Sustained and triggered release by microencapsulation

Licentiate thesis, 2021

Uncontrolled growth of microorganisms is problematic in areas ranging from wound care to aquaculture and ship hulls. In chronic and hard-to-heal wounds, a bacterial biofilm can impair wound healing. The growth of marine microorganisms, so-called biofouling, on equipment used in aquaculture can decrease productivity and thereby result in a loss of revenue. To counteract these problems and minimize microbial growth, antimicrobial substances have been developed. For efficient use of these antimicrobial substances that enables long-term protection without excessive use, their release from materials should be controlled.

In this work, microencapsulation was used as a means of controlling the rate at which a model hydrophobic substance was released in two different ways. A slow sustained release microparticle system with a complete release over a period of weeks was developed. These microcapsules were also incorporated into cellulose fibers, to produce a nonwoven material possessing controlled release properties. As a complement to this, a fast triggered release system was developed where a significant release could be seen within minutes of the trigger event.

Through a combination of these two types of controlled release, a hypothetical release profile could be tailored to fit specific applications. The triggered release microparticles could initially increase the antimicrobial concentration above a certain effective concentration, and the sustained release microparticles would maintain the concentration above the effective concentration for a prolonged time. The use in a nonwoven fiber material was illustrated in this work, although use in e.g. continuous fibers or painted coatings could also easily be conceived.