active substances with a direct anti-cancer effect has been extensively discussed. In this section, attention is paid to metallic nanoparticles, metal oxides, magnetic nanoparticles, and others. The use of complex compounds in biomedicine is also described. A group of compounds showing significant potential in anti-cancer therapies are natural compounds, which have also been discussed.

Antimonene: a tuneable post-graphene material for advanced applications in optoelectronics, catalysis, energy and biomedicine

The post-graphene era is undoubtedly marked by two-dimensional (2D) materials such as quasi-van der Waals antimonene. This emerging material has a fascinating structure, exhibits a pronounced chemical reactivity (in contrast to graphene), possesses outstanding electronic properties and has been postulated for a plethora of applications. However, chemistry and physics of antimonene remain in their infancy, but fortunately recent discoveries have shed light on its unmatched allotropy and rich chemical reactivity offering a myriad of unprecedented possibilities in terms of fundamental studies and applications. Indeed, antimonene can be considered as one of the most appealing post-graphene 2D materials reported to date, since its structure, properties and applications can be chemically engineered from the ground up (both using top-down and bottom-up approaches), offering an unprecedented level of control in the realm of 2D materials. In this review, we provide an in-depth analysis of the recent advances in the synthesis, characterization and applications of antimonene. First, we start with a general introduction to antimonene, and then we focus on its general chemistry, physical properties, characterization and synthetic strategies. We then perform a comprehensive study on the allotropy, the phase transition mechanisms, the oxidation behaviour and chemical functionalization. From a technological point of view, we further discuss the applications recently reported for antimonene in the fields of optoelectronics, catalysis, energy storage, cancer therapy and sensing. Finally, important aspects such as new scalable methodologies or the promising perspectives in biomedicine are discussed, pinpointing antimonene as a cutting-edge material of broad interest for researchers working in chemistry, physics, materials science and biomedicine.

Combined Cancer Immunotheranostic Nanomedicines: Delivery Technologies and Therapeutic Outcomes

Cancer is among the main causes of mortality all over the world. The delayed diagnosis is directly related to the decrease in survival rate. The use of immunotherapy has dramatically changed the treatment outcomes of different types of cancers. However, many patients still do not respond to immunotherapies, and many also suffer from severe immune-related side effects. Recent advances in the fields of nanomedicine bioengineering and in particular imaging offered new approaches which can enhance not only the safety but also the efficacy of immunotherapy. Theranostics has showed great progress as a branch of medicine which integrates both diagnosis and therapy in a single system. The outcomes from animal studies demonstrated an improvement in the diagnostic and immunotherapeutic potential of nanoparticles within the theranostic framework. Herein, we discuss the most recent developments in the application of nanotheranostics for combining tumor imaging and cancer immunotherapies.

Smartphone surface plasmon resonance imaging for the simultaneous and sensitive detection of acute kidney injury biomarkers with noninvasive urinalysis

A surface plasmon resonance imaging (SPRi) platform integrated with a smartphone was constructed for the simultaneous and sensitive detection of acute kidney injury (AKI) biomarkers. The smartphone SPRi platform was developed without the requirement of additional light and power sources. The LED flash of the smartphone was used as the light source for the excitation of surface plasmon resonance of a gold sensor chip based on the Kretschmann configuration, while the reflected light was collected by the camera of the smartphone. This smartphone SPRi system was conveniently fabricated by 3D printing and showed a sensitivity of 1.78 × 10^-5 refractive index unit (RIU). In addition, based on a magnetic nanoparticle-enhanced sandwich immunoassay, the smartphone SPRi system with a gold array chip was employed for the detection of multiple AKI biomarkers, with a low limit of detection (LOD) of 0.19 ng ml^-1, 0.51 ng ml^-1 and 0.7 ng ml^-1 for the simultaneous detection of neutrophil gelatinase-associated lipocalin (NGAL), interleukin-18 (IL-18) and retinol-binding protein (RBP) in urine, respectively. The biosensors demonstrated high specificity and sensitivity for the simultaneous detection of multiple AKI biomarkers in PBST and urine. The smartphone SPRi system provided a portable and cost-effective platform for point-of-care diagnosis, in-field healthcare and environmental monitoring.

