In-situ Nitrogen Oxygen Co-doping Preparation Of Chitosan-based Mesoporous Carbon And The Absorption & Release Characteristics Of Drugs

Mesoporous carbon material is a new type of non-silicon mesoporous material,which has the advantages of high specific surface area,large pore volume,adjustable pore size,and easy-to-modify surface extraordinary properties including high chemical inertiality,excellent electrical conductivity,good biocompatibility and other properties.Therefore,the kind of material has proven to be highly potential in biomedical applications.However,the synthesis process of mesoporous carbon has many complicated steps,high cost,environmental unfriendly,poor dispersibility and wettability,which limit its application in biomedical field.On the basis of traditional study,this study puts forward using chitosan as a new carbon and nitrogen precursor,soft template and double template coupled spray drying technology were used to prepare mesoporous carbon spheres with developed pore,adjustable pore size and good wettability.The structure-activity relationship among its structure,composition,wettability and drug adsorption and release was studied,the main research conclusions are as follows:1.The hydrophilicity of ordered mesoporous carbon CMK-3 was improved by nitrogen and oxygen co-doping to obtain nitrogen and oxygen functional groups.The results showed that the oxygen content of CMK-3 material treated with nitric acid oxidation and N doping increased from 3.21%to 17.9%,and the nitrogen content increased from zero to 5.28%.The specific surface area and pore volume of the modified mesoporous carbon material decreased,and the wettability test show that the wettability behaviors of NO-CMK-3 after nitrogen and oxygen co-doped modification improved,and the contact angle decreased from 161.9°to 138°,so that the hydrophilic of the mesoporous carbon material was improved to a certain extent compared with CMK-3 mesoporous carbon material.2.N-doped mesoporous carbon nanoparticles（NMC_S）were successfully prepared by using soft template method with chitosan and amphiphilic triblock copolymer（F127）by spray drying and direct carbonization technique.The results show that N-doped mesoporous carbon material were found with developed pores,and the nanoparticles have spherical morphology,the average diameter is about 300～400 nm,presented in a worm-like mesoporous construction.The pore size gradually increased in 3.05～6.09 nm intervals and the N content gradually decreased from6.324%to 3.020%with the increasing template dosage.The pore volume and specific surface area first increased and then decreased.When the mass ratio of chitosan and template agent F127 was 6:2,the specific surface area reached 868.9 m²/g,and the pore volume was 0.963 cm³/g.With the increasing nitrogen content,the contact angle decreased from 150.7°to 124.1°.Ammonium persulfate（APS）was further used to Oxidation modified the nitrogen-doped mesoporous carbon to improve the content of carboxyl and hydroxyl groups in mesoporous carbon,and the contact angle was reduced from 133.4°to 58.2°,and the wetting property was greatly improved.3.Nitrogen-oxygen co-doped mesoporous carbon nanoparticles（NMCs-x/3）were successfully prepared using chitosan/F127/TEOS dual template method with spray drying and direct carbonization technique.The effects of C/Si ratio on pore structure,nitrogen content and wetting property of mesoporous carbon materials were examined.Results show that mesoporous carbon materials were found with developed pores,the nanoparticles possessed spherical morphology,presented in a worm-like mesoporous construction,and the nitrogen content was 6.04～4.75%,mainly in the form of pyrrole nitrogen and pyridine nitrogen.The pore size of mesoporous carbon was mainly 2.01～3.65nm.When C/Si ratio was 7:3,the NMC-7/3 had the largest S_BET（2061.6 m²/g）and V_Mes（0.77 cm³/g）.The contact angle was lower than 20°.Therefore,mesoporous carbon materials possessed good hydrophilicity and wettability.4.The adsorption and release properties of the insoluble antitumor drug hydroxycamptothecin（HCPT）were studied by using the prepared materials,results show that the adsorption of HCPT by CMK-3 and NO-CMK-3 was consistent with the Freundlich model,the maximum drug absorption was 811.11 mg/g and 805.93mg/g.The adsorption capacity of NMCs and O-NMCS was 766.97 mg/g and 757.20mg/g.The nitrogen oxygen co-doped mesoporous carbon materials prepared by chitosan double template method had good adsorption capacity for HCPT,which was consistent with Langmuir model.The adsorption capacity of HCPT was up to 1013.51mg·/g.The absorption capacity of NMCs-x towards HCPT is in the following orders:NMCs-5/3>NMCs-6/3>NMCs-7/3>NMCs-8/3,which is consistent with the order of N content on the material surface.5.Mesoporous carbon had a unique structure of nanopores,which can significantly improve the release rate of hydroxy camptothecin.The release rate in 12h for pure drug HCPT,CMK-3,NO-CMK-3,NMCs,O-NMCs was 22.7%,76.43%,72.66%,83.40%,81.11%and 86.67%respectively.The drug release rate is closely related to hydrophilicity,pore volume,specific surface area of mesoporous carbon materials and pH value the released solution,and the drug release rate was more slowly in an acidic environment.6.Therefore,the advantages of the mesoporous carbon materials prepared by using chitosan as C-N source possesses the advantages of simple synthesis,friendly preparation process,controllable specific surface area,pore volume and pore size,and better dispersibility and wettability.Its spherical morphology and nano size are favorable to anti-tumor drug carriers with higher loading for HCPT drugs,and effective control of drug release,suggesting its great potential when used as drug delivery carrier.