The study of MePEG content and chain density on MePEG-PLGA-NP surface with 1H-NMR method / 中国药学杂志

ABSTRACT

OBJECTIVE: 1H-NMR (Nuclear Magnetic Resonance Method) was used to quantitatively determine the MePEG (me-thoxy polyethylene glycol) content and chain density on MePEG-PLGA-NP surface, and study the influences of MePEG molecular weights and proportion on the chemical and physical properties of MePEG-PLGA-NP surface. METHODS: MePEG-PLGA-NP were prepared by self-emulsion solvent diffusion method with methoxy polyethylene glycol-poly(lactic acid-hydroxyl acid) copolymer (Me-PEG-PLGA) as the carriers. And the particle average size and Zeta potential were characterized. 1H-NMR method were used to ascertain the composition of the MePEG-PLGA copolymer and determine the MePEG content and chain density on the MePEG-PLGA-NP surface, and compared with colorimetric assay. RESULTS: The composition of MePEG-PLGA copolymer are basically the same with the labelled amount. When the Molecular weight is at the same, along with the increase of proportion of MePEG, the average size of MePEG-PLGA-NP decrease, the absolute value of the Zeta potential also decrease gradually, MePEG content on particles surface (α) increase gradually, the MePEG chain density on nanoparticles surface (δ) increase gradually, the distance between two adjacent MePEG chains on the surface of the particles (D) decrease; When there is the same proportions, with MePEG chain length increases, nanoparticles are not significantly different on the particle average size and the Zeta potential, whereas α increase gradually, the δ decreases, and D increases; Theavalue of the same MePEG-PLGA-NP determined by colorimetric assay is higher than which is determined by 1H-NMR. CONCLUSION: 1H-NMR method can be used to quantitatively determine the MePEG content and chain density on MePEG-PLGA-NP surface; Compared with the traditional method, the results determined by 1H-NMR method are more accurate. With the experimental limits, MePEG molecular weighs and proportion have influences on the chemical and physical properties of MePEG-PLGA NP surface, such as mean size, Zeta potential and the MePEG content and chain density on nanoparticles surface. Copyright 2012 by the Chinese Pharmaceutical Association.