Biocomposite Materials Derived from Andropogon halepensis: Eco-Design and Biophysical Evaluation

Abstract

This research work presents a "green" strategy of weed valorization for developing silver nanoparticles (AgNPs) with promising interesting applications. Two types of AgNPs were phyto-synthesized using an aqueous leaf extract of the weed Andropogon halepensis L. Phyto-manufacturing of AgNPs was achieved by two bio-reactions, in which the volume ratio of (phyto-extract)/(silver salt solution) was varied. The size and physical stability of Andropogon-AgNPs were evaluated by means of DLS and zeta potential measurements, respectively. The phyto-developed nanoparticles presented good free radicals-scavenging properties (investigated via a chemiluminescence technique) and also urease inhibitory activity (evaluated using the conductometric method). Andropogon-AgNPs could be promising candidates for various bio-applications, such as acting as an antioxidant coating for the development of multifunctional materials. Thus, the Andropogon-derived samples were used to treat spider silk from the spider Pholcus phalangioides, and then, the obtained "green" materials were characterized by spectral (UV-Vis absorption, FTIR ATR, and EDX) and morphological (SEM) analyses. These results could be exploited to design novel bioactive materials with applications in the biomedical field.

Keywords: Andropogon halepensis; Pholcus phalangioides; antioxidant activity; biocomposites; silver nanoparticles; spider silk; “green” synthesis.

Figure 1

Schematic representation of the eco-design and preparation of the materials derived from Andropogon halepensis L. The figure was created with Chemix (https://chemix.org/, accessed on 25 January 2024) and with PowerPoint and Paint 3D. This figure also contains images taken by us with a camera, an optical microscope, and SEM.

Figure 2

Comparative presentation of UV-Vis absorption spectra of Andropogon-derived samples. All AgNPs spectra were normalized at their maximum. The top inset shows the SPR bands of the Andropogon-derived AgNPs. The bottom inset shows the spectrum of Andropogon halepensis aqueous extract (EAh).

Figure 3

Comparative presentation of UV-Vis absorption spectra of the spider silk samples untreated (S) and treated with plant extract (S_EAh) or with silver nanoparticles obtained by Bio-Reaction 1 (S_AgNPs_1n and S_AgNPs_1o) and Bio-Reaction 2 (S_AgNPs_2n and S_AgNPs_2o).

Figure 4

Comparative presentation of FTIR ATR spectra of Andropogon halepensis extract (EAh) and the derived AgNPs phyto-synthesized through Bio-Reaction 1 (AgNPs_1n and AgNPs_1o) and Bio-Reaction 2 (AgNPs_2n and AgNPs_2o). The index “n” refers to the “new” synthesized nanoparticles, while the index “o” refers to the “old” (18 months aged) ones.

Figure 5

Comparative presentation of FTIR ATR spectra of the spider silk samples untreated (S) and treated with plant extract (S_EAh) or with silver nanoparticles obtained by Bio-Reaction 1 (S_AgNPs_1n and S_AgNPs_1o) and Bio-Reaction 2 (S_AgNPs_2n and S_AgNPs_2o) (a). Insets show the magnified regions of the FTIR ATR spectra of the biocomposites (b,c).

Figure 6

Comparative presentation of the electrokinetic potential of the Andropogon-derived silver nanoparticles. The AgNPs samples obtained through Bio-Reaction 1 (AgNPs_1n and AgNPs_1o) are placed next to those obtained through Bio-Reaction 2 (AgNPs_2n and AgNPs_2o) by alternating the aged samples with the fresh ones.

Figure 7

(a) Comparative presentation of the average particle size (Zav, nm) and PdI index of “green”-developed silver nanoparticles, estimated by dynamic light scattering (DLS) measurements; (b) Size distribution profiles of particle population for all types of phyto-developed AgNPs. For comparison, the aged AgNPs samples (AgNPs_1o and AgNPs_2o) are arranged next to the fresh ones (AgNPs_1n and AgNPs_2n).

Figure 8

The SEM images of the phyto-developed AgNPs (AgNPs_1n, AgNPs_1o, AgNPs_2n, and AgNPs_2o) and of the spider silk fibers (S) and spider silk biocomposites with plant extract (S_EAh) or with silver nanoparticles (S_AgNPs_1n, S_AgNPs_1o, S_AgNPs_2n, and S_AgNPs_2o).

Figure 9

The antioxidant activity of the Andropogon halepensis extract (EAh) and the phyto-metallic particles obtained by Bio-Reaction 1 (AgNPs_1n and AgNPs_1o) and Bio-Reaction 2 (AgNPs_2n and AgNPs_2o), estimated using the chemiluminescence technique.