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Revision as of 04:48, 17 February 2012 editBeetstra (talk | contribs)Edit filter managers, Administrators172,031 edits Saving copy of the {{chembox}} taken from revid 477245464 of page Alginic_acid for the Chem/Drugbox validation project (updated: 'UNII').  Latest revision as of 08:01, 20 December 2024 edit 71.230.16.111 (talk) →Alginate hydrogels: again 
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{{Short description|Polysaccharide found in brown algae}}
{{ambox | text = This page contains a copy of the infobox ({{tl|chembox}}) taken from revid of page ] with values updated to verified values.}}
{{chembox {{Chembox
| Verifiedfields = changed | Verifiedfields = changed
| verifiedrevid = 476994139 | verifiedrevid = 477314688
|ImageFile=Alginsäure.svg | ImageFile = Alginsäure.svg
|ImageSize=250px | ImageSize = 250px
|IUPACName= | IUPACName =
|OtherNames=Alginic acid | OtherNames = Alginic acid; E400; <sub>n</sub>
|Section1={{Chembox Identifiers
|OtherNames = E400
|Section1= {{Chembox Identifiers
| CASNo_Ref = {{cascite|correct|CAS}} | CASNo_Ref = {{cascite|correct|CAS}}
| CASNo=9005-32-7 | CASNo = 9005-32-7
| EINECS=232-680-1 | EINECS = 232-680-1
| ATCCode_prefix = A02
| ATCCode_suffix = BX13
| UNII_Ref = {{fdacite|changed|FDA}} | UNII_Ref = {{fdacite|changed|FDA}}
| UNII = <!-- blanked - oldvalue: 8C3Z4148WZ --> | UNII = 8C3Z4148WZ
| PubChem= | PubChem =
| SMILES= | SMILES =
| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}} | ChemSpiderID_Ref = {{chemspidercite|changed|chemspider}}
| ChemSpiderID = NA | ChemSpiderID = None
}} }}
|Section2= {{Chembox Properties |Section2={{Chembox Properties
| Formula=(C<sub>6</sub>H<sub>8</sub>O<sub>6</sub>)<sub>n</sub> | Formula = (C<sub>6</sub>H<sub>8</sub>O<sub>6</sub>)<sub>n</sub>
| MolarMass=10,000 - 600,000 | MolarMass = 10,000 – 600,000
| Appearance= white to yellow, fibrous powder | Appearance = White to yellow, fibrous powder
| Density= 1.601 g/cm<sup>3</sup> | Density = 1.601{{nbsp}}g/cm<sup>3</sup>
| MeltingPt= | MeltingPt =
| BoilingPt= | BoilingPt =
| Solubility= | Solubility =
| pKa = 1.5-3.5 | pKa = 1.5–3.5
}} }}
|Section3= {{Chembox Hazards |Section6={{Chembox Pharmacology
| ATCCode_prefix = A02
| MainHazards=
| ATCCode_suffix = BX13
| FlashPt=
}}
| Autoignition=
|Section7={{Chembox Hazards
| MainHazards =
| FlashPt =
| AutoignitionPt =
}} }}
}} }}
]'', the largest species of giant ]]]
'''Alginic acid''', also called '''algin''', is a naturally occurring, edible ] found in ]. It is ] and forms a viscous ] when hydrated. When the alginic acid binds with sodium and calcium ions, the resulting salts are known as '''alginates'''. Its colour ranges from white to yellowish-brown. It is sold in ], granular, or powdered forms.

It is a significant component of the ] produced by the bacterium '']'', a major pathogen found in the lungs of some people who have ].<ref name="davies">{{cite journal | last=Davies | first=JC | title=Pseudomonas aeruginosa in cystic fibrosis: pathogenesis and persistence. | journal=Paediatric Respiratory Reviews | volume=3 | issue=2 | year=2002 | issn=1526-0542 | pmid=12297059 | pages=128–34| doi=10.1016/S1526-0550(02)00003-3 }}</ref> The biofilm and ''P. aeruginosa'' have a high resistance to ],<ref name="boyd">{{cite journal | last1=Boyd | first1=A | last2=Chakrabarty | first2=AM | title=Pseudomonas aeruginosa biofilms: role of the alginate exopolysaccharide. | journal=Journal of Industrial Microbiology | volume=15 | issue=3 | year=1995 | issn=0169-4146 | pmid=8519473 | pages=162–8| doi=10.1007/BF01569821 | s2cid=42880806 | doi-access=free }}</ref> but are susceptible to inhibition by ].<ref name="Leid">{{cite journal | last1=Leid | first1=JG | last2=Willson | first2=CJ | last3=Shirtliff | first3=ME | last4=Hassett | first4=DJ | last5=Parsek | first5=MR | last6=Jeffers | first6=AK | title=The exopolysaccharide alginate protects Pseudomonas aeruginosa biofilm bacteria from IFN-gamma-mediated macrophage killing. | journal=Journal of Immunology | volume=175 | issue=11 | date=1 November 2005 | issn=0022-1767 | pmid=16301659 | pages=7512–8|url=http://www.jimmunol.org/content/175/11/7512.full.pdf| doi=10.4049/jimmunol.175.11.7512 | s2cid=1011606 | doi-access=free }}</ref>

