Biosynthesis, characterization and antibacterial activity of silver and gold nanoparticles from the

101 Pages·2016·2.34 MB·English

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Biosynthesis, Characterization and Antibacterial Activity of Silver and Gold
Nanoparticles from the Leaf and Bark extracts of Zanthoxylum Capense.
by
MBAVHALELO JADE NEPHAWE

Dissertation in fulfilment of the requirement for the degree
MASTER OF SCIENCE

in
NANOSCIENCE

in the
FACULTY OF SCIENCE
UNIVERSITY OF JOHANNESBURG

Supervisor : Dr. D.T. Ndinteh
Co-supervisors : Dr. V. Mavumengwana
: Dr. N. Niemann

2015
DEDICATION

I dedicate this work to my husband Tshilangano Kenneth Tshikosi, for showing me the
meaning of determination and the value of patience! And for inspiring me to make the
very most of the chances life has granted me.

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ACKNOWLEDGEMENTS

I would first of all like to thank the Lord for giving me the strength to reach for my goals,
endurance to complete my studies, guidance through my life, and for just being there on
the days that the sun didn’t shine.
In pursuit of this academic endeavour I feel that I have been especially fortunate as
inspiration, guidance, direction, co-operation, love and care all came in my way in
abundance and it seems almost an impossible task for me to acknowledge the same in
adequate terms.
I would like to thank my supervisors Dr D.T. Ndinteh, Dr V. Mavumengwana, and Dr N.
Niemann and for the continued support and guidance they provided and the knowledge
that they shared with me throughout my studies. Thank you for the invaluable
contributions to my project, as well as pointing me in the right direction when I needed it.
Thanks for all your effort and inputs in reviewing my work and giving feedback and
constructive criticism on how to best improve it. Most importantly, I would like to thank
them for dedicating their own personal time to make this project a completed success -
all is much appreciated.
Thank you to my friends and colleagues at the Department of Biotechnology and food
technology for their advices, assistance and encouragement. A special thanks to my dear
friends the Big Five for the moral support and encouragement; Tendani Sebola, Sharon
Pelo, Mbali Webb and Nkem Okerafor. You all mean more to me than I would ever be
able to say in words. Thanks to everyone else I shared the lab with and made my
experience at the lab a fruitful one.
I may be failing in my duties if I do not thank all my batch mates for their constant
encouragement. The 2014 NANO UJ group, you are more like brothers and sisters to me.
Thank you for all your support, kind words of encouragement and for providing me with a
social life. I am grateful and honoured to have you all in my live. Penny Mathumba,
Mandla Chabalala, Gauta (Au) Mathlou, Lerato Mabe, Mphoma Matseke, Lwazi and
Koloti. I will relish your memories for years to come.
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Cordial cooperation, friendly collaboration, fruitful advice and guidance were received
from many other persons from the start to the end of this piece of work. I am immensely
grateful to all of them and regret for my inability to mention everyone by name.
This project was made possible by the funding provided by the National Nanoscience
Postgraduate Teaching and Training Platform (NNPTTP) through the Department of
Science and Technology (DST).
Inadequate thought in terms of words and expression, this dissertation owes a lot to my
beloved family and husband for their support, suggestions, inspiration, encouragement &
good wishes for the success of my dissertation.

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PRESENTATIONS

CONFERENCE AND SYMPOSIUM PRESENTATIONS

 Nephawe, M.J., Mavumengwana, V., Niemann, N., and Ndinteh, D.T, Biosynthesis
and Characterization of Silver and Gold Nanoparticles from the Leaf and bark
extracts of Zanthoxylum capense, UJ cross faculty postgraduate symposium, South
Africa (Johannesburg), 13 October 2015. Poster presentation.

 Nephawe, M.J., Mavumengwana, V., Niemann, N., Ndinteh, D.T., Biosynthesis and
Characterization of Silver and Gold Nanoparticles from the Leaf and Bark Extracts
of Zanthoxylum Capense, DST-Howard University Advance-It Women in Stem
Conference, South Africa (Johannesburg), 27-29 October, 2015. Oral presentation.

 Nephawe, M.J., Ndinteh, D.T., Mavumengwana, V., Niemann, N., Biosynthesis and
Antibacterial Activity of Silver and Gold Nanoparticles from aqueous extracts of
zanthoxylum capense, 42nd National Convention of the South African Chemical
Institute, South Africa (Durban), 29 November - 4 December 2015. Oral
presentation.

