Synthesis and evaluation of toxicity and antimicrobial activity of rifampicin associated with iron oxide nanoparticles

Rifampicin has broad-spectrum antimicrobial activity, but it can cause nephrotoxic and hepatotoxic damage because high doses are required. Nanosystems emerge as a perspective to improve the transport systems of this drug. In this work, iron oxide nanoparticles were synthesised, functionalized with lauric acid, and rifampicin was incorporated into the nanosystem. The samples were characterized by spectroscopic techniques: electronics in the visible ultraviolet region (UV-vis), vibrational absorption in the infrared region (IR), X-ray diffractometry (XRD), and dynamic light scattering (DSL). The toxicity of the nanocompounds and the antimicrobial activity against Staphylococcus aureus ATCC 25923 were studied by the Artemia salina lethality and disc diffusion techniques, respectively. As a result, IR analysis showed characteristic vibrations of laurate and rifampicin on the surface of the nanosystem. The presence of magnetic iron oxide was confirmed by XRD and the mean diameter of the crystallites was 8.37 nm. The hydrodynamic diameter of rifampicin associated with the nanosystem was 402 nm and that of the nanosystem without rifampicin was 57 nm. The compounds did not show toxicity to Artemia salina and the in vitro antimicrobial activity against Staphylococcus aureus was slightly decreased when rifampicin was associated with the nanosystem. In general terms, the results showed that iron oxide nanoparticles showed no toxicity and reduced the toxicity of rifampicin by 41.54% when carried compared to free rifampicin. Therefore, magnetic iron oxide nanoparticles may have the potential to act as a platform for associated drugs.

Application of Gamma Radiation on Hard Gelatin Capsules as Sterilization Technique and Its Consequences on the Chemical Structure of the Material.

Hard capsules are made from gelatin, an organic polymer obtained through the hydrolysis of collagen present in animal tissues. Gelatin can be degraded by microorganisms and some strategies can be used to control contaminating micro-organisms. Gamma irradiation is considered as an effective sterilization method; however, its application can alter the chemical structure of the irradiated product. Samples of hard gelatin capsules were irradiated at doses of 5, 15, and 25 kGy at room temperature. The characterizations of the physical and chemical effects were evaluated by scanning electron microscopy, Fourier-transform infrared spectroscopy, X-ray diffractometry, and differential scanning calorimetry techniques. Furthermore, hard gelatin capsule samples were dissolved and inoculated with Bacillus subtilis, a Gram-positive spore-forming bacterium, to evaluate the effect of gamma ray radiation on bacterial counts. The results showed that gamma radiation did not interfere on physical parameters of the capsule, such as moisture content, mass, body and cap length, and disintegration time. Nevertheless, differential scanning calorimetry results demonstrated changes in the glass transition temperature, indicating the formation of crosslinking in irradiated capsules. It was observed that there were significant reductions on the inoculated bacterial population starting from the lowest irradiation dose and there was no detection of bacterial growth from the 15 kGy dose, while in the non-irradiated samples were found with 104 CFU mL-1 of bacteria. Therefore, this work concludes that the gamma radiation is effective on the reduction of the microbial population, cause discrete physical-chemical alterations, and could be used as a hard capsule sterilization technique.