In vitro and in vivo evaluation of thermosensitive chitosan hydrogel for sustained release of insulin

Figures & data

Table 1. Characteristics of thermosensitive CS/β-Gp solutions.

				Gelation time at 37 °C (min)
Sample	β-Gp(% w/v)	NaOH (%w/v)	pH	Sol or gel at 25 °C	For cold solution (keeping at 4 °C)	For warm solution (keeping at 25 °C)	Sol-gel-sol reversibility
CS1	0	0	5.42 ± 0.10	Sol	No gel	No gel	–
CS2	0	0.5	–	Gel (rapidly)	–	–	Non-reversible
CS3	5	0	6.91 ± 0.14	Sol	16.5 ± 1.3	14 ± 2.3	Non-reversible
CS4	6	0	7.01 ± 0.08	Sol	14 ± 1.0	11 ± 2.6	Non-reversible
CS5	8	0	7.19 ± 0.11	Sol	9 ± 1.0	7 ± 1.3	Non-reversible
CS6	9	0	7.25 ± 0.14	Sol	7 ± 2.3	5 ± 1.8	Non-reversible
CS7	10	0	7.45 ± 0.11	Sol	6 ± 0.5	5 ± 0.9	Non-reversible
CS8	12	0	7.52 ± 0.16	Sol	5 ± 1.8	3 ± 0.9	Non-reversible
CS9	14	0	7.63 ± 0.10	Sol	4 ± 1.3	2 ± 1.0	Non-reversible

Data are the mean ± SD (n = 3).

Figure 1. Turbidity changes by time for chitosan solutions incubated at 37 °C in the absence of β-Gp (diamonds) and in the presence of β-Gp (squares).

Figure 2. Storage (G′) and loss (G′′) moduli changes for CS/β-Gp solution (CS 2% w/v) over time at 37 °C: (a) β-Gp 8% (w/v) and (b) β-Gp 14% (w/v).

Figure 3. Insulin release profiles from hydrogels prepared with different concentrations of β-Gp [CS 2% (w/v), insulin 0.3 mg/ml]. Data are mean ± SD (n = 3).

Figure 4. Extrinsic fluorescence at λ_ex = 370 nm and λ_em = 400–550 nm of (a) ANS, (b) pure insulin and (c) insulin in Formulation 1.

Table 2. Characteristics and kinetic profile of insulin-loaded CS/β-Gp hydrogels.

Samples	Gp (% w/v)	Insulin (mg/mL)	Initial burst release (%)	Total insulin release (%)	Release rate (μg/h)	R^2 (Higuchi)
CS-In1	8	0.3	6.13	63.2	0.819	0.9884
CS-In2	14	0.3	5.87	54.2	0.784	0.9861
CS-In3	8	1.0	2.94	23.6	0.344	0.9874
CS-In4	14	1.0	1.87	19.1	0.286	0.9778

Figure 5. Blood glucose profiles after subcutaneous dorsal injection of CS/β-Gp/insulin with different insulin concentrations into (a) normal mice [CS 2% (w/v), β-Gp 8% (w/v)] (b) diabetic mice [CS 2% (w/v), β-Gp 8% (w/v), insulin 0.01 mg/ml]. Data are mean ± SD (n = 4).

Figure 6. Effect of CS/β-Gp/insulin system on blood enzyme level 1-week post-injection after subcutaneous dorsal injection into mice [CS 2% (w/v), β-Gp 8% (w/v), insulin 0.01 mg/ml]: (a) ALP, (b) amylase, (c) AST and (d) CPK. Data are mean ± SD (n = 4).