Photocatalytic Synthesis of Materials for Regenerative Medicine Using Complex Oxides with β-pyrochlore Structure

Abstract

Graft copolymerization of methyl methacrylate onto cod collagen was carried out under visible light irradiation (λ = 400-700 nm) at 20-25 °C using the RbTe_1.5W_0.5O₆, CsTeMoO₆, and RbNbTeO₆ complex oxides with β-pyrochlore structure as photocatalysts. The as-prepared materials were characterized by X-ray diffraction, scanning electron microscopy, and UV-Vis diffuse reflectance spectroscopy. It was also found that RbNbTeO₆ with β-pyrochlore structure was not able to photocatalyze the reaction. Enzymatic hydrolysis of the obtained graft copolymers proceeds with the formation of peptides with a molecular weight (MW) of about 20 and 10 kDa. In contrast to collagen, which decomposes predominantly to peptides with MW of about 10 kDa, the ratio of fractions with MW of about 10 kDa and 20 kDa differs much less, their changes are symbatic, and the content of polymers with MW of more than 20 kDa is about 70% after 1 h in the case of graft copolymers. The data obtained indicate that synthetic fragments grafted to the collagen macromolecule do not prevent the hydrolysis of the peptide bonds but change the rate of polymer degradation. This is important for creating network matrix scaffolds based on graft copolymers by cross-linking peptides, which are products of enzymatic hydrolysis.

Keywords: CsTeMoO6; RbNbTeO6; RbTe1.5W0.5O6; cod collagen; complex oxides; enzymatic hydrolysis; graft copolymer; methyl methacrylate; photocatalysis; scaffold; β-pyrochlores.

Figure 1

Changes in the molecular weight characteristics of different fractions during hydrolysis of a solution (a,b) [49] and dried collagen (c,d) with pancreatin: 1—fraction with MW above 20 kDa; 2—fraction with MW of about 20 kDa; 3—fraction with MW of about 10 kDa.

Figure 2

Scheme of the formation of polymerization radicals.

Figure 3

The MWD curves of initial dried collagen (DCC), PMMA-collagen graft copolymer after photocatalysis using RbTe_1.5W_0.5O₆ (GCMC–1) and CsTeMoO₆ (GCMC–2).

Figure 4

Comparative data on the grafting of MMA onto collagen based on changes in the content of nitrogen using the RbTe_1.5W_0.5O₆ (GCMC–1) and CsTeMoO₆ (GCMC–2) complex oxides as photocatalysts in comparison with the initial (CC) and dried (DCC) cod collagen. * In terms of collagen according to the well-known formula by multiplying the amount of nitrogen in the sample by the coefficient (5.62). The mass fraction of nitrogen in collagen is a * 5.62 (%), where a is the mass fraction of nitrogen in the sample [55].

Figure 5

SEM images of the CsTeMoO₆ photocatalyst after synthesis of the GCMC–2 sample (a,b), the initial compound (c), and EDX-analysis photocatalyst after polymerization (d).

Figure 6

Change in the molecular weight of (a) GCMC–1 and (c) GCMC–2, as well as proportions of different fractions in hydrolysis of (b) GCMC–1 and (d) GCMC-2 with pancreatin: 1—fraction with MW above 20 kDa; 2—fraction with MW of about 20 kDa; 3—fraction with MW of about 10 kDa.

Figure 7

Schematic illustration of proteolytic hydrolysis of the peptide bonds formed by arginine and lysine.