Abstract
In the present investigation, fucoxanthin—one of the major pigments in diatoms—has been extracted from Nanofrustulum shiloi SZCZM1342, and its reducing efficiency in the biogenesis of gold nanoparticles (GNPs) was checked. Fucoxanthin extracted from golden-brown cells of N. shiloi was compared to the healthy, growing biomass of N. shiloi and standard fucoxanthin after separate exposure to 25 mg L−1 aqueous hydrogen tetrachloroaurate solutions at room temperature. Isolated and standard fucoxanthin were found to be able to reduce gold ions within 12 h whereas, the whole biomass turned pink in color after 72 h of reaction. The synthesized particles were characterized by UV-vis spectroscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). UV–vis spectroscopy of purple-colored suspensions showed the absorption band at approximately 520–545 nm, indicating a strong positive signal for GNP synthesis. The SEM study revealed the deposition of GNPs on siliceous frustules of metal-treated diatom cells. The TEM analysis confirmed the GNPs synthesized by whole biomass are triangular, spherical and hexagonal in nature, whereas the particles produced by extracted and standard fucoxanthin are all spherical in nature. This study demonstrates the involvement of fucoxanthin in the reduction of gold ions and subsequent production of gold nanospheres.
Highlights
Biogenesis of biocompatible noble metal nanoparticles, such as gold [1,2,3,4,5], silver [6,7,8,9,10,11], platinum [12] and palladium [13], is a popular choice nowadays because it avoids the use of toxic reducing agents required in traditional chemical synthesis approaches
We report, for the first time, biocompatible spherical-shaped gold nanoparticles (GNPs) production using extracted fucoxanthin from N. shiloi, one of the smallest diatom species known to date, which can occur off marine coasts in masses and form natural blooms [39]
The rapid synthesis of nanoparticles was observed in reaction with 25 mg L−1 Au3+ solution at pH 4, and this condition was further used for characterization
Summary
Biogenesis of biocompatible noble metal nanoparticles, such as gold [1,2,3,4,5], silver [6,7,8,9,10,11], platinum [12] and palladium [13], is a popular choice nowadays because it avoids the use of toxic reducing agents required in traditional chemical synthesis approaches. The main drawback in the green synthesis of nanoparticles is their resulting heterogeneity, i.e., the formation of differently shaped nanoparticles of variable size. The formation of varying shaped particles is very usual in green synthesis as different reducing agents, such as proteins, polysaccharides and pigments [14], work together. Particles with different shapes are not suitable in medical applications [15] because the heterogeneous products lead to unacceptable (variable, unreliable) results. Biosynthesis of nanoparticles with a definite shape is possible by using a single reducing agent [16]. It is very important to identify the reducing agents within a cell and to check their efficacy in synthesizing nanoparticles in isolated conditions
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