Photothermal-chemotherapy with doxorubicin-loaded hollow gold nanospheres: A platform for near-infrared light-trigged drug release

Specific photothermal therapy to the tumors with high EphB4 receptor expression

Photothermal therapy (PTT) employs photo-absorbing agents to generate heat from optical energy, leading to the 'burning' of tumor cells. Real-time imaging of in vivo distribution of photothermal agents and monitoring of post-treatment therapeutic outcomes are very important to design and optimize personalized PTT treatment. In this work, we used chitosan-stearic acid copolymer (CSO-SA) to encapsulate hollow gold nanospheres (HAuNS) and near-infrared (NIR) fluorescent tracer, DiR. Then, the surface of nanoparticles was further conjugated with a peptide (TNYL), which facilitates EphB4-positive tumor targeting delivery. Using a paired tumor mode in vivo and a double tumor-cell co-culture strategy in vitro, we demonstrated the feasibility of increasing the accumulation of our nanoparticles (DiR loaded and TNYL-CSO-SA coated HAuNS (DTCSH)) into EphB4-positive tumors through interaction between TNYL-peptide on the nanoparticles and EpHB4 receptors on tumor cells. When combined with NIR laser irradiation, our nanoparticles induced more EphB4-positive tumor cells death in vitro. We further developed optical imaging to temporally and spatially monitor the biodistribution of DTCSH. Under NIR laser irradiation, PTT exhibited dramatically stronger antitumor effect against EphB4-positive tumors than EphB4-negative tumors. This was attributed to enhanced accumulation of our nanoparticles in EphB4-positive tumors.

Unexpected high photothemal conversion efficiency of gold nanospheres upon grafting with two-photon luminescent ruthenium(II) complexes: A way towards cancer therapy?

The design and development of functional hybrid nanomaterials is currently a topic of great interest in biomedicine. Herein we investigated the grafting of Ru(II) polypyridyl complexes onto gold nanospheres (Ru@AuNPs) to improve the particles' near infrared (NIR) absorption, and ultimately allow for application in photothermal cancer therapy. As demonstrated in this article, these ruthenium(II) complexes could indeed significantly enhance gold nanospheres' two-photon luminescence (PTL) intensity and photothermal therapy (PTT) efficiency. The best dual functional nanoparticles of this study were successfully used for real-time luminescent imaging-guided PTT in live cancer cells. Furthermore, in vivo tumor ablation was achieved with excellent treatment efficacy under a diode laser (808 nm) irradiation at the power density of 0.8 W/cm(2) for 5 min. This study demonstrates that the coupling of inert Ru(II) polypyridyl complexes to gold nanospheres allows for the enhancement of two-photon luminescence and for efficient photothermal effect.

Gold nanorods coated with mesoporous silica shell as drug delivery system for remote near infrared light-activated release and potential phototherapy

In this study, we report the synthesis of a nanoscaled drug delivery system, which is composed of a gold nanorod-like core and a mesoporous silica shell (GNR@MSNP) and partially uploaded with phase-changing molecules (1-tetradecanol, TD, T(m) 39 °C) as gatekeepers, as well as its ability to regulate the release of doxorubicin (DOX). Indeed, a nearly zero premature release is evidenced at physiological temperature (37 °C), whereas the DOX release is efficiently achieved at higher temperature not only upon external heating, but also via internal heating generated by the GNR core under near infrared irradiation. When tagged with folate moieties, GNR@MSNPs target specifically to KB cells, which are known to overexpress the folate receptors. Such a precise control over drug release, combining with the photothermal effect of GNR cores, provides promising opportunity for localized synergistic photothermal ablation and chemotherapy. Moreover, the performance in killing the targeted cancer cells is more efficient compared with the single phototherapeutic modality of GNR@MSNPs. This versatile combination of local heating, phototherapeutics, chemotherapeutics and gating components opens up the possibilities for designing multifunctional drug delivery systems.

Optically modulated cancer therapeutic delivery: past, present and future

Chemotherapeutic regimens are often restricted by dose-limiting toxicities that arise from drug exposure to off-site tissues. Nanoparticle drug carriers that specifically deliver therapeutics to the site of malignant tissue are being actively researched today. One strategy is to utilize materials that are light-responsive, such that the carrier can be triggered to release its drug payload at the distinct time and location of light exposure. This review discusses recent advances in the development of such light-responsive drug carriers. With continued optimization and in vivo validation, these approaches may offer novel treatment options for cancer management.

