Application Of Traceable DOX-loaded AIE Active Polymer Nanoparticles Based On FRET In Anticancer Treatment

Non-covalent encapsulation and covalent modification of fluorescent dyes are the most commonly used strategies to build drug delivery systems with the ability to self-indicate and monitor drug release characteristics.However,there are some problems such as morphological changes in nanostructures and dye leakage.To avoid the above disadvantages,our study designed new self-indicating Nano-based grug delivery system?NDDS?with the ability of tracking drug release process based on Aggregation-induced emission?AIE?and Fluorescence resonance energy transfer?FRET?for cancer treatment.Our study synthesized an amphiphilic and AIE-active polymer FLU-TPE-PEG?FTP?via Suzuki polymerization coupling reaction.The TPE unit in FTP acted as an AIE-active group.When the polymer is dispersed in water,it will self-assemble and aggregate to produce the AIE effect.In THF-H₂O mixed solvents with different Water fraction?f_w?,when f_w increased from 0%to 99%,the green fluorescence emission of FTP gradually increased to nearly 18 times than the original,showing obvious AIE behavior.At the same time,there is an intramolecular FRET process from the fluorene unit to the TPE unit in the polymer,which can increase the emission wavelength of the polymer and significantly enhance the green fluorescent emission intensity of the TPE unit.Loaded with DOX,FTP nanoparticles?DOX@FTP NPs?were obtained by nano-precipitation method.The fluorescence emission spectrum of FTP could well overlap with the UV-visible absorption spectra of DOX in the range of 400-630 nm.The DOX loaded in DOX@FTP NPs could sharply quench the green fluorescence emission of FTP.The fluorescence lifetime of the DOX loaded nanoparticles was longer than that of the blank nanoparticles?the fluorescence lifetimes of the 30%e.q.DOX@FTP NPs was 2.35 ns and the blank nanoparticles was 1.43 ns?.The above results together showed that there was a FRET process from FTP to DOX in nanoparticles.Meanwhile,the optimal feeding ratio of drug loaded nanoparticles was determined to be 30%e.q.based on data such as FTP fluorescence quenching,particle size and drug loading content.The particle size of 30%e.q.DOX@FTP NPs was 54.02±1.51nm and the zeta potential was-1.13±0.06mV.They were observed to be spherical with a uniform distribution of particle size.The drug loading content of DOX@FTP NPs was21.77±1.02%,and the encapsulation efficiency was 92.74±1.12%.DOX@FTP NPs showed good stability in PBS?pH 7.4?,and had almost no hemolysis,indicating that the drug delivery system had high stability and biocompatibility.At the same time,DOX@FTP NPs could selectively respond to acidic pH?pH 5.5?with 78%of DOX released in 24 h.However,there was a slow drug release behavior at pH 7.4 PBS?25%DOX released in 24 h?.MCF-7 Cells were used to study in vitro anti-tumor activity and the traceable drug release process based on FRET of DOX@FTP NPs.MTT results showed that the blank FTP NPs were almost non-cytotoxic,while DOX@FTP NPs could effectively kill tumor cells.Observation of cell uptake by confocal laser scanning microscope showed that the uptake of DOX@FTP NPs by MCF-7 cells was time-dependent and most of the nanoparticles entered into the lysosome after 8 h of incubation.The ratio of the average red fluorescence intensity(F_Red)to the average blue fluorescence intensity(F_Blue)in the intracellular fluorescence image gradually decreased with time,indicating that the FRET effect between DOX and the carrier polymer is weakened,which characterized the release of DOX.The in vivo distribution results showed that DOX@FTP NPs had strong tumor targeting and long circulation characteristics in MCF-7 tumor-bearing nude mice.To prove that the drug release process can still be monitored based on the FRET effect in the tumor microenvironment,DOX@FTP NPs were injected intratumorally into tumor-bearing mice and the tumor sections were made.The fluorescence image results showed that the fluorescence intensity of loaded DOX in nanoparticles decreased significantly over time.The results of model animal antitumor pharmacodynamic studies showed that in vivo DOX@FTP NPs implied antitumor activity equivalent to that of DOX·HCl.The body weight of the mice in the DOX@FTP NPs group did not change significantly during the administration,and the tissue sections of important organs did not show significant pathological changes,indicating that DOX@FTP NPs had higher safety.The study indicated that DOX@FTP NPs had strong anti-tumor ability and low toxicity.The AIE characteristic can strengthen the self-indicating ability of nanoparticles and the intermolecular FRET process from FTP to DOX can effectively monitor the release of DOX.The study provided new monitorable NDDS based on the AIE and FRET effects.