Development and Optimization of Polymeric Carriers for Lymphatic Imaging and Drug Delivery

Many cancers, including melanoma and breast cancer, metastasize via the lymphatic system, a mono-directional network of vessels and nodes that parallels the circulatory system. Accurate determination of the lymph nodes involved in the early lymphatic spread of the primary tumor is paramount for survival of the patient. Melanoma and breast cancer, when detected early offer promising 5-year survival rates of more than 90%; however, once the metastases have spread beyond the lymph node basin draining the primary tumor, the typical first metastatic site, to successive lymph nodes or organs, the 5-year survival dramatically drops to less than 20%. However, conventional systemic chemotherapy offers limited penetration into the lymphatic to treat lymphatic metastases, and often the dose limiting toxicities associated with systemic chemotherapy limit the dose to below that needed for effective treatment. Therefore, there is a great need to develop localized treatment and imaging agents for the delivery and identification of the tumor lymphatics and metastases, which can offer enhanced detection and improved efficacy and reduced toxicity over systemic therapy. Specific targeting of the lymphatics is possible by utilizing the natural structure of the lymphatic capillaries by tailoring the size and charge of the carriers to 10 to 100 nm in diameter and modifying the surface charge to be neutral to anionic in nature. Herein this dissertation focuses on the development and optimization of two different polymeric platforms for enhanced lymphatic uptake by tailoring the size and degree of anionic charge, utilizing hyaluronan and star polymers, respectively, as intralymphatic delivery platforms for the use in imaging and treatment of lymphatically metastatic cancers, such as melanoma and breast cancer. Further, the development of a geldanamycin-polymer conjugate utilizing the optimized star polymer and evaluation of its efficacy in three orthotopic tumor models for melanoma and breast cancer will also be discussed

Drug delivery to the lymphatic system: importance in future cancer diagnosis and therapies

This is an Accepted Manuscript of an article published by Taylor & Francis in Expert Opinion on Drug Delivery on 2009-08, available online: http://www.tandfonline.com/10.1517/17425240903085128.Cancer is the second leading cause of death in the US. Currently, protocols for cancer treatment include surgery to remove diseased and suspect tissues, focused radiation, systemic chemotherapy, immunotherapy and their combinations. With conventional chemotherapy, it is almost impossible to deliver anticancer drugs specifically to the tumor cells without damaging healthy organs or tissues. Over the past several decades, efforts have been made to improve drug delivery technologies that target anticancer drugs specifically to tumor cells. It has been known for over four decades that the lymphatics are the first site of metastasis for most solid cancers; however, few efforts have been made to localize chemotherapies to lymphatic tissues. Trials of several systemic targeted drug delivery systems based on nanoparticles containing chemotherapeutic agents (e.g., liposomal doxorubicin) have shown similar antitumor activity but better patient tolerance compared with conventional formulations. Animal studies have demonstrated that nanoparticles made of natural or synthetic polymers and liposomal carriers have higher accumulation in the lymph nodes and surrounding lymphatics compared to conventional intravenous therapies. This combination has the potential to both reduce nonspecific organ toxicities and increase the chemotherapeutic dose to the most likely sites of locoregional cancer metastasis

Impact of Molecular Weight on Lymphatic Drainage of a Biopolymer-Based Imaging Agent

New lymphatic imaging technologies are needed to better assess immune function and cancer progression and treatment. Lymphatic uptake depends mainly on particle size (10–100 nm) and charge. The size of carriers for imaging and drug delivery can be optimized to maximize lymphatic uptake, localize chemotherapy to lymphatic metastases, and enable visualization of treatment deposition. Toward this end, female BALB/c mice were injected subcutaneously in the hind footpad or forearm with a series of six different molecular weight hyaluronan (HA) near-infrared dye (HA-IR820) conjugates (ca. 5–200 nm). Mice were imaged using whole body fluorescent imaging over two weeks. HA-IR820 fluorescence was clearly visualized in the draining lymphatic capillaries, and in the popliteal and iliac or axillary lymph nodes. The 74-kDa HA-IR820 had the largest lymph node area-under-the-curve. In contrast to prior reports, mice bearing limb tumors exhibited three-fold longer retention of 74-kDa HA-IR820 in the popliteal node compared to mice without tumors. HA conjugate kinetics and disposition can be specifically tailored by altering their molecular weight. The specific lymphatic uptake and increased nodal retention of HA conjugates indicate significant potential for development as a natural biopolymer for intralymphatic drug delivery and imaging

