China
Africa
Explore chapters and articles related to this topic
VNPs as Tools for Nanomedicine
Published in Nicole F Steinmetz, Marianne Manchester, Viral Nanoparticles, 2019
Nicole F Steinmetz, Marianne Manchester
The development of phage display technologies has led to the identification of tumor-specific markers and their ligands, as well as vascular homing peptides (Arap et al., 2002; Hajitou et al., 2006a; Nanda & St. Croix, 2004; Ruoslahti, 2002). A prominent ligand identified using this approach is the RGD motif. The RGD sequence is a popular targeting ligand used. RGD peptides recognize the integrins αvβ3 and αvβ5, which are overexpressed on tumor endothelium and cancer cells (Li et al., 2003; Meyer et al., 2006; Sipkins et al., 1998; Winter et al., 2003).
Recent Developments in Transdermal Drug Delivery Systems Based on an Electrospun Nanofibrous Scaffold
Published in Mangala Joshi, Nanotechnology in Textiles, 2020
Use of biopolymers for scaffold fabrication is limited because of their rapid degradation and reduced mechanical strength, where synthetic polymers lack extracellular mimicking properties (RGD motif), which is vital for cell adhesion and proliferation onto the scaffold. Because of this limitation, here we synthesized a hybrid polymer that has a synthetic polymer part and a biopolymer part. In the last system, we prepared a novel hybrid polymer (Bio-Syn) as the base polymer by grafting a synthetic diblock copolymer into a gelatin backbone using the Michael addition reaction [48]. A blend of 10% Bio-Syn/0.25% HA/0.625% CS/0.5%–1% sericin is solubilized in a mixture of glacial acetic acid and ethyl acetate (5:1) for the electrospinning process. The mean fiber diameter of 193 ± 49 nm was witnessed in SEM. Because of synthetic polymer grafting into the gelatin backbone, we observed increased mechanical strength and degradation behavior compared with the previous two systems (Table 11.1). A release study showed GAGs release of 21.2% and sericin release of 22.6%, which is significantly higher than in the case of the CatGel System. Relatively less electrostatic interaction between GAGs and Bio-Syn might be responsible for this phenomenon. An in vitro cellular study showed a significant cellular growth in all the scaffolds with a bioactive component compared to the native Bio-Syn scaffold and the polystyrene plate control. In epithelial differentiation of hMSC, we observed no significant difference in marker expression while comparing different scaffold types. However, the ddCt values are significantly higher for both K14 and p63 compared to the previous two electrospun scaffold systems. On the basis of a comparative analysis (Table 11.1), we concluded that the Bio-Syn scaffold system is comparatively better than the other two systems. Hence, we decided to evaluate the in vivo efficacy of this system in second-degree burn wound healing in a Wistar rat model. After 21 days of burn wound healing experiment, we observed that the Bio-Syn scaffold loaded with 1% sericin showed a significant improvement in wound closure and prohealing marker expression in comparison with Neuskin™ and cotton gauze control.
Organic Bioelectronics Based on Mixed Ion–Electron Conductors
Published in John R. Reynolds, Barry C. Thompson, Terje A. Skotheim, Conjugated Polymers, 2019
Magnus Berggren, Erik O. Gabrielsson, Daniel T. Simon, Klas Tybrandt
It is known that the density and orientation of ECM proteins can be controlled by the surface tension of the carrying substrate. As introduced earlier in this section, conjugated polymer films with mixed ion–electron conductivity define an interesting platform for electronic control over the surface tension, thus providing a tool to regulate ECM and the growth processes of cells. In early experiments in the 1990s, polypyrrole (PPy) was explored to control protein adsorption and cell cultures.18 Aortic endothelial cells were cultured on PPy (oxidized), pre-coated with Fn. In its pristine state, i.e., non-switched, as-prepared, PPy could serve as a hosting surface for the cells in either a chemically defined medium or in the presence of serum. When the polymer was switched to its neutral state,* the extension and spreading of cells was inhibited without affecting cell viability. In this early experiment, the change in electric field and/or discharge of dopant ions upon electric switching was tentatively proposed as the explanation for active control of cell growth and spreading. More recently, it has been shown that by switching the electroactive polymer surface, control over the conformation of proteins19,20 rather than the density or release of dopants impacts the protein adsorption or cell growth in a direct manner. The presence and conformation of proteins are crucial in dictating the adhesion characteristics of cells while seeded onto and into artificial surfaces and scaffolds. Receptors, such as the Arg-Gyl-Asp (RGD)-binding motif (amino acid sequence) on Fn, provide a signaling template to initiate proliferation and further cell division protocols. As the transmembrane integrin dimers, located within the cell walls, couple to the RGD motif, a coordination and signaling protocol is initiated to promote cell development (Figure 22.1d). For MDCK cells seeded along electronic surface switches, based on poly(3,4-ethylenedioxythiophene) tosylate (PEDOT:tosylate), the PEDOT state has a major impact on the growth processes. Along PEDOT:tosylate surfaces, in which PEDOT is reduced to its neutral state, a high density of Fn was found with RGD receptors well exposed for integrin coupling. Thus, along those surfaces, MDCK-based epithelial tissue is formed, characterized by functional tight junctions and an overall high cell viability. Conversely, for a PEDOT surface switched to its p-doped (oxidized) state, the RGD receptors were found to be less expressed, due to an unfavorable Fn conformation. Along these surfaces, the cells do not spread and divide to form tissues, rather they adhere at low concentrations and swiftly enter apoptosis, see Figure 22.2.
Development of arginine-glycine-aspartate-immobilized 3D printed poly(propylene fumarate) scaffolds for cartilage tissue engineering
Published in Journal of Biomaterials Science, Polymer Edition, 2018
Chi Bum Ahn, Youngjo Kim, Sung Jean Park, Yongsung Hwang, Jin Woo Lee
Although Lan et al. have successfully introduced RGD moieties into PPF-based scaffold simply by immersing scaffolds into peptide solutions to promote cell adhesion and proliferation of MC3T3-E1 pre-osteoblasts, this could be achieved through non-specific absorption of RGD peptides into the scaffold [44]. Therefore, in this study, to maximize initial adhesion, retention, and proliferation of seeded cells within the scaffolds, we have introduced covalently bound RGD motif onto the p(PF-co-DEF) scaffolds to evaluate their functional contributions to cellular functions of seeded cells. Particularly, we have compared three different RGD motifs via various immobilization methods, such as C-terminus, N-terminus, and plasma-associated RGD incorporations. Isolated chondrocytes were seeded into RGD-immobilized p(PF-co-DEF) scaffolds and in vitro cultured for 2 weeks. The proliferation of seeded cells within control scaffold (no RGD peptide) or RGD-immobilized scaffolds was evaluated by MTS assay.