Professor Hyung Joon Cha (Department of Chemical Engineering) and his team have succeeded in developing a highly condensed liquid bio-adhesive material based on the mussel adhesive proteins (MAPs) by complex coacervation, which shows superior adhesive properties. Recently, MAPs found in byssus of mussel, have come to be recognized as useful biomaterials for direct use as bio-adhesives in medical applications and in the engineering of new marine-inspired adhesive materials. As purified natural MAPs are difficult to obtain, it has not been possible to experimentally validate the complex coacervation model from mussel, which make the results more valuable and remarkable.

Professor Cha’s team has used the characteristics of mussels that grow attached on boulders as secreting adhesive proteins. Byssus is composed of byssal thread and plaque in edges. MAPs exhibit both non-toxicity and strong attachment to any type of inorganic or organic surface in a wet environment. Various type of MAPs has been defined by fp, abbreviation for foot protein, and types 1 (fp-1), 3 (fp-3), and 5 (fp-5) MAPs have been extensively studied. However, the details of the adhesion process, including condensation of MAPs in vacuoles, and secretion as a watery liquid but with no dispersion into the surrounding water, have remained poorly understood. The team has already been able to solve the problem of getting the materials by complex coacervation.

In the present study, the team investigated the formation of complex coacervates using hybrid MAPs (fp-151 and fp-131) and hyaluronic acid (HA). A coacervate is a tiny spherical droplet of assorted oppositely charged polymers which are held together by electrostatic interaction.

Complex coacervation refers to the phase separation of a liquid precipitate when solutions of two hydrophilic colloids are mixed under suitable conditions. HA is an anionic polysaccharide that contributes to cell production and migration as one of the major components of the extracellular matrix, and is found in all tissues and body fluids of vertebrates, as well as in some bacteria. In addition to those, microencapsulation of oil particles was performed using complex coacervation to demonstrate potential application in the field of adhesive drug carriers.

This microencapsulation system could be effectively used in the development of new adhesive biomaterials. It includes self-adhesive microencapsulated drug carriers for biotechnological and biomedical applications such as bio-cosmetic products and food additives. “Through this research, we have developed a bio-adhesive material with extraordinary physical characteristics, and it is significant that we have found the mechanism of mussels’ secretion of concentrated adhesive substance. We believe this has opened various possibilities of utilization of bio-adhesive materials,” commented Professor Cha.

The results of the study were published in the March 1, 2010, online issue of Biomaterials, the May issue of the journal Biomaterials. This work is supported by the National Research Laboratory program and the Brain Korea 21 program from the Ministry of Education, Science and Technology, Korea.