Communication Formation of Stable Gold Nanoparticles from Cannabis Indica Leaves Anjul Khadria 1,2 * and Subhankar Paul 1 * 1 Structural Biology and Nanomedicine Laboratory, Department of Biotechnology and Medical Engineering, National Institute of Technology, Rourkela, Odisha, 769008, India 2Current address: Caltech Optical Imaging Laboratory, Andrew and Peggy Cherng Department of Medical Engineering, California Institute of Technology, Pasadena, California, 91125, USA * Correspondence: anjul.nitrkl@gmail.com; spaul@nitrkl.ac.in, Abstract: Gold nanoparticles have been increasingly used in several electronic, material fabrication, and biomedical applications. Several methods have been reported to prepare gold nanoparticles of various shapes and sizes with different photophysical properties. Although useful to prepare gold nanoparticles, most of the methods are not stable enough and under degradation if stored at room temperatures (up to 30 °C) for a few days. In this paper, we report a novel environmentally friendly method to synthesize self-assembled gold nanoparticles by using leaf extract of Cannabis indica as a reducing agent. The nanoparticles were found to be stable for more than a month when stored at room temperature (30 °C). They were able to form stable conjugates with bovine α-lactalbumin pro- tein that may possess anti-cancerous properties. Keywords: Gold nanoparticles; nanomaterials; alpha-lactalbumin protein; Cannabis indica 1. Introduction The use of gold nanoparticles has increased exponentially in several biomedical and non-biomedical applications. 1 Gold nanoparticles have been shown to possess anti-can- cerous activity by several studies, and recently it has been clinically shown to treat local- ized prostate tumors. 2 Due to their excellent photophysical properties, they have also been explored to be used as theranostic agents. 3 Gold nanoparticles have emerged as one of the most promising agents for the treatment of various types of cancer due to several ad- vantages associated with them such as, (a) ease of cellular uptake by endocytosis, (b) ease of large scale synthesis and characterization, (c) ability to form stable complexes with a wide range of biomolecules, (d) biocompatibility, and (e) unique physicochemical prop- erties. Gold nanoparticles of different shapes and sizes have different properties with dif- ferent effects on cancer cells. 4 Conjugates of bovine α-lactalbumin (BLA) protein with oleic acid commonly known as BAMLET (bovine alpha-lactalbumin made lethal to tumors) have been successfully shown to be anti-cancerous; however, oleic acid is toxic to healthy cells as well. 5,6 Biocompatible gold nanoparticles have been shown to replace oleic acid in the BAMLET conjugate to form gold nanoparticle-BLA conjugates that have anti-cancer- ous properties without affecting healthy cells. 7 One of the significant challenges of syn- thesizing gold nanoparticles is making them stable at temperatures up to 30 °C, which will give them long shelf life and make them biocompatible to form stable conjugates with proteins. 8 Several nanoparticle synthesis methodologies require high temperatures and toxic chemicals, which can be harmful to the proteins. In this study, we report the synthe- sis of stable cross-shaped self-assembled gold nanoparticles using Cannabis indica leaves and the formation of its conjugates with the BLA protein. 2. Materials and Methods Preprints (www.preprints.org) | NOT PEER-REVIEWED | Posted: 8 June 2022 doi:10.20944/preprints202206.0117.v1 © 2022 by the author(s). Distributed under a Creative Commons CC BY license.