6
Properties of Chitin and Chitosan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100
7
Limitations of Using Chitin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102
8
Chemical Modifications of Chitosan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102
8.1 Chitosan-g-PEG Copolymer [113] . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103
8.2 Chitosan-4-Thiol-Butylamidine [117] . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104
8.3 mPEG-Grafted Phthaloyl Chitosan [120] . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104
8.4 N-Maleated Chitosan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105
9
Importance of Engineering Chitosan-Based Nanoparticles, Nanospheres, and Nanogels 105
9.1 Chitosan-Based Nanoparticles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106
9.2 Chitosan-Based Nanospheres . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110
9.3 Chitosan-Based Nanogels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116
10 Biomedical Applications of Chitosan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120
11 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123
1 Introduction
The advent of nanotechnology has given tremendous impetus to the development of
polysaccharide-based nanomaterials. There are huge differences between the bulk
polysaccharides and nanopolysaccharides in every aspect. No vast amount of
research has yet been done on engineering of polysaccharides via nanotechnology.
This chapter will mainly deal with chitosan rather than other polysaccharides,
namely cellulose, starch, gelatin, alginate, pullulan, carrageenan, and pectin to
name a few. Chitin exists widely in cell walls of some microorganisms such as
fungi, molds, and yeasts [1] and in the cuticular and exoskeletons of invertebrates
such as crab, shrimp, prawn, lobster, squid pen and insects (for example, beetles) [2].
Chitosan exists naturally in only a few species of fungi. Chitosan, a fundamental
derivative of chitin, is composed of glucosamine and N-acetyl glucosamine units
[3–5]. Despite its abundant availability in nature, its exploitation is not very pronounced. Due to the presence of amino groups as well as hydroxyl groups, chitosan
can be easily tailored to synthesize different derivatives of interest [6]. Over the last
two decades, the studies on chitin and chitosan have intensified as a consequence of
their excellent biological properties such as being biodegradable in the human body,
biocompatibility, nontoxicity, immunological activity, antibacterial activity, and
wound-healing activity [7]. In recent studies, chitosan has been shown to be a very
good biomedical candidate for applications ranging from drug delivery to cell
delivery to gene delivery to wound healing [8–12]. But, the solubility of chitosan
has been a major constraint for its versatile application. Chitosan is not soluble in
conventional organic solvents; it is only soluble in acetic acid and a few inorganic
acids such as hydrochloric acid [13–15]. Therefore, it has been a major challenge to
improve the solubility of chitosan. It is believed that application of nanotechnology
to engineer chitosan may not only boost its solubility properties but also change its
material characteristics, which would be beneficial for further processing for its
commercialization in various products. This belief has led the chitin and chitosan
researchers not only to escalate fundamental research on chitosan but also to work
aggressively on applied research to develop chitosan-based nanoproducts by
88
J. Dutta
Properties of Chitin and Chitosan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100
7
Limitations of Using Chitin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102
8
Chemical Modifications of Chitosan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102
8.1 Chitosan-g-PEG Copolymer [113] . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103
8.2 Chitosan-4-Thiol-Butylamidine [117] . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104
8.3 mPEG-Grafted Phthaloyl Chitosan [120] . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104
8.4 N-Maleated Chitosan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105
9
Importance of Engineering Chitosan-Based Nanoparticles, Nanospheres, and Nanogels 105
9.1 Chitosan-Based Nanoparticles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106
9.2 Chitosan-Based Nanospheres . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110
9.3 Chitosan-Based Nanogels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116
10 Biomedical Applications of Chitosan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120
11 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123
1 Introduction
The advent of nanotechnology has given tremendous impetus to the development of
polysaccharide-based nanomaterials. There are huge differences between the bulk
polysaccharides and nanopolysaccharides in every aspect. No vast amount of
research has yet been done on engineering of polysaccharides via nanotechnology.
This chapter will mainly deal with chitosan rather than other polysaccharides,
namely cellulose, starch, gelatin, alginate, pullulan, carrageenan, and pectin to
name a few. Chitin exists widely in cell walls of some microorganisms such as
fungi, molds, and yeasts [1] and in the cuticular and exoskeletons of invertebrates
such as crab, shrimp, prawn, lobster, squid pen and insects (for example, beetles) [2].
Chitosan exists naturally in only a few species of fungi. Chitosan, a fundamental
derivative of chitin, is composed of glucosamine and N-acetyl glucosamine units
[3–5]. Despite its abundant availability in nature, its exploitation is not very pronounced. Due to the presence of amino groups as well as hydroxyl groups, chitosan
can be easily tailored to synthesize different derivatives of interest [6]. Over the last
two decades, the studies on chitin and chitosan have intensified as a consequence of
their excellent biological properties such as being biodegradable in the human body,
biocompatibility, nontoxicity, immunological activity, antibacterial activity, and
wound-healing activity [7]. In recent studies, chitosan has been shown to be a very
good biomedical candidate for applications ranging from drug delivery to cell
delivery to gene delivery to wound healing [8–12]. But, the solubility of chitosan
has been a major constraint for its versatile application. Chitosan is not soluble in
conventional organic solvents; it is only soluble in acetic acid and a few inorganic
acids such as hydrochloric acid [13–15]. Therefore, it has been a major challenge to
improve the solubility of chitosan. It is believed that application of nanotechnology
to engineer chitosan may not only boost its solubility properties but also change its
material characteristics, which would be beneficial for further processing for its
commercialization in various products. This belief has led the chitin and chitosan
researchers not only to escalate fundamental research on chitosan but also to work
aggressively on applied research to develop chitosan-based nanoproducts by
88
J. Dutta