Radiation-Induced Effect on Spin-Selective Electron Transfer through Self-Assembled Monolayers of ds-DNA

Chiral Induced Spin Selectivity

Since the initial landmark study on the chiral induced spin selectivity (CISS) effect in 1999, considerable experimental and theoretical efforts have been made to understand the physical underpinnings and mechanistic features of this interesting phenomenon. As first formulated, the CISS effect refers to the innate ability of chiral materials to act as spin filters for electron transport; however, more recent experiments demonstrate that displacement currents arising from charge polarization of chiral molecules lead to spin polarization without the need for net charge flow. With its identification of a fundamental connection between chiral symmetry and electron spin in molecules and materials, CISS promises profound and ubiquitous implications for existing technologies and new approaches to answering age old questions, such as the homochiral nature of life. This review begins with a discussion of the different methods for measuring CISS and then provides a comprehensive overview of molecules and materials known to exhibit CISS-based phenomena before proceeding to identify structure-property relations and to delineate the leading theoretical models for the CISS effect. Next, it identifies some implications of CISS in physics, chemistry, and biology. The discussion ends with a critical assessment of the CISS field and some comments on its future outlook.

Light-Amplified CISS-Based Hybrid QD-DNA Impedimetric Device for DNA Hybridization Detection

We design and build a novel light-amplified electrochemical impedimetric device based on the CISS effect to detect DNA hybridization using a hybrid quantum dot (QD)-DNA monolayer on a ferromagnetic (FM) Ni/Au thin film for the first time. Using spin as a detection tool, the current research considers the chiral-induced spin selectivity (CISS) phenomenon. After injecting a spin current into the QD-DNA system with opposite polarities (up and down), the impedimetric device revealed a large differential change in the charge-transfer resistance (ΔR_ct) of ∼100 ohms for both spins. Nearly, a threefold increase in the ΔR_ct value to ∼270 ohms is observed when light with a wavelength of 532 nm is illuminated on the sample, owing to the amplified CISS effect. The yield of spin polarization as extracted from the Nyquist plot increases by a factor of more than 2 when exposed to light, going from 6% in the dark to 13% in the light. The impact of light on the CISS effect was further corroborated by the observation of the spin-dependent asymmetric quenching of photoluminescence (PL) in the same hybrid system. These observations are absent in the case of a noncomplementary QD-DNA system due to the absence of a helical structure in DNA. Based on this, we develop a spin-based DNA hybridization sensor and achieve a limit of detection of 10 fM. These findings open a practical path for the development of spin-based next-generation impedimetric DNA sensors and point-of-care devices.

CISS-Based Label-Free Novel Electrochemical Impedimetric Detection of UVC-Induced DNA Damage

In this work, we demonstrate chiral-induced spin selectivity (CISS)-based label-free electrochemical impedimetric detection of radiation-induced DNA damage using the electrons' spin as a novel tool of sensing. For this, self-assembled monolayers (SAMs) of short ds-DNA (of length 7.14 nm) are prepared on arrays of multilayer thin film devices comprising a gold overlay (500 μm diameter with 10 nm thickness) on a nickel thin film (100 nm) fabricated by the physical vapor deposition technique. Subsequently, the SAMs of ds-DNA are exposed to ultraviolet C (UVC) radiation for a prolonged period of 8 h to induce structural perturbations in DNA. The susceptibility of DNA to radiation-induced damage was probed by recording the spin-dependent electrochemical impedimetric spectra, wherein a continuous sinusoidal wave of the amplitude of 10 mV was superimposed on DC bias in the frequency range of 10⁰-10⁵ Hz, with simultaneous spin injection through the attached DNA. The inherent correlation between the charge-transfer resistance (R _ct) and the spin selectivity of electrons through DNA was taken into account for the detection of DNA damage for the first time with a limit of detection achieved up to 10 picomolar concentrations of DNA. As the spin-polarized electrons directly probe the structural symmetry, it is robust against perturbation from electronic signals usually found in conventional electrochemical biosensors.