Delivery of vincristine sulfate-conjugated gold nanoparticles using liposomes: a light-responsive nanocarrier with enhanced antitumor efficiency

Rapid drug release at the specific site of action is still a challenge for antitumor therapy. Development of stimuli-responsive hybrid nanocarriers provides a promising strategy to enhance therapeutic effects by combining the unique features of each component. The present study explored the use of drug–gold nanoparticle conjugates incorporated into liposomes to enhance antitumor efficiency. A model drug, vincristine sulfate, was physically conjugated with gold nanoparticles and verified by UV-visible and fourier transform infrared spectroscopy, and differential scanning calorimetry. The conjugates were incorporated into liposomes by film dispersion to yield nanoparticles (113.4 nm) with light-responsive release properties, as shown by in vitro release studies. Intracellular uptake and distribution was studied in HeLa cells using transmission electron microscopy and confocal laser scanning microscopy. This demonstrated liposome internalization and localization in endosomal–lysosomal vesicles. Fluorescence intensity increased in cells exposed to UV light, indicating that this stimulated intracellular drug release; this finding was confirmed by quantitative analyses using flow cytometry. Antitumor efficacy was evaluated in HeLa cells, both in culture and in implants in vivo in nude mice. HeLa cell viability assays showed that light exposure enhanced liposome cytotoxicity and induction of apoptosis. Furthermore, treatment with the prepared liposomes coupled with UV light exposure produced greater antitumor effects in nude mice and reduced side effects, as compared with free vincristine sulfate.

Multifunctional hollow gold nanoparticles designed for triple combination therapy and CT imaging

Hollow gold nanoparticles (HGNP) are a novel class of hybrid metal nanoparticles whose unique optical and morphological properties have spawned new applications including more effective cancer therapy. The shell thickness of HGNPs can tune the surface plasmon resonance to the near infrared light, resulting in photothermal ablation of tumors with optimal light penetration in tissue. The hollow cavity within a HGNP is able to accommodate a high payload of chemotherapeutic agents. They have also been used for enhancing radiosensitization in tumors during radiotherapy due to the high X-ray absorption capability of gold particles. However, no report has yet been published that utilize HGNPs for the triple combination therapy and CT imaging. In this study, we synthesized HGNPs which exhibit better response to radiation for therapy and imaging and demonstrated the effects of combined chemotherapy, thermal and radiotherapy. This combination strategy presented delayed tumor growth by 4.3-fold and reduced tumor's weight by 6.8-fold compared to control tumors. In addition, we demonstrated the feasibility of HGNP as a CT imaging agent. It is expected that translating these capabilities to human cancer patients could dramatically increase the antitumor effect and potentially overcome resistance to chemotherapeutic agents and radiation.

Hybridized doxorubicin-Au nanospheres exhibit enhanced near-infrared surface plasmon absorption for photothermal therapy applications

Photothermal therapy (PTT) employs photosensitizing agents, which are taken up by cells and generate heat when irradiated with near-infrared (NIR) light, to enable the photoablation of cancer cells. High absorption in the NIR region is crucial for a photosensitizing agent to achieve efficient PTT. Different combinations between gold nanoparticles and fluorescent agents always influence their spectrum properties. Herein, we fabricated a novel combination of a fluorescent agent (doxorubicin, DOX, also a popular chemotherapeutic agent) with gold nanospheres by synthesizing hybridized DOX-Au nanospheres (DAuNS), where a part of the DOX molecules and Au co-formed a hybridized matrix as the shell and the remaining DOX molecules precipitated as the core. The unique structure of DAuNS induced interesting changes in the characteristics including spectrum properties, morphology, drug loading and antitumor activity. We observed that DAuNS exhibited a significantly enhanced surface plasmon absorption in the NIR region, inducing a more efficient photothermal conversion and stronger tumor-cell killing ability under NIR laser irradiation. In addition, our study presents a new and simple platform to load a drug into nanoparticles. DAuNS could be a promising nanoparticle with the "two punch" efficacy of PTT and chemotherapy and could be used in clinical applications due to its controllable synthesis, small size, and narrow size distribution.

