(196o) Effect of the Cross-Linking Agent (sodium polyphosphate) on Performances of Nacs-Wsc Microcapsules

Effect of the cross-linking agent
(sodium polyphosphate) on performances of NaCS-WSC microcapsules

Qing-Xi Wu^1,2,
Yi-Xin Guan¹, Jun-Jie Yuan¹, and Shan-Jing Yao^1*

(¹College of Chemical
and Biological Engineering, Zhejiang University, Hangzhou 310027, China; ²School
of Life Sciences, Anhui University, Hefei 230601, China)

Microcarriers prepared with polyelectrolyte
complexes (PECs) using natural polysaccharides as raw materials have attracted
great attentions due to their mild process conditions, favorable properties and
vital applications in biomedical and bioengineering fields. Among which,
chitosan-related polysaccharides such as water soluble chitosan (WSC) and cellulose-related substances such as sodium cellulose
sulfate (NaCS) are representatives of challenging biomaterials. However, the
poor mechanical property of the PECs becomes the obstacle encountered in
applications.

In the previous work, we found that small
cross-linking agent like sodium polyphosphate (PPS) had evident effects on microcapsule¡¯s morphology. Thus, it¡¯s important
to study the PEC formation process under conditions of using cross-linking
agent. In this work, the effect of PPS on performances of NaCS-WSC microcapsules
was investigated in detail, while NaCS-Chitosan (CS) microcapsules were chosen
as the control. Compared with the microcapsules that formed without cross-linking
agent, PPS as the cross-linking agent could penetrate through the PEC film and
form tighter interior structures. The NaCS-WSC-PPS microcapsules had lower
swelling ratios which may be ascribed to their tighter interior microstructures
compared with NaCS-WSC microcapsules. PPS also had important effect on the
total mass of PECs produced; and the decline of zeta potential of NaCS-WSC-PPS
microcapsules was lower than that of NaCS-WSC microcapsules, indicating
PPS participated in the interactions and played an important role in the
microcapsules¡¯ formation process. Similar results were found in the controls. Due to the unique
physicochemical properties of WSC and CS, the NaCS-WSC microcapsules and NaCS-CS
microcapsules that were prepared with or without PPS had distinct
microstructures. As is known, CS can only be dissolved in water under acidic solutions,
while WSC can be directly dissolved and protonated in acid-free aqueous
providing ¨CNH₃⁺ groups quickly, which resulted in the
microstructure¡¯s difference.

The NaCS-WSC microcapsules prepared with the PECs
could be good candidates as enzyme-triggered controlled release drug carriers targeted
for colon. Therefore, it may be a strategy to improve the mechanical properties
and performances of the PEC microcapsules using PPS as the cross-linking agent.

Keywords: Polyelectrolyte complexes; Cross-linking agent; Microcarriers

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