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Latex

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This article is about the polymer. For the document preparation system and markup language, see LaTeX. For other uses, see Latex (disambiguation).
Tapping of latex from a tree, for use in rubber production

Latex is an emulsion (stable dispersion) of polymer microparticles in water.[1] Latices are found in nature, but synthetic latices are common as well.

In nature, latex is found as a milky fluid, which is present in 10% of all flowering plants (angiosperms).[2] It is a complex emulsion that coagulates on exposure to air, consisting of proteins, alkaloids, starches, sugars, oils, tannins, resins, and gums. It is usually exuded after tissue injury. In most plants, latex is white, but some have yellow, orange, or scarlet latex. Since the 17th century, latex has been used as a term for the fluid substance in plants, deriving from the Latin word for "liquid".[3][4][5] It serves mainly as defense against herbivorous insects.[2] Latex is not to be confused with plant sap; it is a distinct substance, separately produced, and with different functions.

The word latex is also used to refer to natural latex rubber, particularly non-vulcanized rubber. Such is the case in products like latex gloves, latex condoms, latex clothing, and balloons.

IUPAC definition.

Latex: Colloidal dispersion of polymer particles in a liquid.[6][a]
Synthetic latex: Latex obtained as a product of an emulsion, mini-emulsion, micro-emulsion, or dispersion polymerization.[6]

Biology

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Articulated laticifers

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The cells (laticifers) in which latex is found make up the laticiferous system, which can form in two very different ways. In many plants, the laticiferous system is formed from rows of cells laid down in the meristem of the stem or root. The cell walls between these cells are dissolved so that continuous tubes, called latex vessels, are formed. Since these vessels are made of many cells, they are known as articulated laticifers. This method of formation is found in the poppy family and in the rubber trees (Para rubber tree, members of the family Euphorbiaceae, members of the mulberry and fig family, such as the Panama rubber tree Castilla elastica), and members of the family Asteraceae. For instance, Parthenium argentatum the guayule plant, is in the tribe Heliantheae; other latex-bearing Asteraceae with articulated laticifers include members of the Cichorieae, a clade whose members produce latex, some of them in commercially interesting amounts. This includes Taraxacum kok-saghyz, a species cultivated for latex production.[7]

Non-articulated laticifers

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In the milkweed and spurge families, on the other hand, the laticiferous system is formed quite differently. Early in the development of the seedling, latex cells differentiate, and as the plant grows these latex cells grow into a branching system extending throughout the plant. In many euphorbs, the entire structure is made from a single cell – this type of system is known as a non-articulated laticifer, to distinguish it from the multi-cellular structures discussed above. In the mature plant, the entire laticiferous system is descended from a single cell or group of cells present in the embryo.

The laticiferous system is present in all parts of the mature plant, including roots, stems, leaves, and sometimes the fruits. It is particularly noticeable in the cortical tissues. Latex is usually exuded as a white liquid, but is some cases it can be clear, yellow or red, as in Cannabaceae.[2]

Productive species

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Latex is produced by 20,000 flowering plant species from over 40 families. These include both dicots and monocots. Latex has been found in 14 percent of tropical plant species, as well as six percent of temperate plant species.[8] Several members of the fungal kingdom also produce latex upon injury, such as Lactarius deliciosus and other milk-caps. This suggests it is the product of convergent evolution and has been selected for on many separate occasions.[2]

Defense function

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Rubber tapping latex

Latex functions to protect the plant from herbivores. The idea was first proposed in 1887 by Joseph F. James, who noted that latex of milkweed

carries with it at the same time such disagreeable properties that it becomes a better protection to the plant from enemies than all the thorns, prickles, or hairs that could be provided. In this plant, so copious and so distasteful has the sap become that it serves a most important purpose in its economy.[9]

Evidence showing this defense function include the finding that slugs will eat leaves drained of their latex but not intact ones, that many insects sever the veins carrying latex before they feed, and that the latex of Asclepias humistrata (sandhill milkweed) kills by trapping 30% of newly hatched monarch butterfly caterpillars.[2]

Other evidence is that latex contains 50–1000× higher concentrations of defense substances than other plant tissues. These toxins include ones that are also toxic to the plant and consist of a diverse range of chemicals that are either poisonous or "antinutritive."

Latex is actively moved to the area of injury; in the case of Cryptostegia grandiflora, latex more than 70 cm from the site of injury is mobilized.[2] The large hydrostatic pressure in this vine enables an extremely high flow rate of latex. In a 1935 report the botanist Catherine M. Bangham observed that "piercing the fruit stalk of Cryptostegia grandiflora produced a jet of latex over a meter long, and maintained [this jet] for several seconds."[10]

The clotting property of latex is functional in this defense since it limits wastage and its stickiness traps insects and their mouthparts.[2]

While there exist other explanations for the existence of latex including storage and movement of plant nutrients, waste, and maintenance of water balance that "[e]ssentially none of these functions remain credible and none have any empirical support".[2]

Applications

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Opium poppy exuding fresh latex from a cut

The latex of many species can be processed to produce many materials.

