Construction Of Cyclodextrin Functionalized Carbon Nanotubes As Drug Delivery System And Preliminary Inquiry Into Their Anti-tumor Effect

Formononetin(FMN)is one of antitumor agents that can prevent breast,prostate and colon cancer.However,it has serious side effects in clinical administration because of its poor hydrosolubility and bioavailability.So it is necessary to find a suitable delivery system for the entrapment of FMN.Due to the special structural features,carbon nanotubes(CNTs)can be combined with FMN easily through π-π stacking interactions,meanwhile transfer the drug into the cell or tissue through the ability of translocation across cytomembrane to produce effect.However,pristine CNTs have poor dispersity because of their highly hydrophobic surfaces,large size,coupled with van der Waals forces and strong π-π interactions between the individual tubes.Therefore,this study chose carboxylic groupfunctionalized single-walled carbon nanotubes and multi-walled carbon nanotubes(SWCNTs-COOH and MWCNTs-COOH),as well as hydroxypropyl-β-cyclodextrin modified SWCNTs-COOH and MWCNTsCOOH(HP-β-CD-SWCNTs and HP-β-CD-MWCNTs)for the carriers of FMN.The details are as follows:1)SWCNTs-COOH and MWCNTs-COOH combined with FMN through π–π stacking to obtained FMN-SWCNTs-COOH and FMNMWCNTs-COOH compositions.A derivation method was established utilizing high-performance liquid chromatography(HPLC)to determine the content of FMN so that the entrapment efficiency and loading capacity could be calculated.The compositions were characterized using Fourier-transform infrared spectrometry(FTIR),laser particle size analysis,x-ray diffractometry(XRD),differential scanning calorimetry(DSC)and scanning electron microscopy(SEM).Using SWCNTsCOOH as model,the adsorption behavior of FMN on CNTs-COOH was investigated.In addition,the release behavior of the compositions was also observed.The results indicated that the linear relation was well between peak area and FMN concentration in the range of 0.12~24.00 μg/ml.Precision and recovery rate test results were consistent with the methodological requirements.The entrapment efficiency and loading capacity of FMN-SWCNTs-COOH were(65.66 ± 2.29)% and(25.25 ± 3.48)% respectively.The entrapment efficiency and loading capacity of FMN-MWCNTs-COOH were(28.77 ± 0.15)% and(12.05 ± 0.20)% respectively.According to the result of characterization,FMN was successfully loaded into the CNTs-COOH.The absorption of FMN on SWNTs-COOH reached equilibrium after 150 min and could be explained by pseudo-second-order model.The release of FMNSWCNTs-COOH and FMN-MWCNTs-COOH was sustained and the cumulative release rate of them was higher at p H 7.4 than at p H 5.3.2)SWCNTs-COOH and MWCNTs-COOH were modified by HP-β-CD to obtained HP-β-CD-SWCNTs and HP-β-CD-MWCNTs compositions.After proving that HP-β-CD was grafted to the surface of SWCNTs-COOH and MWCNTs-COOH successfully by FTIR,the study employed HP-β-CD-SWCNTs and HP-β-CD-MWCNTs to noncovalently bind FMN for the purpose of obtaining HP-β-CD-SWCNTsFMN and HP-β-CD-MWCNTs-FMN.The samples were characterized by laser particle size analysis,XRD,SEM.The release behavior of HP-β-CD-SWCNTs-FMN and HP-β-CD-MWCNTs-FMN was investigated.The results indicated that the entrapment efficiency and loading capacity of HP-β-CD-SWCNTs-FMN were(88.66 ± 3.13)% and(8.43 ± 1.11)% respectively.The entrapment efficiency and loading capacity of HP-β-CD-SWCNTs-FMN were(50.60 ± 1.92)% and(7.20 ± 0.98)% respectively.The research on drug release kinetics demonstrated that the release behavior of HP-β-CD-SWCNTs-FMN and HP-β-CD-MWCNTsFMN had p H-sensitive property.3)The in vitro cytotoxicity studies of FMN,FMN-MWCNTs-COOH,HP-β-CD-SWCNTs-FMN and HP-β-CD-MWCNTs-FMN were performed using WST-1 assay.AO/EB staining method was adopted to verify whether these complexes could cause cell apoptosis and observe the shape of apoptotic cells.The detection of reactive oxygen species(ROS)and mitochondrial membrane potential was utilized to investigated the proportion of cell apoptosis.The results suggested that HP-β-CD-SWCNTs-FMN and HP-β-CD-MWCNTs-FMN had stronger inhibition toward specific tumor cells than FMN and FMN-MWCNTsCOOH in the same conditions.The results of AO/EB staining showed that FMN,FMN-MWCNTs-COOH,HP-β-CD-SWCNTs-FMN and HP-β-CD-MWCNTs-FMN could induce apoptosis in Hela cells through ROS-mediated mitochondrial dysfunction pathway.The above results indicated that cyclodextrin functionalized carbon nanotubes were a good sustained-release drug delivery system.Compared with unmodified carbon nanotubes,their water dispersibility was improved and the anti-tumor activity was increased.Therefor,cyclodextrin-functionalized carbon nanotubes were promising drug carriers.