title: Label-free DNA microarray bioassays using a near-field scanning microwave microscope.
abstract: A near-field scanning microwave microscope (NSMM) is used to readout and visualize homemade 10-mer oligonucleotide microarrays and an Agilent 60-mer DNA microarray as a realistic test of NSMM applicability to multiplexed sequence analysis. Sensitive characterization of DNA coverage and high resolution mapping of DNA spots in the microarray were realized by measuring the change of microwave reflection coefficient (S₁₁) at about 4 GHz operating frequency. Hybridization between target (free) and capture (immobilized) sequences leads to changes in the microwave reflection coefficient, which were measured by the NSMM. These changes are caused by hybridization-induced modification of the dielectric permittivity profile of the DNA film. The dynamic range based on analysis of the 10-mer microarrays is over 3 orders of magnitude with the detection limit estimated below 0.01 strands/μm². The NSMM method should be readily capable of detecting target coverages down to 98% of probe coverage. We also directly image the patterned DNA microarray by NSMM with a 2 μm resolution. The complementary optical image of the DNA microarray visualized by using a relative fluorescent intensity metric agrees well with the NSMM results.
authors.affiliation: Department of Physics and Basic Science Institute for Cell Damage Control, Sogang University, Seoul 121-742, Republic of Korea. klee@sogang.ac.kr
authors.forename: Kiejin
authors.initials: K
authors.lastname: Lee
authors.forename: Arsen
authors.initials: A
authors.lastname: Babajanyan
authors.forename: Harutyun
authors.initials: H
authors.lastname: Melikyan
authors.forename: Chongchel
authors.initials: C
authors.lastname: Kim
authors.forename: Seungwan
authors.initials: S
authors.lastname: Kim
authors.forename: Jungho
authors.initials: J
authors.lastname: Kim
authors.forename: Jung-Ha
authors.initials: JH
authors.lastname: Lee
authors.forename: Barry
authors.initials: B
authors.lastname: Friedman
authors.forename: Rastislav
authors.initials: R
authors.lastname: Levicky
authors.forename: Sergey
authors.initials: S
authors.lastname: Kalachikov
mesh_terms: D001681:Biological Assay; D004247:DNA / Q000737:chemistry*; D006801:Humans; D057230:Limit of Detection; D018625:Microscopy, Atomic Force; D008872:Microwaves; D036103:Nanotechnology; D009693:Nucleic Acid Hybridization; D020411:Oligonucleotide Array Sequence Analysis / Q000379:methods*; D017422:Sequence Analysis, DNA / Q000379:methods*
chemical_list: D004247:DNA