Facile synthesis of gold nanorods/hydrogels core/shell nanospheres for pH and near-infrared-light induced release of 5-fluorouracil and chemo-photothermal therapy

We described a facile synthesis of pH and near-infrared (NIR) light dual-sensitive core/shell hybrid nanospheres, consisting of gold nanorods (GNR) as the core and poly(N-isopropylacrylamide-co-methacrylic acid) as the shell, p(NIPAM-MAA). The resultant GNR/p(NIPAM-MAA) nanospheres showed a core/shell structure, with an average diameter of ∼110nm and a strong longitudinal surface plasmon band at NIR region. Due to the photothermal effect of GNR and pH/thermal-sensitive volume transition of p(NIPAM-MAA) hydrogels, the nanospheres with loading of 5-fluorouracil (5-FU) by electrostatic interactions were developed as a smart carrier for pH- and photothermal-induced release of 5-FU. Experimental results testified that the cumulative release of 5-FU from nanospheres was markedly increased in a mild acidic medium. Moreover, a NIR light (808nm) irradiation triggered a greater and faster release of 5-FU, which was further testified by relevant results from in vitro cytotoxicity assay, in vivo tumor growth inhibition and histological images of ex vivo tumor sections. These results revealed significant applications of GNR/p(NIPAM-MAA) nanospheres in controlled release of anticancer agents and photothermal ablation therapy of tumor tissues, accompanied by synergistic effect of chem-photothermal therapy.

Controlled Drug Release from Pharmaceutical Nanocarriers

Nanocarriers providing spatiotemporal control of drug release contribute to reducing toxicity and improving therapeutic efficacy of a drug. On the other hand, nanocarriers face unique challenges in controlling drug release kinetics, due to the large surface area per volume ratio and the short diffusion distance. To develop nanocarriers with desirable release kinetics for target applications, it is important to understand the mechanisms by which a carrier retains and releases a drug, the effects of composition and morphology of the carrier on the drug release kinetics, and current techniques for preparation and modification of nanocarriers. This review provides an overview of drug release mechanisms and various nanocarriers with a specific emphasis on approaches to control the drug release kinetics.

Multifunctional nanoparticles: recent progress in cancer therapeutics

In recent times, several biocompatible nanomaterials with different morphologies and compositions, such as metals, metal oxides, and polymers, have been employed as multi-functional biomaterials to target cancer cells.

Design of hybrid nanovehicles for remotely triggered drug release: an overview

This review addresses the advantages of remote triggers, e.g. ultrasounds, near infrared light and alternating magnetic fields, the fabrication of the hybrid nanovehicles, the release mechanisms and the next challenges.

Highly efficient loading of doxorubicin in Prussian Blue nanocages for combined photothermal/chemotherapy against hepatocellular carcinoma

Doxorubicin-loaded Prussian Blue-based nanoparticles for combined photothermal/chemotherapy against hepatocellular carcinoma.

Synergistic anticancer activity of photo- and chemoresponsive nanoformulation based on polylysine-functionalized graphene

Multimodal therapeutic agents based on nanomaterials for cancer combination therapy have attracted increasing attention. In this report, a novel photo- and chemoactive nanohybrid was fabricated by assembling photosensitizer Zn(II)-phthalocyanine (ZnPc) and anticancer drug doxorubicin (DOX) on the biocompatible poly-l-lysine (PLL)-grafted graphene (G-PLL). This nanocomplex of G-PLL/DOX/ZnPc showed excellent physiochemical properties, including high solubility and stability in biological solutions, high drug loading efficiency, pH-triggered drug release, and ability to generalize (1)O2 under light excitation. Compared to free drug molecules, cells treated with G-PLL/DOX/ZnPc showed a higher cellular uptake. In particular, G-PLL/DOX/ZnPc elicited a remarkable synergistic anticancer activity owing to combined photodynamic and chemotherapeutic effects. The combination dose reduction indexes revealed that combining DOX with ZnPc provided strong synergistic effects (combination index < 0.1) against three cancer cell lines tested (HeLa, MCF-7, and B16). Thus, this study demonstrates programmable dual-modality therapy exemplified by G-PLL/DOX/ZnPc to synergistically treat cancers.

