Tetrakis(hydroxymethyl)phosphonium Sulfate: Antibacterial Hydrogels, Formulations & Oilfield Use

Tetrakis(hydroxymethyl)phosphonium sulfate is incompatible with oxidizing materials and alkalis, and its solution is a clear colorless viscous liquid. Tetrakis(hydroxymethyl)phosphonium sulfate's production and use as a textile crease and flame retardant may result in its release to the environment through various waste streams. Its use as a biocide in hydrofracking will result in its direct release to the environment. If released to air, an estimated vapor pressure of 8.1 mm Hg at 25 °C indicates tetrakis(hydroxymethyl)phosphonium sulfate will exist solely as a vapor in the atmosphere. f released into water, tetrakis(hydroxymethyl)phosphonium sulfate is not expected to adsorb to suspended solids and sediment based upon the estimated Koc. Volatilization from water surfaces is not expected to be an important fate process based upon this compound's estimated Henry's Law constant. An estimated BCF of 3 suggests the potential for bioconcentration in aquatic organisms is low. Hydrolysis is expected to be an important environmental fate process since this compound contains functional groups that hydrolyze under environmental conditions (pH 5 to 9).

Self-assembled DNA-THPS hydrogel as a topical antibacterial agent

Bacterial wound infection not only affects the wound healing but also poses threats of systemic infection sepsis as well as organ failure, which are potentially life-threatening. There has been great interest in preparing DNA hydrogels in the past decades and have presented as an interesting material and they have, for example, been explored as antigen delivery system, switchable material for aptamer-based fluorescent detection and delivery vehicle for light-triggered cancer therapy. Herein, we propose a new potential antimicrobial agent to combine with DNA to fabricate DNA-based hydrogel. Tetrakis(hydroxymethyl)phosphonium sulfate (THPS), a cationic phosphonium salt, has attracted extensive industrial and agricultural interest as a pesticide and broad-spectrum microbiocide for water treatment. In this study, THPS was proved to be capable of cross-linking DNA by taking advantage of intermolecular electrostatic interaction and hydrogen bonding. DNA played roles of hydrogelator and building block while THPS was used as a trigger and antibacterial ability donor in the formation of the obtained hydrogel, which named as DNT hydrogel. In this way, Tetrakis(hydroxymethyl)phosphonium sulfate could achieve the lasting and controllable release at the same time.[1]

THPS is a positively charged sulfate salt and rich in -OH functional groups, which can interact with the phosphate backbone of DNA via intermolecular electrostatic interaction. Besides, Tetrakis(hydroxymethyl)phosphonium sulfate, as a small organic molecule, can take advantage of its molecular rotation to combine with nitrogenous bases in the groove of DNA via hydrogen bonding. Based on these speculations, we assumed that the hydrogelation was achieved by intermolecular electrostatic interaction and hydrogen bonding. The hydrogel formation simultaneously took advantages of intermolecular electrostatic interaction and hydrogen bonding between DNA and Tetrakis(hydroxymethyl)phosphonium sulfate. The broad-spectrum antimicrobial mechanism was based on the disruption of bacterial cell membrane without detectable toxicity to mammalian cells. These results may indicate great potential of the DNT hydrogel as an antimicrobial material to accelerate wound healing and against wound infections. In the meantime, the low cost and simple preparation may also make it attractive in biomedical field.

Tetrakis(hydroxymethyl)phosphonium sulfate in commercial formulations

Biocides are compounds that are widely used for controlling the growth of microorganisms such as bacteria, fungi, and algae in water used in industrial processes, particularly in cooling systems. For instance, chlorine, bromine, hydrogen peroxide, and ozone are oxidant biocides, whereas quaternary ammonium salts, carbamates, glutaraldehyde, organothiocyanates, biguanides, isothiazolins, tetrakis(hydroxymethyl)phosphonium sulfate (THPS), and 2,2-dibromo-3-nitrilo-propionamide are nonoxidant biocides. THPS is considered an environmentally friendly biocide because it is easily degraded by oxidation to trishydroxymethylphosphine oxide (THPO). In aquatic environments, THPO is considered to be a very low toxicity agent that can be further mineralized to form carbon dioxide, water, and phosphate. In this paper, a novel and simple CE–C4D method is described and evaluated as an alternative analytical method for the determination of THPS in water. Using this method, commercial formulations of Tetrakis(hydroxymethyl)phosphonium sulfate and four different samples of tap water and cooling water treated with the biocide were analyzed. To the best of our knowledge, this is the first time CE was used for THPS determination.[2]

The negative peaks obtained with C4D means that the detected species have conductivities (or electrophoretic mobilities) lower than the BGE. Peak 1 corresponds to an anionic species, and its peak area was demonstrated to have a linear relationship with the Tetrakis(hydroxymethyl)phosphonium sulfate concentration. The anionic species formed by the interaction between the borate ions in the BGE with the THP allowed the determination of the biocide Tetrakis(hydroxymethyl)phosphonium sulfate by CE–C4D. The proposed method was demonstrated to be rapid, simple, precise, and accurate for monitoring THPS in water, particularly treated water used in cooling systems. Compared to the standard iodometric titration method, the CE–C4D method has the advantage of requiring a lower amount of sample and reagents, and a smaller amount of residues was generated. The proposed method also demonstrated potential for monitoring THPS degradation in water.

Tetrakis(hydroxymethyl)phosphonium sulfate in a light oil-producing oilfield

Samples of (I) produced waters, (II) central processing facility (CPF) waters and (III) pipeline solids were collected from a light oil-producing field. The biocide, tetrakis(hydroxymethyl)phosphonium sulfate (THPS) was routinely used in the CPF. Samples monitoring indicated that THPS was effective in microbial control but also increased concentrations of sulfate and phosphate in transitioning from Type I to Type II waters. Type II waters had high concentrations (up to 60 mM) of acetate but low most probable numbers (MPNs) of acid-producing and sulfate-reducing bacteria, indicating the presence of active biocide, as high MPNs were found in Type I waters. Solids had high phosphate and high MPNs, indicating that THPS was inactive. Solids had oil and an anaerobic community dominated by Acetobacterium, which may contribute to conversion of oil to acetate. The presence of Tetrakis(hydroxymethyl)phosphonium sulfate prevented the use of this acetate in Type II waters, where it accumulated to unusually high concentrations.[3]

References

[1]Jiang X, Li M, Guo X, Yang M, Rasooly A. Self-assembled DNA-THPS hydrogel as a topical antibacterial agent for wound healing. ACS Appl Bio Mater. 2019 Mar 18;2(3):1262-1269. doi: 10.1021/acsabm.8b00818. Epub 2019 Feb 21. PMID: 35005454; PMCID: PMC8733899.

[2]Marques, Thaís Tamye et al. “Determination of tetrakis(hydroxymethyl)phosphonium sulfate in commercial formulations and cooling water by capillary electrophoresis with contactless conductivity detection.” Journal of separation science vol. 38,5 (2015): 852-7. doi:10.1002/jssc.201401288

[3]Sharma, Mohita et al. “Effect of long term application of tetrakis(hydroxymethyl)phosphonium sulfate (THPS) in a light oil-producing oilfield.” Biofouling vol. 34,6 (2018): 605-617. doi:10.1080/08927014.2018.1476500

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