Progress of Mesoporous Silica Coated Gold Nanorods for Biological Imaging and Cancer Therapy

For unique surface plasmon absorption and fluorescence characteristics, gold nanorods have been developed and widely employed in the biomedical field. However, limitations still exist due their low specific surface area, instability and tendency agglomerate in cytoplasm. Mesoporous silica materials have been broadly applied in field of catalysts, adsorbents, nanoreactors, and drug carriers due to its unique mesoporous structure, highly comparative surface area, good stability and biocompatibility. Therefore, coating gold nanorods with a dendritic mesopore channels can effectively prevent particle agglomeration, while increasing the specific surface area and drug loading efficiency. This review discusses the advancements of GNR@MSN in synthetic process, bio-imaging technique and tumor therapy. Additionally, the further application of GNR@MSN in imaging-guided treatment modalities is explored, while its promising superior application prospect is highlighted. Finally, the issues related to in vivo studies are critically examined for facilitating the transition of this promising nanoplatform into clinical trials.

In situ formation of alginic acid-gold nanohybrids for application in cancer photothermal therapy

Gold-based nanoparticles present excellent optical properties that propelled their widespread application in biomedicine, from bioimaging to photothermal applications. Nevertheless, commonly employed manufacturing methods for gold-based nanoparticles require long periods and laborious protocols that reduce cost-effectiveness and scalability. Herein, a novel methodology was used for producing gold-alginic acid nanohybrids (Au-Alg-NH) with photothermal capabilities. This was accomplished by promoting the in situ reduction and nucleation of gold ions throughout a matrix of alginic acid by using ascorbic acid. The results obtained reveal that the Au-Alg-NHs present a uniform size distribution and a spike-like shape. Moreover, the nanomaterials were capable to mediate a temperature increase of ≈11°C in response to the irradiation with a near-infrared region (NIR) laser (808 nm, 1.7 W cm-2 ). The in vitro assays showed that Au-Alg-NHs were able to perform a NIR light-triggered ablation of cancer cells (MCF-7), being observed a reduction in the cell viability to ≈27%. Therefore, the results demonstrate that this novel methodology holds the potential for producing Au-Alg-NH with photothermal capacity and higher translatability to the clinical practice, namely for cancer therapy.

Photothermal Effect of Gold Nanoparticles as a Nanomedicine for Diagnosis and Therapeutics

Gold nanoparticles (AuNPs) have received great attention for various medical applications due to their unique physicochemical properties. AuNPs with tunable optical properties in the visible and near-infrared regions have been utilized in a variety of applications such as in vitro diagnostics, in vivo imaging, and therapeutics. Among the applications, this review will pay more attention to recent developments in diagnostic and therapeutic applications based on the photothermal (PT) effect of AuNPs. In particular, the PT effect of AuNPs has played an important role in medical applications utilizing light, such as photoacoustic imaging, photon polymerase chain reaction (PCR), and hyperthermia therapy. First, we discuss the fundamentals of the optical properties in detail to understand the background of the PT effect of AuNPs. For diagnostic applications, the ability of AuNPs to efficiently convert absorbed light energy into heat to generate enhanced acoustic waves can lead to significant enhancements in photoacoustic signal intensity. Integration of the PT effect of AuNPs with PCR may open new opportunities for technological innovation called photonic PCR, where light is used to enable fast and accurate temperature cycling for DNA amplification. Additionally, beyond the existing thermotherapy of AuNPs, the PT effect of AuNPs can be further applied to cancer immunotherapy. Controlled PT damage to cancer cells triggers an immune response, which is useful for obtaining better outcomes in combination with immune checkpoint inhibitors or vaccines. Therefore, this review examines applications to nanomedicine based on the PT effect among the unique optical properties of AuNPs, understands the basic principles, the advantages and disadvantages of each technology, and understands the importance of a multidisciplinary approach. Based on this, it is expected that it will help understand the current status and development direction of new nanoparticle-based disease diagnosis methods and treatment methods, and we hope that it will inspire the development of new innovative technologies.

