SYNTHESIS, CHARACTERIZATION AND CYTOCOMPATIBILITY OF HIGHLY POROUS, THREE DIMENSIONAL POLY (1, 10 DECANEDIOL CO-TRICARBALLYLATE) BASED SCAFFOLDS FOR CARDIAC & OTHER TISSUE ENGINEERING APPLICATIONS

Electrospinning is one of the recently developed methods that produces scaffolds resembling the natural extracellular matrix. It can utilize a wide array of natural and synthetic polymer materials to produce three dimensional, porous, biocompatible, biodegradable scaffolds by the aid of different variations of the machine setup. Reactive electrospinning is one type that produces in-situ cross-linked scaffolds. It has the advantages of being fast and efficient with tunable scaffold mechanical, morphological and thermal characteristics. In this work, we aim to synthesize, characterize and investigate the in vitro cytocompatibility of electrospun scaffolds of acrylated Poly (1, 10 decanediol-co-tricarballylate) (APDT) copolymer using photo-reactive electrospinning process with UV radiation for crosslinking, to be used for cardiac tissue engineering applications. The pre-polymer was synthesized via a poly condensation reaction between tricarballylic acid and decanediol. This was followed by an acrylation reaction to render the polymer UV photocrosslinkable. The effect of adding polyvinyl pyrrolidone (PVP) to act as chain entanglement enhancer on the porous structure formation was also investigated. An optimized solution with concentrations of 20% (w/v) APDT and 8% (w/v) PVP in ethanol was successfully electrospun. Effect of PVP molecular weight was also assessed. Porous scaffolds produced by solvent free particulate leaching method using sodium chloride and trehalose as porogens were also prepared for comparison purposes. Characterization of the produced scaffolds was performed using chemical, thermal, and morphological techniques followed by in-vitro cell viability testing using H9C2 cardiomyoblasts and adipose tissue derived mesenchymal stem cells. Chemical and thermal characterization confirmed the successful synthesis of the polymer. Morphological analysis revealed successful production of the porous scaffolds with porosity of more than 70% and a higher fiber diameter and smaller pore size in case of higher molecular weight PVP. In addition, mechanical testing confirmed the elastomeric nature of the scaffolds that is required to withstand cardiac contraction and relaxation. Finally, cell viability assay showed no significant indirect cytotoxic effect on the cardiomyoblasts. Moreover, cell scaffolds interaction study showed noticeable cell attachment and growth on the electrospun scaffolds more than the references. This rendered our scaffolds a very promising candidate for cardiac tissue engineering applications.NPRP grant # NPRP 09-969-3-251 from Qatar National Research Foundation (a member of Qatar Foundation

Fabrication of silk-based composite scaffold for bone-ligament-bone graft using aqueous polymeric dispersion technique

Tissue engineering is a promising technology for treating tissue defects or replacing nonfunctional tissues/organs. It relies upon a temporary scaffold that is basically an artificial structure which provides the support for 3D tissue formation or organogenesis. Ideally, scaffolds should be able to accommodate human cells, orchestrate their growth and differentiation leading to tissue regeneration and ultimately make it feasible for implantation. Major sports injuries involve the damage of cartilages, ligaments, tendons and the enthesis. Since ligament injury is most common and ligament-alone grafts are not so successful to replace the injured ligaments, the researchers are experimenting with the construction of a composite scaffold which can guide the stem cells to differentiate into fibrocartilage that bridges of Bone-Ligament interface i.e. enthesis. In the current project, a composite silk-based scaffold was fabricated by incorporating multiple compartments for B-L-B graft. The core scaffold was prepared by knitting the silk fibers (from Bombyx mori) to provide required mechanical strength. The individual compartments over the knitted scaffold were coated with specific biocompatible components (i.e. hydroxyapatite for bone, Polyethylene oxide and & Polyethylene glycol for ligament and cartilage) blended with gelatin using Aqueous Polymer Dispersion (APD) Technique. The morphology of fabricated scaffolds was studied under optical microscope and SEM (Scanning Electron Microscope) while the mechanical properties were analysed through the Texture Analyzer. The particle sizes were found to be between 10-1000 nm. It was concluded that silk based multi-compartmental scaffolds fabricated from APD technique are suitable for enthesis tissue engineering due to their porosity and matching mechanical properties. However, the scaffolds need to be confirmed for their bioactivity by culturing live cells on respective compartment

Chapter Fabrication Methodologies of Biomimetic and Bioactive Scaffolds for Tissue Engineering Applications

Tissue engineering has offered wide technologies for developing functional biomaterials substitutes for repair and regeneration of damaged tissue and organs. Biomimetic materials with their inherent nature to mimic natural materials are possible through the recent advances in the fabrication technology. With the help of porous or dense implants made with biodegradable materials, it is possible to incorporate different vital growth factors, genes, drugs, stem cells and proteins. In this review, we presented various fabrication methodologies of biomimetic and bioactive scaffolds for tissue engineering applications. An overview of the nanocomposites of biomaterials is presented. Further an example of one of the hybrid nanocomposite material is given for additive manufacturing

The Integration of Nanotechnology and Biology for Cell Engineering: Promises and Challenges

