Bioactive glasses have been well established has third
generation biomaterials for the treatment of bone defects, devoid of adverse
immunological response. This is due to the formation of hydroxylapitite, having
similar chemical composition to natural bone on the glass surface when immersed
in biological fluids. Bioactive glasses containing Strontium (Sr) are well
known for stimulating high degree of cellular responses leading to high rate of
bone regeneration in-vivo and in-vitro. The current study investigated
the performance of a bioactive glass composite prepared using a Sr-substituted
glass encapsulated in starch as a biomaterial while sodium metasilicate was
used as a low-cost substitute for alkoxysilane precursors. The glass was
prepared using a new solution precipitation method followed by a sodium
wash-out technique to remove the residual sodium that impregnated the gel
network structure. The obtained materials were characterizied using scanning
electron microscopy (SEM), X-ray diffractometry (XRD) and Fourier transform
infrared spectroscopy (FTIR). The results obtained showed that the composite
gave a better surface morphology compared with the parent glass. Furthermore,
the diffraction pattern of the bioglass composite gave a better ordering of the
material structure. Bioactivity assessment showed the formation of
hydroxyapatite after immersion in stimulated body fluid which increased in
density after 14 days incubation. The composite gave a higher apatite
nucleation reaction in SBF during the same period of immersion. Degradability
in SBF was also observed, which gave an indication that the materials could
undergo controlled degradability in biological fluids, which is a key
requirement for a material intended for use in bone regeneration. The performance
of the materials indicates that they could serve as low-cost potential
candidate biomaterials for use in bone regeneration.
Table of
Contents
TITLE PAGE
DECLARATION iii
CERTIFICATION iv
DEDICATION v
ACKNOWLEDGEMENT vi
ABSTRACT viii
TABLE OF CONTENT ix
TABLE OF FIGURE xi
LIST OF TABLE xii
CHAPTER ONE 1
1.0. INTRODUCTION 1
1.1 Background to the Study 1
1.2. Statement of the Problem 3
1.3. Aim of the Study 3
1.4 Specific Objectives 3
1.5. Significance of the Study 4
1.6. Operational Definition of Terms 4
CHAPTER TWO 8
2.0. LITERATURE REVIEW 8
2.1. A Historical Overview 8
2.1. Bioactive Glass (BGs) 12
2.2. Interaction of BGs with the Physiological
Environment: General Features. 13
2.2.1. Classes of Bioactivity 13
2.3. Mechanism of Bioactivity 17
2.4. Melt-Derived Bioactive Glasses 20
2.5. Sol–Gel-Derived Bioactive Glasses 23
2.6. Bone Regeneration 25
2.7. Bioactive Glass Coatings. 27
2.8. Strontium (Sr) containing Bioglasses 29
2.8.1. Silicate Sr-doped BGs 32
2.8.2. Borate Sr-doped BGs 33
2.8.3. Phosphate Sr-doped BGs 34
CHAPTER THREE 37
3.0. METHODOLOGY, MATERIALS AND METHODS 37
3.1. Materials 37
3.2. METHODS 38
3.2.1. Synthesis of Sr–doped bioactive glass by the Sol-Gel method 38
3.2.2. Preparation of Starch/PVA 39
3.2.3. Incoporation of Sr-doped bioactive glass/Starch 39
3.2.4 Preparation procedure of SBF 39
3.3.5. Bioactivty test in SBF 40
3.3.6. Characterisation
techniques 41
3.3.6.1. Morphology and Elemental
composition 41
3.2.6.2. Phase composition 41
3.2.6.3. Nature of bonds present 41
CHAPTER FOUR 42
4.0.
RESULTS AND DISCUSSION 42
4.1. SCANNING ELECTRON
MICROSCOPY (SEM) 42
4.1.1. Sr-doped Glass and
composite 42
4.1.2. Sr-doped Bioglass
Composite 44
4.2.
