Rhodamine B doped silica encapsulation matrices for the protection of photosynthetic organisms

•This silica encapsulation matrix protects microalgae from harmful UV light.•The material formulation is based on the electrostatic adsorption of Rhodamine B.•The proposed synthesis is inexpensive, not time consuming, and easy to scale up.•It is useful for applications that are exposed to UV radiation.•It is valuable for external sterilization procedures in industrial applications.

An advanced encapsulation matrix that efficiently protects microalgae from harmful UV light without causing toxicity to the entrapped culture is developed based on the electrostatic adsorption of the dye Rhodamine B on silica preformed particles during sol-gel synthesis. The three microalgae (Chlorella vulgaris, Pseudokirchneriella subcapitata and Chlamydomonas reinhardtii) were previously immobilized in alginate following the Two-step procedure. Once entrapped in the silica gel, Rhodamine B act as an inner cut-off filter, protecting the encapsulated organisms from UV radiation. This matrix allows the sterilization of encapsulation devices without affecting the viability of the entrapped microalgae cells. The condensation of Si(IV) in the presence of silica particles with adsorbed dye generates silica matrices with good mechanical stability. Furthermore; no appreciable differences in microstructure, as assessed by SAXS (Small Angle X-ray Scattering), are caused by the addition of the dye.