Abstract
The excellent biocompatible and monodispersed gold nanoparticles (AuNPs) functionalized by amino based ionic liquid (IL) have been synthesized for the demonstration of their interaction with human serum albumin (HSA). Amino based IL stabilizes the surface of AuNPs and provides a colorimetric sensor platform. The size of synthesized IL–AuNPs was identified by use of transmission electron microscopy (TEM) and dynamic light scattering (DLS) techniques. Molecular interaction of functionalized AuNPs with HSA have been investigated using multispectroscopic techniques, such as UV-Vis, fluorescence and Fourier transform infra-red (FT-IR) spectroscopy. The fluorescence and synchronous fluorescent intensity together indicated that IL–AuNPs exhibits a strong ability to quench the intrinsic fluorescence of HSA via a dynamic quenching mechanism. Moreover, the binding constant (Ka), Stern–Volmer quenching constant (KSV) and different thermodynamic parameters, namely Gibb's free energy (ΔG), enthalpy (ΔH) and entropy (ΔS) have been evaluated at different temperatures. This interactive study focuses on the nature of surface modification of IL–AuNPs via HSA for selective detection of glutamine (Glu) with a lower limit of detection of 0.67 nM in the linear range of 10–100 nM for Glu.
Highlights
Serum albumins are proteins found in blood plasma which account for about 60% of the total protein corresponding to a concentration of 42 g LÀ1 and are responsible for about 80% of the osmotic pressure of blood.[1,2,3] Both bovine serum albumin (BSA) and human serum albumin (HSA) are thiol containing proteins.[4]
Fourier transform infra-red (FT-IR) spectra of AuNPs, ionic liquid (IL)–AuNPs and IL–AuNPs with HSA were taken via diffused re ectance method performed on a Nicolet iS10 FT-IR (Thermo sher) using KBr matrix in the range of 500 to 4000 cmÀ1 at room temperature
IL–AuNPs and IL–AuNPs with HSA were characterized by transmission electron microscopy (TEM), dynamic light scattering (DLS) and FT-IR techniques
Summary
Serum albumins are proteins found in blood plasma which account for about 60% of the total protein corresponding to a concentration of 42 g LÀ1 and are responsible for about 80% of the osmotic pressure of blood.[1,2,3] Both bovine serum albumin (BSA) and human serum albumin (HSA) are thiol containing proteins.[4]. A lot of research work has been focused in understanding the mechanism behind interaction of NPs with serum albumins.[4,7,13,14,15] The major interaction for NPs–HSA binding involves p–p stacking, electrostatic and hydrophobic interactions.[16] The nature and sources of the interaction of NPs with HSA contribute in unraveling the binding mechanism between them.[7] Hemmateenejad et al.[17] investigated the interaction of ZnS-NPs with HSA and indicated that uorescence of HSA is quenched through static mechanism They showed the spontaneous binding reaction and proved that conformational structure of HSA molecules could be changed in the presence of ZnS-NPs using synchronous uorescence spectroscopy. Based on the HSA quenched by IL–AuNPs, different parameters as Stern–Volmer quenching constant (KSV), enthalpy (DH), entropy (DS) and Gibb's free energy (DG) were calculated by uorescence and UV-Vis technique at different temperature This interaction study has been applied to investigate their effect for the detection of amino acids found in human blood.
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