Targeted delivery and enhanced uptake of chemo-photodynamic nanomedicine for melanoma treatment

Nanoparticles (NPs) modified with targeting ligands have often shown great potential in targeted drug delivery for tumor therapy. However, the clearance of NPs by the monocyte-phagocyte system (MPS) and the relatively low cellular uptake by tumor cells have significantly limited the antitumor efficacy of a variety of nanomedicines. Tumor microenvironment-mediated multidrug resistance also reduces the antitumor efficacy of internalized nanomedicines. Herein, we developed an innovative nanomedicine for combined chemo-photodynamic therapy of melanoma through targeted drug delivery and significantly improved the cellular uptake of the nanomedicine through the charge-reversal phenomenon. An amphiphilic platinum (IV)-polyethylenimine-chlorin e6 (Pt(IV)-PEI-Ce6) polymer was designed, prepared, and self-assembled into NPs (PPC) in an aqueous solution, and these NPs were subsequently coated with hyaluronic acid (HA) to afford PPC@HA. The surface-coated HA provided PPC with a negatively charged surface potential to reduce the clearance by the MPS during systemic circulation and enhanced the targeted delivery of PPC to CD44-overexpressing melanoma cells. Upon accumulation in the tumor site, hyaluronidase overexpressed in the tumor induced HA degradation to release the positively charged PPC, resulting in an increased internalization of PPC into tumor cells. Bioactive Pt(II) was released in response to high glutathione level in the tumor cells for effective tumor chemotherapy. Under 650 nm laser irradiation, Ce6 produced reactive oxygen species (ROS), thus driving photodynamic therapy. Finally, PPC@HA exhibited combined photodynamic-chemotherapeutic antitumor efficacy against the melanoma cells in mice. STATEMENT OF SIGNIFICANCE: Tumors are one of the greatest threats to human health, and chemotherapy has been one of the most common therapeutic modalities for treating tumors; however, many challenges related to chemotherapy remain, such as low delivery efficiency, side effects, and unsatisfactory therapeutic efficacy. Nanomedicines modified with targeting ligands have often shown great potential in improving targeted drug delivery for tumor therapy; however, the clearance of nanomaterials by the monocyte-phagocyte system and the relatively low cellular uptake by tumor cells have significantly limited the antitumor efficacy of a variety of nanomedicines. Herein, we developed a novel charge-reversal-based, hyaluronic acid-coated, Pt(IV) prodrug and chlorin e6-based nanomedicine to improve systemic circulation and targeted accumulation of the nanomedicine in the tumor tissue and to enhance its intracellular uptake. This nanomedicine may provide a potential new platform to improve the drug content inside tumor cells and to effectively inhibit tumor growth through combined chemotherapy and photodynamic therapy.

Supramolecular micelles as multifunctional theranostic agents for synergistic photodynamic therapy and hypoxia-activated chemotherapy

Photodynamic therapy (PDT), where a photosensitizer (under light irradiation) converts molecular oxygen to singlet oxygen to elicit programmed cell death, is a promising cancer treatment modality with a high temporal and spatial resolution. However, only limited cancer treatment efficacy has been achieved in clinical PDT due to the hypoxic conditions of solid tumor microenvironment that limits the generation of singlet oxygen, and PDT process often leads to even more hypoxic microenvironment due to the consumption of oxygens during therapy. Herein, we designed novel supramolecular micelles to co-deliver photosensitizer and hypoxia-responsive prodrug to improve the overall therapeutic efficacy. The supramolecular micelles (CPC) were derived from a polyethylene glycol (PEG) system dually tagged with hydrophilic cucurbit[7]uril (CB[7]) and hydrophobic Chlorin e6 (Ce6), respectively on each end, for synergistic antitumor therapy via PDT of Ce6 and chemotherapy of a hypoxia-responsive prodrug, banoxantrone (AQ4N), loaded into the cavity of CB[7]. In addition, CPC was further modularly functionalized by folate (FA) via strong host-guest interaction between folate-amantadine (FA-ADA) and CB[7] to produce a novel nanoplatform, AQ4N@CPC-FA, for targeted delivery. AQ4N@CPC-FA exhibited enhanced cellular uptake, negligible cytotoxicity and good biocompatibility, and improved intracellular reactive oxygen species (ROS) generation efficiency. More importantly, in vivo evaluation of AQ4N@CPC-FA revealed a synergistic antitumor efficacy between PDT of Ce6 and hypoxia-activated chemotherapy of AQ4N (that can be converted to chemotherapeutic AQ4 for tumor chemotherapy in response to the strengthened hypoxic tumor microenvironment during PDT treatment). This study not only provides a new nanoplatform for synergistic photodynamic-chemotherapeutic treatment, but also offers important new insights to design and development of multifunctional supramolecular drug delivery system. STATEMENT OF SIGNIFICANCE: Photodynamic therapy (PDT) has exhibited a variety of advantages for cancer phototherapy as compared to traditional chemotherapy. However, the unsatisfactory therapeutic efficacy by PDT alone as a result of the enhanced tumor hypoxia during PDT has limited its clinical application. Herein, we designed multifunctional supramolecular micelles to co-deliver photosensitizer and hypoxia-responsive prodrug to improve the overall therapeutic efficacy. The supramolecular micelles are biocompatible and possess strong red absorption, controlled drug release profile, and ultimately enhanced therapeutic outcome via PDT-chemotherapy. This study not only provides a new nanoplatform for synergistic photodynamic-chemotherapeutic treatment of cancer, but also offers important new insights to design and development of multifunctional supramolecular drug delivery tool for multi-modality cancer therapy.