The changes in the structure of 45S5 BioglassÒ and its heat-treated versions upon SrO substitution were investigated by solid-state multinuclear magic angle spinning nuclear magnetic resonance (MAS-NMR), X-ray diffraction and differential scanning calorimetry. A series of the melt-derived glasses with SrO gradually substituted for calcium (0, 25, 50, 75 and 100%) on a molar basis was synthesised. The glass transition temperature, T g , and crystallisation temperature decreased upon SrO substitution. Glasses with 75 and 100% of SrO substitution showed a minor crystalline phase. 31 P MAS-NMR showed that phosphorus is present as orthophosphate in the entire glass series; 29 Si MAS-NMR data showed a predominantly Q 2 silicate network. A small step change in the position of the 31 P and 29 Si MAS-NMR signals found between the glasses with 25 and 50% of SrO substitution is attributed due to an increase in the ring-type fraction of the Q 2 silicate glass over the mainly chain topology in the original 45S5 glass. On heat treatment combeite (Na 2 Ca 2 Si 3 O 9 ) and combeite-type (Na 2 CaSi 2 O 6 ) silicate phases were identified. For glasses with increasing SrO contents the equivalent Sr 2+ substituted phases were formed (viz. Na 2 Sr 2 Si 3 O 9 and Na 2 SrSi 2 O 6 ) above 600 C. The polymerisation degree of phosphorus increased and in addition to orthophosphate amorphous pyro-and meta-phosphate species were observed on heat treatment between 600 and 650 C, the amount of which reduced with SrO substitution. Above 800 C, changes in 31 P MAS-NMR spectra suggested that several phosphate containing phases crystallised and the fraction of the remaining glass was below the detection limit. In contrast to the SrO containing glasses, in the original 45S5 composition a significant fraction of phosphorus remained amorphous even after heat treatment at temperatures above 800 C.

Aluminium silicate nanotubes (ASNT), with a length to width ratio of four, were synthesized from aluminium chloride and sodium silicate, and the ASNT hydrogel was easily prepared by adjusting the pH to 7. The hydrogel nanotube concentration was 1.5 wt%. Laccase, a type of oxidase, was encapsulated during ASNT hydrogel formation. This encapsulation method will have fewer negative effects on the relatively unstable enzyme because of the milder conditions used, which are different from sol-gel silica formation by acidic catalysis using strong acids such as hydrochloric acid. The obtained hydrogels were fully characterized by various methods such as field-emission scanning electron microscopy and Fourier transform infrared spectroscopy. The ASNT-hydrogel encapsulated enzyme worked well; notably, laccase-ASNT hydrogels prepared from the shortest nanotubes exhibited a higher activity than the free laccase in solution because of an improvement in the substrate affinity of the encapsulated enzyme. Tryptophan fluorescence spectroscopy indicated that the highly ordered structure of laccase was not altered once bound to the nanotubes within the hydrogel. Notably, after nine repeated reactions, laccase encapsulated in the ASNT hydrogel retained its activity. The cycle performance of the encapsulated enzyme indicates that no enzyme was released from the ASNT hydrogel. In addition, the laccase-ASNT hydrogel was easily used to prepare transparent thin films on glass cover slips, while still maintaining the enzyme activity. Another oxidase, myoglobin, was also encapsulated in the same type of ASNT hydrogel.Although free myoglobin in solution demonstrated oxidation activity, the activity of the bound protein was remarkably decreased due to changes in its tertiary structure when inside the ASNT hydrogel.

Nonwoven fabrics prepared via an electrospinning method, so-called electrospun fibermats, are expected to be promising scaffold materials for bone tissue engineering. In the present work, poly(L-lactic acid) (PLLA) fibermats, consisting of fibers with diameters ranging from 1 to 10 μm, were prepared by electrospinning. Mouse osteoblast-like cells (MC3T3-E1) were seeded on the fibermats with various fiber diameters (10, 5 and 2 μm; they are denoted by samples A, B and C, respectively) and cultured in two different directions in order to compare the migration behaviours into the scaffold of the normal condition and the anti-gravity condition. The cells in/on the fibermats were observed by laser confocal microscopy to estimate the cellular migration ability into them. When the MC3T3-E1 cells were cultured in the normal direction, the thickness of their layer increased to approx. 90 μm in the sample A, consisting of 10-μm fibers after 13 days of culture, while that in the sample C, consisting of 2-μm fibers, did not increase. When the MC3T3-E1 cells were cultured in the anti-gravity condition, the thickness of the cell layer in the sample A increased to approx. 60 μm. These results mean that the MC3T3-E1 cells migrated into the inside of sample A in either the normal direction or the anti-gravity one. The cellular proliferation showed no significant difference among the fibermats with three different fiber diameters; MC3T3-E1 cells on the fibermat with 2 μm fiber diameter grew two-dimensionally, while they grew three-dimensionally in the fibermat with 10 μm fiber diameter.