This talk describes the interaction of  SiO₂,ZnO  and organic  polymeric nanoparticles with the chip-supported phospholipid membranes [1] of the ENNSATOX nanosensor. SiO₂ dispersions of particle size 14 to 150 nm were tested and were found to be stable within the time of the experiment. The interaction  of SiO₂ particle dispersions with  dioleoyl lecithin (DOPC) membranes were characterised by an interference with the electrically-induced phase transitions (Figure 1) and inversely related to  the particle size (Figure 2)  and impedance measurements of the SiO₂-DOPC interaction confirmed this finding. Uniquely novel experiments using  scanning electron microscopy (SEM) showed that SiO₂ nanoparticles of all size ranges adsorbed on the DOPC surface (Figure 3).  It can be concluded from these  results that the relationship of SiO₂ activity on the DOPC membrane  with particle size is due to  the  geometrical proximity of the SiO₂ surface to the DOPC polar groups. A one parameter geometric   model was fitted to the data as shown in Figure 3  and an interfacial distance of 3.2nm was estimated within which the SiO₂ surface influenced the fluidity of the DOPC. 

Similar experiments were carried out with ZnO nanoparticle dispersions from different sources.  Only the ZnO dispersions of small particle size were found to interact strongly with the DOPC membrane. The solubility of the ZnO and the release of Zn²⁺from the nanoparticles was also measured using the ENNSATOX nanosensor.   In comparison with the inorganic nanoparticles, experiments were also carried out investigating the interaction organic polymers and organic polymeric nanoparticles with DOPC membranes.  The polymers showed considerably stronger DOPC membrane activity. The rates of interaction of the inorganic nanoparticles, the organic polymers and the organic polymeric nanoparticles with the DOPC membrane are compared.

The biological relevance of the ENNSATOX nanosensor has been tested by intercalibrating the  results from the sensor with those obtained from the interaction of the nanoparticles with biological organisms of increasing levels of complexity.

References

[1] Z. Coldrick, et al 2009, Electrochim.Acta 54,4944-4962.  

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