The label-free DNA sensing techniques are currently receiving considerable attention for the determination of pathogenic genes and the diagnosis of genetic disease, etc. Based on magnetic separation and preconcentration, a novel label-free chemiluminescence (CL) detection protocol was presented as exemplified by the successful determination of specific DNA sequence—telomere. This method was composed of three steps: (1) the dT₂₀ arm modified in the magnetic beads was hybridized with the dA₂₀-modified capture DNA; (2) the first step was followed by the second hybridization of the bead-captured probe with telomere; (3) the amount of telomere was determined by the guanine CL reaction with 3,4,5-trimethoxyphenylglyoxal (TMPG). The results showed that this simple and sensitive protocol was much suitable for the determination of specific DNA sequence such as telomere with a good linear correlation in the concentration range of 5×10^－9～1×10^－7 mol/L (R²＝0.9918).

Key words: specific sequence DNA, telomere, label-free, chemiluminescence, magnetic bead