Development of nanoscale approaches for ovarian cancer therapeutics and diagnostics

Ovarian cancer is the deadliest of all gynecological cancers and the fifth leading cause of death due to cancer in women. This is largely due to late-stage diagnosis, poor prognosis related to advanced-stage disease, and the high recurrence rate associated with development of chemoresistance. Survival statistics have not improved significantly over the last three decades, highlighting the fact that improved therapeutic strategies and early detection require substantial improvements. Here, we review and highlight nanotechnology-based approaches that seek to address this need. The success of Doxil, a PEGylated liposomal nanoencapsulation of doxorubicin, which was approved by the FDA for use on recurrent ovarian cancer, has paved the way for the current wave of nanoparticle formulations in drug discovery and clinical trials. We discuss and summarize new nanoformulations that are currently moving into clinical trials and highlight novel nanotherapeutic strategies that have shown promising results in preclinical in vivo studies. Further, the potential for nanomaterials in diagnostic imaging techniques and the ability to leverage nanotechnology for early detection of ovarian cancer are also discussed.

Near-infrared light-sensitive liposomes for the enhanced photothermal tumor treatment by the combination with chemotherapy

PURPOSE

To develop a near-infrared (NIR) light-sensitive liposome, which contains hollow gold nanospheres (HAuNS) and doxorubicin (DOX), and evaluate their potential utility for enhancing antitumor activity and controlling drug release.

METHODS

The liposomes (DOX&HAuNS-TSL) were designed based on a thermal sensitive liposome (TSL) formulation, and hydrophobically modified HAuNS were attached onto the membrane of the liposomes. The behavior of DOX release from the liposomes was investigated by the dialysis, diffusion in agarose gel and cellular uptake of the drug. The biodistribution of DOX&HAuNS-TSL was assessed by i.v. injection in tumor-bearing nude mice. Antitumor efficacy was evaluated both histologically using excised tissue and intuitively by measuring the tumor size and weight.

RESULTS

Rapid and repetitive DOX release from the liposomes (DOX&HAuNS-TSL), could be readily achieved upon NIR laser irradiation. The treatment of tumor cells with DOX&HAuNS-TSL followed by NIR laser irradiation showed significantly greater cytotoxicity than the treatment with DOX&HAuNS-TSL alone, DOX-TSL alone (chemotherapy alone) and HAuNS-TSL plus NIR laser irradiation (Photothermal ablation, PTA, alone). In vivo antitumor study indicated that the combination of simultaneous photothermal and chemotherapeutic effect mediated by DOX&HAuNS-TSL plus NIR laser presented a significantly higher antitumor efficacy than the PTA alone mediated by HAuNS-TSL plus NIR laser irradiation.

CONCLUSIONS

Our study could be as the valuable reference and direction for the clinical application of PTA in tumor therapy.

Cancer theranostics with gold nanoshells

Gold nanoshells (AuNSs) present a vivid example of integrating nanoscience in order to solve a biomedical problem. AuNSs exhibit tunable surface plasmon resonance, which can be tuned to the near-infrared region in order to realize optimal tissue penetration. The highly efficient light-to-heat transformation by AuNSs during laser irradiation causes thermal damage to the tumor without damaging healthy organs. Transient nanobubbles can form around AuNSs during laser treatment and induce mechanical stress specifically in tumor cells. AuNSs also serve as a versatile platform for the delivery of various diagnostic and therapeutic agents. In this article, we describe the physicochemical properties of AuNSs in the context of their design, preparation and application in cancer theranostics. Ultimately, we look beyond the current research on AuNSs and discussed future challenges to their successful translation into clinical use.

Light-activatable gold nanoshells for drug delivery applications

Gold nanoshells (AuNSs) are currently being investigated as nanocarriers for drug delivery systems and have both diagnostic and therapeutic applications, including photothermal ablation, hyperthermia, drug delivery, and diagnostic imaging, particularly in oncology. AuNSs are valuable for their localized surface plasmon resonance, biocompatibility, low immunogenicity, and facile functionalization. AuNSs used for drug delivery can be spatially and temporally triggered to release controlled quantities of drugs inside the target cells when illuminated with a near-infrared (NIR) laser. Recently, many research groups have demonstrated that these AuNS complexes are able to deliver antitumor drugs (e.g., doxorubicin, paclitaxel, small interfering RNA, and single-stranded DNA) into cancer cells, which enhances the efficacy of treatment. AuNSs can also be functionalized with active targeting ligands such as antibodies, aptamers, and peptides to increase the particles' specific binding to the desired targets. This article reviews the current research on NIR light-activatable AuNSs used as nanocarriers for drug delivery systems and cancer theranostics.

