Biosynthesis of Metal and Metal Oxide Nanoparticles Using Microbial Cultures: Mechanisms, Antimicrobial Activity and Applications to Cultural Heritage

Abstract

Nanoparticles (1 to 100 nm) have unique physical and chemical properties, which makes them suitable for application in a vast range of scientific and technological fields. In particular, metal nanoparticle (MNPs) research has been showing promising antimicrobial activities, paving the way for new applications. However, despite some research into their antimicrobial potential, the antimicrobial mechanisms are still not well determined. Nanoparticles’ biosynthesis, using plant extracts or microorganisms, has shown promising results as green alternatives to chemical synthesis; however, the knowledge regarding the mechanisms behind it is neither abundant nor consensual. In this review, findings from studies on the antimicrobial and biosynthesis mechanisms of MNPs were compiled and evidence-based mechanisms proposed. The first revealed the importance of enzymatic disturbance by internalized metal ions, while the second illustrated the role of reducing and negatively charged molecules. Additionally, the main results from recent studies (2018–2022) on the biosynthesis of MNPs using microorganisms were summarized and analyzed, evidencing a prevalence of research on silver nanoparticles synthesized using bacteria aiming toward testing their antimicrobial potential. Finally, a synopsis of studies on MNPs applied to cultural heritage materials showed potential for their future use in preservation.

New horizons on advanced nanoscale materials for Cultural Heritage conservation

“…85,87,88 Finally, nanoscale materials like metal (or metal oxide) particles, nanocarriers, and inorganic-organic hybrids have been explored in the past few years to counteract microorganisms, corrosion, environmental pollutants (as acetic acid), and weathering, or to provide mechanical consolidation. Some examples include silver 89,90 or titanium dioxide nanoparticles, 91,92 and zinc oxide micro-or nanoparticles, [93][94][95] also embedded in polymer matrices, layered double hydroxides nanocarriers, 96 mesoporous silica nanoparticles, 97 halloysite nanotubes, 98,99 cellulose nanocrystals/fibrils or lignin nanoparticles, 100 cellulose-fibroin colloidal dispersions, 101 and starch nanoparticles. 102 These examples are representative of the potential that nanoscience and colloids have in the formulation of materials for the preservation of CH, with particular emphasis on bio-or biomimetic systems with enhanced properties and reduced ecotoxicity.…”

Sol–Gel-Derived TiO2 and TiO2/Cu Nanoparticles: Synthesis, Characterization, and Antibacterial Efficacy

“…In terms of the antibacterial properties of the nanomaterials, the ability of the bacterial cells to regrow on the nutrient agar plates following their incubation on the MIC assay shows that the Cu-TiO 2 nanoparticles are bacteriostatic, and not bactericidal (i.e., they inhibit bacterial growth without killing the cells. , The clinical importance of bactericidal and bacteriostatic samples, however, is still under dispute and is not used to rule out the potential application of samples as antimicrobial agents. In general, the results in Figure a,b have shown that no significant differences in the antimicrobial activity of the TiO 2 nanoparticles were observed in the presence and the absence of copper.…”

Manganese Nanoparticles: Synthesis, Mechanisms of Influence on Plant Resistance to Stress, and Prospects for Application in Agricultural Chemistry

“…The synthesis of metal NPs using bacteria has been described in most detail in ref 83. Bacteria can synthesize Mn NPs in two ways: intracellular and extracellular.…”