ABSTRACT
4. Perspective of the Future Research
This chapter highlighted some of the recent developments of macrocyclic molecules functionalized inorganic QDs as a smart optical nanomaterial in the application of fl uorescent sensor. Owing to host-guest interaction of macrocyclic molecules, the modifi cation and functionalized of QDs with macrocyclic molecules is quite simple, rapid and effi cient to develop as the smart sensor. The macrocyclic molecules not only can serve as ligands to stabilize the photophysics properties of QDs but also can afford the recognition units for a special analyze. The combination of QDs and host molecule provided a fl exible and versatile method to determine
DNA, protein and other biomolecules. Highly fl uorescent and selective nanosensors were achieved due to a synergic manner of the typical optical properties of QDs and selective recognition properties of the host molecules.
Among the various sensing mechanisms including electron transfer, energy transfer, electrostatic interaction, QDs based FRET assay has obtained broad attention and can be developed as an effective way to fabricate smart materials. As FRET is sensitive to molecular rearrangements on the 1–10 nm range, researchers have long used this photophysical process to monitor intracellular interactions and binding events (Miyawaki 2003). Due to the FRET assay is usually showed with “turn on” or dual emission fl uorescence response, the FRET assay can be utilized in selective and sensitive detection in complex environment with minimal interference. Recent years, QDs as FRET donor has also been reported (Willard et al. 2001). Compared with other fl uorescent nanomaterials and organic fl uorescent dyes, one unique advantage is obvious: QDs donor emission could be size-tuned to improve spectral overlap with a particular FRET acceptor which can improve the FRET effi ciency. Thereafter, macrocyclic molecules functionalized QDs based on FRET mechanism will be one of the most promising methods for fl uorescence-based biosensing.
With the development of chemosensors based on macrocyclic molecules-coated QDs gradually to mature, the use of QDs functionalized with host molecules as smart sensors in fl uorescence imaging will be the focal point in future’s work, and increasing trend on converging QDs with other nanotechnol ogy and biotechnologies can be more and more favored. The emission of QDs can easily be tuned to near-infrared region which is suitable for deep tissue imaging. Furthermore, the small size of encapsulated QDs (20–30 nm) indicated the QDs can be loaded into cells readily through endocytosis, electroporation, direct microinjection.
Peculiarly, cellular components labelled with QDs including nucleus, mitochondria has also been reported (Derfus et al. 2004, Guo et al. 2003).
Despite the widely application of QDs in imaging in vitro and in vivo, the use of QDs with host molecule for fl uorescence imaging is rarely reported.
With the merits of QDs and host-guest interaction, we envision that smart fl uorescent sensors composited of QDs and macrocyclic molecules will provide a powerful tool to study inorganic and organic species in biological process with fl uorescence imaging in vitro and in vivo.
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