Contrasting Effect of Gold Nanoparticles and Nanorods with Different Surface Modifications on the Structure and Activity of Bovine Serum Albumin
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- 作者：Soumyananda Chakraborty ; Prachi Joshi ; Virendra Shanker ; Z. A. Ansari ; Surinder P. Singh ; Pinak Chakrabarti
- 刊名：Langmuir
- 出版年：2011
- 出版时间：June 21, 2011
- 年：2011
- 卷：27
- 期：12
- 页码：7722-7731
- 全文大小：1070K
- 年卷期：v.27,no.12(June 21, 2011)
- ISSN：1520-5827
文摘
Nanoparticles exposed to biofluids become coated with proteins, thus making protein鈥搉anoparticle interactions of particular interest. The consequence on protein conformation and activity depends upon the extent of protein adsorption on the nanoparticle surface. We report the interaction of bovine serum albumin (BSA) with gold nanostructures, particularly gold nanoparticles (GNP) and gold nanorods (GNR). The difference in the geometry and surface properties of nanoparticles is manifested during complexation in terms of different binding modes, structural changes, thermodynamic parameters, and the activity of proteins. BSA is found to retain native-like structure and properties upon enthalpy-driven BSA鈥揋NP complexation. On the contrary, the entropically favored BSA鈥揋NR complexation leads to substantial loss in protein secondary and tertiary structures with the release of a large amount of bound water, as indicated by isothermal calorimetry (ITC), circular dichroism (CD), and Fourier transform infrared (FTIR) and fluorescence spectroscopies. The esterase activity assay demonstrated a greater loss in BSA activity after complexation with GNR, whereas the original activity is retained in the presence of GNP. The formation of large assemblies (aggregates) and reduced average lifetime, as evidenced from dynamic light scattering and fluorescence decay measurements, respectively, suggest that GNR induces protein unfolding at its surface. The effect of temperature on the CD spectra of BSA鈥揋NP was found to be similar to that of pristine BSA, whereas BSA鈥揋NR shows distortion in CD spectra at lower wavelengths, strengthening the perception of protein unfolding. High binding constant and entropy change for BSA鈥揋NR complexation determined by ITC are consistent with large surfacial interaction that may lead to protein unfolding. The present work highlights the differential response of a protein depending on the nature of the nanostructure and its surface chemistry, which need to be modulated for controlling the biological responses of nanostructures for their potential biomedical applications.