Lymphatic trafficking kinetics and near-infrared imaging using star polymer architectures with controlled anionic character

Targeted lymphatic delivery of nanoparticles for drug delivery and imaging is primarily dependent on size and charge. Prior studies have observed increased lymphatic uptake and retentions of over 48 hrs for negatively charged particles compared to neutral and positively charged particles. We have developed new polymeric materials that extend retention over a more pharmaceutically relevant 7-day period. We used whole body fluorescence imaging to observe in mice the lymphatic trafficking of a series of anionic star poly-(6-O-methacryloyl-D-galactose) polymer-NIR dye (IR820) conjugates. The anionic charge of polymers was increased by modifying galactose moieties in the star polymers with succinic anhydride. Increasing anionic nature was associated with enhanced lymphatic uptake up to a zeta potential of ca. -40 mV; further negative charge did not affect lymphatic uptake. Compared to the 20% acid-conjugate, the 40 to 90% acid-star-polymer conjugates exhibited a 2.5- to 3.5-fold increase in lymphatic uptake in both the popliteal and iliac nodes. The polymer conjugates exhibited node half-lives of 2 to 20 hrs in the popliteal nodes and 19 to 114 hrs in the deeper iliac nodes. These polymer conjugates can deliver drugs or imaging agents with rapid lymphatic uptake and prolonged deep-nodal retention; thus they may provide a useful vehicle for sustained intralymphatic drug delivery with low toxicity

Lymphatic trafficking kinetics and near-infrared imaging using star polymer architectures with controlled anionic character

This is the published version. Copyright ElsevierTargeted lymphatic delivery of nanoparticles for drug delivery and imaging is primarily dependent on size and charge. Prior studies have observed increased lymphatic uptake and retentions of over 48 hrs for negatively charged particles compared to neutral and positively charged particles. We have developed new polymeric materials that extend retention over a more pharmaceutically relevant 7-day period. We used whole body fluorescence imaging to observe in mice the lymphatic trafficking of a series of anionic star poly-(6-O-methacryloyl-D-galactose) polymer-NIR dye (IR820) conjugates. The anionic charge of polymers was increased by modifying galactose moieties in the star polymers with succinic anhydride. Increasing anionic nature was associated with enhanced lymphatic uptake up to a zeta potential of ca. -40 mV; further negative charge did not affect lymphatic uptake. Compared to the 20% acid-conjugate, the 40 to 90% acid-star-polymer conjugates exhibited a 2.5- to 3.5-fold increase in lymphatic uptake in both the popliteal and iliac nodes. The polymer conjugates exhibited node half-lives of 2 to 20 hrs in the popliteal nodes and 19 to 114 hrs in the deeper iliac nodes. These polymer conjugates can deliver drugs or imaging agents with rapid lymphatic uptake and prolonged deep-nodal retention; thus they may provide a useful vehicle for sustained intralymphatic drug delivery with low toxicity.This work was supported by awards from the American Cancer Society (RSG-08-133-01-CDD), the Susan G. Komen Foundation (KG090481), a Pfizer Predoctoral Scholarship to TRB, and a PhRMA Foundation Predoctoral Fellowship to TRB. Also, the authors would like to thank Dr. Sarah Kieweg and Thora Whitmore for the use of the Advanced Rheometer 2000. TRB performed imaging studies and SD characterized and synthesized the materials; their contributions and authorship were equal in this study