pH-triggered MgAlZr layered double hydroxides for modification of collagen fibers with enhanced thermal stability and UV resistance

Modification of collagen with multifunctional nanoparticles is the key to fabrication of functional collagen-based bionanocomposites. In this study, we have reported a novel modification approach for collagen fibers with ternary layered double hydroxides (MgAlZr-LDH) to fabrication of bionanocomposites with enhanced thermal stability and the UV resistance, focusing on influences of pH on the growth and binding of the LDH within the collagen fibers. The LDH with an average layers diameter of 43-62 nm are synthesized by tuning Al/Zr molar ratios. By decreasing pH of the LDH suspension from 7.0 to 3.0, leaching of Mg2+ from the nanoparticles can result in the dissolution of the LDH. Moreover, increasing of binding pH from 3.0 to 6.0 can promote the growths of the LDH within the collagens exhibiting a relatively uniform distribution without destroying natural D -periodic banding of the collagen fibrils. Al3+ and Zr4+ of the LDH can mainly coordinate with-COOH and-NH2 of collagen molecules, respectively. The LDH cannot enter the gap of the collagen molecules in microfibrils. The presence of hydrogen bonds between the collagens and the LDH can maintain the triple-helical structure of collagen molecules. Furthermore, incorporation of the LDH into collagen fibers can enhance the hydrothermal and thermal stability and the UV resistance of the fiber matrix. These results provide a theoretical basis for guiding applications of LDH as building blocks in multifunctional bionanocomposites.