Improved DNA chip with poly(amidoamine) dendrimer peripherally modified with biotin and avidin

Important properties for a biosensor are the sensitive detection of target DNA at low concentration, the specific and accurate distinction of the target and other DNA having a similar sequence, and measurement capability over a wide range of target concentrations. To these ends, generation 3 polyamidoamine (PAMAM) dendrimer was used to improve DNA chip properties. PAMAM dendrimer surface amine moieties were modified to biotin and immobilized on glass slides using biotin-avidin conjugation. The surface morphologies of the avidin-biotin-dendrimer complexes were observed using atomic force microscopy and scanning electron microscopy. Detection sensitivity for fluorescence-labeled target DNA increased approximately 4-fold by the dendrimer coating. Dendrimer coating also markedly improved the dynamic range and detection of single nucleotide polymorphisms. Dendrimer complex morphology had little effect on the sensitivity.