When combined selleck chemicals llc with the measured released rifampicin, the total rifampicin amount detected did not reach 100%. The fact that rifampicin oxidizes to rifampicin quinone which is further degraded to compounds with no UV-absorbance, explains why part of the rifampicin seems to have disappeared.25 Unfortunately, this affects the accuracy of this method in analyzing the released rifampicin. However, the method can be used to estimate the rifampicin release and compare the composites with each other. In in vivo conditions, the situation may be different. Le Guellec et al.27 found that rifampicin stability was better in rifampicin containing plasma samples taken from patients treated with rifampicin than in plasma samples where rifampicin was added in the laboratory.
This improved stability suggests that rifampicin may be more stable in vivo than in vitro. Inhibition zone testing The effect of the rifampicin releasing composite containing 50 wt% of ��-TCP against the common osteomyelitis causing bacteria Pseudomonas aeruginosa was tested using bioluminescence imaging. The results are illustrated with Figure 2, where the bioluminescence imaging results (16 h incubation) of a 6-well plate cultured with Pseudomonas aeruginosa and rifampicin containing composite pellets are shown. The antibiotic containing composite pellets are on the lower row and control pellets without antibiotics are on the top row. The results show that the composite material releases rifampicin in levels high enough to eradicate Pseudomonas aeruginosa. The inhibition zone can be seen as dark blue area surrounding the antibiotic releasing pellets in Figure 2.
The blue area indicates dead bacteria whereas the other colors indicate still living bacteria. First signs of the forming inhibition zone were observed already after two hours of incubation. If compared with the bioluminescence results of ciprofloxacin releasing pellets1 the inhibition zone was smaller with rifampicin. The larger molecular weight of rifampicin may affect the diffusion of the antibiotic in agar and make it rather slow, which is seen as the slow growth of the inhibition zone. However, as seen in the drug release results, the initial burst was larger with rifampicin releasing pellets than with ciprofloxacin pellets and this is probably due to the better solubility of rifampicin. Figure 2.
Bioluminescence results of the rifampicin containing (8 wt%) composites of poly(L-lactide-co-��-caprolactone) and 50 wt% of ��-tricalcium phosphate on a bacterial culture of light emitting Pseudomonas aeruginosa. Pellets … In vitro degradation of the composites Molecular structure The 1H NMR spectra were measured from eight samples (raw material PLCL, plain rifampicin, PLCL + Entinostat R at 0, 26 and 52 weeks and PLCL + TCP50 + R at 0, 26 and 52 weeks in vitro). The 1H NMR signals of the polymer were assigned and the data were analyzed in the same way as in our accompanying study.