Preparation and characterization of structured hydrogel microparticles based on cross-linked hyperbranched polyglycerol

Marion H.M. Oudshoorn, Roel Penterman, Robert Rissmann, Joke A. Bouwstra, Dirk J. Broer, Wim E. Hennink

    Research output: Contribution to journalArticleAcademicpeer-review

    43 Citations (Scopus)

    Abstract

    The aim of this work was to obtain well-defined HyPG-MA (methacrylated hyperbranched polyglycerol) microparticles with uniform sizes. Therefore, three different preparation methods were evaluated. First, we assessed a micromolding technique using rigid SU-8 (a photoresist based on epoxies) grids. Independent of the surface treatment of the SU-8 grid or the type of polymer used, approximately 50% of the microgels remained attached to the SU-8 grid or broke into smaller particles during the release process in which drying of the gels was followed by a sonication process. Although 90% methacrylate conversion could be obtained, this method has some additional drawbacks as the obtained dried microgels did not rehydrate completely after the drying step. Second, a soft micromolding technique was evaluated using elastomeric PDMS (poly(dimethyl siloxane)) grids. The use of these flexible grids resulted in a high yield (80-90% yield; >90% methacrylate conversion) of microgels with a well-defined size and shape (squares 100 μm × 100 μm × 50 μm or hexagons with Ø 30 μm and a thickness of 20 μm) without the occurrence of water evaporation. However, a number of particles showed a less-defined shape as not all grids could be filled well. The microgels showed restricted swelling, implying that these gels are dimensionally stable. Third, an alternative method referred to as photolithography was evaluated. This method was suitable to tailor accurately the size and shape of HyPG-MA microgels and additionally gained 100% yield. Well-defined HyPG-MA microgels in the size range of 200-1400 μm (thickness of 6, 20, or 50 μm), with a methacrylate conversion of >90%, could easily be prepared by adding an inhibitor (e.g., 1% (w/v) of vitamin C) to the polymer solution to inhibit dark polymerization. Microgels in the size range of 30-100 μm (>90% conversion) could only be obtained when applying the photomask in direct contact with the polymer solution and using a higher (i.e., 2% (w/v)) concentration of vitamin C. Additionally, the microgels showed limited swelling, indicating that rather dimensionally stable particles were obtained. In conclusion, this paper shows that photolithography and soft micromolding, as compared to rigid micromolding, are the most appropriate techniques to fabricate structured HyPG-MA microgels with a tailorable and well-defined size and shape. These microgels have great potential in tissue engineering and drug delivery applications.

    Original languageEnglish
    Pages (from-to)11819-11825
    Number of pages7
    JournalLangmuir
    Volume23
    Issue number23
    DOIs
    Publication statusPublished - 6 Nov 2007

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    Methacrylates
    Hydrogel
    Vitamins
    microparticles
    Photolithography
    Polymer solutions
    Hydrogels
    Swelling
    Drying
    Gels
    grids
    Photomasks
    preparation
    Ascorbic Acid
    Sonication
    Bioelectric potentials
    Photoresists
    Drug delivery
    Tissue engineering
    Siloxanes

