Credit: © 2008 ACS

Polymers have been used to deliver drugs, enzymes and a host of diagnostic agents into the cell because they can be easily engineered to have useful properties such as specificity and stability. Now, researchers from the University of Basel have shown that certain blends of polymers are stable enough to be used as nanoscale bioreactors that could act as functional components of the cell.

Patrick Hunziker and colleagues1 made the vesicles by joining three types of polymer chains together to form a tri-block copolymer. The vesicles (typically less than 200 nm in size) were loaded with trypsin — an enzyme that cleaves certain peptide bonds — and functionalized with a ligand so that they targeted macrophages, which are specific cells of the immune system known to be important in various diseases. Fluorescent staining showed that the vesicles entered the macrophages and remained stable for a long time, and that the trypsin inside the vesicle was able to process peptide substrates that were added to the cell culture. The membrane of the vesicle protected the trypsin from the external environment while allowing the peptide substrates to enter, thereby forming a nanoreactor inside the cell.

The authors suggested that vesicles made with various combinations of polymers, ligands and enzymes may be targeted to cells to modify their functions involved in diseases such as cancer and atherosclerosis.