Preparation And Application Of Drug Carriers With Smart Response Properties

ObjectiveThe stimuli-responsive drug carriers have wide application prospects in biomedicine,drug delivery,disease diagnosis and treatment due to their high bioavailability,low toxic side effects on normal cells,targeted delivery in pathological sites and good biocompatibility.The difference between pathological microenvironment and normal environment makes these drug carriers can be applied to drug delivery systems.The drug carriers are usually responded actively to low pH,high concentration of glutathione and trypsin.The stimulation-responsive drug carriers can promote the release of drug at pathological positions due to the internal stimuli of pathological positions and it can avoid toxic side effects of drugs on normal cells in healthy tissue environments.Drug delivery system can improve the efficacy and safety of the drug,prolong the action time of drug in pathological sites,give priority to enrichment in pathological sites,and overcome the drawbacks of drug non-specific targeting.In this paper,edaravone-loaded CaCO₃ composite microspheres and DOX-loaded BSA-TP composite nanospheres were prepared by in situ encapsulation.These composite particles could be used as the stimuli-responsive delivery system because of their stimulus response characteristics of internal factors.MethodsEgg white protein could be used as a template for preparing CaCO₃composite microspheres loaded with Edaravone（Eda@CaCO₃-EW MSs）.Bovine serum albumin（BSA）and green tea polyphenol（TP）were used to prepare the nanocarriers loaded with doxorubicin（DOX）.These nanocarriers were further modified with folate,briefly named as DOX@BSA-TP-FA NSs.The samples morphology was characterized by scanning electron microscopy（SEM）and transmission electron microscopy（TEM）.The composition of samples was identified by Fourier transform infrared spectroscopy（FTIR）with the KBr disk method.Laser confocal scanning microscopy（CLSM）was used to study the effects of composite particles on cells under different conditions.In the presence of microenvironment stimulus,the composite particles exhibited smart responsive and great control release abilityas in vitro release study and MTT experiments.Results（1）The Eda@CaCO₃-EW MSs composite microspheres had good dispersity and the single microsphere was composed of numerous nanospheres,the diameter of products ranged from 7 to 10μm.The DOX@BSA-TP-FA NSs had good dispersity,with average size of about 220 nm in diameter.（2）The drug loading efficiency and drug loading content of Eda@CaCO₃-EW MSs were 89.4%and 19.2%,respectively;The drug loading efficiency and drug loading content of DOX@BSA-TP-FA NSs were 86.4%and23.5wt%,respectively.（3）According to Fourier transform infrared spectroscopy（FTIR）,thermogravimetric data（TG）and high performance liquid chromatography（HPLC）,it confirmed the successful synthesis of the Eda@CaCO₃-EW MSs;according to Fourier transform infrared spectroscopy and UV-vis spectrophotometer,DOX was successfully encapsulated in nanospheres.（4）At pH=7.4,a small amount of edaravone was released from Eda@CaCO₃-EW MSs（5.4%）within 9 h,at pH=5.0,the release amount of edaravone increased to 94.4%within 6 h.（5）In vitro release study of DOX released from DOX@BSA-TP-FA NSs was showed that the accumulated release of DOX@BSA-TP-FA NSs was only12.7%in 0.01 mmol GSH at pH=7.4;the DOX release rate was close to 61.4%in 10 mmol GSH at pH=7.4;the release amount of DOX from DOX@BSA-TP-FA NSs increased to 85.5%when the cell cultured with 10mmol GSH+0.04 mmol trypsin buffer solutions at pH=7.4.（6）MTT experiments showed that the Eda@CaCO₃-EW MSs could protect and promote proliferation and differentiation of osteoblasts under stimulation of H₂O₂（800μmol/L）at pH=5.0.（7）MTT results showed that these DOX@BSA-TP-FA NSs showed higher cytotoxicity than free DOX,DOX@BSA-TP-FA NSs had low cytotoxicity to normal cells and it could reduce cells injury induced by DOX.Conclusions（1）The way of egg white protein used as a template for preparing CaCO₃composite microspheres loaded with edaravone（Eda@CaCO₃-EW MSs）used for potential minimally invasive treatment of osteomyelitis was feasible and effective.The Eda@CaCO₃-EW MSs could protect and promote proliferation and differentiation of osteoblasts under stimulation of H₂O₂ and lower pH.When pH=7.4,the Eda@CaCO₃-EW MSs were relatively stable and only a small amount of edaravone was released from composite microspheres.When pH=5.0,mineral part of the composite microspheres was used to neutralize the acidic environment,at the same time,edaravone encapsulated in CaCO₃microspheres was released to resist oxidative stress.（2）BSA and TP were used to prepare nanospheres loaded with DOX and modified with folate（DOX@BSA-TP-FA NSs）.The DOX@BSA-TP-FA NSs was very stable in 0.01 mmol GSH at pH=7.4;the DOX release rate was close to61.4%in 10 mmol GSH at pH=7.4;the release amount of DOX from DOX@BSA-TP-FA NSs increased more when the cell cultured with 10 mmol GSH+0.04 mmol trypsin buffer solutions at pH=7.4.In addition,the DOX@BSA-TP-FA NSs showed higher cytotoxicity than free DOX and it could reduce cells injury induced by DOX.