Ya-Na Wu

In vivo Photoacoustic Molecular Imaging with Simultaneous Multiple Selective Targeting Using Antibody-Conjugated Gold Nanorods

The use of gold nanorods for photoacoustic molecular imaging with simultaneous multiple targeting is reported. Multiple targeting is done by utilizing the tunable optical absorption property of gold nanorods. This technique allows multiple molecular signatures to be obtained by simply switching laser wavelength. HER2 and EGFR were chosen as the primary target molecules for examining two cancer cells, OECM1 and Cal27. Both in vitro and in vivo mouse model imaging experiments were performed, with contrast enhancement of up to 10 dB and 3.5 dB, respectively. The potential in improving cancer diagnosis is demonstrated.

Photoacoustic Imaging of Multiple Targets Using Gold Nanorods

Photoacoustic (PA) imaging has been used mainly for anatomical and functional imaging. Although functionalized nanoparticles also have been developed for PA molecular imaging, only single targeting has been demonstrated. In this study, PA imaging of multiple targets using gold nanorods is demonstrated experimentally using HER2 and CXCR4 as target molecules. The two corresponding monoclonal antibodies were conjugated to two types of gold nanorod with different aspect ratios. Gold nanorods with mean aspect ratios of 5.9 and 3.7 exhibited peak optical absorptions at 1000 and 785 nm, respectively. Appropriate selection of laser irradiation wavelength enhances PA signals by 7-12 dB and allows signals from gold nanorods corresponding to specific bindings to be distinguished. This approach potentially allows the expression levels of different oncogenes of cancer cells to be revealed simultaneously.

Solid-state synthesis of monocrystalline iron oxide nanoparticle based ferrofluid suitable for magnetic resonance imaging contrast application

A new γ-Fe2O3 MION ferrofluid has been developed with a salt-assisted solid-state reaction. Characterizations show that the ferrofluid is composed of maghemite nanoparticles with a mean diameter of 2.7 nm. Though the nanoparticles are ultrafine, they are well crystallized, with a saturation magnetization value of 34.7 emu g−1, making them suitable for MRI applications. In spite of the absence of any surfactant, the ferrofluid can be stable for more than 6 months. An in vitro cytotoxicity test revealed good biocompatibility of the maghemite nanoparticles, suggesting that they may be further explored for biomedical applications. NMR measurements revealed significantly reduced water proton relaxation times T1 and T2. The MR images of the nanoparticles in aqueous dispersion were investigated using a 3 T clinical MR imager. These preliminary experiments have demonstrated the potential of the as-synthesized ultrafine, cap-free maghemite MIONs in functional molecular imaging for biomedical research and clinical diagnosis.

Multiple targeting in photoacoustic imaging using bioconjugated gold nanorods

Cancer cells presented altered surface molecules to encourage their growth and metastasis. Expression of oncogeneic surface molecules also play important roles in the prediction of clinical outcome and treatment response of anti-cancer drugs. It is thus conceivable that imaging of cancer lesions while simultaneously obtaining their pathogenic information at molecular level of as many oncogenic proteins as possible is of great clinical significance. Gold nanoparticles have been used as a contrast agent for photoacoustic imaging. In addition, gold nanoparticles can be bioconjugated to probe certain molecular processes. An intriguing property of gold nanoparticles is its ability to tailor its optical properties. For example, size effects on the surface plasmon absorption of spherical gold nanoparticles have shown that the peak optical absorption red-shifts with the increasing particle size. In addition, the optical absorption spectrum of cylindrical gold nanoparticles (i.e., gold nanorods) exhibits a strong absorption band that is directly related to the aspect ratio. With these unique characteristics, selective targeting can be achieved in photoacoustic molecular imaging. Specifically, gold nanorods with different aspect ratios can be bioconjugated to different antibodies. Multiple targeting and simultaneous detection can then be achieved by using laser irradiation at the respective peak optical absorption wavelength. In this study, photoacoustic multiple targeting using gold nanorods is experimentally demonstrated. We have chosen Her2 and CXCR4 as our primary target molecule as Her2 expression is associated with growth characteristics and sensitivity to Herceptin chemotherapy. On the other hand, CXCR4 expression predict the organ-specific metastatic potential of the cancer cells for clinical intervention in advance. Monoclonal antibody (mAb) against Her2/neu was conjugated to nanorods with several different aspect ratios. The agarose gel is suitable for photoacoustic signal acquisition. A wavelength tunable Ti-Sapphire laser was used for laser irradiation and a 1 MHz ultrasound transducer was used for acoustic detection. The optical wavelength of the laser was tuned between 800 nm and 940 nm, corresponding to gold nanorods of an aspect ratio ranging from 3.7 to 5.9. The results clearly show the potential of photoacoustic molecular imaging with multiple targeting in revealing different oncogene expression levels of the cancer cells.

Surface functionalization of carbon nanomaterials by self-assembling hydrophobin proteins.

Class I fungal hydrophobins are small surface-active proteins that self-assemble to form amphipathic monolayers composed of amyloid-like rodlets. The monolayers are extremely robust and can adsorb onto both hydrophobic and hydrophilic surfaces to reverse their wettability. This adherence is particularly strong for hydrophobic materials. In this report, we show that the class I hydrophobins EAS and HYD3 can self-assemble to form a single-molecule thick coating on a range of nanomaterials, including single-walled carbon nanotubes (SWCNTs), graphene sheets, highly oriented pyrolytic graphite, and mica. Moreover, coating by class I hydrophobin results in a stable, dispersed preparation of SWCNTs in aqueous solutions. No cytotoxicity is detected when hydrophobin or hydrophobin-coated SWCNTs are incubated with Caco-2 cells in vitro. In addition, we are able to specifically introduce covalently linked chemical moieties to the hydrophilic side of the rodlet monolayer. Hence, class I hydrophobins provide a simple and effective strategy for controlling the surfaces of a range of materials at a molecular level and exhibit strong potential for biomedical applications.