    Cite this

    Oudshoorn, M. H. M., Penterman, R., Rissmann, R., Bouwstra, J. A., Broer, D. J., & Hennink, W. E. (2007). Preparation and characterization of structured hydrogel microparticles based on cross-linked hyperbranched polyglycerol. Langmuir, 23(23), 11819-11825. https://doi.org/10.1021/la701910d
    Oudshoorn, Marion H.M. ; Penterman, Roel ; Rissmann, Robert ; Bouwstra, Joke A. ; Broer, Dirk J. ; Hennink, Wim E. / Preparation and characterization of structured hydrogel microparticles based on cross-linked hyperbranched polyglycerol. In: Langmuir. 2007 ; Vol. 23, No. 23. pp. 11819-11825.
    @article{ac77cc7a5bf941dcb8bf30f84c1c4c30,
    title = "Preparation and characterization of structured hydrogel microparticles based on cross-linked hyperbranched polyglycerol",
    abstract = "The aim of this work was to obtain well-defined HyPG-MA (methacrylated hyperbranched polyglycerol) microparticles with uniform sizes. Therefore, three different preparation methods were evaluated. First, we assessed a micromolding technique using rigid SU-8 (a photoresist based on epoxies) grids. Independent of the surface treatment of the SU-8 grid or the type of polymer used, approximately 50{\%} of the microgels remained attached to the SU-8 grid or broke into smaller particles during the release process in which drying of the gels was followed by a sonication process. Although 90{\%} methacrylate conversion could be obtained, this method has some additional drawbacks as the obtained dried microgels did not rehydrate completely after the drying step. Second, a soft micromolding technique was evaluated using elastomeric PDMS (poly(dimethyl siloxane)) grids. The use of these flexible grids resulted in a high yield (80-90{\%} yield; >90{\%} methacrylate conversion) of microgels with a well-defined size and shape (squares 100 μm × 100 μm × 50 μm or hexagons with {\O} 30 μm and a thickness of 20 μm) without the occurrence of water evaporation. However, a number of particles showed a less-defined shape as not all grids could be filled well. The microgels showed restricted swelling, implying that these gels are dimensionally stable. Third, an alternative method referred to as photolithography was evaluated. This method was suitable to tailor accurately the size and shape of HyPG-MA microgels and additionally gained 100{\%} yield. Well-defined HyPG-MA microgels in the size range of 200-1400 μm (thickness of 6, 20, or 50 μm), with a methacrylate conversion of >90{\%}, could easily be prepared by adding an inhibitor (e.g., 1{\%} (w/v) of vitamin C) to the polymer solution to inhibit dark polymerization. Microgels in the size range of 30-100 μm (>90{\%} conversion) could only be obtained when applying the photomask in direct contact with the polymer solution and using a higher (i.e., 2{\%} (w/v)) concentration of vitamin C. Additionally, the microgels showed limited swelling, indicating that rather dimensionally stable particles were obtained. In conclusion, this paper shows that photolithography and soft micromolding, as compared to rigid micromolding, are the most appropriate techniques to fabricate structured HyPG-MA microgels with a tailorable and well-defined size and shape. These microgels have great potential in tissue engineering and drug delivery applications.",
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    Oudshoorn, MHM, Penterman, R, Rissmann, R, Bouwstra, JA, Broer, DJ & Hennink, WE 2007, 'Preparation and characterization of structured hydrogel microparticles based on cross-linked hyperbranched polyglycerol', Langmuir, vol. 23, no. 23, pp. 11819-11825. https://doi.org/10.1021/la701910d

    Preparation and characterization of structured hydrogel microparticles based on cross-linked hyperbranched polyglycerol. / Oudshoorn, Marion H.M.; Penterman, Roel; Rissmann, Robert; Bouwstra, Joke A.; Broer, Dirk J.; Hennink, Wim E.

    In: Langmuir, Vol. 23, No. 23, 06.11.2007, p. 11819-11825.

    Research output: Contribution to journalArticleAcademicpeer-review

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    AU - Oudshoorn, Marion H.M.

    AU - Penterman, Roel

    AU - Rissmann, Robert

    AU - Bouwstra, Joke A.

    AU - Broer, Dirk J.

    AU - Hennink, Wim E.

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    AB - The aim of this work was to obtain well-defined HyPG-MA (methacrylated hyperbranched polyglycerol) microparticles with uniform sizes. Therefore, three different preparation methods were evaluated. First, we assessed a micromolding technique using rigid SU-8 (a photoresist based on epoxies) grids. Independent of the surface treatment of the SU-8 grid or the type of polymer used, approximately 50% of the microgels remained attached to the SU-8 grid or broke into smaller particles during the release process in which drying of the gels was followed by a sonication process. Although 90% methacrylate conversion could be obtained, this method has some additional drawbacks as the obtained dried microgels did not rehydrate completely after the drying step. Second, a soft micromolding technique was evaluated using elastomeric PDMS (poly(dimethyl siloxane)) grids. The use of these flexible grids resulted in a high yield (80-90% yield; >90% methacrylate conversion) of microgels with a well-defined size and shape (squares 100 μm × 100 μm × 50 μm or hexagons with Ø 30 μm and a thickness of 20 μm) without the occurrence of water evaporation. However, a number of particles showed a less-defined shape as not all grids could be filled well. The microgels showed restricted swelling, implying that these gels are dimensionally stable. Third, an alternative method referred to as photolithography was evaluated. This method was suitable to tailor accurately the size and shape of HyPG-MA microgels and additionally gained 100% yield. Well-defined HyPG-MA microgels in the size range of 200-1400 μm (thickness of 6, 20, or 50 μm), with a methacrylate conversion of >90%, could easily be prepared by adding an inhibitor (e.g., 1% (w/v) of vitamin C) to the polymer solution to inhibit dark polymerization. Microgels in the size range of 30-100 μm (>90% conversion) could only be obtained when applying the photomask in direct contact with the polymer solution and using a higher (i.e., 2% (w/v)) concentration of vitamin C. Additionally, the microgels showed limited swelling, indicating that rather dimensionally stable particles were obtained. In conclusion, this paper shows that photolithography and soft micromolding, as compared to rigid micromolding, are the most appropriate techniques to fabricate structured HyPG-MA microgels with a tailorable and well-defined size and shape. These microgels have great potential in tissue engineering and drug delivery applications.

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