Biomedical Engineering Reference
In-Depth Information
time [240]. LBL assembly chitosan-alginate microshells are also effective drug release car-
riers. The forming process of the microshell that uses the melamine formaldehyde as the
core and the loading-releasing behaviors for anticancer drugs are illustrated in Figure 4.22
[241]. The constructed microshells display an intact spherical shape with an inner hollow
and shells [242]. The microshells are stable and can retain spherical shape structure intact
for a period of at least 1 month due to the interaction between the -NH 2 groups of chitosan
and -COOH groups of alginate. The release rate of encapsulated drug from chitosan-
alginate microshells decreases with increasing the number of assembly layers. Increasing
the deposition temperature can increase the thickness and perfection of the chitosan-alg-
inate multilayer assembly film and provide an efficient method for controlling the release
rate [243]. Cross-linking neighboring layers will be an effective method for protecting the
multilayer film made by LBL assembly from enzymatic erosion and for prolonging the
release of the encapsulated drug [244]. The EDC cross-linking can improve the alginate-
chitosan films' resistance to pepsin erosion more effectively than GA cross-linking. The
reason is that the EDC joins chitosan and alginate macromolecules together over the mul-
tilayer film, thus producing a more compact alginate-chitosan multilayer film with lower
mobility. When chitosan is partially degraded, the chitosan residues are still linked to the
alginate chains, which will enhance the film stability. GA cross-linking only occurs among
chitosan macromolecules, which contributes little towards the film stability [245].
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