OBJECTIVE To design and synthesize rifamycin S derivatives and load them into milk exosomes to evaluate their in vitro antimicrobial activity.METHODS Rifamycin S derivatives were synthe-sized and characterized by mass spectrometry and NMR.Using the dilution assay method,the inhibitory activity of each rifamycin S derivatives molecule against Staphylococcus aureus and Pseudomonas aerugi-nosa was determined,and the IC50 was calculated.Derivatives molecules with excellent antimicrobial activity were selected and loaded into milk exosomes using the ultrasonication method,resulting in the preparation of milk exosome-loaded rifamycin S derivatives.The antimicrobial activity against Staphylo-coccus aureus was determined using the dilution assay method.The inhibitory effect of the exosome-loaded rifamycin S derivatives on Staphylococcus aureus residing within macrophages was detected using the plate colony counting method.RESULTS Three rifamycin S derivatives were successfully designed and synthesized,which demonstrated superior antimicrobial activity against Staphylococcus aureus(the parent compound's antimicrobial activity is merely from 1/20 to 1/80 of that of the three rifamycin S derivatives)and Pseudomonas aeruginosa(the parent compound's antimicrobial activity is only 1/14 and 1/9 of that of compound 1 and compound 3)compared to the parent compound.The loading of milk exosomes with the rifamycin S derivatives compound 3 was successfully achieved,with a loading efficiency of 10.9％.The antimicrobial activity of the compound after exosome loading was significantly enhanced against Staphylococcus aureus in vitro and against Staphylococcus aureus residing within macrophages(P＜0.01).CONCLUSION The designed and synthesized derivatives of rifamycin S possess stronger anti-microbial activity,and their antibacterial efficacy against both extracellular and intracellular bacteria can be further enhanced after loading into exosomes.

OBJECTIVE To design and synthesize rifamycin S derivatives and load them into milk exosomes to evaluate their in vitro antimicrobial activity.METHODS Rifamycin S derivatives were synthe-sized and characterized by mass spectrometry and NMR.Using the dilution assay method,the inhibitory activity of each rifamycin S derivatives molecule against Staphylococcus aureus and Pseudomonas aerugi-nosa was determined,and the IC50 was calculated.Derivatives molecules with excellent antimicrobial activity were selected and loaded into milk exosomes using the ultrasonication method,resulting in the preparation of milk exosome-loaded rifamycin S derivatives.The antimicrobial activity against Staphylo-coccus aureus was determined using the dilution assay method.The inhibitory effect of the exosome-loaded rifamycin S derivatives on Staphylococcus aureus residing within macrophages was detected using the plate colony counting method.RESULTS Three rifamycin S derivatives were successfully designed and synthesized,which demonstrated superior antimicrobial activity against Staphylococcus aureus(the parent compound's antimicrobial activity is merely from 1/20 to 1/80 of that of the three rifamycin S derivatives)and Pseudomonas aeruginosa(the parent compound's antimicrobial activity is only 1/14 and 1/9 of that of compound 1 and compound 3)compared to the parent compound.The loading of milk exosomes with the rifamycin S derivatives compound 3 was successfully achieved,with a loading efficiency of 10.9％.The antimicrobial activity of the compound after exosome loading was significantly enhanced against Staphylococcus aureus in vitro and against Staphylococcus aureus residing within macrophages(P＜0.01).CONCLUSION The designed and synthesized derivatives of rifamycin S possess stronger anti-microbial activity,and their antibacterial efficacy against both extracellular and intracellular bacteria can be further enhanced after loading into exosomes.

OBJECTIVE To construct an insulin-resistant(IR)small intestinal organoid model of mice and study the protective effect of flavanomarein(FM)on the intestinal mucosal barrier in the model.METHODS ①Small intestinal organoid models of C57BL/6J and db/db of mice were constructed.The expressions of Ki-67,E-cadherin(E-cad),lysozyme(Lyz)and mucin-2(Muc-2)in small intestinal organ-oids were detected by 3D immunofluorescence.RT-qPCR was used to detect the expressions of fibro-nectin(Fn),glucagon-like peptide-1(GLP-1)and peotide YY(PYY)mRNA while Western blotting was used to detect the expressions of Fn,GLP-1 and PYY protein.The Lyz secretion level was detected by ELISA.② Small intestinal organoids were divided into five groups:C57BL/6J mice 'small intestinal organ-oids as the normal control group,db/db mice' intestinal organoids as the IR model group,db/db mice small intestinal organoids with flavanomarein 25,50 and 100 μmol·L-1 intervention for 48 h as IR model+ FM groups.RT-qPCR was used to detect the expression of Lyz mRNA while Western blotting was used to detect the expression of Lyz protein.RESULTS ① On the 6th day of small intestinal organoid culture,a ring structure with a clear luminal structure was formed and an IR mouse small intestinal organoid model was established.3D Immunofluorescence detection showed that the established small intestinal organoids all expressed Ki-67,E-cad,Lyz and MUC-2.Compared with the normal control group,the expres-sion of Fn mRNA in the IR model group was significantly increased(P<0.05)while the expressions of GLP-1 and PYY mRNA were significantly decreased(P<0.05).Compared with the normal control group,the expression of Fn protein in the IR model group was significantly decreased(P<0.05)while the expressions of GLP-1 and PYY protein were significantly increased(P<0.05).ELISA results showed that compared with the normal control group,the secretion levels of Lyz in the IR model group were signifi-cantly decreased(P<0.01).② RT-qPCR results showed that compared with the normal control group,the expression of Lyz mRNA in the IR model group was significantly decreased(P<0.01).Compared with the IR model group,the expression of Lyz mRNA in the IR model+FM 50 and 100 μmol·L-1 groups was significantly increased(P<0.05,P<0.01).Western blotting results showed that compared with the normal control group,the expression of Lyz protein in the IR model group was significantly decreased(P<0.01).Compared with the IR model group,the expression of Lyz protein in the IR model+FM 50 and 100 μmol·L-1 groups was significantly increased(P<0.05,P<0.01).CONCLUSION The constructed IR mouse small intestinal organoid model provides a more complete in vitro research model for exploring the pathophysiological mechanism by which drug interventions help repair the intestinal mucosal barrier.FM may maintain the intestinal mucosal barrier by reversing the decrease in Lyz expression levels in IR mice,thereby improving IR.