In vivo immune cell distribution of gold nanoparticles in naïve and tumor bearing mice

Gold nanoparticles (AuNP) have been widely used for drug delivery and have recently been explored for applications in cancer immunotherapy. Although AuNPs are known to accumulate heavily in the spleen, the particle distribution within immune cells has not been thoroughly studied. Here, cellular distribution of Cy5 labeled 50 nm AuNPs is characterized within the immune populations of the spleen from naïve and tumor bearing mice using flow cytometry. Surprisingly, approximately 30% of the detected AuNPs are taken up by B cells at 24 h, with about 10% in granulocytes, 18% in dendritic cells, and 8% in T cells. In addition, 3% of the particles are detected within myeloid derived suppressor cells, an immune suppressive population that could be targeted for cancer immunotherapy. Furthermore, it is observed that, over time, the particles traveled from the red pulp and marginal zone to the follicles of the spleen. Taking into consideration that the particle cellular distribution does not change at 1, 6 and 24 h, it is highly suggestive that the immune populations carry the particles and migrate through the spleen instead of the particles migrating through the tissue by cell-cell transfer. Finally, no difference is observed in particle distribution between naïve and tumor bearing mice in the spleen, and nanoparticles are detected within 0.7% of dendritic cells of the tumor microenvironment. Overall, these results can help inform and influence future AuNP delivery design criteria including future applications for nanoparticle-mediated immunotherapy.

Gold nanoparticles in breast cancer treatment: promise and potential pitfalls

Despite remarkable achievements in the treatment of breast cancer, some obstacles still remain. Gold nanoparticles may prove valuable in addressing these problems owing to their unique characteristics, including their enhanced permeability and retention in tumor tissue, their light absorbance and surface plasmon resonance in near-infrared light, their interaction with radiation to generate secondary electrons, and their ability to be conjugated with drugs or other agents. Herein, we discuss some basic concepts of gold nanoparticles, and early results from studies regarding their use in breast cancer, including toxicity and side effects. We also discuss these particles' potential clinical applications.

Bacterial killing by light-triggered release of silver from biomimetic metal nanorods

Illumination of noble metal nanoparticles at the plasmon resonance causes substantial heat generation, and the transient and highly localized temperature increases that result from this energy conversion can be exploited for photothermal therapy by plasmonically heating gold nanorods (NRs) bound to cell surfaces. Here, plasmonic heating is used for the first time to locally release silver from gold core/silver shell (Au@Ag) NRs targeted to bacterial cell walls. A novel biomimetic method of preparing Au@Ag core-shell NRs is employed, involving deposition of a thin organic polydopamine (PD) primer onto Au NR surfaces, followed by spontaneous electroless silver metallization, and conjugation of antibacterial antibodies and passivating polymers for targeting to gram-negative and gram-positive bacteria. Dramatic cytotoxicity of S. epidermidis and E. coli cells targeted with Au@Ag NRs is observed upon exposure to light as a result of the combined antibacterial effects of plasmonic heating and silver release. The antibacterial effect is much greater than with either plasmonic heating or silver alone, implying a strong therapeutic synergy between cell-targeted plasmonic heating and the associated silver release upon irradiation. The findings suggest a potential antibacterial use of Au@Ag NRs when coupled with light irradiation, which has not been previously described.

Near-infrared light-responsive nanomaterials in cancer therapeutics

Near-infrared light sensitive nanomaterials provide ideal nanoplatforms in site specific noninvasive cancer therapy.

pH-responsive gold nanoparticles-in-liposome hybrid nanostructures for enhanced systemic tumor delivery

We report a pH-responsive gold nanoparticles-in-liposome hybrid nanostructure, which effectively combines the pH-responsive assembly and surface plasmon property changes of 'smart' gold nanoparticles and enhanced systemic circulation and tumor accumulation of the PEG-grafted liposomes.

