Preventing Metastasis Using Gold Nanorod-Assisted Plasmonic Photothermal Therapy in Xenograft Mice

Despite significant research regarding metastasis, there has been limited success in preventing it. However, gold nanoparticle (AuNP) technology has shown the potential to inhibit metastasis. Our earlier studies of gold nanorod-assisted plasmonic photothermal therapy (AuNRs-PPTT), where gold nanorods (AuNRs) were irradiated with near-infrared (NIR) light to induce heat, were utilized in slowing cancer cell migration in vitro. Herein, we have expanded the in vitro studies of the AuNRs-PPTT to xenograft mice to inhibit metastasis of mammary gland tumors. The study duration was 32 days from 4T1 cancer cell injections in four treatment groups: control (PBS), NIR Only, AuNRs, and AuNRs + NIR. Multiple AuNRs-PPTT treatment sessions with intratumoral AuNRs injections were conducted every 7 days on average on the mice. Photoacoustic spectroscopy has been utilized to study the distribution and aggregation of AuNRs within the tumors and the drainage of particles to the sentinel right subiliac lymph node. The photoacoustic results revealed that the AuNRs' shapes are still stable regardless of their heterogeneous distributions inside the mammalian tumor and lymph nodes. Bioluminescence imaging was used to monitor metastasis using luciferin labeling techniques and has shown that AuNRs-PPTT inhibited metastasis completely within the first 21 days. Moreover, proteomics was run to determine the most pivotal inhibitory pathways: NETosis, cell growth, cell proliferation, inflammation, and extracellular matrix (ECM) degradation. These five mechanisms are interdependent within related networks, which synergistically explains the molecular mechanism of metastasis inhibition by AuNRs-PPTT. The current in vivo data ensures the viability of PPTT applications in inhibiting metastasis in humans.

Therapeutic potential of targeted-gold nanospheres on collagen-induced arthritis in rats

Rheumatoid arthritis (RA) is a chronic inflammatory autoimmune disease that causes functional disability due to bone destruction and severe joint pain. Current anti-rheumatic treatments develop severe complications and do not provide complete remission. Gold nanoparticles (AuNPs) have garnered attention because of their unique physical and chemical properties. In this study, we have evaluated the therapeutic effects of gold nanospheres (AuNSs) with two different ligands (targeted-nanoparticles) against collagen-induced arthritis (CIA) and compared the outcomes with conventional methotrexate (MTX) and biological (infliximab) treatments. Clinical evaluation was performed by radiographic and histological examinations. The bioaccumulation of AuNSs in vital organs was assessed. The mechanistic studies targeting pro-inflammatory/anti-inflammatory and angiogenic mediators' expressions were performed. Radiographic examination showed that the targeted AuNSs reduced joint space narrowing and bone erosion. Moreover, histopathological examination of rat ankle joints demonstrated that targeted AuNSs reduce bone and cartilage degeneration/inflammation. Gold nanospheres-conjugated with nucleus localized peptide (nuclear membrane-targeted) (AuNSs@NLS) has resolved bone destruction and inflammation compared to gold nanospheres-conjugated at polyethylene glycol (AuNSs@PEG). Although the AuNSs accumulated in different organs in both cases, they did not induce any toxicity or tissue damage. The two different targeted AuNSs significantly suppress inflammatory and angiogenic mediators' expression and induced anti-inflammatory cytokine production, but the AuNSs@NLS had superior therapeutic efficacy. In conclusion, these results suggested that nuclear membrane-targeted AuNSs effectively attenuated arthritis progression without systemic side effects.

