SYNTHESIS AND CHARACTERIZATION OF STARCH
NANOPARTICLES AND CARBON NANODOTS
Siti Nur Akmar binti Mohd Yazid
Master of Science
(Physical Chemistry)
2013
Faculty of Resource Science and Technology
SYNTHESIS AND CHARACTERIZATION OF STARCH NANOPARTICLES AND
CARBON NANODOTS
SITI NUR AKMAR BINTI MOHD YAZID
A thesis submitted
in fulfillment of the requirements for the
Master of Science
Faculty of Resource Science and Technology
UNIVERSITI MALAYSIA SARAWAK
2013
DECLARATION
No portion of the work referred to in this dissertation has been submitted in support of an
application for another master of qualification of this or any other university/institution of
higher learning.
…………………………………………………
Siti Nur Akmar binti Mohd Yazid (10021658)
Department of Chemistry (Physical Chemistry)
Faculty of Resource Science and Technology
Universiti Malaysia Sarawak
i
ACKNOWLEDGEMENTS
In the name of Allah, the Most Beneficent, the Most Merciful
Alhamdulillah, all praises to Allah for the strengths and His blessing in completing
this thesis. A special appreciation goes to my supervisor, Dr. Chin Suk Fun and my co-
supervisor, Assoc. Prof. Dr. Pang Suh Cem for their positive encouragement, valuable
suggestions and a warm spirit throughout the whole duration of my study. Not forgotten my
appreciation to Dr. Ng Sing Muk from School of Engineering, Computing and Science,
Swinburne University of Technology for his support and knowledge regarding this topic.
I owe thanks to all staffs and lab technicians from Faculty of Resource Science and
Technology Universiti Malaysia Sarawak for the co-operations. My acknowledgement also
goes to Ministry of Higher Education Malaysia for their financial supports under Fundamental
Research Grant Scheme (FRGS), grant no: 01(17)746/2010(32) and MyBrain15 (MyMaster)
scholarship. Not forgotten my appreciation to SIRIM Berhad, Selangor for the X-Ray
Diffractometry measurement service.
Sincere thanks to my friends Ain, Aressa, Fiona, Jessica and all others for their
kindness and moral supports during my study. Thanks for the friendship and memories.
Finally, I would like to acknowledge my family for their love, trust and all their efforts to
provide me the finest of things I ever needed. I could never have been able to pursue my
higher education without their encouragement and support. Thank you very much my dear
family.
ii
ABSTRACT
Starch is a well-known, versatile, and inexpensive biopolymer and it is a promising precursor
material for preparation of nanoparticles. In this research, starch nanoparticles were
synthesized from native sago starch and the potential applications of these starch
nanoparticles as controlled release carriers were evaluated. Curcumin was loaded into starch
nanoparticles by using a simple precipitation in water-in-oil microemulsion approach. The
effects of synthesis parameters such as types of reaction medium, types of surfactant and its
concentrations, oil/ethanol ratios and curcumin concentration were found to affect the particle
sizes, morphology and loading efficiency of the curcumin loaded starch nanoparticles.
Curcumin was observed to release out from starch nanoparticles in a slow and sustanable way
over the period of 10 days. In addition, these starch nanoparticles were used as precursors for
the synthesis of fluorescent carbon nanodots (C-dots). The C-dots were synthesized by
carbonization and surface oxidation of preformed sago starch nanoparticles. The fluorescence
of these C-dots were found to be significantly quenched in the presence of Sn(II) ions, and
such changes could therefore be utilized as a highly sensitive sensing probe for detecting
Sn(II) ions. Parameters which influence the sensing characteristics of the C-dots probe had
been optimized with its highest fluorescence intensity obtained at an optimum concentration
of 1.75 mM in aqueous solution. The C-dots probe was highly selective and exhibited low
interference responses towards several heavy metal ions tested. Based on spectroscopic study,
the fluorescence quenching mechanism appeared to be predominantly of the static type
compared to the dynamic one. Under optimum conditions, the probe exhibited a linear
response range of Sn(II) ions concentration up to 4.00 mM, and with a detection limit (LOD)
of 0.36 μM.
