Ultrastable Surfactant Free Silver Nanoparticles Study for Application in Green Housing and Cancer Treatment
Authors: Rauwel Erwan , Küünal Siim , Rauwel Protima , Guha Mithu , Kutti Sander , Wragg David 
Published: February 2020

Metallic nanoparticles (MNPs) with diameter ranging from 2 to 100nm have received extensive attention during the past decades due to their unique properties and potential applications in main fields like catalysis, optics, electronics and medicine,1 having attracted considerable attention for their special chemical and physical properties due to their high potential applications such as magnetic data storage, magnetic hyperthermia therapy, gene delivery for the magnetic nanoparticles, but also catalysis, optoelectronics, cancer therapy for noble-metal nanoparticles. The main interest in MNPs comes from their unique chemical and electronic properties due to their large surface-to-volume ratio.2 The advances in preparing MNPs, specifically using sol-gel methods, have improved the NP samples remarkably giving monodisperse nanoparticles with a good size and shape control and distribution during the synthesis.
There is a need for a simple, reliable, surfactant free low cost method for producing homogeneous stable metal nanoparticles and we recently developed one that enables the production of surfactant-free stable MNPs under air. Their unusual stability in air allows applications previously difficult to implement with metal nanoparticles produced using conventional methods due to their pyrophoric properties.
The antimicrobial and antifungal properties of silver ion or salts are well known, but the effects of AgNP on specific bacteria and fungi have not been revealed clearly. Using straws as a building material for insulating houses is a growing trend in green housing projects through Europe. Consisting of organic porous materials, they are prone to degrade over time due to the activity of different microorganisms (fungi and bacteria) when moisture is present. This degradation induces structural damages, instability and airborne microorganisms that can induce allergies in the whole ecohouse. Using chemicals to prevent these damages may also induce potential health risk like allergy and chemicals also degrade with time.3

We investigated the use of the antimicrobial properties of the silver nanoparticles on these organisms for the straw protection. The second advantage is that AgNPs do not degrade with time and can be recycled after use.
For this study, stable AgNPs were prepared in a glove box using silver acetate. The mixture was transferred into a stainless steel autoclave, carefully sealed and then heated in a furnace at 200ºC for 2 days. The structural properties of these silver nanoparticles were studied by XRD, TGA and HRTEM. XRD measurements showed that NPs have cubic structure and HRTEM micrographs revealed highly crystalline monodisperse nanoparticles. TGA measurements did not show any weight loss demonstrating the high purity of these silver nanoparticles.
The effect of silver nanoparticles on these microorganisms will be presented as a potential solution for green housing improvement. However, the inhalation of silver nanoparticles, like in the case of chemicals could provoke allergic reactions.5 To validate such potential use of silver nanoparticles instead of chemicals their toxicity was studied using Human Embryon Kidney Cells(HEK 293), Hela cells (used for cancer research) and cancer cells. The effect of these nanoparticles on human cells will be discussed in terms of possible application in green housing, but also for biomedical applications and cancer treatment.
Acknowledgements
Financial support from through the inGAP project (Innovative Natural Gas Processes and Products) and Marie Curie (PERG05-GA-2009-249243) and the European Social Fund's Doctoral Studies and Internationalization Program “DoRa” Activity 6 under project 1.2.0201.08-0001 in Estonia is acknowledged.
1. S.Y.Li et al., Nano LIFE 2, 123002 (2012)
2. A.I. Rusanov Surf. Sci. Rep. 58111 (2005).
3. A.M. Madsen, S.Nielsen International Journal of Hygiene and Environmental Health 213, 278 (2010).
4. E.Rauwel, M.Karmaoui and P.Rauwel Metal nanoparticles, WO/2012/004573
5. H.-C.Chuang, T.-C.Hsiao, C.-K.Wu, H.-H.Chang, C.-H.Lee, C.-C.Chang, T.-J.Cheng International Journal of Nanomedicine 84495 (2013)