HER2-targeting two-dimensional black phosphorus as a nanoplatform for chemo-photothermal therapy in breast cancer.

Trastuzumab (Tmab) targeted therapy or its combination with chemotherapy is normally insufficient to elicit a comprehensive therapeutic response owing to the inherent or acquired drug resistance and systemic toxicity observed in highly invasive HER2-positive breast cancer. In this study, we propose a novel approach that integrates photothermal therapy (PTT) with targeted therapy and chemotherapy, thereby achieving additive or synergistic therapeutic outcomes. We utilize PEGylated two-dimensional black phosphorus (2D BP) as a nanoplatform and photothermal agent to load chemotherapeutic drug mitoxantrone (MTO) and conjugate with Tmab (BP-PEG-MTO-Tmab). The in vitro and in vivo experiments demonstrated that the HER2-targeting BP-PEG-MTO-Tmab complexes exhibited desirable biocompatibility, safety and enhanced cancer cell uptake efficiency, resulting in increased accumulation and prolonged retention of BP and MTO within tumors. Consequently, the complex improved photothermal and chemotherapy treatment efficacy in HER2-positive cells in vitro and a subcutaneous tumor model in vivo, while minimized harm to normal cells and showed desirable organ compatibility. Collectively, our study provides compelling evidence for the remarkable efficacy of targeted and synergistic chemo-photothermal therapy utilizing all-in-one nanoparticles as a delivery system for BP and chemotherapeutic drug in HER2-positive breast cancer.

Three-Dimensional Printing Enabled Droplet Microfluidic Device for Real-Time Monitoring of Single-Cell Viability and Blebbing Activity.

Droplet-based microfluidics with the characteristics of high throughput, low sample consumption, increasing reaction speed, and homogeneous volume control have been demonstrated as a useful platform for biomedical research and applications. The traditional fabrication methods of droplet microfluidics largely rely on expensive instruments, sophisticated operations, and even the requirement of an ultraclean room. In this manuscript, we present a 3D printing-based droplet microfluidic system with a specifically designed microstructure for droplet generation aimed at developing a more accessible and cost-effective method. The performance of droplet generation and the encapsulation capacity of the setup were examined. The device was further applied to measure the variation in cell viability over time and monitor the cell's blebbing activity to investigate its potential ability and feasibility for single-cell analysis. The result demonstrated that the produced droplets remained stable enough to enable the long-time detection of cell viability. Additionally, cell membrane protrusions featuring the life cycle of bleb initiation, expansion, and retraction can be well-observed. Three-dimensional printing-based droplet microfluidics benefit from the ease of manufacture, which is expected to simplify the fabrication of microfluidics and expand the application of the droplet approach in biomedical fields.

Facile Synthesis of Basic Copper Carbonate Nanosheets for Photoacoustic Imaging-Guided Tumor Apoptosis and Ferroptosis and the Extension Exploration of the Synthesis Method.

Elimination of tumor cells using carbonate nanomaterials with tumor microenvironment-responsive capacity has been explored as an effective strategy. However, their therapeutic outcomes are always compromised by the relatively low intratumoral accumulation and limited synthesis method. Herein, a novel kind of basic copper carbonate nanosheets was designed and prepared using a green synthesis method for photoacoustic imaging-guided tumor apoptosis and ferroptosis therapy. These nanosheets were synthesized with the assistance of dopamine and ammonium bicarbonate (NH4HCO3) and the loading of glucose oxidase (GOx). NH4HCO3 could not only provide an alkaline environment for the polymerization of dopamine but also supply carbonates for the growth of nanosheets. The formed nanosheets displayed good acid and near-infrared light responsiveness. After intercellular uptake, they could be degraded to release Cu2+ and GOx, generating hydroxyl radicals through a Cu+-mediated Fenton-like reaction, consuming glucose, up-regulating H2O2 levels, and down-regulating GSH levels. Tumor elimination could be achieved by hydroxyl radical-induced apoptosis and ferroptosis. More amusingly, this synthesis method can be extended to several kinds of mono-element and multi-element carbonate nanomaterials (e.g., Fe, Mn, and Co), showing great potential for further tumor theranostics.

Evaluation of stability and antitumor activity of two-dimensional black phosphorus modified with positively charged protein.

