Background: Patients with systemic lupus erythematosus (SLE) develop a wide variety of serologic manifestations, including double-stranded DNA autoantibodies (anti-dsDNA). The determination of the potentially pathogenic autoantibodies is diagnostically relevant.
Methods: We developed a novel surface plasmon resonance (SPR) biosensor chip for studies of dsDNA and anti-dsDNA binding. A synthetic oligonucleotide was coupled to biotinylated human transferrin, hybridized with the complementary antistrand, and ligated with a human recombinant dsDNA fragment 233 bp in length. After surface immobilization of this antigenic construct, diluted sera from SLE patients and healthy donors were analyzed with the resulting SPR biosensor system.
Results: This SPR biosensor allowed specific detection of anti-dsDNA. In pilot experiments, sera from SLE patients were distinguished from control sera. We also confirmed the specificity of this biosensor by supplementing anti-dsDNA-positive sera with salmon sperm DNA, which blocked the surface binding of anti-dsDNA in a concentration-dependent manner.
Conclusions: An SPR biosensor monitors interactions in real time under homogeneous conditions, providing information about binding kinetics and affinities. Its applicability critically depends on the design of the solid-state surface of the sensor chips. Covalently immobilizing dsDNA as the antigen to the surface in a flow-through cell assured maximal stability for multiple serum injections and regeneration cycles. This technique, which adds a new analytic quality to existing methods, may be beneficial in the diagnosis and clinical monitoring of SLE.