Nano-micellar Composite Hydrogel Loaded Zinc Phthalocyanine For Photodynamic Anticancer Research

Zn phthalocyanine?Zn Pc?is a highly effective second-generation photosensitizer with good photophysical and photochemical properties,and can be used for photodynamic therapy of cancer.However,due to the?-?interaction between conjugated molecules,Zn Pc has poor solubility and strong crystallization tendency,which prevents its direct use.This article used a drug delivery system-nanomicelle composite hydrogel to encapsulate the Zn Pc.On the one hand,nanomicelles can significantly enhance the solubility and permeability of Zn Pc;on the other hand,the hydrogel keeps the Zn Pc at the tumor site for a long time,reducing the harmful diffusion caused by the drug dilution effect.In this paper,the preparation,properties,photodynamic properties and cytotoxicity of drug-loaded nano-mixed micelles and drug-loaded nano-micelle composite hydrogels were investigated.Ultrasound injection combined with dialysis was used to prepare drug-loaded mixed micelles.The optimal formula for drug-loaded mixed micelles was 1 m L N,N-dimethylformamide?DMF?,15/20/30 mg sodium deoxycholate?SDC?,and 50 mg D-alpha tocopheryl polyethylene glycol succinate?TPGS?.The morphologies correspond to spherical,short rods and long rods shape,respectively.The particle size were about 106 nm,344 nm and 80 nm,respectively.Taking drug-loaded nanomicelles as the core,a drug-loaded nanomicelle composite hydrogel with F127 as the gel matrix was prepared by“cold method”.The optimized formula was 18%F127,and the concentration of spherical micelles was 1.5 mg/m L.The stability of the drug-loaded micelles was investigated using an ultraviolet spectrophotometer and a particle size analyzer.The results confirmed that the absorption curves and particle sizes of the three mixed micelles did not change significantly,indicating that the mixed micelles had good stability.The Zeta potential of the micelles was measured with a particle size analyzer.The range of the Zeta potential of the three mixed micelles was-?7.61?17.65?m V.It confirmed that the shell composed of the PEG chain of TPGS would prevent the mixed micelles from further aggregation or fusion.Using ultraviolet to measure the encapsulation rate,drug loading and drug release,the results showed that the encapsulation rate was higher than 90%,and the drug loading was higher than 14%,which was higher than the currently reported results;the drug release results proved that three mixed micelles had the characteristics of slow drug release,and the drug-loaded nanomicelle composite hydrogel had slower drug release than the drug loaded micelles.A rheometer was used to determine the rheological properties of drug-loaded nanomicelle composite hydrogels.The results showed that the phase transition temperature and gel time were 28.3±0.3?and 30.8±3.2 s,respectively.The shear thinning behavior exhibited can be beneficial to the diffusion of Zn Pc in the target area,and the good thixotropy can help to adapt to the deformation of the human body.The photodynamic properties of drug-loaded nanomicelles and drug-loaded nanomicelles composite hydrogels were determined by ultraviolet/fluorescence spectrophotometer.The singlet oxygen quantum yields??73(_?35?)of drug-loaded mixed micelles were 0.85±0.01,0.74±0.03 and 0.90±0.01,corresponding to about 1.51 times,1.32 times and 1.61 times of free Zn Pc(?37?_?35??28?.056),respectively.The fluorescence quantum yields of the three micelles were 0.10±0.04,0.19±0.10,and 0.08±0.02,respectively.This range of values may allow drug-loaded nanomicelles to be used for diagnostic imaging and image-guided therapy.These mixed micelles were photostable in the timescale typically used in photodynamic therapy,and only a small photobleaching event was observed after 20 minutes of light irradiation.Because hydrogel matrix can reduce the rotation and intermolecular collision of the Zn Pc molecules,leading to the enhancement of fluorescence intensity and ¹O₂generation.The nanomicelle composite hydrogel only observed a small photobleaching event after 20 minutes of irradiation.The experimental results proved that the nanomicelle composite hydrogel can significantly improve the photodynamic properties of Zn Pc.Human lung cancer cell A549 cells were selected as the model,and the cytotoxicity of drug-loaded nano-mixed micelles and drug-loaded nano-micelles composite hydrogels was investigated by MTT method.The results showed that the cytotoxicity of drug-loaded mixed micelles was significantly stronger than that of free Zn Pc,and the IC₅₀of spherical micelles was lower than that of rod micelles,which may be related to its mechanism of action.After 20 minutes of irradiation,the cell viability of cells treated with drug-loaded nanomicelle composite hydrogel was significantly reduced,which was due to the faster rate of singlet oxygen generation per unit time of drug-loaded nanomicelle composite hydrogel.This result proved that the nanomicelle composite hydrogel can be used as the dominant carrier of Zn Pc.