Improving the Flow Cytometry-based Detection of the Cellular Uptake of Gold Nanoparticles

Due to the considerable amount of applications of gold nanoparticles (AuNPs) in biological systems, there is a great need for an improved methodology to quantitatively measure the uptake of AuNPs in cells. Flow cytometry has the ability to measure intracellular AuNPs by collecting the light scattering from a large population of live cells through efficient single cell analysis. Traditionally, the side scattering setting of the flow cytometer, which is associated with a 488 nm excitation laser (SSC channel), is used to detect nanoparticle uptake. This method is limited as AuNPs do not have the optimized response when excited with this laser. Here, we reported that the use of more red-shifted excitation lasers will greatly enhance the optical signal needed for the flow cytometry-based detection of AuNSs (26 nm in diameter) and AuNRs (67 nm × 33 nm, length × width) uptake in triple negative breast cancer cells (MDA-MB-231).

Gold Nanorod-Assisted Photothermal Therapy Decreases Bleeding during Breast Cancer Surgery in Dogs and Cats

For localized tumors, gold nanorod (AuNR)-assisted plasmonic photothermal therapy (PPTT) is a potentially effective alternative to traditional surgery, in which AuNRs absorb near-infrared light and convert it to heat in order to kill cancer cells. However, for large tumors (volume ≥ 20 cm3), an uneven distribution of AuNRs might cause inhomogeneity of the heat distribution inside the tumor. Surgery is frequently recommended for removing large tumors, but it is associated with a high risk of cancer recurrence and metastasis. Here, we applied PPTT before surgery, which showed improved treatment for large tumors. We divided the animals (eight cats/dogs) into two groups: Group I (control), where three cases were solely treated with surgery, laser, or AuNRs alone, resulting in recurrence and metastasis; and Group II, where animals were treated with PPTT before surgery. In Group II, four out of the five cases had tumor regression without any recurrence or metastasis. Interestingly, we observed that applying PPTT before surgery displayed reduced bleeding during tumor removal, supported by histopathology that showed altered blood vessels. In conclusion, our study showed that applying AuNR-assisted PPTT (AuNRs-PPTT) before surgery could significantly affect blood vessels inside the tumor, leading to a decreased amount of bleeding during surgery, which can potentially decrease the risk of metastasis and blood loss during surgery.

Gold Nanorod Photothermal Therapy Alters Cell Junctions and Actin Network in Inhibiting Cancer Cell Collective Migration

Most cancer-related deaths come from metastasis. It was recently discovered that nanoparticles could inhibit cancer cell migration. Whereas most researchers focus on single-cell migration, the effect of nanoparticle treatment on collective cell migration has not been explored. Collective migration occurs commonly in many types of cancer metastasis, where a group of cancer cells move together, which requires the contractility of the cytoskeleton filaments and the connection of neighboring cells by the cell junction proteins. Here, we demonstrate that gold nanorods (AuNRs) and the introduction of near-infrared light could inhibit the cancer cell collective migration by altering the actin filaments and cell junctions with significantly triggered phosphorylation changes of essential proteins, using mass spectrometry-based phosphoproteomics. Further observation using super-resolution stochastic optical reconstruction microscopy (STORM) showed the actin cytoskeleton filament bundles were disturbed, which is difficult to differentiate under a normal fluorescence microscope. The decreased expression level of N-cadherin junctions and morphological changes of tight junction protein zonula occludens 2 were also observed. All of these results indicate possible functions of the AuNR treatments in regulating and remodeling the actin filaments and cell junction proteins, which contribute to decreasing cancer cell collective migration.

Nuclear Membrane-Targeted Gold Nanoparticles Inhibit Cancer Cell Migration and Invasion

