Study On Doxorubicin Magnetic Thermosensitive Liposomes

The magnetic thermosensitive liposomes (MTSLs), capable oftemperature-triggered content released at the site of interest, can be ofgreat importance for therapy of tumors. In this paper, we mainly study theconditions of preparation technology, physicochemical property andpharmacodynamics of Doxorubicin magnetic thermosensitive liposomes(DOX-MTSLs) with magnetic thermosensitive liposomes as a carrier,Doxorubicin (DOX) as a model drug. We developed an optimizedtemperature sensitive liposomal system to be used with mild hyperthermia:highly stable as a drug storage at physiological temperature or with noalternative magnetic field, while a sharp gel-to-liquid phase transitiontemperature (T_m) of the bilayer in Alternative magnetic field (AMF), withsubsequent rapid release of entrapped compounds such as a kind of drugsto reach the tumor-targeted, multiple and impulse effective.In this sduty, we adopt the follwing methods, Doxorubicin magneticthermosensitive liposomes encapsulated with Doxorubicin (DOX) werepreparedwith1,2-dipalmitoyl-sn-glycero-3-phosphocholine(DPPC),1-myristoyl-2-stearoyl-sn-glycero-3-phosphocholine(MSPC) and Cholesterol byreversed evaporation combined with (NH₄)₂SO₄-gradient method. Theoptimum formula was selected according to the entrapment efficiency,thermosensitivity and magnetism. The entrapment efficiency wasdetermined by Mini-column centrifugation-RP-HPLC method. The Fe₃O₄concentration was measured by O-phenanthroline method. Thetransformation temperature was determined by differential scanningcaliorimetric (DSC). The particle size and Zeta electric potential weremeasured by transmission electron microscopy (TEM) and the laserscattering particle size distribution analyzer. The in vitro release behavior of DOX-MTSLs at different temperatures and different time points werestudied by dialyzer in constant temperature water and simulated therelease regression equation at (41±0.5)℃. The heating effect ofDOX-MTSLs was determined in the high alternation magnetic field(AMF). The inhibition ratios of MCF-7 with free drug-DOX andDOX-MTSLs were measured by MTT.The results showed that the optimum recipe preparation ofDOX-MTSLs was founded on DOX/DPPC of 1:20(w/w),DPPC/Ch of4:1(mol/mol),the concentration of magnetic fluid 15 mg·mL^-1 , pH valueof 7.4, with preparation temperature of 45℃,the volume of water tooil(W/O) of 1:3, incubation temperature of 60℃for 30 min. The averageentrapment efficiency of three batches ofDOX-MTSLs(100416,100507,100517, self-preparation) were(82.77±0.88)%, (83.03±1.38)% and (80.68±0.42)% (n=3), the drug contentwas (2.03±0.02) mg·mL^-1 and the final concentration of encapsulated Fe3O4was (3.19±0.05) mg·mL^-1．The phase -transition temperature (T_m) was40.03℃specially. The average particle size of DOX-MTSLs were(177.1±20.5) nm (n=3), and the polydispersity index (PDI) was 0.700,Zeta degree is (-30.6±2.1) mv. When the temperature increased from 25℃to 37℃, the in vitro drug release was very slow and incomplete (15.45%and 19.54%) even up to 10h. However, at the Phase transition temperature(Tm) 41℃, the in vitro drug release significantly reached 90.99% within 2hand continued to release. The release of DOX from the DOX-MTSLs wasshown to be temperature dependent and the in vitro release model wasfitting the kinetic equation of Higuchi at (41±0.5)℃, with a gel-to-liquidphase-transition temperature suitable for mild hyperthermia(41～43℃).The heating temperature and balanceable temperature DOX-MTSLs (Fe₃O₄3.19 mg·mL^-1) were respectively raised to 39.9℃in 10min and to 56.7℃in 40 min in high Alternative magnetic field of 80KHZ and current 12A.The inhibition ratios of MCF-7 in groups of free drug-DOX in different concerntrations(10.0, 5.0, 2.5, 1.0, 0.5μg·mL-1) were (88.55±.0.71)%,(86.19±1.37)%, (73.84±1.86)% , (32.13±1.94)% and (8.74±0.99)%(n=3);the inhibition ratios of MCF-7 in groups of DOX-MTSLs in differentconcerntrations(10.0, 5.0, 2.5, 1.0, 0.5μg·mL-1) were (89.61±0.69)%,(87.49±0.65)%, (76.33±1.70)%, (40.72±1.04)% and (30.85±0.36)%respectively(n=3)。In summary, our study indicated that under the optimized conditionsthe small DOX-MTSLs with high entrapment efficiency, goodthermosensitivity and perfect magnetic susceptibility could be obtained.Compared to the free drug-DOX, the DOX-MTSLs had the higherinhibition ratios of MCF-7 and increased much more drug concentraion intumor cells. The prepared DOX-MTSLs were reached the expectations inthis research.