posted on 2020-10-21, 19:21authored byYing Bao, Yang Li, Ling Ling, Xiaoxuan Xiang, Xiaoxia Han, Bing Zhao, Xinhua Guo
The use of silver nanoparticles (Ag
NPs) as substrates to obtain
satisfactory Raman spectra of native proteins is a simple and valuable
but challenging process. Herein, the Ag NPs modified with aluminum
and iodide ions (Ag IANPs) were introduced for Raman detection of
proteins, including acidic BSA (PI 4.7), catalase (PI 5.4), β-casein
(PI 4.5), α-casein (PI 4.0), insulin (PI 5.35), basic myoglobin
(PI 6.99), and lysozyme (PI 11.2). The Raman signals of all the detected
proteins were significantly improved in comparison with the reported
spectra obtained by using Ag NPs containing Na2SO4, I–, and Mg2+. Specifically, detection
sensitivities of the acidic proteins were drastically increased. The
limit of detection (LOD) of bovine serum albumin (BSA), α-casein,
and β-casein was 0.03 ng/mL. The LOD of insulin and catalase
were 0.3 and 3 ng/mL, respectively. As the bands corresponding to
disulfide bonds, α-helices, residues of Phe, Trp, and Tyr, and
carboxyl groups were also greatly enhanced, it was easy to monitor
the folding of native protein and the denaturation of protein under
acidic and heated conditions. Thus, Ag IANPs as substrates open a
way for surface-enhanced Raman spectroscopy (SERS) detection of proteins.
Hence, the method can provide more valuable information about protein
and, therefore, has the potential for wide applications.