Development and Characterization of Zein/Eudragit Composite Nanoparticles for Insulin Intranasal Delivery

Abstract

Diabetes mellitus (DM) is a chronic metabolic disorder characterized by elevated blood glucose levels, primarily due to impaired insulin secretion or action. The standard treatment for Type 1 Diabetes Mellitus still involves daily parenteral insulin administration, which presents several challenges including patient discomfort, reduced adherence, and the potential for peripheral hyperinsulinemia. Intranasal administration has emerged as a promising alternative due to the nasal cavity's high vascularization, ease of access, and significant absorption capacity, though certain physiological barriers remain. This study aimed to develop and characterize Zein-Eudragit nanoparticles (NPS) as carriers for insulin (ZEU/INS NPS) intended for intranasal administration. The NPS were prepared using a liquid-liquid dispersion method, and the production process was optimized through a 2⁴ factorial design. The resulting NPS were evaluated in terms of physicochemical properties, including particle size, polydispersity index (PDI), zeta potential, Fourier-transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), thermogravimetric analysis (TG), and morphology. Additionally, the physical stability of the NPS during storage, in vitro insulin release, and in vitro mucoadhesion were assessed. The optimized nanoparticle formulation exhibited a mean particle size below 200 nm, a PDI of less than 0.3, a zeta potential of approximately +30 mV, and an encapsulation efficiency of 42%. FTIR analysis confirmed the interaction between nanoparticle components following insulin encapsulation, and DSC/TG analysis demonstrated the thermal stability of the system. NPS stored under refrigerated conditions maintained their stability for up to 60 days. In vitro release studies revealed that about 60% of the encapsulated insulin was released over a 24 h period. The in vitro mucoadhesion assay further supported the potential of these NPS to enhance the residence time in the nasal cavity. Overall, ZEU/INS NPS successfully demonstrated favorable physicochemical characteristics for the intranasal delivery of insulin. These findings suggest that these NPS offer significant promise as an effective and noninvasive delivery system for insulin.

1

GR Residual Plot. (A) Probability plot, (B) adjusted versus fitted values plot, (C) histogram, (D) residuals versus order plot.

2

Pareto chart depicting the individual effects of zein, Eudragit, O/A ratio, and incubation time on GR.

3

Main Effects Plot for GR. The blue dots indicate the conditions at the extremes of the levels tested for each factor, while the red dots represent the central conditions of the experimental design. The dotted line shows the global mean of the response, serving as a reference to compare the observed variations.

4

Size distribution of a representative ZEU/INS NPS sample.

5

SEM micrographs of the prepared Zein/Eudragit composite NPS containing insulin at different magnifications: (A) 15,000×; (B) 30,000×.

6

FTIR spectra of ZEU/INS NPS (A), ZEU NPS (B), insulin (C), zein (D), Eudragit (E), physical mixture (zein + Eudragit) (F).

7

TG/DTG curves of ZEU/INS NPS (A), ZEU NPS (B), zein (C), Eudragit (D), physical mixture (zein + Eudragit) (E).

8

DSC curves of ZEU/INS NPS (A), ZEU NPS (B), zein (C), Eudragit (D), and physical mixture (zein + Eudragit) (E).

9

ZEU/INS NPS under different storage conditions (n = 3). Mean diameter (A), PDI (B), zeta potential (C), drug content (D). ^a,b,c,dSame letters indicate statistical equality and different letters indicate statistical inequality (one-way ANOVA with Tukey’s post-test and α < 0.05).

10

In vitro insulin release from ZEU/INS NPS in simulated nasal fluid (pH = 6.5) over 24 h (n = 3).