Photothermal therapy of tumors in lymph nodes using gold nanorods and near-infrared laser light

Lymph node dissection for regional nodal metastasis is a primary option, but is invasive and associated with adverse effects. The development of non-invasive therapeutic methods in preclinical experiments using mice has been restricted by the small lymph node size and the limited techniques available for non-invasive monitoring of lymph node metastasis. Here, we show that photothermal therapy (PTT) using gold nanorods (GNRs) and near-infrared (NIR) laser light shows potential as a non-invasive treatment for tumors in the proper axillary lymph nodes (proper-ALNs) of MXH10/Mo-lpr/lpr mice, which develop systemic swelling of lymph nodes (up to 13mm in diameter, similar in size to human lymph nodes). Tumor cells were inoculated into the proper-ALNs to develop a model of metastatic lesions, and any anti-tumor effects of therapy were assessed. We found that GNRs accumulated in the tumor in the proper-ALNs 24h after tail vein injection, and that irradiation with NIR laser light elevated tumor temperature. Furthermore, combining local or systemic delivery of GNRs with NIR irradiation suppressed tumor growth more than irradiation alone. We propose that PTT with GNRs and NIR laser light can serve as a new therapeutic method for lymph node metastasis, as an alternative to lymph node dissection.

Gold nanoparticle mediated cancer immunotherapy

Significant progress has been made in the field of cancer immunotherapy, where the goal is to activate or modulate the body's immune response against cancer. However, current immunotherapy approaches exhibit limitations of safety and efficacy due to systemic delivery. In this context, the use of nanotechnology for the delivery of cancer vaccines and immune adjuvants presents a number of advantages such as targeted delivery to immune cells, enhanced therapeutic effect, and reduced adverse outcomes. Recently, gold nanoparticles (AuNP) have been explored as immunotherapy carriers, creating new AuNP applications that merit a critical overview. This review highlights recent advances in the development of AuNP mediated immunotherapies that harness AuNP biodistribution, optical properties and their ability to deliver macromolecules such as peptides and oligonucleotides. It has been demonstrated that the use of AuNP carriers can improve the delivery and safety of immunotherapy agents, and that AuNP immunotherapies are well suited for synergistic combination therapy with existing cancer therapies like photothermal ablation.

FROM THE CLINICAL EDITOR

Cancer immunotherapy approaches are rapidly evolving and are some of the most promising avenues to approach malignancies. This review summarizes the role of gold nanoparticles in immunotherapy agent delivery, and in the development of synergistic therapies such as photothermal ablation.

REVIEW OF METAL, CARBON AND POLYMER NANOPARTICLES FOR INFRARED PHOTOTHERMAL THERAPY

The aim of this review is to provide an up-to-date overview of nanoparticles developed for use as photothermal therapy agents (PTT) over the past five years. The main emphasis is on nanoparticles that absorb near infrared (NIR) light for PTT of cancer. Mild hyperthermia, including drug delivery, versus thermal ablation is also discussed. Recent advances in the synthesis of highly anisotropic novel metal nanoparticles for PTT are described. New metals and metal oxide complexes, as well as the use of quantum dots for PTT and as imaging agents are newer areas of development that are explained. This review also highlights current progress in the development of carbon nanoparticles, including reduced graphene oxide for both thermal ablation as well as drug delivery. The review culminates in the recent use electrically conductive polymer nanoparticles for hyperthermia. The advantages and unique features of these contemporary nanoparticles being used for PTT are highlighted. The goal of the present work is to describe the recent evolution of nanoparticles for NIR stimulated PTT, and highlight the innovations and future directions.

Hydrophobic anticancer drug delivery by a 980 nm laser-driven photothermal vehicle for efficient synergistic therapy of cancer cells in vivo

A novel 980 nm laser-driven hydrophobic anticancer drug-delivery platform based on hollow CuS nanoparticles is constructed in this work. The excellent synergistic therapy combining drug treatment and photothermal ablation of cancer cells both in vitro and in vivo is demonstrated, which opens up new opportunities for biological and medical applications.

