We present a molecular dynamics study of the helical conformation of the naturally occurring poly(γ‐D ‐glutamic acid) in the un‐ionized state. The study was conducted in both aqueous solution and gas‐phase considering a 20 residue polypeptide. The results indicated that the left‐handed helix with 19‐membered ring hydrogen bonds set between the CO of the amide group i and the NH of amide group i + 3 is very stable in aqueous solution. This conformation was recently proposed for this poly(γ‐amino acid) from a conformational search study. A detailed picture of the most relevant structural details of the helical conformation of poly(γ‐D ‐glutamic acid) is provided. 相似文献
This paper reports dual-function (high cell attachment and cell viability) fibrous scaffolds featuring aligned fibers, displaying good biocompatibility and no cytotoxicity. These scaffolds are fabricated through the electrospinning of a co-polypeptide comprising molar equivalents of N6-carbobenzyloxy-l -lysine and γ-benzyl-l -glutamate, with the lysine moieties enhancing cell adhesion and the neural-stimulating glutamate moieties improving cell viability. These new scaffolds allow neural cells to attach and grow effectively without any special surface treatment or coating. Pheochromocytoma (PC-12) cells grown on these scaffolds exhibit better neuronal activity and longer neurite length, relative to those grown on scaffolds prepared from their respective homo-polypeptides. When the scaffolds are partially hydrolyzed such that they present net positive charge and increased hydrophilicity, the cell viability and neurite growth both increase further. Accordingly, these novel co-polypeptide fibrous scaffolds have potential applications in neural tissue engineering. 相似文献
Poly(γ‐benzyl‐l ‐glutamate)‐block‐poly(ethylene glycol) (PBLG‐b ‐PEG) rod–coil block copolymers and poly(γ‐benzyl‐l ‐glutamate) (PBLG) homopolymers can cooperatively self‐assemble into superhelical structures in aqueous solution. Herein, we discovered that the helices can have multiple strands with tunable characteristics. The strand number was dependent on the initial polymer concentration of the self‐assembly, the self‐assembly temperature, and the weight fraction of the block copolymers in the mixture. Higher initial polymer concentrations or lower weight fractions of the block copolymers induced the formation of helices with larger diameters and higher strand numbers, and helices prepared at higher temperatures had higher strand numbers. Based on an analysis of the correlation between the geometric parameters of the helices and the strand number, a possible mechanism for the formation of multistranded superhelices is suggested. 相似文献
Correct structural assignment of small molecules and natural products is critical for drug discovery and organic chemistry. Anisotropy‐based NMR spectroscopy is a powerful tool for the structural assignment of organic molecules, but it relies on the utilization of a medium that disrupts the isotropic motion of molecules in organic solvents. Here, we establish a quantitative correlation between the atomic structure of the alignment medium, the molecular structure of the small molecule, and molecule‐specific anisotropic NMR parameters. The quantitative correlation uses an accurate three‐dimensional molecular alignment model that predicts residual dipolar couplings of small molecules aligned by poly(γ‐benzyl‐l ‐glutamate). The technique facilitates reliable determination of the correct stereoisomer and enables unequivocal, rapid determination of complex molecular structures from extremely sparse NMR data. 相似文献
Structural simulation of the smooth muscle layer plays an important role in tissue engineering of blood vessels for the replacement of damaged arteries. However, it is difficult to construct small‐diameter tubular scaffolds to homogenously locate and align smooth muscle cells (SMCs). In this work, novel temperature responsive shape‐memory scaffolds are designed for SMC culturing. The scaffolds are composed of an outer layer of poly(lactide–glycolide–trimethylene carbonate) (PLGATMC) for programming the deformation from planar to small‐diameter tubular shape and an inner layer of aligned nanofibrous membrane of poly(lactide–glycolide)/chitosan (PLGA/CS) to regulate cell adhesion, proliferation, and morphology. The SMC behaviors and functions are dependent on the PLGA/CS ratios of membranes, and the scaffold with PLGA/CS 7:3 membrane exhibits the most suitable ability to regulate SMC behavior. The PLGA/CS@PLGATMC scaffold can be deformed into a temporary planar at 20 °C for convenient seeding and attachment of SMCs and then immediately self‐rolled into 3D tube at 37 °C. The proposed strategy offers a practical approach for the development of small‐diameter vascular scaffolds from 2D planar into 3D tubular shape by self‐rolling. 相似文献
