Insulin-loaded poly(acrylic acid)-cysteine nanoparticles: Stability studies towards digestive enzymes of the intestine

Figures & data

Figure 1.  Particle size distributions directly after precipitation (-□-), after oxidation (-▴-), and after release from the lipid formulation (-⧫-). Indicated values are means ± SD (n ≥ 3).

Table 1.  Characterization of the utilized PAA₁₀₀-Cys nanoparticles regarding mean particle diameter, zeta potential, and drug load. Indicated values are means ± SD (n ≥ 3).

Formulation step	Mean diamter (nm)	Zeta potentian (meV)	Drug load (%)
After addition of PVP	136.7 ± 49.6	−14.3 ± 0.6	Not determined
After oxidation with iodine	122.0 ± 32.6	Not determined	7.0 ± 0.4
After embedment in triglyceride	265.3 ± 100.0	Not determined	Not determined

Figure 2.  In vitro release of insulin from PAA₁₀₀-Cys nanoparticles as a percentage of the total amount of insulin present in the utilized formulation. Indicated values are means ± SD (n ≥ 3).

Figure 3.  Degradation of insulin by trypsin in an aqueous solution (⧫), as a solid dispersion of insulin in triglyceride (▴), and as a solid dispersion of insulin-loaded PAA₁₀₀-Cys nanoparticles in triglyceride (▪). Indicated values are means ± SD (n ≥ 3).

Figure 4.  Degradation of insulin by α-chymotrypsin in an aqueous solution (⧫), as a solid dispersion of insulin in triglyceride (▴), and as a solid dispersion of insulin-loaded PAA₁₀₀-Cys nanoparticles in triglyceride (▪). Indicated values are means ± SD (n ≥ 3).

Figure 5.  Degradation of insulin by elastase in an aqueous solution (⧫), as a solid dispersion of insulin in triglyceride (▴), and as a solid dispersion of insulin-loaded PAA₁₀₀-Cys nanoparticles in triglyceride (▪). Indicated values are means ± SD (n ≥ 3).