Melanin-like Phase-transition Nanoparticles For Enhanced Ultrasound/Photoacoustic Imaging

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PREPARATION,CHARACTERIZATION AND BIOSAFETY EVALUATION OF MELANIN-LIKE PHASE-TRANSITION NANOPARTICLESObjective:To prepare a phase-shift nanoparticle modified by melanin-like polydopamine(PDA),and evaluate its general physical and chemical properties,photo-induced phase transition and biosafety.Methods:Polymericpoly(lactic-co-glycolic)acid(PLGA)nanoparticles encapsulated with perfluoropentane(PFP)(PFP@PLGA nanoparticles,PP-NPs)was firstly made by sonication process,then polydopamine coatings were generated from solution oxidation,and PDA modified nanoparticles(PFP@PLGA@PDA nanoparticles,PPP-NPs)were prepared.Size and zeta potential distribution,morphology,drug loading of PDA and UV-vis-NIR absorption spectrum were subsequently characterized.Laser irradiation was used to investigate the photo-induced phase transition ability of PPP-NPs.For biosafety evaluation,there were 4 groups:PPP-NPs group,PP-NPs group,PDAs group and blank control group.4T1 mouse breast cancer cells were used to value cytotoxicity.KM mice were treated with different nanoparticles through tail vein injection,whose blood samples were respectively collected for blood routine test and biochemical test,on the1st,7th,14th,30th days after injection.Major organs(heart,liver,spleen,lung and kidney)of mice were collected for Hematoxylin and Eosin(HE)-stained slides.Results:The prepared PP-NPs solution was milk white,while PPP-NPs solution was dark brown.PPP-NPs showed a well-defined core-shell structured spherical morphology under transmission electron microscopy(TEM).The mean diameter of PP-NPs was(193.32±29.15)nm,which of PPP-NPs was(209.40±36.15)nm.Zeta potential of PP-NPs was-(20.08±3.14)mV,that of PPP-NPs was+(13.26±2.94)mV.PPP-NPs and PDA showed similar absorption spectra in the 400-900nm region,while PP-NPs showed little light absorption in this region.For PDA,the regression equation of the standard curve was Y=0.005864X+0.1402(R~2=0.9968),and the drug loading was(30.57±2.89)%.Before laser irradiation,the size and shape of PPP-NPs was observed to be uniform under light microscope,and the dispersion was good in the aqueous solution.After laser irradiation,the temperature of PPP-NPs increased,and the degree of increase was related to the concentration of nanoparticles(R~2=0.9979),and amounts of microbubbles caused by liquid-gas phase transition could be observed under light microscope,no such changes were observed in PP-NPs group.After 24 hours incubation with 4T1 mouse breast cells,the cell viabilities of PPP-NPs,PP-NPs and PDAs groups at all concentrations were greater than 90%,with no statistical difference between the groups(P>0.05).Mice with a single injection of PPP-NPs,PP-NPs,or PDAs through tail vein had maintained healthy status during the test period,and there was no significant difference in body weight between treated groups and the blank control group(P>0.05).Blood biochemical tests in each group of mice were all within the normal range,and with no significant difference(P>0.05).Neither the results in blood routine tests(P>0.05).HE staining of major organs in PPP-NPs group,showed no apparent physiological abnormalities.Conclusion:A polydopamine surface-modified nanoparticle was successfully prepared,with the ability of photo-induced phase transition and great biosafety.PART ? MELANIN-LIKE PHASE-TRANSITION NANOPARTICLES FOR ENHANCED ULTRASOUND AND PHOTOACOUSTIC IMAGING IN BREAST CANCERObjective: To observe the ability of melanin-like phase-shift nanoparticles PPP-NPs for enhanced ultrasonography(US)and photoacoustic imaging(PA)in vitro,and explore the dual-model imaging effect in mouse 4T1 breast xenograft cancer model.Methods: PPP-NPs and PP-NPs suspension in holes of agar-based phantoms were irradiated by a laser(800nm,1.5W/cm2)for different durations(0,3,5,10,15,20min)respectively,B-mode and CEUS images of which were collected for analysis of ultrasonography(US)performance.Photoacoustic(PA)imaging of nanoparticles with different concentrations and durations were also analyzed by photoacoustic device.Mouse 4T1 breast xenograft cancer models were made by means of injecting 4T1 cells subcutaneously to the back of female nude mice(4-6 weeks,body weight 18-20g),which were randomly divided into three groups(PPP-NPs group,PP-NPs group and PBS group,6 mice in each group),US an PA performance in vivo were later analyzed after administration through vail veins.Results: For enhanced ultrasound imaging in vitro,only PPP-NPs suspension showed significantly increased intensity of echo both in B-mode and CEUS after laser irradiation(P<0.05).In vitro PA imaging experiments showed that the PA signals of PPP-NPs suspension were raised significantly with the increase of concentration(P<0.05),and remained stable for a long duration(P>0.05).While PP-NPs suspension consistently displayed nearly no such signals.In in vivo ultrasonic study,similar echo signals were observed in the tumors of the 3 groups before laser irradiation,but significantly enhanced high-intensity signals were found in B-mode and CEUS images in mice from PPP-NPs group after laser irradiation,while,no such echo intensity changes were found in PP-NPs group and PBS group.In vivo photoacoustic study showed that,before,and in 1,4 and 24 h after the injection of PPP-NPs suspension,the intensity of photoacoustic signals were(0.12±0.03),(0.22±0.04),(0.67±0.08)and(0.37±0.06),respectively(P<0.05).No photoacoustic signal was observed in PP-NPs group and PBS group.Conclusion: The PPP-NPs nanoparticles,successfully accumulated at tumor region,could be photoacoustic/ultrasound dual-mode agents for further clinical application.