title: Label-free capacitive DNA sensor using immobilized pyrrolidinyl PNA probe: effect of the length and terminating head group of the blocking thiols.
abstract: This paper reports, for the first time, the influence of the length and the terminating head group of blocking thiols on the sensitivity and specificity of a label-free capacitive DNA detection system using immobilized pyrrolidinyl peptide nucleic acid (acpcPNA) probes. A C-terminal lysine-modified acpcPNA was immobilized through four different alkanethiol self-assembled monolayers (SAMs), i.e., 3-mercaptopropionic acid (MPA), thioctic acid (TA), thiourea (TU) and mercaptosuccinic acid (MSA). The hybridization between the acpcPNA probes and the target DNA was directly measured using the capacitive system. Five blocking thiols of various lengths (C=3, 6, 8, 9 and 11), with the -OH terminating head group, i.e., 3-mercapto-1-propanol (3-MPL), 6-mercapto-1-hexanol (6-MHL), 8-mercapto-1-octanol (8-MOL), 9-mercapto-1-nonanol (9-MNL), 11-mercapto-1-undecanol (11-MUL) and another blocking thiol (C=11) with a -CH(3) terminating head group, and 1-dodecanethiol (1-DDT) were investigated. The blocking thiol with the same length as the total spacer of the immobilized acpcPNA gave the highest sensitivity and specificity with the -OH terminating head group providing a slightly better signal than the -CH(3) group. Under the optimized conditions, the immobilized acpcPNA probes provided a wide linear range for DNA detection (1.0 × 10(-11)-1.0 × 10(-8)M) with a very low detection limit in the picomolar range. The modified acpcPNA electrode could be reused through at least 58 cycles. The high sensitivity and very low detection limits are potentially useful for the analysis of ultra-trace levels of DNA in samples. Preliminary studies were also performed to see the effect of probe concentration and target length.
authors: Trace Analysis and Biosensor Research Center, Prince of Songkla University, Hat Yai, Songkhla 90112, Thailand.
authors: Orawan
authors: O
authors: Thipmanee
authors: Saluma
authors: S
authors: Samanman
authors: Supannee
authors: S
authors: Sankoh
authors: Apon
authors: A
authors: Numnuam
authors: Warakorn
authors: W
authors: Limbut
authors: Proespichaya
authors: P
authors: Kanatharana
authors: Tirayut
authors: T
authors: Vilaivan
authors: Panote
authors: P
authors: Thavarungkul
mesh_terms: D001483:Base Sequence; D015374:Biosensing Techniques / Q000295:instrumentation*; D004247:DNA / Q000032:analysis*; D025802:Electric Capacitance; D057230:Limit of Detection; D009693:Nucleic Acid Hybridization; D020135:Peptide Nucleic Acids / Q000737:chemistry*; D011759:Pyrrolidines / Q000737:chemistry*; D013438:Sulfhydryl Compounds / Q000737:chemistry; D014159:Transducers
chemical_list: D020135:Peptide Nucleic Acids; D011759:Pyrrolidines; D013438:Sulfhydryl Compounds; D004247:DNA; C032519:pyrrolidine