Лако-красочные материалы — производство

All external cavities of the body are lined with a continuous, thick, gel-like structure called mucin. Although the thickness varies depending on the type of tissue [3,4], this layer serves as a protective barrier between the cell surface and its external surroundings. Mucin is secreted by goblet cells and special exocrine glands [5] and can be considered a natural bioadhesive capable of binding to the underlying epithelial tissue. This binding results in a continuous, unstirred gel layer over the mucosa and thus serves as a barrier between a drug delivery system and the underlying mucosal epithelium. Mucus is a mixture of mucin glycoproteins, water, electrolytes, enzymes, bacteria, and sloughed epithelial cells [5]. Most of the content of mucus is an aqueous fluid containing macromolecules [6], with the mucin glycoproteins making up less than 5% of the total weight [7].

Mucin glycoproteins are macromolecules linked together by cross-linking disulfide bonds, physical entanglement [6], and secondary bonds to form a continuous network. These glycoproteins have an abundance of oligosaccharide side chains [6], with their terminal ends usually being either sialic acid [8,9] or L-fucose [10,11]. The entire mucin network at physiological pH has a net negative charge due to these sialic acid residues (pKa = 2.6) and additional sulfate residues [12]. Thus mucin can be viewed as an anionic polyelectrolyte consisting of hydrated, cross-linked, linear, flexible glycoprotein molecules with sufficient overlap and interpenetration to form a continuous network. Since mucus is continually being formed, secreted, and removed from these tissues, its turnover rate must be taken into consideration when designing a bioadhesive dosage form.