Two-dimensional black phosphorus (2D BP), a novel 2D photoelectric material with excellent near-infrared optical absorption, biocompatibility, and degradability, has shown enormous potential in biomedical field. However, under the action of light, oxygen and water, 2D BP is easily degraded to phosphate and phosphonate. In this work, trastuzumab (Tmab) as a positively charged protein was used to modify 2D BP through electrostatic interaction to form BP-Tmab. The Tmab layer on the surface of 2D BP can effectively protect BP from water, which significantly enhanced the water stability of BP. PEGylated 2D BP (BP-PEG) as a control was also prepared. After 7 days in air-exposed water, the attenuation value of BP-Tmab was only 6.62 ± 2.72% at room temperature, which was much lower than that of naked 2D BP (52.47 ± 2.26%) and BP-PEG (25.84 ± 2.80%) under the same conditions. The result was further confirmed by the temperature changes at different time points under laser irradiation, suggesting that the degradation of BP was effectively reduced by Tmab modification. In addition, BP-Tmab displayed satisfactory biocompatibility and can effectively destroy cancer cells under laser irradiation, showing an excellent photothermal therapy effect.

Repolarizing tumor-associated macrophages by layered double hydroxide-based deacidification agent for tumor chemodynamic therapy and immunotherapy.

Tumor-associated macrophages (TAMs)-mediated immunotherapy has attracted extensive attention in tumor elimination. However, the acidic tumor microenvironment (TME) severely limits the phenotype of TAMs to pro-tumoral M2 state, suppressing immune response efficacy against tumors. Herein, novel poly(acrylic acid) (PAA)-coated, doxorubicin (DOX)-loaded layered double hydroxide (LDH) nanosheets (NSs) were developed as deacidification agent to repolarize TAMs from pro-tumoral M2 to anti-tumoral M1 phenotype for tumor elimination through combined chemodynamic therapy and immunotherapy. When located in tumor regions, LDH-PAA@DOX NSs display good deacidification capacity to neutralize acidic TME, achieving the repolarization of TAMs to M1 phenotype and further activating CD8+ T cells. During the deacidification process, these NSs are acid-responsive and degrade to release Fe3+ and DOX. The former can be reduced to Fe2+ by intracellular glutathione, meanwhile disrupting the antioxidant defense system of tumor cells. The latter can damage tumor cells directly and further stimulate the production of hydrogen peroxide, providing abundant substrate for the Fenton reaction. Toxic hydroxyl radical is excessively produced through Fe2+-mediated Fenton reaction to cause intratumoral oxidative stress. In vivo data revealed that significant tumor elimination can be achieved under LDH-PAA@DOX treatment. This work not only provides a promising paradigm for neutralizing acidic TME using deacidification agent but also highlights the effectiveness of combined chemodynamic therapy and immunotherapy in tumor treatment.

CD146 interaction with integrin ß1 activates LATS1-YAP signaling and induces radiation-resistance in breast cancer cells.

Radiotherapy is an indispensable modality in comprehensive treatment of breast cancer. However, inherent or acquired radiation resistance of tumors compromises the efficacy of radiotherapy. Herein, we found that CD146, a unique epithelial-to-mesenchymal transition (EMT) inducer particularly highly expressed in triple-negative breast cancer (TNBC), is dramatically induced by ionizing irradiation. Further study demonstrates that CD146 promotes tumor cell radioresistance in vitro and in vivo. Specifically, we report the underlying mechanism that CD146 activates YAP protein, and drives its relocation from plasma to nucleus by regulating LATS1, and promoting abnormal DNA damage repair, as well as inducing EMT and stemness. Moreover, CD146 can form a novel co-receptor complex with integrin ß1 and induces radiation-resistance in breast cancer. Dual inhibition of CD146 and integrin ß1 activity had a stronger inhibitory effect on breast cancer tumor growth and synergistically increased their sensitivity to radiotherapy. This study identifies a unique function of CD146 implicates with integrin ß1 and YAP signaling, contributing to radiation resistance. Targeted therapy against CD146 or inhibition of integrin ß1 is a potential strategy to overcome radiotherapeutic resistance of breast cancer.

Efficient Capture and Separation of Cancer Cells Using Hyaluronic Acid-Modified Magnetic Beads in a Microfluidic Chip.

