title: Targeted photothermal ablation of murine melanomas with melanocyte-stimulating hormone analog-conjugated hollow gold nanospheres.
abstract: OBJECTIVE
  To develop melanoma-targeted hollow gold nanospheres (HAuNS) and evaluate their potential utility for selective photothermal ablation in melanoma.
  
  
  METHODS
  A new class of photothermal coupling agents based on HAuNS was synthesized. HAuNS were stabilized with polyethylene glycol (PEG) coating and attached with alpha-melanocyte-stimulating hormone (MSH) analog, [Nle4,D-Phe7]alpha-MSH (NDP-MSH), which is a potent agonist of melanocortin type-1 receptor overexpressed in melanoma. The intracellular uptake of the NDP-MSH-conjugated PEGylated HAuNS (NDP-MSH-PEG-HAuNS) and the distribution of beta-arrestin were examined in murine B16/F10 melanoma cells. The biodistribution of NDP-MSH-PEG-HAuNS was assessed at 4 hours post i.v. injection in tumor-bearing nude mice. Photothermal ablation effect of the nanoparticles was evaluated both histologically using excised tissue and functionally by [18F]fluorodeoxyglucose positron emission tomography.
  
  
  RESULTS
  NDP-MSH-PEG-HAuNS consist only of a thin gold wall with hollow interior (outer diameter, 43.5 +/- 2.3 nm; shell thickness, 3-4 nm), which displays strong and tunable resonance absorption in near-IR region (peak, 808 nm). The nanoparticles were specifically taken up by melanoma cells, which initiated the recruitment of beta-arrestins, the adapters to link the activated G-protein-coupled receptors to clathrin, indicating the involvement of receptor-mediated endocytosis. This resulted in enhanced extravasation of NDP-MSH-PEG-HAuNS from tumor blood vessels and their dispersion into tumor matrix compared with nonspecific PEGylated HAuNS. Successful selective photothermal ablation of B16/F10 melanoma with targeted HAuNS was confirmed by histologic and [18F]fluorodeoxyglucose positron emission tomography evaluation at 24 hours post near IR-region laser irradiation at a low-dose energy of 30 J/cm2.
  
  
  CONCLUSIONS
  NDP-MSH-PEG-HAuNS have the potentials to mediate targeted photothermal ablation of melanoma.
authors.affiliation: Department of Experimental Diagnostic Imaging, The University of Texas M. D. Anderson Cancer Center, Houston, Texas 77030, USA.
authors.forename: Wei
authors.initials: W
authors.lastname: Lu
authors.forename: Chiyi
authors.initials: C
authors.lastname: Xiong
authors.forename: Guodong
authors.initials: G
authors.lastname: Zhang
authors.forename: Qian
authors.initials: Q
authors.lastname: Huang
authors.forename: Rui
authors.initials: R
authors.lastname: Zhang
authors.forename: Jin Z
authors.initials: JZ
authors.lastname: Zhang
authors.forename: Chun
authors.initials: C
authors.lastname: Li
mesh_terms: D055011:Ablation Techniques / Q000379:methods*; D000512:Alpha Particles; D000818:Animals; D006046:Gold; D008546:Melanoma, Experimental / Q000628:therapy*; D051379:Mice; D008819:Mice, Nude; D054118:Nanospheres / Q000627:therapeutic use*; D010789:Phototherapy / Q000379:methods*; D000521:alpha-MSH / Q000031:analogs & derivatives* / Q000627:therapeutic use
chemical_list: D000521:alpha-MSH; D006046:Gold; C027756:MSH, 4-Nle-7-Phe-alpha-