Most cancer patients die from metastasis. Recent studies have shown that gold nanoparticles (AuNPs) can slow down the migration/invasion speed of cancer cells and suppress metastasis. Since nuclear stiffness of the cell largely decreases cell migration, our hypothesis is that targeting AuNPs to the cell nucleus region could enhance nuclear stiffness, and therefore inhibit cell migration and invasion. Our results showed that upon nuclear targeting of AuNPs, the ovarian cancer cell motilities decrease significantly, compared with nontargeted AuNPs. Furthermore, using atomic force microscopy, we observed an enhanced cell nuclear stiffness. In order to understand the mechanism of cancer cell migration/invasion inhibition, the exact locations of the targeted AuNPs were clearly imaged using a high-resolution three-dimensional imaging microscope, which showed that the AuNPs were trapped at the nuclear membrane. In addition, we observed a greatly increased expression level of lamin A/C protein, which is located in the inner nuclear membrane and functions as a structural component of the nuclear lamina to enhance nuclear stiffness. We propose that the AuNPs that are trapped at the nuclear membrane both (1) add to the mechanical stiffness of the nucleus and (2) stimulate the overexpression of lamin A/C located around the nuclear membrane, thus increasing nuclear stiffness and slowing cancer cell migration and invasion.

Gold Nanorods as Drug Delivery Vehicles for Rifampicin Greatly Improve the Efficacy of Combating Mycobacterium tuberculosis with Good Biocompatibility with the Host Cells

TB remains a challenging disease to control worldwide. Nanoparticles have been used as drug carriers to deliver high concentrations of antibiotics directly to the site of infection, reducing the duration of treatment along with any side effects of off-target toxicities after systemic exposure to the antibiotics. Herein we have developed a drug delivery platform where gold nanorods (AuNRs) are conjugated to rifampicin (RF), which is released after uptake into macrophage cells (RAW264.7). Due to the nature of the macrophage cells, the nanoparticles are actively internalized into macrophages and release RF after uptake, under the safety frame of the host cells (macrophage). AuNRs without RF conjugation exhibit obvious antimicrobial activity. Therefore, AuNRs could be a promising antimycobacterial agent and an effective delivery vehicle for the antituberculosis drug Rifampicin for use in tuberculosis therapy.

Treatment of natural mammary gland tumors in canines and felines using gold nanorods-assisted plasmonic photothermal therapy to induce tumor apoptosis

Plasmonic photothermal therapy (PPTT) is a cancer therapy in which gold nanorods are injected at the site of a tumor before near-infrared light is transiently applied to the tumor causing localized cell death. Previously, PPTT studies have been carried out on xenograft mice models. Herein, we report a study showing the feasibility of PPTT as applied to natural tumors in the mammary glands of dogs and cats, which more realistically represent their human equivalents at the molecular level. We optimized a regime of three low PPTT doses at 2-week intervals that ablated tumors mainly via apoptosis in 13 natural mammary gland tumors from seven animals. Histopathology, X-ray, blood profiles, and comprehensive examinations were used for both the diagnosis and the evaluation of tumor statuses before and after treatment. Histopathology results showed an obvious reduction in the cancer grade shortly after the first treatment and a complete regression after the third treatment. Blood tests showed no obvious change in liver and kidney functions. Similarly, X-ray diffraction showed no metastasis after 1 year of treatment. In conclusion, our study suggests the feasibility of applying the gold nanorods-PPTT on natural tumors in dogs and cats without any relapse or toxicity effects after 1 year of treatment.

Photothermal therapeutic effect of PEGylated gold nano-semicubes in chemically-induced skin cancer in mice

BACKGROUND

The photothermal properties of gold nanoparticles (GNPs) are promising therapeutic modality for cancer. The study objective is to evaluate the therapeutic effect of the prepared PEGylated gold nano-semicubes (PEG-GNSCs) in skin cancer. The synthesized PEG-GNSCs were intermediate between cubic and rod shapes (low aspect ratio- rods).

METHODS

In vitro toxicity was investigated in human skin melanoma Sk-Mel-28 cells, and skin squamous cell carcinoma was induced in CD1 mice by dimethylbenzanthracene (DMBA) and 12-O-tetradecanoyl-phorbol-13-acetate (TPA).

