Engineering Plastic Surfaces to Influence Cellular Behaviour in Biological Assays

Working to Surface Thicknesses of 20-50 nm: Germany-based original equipment manufacturer Greiner Bio-One, whose moulding expertise dates back to 1953, has written the following discussion about developing customised platforms for the life science sector using injection moulding and surface engineering technology.

The selective and reliable control of the interaction of biomolecules with a polymer phase such as an organic functional layer and solid substrates is one of the major current development topics. In this context, nanobiotechnology can be seen as a young and rapidly developing field at the crossroads of biotechnology and material science which is able to solve problems with the utilisation of novel biological assays.

Several methods of polymer modification are the toolbox for the generation of functional layers with specific characteristics in order to be able to meet the needs of applications such as tissue culture or microarray technologies in the best possible way.

In addition, the combination of thin functional layers with nanostructures can be the solution to overcome the remaining challenges and to provide the best possible platforms to be able to open the gate to new applications and assays.

Presently, the main focus of product developments comprise of the following.

Optimisation of cell adhesion of sensitive cell lines: In general, the propagation of cells and tissue in vitro can be challenging and, therefore, synthetic surfaces to support the cell cultivation are of great interest. These non-biological polymer modifications are mimicking the cellular surrounding to positively influence the cell adhesion.

Ways of minimising the cell adhesion (cell repelling surface) are of interest in the field of stem cell research. To be able to meet this need, the successful surface needs to prevent any interaction with cells, either by ionic, covalent coupling or  hydrogen bonding means, together with the need to be e-beam or gamma sterilised without loss of performance. Similar surfaces can be used for preventing the protein adsorption in the context of high throughput screening (HTS) applications. HTS uses robotics and other advanced technologies to conduct many thousands, even millions, of tests at once.

Enzyme-linked immunosorbent assays (ELISAs) use peptides, antibodies and proteins with colour changes to identify a substance. The method relies on ionic adsorption to immobilise the biomolecule. Therefore, physico-chemical forces such as hydrophobic bonds, hydrophilic interactions and H-bonding are relevant.

Polystyrene, the most widely used material for immunological microplates, has hydrophobic characteristics. Because for most ELISA applications the presence of hydrophilic groups is beneficial, several physical treatments are established in order to generate hydrophilic, polar and protic chemical groups on the surface.

In the last decade the covalent immobilisation of antibodies, proteins and DNA became a topic of great interest within microarray technology. The challenge here is the synthesis of a surface with a suitable contact angle for an optimal spot morphology, a high binding capacity to reach a satisfying sensitivity as well as reduced non-specific binding.

The solution and alternative to the first generation layers, formed via a sol-gel process, are organic 3D architectures with 20-50 nm thickness. The sol-gel process is a method of producing solid materials from small molecules using a combination of a sol (coloidal solution) and a gel.

With these platforms the microarray technology can be used in many applications such as genotyping in clinical diagnostics and expression profiling.

Hydrophobic materials are mainly used in protein crystallisation platforms. The reliable and stable, biocompatible, hydrophobic surface can be the crucial benefit for the crystallisation of membrane proteins in small volumes and in buffer solutions with certain detergents.

These manifold developments prove the advantages of surface modification for biotechnology and biomedical applications. Upcoming challenges will deal with biocompatibility and the enhanced use of these techniques in medical devices.

For more information please contact Greiner Bio-One in the UK at oem@uk.gbo.com.