title: Theranostic nanoparticles for enzyme-activatable fluorescence imaging and photodynamic/chemo dual therapy of triple-negative breast cancer.
abstract: BACKGROUND
  Triple-negative breast cancer (TNBC) is a highly diverse group of cancers characterized by tumors that does not express estrogen and progesterone receptors, as well as human epidermal growth factor receptor 2 (HER2) gene expression. TNBC is associated with poor prognosis due to high rate of recurrence and distance metastasis, lack of response to hormonal or HER2-targeted therapies, and partial response to chemotherapy. Hence, development of new therapeutic strategies to overcome such limitations is of great importance. Here we describe the application of photosensitizer-conjugated and camptothecin (CPT)-encapsulated hyaluronic acid (HA) nanoparticles as enzyme-activatable theranostic nanoparticles (EATNP) for near-infrared (NIR) fluorescence imaging and photodynamic/chemo dual therapy of TNBC.
  
  
  METHODS
  For the preparation of EATNPs, chlorin e6 (Ce6), a second generation photosensitizer, was covalently conjugated to a monomethoxy poly(ethylene glycol)-grafted HA backbone. Ce6-conjugated HA (Ce6-HA) formed self-assembled nanoparticles (i.e., Ce6-HA NPs) in an aqueous solution. Subsequently, CPT, a topoisomerase 1 inhibitor with remarkable anticancer efficacy but with low water solubility, was encapsulated inside the hydrophobic core of Ce6-HA NPs thereby forming EATNPs.
  
  
  RESULTS
  Fluorescence and singlet oxygen generation (SOG) of EATNPs are quenched in its native state. Treatment of EATNPs with hyaluronidase (HAdase) induces enzyme concentration-dependent activation of NIR fluorescence and SOG. Moreover, HAdase-mediated degradation of the nanoparticles also triggers the release of CPT from the EATNPs. In vitro confocal microscopy and cytotoxicity tests confirmed that EATNPs were efficiently introduced into MDA-MB-231 TNBC cell line, thereby inducing better cytotoxicity than that by free CPT. Additional light irradiation onto the EATNP-treated cells significantly increased therapeutic efficacy in TNBC, which indicates that EATNP plays an important role in enzyme-activated NIR fluorescence imaging and photodynamic/chemo dual therapy of TNBC.
  
  
  CONCLUSIONS
  We found that HAdase may switch on NIR fluorescence and SOG of EATNPs. Moreover, CTP release from the nanoparticles is triggered by the enzyme HAdase. In vitro cell study showed potential utility of EATNPs for fluorescence imaging and photodynamic/chemo dual therapy of TNBC.
authors.affiliation: Molecular Imaging & Therapy Branch, Division of Convergence Technology, National Cancer Center, Goyang, Gyeonggi-do, Korea.
authors.forename: Jaehee
authors.initials: J
authors.lastname: Choi
authors.affiliation: Molecular Imaging & Therapy Branch, Division of Convergence Technology, National Cancer Center, Goyang, Gyeonggi-do, Korea.
authors.forename: Hyunjin
authors.initials: H
authors.lastname: Kim
authors.affiliation: Molecular Imaging & Therapy Branch, Division of Convergence Technology, National Cancer Center, Goyang, Gyeonggi-do, Korea.
authors.forename: Yongdoo
authors.initials: Y
authors.lastname: Choi
keywords: Chemotherapy; fluorescence imaging; photodynamic therapy (PDT); theranostic nanoparticles; triple-negative breast cancer (TNBC)