Fluorescent nanocrystals reveal regulated portals of entry into and between the cells of Hydra

PLoS One. 2009 Nov 2;4(11):e7698. doi: 10.1371/journal.pone.0007698.


Initially viewed as innovative carriers for biomedical applications, with unique photophysical properties and great versatility to be decorated at their surface with suitable molecules, nanoparticles can also play active roles in mediating biological effects, suggesting the need to deeply investigate the mechanisms underlying cell-nanoparticle interaction and to identify the molecular players. Here we show that the cell uptake of fluorescent CdSe/CdS quantum rods (QRs) by Hydra vulgaris, a simple model organism at the base of metazoan evolution, can be tuned by modifying nanoparticle surface charge. At acidic pH, amino-PEG coated QRs, showing positive surface charge, are actively internalized by tentacle and body ectodermal cells, while negatively charged nanoparticles are not uptaken. In order to identify the molecular factors underlying QR uptake at acidic pH, we provide functional evidence of annexins involvement and explain the QR uptake as the combined result of QR positive charge and annexin membrane insertion. Moreover, tracking QR labelled cells during development and regeneration allowed us to uncover novel intercellular trafficking and cell dynamics underlying the remarkable plasticity of this ancient organism.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Annexins / chemistry
  • Cadmium Compounds / chemistry
  • Calcium / metabolism
  • Cytological Techniques
  • Fluorescent Dyes / pharmacology
  • Hydra / physiology*
  • Hydrogen-Ion Concentration
  • Microscopy, Fluorescence / methods
  • Nanoparticles / chemistry*
  • Nanotechnology / methods
  • Quantum Dots
  • Selenium Compounds / chemistry
  • Sulfides / chemistry
  • Surface Properties
  • Tissue Distribution


  • Annexins
  • Cadmium Compounds
  • Fluorescent Dyes
  • Selenium Compounds
  • Sulfides
  • cadmium sulfide
  • cadmium selenide
  • Calcium