Barcoded Silica Nanotubes for Bioanalysis
Lee, Sang Bok
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Analysis of the chemical/biological species involved in health care is the most important step for diseases diagnosis and new drug screening. Barcoded nano/microparticles are attracting more and more interest for detection and identification of multiplexed chemical/biological species simultaneously. However, the development of barcoded particles is still in an early stage. To solve problems existing in current barcoded particles, such as spectral overlap and degradation of materials, our group has invented barcoded silica nanotubes (SNTs) and applied them to multiplexed immunoassays and cancer marker detection as coding materials. Barcode SNTs are fabricated by a multistep anodization template synthesis method. Each barcoded SNT has several segments with different reflectance values depending on their diameters and wall thicknesses. Therefore, the barcode of each SNT can be "read-out" with a conventional optical microscope. Barcoded SNTs have shown high stability and dispersibility in aqueous buffer media. Suspension arrays with barcoded SNTs have shown high sensitivity and high selectivity for the detection of multianalytes in the multiplexed immunoassays. Magnetic field separation is one promising technique to replace tedious filtration or centrifugation separation for rapid, gentle, and reliable isolation of target analytes. Barcoded SNTs have been coupled with magnetic bead (MB) separation for protein detection and analysis. The species and number of final collected SNTs represent the types and amount of analyte proteins, respectively. By using barcoded SNTs instead of fluorescence as signals, these suspension arrays overcome the problems existing in current MB suspension arrays, such as fluorescence quenching and interference of MBs' autofluorescence. Barcoded magnetic nanotubes (BMNTs) have also been successfully fabricated as dual-functional microcarriers for multiplexed immunoassays and cancer biomarker detection with magnetic separation. BMNTs combine the shape variety of barcoded SNTs and superparamagnetic properties of magnetic nanotubes. BMNTs overcome the problems in the existing dual-functional particles. The iron oxide nanocrystals are evenly dispersed in the inner void of the tubular structures without interference with the optical barcoded patterns. BMNTs have shown high selectivity when applied in multiplexed assays and cancer biomarker detection. The identification of BMNTs with software shows promising results for rapid data analysis. The dual-functional BMNTs provide a promising way for ultrafast, gentle, efficient, and automated detection of target chemical/biochemical molecules for diagnosis and drug screening.