Editing Biophoton

{{Short description|Photon from a biological source}}
{{For|the science of interactions of light and living beings|biophotonics}}

'''Biophotons''' (from the [[Greek language|Greek]] βίος meaning "life" and φῶς meaning "light") are [[photons]] of light in the [[ultraviolet]] and [[visible light]] range that are produced by a [[biological system]].  They are non-thermal in origin, and the emission of biophotons is technically a type of [[bioluminescence]], though the term "bioluminescence" is  generally reserved for higher [[luminance]] systems (typically with emitted light visible to the naked eye, using biochemical means such as [[luciferin]]/[[luciferase]]). The term ''biophoton'' used in this narrow sense should not be confused with the broader field of [[biophotonics]], which studies the general interaction of light with biological systems.

Biological tissues typically produce an observed [[irradiance|radiant emittance]] in the visible and ultraviolet frequencies ranging from 10<sup>−17</sup> to 10<sup>−23</sup> W/cm<sup>2</sup> (approx 1–1000 photons/cm<sup>2</sup>/second).<ref name="Popp-2003"/> This low level of light has a much weaker intensity than the visible light produced by bioluminescence, but biophotons are detectable above the background of [[thermal radiation]] that is emitted by tissues at their normal temperature.<ref name="coherence">{{cite journal | vauthors = Cifra M, Brouder C, Nerudová M, Kučera O | title = Biophotons, coherence and photocount statistics: A critical review | journal = Journal of Luminescence | volume = 164 | pages = 38–51 | date = 2015 | doi = 10.1016/j.jlumin.2015.03.020 | arxiv = 1502.07316 | bibcode = 2015JLum..164...38C | s2cid = 97425113 }}</ref> Biophoton emission is also known as "ultraweak photon emission" (UPE).<ref>{{Cite web|url=https://phys.org/news/2025-05-emit-faint-extinguishes-death.html|title=Living beings emit a faint light that extinguishes upon death, according to a new study|website=Phys.org|language=en-us|date=2025-05-17|access-date=2025-05-17}}</ref>

While detection of biophotons has been reported by several groups,<ref name="Biophoton detection as a novel tech">{{cite journal | vauthors = Takeda M, Kobayashi M, Takayama M, Suzuki S, Ishida T, Ohnuki K, Moriya T, Ohuchi N | display-authors = 6 | title = Biophoton detection as a novel technique for cancer imaging | journal = Cancer Science | volume = 95 | issue = 8 | pages = 656–61 | date = August 2004 | pmid = 15298728 | doi = 10.1111/j.1349-7006.2004.tb03325.x | s2cid = 21875229 | doi-access = free | pmc = 11160017 }}</ref><ref>{{cite journal | vauthors = Rastogi A, Pospísil P | title = Ultra-weak photon emission as a non-invasive tool for monitoring of oxidative processes in the epidermal cells of human skin: comparative study on the dorsal and the palm side of the hand | journal = Skin Research and Technology | volume = 16 | issue = 3 | pages = 365–70 | date = August 2010 | pmid = 20637006 | doi = 10.1111/j.1600-0846.2010.00442.x | s2cid = 24243914 }}</ref><ref>{{cite journal | vauthors = Niggli HJ | title = Artificial sunlight irradiation induces ultraweak photon emission in human skin fibroblasts | journal = Journal of Photochemistry and Photobiology B: Biology | volume = 18 | issue = 2–3 | pages = 281–5 | date = May 1993 | pmid = 8350193 | doi = 10.1016/1011-1344(93)80076-L }}</ref> hypotheses that such biophotons indicate the state of biological tissues and facilitate a form of cellular communication are still under investigation,<ref name="Bajpai 2009">{{cite book | vauthors = Bajpai R | chapter = Biophotons: a clue to unravel the mystery of "life" | title = Bioluminescence in Focus - a collection of illuminating essays | veditors = Meyer-Rochow VB | location = Kerala, India | publisher = Research Signpost |date=2009|volume= 1 | pages=357–385 | oclc = 497860307 | isbn = 9788130803579 }}</ref><ref name="pmid29293442">{{cite journal | vauthors = Zarkeshian P, Kumar S, Tuszynski J, Barclay P, Simon C | title = Are there optical communication channels in the brain? | journal = Frontiers in Bioscience (Landmark Edition) | volume = 23 | issue = 8| pages = 1407–1421 | date = March 2018 | pmid = 29293442 | doi = 10.2741/4652 | arxiv = 1708.08887 | s2cid = 29847303 | url = https://www.technologyreview.com/s/608797/are-there-optical-communication-channels-in-our-brains/ }}</ref>  [[Alexander Gurwitsch]], who discovered the existence of biophotons, was awarded the [[State Stalin Prize|Stalin Prize]] in 1941 for his work.<ref name="Beloussov_1997">{{cite journal | vauthors = Beloussov LV, Opitz JM, Gilbert SF | title = Life of Alexander G. Gurwitsch and his relevant contribution to the theory of morphogenetic fields | journal = The International Journal of Developmental Biology | volume = 41 | issue = 6 | pages = 771–7; comment 778–9 | date = December 1997 | pmid = 9449452 | url = http://www.intjdevbiol.com/paper.php?doi=9449452 }}</ref>

