Nanoparticles Based on Chitosan Derivatives - Advances in Biomaterials Science and Biomedical Applications - page 247

gastrointestinal (GI) epithelium was more efficient than that produced by non-modified TMC
nanoparticles. However, alginate modification barely had any effect on the trans-epithelial
electrical resistance or on paracellular protein transport. Then the hypothesis was made that
alginate modification facilitated nanoparticle transport across the Caco-2 monolayer by the
transcellular route (transcytosis) by virtue of a reduction of particle size to 100-200 nm (16).
The supposedly permeated nanoparticles were assayed by measuring the fluorescence of
fluorescein-labelled BSA, which was assumed to be completely associated with the particles.
Similar nanoparticles as the above were loaded with urease, a vaccine protein against
Helicobacter pylori infection. Immunization studies in mice showed that oral administration of
urease-loaded TMC nanoparticles generated high titers of both IgG and S-IgA antibodies. The
immunostimulating effect was caused by nanoparticle mucoadhesivity and transcytosis by M
cells in gut associated lymphoid tissue [16].

OVA-loaded nanoparticles have been prepared from TMC using unmethylated CpG DNA as
adjuvant and crosslinker, in place of TPP, for nasal vaccination in mice [15]. TMC/CpG/OVA
showed similar physical properties as TMC/TPP/OVA in terms of particle size, zeta-potential
and antigen release characteristics, but TMC/CpG/OVA induced a 10-fold higher IgG2a
response than TMC/TPP/OVA, and a strong humoral and Th1 type cellular immune responses
after nasal vaccination [15].

Nanoparticles derived from the polyelectrolytic complexation of TMC by the polyanionic
mono- N -carboxymethyl chitosan (MCC), and loaded with fluorescein-labelled BSA were
taken up into mouse Balb/c monocyte macrophages. Mice were nasally immunized with
tetanus toxoid-loaded TMC/MCC complex nanoparticles. These were shown to induce both
mucosal and systemic immune response [24].

Insulin was formulated into nanoparticles formed from quaternized chitosans such as TMC
or DEMC via either ionotropic gelation with TPP, or polyelectrolyte complexation by the
polyanionic insulin. The PEC method resulted in higher insulin loading efficiency and
nanoparticle zeta-potential [31].

Similar nanoparticulate systems loaded with insulin were prepared from other quaternized
chitosans, namely, N- triethyl chitosan (TEC) and N -dimethylethyl chitosan (DMEC), by the
PEC method [30]. Insulin was transported ex vivo across the colon membrane of rats when it
was formulated into nanoparticles made of quaternized derivatives, better than into those
made of plain chitosan. In vivo colon absorption of insulin was enhanced by using insulin-
loaded nanoparticles compared to free insulin. Insulin absorption from rat colon was evaluated
by its hypoglycemic effect [30].

Poly(γ-glutamic acid) was used by Mi et al. [25] as the anionic polyelectrolyte complexing
agent to prepare nanoparticles from TMC by the PEC method, for the oral delivery of insulin.
According to the authors insulin was transported across the Caco-2 cell in vitro model of GI
epithelium via the paracellular route. In fact, CLSM confirmed the opening of the tight
junctions between cells caused by the nanoparticles. The authors propose a mechanism
whereby the orally administered nanoparticles with mucoadhesive TMC on their surfaces may
adhere and infiltrate into the intestinal mucus, mediate the opening of tight junctions between