Study On The Treatment Of Salmonella Infection With Nitric Oxide-responsive Nanovesicles

Enteritis caused by Salmonella infection is a very common clinical intestinal disease,which poses a great threat to human health.However,due to the peculiarity of the intestinal environment,the use of antibiotics will destroy the beneficial flora of the intestinal tract,causing an imbalance in the intestinal ecological environment and bringing about a series of side effects.At the same time,the abuse of antibiotics has also accelerated the mutation of Salmonella,making future treatment more difficult.The targeted release strategy of antibiotics can have minimal negative impact on the intestinal flora and can greatly reduce the dosage of antibiotics,which is an excellent therapeutic strategy.As a facultative intracellular bacteria,Salmonella can cause an inflammatory response after infecting the intestine,and macrophages respond quickly to phagocytose and kill Salmonella.However,more and more reports have pointed out that Salmonella can use macrophages as a refuge to evade the body’s immune system and drug attack by inducing macrophage apoptosis.Therefore,for enteritis caused by Salmonella infection,designing an effective carrier to transport the drug into macrophages becomes the key to the treatment.Bacterial infection can cause high expression of inducible nitric oxide synthase(i NOS),so there is often a large amount of nitric oxide(NO)at the site of infection.We designed and synthesized the amphiphilic molecule In-DAP-C12 with prebiotic inulin as hydrophilic group,dodecyl as hydrophobic group and NO responsive group,o-phenylenediamine monoamide(grafting rate of 22.9%)as the linker arm.The amphiphilic molecule could self-assemble in water to form encapsulated ciprofloxacin lactate nanomicelles In-DAP-C12-Cip with a critical micelle concentration of 15.85 μg/m L and a drug loading rate of 9.43% with good stability.In vitro antibacterial experiments showed that the drug delivery system has better antibacterial ability than positive drugs,with a 24 h bactericidal rate of more than 99%,and also proved that it has good nitric oxide responsive drug release properties.Phagocytosis assays and intracellular bacterial clearance assays showed that the drug delivery system could enter macrophages and eliminate Salmonella hidden in them with a clearance rate of over 99.99%and a reduction in Salmonella load to 1/2 that of the free antibiotic treated group.In vivo antibacterial experiments have shown that In-DAP-C12-Cip nanomicelles have better antibacterial activity than free antibiotics in macrophage-rich immune organs(mesenteric lymph nodes,liver and spleen),with antibacterial effects of up to 90% in all cases and even more than 99% in mesenteric lymph nodes.All showed superior therapeutic effects compared to free antibiotics.Meanwhile,the toxicity experiments in vitro and in vivo also showed that the drug-loaded micelles have good biocompatibility.Therefore,the drug-carrying system we designed is expected to be applied in the clinical treatment of Salmonellosis.