Thiomer

[2][3] Sulfhydryl ligands of low molecular mass are covalently bound to a polymeric backbone consisting of mainly biodegradable polymers, such as chitosan,[4][5] hyaluronic acid,[6] cellulose derivatives,[7] pullulan,[8][9] starch,[10] gelatin,[11] polyacrylates,[12] cyclodextrins,[13][14] or silicones.

[15] Thiomers exhibit properties potentially useful for non-invasive drug delivery via oral, ocular, nasal, vesical, buccal and vaginal routes.

[22] Thiomers are capable of forming disulfide bonds with cysteine substructures of the mucus gel layer covering mucosal membranes.

Because of the formation of inter- and intrachain disulfide bonds during the swelling process, the stability of the polymeric drug carrier matrix is strongly improved.

Many non-invasively administered drugs such as therapeutic peptides or nucleic acids are degraded on the mucosa by membrane bound enzymes, strongly reducing their bioavailability.

In case of oral administration, this ‘enzymatic barrier’ is even more pronounced as an additional degradation caused by luminally secreted enzymes takes place.

Because of their capability to bind zinc ions via thiol groups, thiomers are potent inhibitors of most membrane bound and secreted zinc-dependent enzymes.

Due to this enzyme inhibitory effect, thiolated polymers can significantly improve the bioavailability of non-invasively administered drugs[41][42][43] In vitro, thiomers were shown to have antimicrobial activity towards Gram-positive bacteria.

[49][50][51] In comparison to most low molecular weight permeation enhancers, thiolated polymers offer the advantage of not being absorbed from the mucosal membrane.

[57][58] As thiolated polymers exhibit biocompatibility, cellular mimicking properties and efficiently support proliferation and differentiation of various cell types, they are used as scaffolds for tissue engineering.