Metabolic Disruption of Gold Nanospheres, Nanostars and Nanorods in Human Metastatic Prostate Cancer Cells

Nanomaterials offer a broad spectrum of applications in biomedicine. The shapes of gold nanoparticles could modulate tumor cell behavior. Spherical (AuNP_sp), stars (AuNP_st) and rods (AuNP_r) shapes of polyethylene glycol coated-gold nanoparticles (AuNPs-PEG) were synthesized. Metabolic activity, cellular proliferation, and reactive oxygen species (ROS) were measured and the impact of AuNPs-PEG in metabolic enzymes function was evaluated by RT-qPCR in PC3, DU145, and LNCaP prostate cancer cells. All AuNPs were internalized, and the different morphologies of AuNPs showed to be an essential modulator of metabolic activity. For PC3 and DU145, the metabolic activity of AuNPs was found to rank in the following order from lowest to highest: AuNP_sp-PEG, AuNP_st-PEG, and AuNP_r-PEG. Regarding LNCaP cells, the AuNP_st-PEG were less toxic, followed by AuNP_sp-PEG and AuNP_r-PEG, but it seems not to be dose-dependent. The proliferation was lower in AuNP_r-PEG in PC3 and DU145 cells but was stimulated around 10% in most conditions (0.001-0.1 mM) in LNCaP cells (not statistically significant). For 1 mM, LNCaP cells showed a significant decrease in proliferation only for AuNP_r-PEG. The outcomes of the current study demonstrated that different AuNPs conformations influence cell behavior, and the correct size and shape must be chosen considering its final application in the field of nanomedicine.

Application of Gold Nanoparticles as Radiosensitizer for Metastatic Prostate Cancer Cell Lines

More than 50% of all prostate cancer (PCa) patients are treated by radiotherapy (RT). Radioresistance and cancer recurrence are two consequences of the therapy and are related to dose heterogeneity and non-selectivity between normal and tumoral cells. Gold nanoparticles (AuNPs) could be used as potential radiosensitizers to overcome these therapeutic limitations of RT. This study assessed the biological interaction of different morphologies of AuNPs with ionizing radiation (IR) in PCa cells. To achieve that aim, three different amine-pegylated AuNPs were synthesized with distinct sizes and shapes (spherical, AuNP_sp-PEG, star, AuNP_st-PEG, and rods, AuNP_r-PEG) and viability, injury and colony assays were used to analyze their biological effect on PCa cells (PC3, DU145, and LNCaP) when submitted to the accumulative fraction of RT. The combinatory effect of AuNPs with IR decreased cell viability and increased apoptosis compared to cells treated only with IR or untreated cells. Additionally, our results showed an increase in the sensitization enhancement ratio by cells treated with AuNPs and IR, and this effect is cell line dependent. Our findings support that the design of AuNPs modulated their cellular behavior and suggested that AuNPs could improve the RT efficacy in PCa cells.

Modulation Technique of Localized Surface Plasmon Resonance of Palladium Nanospheres by Coating with Titanium Dioxide Shell for Application to Photothermal Therapy Agent

