Electrospun polyester nanofibers modified with cyclodextrin polymer
Cyclodextrins (CDs) are cyclic (R-1,4)-linked
oligosacharides that consist of 6 (α- CD), 7 (β-CD) or 8 (γ-CD) glucopyranose
subunits. They present a characteristic cage-like structure which allows to
host molecules that present an appropriate dimension and polarity (Figure 1). In fact, the
supramolecular structure posses an hydrophilic external surface and a
hydrophophic cavity which make cyclodextrins useful to dissolve non-polar
compounds in polar environments. The non-polar compounds form inclusion
complexes with the cyclodextrin cavities involving non-covalent bonds which
makes this interaction reversible.
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| Figure 1. Chemical and conformation structures of γ-CD |
The dimensions of cyclodextrins are
defined in terms of outer diameter, cavity diameter, height of torus and cavity
volume (Figure 2). These dimensions depend directly on the number of glucopyranose
subunits and mark the type of analytes that are able to enter in the cavity to
form an inclusion complex.
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| Figure 2. Dimensions of α- CD, β-CD and γ-CD |
The use of cyclodextrins to extract
phenantrene from aqueous solutions has been proposed by researchers from the
university of Bilken at Ankara (Turkey) (1). The high water solubility of
cyclodextrins, which can be a problem in the extraction procedure, is avoided
by their immobilization by physic interactions in electrospun polyester (PET)
nanofibers disposed in the form of a mat. Prior to their immobilization, cyclodextrins
are polymerized in the presence of PET nanofibers using citric acid as
cross-linker. The final material is characterized by a great variety of
techniques such as scanning electron microscopy, X-ray spectroscopy and
thermogravimetrical analysis.
Nanofibers modified with
cyclodextrin shows a better interaction with phenanthrene that bare fibers.
Among the synthesized fibers, those based on α- cyclodextrin present a higher
host capacity. This aspect is specially interesting considering that the molecular
volume of phenathrene results to be 168.48 Å3 (data obtained from www.chemspider.com) which is very close to the cavity volume of α- cyclodextrin
(174 Å3). This aspect shows a clear relationship between the host and
guest volumes.
Although this article does not
describe a typical microextraction application, we encourage our readers to
give a closer view to the manuscript. In the original manuscript you will find
the optimized synthetic procedure as well as the complete characterization of
the material.
Reference:
(1) Surface modification of
electrospun polyester nanofibers with cyclodextrin polymer for the removal of
phenanthrene from aqueous solution. Link to the article
Thanks for your post. Quick question - what are the dimensions of the cyclodextrin 'buckets' at the bottom part of the cavity? For molecules, this dimension may not be a factor, but I am designing an experiment where we would be dropping sub-nano sized oil droplets into the cyclodextrins. Thus, I need the constraining dimension of the smaller side (the bottom of the bucket). If you know of a published paper that I can cite, that would be great. Thanks for your time.
ReplyDeleteSorry to reply to my own post, but I found said article. If anyone has any experience or comments on the idea of putting oil droplets inside CD's, I'd be very happy to hear from you.
ReplyDeleteThe article is from ACS: Saenger W, et. al.; Structures of the Common Cyclodextrins and Their Larger Analogues-Beyond the Doughnut. Chem Rev. 1998 Jul 30;98(5):1787-1802. Pubmed ID: 11848949
Thank you so much for your comment and sorry for the delay on the response. Finally, you found the reference.
ReplyDeleteSub-nano sized oil droplets and cyclodextrins: That sounds very interesting