Robert White

All Publications

• Microfabricated magnetic sifter for high-throughput and high-gradient magnetic separation 7th International Conference on Scientific and Clinical Applications of Magnetic Carriers Earhart, C. M., Wilson, R. J., White, R. L., Pourmand, N., Wang, S. X. ELSEVIER SCIENCE BV. 2009: 1436–39

  Abstract

  A microfabricated magnetic sifter has been designed and fabricated for applications in biological sample preparation. The device enables high-throughput, high-gradient magnetic separation of magnetic nanoparticles by utilizing columnar fluid flow through a dense array (~5000/mm(2)) of micropatterned slots in a magnetically soft membrane. The potential of the sifter for separation of magnetic nanoparticles conjugated with capture antibodies is demonstrated through quantitative separation experiments with CD138-labelled MACS nanoparticles. Capture efficiencies ranging from 28-37% and elution efficiencies greater than 73% were measured for a single pass through the sifter.

  View details for DOI 10.1016/j.jmmm.2009.02.062

  View details for Web of Science ID 000265278000025

  View details for PubMedCentralID PMC2707938

• Multiplex protein assays based on real-time magnetic nanotag sensing PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Osterfeld, S. J., Yu, H., Gaster, R. S., Caramuta, S., Xu, L., Han, S., Hall, D. A., Wilson, R. J., Sun, S., White, R. L., Davis, R. W., Pourmand, N., Wang, S. X. 2008; 105 (52): 20637-20640

  Abstract

  Magnetic nanotags (MNTs) are a promising alternative to fluorescent labels in biomolecular detection assays, because minute quantities of MNTs can be detected with inexpensive giant magnetoresistive (GMR) sensors, such as spin valve (SV) sensors. However, translating this promise into easy to use and multilplexed protein assays, which are highly sought after in molecular diagnostics such as cancer diagnosis and treatment monitoring, has been challenging. Here, we demonstrate multiplex protein detection of potential cancer markers at subpicomolar concentration levels and with a dynamic range of more than four decades. With the addition of nanotag amplification, the analytic sensitivity extends into the low fM concentration range. The multianalyte ability, sensitivity, scalability, and ease of use of the MNT-based protein assay technology make it a strong contender for versatile and portable molecular diagnostics in both research and clinical settings.

  View details for DOI 10.1073/pnas.0810822105

  View details for Web of Science ID 000262092800015

  View details for PubMedID 19074273

  View details for PubMedCentralID PMC2602607

• Giant Magnetoresistive Sensors for DNA Microarray IEEE International Magnetics Conference (INTERMAG) Xu, L., Yu, H., Han, S., Osterfeld, S., White, R. L., Pourmand, N., Wang, S. X. IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC. 2008: 3989–91

  Abstract

  Giant magnetoresistive (GMR) sensors are developed for a DNA microarray. Compared with the conventional fluorescent sensors, GMR sensors are cheaper, more sensitive, can generate fully electronic signals, and can be easily integrated with electronics and microfluidics. The GMR sensor used in this work has a bottom spin valve structure with an MR ratio of 12%. The single-strand target DNA detected has a length of 20 bases. Assays with DNA concentrations down to 10 pM were performed, with a dynamic range of 3 logs. A double modulation technique was used in signal detection to reduce the 1/f noise in the sensor while circumventing electromagnetic interference. The logarithmic relationship between the magnetic signal and the target DNA concentration can be described by the Temkin isotherm. Furthermore, GMR sensors integrated with microfluidics has great potential of improving the sensitivity to 1 pM or below, and the total assay time can be reduced to less than 1 hour.

  View details for DOI 10.1109/TMAG.2008.2002795

  View details for Web of Science ID 000262221300159

  View details for PubMedCentralID PMC2933090

• Giant magnetoresistive biochip for DNA detection and HPV genotyping BIOSENSORS & BIOELECTRONICS Xu, L., Yu, H., Akhras, M. S., Han, S., Osterfeld, S., White, R. L., Pourmand, N., Wang, S. X. 2008; 24 (1): 99-103

  Abstract

  A giant magnetoresistive (GMR) biochip based on spin valve sensor array and magnetic nanoparticle labels was developed for inexpensive, sensitive and reliable DNA detection. The DNA targets detected in this experiment were PCR products amplified from Human Papillomavirus (HPV) plasmids. The concentrations of the target DNA after PCR were around 10 nM in most cases, but concentrations of 10 pM were also detectable, which is demonstrated by experiments with synthetic DNA samples. A mild but highly specific surface chemistry was used for probe oligonucleotide immobilization. Double modulation technique was used for signal detection in order to reduce the 1/f noise in the sensor. Twelve assays were performed with an accuracy of approximately 90%. Magnetic signals were consistent with particle coverage data measured with Scanning Electron Microscopy (SEM). More recent research on microfluidics showed the potential of reducing the assay time below one hour. This is the first demonstration of magnetic DNA detection using plasmid-derived samples. This study provides a direct proof that GMR sensors can be used for biomedical applications.

  View details for DOI 10.1016/j.bios.2008.03.030

  View details for Web of Science ID 000259425300015

  View details for PubMedID 18457945

  View details for PubMedCentralID PMC2573902

• DOMAIN-WALL MOBILITIES IN YFEO3 JOURNAL OF APPLIED PHYSICS Tsang, C. H., White, R. L., White, R. M. 1978; 49 (3): 1838-1840

  View details for Web of Science ID A1978EU95400190