Biosynthesis of TiO2 nanoparticles

May 29, 2024, 11:58 AM

TDD-global

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This article reviews the biogenic synthesis of TiO2 nanoparticles, highlighting the advantages of microbial methods over chemical synthesis. It discusses the role of various microorganisms and plant extracts in producing stable nanoparticles with potential antimicrobial properties. Key mechanisms like bioabsorption and extracellular complexation are explored, along with the impact of environmental factors on synthesis.

Living systems are involved in the production of nanoparticles which are more stable as compared with chemically synthesized nanoparticles. Nanoparticles synthesized using microorganisms are found to have less aggregation behavior due to presence of more repulsive forces. Utility of nanoparticles is mainly dependent upon its size, shape as well as stability. Hence, researchers focus on the biogenic synthesis of nanoparticles which can fulfill the criteria.

TiO2 nanoparticles which naturally exists in three different crystalline forms anatase, rutile and brookite can be produced using biological agent. Extensive research is carried on the biosynthesis of nanoparticles. Biosynthesis of nanoparticles is one of the growing areas in the field of nanotechnology. Various reports are available on the utilization of bacteria, fungi, algae, plant material and enzymes for the biosynthesis of nanoparticles.

The mechanisms involved in the microbial synthesis of nanoparticles are bio absorption, extracellular complexation or precipitation of metals, bioaccumulation, efflux systems, and alteration of solubility and toxicity via reduction or oxidation and lack of specific metal transport systems. Negative electrokinetic potential, bio sorption and bio reduction ability of the microorganisms makes them suitable candidate to synthesize nanoparticles. There is information on synthesis of TiO2 nanoparticles using fungal pathogen Fusarium oxysporium. Saccharomyces cerevisiae and Lactobacillus sp. have been reported to produce 30 and 18 nm TiO2 nanoparticles using TiO (OH)2. Energy source, pH and overall oxidation reduction potential were found to be important factors in the synthesis of TiO2 nanoparticles, while in the case of Saccharomyces cerevisiae, oxidase enzyme plays an important role . TiO2 nanoparticles in anatase form were synthesized using Curcuma longa plant extract due to its content of terpenoids, flavonoids and proteins.

Fenugreek (Trigonella foenum graecum (L.)) has been studied to synthesize TiO2 nanoparticles with antimicrobial property. There is a report on the synthesis of rutile TiO2 nanoparticles using custard apple peel extract and precursor TiO (OH)2. The presence of OH group in the chemical constituents of Annona squamosa was found to be responsible to dehydrate titanyl hydroxide to TiO2 and stabilize the nanoparticles. TiO2 nanoparticles produced using Vigna radiata (green gram) legumes showed antibacterial, antioxidant and cytotoxicity activity against Mg 63 osteosarcoma cell lines. Titanium dioxide nanoparticles due to Lactobacillus crispatus has been found to reduce biofilm formation; hemolysin and also urease which are responsible to develop multidrug resistance ability in the pathogens. Electrostatic interaction between Lactobacillus sp. and metal clusters are responsible for the metal nanoparticles synthesis. The production of anatase TiO2 nanoparticles mediated by Bacillus subtilis has been studied.

Guava (Psidium guajava) leaf extract mediated TiO2 nanoparticles showed antioxidant and antimicrobial activities. Guava leaf extract contains alcohol, primary and aromatic amines which assists in the synthesis of TiO2 nanoparticles. TiO2 nanoparticles made by using Aspergillus flavus TFR7 and bulk TiO2, was used as foliar spray (10 mg/l) on mung bean (Vigna radiata L.). This fungal mediated TiO2 found to enhance the vigor index of mung bean. Fungi secrete capping proteins which play the role of encapsulation of nanoparticles while associated proteins contributes in the mineralization of precursor salt. Aspergillus niger and Aspergillus tubingensis TFR-5 have also been reported to have the capability to produce TiO2 nanoparticles.