X-Ray Diffractometry (XRD) Analysis 45
4.2.1. Diffraction patterns of
the Sr-doped Bioactive Glass 45
4.2.2. Diffraction patterns of
the Sr-doped Bioglass Composite 46
4.3. FOURIER TRANSFORM INFRARED (FTIR) ANALYSIS 47
CHAPTER FIVE 51
CONCLUSION AND RECOMMENDATION 51
5.0. Conclusion 51
REFERENCES 52
Jones, R. J., Gentleman, E., and Polak, J. (2007) Bioactive Glass
Scaffolds for Bone Regeneration. Journal
of mineralogical of American, 3 (6): 393–399. 56
TABLE OF FIGURE
Figure 1 Compositional diagram for bone-bonding 11
Figure 2 Schematic representation of (A) melt-quenching and
(B) sol-gel route for bioactive glass synthesis and final products (Kargozar et
al., 2019). 22
Figure 3 Schematic of reactions in the sol–gel process:
formation of silica tetrahedral and nanoparticles at room temperature 25
Figure 4 Diagram illustrating how a porous bioactive glass
scaffold could be used to regenerate a bone defect 27
Figure 5 Figure 4.1: (a) Sr-doped bioglass after sinitering
and (b) Sr-doped bioglass composite 43
Figure 6Figure 4.2: SEM images of samples after immersion in
SBF (a) Sr-doped glass, (b) composite for 7 days, (c) Sr-doped glass and (d)
composite for 14 days 44
Figure 7 Figure 4.3:
XRD result (a) Sr-doped and (b) composite for 0 day in SBF 46
Figure 8 Figure 4.4: XRD result, (a) Sr-doped bioglass for 7
days, (b) composite for 7 days, (c) for Sr-doped bioglass for 14 days and (d)
for composite for 14 days in SBF 47
Figure 9 Figure 4.5: FTIR result (a) Sr-doped glass, (b)
composite at 0 day 49
Figure 10 Figure 4.6: FTIR result, samples after immersion in
SBF (a) Sr-doped glass, (b) composite for 7 days, (c) Sr-doped glass and (d)
composite for 7 days 49
Figure 11 Figure 4.7: FTIR result, samples after immersion in
SBF (a) Sr-doped glass, (b) composite for 14 days, (c) Sr-doped glass and (d)
composite for 14 days 50
LIST
OF TABLE
Table 1 Tables 3.0: List of reagents used for the
experiment 37
Table 2 Tables 3.1: List of equipments/ apparatus. 37
Table 3 Table 3.2: Composition of the Sr-doped
bioactive glass 38
Table 4 Table 3.3: Nominal ion concentration of
SBF in comparison with those in human blood plasma 40
Table 7 Table 4.1: The spectra frequency and their
assignment of Sr-doped glass and composite at 0 day 48
Bioactive
glasses are amorphous, silicate-based materials that bond to bone and stimulate
new bone growth while degrading over time, making them candidate materials for
bone regeneration. It has been
traditionally used in the clinical practice to fill and restore osseous defects
due to their unique ability to bond to host bone and stimulate new bone growth
without eliciting adverse immunological response (Baino, 2016).
In
2016 Baino reported that BGs are able to stimulate more bone regeneration than
other bioactive ceramics used in the past but they lag behind other bioactive
ceramics in terms of commercial success, thought it has not yet reached its
potential but research activity is growing.
After
a preliminary definition of biomaterial in the 1950s, mainly based on the
criterion of maximum biochemical and biological inertness in contact with body
fluids (first-generation materials) (Hench , 2010 and Elisa et
al., 2018), the discovery of Bioglass® by Larry L. Hench in 1969 (Hench,
2006) constituted for the first time in the story of biomaterials an
alternative, extending the concept of biocompatibility to all those materials
which were able to enhnce and to promote a positive response of the living
system through the formation of a strong tissue implant bond (second-generation
materials) and the genetic activation of specific cell pathways (third generation
smart materials) (Hench ,1998).
Bioglass®
actually represents the first example of a biomaterial belonging to the third
generation, this so because of the biological role played by its ionic
dissolution products, which is directly released in the physiological
environment (Hoppe, 2011), in addition to its capability to strongly bond the
host tissue (primarily bone) with the formation of an interfacial calcium
phosphate layer (Andersson, 1990, 1991).
According
to Jones in 2013, the first artificial material that was found to form a
chemical bond with bone, launching the field of bioactive ceramics. The in vivo
studies shows that bioactive glasses bond with bone more rapidly than other
bioceramics materials, and these studies indicated that their osteogenic
properties are due to their dissolution products, stimulating osteoprogenitor cells at the genetic
level. Hence, hydroxyapatite (HA) is highly
osteoconductive and is able to form a strong bond with the surrounding living
bone (Bates, 2007).
Since
its discovery, 45S5 Bioglass® (45S5) opened unimaginable scenarios in the
field of tissue regeneration, mainly thanks to its osteoinductive and
osteoconductive ability (Cho, 2002). In vitro studies reported that, during the
dissolution of 45S5, the ion release seems to induce angiogenesis and stimulate
osteoblasts proliferation and new bone growth (Audigé, 2005).
However,
some bioactive glasses are able to bond to bone. According to Li et al, 2017 bone regeneration is
necessary to address various degrees and locations of bone defects. Regardless
of whether large bone defects are caused by trauma, infection, tumor excision,
and skeletal necrosis or by periodontitis, insufficient implant bone, and
osteoporosis, they all require treatment involving bone regeneration.
