Bioactivity of biomaterials was a new requirement, especially in tissue engineering and drug delivery. As a traditional used biomaterial, polylactide (PLA) had no bioactivity, of course, and it still had few reactive groups to introduce some bioactive molecules in its bulk. Here, we want to introduce carboxyl groups and amino groups in the side chain of PLA to get more reactive groups for incorporating bioactive molecular later and to maintain the structure of main chain to keep its biodegradability, and to settle the acidity of PLA during hydrolysis at the same time. It was performed as follows: first, maleic anhydride was covalently grafted onto the side chain of PLA by a free radical reaction at 100 degrees C for 20 h with BPO as the initiator. Then, by amidation with a maleic anhydride group on PLA at room temperature, hexanediamine was incorporated. The resulting polymers have been characterized via GPC, (13)C NMR, DSC, and TGA. The graft ratio was tested by titration. The pH changes during hydrolysis in 0.1 M PBS with pH 7.4 of PLA, MPLA, and HPLA were investigated. All the results showed that this research has grafted maleic anhydride and then hexanediamine in the bulk of PLA. The molecular weight degradation during reaction was less than 20%. The graft ratios of were 2.68, 2.36, and 1.86%, respectively in 5, 10, and 20% raw MA in MPLA; and the anhydride groups grafted in MPLA can completely react with hexanediamine at room temperature. The pH value of HPLA remained neutral within 12 weeks' hydrolysis compared with the resulted acidity of PLA and MPLA.

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Photodegradation of organic dye molecules has attracted extensive attention because of their high toxicity to water resources. Compared with traditional UV-visible spectroscopy, SERS technology can reflect more sensitively the catalytic degradation process occurring on the surface of the catalysts. In this paper, we report the synthesis and structure of Fe3O4@SiO2@TiO2@Ag composite, which integrates SERS active Ag nanostructure with catalytically active titania. The degradation of the typical dye molecule crystal violet (CV), as an example, is investigated in the presence of the as-prepared Fe3O4@SiO2@TiO2@Ag composite structure, which exhibits high catalytic activity and good SERS performance. At the same time, renewable photocatalytic activity was also investigated.