Nanoemulsions coated with alginate/chitosan as oral insulin delivery systems: preparation, characterization, and hypoglycemic effect in rats

Figures & data

Figure 1 Schematic diagrams of w/o microemulsion, multiple emulsion and coated nanoemulsion respectively.

Abbreviations: w/o, water in oil; HLB, hydrophilic lipophilic balance.

Table 1 Mean zeta potential values of different formulations to form Alg/Chit-coated nanoemulsion

Conc of Ca^2+ (0.06% Chit, 0.067% Alg)	Zeta potential (mv)	Conc of Chit (0.05% Ca^2+, 0.067% Alg)	Zeta potential (mv)	Conc of Alg (0.05% Ca^2+, 0.06% Chit)	Zeta potential (mv)
0.05%	−69.47 ± 0.87	0.06%	−56.90 ± 1.27	0.067%	−55.57 ± 1.10
0.10%	−60.60 ± 1.65	0.12%	−53.23 ± 2.05	0.133%	−55.33 ± 0.76
0.30%	−45.97 ± 0.15	0.24%	−52.03 ± 0.75	0.201%	−59.00 ± 1.61
		0.48%	−0.97 ± 0.67	0.333%	−70.30 ± 2.19

Notes:

* When Alg concentration is 0.067% without Ca²⁺ and Chit addition, the zeta potential is −62.25 ± 2.13 mv; n = 3; mean ± SD.

Abbreviations: Alg, Alginate; Chit, chitosan.

Figure 2 The effects of Ca²⁺ (A), Chit (B) and Alg (C) concentration on particle size and entrapment ratio of coated nanoemulsion.

Notes: Mean ± SD, n = 3.

Abbreviations: Chit, Chitosan; Alg, Alginate.

Table 2 Summary of formulation compositions for in vitro and in vivo study

Constituents	Values (mg)
Insulin	600
Span80	1300
Lipoid S75	320
Labrafac CC	3780
Cremophor EL	420
CaCl2	0.5
Alg	9.4
Chit	8.4
Water	14,000

Abbreviations: Alg, Alginate; Chit, chitosan.

Figure 3 Transmission electron microscopy photographs of uncoated nanoemulsion (A) and coated nanoemulsion (B).

Figure 4 CD spectra of free insulin in solution, free insulin mixed with emulsion and insulin in Alg/Chit-coated nanoemulsion.

Abbreviations: CD, circular dichroism; Alg, Alginate; Chit, chitosan.

Figure 5 The insulin leakage from coated nanoemulsion in pH 1–3 simulated gastric juice.

Notes: Mean ± SD, n = 3.

Abbreviation: SD, standard deviation.

Figure 6 In vitro insulin release profile from Alg/Chit-coated nanoemulsion, uncoated nanoemulsion and multiple emulsion in simulated gastric juice (pH 2.5 media).

Notes: Mean ± SD, n = 3.

Abbreviations: Alg, Alginate; Chit, chitosan.

Figure 7 Plasma glucose level versus time profiles of Wistar rats after oral administration of 50 IU/Kg Alg/Chit-coated nanoemulsion, multiple emulsion, uncoated nanoemulsion, and insulin solution, compared to sc 1 IU/kg insulin.

Notes: Mean ± SD, n = 6; *P < 0.05 and **P < 0.01 compared with control group.

Abbreviations: Alg, Alginate; Chit, chitosan, sc, subcutaneous.

Figure 8 Plasma glucose level versus time profiles of Wistar rats after oral administration of Alg/Chit-coated nanoemulsion in 50 IU/kg, 25 IU/kg, 12.5 IU/kg and free insulin solution as control.

Notes: Mean ± SD, n = 6; *P < 0.05 and **P < 0.01 by comparing dosage 50 IU/kg with 12.5IU/kg; ^#P < 0.05 by comparing dosage 25 IU/kg with 12.5 IU/kg; ^P < 0.05 by comparing dosage 50 IU/kg with 25 IU/kg.

Abbreviation: sc, subcutaneous.

Figure 9 Plasma glucose level versus time profiles of GK rats after oral administration of free insulin solution, Alg/Chit-coated nanoemulsion 50 IU/kg, 25 IU/kg and 12.5 IU/kg, compared with sc 1 IU/kg insulin.

Notes: Mean ± SD, n = 6; *P < 0.05 and **P < 0.01 compared with control group.

Abbreviations: GK, Goto-Kakizaki; sc, subcutaneous.