Magnetic Beads Compatibility as DNA Hybridization Labels in Integrated Thermal-Magnetic Biosensor

Abstract

In this paper, we investigated the applicative using of thermal-magnetic biosensor (TMAGS) for DNA detection. TMAGS is a planar device composed by a primary microcoil able to generate a magnetic field which induces a voltage equal and opposite on two secondary coils. The presence of magnetic material on one of the two secondary coils causes a variation of induced magnetic field especially in the area where the magnetic material is located. In particular, here, we studied the compatibility of two different typologies of beads (MNB1 and MNB2) as magnetic labels towards DNA hybridization process in TMAGS device. These two types of beads differ in size (1 and 0.1 μm), magnetic material location (core or shell), and chemical surface proprieties (electrostatic or covalent bonds possible). In particular, in the first part of the work, we investigate the response of the TMAGS architectures versus the two-bead topology and we found MNB1 exhibits a better output voltage signal (on average 30% higher than the voltage signal of MNB2). On the contrary, when they are employed as magnetic label in a real DNA hybridization process in TMAGS device, only MNB2 typology gives positive results. We ascertain that both the size of the bead and the nature of the chemical bond between the magnetic label (beads) and the DNA target, that must be a covalent bond, play a key role on the success of hybridization reaction. Therefore, a compromise between magnetic content (bead size) and nature of bead-target chemical bond must be selected for the future employment of these devices in molecular detection.