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Phosphonium ionic liquids - leading the way in medical applications

In medical and other sterile environments, surfaces such as  bandages, etc. are required to be as clean and bacteria and virus free as possible. While there are many ways to clean a surface, the ability of a surface to “clean itself” is an attractive property. Over the years this concept has been developed by forming polymers for materials that are inherently active to kill a variety of bacteria. Research for the use of phosphonium ionic liquids has been developed for many years and used in applications for industrial water treatment (1). Over the last several years, this knowledge has been applied  to polymer and coatings chemistry. As microbial infections remain a viable threat in medical situations, this field needs to continue to develop.

Phosphonium salts can be synthesized from a variety of phosphines (triethylphosphine [CYTOP® 320], tributylphosphine [CYTOP® 340], trihexylphosphine [CYTOP® 360], etc.). The incorporation of the phosphorus can be undertaken by addition to the monomer directly or via post polymerization modification (2). In both cases, this immobilizes the phosphonium salt. Representative examples are depicted in Figures 1 and 2 (3, 4). These systems showed effective microbial control against Staphylococcus aureus, Escherichia coli, Bacillus subtilis, Aspergillus flavus, Fusarium oxysporum and Candida albicans.

Figure 1: Phosphonium incorporation into polymer backbone using Tributylphosphonium (CYTOP® 340)

Figure 2:  Trihexylphosphonium (CYTOP® 360) incorporation into polymer backbone

An additional advantage of incorporating the antimicrobial component into the polymer is many antimicrobials are small molecules which can be toxic to humans - while in the polymer form the risk and hazards to people can be reduced.

Furthermore - these phosphonium salts can be incorporated into other medical related systems that can potentially improve drug delivery . In therapeutics, many traditional systems can have poor targeting or difficulty in controlling dosage, amongst a myriad of other challenges. Controlled drug delivery is an ongoing and attractive research field. Phosphonium salts can be combined with polyanions in polyelectrolyte networks which may be incorporated into drug delivery systems (Scheme 2). The relevant phosphonium salts can be based on trialkylphosphines such as triethylphosphine (CYTOP® 320) or tributylphosphine (CYTOP® 340).(5)

Scheme 2: Synthesis of Monomers, Polymers and Relevant Ionic Networks

The tools available now to incorporate phosphonium ionic liquids into polymers are vast and well established. Focusing on their unique properties and challenging applications, such as the ones presented in the medical field represent great avenues to develop new research breakthroughs. With the phosphonium ionic liquids being both tunable, and antimicrobial in nature they are lending themselves well to medical applications. Furthermore, the understanding of drug delivery systems is enabling these polymer networks to be applied in alternative medical applications as well.

CYTOP® 320, CYTOP® 340 and CYTOP® 360 are clear, colorless, pyrophoric liquids.  They must be handled under an inert atmosphere. To learn more about other ligands for catalysis, please refer to the Solvay website.

References

1.    Green Chemistry, 2005, 7, 855-862.
2.    RSC Advances, 2016, 6, 86151-86157.
3.    Reactive & Functional Polymers, 2006, 66, 419-429.
4.    Chemical Science, 2022, 13, 345.
5.    Langmuir, 2020, 36, 8253-8264.

Featured Products

97-6300Triethylphosphine, 99% [CYTOP® 320 ORGANOPHOSPHINE] (554-70-1)

97-5801 Tri-n-butylphosphine, min. 93% [CYTOP® 340 ORGANOPHOSPHINE] (998-40-3)

97-1312 Tri-n-hexylphosphine, min. 96% [CYTOP® 360 ORGANOPHOSPHINE] (4168-73-4)

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All products sold in collaboration with Solvay

Phosphorus Ligands and Compounds Booklet