iii
SINTESIS DAN PENCIRIAN NANOPARTIKEL KANJI DAN NANODOT-NANODOT
KARBON
ABSTRAK
Kanji ialah biopolimer yang mudah diperoleh, murah dan juga merupakan prekursor yang
sesuai bagi menghasilkan nanopartikel-nanopartikel. Dalam kajian ini, nanopartikel kanji
telah disintesis daripada sumber kanji sagu asli dan potensi aplikasinya sebagai pengawal
pelepasan ubat telah dikaji. Curcumin telah dimuatkan ke dalam nanopartikel kanji
menggunakan kaedah pemendakan dalam medium tindak balas mikroemulsi air-kepada-
minyak. Parameter seperti jenis medium tindak balas, jenis dan kepekatan surfaktan, nisbah
minyak/ethanol, dan kepekatan curcumin telah dikenalpasti mempengaruhi saiz partikel,
morfologi dan kecekapan pemuatan curcumin ke dalam nanopartikel kanji. Curcumin telah
terbebas daripada nanopartikel-nanopartikel kanji secara perlahan dan berterusan selama 10
hari. Sebagai tambahan, nanopartikel kanji juga telah digunakan sebagai prekursor untuk
mensintesis nanodot-nanodot karbon (C-dots) pendaflor. C-dots ini telah disintesis melalui
proses karbonisasi dan pengoksidaan nanopartikel kanji. C-dots telah digunakan sebagai
sensor pendaflour bagi pengesanan ion stanum (Sn(II)). Kepekaan yang tinggi terhadap ion
Sn(II) telah dicapai pada kepekatan optima 1.75 mM dalam larutan akues. Pendaflour C-dots
menunjukkan tindak balas yang kurang peka terhadap ion logam berat lain yang telah diuji.
Berdasarkan kajian spektroskopi, mekanisma kejutan pendaflour C-dots adalah lebih terjurus
kepada jenis statik berbanding jenis dinamik. Pada kondisi yang optimum, kepekaan
pendaflour yang dicapai oleh C-dots adalah linear kepada kepekatan ion Sn(II) sehingga
mencapai kepekatan 4.00 mM dan had pengesanannya (LOD) sehingga 0.36 µM.
iv
TABLE OF CONTENTS
Page
Acknowledgements i
Abstract ii
Abstrak iii
Table of Contents iv
List of Tables viii
List of Figures ix
List of Abbreviations xi
List of Symbols xii
CHAPTER 1 INTRODUCTION
1.1 Background 1
1.2 Objectives 4
1.3 Scopes of Study 5
CHAPTER 2 LITERATURE REVIEW
2.1 Native Sago Starch 6
2.2 Physicochemical Properties of Sago Starch 6
2.3 Polymeric Nanoparticles 7
2.4 Curcumin 9
2.4.1 Anticancer Properties of Curcumin 10
2.4.2 The Safety of Curcumin Formulation 11
2.4.3 Low Bioavailability of Curcumin 12
v
2.5 Synthesis of Curcumin Loaded Polymeric Nanoparticles 13
2.5.1 Nanoprecipitation 14
2.5.2 Microemulsion System 17
2.6 Fluorescent Carbon Nanodots 18
2.7 Synthesis of Carbon Nanodots 18
2.7.1 Combustion/Hydrothermal/Acidic Oxidation 19
2.7.2 Other Synthesis Methods 20
2.8 Applications of Carbon Nanodots as Fluorescence Probes 21
CHAPTER 3 FORMULATION OF CURCUMIN LOADED STARCH
NANOPARTICLES
3.1 Introduction 22
3.2 Materials and Method 24
3.2.1 Materials 24
3.2.2 Loading of Curcumin into Starch Nanoparticles 24
3.2.3 Characterization of Curcumin Loaded Starch Nanoparticles 25
3.2.4 Loading Efficiency of Curcumin 25
3.2.5 Curcumin Release Evaluation 26