Toroidal dipole-modulated dipole-dipole double-resonance in colloidal gold rod-cup nanocrystals for improved SERS and second-harmonic generation

Colloidal metal nanocrystals (NCs) show great potential in plasmon-enhanced spectroscopy owing to their attractive and structure-depended plasmonic properties. Herein, unique Au rod-cup NCs, where Au nanocups are embedded on the one or two ends of Au nanorods (NRs), are successfully prepared for the first time via a controllable wet-chemistry strategy. The Au rod-cup NCs possess multiple plasmon modes including transverse and longitudinal electric dipole (TED and LED), magnetic dipole (MD), and toroidal dipole (TD) modulated LED resonances, producing large extinction cross-section and huge near-field enhancements for plasmon-enhanced spectroscopy. Particularly, Au rod-cup NCs with two embedded cups show excellent surface-enhanced Raman spectroscopy (SERS) performance than Au NRs (75.6-fold enhancement excited at 633 nm) on detecting crystal violet owing to the strong electromagnetic hotspots synergistically induced by MD, LED, and TED-based plasmon coupling between Au cup and rod. Moreover, the strong TD-modulated dipole-dipole double-resonance and MD modes in Au rod-cup NCs bring a 37.3-fold enhancement of second-harmonic generation intensity compared with bare Au NRs, because they can efficiently harvest photoenergy at fundamental frequency and generate large near-field enhancements at second-harmonic wavelength. These findings provide a strategy for designing optical nanoantennas for plasmon-enhanced applications based on multiple plasmon modes.

ELECTRONIC SUPPLEMENTARY MATERIAL

Supplementary material (SEM image of Au rod-one-cup NCs; TEM image of Au/PbS hybrids; SEM image of Au rod-two-cup NCs; low-amplification SEM image of Au rod-two-cup NCs; experimental extinction and calculated electric field distributions of Au NR excited at different wavelengths; calculated absorption and scattering spectra of Au rod-one-cup NCs; schematic illustration of the cut plane and the corresponding magnetic field distribution under L3 excitation; Raman spectra of CV (10^-6 M) adsorbed on Au rod-cup NCs with different cup sizes; calculated magnetic field distribution of Au rodcup NCs excited at 532 and 633 nm; calculated electric field distributions of Au rod-one-cup NC excited at 600 nm along TE and LE; the models of Au rod-cup NCs used in the simulations) is available in the online version of this article at 10.1007/s12274-022-4562-5.

Chemodynamic and Photothermal Combination Therapy Based on Dual-Modified Metal-Organic Framework for Inducing Tumor Ferroptosis/Pyroptosis

Single therapy for tumor therapy always exerts limited ability for the constraints on the reaction condition and the unavoidable multidrug resistance, which seriously influences the therapy effect in the clinic. Herein, a combination treatment nanosystem (MP@PI) based on chemodynamic therapy (CDT) and photothermal therapy (PTT) is constructed for triggering ferroptosis/pyroptosis, which is the metal-organic framework (MOF) modified with polydopamine (PDA) and IR820 to loaded with piperlongumine (PL). The MOF and PL respectively served as the iron source and H₂O₂ source, performing chemodynamic therapy (CDT) for eliciting ferroptosis. Meanwhile the iron source induces pyroptosis in tumor cells. PDA is not only pH responsive to release PL but also CDT-assisted which due to PDA consumes the glutathione to decrease the expression of glutathione peroxide 4. The photosensitizer IR820 exerts photothermal effects under near-infrared light and further facilitates the ferroptosis/pyroptosis. In addation, the MP@PI nanoplatform evokes the immune response in vivo and enhances the antitumor effects further. Overall, MP@PI is a kind of promising cancer therapy strategy through CDT and PTT combination, inducing ferroptosis and pyroptosis.

Assembly of gold nanorods with L-cysteine reduced graphene oxide for highly efficient NIR-triggered photothermal therapy

Near-infrared (NIR) photothermal therapy is an effective partner to the chemotherapy of tumors with the merits of high therapeutic ability and slight side effect on normal tissues. Herein, we synthesized gold nanorods and assembled them with L-cysteine reduced graphene oxide (AuNR@Lcyst-rGO) for efficient photothermal therapy. The high therapeutic efficacy of AuNR@Lcyst-rGO can be due to the high photothermal effect of gold nanorods and reduced graphene oxide, and the synergistic effect of them. The nontoxicity of L-cysteine also guarantees the comfortable biocompatibility of reduced graphene oxide, which is essential for the photothermal absorber used in human tissue. The results demonstrate that assembly of gold nanorods with reduced graphene oxide (AuNR@Lcyst-rGO) is a promising photothermal agent with high efficient NIR-triggered photothermal therapy efficiency, excellent stability, superior biocompatibility.

