clays and binders


According to PubChem the molecular formula of Compounds with similar formulas that include

Images of sepiolite and related compounds from PubChem

One of th main differences seems to be the ratio of magnesium to silicon.

  • sepiolite powder is H8Mg2O10Si3.
  • Chrysotile; chrysotile asbestos H4Mg3O9Si2 In the acidic environment of the stomach or the phagosome of a pulmonary macrophage, the layer of Mg2+ between layers of silica, aka asbestos, is leached away. Asbestos is released [1]
  • Quincite H8Mg2O10Si3+4 There does not seem to be much information on this compound. This must refer to some sort of halide salt
  • Antigorite H10Mg3O9Si2 This compound induces PGE2, reactive oxygen species, and monocyte-macrophage J774 cells. [2]

Not to be confused with talc

Another study examined the affect of talc on the J774 macrophage cell line and found evidence of toxicity. [3] No comment was made as to whether the acidity of the phagosome may have selectively dissolved the magnesium oxide layer leaving only the silica/asbestos layer.

The TALC image on the left is from PubChem, the center from an Internet search, and he one on the right from a creative commons image from Research Gate

And Back to sepiolite

Sepiolite does not cause the unscheduled DNA synthesis that is associated with other asbestos like minerals as a tumor promoter. [4]

Transmission electron micrograph of untreated sepiolite.

Sepiolite binding of proteins and amino acids

“The addition of small quantities 1–2% (w/w) of the sepiolite clay EXAL to animal feed increases the feed efficiency and weight of animals. -Chymotrypsin, lipase and -amylase from bovine pancreas adsorbed on to EXAL at different pH values form active stable complexes at enteric pH values. The enzymes are chemisorbed on EXAL by interaction between NH3+ groups of lysines and basic sites of the solid surface. The derivatives obtained are stable, regardless of changes in pH, and the relation between their activity and pH is complementary to that observed with the native enzyme. Therefore, these enzyme-EXAL derivatives are resistant to proteolysis and increase the amount of active digestive enzymes in the intestine. A more efficient utilization of feed would take place in animals that have ingested EXAL than in those which have not ingested the sepiolite.” [5]

Luciano Brandão-Lima and coworkers from Brazil published a followup study 30 years later in 2021. In this study they compared sepiolite with AlMgO4Si+, aka Veegum®, as absorbants of three amino acids. “The amount of 1.0 g of sepiolite (Sep) or Veegum® (Veg) was suspended in 30.0 mL of an aqueous solution of the amino acid (concentration of 0.01 mol L−1). The amino acids used were: L-lysine (Lys), L-methionine (Met) or L-tryptophan (Trp). The isoelectric point of silica is 1.7-3.5. (Marek Kosmulski, “Chemical Properties of Material Surfaces”, Marcel Dekker, 2001.)

Left pKa of three amino acids used in the Brandão-Lima study [5] A plot of relative amounts of charged species of the amino acid glycine as a function of pH. The vertical green line indicates teh isoeelctric point at which the net charge is zero. Right, clays and metal oxides also have isoelectric points.

Sepiolite binds to phospholipids

This is a direct quotation of the abstract

“Biomimetic interfaces based on phosphatidylcholine (PC) assembled to the natural silicate sepiolite were prepared for the stable immobilization of the urease and cholesterol oxidase enzymes. This is an important issue in practical advanced applications such as biocatalysis or biosensing. The supported lipid bilayer (BL-PC), prepared from PC adsorption, was used for immobilization of enzymes and the resulting biomimetic systems were compared to several other supported layers including a lipid monolayer (ML-PC), a mixed phosphatidylcholine/octyl-galactoside layer (PC-OGal), a cetyltrimethylammonium monolayer (CTA), and also to the bare sepiolite surface. Interfacial characteristics of these layers were investigated with a focus on layer packing density, hydrophilicity/hydrophobicity, and surface charge, which are being considered as key points for enzyme immobilization and stabilization of their biological activity. Cytoplasmic urease and membrane-bound cholesterol oxidase, which served as model enzymes, were immobilized on the different PC-based hybrid materials to probe their biomimetic character. Enzymatic activity was assessed by cyclic voltammetry and UV-vis spectrophotometry. The resulting enzyme/bio-organoclay hybrids were applied as active phase of a voltammetric urea biosensor and cholesterol bioreactor, respectively. Urease supported on sepiolite/BL-PC proved to maintain its enzymatic activity over several months while immobilized cholesterol oxidase demonstrated high resusability as biocatalyst. The results emphasize the good preservation of bioactivity due to the accommodation of the enzymatic system within the biomimetic lipid interface on sepiolite.”

