There is an ongoing need for more effective and less costly bone substitutes. It has previously been proposed that silica-containing bioactive glass would be more effective as a bone repair material because of its physiochemical properties. Three newly synthesized silica-containing bioactive glass formulations, HA-31 (25%), HA-11 (50%), and HA-13 (75%), were tested as biocompatible substrates for the continued proliferation and phenotype expression of human bone cells in vitro. Two currently available bioactive glasses (BioGlass(R), Hydroxyapatite) served as comparisons. The biocompatibility of these bioglasses, as well as their osteoconductive properties, was assessed by employing primary cultures of human osteoblasts and human synoviocytes for 4 days. The results obtained demonstrated that the three new bioglasses enhanced the proliferative response of osteoblasts compared with osteoblasts cultured alone. Reverse Transcription Polymerase Chain Reaction (RT-PCR) analysis indicated that osteoblasts retained their phenotypic expression by continued expression of collagen type I and alkaline phosphatase. The newly synthesized preparations of silica-containing bioactive glass did not induce stimulation of proinflammatory markers iNOS and IL-1beta in synoviocytes. In conclusion, the newly synthesized silica-containing bioactive glasses are biocompatible substrate for bone-forming osteoblasts. However, the formulations tested did not show significant advantage over the currently available bioactive glasses in vitro.

A mathematical model has been developed to predict the extent of sulphate reduction by sulphate-reducing bacteria (SRB) in an underground nuclear waste disposal vault and the consequences for corrosion of the waste package. The model is based on a series of massbalance equations that describe the kinetics of sulphate reduction by two types of SRB (one organotrophic and one chemoheterotrophic), the growth and death of SRB, the supply and consumption of nutrients (acetate and hydrogen) and reactants (SO42−) and the consumption of sulphide by precipitation with aqueous Fe(II) or by container corrosion. The disposal vault is described by a series of 1-D mass-transport barriers representing the buffer and backfill materials and fractured rock. The model can also be used to simulate the effects of γ-radiation and desiccation of the buffer and backfill materials on the extent of microbial activity.

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