Personal and healthcare products

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Natural rubber is the most important product obtained from latex; more than 12,000 plant species yield latex containing rubber, though in the vast majority of those species the rubber is not suitable for commercial use.[12] This latex is used to make many other products including mattresses,[13] gloves, swim caps, condoms, catheters and balloons.[citation needed]

Opium and opiates

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Dried latex from the opium poppy is called opium, the source of several useful analgesic alkaloids such as codeine, thebaine, and morphine, the latter two of which can then further be used in the synthesis and manufacture of other (typically stronger) opioids for medicinal use, and of heroin for the illegal drug trade. The opium poppy is also the source of medically useful non-analgesic alkaloids, such as papaverine and noscapine.[citation needed]

Clothing

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Main article: Latex clothing

Latex is used in many types of clothing. Worn on the body (or applied directly by painting), it tends to be skin-tight, producing a "second skin" effect.[14]

Industrial and biological applications of synthetic latices

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Synthetic latices are used in coatings (e.g., latex paint) and glues because they solidify by coalescence of the polymer particles as the water evaporates. These synthetic latices therefore can form films without releasing potentially toxic organic solvents in the environment. Other uses include cement additives and to conceal information on scratchcards. Latex, usually styrene-based, is also used in immunoassays.[15]

Allergic reactions

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Main article: Latex allergy

Some people only experience a mild allergy when exposed to latex, with symptoms such as eczema, contact dermatitis, or developing a rash.[16]

Others have a serious latex allergy, and exposure to latex products such as latex gloves can cause anaphylactic shock. Guayule latex has only 2% of the levels of protein found in Hevea latices, and it is being researched as a lower-allergen substitute.[17] Additionally, chemical processes may be employed to reduce the amount of antigenic protein in Hevea latex, yielding alternative materials such as Vytex Natural Rubber Latex which provide significantly reduced exposure to latex allergens.

About half of people with spina bifida are also allergic to natural latex rubber. People who have had multiple surgeries and who have had prolonged exposure to natural latex are also more susceptible to a latex allergy.[18]

Latex-fruit syndrome

Many people with latex allergy also experience allergic reactions to certain fruits. This association has led to research regarding latex-fruit syndrome (LFS). This is a phenomenon characterized by cross-reactivity between natural latex rubber allergens and certain fruit allergens, leading to allergic reactions in sensitized individuals. It was described for the first time by Blanco et al. in 1994.[19]

In a 2024 comprehensive review by Gromek et al., the last 30 years of research on LFS were summarized, focusing on its prevalence, common cross-reactions, and clinical manifestations. The review found that the prevalence of LFS in latex-allergic patients varies widely, ranging from 4% to 88%, depending on diagnostic methods, geographical regions, and study populations. The most commonly implicated fruits in LFS include banana, avocado, kiwifruit, and papaya. Clinical manifestations are predominantly systemic, with 73% of hypersensitivity symptoms being systemic and 27% localized. Gromek et al. also highlighted the need for standardized diagnostic criteria and severity grading systems to improve the accuracy of LFS diagnosis and treatment.[20]

Microbial degradation

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Several species of the microbe genera Actinomycetes, Streptomyces, Nocardia, Micromonospora, and Actinoplanes are capable of consuming rubber latex.[21] However, the rate of biodegradation is slow, and the growth of bacteria utilizing rubber as a sole carbon source is also slow.[22]

See also

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Notes

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  1. ^ The polymer in the particles may be organic or inorganic.[6]

