Background: The use of new nano materials in biology and medicine has been the focus of interest in recent years. The unique physico-chemical properties of carbon nanotubes have made them an excellent candidate in biology and medicine. One of the key advantages of carbon nanotubes in biomedical applications is that they can be easily internalized by cells, and therefore can act as delivery vehicles for a variety of molecules relevant to therapy and diagnosis. Carbon nanotubes can be single-walled or multi-walled and are now produced in substantial quantities for a variety of commercial applications. The clinical applications of using carbon nanotubes in medicine will depend on the outcomes of efficacy and Immunotoxicological studies, which will provide the necessary risk-to-benefit assessments for carbon-nanotube based materials. Methods: The objective of the present study was to evaluate the in vitro inflammatory properties of single walled carbon nanotubes functionalized with polyethylene glycol (PEG-SWNT). Human monocytic cell line THP-1 was cultured with various concentrations of PEG-SWNT in different time points and the expression of several innate immunity receptor genes was analyzed by real time quantitative PCR method. In this study the expression of several pattern recognition receptors (PRRs) including TLR2, TLR4, CD14 and adaptor protein MyD88 was analyzed in the PEG-SWNT treated THP-1 cells. Results: According to our results a significant up-regulation of TLR2, TLR4, CD14 and MyD88 was observed when THP-1 cells were treated with various concentrations (10 µg/ml, 50 µg/ml and 100 µg/ml) of PEG-SWNT. However, when the cells were treated with 200µg/ml PEG-SWNT, the expression of PRRs was down-regulated which might suggest that, higher concentration of PEG-SWNT is toxic for the cells. Conclusion: the results presented in this study shows that PEG-SWNT could trigger cellular inflammatory responses as was shown by the expression analysis of genes involved in innate immunity and inflammation.

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