Interaction of cisplatin and two potential antitumoral platinum(II) complexes with a model lipid membrane: a combined NMR and MD study.

In this study, the interaction of cisplatin (1) and two potential antitumoral Pt(II) complexes (2 and 3) with a model DMPC bilayer was investigated by multinuclear NMR spectroscopy and MD simulations in order to understand its implication for the different antitumoral properties shown by the three complexes. In particular, (31)P, (13)C and (2)H solid state NMR experiments were performed to obtain information on the phase structure, phase transitions and structural and dynamic changes in the phospholipid bilayer upon interaction with the platinum complexes. On the other hand, MD calculations yielded free energy profiles for the different complexes across the bilayer; the results were analysed to obtain MD predictions on complex distribution with respect to the bilayer, as well as to establish their effects on the conformational equilibrium of the DMPC acyl chains. The combination of NMR and MD approaches highlighted that, whereas the more hydrophilic cisplatin tends to remain in the polar head group region causing a decrease in flexibility of the bilayer, the two new complexes enter into the bilayer. In particular, complex 2 is preferentially located relatively close to the surface, only slightly affecting the bilayer structure and mobility, while complex 3 penetrates more deeply, strongly perturbing the bilayer and giving rise to lateral phase separation.

Contamination of the turbine air chamber: a risk of cross infection.

In the present work, we evaluated (a) the influx of contaminating fluid into the air chamber when a high-speed turbine stops rotating, (b) the significance of a series of variables (type of handpiece and dental unit, shape of the bur, number of stops set on the turbine) which condition it, and (c) the time required to expel the contaminating fluid from the turbine head. Results showed that contamination takes place every time the turbine stops rotating with the bur in contact with an external fluid. The main variable affecting the influx of contaminating fluid into the air chamber of the turbine head was represented by the shape of the bur (F=54.9; p<0.01). Another significant variable was the type of handpiece and dental unit (F=7.3; p<0.01). The number of stops set on the turbine was irrelevant (F=0.03; p=n.s.). The expulsion of the contaminant from the turbine head showed 2 different exponential rates: a very rapid-elimination phase within 30 s and a slow-elimination phase between 60 and 300 s. In order to remove over 99% of the contaminant from the air chamber, a turbine had to run for more than 4-7 min depending on the type of the handpiece. In conclusion, data from the present study suggest that a significant cross-infection potential exists with high-speed handpieces whenever they are only externally scrubbed and disinfected so the internal cleaning and sterilization between patients is mandatory. The practice of flushing by running the turbines between patients should be discouraged.