Although plasmonic palladium (Pd) nanospheres are thermodynamically stable and have high photothermal conversion due to the free and bound electron coupling associated with the intrinsic high interband transition, they have not attracted attention as a photothermal conversion material for next-generation photothermal cancer therapy. This is because the Pd nanospheres generate the localized surface plasmon resonance (LSPR) intrinsically in the ultraviolet region, which is far away from the biological transparent window (750-900 nm). In this study, we controlled the LSP wavelength of Pd nanospheres by coating with high refractive index TiO₂ shells taking advantage of the Pd LSPR which is highly sensitive to changes in the local refractive index around the nanospheres. Our calculations indicated that the absorption cross section at 808 nm (corresponding to the wavelength used for photothermal treatment) was increased by 4.5 times by redshifting the LSPR and increasing the extinction intensity associated with the coating with TiO₂ shell. Experiments confirmed the theoretical prediction in that the LSPR of the synthesized Pd nanospheres with a diameter of 81 nm was significantly redshifted by coating with amorphous TiO₂ shell, resulting in significant large extinction intensity at 808 nm. The photothermal conversion efficiency was estimated to be 50%. In vitro cell tests, HeLa cells incubated with 100-300 μg/mL TiO₂-coated Pd nanospheres were efficiently killed by irradiating 808 nm laser (1.8 W) even though the nanospheres with the same concentrations showed little cytotoxicity. These results indicate that the Pd nanospheres coated with high refractive index shells can be promising as a photothermal therapy agent.

Retinoic Acid-Loaded Dendritic Polyglycerol-Conjugated Gold Nanostars for Targeted Photothermal Therapy in Breast Cancer Stem Cells

The existence of cancer stem cells (CSCs) poses a major obstacle for the success of current cancer therapies, especially the fact that non-CSCs can spontaneously turn into CSCs, which lead to the failure of the treatment and tumor relapse. Therefore, it is very important to develop effective strategies for the eradication of the CSCs. In this work, we have developed a CSCs-specific targeted, retinoic acid (RA)-loaded gold nanostars-dendritic polyglycerol (GNSs-dPG) nanoplatform for the efficient eradication of CSCs. The nanocomposites possess good biocompatibility and exhibit effective CSCs-specific multivalent targeted capability due to hyaluronic acid (HA) decorated on the multiple attachment sites of the bioinert dendritic polyglycerol (dPG). With the help of CSCs differentiation induced by RA, the self-renewal of breast CSCs and tumor growth were suppressed by the high therapeutic efficacy of photothermal therapy (PTT) in a synergistic inhibitory manner. Moreover, the stemness gene expression and CSC-driven tumorsphere formation were significantly diminished. In addition, the in vivo tumor growth and CSCs were also effectively eliminated, which indicated superior anticancer activity, effective CSCs suppression, and prevention of relapse. Taken together, we developed a CSCs-specific targeted, RA-loaded GNSs-dPG nanoplatform for the targeted eradication of CSCs and for preventing the relapse.

Research advances in integrated theranostic probes for tumor fluorescence visualization and treatment

At present, cancer is obviously a major threat to human health worldwide. Accurate diagnosis and treatment are in great demand and have become an effective method to alleviate the development of cancer and improve the survival rate of patients. A large number of theranostic probes that combine diagnosis and treatment methods have been developed as promising tools for tumor precision medicine. Among them, fluorescent theranostic probes have developed rapidly in the frontier research field of precision medicine with their real time, low toxicity, and high-resolution merit. Therefore, this review focuses on recent advances in the development of fluorescent theranostic probes, as well as their applications for cancer diagnosis and treatment. Initially, small-molecule fluorescent theranostic probes mainly including tumor microenvironment-responsive fluorescent prodrugs and phototherapeutic probes were introduced. Subsequently, nanocomposite probes are expounded based on four types of nano-fluorescent particles combining different therapies (chemotherapy, photothermal therapy, photodynamic therapy, gene therapy, etc.). Then, the capsule-type "all in one" probes, which occupy an important position in theranostic probes, are summarized according to the surface carrier type. This review aims to present a comprehensive guide for researchers in the field of tumor-related theranostic probe design and development.

