The Utilization of Tunable Transducer Elements Formed by the Manipulation of Magnetic Beads with Different Sizes via Optically Induced Dielectrophoresis (ODEP) for High Signal-to-Noise Ratios (SNRs) and Multiplex Fluorescence-Based Biosensing Applications

Abstract

Magnetic beads improve biosensing performance by means of their small volume and controllability by magnetic force. In this study, a new technique composed of optically induced dielectrodphoresis (ODEP) manipulation and image processing was used to enhance the signal-to-noise ratio of the fluorescence for stained magnetic beads. According to natural advantages of size-dependent particle isolation by ODEP manipulation, biomarkers in clinical samples can be easily separated by different sizes of magnetic beads with corresponding captured antibodies, and rapidly distinguished by separated location of immunofluorescence. To verify the feasibility of the concept, magnetic beads with three different diameters, including 21.8, 8.7, and 4.2 μm, were easily separated and collected into specific patterns in the defined target zone treated as three dynamic transducer elements to evaluate fluorescence results. In magnetic beads with diameter of 4.2 μm, the lowest signal-to-noise ratio between stained and nonstained magnetic beads was 3.5. With the help of ODEP accumulation and detection threshold setting of 32, the signal-to-noise ratio was increased to 77.4, which makes this method more reliable. With the further optimization of specific antibodies immobilized on different-size magnetic beads in the future, this platform can be a potential candidate for a high-efficiency sensor array in clinical applications.

Virtual Filter Membranes in a Microfluidic System for Sorting and Separating Size-Based Micro Polystyrene Beads by Illumination Intensity Design in Optically Induced Dielectrophoresis (ODEP)

“…In the structure of this microfluidic chip, briefly, a primary microchannel (e.g., length = 20.0 mm, width = 1.0 mm, height = 50.0 µm) with two holes (e.g., diameter = 1.0 mm, height = 50.0 µm) was designed for loading/removing a microparticle suspension sample as well as for sample transportation/collection. The structure of the ODEP microfluidic chip is schematically illustrated in Figure 1B, encompassing a fabricated polydimethylsiloxane (PDMS) connector (e.g., Layer 1), an indium-tin-oxide (ITO) glass (e.g., Layer 2), a double-sided adhesive tape (thickness: 50 µm) with a fabricated microchannel (e.g., Layer 3), and an ITO glass coating with a photoconductive material containing a 20-nm-thick n-type hydrogenated amorphous silicon layer and a 1-µm-thick hydrogenated amorphous silicon layer (e.g., Layer 4) [28]. The fabrication of the ODEP microfluidic chip can be divided into four separate parts from Layers 1 to 4.…”

“…No overlapping diameter region was observed, indicating decreased interference in the ODEP manipulation. Based on our previous findings [28], the basic conditions were selected as 10 Vpp and 1.5 MHz for the chip bias condition and rectangular light bar with a maximum light intensity of 3.25 mW cm −2 for ODEP manipulation. As shown in Figure 3B, the ODEP manipulation velocity was 185.1 ± 14.0, 136.8 ± 19.3, and 73.6 ± 12.3 μm/s for PS microparticles of three different diameters, including 15.8, 10.8, and 5.8 μm PS microparticles, respectively.…”

“…To simplify the microfluidic structure, in this study, we propose a novel "virtual filter membrane" design with a straight microchannel and the modification of illumination patterns with different ODEP forces to separate microparticles with different dimensions. In particular, in a previous report, modification of the intensity of the illumination pattern was demonstrated to modify the ODEP force to microparticles [28]. Therefore, in this study, a light screening membrane constructed using three light intensities is proposed as a "virtual filter membrane" to investigate the screening and separation of microparticles with different diameters for the first time.…”

Combination of an Optically Induced Dielectrophoresis (ODEP) Mechanism and a Laminar Flow Pattern in a Microfluidic System for the Continuous Size-Based Sorting and Separation of Microparticles

“…Overall, one can simply use dynamic or stationary optical images that are illuminated on the photoconductive layer to manipulate microparticles in a manageable manner. Reports in the literature have demonstrated the utilization of the ODEP mechanism for various applications, including the manipulation of magnetic microparticles for biosensing [ 27 ], the sorting and separation of cells with varied degrees of cell viability [ 28 ], the isolation and purification of cells in samples [ 29 ], and the sorting and separation of PS (polystyrene) microbeads of different sizes [ 26 , 30 ].…”