Mini-emulsion solvent evaporation: a simple and versatile way to magnetic nanosensors

Magnetic optical sensor particles were prepared using a mini-emulsion solvent evaporation (MESE) technique. The resulting nanoparticles (NPs) have diameters around 100?nm and relatively narrow size distribution (PDI < 0.2). Incorporation of probes for oxygen or pH resulted in magnetic sensor particles for bioprocess monitoring and imaging applications. The MESE technique yields sensing NPs in higher quantities than obtained by a previously reported nanoprecipitation method, and the size of the NPs is smaller than that of particles made by spray-drying of sensor cocktails. Moreover, the technique is flexible in terms of polymers, solvents and indicators used in that it may be applied??at least in principle??to numerous combinations of two-phase systems.