LAUSR

In this work, a new kind of smart nanocarriers that combine pH-responsive delivery and fluorescent markings was developed. The smart nanocarriers were based on the host–guest interaction between beta-cyclodextrin (β-CD) and rhodamine (R) which has closed-loop-hydrophobic and open-loop-hydrophilic structure in different pH. Small-size β-NaYF4:Yb,Er upconversion nanoparticles (UCNPs) with a diameter of 19 ± 2 nm, as a nanocarrier, were modified with β-CD to form water-soluble carrier. Rhodamine was conjugated with Ganoderma applanatum polysaccharide (GAP) through reductive amination reaction to form rhodamine polysaccharide complex (R-GAP). R-GAP was loaded on UCNPs in alkaline condition, and released detected by fluorescence resonance energy transfer (FRET) effect, based on the spectral overlap between UCNPs and R, under acidic conditions, besides the maximum release amounts of R-GAP reach up to 67.3% at pH 5.5. The in vitro cell cytotoxicity of R-GAP-loaded UCNPs to human colorectal cancer cell (SWWC1116) showed that R-GAP-CD-UCNPs have a better inhibition than the simple R-GAP. Confocal laser scanning microscopy (CLSM) was used to observe the localization of R-GAP in SWWC1116, and we found that R-GAP entered the cell plasm. Cell cycle analysis demonstrates that R-GAP can block SWWC1116 cells in the G2 phase. In summary, this study developed an effective strategy for pH-sensitive delivery system and fluorescent markings of polysaccharide drugs.