==Detection and measurement==
Biophotons may be detected with [[photomultiplier]]s or by means of an ultra low noise [[CCD camera]] to produce an image, using an exposure time of typically 15 minutes for plant materials.<ref name="Biophoton imaging: a nondestructive">{{cite journal | vauthors = Bennett M, Mehta M, Grant M | title = Biophoton imaging: a nondestructive method for assaying R gene responses | journal = Molecular Plant-Microbe Interactions | volume = 18 | issue = 2 | pages = 95–102 | date = February 2005 | pmid = 15720077 | doi = 10.1094/MPMI-18-0095 | doi-access =  }}</ref><ref name="Biophoton detection as a novel tech"/> Photomultiplier tubes have been used to measure biophoton emissions from fish eggs,<ref>{{cite web| vauthors = Yirka B |title=Research suggests cells communicate via biophotons|url=http://phys.org/news/2012-05-cells-biophotons.html|date=May 2012|access-date=26 January 2016}}</ref> and some applications have measured biophotons from animals and humans.<ref>{{cite journal | vauthors = Kobayashi M, Kikuchi D, Okamura H | title = Imaging of ultraweak spontaneous photon emission from human body displaying diurnal rhythm | journal = PLOS ONE | volume = 4 | issue = 7 | pages = e6256 | date = July 2009 | pmid = 19606225 | pmc = 2707605 | doi = 10.1371/journal.pone.0006256 | bibcode = 2009PLoSO...4.6256K | doi-access = free }}</ref><ref>{{cite journal | vauthors = Dotta BT, Saroka KS, Persinger MA | title = Increased photon emission from the head while imagining light in the dark is correlated with changes in electroencephalographic power: support for Bókkon's biophoton hypothesis | journal = Neuroscience Letters | volume = 513 | issue = 2 | pages = 151–4 | date = April 2012 | pmid = 22343311 | doi = 10.1016/j.neulet.2012.02.021 | s2cid = 207135123 }}</ref><ref>{{cite journal| vauthors = Joines WT, Baumann SB, Kruth JG |title=Electromagnetic emission from humans during focused intent|journal=Journal of Parapsychology|date=2012|volume=76|issue=2|pages=275–294}}</ref> Electron Multiplying CCD (EM-CCD) optimized for the detection of ultraweak light<ref>{{cite journal | vauthors = Khaoua I, Graciani G, Kim A, Amblard F | title = Detectivity optimization to detect of ultraweak light fluxes with an EM-CCD as binary photon counter array | journal = Scientific Reports | volume = 11 | issue = 1 | pages = 3530 | date = February 2021 | pmid = 33574351 | pmc = 7878522 | doi = 10.1038/s41598-021-82611-8 | bibcode = 2021NatSR..11.3530K }}</ref> have also been used to detect the bioluminescence produced by yeast cells at the onset of their growth.<ref>{{cite journal | vauthors = Khaoua I, Graciani G, Kim A, Amblard F | title = Stochastic light concentration from 3D to 2D reveals ultraweak chemi- and bioluminescence | journal = Scientific Reports | volume = 11 | issue = 1 | pages = 10050 | date = May 2021 | pmid = 33976267 | pmc = 8113247 | doi = 10.1038/s41598-021-88091-0 | bibcode = 2021NatSR..1110050K }}</ref>

