Selected Review Articles

• Teo WE, He W, Ramakrishna S (2006) Electrospun scaffold tailored for tissue-specific extracellular matrix. Biotechnology Journal vol. 1 pg. 918-929. (Top download in Biotechnology Journal in September 2006)

3D mineralized nanofibrous scaffold

Published work:

1. W.E. Teo, S. Liao, C. Chan and S. Ramakrishna. (2011) Fabrication and characterization of hierarchically organized nanoparticle-reinforced nanofibrous composite scaffolds. Acta. Biomater. vol 7 pg. 193-202.
2. Wee Eong Teo. Natured Inspired Composite Nanofibers. 2009. Link to thesis

Overview:

Nature's structural organization often begin at the nanoscale level. Bone is one of the most widely investigated natural composites and by replicating its structure, one can learn about how nano-components interact with one another. In this study, a 3D structure assembled from polymer nanofibers and calcium phosphate nanoparticles were constructed.

Hierarchical organization of fabricated nanofibrous composite (Teo WE et al. Acta Biomater (2010), doi:10.1016/j.actbio.2010.07.041)

Two different distributions of nanoparticles in the nanofibrous composite was constructed and their compressive properties were compared. The nanofibrous composite with evenly distributed nanoparticles along the nanofibers has significantly higher compressive modulus and strength than the other with nanoparticles concentrated on its periphery.

See related work

1. W.E Teo, S. Liao, C.K. Chan, S. Ramakrishna (2008) Remodeling of Three-dimensional Hierarchically Organized Nanofibrous Assemblies. Current Nanoscience vol. 4 pg. 361-369.

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Nanofibrous intraluminal guidance channel for peripheral nerve regeneration

Published work:

1. H S Koh, T. Yong, W E Teo, C K Chan, M E Puhaindran, T C Tan, A Lim, B H Lim, S Ramakrishna. (2010) In vivo study on novel nanofibrous intra-luminal guidance channels to promote nerve regeneration. Journal of Neural Engineering vol. 7 pg. 046003 (14pp).

Overview:

In a rat sciatic nerve in vivo study, nanofibrous conduit with nanofibrous yarn as intraluminal guidance channel was shown to promote earlier functional response than auto-graft.The yarn was made of longitudinally aligned nanofibers which may have guided nerve axon outgrowth to bridge the gap quickly unlike autograft where resorption of the extra-cellular matrix has to take place first. However, in terms of neurophysiology tests and immuno-histochemistry staining, auto-graft showed better results than nanofibrous conduit with guidance channel. This is probably due to functional components already present in the autograft that are not removed during the resorption stage.

Structural organization of nerve guidance conduit (H S Koh et al. J. Neural Eng. 2010; 7: 046003. © Copyright (2010) IOP Publishing Ltd. http://www.iop.org.)

See related work

1. Wee-Eong Teo, Renuga Gopal, Ramakrishnan Ramaseshan Kazutoshi Fujihara, Seeram Ramakrishna (2007) A dynamic liquid support system for continuous electrospun yarn fabrication. Polymer vol. 48 pg. 3400-3405.

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Collagen with GAG nanofibers

Published work:

1. Shao Ping Zhong, Wee Eong Teo, Xiao Zhu, Roger Beuerman, Seeram Ramakrishna, Lin Yue Lanry Yung (2007) Development of a novel collagen-GAG nanofibrous scaffold via electrospinning. Materials Science and Engineering C vol. 27 pg. 262-266.
2. Shaoping Zhong, Wee Eong Teo, Xiao Zhu, Roger W. Beuerman, Seeram Ramakrishna and Lin Yue Lanry Yung (2006) An aligned nanofibrous collagen scaffold by electrospinning and its effects on in vitro fibroblast culture. Journal of Biomedical Materials Research vol. 79A pg. 456-463.
3. Shaoping Zhong, Wee Eong Teo, Xiao Zhu, Roger Beuerman, Seeram Ramakrishna, and Lin Yue Lanry Yung. (2005) Formation of Collagen-Glycosaminoglycan Blended Nanofibrous Scaffolds and Their Biological Properties. Biomacromolecules vol. 6 pg. 2998 – 3004.

Overview:

Glycosaminoglycans (GAG) is an important constituent in the extracellular matrix. Although collagen has been electrospun, incorporation of GAGs such as chondroitin sulfate (CS) into it is a challenge as they are generally insoluble to the solvents commonly used for electrospinning collagen. In this research, chondroitin sulfate (CS) sodium salt was used and it is readily soluble in water. By first dissolving CS and collagen into water and tri-fluoroethanol respectively before mixing the two solution, we were able to obtain a blended mixture which can be electrospun to give nanofibers.In vitro culture using rabbtit conjuctiva fibroblast was used to investigate the effectiveness of incorporating CS into collagen. Cross-linked CS-collagen scaffold demonstrated the highest proliferation compared to cross-linked collagen scaffold and non-crosslinked counterparts.

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Nanofibers made of poly(L-lactic acid)-co-poly(e-caprolactone) with and without collagen as vascular scaffold

Published work:

1. Wei He, Zuwei Ma, Wee Eong Teo, Yi Xiang Dong, Peter Ashley Robless, Thiam Chye Lim, Seeram Ramakrishna (2009) Tubular nanofiber scaffolds for tissue engineered small-diameter vascular grafts. Journal of Biomedical Materials Research Part A. vol. 90A pg. 205-216.
2. W. He, T. Yong, W.E. Teo, Z.W. Ma, R. Inai and S. Ramakrishna (2006) Biodegradable Polymer Nanofiber Mesh to Maintain Functions of Endothelial Cells. Tissue Engineering vol. 12 pg. 2457-2466.
3. He W, Yong T, Teo WE, Ma ZW, Ramakrishna S. (2005) Fabrication and Endothelialization of Collagen-Blended Biodegradable Polymer Nanofibers: potential vascular grafts for the blood vessel tissue engineering. Tissue Engineering vol. 11 pg. 1574-1588.
4. Wei He, ZuWei Ma, Thomas Yong, Wee Eong Teo and Seeram Ramakrishna. (2005) Fabrication of collagen-coated biodegradable polymer nanofiber mesh and its potential for endothelial cells growth. Biomaterials vol. 26 pg. 7606 – 7615.

Overview:

Poly(L-lactic acid)-co-poly(e-caprolactone) nanofibers, poly(L-lactic acid)-co-poly(e-caprolactone) and collagen blended nanofibers, and collagen coated poly(L-lactic acid)-co-poly(e-caprolactone) nanofibers were investigated for use as vascular grafts. Type I collagen was blended with poly(L-lactic acid)-co-poly(e-caprolactone) [P(LLA-CL), 70:30] at a ratio of 1:1 using 1,1,1,3,3,3-Hexafluoro-2-propanol (HFP) as the common solvent. The electrospun nanofibers have a diameter in the range of 100 to 200 nm. Tensile properties of the random nanofibers mat gave a tensile strength of 1.54 MPa and a ultimate strain of 66%. These values are close to that of coronary artery.

In an in vivo model, a tubular nanofibrous scaffold made out of poly(L-lactic acid)-co-poly(e-caprolactone) were implanted into a excised inferior superficial epigastric vein of a rabbit. No collagen was added in this study as it may cause thrombogenesis. After 7 weeks, the scaffold remains intact. A thick fibrous tissue were found on the external surface of the scaffold but no cell infiltration was observed. Although there was no blood cloting in the lumen of the scaffold, no endothelial cell was found.

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