Surface Coating-Modulated Phytotoxic Responses of Silver Nanoparticles in Plants and Freshwater Green Algae

Abstract

Silver nanoparticles (AgNPs) have been implemented in a wide range of commercial products, resulting in their unregulated release into aquatic as well as terrestrial systems. This raises concerns over their impending environmental effects. Once released into the environment, they are prone to various transformation processes that modify their reactivity. In order to increase AgNP stability, different stabilizing coatings are applied during their synthesis. However, coating agents determine particle size and shape and influence their solubility, reactivity, and overall stability as well as their behavior and transformations in the biological medium. In this review, we attempt to give an overview on how the employment of different stabilizing coatings can modulate AgNP-induced phytotoxicity with respect to growth, physiology, and gene and protein expression in terrestrial and aquatic plants and freshwater algae.

Keywords: gene expression; green algae; growth; oxidative stress; photosynthesis; plants; protein expression; silver nanoparticles.

Figure 1

Proportional representation of coatings used for AgNP stabilization in plant (A) and algal (B) research.

Figure 2

Uptake of differently coated and uncoated AgNPs in plants and freshwater algae and their effects on growth and morphology. EPS—extracellular polymeric substances. Figure was created with BioRender.com. Accessed on 24 November 2021.

Figure 3

Effect of differently coated AgNPs on plant and algal cells by direct interaction or through ROS formation. ROS—reactive oxygen species, ER—endoplasmic reticulum, CAT—catalase, SOD—superoxide dismutase, POD—peroxidase. Adapted from “Structural Overview of a Plant Cell” by BioRender.com (2021). Retrieved from https://app.biorender.com/biorender-templates. Accessed on 17 December 2021.

Figure 4

Structural and functional changes of the photosynthetic apparatus in plants and freshwater algae upon exposure to AgNPs with different surface coatings. RuBP—ribulose 1,5-bisphosphate, 3-PGA—3-phosphoglyceric acid, G3P—glyceraldehyde 3-phosphate, PS—photosystem, PQ—plastoquinone, Cyt b6f—cytochrome b6f, PC—plastocyanin, Fd—ferredoxins. Figure was adapted from “Light Dependent Reactions of Photosynthesis” by BioRender.com (2021). Retrieved from https://app.biorender.com/biorender-templates. Accessed on 24 November 2021.