- Email: [email protected]
Biophotons: ultraweak light emission from living systems
168
Biophotons:
ultraweak
Balasigamani
Devaraj*,
Spontaneous
ultraweak
light emission
result from living systems, emission’,
occur
system.
production
The detection
emission
and statistical
excitations
governing
Examples
features
area of research
biology,
medicine,
biophysical
the
primary
at various
show that biophoton
emission
future applications
environmental
levels is an in
sciences
and
Yamagata
990,
food technology.
Addresses Biophotonics
Japan *e-mail: [email protected] tTohoku Institute of Technology, 35-1 Taihaku-ku, Sendai 982, Japan Current Opinion 2:188-193
in Solid State
Electronic
identifier:
0 Current
Chemistry
Matsuei,
Yagiyama
8 Materials
Kasumi-cho,
Science
1997,
1359-0286-002-00188 Ltd ISSN
_
In the present paper, we review ‘biophoton emission phenomena’, that is spontaneous ultraweak light emission from living systems not detectable by the human eye and it is basically considered to be different than bioluminescence. The characteristics, biological significance and interesting aspects of biophoton emission with possible future applications will be discussed. Progress in the area of biophoton emission studies is coupled to the development of highly sensitive measuring systems and we hope that this review serves as a challenge to motivate researchers to improve the photonic sensing technology for the characterization of biophoton emission phenomena.
Biophoton Information Laboratories, 2-2-l
lnabit
processes
field and vice versa.
with potential
pharmacology,
to
a living
of biophoton because
and living systems
hierarchy
exciting
within
of underlying
to the photon
from organisms
of the biological
states
importance
endogenous
transferred
that
to as ‘biophoton
and characterization
coherence
Usa and Humio
in nature and are coupled
of excited
may be of significant
are directly
Masashi
phenomena
also referred
quite generally
the endogenous
light emission from living systems
1359-0286
emission
All living organisms regardless of their evolutionary hierarchy, spontaneously emit ultraweak light commonly referred to as ‘biophoton emission’. The origin of biophoton emission studies can be traced back to a controversial Russian report by Guruwitsch in the 192Os, called the ‘hlitogenetic radiation theory’ [l]. According to this theory, dividing cells emit ultraweak far-UV light that is capable of inducing cell division when incident on nondividing cells. The controversy that dividing cells emit 1JV light remains unresolved despite the efforts of numerous groups across the world and is excellently reviewed in a report by Quickenden et a/.[Z].
Introduction Light from time immemorial has always been an integral part of living systems and is one of the prime movers of the evolution process. Natural light sources such as the sun, moon and stars have fascinated and captured the attention of everyone irrespective of their backgrounds. The quest to understand the characteristics, generation and emission mechanisms of light, even now, remains an exciting area of research, attracting the involvement of scientists from all branches of science. Inventions and applications of light bulbs, fluorescent lamps, LEDs and lasers are a testimony to the success that physicists and engineers have achieved over the years in harnessing the properties of light for every day use. There is yet another category of natural light source, which is of biological origin. The more familiar kinds of these sources, that emit visible light, are from fireflies, jelly fishes and some fishes (Fig. 1). The phenomenon of light emission from these sources is well characterized and is referred to as ‘bioluminescence’ or ‘biological luminescence’. Light emission from the above mentioned sources also have a recognized purpose in nature, such as mating signals or to attract the prey.
In the meantime, the availability of photomultiplier tubes has opened up new avenues for the study of biophoton emission phenomena. Figure 1 is a broad representation of various biological light emitting sources that have been reported in the literature. Based on the available reports we summarize the following characteristics of biophoton emission: it can be observed generally from all organisms both at the microscopic and macroscopic scale without any external inducements; emission intensity is very low down to the order of -10-13 W.cm-2 or less; emission occurs over a wide spectral range spanning from the UV to the near-IR wavelength regions: emission mechanisms are not clear but are speculated as being due to the endogenous production of excited states as a consequence of metabolic reactions within the organisms: and two-dimensional biophoton imaging studies show that the emission intensity is localized.
