Exploiting anticancer and antimicrobial activities of biosynthetic gold nanoparticles by Pseudomonas aeruginosa (PAO1)

Abstract

Biosynthetic gold nanoparticles (bAuNPs) have emerged as a disruptive, eco-friendly and cost-effective alternative to overcome the limitations of conventional synthesis methods, namely, the need to use hazardous chemicals and high temperatures. Among the wide range of possible applications of bAuNPs, their potential as atitumor and antimicrobial agents has been explored. However, there are limited studies that describe the dependence on physicochemical parameters to control the shape, size, aggregation, and yields during bAuNP synthesis. Some studies have used Pseudomonas aeruginosa (PAO1) extracts for the biological synthesis of AuNPs. The main focus of the present study was to disclose which conditions of PAO1 cultures lead to higher bAuNPs synthesis yields, to understand the influence of different conditions on bAuNPs biosynthesis (temperature, pH and incubation period), and to evaluate how bAuNPs shapes and sizes affect the antibacterial and antitumor activity. UV-Vis spectroscopy, TEM, and ATR-FT-IR analysis were used to characterize the biosynthetic AuNPs. It is speculated that bAuNPs are produced by means of redox reactions. In this sense, DCIP (2,6- Dichlorophenolindophenol) was used as an indicator of the reduction potential of PAO1. It was exploited both anticancer and antibacterial to disclose the bAuNPs biological activity. An anticancer screening of bAuNP activity was performed on prostate cell carcinoma. A model concerning normal and neoplastic epithelial cells were used in the present study. In vitro assays were performed using the neoplastic prostate cell line PC3 and the normal epithelial cell (HPEpiC). Cellular viability, cellular proliferation, cellular migration, and Interleukin 6 (IL-6) levels were determined. The activity of bAuNPs on bacteria was screened in bacteria growth (kinetics) and in viability, in two Gram-negative bacteria and in one Gram-positive bacterium. PC3 cancer cells were most affected by bAuNPs synthesized at pH 9.0 for 24h and at 58 ºC showing a significant reduction in cell viability, cellular migration, and IL-6 levels of PC3 cells without significant effects in HPEpiC cells. Regarding the antimicrobial assays, the effect on bacterial growth and viability was more significant in Gram-negative bacteria. Furthermore, bAuNPs synthesis at pH 9.0 for 24 h at 58ºC prompted smaller, more spherical, and less aggregated bAuNPs. These properties may enhance the internalization of bAuNPs in cells, thereby increasing both antitumor and antibacterial activity. Along with the bioactive potential of bAuNPs, the control of shape, size, and aggregation could be used to improve therapeutic approaches for prostate cancer and bacterial infections, contributing for more targeted, cheaper, and greener therapies.

Date of Award	15 Feb 2023
Original language	English
Awarding Institution	Universidade Católica Portuguesa
Supervisor	Ruben Miguel Pereira Fernandes (Supervisor) & Carla Patrícia Fernandes Pereira (Co-Supervisor)