Controlling the flow of solution over the sensor surface is vital for the correct performance of a biosensor system, precise control allows optimisation of conditions for specific molecular interactions. This process is performed by liquid handling systems, which can be divided into two main groups – flow through and cuvette systems.
In a flow through system, sample or buffer is constantly passed over the sensor surface to provide a specific hydrodynamic environment. The continuous flow also washes desorbed material away from the sensor, which prevents analytes from re-binding and interfering with measurements. Flow rate and exposed sensor surface area can be controlled for ideal results in the particular experiment being performed. In general, kinetic rate calculation experiments utilise small volume, high velocity flow, whereas ‘ligand fishing’ experiments (to isolate a specific analyte from a complex mixture) use large surface areas with little to no buffer flow.
One drawback to continuous flow systems is the limited maximum association time, which can lead to difficulties when studying analytes with low association constants. Although their baseline noise is usually somewhat higher, cuvette systems provide an alternative in which the sample is injected into a well over the sensor surface, where it can be incubated for a longer period. This incubation can be halted at any time for measurement, allowing the measurement of binding processes with relatively small sample volumes over a very long time.
Choosing the correct system for liquid handling is an important part of experiment design. If you need help to decide on the appropriate system, or are simply after some tips and tricks, we would encourage you to get in touch with the experts here at XanTec bioanalytics.