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Effects of Stereoregularity of Multiblock Copoly( rac ‐lactide)s on Stereocomplex Microparticles and Their Insulin Delivery
Author(s) -
Hu Junli,
Tang Zhaohui,
Qiu Xueyu,
Han Yadong,
Du Qing,
Chen Xuesi,
Jing Xiabin
Publication year - 2005
Publication title -
macromolecular bioscience
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.924
H-Index - 105
eISSN - 1616-5195
pISSN - 1616-5187
DOI - 10.1002/mabi.200500157
Subject(s) - lactide , crystallinity , insulin , crystallization , copolymer , materials science , amphiphile , particle size , diffusion , micrometer , chemistry , chemical engineering , microparticle , polymer chemistry , polymer , composite material , organic chemistry , optics , physics , medicine , engineering , thermodynamics , endocrinology
Summary: Uniform stereocomplex microparticles ranging from nanometer to micrometer size are prepared by using stereo multiblock copoly( rac ‐lactide)s (smb‐PLAs) with different stereoregularity. At comparable molecular weights, as the smb‐PLA stereoregularity decreases from 88% to 76%, the crystallinity of the microparticles decreases noticeably, as proved by DSC and WAXD. At the same time, the shape of the microparticles varies from the flower shape to the sphere shape and the particle size increases markedly from 700–2700 nm as shown by SEM. However, all insulin‐loaded microparticles are of cake‐shape and their sizes depend on the stereoregularity. The crystallization of smb‐PLAs facilitated by insulin is evidenced by the increase of T m and Δ H f in DSC. The highest insulin‐loading content of 14.2% and ‐entrapment efficiency of 82.8% are obtained from the smb‐PLA with the highest stereoregularity of 88%. Release studies in vitro show the least first‐day release at about 25% followed by continuous release of another 70% of insulin over one month. Stereocomplex microparticles of smb‐PLAs with lower stereoregularity resulted in a relatively lower insulin‐entrapment efficiency and ‐loading content, a larger first‐day release, and also complete release of 90% of the total amount within one month. The release system follows a diffusion mechanism. By contrast, atactic PLA shows a very low entrapment efficiency of 16.7%.Structure of a stereo multiblock copoly( rac ‐lactide).