LabelFree Detection of Zeptomol miRNA via Peptide Nucleic Acid Hybridization Using Novel Cyclic Voltammetry Method To harness the applicability of microribonucleic acid (miRNA) as a cancer biomarker, the detection sensitivity of serum miRNA needs to be improved. This study evaluated the detection sensitivity of miRNA hybridization using cyclic voltammograms (CVs) and microelectrode array chips modified with peptide nucleic acid (PNA) probes and 6hydroxy1hexanethiol. We investigated the PNA probe modification pattern on array chips using fluorescently labeled cDNA. The pattern was not uniformly spread over the working electrode (WE) and had a onedimensional swirllike pattern. Accordingly, we established a new ionchannel sensor model wherein the WE is negatively biased through the conductive xcfx80xe2x80x93xcfx80 stacks of the PNADNA duplexes. This paper discusses the mechanism underlying the voltage shift in the CV curves based on the electric doublelayer capacitance. Additionally, the novel hybridization evaluation parameter xcex94E is introduced. Compared to conventional evaluation using oxidation current changes, xcex94E was more sensitive. Using xcex94E and a new hybridization system for ultrasmall amounts of aqueous solutions (as low as 35 pL), 140 zeptomol labelfree miRNA were detected without polymerase chain reaction (PCR) amplification at an adequate sensitivity. Herein, the differences in the target molar amount and molar concentration are elucidated from the viewpoint of hybridization sensitivity.

An Electrochemical Immunosensor Based on a SelfAssembled Monolayer Modified Electrode for LabelFree Detection of xcexb1Synuclein This research demonstrated the development of a simple, costeffective, and labelfree immunosensor for the detection of xcexb1synuclein (xcexb1Syn) based on a cystamine (CYS) selfassembled monolayer (SAM) decorated fluorinedoped tin oxide (FTO) electrode. CYSSAM was formed onto the FTO electrode by the adsorption of CYS molecules through the head sulfur groups. The free amine (xe2x80x93NH2) groups at the tail of the CYSSAM enabled the immobilization of antixcexb1Synantibody, which concurrently allowed the formation of immunocomplex by covalent bonding with xcexb1Synantigen. The variation of the concentrations of the attached xcexb1Syn at the immunosensor probe induced the alternation of the current and the charge transfer resistance (Rct) for the redox response of Fe(CN)63xe2x88x924xe2x88x92, which displayed a linear dynamic range from 10 to 1000 ngmL with a low detection limit (SN  3) of ca. 3.62 and 1.13 ngmL in differential pulse voltammetry (DPV) and electrochemical impedance spectra (EIS) measurements, respectively. The immunosensor displayed good reproducibility, antiinterference ability, and good recoveries of xcexb1Syn detection in diluted human serum samples. The proposed immunosensor is a promising platform to detect xcexb1Syn for the early diagnose of Parkinsonxe2x80x99s disease, which can be extended for the determination of other biologically important biomarkers.