Multifunctional Layer-by-Layer Coating of Digitally Encoded Microparticles

Abstract

In the field of medical diagnostics there is a growing need for inexpensive, accurate, and quick "multiplexing" assays. By making use of encoded microparticles, such assays allow simultaneous determination of the presence of several analytes in a biological sample. The microparticles under investigation in this study are encoded by writing a digital dot or bar code in their central plane. This study evaluates to what extent a "multifunctional" coating can be applied around the digitally encoded microparticles by the layer-by-layer (LbL) technology. We show that a LbL coating containing CrO2 nanoparticles allows (a) an optimal (optical) readout of the dot and bar codes, (b) a perfect orientation of the microparticles, necessary to be able to read the code, and (c) an optimal coupling of capture probes to the surface of the microparticles.

Evaluation of Encoded Layer‐By‐Layer Coated Microparticles As Protease Sensors

“…LbL Coating of the Microparticles: The LbL coating of the green fluorescent (carboxyl-functionalized) polystyrene microparticles (Spherotech, Libertyville, IL, USA, diameter ¼ 39 mm) occurred as follows according to the literature [10]: PAH (70 kDa, Sigma-Aldrich) and PSS (70 kDa, Sigma-Aldrich) stock solutions were prepared in 0.5 M NaCl (2 mg mL À1 ). As illustrated in Figure 1 (step I), the microspheres were LbL-coated by suspending approximately 400 000 microspheres in 1 mL of PAH solution; the suspension was continuously vortexed (1000 rpm, 25 8C) for 15 min.…”

“…The probe can be an antibody (for screening antigens) or a single-stranded oligonucleotide (for single nucleotide polymorphism detection). [10,11] A major advantage of encoded beads is that they allow 'multiplexed' analysis of biological samples being the simultaneous analysis of numerous analytes (antigens, DNA fragments, . .…”

“…[13][14][15][16] We reported previously that the polystyrene core of a memobead can be successfully LbL-coated with polyanions, polycations, and magnetic CrO 2 nanoparticles. As explained in detail by Derveaux et al, [10] the magnetic CrO 2 nanoparticles allow an optimal positioning of the memobeads in a magnetic field (step II in Fig. 1), which is necessary to read the code at the time of decoding.…”

“…For non-embedded P1 beads, the red surface fluorescence increases linearly for P1 concentrations between Step I: Carboxyl-functionalized green fluorescent polystyrene microparticles (approximately 40 mm in size) are coated by alternating adsorption of positively charged poly-allylaminehydrochloride (PAH, red strands) and negatively charged polystyrenesulfonate (PSS, blue strands). Magnetic chromium dioxide nanoparticles (<500 nm, CrO 2 NP , black dots) are incorporated in the LbL film to allow accurate positioning of the beads in a magnetic field at the time of encoding (Step II) and decoding (Step VI) [10].…”

Evaluation of Digitally Encoded Layer‐by‐layer Coated Microparticles as Cell Carriers

“…[29][30][31][32] This paper studies whether photophysically encoded microparticles, recently introduced by our group for various applications [33][34][35] and named 'memobeads', are suitable to grow cells on. As shown in Figures 2B,C, photophysically encoded microparticles carry a digital code (like a dotcode or a barcode) in their middle plane.…”