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ABSTRACT

The biosynthesis of nanoparticles has many advantages over tedious, expensive and toxic
physical and chemical methods of synthesis. Plants are stocked with valuable metabolites
that are capable of reducing metal salts to form nanoparticles. In this study, aqueous leaf
and bark extracts of Zanthoxylum capense were reacted with AgNO and HAuCl to
3 4
determine the plants reducing abilities and hence synthesis of Ag and Au nanoparticles
capabilities. The goal was to develop a reliable, eco-friendly and easy process for the
synthesis of silver and gold nanoparticles using extracts of medicinal plant Zanthoxylum
capense.
Characterization of the nanoparticles formed by the aqueous extracts was performed
using Ultraviolet visible (UV-vis) spectroscopy, Dynamic light scattering, Fourier
transforms infrared spectroscopy (FTIR), Transmission electron microscope (TEM).
Nanoparticles were characterised by measuring their relevant physicochemical
properties. Among the determined properties are size, shape, zeta potential and surface
charge. UV-vis spectrophotometry was used as a confirmatory as well as a characterizing
tool. Phytochemical tests revealed that the leaf and bark extracts of the plant contained
“alkaloids, sterols, terpenoids, flavonoids, steroids, phlabotannins and reducing sugars”
which were linked as potential reducing agents.
Synthesized nanoparticles were confirmed by the change of colour of gold and silver and
growth of nanoparticles were monitored by surface Plasmon behaviour using UV-Vis
Spectroscopy. Water soluble biomolecules present in the plant were responsible for the
conversion of silver and gold ions to Ag-NPs and Au-NPs. UV-Vis Spectrum of synthesized
Ag-NPs and Au-NPs exhibited peaks at 419 and 567 nm corresponding to its surface
plasmon absorption. Transmission electron microscopy showed polydispersed Ag-NPs
ranging from 2-30 nm and Au-NPs ranging from 5-45 nm. The FT-IR results indicate the
presence of different functional groups present in the biomolecule capping the
nanoparticles.
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The disk diffusion assay showed Au/Ag nanoparticles to have enhanced activity against
bacteria K. oxycota, B. subtilis, S. epidermidis, P. vulgaris, M. smegmatis and S. aureus
with zones of clearance of 4.1 mm, 4.2 mm, 4.3 mm, 5.8 mm, 6 mm, and 7.5 mm
respectively. The antimicrobial activities of the plant as well as Au-NPs were tested using
the minimum inhibitory concentrations (MIC) assay against a panel of microorganisms.
The highest sensitivities observed for the Au-NPs were that against S. aeruginosa, M.
smegmatis and B. cereus with a MIC value of 2, 1 and 2 mg/ml.
The size and shape of NPs are the keys to their biomedical properties. Green synthesis of
NPs is a feasible way for the future. This study showed that NPs can be synthesized very
easily. The phytochemicals present in Z. capense extracts reduce the silver and gold ions
into metallic nanoparticles. This strategy reduces the cost of production and the
environmental impact.

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TABLE OF CONTENTS
Section Page
Affidavit ................................................................................................................... i
Dedication ............................................................................................................... ii
Acknowledgements ................................................................................................ iii
Presentations ......................................................................................................... v
Abstract .................................................................................................................. vi
Table of contents .................................................................................................. viii
List of figures .......................................................................................................... xi
List of schematics ................................................................................................. xiii
List of tables’ ........................................................................................................ xiv
List of abbreviations .............................................................................................. xv
List of Units ........................................................................................................... xvi

CHAPTER ONE ............................................................................................................................... 1
GENERAL INTRODUCTION ......................................................................................................... 1
1.0 Background ................................................................................................................................ 1
1.1 Aims and Objectives ............................................................................................................. 3
1.1.1 Aim ................................................................................................................................... 3
1.1.2 Objectives ....................................................................................................................... 3
CHAPTER TWO .............................................................................................................................. 4
LITERATURE REVIEW .................................................................................................................. 4
2.1 Background Information on medicinal plants ....................................................................... 4
2.1.1 Traditional Medicine .......................................................................................................... 5
2.1.2 Traditional Medicine in South Africa ............................................................................... 5
2.2 The Plant Family Rutaceae ..................................................................................................... 6
2.2.1 The Genus Zanthoxylum .................................................................................................. 7
2.3 The Plant Zanthoxylum Capense (Thunb.) Harv. ................................................................ 7
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2.3.1 Botanical Description 0f Zanthoxylum Capense ........................................................... 7
2.3.2 Plant Distribution ................................................................................................................ 8
2.3.3 Zanthoxylum capense Traditional Medicinal uses ........................................................ 9
2.3.4 Chemical constituents of Zanthoxylum capense ........................................................ 11
2.4 Nanotechnology ...................................................................................................................... 13
2.5 Nanoparticles ........................................................................................................................... 14
2.6 Classification of nanoparticles .............................................................................................. 15
2.6.1 Silver Nanoparticles ........................................................................................................ 15
2.6.2 Gold Nanoparticles .......................................................................................................... 17
2.7 Methods for Nanoparticle Synthesis .................................................................................... 18
2.7.1 Physical Synthesis .......................................................................................................... 21
2.7.2 Chemical Synthesis ......................................................................................................... 21
2.7.3 Biosynthesis ..................................................................................................................... 22
2.8 Size and Shape of Nanoparticles ......................................................................................... 25
2.9 Antibacterial Activity of Nanoparticles ................................................................................. 27
CHAPTER THREE ........................................................................................................................ 30
EXPERIMENTAL METHODOLOGY .......................................................................................... 30
3.1 Reagents and chemicals ....................................................................................................... 30
3.2 Collection and Preparation of Plant Materials .................................................................... 30
3.2.1 Preparation of Leaf Extracts .......................................................................................... 30
3.2.2 Preparation of 0.1 M NaAuCl solution ........................................................................ 30
4
3.3 Phytochemical Screening of Plant Extracts ........................................................................ 31
3.3.1 Terpenoids (Salkowski’s Test) ....................................................................................... 31
3.3.2 Steroids Test .................................................................................................................... 31
3.3.3 Alkaloids (Dragendroff’s Test) ....................................................................................... 31
3.3.4 Flavonoids Test ................................................................................................................ 31
3.3.5 Tannins.............................................................................................................................. 32
3.3.6 Phlobatannins .................................................................................................................. 32
3.3.7 Reducing Sugars ............................................................................................................. 32
3.4 Biosynthesis of Silver and Gold Nanoparticles from Leaf and Bark Extracts of
Zanthoxylum capense ................................................................................................................... 32
3.4.1 Synthesis of Silver Nanoparticles ................................................................................. 32
3.4.2 Synthesis of Gold Nanoparticles ................................................................................... 32
3.5 Characterization of the synthesized silver and gold Nanoparticles................................. 33
3.5.1 UV-visible Spectra Analysis ........................................................................................... 33
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