Degradable mesoporous semimetal antimony nanospheres for near-infrared II multimodal theranostics

Metallic and semimetallic mesoporous frameworks are of great importance owing to their unique properties and broad applications. However, semimetallic mesoporous structures cannot be obtained by the traditional template-mediated strategies due to the inevitable hydrolytic reaction of semimetal compounds. Therefore, it is yet challenging to fabricate mesoporous semimetal nanostructures, not even mention controlling their pore sizes. Here we develop a facile and robust selective etching route to synthesize monodispersed mesoporous antimony nanospheres (MSbNSs). The pore sizes of MSbNSs are tunable by carefully controlling the partial oxidation of Sb nuclei and the selective etching of the as-formed Sb₂O₃. MSbNSs show a wide absorption from visible to second near-infrared (NIR-II) region. Moreover, PEGylated MSbNSs are degradable and the degradation mechanism is further explained. The NIR-II photothermal performance of MSbNSs is promising with a high photothermal conversion efficiency of ~44% and intensive NIR-II photoacoustic signal. MSbNSs show potential as multifunctional nanomedicines for NIR-II photoacoustic imaging guided synergistic photothermal/chemo therapy in vivo. Our selective etching process would contribute to the development of various semimetallic mesoporous structures and efficient multimodal nanoplatforms for theranostics.

2D antimonene-integrated composite nanomedicine for augmented low-temperature photonic tumor hyperthermia by reversing cell thermoresistance

The overexpression of heat shock proteins (HSPs) in tumor cells can activate inherent defense mechanisms during hyperthermia-based treatments, inducing thermoresistance and thus diminishing the treatment efficacy. Here, we report a distinct "non-inhibitor involvement" strategy to address this issue through engineering a calcium-based nanocatalyst (G/A@CaCO₃-PEG). The constructed nanocatalyst consists of calcium carbonate (CaCO₃)-supported glucose oxidase (GOD) and 2D antimonene quantum dots (AQDs), with further surface modification by lipid bilayers and polyethylene glycol (PEG). The engineered G/A@CaCO₃-PEG nanocatalyst features prolonged blood circulation, which is stable at neutral pH but rapidly degrades under mildly acidic tumor microenvironment, resulting in rapid release of drug cargo in the tumor microenvironment. The integrated GOD effectively catalyzes the depletion of glucose for reducing the supplies of adenosine triphosphate (ATP) and subsequent down-regulation of HSP expression. This effect then augments the therapeutic efficacy of photothermal hyperthermia induced by 2D AQDs upon irradiation with near-infrared light as assisted by reversing the cancer cells' thermoresistance. Consequently, synergistic antineoplastic effects can be achieved via low-temperature photothermal therapy. Systematic in vitro and in vivo evaluations have demonstrated that G/A@CaCO₃-PEG nanocatalysts feature potent antitumor activity with a high tumor-inhibition rate (83.92%). This work thus paves an effective way for augmenting the hyperthermia-based tumor treatments via restriction of the ATP supply.

An Activatable Probe with Aggregation-Induced Emission for Detecting and Imaging Herbal Medicine Induced Liver Injury with Optoacoustic Imaging and NIR-II Fluorescence Imaging