The efficient isolation and specific discrimination of circulating tumor cells (CTCs) is expected to provide valuable information for understanding tumor metastasis and play an important role in the treatment of cancer patients. In this study, we developed a novel and rapid method for efficient capture and specific identification of cancer cells using hyaluronic acid (HA)-modified SiO2-coated magnetic beads in a microfluidic chip. First, polyacrylamide-surfaced SiO2-coated magnetic beads (SiO2@MBs) were covalently conjugated with HA, and the created HA-modified SiO2@MBs (HA-SiO2@MBs) display binding specificity to HeLa cells (a human cervical carcinoma cell line) overexpressing CD44 receptors. After incubating the HA-SiO2@MBs with cancer cells for 1 h, the mixture of MBs and cells was drawn into a designed microfluidic channel with two inlets and outlets. Through the formation of lamellar flow, cells specifically bound with the HA-SiO2@MBs can be separated under an external magnetic field with a capture efficiency of up to 92.0%. The developed method is simple, fast, and promising for CTC separation and cancer diagnostics applications.

Antitumor Efficacy of Doxorubicin-Loaded Electrospun Attapulgite-Poly(lactic-co-glycolic acid) Composite Nanofibers.

Currently, cancer chemotherapeutic drugs still have the defects of high toxicity and low bioavailability, so it is critical to design novel drug release systems for cancer chemotherapy. Here, we report a method to fabricate electrospun drug-loaded organic/inorganic hybrid nanofibrous system for antitumor therapy applications. In this work, rod-like attapulgite (ATT) was utilized to load a model anticancer drug doxorubicin (DOX), and mixed with poly(lactic-co-glycolic acid) (PLGA) to form electrospun hybrid nanofibers. The ATT/DOX/PLGA composite nanofibers were characterized through various techniques. It is feasible to load DOX onto ATT surfaces, and the ATT/DOX/PLGA nanofibers show a smooth and uniform morphology with improved mechanical durability. Under neutral and acidic pH conditions, the loaded DOX was released from ATT/DOX/PLGA nanofibers in a sustained manner. In addition, the released DOX from the nanofibers could significantly inhibit the growth of tumor cells. Owing to the significantly reduced burst release profile and increased mechanical durability of the ATT/DOX/PLGA nanofibers, the designed organic-inorganic hybrid nanofibers may hold great promise as a nanoplatform to encapsulate different drugs for enhanced local tumor therapy applications.

Iron oxide nanoparticles as a drug carrier reduce host immunosuppression for enhanced chemotherapy.

Chemotherapy is still regarded as the main modality for cancer treatment. However, it often suppresses the host immune system, resulting in limited therapeutic effects. It is desirable to design a novel chemotherapeutic agent to reduce the level of immunosuppression. Herein, we designed bovine serum albumin (BSA)-bioinspired iron oxide nanoparticles (IONPs) as a nanocarrier to load anticancer drug mitoxantrone (MTX) for enhanced chemotherapy of orthotopic breast cancer. The treatment with IONPs@BSA-MTX complexes increased CD3+CD4+ and CD3+CD8+ T lymphocytes more than free MTX. The complexes effectively restored the host immune system and exhibited a better anticancer efficacy than free MTX. It was worth noting that the BSA-inspired IONPs were a satisfactory contrast agent for magnetic resonance imaging of tumors and lymph nodes. Our work provides a novel strategy for enhanced chemotherapy with low levels of immunosuppression in the treatment of breast cancer and other cancers.

Polyethyleneimine-Based Drug Delivery Systems for Cancer Theranostics.

With the development of nanotechnology, various types of polymer-based drug delivery systems have been designed for biomedical applications. Polymer-based drug delivery systems with desirable biocompatibility can be efficiently delivered to tumor sites with passive or targeted effects and combined with other therapeutic and imaging agents for cancer theranostics. As an effective vehicle for drug and gene delivery, polyethyleneimine (PEI) has been extensively studied due to its rich surface amines and excellent water solubility. In this work, we summarize the surface modifications of PEI to enhance biocompatibility and functionalization. Additionally, the synthesis of PEI-based nanoparticles is discussed. We further review the applications of PEI-based drug delivery systems in cancer treatment, cancer imaging, and cancer theranostics. Finally, we thoroughly consider the outlook and challenges relating to PEI-based drug delivery systems.

Colorimetric detection of Cr3+ ions in aqueous solution using poly(γ-glutamic acid)-stabilized gold nanoparticles.