Alginate was discovered by British chemical scientist E. C. C. Stanford in 1881, and he patented an extraction process for it in the same year.<ref name="extract" /> The alginate was extracted, in the original patent, by first soaking the algae in water or diluted acid, then extracting the alginate by soaking it in ], and finally precipitating the alginate from solution.<ref>{{Citation |last1=Pereira |first1=Leonel |title=Introductory Chapter: Alginates - A General Overview |date=2020-02-05 |work=Alginates - Recent Uses of This Natural Polymer |url=https://www.intechopen.com/chapters/68305 |access-date=2024-08-06 |publisher=IntechOpen |language=en |isbn=978-1-78985-642-2 |last2=Cotas |first2=João}}</ref>{{Better citation needed|reason=The current source is insufficiently reliable (]).|date=August 2024}}

==Structure==
Alginic acid is a linear ] with ]ic blocks of (1→4)-linked β-D-] (M) and α-L-] (G) residues, respectively, ] linked together in different sequences or blocks. The ]s may appear in homopolymeric blocks of consecutive ] (G-blocks), consecutive ] (M-blocks) or alternating M and G-residues (MG-blocks). α-L-guluronate is the C-5 ] of β-D-mannuronate.{{Citation needed|date=August 2024}}

==Forms==
Alginates are refined from brown ]. Throughout the world, many of the ] class brown seaweeds are harvested to be processed and converted into sodium alginate. Sodium alginate is used in many industries including food, animal food, fertilisers, textile printing, and pharmaceuticals. Dental impression material uses alginate as its means of gelling. Food grade alginate is an approved ingredient in processed and manufactured foods.<ref>{{cite web|title=Alginates|url=https://www.ams.usda.gov/sites/default/files/media/Alginates%20TR%202015.pdf|publisher=Agricultural Marketing Service, US Department of Agriculture|access-date=1 March 2018|date=5 February 2015}}</ref>

Brown seaweeds range in size from the giant ] '']'' which can be 20–40 meters long, to thick, leather-like seaweeds from 2–4 m long, to smaller species 30–60&nbsp;cm long. Most brown seaweed used for alginates are gathered from the wild, with the exception of '']'', which is cultivated in China for food and its surplus material is diverted to the alginate industry in China.

Alginates from different species of brown seaweed vary in their chemical structure, resulting in different physical properties of alginates. Some species yield an alginate that gives a strong ], another a weaker gel, some may produce a cream or white alginate, while others are difficult to gel and are best used for technical applications where color does not matter.<ref>FAO fisheries technical paper 441, Tevita Bainiloga Jnr, School of Chemistry, University College, University of New South Wales and Australian Defence Force Academy Canberra Australia</ref>

Commercial grade alginate is extracted from giant ] '']'', '']'', and types of '']''. Alginates are also produced by two ]l ] '']'' and '']'', which played a major role in the unravelling of its ] ]. Bacterial alginates are useful for the production of micro- or nanostructures suitable for medical applications.<ref name=2Remminghorst>{{cite book |author=Remminghorst and Rehm|year=2009|chapter=Microbial Production of Alginate: Biosynthesis and Applications|title=Microbial Production of Biopolymers and Polymer Precursors|publisher=Caister Academic Press|isbn = 978-1-904455-36-3}}</ref>

Sodium alginate (NaC<sub>6</sub>H<sub>7</sub>O<sub>6</sub>) is the ] of alginic acid. Sodium alginate is a gum.

Potassium alginate (KC<sub>6</sub>H<sub>7</sub>O<sub>6</sub>) is the potassium ] of alginic acid.

] (CaC<sub>12</sub>H<sub>14</sub>O<sub>12</sub>) is the calcium salt of alginic acid. It is made by replacing the sodium ion in sodium alginate with a calcium ion (]).

