Biodegradable nanofibrous poly(L-lactic acid) (PLLA) scaffold was prepared by an electrospinning process for use in tissue
regeneration. The nanofiber scaffold was treated with oxygen plasma and then simultaneously in situ grafted with hydrophilic
acrylic acid (AA) to obtain PLLA-g-PAA. The fiber diameter, pore size, and porosity of the electrospun nanofibrous PLLA scaffold were estimated as 250∼750 nm,
∼30 µm, and 95%, respectively. The ultimate tensile strength was 1.7 MPa and the percent elongation at break was 120%. Although
the physical and mechanical properties of the PLLA-g-PAA scaffold were comparable to those of the PLLA control, a significantly lower contact angle and significantly higher ratio
of oxygen to carbon were notable on the PLLA-g-PAA surface. After the fibroblasts were cultured for up to 6 days, cell adhesion and proliferation were much improved on
the nanofibrous PLLA-g-PAA scaffold than on either PLLA film or unmodified nanofibrous PLLA scaffold. The present work demonstrated that the applications
of plasma treatment and hydrophilic AA grafting were effective to modify the surface of electrospun nanofibrous polymer scaffolds
and that the altered surface characteristics significantly improved cell adhesion and proliferation.
"A recently published review  comparing different nanofiber/cell combinations found optimal pore diameter for nanofiber scaffolds ranging from 5 to 50 μm. With respect to PLLA nanofibers produced from DCM pore diameter of 30 μm were reported  while PLLA-collagen blend nanofiber scaffolds showed pore diameter below 2 μm . Here the low pore diameter might be one reason for the lack of colonization. "
[Show abstract][Hide abstract] ABSTRACT: The reconstruction of large bone defects after injury or tumor resection often requires the use of bone substitution. Artificial scaffolds based on synthetic biomaterials can overcome disadvantages of autologous bone grafts, like limited availability and donor side morbidity. Among them, scaffolds based on nanofibers offer great advantages. They mimic the extracellular matrix, can be used as a carrier for growth factors and allow the differentiation of human mesenchymal stem cells. Differentiation is triggered by a series of signaling processes, including integrin and bone morphogenetic protein (BMP), which act in a cooperative manner. The aim of this study was to analyze whether these processes can be remodeled in artificial poly-(l)-lactide acid (PLLA) based nanofiber scaffolds in vivo. Electrospun matrices composed of PLLA-collagen type I or BMP-2 incorporated PLLA-collagen type I were implanted in calvarial critical size defects in rats. Cranial CT-scans were taken 4, 8 and 12 weeks after implantation. Specimens obtained after euthanasia were processed for histology and immunostainings on osteocalcin, BMP-2 and Smad5. After implantation the scaffolds were inhomogeneously colonized and cells were only present in wrinkle- or channel-like structures. Ossification was detected only in focal areas of the scaffold. This was independent of whether BMP-2 was incorporated in the scaffold. However, cells that migrated into the scaffold showed an increased ratio of osteocalcin and Smad5 positive cells compared to empty defects. Furthermore, in case of BMP-2 incorporated PLLA-collagen type I scaffolds, 4 weeks after implantation approximately 40 % of the cells stained positive for BMP-2 indicating an autocrine process of the ingrown cells. These findings indicate that a cooperative effect between BMP-2 and collagen type I can be transferred to PLLA nanofibers and furthermore, that this effect is active in vivo. However, this had no effect on bone formation. The reason for this seems to be an unbalanced colonization of the scaffolds with cells, due to insufficient pore size.
Journal of Materials Science Materials in Medicine 06/2012; 23(9):2227-33. DOI:10.1007/s10856-012-4697-0 · 2.59 Impact Factor
"Poly(Llactic acid) (PLLA) is a frequently used non-cytotoxic and biodegradable polymer in preparing electrospun fibers for drug delivery and tissue engineering applications [31e34]. However, the surface modification of PLLA fiber for bioconjugation poses a major challenge . Electrospun fiber mats prepared from other noncytotoxic polymers such as poly(vinyl alcohol), collagen , dextran , or hyaluronic acid  require additional treatment steps, such as heat curing or cross-linking to avoid the loss of fiber structure through gel formation on contact with aqueous media. "
[Show abstract][Hide abstract] ABSTRACT: With the emergence of "super bacteria" that are resistant to antibiotics, e.g., methicillin-resistant Staphylococcus aureus, novel antimicrobial therapies are needed to prevent associated hospitalizations and deaths. Bacteriophages and bacteria use cell lytic enzymes to kill host or competing bacteria, respectively, in natural environments. Taking inspiration from nature, we have employed a cell lytic enzyme, lysostaphin (Lst), with specific bactericidal activity against S. aureus, to generate anti-infective bandages. Lst was immobilized onto biocompatible fibers generated by electrospinning homogeneous solutions of cellulose, cellulose-chitosan, and cellulose-poly(methylmethacrylate) (PMMA) from 1-ethyl-3-methylimidazolium acetate ([EMIM][OAc]), room temperature ionic liquid. Electron microscopic analysis shows that these fibers have submicron-scale diameter. The fibers were chemically treated to generate aldehyde groups for the covalent immobilization of Lst. The resulting Lst-functionalized cellulose fibers were processed to obtain bandage preparations that showed activity against S. aureus in an in vitro skin model with low toxicity toward keratinocytes, suggesting good biocompatibility for these materials as antimicrobial matrices in wound healing applications.
[Show abstract][Hide abstract] ABSTRACT: Growing demand for tissues and organs for transplantation and the inability to meet this need using by autogeneic (from the host) or allogeneic (from the same species) sources has led to the rapid development of tissue engineering as an alternative. Tissue engineering aims to replace or facilitate the regrowth of damaged or diseased tissue by applying a combination of biomaterials, cells and bioactive molecules. This review focuses on synthetic polymers that have been used for tissue growth scaffold fabrication and their applications in both cell and extracellular matrix support and controlling the release of cell growth and differentiation supporting drugs.
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