Study Of Fluorescence Properties And Interfacial Microstructure Of Microemulsion

Nanoscale microemulsions have been utilized as delivery carriers for nutraceuticals and active biological drugs.While real-time monitoring of these active factors was difficult,and some complex fluorescent materials were usually needed to mark them.Herein,we designed and synthesized a novel oil in water(O/W)food-grade microemulsion based on isoamyl acetate,polyoxyethylene castor oil EL(CrEL),and water.Unexpectedly,it was found that the microemulsion can emit fluorescence.The fluorescence properties of the microemulsion were characterized systematacially.The luminous mechanism and the effect of environmental factors on the fluorescence intensity of the microemulsion were also studied.It was revealed that the microemulsion emit bright blue fluorescence,thus exhibiting its potential for active drug detection with label-free strategy.And it exhibited excitation-dependent emission and distinct red-shift with longer excitation wavelengths.Lifetime and quantum yield of fluorescent microemulsion were 2.831 ns and 5.0 %,respectively.An excellent fluorescent stability of the microemulsion was confirmed by altering pH,ionic strength,temperature,and time.Moreover,the probable mechanism of fluorochromic phenomenon was in connection with aromatic ring structure of polyoxyethylene ether substituent in CrEL.Then,Carbon dots(CDs)were introduced into microemulsion to investigate the interfacial microstructure of the microemulsion.At first,CDs were synthesized by one-step microwave.Secondly,CDs were added into microemulsion,and it’s interaction with surfactant was studied by FT-IR and NMR.At the same time,microstructure of the microemulsion was observed by TEM and cryo-EM.Finally,effect of CDs on stability of the ALA-loaded microemulsion and the in vitro release of ALA were explored.Results showed that the addition of CDs made the water layer of microemulsion thinner and the oil/water interface better defined.Combined the results of FT-IR and NMR,interfacial models of microemulsion were proposed,and it was proved that the interface of the microemulsion was discrete.At last,it was demonstrated that the antioxidant capacity of ALA-loaded ME was substantially enhanced after introducing CDs,and the optimum concentration was 2 mg/mL.Interestingly,CDs don’t affect the in vitro release of ALA,and the release ratio could be adjusted by changing environmental pH.