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You searched for +publisher:"University of Pretoria" +contributor:("Prof V Vargha"). Showing records 1 – 2 of 2 total matches.

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University of Pretoria

1. Chetty, Avashnee Shamparkesh. Thermoresponsive 3D scaffolds for non-invasive cell culture.

Degree: Chemical Engineering, 2013, University of Pretoria

Conventionally, adherent cells are cultured in vitro using flat 2D cell culture trays. However the 2D cell culture method is tedious, unreliable and does not replicate the complexity of the 3D dynamic environment of native tissue. Nowadays 3D scaffolds can be used to culture cells. However a number of challenges still exist, including the need for destructive enzymes to release confluent cells. Poly(Nisopropylacrylamide) (PNIPAAm), a temperature responsive polymer, has revolutionised the cell culture fraternity by providing a non-invasive means of harvesting adherent cells, whereby confluent cells can be spontaneously released by simply cooling the cell culture medium and without requiring enzymes. While PNIPAAm monolayer cell culturing is a promising tool for engineering cell sheets, the current technology is largely limited to the use of flat 2D substrates, which lacks structural and organisational cues for cells. The aim of this project was to develop a 3D PNIPAAm scaffold which could be used efficiently for non-invasive 3D culture of adherent cells. This project was divided into three phases: Phase 1 (preliminary phase) involved development and characterisation of cross-linked PNIPAAm hydrogels; Phase 2 involved development and characterisation of PNIPAAm grafted 3D non-woven scaffolds, while Phase 3 focused on showing proof of concept for non-invasive temperature-induced cell culture from the 3D PNIPAAm grafted scaffolds. In Phase 1, PNIPAAm was cross-linked with N,N’-methylene-bis-acrylamide (MBA) using solution free-radical polymerisation to form P(PNIPAAm-co-MBA) hydrogels. A broad cross-link density (i.e. 1.1 - 9.1 Mol% MBA) was investigated, and the effect of using mixed solvents as the co-polymerisation medium. The P(PNIPAAm-co-MBA) gels proved unsuitable as a robust cell culture matrix, due to poor porosity, slow swelling/deswelling and poor mechanical properties. Subsequently, in Phase 2, polypropylene (PP), polyethylene terephthalate (PET), and nylon fibers were processed into highly porous non-woven fabric (NWF) scaffolds using a needle-punching technology. The NWF scaffolds were grafted with PNIPAAm using oxyfluorination-assisted graft polymerisation (OAGP). The OAGP method involved a 2 step process whereby the NWF was first fluorinated (direct fluorination or oxyfluorination) to introduce new functional groups on the fibre surface. The functionalised NWF scaffolds were then graft-polymerised with NIPAAm in an aqueous medium using ammonium persulphate as the initiator. Following oxyfluorination, new functional groups were detected on the surface of the NWF scaffolds, which included C-OH; C=O; CH2-CHF, and CHF-CHF. PP and nylon were both easily modified by oxyfluorination, while PET displayed very little changes to its surface groups. Improved wetting and swelling in water was observed for the oxyfluorinated polymers compared to pure NWF scaffolds. PP NWF showed the highest graft yield followed by nylon and then PET. PNIPAAm graft yield on the PP NWF was ~24 ±6 μg/cm2 on grafted pre-oxyfluorinated NWF… Advisors/Committee Members: Prof W W Focke (advisor), Prof V Vargha (advisor).

Subjects/Keywords: Poly-n-isopropylacrylamide; Graft polymerization; 3d scaffolds; Nonwovens; Cell culture; Hydrogels; UCTD

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Chetty, A. (2013). Thermoresponsive 3D scaffolds for non-invasive cell culture. (Doctoral Dissertation). University of Pretoria. Retrieved from http://hdl.handle.net/2263/25463

Chicago Manual of Style (16th Edition):

Chetty, Avashnee. “Thermoresponsive 3D scaffolds for non-invasive cell culture.” 2013. Doctoral Dissertation, University of Pretoria. Accessed February 21, 2020. http://hdl.handle.net/2263/25463.

MLA Handbook (7th Edition):

Chetty, Avashnee. “Thermoresponsive 3D scaffolds for non-invasive cell culture.” 2013. Web. 21 Feb 2020.

Vancouver:

Chetty A. Thermoresponsive 3D scaffolds for non-invasive cell culture. [Internet] [Doctoral dissertation]. University of Pretoria; 2013. [cited 2020 Feb 21]. Available from: http://hdl.handle.net/2263/25463.

Council of Science Editors:

Chetty A. Thermoresponsive 3D scaffolds for non-invasive cell culture. [Doctoral Dissertation]. University of Pretoria; 2013. Available from: http://hdl.handle.net/2263/25463


University of Pretoria

2. [No author]. Thermoresponsive 3D scaffolds for non-invasive cell culture .

