Grace J Lim

Wake Forest University, Winston-Salem, North Carolina, United States

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Publications (7)33.08 Total impact

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    ABSTRACT: In the past several decades, many attempts have been made to prevent the rejection of transplanted cells by the immune system. Cell encapsulation is primary machinery for cell transplantation and new materials and approaches were developed to encapsulate various types of cells to treat a wide range of diseases. This technology involves placing the transplanted cells within a biocompatible membrane in attempt to isolate the cells from the host immune attack and enhance or prolong their function in vivo. In this chapter, we will review the situation of cell microencapsulation field and discuss its potentials and challenges for cell therapy and regeneration of tissue function.
    Advances in experimental medicine and biology 01/2010; 670:126-36. · 1.83 Impact Factor
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    ABSTRACT: As yet no transdermal topical formulations have been developed for the treatment of chronic itch. We developed a formulation containing 2 mg butorphanol tartrate in 100 microl purified water encapsulated into multilamellar phospholipid vesicles. Drug permeation experiments were studied with Franz diffusion chambers using human skin in vitro and on rat skin in vivo. Histological analysis of rat skins was performed to evaluate skin irritation of the formulation in vivo. Physical properties showed stable formulation with desirable viscosity. In vitro dermal penetration rate data suggest that there was significant permeation at time-points 2 h and 4 h, and a steady state was achieved afterwards to 24 h. Maximal plasma butorphanol concentration was noted at 2 h and steady state was achieved at 8 h. Visual skin assessment as well as histological analysis of excised rat skin did not demonstrate any evidence of inflammation and irritation. In vitro and in vivo analysis demonstrated release of a consistent amount of butorphanol in a sustained manner for 24 h. This liposomal transdermal delivery formulation could serve as a method to deliver butorphanol for patients with chronic pruritus.
    Acta Dermato Venereologica 02/2008; 88(4):327-30. · 3.49 Impact Factor
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    ABSTRACT: Blood vessels are diverse in size, mechanical and biochemical properties, cellular content, and ultrastructural organization depending on their location and specific function. Therefore, it is required to control the fabrication of vascular grafts for obtaining desirable characteristics of blood vessel substitutes. In this study we have fabricated various scaffolds using the electrospinning technique with blends of collagen, elastin, and several biodegradable polymers. Biocompatibility, dimensional stability in vitro and mechanical properties were evaluated. Materials were blended at a relative concentration by weight of 45% collagen, 15% elastin, and 40% synthetic polymer to mimic the ratio of collagen and elastin in native blood vessels. The fabricated scaffolds are composed of randomly oriented fibers with diameters ranging from 477 to 765 nm. The electrospun scaffolds are nontoxic, dimensionally stable in an in vitro culture environment, easily fabricated, and possess controlled mechanical properties that simulate the ultrastructure of native blood vessels. The present study suggests that the introduction of synthetic biodegradable polymers enabled tailoring of mechanical properties of vascular substitutes and improving compliance matching for vascular tissue engineering.
    Journal of Biomedical Materials Research Part A 01/2008; 83(4):999-1008. · 2.83 Impact Factor
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    ABSTRACT: In spite of long term clinical use of decellularized bladder submucosa matrix (BSM), little is known about the active factors within this material. In this paper, we analyzed the biological factors from the decellularized BSM using ELISA, Western blotting, and immunohistochemistry for the purpose of effective utilization of this material in the field of regenerative medicine. At least 10 growth factors, including VEGF, BMP4, PDGF-BB, KGF, TGFbeta1, IGF, bFGF, EGF and TGFalpha were found to be preserved in the decellularized BSM. The existence of collagen (type 1, 2, 3, 4), laminin and elastin within the matrix was also demonstrated. The soluble BSM extracts showed a conspicuous effect on cell proliferation when added as a supplement in vitro. These findings demonstrate that growth factors and extracellular matrix in the BSM maintain valuable biological activity even after the decellularization and extraction processes, thus supporting the wide applicability of BSM in tissue regeneration. The identification and characterization of growth factors and extracellular matrix in the BSM is a prerequisite for understanding tissue regeneration using this scaffold.
    Biomaterials 11/2007; 28(29):4251-6. · 8.31 Impact Factor
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    ABSTRACT: Numerous materials have been proposed for bone tissue regeneration. However, none has been shown to be entirely satisfactory. In this study we fabricated a hybrid composite scaffold composed of poly(D,L-lactide-co-glycolide) (PLGA) and a naturally derived collagen matrix derived from porcine bladder submucosa matrix (BSM), and evaluated the biological activities and physical properties of the scaffold for use in bone tissue regeneration. The BSM-PLGA composite scaffolds are able to promote cellular interactions and possess uniformly interconnected pores with adequate structural integrity. The composite scaffolds were tested with both human embryonic stem (hES) cells and bovine osteoblasts (bOB). Cells seeded on the composite scaffolds readily attached, infiltrated and proliferated, as confirmed by cell viability and mitochondrial metabolic activity. Use of the composite scaffolding system with cells may enhance the formation of bone tissue for therapeutic regeneration.
    Biomaterials 07/2006; 27(18):3466-72. · 8.31 Impact Factor
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    ABSTRACT: Autologous and synthetic vessel grafts have been used as a vascular substitute for cardiovascular bypass procedures. However, these materials are limited by the availability of appropriate caliber autologous vessels, increased susceptibility to thrombosis and intimal hyperplasia following surgery. Electrospinning technology offers the potential for controlling composition, structure and mechanical properties of biomaterials. Vascular graft scaffolds have been fabricated using electrospun polymer blends of Type I collagen, elastin from ligamentum nuchae, and poly (d,l-lactide-co-glycolide). This study demonstrates improved electrospinning characteristics versus previous studies by increasing polymer concentration and adding PLGA to the polymer blend. Additionally, new in vitro biocompatibility and mechanical testing data is presented. The scaffolds possess tissue composition and mechanical properties similar to native vessels. The electrospun vessel matrix is biocompatible and does not elicit local or systemic toxic effects when implanted in vivo. This study demonstrates the promise of electrospinning as a fabrication process for a functional vascular graft for clinical use.
    Biomaterials 04/2006; 27(7):1088-94. · 8.31 Impact Factor
  • Grace J. Lim, Anthony Atala
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    ABSTRACT: Diabetes mellitus, a disorder of glucose homeostasis, is a leading cause of morbidity and premature mortality in the world. During the last 75 years, since the discovery of insulin therapy, there have been no new major developments in treating this disease. Thus, the ability to engineer pancreatic tissue is an attractive approach, and as tissue engineering technology advances, this novel therapy is now becoming a reality. Transplantation of engineered pancreatic islets will not only eliminate the need for daily insulin injections, but will also prove effective in preventing or retarding the development of complications associated with diabetes. In this chapter, current technologies for pancreatic tissue engineering, novel sources for insulin producing b-cells, and safe transplantation techniques to treat diabetes are discussed.