Biosynthesis of silver nanoparticles using Euglena gracilis, Euglena intermedia and their extract

Area of Science:

• Biotechnology
• Nanotechnology
• Microbiology

Background:

• Silver nanoparticles (AgNPs) exhibit broad-spectrum antimicrobial properties and are utilized in various biomedical applications.
• Microalgae, such as Euglena species, are increasingly explored for their potential in green synthesis of nanoparticles due to their metabolic capabilities.
• Understanding the biosynthesis pathways and characteristics of AgNPs produced by microalgae is crucial for their efficient application.

Purpose of the Study:

• To investigate and report the extracellular and intracellular biosynthesis of silver nanoparticles (AgNPs) using two distinct Euglena strains: Euglena gracilis (EG) and Euglena intermedia (EI).
• To characterize the synthesized AgNPs, including their size, shape, and optical properties.
• To identify the capping and stabilizing agents involved in the biosynthesis process.

Main Methods:

• Biosynthesis of AgNPs was performed both in vivo (intracellular) and in vitro (extracellular) using EG and EI strains.
• UV-visible spectroscopy was employed to confirm the plasmon resonance of AgNPs.
• Inductively coupled plasma-atomic emission spectrometry (ICP-AES) was used to quantify silver ion uptake.
• Transmission electron microscopy (TEM) coupled with energy-dispersive X-ray analysis (EDX) was utilized for morphological and elemental characterization.
• Fourier transform infrared spectroscopy (FTIR) was performed to identify functional groups involved in stabilization.

Main Results:

• AgNPs synthesized by both Euglena strains exhibited a characteristic absorption peak around 420 nm, indicative of surface plasmon resonance.
• ICP-AES results showed comparable silver ion uptake by both EI and EG strains.
• TEM analysis revealed spherical AgNPs with polydispersal size distributions: 6–24 nm for in vivo synthesis and 15–60 nm for in vitro synthesis.
• EDX confirmed the presence of silver in the synthesized nanoparticles.
• FTIR analysis identified bioactive functional groups, particularly amines, acting as capping and stabilizing agents.

Conclusions:

• Both Euglena gracilis and Euglena intermedia are effective sources for the biosynthesis of silver nanoparticles through both extracellular and intracellular pathways.
• The synthesized AgNPs possess characteristics suitable for various applications, with amine groups playing a key role in their stabilization.
• This study represents the first report utilizing these two Euglena species for dual in vivo and in vitro AgNP biosynthesis, highlighting a novel and sustainable approach.