Real-time synthesis and detection of plasmonic metal (Au, Ag) nanoparticles under monochromatic X-ray nano-tomography

Plasmonic nanostructures are of immense interest of research due to its widespread applications in microelectronics, photonics, and biotechnology, because of its size and shape-dependent localized surface plasmon resonance response. The great efforts have been constructed by physicists, chemists, and material scientists to deliver optimized reaction protocol to tailor the size and shape of nanostructures. Real-time characterization emerges out as a versatile tool in perspective to the optimization of synthesis parameters. Moreover, in the past decades, radiation-induced reduction of metallic-salt to nanoparticles dominates over the conventional direct chemical reduction process which overcomes the production of secondary products and yields ultra-high quality and pure nanostructures. Here we show, the real-time/in-situ synthesis and detection of plasmonic (Au andAg) nanoparticles using single synchrotron monochromatic 6.7 keV X-rays based Nano-Tomography beamline. The real-time X-ray nano-tomography of plasmonic nanostructures has been first-time successfully achieved at such a low-energy that would be leading to the possibility of these experiments at laboratory-based sources. In-situ optical imaging confirms the radiolysis of water molecule resulting in the production of \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$e_{aq}^-,\,OH^\bullet ,$$\end{document}eaq-,OH∙, and \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$O_2^-$$\end{document}O2- under X-ray irradiation. The obtained particle-size and size-distribution by X-ray tomography are in good agreement to TEM results. The effect of different chemical environment media on the particle-size has also been studied. This work provides the protocol to precisely control the size of nanostructures and to synthesize the ultrahigh-purity grade monodisperse nanoparticles that would definitely enhance the phase-contrast in cancer bio-imaging and plasmonic photovoltaic application.

Ce6-Conjugated and polydopamine-coated gold nanostars with enhanced photoacoustic imaging and photothermal/photodynamic therapy to inhibit lung metastasis of breast cancer

Metastasis is the main cause of treatment failure in breast cancer, and integrated phototheranostics is a promising strategy to achieve both precision theranostics and metastasis inhibition. In this work, a multifunctional phototheranostic nanoprobe composed of chlorin e6 (Ce6)-conjugated and polydopamine (PDA)-coated gold nanostars (AuNSs) was synthesized for simultaneous photoacoustic (PA) imaging, photothermal therapy (PTT) and photodynamic therapy (PDT). Under the irradiation of near infrared laser, AuNSs@PDA showed enhanced photothermal conversion and amplified PA imaging performance, compared with single AuNSs. By the covalent conjugation of Ce6, the AuNSs@PDA-Ce6 nanoprobe showed robust stability and excellent singlet oxygen (1O2) generation ability. Under the combination of PTT/PDT, the AuNSs@PDA-Ce6 nanoprobes significantly reduced the growth of 4T1 tumors and suppressed their lung metastasis. All the results demonstrated the considerable potential of AuNSs@PDA-Ce6 phototheranostic nanoprobes for precision theranostics and metastasis inhibition of breast cancer.

Strategies to improve the photothermal capacity of gold-based nanomedicines

The plasmonic photothermal properties of gold nanoparticles have been widely explored in the biomedical field to mediate a photothermal effect in response to the irradiation with an external light source. Particularly, in cancer therapy, the physicochemical properties of gold-based nanomaterials allow them to efficiently accumulate in the tumor tissue and then mediate the light-triggered thermal destruction of cancer cells with high spatial-temporal control. Nevertheless, the gold nanomaterials can be produced with different shapes, sizes, and organizations such as nanospheres, nanorods, nanocages, nanoshells, and nanoclusters. These gold nanostructures will present different plasmonic photothermal properties that can impact cancer thermal ablation. This review analyses the application of gold-based nanomaterials in cancer photothermal therapy, emphasizing the main parameters that affect its light-to-heat conversion efficiency and consequently the photothermal potential. The different shapes/organizations (clusters, shells, rods, stars, cages) of gold nanomaterials and the parameters that can be fine-tuned to improve the photothermal capacity are presented. Moreover, the gold nanostructures combination with other materials (e.g. silica, graphene, and iron oxide) or small molecules (e.g. indocyanine green and IR780) to improve the nanomaterials photothermal capacity is also overviewed.

