Affinity analysis of somatostatin and somatostatin receptor by surface plasmon resonance

For drug development and quality monitoring targeted at somatostatin (SST), a sensitive and reliable method is needed to detect the binding of somatostatins (SSTs) to their receptors-somatostatin receptors (SSTRs). In this study, interactions between SSTs (SST14, SST28) and SSTRs (SSTR2, SSTR4) have been measured by using surface plasmon resonance (SPR). SSTRs were covalently immobilized on the surfaces of the CM5 sensor chip via amine coupling and SSTs were injected into the flow channels. The results revealed that SST14 bound to SSTR4 with a much higher affinity than to SSTR2. Meanwhile, SST28 bound to SSTR4 with a slightly higher affinity when compared to SSTR2. SST14 and SST28 interacted with SSTR2 with a similar affinity, but SST14 had a relatively higher affinity of interaction with SSTR4 when compared to SST28. Furthermore, our study demonstrated that SSTR2-CM5 is capable of quantitating SST14 and SST28 with a detection range of 5 μg mL^-1 to 50 μg mL^-1 and 5 μg mL^-1 to 40 μg mL^-1, respectively. Therefore, the SPR technique not only offers a potentially sensitive and reproducible method for SSTR-selective drug discovery, but also might provide a rapid and quantitative bioassay for monitoring manufactural batch consistency.