Preparation And Characterization Of The Composite Hydrogel With Microspheres Loading Leptin And Vascular Endothelial Growth Factor

Objective:Combined radiation and wound injury（CRWI）often occurs in patients with maxillofacial malignancy after postoperative radiotherapy,which performs as cell necrosis,vascular occlusion,uncontrollable inflammation,prone to infection,and persistent refractory.The number of patients affected by oral and maxillofacial malignant tumors in China ranks among the top in the world,and due to the large number of CRWI patients caused by radiotherapy,it is a difficult clinical problem that needs to be solved urgently.In our previous studies,we found that leptin（LP）could regulate the inflammatory response in the early stage of skin flap tissue healing after ionizing radiation;vascular endothelial growth factor（VEGF）can accelerate CRWI healing by promoting local blood vessel formation in wounds;sodium alginate（SA）microsphere is widely used in local sustained-release drugs;pluronic hydrogel is often used as wound dressings due to its excellent temperature sensitivity.Therefore,this study intends to prepare a composite hydrogel with nanoparticle loading LP and VEGF based on the previous work,and test and evaluate its vitro character,so as to provide a new therapy for clinical treatment of CRWI.Methods:According to previous experiments,sodium alginate（SA）microspheres loading leptin（LP）and vascular endothelial growth factor（VEGF）were prepared by emulsification method,and LP-SA and VEGF-SA microspheres were incorporated into pluronic hydrogel to obtain the composite hydrogel with microspheres loading LP and VEGF.Scanning electron microscopy（SEM）was used to observe the microstructure of microspheres and hydrogels;enzyme linked immunosorbent assay（ELISA）was used to detect the encapsulation efficiency,the drug loading rate and in vitro release of LP and VEGF in microspheres;using the rotary rheometer to determine the phase transition temperature and phase transition time of the hydrogel.Results:1.The prepared composite hydrogel with microspheres loading LP and VEGF is translucent to the naked eye.Under SEM,the microspheres are spherical with an average particle size of about 450 nm;longitudinal section of pluronic hydrogel is lamellar,and the pores are interpenetrated with each other and the pore size is between 50-200μm;the microspheres are scattered and distributed in the loose and porous hydrogel.2.The encapsulation efficiency of LP is 48.01%,the drug loading rate is 1.80 x10^-4%,and the cumulative release time in vitro is 16 d with the release amount reaching 83.01%;the encapsulation efficiency of VEGF is 49.58%,the drug loading rate is 1.47 x 10^-4%,and the cumulative release time in vitro is 16 d with the release amount reaching 81.98%.3.The optimal concentration of pluronic hydrogels is 16%F127 and 2%F68.The phase transition time of the composite hydrogels with microspheres loading LP and VEGF is 8 s,and the phase transition temperature is 21.2℃.Conclusions:1.Successfully synthesized the composite hydrogel with sodium alginate sustained-release microspheres loading LP and VEGF.2.The sodium alginate sustained-release microspheres loading with LP and VEGF prepared in this experiment have regular shapes,smaller particle diameters,higher encapsulation efficiency,and better sustained-release effects;the composite hydrogels prepared with 16%F127 and 2%F68 pluronic solution has good temperature sensitivity and suitable phase transition time;sodium alginate sustained-release microspheres loading LP and VEGF are scattered in the pluronic hydrogels of 3D structure,so above all laid a good foundation for subsequent experiments.