Smart Gold Nanostructures for Light Mediated Cancer Theranostics: Combining Optical Diagnostics with Photothermal Therapy

Nanotheranostics, which combines optical multiplexed disease detection with therapeutic monitoring in a single modality, has the potential to propel the field of nanomedicine toward genuine personalized medicine. Currently employed mainstream modalities using gold nanoparticles (AuNPs) in diagnosis and treatment are limited by a lack of specificity and potential issues associated with systemic toxicity. Light-mediated nanotheranostics offers a relatively non-invasive alternative for cancer diagnosis and treatment by using AuNPs of specific shapes and sizes that absorb near infrared (NIR) light, inducing plasmon resonance for enhanced tumor detection and generating localized heat for tumor ablation. Over the last decade, significant progress has been made in the field of nanotheranostics, however the main biological and translational barriers to nanotheranostics leading to a new paradigm in anti-cancer nanomedicine stem from the molecular complexities of cancer and an incomplete mechanistic understanding of utilization of Au-NPs in living systems. This work provides a comprehensive overview on the biological, physical and translational barriers facing the development of nanotheranostics. It will also summarise the recent advances in engineering specific AuNPs, their unique characteristics and, importantly, tunability to achieve the desired optical/photothermal properties.

New insights into the synthesis, toxicity and applications of gold nanoparticles in CT imaging and treatment of cancer

The past decades have witnessed enormous development of gold nanoparticles (AuNPs) and their applications in the biomedical field, an area in which they show infinite potential. Abundant investigations have been conducted in improving AuNP synthesis, aimed at obtaining water-dispersible ultrasmall AuNPs, which can exhibit biocompatibility, renal clearance and minimal toxicity. Due to their excellent x-ray attenuation ability, special optical properties and surface modification properties, AuNPs are reported to be promising as computed tomography contrast agents and can be applied in radiotherapy, photothermal and photodynamic therapies, and drug delivery. In this review, synthesis methods and toxicity of AuNPs have been summarized, emphasizing the preparation of ultra-small AuNPs. Applications of AuNPs in computed tomography imaging and cancer treatment are also considered, revealing their potential in the clinic.

Synthesis of porphyrin-conjugated silica-coated Au nanorods for synergistic photothermal therapy and photodynamic therapy of tumor

Synergistic therapy of tumor has attracted the attention of an increasing number of researchers because of its higher efficiency compared to single therapy. Herein, 4-carboxyphenyl porphyrin-conjugated silica-coated gold nanorods (AuNR@SiO₂-TCPP) were synthesized. The synergistic treatment of photothermal therapy and photodynamic therapy on A549 cancer was researched in vivo and in vitro. In the AuNR@SiO₂-TCPP, Au NRs and TCPP act as photothermal agent and photosensitizer, respectively. The temperature of the AuNR@SiO₂-TCPP (0.11 nmol L^-1) rises to 56.8 °C for 10 min under the illumination of 808 nm laser (2 Wcm^-2). In MTT assays, the viability of A549 cancer cell treated with AuNR@SiO₂-TCPP (100 μg ml^-1) is only 21%. In animal experiments, the relative tumor volumes in mice receiving AuNR@SiO₂-TCPP (5 mg kg^-1) with 660 and 808 nm irradiations were significantly inhibited and the average value is decreased to 0.78 while the average value of the control group is increased to 7.2. These results demonstrate that the AuNR@SiO₂-TCPP is a potential nanomedicine against tumor for clinical application in the near future.

Organic Nanotheranostics for Photoacoustic Imaging-Guided Phototherapy

Phototherapies including photothermal therapy (PTT) and photodynamic therapy (PDT) have emerged as one of the avant-garde strategies for cancer treatment. Photoacoustic (PA) imaging is a new hybrid imaging modality that shows great promise for real-time in vivo monitoring of biological processes with deep tissue penetration and high spatial resolution. To enhance therapeutic efficacy, reduce side effects and minimize the probability of over-medication, it is necessary to use imaging and diagnostic methods to identify the ideal therapeutic window and track the therapeutic outcome. With this regard, nanotheranostics with the ability to conduct PA imaging and PTT/PDT are emerging. This review summarizes the recent progress of organic nanomaterials including nearinfrared (NIR) dyes and semiconducting polymer nanoparticles (SPNs) in PA imaging guided cancer phototherapy, and also addresses their present challenges and potential in clinical applications.

