Detecting and Monitoring of Cancer at the Cellular Level - Vibrational Spectroscopy for Tissue Analysis - page 165

(by centrifuging, rinsing with distilled water, and keeping in a vacuum oven)
and five spectra were collected from randomly selected areas of the sample.
reproducibility Check
Due to the crucial importance of reproducibility in spectroscopic stud-
ies [12], some other potentially important factors were also considered.
According to Schroeder et al. [13], key parameters needed to be carefully
considered for a reproducible Raman experimental setup including: (1) the
adjustment of laser power levels and monitoring of laser output stability;
(2) the duration of data collection as it effects (a) the number of scans that
can be obtained to improve signal to noise, and (b) the amount of thermo-
luminescence; and (3) sample preparation methods, which can be accom-
plished in different forms. It is also believed that the repeatability of Raman
measurements could be evaluated by increasing the number of the spectra
collected from every sample [12]. Behrens et al. used a different approach
for checking the reproducibility of their research [14]. In addition to concen-
trating on the instrumental reproducibility aspect of the data (which has
also been considered by some other research groups [13,15]), they limited
their experiments to only one objective, one laser power, and one aperture
size. Sadezky et al. took other factors into account to create a unique pat-
tern for their experiments [15] including the focus of the laser beam and the
exposure time. The spectral resolution and spectral region covered could
be other important factors in establishing a reproducible pattern [16]. It is
believed that storage conditions would minimise the changes in spectral
characteristics [17]. Kateinen et al. also focused on instrumental reproduc-
ibility, and followed a constant timing pattern for all experiments [18]. The
reproducibility factors that were considered by Niemela et al. [19] are as
follows: (a) laser power, (b) Raman range, (c) resolution, (d) size of spot,
(e) proper focus, (f) constant number of spectra from every sample, and
(g) constant measurement time.
It is important to establish a set of sample-specific parameters to produce
reproducible results. These parameters for cell line works are tabulated in
Table 6.1 and have been considered to establish a reproducible method for all
of the experiments conducted in this research work.
Spectral analysis
A total of 60 spectra were collected from six pairs of 833K samples, including
six sensitive and six resistant ones. Figure 6.1 illustrates the spectra collected
from sensitive and resistant samples, respectively.
In order to have a clear understanding of the chemical bands and func-
tional groups existing in 833K samples, a brief explanation of the definitions
of the observed peaks is presented in Table 6.2. This information has been
derived from our published review works [20,21].