3.2.6 Swelling Studies 27
3.3 Results and Discussion 28
3.3.1 Curcumin loaded in starch nanoparticles 28
3.3.2 Optimization of Loading Efficiency of Curcumin into Starch
Nanoparticles
30
3.3.2.1 Effect of Reaction Medium 30
vi
3.3.2.2 Effect of Surfactants 33
3.3.2.3 Effect of Surfactant Concentration 34
3.3.2.4 Effect of Oil/Ethanol Ratio 36
3.3.2.5 Effect of Curcumin Concentration 37
3.3.3 Curcumin Release Studies 38
3.4 Conclusion 41
CHAPTER 4
DETECTION OF SN(II) IONS VIA QUENCHING OF THE
FLUORESCENCE OF CARBON NANODOTS
4.1 Introduction 42
4.2 Materials and Method 44
4.2.1 Materials 44
4.2.2 Synthesis of Carbon Nanodots 44
4.2.3 Procedures for Spectrofluorometric of Sn(II) Ions 45
4.2.4 Characterization of Carbon Nanodots 45
4.3 Results and Discussion 46
4.3.1 Characterization of Carbon Nanodots 46
4.3.2 Factors Affecting Fluorescence Intensity of Carbon Nanodots 50
4.3.2.1 Effect of Carbon Nanodots Concentration 50
4.3.2.2 Effect of pH 51
4.3.2.3 Interference of Metal Ions 53
4.3.3 Analytical Performance of Carbon Nanodots in Sn(II) Ions 55
4.4 Conclusion 58
vii
CHAPTER 5 CONCLUSION AND RECOMMENDATIONS
5.1 Concluding Remarks 59
5.2 Recommendations for Future Works 60
REFERENCES 61
APPENDIX A 81
APPENDIX B 82
APPENDIX C 84
APPENDIX D 89
APPENDIX E 91
APPENDIX F 94
viii
List of Tables Page
Table 3.1 Effects of reaction medium on average particles diameter of curcumin
loaded starch nanoparticles
32
Table 3.2 Effects of surfactant concentration on average particles diameter of
curcumin loaded starch nanoparticles
36
Table 4.1 Comparison of the detection limits for Sn(II) ions detection 56
ix
List of Figures Page
Figure 2.1 Linear and branched starch polymers. 7
Figure 2.2 Types of polymeric nanoparticle. 9
Figure 2.3 Curcuma longa plant and chemical structure of curcumin. 10
Figure 2.4 Schematic representation of the nanoprecipitation technique. 15
Figure 2.5 Schematic representation of the three most commonly microemulsion
system.
17
Figure 3.1 Photographic images of (a) free curcumin were poorly soluble in
aqueous media and macroscopic flakes can be seen floating in the
bottle, and (b) the curcumin loaded starch nanoparticles were fully
dispersible in aqueous media.
28
Figure 3.2 TEM image of curcumin loaded starch nanoparticles. 29
Figure 3.3 (a) Fluorescent image of curcumin loaded starch nanoparticles and, (b)
UV spectra of (i) curcumin solution and (ii) curcumin loaded starch
nanoparticles.
30
Figure 3.4 Effect of reaction medium on loading efficiency of curcumin into starch
nanoparticles.
31
Figure 3.5 SEM images of curcumin loaded starch nanoparticles formulated
through nanoprecipitation in (a) absolute ethanolic solution, (b)
cyclohexane/ethanol microemulsion, (c) sunflower oil/ethanol
microemulsion, and (d) oleic acid/ethanol microemulsion reaction
medium.
32
Figure 3.6 Effect of types of surfactant on loading efficiency of curcumin into
starch nanoparticles.
