Abstract
The microphases and miscibility in binary curcumin(Cur)solid dispersions(SDs)with amorphous polyvinylpyrrolidone K30(PVP K30)and semi-crystalline poloxamer(P407)and poly(ethylene glycol)6000(PEG6000)as carriers were investigated by fluorescence contrasting utilizing confocal laser scan-ning microscopy.A super sensitive fluorophore P4 with typical aggregation-caused quenching properties was employed to stain the continuous polymer phases and contrasted with the autofluorescence of the model drug Cur.In addition,differential scanning calorimetry(DSC)and powder X-ray diffraction(PXRD)were utilized to assist in explanation of the fluorescence results.In all three SD systems,there is always a homogenous polymer phase stained by P4 and it is difficult to adulterate Cur crystals by P4.Cur-enriched rather than polymer-enriched domains could be detected.In the Cur-PVP K30 system,Cur exists in an amorphous form at a Cur loading level of 50％and below,while Cur crystallines phase out and continu-ously grow with the increase of Cur loading from 60％to 90％.The phase behaviors in the Cur-P407 and Cur-PEG 6000 systems are similar but with minor differences.In both systems,Cur phases out as clusters of drug-enriched domains at a loading level of 20％and below,which however cannot be correlated with crystallization,as evidenced by both DSC and PXRD.There is a transition from an amorphous to a crys-talline state from 20％to 30％Cur loading,above which Cur crystallines can be detected.It is interesting that a co-mix phase of both Cur-and PEG 6000-enriched domains can be identified at Cur loading levels of 10％and less.Taking together,it is concluded that contrasting Cur autofluorescence with the signals of P4 proves to be a functional strategy to reveal multiple phases in the binary SD systems investigated.
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