4 results
Drug Delivered Poly(ethylene glycol) Diacrylate (PEGDA) Hydrogels and Their Mechanical Characterization Tests for Tissue Engineering Applications
- Kerolos Hanna, Ozgul Yasar-Inceoglu, Ozlem Yasar
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- Journal:
- MRS Advances / Volume 3 / Issue 30 / 2018
- Published online by Cambridge University Press:
- 30 January 2018, pp. 1697-1702
- Print publication:
- 2018
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Tissue Engineering has been studied to develop tissues as an alternative approach to the organ regeneration. Successful artificial tissue growth in regenerative medicine depends on the precise scaffold fabrication as well as the cell-cell and cell-scaffold interaction. Scaffolds are extracellular matrices that guide cells to grow in 3D to regenerate the tissues. Cell-seeded scaffolds must be implanted to the damaged tissues to do the tissue regeneration. Scaffolds’ mechanical properties and porosities are the two main scaffold fabrication parameters as the scaffolds must be able to hold the pressure due to the surrounding tissues after the implantation process. In this research, scaffolds were fabricated by photolithography and Poly(ethylene glycol) Diacrylate (PEGDA) which is a biocompatible and biodegradable material was used as a fabrication material. In order to compare the compressive properties of PEGDA only with the compressive properties of drug delivered PEGDA, firstly, PEGDA only solutions were prepared. Then, PEGDA was mixed with Meloxicam 15 mg, Hydrochlorothiazide 12.5 mg, Cyclobenzaprine 10 mg and Spironolactone-hctz 25-25 mg respectively and they were placed under the UV light for about 15 minutes to solidify the cylindrical shaped hydrogels. 5 samples from each group were fabricated under the same conditions. Laboratory temperature, photoinitiator concentration and UV light intensity was kept constant during the fabrication process. After the fabrication was completed, Instron 3369 universal mechanical testing machine with the 5 mm/min compression rate was used to do the compression tests to compare the drug effects on PEGDA hydrogels. Our results indicate that average ultimate strength of PEGDA only samples was 3.820 MPa. Also, due to the fact that Meloxicam 15 mg and PEGDA mixture did not solidify under the UV light at all, compression test could not be performed for PEGDA- Meloxicam 15 mg mixture. However, Hydrochlorothiazide 12.5 mg, Cyclobenzaprine 10 mg and Spironolactone-hctz 25-25 mg dissolved within the PEGDA completely and our compression results show that average ultimate strengths were 3.372 MPa, 1.602 MPa, 1.999 MPa respectively. This preliminary research showcases that compressive properties of the PEGDA-based photopolymerized scaffolds can be altered with the control of the drug type and drug concentration.
Multi Material 3D Scaffold Printing with Maskless Photolithography
- Joyce Tam, Ozlem Yasar
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- Journal:
- MRS Advances / Volume 2 / Issue 24 / 2017
- Published online by Cambridge University Press:
- 12 January 2017, pp. 1303-1308
- Print publication:
- 2017
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In today’s technology, organ transplantation is found very challenging as it is not easy to find the right donor organ in a short period of time. In the last several decades, tissue engineering was rapidly developed to be used as an alternative approach to the organ transplantation. Tissue engineering aims to regenerate the tissues and also organs to help patients who waits for the organ transplantation. Recent research showed that in order to regenerate the tissues, cells must be seeded onto the 3D artificial laboratory fabricated matrices called scaffolds. If cells show healthy growth within the scaffolds, they can be implanted to the injured tissue to do the regeneration. One of the biggest limitation that reduces the success rate of tissue regeneration is the fabrication of accurate thick 3D scaffolds. In this research “maskless photolithography” was used to fabricate the scaffolds. Experiment setup consist of digital micro-mirror devices (DMD) (Texas Instruments, DLi4120), optical lens sets, UV light source (DYMAX, BlueWave 200) and PEGDA which is a liquid form photo-curable solution. In this method, scaffolds are fabricated in layer-by-layer fashion to control the interior architecture of the scaffolds. Working principles of the maskless photolithography is, first layer shape is designed with AutoCAD and the designed image is uploaded to the DMD as a bitmap file. DMD consists of hundreds of tiny micro-mirrors. When the UV light is turned on and irradiated the DMD, depending on the micro-mirrors’ angles, UV light is selectively reflected to the low percentage Polyethylene (glycol) Diacrylate (PEGDA) photo-curable solution. When UV light penetrates into the PEGDA, only the illuminated part is solidified and non-illuminated area still remains in the liquid phase. In this research, scaffolds were fabricated in three layers. First layer and the last layer are solid layers and y-shape open structure was sandwiched between these layers. After the first layer is fabricated with DMD, a “y-shape” structure was fabricated with the 3D printer by using the dissolvable filament. Then, it was placed onto the first solid layer and covered with fresh high percentage PEGDA solution. UV light was reflected to the PEGDA solution and solidified to make the second and third layers. After the scaffold was fabricated, it is dipped into the limonene solution to dissolve the y-shape away. Our results show that thick scaffolds can be fabricated in layer-by-layer fashion with “maskless photolithography”. Since the UV light is stable and does not move onto the PEGDA, entire scaffold can be fabricated in one single UV shot which makes the process faster than the current fabrication techniques.
