Study On The Preparation And Properties Of Temozolomide Loaded On Polyethylene Glycol Modified Graphene Oxide Composite

Graphene oxide（GO）,a derivative of graphene,has many oxygen-containing functional groups such as hydroxyl group,carboxyl group,an epoxy group.GO has a unique two-dimensional structure,good hydrophilicity,and mechanical properties,high specific surface energy,so it has good adsorption for many chemicals,which make it be an ideal drug carrier.With the profound study of graphene oxide,people successively modified GO with polyethylene glycol（PEG）,iron tetroxide,folic acid,etc.to obtain functional graphene oxide which can load with insoluble drugs and form nanosuspension solution with good dispersion and slow release in water to target tumor sites and improve the treatment effect.Glioma is a kind of malignant tumor in the central nervous system,which is mainly treated by postoperative radiotherapy and chemotherapy.As radiotherapy may cause the recurrence of residual tumor cells,drug chemotherapy is the main auxiliary method of glioma treatment.Temozolomide（TMZ）is a kind of alkylating agent chemotherapeutic drug with strong pertinence,high specificity and remarkable curative effect,which is slightly soluble in water and insoluble in the organic phase.At present,the listed TMZ preparation can produce nausea,vomiting,hemolysis,allergy and other adverse reactions.To reduce the adverse reactions,TMZ liposomes has been prepared,but the entrapment rate is only about 30%,which has no practical application value.Therefore,to find new carriers to load TMZ,to improve the loading rate and efficacy,and to reduce side effects has become the current research hotspot.In this paper,firstly,polyethylene 2000,p-toluenesulfonyl chloride（Ts Cl）and ammonia are used as the raw materials to synthesize the diamino terminated polyethylene glycol（PEG（NH₂）₂）by esterification and Gabriel methods.The PEG（NH₂）₂ is characterized by Infrared spectrum（IR）,NMR hydrogen spectrum（¹H-NMR）,Ultraviolet-visible spectra（UV-Vis）,X-ray energy spectrum（XPS）and X-ray diffraction（XRD）.The synthesis conditions of PEG（NH₂）₂ are optimized by single factor and orthogonal experiments,and the yield of PEG（NH₂）₂ is 78.49%.Secondly,carboxy graphene oxide（NGO）is prepared with GO,Na OH,and chloroacetic acid as raw materials,and then NGO and PEG（NH₂）₂ is used to synthesize polyethylene glycol-modified graphene oxide（GO-PEG）composite by amidation reaction.Pegylated graphene oxide loaded temozolomide（GO-PEG-TMZ）is prepared by loading TMZ onto the composite.GO-PEG composite and GO-PEG-TMZ are characterized by SEM,IR,XRD,UV Vis,and XPS.The particle sizes of GO and GO-PEG are determined using dynamic light scattering（DLS）.The drug loading rate of GO-PEG is determined by HPLC,and the results show that when the carrier concentration is 0.10 mg/m L and the drug concentration is 0.70 mg/m L,the highest drug loading rate is 86.02%,and the drug loading is 80.76%.In vitro release of GO-PEG-TMZ is investigated the release behavior of TMZ API and preparation in two different p H phosphate buffer（PBS）.The results show that the cumulative release rate of both in PBS medium with p H=5.0 is higher and p H dependent,TMZ release rate is faster,and the cumulative release rate reaches the maximum value of 97.67%in 6 h.However,the cumulative release time of GO-PEG-TMZ reaches the maximum value of 71.12%after 12 h,which shows a certain slow release.At the same time,the release behavior of the GO-PEG-TMZ and TMZ are fitted to the kinetic model,which conform to the Ritger-Peppas equation model.Finally,the CCK-8 method is used to investigate the effects of GO-PEG,TMZ,and GO-PEG-TMZ on the growth of C6 cells.The results show that TMZ and GO-PEG-TMZ have significant inhibitory effects on glioma cells,and show a dependence on the administration time and dose,while the inhibition of GO-PEG composite is much weak.The IC₅₀ of TMZ and GO-PEG-TMZ experimental groups are significantly different from that of the GO-PEG experimental group（p<0.001）.To sum up,this research in the synthesis of PEG-modified graphene oxide has good stability,low cytotoxicity and high loading rate of TMZ.The novel TMZ preparation has a high cumulative release rate and a high lethality to C6 cells.This study provides a research basis for developing the preparation of GO composite loaded TMZ,improving the chemotherapy effect of TMZ and reducing toxic and side effects of TMZ.