Preparation And Performance Study Of Cyclophosphamide-loaded Magnetic Chitosan Microspheres

Anti-cancer drugs usually injure normal healthy cells while killing cancer cellsdue to their non-specificity, which produces serious side effects to the human bodyduring clinical chemotherapy. Therefore, Targeted therapy has become a hot area ofresearch in the anti-cancer therapy. Magnetic targeted drugs delivery system is anovel drug delivery system in recent years, which could be selectively localized to thetarget site of tumor tissue under the action of external magnetic field and then obtain astable drug release to pathological position, thus have the advantages of highefficiency, sensitivity and low toxicity. Among then, Magnetic polymer microspheresare the most studied and frequently used delivery system. In this work, thedrug-loaded magnetic polymer microspheres were prepared by the cross-linkingemulsion method based on extensive biocompatible and biodegradable chitosan,anti-cancer drug cyclophosphamide （CTX） and magnetic nanoparticles Fe₃O₄, and theproperties of magnetic polymer microspheres was studied systematically. Primaryresults have been obtained as follows：1) The Fe₃O₄nanoparticles were synthesized through chemical co-precipitationmethod with ammonia water as precipitator. Experimental results showed that theobtained Fe₃O₄nanoparticles were finely dispersed with an average particle sizebetween50-80nm. The characteristic infrared absorption peak of Fe₃O₄was detectedat586.91cm^-1.the saturation magnetization of Fe₃O₄was about69.14emu/g, andnanoparticles possessed prominent release effect．2) The cyclophosphamide-loaded magnetic chitosan microspheres were preparedby the cross-linking emulsion method, and an orthogonal experiment design andstatistical analysis were adopted to study the effects of several factors in preparationon encapsulation efficiency and drug loading. The sequence of the four factors onencapsulation efficiency was below: chitosan concentration﹥Oil/water volume ratio﹥drug content﹥stirring rate; The sequence on drug loading was below: drug content﹥chitosan concentration﹥stirring rate﹥Oil/water volume;The optimal processeswere as follows：the chitosan concentration was2%, Oil/water volume ratio was4:1, drug content was1:3（w/w）, stirring rate was500r/min, thus the encapsulationefficiency and drug loading reached52.27%and11.05%respectively. The preparedchitosan microspheres were spherical, uniform and monodispersed with a meandiameter1325.6nm. The saturation magnetization of magnetic chitosan microsphereswas about10.96emu/g with remanence and coercivity was almost zero. The surfacereactive amino group content of microspheres was386μmol/g．3)The in vitro cyclophosphamide release studies from the magnetic chitosanmicrospheres were performed by HPLC method through dynamic dialysis technologyin different release media. Results showed the cyclophosphamide release frommagnetic chitosan microspheres followed a biphasic pattern character with an initialrapid release process, and a slowly sustained release phase subsequently. Thecyclophosphamide release obeyed the ambiexponent model equation, Q%=71.9760－35.7890exp（-0.097t）－34.7883exp（-0.0909t） and its determination coefficient R²wasabove0.9832.4) The magnetic chitosan microspheres did not cause hemolysis in vitro, and noobvious change existed in blood routine examination before and after injecting intoexperimental animals, which shows excellent blood compatibility; Subcutaneousimplant test of magnetic chitosan microspheres indicated favourable tissuecompatibility; MTT assay demonstrated different concentration of magnetic chitosanmicrospheres leach liquor had a good compatibility with cells.