Quartz crystal microbalance (QCM) biosensors for recombinant human interferon-beta (rhIFN-beta) were constructed by utilizing antisense peptides adhering to the QCM gold surfaces. Two antisense peptides, both corresponding to the N-terminal fragment 1-14 of rhIFN-beta, were used in this study. Antisense peptide AS-1 was the original antisense peptide and AS-2 was the modified antisense peptide based on the antisense peptide degeneracy. Both antisense peptides were immobilized on the gold electrodes of piezoelectric crystals, respectively, via a self-assembling monolayer of 1,2-ethanedithiol. The binding affinity between rhIFN-beta and each immobilized antisense peptide in solution was evaluated using a quartz crystal microbalance-flow injection analysis (QCM-FIA) system. The dissociation constant of rhIFN-beta on the antisense peptide AS-1 and AS-2 biosensor was (1.89+/-0.101) x 10(-4) and (1.22+/-0.0479) x 10(-5) mol L(-1), respectively. The results suggested that AS-2 had a higher binding affinity to rhIFN-beta than AS-1. The detection for rhIFN-beta using each biosensor was precise and reproducible. The linear response ranges of rhIFN-beta binding to both biosensors were same with a concentration range of 0.12-0.96 mg mL(-1). The results demonstrated the successful construction of highly selective QCM biosensors using antisense peptide approach, and also confirmed the feasibility of increasing antisense peptide binding affinity by appropriate sequence modification.