Monitoring of chemical and biological species dispersed in biologic fluids is one of the most promising research topics in the field of photonics due to the large number of practical applications that can result from it, ranging from the environment monitoring to biomedicine. Slotted structures typically enhance the light-matter interaction and their use in the context of biosensing is receiving a growing interest. The talk, after a short overview of the photonic biosensing, critically reviews some selected last achievements in the research field of slotted structures for biosensing. The physics describing the behaviour of light within them is in many ways analogous to the behaviour of electrons in semiconductors. In both cases, it is the periodicity of the structure that is most important: a periodic structure can only support certain wavelengths. In the case of semiconductors it is a periodic arrangement of atoms, and hence electric potential, that results in the formation of allowed electronic bands. Similarly, for photonic crystals the periodic arrangement of dielectric material results in the formation of allowed photonic bands. In its simplest form, the one-dimensional case, the photonic crystal is recognizable as a Bragg mirror.