This one is kind of interesting because mixes membrane bound enzymes

Sepiolite and DNA

This study had a lot of structural information. [7]

One of the advantages of fibrous clays, such as sepiolite, compared to “conventional” clays based on layered silicates (i.e., smectites and vermiculites) is the high density of surface silanol groups, which allows hydrogen bonding interactions at the silicate interacting with diverse organic species. Moreover, this silicate possesses a cation-exchange capacity (10–20 mEq/100 g), which is the result of partial isomorphous substitutions of magnesium by aluminum and other trivalent metals in the octahedral sheet of the structure of sepiolite. Therefore, the negatively charged surface may also ensure ionic interactions in the assembly of sepiolite with inorganic cations, in addition to positively charged molecular species.

In terms of an absorbant for digestive enzymes, a recent post suggests a pathway for their absorption from the small intestine.

Heavy Metal Detox

This report came from the Hunan province of China. [9] A rather large deposit of sepiolite had been discovered in their province. The authors were also concerned with heavy metal contamination in water sources for towns along the Xiangjiang River. These heavy metals included: Mn, Cu, Pb, Zn, Cd, Ni, As, and Hg. [9] These problems are not as common in the U.S. with notable exceptions like the lead contaminated water of Flint Michigan. We may also be exposed to Hg, mercury in tuna. A report from USGS estimates between 0.41 to .51 ug/g Hg per g wet mass of Pacific blue fin tuna caught off the coast of California. Addition of sepiolite to wild caught fish that tend to be contaminated with heavy metals ha a certain level of appeal. These surface modifications were used to increase heavy metal binding

  1. Acid modification The H+ from the acid will displace the Ca2+, Mg2+, Na+, and K+ inpurities.
  2. Thermal modification of sepiolite is calcining (heating to ~500 °C) natural sepiolite at different temperatures. This drives off water molecules and increases porosity.
  3. Magnetic Modification of sepiolite provides an effective way to facilitate separation and/or reuse. Fe3+ present in the modified sepiolite has oxidative properties. The phase structure of magnetic sepiolite did not show any obvious change.
  4. Organic Modification uses a range of molecules such as surfactants, polymerised organic matter, or microorganisms .
  5. 4.5. Acid Thermal Treatment
modified from Wang 2018 [9]

It would appear that heat and acid treatment is best for removal of unstated amounts of Cd2+ and Hg2+ from water. Would mixing this clay remove heavy metals from our diets?

Is Sepiolite safe?

Sepiolite is also an ingredient in synthetic cat litter. The featured image is from the previous post. This site a somewhat more interesting image of the sepiolite from cat litter. This particular article reiterates the concept of channels addressed in the previous post. It is debatable as to whether or not sepiolite cat litter absorbs small molecule odorants in addition to water. The use of sepioite in cat litter certainly adds an interesting dimension to its use as a medicinal clay.

Re-evaluation of calcium silicate (E 552), magnesium silicate, magnesium trisilicate, and talc as food additives [11]

This was a European Union publication that was not that well organized to a central theme.  Renal injury of these silicates in guinea pigs and dogs was noted. [1]  Other mention was made of contamination with fluoride and heavy metals in these silicates that end up in food. [11] Dietary exposure to silicates as supplements was 31 mg/kg bw per day at the mean level in children and up to 46 mg/kg bw per day at the high level in the elderly. [1]  It was not clear if this supplement exposure was as the magnesium trisilicate antacid. Based on the food supplement scenario considered as most representative for risk characterization, exposure to silicates (E 552–553) for all population groups was below the maximum daily dose of magnesium trisilicate used as an antacid (4 g/person per day)  [1]  Mention was made of silicates in tablets with coatings, chocolate coatings, coatings on meat sausages, syrups, and so on.  [11]

This is a somewhat appalling quote:

“Pure bred Beagle dogs (6–9 animals/sex per group; approximately 6 months old) were fed diets containing magnesium trisilicate (1,800 mg/kg bw per day) for 4 weeks. The protocol was the same as the one used for the rat study described above …A few of the dogs had polydipsia and polyuria, and most of the treated animals had occasional soft faces discolored by unabsorbed test substance. All animals developed gross cortical lesions of the kidney.”  [11]

And human studies

Here are some bullet points of case reports in the EU review. [11]

  • A case report involving a patient had taken 2g magnesium trisilicate (as an antacid) with every meal for many years also presented with renal colic . This situation may have been several decades in the making. [11]
  • Another citation reported magnesium trisilicate use being associated with only 0.1–0.2% of all urinary stones in humans.
  • Some cases have been described in children…where they were associated with consumption of milk thickener containing 5.5% silicates in one case of a 6-month-old boy

Safety and efficacy of a feed additive consisting of sepiolite for all animal species [12]

This review also became a bit much. The EU consortium seemed concerned about contaminating fluoride. [12] Another review covered heavy metal absorbing capacity for treatment of contaminated water. [13]