In vitro and in vivo mapping of drug release after laser ablation thermal therapy with doxorubicin-loaded hollow gold nanoshells using fluorescence and photoacoustic imaging

Doxorubicin-loaded hollow gold nanoshells (Dox@PEG-HAuNS) increase the efficacy of photothermal ablation (PTA) not only by mediating efficient PTA but also through chemotherapy, and therefore have potential utility for local anticancer therapy. However, in vivo real-time monitoring of Dox release and temperature achieved during the laser ablation technique has not been previously demonstrated before. In this study, we used fluorescence optical imaging to map the release of Dox from Dox@PEG-HAuNS and photoacoustic imaging to monitor the tumor temperature achieved during near-infrared laser-induced photothermal heating in vitro and in vivo. In vitro, treatment with a 3-W laser was sufficient to initiate the release of Dox from Dox@PEG-HAuNS (1:3:1 wt/wt, 1.32 × 10(12)particles/mL). Laser powers of 3 and 6W achieved ablative temperatures of more than 50°C. In 4T1 tumor-bearing nude mice that received intratumoral or intravenous injections of Dox@PEG-HAuNS, fluorescence optical imaging (emission wavelength = 600 nm, excitation wavelength = 500 nm) revealed that the fluorescence intensity in surface laser-treated tumors 24h after treatment was significantly higher than that in untreated tumors (p = 0.015 for intratumoral, p = 0.008 for intravenous). Similar results were obtained using an interstitial laser to irradiate tumors following the intravenous injection of Dox@PEG-HAuNS (p = 0.002 at t = 24h). Photoacoustic imaging (acquisition wavelength = 800 nm) revealed that laser treatment caused a substantial increase in tumor temperature, from 37 °C to ablative temperatures of more than 50 °C. Ex vivo analysis revealed that the fluorescence intensity of laser-treated tumors was twice as high as that of untreated tumors (p = 0.009). Histological analysis confirmed that intratumoral injection of Dox@PEG-HAuNS and laser treatment caused significantly more tumor necrosis compared to tumors that were not treated with laser (p<0.001). On the basis of these findings, we conclude that fluorescence optical imaging and photoacoustic imaging are promising approaches to assessing Dox release and monitoring temperature, respectively, after Dox@PEG-HAuNS-mediated thermal ablation therapy.

Near-infrared light-mediated nanoplatforms for cancer thermo-chemotherapy and optical imaging

While thermo-chemotherapy has proved to be effective in optimizing the efficacies of cancer treatments, traditional chemotherapy is subject to adverse side effects and heat delivery is often challenging in operation. Some photothermal inorganic nanoparticles responsive to near infrared light provide new opportunities for simultaneous and targeted delivery of heat and chemotherapeutics to the tumor sites in pursuit of synergistic effects for efficacy enhancement. The state of the art of nanoparticle-induced thermo-chemotherapy is summarized and the advantages and challenges of the major nanoplatforms based on gold nanoparticles, carbon nanomaterials, palladium nanosheets, and copper-based nanocrystals are highlighted. In addition, the optical-imaging potentials of the nanoplatforms that may endow them with imaging-guided therapy and therapeutic-result-monitoring capabilities are also briefly discussed.

Specific tumor delivery of paclitaxel using glycolipid-like polymer micelles containing gold nanospheres

It is difficult for most of the drug delivery systems to really display a temporal and spatial release of entrapped drug once the systems are iv administrated. We hypothesized that the photothermal effect, mediated by a near-infrared (NIR) laser and hollow gold nanospheres (HAuNS), can modulate paclitaxel (PTX) release from polymer micelles, and further result in the enhanced antitumor activity of the micelles. We loaded PTX and HAuNS, which display strong plasmon absorption in the NIR region, into glycolipid-like polymer micelles with an excellent cell internalization capability. The surface of the micelles was conjugated successfully with a peptide, which has the specific-binding with EphB4, a member of the Eph family of receptor tyrosine kinases overexpressed on cell membrane of numerous tumors, to increase the delivery of PTX into tumor cells. Rapid and repetitive drug release from our polymer (HP-TCS) micelles could be readily achieved upon NIR laser irradiation. Our data demonstrated the specific delivery of HP-TCS micelles into positive-EphB4 tumors using a duel-tumor model after iv administration during the whole experiment process (1-48 h). Interestingly, significantly higher uptake of the micelles by SKOV3 tumors (positive-EphB4) than A549 tumors (negtive-EphB4) was observed, with increased ratio on experiment time. However, the specific cell uptake was observed only during the short incubation time (1-4 h) in vitro. Our data also indicated the treatment of tumor cells with the micelles followed by NIR laser irradiation showed significantly greater toxicity activity than the treatment with the micelles alone, free PTX and the micelles (without PTX loading) plus NIR laser irradiation. The enhanced toxicity activity to tumor cells should be attributed to the enhanced drug cellular uptake mediated by the glycolipid-like micelles, chemical toxicity of the released drug from the micelles due to the trigger of NIR laser, and the photothermal ablation under NIR laser irradiation.