Gold nanostructures as cancer theranostic probe: promises and hurdles

Gold nanostructures (GNSts) have emerged as substitute for conventional contrast agents in imaging techniques and therapeutic probes due to their tunable surface plasmon resonance and optical properties in near-infrared region. Thus GNSts provide platform for the amalgamation of diagnosis and treatment (theranostics) into a single molecule for a more precise treatment. Hence, the article talks about the application of GNSts in imaging techniques and provide a holistic view on differently shaped GNSts in cancer theranostics. However, with promises GNSts also face various hurdles for their use as theranostic probe which are primarily associated with toxicity. Finally, the article attempts to discuss the challenges faced by GNSts and the way ahead that need to be traversed to place them in nanomedicine.

Nanomaterials as photothermal therapeutic agents

Curing cancer has been one of the greatest conundrums in the modern medical field. To reduce side-effects associated with the traditional cancer therapy such as radiotherapy and chemotherapy, photothermal therapy (PTT) has been recognized as one of the most promising treatments for cancer over recent years. PTT relies on ablation agents such as nanomaterials with a photothermal effect, for converting light into heat. In this way, elevated temperature could kill cancer cells while avoiding significant side effects on normal cells. This theory works because normal cells have a higher heat tolerance than cancer cells. Thus, nanomaterials with photothermal effects have attracted enormous attention due to their selectivity and non-invasive attributes. This review article summarizes the current status of employing nanomaterials with photothermal effects for anti-cancer treatment. Mechanisms of the photothermal effect and various factors affecting photothermal performance will be discussed. Efficient and selective PTT is believed to play an increasingly prominent role in cancer treatment. Moreover, merging PTT with other methods of cancer therapies is also discussed as a future trend.

Gold nanostars for cancer cell-targeted SERS-imaging and NIR light-triggered plasmonic photothermal therapy (PPTT) in the first and second biological windows

Gold nanostars were developed for cancer cell-targeted NIR-I/II SERS-imaging and PPTT.

Fabrication of Multifoliate PtRu Bimetallic Nanocomplexes for Computed Tomography Imaging and Enhanced Synergistic Thermoradiotherapy

To improve the efficiency of cancer therapy, we developed multifoliate PEGylated PtRu bimetallic nanocomplexes (PtRu-PEG BNCs) as multifunctional theranostic nanoagents for computed tomography (CT) imaging and synergistic thermoradiotherapy. The synthesized PtRu-PEG BNCs with uniform size and morphology exhibit excellent stability, notable photothermal effect, and good biocompatibility. As compared with other platinum nanomaterials, the PtRu-PEG BNCs are able to absorb near-infrared laser energy and present excellent photothermal conversion efficiency (44.5%). Multifoliate PtRu-PEG BNCs can be applied to CT imaging and radiotherapy (RT) because of the presence of platinum. Unlike a single therapy method, the integration of photothermal therapy with RT can effectively induce cell apoptosis and generate an obvious synergistic effect. Hence, the as-prepared nanocomplexes can be used as multifunctional theranostic nanoagents.

