Synthesis of cellulose nanoparticles conjugated with gold and investigation of diazinon toxin absorption by it

Dissertation for obtaining a Master's Degree in Agricultural Engineering (M.Sc)

Trend: Food Science and Industry

Abstract

Diazinon is an organophosphorus insecticide and is used in large quantities by farmers. This poison can easily find its way into food and exert its toxic effects on humans. Diazinon poison, like other organophosphorus poisons, inhibits some enzymes, especially acetylcholinesterase. Due to the high human and environmental risks, this pesticide is one of the most important occupational risks among farmers in developing countries. The aim of this study was to synthesize gold-conjugated nanocellulose and investigate the possibility of surface absorption of diazinon poison by it. After the synthesis of cellulose nanoparticles by acid hydrolysis method and its conjugation with the help of cross-linker, different concentrations of it were exposed to diazinon poison and the amount of poison absorption was evaluated at different times and pH. Also, the ability of conjugated nanoparticles to remove diazinon in green cucumber fruit that was previously contaminated with different concentrations of diazinon was also investigated. This research showed that gold-conjugated nanocellulose is a good adsorbent for diazinon in food. Examining the amount of absorption in green cucumber fruit showed that this nanoparticle can absorb up to 75% of diazinon in the fruit. Incubation times of more than one hour do not have much effect on the absorption process. Conjugated cellulose nanoparticles have the best absorption efficiency of diazinon under game conditions.

Key words: diazinon; cellulose; gold; surface absorption; nano particle; Conjugation

1- Introduction

Today, the increase in population followed by the increase in food consumption, especially agricultural products, has prompted farmers to increase the amount of their products. Pesticides are substances or mixtures of substances that are used to prevent, destroy, repel or reduce pests. But it should be kept in mind that exposure to pesticides is one of the most important occupational risks among farmers in developing countries. Diazinon is a broad-spectrum insecticide and is used against household insects, garden pests, ornamental plants, pets and even mosquitoes. Diazinon has the ability to decompose quickly, but in environmental conditions with low temperature, low humidity and lack of appropriate microbial decomposition activities, it is able to remain active in the soil for more than 6 months. Due to the rapid distribution of this poison in case of entering water sources and also its general effect on non-target organisms such as invertebrates, mammals, birds and fish (and especially aquatic species), it is one of the poisons that poses great environmental risks. This poison is absorbed through digestion, skin, and inhalation, and it is easily absorbed through the intestines and within a few hours, and it is quickly and in a short time metabolized into diazoxone in the liver. Diazinon is oxidized by microsomal enzymes to its metabolites such as diazoxone, hydroxydiazoxone and hydroxydiazinon, all of which are cholinesterase enzyme inhibitors. Inhibition of this enzyme has a destructive effect on the central or peripheral nerves, and even this poison affects the threshold of electrical stimulation and in some cases leads to epilepsy, convulsions and stimulation of the central nervous system. In addition, diazinon may cause gene mutation, chromosome destruction, negative effect on cell differentiation, induce cell death, stop mitotic division in the embryo and reduce DNA synthesis. To remove the diazinon poison, many things have been proposed, among which we can mention titanium oxide-silicon oxide nanocatalysts, alumina and zinc oxide nanoparticles. Of course, it should be noted that none of these materials, which have been introduced as absorbents, are specialized absorbents, and they can probably be absorbed by other materials as well. Also, these absorbents are toxic to human and animal cells and cause digestive and neurological complications. We think that it is necessary to provide a specialized adsorbent that, in addition to its absorption power, has minimum toxicity for humans and animals, so that it can be used in the future inside or on foods that are contaminated with diazinon poison. Based on theoretical studies, our guess is that cellulose nanoparticles conjugated with gold can be a suitable absorbent for diazinon.This hypothesis will first be studied in the simulator software and then under different conditions of temperature, pH and time, the amount of absorption will be carefully examined. Also, finally, the amount of absorption in real conditions, i.e. in the presence of foods (such as wheat and cucumber) that also contain diazinon, are investigated (Fu et al., 2001). Agricultural activities have become. Modern agriculture, plant breeding, pesticides, pest control and fertilizer, and technological advances have greatly increased the yield, but these advantages have been accompanied by extensive environmental damage, including more irrigation, more consumption of pesticides and fertilizers, and pollution of different layers of soil and underground water, and negative effects on human health. The definition given by the American Environmental Protection Agency (EPA) of a pesticide is that a pesticide is a substance or a mixture of substances that is used to prevent, destroy, repel or reduce any pest. The use of various poisons in the fight against health pests and disease carriers has a very long history, so that the ancient Chinese and Romans used chemical compounds in the fight against various pests. Although the control of the pathogen (using pesticides) is beneficial in the agricultural sector, but pesticides cause disease and death in humans, these problems are caused by different conditions of direct and indirect human contact with pesticides. Studies show that only in the United States, more than two billion pounds of pesticides are used annually in various sectors including agriculture, forestry, etc. For example, the American Public Health Association has estimated that nearly 1,275,000 American farmers are exposed to various pesticides. It is noteworthy that in developing countries compared to developed countries, due to the increased consumption and availability of various pesticides, poisoning with these poisons also has a high incidence rate. For example, in China alone, poisoning with pesticides, which are mostly organophosphorus poisons, causes the death of about 175,000 people per year (Fu et al., 2001). In Iran, according to the statistics center, in 1375, the total sale of agricultural pesticides was 15.8 thousand tons, and in 1380, the sales amount of agricultural pesticides was 15.8 thousand tons, and in 1380, the sales amount was Poisons have reached 27.2 thousand tons. According to the chemical safety profile information, nearly 27,000 tons of pesticides are consumed in Iran, including 101 types of insecticides, herbicides, fungicides, acaricides, snail killers, and nematicides. The number of poisons registered in 2018 in the country was 252, which includes 26% insecticides, 33% herbicides, 21% fungicides, 7% raticides, and 5% acaricides. Also, these 252 items were in the following categories:

Diazinon is an organophosphate insecticide that is used in large quantities by farmers.  This toxin can easily enter foods and exert noxious effects on humans. Like other organophosphates, diazinon causes inhibition of some enzymes, particularly acetylcholine esterase. Due to hazards for humans and the environment, diazinon is one of the most important occupational risks among farmers in developing countries. The purpose of this study was to evaluate the possibility of diazinon adsorption by gold-conjugated nanocellulose. After synthesis of nanocellulose by acid hydrolysis and its conjugation with gold, different concentrations of this conjugate were exposed to diazinon, and its adsorption was evaluated at different pH and incubation times. Also, its ability to remove diazinon in diazinon-treated cucumber was also examined. This study showed that gold-conjugated nanocellulose is a suitable adsorbent for removal of diazinon in foodstuffs. In cucumber, the adsorption was 75% by conjugated nanocellulose. Incubation times more than one hour did not affect adsorption rate. It was also found that conjugated nanocellulose had the best efficacy at alkaline pH.