Thomas D. MacDonald

Intrinsically Copper‐64‐Labeled Organic Nanoparticles as Radiotracers

PET friendly: labels for PET imaging are incorporated into completely organic porphysomes by using a fast (30 min), one-pot, high-yielding (>95 %) procedure to produce highly stable (>48 h) radiolabeled nanoparticles that show the highest specific activity ever reported for a (64) Cu-labeled nanoparticle. These (64) Cu-porphysomes can be accurately and noninvasively tracked in vivo.

Enzymatic Regioselection for the Synthesis and Biodegradation of Porphysome Nanovesicles

We recently reported that porphyrin–phospholipid conjugates can self-assemble into “porphysome” nanovesicles composed of a dense porphyrin bilayer. Porphysomes exhibit structurally driven nanoscale optical properties and have intrinsic capabilities for multimodal imaging, drug delivery, and photothermal therapy. Previous studies were based on porphysomes formed from a mixture of two chemically similar phospholipid–porphyrin regioisomers. However, use of a mixture of regioisomers is far from ideal for robust nanoparticle characterization in vitro and in vivo. In general, difficulties in synthesizing, detecting, and distinguishing phospholipid regioisomers have prevented examination of their in vivo fate until now. To our knowledge, the results reported herein are the first to demonstrate in vivo enzymatic biodegradability for any intrinsically optically active nanoparticle, a feature that might be important when considering the use of new nanomaterials in human clinical trials. Chemically modified phospholipids have proven useful for diverse biotechnology applications. Phospholipids can be labeled at various positions on their head group or side chain. While head-group modification can readily be achieved using the primary amine group of phosphatidylethanolamine, side-chain modification is less straightforward but is appropriate for conjugating more hydrophobic ligands while maintaining an amphipathic phospholipid character. Recently, phospholipids modified with cholesterol, retinoic acid, and porphyrin side chains have been developed that display useful properties for drug-delivery, immunological, and biophotonic applications. Synthesis of single sidechain-modified phospholipids is often affected by acyl migration of the side chains. The resulting regioisomers (e.g., Figure 1a) have similar structures, which make their separation impractical and their detection challenging or impossible using techniques such as HPLC, NMR spectroscopy, and mass spectrometry. Regioselective phospholipid side-chain modification has been achieved using a number of techniques. Synthesis of modified phospholipids has been performed in multistep reactions using a modified glycerol backbone, with protecting groups sometimes being required. Acylation of lyso-

An MRI‐Sensitive, Non‐Photobleachable Porphysome Photothermal Agent

Photothermal therapy makes use of photothermal sensitizers and laser light to thermally ablate diseased tissues. Porphysome nanoparticles offer a nontoxic alternative to inorganic nanocrystals for the efficient conversion of light into heat. Mn(3+) ions were incorporated directly into the building blocks of our porphysome nanoparticles, thus imparting MRI sensitivity while simultaneously improving photostability and maintaining high photothermal efficiency. Mn porphysomes are as photothermally effective as free-base porphysomes and can rival gadolinium diethylenetriaminepentaacetate (Gd-DTPA) for MRI contrast generation. Their MRI contrast generation, photothermal efficiency, and photostability are unprecedented for an all-organic nanoparticle composed of a single functional component.

Inherently Multimodal Nanoparticle-Driven Tracking and Real-Time Delineation of Orthotopic Prostate Tumors and Micrometastases

Prostate cancer is the most common cancer among men and the second cause of male cancer-related deaths. There are currently three critical needs in prostate cancer imaging to personalize cancer treatment: (1) accurate intraprostatic imaging for multiple foci and extra-capsular extent; (2) monitoring local and systemic treatment response and predicting recurrence; and (3) more sensitive imaging of occult prostate cancer bone metastases. Recently, our lab developed porphysomes, inherently multimodal, all-organic nanoparticles with flexible and robust radiochemistry. Herein, we validate the first in vivo application of 64Cu-porphysomes in clinically relevant orthotopic prostate and bony metastatic cancer models. We demonstrate clear multimodal delineation of orthotopic tumors on both the macro- and the microscopic scales (using both PET and fluorescence) and sensitively detected small bony metastases (<2 mm). The unique and multifaceted properties of porphysomes offers a promising all-in-one prostate cancer imaging agent for tumor detection and treatment response/recurrence monitoring using both radionuclide- and photonic-based strategies.

Porphyrin-Lipid Stabilized Nanoparticles for Surface Enhanced Raman Scattering Based Imaging

A porphyrin-phospholipid conjugate with quenched fluorescence was utilized to serve as both the Raman dye and a stabilizing, biocompatible surface coating agent on gold nanoparticles. Through simple synthesis and validation with spectroscopy and confocal microscopy, we show that this porphyrin-lipid stabilized AuNP is a novel SERS probe capable of cellular imaging. To date, this is the first use of porphyrin as a Raman reporter molecule for SERS based imaging.