==Production==
The manufacturing process used to extract sodium alginates from brown seaweed fall into two categories: 1) calcium alginate method and, 2) alginic acid method.{{clarification needed|reason=no details of the named processes are given - details and citations needed|date=March 2024}}

Chemically the process is simple, but difficulties arise from the physical separations required between the slimy residues from viscous solutions and the separation of gelatinous precipitates that hold large amounts of liquid within their structure, so they resist ] and ].<ref>FAO Fisheries Technical Paper, 2003</ref> The conventional process involves large amounts of reagents and solvents, as well as time-consuming steps.<ref name="extract"/> Simpler and newer techniques, such as microwave-assisted extraction, ultrasound, high pressure, pressurized fluid extraction, and enzyme-assisted extraction, are the subject of research.<ref name="extract"/>

The most common, conventional extraction process involves six steps: pre-treatment of the algal biomass, acid treatment, alkaline extraction, precipitation, bleaching, and drying. <ref name="extract">{{Cite journal |last1=Bojorges |first1=Hylenne |last2=López-Rubio |first2=Amparo |last3=Martínez-Abad |first3=Antonio |last4=Fabra |first4=María José |date=2023-10-01 |title=Overview of alginate extraction processes: Impact on alginate molecular structure and techno-functional properties |url=https://www.sciencedirect.com/science/article/pii/S0924224423002571 |journal=Trends in Food Science & Technology |volume=140 |pages=104142 |doi=10.1016/j.tifs.2023.104142 |issn=0924-2244|hdl=10261/336757 |hdl-access=free }}</ref> Pre-treatments mainly aim at either breaking the cell wall to help extract the alginate, or removing other compounds and contaminants from the algae.<ref name="extract"/> Drying is of the first kind, also helping to prevent bacterial growth; algae which is dried is also usually powdered to expose more surface area.<ref name="extract"/> Common treatments to remove contaminants include treatments with ] and ], the latter of which is very common; ethanol solutions help remove compounds bonded to the alginate, and formaldehyde solutions help prevent enzymatic or microbial reactions.<ref name="extract"/>

The algae is then treated with an acidic solution to help disrupt cell walls, which converts the alginate salts into insoluble alginic acid; a subsequently applied alkaline solution (pH 9-10), usually ], converts it back into water-soluble sodium alginate, which is then precipitated.<ref name="extract"/> It is also possible to extract the alginate directly with an alkaline treatment, but this is less common.<ref name="extract"/>

Alginic acid is usually precipitated, through different techniques, with either an alcohol (usually ethanol), ], or ].<ref name="extract"/> After the alginin is precipitated into a fine paste, it is dried, ground to the desired grain size, and finally purified through a variety of techniques.<ref name="extract"/> Commercial alginate for biomedical and pharmaceutical use is extracted and purified through more rigorous techniques, but these are trade secrets.<ref name="extract"/>

===Derivatives===
Various alginate-based materials can be produced, including porous scaffold material, alginate hydrogel, nonwoven fabric, and alginate membranes.<ref name=":0"/> Techniques used to produce these include ion cross-linking, microfluidic spinning, freeze drying, wet spinning, and immersive centrifugal jet spinning.<ref name=":0"/>

Calcium salt{{Clarification needed|date=August 2024}} can be released in drops into a calcium alginate solution to induce ionic cross-linking, which produces the hydrogel. Freeze-drying the hydrogel to eliminate water produces the porous scaffold material.<ref name=":0"/>

Wet spinning consists of extruding an alginate solution from a spinneret into a calcium salt solution to induce ionic cross-linking (forming the gel), and then ] the fibers out of the bath with draft rollers. Microfluidic spinning, a simpler and more eco-friendly implementation of the process, involves introducing calcium salt flows flowing alongside and touching a central "core" flow of alginate. These flows form a "sheath". The fiber then emerges from the core flow. This technique can be used to produced shaped and grooved fibers.<ref name=":0"/>

]
Alginate fiber, which is used in fabric, is usually produced through either microfluidic spinning or wet spinning, or ] to obtain thinner fibers.<ref name=":0"/> The fabric, which can be used in wound dressing and other applications, is produced by ] and then needle punching {{Clarification needed|date=August 2024}} the fibers.<ref name=":0"/>

