May 10, 2008 / Vol. 6, No. 5 / CHINESE OPTICS LETTERS 369
A study on the best irradiation dose of X-ray for Hep-2
cells by Fourier transform infrared spectroscopy
Renming Liu (
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)
1
, Weiyue Tang (
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)
2
, Guangshui Zhang (
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)
2
,
Fengqiu Zhang (
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)
2
, and Xinhui Yan (
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)
3
1
Department of Physics and Electronic Science, Chuxiong Normal University, Chuxiong 675000
2
Physical Engineering College, Zhengzhou University, Zhengzhou 450052
3
The People’s Hospital of Henan Province, Zhengzhou 450000
Received November 26, 2007
Fourier transform infrared spectroscopy (FTIR) was employed to study t he human epidermis larynx car-
cinoma cell lines (Hep-2) which were irradiated by different doses of X-ray. The results show that (1) the
irradiation of X-ray damages the structure of the CH
3
groups of the thymine in DNA, which restrains the
reproduction of Hep- 2 cells effectively, (2) the 8 Gy dose of X-ray irradiation changes the framework and
the relative contents of some proteins, lipids and the nucleic acid molecules intercellular in the greatest
degree, and (3) the 8 Gy dose of X-ray irradiation is the best irradiation dose for lowering the degree
of the cancerization of Hep-2 cells according to the criteria for the degree of the cancerization reported
recently. Meanwhile, the apoptosis of these cells were detected by using flow cytometry (FCM) primarily.
It shows that the apoptotic ratio of the Hep-2 cells depends on the irradiation dose to some extent, but is
not linearly. And the apoptotic ratio of the 12 Gy dose group is the maximum (20.36%), but the apoptotic
ratios of the 2 to 8 Gy dose groups change little.
OCIS codes: 300.6300, 040.3060, 340.7480, 170.1530.
Larynx cancer is a kind of familiar carcinomas of the head
neck cancers, and the incidence of this cancer account
for about 5% of all human cancers worldwide. Unfortu-
nately, the incidence of this cancer is rising recent years
with the air pollution, smoking, drinking, and other fac-
tors. Especially, smoking is one of the most principal
inducements to this cancer. The ways of the therapy for
the larynx carcinomas are chemotherapeutics, actinothe-
raphy, and operations. As we all known that X-ray is
a kind of short wave electromagnetic waves, when the
carcinomatous cells are irradiated by X-ray, some pro-
teins, lipids, and the nucleic acid will be damaged or
repaired synchronously, so X-ray radiation would induce
the startup of some apoptotic mechanism
[1−4]
. Conse-
quently, X-ray has been used to cure the malignant tu-
mors in clinic up to today. But to the clinic, there is
not a very scientific dose reference of X-ray irradiation
for the larynx cancer therapy, and the design of the ir-
radiation dose is always according to the experiences of
the doctors, so it is quite subjective. Spectroscopic anal-
ysis is an effective method in analyzing structure, com-
ponents, and the contents of various materials due to its
superduper sensitivity
[5−8]
. It is one of the most effective
tools for studying the stages of the biomolecules and cells.
Infrared radiation (IR) has become one of the most com-
mon tools in analyzing since its discovery in 1801 by
Willism Herschel. And with the development of the com-
puter technology and the data processing technology in
the mid-1970s, Fourier transform infrared spectroscopy
(FTIR) has developed to be one of the most important
analytic tools in many fields. Recently, FTIR was em-
ployed to study the cells or tissues of the uterus, colon,
liver, lung, breast, and other cancers
[9−11]
. The merits
of it are accurate, convenient, and economical. Thus we
employ the FTIR technique to study the best X-ray ir-
radiation dose for Hep-2 cells in this paper, and expect
to provide a reference of X-ray irradiation dose for the
human larynx carcinomas therapy in the future.
A human laryngeal squamous cell carcinoma cell
line (Hep-2) was obtained from the pathology lab of
Zhengzhou University, China. The cell line was main-
tained in RPMI1640 medium (Gibco Co., USA), sup-
plemented with 10% heat-inactivated fetal bovine serum
(Gibco Co.) at 37
◦
C in a humidified 5% CO
2
atmo-
sphere. The cells were harvested in exponential growth
phase from the culture medium, counted and replanted in
35 culture dishes (the number of the cells in each culture
dish is the same), labeled and cultured for 48 h subse-
quently.
These 35 culture dishes were divided into 7 groups
(each group included 5 parallel groups) which included
6 different X-ray irradiation dose groups (1, 2, 5, 8, 10
and 12 Gy) and a control group (0 Gy) for X-ray irradia-
tion. The X-ray irradiation was carried out at room tem-
perature by using an X-ray generator (6MeV-linear ac-
celerator, Siemens Co., Germany), the distance between
the orifice which X-ray came out from and the culture
dishes was 100 cm, and the irradiation area was 10 × 10
(cm). After that, these cells were cultivated at 37
◦
C in
a humidified 5% CO
2
atmosphere for 48 h sequentially.
Then, taking out all the 35 culture dishes of the cells
to harvest, count, and wash in phosphate buffer saline
(PBS) 3 times gently (each group had a same cell num-
ber of 10
6
). Lastly, a vacuum freeze-drying equipment
(ALPHA 1-2LD, CHRIST Co., Germany) was employed
to dry the cells and then the FTIR spectra in the range
of 4000 − 500 cm
−1
were collected by Fourier transform
infrared spectrometer (NEXUS-470, Nicolet Co., USA),
as shown in Fig. 1. Table 1 shows the absorption bands
in FTIR spectra and their assignation. And the intensity
ratios at 1654/1542, 1454/1400, and 2958/2847 cm
−1
for
each group are shown in Fig. 2 and Table 2. On the other
1671-7694/2008/050369-04
c
2008 Chinese O ptics Letters