Preformulation Characterization of Hydroxypropyl Cellulose Microparticles for Drug Delivery Applications: A Basis for Rational Design and Process Optimization

T. Georgievska, S. Trajkovic, D. Stojanov, M. S. Pecova and K. Lisichkov

Abstract
This study explores early formulation parameters influencing hydroxypropyl cellulose (HPC)-based microparticles as carriers for paracetamol, with the aim of establishing a modified-release drug delivery system and informing future design optimization. Microparticles were prepared via the oil-in-oil emulsion/solvent evaporation method using acetone, HPC as a thermo-responsive polymer, and Tween 80 as a non-conventional surfactant. Polymer content and phase ratio were varied to assess effects on encapsulation efficiency and dissolution behavior. Characterization by FTIR, DSC, UV-Vis, laser diffraction, and microscopy confirmed spherical morphologies (495–760 µm), thermal stability, and successful drug encapsulation (up to 73 %). In vitro dissolution at pH 6.8 revealed modified release profiles, with kinetics best described by the Weibull model, indicating Fickian diffusion as the dominant mechanism. Polymer content emerged as the key variable affecting critical quality attributes. These findings provide a foundation for rational formulation and process optimization, to be further refined through D-optimal experimental design.

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Keywords
acetaminophen, oil-in-oil emulsion solvent evaporation method, drug delivery systems, hydroxypropyl cellulose