==Uses==
As of 2022 alginate had become one of the most preferred materials as an abundant natural biopolymer.<ref name=":0">{{Cite journal |last1=Zhang |first1=Xiaolin |last2=Wang |first2=Xinran |last3=Fan |first3=Wei |last4=Liu |first4=Yi |last5=Wang |first5=Qi |last6=Weng |first6=Lin |date=2022-08-08 |title=Fabrication, Property and Application of Calcium Alginate Fiber: A Review |journal=Polymers |volume=14 |issue=15 |pages=3227 |doi=10.3390/polym14153227 |doi-access=free |issn=2073-4360 |pmc=9371111 |pmid=35956740}}</ref> It is particularly useful as a ] because of its nontoxicity, ], and ], and can imitate local bioenvironments; its degradation product can be easily cleared by the kidneys.<ref name=":0" />

Alginate absorbs water quickly, which makes it useful as an additive in ] products such as ], and in the manufacture of paper and textiles.{{Citation needed|date=August 2024}}

Alginate is also used for ] and ] fabrics, in the food industry as a ] agent for drinks, ice cream, cosmetics, as a ] for jellies, known by the ] and sausage casing.<ref>{{cite web |title=What is Sodium Alginate (E401) in food? Properties, Uses, Safety |author= |work=FOODADDITIVES |date=14 May 2020 |url= https://foodadditives.net/thickeners/sodium-alginate/}}</ref><ref>{{cite book |title=Bioactive Seaweeds for Food Applications |first1=Yimin|last1=Qin |date=17 July 2018 |url=https://www.sciencedirect.com/topics/food-science/sausage-casing|doi=10.1016/C2016-0-04566-7|isbn=978-0-12-813312-5 |archive-url=https://web.archive.org/web/20231109163125/https://www.sciencedirect.com/topics/food-science/sausage-casing |archive-date=2023-11-09 }}</ref> Sodium alginate is mixed with ] protein to make ].<ref>{{cite book |last1=Arasaki |first1=Seibin |title=Low Calorie, High Nutrition Vegetables from the Sea |last2=Arasaki |first2=Teruko |publisher=Japan Publications, Inc. |date=January 1983 |isbn=0-87040-475-X |edition=1st |location=Tokyo, Japan |pages=35}}</ref>

Alginate is used as an ingredient in various ] preparations, such as ], in which it combines with ] to inhibit ]. {{Citation needed|date=August 2024}}

Sodium alginate is used as an ]-making material in ], ]s, ], and for creating positives for small-scale ]. {{Citation needed|date=August 2024}}

Sodium alginate is used in ] and as a thickener for ]s in ].{{citation needed|date=October 2015}} Alginates do not react with these dyes and wash out easily, unlike ]-based thickeners. It also serves as a material for ].<ref>{{cite journal|title = Microencapsulation and storage stability of polyphenols from Vitis vinifera grape wastes|journal = Food Chemistry|date = 2016-01-01|pages = 614–621|volume = 190|doi = 10.1016/j.foodchem.2015.05.117|pmid = 26213018|first1 = Oier|last1 = Aizpurua-Olaizola|first2 = Patricia|last2 = Navarro|first3 = Asier|last3 = Vallejo|first4 = Maitane|last4 = Olivares|first5 = Nestor|last5 = Etxebarria|first6 = Aresatz|last6 = Usobiaga| url=https://figshare.com/articles/journal_contribution/5028350 }}</ref>

Calcium alginate is used in different types of medical products, including skin ]s to promote healing,<ref>{{cite journal|journal=Wound Repair Regen|year=2002|volume=10|issue=5|pages=271–85|title=Calcium: a potential central regulator in wound healing in the skin|author=Lansdown AB|pmid=12406163|doi=10.1046/j.1524-475x.2002.10502.x|s2cid=10092676}}</ref><ref>{{cite journal|last1=Stubbe|first1=Birgit|last2=Mignon|first2=Arn|last3=Declercq|first3=Heidi|last4=Vlierberghe|first4=Sandra Van|last5=Dubruel|first5=Peter|date=2019|title=Development of Gelatin-Alginate Hydrogels for Burn Wound Treatment|journal=Macromolecular Bioscience|language=en|volume=19|issue=8|pages=1900123|doi=10.1002/mabi.201900123|pmid=31237746|s2cid=195355185|issn=1616-5195|url=https://lirias.kuleuven.be/bitstream/123456789/663375/3/Development%20of%20Gelatin-Alginate%20Hydrogels%20for%20Burn%20Wound%20Treatment.docx }}</ref> and may be removed with less pain than conventional dressings.{{citation needed|date=October 2015}}

