"Bio-printing" — an efficient new method in biotechnology

Zurich, Switzerland, 1 September 2001—Scientists at IBM Research - Zurich and the University of Zurich have developed a new printing method that may greatly improve the ability to extract molecules from fluids and to place them in arbitrary patterns on surfaces, which is widely required for investigation and analysis in biotechnology.

Interaction between myriads of different biomolecules is essential to life. So-called ligand and receptor molecules interact by binding to each other for various functions in living organisms such as replication of genetic information, transport of substances, exchange of information between cells, destruction of viruses, and many other processes.

Binding of partner molecules in a two-dimensional array to the surface of a substrate has promising applications in biotechnology. Layers of specialized proteins are used, for example, to guide the attachment and growth of cells. This allows the response of individual cells to external stimuli such as a current, light, or a drug to be studied. In immunology, the binding of antibodies and antigens to a surface is done routinely to diagnose diseases. In both examples, a key step is to coat the surface with one of the binding partners from a solution. Today's method to do this first requires tedious purification of such binding partners, mostly proteins, from a natural source or from specific cell cultures.

The new approach developed by the scientists in Switzerland is based on rubber stamps for performing a process called affinitiy contact printing, which will make it far simpler, faster, and less expensive to create patterned protein-coated surfaces in consecutive steps using the same tool.

Deposition of a target protein on a substrate first requires that the stamp be coated with corresponding antibodies that will capture the target proteins in a few drops of solution brought onto the stamp. Unlike previous methods, this solution does not have to be pure. Binding forces between the antibodies and the proteins are strong and selective enough that the stamp can be rinsed without losing the captured proteins. In the printing process the captured proteins bind to the substrate surface and separate from the antibodies when the stamp is removed.

"Our experiments show that the printed molecules do not suffer from mechanical forces exerted during the printing process and retain their activity," says Emmanuel Delamarche of IBM Research - Zurich. "Another favorable aspect of our technique is its potential to orient proteins and to fabricate biological layers in a controlled way, which improves the performance of biosensors substantially."

"We have demonstrated the power of our technique by extracting cell adhesion molecules (CAMs) used to immobilize cells and printing them on a substrate to grow lines of neurons," explains André Bernard, who led the project at IBM Research - Zurich . "Well-defined stamp structures allow the printing of high-resolution patterns of proteins, which makes it possible to investigate a single cell at a time if required."

"With this new method, we captured CAMs from a crude solution and deposited them on a substrate in a few minutes," says Peter Sonderegger from the University of Zurich, who has 20 years of experience in neuronal cell research. "Using conventional methods, purification of the CAMs alone is a tedious and lossy process, which can take more than a week."

Affinity contact printing is not limited to antibody-based capture; any type of ligand-receptor interaction may be exploited, and the stamp can be reused for many capturing and printing cycles. Moreover, the stamp can be patterned to create structured layers, which will allow several analytes to be screened in parallel. Thus, the new contact printing method "may become a versatile tool for extracting, affinity purifying, concentrating and patterning precious biomolecules in a single step," the authors conclude in their scientific publication, which appeared in Nature Biotechnology, Vol. 19, No. 9, pp. 866-869, September 2001.

The authors of the publication entitled "Affinity capture of molecules from solution and their dissociation by contact printing" are André Bernard, now with LifeBits AG in Tübingen, Germany, Emmanuel Delamarche and Bruno Michel of IBM Research - Zurich, Dora Fitzli, Peter Sonderegger, and Hans Rudolf Bosshard of the Biochemistry Institute of the University of Zurich, and Hans Biebuyck, now with IGEN International in Gaithersburg, MD, USA.