Fluorescence enhancement from single gold nanostars: towards ultra-bright emission in the first and second near-infrared biological windows

Gold nanostars (AuNSs) are promising agents for the development of high-performance diagnostic devices, by enabling metal enhanced fluorescence (MEF) in the physiological near-infrared (NIR) and second near-infrared (NIR-II) windows. The local electric field near their sharp tips and between their branches can be enhanced by several orders of magnitude, holding great promise for large fluorescence enhancements from single AuNS particles, rather than relying on interparticle coupling in nanoparticle substrates. Here, guided by electric field simulations, two different types of AuNSs with controlled morphologies and plasmonic responses in the NIR and NIR-II regions are used to investigate the mechanism of MEF from colloidal AuNSs. Fluorophore conjugation to AuNSs allows significant fluorescence enhancement of up to 30 times in the NIR window, and up to 4-fold enhancement in the NIR-II region. Together with other inherent advantages of AuNSs, including their multispike morphology offering easy access to cell membranes and their large surface area providing flexible multifunctionality, AuNS are promising for the development of in vivo imaging applications. Using time-resolved fluorescence measurements to deconvolute semi-quantitatively excitation enhancement from emission enhancement, we show that a combination of enhanced excitation and an increased radiative decay rate, both contribute to the observed large enhancement. In accordance to our electric field modelling, however, excitation enhancement is the component that varies most with particle morphology. These findings provide important insights into the mechanism of MEF from AuNSs, and can be used to further guide particle design for high contrast enhancement, enabling the development of MEF biodetection technologies.

Formation of Gold Nanostar-Coated Hollow Mesoporous Silica for Tumor Multimodality Imaging and Photothermal Therapy

Development of multifunctional nanoplatforms for tumor multimode imaging and therapy is of great necessity. Herein, we report a new type of Au nanostar (NS)-coated, perfluorohexane (PFH)-encapsulated hollow mesoporous silica nanocapsule (HMS) modified with poly(ethylene glycol) (PEG) for tumor multimode ultrasonic (US)/computed tomography (CT)/photoacoustic (PA)/thermal imaging, and photothermal therapy (PTT). HMSs were first synthesized, silanized to have thiol surface groups, and coated with gold nanoparticles via a Au-S bond. Followed by growth of Au NSs on the surface of the HMSs, encapsulation of PFH in the interior of the HMSs, and surface conjugation of thiolated PEG, multifunctional HMSs@Au-PFH-mPEG NSs (for short, HAPP) were formed and well-characterized. We show that the HAPP are stable in a colloidal manner and noncytotoxic in the studied range of concentrations, possess multimode US/CT/PA/thermal imaging ability, and can be applied for multimode US/CT/PA/thermal imaging of tumors in vivo after intravenous or intratumoral injection. Additionally, the near-infrared absorption property of the HAPP enables the use of the HAPP for photothermal ablation of cancer cells in vitro and a tumor model in vivo after intratumoral injection. The developed multifunctional HAPP may be used as a novel multifunctional theranostic nanoplatform for tumor multimode imaging and PTT.

Chitosan coated tungsten trioxide nanoparticles as a contrast agent for X-ray computed tomography

Recent advances have shown that inorganic nanoparticles (NPs) based on heavy elements are highly appropriate for X-ray computed tomography (CT). In this contribution, tungsten trioxide NPs are prepared by the electrical arc discharge (EAD) method in DI water. The effect of chitosan (CTS) and glutaraldehyde (GTA) as coating and cross-linking agent, respectively, on the hydrodynamic size and zeta potential of prepared tungsten trioxide NPs is investigated. It is found that zeta potential increases by increasing the amounts of CTS. Meanwhile, by increasing the volume of glutaraldehyde (GTA), the final particle size increases whereas the zeta potential deceases. Chitosan coated tungsten trioxide demonstrated no significant cytotoxicity at concentration up to 5mg/mL after 24h. Finally, the X-ray attenuation of prepared chitosan coated tungsten trioxide NPs are higher than Iohexol as the commercially available iodinated contrasting agent at the same concentrations.

pH-Dependent Transmembrane Activity of Peptide-Functionalized Gold Nanostars for Computed Tomography/Photoacoustic Imaging and Photothermal Therapy