Detection emission
and characterization
of biophoton
Progress in the detection and characterization of biophoton emission is directly coupled to the development and availability of measurement systems. As mentioned in the
189
Biophotons: ultraweak light emission from living systems Devaraj, Usa and lnaba
Figure 1
emission intensity at a wavelength of 500 nm and detection bandwidth of 1Hx emission intensity (IV /cm’)
(photon / sec*cmZ, Classification
Examples
Light emission types Enzymatic reactions (luciferin-h&erase
Relatively
strong light emission
Specific light
Bioluminescence
phenomena
emitting substance exists
Ultraweak chem&mrinescence
--B
zz=F==z G Ultraweak light = = B emission a 5 phenomena B 102 zzzz
Ultraweak biophoton emission phenomena
reactions)
Photinus, Photobacterium, Reniila, Pyrophorus, Cypridina, Octochaetus,
HetITOCXpUS
Nonenzymatic Aequoria, Halistaura, Gonyaulax, reactions (photoprotein, Chaetopterus, Meganyctiphanea etc.) Phenomena resulting from auto-oxidation and thermal oxidation of oils and fats, Nonenzymatic foods [49], medicines, polymers, paints, reactions rubber, lipids and proteins
Exist extensively in nature in organic compounds and in Enzymatic reactions conjunction with life processes, living functions and biological Ultraweak darkactivities chemiltiescence that does not require external excitation
Microsome lipid peroxides, Sodium linoleate-lipoxidases, Xanthine oxidaseacetaldehydes [SO,5 I ] p=
Detected quite generallyfrom microscopic and macroscopic systems: microbes, leukocytes, macrophages, tumor cells, nerves, muscle, tissues, organs, human breath and body fluids and plants
-B
W B = -
m
IO_‘6
10-l’
10’ 0 Classification
B = m B B m B -
and characteristics
sides provide an approximate
of various light emission phenomena
associated
and highly sensitive detection scheme that is capable of detecting 103-104 photons.s-l.cm2 or less, over a large surface area of 20cmz or more. Our earlier studies have shown that single photoelectron counting methods with a photomultiplier tube as the detector are best suited for such measurements [3-S]. The thermal noise (dark current) of the photomultiplier tube is further reduced by placing it in a vacuum chamber and cooled to a temperature beyond which there is no further reduction in the thermal noise. Spectral characterization of biophoton emission is usually performed with a colored glass filters based filter spectral analyzer system (FISAS) [6,7] or with a large area reflection grating based polychrometer incorporating a two-dimensional photon counting detector [8]. Since biophoton emission spectra do not exhibit sharp peaks, spectral resolution is traded for sensitivity in the above spectroscopes.
Current
Opinionin SolidState & MaterialsScience
with life and biological activities (scales indicated
estimation of the magnitude of the emission intensity). See [49-511
previous paragraph, the very nature of biophoton emission imposes stringent requirements on detectors for effective characterization. Simply put, one requires a low noise
1997
on both
for examples of light emission phenomena.
Spatial distribution of biophoton emission is usually performed with two-dimensional photon counting tubes [9-12,13*]. However, we have recently reported that in the wavelength region of above 700nm the cooled CCD camera is advantageous over the two-dimensional photon counting tube [14]. The techniques mentioned above essentially form the basis for detection and characterization of biophoton emission. Despite the long history of biophotons, progress in this area is seriously hampered by the nonavailability of suitable detectors resulting in fewer reports. Hence, we have also included some earlier reports with a view to generate enough interest to improve the performance of low level light detectors such as photomultiplier tubes or to develop alternatives.
Biophoton
emission from microbes
Using yeast and bacterial cultures Quickenden et a/. [1.5-181 have reported the detection of ultraweak light emission during different stages of growth. The emission spectra exhibited UV components during an exponential
190
Optical and magnetic materials
phase of growth in both cases. But their attempts at inducing yeast cell division using the UV components were unsuccessful. Godlewski et a/. [19] reported that biophoton emission from yeast cultures exhibited an increase in emission intensities and distinct changes in emission spectra were observed when the metabolism of the cells was drastically altered suggesting that ultraweak light emission studies could be used as a parameter to quantitatively estimate the degree of perturbation and the capacity of homeostasis (the ability of an organism to maintain constant internal environment by regulating its physiological processes). They also detected a UV component in their spectrum that was attributed to different types of excited oxygen species.
