## 5 Nanochitosan Synthesis Approaches
### Ionotropic Gelation  
Gelation is one of the common and modest methods for fabrication of chitosan nanoparticles. These nanoparticles can be formedby electrostatic interaction between amino group of chitosan and cross-linking agent (trippolphosphate; (TPP)). In this method, chitosan and cross-linking agent is dissolved separately in acetic acid and water respectively. Then, cross-linking agent is added further to chitosan solution (in the presence or absence of surfactants, i.e., Tween 80, Polyethylene glycol) to form nanoparticles under mechanical stirring (see Figure 3). In this case, the amount and type of surfactants (stabilizers) can control the size and surface charges of the nanoparticles formed [26].  
\begin{table}
\begin{tabular}{c c c c} \hline
**Morphology** & **The Role Chitosan Played** & **Preparation Method** & **Application** \\ \hline \multirow{8}{*}{Nanosphere} & Magnetic nanoparticle-loaded & \multirow{2}{*}{Covalent modification, self-assembly} & siRNA Delivery \\  & chitosan-deoxycholic acid nanodroplets & & \\ \cline{2-4}  & Smart pH-responsive nanocarrier & \multirow{2}{*}{Covalent modification/electrostatic adsorption} & Targeted delivery of unsolic acid \\ \cline{2-4}  & & Covalent adsorption & \\ \cline{2-4}  & \multirow{2}{*}{Thermoresponsivenessnospheres} & Covalent & \multirow{2}{*}{Release drug for the treatment of osteoarthritis} \\  & & & evaporation method & \\ \hline \multirow{8}{*}{Nano-particles} & Uniform core-shell nanoparticles & Ion crosslinking & Enhance oral delivery of insulin \\  & \multirow{2}{*}{\(N\)-trimethyl chitosan nanoparticles} & \multirow{2}{*}{Covalent modification/self-assembly} & Oral delivery to treat breast cancer \\ \cline{2-4}  & Chitosan-modified PLGA nanoparticles & Ion crosslinking & Tumor-targeted drug delivery \\ \cline{2-4}  & EGFR-targeted chitosan nanoparticles & Covalent modification/self-assembly & siRNA delivery \\ \cline{2-4}  & Indomethacin-conjugated chitosan & \multirow{2}{*}{Covalent modification/self-assembly} & Prodrug and tumor-targeted \\ \cline{2-4}  & oligosaccharides nanoparticle nanoparticle & \multirow{2}{*}{Covalent modification/self-assembly} & drug delivery \\ \hline \multirow{8}{*}{Inorganic nano-materials} & Viable smart targeted nanonevelope delivery system & \multirow{2}{*}{Covalent modification/semicon treatment} & Dox encapsulated and targeted therapy \\ \cline{1-1} \cline{2-4}  & Multifunctional magnetic nanoparticles & \multirow{2}{*}{Covalent modification/semicon treatment} & Thermo-Chemotherapy Intracellular Imaging \\ \cline{1-1} \cline{2-4}  & \multirow{2}{*}{Combinatorial nanocarrier} & Covalent modification/ion crosslinking & Drug delivery for breast cancer \\ \cline{1-1} \cline{2-4}  & Magnetic thymine-imprinted chitosan nanoparticles & \multirow{2}{*}{Physical adsorption} & Gene therapy \\ \cline{1-1} \cline{2-4}  & Functional hollow microspheres constructed from MOF shells & \multirow{2}{*}{Covalent modification/Physical adsorption} & Drug delivery and targeted \\ \cline{1-1} \cline{2-4}  & & & adsorption \\ \hline \end{tabular}
\end{table}
Table 1: _Cont._  
Figure 3: Ionotropic gelation technique.