Detection of heavy metal ions in water is of paramount significance for environmental pollution control. Here, we report the use of γ-polyglutamic acid (γ-PGA)-stabilized gold nanoparticles (γ-PGA-Au NPs) as a probe to sense trivalent chromium (Cr3+) in aqueous solution. In our study, γ-PGA-Au NPs were first formed through one-step sodium borohydride reduction of Au salt in the presence of γ-PGA. The formed γ-PGA-Au NPs with a mean particle size of 4.6 nm show desirable colloidal stability and a significant color change from wine red to gray after exposure to Cr3+ ions, which is visible to the naked eye and easily detected by colorimetric assay using UV-vis spectrometry. The limit of detection of Cr3+ ions is 100 ppb by the naked eye and 0.2 ppb by UV-vis spectroscopy, respectively. We further show that the detection of Cr3+ using γ-PGA-Au NPs has excellent selectivity, and the recovery percentage is higher than 82% for different water samples such as lake water, river water, tap water or mineral water. Our study demonstrates that γ-PGA-Au NPs can be utilized as an efficient probe for colorimetric sensing of Cr3+ ions in a water environment.

Biodegradable pH-responsive amorphous calcium carbonate nanoparticles as immunoadjuvants for multimodal imaging and enhanced photoimmunotherapy.

Development of bioresponsive theranostic nanoparticles to enhance cancer diagnostics and control cancer metastasis is highly desirable. In this study, we developed such a bioresponsive theranostic nanoparticle for synergistic photoimmunotherapy. In particular, these nanoparticles were constructed by embedding indocyanine green (ICG) into Mn2+-doped amorphous calcium carbonate (ACC(Mn)) nanoparticles, followed by loading of the Toll-like-receptor-7 agonist imiquimod (IMQ). The IMQ@ACC(Mn)-ICG/PEG nanoparticles respond to the acidic pH of the tumor microenvironment (TME) and co-deliver ICG and IMQ into the tumor. Selective phototherapy was achieved upon activation using a near-infrared laser. In the presence of IMQ and arising from phototherapeutically treated tumor cells, tumor-associated antigens give rise to a strong antitumor immune response. Reversal of the immunosuppressive TME via H+ scavenging of the tumor through ACC nanoparticles effectively inhibits tumor metastases. Moreover, the combination of ICG and Mn2+ also serves as an advanced contrast agent for cancer multimode imaging. Overall, these bioresponsive nanoparticles provide a promising approach for cancer theranostics with promising potential for future clinical translation.

Immunologically modified MnFe2O4 nanoparticles to synergize photothermal therapy and immunotherapy for cancer treatment.

Immunotherapy has been a promising candidate for cancer treatment. The combination of photothermal therapy (PTT) and immunotherapy have shown to cause tumor ablation and induce host immune response. However, this strategy is often hampered by a limited immune response and undesirable immunosuppression. In this work, we developed an immunologically modified nanoplatform, using ovalbumin (OVA)-coated PEGylated MnFe2O4 nanoparticles (NPs) loaded with R837 immunoadjuvant (R837-OVA-PEG-MnFe2O4 NPs) to synergize PTT and immunotherapy for the treatment of breast cancer. The designed R837-OVA-PEG-MnFe2O4 NPs are able to elicit significant immune responses in vitro and in vivo. MnFe2O4 NPs also allowed for a reduction of systemic immunosuppression through downregulation of M2-associated cytokines. More importantly, the R837-OVA-PEG-MnFe2O4 NPs under laser irradiation effectively inhibited tumor growth and prevented lung metastases, leading to a prolonged survival time and improved survival rate. In addition, the designed multitasking MnFe2O4 NPs showed as a good contrast agent for magnetic resonance (MR) imaging to detect orthotopic breast tumor in vivo. Our work provides a novel strategy for combined PTT and improved immunotherapy in the treatment of breast and other metastatic cancers.

Sharpening upconversion nanoparticles to reduce surface quenching.

Lanthanide-doped upconversion nanocrystals with different surface sharpness properties were synthesized to study the effects of surface sharpness on optical performance. Nanocrystals with hexagonal sharp surfaces showed a significant reduction in the number of surface defects and increased the luminescence intensity by 2.5 times compared to nanocrystals with spherical surfaces.