Biophoton
Fiaure 2
emission from plants
Biophoton emission from germinating seedlings and leaves continues to be of interest since the initial report by Guruwitsch. Scott eta/. [9] reported the first biophoton image of a germinating soybean seedling using a two-dimensional photon counting tube and attributed a localized intensity of the light emission to an increase in metabolism during cell division. Suzuki et al. [ZO] imaged an injured adzuki seedling and reported localized higher emission intensities around the injured region suggesting that the observed light emission was a reflection of the defense mechanisms of the plant to injury or infection [Zl]. Figure 2 is a representative biophoton image of an injured soybean seedling showing localization of the light emission in the injured region with a cross-shaped cut to the cotyledon (embryonic leaf) [ZO].
(b)
4
In an exhaustive study using 2000 germinating red bean seedlings, Kai et al. [ 11,12] recently reported a relationship of growth dynamics with that of biophoton emission. Their study suggested that biophoton emission intensity linearly increases with the acceleration of root growth and the germination rate of the seedlings .can be predicted by measuring the biophoton emission intensity.
‘C 1997
Representative biophoton Schauf et a/. [lo] imaged biophoton emission from germinating cucumber seedlings and concluded that the light emitting region was distant from the light generating region. They proposed that the conduction of light was due to the light guiding ability (as in optical fibres) of the plant tissues. More recently, Kobayashi et a/. [14,22**] analyzed spatiotemporal distribution and spatial and temporal correlations of the biophoton emission from germinating soybean seedlings under conditions of physical, chemical or mechanical stress. The intense light emitting regions in their report were also observed at a distant site, away from the location of the stress. They suggested that living systems maintain a complex order both at the cellular level and at the macroscopic level and hence it is natural to assume that any form of external stimulus would disturb the order and manifest itself at different locations. Results reported by Schauf et a/. [lo] and Kobayashi et a/. [14,22”] have also
Current Op~mon m Solid State & Mater&
image and schematic.
Science
(a) Ultraweak
biophoton emission image of an injured soybean seedling is displayed along with (b) a schematic representation of the sample indicating the injury position as a cross shaped cut to the cotyledon. The measurement
time was approximately
40 min.
suggested that mechanisms of signal transfer within a complex living system could be explored by analyzing the two-dimensional image patterns of their biophoton emission. Biophoton emission measurements have also been used to monitor various physiological aspects of the plant system such as membrane transport, growth and differentiation. Usa et a/. [23] reported that the temporal variations of the biophoton emission intensity, from a germinating soybean, were similar to the bioelectric surface potential of soybean seedlings. Temperature dependence of biophoton emission from whole leaves of different plants [24] sug-
Biophotons: ultraweak light emission from living systems Devaraj, Usa and lnaba
gests that biophoton emission measurements can be used to differentiate chilling-sensitive and chilling-resistant plants. Processes such as growth and differentiation can also be studied by monitoring the biophoton emission [ZS”].
Studies of the mechanisms that lead to biophoton emission by plants have been made by several groups [26-321. Although the exact mechanisms are not known at the moment, it is generally agreed that the biophoton emission is based on oxidative processes that lead to the endogenous production of excited states.
Biophoton emission from mammalian and tissues
191
pattern or localization. The image was clearer (Fig. 3b) 48 hours after injury and resembled the shape of the wound, while the emission intensity was continuously rising. The emission intensity was maximum between the third and the fifth day after injury (Fig. 3c) corresponding to the activation of the immune system as reported by biochemical and immunological techniques [41]. From the sixth day of the injury (Fig. 3d) the emission intensity began to decrease and on the eighth day of the injury when the wound had completely healed, the image did not show any clear pattern (see Fig. 3a). Biophoton emission intensity returned to normal levels after the scab had fallen off.
cells
Ultraweak light emission from various cells, organelles and organisms [33,34] including humans is also reported to occur under different physiological conditions. In an earlier report [35] we attributed the biophoton emission from mammalian nuclei to the peroxidation of the nuclear membrane, a physiological process that can be related to aging. We also measured the temperature dependence of the biophoton emission from the nuclei and estimated the critical temperature at which the membranes would undergo phase transitions [36]. The phase transitions of the nuclear membranes are crucial to an understanding of the information transfer to and from the nucleus, the store house of genetic information. Niggli [37] and Kimura et a/. [38] have also reported biophoton emission from cell cultures and a medium of the cell cultures respectively. Using 2D imaging studies, Amano eta/.[ 13.1 have reported a higher localized intensity of biophoton emission from the leg of a mouse in a region that was transplanted with bladder cancer cells. Their results suggested that biophoton emission measurements could be used as a noninvasive probe to monitor surface or subsurface cancerous regions. As in plants, biophoton emission measurements can also be used to monitor injury and wound healing in animals [39,40]. In Figure 3a, the 2D image obtained immediately after injury to the back of a mouse did not show any clear
Two-dimensional images of biophoton emission from a healthy human hand exhibit a characteristic pattern with higher intensity levels in the region of index and middle fingers and lower intensity in the middle of the palm region [39,40]. It was also observed that the biophoton emission intensity from the hands of patients with hypothyroidism (a lower state of metabolic activity) was always lower than normal. Lower emission intensity is also observed in the case of patients whose thyroid glands had been removed [39]. The results suggest that the biophoton emission from the different parts of the human body surface could serve as a useful marker in detecting physiological malfunctions that otherwise require complex and expensive assays.
