mechanical strength, stability, and chemical adjustability based on polymers. On
account of these outstanding advantages, CD polymers have already attracted more
and more attention.
In this chapter, the latest progresses in the construction of CD polymers and their
applications in medical biology will be reviewed. And we hope it can provide
inspiration for the constructions and functions of new supramolecular polymers
based on CDs.
19.2 Linear CD Polymers
Linear CD polymers are the most widely used and most researched type of CD
polymers all over the world. Researchers generally constructed CD polymers using
covalent linkages, copolymerization, host-guest interactions, and so on. Therefore,
linear CD polymers, which have characteristics of easy modification, good biocompatibility, multifunction, and water-solubility, have a good application in the field of
medical biology.
19.2.1 CD Covalently Linked to the Polymers
CD is a kind of macrocyclic host that is easy to be modified, especially the hydroxyl
groups of CDs located on C6. Therefore, numerous CD derivatives have been
synthesized since their discovery [14]. Among these compounds, some CD derivatives have functional groups that can be polymerized. On the other hand, a portion of
CD derivatives can react with the side chains of the polymers. Therefore, researchers
have built a variety of polymers in which CD was covalently grafted onto the
polymer chains by using those CD derivatives. Typically, CDs are on the side
chain of the polymer. Only in a small portion of the polymers, CDs are on the
backbone of the polymers. The CD polymers obtained by the method described
above not only have the characteristics of linear polymers but also can utilize the
cavities of CDs to encapsulate a plurality of compounds. The combination of linear
polymers and CD chemistry makes the linear CD polymers be useful in drug
delivery, cancer therapy, photodynamic therapy, biomaterials, and so on.
One type of linear CD polymers is that CDs are on the side chain of the polymer.
Previously, our group reported CD-modified hyaluronic acid (HA-CD) which is
obtained by amide condensation reaction between the amino groups of CD derivatives and the carboxyl group of the hyaluronic acid located on side chains (Fig. 2a)
[15]. Hyaluronic acid (HA), a water-soluble, biocompatible, and biodegradable
polysaccharide, has been used as a targeting agent and delivery vehicle in many
drug-delivery systems [16, 17], which can realize targeted recognition of cancer cells
that overexpress HA receptors on the cancer cell surface [18–20]. Such CD polymer
(HA-CD), which combined the advantages of CD and HA, not only maintains the
targeting of cancer cells from HA but also can utilize the cavity of CD to encapsulate
adamantane or other groups. Additionally, HA-CD has been used as building blocks
for constructing multifunctional biomaterials. In this work, we constructed a series of
19 Construction and Applications of Cyclodextrin Polymers in Biology
539
account of these outstanding advantages, CD polymers have already attracted more
and more attention.
In this chapter, the latest progresses in the construction of CD polymers and their
applications in medical biology will be reviewed. And we hope it can provide
inspiration for the constructions and functions of new supramolecular polymers
based on CDs.
19.2 Linear CD Polymers
Linear CD polymers are the most widely used and most researched type of CD
polymers all over the world. Researchers generally constructed CD polymers using
covalent linkages, copolymerization, host-guest interactions, and so on. Therefore,
linear CD polymers, which have characteristics of easy modification, good biocompatibility, multifunction, and water-solubility, have a good application in the field of
medical biology.
19.2.1 CD Covalently Linked to the Polymers
CD is a kind of macrocyclic host that is easy to be modified, especially the hydroxyl
groups of CDs located on C6. Therefore, numerous CD derivatives have been
synthesized since their discovery [14]. Among these compounds, some CD derivatives have functional groups that can be polymerized. On the other hand, a portion of
CD derivatives can react with the side chains of the polymers. Therefore, researchers
have built a variety of polymers in which CD was covalently grafted onto the
polymer chains by using those CD derivatives. Typically, CDs are on the side
chain of the polymer. Only in a small portion of the polymers, CDs are on the
backbone of the polymers. The CD polymers obtained by the method described
above not only have the characteristics of linear polymers but also can utilize the
cavities of CDs to encapsulate a plurality of compounds. The combination of linear
polymers and CD chemistry makes the linear CD polymers be useful in drug
delivery, cancer therapy, photodynamic therapy, biomaterials, and so on.
One type of linear CD polymers is that CDs are on the side chain of the polymer.
Previously, our group reported CD-modified hyaluronic acid (HA-CD) which is
obtained by amide condensation reaction between the amino groups of CD derivatives and the carboxyl group of the hyaluronic acid located on side chains (Fig. 2a)
[15]. Hyaluronic acid (HA), a water-soluble, biocompatible, and biodegradable
polysaccharide, has been used as a targeting agent and delivery vehicle in many
drug-delivery systems [16, 17], which can realize targeted recognition of cancer cells
that overexpress HA receptors on the cancer cell surface [18–20]. Such CD polymer
(HA-CD), which combined the advantages of CD and HA, not only maintains the
targeting of cancer cells from HA but also can utilize the cavity of CD to encapsulate
adamantane or other groups. Additionally, HA-CD has been used as building blocks
for constructing multifunctional biomaterials. In this work, we constructed a series of
19 Construction and Applications of Cyclodextrin Polymers in Biology
539