Publications (8)35.14 Total impact
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Article: Cryogenic electrospinning: proposed mechanism, process parameters and its use in engineering of bilayered tissue structures.
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ABSTRACT: Background: Conventional electrospun scaffolds have very small pores, thus limiting cellular infiltration, tissue ingrowth and vascularization in tissue engineering applications. The cryogenic electrospinning process overcame the small pore size constraints found in conventional electrospun scaffolds. Aim: The aim of this paper is to propose a mechanism for cryogenic electrospinning and how scaffold pore size can be controlled. Materials & methods: We studied the roles of ice crystals in controlling the pore size of cryogenic electrospun scaffolds (CES). Based on this understanding, we have successfully fabricated a bilayered scaffold with distinctly different pore sizes. Results: Our study showed that CES pore size was dependent on the structure of the frost layer formed and hence the factors affecting ice deposition. The bilayered scaffold was able to support the coculture of human dermal fibroblasts and keratinocytes. Conclusion: The larger pores of CES add versatility to the use of electrospun scaffolds in tissue engineering applications.Nanomedicine 04/2013; 8(4):555-66. · 5.05 Impact Factor -
Article: Multicomponent Fibers by Multi-interfacial Polyelectrolyte Complexation.
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ABSTRACT: In multi-interfacial polyelectrolyte complexation (MIPC), fusion of nascent fibers from multiple interfaces brings the interfaces to a point from which a composite fiber is drawn. MIPC applied to two, three, and four polyelectrolyte complex interfaces leads to various patterned multicomponent fibers. Cells encapsulated in these fibers exhibit migration, aggregation and spreading in relation to the initial cell or matrix pattern.Advanced healthcare materials. 01/2012; 1(1):101-5. -
Article: The use of a library of industrial materials to determine the nature of substrate-dependent performance of primary adherent human cells.
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ABSTRACT: We developed a library of industrial materials, which can be applied to any adherent cell type for determining cell-material interactions. Bulk and surface chemistry as well as other material properties were characterized. The library covered broad ranges of various material properties. We applied the library to primary human endothelial and epithelial cells, which play important roles in tissue engineering and biomedical applications. The results revealed that substrate stiffness was the major determinant of cell performance. The ability to grow and differentiate on stiff or more compliant materials was cell type-dependent, but cell performance was consistently best on stiff and smooth materials. These results give new insights into the nature of substrate-dependent performance of primary human cells and are potentially useful for the development of improved biomaterials. The materials of the library can be easily accessed by the scientific community to determine cell-material interactions of any adherent cell type of interest.Biomaterials 01/2012; 33(2):353-64. · 7.40 Impact Factor -
Article: A 3D microfibrous scaffold for long-term human pluripotent stem cell self-renewal under chemically defined conditions.
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ABSTRACT: Realizing the potential of human pluripotent stem cell (hPSC)-based therapy requires the development of defined scalable culture systems with efficient expansion, differentiation and isolation protocols. We report an engineered 3D microfiber system that efficiently supports long-term hPSCs self-renewal under chemically defined conditions. The unique feature of this system lies in the application of a 3D ECM-like environment in which cells are embedded, that affords: (i) uniform high cell loading density in individual cell-laden constructs (∼10(7) cells/ml); (ii) quick recovery of encapsulated cells (<10min at 37°C) with excellent preservation of cell viability and 3D multicellular structure; (iii) direct cryopreservation of the encapsulated cells in situ in the microfibers with >17-fold higher cell viability compared to those cultured on Matrigel surface; (iv) long-term hPSC propagation under chemically defined conditions. Four hPSC lines propagated in the microfibrous scaffold for 10 consecutive passages were capable of maintaining an undifferentiated phenotype as demonstrated by the expression of stem cell markers and stable karyotype in vitro and the ability to form derivatives of the three germ layers both in vitro and in vivo. Our 3D microfibrous system has the potential for large-scale cultivation of transplantable hESCs and derivatives for clinical applications.Biomaterials 12/2011; 33(8):2419-30. · 7.40 Impact Factor -
Article: Fabrication and in vitro and in vivo cell infiltration study of a bilayered cryogenic electrospun poly(D,L-lactide) scaffold.
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ABSTRACT: Cryogenic electrospinning has previously been demonstrated for controlling the pore sizes of electrospun scaffolds, which has been impossible with traditional electrospinning processes. This article describes the application of the cryogenic technique to fabricate a bilayered electrospun poly(D,L-lactide) scaffold (BLES) in a single uninterrupted process. The resulting BLES consisted of a traditional electrospun (ES) fibrous layer with a dense pore area of 17 +/- 3 microm(2) adjacent to a cryogenic electrospun layer (CES) with a pore area of 3300 +/- 500 microm(2). The significance of this bilayered scaffold was to mimic the anatomical structure of tissues with dense basement membrane followed by loose and highly porous connective tissue such as skin and blood vessels. Cell infiltration in the BLES was compared in vitro and in vivo. Both studies suggested the CES supported high cell infiltration, whereas the ES could serve as a physical barrier to prevent cell infiltration across the CES-ES boundary because of its size exclusion. The bilayered structure produced by this technique suggests a great potential for engineering tissues with similar architectures.Journal of Biomedical Materials Research Part A 09/2010; 94(4):1141-9. · 2.63 Impact Factor -
Article: In vitro cell infiltration and in vivo cell infiltration and vascularization in a fibrous, highly porous poly(D,L-lactide) scaffold fabricated by cryogenic electrospinning technique.
