Norfloxacin delivery systems based on MCM-type silica carriers designed for the treatment of severe infections

Mesoporous MCM-type silica (pristine and vinyl functionalized MCM-41, as well as MCM-48) materials were employed as carriers for norfloxacin, a poorly-water soluble antibiotic from the fluroquinolones class. Small MCM-41 nanoparticles were obtained by a new synthesis procedure that afforded the formation of spherical particles of around 60 nm diameter with large specific surface area and total pore volume values, features that synergistically contribute to the improvement of the drug release profile. The antibiotic-loaded materials were obtained through incipient wetness impregnation method having 20%(wt) drug content. Because of small pores diameter, all employed carriers favored the encapsulation of norfloxacin in amorphous state, which was proved by wide-angle X-ray diffraction (XRD). The carriers and drug-loaded samples were characterized by various techniques: FTIR spectroscopy, small- and wide-angle XRD, TEM analysis and N2 adsorption-desorption isotherms. The in vitro release experiments were performed at 37 °C in saline phosphate buffer solution pH 7.4 and showed an enhanced antibiotic solubility. The antimicrobial activity against E. coli ATCC 25922 of developed norfloxacin delivery systems preserved the antibiotic bactericidal activity after the drug encapsulation. Hence, these norfloxacin delivery systems could be suitable for applications, such as severe infections, where high initial drug concentration is desired immediately after administration.