Moreover,
this approach carries the risk of disease transmission and unsatisfactory bone
integration.
Technological
advancement has brought about 3D-printed scaffolds which have aroused wide
concern over the past few decades due to their unique physical properties for
tissue regeneration engineering and vascularized bone regeneration (Zhang,
2017).
Over
the last 50 years, numerous studies have been conducted to optimize the
response of the body to BGs and extend their use to a wider range of specific
clinical application (Brink, 1997 and Oudadesse, 2011).
The
improvement and acceleration of bone repair still are partially unmet needs in
bone regenerative therapies. Hence, strontium (Sr)-containing bioactive glasses
(BGs) is regarded as a highly promising materials to tackle this challenge.
In
the present study, we provide a comprehensive overview of Sr-containing glasses
along with the current state of their clinical use and general route to sol-gel
bioactive glasses involve the use alkoxysilane silica precursors. Alkoxysilanes
are generally very expensive and toxic on inhalation
The
aim of this study is to prepare Sr-doped bioactive glass composite by solution
precipitation technique using sodium metasilicate as an inexpensive substitute
to alkoxysilane precursors.
• To
prepare the bioactive glass doped with strontium.
• To
prepare the bioactive glass and bioactive glass/polymer composite.
• To
characterize the Sr-doped bioactive glass and starch-based composite to
evaluate their bone bonding ability.
· The
design of a novel route for preparing bioactive glasses and composites from
metal silicates.
· Economic
and less toxic route for preparing bioactive glasses and composites attractive
for commercial scale production.
• Bioactive Glasses
Bioactive glasses are amorphous silicate-based
materials which are compatible with the human body, bond to bone and can
stimulate new bone growth while dissolving over time (Baino,
2016).
• Bone Regeneration
Bone regeneration is called Bone healing, or fracture
healing, is a proliferative physiological process in which the body facilitates
the repair of a bone fracture.
• Maxillofacial
Maxillofacial refers to the face and jaws.
• Mesoporous Material
A mesoporous material has openings within its
structure that are between 2 and 50 nanometers (nm) in diameter.
• Musculoskeletal
This system includes bones, muscles, tendons,
ligaments and soft tissues.
• Necrosis
It is the death of most or all of the cells in an
organ or tissue due to disease, injury, or failure of the blood supply.
•Osteoconduction
This simply means that bone grows on a surface. The
phenomenon is regularly seen in the case of bone implants. Implant materials of
low biocompatibility such as copper, silver and bone cement shows little or no
osteoconduction.
• Osteoclast & Osteoblast
Aged bone resorption is refers to as osteoclasts while
osteoblasts are responsible for new bone formation
• Osteoarthritis
This is the degeneration of joint cartilage and the
underlying bone, most common from middle age onward. It causes pain and
stiffness, especially in the hip, knee, and thumb joints.
• Osteoporosis
Osteoporosis is a medical condition in which the bones
become brittle and fragile from loss of tissue, typically as a result of
hormonal changes, or deficiency of calcium or vitamin D.
• Osteogenesis & Osteogenesis Imperfecta (Oi)
Osteogenesis is the development and formation of bone.
Osteogenesis imperfecta (OI) is a genetic or heritable
disease in which bones fracture (break) easily, often with no obvious cause or
injury. OI is also known as brittle bone disease, and the symptoms can range
from mild with only a few fractures to severe with many medical complications
(Kang et al., 2017).
• Periodontitis
This is an inflammation of the tissue around the
teeth, often causing shrinkage of the gums and loosening of the teeth.
• Prostheses
The term prostheses is an artificial body part, such
as a limb, a heart, or a breast implant.
A prosthesis substitutes for a part of the body that
may have been missing at birth, or that is lost in an accident or through
amputation.
• Scaffolds
Scaffolds can be said to be the masterpiece of bone
tissue engineering. A bone scaffold is the 3D matrix that allows and stimulates
the attachment and proliferation of osteoinducible cells on its surfaces.
• Skeletogenesis
Skeletogenesis is simply the process
of skeleton formation.
• Strontium Ranelate (Sr)
Strontium ranelate is a medication used for the
management of severe osteoporosis in high-risk postmenopausal women and adult
men.
• In-Vitro, In-Vivo & In-Situ
In vitro is Latin for “within the glass.” When
something is performed in vitro, it happens outside of a living organism.
In vivo is Latin for “within the living.” It refers to
work that’s performed in a whole, living organism.
In situ means “in its original place.” It lies
somewhere between in vivo and in vitro. Something that’s performed in situ
means that it’s observed in its natural context, but outside of a living
organism.
• Ossification
Ossification is the natural process of bone formation;
it is the hardening (as of muscular tissue) into a bony substance.
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