  1. Bernstein D, Dunnigan J, Hesterberg T, Brown R, Velasco JA, Barrera R, Hoskins J, Gibbs A. Health risk of chrysotile revisited. Crit Rev Toxicol. 2013 Feb;43(2):154-83. PMC free article
  2. Cardile V, Lombardo L, Belluso E, Panico A, Capella S, Balazy M. Toxicity and carcinogenicity mechanisms of fibrous antigorite. Int J Environ Res Public Health. 2007 Mar;4(1):1-9. PMC free article
  3. Mandarino A, Gregory DJ, McGuire CC, Leblanc BW, Witt H, Rivera LM, Godleski JJ, Fedulov AV. The effect of talc particles on phagocytes in co-culture with ovarian cancer cells. Environ Res. 2020 Jan;180:108676. PMC free article
  4. Denizeau F, Marion M, Chevalier G, Cote MG. Absence of genotoxic effects of nonasbestos mineral fibers. Cell Biol Toxicol. 1985 Jan;1(2):23-32.
  5. Cabezas, M. & Salvador, D. & Sinisterra, J.. (2007). Stabilization-activation of pancreatic-enzymes adsorbed on to a sepolite clay. Journal of Chemical Technology and Biotechnology. 52. 265 – 274. 10.1002/jctb.280520213.
  6. Brandão-Lima LC, Silva FC, Costa PVCG, Alves-Júnior EA, Viseras C, Osajima JA, Bezerra LR, de Moura JFP, de A Silva AG, Fonseca MG, Silva-Filho EC. Clay Mineral Minerals as a Strategy for Biomolecule Incorporation: Amino Acids Approach. Materials (Basel). 2021 Dec 22;15(1):64. PMC free article
  7. Wicklein B, Darder M, Aranda P, Ruiz-Hitzky E. Phospholipid-sepiolite biomimetic interfaces for the immobilization of enzymes. ACS Appl Mater Interfaces. 2011 Nov;3(11):4339-48. doi: 10.1021/am201000k. Epub 2011 Oct 21. PMID: 21970377.
  8. Castro-Smirnov FA, Piétrement O, Aranda P, Bertrand JR, Ayache J, Le Cam E, Ruiz-Hitzky E, Lopez BS. Physical interactions between DNA and sepiolite nanofibers, and potential application for DNA transfer into mammalian cells. Sci Rep. 2016 Nov 3;6:36341. free article
  9. Wang Z, Liao L, Hursthouse A, Song N, Ren B. Sepiolite-Based Adsorbents for the Removal of Potentially Toxic Elements from Water: A Strategic Review for the Case of Environmental Contamination in Hunan, China. Int J Environ Res Public Health. 2018 Aug 3;15(8):1653. PMC free article
  10. Crawford JS, Potter SR. Magnesium trisilicate mixture BP. Its physical characteristics and effectiveness as a prophylactic. Anaesthesia. 1984 Jun;39(6):535-9. PMC free article
  11. EFSA Panel on Food Additives and Nutrient Sources added to Food (ANS), Younes M, Aggett P, Aguilar F, Crebelli R, Dusemund B, Filipič M, Frutos MJ, Galtier P, Gott D, Gundert-Remy U, Kuhnle GG, Leblanc JC, Lillegaard IT, Moldeus P, Mortensen A, Oskarsson A, Stankovic I, Waalkens-Berendsen I, Woutersen RA, Wright M, Boon P, Gürtler R, Mosesso P, Parent-Massin D, Tobback P, Chrysafidis D, Rincon AM, Tard A, Lambré C. Re-evaluation of calcium silicate (E 552), magnesium silicate (E 553a(i)), magnesium trisilicate (E 553a(ii)) and talc (E 553b) as food additives. EFSA J. 2018 Aug 2;16(8):e05375. PMC free article
  12. EFSA Panel on Additives and Products or Substances used in Animal Feed (FEEDAP), Bampidis V, Azimonti G, Bastos ML, Christensen H, Dusemund B, Fašmon Durjava M, Kouba M, López-Alonso M, López Puente S, Marcon F, Mayo B, Pechová A, Petkova M, Ramos F, Sanz Y, Villa RE, Woutersen R, Aquilina G, Bories G, Tosti L, Anguita M, Galobart J, Holczknecht O, Innocenti ML, Manini P, Pizzo F.(2022) Safety and efficacy of a feed additive consisting of sepiolite for all animal species (Sepiol S.A and Tolsa, S.A). EFSA J. 2022 Apr 20;20(4):e07250. PMC free article
  13. Song N, Hursthouse A, McLellan I, Wang Z. Treatment of environmental contamination using sepiolite: current approaches and future potential. Environ Geochem Health. 2021 Jul;43(7):2679-2697. PMC free article

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