Enzymatically triggered release of dye model compounds from zein particles

• Zein as a responsive release system is promising for use in paints and plasters.
• The release system makes materials more sustainable as it requires less biocide.
• The built industry can use the release system to enhance material lifetime.
• Encapsulation of dyes was performed as model system for encapsulation of biocides.
• Charge and size are important parameters for dye encapsulation in zein.

A responsive release system consisting of biocide encapsulated by the hydrophobic protein zein was investigated, in which a biocide will be released if growth of micro-organisms occurs. Because biocide release is difficult to detect, a model system using dyes with different size, polarity and charge was developed first to study the applicability of the zein matrix as an enzyme triggered responsive release system. The responsive release efficiency was highest for dyes with a positive charge, that have limited flexibility and the possibility of aromatic interactions with the matrix. The positively charged dyes showed a larger effect than negatively charged dyes. Additives were shown to enhance the release efficiency of the system. The most efficient release system combines the dye methyl violet with the additive oleic acid. These compounds interact to form a larger, more hydrophobic moiety. A plasticizing effect is thought also to be important, since even without clear specific interactions between dye and additives, release properties are enhanced. The charge of the additives seemed to be more important than their size, and both hydrophobic and ionic interactions were shown to play a role.

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