==Alginate hydrogels==
In research on bone reconstruction, alginate ] have favorable properties encouraging regeneration, such as improved ], ], and ].<ref>{{cite journal|pmid=25020082|year=2015|last1=Venkatesan|first1=J|title=Alginate composites for bone tissue engineering: A review|journal=International Journal of Biological Macromolecules|volume=72|pages=269–81|last2=Bhatnagar|first2=I|last3=Manivasagan|first3=P|last4=Kang|first4=K. H.|last5=Kim|first5=S. K.|doi=10.1016/j.ijbiomac.2014.07.008}}</ref> Alginate hydrogel is a common biomaterial for bio-fabrication of scaffolds and tissue regeneration.<ref>{{cite journal|last1=Rastogi|first1=Prasansha|last2=Kandasubramanian|first2=Balasubramanian|date=2019-09-10|title=Review of alginate-based hydrogel bioprinting for application in tissue engineering|url=https://doi.org/10.1088/1758-5090/ab331e|journal=Biofabrication|language=en|volume=11|issue=4|pages=042001|doi=10.1088/1758-5090/ab331e|pmid=31315105|bibcode=2019BioFa..11d2001R|s2cid=197543168|issn=1758-5090}}</ref>

Covalent bonding of thiol groups to alginate improves in-situ gelling and mucoadhesive properties; the thiolated polymer (]) forms disulfide bonds within its polymeric network and with cysteine-rich subdomains of the mucus layer.<ref>{{cite journal |last1=Leichner |first1=C |last2=Jelkmann |first2=M |last3=Bernkop-Schnürch |first3=A |title=Thiolated polymers: Bioinspired polymers utilizing one of the most important bridging structures in nature |journal=Adv Drug Deliv Rev |date=2019 |volume=151-152 |pages=191–221 |doi=10.1016/j.addr.2019.04.007 |pmid=31028759|s2cid=135464452 }}</ref> Thiolated alginates are used as in situ gelling hydrogels,<ref>{{cite journal |last1=Xu |first1=G |last2=Cheng |first2=L |last3=Zhang |first3=Q | last4=Sun|first4=Y | last5=Chen |first5=C |last6=Xu |first6=H |last7=Chai |first7=Y | last8=Lang|first8=M |title= In situ thiolated alginate hydrogel: Instant formation and its application in hemostasis|journal= J Biomater Appl |date=2016 |volume=31 |issue=5 |pages=721–729 |doi=10.1177/0885328216661557|pmid= 27485953|s2cid=4267830 }}</ref> and are under preliminary research as possible mucoadhesive drug delivery systems.<ref>{{cite journal |last1=Kassem |first1=AA |last2=Issa |first2=DA |last3=Kotry |first3=GS | last4=Farid |first4=RM |title= Thiolated alginate-based multiple layer mucoadhesive films of metformin for intra-pocket local delivery: in vitro characterization and clinical assessment |journal= Drug Dev. Ind. Pharm. |date=2017 |volume=43 |issue=1 |pages=120–131 |doi=10.1080/03639045.2016.1224895 |pmid=27589817 |s2cid=25076932 }}</ref> Alginate hydrogels may be used for drug delivery, exhibiting responses to pH changes, temperature changes, redox, and the presence of enzymes.<ref>{{cite journal |last1=Abasalizadeh |first1=Farhad |last2=Moghaddam |first2=Sevil |last3=Alizadeh |first3=Effat |last4=Fazljou |first4=Mohammad |last5=Torbati |first5=Mohammadali |last6=Akbarzadeh |first6=Abolfazl |date=13 March 2020 |title=Alginate-based hydrogels as drug delivery vehicles in cancer treatment and their applications in wound dressing and 3D bioprinting |journal=Journal of Biological Engineering |volume=14 |issue=8 |page=8 |doi=10.1186/s13036-020-0227-7|doi-access=free |pmid=32190110 |pmc=7069202 }}</ref>

==See also==
* ]: a polysaccharide in animals.
* ]

==References==
{{Reflist}}

==External links==
* {{Webarchive|url=https://web.archive.org/web/20130917233613/http://www.cybercolloids.net/library/alghistory/history-alginate-chemistry-seaweeds |date=2013-09-17 }}
* {{Webarchive|url=https://web.archive.org/web/20130917065320/http://www.cybercolloids.net/library/alginate/introduction-alginate-production |date=2013-09-17 }}

{{Drugs for peptic ulcer and GORD}}
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{{DEFAULTSORT:Alginic Acid}}
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