In vitro characterization of tramadol-hcl-loaded polyoxalate microspheres designed for controlled drug release

This study evaluates the properties of Tramadol-HCl-loaded polyoxalate (TH-loaded POX) microspheres prepared by oil-in-oil (O₁/O₂) emulsion solvent evaporation method, specifically designed for sustained drug release. Morphology and physicochemical characteristics of the as-fabricated were studied by scanning electron microscopy (SEM), X-ray diffraction (XRD), differential scanning calorimeter (DSC) and Fourier transform infrared (FTIR) spectroscopy, while the encapsulation efficiency and release profile of drug (Tramadol-HCl, TH) from POX microspheres were assessed by high-performance liquid chromatography (HPLC). The influence of reaction temperature, stirring speed, initial drug ratio, molecular weight (M_w) and concentration of polyoxalate (POX) on the fabrication of TH-loaded POX microspheres were investigated. Results showed that the characteristics of the microspheres and drug-loaded content can be optimized by adjusting the parameters of preparation conditions. Also, the degradation behavior of TH-loaded POX microspheres was evaluated from in vitro test for 2 weeks. Overall, the results showed that POX microsphere can be one of the promising polymers for controlled injection release formulation with site-specific drug release capabilities.