Progress in multifunctional nanomaterials for tumor therapy mostly depends on the development of tumor-targeting delivery strategies. One approach is to explore a pH-responsive strategy to target the slightly acidic solid tumor microenvironment. A novel class of pH (low) insertion peptides (pHLIPs) with pH-dependent transmembrane activity can fold and rapidly insert into the lipid bilayer of tumor cells triggered by acidity, facilitating the cellular internalization of nanomaterials synchronously. Here, we innovatively decorated gold nanostars (GNSs) with pHLIPs (GNS-pHLIP) to improve their targeting ability and photothermal therapeutic (PTT) efficiency. The obtained GNS-pHLIP exhibited the excellent characteristics of uniform size and good biocompatibility. As compared to GNS-mPEG, the cellular internalization of GNS-pHLIP was 1-fold higher after a 2 h incubation with cells in media at pH 6.4 than at pH 7.4. Moreover, the tumor accumulation of the GNS-pHLIP was 3-fold higher than that of GNS-mPEG after intravenous injection into MCF-7 breast tumor animal models for 24 h. Furthermore, GNS-pHLIP exhibited stronger signals than the GNS-mPEG through computed tomography (CT) and photoacoustic (PA) imaging. Simultaneously, the desirable targeting efficiency significantly improved the PTT efficacy to tumors, with low side effects on normal tissues. The results clearly demonstrate that the GNS-pHLIP successfully took advantage of the tumor-targeting ability of pHLIPs and the good characteristics of GNSs, which may contribute to the study of tumor imaging and therapy.

T 1-Weighted MR/CT dual-modality imaging-guided photothermal therapy using gadolinium-functionalized triangular gold nanoprism

Triangular gold nanoprism decorated with gadopentetic acid (TGP–PEG–Gd) for PTT guided by T₁-weighted MR/CT dual-modality imaging.

Facile synthesis of multifunctional Fe3O4@SiO2@Au magneto-plasmonic nanoparticles for MR/CT dual imaging and photothermal therapy

Monodispersed and well-defined Fe₃O₄@SiO₂@Au magneto-plasmonic nanoparticles were synthesized by a facile method. They were demonstrated to be excellent MR/CT dual imaging and photothermal therapy theranostic agents.

Recent advances in different modal imaging-guided photothermal therapy

Photothermal therapy (PTT) has recently attracted considerable attention owing to its controllable treatment process, high tumour eradication efficiency and minimal side effects on non-cancer cells. PTT can melt cancerous cells by localising tissue hyperthermia induced by internalised therapeutic agents with a high photothermal conversion efficiency under external laser irradiation. Numerous in vitro and in vivo studies have shown the significant potential of PTT to treat tumours in future practical applications. Unfortunately, the lack of visualisation towards agent delivery and internalisation, as well as imaging-guided comprehensive evaluation of therapeutic outcome, limits its further application. Developments in combined photothermal therapeutic nanoplatforms guided by different imaging modalities have compensated for the major drawback of PTT alone, proving PTT to be a promising technique in biomedical applications. In this review, we introduce recent developments in different imaging modalities including single-modal, dual-modal, triple-modal and even multi-modal imaging-guided PTT, together with imaging-guided multi-functional theranostic nanoplatforms.

Influence of cell size on cellular uptake of gold nanoparticles

Cell size affects cellular uptake of gold nanoparticles (AuNPs).

PEGylated gold nanoprisms for photothermal therapy at low laser power density

Small-sized PEGylated gold nanoprisms with ultrahigh photothermal conversion efficacy were achieved to induce photothermal therapy under a low power density laser.

Facile preparation of albumin-stabilized gold nanostars for the targeted photothermal ablation of cancer cells

BSA–FA conjugation was used as a stabilizer to synthesize gold nanostars (BSA–FA–AuNSs). The prepared BSA–FA–AuNSs should have a great potential as photothermal conversion agents for the receptor-mediated treatment of cancer cells.