Green synthesis of silver nanoparticles and characterization of their inhibitory effects on AGEs formation using biophysical techniques

Abstract

Advanced glycation end-products (AGEs) resulting from non-enzymatic glycation are one of the major factors implicated in secondary complications of diabetes. Scientists are focusing on discovering new compounds that may be used as potential AGEs inhibitors without affecting the normal structure and function of biomolecules. A number of natural and synthetic compounds have been proposed as AGE inhibitors. In this study, we investigated the inhibitory effects of AgNPs (silver nanoparticles) in AGEs formation. AgNPs (~30.5 nm) synthesized from Aloe Vera leaf extract were characterized using UV-Vis spectroscopy, energy-dispersive X-ray spectroscopy (EDX), high resolution-transmission electron microscopy, X-ray diffraction and dynamic light scattering (DLS) techniques. The inhibitory effects of AgNPs on AGEs formation were evaluated by investigating the degree of reactivity of free amino groups (lysine and arginine residues), protein-bound carbonyl and carboxymethyl lysine (CML) content, and the effects on protein structure using various physicochemical techniques. The results showed that AgNPs significantly inhibit AGEs formation in a concentration dependent manner and that AgNPs have a positive effect on protein structure. These findings strongly suggest that AgNPs may play a therapeutic role in diabetes-related complications.

Figure 1

(1.1)UV–vis absorption spectrum of (A) silver nitrate (1 mM) and silver nanoparticles (B) synthesized using extract of fresh Aloe vera leaf.(1.2) HR-TEM micrograph (A) and EDX spectrum (B) of green synthesized silver nanoparticles.

Figure 2

(1.1)DLS histogram showing particle size distribution of synthesized silver nanoparticles.(1.2) X-ray powder diffraction pattern of green synthesized silver nanoparticles.

Figure 3. UV absorbance spectra of HSA and MG with varied concentrations of AgNP incubated at 37 °C for 6 days.

UV absorbance was monitored at 280 nm.

Figure 4. Fluorescence emission intensity profiles of HSA and MG with varied concentrations of AgNP.

Fluorescence intensities were measured at excitation and emission wavelengths of 365 nm and 444 nm, respectively.

Figure 5. HPLC/UV elution profiles of HSA with MG mixtures with or without AgNP after 6 days of incubation.

(A) Native HSA, (B) HSA–MG mixtures without AgNP, (C) HSA–MG with AgNP (0.09 mM), (D) HSA–MG with AgNP (0.185 mM), and (E) HSA–MG with AgNP (0.27 mM). All readings were taken in triplicate. UV Absorbance was measured at 280 nm.

Figure 6

(A)CD profiles of HSA–MG with and without various concentrations of AgNPs incubated at 37 °C for 6 days. All samples were appropriately diluted with deionized water before obtaining the CD profile. Repeat studies revealed no significant difference in CD profiles. (B) FTIR profiles of Amide I and Amide II bands of HSA and MG mixtures with and without AgNPs after 6 days of incubation. All readings were taken in triplicate.