Nanobiotechnology for health-care

Interaction of arsenic sulfide nanoparticles with albumin
Lukáčová Bujňáková, Z.1, Dutková, E.1, Melnyk, I.1, Tóthová, E.1, Varhač, R.2, Jakubíková, J.3
1Institute of Geotechnics, Slovak Academy of Sciences, Watsonova 45, 04001 Košice, Slovakia, E-mail: bujnakova@saske.sk 
2Faculty of Science, P.J. Šafárik University in Košice, Šrobárova 2, 04154 Košice, Slovakia
3 Cancer Research Institute BMC, Slovak Academy of Sciences, Dúbravská cesta 9, 84505 Bratislava, Slovakia 

The interactions of nanomaterials with biological molecules represent so called nano-bio interface processes. Arsenic sulfide (As4S4) nanoparticles have been recently intensively studied as a promising drug in cancer treatment. Albumin is a heart-shaped globular protein and it is the major component of blood plasma. It has also been widely used in clinically approved formulations and is one of the most attractive materials for the development of novel nanomedicine. However, only few studies have focused on the preparation technology of albumin-based nanoparticles with large scale, uniform and stable particle size distribution. The wet stirred media milling is a scalable method applicable to poorly water-soluble drugs with different physico-chemical properties. The main advantage is the production of nanosuspensions with high drug loading.  
For the first time, the interaction between As4S4 and bovine serum albumin has been studied by our research group. At first, the sorption kinetics of albumin onto As4S4 nanoparticles was investigated. Subsequently, its structural changes influenced by interaction with As4S4 nanoparticles as well as ultra-fine milling were studied in deep. Both the dynamic and static quenching was detected after analyzing the fluorescence quenching spectra of albumin-As4S4 samples. From the synchronous fluorescence spectra we have investigated, that the fluorescence from tryptophan is more intense and gets more efficiently quenched than those from tyrosine residues in the presence of As4S4, implying that the tryptophan can be closer to the binding site. From the circular dichroisms spectra the α-helical content of pure, non-milled albumin was calculated as 50%. On the other hand, the α-helical content of pure milled albumin was reduced to 39% and upon interaction with As4S4 nanoparticles to 30%. These reductions indicate conformational changes in secondary structure of albumin introduced by milling as well by As4S4 nanoparticles. These results are supported with the deconvolution of the peaks attributed to the amide I in Fourier-transform infrared spectra. Moreover, the biological activity of prepared albumin-As4S4 system was tested.