Biophoton emission from human body fluids and breath Biophoton emission studies on blood plasma, urine and breath have been performed in order to explore the feasibility of its use as a diagnostic technique to measure the oxidative stress and pathological states of the body [4244]. Yoda et al. [42] have reported higher intensities of biophoton emission from the blood of smokers when compared to the blood of nonsmokers. They also observed that the emission intensity of blood plasma of hemodialysis patients was higher than normal [43,44]. The emission spectra under various atmospheric conditions suggested that the hemodialysis patients were more vulnerable
Figure 3
0 1997 Current Opinion in Solid State 8 Materials Science
Three-dimensional displays of ultraweak biophoton emission images of the back of an injured mouse (a) immediately after injury, (b) two days after injury, (c) four days after injury and (d) six days after injury.
192
Optical and magnetic materials
to oxidative stress than normal. Biophoton emission of human breath under exercise is reported to increase gradually and correspond to ‘minute ventilation’, that is the volume of expired air per minute [44]. The emission intensity remained high even after the exercise had stopped. This increase in the light emission intensity was suggested to be due to the photoemissive generated from a leak in metabolic pathways exercise, and this increase in intensity can be monitor physical stress of the body.
species during used to
Conclusions Detection and characterization [45-G] of biophoton emission is an exciting area of research with potential applications in biology, medicine, pharmacology, environmental technology and food science and technology. In the senior author’s words, “I find the biophoton emission phenomena fascinating in spite of my involvement with it for almost thirty years.” It remains to be verified whether this light emission is of any fundamenral importance or is just a by-product of metabolism with no major consequence. But our experience with the way nature works shows that living systems are highly organized and efficient to emit photon energy levels, especially in the UV to near-IR wavelength regions without any purpose. The mechanisms and specific emitters of biophotons are not well understood at the moment and nor is the transport of biophotons through the tissues. However, the feasibility of noninvasively monitoring a physiological process of a living system at the surface is an attractive proposition of major value. The low intensity of this emission, when coupled to the broad wavelength region over which this emission occurs, however, is a serious limitation for further progress and should provide a challenge to researchers and engineers involved in advanced photonic sensing technology. The biophoton emission could be produced in a highly heterogeneous and structured biological media through feedback mechanisms involving biochemical and biophysical reactions that are spatially confined and follow ordered kinetics. Accordingly, exact measurements to examine such characteristics in the near future seem interesting and appealing. These could also be of significant importance because the coherence and statistical features of the underlying primary excitations are directly transferred to the photon field and vice-versa; that is, the statistics governing endogenous biophysical processes are, in principle, experimentally accessible via their biophoton fields.
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22. ..
Kobayashi M, Devaraj B, Usa M, Tanno Y, Takeda M, lnaba H: Development and applications of new technology for twodimensional soace-time characterization and correlation analysis of ultraweak biophoton emission. Frontiers Med Biol Eng 1996, 7:299-309. This paper discusses the spatiotemporal variations ot the blophoton emlssion from soy bean seedlings after physical and chemical stimulation to the root tip. A possible method to monitor biological signal transfer is suggested.
Biophotons:
ultraweak
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Usa M, Kobayashi M, Scott RQ, Maeda T, Hiratsuka R, lnaba H: Simultaneous measurement of biophoton emission and biosurface electric potential from germinating soybean(Glycine max). Proroplasma 1989, 149:64-66.
24.
Roschger P, Scott RQ Devaraj B, lnaba H: Observation of phase transitions in intact leaves by intrinsic low-level chamiluminescence. Photochem Pbotobiol 1993, 57:580-583.