33
Figure 3.7 Effect of surfactant concentration on loading efficiency of curcumin into
starch nanoparticles.
35
Figure 3.8 Effect of oil to ethanol volume (oil:ethanol) on loading efficiency of
curcumin into starch nanoparticles.
37
Figure 3.9 Effect of curcumin concentration on loading efficiency of curcumin into
starch nanoparticles.
38
Figure 3.10 Swelling ratio of starch nanoparticles and release profile of curcumin
from starch nanoparticles as a function of time.
40
Figure 4.1 TEM images of (a) native starch nanoparticles, and (b) carbon nanodots. 47
x
Figure 4.2 (a) TEM image of C-dots (The inset shows a particle size distribution of
the C-dots), and (b) fluorescence spectrum of C-dots prepared from
starch nanoparticles (excitation wavelengths are 277 and 327 nm).
47
Figure 4.3 Fluorescent emission spectra of C-dots (a) in contour plot having
excitation wavelength ranging from 200-400 nm, and (b) emissions
recorded specifically with excitation at (i) 320, (ii) 290, and (iii) 260
nm.
48
Figure 4.4 FTIR spectra of (a) native starch nanoparticles, (b) carbon nanoparticles,
and (c) C-dots.
49
Figure 4.5 (a) UV absorbance spectrum, and (b) X-ray diffraction pattern of C-
dots.
50
Figure 4.6 Effect of C-dots concentration on fluorescence intensity of C-dots. 51
Figure 4.7 Effect of pH on fluorescence intensity of C-dots. 52
Figure 4.8 Effect of types of interferent on fluorescence intensity of C-dots in
water.
54
Figure 4.9 Fluorescence effect of Sn(II) ions concentration on the C-dots in (a)
water, and (b) buffer solution of pH 5.
55
Figure 4.10 UV absorbance spectra of (a) C-dots control solution, and (b) C-dots
and Sn(II) ion in water.
57
xi
List of Abbreviations
AgNO3 Silver nitrate
Al(NO3)2 Aluminium (II) nitrate
Ca(NO3)2 Calcium (II) nitrate
C-dots Carbon nanodots
Co(NO3)2 Cobalt (II) nitrate
Cu(NO3)2 Copper (II) nitrate
DNA Deoxyribonucleic acid
FTIR Fourier Transform Infrared Radiation
h Hour
H2SO4 Sulphuric acid
HgCl2 Mercury (II) chloride
HNO3 Nitric acid
LF Loading efficiency
LOD Detection limit
Ni(NO3)2 Nickel (II) nitrate
o/w Oil-in-water
Pb(NO3)2 Lead (II) nitrate
PLGA Poly(D,L-lactide-co-glycolide)
Q-dots Quantum dots
SD Standard deviation
SEM Scanning electron microscope
Sn Tin
SnCl2 Tin (II) chloride
SNPs Starch nanoparticles
TEM Transmission electron microscope
UV Ultraviolet
w/o Water-in-oil
w/v Weight over volume
XRD X-ray diffractometry
Zn(NO3)2 Zinc (II) nitrate
xii
List of Symbols
Abs Absorbance
a.u. Arbitrary units
cm Centimeter (10-2
)
ºC Degree celcius
g Gram g/L Gram per liter
kg Kilogram
kV Kilovolt
µA Microampere (10-6
)
µL Microliter (10-6
)
µm Micrometer (10-6
)
mg Miligram
mL Mililiter (10-3
)
mg/L Miligram per liter mg/mL Miligram per mililiter
mM Milimolar (10-3
)
µM Micromolar (10-6
)
M Molarity
nm Nanometer (10-9
)
W Watt
% Percentage
% T Percentage of transmittance
1
CHAPTER 1
INTRODUCTION
1.1 Background
Starch is a type of carbohydrate (polysaccharide) that generated from carbon dioxide
and water by photosynthesis in plants (BeMiller & Whistler, 2009). Owing to its complete
biodegradability, availability, low cost and renewability, starch is considered as a promising
precursor for diverse areas of nanoparticle technology. Starch occurs as a semi crystalline
macroscopic granules with diameters ranging of 2 to 100 µm and mainly composes of two
biopolymers, namely amylose and amylopectin. Amylose is a linear (1-4)-linked-α-D-glucan
and amylopectin is a highly branched molecule which consists of short chains of (1-6)-α-
linked branches (Ahmad et al., 1999; Cardoso et al., 2007; Nadiha et al., 2010).
