Concerns over the use of silver nanoparticles in fresh produce have been tackled by US researchers claiming to have developed methods for their detection.
Engineered nanomaterials such as silver nanoparticles (Ag NPs) have been increasingly used in agriculture due to their antimicrobial and insecticidal properties, said the University of Missouri researchers.
Contamination of Ag NPs in pears was detected, characterized, and quantified by transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), and inductively coupled plasma optical emission spectrometry (ICP-OES).
TEM and SEM were selected to detect the Ag NPs in fruits because they have been used to characterize the size, shape, and structure of nanomaterials and can directly detect and visualize the penetration and interaction of NPs with plant tissues.
ICP-OES was used to determine the metal content in the soil and plant samples with high accuracy.
Conventional techniques such as optical microscope are unsuitable for measuring extremely small size of nanoparticles, said the researchers.
Penetration of pear skin
Mengshi Lin et al studied the residue and penetration of silver nanoparticles on pear skin.
The scientists put the pears in a silver nanoparticle solution similar to pesticide application and then washed and rinsed them repeatedly.
Pear samples were treated with two different sizes (20 and 70nm in diameter) of Ag NPs and stored for different times.
It was found that both 20 and 70nm Ag NPs were still attached on the pear skin after four days of treatment followed by rinsing with deionized water and smaller particles were able to penetrate the skin and reach the pear pulp.
The results reveal that 20nm Ag NPs could penetrate the pear skin and pulp, while 70nm Ag NPs did not.
Nanotech safety debate
"More than 1,000 products on the market are nanotechnology-based products," said Lin, associate professor of food science in the MU College of Agriculture, Food and Natural Resources.
"This is a concern because we do not know the toxicity of the nanoparticles. Our goal is to detect, identify and quantify these nanoparticles in food and food products and study their toxicity as soon as possible.
"The penetration of silver nanoparticles is dangerous to consumers because they have the ability to relocate in the human body after digestion," Lin said.
"Therefore, smaller nanoparticles may be more harmful to consumers than larger counterparts."
Future research is needed on the contamination and penetration of different type of nanoparticles on other fruits, crops, and agricultural products, they concluded.
Source: Journal of Agricultural Chemistry
“Detection of Engineered Silver Nanoparticle Contamination in Pears”
Authors: Zhong Zhang, Fanbin Kong, Bongkosh Vardhanabhuti, Azlin Mustapha, and Mengshi Lin