Application of quality by design approach for intranasal delivery of rivastigmine loaded solid lipid nanoparticles: Effect on formulation and characterization parameters

• Identification of process parameters affecting quality attributes of rivastigmine SLN.
• Determination of process parameters by 33 by full factorial design.
• Characterization of SLN for physicochemical properties and nasal permeation study.
• Microscopic characterization of nasal mucosa for assessment of excipient toxicity.

In the present investigation, Quality by Design (QbD) approach was applied on the development and optimization of solid lipid nanoparticle (SLN) formulation of hydrophilic drug rivastigmine (RHT). RHT SLN were formulated by homogenization and ultrasonication method using Compritol 888 ATO, tween-80 and poloxamer-188 as lipid, surfactant and stabilizer respectively. The effect of independent variables (X1 – drug: lipid ratio, X2 – surfactant concentration and X3 – homogenization time) on quality attributes of SLN i.e. dependent variables (Y1 – size, Y2 – PDI and Y3 – %entrapment efficiency (%EE)) were investigated using 33 factorial design. Multiple linear regression analysis and ANOVA were employed to indentify and estimate the main effect, 2FI, quadratic and cubic effect. Optimized RHT SLN formula was derived from an overlay plot on which further effect of probe sonication was evaluated. Final RHT SLN showed narrow size distribution (PDI- 0.132 ± 0.016) with particle size of 82.5 ± 4.07 nm and %EE of 66.84 ± 2.49. DSC and XRD study showed incorporation of RHT into imperfect crystal lattice of Compritol 888 ATO. In comparison to RHT solution, RHT SLN showed higher in-vitro and ex-vivo diffusion. The diffusion followed Higuchi model indicating drug diffusion from the lipid matrix due to erosion. Histopathology study showed intact nasal mucosa with RHT SLN indicating safety of RHT SLN for intranasal administration.

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