Yuanpeng Li

University of Minnesota Duluth, Duluth, Minnesota, United States

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Publications (11)45.7 Total impact

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    ABSTRACT: In this paper, we report a magnetic nanoparticle (MNP) detection scheme without the presence of any external magnetic field. The proposed magnetic sensor uses a patterned groove structure within the sensor so that no external magnetic field is needed to magnetize the MNPs. An example is given based on a giant magnetoresistance (GMR) sensing device with a spin valve structure. For this structure, the detection of MNPs located inside the groove and near the free layer is demonstrated under no external magnetic field. Micromagnetic simulations are performed to calculate the signal to noise level of this detection scheme. A maximum signal to noise ratio (SNR) of 18.6 dB from one iron oxide magnetic nanoparticle with 8 nm radius is achieved. As proof of concept, this external-field-free GMR sensor with groove structure of 200 nm × 200 nm is fabricated using a photo and an electron beam integrated lithography process. Using this sensor, the feasibility demonstration of the detection SNR of 9.3 dB is achieved for 30 μl magnetic nanoparticles suspension (30 nm iron oxide particles, 1 mg/ml). This proposed external-field-free sensor structure is not limited to GMR devices and could be applicable to other magnetic biosensing devices.
    Applied Physics Letters 03/2014; 104(12):122401-122401-5. DOI:10.1063/1.4869029 · 3.52 Impact Factor
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    ABSTRACT: A detection scheme for real-time Brownian relaxation of magnetic nanoparticles (MNPs) is demonstrated by a mixing-frequency method in this paper. MNPs are driven into the saturation region by a low frequency sinusoidal magnetic field. A high frequency sinusoidal magnetic field is then applied to generate mixing-frequency signals that are highly specific to the magnetization of MNPs. These highly sensitive mixing-frequency signals from MNPs are picked up by a pair of balanced built-in detection coils. The phase delays of the mixing-frequency signals behind the applied field are derived, and are experimentally verified. Commercial iron oxide MNPs with the core diameter of 35 nm are used for the measurement of Brownian relaxation. The results are fitted well with Debye model. Then a real-time measurement of the binding process between protein G and its antibody is demonstrated using MNPs as labels. This study provides a volume-based magnetic sensing scheme for the detection of binding kinetics and interaction affinities between biomolecules in real time.
    Applied Physics Letters 05/2011; 98(21). DOI:10.1063/1.3595273 · 3.52 Impact Factor
  • The Journal of Urology 04/2011; 185(4). DOI:10.1016/j.juro.2011.02.672 · 3.75 Impact Factor
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    ABSTRACT: We have studied the potential energy and effective field induced by the presence of a single superparamagnetic particle above a magnetic domain wall in a 5 nm ferromagnetic film (Ms = 800 emu/cm3) with uniaxial crystalline anisotropy (Ku < 107 erg/cm3). The wall width, wall type (head-to-head, Néel, and perpendicular Bloch), film dimensions, particle height, and external applied field are found to affect the performance of particle sensing systems. Results and optimization strategies derived from this model are presented. The calculated change in depinning field (DeltaHdp) is compared against experimental data and micromagnetic simulation. This comparison provides justification for further development in terms of integration with micromagnetic simulations.
    Journal of Applied Physics 04/2011; 109(7). DOI:10.1063/1.3549558 · 2.19 Impact Factor
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    ABSTRACT: This study presents a three-layer competition-based assay for ultrasensitive detection and quantification of endoglin from unprocessed human urine samples using a giant magnetoresistive (GMR) sensor and high-moment magnetic nanoparticle-based biosensing technology. This biosensing platform detects as few as 1000 copies of endoglin at concentrations as low as 83 fM with high detection specificity and has a three-order dynamic range. The results reveal that endoglin levels in urine have the potential to predict for the presence of prostate cancer and to distinguish between prostate cancers of different grades.
    Analytical Chemistry 03/2011; 83(8):2996-3002. DOI:10.1021/ac2005229 · 5.83 Impact Factor