References

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  1. ^ Wang, Hui; Yang, Lijuan; Rempel, Garry L. (2013). "Homogeneous Hydrogenation Art of Nitrile Butadiene Rubber: A Review". Polymer Reviews. 53 (2): 192–239. doi:10.1080/15583724.2013.776586. S2CID 96720306.
  2. ^ a b c d e f g h Anurag A. Agrawal; d Kotaro Konno (2009). "Latex: a model for understanding mechanisms, ecology, and evolution of plant defense Against herbivory". Annual Review of Ecology, Evolution, and Systematics. 40: 311–331. doi:10.1146/annurev.ecolsys.110308.120307.
  3. ^ Paul G. Mahlberg (1993). "Laticifers: an historical perspective". The Botanical Review. 59 (1): 1–23. Bibcode:1993BotRv..59....1M. doi:10.1007/bf02856611. JSTOR 4354199. S2CID 40056337.
  4. ^ Harper, Douglas. "latex". Online Etymology Dictionary.
  5. ^ latex. Charlton T. Lewis and Charles Short. A Latin Dictionary on Perseus Project.
  6. ^ a b c Stanislaw Slomkowski; José V. Alemán; Robert G. Gilbert; Michael Hess; Kazuyuki Horie; Richard G. Jones; Przemyslaw Kubisa; Ingrid Meisel; Werner Mormann; Stanisław Penczek; Robert F. T. Stepto (2011). "Terminology of polymers and polymerization processes in dispersed systems (IUPAC Recommendations 2011)" (PDF). Pure and Applied Chemistry. 83 (12): 2229–2311. doi:10.1351/PAC-REC-10-06-03. S2CID 96812603. Archived (PDF) from the original on 2013-10-20.
  7. ^ "Taraxacum kok-saghyz". Pfaf.org. Archived from the original on 2014-03-20. Retrieved 2013-03-21.
  8. ^ Thomas M. Lewinsohn (1991). "The geographical distribution of plant latex". Chemoecology. 2 (1): 64–68. Bibcode:1991Checo...2...64L. doi:10.1007/BF01240668. S2CID 44594197.
  9. ^ Joseph F. James (1887). "The milkweeds". The American Naturalist. 21 (7): 605–615. doi:10.1086/274519. JSTOR 2451222.
  10. ^ Buttery, R. R.; Boatman, S. G. (1976). Kozlowski, T. T. (ed.). Water Deficits and Plant Growth, Volume IV: Soil Water Measurement, Plant Responses, and Breeding for Drought Resistance. Vol. IV (1st ed.). New York, New York 10003: Academic Press, Inc. p. 252. ISBN 978-0124314269.{{cite book}}: CS1 maint: location (link)
  11. ^ Mathews, Jennifer P. (2009). Chicle: The chewing gum of the Americas, from the ancient Maya to William Wrigley. Tucson: University of Arizona Press. ISBN 978-0-8165-2821-9.
  12. ^ J. E. Bowers (1990). Natural Rubber-Producing Plants for the United States. Beltsville, MD: National Agricultural Library. pp. 1, 3. OCLC 28534889.
  13. ^ Yurkovich, Dror. "Dunlop latex vs. Talalay latex". Getha. Archived from the original on 2021-04-13. Retrieved 2021-04-22.
  14. ^ Kink and everyday life : interdisciplinary reflections on practice and portrayal. Kylo-Patrick R. Hart, Teresa Cutler-Broyles. Bingley. 2021. ISBN 978-1-83982-918-5. OCLC 1262726608. Archived from the original on 2024-06-02. Retrieved 2021-12-29.{{cite book}}: CS1 maint: location missing publisher (link) CS1 maint: others (link)
  15. ^ Akamine, Y.; Sato, S.; Kagaya, H.; Ohkubo, T.; Satoh, S.; Miura, M. (2018-04-20). "Comparison of electrochemiluminescence immunoassay and latex agglutination turbidimetric immunoassay for evaluation of everolimus blood concentrations in renal transplant patients". Journal of Clinical Pharmacy and Therapeutics. 43 (5): 675–681. doi:10.1111/jcpt.12686. ISSN 0269-4727. PMID 29679392.
  16. ^ "Latex Allergy | Causes, Symptoms & Treatment". ACAAI Public Website. Archived from the original on 2019-03-24. Retrieved 2019-03-24.
  17. ^ Anderson, Christopher D.; Daniels, Eric S. (8 May 2018). Emulsion Polymerisation and Latex Applications. iSmithers Rapra Publishing. ISBN 9781859573815. Archived from the original on 2 June 2024. Retrieved 8 May 2018 – via Google Books.
  18. ^ "Latex allergy - Symptoms and causes". mayoclinic.com. Archived from the original on 7 October 2013. Retrieved 8 May 2018.
  19. ^ Blanco, C.; Carrillo, T.; Castillo, R.; Quiralte, J.; Cuevas, M. (October 1994). "Latex allergy: clinical features and cross-reactivity with fruits". Annals of Allergy. 73 (4): 309–314. ISSN 0003-4738. PMID 7943998.
  20. ^ Gromek, Weronika; Kołdej, Natalia; Świtała, Szymon; Majsiak, Emilia; Kurowski, Marcin (2024-07-19). "Revisiting Latex-Fruit Syndrome after 30 Years of Research: A Comprehensive Literature Review and Description of Two Cases". Journal of Clinical Medicine. 13 (14): 4222. doi:10.3390/jcm13144222. ISSN 2077-0383. PMC 11278189. PMID 39064262.
  21. ^ Helge B. Bode; Axel Zeeck; Kirsten Plückhahn; Dieter Jendrossek (September 2000). "Physiological and Chemical Investigations into Microbial Degradation of Synthetic Poly(cis-1,4-isoprene)". Applied and Environmental Microbiology. 66 (9): 3680–3685. Bibcode:2000ApEnM..66.3680B. doi:10.1128/aem.66.9.3680-3685.2000. PMC 92206. PMID 10966376.
  22. ^ Rose, K.; Steinbuchel, A. (2 June 2005). "Biodegradation of Natural Rubber and Related Compounds: Recent Insights into a Hardly Understood Catabolic Capability of Microorganisms". Applied and Environmental Microbiology. 71 (6): 2803–2812. Bibcode:2005ApEnM..71.2803R. doi:10.1128/AEM.71.6.2803-2812.2005. PMC 1151847. PMID 15932971.
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  • Media related to latex at Wikimedia Commons
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