pH-responsive assembly of gold nanoparticles and "spatiotemporally concerted" drug release for synergistic cancer therapy

A challenge in using plasmonic nanostructure-drug conjugates for thermo-chemo combination cancer therapy lies in the huge size discrepancy; the size difference can critically differentiate their biodistributions and hamper the synergistic effect. Properly tuning the plasmonic wavelength for photothermal therapy typically results in the nanostructure size reaching ∼100 nm. We report a new combination cancer therapy platform that consists of relatively small 10 nm pH-responsive spherical gold nanoparticles and conjugated doxorubicins. They are designed to form aggregates in mild acidic environment such as in a tumor. The aggregates serve as a photothermal agent that can selectively exploit external light by their collective plasmon modes. Simultaneously, the conjugated doxorubicins are released. The spatiotemporal concertion is confirmed at the subcellular, cellular, and organ levels. Both agents colocalize in the cell nuclei. The conjugates accumulate in cancer cells by the rapid phagocytic actions and effective blockage of exocytosis by the increased aggregate size. They also effectively accumulate in tumors up to 17 times over the control because of the enhanced permeation and retention. The conjugates exhibit a synergistic effect enhanced by nearly an order of magnitude in cellular level. The synergistic effect is demonstrated by the remarkable reductions in both the therapeutically effective drug dosage and the photothermal laser threshold. Using an animal model, effective tumor growth suppression is demonstrated. The conjugates induce apoptosis to tumors without any noticeable damage to other organs. The synergistic effect in vivo is confirmed by qRT-PCR analysis over the thermal stress and drug-induced growth arrest.

Remotely Triggered Drug Release from Gold Nanoparticle-based Systems

Nanoparticles are attractive drug carriers that can combine drug molecules and targeting moieties in order to improve treatment efficacy and reduce unwanted side effects. In addition, activatable nanoparticles may enable drug release in the target sites at accurate timings or conditions, in which drug discharge can be controlled by specific stimuli. Especially, gold nanoparticles provide a great opportunity as drug carriers because of the following advantageous features: i) simple formulation with various sizes and shapes and non-toxicity; ii) easy incorporation of targeting molecules, drugs or other therapeutic molecules on them; iii) triggered drug release by means of external or internal stimuli. In this chapter, we describe relevant examples of the preparation techniques and the performance of various types of gold nanoparticles for drug delivery as well as theranostics.

Gold nanorods carrying paclitaxel for photothermal-chemotherapy of cancer

Nanotechnology-based photothermal therapy has emerged as a promising treatment for cancer during the past decade. However, heterogeneous laser heating and limited light penetration can lead to incomplete tumor cell eradication. Here, we developed a method to overcome these limitations by combining chemotherapy with photothermal therapy using paclitaxel-loaded gold nanorods. Paclitaxel was loaded to gold nanorods with high density (2.0 × 10(4) paclitaxel per gold nanorod) via nonspecific adsorption, followed by stabilization with poly(ethylene glycol) linked with 11-mercaptoundecanoic acid. Paclitaxel was entrapped in the hydrophobic pocket of the polymeric monolayer on the surface of gold nanorods, which allows direct cellular delivery of the hydrophobic drugs via the lipophilic plasma membrane. Highly efficient drug release was demonstrated in a cell membrane mimicking two-phase solution. Combined photothermal therapy and chemotherapy with the paclitaxel-loaded gold nanorods was shown to be highly effective in killing head and neck cancer cells and lung cancer cells, superior to photothermal therapy or chemotherapy alone due to a synergistic effect. The paclitaxel-gold nanorod enabled photothermal chemotherapy has the potential of preventing tumor reoccurrence and metastasis and may have an important impact on the treatment of head and neck cancer and other malignancies in the clinic.