Thiomers and their potential applications in drug delivery

ABSTRACT

Introduction: Thiomers are the product of the immobilization of sulfhydryl-bearing ligands onto the polymer backbone of a conventional polymer, which results in a significant improvement in mucoadhesion; in situ gelation and efflux inhibition compare with unchanged polymers. Because of thiol groups, thiomers have more reactivity and enhanced protection against oxidation. Since the late 1990s, extensive work has been conducted on these promising polymeric excipients in the pharmaceutical field.

Areas covered: This review covers thiomers, their classification and their different properties. Various techniques for the synthesis, purification and characterization of thiomers are described in detail. This review also encompasses their various properties such as mucoadhesion, permeation enhancement, in situ gelation and efflux inhibition, as well as different formulations based on thiomers. In addition to the use of thiomers as multifunctional excipients, this review also encompasses their use as drugs.

Expert opinion: The synthesis is realized by linkage of sulfhydryl-bearing ligands but reported methods give low yields. Higher degrees of modification are not necessary and would probably lead to extreme changes in properties. Nevertheless, an accurate characterization of the final product is important. The scale-up procedure for industrial manufacturing has been adapted to produce GMP materials; Lacrimera® eye drops have already entered the European market.

KEYWORDS:

• Mucoadhesion
• oral delivery
• preactivated thiomers
• S-nitrosothiomers
• thiomers

Article highlights

• Several methods have been described to produce thiomers, but the yields of these reactions are low

• An accurate characterization of the final products is important

• Thiomers have good mucoadhesive properties

• Thiomers have been used to enhance the permeation of drugs across biological barriers

• Thiomers have efflux pump inhibiting properties

• Some thiomers have in situ gel properties

• Some thiomers can be used to produce tablets, nanoparticles or microparticles

• From these thiomers, S-nitrosothiomers have been synthesized and proposed as new NO donors

This box summarizes key points contained in the article.

Declaration of interest

The authors have no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties.

Additional information

Funding

This paper was not funded.