Third-harmonic generation microscopy reveals dental anatomy in ancient fossils

Fossil teeth are primary tools in the study of vertebrate evolution, but standard imaging modalities have not been capable of providing high-quality images in dentin, the main component of teeth, owing to small refractive index differences in the fossilized dentin. Our first attempt to use third-harmonic generation (THG) microscopy in fossil teeth has yielded significant submicrometer level anatomy, with an unexpectedly strong signal contrasting fossilized tubules from the surrounding dentin. Comparison between fossilized and extant teeth of crocodilians reveals a consistent evolutionary signature through time, indicating the great significance of THG microscopy in the evolutionary studies of dental anatomy in fossil teeth.

Combined Multi-Target Molecular Ultrasonography and Photothermal Therapy Using Cancer Targeting Gold Nano Rod Probes

Ultrasound imaging is a relatively low cost, portable and non-invasive medical imaging modality for the diagnosis of a wide spectrum of diseases. Molecular imaging of diseases provide valuable information for improved disease diagnosis and management and has been developed to integrate into various medical imaging platform. However, no molecular probes has been developed for ultrasound imaging to date. In this study, we synthesized gold nano rod (AuNRs) with controllable aspect ratio as the core of molecular probe. The AuNR was modified with poly-ethylene glycol (PEG) and monocolonal antibody specific for the target biomolecules such as Her-2, CXCR4, EGFR in this research. The molecular photoacoustic ultrasonography. The AuNR probe exhibit surface plasmonic resonance frequency (SPR) proportional to their aspect ratio. Two type of AuNR with SPR at 785 nm and 1000 nm, respectively, were synthesized. The SPR spectra fall into NIR range of biological optical window and thus enabled better tissue penetration of the laser light. Interaction of AuNRs with laser irradiation was able to generate acoustic wave for image reconstruction and precision dynamic measurement of local fluid flow. In vitro study demonstrated a significant photoacoustic molecular imaging of Her-2 in the wild type cancer cells compared to the gene knock down cells mediated by stable transfection of RNAi. The use of molecular probes with different peak SPR frequencies enabled a differential molecular diagnosis of expression level of EGFR or Her2 oncogenes in two cell line models by modulation of laser wavelength. Molecular imaging of cancer bearing animals also obtained primary success with an augmentation in signal intensity from 3 db to 5 db by using multiple cocktail molecular probes. In addition, AuNR was found to absorb laser light with corresponding SPR frequency to generate local heat at nanometer scale range, which could be applied for precision hyperthermia therapy. AuNRs conjugated HER-2 antibodies successfully target tumor cells of high expression level and induced cancer cell death upon laser irradiation while spare the control cell line of low expression level. A laser wave length guided selective targeting cancer cell therapy was demonstrated using two types of molecular probes (anti-EGFR and anti-Her2) with different peak SPR and four different cancer cell lines. Combined cocktail probes targeting to the same cancer cell significantly improve therapeutic efficacy. In conclusion, a novel AuNR-molecular probe system that combined the power of photoacoustic molecular imaging and targeting therapy in one was developed and demonstrated to be effective. Future preclinical and clinical evaluation is warranted.

Ex vivo and in vivo oral cancer diagnosis using backward-collected third harmonic generation biopsy

Ex vivo and in vivo oral cancer diagnoses are demonstrated using noninvasive third-harmonic-generation biopsy. Through its superior spatial resolution on nucleus, oral cancer cells in hamster oral cavities are successfully identified without any exogenous markers.

Molecular imaging of cancer cells using plasmon-resonant-enhanced third-harmonic-generation microscopy with silver nanoparticles

We demonstrate molecular-specific third-harmonic-generation microscopy in cultured oral squamous cell carcinoma lines by using silver nano-particles as contrast agent. Through surface plasmon resonance enhancement, cancer cells are clearly identified with their molecular signature.

Zero-valent iron based nanoparticles selectively inhibit cancerous cells through mitochondria-mediated autophagy

How to improve the selectivity and efficacy of anticancer agents and to reduce side effects has always been a big challenge in clinical cancer therapy. Chemotherapeutic agents are usually toxic to both cancer and normal tissues, thus rendering compromised overall clinical outcome. Here we developed zero-valent iron nanoparticles (ZVI NPs) that exhibited selectivity toward higher toxicity to most cancerous cells thus opening a new era of anti-cancer therapy or adjuvant therapy through a novel molecular signaling pathway. We used head-and-neck cancer (HNC) cells and ovarian cancer (OVCA) cells to test the anti-cancer properties of ZVI NPs. The ZVI NPs served as a strong reactive oxygen species (ROS) inducer and caused irreversible mitochondria membrane potential lost in sensitive cancer cells that lead to cancer cell autophagy and growth suppression, while not significantly affect normal cell population. Further, the cytotoxicity of the ZVI NPs is highly depended on its redox state as oxidation of the NPs upon aging reduced their cytotoxic potency. In vivo study revealed a dose dependent tumor size reduction in tumor-bearing mice model without significant weight loss and pathological signs. These results suggest that ZVI NPs may serve as a new class of anticancer agent for a wide spectra of neoplastic diseases.