Starch nanoparticles have been extensively studied for biomedical application, such as
controlled release nanocarriers (Simi & Abraham, 2007; Santander-Ortego et al., 2010).
Starch nanoparticles showed promising potentials due to their controlled release properties,
subcellular sizes and biocompatibility with tissue and cells (Xiao et al., 2012). Controlled
release technology represents one of the most rapidly advancing areas in the treatment of
various diseases as they provide prolonged delivery of a drug in the body. Drug loaded in
nanocarriers are usually release by diffusion, swelling, erosion or degradation (Gelperina et
al., 2005).
In 2007, Saboktakin et al. has synthesized carboxymethyl starch (CMS) nanoparticles
by a graft copolymerization method and loaded the CMS nanoparticles with salicylic acid
2
(SA) anti inflammatory drugs. The release profiles of SA loaded CMS were studied in both
enzyme-free simulated gastric fluid (SGF) and simulated intestinal fluid (SIF). The release of
SA was faster in SIF which suggested that the modified CMS have great potential for colon
drug delivery. Another study on starch nanoparticles as controlled release nanocarriers had
been reported by Simi & Abraham (2007). Fatty acid grafted starch nanoparticles were
prepared by dialysis method. The modified hydrophobic starch nanoparticles were loaded
with indomethacin where the maximum loading efficiency of indomethacin in starch
nanoparticles was found to be 16%. Indomethacin was slowly released from starch
nanoparticles due to their cross-linked surface, which suggested that the starch nanoparticles
can be used as nanocarriers for oral drug delivery.
Further research was carried out by Santander-Ortega et al. (2010) on the preparation
of propyl starch nanoparticles using an oil-in-water emulsion diffusion technique. These
propyl starch nanoparticles were loaded by different types of drug (flufenamic acid,
testosterone and caffeine) and undergone permeation studies upon human skin. The drug
loaded starch nanoparticles have enhanced the effect of drugs at the target sites as compared
to free drug. Xiao et al. (2012) synthesized dialdehyde starch nanoparticles (DASNPs) using a
water-in-oil microemulsion method at room temperature, followed by conjugation with 5-
fluorouracil (5-Fu) into DASNPs. The DASNPs obtained have an average diameter of 90 nm
and the 5-Fu binding DASNPs have enhanced breast cancer cell (MF-7) inhibition in vitro as
compared with free 5-Fu.
Starch also can be used as a precursor for the preparation of fluorescent carbon
nanodots (C-dots). C-dots are class of recently discovered fluorescence nanomaterials as a
promising alternative to toxic semiconductive quantum dots. Some advantages of C-dots are
small particle sizes, low toxicity, cheaper, stable, easily modified and large Stokes shift (Hsu
3
& Chang, 2012; Lai et al., 2012; Lin et al., 2012; Zhou et al., 2012). The fluorescence
properties of C-dots can either be quenched efficiently by electron acceptor or electron donor
molecules in solution. The unique property of C-dots showed a great potential application as
sensor probes. Li et al. (2011), on the other hand, used C-dots obtained from carbon soot, as a
fluorescent sensing platform for silver ions detection, whereas Lin et al. (2011) used C-dots
for detection of nitrites in pond water, river water and pure milk. Recently, Zhou et al. (2012)
demonstrated C-dots as a fluorescence probe for sensing of mercury ions and biothiols with
high sensitivity and selectivity.
