Preparation And Antibacterial Effects Of Copper-loaded Polydopamine Nanoparticles

Chapter ?.Preparation and Characterization of Copper-loaded Polydopamine NanoparticlesObjective:To prepare Cu²⁺loaded polydopamine(CuPDA)nanoparticles and to evaluate their photothermal conversion efficiency under near infrared(NIR)irradiation.Methods:In Tris-ethanol solution,Cu²⁺and H₂O₂ were used to catalyze the rapid oxidative polymerization of dopamine(DA)to prepare CuPDA nanoparticles.The feed ratio,solvent ratio and H₂O₂were optimized according to the absorption at near-infrared808 nm and the amount of Cu²⁺loaded.Scanning electron microscopy(SEM),Fourier Transform Infrared Spectroscopy(FTIR),Energy Dispersive X-ray Spectroscopy(EDS)were used to study the morphology and structure of CuPDA nanoparticles.Atomic Absorption Spectrometry(AAS)was used to caculate the amount of Cu²⁺loaded and released rate.The photothermal conversion efficiency?was caculated to evaluate the photothermal performance of CuPDA nanopaticles.Results:CuPDA nanoparticles had maximum absorption at 808 nm,related high Cu²⁺loaded ratio and rapid reaction time when the molar ratio of DA:Cu²⁺was 1:1.0,the volume ratio of solvent Tris:ethanol was 3:2,and 0.9 mmol H₂O₂ was added to the reaction.SEM showed that CuPDA nanoparticles were relatively uniform spherical particles with a diameter of about 200 nm.EDS confirmed the presence of copper on CuPDA nanoparticles.FTIR confirmed the polymerization of DA to PDA.The Cu²⁺content in the prepared CuPDA nanoparticles was 205.3?g/mg.The release rate of Cu²⁺in 24 h was 18.74%,and the photothermal conversion efficiency?of CuPDA nanoparticles was 25.6%.Conclusions:Cu²⁺loaded polydopamine(CuPDA)nanoparticles prepared by DA self-polymerization catalized by Cu²⁺and H₂O₂ were prepared.The achieved nanoparticles could release Cu²⁺constantly with high photothermal conversion efficiency.Chapter?.Antibacterial and Antibiofilm Effects of Copper-loaded Polydopamine NanoparticlesObjectives:To analyse the antibacterial effects of CuPDA nanoparticles on suspended E.coli,S.aureus and P.aeruginosa,and on mature P.aeruginosa biofilm.Methods:After different concentrations of CuPDA or PDA nanopaticles were added to suspend bacteria,with or without NIR irradiation,the flat colony counting method was used to determine the survival rate of bacteria under different incubation time to evaluate the antibacterial effects of CuPDA and PDA on suspended bacteria.Then CuPDA or PDA was added to the cultivated mature P.aeruginosa biofilm,after incubation under different conditions,the survival rate of biofilm was determined by the dye of crystal violet.Results:Without NIR irradiation and nanoparticles incubated with suspended bacteria for 1 h,PDA concentations increased from 50?g/m L to 400?g/m L,the survival rates of the three bacteria remained 100%.CuPDA(50?g/m L)decreased the survival rates of E.coli and S.aureus to less than 1%,but the survival rate of P.aeruginosa was93.5%.The survival rate of P.aeruginosa decreased to 85.6%in 400?g/m L CuPDA group.When the incubation time were extended to 4h and 6 h,the survival rate of P.aeruginosa in 50?g/m L PDA group was still 100%.But the survival rate of P.aeruginosa in 50?g/m L CuPDA groups decreased to 0.2%and 0%at 4 h and 6 h,respectively.Correlation of Cu²⁺release rate and antibacterial rate showed that Cu²⁺was the main factor that killed bacteria under no NIR irradation.After applying NIR for 5 min then incubating for 1 h,the survival rates of E.coli,S.aureus and P.aeruginosa in 400?g/m L PDA group were 3.3%,20.6%and 11.5%,respectively.But in 100?g/m L CuPDA group,the survival rates of E.coli,S.aureus and P.aeruginosa were all less than 1%.When the incubation time was extended to 6 h,in 50?g/m L PDA group,the survival rate of P.aeruginosa decreased to 70%after 1hour incubation,and remained unchanged after 2h,6 h incubation.For 50?g/m L CuPDA,the survival rate of P.aeruginosa was 67.4%,0%and 0%after 1 h,2h and 6h incubation,respectively,indicating that CuPDA had continuous antibacterial effect.For mature P.aeruginosa biofilm,without NIR,when 800ug/m L PDA or CuPDA were incubated with biofilm for 12 h,the rates of residual biomass in biofilm in PDA and CuPDA group were 100%and 61.4%respectively.After applying 10 min NIR and incubating for 12 h,the rate of residual biomass in biofilm in the PDA and CuPDA group were 62.5%and 33.9%respectively.CuPDA had better photothermal antibacterial and anti-biofilm effects than PDA.Conclusions:In the absence of NIR,the Cu²⁺released by CuPDA nanoparticles had good antibacterial properties against suspended E.coli,S.aureus and P.aeruginosa,and also had certain anti-biofilm effects on the mature P.aeruginosa biofilm.Under5 min or 10 min NIR irradiation,antibacterial and anti-biofilm properties were further enhanced.With or without NIR,CuPDA had better antibacterial and anti-biofilm performances than PDA.