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Control of silk microsphere formation using polyethylene glycol (PEG)

Paper ID Volume ID Publish Year Pages File Format Full-Text
16 3 2016 13 PDF Available
Title
Control of silk microsphere formation using polyethylene glycol (PEG)
Abstract

A one step, rapid method to prepare silk microspheres was developed, with particle size controlled by the addition of polyethylene glycol (PEG). PEG molecular weight (4.0 K–20.0 KDa) and concentration (20–50 wt%), as well as silk concentration (5–20 wt%), were key factors that determined particle sizes varying in a range of 1–100 μm. Addition of methanol to the PEG-silk combinations increased the content of crystalline β-sheet in the silk microspheres. To track the distribution and degradation of silk microspheres in vivo, 3-mercaptopropionic acid (MPA)-coated CdTe quantum dots (QDs) were physically entrapped in the silk microspheres. QDs tightly bound to the β-sheet domains of silk via hydrophobic interactions, with over 96% of the loaded QDs remaining in the silk microspheres after exhaustive extraction. The fluorescence of QDs-incorporated silk microspheres less stable in cell culture medium than in phosphate buffer solution (PBS) and water. After subcutaneous injection in mice, microspheres prepared from 20% silk (approx. 30 μm diameter particles) still fluoresced at 24 h, while those prepared from 8% silk (approx. 4 μm diameter particles) and free QDs were not detectable, reflecting the QDs quenching and particle size effect on microsphere clearance in vivo. The larger microspheres were more resistant to cell internalization and degradation. Since PEG is an FDA-approved polymer, and silk is FDA approved for some medical devices, the methods developed in the present study will be useful in a variety of biomedical applications where simple, rapid and scalable preparation of silk microspheres is required.Statement of SignificanceThe work is of significance to the biomaterial and controlled release society because it provides a new option for fabricating silk microspheres in one simple step of mixing silk and polyethylene glycol (PEG), with the size and properties of microspheres controllable by PEG molecular weight as well as PEG and silk concentrations. Although fabrication of silk microspheres have been reported previously using spray-drying, liposome-templating, polyvinyl alcohol (PVA) emulsification, etc., applications were hindered due to harsh conditions (temperature, solvents, etc.) and complicated procedures used as well as low yield and less controllable particle size (usually <10 μm). Since PEG is an FDA-approved polymer, and silk is FDA approved for some medical devices, the methods developed in the present study will be useful in a variety of biomedical applications where simple, rapid and scalable preparation of silk microspheres is required.

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Keywords
Silk; Polyethylene glycol (PEG); Microspheres; Quantum dots (QDs)
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Publisher
Database: Elsevier - ScienceDirect
Journal: Acta Biomaterialia - Volume 39, 15 July 2016, Pages 156–168
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Bioengineering
Get Full-Text Now
Don't Miss Today's Special Offer
Price was $35.95
You save - $31
Price after discount Only $4.95
100% Money Back Guarantee
Full-text PDF Download
Online Support
Any Questions? feel free to contact us