On Thursday 7/11/2019 at the discussion room in Building C at of Technology Graduate Student Sally Abdul-Hussein Kadhum Discussed her thesis entitled

"Fabrication of polymeric composite porous 3D scaffold for bone tissue engineering "

 From the following

She was awarded Pass with credit after fulfilling all the corrections required by the committee

Abstract

the bone defects and the related bone disease remain a major challenge in orthopedic surgery. To solve this problem, tissue engineering is one of the methods of promoting bone regeneration. Scaffold is one of the major components of tissue engineering. This study aims to the fabrication of new bio nanocomposites based on the polymers blend to be used for bone scaffold. So, design a scaffold of a three-dimensional porous hybrid bio active composite that closely mimics the structure and function of the extracellular matrix of the native tissue.

In this work, attempts were done to develop and fabricate two groups of polymeric blends as biological system by utilizing hand lay-up technique. The first set of polymeric blend consists of (Acrylic bone cement: X% poly methyl methacrylate (PMMA)). Whereas, the samples of the second group were prepared from the same materials but in a reverse position.

Mechanical properties, such as (Tensile, flexural, impact, hardness, and wear) were studied. Microstructure, and pore size have been investigated, and interconnection was analyses by scanning electron microscope (SEM). Physical analyzed conducted by (Fourier transform infrared (FTIR) and differential scanning calorimeter (DSC)), in addition to study the water absorption and open porosity for all the prepared samples.

According to the results of the mechanical and physical tests, one sample has been selected which is (Acrylic bone cement: 15% PMMA) as the optimum sample, which was used as a matrix to prepare bio nanocomposites reinforced with different nano powders that are zirconia (ZrO2) and magnesia (MgO) with selected weight percentages (0, 0.5, 1, 1.5 and 2%), and hydroxyapatite (HA) with the selected weight percentages (0, 5, 10, 15 and 20%). Moreover, the best bio nanocomposite sample, which has the higher mechanical properties, is ((Acrylic bone cement: 15% PMMA): 1.5% ZrO2), and it has been selected to prepare the hybrid composites reinforced with Salvadora Persica fibers (Miswak fibers).

The results showed that the addition of 0.5 weight % of Salvadora Persica fibers produced a higher mechanical property. In vitro biological activity against two types of gram-positive bacteria and against other two types of gram-negative bacteria were studied. The results clarified that there is no biological influence on all the tested samples.

Porosity is an important issue in the scaffold morphological structure. It is induced by a solvent casting method (By mixing with an effervescent components, which are sodium bicarbonate (NaHCO3) and citric acid (C6H8O7) at weight ratio (1:1)). The hybrid composites ((Acrylic bone cement: 15% PMMA): 1.5 % ZrO2: X% Salvadora Persica fibers) were used to produce a porous structure for bone scaffold.

Wear resistance clearly reduced with the addition of Salvadora Persica fibers to the porous hybrid bioactive composites, whereas, the water absorption and open porosity increased with an increase of Salvadora Persica fibers content composite.

Based on the mechanical and physical tests results, the optimum sample of porous hybrid bioactive composites was selected in order to design a three- dimensional bone scaffold consisting of core and structural shell with dimensions (8 mm length, 7 mm diameter with 2.6 mm internal cavity).

The SEM test manifested a homogeneous, porous structural morphology, with pores size within the range of 200 µm – 500 µm. At the same time, it interspersed small pores within the range of 20 µm- 100 µm, as well as, there are about 38% of these pores form the internal interconnections that occur through a large hole. This multi scale, which will satisfy the pore size, is required for enhancing the bone tissue regeneration.

FTIR test results didn’t elucidate any  new peak, or shift in peaks sites. DSC test indicated that there is a positive change in the values of glass transition temperature (Tg), and all samples are of a single-phase structure.

The interface interaction between the bone tissue and the fabricated bone scaffolds was estimated by in vivo in order to assess the bone regeneration.  In vivo study, ten rabbits were used and divided into two equal groups (Control and treated group). The control group includes two stages, the first stage, surgically induced bone defect by removing of (8 mm) length of the all thicknesses of bone tissue and  in the second stage, the defect was substituted by the fabricated bone scaffold and fixation by intramedullary pinning. While, the treated group is same as in the control group, but injecting of the auto bone marrow (1 cc) in the cavity and around the scaffold.

After 2, 4, and 6, weeks post-operative radiographic images were taken for both groups. Also, histopathological examination was done after 6 weeks post operation for both groups.

The radiographic examination showed a significance periosteal reaction in the area of proximal and distal part of the bone defect with the formation of callus in which the ends of the bone defect connected at the end of 4 weeks post-operative in control and treated group, respectively. On the other hands, the histopthological findings were coincided with the radiographic results, in which the formation of fibrous connective tissue, cartilage and bony tissues (woven bone, trabecular bone, and compact bone) are more advanced in treated group compared with the control group. 

The bone scaffold manufactured in this work from (Porous hybrid biopolymer composite materials) is expected to be a good candidate for bone tissue engineering

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