Results
Synthesis of CSL-gel and
characterization of chitosan core-shell
To obtain the sustained release of lentinan and calcium ions, we
developed a novel and multiple-functional hydrogel by cross-linking the
mixed solution of sodium alginate and lentinan with calcium ions to form
a hydrogel precursor (SL-gel). A chitosan shell was built on the surface
of SL-gel to form a lentinan-loaded hydrogel with a core-shell structure
(CSL-gel) (Figure 1a ), which is expected to provide the stable
and sustained release of lentinan (LNT) and calcium ions (Figure
1b ). To assess the formation of chitosan shell on the surface of
CSL-gel, scanning electron microscopy (SEM) and Zeta potential were
employed. SEM images of SL-gel and CSL-gel were illustrated inFigure 1c . SEMs showed that the surface of the SL-gel with
large pores was loose, but a dense chitosan shell covering the SL-gel
was observed on the surface of CSL-gel (Figure 1c ). Moreover,
the elemental analysis showed that elemental nitrogen was detected on
the surface of the CSL-hydrogel (Table 2 ), indicating that
chitosan was added on the surface of CSL-gel. To avoid the influence of
LNT on the FTIR and zeta analysis, we performed the Fourier transform
infrared spectrometry (FTIR) and zeta analysis using the hydrogel
without LNT to characterize the chitosan shell. Figure 1dshowed a shared peak located at approximately 3340
cm−1 was observed in the FTIR spectrum of the S-gel
and CS-gel. However, the CS-gel features a fully developed peak on 3340
cm-1, which is attributed to the overlap associated
with the peaks of the −OH stretching vibration of SA and the −NH
stretching vibration of the chitosan in comparison to the S-hydrogel.
Besides, the CS-gel exhibited a peak at approximately 2927
cm-1, which was formed by the C−H stretching vibration
of chitosan, suggesting that the reaction of adding chitosan to the
S-gel was successful. Sodium alginate is composed of carbon, hydrogen,
and oxygen, and the surface is negatively charged. The zeta potential
analysis showed that the surface of CS-gel has a positive charge, but
the S-gel with a negative charge (Figure 1e ). Taken together,
our findings strongly indicate that a chitosan shell is added to the
SL-gel, which has the potential to stabilize the structure of CSL-gel
and provide the sustained release of LNT and calcium ions.