Natural polymers silk fibroin

Zhang et al. also used a blend of natural and synthetic polymers to try and improve the biocompatibility, mechanical, chemical, and physical properties of tissue engineering scaffolds [42], In this study, the natural polymer, silk fibroin, was selected for biocompatibility, permeability. 

The attractive properties of silk fibers as a natural, sustainable product have inspired researchers to look for options to fabricate such fibers without the use of worms or spiders. Furthermore, these natural polymers, silk proteins (both fibroin and spidroin), allow for adjustable mechanical properties, thermal resistance (Drummy et al., 2005 Motta et al., 2002), as well as biomedical compatibility (Vepari and Kaplan, 2007). 

Several examples have been described in which a chiral natural polymer, such as silk fibroin or chitosan, act as chiral ligand and support at the same time. In such cases, the chiral ligand (the monomer or monomers coordinating... 

Besides the previously mentioned collagen, a wide variety of natural polymers have been involved in the synthesis of bio-nanohybrid materials with potential application in bone repair and dental prostheses. For instance, some recent examples refer to bionanocomposites based on the combination of HAP with alginate [96,97], chitosan [98,99], bovine serum albumin (BSA) [100], sodium caseinate [101], hyaluronic acid [102], silk fibroin [103,104], silk sericin [105], or polylactic add (PLA) [106,107]. These examples illustrate the increasing interest in the subject of HAP-based biohybrid materials, which has led to almost 400 articles appeared in scientific journals in 2006 alone. 

The first successful experiments were reported by Schwab [16] Cu, Ni and Pt on quartz HI were used to dehydrogenate racemic 2-butanol 23. At low conversions, a measurable optical rotation of the reaction solution indicated that one enantiomer of 23 had reacted preferentially (eeright-handed quartz gave the opposite optical rotation it was deduced that the chiral arrangement of the crystal was indeed responsible for this kinetic resolution (for a review see [8]). Later, natural fibres like silk fibroin H5 (Akabori [21]), polysaccharides H8 (Balandin [23]) and cellulose H12 (Harada [29]) were employed as chiral carriers or as protective polymer for several metals. With the exception of Pd/silk fibroin HS, where ee s up to 66% were reported, the optical yields observed for catalysts from natural or synthetic (H8, Hll. H13) chiral supports were very low and it was later found that the results observed with HS were not reproducible [4],... 

In order to improve the properties and the spinnability, fibroin sometimes has been electrospun together with other natural or synthetic polymers (Jin et al., 2002 Park et al., 2004, 2006 Wang et al., 2004, 2006). For instance, Jin et al. (2002) developed an aqueous process for silk electrospinning in combination with PEO. More recently, Cao (2008) used PVA/Silk Fibroin (SF), Gelatin/SF, and Hydroxyapatite (HAP)/SF to produce double-layered (core-shell) nanofibers (mats) by coelectrospinning. 

The use of chemiluminescence technique has expanded to others natural polymers. Recently, Millington et al. reported studies on polymers such as the fibrous proteins wool and feather keratin, silk fibroin, and reconstituted collagen from bovine skin, which revealed new information about their degradation [81]. The potential of CL to analyze the effectiveness of treatments to protect the polymer during processing could contribute to diminish the loss of properties of the types of polymers widely used in textile industry. 

Most of the recent reported polymer/CW nanocomposites were prepared by this method. The reported polymer matrixes contain poly(styrene-co-butyl acrylate) [36], poly(caprolactone) [37], natural rubber [39,140,141], soy protein isolate [38], poly(vinyl alcohol) [42, 44], chitosan [41, 141], silk fibroin, [142], alginate [44], starch [143], hyaluronan-gelatin [55], and waterborne polyurethane [144, 145]. 

Among the various synthetic materials that were initially tested such as nylon, Orion , Ivalon , only PTFE (Teflon ) and PET (Daaon ) have been shown to resist biodegradation in the body. i- Other synthetic and natural polymers, such as polyurethanes and silk fibroin, are also discussed in this chapter as they remain potential alternatives for certain current and future vascular applications. 

Natural polymers such as collagen, elastin, and fibrin make up much of the body s native extracellular matrix (ECM), and they were explored as platforms for tissue engineered constructs [34,47 9]. Polysaccharides such as chitosan, starch, alginate, and dextran were also studied for these purposes. Simultaneously, silk fibroin was widely explored for vascular applications due to its higher mechanical properties in comparison to other natural polymers, such as fibrin [48]. The utilization of natural polymers to create tissue-engineered scaffolds has yielded promising results, both in vitro and in vivo, due in part to the enhanced bioactivity provided by materials normally found within the human body [50]. However, their mechanical response is usually below the required values therefore, synthetic polymers have been explored to achieve the desired properties. 

Significant improvement of functional properties has been reported for fibers obtained from blends of chitin with various natural polymers such as cellulose, silk fibroin and glycosaminoglycans [48, 50, 51]. Fibers of chitosan blended with alginate, collagen and gelatin have been evaluated for wound dressing and artificial skin applications [52, 53, 108, 136]. 

As stated above, silk fibroin is a natural polymer and has thus established a good reputation for bone tissue engineering applications due to its many unique properties, including exceptional... 

PU is a strong, hard-wearing, tear-resistant, flexible, oil-resistant, and blood-compatible polymer. The functional properties of natural macromolecules can be merged with those of synthetic polymers having controllable structures and properties for the production of polymer/protein hybrids. In tissue engineering, silk fibroin/PU blend film can be used as scaffold material for artificial blood vessels [466] (Figure 2.62). Bacterial synthesized cellulose, which was designed... 

Natural Matrix Based Polymer Composites 489 Table 14.2 Cell and tissue applications of silk fibroin scaffolds [24]. 

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