Study On The Bone Marrow Targeted Cytarabine Polybutyl-cyanoacrylate Nanoparticles

Bone marrow is the biggest haematogenous organ as well as an important immunity organ in human body. Most drugs which are ordinarily prepared have difficulties to enter bone marrow because of the influence of marrow-blood barrier (MBB), which results in many difficulties in the diagnoses and therapy of some diseases relating to bone marrow. Especially in the treatment of Leukemia, in order to inhibit the regeneration of abnormal leucocytes, drugs of high-dose are usually used to achieve the efficient concentration in bone marrow, which enhances the incidence rate of the adverse reactions. So how to increase the distribution in bone marrow, enhance the treat effect, decrease the side and adverse effect employing pharmaceutics methods becomes the striking issue for most pharmacists.In this study, Cytarabine(Ara-C) was taken as the model drug and loaded by Butyl-cyanoacrylate (BCA) to prepare Cytarabine Polybutylcyanoacrylate Nanoparticles (Ara-C-PBCA-NP) having characteristics of targeting to bone marrow in order to enhance the anti-leukemia effect and reduce the toxicity of Ara-C. The formulation and preparation technology of Ara-C-PBCA-NP colloidal solution and its lyophilization injection were systematically studied, and the release kinetics in vitro, characteristics of distribution and pharmacokinetics in vivo were examined. All aspects of Ara-C-PBCA-NP were investigated in detail and systematically, including the formulation and preparation process, physical and chemical properties of Ara-C-PBCA-NP colloidal disperse system and lyophilization injection release kinetics in vitro, distribution and pharmacokinetics in vivo etc..The particle size, particle distribution, associating ratio(AR) and drug loading(DL) were employed as criterions to evaluate the influence of different preparation technology, pH, concentration of Ara-C, BCA, Poloxamer 188, additives, etc.. On the properties of Ara-C-PBCA-NP by single-factor trial and the main influence factors were taken out. As a result, the ratio of Ara-C and BC A amount, the concentration of Poloxamer 188 and pH were proved to have great effects on the properties of Ara-C-PBCA-NP. Orthogonal design was applied to optimize the formulation and preparation technology. The particle size of Ara-C-PBCA-NP after optimization was 56nm, and the associating ratio and drug loading were 53.38±0.85 % and 11.77±0.17% respectively which was significantly better than other reported Ara-C colloidal particulate preparations.The formulation of Ara-C-PBCA-NP lyophilization injection was established based on the criterions of its appearance, color and dispersing properties. Ara-C-PBCA-NP was freeze-dried with 4% mannitose as supporting agents, as a result, the problem that the colloidal solution has poor physical and chemical stabilities and is difficult to disperse in water was resolved. The stability of Ara-C-PBCA-NP was not affected by the lyophilization process with nearly unchanged particle size, associating ratio, drug loading, pH etc.. The stability of Ara-C-PBCA-NP lyophilization injection was examined using the quality criterions such as particle size, associating ratio, drug loading, pH etc., and the results showed that Ara-C-PBCA-NP lyophilization injection was stable within three months at least. The release trail in vitro was investigated and the results showed that the Ara-C-PBCA-NP solution and its lyophilization injection have similar release kinetics and both releasing curves could be well explained by biexponential equation. Both preparations had sustained-release character.The distribution and pharmacokinetics of Ara-C-PBCA-NP lyophilization and Ara-C solution after i.v. administration in mice were studied. The pharmacokinetical characteristic of Ara-C-PBCA-NP in vivo is significantly different from Ara-C solution. Using the Ara-C solution as reference, the targeting characteristics ofAra-C-PBCA-NP lyophilization injection was evaluated. The peak concentration of Ara-C in bone marrow was increased by 1.56 fold and its AUC (AUQ) was increased by 8.93 fold. The overall drug targeting efficiency (Tec) was increased from 3.75% to 22.87%. The overall weighted-average drug targeting efficiency (TeQ) was increased from 6.75% to 30.73%. Meanwhile TeQ in other organs was decreased except liver. Conclusion could be drawn that Ara-C-PBCA-NP lyophilization injection could greatly increase the distribution of Ara-C in bone marrow which met the requirement of clinical application.In the kinetics study in rabbit, the concentration-time curves of Ara-C-PBCA-NP lyophilization injection and Ara-C solution after i.v. administration was examined by the RP-HPLC. Program 3p87 was applied to calculate pharmacokinetic parameters and chose the best compartment model. The results showed that both preparations' pharmacokinetics process were conformed to the two-compartment model. Statistic test showed that there was significant difference between \\nfi > MRT and CL of Ara-C-PBCA-NP lyophilization injection and Ara-C solution. In contrast to Ara-C solution, ti/2 fi -. MRT of Ara-C-PBCA-NP lyophilization injection were markedly longer, and CL was significantly reduced, as a result, the circulating time of the drug in blood was markedly prolonged which helped to increase the drug concentration in bone marrow so as to enhance its anti-leukemia effect.To sum up, the results of this study revealed that Ara-C-PBCA-NP using Poly-butylcyanoacrylate as loading material could be easily prepared and lyophilization injection resolved such problems as the poor stability and dispersing ability of Ara-C colloid solution. Ara-C-PBCA-NP lyophilization injection has changed the distribution and pharmacokinetics process of animals in vivo. The lyophilization injection could significantly increase the drug level in the targeting organ-bone marrow. Hence the treatment effect was greatly enhanced and the side effect of Ara-C was markedly decreased. Ara-C-PBCA-NP lyophilization injection was an effective strategy for delivering drugs to bone marrow and offered anoriginal method and a new dosage form for the treatment of leukemia using chemical medicines.Currently, there has been no report about bone marrow targeted nanoparticles using Ara-C as model drug in the world, so this study make great complements for bone marrow-targeted drug delivery system and will definitely propel the clinic application of bone marrow-targeted drug delivery system.