Surface plasmon resonance biosensing toward real biological sample analysis

The development of monolayer chemistry based on amino acid and short peptides decreases significantly the nonspecific adsorption from biological samples such as serum. Nonspecific adsorption of proteins onto the surface of biosensors currently limits the applicability of many biosensing techniques in real biological samples. In order to minimize this problem, a methodology to immobilize short peptides on surface plasmon resonance (SPR) biosensors was developed using a short chain alkyl thiol monolayer derived with the selected peptides. The chain length of the alkane thiol linking the amino acid to the gold surface influences the physico-chemical properties of the layer and the amount of nonspecifically adsorbed proteins. Varying the composition of the monolayer with peptides formed from the natural amino acids investigates the physico-chemical properties required to minimize nonspecific adsorption of serum. It was observed from monolayers of single amino acids that the composition of the side chain of the amino acid greatly influences the resistance to nonspecific adsorption, with more polar, ionic and small chains resulting in an improved performance in biological samples. Building peptides of different lengths resulted in a further decrease of the amount of nonspecifically bound proteins from serum. Leaving the terminal carboxylic acid end of the peptide unreacted provides an anchoring point for a molecular receptor in the design of a biosensor. Biosensing will be demonstrated with a model system of β-lactamase.