title: NMR-DMF: a modular nuclear magnetic resonance-digital microfluidics system for biological assays.
abstract: We present a modular nuclear magnetic resonance-digital microfluidics (NMR-DMF) system as a portable diagnostic platform for miniaturized biological assays. With increasing number of combinations between designed probes and a specific target, NMR has become an accurate and rapid assay tool, which is capable of detecting particular kinds of proteins, DNAs, bacteria and cells with a customized probe quantitatively. Traditional sample operation (e.g., manipulation and mixing) relied heavily on human efforts. We herein propose a modular NMR-DMF system to allow the electronic automation of multi-step reaction-screening protocols. A figure-8 shaped coil is proposed to enlarge the usable inner space of a portable magnet by 4.16 times, generating a radio frequency (RF) excitation field in the planar direction. By electronically managing the electro-wetting-on-dielectric (EWOD) effects over an electrode array, preloaded droplets with the inclusion of biological constituents and targets can be programmed to mix and be guided to the detection site (3.5 × 3.5 mm(2)) for high-sensitivity NMR screening (static B field: 0.46 T, RF field: 1.43 mT per ampere), with the result (voltage signal) displayed in real-time. To show the system's utility, automated real-time identification of 100 pM of avidin in a 14 μL droplet was achieved. The system shows promise as a robust and portable diagnostic device for a wide variety of biological analyses and screening applications.
authors.affiliation: State-Key Laboratory of Analog and Mixed-Signal VLSI and FST-ECE, University of Macau, China. pimak@umac.mo.
authors.forename: Ka-Meng
authors.initials: KM
authors.lastname: Lei
authors.forename: Pui-In
authors.initials: PI
authors.lastname: Mak
authors.forename: Man-Kay
authors.initials: MK
authors.lastname: Law
authors.forename: Rui P
authors.initials: RP
authors.lastname: Martins
mesh_terms: D001360:Avidin / Q000737:chemistry; D001419:Bacteria / Q000737:chemistry*; D007501:Iron; D009682:Magnetic Resonance Spectroscopy / Q000295:instrumentation* / Q000379:methods; D053768:Metal Nanoparticles / Q000737:chemistry; D044085:Microfluidics / Q000295:instrumentation* / Q000379:methods; D015335:Molecular Probes / Q000737:chemistry*
chemical_list: D015335:Molecular Probes; D001360:Avidin; D007501:Iron