Further, the negatively charge nanospheres with a size less than 300 nm could
provide attractive forces for positively charged drugs. Since many anticancer
drugs are positively charged at physiological conditions, the nanospheres prepared
in this study are suitable for loading of these drugs. In another study, Choochottiros
et al. [120] showed that the surface charge of amphiphilic chitosan nanospheres was
negative, resulting in good dispersion at neutral to high pH, but significant precipitation at low pH.
Aiping et al. [163] demonstrated the synthesis of a novel biocompatible
N-succinyl chitosan (NSCS) with well-designed structure. NSCS can self-assembly
in regular nanospheres in distilled water. The NSCS nanospheres are obtained
spontaneously under very mild conditions without the need for high temperature,
organic solvent, surfactant, or special experimental technology. From X-ray diffraction analysis, it can be known that the crystal behavior of NSCS is weaker than
that of chitosan, which is due to the decrease in the intermolecular hydrogen
bonding. As a result, NSCS is easy to disperse in distilled water to obtain a stable
and transparent colloidal dispersion. TEM was used to check the morphology of the
colloid of NSCS and the result shows that NSCS colloids possess regular spherical
morphology. The size of the NSCS nanospheres was in the range of 50–100 nm.
The NSCS nanospheres have great potential to be used as a novel drug matrix for
controlled-release drug delivery.
In recent years, magnetic DDSs have received increasing attention from
researchers due to their ability to deliver drugs to the targeted site with the help of
an external magnetic field [164–167]. Current approaches to magnetic DDSs usually
contain three main steps. First, superparamagnetic nanoparticles are manufactured
and second the magnetic nanoparticles are dispersed in shell monomer or polymer.
Finally, the DDS is formed after polymerization of shell monomer or crosslinking of
shell polymer via chemical bonds. However, surfactants and organic solvents are
inevitably used during the synthesis, which brings potential toxicity to the
synthesized magnetic DDSs. Therefore, Wang et al. [168] adopted a facile method
for the synthesis of chitosan–(acrylic acid) magnetite nanospheres (CS–AA-Fe 3 O 4 ).
In this method, CS–AA-Fe 3 O 4 is formed in a completely aqueous system and no
surfactant is used. Moreover, the CS–AA polyelectrolyte complex was formed via
electrostatic interactions, rather than chemical bonds. The size of the CS–AA-Fe 3 O 4
nanosphere as determined by laser particle size analyzer was 130 nm before swelling
in PBS solution. After swelling, the hydrodynamic size of CS–AA-Fe 3 O 4 was
increased to 330 nm, which makes it potentially interesting as a DDS.
Of late, significant interest has been paid to hollow polymeric nanostructures
(HPNSs) because of the new functionalities and unique physiochemical properties
anticipated from polymeric materials at the nanoscale. The development of HPNSs
is reflected by the rapid increase in the number of scientific publications and patents
on this subject in recent years. HPNSs in the size range of 1–1,000 nm with
spherical or cylindrical geometries are of special interest. Spherical HPNSs generally include hollow polymeric nanospheres (HPNSPs), vesicles, or nanopolymersomes. Cylindrical HPNSs are basically polymeric nanotubes (PNTs). In view
of possible biomedical applications, HPNSPs are potentially useful as encapsulates
Engineering of Polysaccharides via Nanotechnology
113
provide attractive forces for positively charged drugs. Since many anticancer
drugs are positively charged at physiological conditions, the nanospheres prepared
in this study are suitable for loading of these drugs. In another study, Choochottiros
et al. [120] showed that the surface charge of amphiphilic chitosan nanospheres was
negative, resulting in good dispersion at neutral to high pH, but significant precipitation at low pH.
Aiping et al. [163] demonstrated the synthesis of a novel biocompatible
N-succinyl chitosan (NSCS) with well-designed structure. NSCS can self-assembly
in regular nanospheres in distilled water. The NSCS nanospheres are obtained
spontaneously under very mild conditions without the need for high temperature,
organic solvent, surfactant, or special experimental technology. From X-ray diffraction analysis, it can be known that the crystal behavior of NSCS is weaker than
that of chitosan, which is due to the decrease in the intermolecular hydrogen
bonding. As a result, NSCS is easy to disperse in distilled water to obtain a stable
and transparent colloidal dispersion. TEM was used to check the morphology of the
colloid of NSCS and the result shows that NSCS colloids possess regular spherical
morphology. The size of the NSCS nanospheres was in the range of 50–100 nm.
The NSCS nanospheres have great potential to be used as a novel drug matrix for
controlled-release drug delivery.
In recent years, magnetic DDSs have received increasing attention from
researchers due to their ability to deliver drugs to the targeted site with the help of
an external magnetic field [164–167]. Current approaches to magnetic DDSs usually
contain three main steps. First, superparamagnetic nanoparticles are manufactured
and second the magnetic nanoparticles are dispersed in shell monomer or polymer.
Finally, the DDS is formed after polymerization of shell monomer or crosslinking of
shell polymer via chemical bonds. However, surfactants and organic solvents are
inevitably used during the synthesis, which brings potential toxicity to the
synthesized magnetic DDSs. Therefore, Wang et al. [168] adopted a facile method
for the synthesis of chitosan–(acrylic acid) magnetite nanospheres (CS–AA-Fe 3 O 4 ).
In this method, CS–AA-Fe 3 O 4 is formed in a completely aqueous system and no
surfactant is used. Moreover, the CS–AA polyelectrolyte complex was formed via
electrostatic interactions, rather than chemical bonds. The size of the CS–AA-Fe 3 O 4
nanosphere as determined by laser particle size analyzer was 130 nm before swelling
in PBS solution. After swelling, the hydrodynamic size of CS–AA-Fe 3 O 4 was
increased to 330 nm, which makes it potentially interesting as a DDS.
Of late, significant interest has been paid to hollow polymeric nanostructures
(HPNSs) because of the new functionalities and unique physiochemical properties
anticipated from polymeric materials at the nanoscale. The development of HPNSs
is reflected by the rapid increase in the number of scientific publications and patents
on this subject in recent years. HPNSs in the size range of 1–1,000 nm with
spherical or cylindrical geometries are of special interest. Spherical HPNSs generally include hollow polymeric nanospheres (HPNSPs), vesicles, or nanopolymersomes. Cylindrical HPNSs are basically polymeric nanotubes (PNTs). In view
of possible biomedical applications, HPNSPs are potentially useful as encapsulates
Engineering of Polysaccharides via Nanotechnology
113