Whilte herbal medicines are widely used for health promotion and therapy for chronic conditions, inappropriate use of them may cause adverse effects like liver injury, and accurately evaluating their hepatotoxicity is of great significance for public health. Herein, an activatable probe QY-N for diagnosing herbal-medicine-induced liver injury by detecting hepatic NO with NIR-II fluorescence and multispectral optoacoustic tomography (MSOT) imaging is demonstrated. The probe includes a bismethoxyphenyl-amine-containing dihydroxanthene serving as electron donor, a quinolinium as electron acceptor, and a butylamine as recognition group and fluorescence quencher. The hepatic level of NO reacts with butylamine, thereby generating the activated probe QY-NO which exhibits a red-shifted absorption band (700-850 nm) for optoacoustic imaging and generates strong emission (910-1110 nm) for NIR-II fluorescence imaging. QY-NO is aggregation-induced-emission (AIE) active, which ensures strong emission in aggregated state. QY-N is utilized in the triptolide-induced liver injury mouse model, and experimental results demonstrate the QY-N can be activated by hepatic NO and thus be used in detecting herbal-medicine-induced liver injury. The temporal and spatial information provided by three-dimensional MSOT images well delineates the site and size of liver injury. Moreover, QY-N has also been employed to monitor rehabilitation of liver injury during treatment process.

Development of Nickel Selenide@polydopamine Nanocomposites for Magnetic Resonance Imaging Guided NIR-II Photothermal Therapy

The penetration depth of near-infrared laser has greatly restricted the development of most photothermal agents. Recently, photothermal agents in the second near-infrared (NIR-II) window have drawn great attention as they can overcome above barrier. Herein, a novel "all in one" NIR-II responsive nanoplatform (nickel selenide @polydopamine nanocomposites, NiSe@PDA NCs) based on in situ coating the polydopamine (PDA) on the surface of biomineralized nickel selenide nanoparticles (NiSe NPs) for dual-model imaging-guided photothermal therapy is reported. Under the illumination of NIR-II laser (1064 nm), the photothermal conversion efficiency of NiSe@PDA NCs can reach 48.4%, which is higher than that of single NiSe NPs due to the enhanced molar extinction coefficient. In addition, because of the paramagnetic effect of NiSe NPs, the constructed NiSe@PDA NCs can be acted as T₁ contrast agent for magnetic resonance imaging (MRI). Most importantly, the MRI contrast effect is enhanced with the coating of PDA layer due to the loose structure of PDA. Ultimately, both in vitro and in vivo experiments demonstrate that the developed NCs can achieve efficient MRI-guided photothermal therapy for treating malignant tumor. Therefore, the designed NiSe@PDA NCs with excellent features show great potential for clinical MRI-guided cancer therapy.

Emerging two-dimensional monoelemental materials (Xenes): Fabrication, modification, and applications thereof in the field of bioimaging as nanocarriers

In recent years, more and more research enthusiasm has been devoted to the development of emerging two-dimensional (2D) monoelement materials (Xenes) and explored potential applications in various fields, especially biomedicine and bioimaging. The inspiring results attribute to their excellent physicochemical properties, including adjustable band gap, surface electronic layout characteristics, and so on, making it easier for surface modification in order to meet designated needs. As a popular interdisciplinary research frontier, a variety of methods for fabricating 2D Xenes have recently been adopted for pre-preparing future practical bioimaging applications, which implies that these materials will have broad clinical application prospects in the future. In this review, we will concentrate on the family of 2D Xenes and summarize their fabrication and modification methods firstly. Then, their applications in bioimaging as nanocarriers will be described according to the Periodic Table of Elements. In addition, current challenges and prospects for further clinical applications will be under discussion and use black phosphorus as a typical example. At last, general conclusion will be made that it is worth expecting that 2D Xenes will play a key role in the next generation of oncologic bioimaging in the future. This article is categorized under: Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease Toxicology and Regulatory Issues in Nanomedicine > Toxicology of Nanomaterials Toxicology and Regulatory Issues in Nanomedicine > Regulatory and Policy Issues in Nanomedicine.

A high-contrast photoacoustic agent with near-infrared emission

Benzobisthiadiazole as a typical electron acceptor, has been widely used to design fluorescent dyes and photoacoustic (PA) agents. With the strategy of constructing donor-acceptor-donor (D-A-D) type of electron characteristics, benzobisthiadiazole derivatives tend to behave stable in near-infrared absorption and emission, which is beneficial to PA imaging. In this chapter, two molecular design strategies are combined to improve the photoacoustic imaging effects of new PA contrast agent IR-1302 NPs, by installing strengthened conjugated bridges and electron donors. The nanoparticles exhibit high-contrast noninvasive photoacoustic imaging in tumor models with longer wavelength absorption and emission and show potential as a clinic contrast agent.