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ABSTRACT: One of the obstacles limiting the application of electrospun scaffolds for tissue engineering is the nanoscale pores that inhibit cell infiltration. In this article, we describe a technique that uses ice crystals as templates to fabricate cryogenic electrospun scaffolds (CES) with large three-dimensional and interconnected pores using poly(D,L-lactide) (PLA). Manipulating the humidity of the electrospinning environment the pore sizes are controlled. We are able to achieve pore sizes ranging from 900 +/- 100 microm(2) to 5000 +/- 2000 microm(2) depending on the relative humidity used. Our results show that cells infiltrated the CES up to 50 microm in thickness in vitro under static culture conditions whereas cells did not infiltrate the conventional electrospun scaffolds. In vivo studies demonstrated improved cell infiltration and vascularization in the CES compared with conventionally prepared electrospun scaffolds. In gaining control of the pore characteristics, we can then design CES that are optimized for specific tissue engineering applications.Journal of Biomedical Materials Research Part A 10/2008; 91(1):231-40. · 2.63 Impact Factor -
Article: Effect of electrospun poly(D,L-lactide) fibrous scaffold with nanoporous surface on attachment of porcine esophageal epithelial cells and protein adsorption.
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ABSTRACT: Electrospun scaffolds have been increasingly used in tissue engineering applications due to their size-scale similarities with native extracellular matrices. Their inherent fibrous features may be important in promoting cell attachment and proliferation on the scaffolds. In this study, we explore the technique of fabricating electrospun fibers with nano-sized porous surfaces and investigate their effects on the attachment of porcine esophageal epithelial cells (PEECs). Porosity was introduced in electrospun poly(D,L-lactide) fibers by creating vapor-induced phase separation conditions during electrospinning. The nanoporous fiber scaffolds were mechanically weaker than the conventional solid fiber scaffolds and solvent-cast films of the same polymer. However, the nanoporosity of the fibers was found to enhance the levels of adsorbed protein from a dilute solution of fetal bovine serum. The amount of protein adsorbed by nanoporous fiber scaffolds was approximately 80% higher than the solid fiber scaffolds. This corresponds to an estimated 62% increase in surface area of the porous fibers than the solid fibers. By comparison, the solvent-cast films adsorbed low levels of protein from the FBS solution. In addition, the porous fibers were found to be advantageous in enhancing initial cell attachment as compared with the solid fibers and solvent-cast films. It was observed that nanoporous fiber scaffolds seeded with PEECs had significantly greater number of viable cells attached than the solid fiber scaffolds after 10 and 24 h in culture. Hence, our results indicate that nanosized porous surfaces on electrospun fibers enhance both protein adsorption and cell attachment. These findings provide a method to improve cell-matrix interactions of electrospun scaffolds for tissue engineering applications.Journal of Biomedical Materials Research Part A 06/2008; 89(4):1040-8. · 2.63 Impact Factor -
Article: Esophageal epithelium regeneration on fibronectin grafted poly(L-lactide-co-caprolactone) (PLLC) nanofiber scaffold.
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ABSTRACT: In order to mimic normal epithelium regeneration on synthetic scaffold in vitro, biodegradable elastic poly(l-lactide-co-caprolactone) (PLLC) was processed into nanofibrous scaffold using electrospinning technology. An adhesive protein, fibronectin (Fn), was grafted onto the scaffold fiber surface via a two-step reaction: polyester aminolysis followed by Fn coupling via glutaraldehyde. Tensile testing was performed to measure the effect of aminolysis on the scaffold mechanical properties. The strain decreased but the tensile strength remained almost constant after aminolysis. However, no obvious difference of the nanofiber surface morphology was found after Fn grafting using scanning electron microscopy (SEM). Porcine esophageal epithelial cells were seeded on the Fn bonded scaffold to test the cell growth promotion against the control unmodified PLLC nanofiber scaffold using tissue culture polystyrene (TCPS) plate as a reference. Anti-cytokeratin AE1/AE3 was used as the primary antibody to confirm the esophageal epithelial phenotype. SEM observation, immunostaining and Western Blotting to compare the collagen type IV synthesis showed that the Fn grafted on PLLC scaffold greatly promotes epithelium regeneration. This modified scaffold is expected to be a good candidate for functional esophagus substitutes.Biomaterials 03/2007; 28(5):861-8. · 7.40 Impact Factor
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Institutions
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2007–2013
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Nanyang Technological University
- • School of Mechanical and Aerospace Engineering
- • Biomedical Engineering Research Center
Singapore, Singapore
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