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    ABSTRACT: Early recognition and prevention of chronic disease, such as lung cancer, require a fast, accurate detection and longitudinal monitoring on potential biomarkers, which could identify the molecule change in the initial stage of the chronic disease. Here we report the realization of specific and accurate quantification of a low-abundance serum protein in unprocessed human sera, using our novel giant magnetoresistive (GMR) biosensing system with uniform high-magnetic-moment nanoparticles and a competition based detection scheme. Only one antibody is needed for such detection scheme. The quantification of interleukin-6 (IL-6, a low-abundance protein and a potential cancer biomarker), as low as 125 fM IL-6 proteins, directly in 4 muL of unprocessed human sera was demonstrated within 5 minutes by such system. The results nicely differentiate normal individuals and lung cancer patients. This platform has great potential to facilitate the identification and validation of disease biomarkers.
    12/2010; DOI:10.1063/1.3530018
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    ABSTRACT: A novel giant magnetoresistive sensor and uniform high-magnetic-moment FeCo nanoparticles (12.8 nm)-based detecting platform with minimized detecting distance was developed for rapid biomolecule quantification from body fluids. Such a system demonstrates specific, accurate, and quick detection and quantification of interleukin-6, a low-abundance protein and a potential cancer biomarker, directly in 4 muL of unprocessed human sera. This platform is expected to facilitate the identification and validation of disease biomarkers. It may eventually lead to a low-cost personal medical device for chronic disease early detection, diagnosis, and prognosis.
    Journal of the American Chemical Society 03/2010; 132(12):4388-92. DOI:10.1021/ja910406a · 11.44 Impact Factor
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    ABSTRACT: The apparent density, an intrinsic physical property of polymer beads, plays an important role in the application of beads in micro-total analysis systems and separation. Here we have developed a new, facile and milligram-scale method to describe the motion of beads in aqueous solution and further detect the apparent density of beads. The motion of beads in solutions is determined by the viscosity of solutions and the density difference between beads and solutions. In this study, using various glycerol aqueous solutions with certain viscosities and densities, the motion time (i.e. floating or sedimentation time) of hybrid polymer beads was experimentally measured and theoretically deduced, and consequently, the apparent density of monodisperse beads can be quickly and easily calculated. The results indicated that the present method provided a more precise way to predict the movement of hybrid beads in aqueous solution compared with the approach for commercial use. This new method can be potentially employed in flow cytometry, suspension stability, and particle analysis systems.
    Talanta 03/2010; 80(5):1681-5. DOI:10.1016/j.talanta.2009.10.004 · 3.51 Impact Factor
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    ABSTRACT: Zeptomole detector: A highly sensitive giant-magnetoresistive chip and FeCo nanoparticles can be used to linearly detect 600-4500 copies of streptavidin. Under unoptimized conditions, this system also detects human IL-6 with a sensitivity 13-times higher than that of standard ELISA techniques.
    Angewandte Chemie International Edition 03/2009; 48(15):2764-7. DOI:10.1002/anie.200806266 · 11.34 Impact Factor
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    ABSTRACT: In this paper, we present a ultra high sensitive (Zeptomole, 10(-21)) technique to enable the detection of any potential low abundance biomarkers. We demonstrated for the first time the detection of sub 13nm high-moment magnetic nanoparticle and the implementation of a novel magnetoresistive (GMR) biosensor concept with higher sensitivity and 10 times lower external field in real biomarker sensing schemes. A potential lung cancer biomarker, interleukin-6 (IL-6), was successfully detected with extremely low concentration (as few as only 200 pieces of IL-6). Together with other features of GMR sensor systems like low-cost, portability, easy-to-use, our demonstrated device may lead to future family-based personalized medicine for cancer prevention.
    Conference proceedings: ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference 01/2009; 2009:5432-5. DOI:10.1109/IEMBS.2009.5332479
  • Journal of Medical Devices 01/2008; 2(2). DOI:10.1115/1.2936202 · 0.62 Impact Factor