The typical observed [[Irradiance|radiant emittance]] of biological tissues in the visible and ultraviolet frequencies ranges from 10<sup>−17</sup> to 10<sup>−23</sup> W/cm<sup>2</sup> with a photon count from a few to nearly 1000 photons per cm<sup>2</sup> in the range of 200&nbsp;nm to 800&nbsp;nm.<ref name="Popp-2003">{{cite journal | vauthors = Popp FA | title = Properties of biophotons and their theoretical implications | journal = Indian Journal of Experimental Biology | volume = 41 | issue = 5 | pages = 391–402 | date = May 2003 | pmid = 15244259 | url = http://nopr.niscair.res.in/handle/123456789/17031 }}</ref>

== Proposed physical mechanisms ==

Chemi-excitation via [[oxidative stress]] by [[reactive oxygen species]] or [[catalysis]] by [[enzymes]] (i.e., [[peroxidase]], [[lipoxygenase]]) is a common event in the biomolecular [[wikt:milieu|milieu]].<ref name=pmid7635351>{{cite journal | vauthors = Cilento G, Adam W | title = From free radicals to electronically excited species | journal = Free Radical Biology & Medicine | volume = 19 | issue = 1 | pages = 103–14 | date = July 1995 | pmid = 7635351 | doi = 10.1016/0891-5849(95)00002-F }}</ref> Such reactions can lead to the formation of [[Spin triplet|triplet]] excited species, which release [[photons]] upon returning to a lower [[energy level]] in a process analogous to [[phosphorescence]]. That this process is a contributing factor to spontaneous biophoton emission has been indicated by studies demonstrating that biophoton emission can be increased by depleting assayed tissue of [[antioxidants]]<ref name=pmid2801215>{{cite journal | vauthors = Ursini F, Barsacchi R, Pelosi G, Benassi A | title = Oxidative stress in the rat heart, studies on low-level chemiluminescence | journal = Journal of Bioluminescence and Chemiluminescence | volume = 4 | issue = 1 | pages = 241–4 | date = July 1989 | pmid = 2801215 | doi = 10.1002/bio.1170040134 }}</ref> or by addition of carbonyl derivatizing agents.<ref name=pmid11467852>{{cite journal | vauthors = Kataoka Y, Cui Y, Yamagata A, Niigaki M, Hirohata T, Oishi N, Watanabe Y | title = Activity-dependent neural tissue oxidation emits intrinsic ultraweak photons | journal = Biochemical and Biophysical Research Communications | volume = 285 | issue = 4 | pages = 1007–11 | date = July 2001 | pmid = 11467852 | doi = 10.1006/bbrc.2001.5285 }}</ref> Further support is provided by studies indicating that emission can be increased by addition of [[reactive oxygen species]].<ref name=pmid6928628>{{cite journal | vauthors = Boveris A, Cadenas E, Reiter R, Filipkowski M, Nakase Y, Chance B | title = Organ chemiluminescence: noninvasive assay for oxidative radical reactions | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 77 | issue = 1 | pages = 347–51 | date = January 1980 | pmid = 6928628 | pmc = 348267 | doi = 10.1073/pnas.77.1.347 | bibcode = 1980PNAS...77..347B | doi-access = free }}</ref>