RESULTS

The calculated IC₅₀ in Sk-Mel-28 cells was 3.41μg/ml of PEG-GNSCs, in presence of laser exposure. Photothermal therapy using laser-stimulated PEG-GNSCs resulted in inhibited volume of skin tumors. Our findings indicated that the inflammatory mediators, nitric oxide and cycloxygenase-2, were inhibited in mice after being treated with low and high doses of PEG-GNSCs, accompanied with laser exposure. However, the tumor necrosis factor -α was markedly elevated, while there was no change in 5-lipoxygenase. The pro-angiogenic factor vascular endothelial growth factor was inhibited, while histone acetylation and apoptosis were induced in tumor-bearing groups, after being treated with laser-stimulated PEG-GNSCs.

CONCLUSION

The present study indicated the promising photothermal therapeutic effect of laser-stimulated PEG-GNSCs as an effective modality to inhibit the tumor growth, the angiogenesis and partially the inflammation.

Abstract 3903: Optimizing the antitumor efficacy of AuNR-assisted plasmonic photothermal therapy and its molecular impact

Plasmonic gold nanorods (AuNRs) are very promising for biomedical applications because of their strongly enhanced radiation (e.g. absorption and scattering) and non-radioactive photothermal properties due to surface plasmon resonance. In plasmonic photothermal therapy (PPTT), AuNRs absorb near infrared (NIR) laser and induce localized heat (i.e., hyperthermia) which can promote tumor tissue ablation. However, the lack of comprehensive studies to improve the efficiency of AuNRs has hindered their application. The objectives of this study were to perform a systematic analysis to optimize AuNR-PPTT based on different sizes, formulation and concentration along with various laser powers for cancer therapy in vitro and in vivo. We used AuNRs of sizes 26×6 nm and 72×19 nm with concentrations of 2.5, 5 and 10 nM, followed by 2 min of 0.5, 1, 1.78 W/cm2 NIR 808 nm diode laser exposure both in vitro and in vivo. For in vitro studies, we studied several head and neck squamous cell carcinoma (HNSCC) cell lines. We conducted an in vivo antitumor efficacy study in nude mice bearing human HNSCC Tu686 xenograft tumors with three formulations of AuNRs (72×19 nm and 26×6 nm with or without rifampicin (Rf) conjugation).Single dose intratumoral injection of 5 nM and 10 nM AuNRs (26×6 nm), followed by 2 min of 1.78 W/cm2 NIR laser exposure inhibited tumor growth and the 2.5 nM dose led to moderate antitumor efficacy. However, we observed severe skin burning at higher concentrations. In contrast, AuNRs (72×19nm) had no remarkable antitumor efficacy at high laser power. Impressively, small AuNR-conjugated Rf (AuNR-Rf) accumulated AuNRs inside the cell and had very significant antitumor efficacy (p<0.05) without any skin burning at 2.5 nM concentration. We confirmed our observations by immunohistochemistry staining of proliferation marker Ki67 in tumor tissues. To understand the molecular impact, we applied the optimized treatment in vitro. AuNR-Rf was able to induce apoptosis in 24 hours of treatment and decreased cell viability, as supported by immunoblotting of PARP and caspase 3 cleavage. In addition, we found that mutant p53 was completely abolished in AuNR-PPTT treatment. Overall, we have demonstrated that 2.5 nM AuNR with 1.78 W/cm2 NIR laser has no remarkable toxicities and optimal antitumor efficacy was observed by conjugation with Rf. In future studies, we will explore potential novel biomarkers by next generation sequencing (NGS) in mouse tumor tissues to determine the response to AuNR-PPTT. (This study supported by U01CA151802).

[M.A.R. and M.R.K.A. contributed equally to this work.]

Citation Format: Mohammad Aminur Rahman, Moustafa R. K. Ali, Zhixiang Zhao, Georgia Z. Chen, Mostafa A. El-Sayed, Dong M. Shin. Optimizing the antitumor efficacy of AuNR-assisted plasmonic photothermal therapy and its molecular impact. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 3903.

