A 'grafting- from' approach to synthesize microparticle-supported conjugated polyelectrolyte brushes is presented. Poly(3-bromohexylthiophene) is selectively grown from monodisperse organosilica microparticles by surface-initiated Kumada catalyst-transfer polycondensation (SI-KCTP) and then ionizable amino groups are introduced by a two-step polymer analogous transformation. Optical properties of the resulting microparticle-supported conjugated polyelectrolyte brushes were found to be dependent on the surrounding chemical environment and thus the particles are promising materials for sensor applications.