Chitosan was a kind of biodegradable, biocompatible, non-toxic polymer composed of β-(1–4) glucosamine, which always exhibited biocompatibility, anti-inflammatory, antibacterial, anti-tumor activity and anti-cancer properties, thereinto, antibacterial activity was the most important properties. And then, chitosan was applied in medicine, biotechnology, food and gene therapy according to its action on gram-positive and gram-negative bacteria. The pyrazole substituted chitosan Schiff base derivatives chitosan was synthesized by heterocyclic pyrazole, 2-acetylthiophene, 2-acetylfuran and 3-acetylpyridine, and exhibited good inhibitory effect on gram-negative bacteria, gram-positive bacteria and fungi, and was consistent with the green antibacterial materials development trend.
Dialdehyde starch (DAS) was synthesized by the selective oxidation starch, exhibited antiviral activity [5, 6]and direct drug attachment, so it would be a good drug carrier material. The aldehyde groups gave DAS the antibacterial activity, could irreversibly destroy the bacterial cell wall and plasma membrane, and then led to the decay and death of bacterial cells. Dialdehyde β-cyclodextrin with different oxidation degrees were synthesized by β-cyclodextrin, sodium periodate and sodium alginate, and their antibacterial properties against E. coli, S. aureus and B. subtilis were significant.
Metal and its complexes could store oxygen and were used in disinfection, bacteriostasis and other aspects through destroying the cell membrane protein. For example, Cu(II), Ag(II), Zn(II), Co(II) and their complexes showed good inhibitory effects on E. coli, S. aureus, Salmonella and B. subtilis[11, 12]. Azo Schiff base ligand 2-hydroxy-3-methoxy-5-(tolyldiazenyl) benzalde-hyde oxime, synthesized by 2-hydroxy-3-methoxy-5-(p-tolyldiazenyl) benzaldehyde oxime and 2-hydroxy-3-methoxy-5-(tolyldiazenyl) benzaldehyde, and its metal complexes [Ni(II), Cu(II), Zn(II)] showed best bacteriostatic effect on gram-positive and gram-negative. Thiosemicarbazide, 3-methoxy-2-hydroxybenzaldehyde and their metal complexes [Co(II), Ni(II), Cu(II), Zn(II)] also showed good considerable antifungal activity on A. flavus and C. albicans.
Metal ions complexes of Schiff base ligand derived from chitosan could permeate the bacterial cell membrane efficiently, and then easily prevent or inhibit the bacterial growth. In addition, the metal ions could easily combine with oxygen in organisms, and then denatured proteins or enzymes [16, 17] through effect on the synthesis of amino acids, proteins, lipoproteins and coenzymes according with the formation of stable complexes. The antibacterial activity of chitosan Schiff base metal complexes [Cu(II)[18, 19], Ag (II)[20, 21], Zn(II)] against E. coli, S. aureus, salmonella and B. subtilis was significantly higher than that of free ligand, and increased with the increase of the minimum concentration[23, 24]. A novel water-soluble isoniazid grafted O-carboxymethyl chitosan Schiff base was synthesized by chitosan, 1,3-diphenyl-1, 3-propanedione and mono chloroacetic acid, and then its metal complexes [Co(II), Cu(II), Zn(II)] was obtained, moreover, the results of antibacterial activity tests showed that the metal complexes exhibited better inhibitory effect on P. aeruginosa and S. aureus. A new class of organic-inorganic hybrid material was synthesized by O-Carboxymethyl chitosan Schiffs base, (3 -Aminopropyl) triethoxysilane, 2-hydroxy-1-naphthaldehyde and nano-silica, and then its Cu(II) metal complexes was obtained. At the same time, the results of antibacterial activity tests showed that nano-hybrid material exhibited better inhibitory effect on gram-positive (E. coli) and gram-negative (B. subtilis) bacteria.
Carboxymethyl chitosan dialdehyde starch Schiff base was synthesized by crosslinking reaction between dialdehyde starch and carboxymethyl chitosan, and then was coordinated by metal ions (Cu[II], Zn[II], Ni[II], Ag[I]). All products were characterized by XRD, SEM, EDS, TGA and FT-IR. The antibacterial activity of carboxymethyl chitosan dialdehyde starch Schiff base and its metal complexes against E. coli and S. aureus was tested, and the results showed that (1) carboxymethyl chitosan dialdehyde starch Schiff base and its metal complexes represented obvious antibacterial activity; (2) the antibacterial activity of the metal complexes was higher than that of carboxymethyl chitosan dialdehyde starch Schiff base.