Kai S, Ohya T, Morita K, Fujimoto T: Growth control and biophoton radiation by plant hormones in red bean. Jpn J Appl Phys 1 1995, 34:6530-6538. This paper discusses the study of growth and differentiation processes of germinating seedlings by monitoring the biophoton emission. 25. ..
26.
Abeles FB: Plant chemiluminescenca. 1906, 37:49-72.
27.
Hideg E, Kobayashi M, lnaba H: Spontaneous ultraweak light emission from respiring spinach leaf mitochondria. BBA Bioenergetics 1991, 1098:27-31.
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Hideg E, lnaba H: Biophoton emission (ultraweak photoemission) from dark adapted spinach chloroplasts. Phofochem Photobioll991, 53:137-l 42.
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Grass0 F, Musumeci F, Triglia A, Pagan0 M: Spectra of photons emitted from germinating seeds. Nuovo Cimento D-Cond Maff At 1991,13:891-897.
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Watanabe H, Nagoshi T, Suzuki S, Kobayashi M, Usa M, lnaba H: Chamiluminescance in the crude extracts of soybean saadinas. Postulated mechanism on the formation of hydrop&oxida intermediates. BBA - Bioenergetics 1992, 1117:107-113.
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Biophotons:
ultraweak
Balasigamani
Devaraj*,
Spontaneous
ultraweak
light emission
result from living systems, emission’,
occur
system.
production
The detection
emission
and statistical
excitations
governing
Examples
features
area of research
biology,
medicine,
biophysical
the
primary
at various
show that biophoton
emission
future applications
environmental
levels is an in
sciences
and
Yamagata
990,
food technology.
Addresses Biophotonics
Japan *e-mail: [email protected] tTohoku Institute of Technology, 35-1 Taihaku-ku, Sendai 982, Japan Current Opinion 2:188-193
in Solid State
Electronic
identifier:
0 Current
Chemistry
Matsuei,
Yagiyama
8 Materials
Kasumi-cho,
Science
1997,
1359-0286-002-00188 Ltd ISSN
_
In the present paper, we review ‘biophoton emission phenomena’, that is spontaneous ultraweak light emission from living systems not detectable by the human eye and it is basically considered to be different than bioluminescence. The characteristics, biological significance and interesting aspects of biophoton emission with possible future applications will be discussed. Progress in the area of biophoton emission studies is coupled to the development of highly sensitive measuring systems and we hope that this review serves as a challenge to motivate researchers to improve the photonic sensing technology for the characterization of biophoton emission phenomena.
Biophoton Information Laboratories, 2-2-l
lnabit
processes
field and vice versa.
with potential
pharmacology,
to
a living
of biophoton because
and living systems
hierarchy
exciting
within
of underlying
to the photon
from organisms
of the biological
states
importance
endogenous
transferred
that
to as ‘biophoton
and characterization
coherence
Usa and Humio
in nature and are coupled
of excited
may be of significant
are directly
Masashi
phenomena
also referred
quite generally
the endogenous
light emission from living systems
1359-0286
emission
All living organisms regardless of their evolutionary hierarchy, spontaneously emit ultraweak light commonly referred to as ‘biophoton emission’. The origin of biophoton emission studies can be traced back to a controversial Russian report by Guruwitsch in the 192Os, called the ‘hlitogenetic radiation theory’ [l]. According to this theory, dividing cells emit ultraweak far-UV light that is capable of inducing cell division when incident on nondividing cells. The controversy that dividing cells emit 1JV light remains unresolved despite the efforts of numerous groups across the world and is excellently reviewed in a report by Quickenden et a/.[Z].
Introduction Light from time immemorial has always been an integral part of living systems and is one of the prime movers of the evolution process. Natural light sources such as the sun, moon and stars have fascinated and captured the attention of everyone irrespective of their backgrounds. The quest to understand the characteristics, generation and emission mechanisms of light, even now, remains an exciting area of research, attracting the involvement of scientists from all branches of science. Inventions and applications of light bulbs, fluorescent lamps, LEDs and lasers are a testimony to the success that physicists and engineers have achieved over the years in harnessing the properties of light for every day use. There is yet another category of natural light source, which is of biological origin. The more familiar kinds of these sources, that emit visible light, are from fireflies, jelly fishes and some fishes (Fig. 1). The phenomenon of light emission from these sources is well characterized and is referred to as ‘bioluminescence’ or ‘biological luminescence’. Light emission from the above mentioned sources also have a recognized purpose in nature, such as mating signals or to attract the prey.
