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Thiomers

The next generation of mucoadhesive polymers

  • Review Article
  • Published:
American Journal of Drug Delivery

Abstract

In recent years, thiolated polymers (thiomers) have been introduced as a promising new tool in the field of mucoadhesive drug delivery. Generated by the immobilization of sulfhydryl-bearing compounds on the backbone of well established mucoadhesive polymeric excipients, such as chitosan and poly(acrylates), thiomers display significantly increased mucoadhesive properties as a result of a covalent attachment to mucus glycoproteins. Strong cohesive properties obtained by the formation of inter- and intramolecular disulfide bonds result in comparatively higher stability, leading to prolonged disintegration times and sustained drug release from tablets, microparticles, and gels. The transport rate of peptide and protein drugs as well as hydrophilic model compounds across various animal mucosal tissues, studied in Ussing-type diffusion chambers, can be highly improved by the use of thiomers. Furthermore, thiomers exhibit an increased inhibitory effect towards membrane-bound and luminally secreted peptidases, respectively.

The efficacy of thiomer-based drug delivery systems has been confirmed in various in vivo studies. Oral application of salmon calcitonin, insulin, and low-molecular weight heparin as well as intranasal application of human growth hormone embedded in a thiolated carrier matrix to conscious rats resulted in significantly increased bioavailability compared with use of unmodified basis polymers. Moreover, a study performed in human volunteers revealed that ocular inserts based on thiolated poly(acrylic acid) provide a detectable fluorescein concentration on the cornea for >8 hours, whereas the fluorescein concentration rapidly decreased after application of eye drops or inserts based on unmodified polymer.

In light of these promising results, thiomers seem to be a valuable tool for the noninvasive delivery of mainly peptide and protein drugs.

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Acknowledgments

This work was supported by Grant No. P 15373 from the Fonds zur Förderung wissenschaftlicher Forschung (FWF) to Andreas Bernkop-Schnürch. The authors have no conflicts of interest that are directly relevant to the content of this review.

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  1. Department of Pharmaceutical Technology, Institute of Pharmacy, Leopold-Franzens-University Innsbruck, Josef-Möller-Haus, Innrain 52, Innsbruck, 6020, Austria

    Andreas Bernkop-Schnürch & Alexander Greimel

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  1. Andreas Bernkop-Schnürch
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  2. Alexander Greimel
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Correspondence to Andreas Bernkop-Schnürch.

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Bernkop-Schnürch, A., Greimel, A. Thiomers. Am J Drug Deliv 3, 141–154 (2005). https://doi.org/10.2165/00137696-200503030-00001

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