Effects of Microstructure Architecture on the Fracture of Fibrous Materials

Fibrous materials is one of the potential scaffolds used for tissue engineered constructs. One of prerequisite properties for tissue engineered construct is fracture property. The work here study the relationship between microstructure architecture and fracture behaviour of fibrous networks by using finite element analysis. The result shows that fibrous networks are toughened by either reducing the fibre density or cross-link percentage of networks. Such implementation increases the degree of non-affine deformation and produces a more compliant response at the crack-tip region. The non-affine deformation in fibrous networks involves fibre movement like fibre rearrangement and reorientation, where such mechanisms allow stress delocalization to occur at the crack-tip region and results in a better fracture toughness of fibrous networks. The findings form this work provide the design guideline of fibrous materials with enhanced toughness for multiple applications

Electrospinning of aligned nanofibers for biomedical application using a rotating drum collector

Both random and aligned collagen fibers exist in extracellular matrix. The alignment of fiber in tissue engineering scaffolds can affect the cell morphology. Therefore, knowledge in the control of microstructure alignment in electrospun scaffolds is crucial. In this study, a rotating collector drum was designed and fabricated to collect aligned gelatin fibers using an electrospinning technique. The speed of the fabricated rotating drum collector was adjustable and controlled at 1000 rpm, 2000 rpm, and 3000 rpm. Electrospun scaffolds having aligned fibers were successfully produced using the rotating drum at 3000 rpm and compared with random nanofibers collected with the static plate. The speed of the rotating drum collector increased the alignment of the fibers and had little influence on fiber diameter. The results provide process parameters for the fabrication of aligned gelatin fibers

Preparation of siam weed extracts

Siam Weed is a perennial shrub in the Asteraceae family that spreads throughout tropical and subtropical areas of the world. Siam weed has been used as a traditional herbs for ailments such as fever and soft tissue wounds. Previous studies show potential utilization of Siam weed extracts in medical areas. This study is aimed to produce Siam weed extracts to be used to further exploit its application in medical products. We first repeated step of preparation for Siam weed crude extract and then modified the steps to develop a new way of preparation of Siam weed aqueous extract that is suitable for further development of medical application. The chemical properties of the aqueous extract were investigated using Fourier transform infrared spectroscopy (FTIR). This characterization results revealed that the Siam weed aqueous extract was successfully prepared and its chemical properties are similar to that of crude extracts. By maintaining similar chemical properties, Siam weed aqueous extract can be useful to further exploitation of Siam weed extracts in medical applications

Finite Element Modelling for Fracture of Multilayer Fibrous Networks

Tissue engineering involves three-dimensional scaffolds to support cell culture activities and provide mechanical support. One of the potential scaffolds used in tissue engineering is an electrospun scaffold consisting fibres ranging from nano- to micrometer scales deposited on layer stack. The finite element models have been used to study the in-plane deformation of two-dimensional single layer fibrous networks and without considers out-of-plane deformation. While the existing study focuses on two-dimensional study, the out-of-plane deformation of layer structured of electrospun scaffolds through the scaffolds thickness has not been studied. In this study, three-dimensional finite element model was constructed to investigate the fracture of multilayer fibrous networks. The three-dimensional results were compared with the fracture on two-dimensional single layer fibrous network. The result shows that these two models had identical fracture behaviour and similar deformation at the crack-tip region, where the fibres are rearranged and reoriented with similar stress distribution. The work here concludes that two-dimensional single layer fibrous network model is a simple yet effective model for the study of homogeneous fibrous networks

Electrospinning of Polycaprolactone (PCL) and Gelatin Polymeric Fibers

Electrospinning is one of the commonly used polymeric fiber production technique, owing to its versatility and flexibility in spinning a wide range of polymers for various applications including tissue engineering. However, recent researches have been extensively focusing on exploring the electrospinnability of different polymers without fully realizing how the electrospinning parameters influence the electrospun fibrous structure, as the microstructure morphology will significantly affect the performance of electrospun membranes. The present work demonstrates the robustness of electrospinning technique in producing electrospun fibrous membranes with different microstructure morphology by altering the electrospinning parameters. Both PCL and gelatin solutions have been successfully transformed into electrospun fibrous membranes using an electrospinning machine. The PCL fibrous membranes consisted of beads and non-homogenous fibers while the gelatin membranes showed homogenous size of electrospun fibers. Results also revealed that the electrospinning parameters including solution and process parameters determined the microstructure morphology of electrospun membrane. The spindle-like beads in PCL membrane transformed into spherical size at higher solution concentration and applied voltage. Meanwhile, the gelatin membrane demonstrated similar morphology at different tip-collector distance. The size of gelatin fibers was also similar. Through this work, basic understanding on how the electrospinning parameters affect the morphology of different types of polymeric fibrous membrane can provide an insight for other researchers in facilitate production of electrospun membranes with desired microstructure morphology

Synthetic and Natural Fibrous Scaffolds for Soft Tissue Engineering Applications / Weily Khoo ...[et al.]

