Abstract
This paper presents a facile and low-cost strategy for fabrication lysozyme-loaded mesoporous silica nanotubes (MSNTs) by using silk fibroin (SF) nanofiber templates. The “top-down method” was adopted to dissolve degummed silk in CaCl2/ formic acid (FA) solvent, and the solution containing SF nanofibrils was used for electrospinning to prepare SF nanofiber templates. As SF contains a large number of -OH, -NH2 and -COOH groups, the silica layer could be easily formed on its surface by the Söber sol-gel method without adding any surfactant or coupling agent. After calcination, the MSNTs were obtained with inner diameters about 200 nm, the wall thickness ranges from 37 ± 2 nm to 66 ± 3 nm and the Brunauer–Emmett–Teller (BET) specific surface area was up to 200.48 m2/g, the pore volume was 1.109 cm3/g. By loading lysozyme, the MSNTs exhibited relatively high drug encapsulation efficiency up to 31.82% and an excellent long-term sustained release in 360 h (15 days). These results suggest that the MSNTs with the hierarchical structure of mesoporous and macroporous will be a promising carrier for applications in biomacromolecular drug delivery systems.
Highlights
Hollow-structured mesoporous silica nanospheres and nanotubes, which have large void space, high specific surface area, good thermal stability, and biocompatibility, and easy surface modification, have attracted great attention in adsorption and separation, storage, catalysis, and drug delivery systems [1,2,3,4]
The results suggested that the mesoporous silica nanotubes (MSNTs) prepared according to our method exhibited relatively high drug encapsulation efficiency and an excellent long-term sustained release behavior compared with traditional mesoporous silica spheres, they will be preferred silica–based carrier for applications in biomacromolecules drugs delivery system
After the temperature rose to 600 ◦C, the silk fibroin (SF) residual mass was almost zero, indicating that the SF templates had been removed, which was consistent with the Fourier transform infrared spectrometer (FTIR) analysis (Figure 4), the residual mass of different SF@silica NFs (Figure 6b–d) was 43.3, 45.7, and 50.4 wt%, respectively, corresponding to the gradual increase of TEOS dosages. This result indicated that the higher the amount of TEOS added, the more silica deposited on the surface of SF fibers, which was in good agreement with the results shown in Transmission electron microscopy (TEM) images (Figure 5) and further confirmed that the TEOS dosages could adjust the wall thickness of MSNTs
Summary
Hollow-structured mesoporous silica nanospheres and nanotubes, which have large void space, high specific surface area, good thermal stability, and biocompatibility, and easy surface modification, have attracted great attention in adsorption and separation, storage, catalysis, and drug delivery systems [1,2,3,4]. For the fabrication of MSNTs, hard-template strategy is more prevailing due to the fact that MSNTs with highly controllable hollow core diameter, shell thickness, and mesoporosity in the shell. Various templates, such as cylindrical polymer brushes [12], carbon nanotubes [13], and surfactant and nanocrystalline cellulose [14], have been applied to determine the final nanostructure of MSNTs. the synthesis of these templates is complex, high-cost, and difficult to scale up
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