Biofilm is a bacterial community composed of extracellular polymeric substances(EPS)secreted by bacteria.Bacterium in biofilms are more resistant to antimicrobial agents than planktonic bacteria.Traditional medicines have poor therapeutic effects on biofilm-associated infections.Therefore,the new antibacterial agents against pathogenic bacteria should effectively target biofilm and inhibite planktonic pathogens.Chitosan(CS)and Chitosan oligosaccharide(COS)are deacetylated products of chitin that have obvious antibacterial activity against gram-negative and gram-positive bacteria,as well as fungi.However,the high antibacterial concentration(2 mg/m L)may be cytotoxic,which limits its application in the antibacterial field.Therefore,we envisaged the use of chemical coupling with other molecules to increase the activity of CS/COS against biofilms and reduce their cytotoxicity.We designed two conjugates by linking CS/COS with the florfenicol,a common antibiotic,and inulin respectively.i: Florfenicol-chitosan oligosaccharide conjugates(Flo-COS),which were intended to alleviate the resistance of the clinical strain Streptococcus hyovaginalis(S.hyovaginalis)and improve the solubility of florfenicol.The synthesized conjugates were characterized by Nuclear Magnetic Resonance(NMR),Mass Spectrometry techniques.The results showed that each COS molecule was combined with two florfenicol.The activity of the Flo-COS conjugates on S.hyovaginalis biofilm was evaluated by MTT and fluorescent staining.The results showed that the Flo-COS conjugates had a good inhibitory effect on the biofilm formation of S.hyovaginalis,especially for the bacteria deep in the biofilm,compared with florfenicol,the antibacterial activity and water solubility of Flo-COS conjugates increased significantly.ii: Inulin-chitosan conjugates(Inulin-LCS),which were designed to reduce the antibacterial concentration and cytotoxicity of chitosan and improve its water solubility.Analytical methods such as Nuclear Magnetic Resonance(NMR),Infrared and HighPerformance Liquid Chromatography confirmed that inulin was successfully linked to chitosan.The results of anti-biofilm activity showed that the Inulin-LCS conjugates significantly disrupted mature Staphylococcus aureus(S.aureus)biofilm and inhibited the formation of biofilms compared to chitosan.Moreover,Inulin-LCS conjugates could inhibite the growth of planktonic S.aureus.In addition,the Inulin-LCS conjugates have a significant destructive effect on the mature biofilms of Streptococcus hyovaginalis and Pseudomonas aeruginosa.Compared with chitosan,the water solubility of Inulin-LCS conjugates was improved,and the cytotoxicity was reduced. |