Biomedical Engineering Reference
In-Depth Information
This was in spite of the nanoscale dimensions of the nanosensors. Measurements of the intra-
cellular ROS were carried out by incubating the PEBBLE loaded cells with different
concentrations of PMA (phorbol-12-myristate-13-acetate).
Henderson et al. (2009) confirm that the intracellular environment was not affected by
the PEBBLE method used. This was demonstrated by the MTT assays. Furthermore, the
PEBBLE nanosensors have the capacity to monitor normal cellular function in a passive sense
without affecting the normal intracellular function. They report that the generation of nitic
oxide (NO) as well as hydrogen peroxide (H 2 O 2 ) was not affected by the introduction of
the PEBBLE nanosensor into the intracellular environment. The authors propose to use their
PEBBLE nanosensor in the future to other cell types besides those cells capable of phagocy-
tosis. Perhaps alternate delivery methods may be used. The authors feel that the continuous
ability to monitor ROS in intracellular environments would permit a better understanding
of the involvement of ROS in quite a few different biological processes, especially those that
are of a physiological and pathological nature. Finally, Henderson et al. (2009) conclude by
emphasizing two distinct advantages of their PEBBLE nanosensor:
(a) The biocompatability of their nanosensor permits the long-term monitoring of the ROS
species in intracellular environments, and (b) Even though other ROS measurement
techniques are available, the PEBBLE nanaosensor directly measures the changes in
ROS, whereas other techniques have to depend on reaction products or adducts.
5.7 Combined Fluorescence and SERS Molecular Beacon Assay
to Detect Human Viral RNA (Sha et al., 2007)
Sha et al. (2007) have recently developed a dual-mode molecular beacon to measure unlabeled
human viral DNA. Their detection system comprises a combined SERS (surface-enhanced
Raman scattering) and fluorescent molecular beacon assay on nanobarcode TM particles. These
authors indicate that SERS has been used to detect biological analytes ever since Cotton's
(1980) initial work on the detection of cytochrome c and myoglobin. This led to the detection
of anthrax ( Zhang et al., 2005 ), cancer ( Culha et al., 2003 ), glucose ( Shafer-Peltier et al.,
2003 ), DNA and RNA ( Cao et al., 2003; Faulds et al., 2004, 2005; Wabuyele and Vo-Dinh,
2005 ), and protein immunoassays ( Cao et al., 2003 ).
The authors report that due to the uniqueness of the molecular Raman spectra, the detection
of several species simultaneously (multiplexed detection) is possible. These authors indicate
that due to the SERS enhancement and real-time response, a high sensitivity in biomolecular
detection is possible ( Kneipp et al., 1997; Nie and Emory, 1997; Fe Ru et al., 2006 ).
Tyagi and Kramer (1996) initially developed the fluorescent molecular beacon. Sha et al. (2007)
explain that the molecular beacon is a single-stranded “loop-and-stem” DNA oligonucleotide
Search WWH ::




Custom Search