In the meantime, the availability of photomultiplier tubes has opened up new avenues for the study of biophoton emission phenomena. Figure 1 is a broad representation of various biological light emitting sources that have been reported in the literature. Based on the available reports we summarize the following characteristics of biophoton emission: it can be observed generally from all organisms both at the microscopic and macroscopic scale without any external inducements; emission intensity is very low down to the order of -10-13 W.cm-2 or less; emission occurs over a wide spectral range spanning from the UV to the near-IR wavelength regions: emission mechanisms are not clear but are speculated as being due to the endogenous production of excited states as a consequence of metabolic reactions within the organisms: and two-dimensional biophoton imaging studies show that the emission intensity is localized.
Detection emission
and characterization
of biophoton
Progress in the detection and characterization of biophoton emission is directly coupled to the development and availability of measurement systems. As mentioned in the
189
Biophotons: ultraweak light emission from living systems Devaraj, Usa and lnaba
Figure 1
emission intensity at a wavelength of 500 nm and detection bandwidth of 1Hx emission intensity (IV /cm’)
(photon / sec*cmZ, Classification
Examples
Light emission types Enzymatic reactions (luciferin-h&erase
Relatively
strong light emission
Specific light
Bioluminescence
phenomena
emitting substance exists
Ultraweak chem&mrinescence
--B
zz=F==z G Ultraweak light = = B emission a 5 phenomena B 102 zzzz
Ultraweak biophoton emission phenomena
reactions)
Photinus, Photobacterium, Reniila, Pyrophorus, Cypridina, Octochaetus,
HetITOCXpUS
Nonenzymatic Aequoria, Halistaura, Gonyaulax, reactions (photoprotein, Chaetopterus, Meganyctiphanea etc.) Phenomena resulting from auto-oxidation and thermal oxidation of oils and fats, Nonenzymatic foods [49], medicines, polymers, paints, reactions rubber, lipids and proteins
Exist extensively in nature in organic compounds and in Enzymatic reactions conjunction with life processes, living functions and biological Ultraweak darkactivities chemiltiescence that does not require external excitation
Microsome lipid peroxides, Sodium linoleate-lipoxidases, Xanthine oxidaseacetaldehydes [SO,5 I ] p=
Detected quite generallyfrom microscopic and macroscopic systems: microbes, leukocytes, macrophages, tumor cells, nerves, muscle, tissues, organs, human breath and body fluids and plants
-B
W B = -
m
IO_‘6
10-l’
10’ 0 Classification
B = m B B m B -
and characteristics
sides provide an approximate
of various light emission phenomena
associated
and highly sensitive detection scheme that is capable of detecting 103-104 photons.s-l.cm2 or less, over a large surface area of 20cmz or more. Our earlier studies have shown that single photoelectron counting methods with a photomultiplier tube as the detector are best suited for such measurements [3-S]. The thermal noise (dark current) of the photomultiplier tube is further reduced by placing it in a vacuum chamber and cooled to a temperature beyond which there is no further reduction in the thermal noise. Spectral characterization of biophoton emission is usually performed with a colored glass filters based filter spectral analyzer system (FISAS) [6,7] or with a large area reflection grating based polychrometer incorporating a two-dimensional photon counting detector [8]. Since biophoton emission spectra do not exhibit sharp peaks, spectral resolution is traded for sensitivity in the above spectroscopes.
Current
Opinionin SolidState & MaterialsScience
with life and biological activities (scales indicated
estimation of the magnitude of the emission intensity). See [49-511
previous paragraph, the very nature of biophoton emission imposes stringent requirements on detectors for effective characterization. Simply put, one requires a low noise
1997
on both
for examples of light emission phenomena.
Spatial distribution of biophoton emission is usually performed with two-dimensional photon counting tubes [9-12,13*]. However, we have recently reported that in the wavelength region of above 700nm the cooled CCD camera is advantageous over the two-dimensional photon counting tube [14]. The techniques mentioned above essentially form the basis for detection and characterization of biophoton emission. Despite the long history of biophotons, progress in this area is seriously hampered by the nonavailability of suitable detectors resulting in fewer reports. Hence, we have also included some earlier reports with a view to generate enough interest to improve the performance of low level light detectors such as photomultiplier tubes or to develop alternatives.
