In-Situ Formation of Biodegradable Hydrogels by Stereocomplexation of PEG-(PLLA)8 and PEG-(PDLA)8 Star Block Copolymers
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- 作者：Christine Hiemstra ; Zhiyuan Zhong ; Liangbin Li ; Pieter J. Dijkstra ; Jan Feijen
- 刊名：Biomacromolecules
- 出版年：2006
- 出版时间：October 2006
- 年：2006
- 卷：7
- 期：10
- 页码：2790 - 2795
- 全文大小：172K
- 年卷期：v.7,no.10(October 2006)
- ISSN：1526-4602
文摘
Eight-arm poly(ethylene glycol)-poly(<FONT SIZE="-1">L-lactide), PEG-(PLLA)8, and poly(ethylene glycol)-poly(D-lactide), PEG-(PDLA)8, star block copolymers were synthesized by ring-opening polymerization of either L-lactide or D-lactideat room temperature in the presence of a single-site ethylzinc complex and 8-arm PEG (Mn = 21.8 × 103 or 43.5× 103) as a catalyst and initiator, respectively. High lactide conversions (>95%) and well-defined copolymerswith PLLA or PDLA blocks of the desired molecular weights were obtained. Star block copolymers were water-soluble when the number of lactyl units per poly(lactide) (PLA) block did not exceed 14 and 17 for PEG21800-(PLA)8 and PEG43500-(PLA)8, respectively. PEG-(PLA)8 stereocomplexed hydrogels were prepared by mixingaqueous solutions with equimolar amounts of PEG-(PLLA)8 and PEG-(PDLA)8 in a polymer concentrationrange of 5-25 w/v % for PEG21800-(PLA)8 star block copolymers and of 6-8 w/v % for PEG43500-(PLA)8star block copolymers. The gelation is driven by stereocomplexation of the PLLA and PDLA blocks, as confirmedby wide-angle X-ray scattering experiments. The stereocomplexed hydrogels were stable in a range from 10 to70 
f">C, depending on their aqueous concentration and the PLA block length. Stereocomplexed hydrogels at 10w/v % polymer concentration showed larger hydrophilic and hydrophobic domains as compared to 10 w/v %single enantiomer solutions, as determined by cryo-TEM. Correspondingly, dynamic light scattering showed that1 w/v % solutions containing both PEG-(PLLA)8 and PEG-(PDLA)8 have larger "micelles" as compared to 1w/v % single enantiomer solutions. With increasing polymer concentration and PLLA and PDLA block length,the storage modulus of the stereocomplexed hydrogels increases and the gelation time decreases. Stereocomplexedhydrogels with high storage moduli (up to 14 kPa) could be obtained at 37 f">C in PBS. These stereocomplexedhydrogels are promising for use in biomedical applications, including drug delivery and tissue engineering, becausethey are biodegradable and the in-situ formation allows for easy immobilization of drugs and cells.
f">C, depending on their aqueous concentration and the PLA block length. Stereocomplexed hydrogels at 10w/v % polymer concentration showed larger hydrophilic and hydrophobic domains as compared to 10 w/v %single enantiomer solutions, as determined by cryo-TEM. Correspondingly, dynamic light scattering showed that1 w/v % solutions containing both PEG-(PLLA)8 and PEG-(PDLA)8 have larger "micelles" as compared to 1w/v % single enantiomer solutions. With increasing polymer concentration and PLLA and PDLA block length,the storage modulus of the stereocomplexed hydrogels increases and the gelation time decreases. Stereocomplexedhydrogels with high storage moduli (up to 14 kPa) could be obtained at 37 f">C in PBS. These stereocomplexedhydrogels are promising for use in biomedical applications, including drug delivery and tissue engineering, becausethey are biodegradable and the in-situ formation allows for easy immobilization of drugs and cells.