Study On Loading 5-fluorouracil PH Responsive Dendrimer Nanoparticles

Malignant tumor is the most common disease and the frequently encountered disease to threaten human healthy. Antitumor drug delivery directly to the tumor position has already become the hot spot of research. pH responsive dendrimer nanocarrier was designed in this article and 5-fluorouracil was selected as the model drug to prepare 5-fluorouracil nanoparticles, Characteristics and regularities of 5-FU nanoparticles in vitro and in vivo were determined. The main contents were described in details as follows.1.Synthesis of pH responsive dendrimer nanocarrierFirst, polyamidoamine (PAMAM) dendrimers of the fourth generation were synthesized with the diversity method. Polyethylene glycol methyl ether₇₅₀ (mPEG₇₅₀) and poly(N,N-diethylaminoethyl mathacrylate) (pDEA)were used to modify the amine on the PAMAM surface with PAMAM dendrimer as the core. As a result, mPEG-PAMAM-pDEA-dendrimer (PPD-D) was obtained.2.Characteristics of PAMAM dendrimer and PPD-DThe microstructure of PAMAM and PPD-D, such as particle size and charge was determined. The apparent particle size of PAMAM and PPD-D was both <50 nm and the surface Zeta potential was 18.9mV and 15.2mV, respectively. The dynamic light scattering showed that as the surface of PPD-D was covered with the pH-sensitive materials-pDEA chain, it had pH sensitivity.3.Preparation and characteristics of 5-FU nanoparticles5-FU nanoparticles (5-FU-NP) were prepared and the techniques and formulation screening was made.The formulation was optimized with the encapsulation efficiency and drug loading as the evaluation index. pH sensitivity of 5-FU-NP was also proved. The results showed that the apparent particle size of 5-FU-NP was about 40-70nm in different PBS buffer, and the surface Zeta potential was 15.0 mV.4.Physical stability of 5-FU-NPPhysical stability was investigated with heating, centrifugation (<10000rpm) and storing at -4℃.The results indicated that 5-FU-NP could aggregate, precipitate and the content of 5-FU also decreased when 5-FU-NP were heated. However, 5-FU-NP were stable to a great extent with high speed centrifugation (<10000rpm). Content of 5-FU didn't decrease at -4℃for one month. Nanoparticles of high concentration (>5mg/mL) could redisperse easily and the content of 5-FU did not change obviously.5. In vitro release Profiles of 5-FU-NPIn vitro release experiments of 5-FU and 5-FU-NP was carried out with the dialysis method to simulatie the environment in vivo. 5-FU released from the PPD-D were obtained by a dissolution test in different phosphate buffer solution (pH6.5 and pH 7.4 PBS release medium, respectively). The results demonstrated that the release behaviors of 5-FU in PBS (pH6.5, pH7.4) in vitro were uniform fundamentally. However, the release behaviors of 5-FU-NP in weak acid environment (pH6.5) released fast and slowly in the neutral environment.It certificated that 5-FU-NP had good pH sensibility.6.Pharmacokinetics and tissue distribution of 5-FU-NPAfter iv administration to normal Kunming mice, 5-FU-NP were eliminated quickly from blood circulation to major tissue (liver, kidney). The distribution t_1/2 and elimination t_1/2 were 9.62 and 100.93 min, respectively. 5-FU-NP was eliminated in vivo within 8h. The Kunming mice models with Hepatoma (H22) were established. After iv administration to tumor-beared Kunming mice, 5-FU nanoparticles were distributed quickly from blood circulation to tumor, distribution t_1/2 and elimination t_1/2 in mice were 9.50 and 72.5min, respectively. The content of 5-FU in tuomr accounted for 24% of the total dosage within 0.5h after administration and the rest of 5-FU distributed in all the other tissues (liver, kidney, heart, etc.). It demonstrated that 5-FU-NP had obvious tumor targeting.7.Pharmacodynamics experiments of 5-FU nanoparticles in Hepatoma (H22) tumor-bearing Kunming mice.After iv administration of Hepatoma (H22) tumor to Kunming mice for 7 days successively and the evaluation index was the body weight and tumor volume. The results showed that the blank carrier group and the negative control group had no difference. It demonstrated that PPD-D carriers group didn't have toxicity. The tumor inhibition ratio of 5-FU-NP and 5-FU was 93% and 82%, respectively (p<0.05). It proved that 5-FU-NP decreased the toxicity of 5-FU, and increased the tumor targeting. Moreover, therapeutic effects was elevated. pH responsive dendrimer nanocarrier was synthesized and the antitumor drug -5-FU was encapsulated in this article. 5-FU nanoparticles were prepared of nano-size, pH responsive and long circulation. It demonstrated that this dosage form could load drug with high efficiency, decrease toxicity of 5-FU and target to tumor directly.