Sustained-release protamine sulphate-impregnated microspheres may reduce the frequent administration of recombinant interferon α-2b in ovarian cancer: in-vitro characterization.

Parenteral administration of recombinant interferon-α-2b (rINF-α-2b) at a dose of 50×10 IU once a week for 8 weeks is recommended for ovarian cancer. However, short half-life, small therapeutic index and proteolytic degradation cause fluctuations in plasma level and pose barriers in the development of a clinically viable dosage form. Therefore, in the present investigation, fluorescein isothiocynate-tagged rINF-α-2b was loaded into stearic acid (*rINF-α-2b-SMs), pectin (*rINF-α-2b-PMs) and gelatin (*rINF-α-2b-GMs) microspheres. Parameters such as particle size, ζ potential, encapsulation efficiency and in-vitro release were studied to follow the optimization process. The formulation, *rINF-α-2b-GMs of particle size 8.3±2.1 μm with an encapsulation efficiency of 76.0±7.4%, offered 97.4% of *rINF-α-2b release at 288 h. Thus, negatively charged extended-release formulation *rINF-α-2b-GMs was then tethered with a gradient concentration (5-20 mg/ml) of a cationic arginine-rich protein stabilizer, protamine sulphate (Pt). The nanoformulation, *rINF-α-2b-Pt-GMs-15 superimposed with 15 mg/ml of Pt, released 95.0% of *rINF-α-2b at 336 h and was designated as the optimized formulation. The optimized formulation also conserved the primary and secondary structure of *rINF-α-2b as analysed by gel electrophoresis and circular dichroism. Moreover, in-vitro cytotoxicity analysis of SKOV3 cells of the optimized nanoformulation reported significantly (one-way analysis of variance test, P<0.05) lower IC50 (414.3 IU/ml) compared with *rINF-α-2b-GMs (514.3 IU/ml) and pure rINF-α-2b (628.6 IU/ml) at 72 h by offering a prolonged cytotoxic effect. Therefore, *rINF-α-2b-Pt-GMs-15, a promising nanomedicine, warrants further in-depth in-vivo study to scale up the technology for clinical translation.