PEGylated reduced-graphene oxide hybridized with Fe3O4 nanoparticles for cancer photothermal-immunotherapy.

Photoimmunotherapy has attracted much attention recently for the treatment of metastatic tumors. The development of smart nanocomposites for imaging-guided therapies is needed to improve the efficacy of cancer treatment. Herein, a PEGylated nanocomposite was developed for photothermal-immunotherapy. In particular, this nanocomposite was formulated by hybridizing Fe3O4 nanoparticles (FNPs) with reduced-graphene oxide (rGO) through electrostatic interaction, modified by PEG-NH2 on the surface of FNPs/rGO. The FNPs/rGO-PEG nanocomposites are excellent agents for photothermal therapy (PTT) under irradiation by an 805 nm laser. This nanocomposite could promote the activity of the host antitumor immune response efficiently because of the reduction of tumor-associated macrophages by the incorporation of FNPs. In our experiments, we observed FNPs/rGO-PEG based PTT induced immunogenic cell death accompanied by the release of danger-associated molecular patterns. We also found that FNPs/rGO-PEG + laser irradiation of animal tumors could activate dendritic cells (DCs) in tumor draining lymph nodes. In vivo antitumor studies revealed that FNPs/rGO-PEG nanocomposites, when combined with laser irradiation, could result in desirable photothermal effects and destroy primary tumors. Moreover, intratumoral injection of FNPs/rGO-PEG nanocomposites into 4T1 orthotopic mouse breast tumors, in combination with near-infrared laser irradiation, significantly increased the median survival time of tumor-bearing animals. FNPs/rGO-PEG nanocomposites could also be used for magnetic resonance imaging, which may lead to a MRI-guided photothermal-immunotherapy for metastatic cancers. This study could lead to a cancer treatment strategy that combines PTT with immunotherapies using FNPs/rGO-PEG nanocomposites.

NIR-Triggered Phototherapy and Immunotherapy via an Antigen-Capturing Nanoplatform for Metastatic Cancer Treatment.

Combined phototherapy and immunotherapy demonstrates strong potential in the treatment of metastatic cancers. An upconversion nanoparticle (UCNP) based antigen-capturing nanoplatform is designed to synergize phototherapies and immunotherapy. In particular, this nanoplatform is constructed via self-assembly of DSPE-PEG-maleimide and indocyanine green (ICG) onto UCNPs, followed by loading of the photosensitizer rose bengal (RB). ICG significantly enhances the RB-based photodynamic therapy efficiency of UCNP/ICG/RB-mal upon activation by a near-infrared (NIR) laser, simultaneously achieving selective photothermal therapy. Most importantly, tumor-derived protein antigens, arising from phototherapy-treated tumor cells, can be captured and retained in situ, due to the functionality of maleimide, which further enhance the tumor antigen uptake and presentation by antigen-presenting cells. The synergized photothermal, photodynamic, and immunological effects using light-activated UCNP/ICG/RB-mal induces a tumor-specific immune response. In the experiments, intratumoral administration of UCNP/ICG/RB-mal, followed by noninvasive irradiation with an NIR laser, destroys primary tumors and inhibits untreated distant tumors, using a poorly immunogenic, highly metastatic 4T1 mammary tumor model. With the simultaneous use of anti-CTLA-4, about 84% of the treated tumor-bearing mice achieve long-term survival and 34% of mice develop tumor-specific immunity. Overall, this antigen-capturing nanoplatform provides a promising approach for the treatment of metastatic cancers.

Zwitterionic Polydopamine-Coated Manganese Oxide Nanoparticles with Ultrahigh Longitudinal Relaxivity for Tumor-Targeted MR Imaging.

We present the design of antifouling zwitterion-functionalized manganese oxide (Mn3O4) nanoparticles (NPs) modified with folic acid (FA) for targeted tumor magnetic resonance (MR) imaging. In the current work, diethylene glycol-stabilized Mn3O4 NPs were initially prepared via a solvothermal approach, coated with polydopamine (PDA), fluorescently labeled with rhodamine B, conjugated with FA via amide bond formation, and finally covered with zwitterions of l-lysine (Lys). The thus-generated multifunctional Mn3O4 NPs display excellent water dispersibility and colloidal stability, good protein resistance ability, and desirable cytocompatibility. With the PDA and Lys modifications, the multifunctional Mn3O4 NPs own an ultrahigh r1 relaxivity (89.30 mM-1 s-1) and enable targeted tumor MR imaging, owing to the linked FA ligands. The designed antifouling zwitterion-functionalized Mn3O4 NPs may be employed as an excellent MR contrast agent for targeted MR imaging of other biological systems.

