Synthesis of Porous Microparticles with Aligned Porosity

Zhang, Haifei; Edgar, David; Murray, Patricia; Rak-Raszewska, Aleksandra; Glennon‐Alty, Laurence; Cooper, Andrew I.

doi:10.1002/adfm.200701309

Cited by 47 publications

(31 citation statements)

References 26 publications

(26 reference statements)

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“…As the freezing progresses a polymer concentration gradient, as well as a temperature gradient establish across the moving freezing front. This leads to macroscopic instabilities due to which the moving freezing front collapses, leaving behind pockets of unfrozen concentrated polymer solution [21,22]. Further, due to the relatively high temperature T prep , the freezing rate is slow so that the growing solvent crystals can be encapsulated in the concentrated solution and cannot grow further.…”

Section: Porosity Formationmentioning

confidence: 97%

“…This motivated us to investigate the possibility of formation of macroporous organogels with a regular structure. The preparation of aligned porous materials with micrometer-sized pores is of particular importance for applications such as tissue engineering, microfluidics, and organic electronics [21,22]. Here, we report that macroporous organogel networks based on butyl rubber with an aligned pore structure could be prepared in cyclohexane at relatively high subzero temperatures, i.e., at À2 C. The solution crosslinking reactions of PIB were carried out in cyclohexane at a polymer concentration of 5 w/v%.…”

Section: Introductionmentioning

confidence: 98%

See 1 more Smart Citation

Tough organogels based on polyisobutylene with aligned porous structures

Dogu

Okay

2008

Polymer

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Section: Porosity Formationmentioning

confidence: 97%

Section: Introductionmentioning

confidence: 98%

Tough organogels based on polyisobutylene with aligned porous structures

Dogu

Okay

2008

Polymer

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“…There was no evidence of toxicity over a total culture period of 7 days. 119 In other studies, freeze drying of emulsions was investigated to produce organic nanoparticles. An organic dye Oil Red (OR) was dissolved in the oil droplet phase of a W/O emulsion with a PVA solution as an aqueous continuous phase.…”

Section: Microparticles and Nanoparticlesmentioning

confidence: 99%

“…11(B)). 119 The aligned porous microparticles could be collected easily by dissolving the composite material in water and then filtering (Fig. 11(C)).…”

Section: Microparticles and Nanoparticlesmentioning

confidence: 99%

Controlled freezing and freeze drying: a versatile route for porous and micro-/nano-structured materials

Qian

Zhang

2010

J. Chem. Technol. Biotechnol.

411

282

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Freeze drying is a process whereby solutions are frozen in a cold bath and then the frozen solvents are removed via sublimation under vacuum, leading to formation of porous structures. Pore size, pore volume and pore morphology are dependent on variables such as freeze temperature, solution concentration, nature of solvent and solute, and the control of the freeze direction. Aqueous solutions, organic solutions, colloidal suspensions, and supercritical CO 2 solutions have been investigated to produce a wide range of porous and particulate structures. Emulsions have recently been employed in the freeze drying process, which can exert a systematic control on pore morphology and pore volume and can also lead to the preparation of organic micro-and nano-particles. Spray freezing and directional freezing have been developed to form porous particles and aligned porous materials. This review describes the principles, latest progress and applications of materials prepared by controlled freezing and freeze drying. First of all the basics of freeze drying and the theory of freezing are discussed. Then the materials fabricated by controlled freezing and freeze drying are reviewed based on their morphologies: porous structures, microwires and nanowires, and microparticles and nanoparticles. The review concludes with new developments in this area and a brief look into the future.

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“…Water molecules were frozen first, so PU NPs were excluded by ice crystal and stacked with the direction of ice crystal growth to produce the internal network-like structure. [35][36][37] Lowering the solid content could reduce the skin layer and induce the porosity on the surface because the solid content could affect the concentration of NPs on the surface of the microbeads. PU01 and PU02 had different intermolecular forces with water, which further affected the crystallization rate and produce different structure of ice crystal, and hence the structure of microspheres.…”

Section: Discussionmentioning

confidence: 99%

Fabrication of biodegradable polyurethane microspheres by a facile and green process

Lin

Hsu

2014

J. Biomed. Mater. Res.

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Two different compositions of water-based biodegradable polyurethane (PU) in the form of homogeneous nanoparticles (NPs) were synthesized using biodegradable polyesters as the soft segment. The first PU (PU01) was based on poly(ε-caprolactone) (PCL) diol and the second PU (PU02) was based on 40% PCL diol and 60% polyethylene butylene adipate diol. The PU NP dispersions with different solid contents were sprayed into liquid nitrogen and resuspended in water to generate elastic microspheres (50-60 µm) with different nanoporosities. In vitro degradation analysis revealed that microspheres of PU02 (i.e., PU02 MS) degraded faster than those of PU01 (PU01 MS). Methylene blue was encapsulated during microsphere formation and the release was investigated. Microspheres made from a lower content (10%) of PU02 dispersion (i.e., PU02 MS_10) showed a greater burst release of methylene blue in 6 h, whereas those made from a higher content (30%) of PU01 dispersion (i.e., PU01 MS_30) revealed a prolonged release with a significantly lower burst release. Biocompatibility evaluation using L929 fibroblasts demonstrated that cells were attached and proliferated on microspheres after 24 h. On the other hand, microspheres may further self-assemble into films and scaffolds. Surface modification of microspheres by chitosan may modify the self-assembly behavior of microspheres. Microspheres could be stacked to form scaffolds with different macroporosities. Fibroblasts were successfully seeded and grown in the microsphere-stacked scaffolds. We concluded that the biodegradable and elastic microspheres may be facilely produced from a green and sustainable process with potential applications in drug release and three-dimensional cell culture.

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Synthesis of Porous Microparticles with Aligned Porosity

Cited by 47 publications

References 26 publications

Tough organogels based on polyisobutylene with aligned porous structures

Tough organogels based on polyisobutylene with aligned porous structures

Controlled freezing and freeze drying: a versatile route for porous and micro-/nano-structured materials

Fabrication of biodegradable polyurethane microspheres by a facile and green process

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