===Plants===
Imaging of biophotons from leaves has been used as a method for assaying R gene responses.<ref name="Biophoton imaging: a nondestructive"/> These genes and their associated proteins are responsible for [[pathogen]] recognition and activation of defense signaling networks leading to the hypersensitive response,<ref>{{cite journal | vauthors = Iniguez AL, Dong Y, Carter HD, Ahmer BM, Stone JM, Triplett EW | title = Regulation of enteric endophytic bacterial colonization by plant defenses | journal = Molecular Plant-Microbe Interactions | volume = 18 | issue = 2 | pages = 169–78 | date = February 2005 | pmid = 15720086 | doi = 10.1094/MPMI-18-0169 | doi-access = free }}</ref> which is one of the mechanisms of the resistance of plants to pathogen infection. It involves the generation of reactive oxygen species (ROS), which have crucial roles in [[signal transduction]] or as toxic agents leading to cell death.<ref>{{cite journal | vauthors = Kobayashi M, Sasaki K, Enomoto M, Ehara Y | title = Highly sensitive determination of transient generation of biophotons during hypersensitive response to cucumber mosaic virus in cowpea | journal = Journal of Experimental Botany | volume = 58 | issue = 3 | pages = 465–72 | year = 2006 | pmid = 17158510 | doi = 10.1093/jxb/erl215 | doi-access = free }}</ref>

Biophotons have been also observed in the roots of stressed plants. In healthy cells, the concentration of ROS is minimized by a system of biological antioxidants. However, heat shock and other stresses changes the equilibrium between oxidative stress and antioxidant activity, for example, the rapid rise in temperature induces biophoton emission by ROS.<ref>{{cite journal | vauthors = Kobayashi K, Okabe H, Kawano S, Hidaka Y, Hara K | title = Biophoton emission induced by heat shock | journal = PLOS ONE | volume = 9 | issue = 8 | pages = e105700 | year = 2014 | pmid = 25153902 | pmc = 4143285 | doi = 10.1371/journal.pone.0105700 | bibcode = 2014PLoSO...9j5700K | doi-access = free }}</ref>

===Hypothesized involvement in cellular communication===
In the 1920s, the Russian embryologist [[Alexander Gurwitsch]] reported "ultraweak" photon emissions from living tissues in the UV-range of the spectrum. He named them "mitogenetic rays" because his experiments convinced him that they had a stimulating effect on [[cell division]].<ref name=pmid3294029>{{cite journal | vauthors = Gurwitsch AA | title = A historical review of the problem of mitogenetic radiation | journal = Experientia | volume = 44 | issue = 7 | pages = 545–50 | date = July 1988 | pmid = 3294029 | doi = 10.1007/bf01953301 | s2cid = 10930945 }}</ref>

In the 1970s [[Fritz-Albert Popp]] and his research group at the [[University of Marburg]] ([[Germany]]) showed that the spectral distribution of the emission fell over a wide range of wavelengths, from 200 to 750&nbsp;nm.<ref>{{cite journal | vauthors = Wijk RV, Wijk EP | title = An Introduction to Human Biophoton Emission| journal = Forschende Komplementärmedizin und Klassische Naturheilkunde | volume = 12 | issue = 2 | pages = 77–83 | date = April 2005 | pmid = 15947465 | doi = 10.1159/000083763 | s2cid = 25794113 }}</ref>  Popp's work on the biophoton emission's statistical properties, namely the claims on its coherence, was criticised for lack of scientific rigour.<ref name="coherence"/>

