Magnetic micro-barcodes for molecular tagging applications

Abstract

We describe proof-of-principle experiments and theory that demonstrate a new method of performing multiplexed biological assays by using microscopic tags which carry multi-bit magnetic codes to label probe biomolecules. It is demonstrated that these "micro-barcode tags" can be encoded, transported using micro-fluidics and are compatible with surface chemistry. We also present simulations and experimental results which suggest the feasibility of decoding the micro-barcode tags using magnetoresistive sensors. Together, these results demonstrate substantial progress towards meeting the critical requirements of a magnetically encoded, high-throughput and portable biological assay platform. We also show that an extension of our technology could be potentially used to label libraries consisting of~10 4 distinct probe molecules, and could therefore have a strong impact on mainstream medical diagnostics.

Detection of Magnetically Labelled Microcarriers for Suspension Based Bioassay Technologies

“…The wedge shaped signal observed for the in Fig. 8(a) is a representative example and is in agreement with the simulations presented in [9]. It is consistent with the shape of the signal we would expect to see should the tags flow over the sensor at a height of 5 m. It is important to note that PDMS cannot sustain large aspect ratios, therefore our channels, which span 100 m at their widest, had to be made 40 m deep in order to avoid collapse.…”

“…8(b) is unique and shows a much larger distinction between the signals for the different elements than predicted by Hayward et al [9]. It cannot solely be explained by a lower fly height and we suspect it is due to a more complex domain configuration in our magnetic elements.…”

“…The latter however is a far greater challenge. The distance between our thin film elements and the sensor, on the order of a few microns, causes the detectable stray field to not only be very weak but also for there to be a high spatial overlap between the signals from successive elements [9]. This means we need a highly sensitive sensor with as small an active area as possible.…”

Predefinable quantum-dot barcodes

“…The barcodes can be formed using hollow [27,28] or color [29] patterns, microstructures [30][31][32][33] and fluorescent emissions [34][35][36], as well as use of rare elements [37], magnetic elements [38], Raman spectra [39,40], holograms [41,42], DNA-based monomers [43] and optical crystals [44,45]. These barcodes can be categorized into two main types: (1) graphical barcodes that are identified by deciphering the specific geometric patterns, and (2) optical barcodes that are identified by specific spectra or non-imaging optical signals.…”

“…(g) Fluorescentpattern barcodes made by rare earth elements [37]. (h) Bar-pattern barcodes made by magnetic elements [38] List of Tables Table 3.1 Molecular weights, viscosities and shrinkages of monomers [91][92][93]. ........ 40…”