Design and statistical modeling of mannose-decorated dapsone-containing nanoparticles as a strategy of targeting intestinal M-cells

Abstract

The aim of the present work was to develop and optimize surface-functionalized solid lipid nanoparticles (SLNs) for improvement of the therapeutic index of dapsone (DAP), with the application of a design of experiments. The formulation was designed to target intestinal microfold (M-cells) as a strategy to increase internalization of the drug by the infected macrophages. DAP-loaded SLNs and mannosylated SLNs (M-SLNs) were successfully developed by hot ultrasonication method employing a three-level, three-factor Box-Behnken design, after the preformulation study was carried out with different lipids. All the formulations were systematically characterized regarding their diameter, polydispersity index (PDI), zeta potential (ZP), entrapment efficiency, and loading capacity. They were also subjected to morphological studies using transmission electron microscopy, in vitro release study, infrared analysis (Fourier transform infrared spectroscopy), calorimetry studies (differential scanning calorimetry), and stability studies. The diameter of SLNs, SLN-DAP, M-SLNs, and M-SLN-DAP was approximately 300 nm and the obtained PDI was <0.2, confirming uniform populations. Entrapment efficiency and loading capacity were approximately 50% and 12%, respectively. Transmission electron microscopy showed spherical shape and nonaggregated nanoparticles. Fourier transform infrared spectroscopy was used to confirm the success of mannose coating process though Schiff's base formation. The variation of the ZP between uncoated (approximately -30 mV) and mannosylated formulations (approximately +60 mV) also confirmed the successful coating process. A decrease in the enthalpy and broadening of the lipid melting peaks of the differential scanning calorimetry thermograms are consistent with the nanostructure of the SLNs. Moreover, the drug release was pH-sensitive, with a faster drug release at acidic pH than at neutral pH. Storage stability for the formulations for at least 8 weeks is expected, since they maintain the original characteristics of diameter, PDI, and ZP. These results pose a strong argument that the developed formulations can be explored as a promising carrier for treating leprosy with an innovative approach to target DAP directly to M-cells.

Keywords: Box-Behnken design; drug delivery; leprosy; oral route; solid lipid nanoparticle; targeting.

Figure 1

DSC thermograms of bulk drug (DAP), and physical mixtures of drug and eight different lipids (n=3). Abbreviations: DSC, differential scanning calorimetry; DAP, Dapsone.

Figure 2

RSM showing the influence of the independent variables on the selected responses (particle diameter, EE, and LC). Abbreviations: EE, entrapment efficiency; LC, loading capacity; RSM, response surface model.

Figure 2

RSM showing the influence of the independent variables on the selected responses (particle diameter, EE, and LC). Abbreviations: EE, entrapment efficiency; LC, loading capacity; RSM, response surface model.

Figure 3

Linear correlation plots (A, B, C) between observed and predicted values and corresponding residual plots (D, E, F) for the three responses: particle diameter, EE, and LC. Abbreviations: EE, entrapment efficiency; LC, loading capacity.

Figure 4

Transmission electron photomicrographs of (A) SLNs, (B) SLN-DAP, (C) M-SLNs, and (D) M-SLN-DAP (n=3). Abbreviations: M-SLN-DAP, dapsone-loaded mannosylated solid lipid nanoparticles; M-SLNs, mannosylated solid lipid nanoparticles; SLN-DAP, dapsone-loaded solid lipid nanoparticles; SLNs, solid lipid nanoparticles.

Figure 5

Infrared spectra of DAP, SLNs, SLNs-DAP, M-SLNs and M-SLNs-DAP (n=3). Abbreviations: M-SLN-DAP, dapsone-loaded mannosylated solid lipid nanoparticles; M-SLNs, mannosylated solid lipid nanoparticles; SLN-DAP, dapsone-loaded solid lipid nanoparticles; SLNs, solid lipid nanoparticles.

Figure 6

DSC thermograms of DAP (A, B), CP (A), PM (A), SLNs (A, B), SLN-DAP (A, B), M-SLNs (B), and M-SLN-DAP (B) (n=3). Abbreviations: CP, cetyl palmitate; DAP, dapsone; M-SLN-DAP, dapsone-loaded mannosylated solid lipid nanoparticles; M-SLNs, mannosylated solid lipid nanoparticles; PM, physical mixtures; SLN-DAP, dapsone-loaded solid lipid nanoparticles; SLNs, solid lipid nanoparticles; DSC, differential scanning calorimetry.

Figure 7

In vitro DAP release profile of SLN-DAP and M-SLN-DAP in acid and intestinal conditions (A) and only in intestinal conditions (B) (n=3). Abbreviations: DAP, dapsone; M-SLN-DAP, dapsone-loaded mannosylated solid lipid nanoparticles; SLN-DAP, dapsone-loaded solid lipid nanoparticles.

Figure 8

Effect of storage time (at room temperature) on particle diameter, PDI, ZP, EE, and LC of SLN-DAP and M-SLN-DAP formulations (mean ± SD, n=3). Abbreviations: EE, entrapment efficiency; LC, loading capacity; M-SLN-DAP, dapsone-loaded mannosylated solid lipid nanoparticles; PDI, polydispersity index; SD, standard deviation; SLN-DAP, dapsone-loaded solid lipid nanoparticles; ZP, zeta potential.