Introduction: Successful tissue engineering strategies leading to the regeneration of a tissue depend on many factors, starting from the choice of appropriate scaffold material, tailoring the surface functionalities and topography, providing the correct amount of chemical and mechanical stimuli at the appropriate time points, and ensuring the uniform and precise localization of cells. Further challenges arise when more than one cell type has to be employed for the effective regeneration of an organ. Importance: Though the use of nanomaterials has improved tissue engineering, many pitfalls still exist that present a roadblock in the translation of tissue engineering strategies to clinical practice. Apart from employing different materials with distinct surface functionalities and mechanical properties, various strategies have been employed to manipulate the surface topography and chemistry of scaffolds to create a biomimetic microenvironment for effective tissue regeneration. Conclusion: This review provides information about the factors influencing tissue engineering, namely geometry, chemistry, mechanics and cells, and the emerging concepts that may well represent the future of regenerative medicine. Electrospinning techniques and their variants, self-assembly, cell-printing techniques and cell sheet engineering, have all been elaborated in detail. These novel techniques may serve to overcome the challenges currently faced in tissue engineering

Development and characterisation of silsesquioxane-polycaprolactone nanocomposite scaffolds for use in small intestinal tissue engineering

Tissue engineering of small intestine aims to provide a cure to patients suffering from short bowel syndrome by increasing the absorptive surface through neo-intestinal mucosal tissue. So far, preliminary in vivo attempts by a research team in the USA have shown regeneration of neo-intestinal mucosa in rat models with some success; however experiments in this complex field of tissue engineering still remain in infancy and far from clinical use. A fresh perspective is required to further investigate all the three aspects of tissue engineering, namely, the polymer scaffold, the cell supply, and the biomolecules. The concept of nanocomposite polymer is rapidly emerging and has generated a lot of enthusiasm in tissue engineering due to their high surface to volume ratio and hence enhanced performance. This work was focussed to develop and characterise scaffolds for small intestinal tissue engineering using a new nanocomposite polymer of polycaprolactone and silsesquixane, developed in our laboratory. An in vitro study was also performed to test the scaffolds for cell viability and proliferation using rat’s intestinal epithelial cells. Our results have shown that biodegradable polycaprolactone-silsesquioxane nanocomposite can be fabricated in desired scaffold morphology using simple techniques like particulate leaching, and that it supports intestinal cell growth and proliferation. Future studies incorporating these scaffolds for in vivo use in animal models need to be carried out in order to investigate further about their ability to withstand natural forces within the abdomen, and whether they support cell growth based on principles of cell migration, before a more definitive and continuous cell supply is available in form of stem cells cued specifically to intestinal lineage

3D bioactive composite scaffolds for bone tissue engineering

Bone is the second most commonly transplanted tissue worldwide, with over four million operations using bone grafts or bone substitute materials annually to treat bone defects. However, significant limitations affect current treatment options and clinical demand for bone grafts continues to rise due to conditions such as trauma, cancer, infection and arthritis. Developing bioactive three-dimensional (3D) scaffolds to support bone regeneration has therefore become a key area of focus within bone tissue engineering (BTE). A variety of materials and manufacturing methods including 3D printing have been used to create novel alternatives to traditional bone grafts. However, individual groups of materials including polymers, ceramics and hydrogels have been unable to fully replicate the properties of bone when used alone. Favourable material properties can be combined and bioactivity improved when groups of materials are used together in composite 3D scaffolds. This review will therefore consider the ideal properties of bioactive composite 3D scaffolds and examine recent use of polymers, hydrogels, metals, ceramics and bio-glasses in BTE. Scaffold fabrication methodology, mechanical performance, biocompatibility, bioactivity, and potential clinical translations will be discussed

FIBRONECTIN CONJUGATION ONTO THREE-DIMENSIONAL POROUS POLYURETHANE SCAFFOLDS FOR VASCULAR TISSUE ENGINEERING

In tissue engineering, scaffolds serve as the three-dimensional (3D) structural framework controlling cell behavior and ultimately the performance of the final construct. Cell interactions with synthetic scaffolds can be improved by attaching biomolecules such as proteins or peptides. Fibronectin (FN) is a protein that contains several domains including the cell adhesion tri-peptide, Arginine-Glycine-Aspartic Acid, allowing it to mediate cell attachment and proliferation on various substrates. In this work, FN was conjugated on 3D highly porous poly(carbonate) urethane (PCU) scaffolds through grafted poly(acrylic) acid (AA) spacers. Scaffolds were fabricated using a solvent casting-particulate leaching method. AA was grafted on the 3D scaffolds using a ceric ion initiator, and FN was conjugated using an N-hydroxysuccinimide intermediate. Scaffold pore structures were visualized using scanning electron microscopy and Fourier transform infrared spectroscopy was used to monitor reaction progress. A toluidine blue assay was used to quantify grafted AA groups. Survey and high-resolution X-ray photoelectron spectroscopy scans of scaffolds provided changes in atomic composition and chemical groups, respectively. Immunofluorescence studies showed FN to be evenly distributed over the scaffold surfac

Development of a Novel Porogen Insertion System Used in Solid Freeform Fabrication of Porous Biodegradable Scaffolds with Heterogeneous Internal Architectures

This thesis is concerned with the design of a novel system for inserting porogen particles within internal structure of the bone scaffold. The proposed system would be integrated with a 3D printing machine to create macro-pores based on the conventional porogen leaching method. The system is capable of inserting porogens on pre-designed locations within the scaffold structure to realize the generation of macro-porosity within scaffolds. Several alternatives for such a porogen insertion mechanism are proposed based on employing a mechanical actuator for opening and closing the path of porogen particles from a porogen reservoir to the build chamber. Another possible design that offers significant advantages over its actuator-based alternatives is a pneumatic-based mechanism that picks up porogens from a porogen reservoir and places them at pre-designed locations. Among all the presented alternatives, the pneumatic-based system is selected by utilizing the value matrix method, and detail design of the different parts of this system is presented. The required pilot test setups for performing the feasibility study of the proposed method have been designed and successfully developed, and the practicality of the designed porogen insertion mechanism is proven through experiment