Functionalized Beads (LbL Beads)
Virtually all kinds of particles/beads ranging in size from 200 nm to 100 µm can be coated using the Layer-by-Layer (LbL) technology. They can be endowed with additional chemical or physical functions such as color, fluorescence, magnetic force, surface charge or photo activity, all independent of the core material. Also chemical binding functions (carboxyl, amino or aldehyde) can be added in a particularly high density. The higher function density, in contrast to the bare beads, is a result of the nano-roughness of the outer layer. By adding corresponding interim layers, the influence of differing functions such magnetic force or fluorescence can be supressed.
For the core we use monodisperse or polydisperse silica, polystyrene, polymethacrylate, melamine-formaldehyde, or biodegradable PLGA beads, which can themselves be inherently magnetic or fluorescent. We can also encapsulate crystals of insoluble substances, pigments, cells or pollen and, if required, functionalize them with the LbL technology in order to protect them from enzymatic degradation. In addition, hydrophobic particles/beads can be protected against aggregation in water by their surrounding LbL layer.
The fluorescent image illustrates LbL-coated MF beads (Ø 5 µm) with colour combinations Fluorescein, Rhodamine, Cy5 (Superimposition of 3 channels; image size 43 x 43 µm).