Biophoton
emission from microbes
Using yeast and bacterial cultures Quickenden et a/. [1.5-181 have reported the detection of ultraweak light emission during different stages of growth. The emission spectra exhibited UV components during an exponential
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Optical and magnetic materials
phase of growth in both cases. But their attempts at inducing yeast cell division using the UV components were unsuccessful. Godlewski et a/. [19] reported that biophoton emission from yeast cultures exhibited an increase in emission intensities and distinct changes in emission spectra were observed when the metabolism of the cells was drastically altered suggesting that ultraweak light emission studies could be used as a parameter to quantitatively estimate the degree of perturbation and the capacity of homeostasis (the ability of an organism to maintain constant internal environment by regulating its physiological processes). They also detected a UV component in their spectrum that was attributed to different types of excited oxygen species.
Biophoton
Fiaure 2
emission from plants
Biophoton emission from germinating seedlings and leaves continues to be of interest since the initial report by Guruwitsch. Scott eta/. [9] reported the first biophoton image of a germinating soybean seedling using a two-dimensional photon counting tube and attributed a localized intensity of the light emission to an increase in metabolism during cell division. Suzuki et al. [ZO] imaged an injured adzuki seedling and reported localized higher emission intensities around the injured region suggesting that the observed light emission was a reflection of the defense mechanisms of the plant to injury or infection [Zl]. Figure 2 is a representative biophoton image of an injured soybean seedling showing localization of the light emission in the injured region with a cross-shaped cut to the cotyledon (embryonic leaf) [ZO].
(b)
4
In an exhaustive study using 2000 germinating red bean seedlings, Kai et al. [ 11,12] recently reported a relationship of growth dynamics with that of biophoton emission. Their study suggested that biophoton emission intensity linearly increases with the acceleration of root growth and the germination rate of the seedlings .can be predicted by measuring the biophoton emission intensity.
‘C 1997
Representative biophoton Schauf et a/. [lo] imaged biophoton emission from germinating cucumber seedlings and concluded that the light emitting region was distant from the light generating region. They proposed that the conduction of light was due to the light guiding ability (as in optical fibres) of the plant tissues. More recently, Kobayashi et a/. [14,22**] analyzed spatiotemporal distribution and spatial and temporal correlations of the biophoton emission from germinating soybean seedlings under conditions of physical, chemical or mechanical stress. The intense light emitting regions in their report were also observed at a distant site, away from the location of the stress. They suggested that living systems maintain a complex order both at the cellular level and at the macroscopic level and hence it is natural to assume that any form of external stimulus would disturb the order and manifest itself at different locations. Results reported by Schauf et a/. [lo] and Kobayashi et a/. [14,22”] have also
Current Op~mon m Solid State & Mater&
image and schematic.
Science
(a) Ultraweak
biophoton emission image of an injured soybean seedling is displayed along with (b) a schematic representation of the sample indicating the injury position as a cross shaped cut to the cotyledon. The measurement
time was approximately
40 min.
suggested that mechanisms of signal transfer within a complex living system could be explored by analyzing the two-dimensional image patterns of their biophoton emission. Biophoton emission measurements have also been used to monitor various physiological aspects of the plant system such as membrane transport, growth and differentiation. Usa et a/. [23] reported that the temporal variations of the biophoton emission intensity, from a germinating soybean, were similar to the bioelectric surface potential of soybean seedlings. Temperature dependence of biophoton emission from whole leaves of different plants [24] sug-
Biophotons: ultraweak light emission from living systems Devaraj, Usa and lnaba
gests that biophoton emission measurements can be used to differentiate chilling-sensitive and chilling-resistant plants. Processes such as growth and differentiation can also be studied by monitoring the biophoton emission [ZS”].
Studies of the mechanisms that lead to biophoton emission by plants have been made by several groups [26-321. Although the exact mechanisms are not known at the moment, it is generally agreed that the biophoton emission is based on oxidative processes that lead to the endogenous production of excited states.