Various methods have been reported by researchers for the preparation of fluorescent
C-dots using starch as a precursor (Peng & Travas-Sejdic, 2009; He et al., 2011). In 2009,
fluorescent C-dots were synthesized from carbohydrates (glucose, sucrose and starch) using
nitric acid followed by surface passivation using amine-terminated compounds (Peng &
Travas-Sejdic, 2009). Besides, C-dots that were strongly emissive in the visible range under
UV have been synthesized from starch using an acid/alkali-assisted hydrothermal oxidation in
water (He et al., 2011). Unfortunately, these methods involve long reaction duration and
expensive precursors.
In our study, starch nanoparticles were synthesized from native sago starch
(Metroxylon sago) by using simple nanoprecipitation method. The potential application of
starch nanoparticles as controlled release nanocarriers for curcumin was evaluated. Various
synthesis conditions that affect the loading efficiency and release profile were also
investigated. These starch nanoparticles were also used as precursor materials for synthesis of
fluorescent carbon nanodots (C-dots). C-dots were synthesized by carbonization and surface
oxidation of preformed starch nanoparticles (Chin et al., 2012). The potential application of
C-dots as a fluorescent probe for detection of Sn(II) ions in aqueous solution was studied.
4
1.2 Objectives
The objectives of this study are:
a. to prepare starch nanoparticles from locally available sago starch.
b. to study the feasibility of starch nanoparticles as nanocarriers and controlled release
agents for curcumin.
c. to synthesize fluorescent carbon nanodots from starch nanoparticles.
d. to investigate the potential applications of carbon nanodots as a fluorescence probe for
metal ions detection in aqueous solution.
5
1.3 Scopes of Study
The scopes of this study entail the synthesis and characterization of starch-based
nanoparticles from native sago starch for controlled drug release and optical fluorescence
sensing for metal ions. Chapter 1 describes the background and justification of this study.
Chapter 2 provides an introduction of sago starch and its physical properties, and also,
summarizes on the current status of curcumin loaded polymeric nanoparticles as well as
potential applications of carbon nanodots as an optical fluorescence probe. Chapter 3
describes the formulation of curcumin loaded starch nanoparticles by a nanoprecipitation
method. The effects of synthesis conditions on the loading efficiency of curcumin into starch
nanoparticles were investigated. The optimum condition was employed for further curcumin
release studies. Chapter 4 describes on synthesis and characterization of fluorescent carbon
nanodots from starch nanoparticles, as well as its potential application as fluorescence probes
for highly sensitive fluorescence detection of Sn(II) ions in aqueous solution. The final
chapter (Chapter 5) present some concluding remarks and recommendations for future
research works.
6
CHAPTER 2
LITERATURE REVIEW
2.1 Native Sago Starch
Sago is one of the edible starches from palms and belongs to the genus of Metroxylon
sago. Metroxylon sago is also known as „rumbia‟ and widely grown in low-lying swampy
plain in Papua New Guinea, Indonesia, Philippines and Malaysia. It contains a large amount
of starch extracted from stem tissue (McClatchey et al., 2006; Malviya et al., 2010). In
Malaysia, the largest sago-planting areas are found in the state of Sarawak in East Malaysia
where the largest scale sago plantation area is in Mukah District. Metroxylon sago is by far the
most important economic species and is grown commercially in Malaysia for production of
sago starch (Margaret, 2012).
2.2 Physicochemical Properties of Sago Starch
Starch is a type of carbohydrate (polysaccharide) made from thousands of glucose
units. After extraction from plants, starch formed as a flour-like white powder that is insoluble
in cold water. Native starch has different size, shape and chemical content depending on their
botanic origin (Corre et al., 2010). The basic formula for starch is (C6H10O5)n and it consists
of mainly two glycosidic macromolecules which are amylose and amylopectin (Sivak &
Preiss, 1998).
