Encoding microcarriers by spatial selective photobleaching

Abstract

Bead-based assays on very large numbers of molecules in gene expression studies, drug screening and clinical diagnostics, require the encoding of each of the microspheres according to the particular ligand bound to its surface. This allows mixing the uniquely encoded microspheres and subjecting them to an assay simultaneously. When a particular microsphere gives a positive reaction, the substance on its surface can be identified by reading the code. Previously reported techniques for colour encoding polymer microspheres only allow for a limited number of unique codes. Graphical encoding methods use metallic particles, which are rather uncommon in screening applications. Here, we demonstrate a new approach to encode polymer microspheres that are commonly used in screening applications, such as polystyrene microspheres, with a method that provides a virtually unlimited number of unique codes. Patterns can be written in fluorescently dyed microspheres by 'spatial selective photobleaching' and can be identified by confocal microscopy. Such encoded microparticles can find broad application in the collection and analysis of genetic information, high-throughput screening, medical diagnostics and combinatorial chemistry, and can also be used for labelling of consumer goods or as security labels to prevent counterfeiting.

Unbreakable Codes in Electrospun Fibers: Digitally Encoded Polymers to Stop Medicine Counterfeiting

“…As shown in Figure 1C, the aligned fluorescent fibers were cut into small pieces by cold ablation using a PALM MicroBeam System Version 4.0 AxioVert laser equipped with a 355 nm pulsed UV-Laser [30] The fluorescent fiber pieces were encoded by spatial selective photobleaching by exposing well selected regions to a 488 nm laser beam ( Figure 1D). An in-house-developed encoding device was used, being a laser scanning confocal microscope (Nikon) equipped with an argon laser and an acousto-optic modulator [15,16,31,32] . Upon bleaching, the fluorescent molecules lose their fluorescence, giving rise to the code.…”

“…Recently we introduced digitally encoded polystyrene microparticles (named 'memobeads') for the in-product labeling of tablets [14][15][16][17] ; information is written in the middle plane of fluorescently dyed microspheres by 'spatial selective photobleaching' of the fluorescence by the use of a confocal laser scanning microscope.…”

Multiplexed Immunoassays

“…An ideal microparticle encoding technique must satisfy a number of requirements, it must be: 1) machine-readable (decoding); 2) unaffected by the biochemical reactions; 3) robust, with low error rate; 4) able to encode large numbers of particles, each with a unique code; 5) are compatible with biomolecule attachment; and 6) able to mass production with low-cost. To this end, since the 1990s, different technologies for multiplexing have emerged (optical [19][20][21][22][23][24][25][26][27][28] , graphical [29][30][31][32][33] , electronic 34,35 , or physical 36, 37 encoding) for different platforms (flow cytometry or fluorescence microscopy). The features of each encoding strategy are listed in Table 1.…”

Peer Reviewed: Barcoding the Microworld

“…They have also been adapted for coding purposes-optically encoded aluminum stripes were patterned on a silicon wafer with the aid of an etching technique (Figure 2c; SmartBead at www.smartbead.com). The photobleaching or photochroming of coding patterns onto fluorescently activated particles has also been reported as a low-cost and easy-to-implement method that may be able to generate large numbers of codes (29). However, because each pattern is directly "written" on the particle in a sequential fashion, the code-generation rate is rather limited.…”