Comparative analysis of QCM and SPR techniques for the optimization of immobilization sequences

One of the most remarkable procedures to immobilize some biological molecules onto surfaces is the use of self-assembled monolayers (SAMs). The aim of this work is to analyse the influence of formation conditions in the detection capability of two different SAMs. With this purpose two techniques have been implemented: the Quartz Crystal Microbalance with Dissipation (QCM-D) and the Surface Plasmon Resonance (SPR). Thus, several parameters usually involved in the SAM protocols have been characterized, i.e. the nature of the thiolated acid. The influence of its concentration and incubation time has been also taken into account. For the validation of these biological layers, the polymyxin B sulfate salt (PmB), as ligand, and the lipopolysaccharide (LPS), as analyte, have been used. It is demonstrated that both in the QCM and the SPR, the use of SAM improves significantly the detection and immobilization of the target compound and an optimum SAM formation protocol is provided.