Multifuntional role of liposome-mimicking vesicles – Potential nanoreactors and effective storehouses for hemoglobin

Abstract

Liposome-mimicking niosomal vesicles were synthesized using a surfactant having high hydrophile : lipophile (HLB) value i.e. Brij S-20. The effect of Brij concentration, preparation method and Brij : Cholesterol ratio on the niosome structure was thoroughly investigated. Due to high HLB of the surfactant, a low Brij : Cholesterol ratio leads to a more compact niosome structure. Fluorescence studies with diphenyl hexatriene (DPH) and a coumarin dye (C-153) indicate disruption of bilayer integrity of niosomes upon increase of temperature. More significantly, the niosomes show two important functions: (i) they can function as very efficient nanoreactors for synthesis of gold nanoparticles (GNPs); (ii) they also serve as “effective storehouses” for the physiologically important protein hemoglobin (Hb). In niosomes with 1:1 Brij : Cholesterol ratio, small highly crystalline GNPs are formed in the bilayer and larger ones in the aqueous core, thus leaving the surface free for further functionalization. The protein-surfactant interaction has also been studied in detail with an aim to understand the role of the niosomal bilayers in maintaining protein stability. It has been inferred from fluorescence and circular dichroism studies that Hb remains well encapsulated within the niosomal bilayers and is thus not exposed to external perturbations. Moreover, the Soret absorption of Hb is unaffected for several days upon encapsulation in niosomes. More importantly, Hb encapsulated in niosomes does not show significant denaturation even in presence of the well-known denaturant urea. One practical application of this may be in cases of acute renal failure where high urea concentration leads to severe anemia.