Biophoton emission from mammalian and tissues
191
pattern or localization. The image was clearer (Fig. 3b) 48 hours after injury and resembled the shape of the wound, while the emission intensity was continuously rising. The emission intensity was maximum between the third and the fifth day after injury (Fig. 3c) corresponding to the activation of the immune system as reported by biochemical and immunological techniques [41]. From the sixth day of the injury (Fig. 3d) the emission intensity began to decrease and on the eighth day of the injury when the wound had completely healed, the image did not show any clear pattern (see Fig. 3a). Biophoton emission intensity returned to normal levels after the scab had fallen off.
cells
Ultraweak light emission from various cells, organelles and organisms [33,34] including humans is also reported to occur under different physiological conditions. In an earlier report [35] we attributed the biophoton emission from mammalian nuclei to the peroxidation of the nuclear membrane, a physiological process that can be related to aging. We also measured the temperature dependence of the biophoton emission from the nuclei and estimated the critical temperature at which the membranes would undergo phase transitions [36]. The phase transitions of the nuclear membranes are crucial to an understanding of the information transfer to and from the nucleus, the store house of genetic information. Niggli [37] and Kimura et a/. [38] have also reported biophoton emission from cell cultures and a medium of the cell cultures respectively. Using 2D imaging studies, Amano eta/.[ 13.1 have reported a higher localized intensity of biophoton emission from the leg of a mouse in a region that was transplanted with bladder cancer cells. Their results suggested that biophoton emission measurements could be used as a noninvasive probe to monitor surface or subsurface cancerous regions. As in plants, biophoton emission measurements can also be used to monitor injury and wound healing in animals [39,40]. In Figure 3a, the 2D image obtained immediately after injury to the back of a mouse did not show any clear
Two-dimensional images of biophoton emission from a healthy human hand exhibit a characteristic pattern with higher intensity levels in the region of index and middle fingers and lower intensity in the middle of the palm region [39,40]. It was also observed that the biophoton emission intensity from the hands of patients with hypothyroidism (a lower state of metabolic activity) was always lower than normal. Lower emission intensity is also observed in the case of patients whose thyroid glands had been removed [39]. The results suggest that the biophoton emission from the different parts of the human body surface could serve as a useful marker in detecting physiological malfunctions that otherwise require complex and expensive assays.
Biophoton emission from human body fluids and breath Biophoton emission studies on blood plasma, urine and breath have been performed in order to explore the feasibility of its use as a diagnostic technique to measure the oxidative stress and pathological states of the body [4244]. Yoda et al. [42] have reported higher intensities of biophoton emission from the blood of smokers when compared to the blood of nonsmokers. They also observed that the emission intensity of blood plasma of hemodialysis patients was higher than normal [43,44]. The emission spectra under various atmospheric conditions suggested that the hemodialysis patients were more vulnerable
Figure 3
0 1997 Current Opinion in Solid State 8 Materials Science
Three-dimensional displays of ultraweak biophoton emission images of the back of an injured mouse (a) immediately after injury, (b) two days after injury, (c) four days after injury and (d) six days after injury.
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Optical and magnetic materials
to oxidative stress than normal. Biophoton emission of human breath under exercise is reported to increase gradually and correspond to ‘minute ventilation’, that is the volume of expired air per minute [44]. The emission intensity remained high even after the exercise had stopped. This increase in the light emission intensity was suggested to be due to the photoemissive generated from a leak in metabolic pathways exercise, and this increase in intensity can be monitor physical stress of the body.
species during used to
Conclusions Detection and characterization [45-G] of biophoton emission is an exciting area of research with potential applications in biology, medicine, pharmacology, environmental technology and food science and technology. In the senior author’s words, “I find the biophoton emission phenomena fascinating in spite of my involvement with it for almost thirty years.” It remains to be verified whether this light emission is of any fundamenral importance or is just a by-product of metabolism with no major consequence. But our experience with the way nature works shows that living systems are highly organized and efficient to emit photon energy levels, especially in the UV to near-IR wavelength regions without any purpose. The mechanisms and specific emitters of biophotons are not well understood at the moment and nor is the transport of biophotons through the tissues. However, the feasibility of noninvasively monitoring a physiological process of a living system at the surface is an attractive proposition of major value. The low intensity of this emission, when coupled to the broad wavelength region over which this emission occurs, however, is a serious limitation for further progress and should provide a challenge to researchers and engineers involved in advanced photonic sensing technology. The biophoton emission could be produced in a highly heterogeneous and structured biological media through feedback mechanisms involving biochemical and biophysical reactions that are spatially confined and follow ordered kinetics. Accordingly, exact measurements to examine such characteristics in the near future seem interesting and appealing. These could also be of significant importance because the coherence and statistical features of the underlying primary excitations are directly transferred to the photon field and vice-versa; that is, the statistics governing endogenous biophysical processes are, in principle, experimentally accessible via their biophoton fields.
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