hydrolysis of the precursor(s) resulting in the formation of silanol groups (Si-OH). At basic pH, the condensation reaction between silanol moieties results in the formation of siloxane (Si–O–Si) poly- mers creating a matrix for the entrapment of biomolecules (Campàs and Marty, 2006) (Fig. 3G). As an alternative to TMOS and TEOS, silicic acid was used for entrapment of living cells but high NaCl concentrations were formed (Meunier et al., 2010). Other novel silica gels and glass-like materials with more biocom- patibility based on highly reactive precursors are currently being developed (Müller et al., 2013).