Mupirocin calcium microencapsulation via spray drying: feed solvent influence on microparticle properties, stability and antimicrobial activity

Objectives: The aim of this research was to design a controlled release, spray dried, mupirocin calcium-loaded microparticles (MP) with acrylic polymer and assess the influence of a feed solvent at preselected drug:polymer proportions (1:5 and 2:1 (w/w)) on the performance and stability of the prepared MP. Methods: Physicochemical properties of MP were assessed using modulated differential scanning calorimetry (MDSC), and thermogravimetric analyses (TGA), Fourier transformed infrared spectroscopy (FTIR) and X-ray analyses and were correlated with drug release. Morphology and particle size were determined using low-angle laser light scattering and a scanning electron microscope. A time-kill assay was conducted on two strains of Staphylococcus aureus to evaluate the antimicrobial activity of MP. Results and discussion: The MP formed solid dispersions without apparent drug crystallization. Drug-polymer miscibility, morphology, drug release and consequently antimicrobial activity were dependent on drug loading (DL) and the used solvent. The superior control of drug release from MP was achieved for the higher DL (2:1 (w/w) drug:polymer proportion) using solvents in the following order: methanol methanol:ethanol (50:50, w/w) > isopropanol:acetone (40:60, w/w). Moreover, a time-kill assay performed on S. aureus (ATCC 29213) and methicillin-resistant S. aureus strains confirmed the prolonged release and preservation of antimicrobial activity of the microencapsulated drug. The physical aging of the solid dispersion after 10 months of storage had negligible impact on the MP performance. Conclusions: Acrylic-based MP were confirmed as suitable microcarriers for prolonged drug release using a well-established spray drying technique, while solvent influence was strongly related to the DL employed.