Degree: 2013, University of Pretoria

Conventionally, adherent cells are cultured in vitro using flat 2D cell culture trays. However the 2D cell culture method is tedious, unreliable and does not replicate the complexity of the 3D dynamic environment of native tissue. Nowadays 3D scaffolds can be used to culture cells. However a number of challenges still exist, including the need for destructive enzymes to release confluent cells. Poly(Nisopropylacrylamide) (PNIPAAm), a temperature responsive polymer, has revolutionised the cell culture fraternity by providing a non-invasive means of harvesting adherent cells, whereby confluent cells can be spontaneously released by simply cooling the cell culture medium and without requiring enzymes. While PNIPAAm monolayer cell culturing is a promising tool for engineering cell sheets, the current technology is largely limited to the use of flat 2D substrates, which lacks structural and organisational cues for cells. The aim of this project was to develop a 3D PNIPAAm scaffold which could be used efficiently for non-invasive 3D culture of adherent cells. This project was divided into three phases: Phase 1 (preliminary phase) involved development and characterisation of cross-linked PNIPAAm hydrogels; Phase 2 involved development and characterisation of PNIPAAm grafted 3D non-woven scaffolds, while Phase 3 focused on showing proof of concept for non-invasive temperature-induced cell culture from the 3D PNIPAAm grafted scaffolds. In Phase 1, PNIPAAm was cross-linked with N,N’-methylene-bis-acrylamide (MBA) using solution free-radical polymerisation to form P(PNIPAAm-co-MBA) hydrogels. A broad cross-link density (i.e. 1.1 - 9.1 Mol% MBA) was investigated, and the effect of using mixed solvents as the co-polymerisation medium. The P(PNIPAAm-co-MBA) gels proved unsuitable as a robust cell culture matrix, due to poor porosity, slow swelling/deswelling and poor mechanical properties. Subsequently, in Phase 2, polypropylene (PP), polyethylene terephthalate (PET), and nylon fibers were processed into highly porous non-woven fabric (NWF) scaffolds using a needle-punching technology. The NWF scaffolds were grafted with PNIPAAm using oxyfluorination-assisted graft polymerisation (OAGP). The OAGP method involved a 2 step process whereby the NWF was first fluorinated (direct fluorination or oxyfluorination) to introduce new functional groups on the fibre surface. The functionalised NWF scaffolds were then graft-polymerised with NIPAAm in an aqueous medium using ammonium persulphate as the initiator. Following oxyfluorination, new functional groups were detected on the surface of the NWF scaffolds, which included C-OH; C=O; CH2-CHF, and CHF-CHF. PP and nylon were both easily modified by oxyfluorination, while PET displayed very little changes to its surface groups. Improved wetting and swelling in water was observed for the oxyfluorinated polymers compared to pure NWF scaffolds. PP NWF showed the highest graft yield followed by nylon and then PET. PNIPAAm graft yield on the PP NWF was ~24 ±6 μg/cm2 on grafted pre-oxyfluorinated NWF… Advisors/Committee Members: Prof W W Focke (advisor), Prof V Vargha (advisor).

Subjects/Keywords: Poly-n-isopropylacrylamide; Graft polymerization; 3d scaffolds; Nonwovens; Cell culture; Hydrogels; UCTD

Record DetailsSimilar RecordsGoogle PlusoneFacebookTwitterCiteULikeMendeleyreddit

APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

author], [. (2013). Thermoresponsive 3D scaffolds for non-invasive cell culture . (Doctoral Dissertation). University of Pretoria. Retrieved from http://upetd.up.ac.za/thesis/available/etd-06112013-151344/

Chicago Manual of Style (16th Edition):

author], [No. “Thermoresponsive 3D scaffolds for non-invasive cell culture .” 2013. Doctoral Dissertation, University of Pretoria. Accessed February 21, 2020. http://upetd.up.ac.za/thesis/available/etd-06112013-151344/.

MLA Handbook (7th Edition):

author], [No. “Thermoresponsive 3D scaffolds for non-invasive cell culture .” 2013. Web. 21 Feb 2020.

Vancouver:

author] [. Thermoresponsive 3D scaffolds for non-invasive cell culture . [Internet] [Doctoral dissertation]. University of Pretoria; 2013. [cited 2020 Feb 21]. Available from: http://upetd.up.ac.za/thesis/available/etd-06112013-151344/.

Council of Science Editors:

author] [. Thermoresponsive 3D scaffolds for non-invasive cell culture . [Doctoral Dissertation]. University of Pretoria; 2013. Available from: http://upetd.up.ac.za/thesis/available/etd-06112013-151344/

.