Biologically-Targeted Detection of Primary and Micro-Metastatic Ovarian Cancer

Ovarian cancer is the leading cause of morbidity/mortality from gynecologic malignancy. Early detection of disease is difficult due to the propensity for ovarian cancer to disseminate throughout the peritoneum. Currently, there is no single accurate test to detect primary or recurrent ovarian cancer. We report a novel clinical strategy using PPF: a multimodal, PET and optical, folate receptor (FR)-targeted agent for ovarian cancer imaging. The capabilities of PPF were evaluated in primary human ovarian cancer cells, in vivo xenografts derived from primary cells and ex vivo patient omemtum, as the heterogeneity and phenotype displayed by patients is retained. Primary cells uptake PPF in a FR-dependent manner demonstrating approximately a 5- to 25-fold increase in fluorescence. By both PET and fluorescence imaging, PPF specifically delineated FR-positive, ovarian cancer xenografts, with similar tumor-to-background ratios of 8.91±0.91 and 7.94±3.94, and micro-metastatic studding (<1mm), which demonstrated a 3.5-fold increase in PPF uptake over adjacent normal tissue. Ex vivo patient omentum demonstrated selective uptake of PFF by tumor deposits. The ability of PPF to identify metastatic deposits <1mm could facilitate more complete debulking (currently, optimal debulking is <10mm residual tumor), by providing a more sensitive imaging strategy improving treatment planning, response assessment and residual/recurrent disease detection. Therefore, PPF is a novel clinical imaging strategy that could substantially improve the prognosis of patients with ovarian cancer by allowing pre-, post- and intra-operative tumor monitoring, detection and possibly treatment throughout all stages of therapy and tumor progression.

Multimodal Image-Guided Surgical and Photodynamic Interventions in Head and Neck Cancer: From Primary Tumor to Metastatic Drainage

Purpose: The low survival rate of head and neck cancer (HNC) patients is attributable to late disease diagnosis and high recurrence rate. Current HNC staging has inadequate accuracy and low sensitivity for effective diagnosis and treatment management. The multimodal porphyrin lipoprotein-mimicking nanoparticle (PLP), intrinsically capable of positron emission tomography (PET), fluorescence imaging, and photodynamic therapy (PDT), shows great potential to enhance the accuracy of HNC staging and potentially HNC management. Experimental Design: Using a clinically relevant VX-2 buccal carcinoma rabbit model that is able to consistently develop metastasis to regional lymph nodes after tumor induction, we investigated the abilities of PLP for HNC diagnosis and management. Results: PLPs facilitated accurate detection of primary tumor and metastatic nodes (their PET image signal to surrounding muscle ratios were 10.0 and 7.3, respectively), and provided visualization of the lymphatic drainage from tumor to regional lymph nodes by both preoperative PET and intraoperative fluorescence imaging, allowing the identification of unknown primaries and recurrent tumors. PLP-PDT significantly enhanced cell apoptosis in mouse tumors (73.2% of PLP-PDT group vs 7.1% of PLP alone group) and demonstrated complete eradication of primary tumors and obstruction of tumor metastasis in HNC rabbit model without toxicity in normal tissues or damage to adjacent critical structures. Conclusions: PLPs provide a multimodal imaging and therapy platform that could enhance HNC diagnosis by integrating PET/computed tomography and fluorescence imaging, and improve HNC therapeutic efficacy and specificity by tailoring treatment via fluorescence-guided surgery and PDT. Clin Cancer Res; 22(4); 961–70. ©2015 AACR.

Multimodal Nanoparticle for Primary Tumor Delineation and Lymphatic Metastasis Mapping in a Head-and-Neck Cancer Rabbit Model

64 Cu-porphysome nanoparticles enable superior delineation of neoplastic tissues, metastatic lymph nodes, and vascular drainage on head and neck cancer orthotopic rabbit model using positron emission tomography imaging. Additionally, the nanoparticles exhibit selective fluorescence activation in tumor and metastatic lymph nodes, which permits intraoperative real-time visualization of disease tissues to precisely define surgical margins and prevents collateral damage during surgeries.

Porphyrins for Imaging, Photodynamic Therapy, and Photothermal Therapy

The interest in the use of light to detect and treat cancer has grown exponentially concurrent with advances in light technology, understanding of the optical properties of tissues, and the development of optical probes. The medical applications of photonics encompass both diagnostic and therapeutic interventions. As with many oncologic treatment strategies, the clinical utilization of light suffers from some practical constraints. However, these may be circumvented by the use of exogenous contrast agents. In the past century, porphyrins—multimodal, naturally-occurring molecules—have been widely studied, both in nature and in biomedical applications. This chapter discusses the application of light in medicine and the role of porphyrins in photonic diagnostics and interventions as well as applications beyond photonics and strategies for improving on their utilization in oncology.

Porphysomes: Multimodal Nanoparticle for Primary Tumor Delineation and Lymphatic Metastasis Mapping in a Head‐and‐Neck Cancer Rabbit Model (Adv. Healthcare Mater. 14/2015)

On page 2164, J. Chen, J.C. Irish, G. Zheng, and co-workers show how 64 Cu-porphysome nanoparticles enable superior delineation of neoplastic tissues, metastatic lymph nodes, and vascular drainage on a head and neck cancer orthotopic rabbit model by PET imaging. Their selective fluorescence activation in tumor and metastatic lymph nodes permits intraoperative fluorescence guided surgeries.