One biophoton mechanism focuses on injured cells that are under higher levels of [[oxidative stress]], which is one source of light, and can be deemed to constitute a "distress signal" or background chemical process, but this mechanism is yet to be demonstrated.{{citation needed|date=February 2020}} The difficulty of teasing out the effects of any supposed biophotons amid the other numerous chemical interactions between cells makes it difficult to devise a testable hypothesis. A 2010 review article discusses various published theories on this kind of signaling.<ref name=pmid20674588>{{cite journal | vauthors = Cifra M, Fields JZ, Farhadi A | title = Electromagnetic cellular interactions | journal = Progress in Biophysics and Molecular Biology | volume = 105 | issue = 3 | pages = 223–46 | date = May 2011 | pmid = 20674588 | doi = 10.1016/j.pbiomolbio.2010.07.003 }}</ref>

The hypothesis of cellular communication by biophotons was highly criticised for failing to explain how could cells detect photonic signals several orders of magnitude weaker than the natural background illumination.<ref name="communication">{{cite journal | vauthors = Kučera O, Cifra M | title = Cell-to-cell signaling through light: just a ghost of chance? | journal = Cell Communication and Signaling | volume = 11 | issue = 87 | pages = 87 | date = November 2013 | pmid = 24219796 | doi = 10.1186/1478-811X-11-87 | pmc = 3832222 | doi-access = free }}</ref>

== See also ==
*[[Chemiluminescence]]
*[[Luminophore]]
*[[Phosphorescence]]

== References ==
{{Reflist|33em}}

== Further reading ==
{{refbegin}}
* {{cite book | vauthors = Beloussov LV, Voeikov VL, Martynyuk VS |title=Biophotonics and Coherent Systems in Biology |date=2007 |publisher=Springer |location=New York, NY |isbn=978-0387-28378-4 }}
* {{cite journal | vauthors = Hyland GJ | title = Non-thermal bioeffects induced by low-intensity microwave irradiation of living systems. | journal = Engineering Science & Education Journal | date = December 1998 | volume = 7 | issue = 6 | pages = 261–9 | doi = 10.1049/esej:19980606 | doi-broken-date = 7 December 2024 | url = https://www.photonics.com/Article.aspx?PID=5&VID=12&IID=38&AID=2776 | url-access = subscription }}
* {{cite web | vauthors = Kühnert H | url = http://www.lichtdeslebens.de/biophotonen/ | title = Wirkungsweise der Biophotonen | language = German | trans-title = How biophotons work | access-date = 2017-09-18 | archive-date = 2021-08-02 | archive-url = https://web.archive.org/web/20210802204359/https://www.lichtdeslebens.de/biophotonen/ | url-status = dead }}
* {{cite book |vauthors=Popp FA, Li KH, Gu Q |title=Recent advances in biophoton research and its applications |date=1992 |publisher=World Scientific |location=Singapore |isbn=978-981-02-0855-4 |url=http://www.worldscibooks.com/physics/1559.html |archive-url=https://web.archive.org/web/20090220145800/http://www.worldscibooks.com/physics/1559.html |archive-date=2009-02-20 }}
* {{cite conference | vauthors = Tilbury RN, Gregg DJ, Percival JM | title = Ultraweak chemiluminescence from human blood plasma. | conference = 1st internet conference on photochemistry and photobiology | date = 1997 | url = http://www.photobiology.com/v1/tilbury/default.htm }}
{{refend}}

== External links ==
* {{cite web | vauthors = Bischof M | url = http://www.lifescientists.de/publication/bibliography1-1.htm | title = Bibliography on biophoton research and related subjects | work = International Institute of Biophysics | archive-url = https://web.archive.org/web/20100125015551/http://www.lifescientists.de/publication/bibliography1-1.htm | archive-date = 2010-01-25 }}
* {{cite web | vauthors = Hyland GJ | url = http://www.biophotonen-online.de/abstract/abs2000-3.htm | title = Fundaments of Coherence in Biology | work = Biophotonik | archive-url = https://web.archive.org/web/20040519063153/http://www.biophotonen-online.de/abstract/abs2000-3.htm | archive-date = 2004-05-19 }}

[[Category:Bioluminescence]]
[[Category:Photons]]