Enhanced photocatalytic performance of Ag/TiO2 nanohybrid sensitized by black phosphorus nanosheets in visible and near-infrared light.

The efficient utilization of solar energy for environmental cleaning has attracted great attention, where the key is to efficiently harvest the visible and near-infrared (NIR) light which occupies approximately 95% of the solar light energy. Recently, black phosphorus (BP), as a new staring 2D material, has been extensively studied as photocatalytic materials due to its broad light absorption and tunable bandgap. Herein, we report a novel ternary nanocomposite, BP-Ag/TiO2, prepared through controlled deposition of Ag clusters on the surface of TiO2 nanocrystals and then incorporated to BP nanosheets. The BP-Ag/TiO2 nanocomposite has shown excellent photocatalytic activity towards the degradation of methylene blue (MB) under visible and NIR light irradiation. About 100% and even 25% of MB was degraded in 85 min under >420 nm and >780 nm irradiation, respectively. The enhanced photocatalytic activity of BP-Ag/TiO2 nanocomposite was mainly ascribed to the sensitization of BP nanosheets by fully harvest of solar light and high electron-hole separation efficiency. We believe that the BP-Ag/TiO2 nanocomposite will be an effective photofunctional material in full-spectrum solar energy conversion and opens up a new door for the development of solar light driven photocatalysts for the remediation of environmental pollution.

BSA-bioinspired gold nanorods loaded with immunoadjuvant for the treatment of melanoma by combined photothermal therapy and immunotherapy.

The development of therapeutic methods that can effectively delay tumor growth, inhibit tumor metastases, and protect the host from tumor recurrence still faces challenges. Nanoparticle-based combination therapy may provide an effective therapeutic strategy. Herein, we show that bovine serum albumin (BSA)-bioinspired gold nanorods (GNRs) were loaded with an immunoadjuvant for combined photothermal therapy (PTT) and immunotherapy for the treatment of melanoma. In this work, cetyltrimethylammonium bromide (CTAB)-coated GNRs were successively decorated with polyethylene glycol (PEG) and BSA, and loaded with an immunoadjuvant imiquimod (R837). The synthesized mPEG-GNRs@BSA/R837 nanocomplexes under near-infrared (NIR) irradiation could effectively kill tumors and trigger strong immune responses in treating metastatic melanoma in mice. Furthermore, the nanocomplex-based PTT prevented lung metastasis and induced a strong long-term antitumor immunity to protect the treated mice from tumor recurrence. The nanocomplex-based PTT in combination with immunotherapy may be potentially employed as an effective strategy for the treatment of melanoma and other metastatic cancers.

Acetylated Polyethylenimine-Entrapped Gold Nanoparticles Enable Negative Computed Tomography Imaging of Orthotopic Hepatic Carcinoma.

Developing an effective computed tomography (CT) contrast agent is still a challenging task for precise diagnosis of hepatic carcinoma (HCC). Here, we present the use of acetylated polyethylenimine (PEI)-entrapped gold nanoparticles (Ac-PE-AuNPs) without antifouling modification for negative CT imaging of HCC. PEI was first linked to fluorescein isothiocyanate (FI) and then utilized as a vehicle for the entrapment of AuNPs. The particles were then acetylated to reduce its positive surface potential. The designed Ac-PE-AuNPs were characterized by various techniques. We find that the Ac-PE-AuNPs with a uniform size distribution (mean diameter = 2.3 nm) are colloidally stable and possess low toxicity in the studied range of concentration. Owing to the fact that the particles without additional antifouling modification were mainly gathered in liver, the Ac-PE-AuNPs could greatly improve the CT contrast enhancement of normal liver, whereas poor CT contrast enhancement appeared in liver necrosis region caused by HCC. As a result, HCC could be easily and precisely diagnosed. The designed Ac-PE-AuNPs were demonstrated to have biocompatibility through in vivo biodistribution and histological studies, hence holding an enormous potential to be adopted as an effective negative CT contrast agent for diagnosis of hepatoma carcinoma.