Application of Quality by Design in the Development of Hydrogen Sulfide Donor Loaded Polymeric Microparticles

Hydrogen sulfide (H₂S) is a multifaceted gasotransmitter molecule which has potential applications in many pathological conditions including in lowering intraocular pressure and providing retinal neuroprotection. However, its unique physicochemical properties pose several challenges for developing its efficient and safe delivery method system. This study aims to overcome challenges related to H₂S toxicity, gaseous nature, and narrow therapeutic concentrations range by developing polymeric microparticles to sustain the release of H₂S for an extended period. Various formulation parameters and their interactions are quantitatively identified using Quality-by-Design (QbD) approach to optimize the microparticle-based H₂S donor (HSD) delivery system. Microparticles were prepared using a solvent-evaporation coacervation process by using polycaprolactone (PCL), soy lecithin, dichloromethane, Na₂S.9H₂O, and silicone oil as polymer, surfactant, solvent, HSD, and dispersion medium, respectively. The microparticles were characterized for size, size distribution, entrapment efficiency, and H₂S release profile. A Main Effects Screening (MES) and a Response Surface Design (RSD) model-based Box-Behnken Design (BBD) was developed to establish the relationship between critical process parameters (CPPs) and critical quality attributes (CQAs) qualitatively and quantitatively. The MES model identified polymer to drug ratio and dispersion medium quantity as significant CPPs among others, while the RSD model established their quantitative relationship. Finally, the target product performance was validated by comparing predicted and experimental outcomes. The QbD approach helped in achieving overall desired microparticle characteristics with fewer trials and provided a mathematical relationship between the CPPs and the CQAs useful for further manipulation and optimization of release profile up to at least 30 days.