The most effective gold nanorod size for plasmonic photothermal therapy: theory and in vitro experiments

The development of new and improved photothermal contrast agents for the successful treatment of cancer (or other diseases) via plasmonic photothermal therapy (PPTT) is a crucial part of the application of nanotechnology in medicine. Gold nanorods (AuNRs) have been found to be the most effective photothermal contrast agents, both in vitro and in vivo. Therefore, determining the optimum AuNR size needed for applications in PPTT is of great interest. In the present work, we utilized theoretical calculations as well as experimental techniques in vitro to determine this optimum AuNR size by comparing plasmonic properties and the efficacy as photothermal contrast agents of three different sizes of AuNRs. Our theoretical calculations showed that the contribution of absorbance to the total extinction, the electric field, and the distance at which this field extends away from the nanoparticle surface all govern the effectiveness of the amount of heat these particles generate upon NIR laser irradiation. Comparing between three different AuNRs (38 × 11, 28 × 8, and 17 × 5 nm), we determined that the 28 × 8 nm AuNR is the most effective in plasmonic photothermal heat generation. These results encouraged us to carry out in vitro experiments to compare the PPTT efficacy of the different sized AuNRs. The 28 × 8 nm AuNR was found to be the most effective photothermal contrast agent for PPTT of human oral squamous cell carcinoma. This size AuNR has the best compromise between the total amount of light absorbed and the fraction of which is converted to heat. In addition, the distance at which the electric field extends from the particle surface is most ideal for this size AuNR, as it is sufficient to allow for coupling between the fields of adjacent particles in solution (i.e., particle aggregates), resulting in effective heating in solution.

Synthesis and characterization of SiC and SiC/Si3N4 composite nano powders from waste material

In the present work, nano silicon carbide has been prepared by pyrolysis of rice-husk ashes as starting materials. Three rice-husk ash samples having different features were used. The first was coarse-grained rice husk ash (fired husk as is), the second was fine rice husk ash (hand-ground), while the third was ball milled one. Effect of ball milling of the starting ashes for 6h on the formation of nano SiC was investigated and compared with those prepared without milling. The particle sizes of the prepared SiC materials were affected by the milling process. The particle sizes of the obtained nano SiC from ball milled staring materials were smaller than those prepared without milling. The pyrolysis conditions, i.e. the temperature and atmosphere were optimized. The optimum firing temperature to obtain well crystalline nano SiC was 1550°C. The effect of pyrolysis atmosphere, i.e. argon, vacuum and nitrogen was also demonstrated. The pyrolysis in argon exhibited lower efficiency on the formation of SiC than vacuum; while the pyrolysis in nitrogen atmosphere led to formation of SiC/Si(3)N(4) nanocomposite.

Synthesis and optical properties of small Au nanorods using a seedless growth technique

Gold nanoparticles have shown potential in photothermal cancer therapy and optoelectronic technology. In both applications, a call for small size nanorods is warranted. In the present work, a one-pot seedless synthetic technique has been developed to prepare relatively small monodisperse gold nanorods with average dimensions (length × width) of 18 × 4.5 nm, 25 × 5 nm, 15 × 4.5 nm, and 10 × 2.5 nm. In this method, the pH was found to play a crucial role in the monodispersity of the nanorods when the NaBH(4) concentration of the growth solution was adjusted to control the reduction rate of the gold ions. At the optimized pH and NaBH(4) concentrations, smaller gold nanorods were produced by adjusting the CTAB concentration in the growth solution. In addition, the concentration of silver ions in the growth solution was found to be pivotal in controlling the aspect ratio of the nanorods. The extinction coefficient values for the small gold nanorods synthesized with three different aspect ratios were estimated using the absorption spectra, size distributions, and the atomic spectroscopic analysis data. The previously accepted relationships between the extinction coefficient or the longitudinal band wavelength values and the nanorods' aspect ratios found for the large nanorods do not extend to the small size domain reported in the present work. The failure of extending these relationships over larger sizes is a result of the interaction of light with the large rods giving an extinction band which results mostly from scattering processes while the extinction of the small nanorods results from absorption processes.