Dutch researcher Saskia Lindhoud has discovered a new way to package enzymes by causing charged polymers to form a 'ball of hair' around them. Her approach significantly increases the utility of the enzymes. For example, healthy enzymes with a foul taste can be packaged in such a way that they are released in the stomach without being tasted.

Enzymes are molecules that can trigger specific chemical reactions. They are responsible for the taste of beer, the effectiveness of detergents and the digestion of food in our guts. However, the optimal use of enzymes requires that they do not trigger the chemical reactions too early or too late. Moreover, enzymes are quite sensitive to changes in their environment such as temperature fluctuations and changes in the salt concentration or pH. Enzymes can be protected from such influences by means of a packaging. Lindhoud discovered a new way of doing this well.

Hairy balls

Lindhoud used polyelectrolyte complex micelles for the packaging. These consist of at least two types of molecules that have an opposite charge and of which at least one type has a charged and an uncharged block (diblock copolymer). If these molecules are mixed together then the oppositely charged parts of the molecules form a complex because opposite charges attract. The uncharged parts of the molecules prefer not to be located in the core and stick outwards. This results in the automatic formation of balls with hairs on the outside.

As enzymes are also charged they can be packaged into these hairy balls. Yet unfortunately, particles that consist of just enzymes and diblock copolymers are not very robust. Lindhoud therefore substituted a part of the enzymes with a polymer of the same charge. This improved the stability and robustness of the particles. Moreover, Lindhoud discovered that the enzymes preferred not to be located in the core of the particle but on the boundary of this instead. Adding polymers with the same charge increased the surface of this boundary.

The advantage of enzymes packaged using Lindhoud's approach is the ease with which these can be unpackaged again. This is essential for the effective use of enzymes in industrial applications. Lindhoud's research could therefore do more than improve detergents; it could enable new applications of enzymes. One such possible application is the specific delivery of medicines. Saskia Lindhoud carried out her research with a TOP grant from the NWO Division for the Chemical Sciences. She is now a postdoctoral researcher at the University of Bath.