Three-Dimensional Scaffold Fabrication with Inverse Photolithography
- Ramesh Prashad, Ozlem Yasar
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- Journal:
- MRS Advances / Volume 2 / Issue 19-20 / 2017
- Published online by Cambridge University Press:
- 15 December 2016, pp. 1071-1075
- Print publication:
- 2017
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In recent years, tissue engineering has been utilized as an alternative approach to organ transplantation. Success rate of tissue regeneration influenced by the biomaterials, cell sources, growth factors and scaffold fabrication. Design and precise fabrication of scaffolds are required to support cells to expand and migrate to 3D environment. Common scaffold fabrication techniques use heat, adhesives, molds or light. In this research, “inverse-photolithography” which is a light based fabrication technique was used to generate the scaffolds. In order to control the interior architecture of the scaffold “a single vertical strut” and “a y-shape” were fabricated with the 3D printer by using the dissolvable filament. Then, the strut and the y-shape were immersed into the photo-curable solution which is poly(ethylene glycol) diacrylate (PEGDA) and photo-initiator mixture. UV light with the 365nm wavelength was placed up-side down under the solution. Photo-curable mixture was exposed to the UV light for 3 minutes to cure the entire scaffold. Solidified scaffold with the strut and y-shape inside was kept in the limonene solution. Limonene penetrated through the open ended strut and y-shape and it dissolved the 3D printed strut and y-shape away leaving the fabricated PEGDA based scaffolds. This preliminary research showcases, the 3D scaffolds with the controlled interior design, can be fabricated with the “inverse-photolithography” technique.
Fabrication of Lindenmayer System-Based Designed Engineered Scaffolds Using UV-Maskless Photolithography
- Ozlem Yasar, Binil Starly
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- Journal:
- MRS Advances / Volume 1 / Issue 11 / 2016
- Published online by Cambridge University Press:
- 23 March 2016, pp. 749-754
- Print publication:
- 2016
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In the field of tissue engineering, design and fabrication of precisely and spatially patterned, highly porous scaffolds/matrixes are required to guide overall shape of tissue growth and replacement. Although rapid prototyping fabrication techniques have been used to fabricate the scaffolds with desired design characteristics, controlling the interior architecture of the scaffolds has been a challenge due to Computer-aided Design (CAD) constrains. Moreover, thick engineered tissue scaffolds show inadequate success due to the limited diffusion of oxygen and nutrients to the interior part of the scaffolds. These limitations lead to improper tissue regeneration. In this work, in order to overcome these design and fabrication limitations, research has been expanded to generation of scaffolds which have inbuilt micro and nanoscale fluidic channels. Branching channels serve as material delivery paths to provide oxygen and nutrients for the cells. These channels are designed and controlled with Lindenmayer Systems (L-Systems) which is an influential way to create the complex branching networks by rewriting process. In this research, through the computational modeling process, to control the thickness, length, number and the position of the channels/branches, main attributes of L-Systems algorithms are characterized and effects of algorithm parameters are investigated. After the L-System based branching design is completed, 3D tissue scaffolds were fabricated by “UV-Maskless Photolithography”. In this fabrication technique, Polyethylene (glycol) Diacrylate (PEGDA), which is biodegradable and biocompatible polymer, was used as a fabrication material. Our results show that L-System parameters can be successfully controlled to design of 3D tissue engineered scaffolds. Our fabrication results also show that L-System based designed scaffolds with internal branch structures can be fabricated layer-by-layer fashion by Maskless Photolithography. This technology can be easily applied to engineering living systems.
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