Fibrous scaffolds have been extensively studied as grafts for damaged tissue, owing to their physical architecture mimicking the native tissues like articular cartilage and skin. Developing mechanical robust fibrous scaffolds is therefore a critical issue to prevent scaffold failure that limits their applications in tissue engineering. This paper demonstrates our latest development of synthetic and natural fibrous scaffolds having physical architectures and mechanical properties comparable to that of native biological soft tissues. Synthetic fibrous scaffold was produced from gelatin solution using electrospinning technique while natural fibrous scaffold was extracted from small intestinal submucosa (SIS) of cattle. The SIS membrane was first decellurized and further reinforced with alginate hydrogel to form 3D composite scaffold. The physical architectures of both synthetic and natural fibrous scaffolds including thickness and microstructure morphology were characterized. SIS fibrous membrane reinforced with alginate hydrogel demonstrated more than 10 times of increment in scaffold thickness. Through scanning electron microscope (SEM) visualization, the synthetic fibrous scaffold demonstrated microstructures that mimic nanometer fiber and porous structure of soft collagenous tissues. Uniaxial tensile and fracture tests were performed to determine the tensile properties and fracture toughness of fibrous scaffolds. Both types of scaffolds showed tensile strength (0.81 – 38.30 MPa) and fracture toughness (0.86 – 32.52 kJ/m2) comparable to natural soft collagenous tissues. The developed tissue engineered scaffolds not only exhibit physical architectures mimicking native tissue structures but also demonstrate mechanical properties comparable to the native soft tissues

Electrospinning of Polycaprolactone (PCL) and Gelatin Polymeric Fibers / Shing Chee Lim ...[et al.]

Electrospinning is one of the commonly used polymeric fiber production technique, owing to its versatility and flexibility in spinning a wide range of polymers for various applications including tissue engineering. However, recent researches have been extensively focusing on exploring the electrospinnability of different polymers without fully realizing how the electrospinning parameters influence the electrospun fibrous structure, as the microstructure morphology will significantly affect the performance of electrospun membranes. The present work demonstrates the robustness of electrospinning technique in producing electrospun fibrous membranes with different microstructure morphology by altering the electrospinning parameters. Both PCL and gelatin solutions have been successfully transformed into electrospun fibrous membranes using an electrospinning machine. The PCL fibrous membranes consisted of beads and non-homogenous fibers while the gelatin membranes showed homogenous size of electrospun fibers. Results also revealed that the electrospinning parameters including solution and process parameters determined the microstructure morphology of electrospun membrane. The spindle-like beads in PCL membrane transformed into spherical size at higher solution concentration and applied voltage. Meanwhile, the gelatin membrane demonstrated similar morphology at different tip-collector distance. The size of gelatin fibers was also similar. Through this work, basic understanding on how the electrospinning parameters affect the morphology of different types of polymeric fibrous membrane can provide an insight for other researchers in facilitate production of electrospun membranes with desired microstructure morphology

Strategy on the production of bead free electrospun gelatin scaffolds

Electrospun scaffolds consist of micro-scale or nano-scale porous fibrous networks. These electrospun scaffolds had become increasingly popular in tissue engineering filed as it could provide nano-environment for cell culture and produced by using biodegrable polymer. One of the important key to provide such environment for cell culture is the porosity of the electrospun scaffolds as it is highly related with the cell-cell interaction. The porosity of the electrospun scaffolds could be affected by bead formation which is one of the common problems faced in electrospinning process. However, the formation of beads are difficult to be controlled as it depends on environmental factors such as humidity and operating temperature. Controlling these two environmental factors normally requires an expensive control system. This paper aims to solve the problem of bead formation by adjusting material concentration and process parameters without controlling the environmental factors. The parameters studied in this paper include polymer concentration, flow rate, distance between the syringe needle tip and collector and applied voltage. The microstructure of the electrospun scaffolds produced were visualised using scanning electron microscopy (SEM) and were analysed in terms of bead formation and fiber diameter. This study shows that polymer concentration is the best strategy to prevent bead formation in gelatin scaffolds while other process parameters such as applied voltage, distance between the syringe needle tip and the collector as well as flow rate can be used to control the fiber diameter. An understanding of the effects of each parameter provides a guideline to control microstructure morphology by producing bead-free electrospun gelatin scaffolds

Siam-weeb based gelatin electrospun scaffolds

Siam weed (Chromolaena odorata) is a traditional herb used to soothe burns and scars and potentially improve dressing and tissue-engineered construct healing ability. The use of Siam weed is mainly in the form of extract. The state of liquid extract limits the use of Siam weed compared to the state of gels and membrane. However, the development of the hybrid of Siam weed in gel and membrane form is lacking. In this study, Siam weed was harvested and made into aqua extracts. The biocompatibility of the aqua extract with various concentrations was tested using Cell Proliferation Assay. The aqua extract was then incorporated into the gelatin solution and spun into nanofibers using an electrospinning technique. The cell proliferation study shows maximum cell proliferation at the 25 μg/ml concentration. The scanning electron microscope images of the electrospun scaffolds show fibrous networks’ microstructures without beads. The concentration of the hybrid solution was found to affect the morphology of the nanofibers by having diameters in the range of 160 ± 90 to 250 ± 150 nm. The Siam-weed-based gelatin electrospun scaffolds provide a native-like microenvironment and potentially improve wound healing ability for biomedical application