title: Label-free detection of DNA using a light-addressable potentiometric sensor modified with a positively charged polyelectrolyte layer.
abstract: A multi-spot (16 spots) light-addressable potentiometric sensor (MLAPS) consisting of an Al-p-Si-SiO2 structure modified with a weak polyelectrolyte layer of PAH (poly(allylamine hydrochloride)) was applied for the label-free electrical detection of DNA (deoxyribonucleic acid) immobilization and hybridization by the intrinsic molecular charge for the first time. To achieve a preferentially flat orientation of DNA strands and thus, to reduce the distance between the DNA charge and MLAPS surface, the negatively charged probe single-stranded DNAs (ssDNA) were electrostatically adsorbed onto the positively charged PAH layer using a simple layer-by-layer (LbL) technique. In this way, more DNA charge can be positioned within the Debye length, yielding a higher sensor signal. The surface potential changes in each spot induced due to the surface modification steps (PAH adsorption, probe ssDNA immobilization, hybridization with complementary target DNA (cDNA), non-specific adsorption of mismatched ssDNA) were determined from the shifts of photocurrent-voltage curves along the voltage axis. A high sensor signal of 83 mV was registered after immobilization of probe ssDNA onto the PAH layer. The hybridization signal increases from 5 mV to 32 mV with increasing the concentration of cDNA from 0.1 nM to 5 μM. In contrast, a small signal of 5 mV was recorded in the case of non-specific adsorption of fully mismatched ssDNA (5 μM). The obtained results demonstrate the potential of the MLAPS in combination with the simple and rapid LbL immobilization technique as a promising platform for the future development of multi-spot light-addressable label-free DNA chips with direct electrical readout.
authors.affiliation: Institute of Nano- and Biotechnologies, FH Aachen, Campus Jülich, 52428 Jülich, Germany. a.poghossian@fz-juelich.de.
authors.forename: Chunsheng
authors.initials: C
authors.lastname: Wu
authors.forename: Thomas
authors.initials: T
authors.lastname: Bronder
authors.forename: Arshak
authors.initials: A
authors.lastname: Poghossian
authors.forename: Carl Frederik
authors.initials: CF
authors.lastname: Werner
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Schöning
mesh_terms: D018076:DNA, Complementary / Q000032:analysis*; D011073:Polyamines / Q000737:chemistry*; D011199:Potentiometry / Q000379:methods
chemical_list: D018076:DNA, Complementary; D011073:Polyamines; C063994:polyallylamine