subcapitata selleck chemical in suspension was poured into an individual mold (disposable UV–vis cuvette), CaCO3 nanoparticles were gently placed on the surface of the liquid, 10 μL of 2.0% sodium alginate solution was poured on top and 0.2 M CaCl2 solution was immediately added in the form of a mist by means of a nebulizer machine. The second step of the immobilization procedure consisted of a silicate (sodium silicate, Riedel-de Haën; NaOH 10%, SiO2 27%) sol–gel process in the presence of commercial silica nanoparticles (LUDOX HS-40, 40% in water, obtained from Aldrich), leading to a nanoporous monolithic structure.

Monoliths were prepared at room temperature by mixing volumes of the different precursor solutions to obtain a SiO2:H2O molar relation of 0.038 with a fixed proportion of polymeric to particulate silica precursors (1:4) at constant pH 7.0, adjusted with HCl. As described in Section 2, daphnids and microalgae are co-immobilized in calcium alginate capsules of (8.5 ± 0.5) mm diameter and are further immersed in tubes where a mixture of sodium silicate

and colloidal silica is vigorously mixed. This colloidal solution undergoes a rapid sol–gel transition, and alginate capsules are quickly covered with a nanoporous silica gel (time of gelation: 2–3 min). As a result, silica biomaterials with liquid macrocavities containing daphnids and microalgae in M4 culture medium are formed. After 20 min (necessary time for the consolidation of the selleck chemicals silica matrix), the biomaterials are immediately rinsed with distilled water, and fresh M4 medium is added to the tube (see Fig. 1). The high biocompatibility of this silica encapsulation procedure with P.subcapitata microalgal cells

is well established [16]. In this work, only the assessment of initial viability (1 h after encapsulation) is conducted by averaging the content of 10 macrocavities. To this end, the silica hydrogel is removed and samples are exposed to 0.05% potassium citrate to solubilize Molecular motor the calcium alginate shell. The total number of cells inside individual cavities (2.35 × 105) was determined by counting cells in a Mallassez counting chamber; (99.2 ± 1.1)% of P.subcapitata cells remains intact, in good agreement with previous published results [16]. To evaluate the effect of the encapsulation procedure on D. magna, the content of each macrocavity was observed under an optical microscope (100× magnification) and the mobility of daphnids was recorded. The analysis reveals that 98% of the D. magna population (52 out of 53 total daphnids tested) remains active 1 h post-encapsulation, but this percentage drops to ∼32% only 6 h post-encapsulation (17 out of 53 total daphnids tested), and at 24 h post-encapsulation daphnids present no mobility. The complete set of results is presented in Fig. 2. Apart from the possible deleterious effect of the confinement itself, we hypothesized that the low biocompatibility towards D.