Preliminary study of a biodegradable seed: 32P-chromic phosphate-poly (L-lactide) on its biodegradation, pharmacokinetics of 32P nanoparticles after intratumor implantation

Objectives ³²P-chromic phosphate-poly(L-lactide) (³²P-CP-PLLA), with PLLA as the framework for ³²P-CP nanoparticles, is a new biodegradable seed. The objective of this study was to investigate its ultra-structure, pharmacokinetics of ³²P-CP nanoparticles in tumor models.

Methods ³²P-CP-PLLA seeds (seeds group, SG) and ³²P-CP colloids (colloids group, CG), with radioactivity of 18.5MBq, were implanted to the tumor core (HepG-2, Balb/c nu/nu). The stool and urine were collected and radioactivity was counted. Sequential planar images were acquired and region of interest (ROI) was drawn over the tumor. Semiquantitative and quantititative analysis (%ID/g) of the distribution of 32P were made. Ultra-structural changes of seeds were observed by the scanning electron microscope.

Results The maximal %ID/g of the liver, spleen and bone were (1.13±0.04), (0.91±0.02), (1.51±0.04) respectively in SG and higher than that in CG (P<0.05). The ³²P, evacuated in the stool and urine reach 2.57 %, 0.39% in SG and 8.21 %, 1.24% in CG (4 weeks). The radioactivity in tumor decreased to 86.2 %(SG) and 73.8 %(CG) on the 28^th day on images. The effective half-life of ³²P in the tumor was about 12.5d(SG) and 9.8d(CG). ³²P-CP nanoparticles were dispersed uniformly in seeds. Micropores and tunnels were demonstrated to increase and communicate.

Conclusions As a biodegradable seed, ³²P-CP-PLLA may hold promise and warrant further development as a new focal drug delivery carrier of ³²P-CP nanoparticle for tumor therapy.

Research Support Funded by Nation natural science (30670588)