Amylose is a linear (1-4)-linked-α-D-glucan, whereas amylopectin is a highly
branched molecule which consists of short chains of (1-6)-α-linked branches in every 22
7
glucose units (Sivak & Preiss, 1998) (Figure 2.1). The molecular weight of amylose is ranged
between 1.41 x 106
- 2.23 x 106, while for amylopectin the value is from 6.70 x 10
6 - 9.23 x
106 (Mohamed et al., 2008).
The moisture content of the sago starch was ranged between 10.6 - 20.0%, while the
unmodified starch was around 12% at average ambient temperature and humidity conditions
(Ahmad et al., 1999). In addition, by increasing temperature the swelling power of sago
reached its highest level at 80oC and then decreased (Srichuwong et al., 2005).
Figure 2.1: Linear and branched starch polymers (adapted from Fen, 2007).
2.3 Polymeric Nanoparticles
Polymeric nanoparticles are colloidal solid carrier systems with sizes range of 10 -
1000 nm (Ochekpe et al., 2009). Some examples of polymeric materials used in
8
pharmaceutical applications includes poly(vinyl alcohol) (Vimala et al., 2011), poly(lactic
acid) (Gu et al., 2007), poly(D,L-lactide-co-glycolide)(PLGA) (Anand et al., 2010) and
poly(N-vinylcaprolactam) (Rejinold et al., 2011). Natural polymers such as gums (Zhang et
al., 2009), chitosan (Li et al., 2011; Yadav et al., 2012), albumin (Kim et al., 2011), alginate
(Lertsutthiwong et al., 2009; Das et al., 2010) and starch (Danmi et al., 2007; Al-Karawi &
Al-Daraji, 2010) were also being explored as control release agents.
Drug can be dissolved or entrapped in polymeric nanoparticles, or loaded or attached
to nanoparticles depending upon the nanoparticles preparation method (Villiers et al., 2009)
(Figure 2.2). Generally, polymeric nanoparticles are classified as nanocapsules and
nanospheres. Nanocapsule is a vesicular or “reservoir” systems in which the drug is restricted
to an empty enclosed by a tiny polymeric membrane, whereas nanosphere is a matrix systems
in which the drug is dispersed within the polymer throughout the particle (Moinard-Chécot et
al., 2008; Maruthi et al., 2011).
The advantages of using polymeric nanoparticles for drug delivery are due to their
small sizes and their biodegradability (Singh & Lillard, 2009). The nanosize particles allowed
for efficient loading of drugs. The utilization of biodegradable polymers as controlled release
nanocarriers are usually more efficient compared to non biodegradable polymeric
nanoparticles. Biodegradable polymer would degrade to non toxic substances which can be
removed from the body through the normal metabolic pathways (Soppimath et al., 2001).
However, nanoparticles also have limitations as their small size and large surface area can
cause particle-particle aggregations which limit the loading efficiency of drug in polymeric
nanoparticles (Mohanraj & Chen, 2006).
9
Figure 2.2: Types of polymeric nanoparticle (adapted from Kumari et al., 2010).
2.4 Curcumin
Curcumin is a hydrophobic yellow pigment extracted from turmeric, a commonly used
spice, which derived from the rhizomes of Curcuma longa plant. Curcumin is also known as
1,7-bis-(4-hydroxy-3-methoxy-phenyl)-hepta-1,6-diene-3,5-dione (diferuloylmethane) which
exhibits keto-enol tautomerism. In acidic and neutral solutions, curcumin is in keto form
whereas in alkaline medium, curcumin is in a stable enol form (Anand et al., 2007) (Figure
2.3). Curcumin is insoluble in water and ether but soluble in ethanol, dimethysulfoxide and
other organic solvents. The molecular weight of curcumin is 368.37 g/mol and its melting
point is 183ºC (Aggarwal et al., 2003; Sharma et al., 2005; Basnet & Basnet, 2011).
