Optimization of Silver Nanoparticle Synthesis by Banana Peel Extract Using Statistical Experimental Design, and Testing of their Antibacterial and Antioxidant Properties

Abstract

Background: In this study, silver nanoparticles (AgNPs) were synthesized using Banana Peel Extract (BPE), and characterized using UV- Vis absorbance spectroscopy, X-Ray Powder Diffraction (XRD), Atomic Force Microscopy (AFM), and Fourier Transform Infrared Spectroscopy (FTIR). UV-Vis absorbance spectroscopy showed the characteristic plasmon resonance of AgNPs at 433 nm. The synthesized AgNPs were tested for their antibacterial and antioxidant properties. Methods: Nanoparticle size (between 5 and 9 nm) was measured using AFM, whereas their crystallinity was shown by XRD. FTIR identified the ligands that surround the nanoparticle surface. The synthesis conditions were optimised using Central Composite Design (CCD) under Response Surface Methodology (RSM). Silver nitrate (AgNO3) and BPE concentrations (0.25-2.25 mM, 0.2-1.96 % v/v respectively), incubation period (24-120 h) and pH level (2.3-10.1) were chosen as the four independent factors. The fitting parameters (i.e. the wavelength at peak maximum, the peak area, and the peak width) of a Voigt function of the UV- Vis spectra were chosen as the responses. The antibacterial properties of the AgNPs were tested against Escherichia coli and Staphylococcus aureus using the tube dilution test. The synthesized nanoparticles were tested for total phenolic composition (TPC) using the Folin - Ciocalteau method, whereas their radical scavenging activity using the 1,1-diphenyl-2- picrylhydrazyl (DPPH) free radical assay. Results: An optimum combination of all independent factors was identified (BPE concentration 1.7 % v/v, AgNO3 concentration 1.75 mM, incubation period 48 h, pH level 4.3), giving minimum peak wavelength and peak width. The nanoparticles inhibited the growth of E. coli, whereas S. aureus growth was not affected. However, no superiority of AgNPs compared to AgNO3 used for their fabrication (1.75 mM), with respect to antibacterial action, could be here demonstrated. AgNPs were found to present moderate antioxidant activity (44.71± 3.01%), as measured using DPPH assay, while the BPE (used for their fabrication) presented alone (100%) an antioxidant action equal to 86±1%, something expected due to its higher total phenolic content (TPC) compared to that of nanoparticles. Conclusion: Altogether, the results of this study highlight the potential of an eco-friendly method to synthesize nanoparticles and its promising optimization through statistical experimental design. Future research on the potential influence of other synthesis parameters on nanoparticles yield and properties could further promote their useful biological activities towards their successful application in the food industry and other settings.

Solid and liquid green Ag nanoparticles based on banana peel extract as an eco‐friendly remedy for ringworm in pets

“…The IR peak located at 1581 cm −1 was assigned as the bending vibration of C–N bending in the amide group. After reaction with AgNO 3 , this peak was shifted from 1581 to 1575 cm −1 , indicating the possible role of amino groups of the banana peel extract in Ag NPs synthesis 36 . The vibrational peak at 1041 cm −1 was attributed to C–O of carboxylic acid, ester, or ether, C–N of aliphatic amines or alcohol/phenol.…”

“…After reaction with AgNO 3 , this peak was shifted from 1581 to 1575 cm À1 , indicating the possible role of amino groups of the banana peel extract in Ag NPs synthesis. 36 The vibrational peak at 1041 cm À1 was attributed to C-O of carboxylic acid, ester, or ether, C-N of aliphatic amines or alcohol/phenol. The structural shift of IR peak at 1041 to 1025 cm À1 might indicate the contribution of carboxylic and amino groups in the reductive process.…”

Green synthesis of silver nanoparticles using olive mill wastewater and olive stones extract and testing their antimicrobial activities against Escherichia coli and Staphylococcus epidermidis

“…The produced silver nanoparticles, a) AgNP-OMW: AgNO 3 (1 mM), OMW (2% v/v), NaOH (7.9 mM), and b) AgNP-OSE: AgNO 3 (2 mM), OSE (1% v/v), NaOH (0.2 mM), were characterized using x-ray Diffraction (XRD) Patterns and Fourier Transform Infrared (FTIR) experiments, similarly to previous work [36]. Briefly, XRD patterns were recorded employing the D8 Advance Brunker diffractometer (Cu Ka radiation, 40 kV, 40 mA), in the 2θ range (2-80°), with step size 0.02°and 2 s acquisition time per step [36]. FTIR spectra were acquired at 400-4000 cm −1 wavenumbers, employing the Jasco FT/IR-4100 [36].…”

“…Briefly, XRD patterns were recorded employing the D8 Advance Brunker diffractometer (Cu Ka radiation, 40 kV, 40 mA), in the 2θ range (2-80°), with step size 0.02°and 2 s acquisition time per step [36]. FTIR spectra were acquired at 400-4000 cm −1 wavenumbers, employing the Jasco FT/IR-4100 [36]. KBr pellets loaded with 2 wt% of nanoparticle suspensions, were used as samples [36].…”

“…FTIR spectra were acquired at 400-4000 cm −1 wavenumbers, employing the Jasco FT/IR-4100 [36]. KBr pellets loaded with 2 wt% of nanoparticle suspensions, were used as samples [36].…”