Biomedical Engineering Reference
In-Depth Information
(10)
Place a stir bar in a 50-mL round-bottom flask capped with a septum.
(11)
Transfer the desired CdSe precursor (between 3 and 20 mL) into this
flask.
(12)
Heat the solution to 160 °C and allow it to stabilize for 10 min while purg-
ing the ZnS precursor with N
2
.
(13)
Inject the desired volume of ZnS precursor solution dropwise over 2 min
(according to the concentration of CdSe QDs and coating thickness
48
).
(14)
Hold the temperature constant at 160 °C during reaction over 10 min.
(15)
At the end of 10 min, raise the flask out of the oil bath and allow it to cool
down to 60 °C.
(16)
Upon reaching 60 °C, add 1 mL of butanol to avoid solidification and floc-
culation.
(17)
Once the solution reaches RT, transfer the solution to a vial using a transfer
pipette. A visible change in fluorescence should be observed under UV light.
(18)
Characterize the QDs to establish their properties. The absorption and
emission spectra of some QDs are given in
Figure 2.4
.
2.1.3 Water-Soluble QD Core/Shell Synthesis Protocol
The synthesized QDs are hydrophobic and, therefore, cannot be used for bio-
medical applications.
42
The core/shell QDs must be functionalized with second-
ary coatings or “capping” materials such as mercaptopropionic acid or PEG
to improve water solubility and maintain QDs in a nonaggregated state.
42
The
surface of the functionalized QD can be further conjugated with targeting mol-
ecules such as antibodies or receptor ligands as shown in the schematic dia-
gram in
Figure 2.1
, which allows the QD to be attached to a specific tissue or
organ.
26
Various applications of biocompatible CdSe/ZnS-QDs have been dem-
onstrated
45
such as in vivo imaging of breast cancer in vitro
37,41
and imaging of
tumor metastases in vivo in mice.
58
The CdSe/ZnS-QDs coated with targeting
FIGURE 2.4
The emission (left) and absorption (right) spectra of various QDs.
Courtesy of Ocean
NanoTech.
(For color version of this figure, the reader is referred to the online version of this topic)
