Contents lists available at ScienceDirect Microbial Pathogenesis journal homepage: www.elsevier.com/locate/micpath Zero valent silver nanoparticles capped with capsaicinoids containing Capsicum annuum extract, exert potent anti-biofilm effect on food borne pathogen Staphylococcus aureus and curtail planktonic growth on a zebrafish infection model Robert Lotha a , Bhanuvalli R. Shamprasad a , Niranjana Sri Sundaramoorthy b , Ragavi Ganapathy a , Saisubramanian Nagarajan b,** , Aravind Sivasubramanian a,* a Department of Chemistry, School of Chemical and Biotechnology, SASTRA Deemed to be University, Thanjavur, Tamil Nadu, India b Center for Research on Infectious Diseases, School of Chemical and Biotechnology, SASTRA Deemed to be University, Thanjavur, Tamil Nadu, India ARTICLE INFO Keywords: Capsicum annuum L. Staphylococcus aureus Silver nanoparticles Anti-biofilm Danio rerio ABSTRACT Food plants Hungarian wax pepper (HWP) and Green Bell pepper (GBP), belonging to Capsicum annuum were utilized for biogenic fabrication of zero valent, nano-silver (AgNPs) through a photo-mediation procedure. In the bacterial strains evaluated, HWP/GBP AgNPs demonstrated effective bacteriostatic and bactericidal effect against Staphylococcus aureus. Time kill results portrayed that HWP/GBP nano-silver exhibited comparable bactericidal potency on S. aureus. Anti-biofilm potential of HWP/GBP AgNPs displayed significant effects at sub MIC levels, by triggering 50% biofilm reduction of the food spoilage microbe S. aureus, inferring that the anti- biofilm outcome is not dependent on antibacterial result, and this was confirmed by SEM and fluorescence studies. Histopathological analyses of S. aureus infected zebrafish liver did not display any abnormality changes such as extensive cell death and degeneration, upon treatment with HWP/GBP AgNPs and the zero-valent silver nanoparticles were comparatively less toxic and more operative in restraining the bioburden in S. aureus infected zebrafish model by a > 1.7 log fold. Ability of light reduced HWP/GBP AgNPs to alleviate the in vitro and in vivo planktonic mode of growth and curb the biofilm formation of S. aureus is also demonstrated. 1. Introduction Microbial infections are the most important cause for the human diseases accounting about millions of death every year. Diseases caused by food borne pathogens are more prevalent even in developed coun- tries. Food borne diseases comprises of a larger account of illnesses and a wide spectrum of bacteria were reported with food borne diseases, worldwide [1,2]. Numerous reports recommends the use of plant ex- tracts [3], purified compounds [4] for combating the pathogens. With the advent of green synthetic methodologies for nanomaterials as pro- mising agents against the microbes [5,6], there is always a question of toxicity/biosafety on nanomaterials as antimicrobials. Due to the vast resource of plant species, search for new source that possess anti- bacterial and antifungal properties are always in vogue. Plants are also a part of our diet and species like capsicum, cinnamon, cloves, turmeric etc., are an integral part of diet and in such plants, their antimicrobial compounds ensure a dual role; one as food and other as nutraceutical supplements [7,8]. Chillies/peppers belong to the Capsicum genus and have been re- ported to possess antimicrobial activity [9,10] and these activities have been correlated to the capsaicinoids content [11]. The pungency of the chillies/peppers depends on the content of the capsaicinoids as in- dicated by the Scoville scale [12]. The Hungarian wax pepper (HWP) and Green bell pepper (GBP) falls in the lowest scale in Scoville clas- sification and they have less capsaicin content. The less spicy varieties like bell pepper also been reported to have anti-microbial activity [13]. In this report we have made an attempt to elucidate the anti- bacterial activity of AgNPs using less spicy and less capsaicinoids con- taining chillies/peppers extract. Sunlight mediated, bio functionaliza- tion of AgNPs was done, using the HWP/GBP aqueous extracts and in the panel of bacteria tested for antimicrobial activity, the HWP/GBP AgNPs exhibited gratifying antimicrobial/anti-biofilm activity against https://doi.org/10.1016/j.micpath.2018.08.053 Received 8 June 2018; Received in revised form 21 August 2018; Accepted 23 August 2018 * Corresponding author. ** Corresponding author. E-mail addresses: sai@scbt.sastra.edu (S. Nagarajan), arvi@biotech.sastra.edu (A. Sivasubramanian). Microbial Pathogenesis 124 (2018) 291–300 Available online 25 August 2018 0882-4010/ © 2018 Elsevier Ltd. All rights reserved. T