Lactic-co-glycolic Acid-coated Methylene Blue Nanoparticles Antibacterial And Promote Wound Healing And Its Mechanism

Methylene blue?MB?is an antibacterial,antifungal and antiprotozoal drug widely used in aquaculture.In order to carry out the preliminary exploration of the development of new antibacterial methylene blue antibacterial preparations and new therapies for fishing,improve its efficacy and reduce the dosage,this study comprehensively applied nano-coating technology and photodynamic antibacterial synergistic technology,based on the preparation of lactic acid-glycolic acid?PLGA?coated methylene blue?MB?photosensitizer nanoparticles?MPNPs?,the stability,safety,antibacterial activity in vivo and in vitro and its synergistic mechanism were studied.The details are as follows.1.The PLGA is used as the coating material to coat the MB by the double emulsion method.The prepared particles?MPNPs?have a particle size of 240-340 nm,an average particle size of 247.7 nm,and a surface charge of-0.319 m V.Both scanning electron microscopy and transmission electron microscopy observed that the surface of MPNPs was smooth and uniform,which was consistent with the characteristics of nano-scale particles.Fourier infrared absorption spectrum showed that PLGA successfully coated MB.MPNPs below 200?g m L^-1 concentration,the inhibition rate of 4T1 cell survival does not exceed 15%,at 400?g m L^-1 concentration did not cause haemolysis of rabbit red blood cells,MPNPs have good biocompatibility and low cytotoxicity.MPNPs(200?g m L^-1)were treated by tail vein injection and smear to treat staphylococcus aureus skin trauma model in mice.No histological damage was found in heart,liver,spleen,lung,kidney and brain.2.MPNPs(100?g m L^-1)combined with laser irradiation in vitro inhibited E.coli and Staphylococcus aureus inhibition rates?99.99%and 99.67%,respectively?and MIC(25?g m L^-1)were significant It was higher than the inhibition rate of MB combined laser group?80%and 75%respectively?and MIC(100?g m L^-1)external scanning electron microscope and transmission electron microscope to observe the bacterial surface shrinkage and content overflow after MPNPs combined laser treatment.3.MPNPs treatment of methicillin-resistant Staphylococcus aureus?MRSA?skin disease test showed that 100?L MPNPs(200?g m L^-1)applied wounds combined with laser treatment on the 7th day,compared with MB combined laser treatment group lower bacterial load,faster wound healing and better healing.4.In the in vitro solution,the amount of singlet oxygen produced by the MPNPs group under laser excitation is higher than that of the MB group;while in the cell test,the amount of active oxygen produced by the MPNPs group under laser excitation is higher than that of the MB group.The antibacterial synergistic mechanism of MPNPs may be related to the amount of singlet oxygen produced by MB and the increase in lifespan.The results showed that after MB is coated into nanoparticles by PLGA,the antibacterial activity in vivo and in vivo is enhanced,and the mechanism of antibacterial synergism is related to the increase of stimulated active oxygen.This study laid the foundation for the next development of a new immersion-type antibacterial and wound healing preparation for fishing using lactic acid-glycolic acid coated methylene blue nanoparticles as raw materials.