Porous Silica Nanoparticles for Pesticide Delivery

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TEM of mesoporous silica nanoparticle (Dr. Victor Lin group/Iowa State University - Courtesey of Dr Victor Lin group at Iowa State University).

Nearly 10,000 of the 500,000 green leaf-eating insect species are plague species, responsible for the loss of 14-25% of total global agricultural production. Insecticides, chemicals used to alter the metabolism of insects to stop their lifecycle or reproduction, have been used since the 16th century to combat crop destruction, but due to environmental degradation of the chemicals, the quantities in which insecticides must now be used to be effective pose a significant threat to human health. As a result of leaching, UV degradation, and hydrolysis, as much as 90% of applied agrochemicals are ineffective, requiring repeated application of the insecticides which in turn leads to developed insect resistance and elimination of the pest’s natural predators [1]. 

Controlled-release formulations (CRFs) would improve the efficacy of pesticides by ensuring the active compounds are released only at the target site via the regulation of an inert material. One such CRF solution is the use of Mesoporous Silica Nanoparticles (MSNs) to deliver insecticides [2]. MSNs are made by reacting tetraethyl orthosilicate on a template of micellar rods to form porous nanoparticles [3]. The pores are then injected with the desired active compound and covalently capped with gold nanoparticles (AuNPs), which will release the insecticide when the AuNPs come in contact with a chemical uncapping trigger, such as the alkaline solution of an insect’s stomach. The high surface area to volume ratio created by the nanoparticle structure makes MSNs effective delivery carriers, and the size-adjustable 3D open pore structure allows for a regulated adsorption rate [4]. Coating MSNs with additional polymers can also regulate drug release by allowing for a constant release rate caused by the steady degradation of the polymer, as opposed to a single burst of chemicals caused by the breaking of covalent bonds [5].

By decreasing the amount of pesticide used, MSNs also decrease costs to farmers by limiting re-application of expensive chemicals, protect the environment and untargeted organisms, and reduce human pesticide exposure and poisonings [1]. While technological advances in crop preservation are important to reduce agricultural loss, it is equally important to acknowledge all contributing factors to persistent world hunger. Despite the fact that enough food is produced to feed the global population [6], nearly 870 million people still suffer from hunger due to inadequate distribution [6]. To solve the problem of global hunger issues such as inadequate food transportation, food waste (1.3 billion tons), and unaffordable food costs must also be addressed to reach a holistic solution [7]. 

References 

  1. Perlatti, Bruno, Patricia Luisa De Souza Bergo, Maria Fatima Das Gracas Fernandes Da Silva, Joao Batista, and Moacir Rossi. "Polymeric Nanoparticle-Based Insecticides: A Controlled Release Purpose for Agrochemicals." Insecticides - Development of Safer and More Effective Technologies (2013): n. pag.
  2. Torney, François, Brian G. Trewyn, Victor S.-Y. Lin, and Kan Wang. "Mesoporous Silica Nanoparticles Deliver DNA and Chemicals into Plants." Nature Nanotech Nature Nanotechnology 2.5 (2007): 295-300.
  3. Trewyn, Brian G; Nieweg, Jennifer A; Zhao, Yannan; Lin, Victor S.-Y. (2007). "Biocompatible mesoporous silica nanoparticles with different morphologies for animal cell membrane penetration". Chemical Engineering Journal 137 (1): 23–29. doi:10.1016/j.cej.2007.09.045.
  4. Pérez-De-Luque, Alejandro, and Diego Rubiales. "Nanotechnology for Parasitic Plant Control." Pest. Manag. Sci. Pest Management Science 65.5 (2009): 540-45.
  5. Popat, Amirali, Jian Liu, Qiuhong Hu, Michael Kennedy, Brenton Peters, Gao Qing (Max) Lu, and Shi Zhang Qiao. "Adsorption and Release of Biocides with Mesoporous Silica Nanoparticles." Nanoscale 4.3 (2012): 970-75.
  6. Leathers, Howard D., and Phillips Foster. The World Food Problem: Toward Ending Undernutrition in the Third World. Boulder: Lynne Rienner, 2009. Print. p. 133
  7. "What Causes Hunger? | WFP | United Nations World Food Programme - Fighting Hunger Worldwide." World Food Programme, n.d. Web. 28 June 2016.
  8.  Fruijtier-Pölloth, Claudia. "The Toxicological Mode of Action and the Safety of Synthetic Amorphous Silica—A Nanostructured Material." Toxicology 294.2-3 (2012): 61-79.
  9. Slivka, Jeff. "Silica-The Next Environmental Issue." International Risk Management Institute, Apr. 2005. Web. 28 June 2016.

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Summary: 

Mesoporous Silica Nanoparticles (MSNs) were found to be a novel regulated delivery vector of insecticide to target systems by utilizing gold nanoparticles (AuNPs) covalently bonded to the MSN’s to seal the insecticides in the hollow pores of the MSNs. By preventing the pesticides from leeching into the environment and protecting them from external degradation factors, the efficacy of the chemicals will improve, decreasing the quantity needed and the number of reapplications. 

Material: 

Benefit Summary: 

By altering the arrangement of micellar rods on the template, the MSNs can have a range of pore sizes 2-10nm in diameter. This flexibility allows for the use of MSNs as a delivery vector of not only agrochemicals but also entomopathogenic fungi for use as a bio-control agent, DNA to create transgenic plants, or even Boron or Nitrogen-based fertilizers [2]. 

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Risk Summary: 

Commercial forms of Synthetic amorphous silica (SAS) have been found to have no environmental or health risks and are used in a variety of pharmaceutical, cosmetic, and food products. Nanosilica has also shown that is does not bioaccumulate in the environment or in organisms, but Silica itself is a known carcinogen that causes the lung-scaring disease silicosis [8]. Mining, construction, and agricultural workers are at most risk for exposure to respirable crystalline silica and silica containing dust [9]. 

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