Biomedical Engineering – From Theory to Applications

An Ancient Model Organism to Test In Vivo Novel Functional Nanocrystals
fluorescent PEG coated QRs (Figure 6) were challenged to living polyps, which were
monitored over progressive incubation periods.
Fig. 6. A schematic representation of the CdSe/CdS rods used in this study
The scheme shows the asymmetrical shape derived from the synthesis procedure (Carbone
et al, 2007). The method involves coinjecting Cd 2+ and S 2- precursors and preformed
spherical CdSe seeds into an environment of hot surfactants, well suited for the anisotropic
growth of the second shell-material (CdS) on the first underlying core (CdSe). Resulting QRs
are transferred from chloroform to water by wrapping them within an amphiphilic polymer
shell (blue shell in the figure). To these polymer-coated QRs, polyethylene glycol (PEG)
molecules (red shell) can be bound by using an EDC catalyzed cross linking scheme. The
rod samples are an average of 35nm in length and 4 nm in diameter as confirmed by b) the
TEM image of the corresponding sample (generously provided by Dr.A.Quarta, Italian
Institute of Technology, Lecce, Italy)
Unlabelled cells were detectable by fluorescence microscopy, indicating that QRs were not
uptaken by Hydra ectodermal cells. However, an unexpected animal behaviour was
observed which consisted of an intense tentacle writhing, i.e. contractions and bending
along the axial length of each tentacle, as shown in Figure 7.
Fig. 7. Elicitation of tentacle writhing by QRs.
The test was initiated by adding CdSe/CdS core/shell QRs to each well containing six
polyps and motor activity was monitored by continuous video recording using a Camediadigital
camera (Olympus) connected to a cold light Wild stereo microscope a) Hydra polyp
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