Scaffold, an essential element of tissue engineering, should provide proper physical and chemical properties and evolve suitable cell behavior for tissue regeneration. Polycaprolactone/Gelatin (PCL/Gel)‐based nanocomposite scaffolds containing hydroxyapatite nanoparticles (nHA) and vitamin D3 (Vit D3) were fabricated using the electrospinning method. Structural and mechanical properties of the scaffold were determined by scanning electron microscopy (SEM) and tensile measurement. In this study, smooth and bead‐free morphology with a uniform fiber diameter and optimal porosity level with appropriate pore size was observed for PCL/Gel/nHA nanocomposite scaffold. The results indicated that adding nHA to PCL/Gel caused an increase of the mechanical properties of scaffold. In addition, chemical interactions between PCL, gelatin, and nHA molecules were shown with XRD and FT‐IR in the composite scaffolds. MG‐63 cell line has been cultured on the fabricated composite scaffolds; the results of viability and adhesion of cells on the scaffolds have been confirmed using MTT and SEM analysis methods. Here in this study, the culture of the osteoblast cells on the scaffolds showed that the addition of Vit D3 to PCL/Gel/nHA scaffold caused further attachment and proliferation of the cells. Moreover, DAPI staining results showed that the presence and viability of the cells were greater in PCL/Gel/nHA/Vit D3 scaffold than in PCL/Gel/nHA and PCL/Gel scaffolds. The results also approved increasing cell proliferation and alkaline phosphatase (ALP) activity for MG‐63 cells cultured on PCL/Gel/nHA/Vit D3 scaffold. The results indicated superior properties of hydroxyapatite nanoparticles and vitamin D3 incorporated in PCL/Gel scaffold for use in bone tissue engineering. 相似文献
After about three decades of experience, tissue engineering has become one of the most important approaches in reconstructive medical research to treat non‐self‐healing bone injuries and lesions. Herein, nanofibrous composite scaffolds fabricated by electrospinning, which containing of poly(L‐lactic acid) (PLLA), graphene oxide (GO), and bone morphogenetic protein 2 (BMP2) for bone tissue engineering applications. After structural evaluations, adipose tissue derived mesenchymal stem cells (AT‐MSCs) were applied to monitor scaffold's biological behavior and osteoinductivity properties. All fabricated scaffolds had nanofibrous structure with interconnected pores, bead free, and well mechanical properties. But the best biological behavior including cell attachment, protein adsorption, and support cells proliferation was detected by PLLA‐GO‐BMP2 nanofibrous scaffold compared to the PLLA and PLLA‐GO. Moreover, detected ALP activity, calcium content and expression level of bone‐related gene markers in AT‐MSCs grown on PLLA‐GO‐BMP2 nanofibrous scaffold was also significantly promoted in compression with the cells grown on other scaffolds. In fact, the simultaneous presence of two factors, GO and BMP2, in the PLLA nanofibrous scaffold structure has a synergistic effect and therefore has a promising potential for tissue engineering applications in the repair of bone lesions. 相似文献
In this paper, we have developed a method to produce poly(lactic- co-glycolic acid) (PLGA) microfibers within a microfluidic chip for the generation of 3D tissue engineering scaffolds. The synthesis of PLGA fibers was achieved by using a polydimethylsiloxane (PDMS)-based microfluidic spinning device in which linear streams of PLGA dissolved in dimethyl sulfoxide (DMSO) were precipitated in a glycerol-containing water solution. By changing the flow rate of PLGA solution from 1 to 50 microL/min with a sheath flow rate of 250 or 1000 microL/min, fibers were formed with diameters that ranged from 20 to 230 microm. The PLGA fibers were comprised of a dense outer surface and a highly porous interior. To evaluate the applicability of PLGA microfibers generated in this process as a cell culture scaffold, L929 fibroblasts were seeded on the PLGA fibers either as-fabricated or coated with fibronectin. L929 fibroblasts showed no significant difference in proliferation on both PLGA microfibers after 5 days of culture. As a test for application as nerve guide, neural progenitor cells were cultured and the neural axons elongated along the PLGA microfibers. Thus our experiments suggest that microfluidic chip-based PLGA microfiber fabrication may be useful for 3D cell culture tissue engineering applications. 相似文献
Despite the great advances in microsurgery, some neural injuries cannot be treated surgically. Stem cell therapy is a potential approach for treating neuroinjuries and neurodegenerative disease. Researchers have developed various bioactive scaffolds for tissue engineering, exhibiting enhanced cell viability, attachment, migration, neurite elongation, and neuronal differentiation, with the aim of developing functional tissue grafts that can be incorporated in vivo. Facilitating the appropriate interactions between the cells and extracellular matrix is crucial in scaffold design. Modification of scaffolds with biofunctional motifs such as growth factors, drugs, or peptides can improve this interaction. In this review, we focus on the laminin‐derived Ile‐Lys‐Val‐Ala‐Val peptide as a biofunctional epitope for neuronal tissue engineering. Inclusion of this bioactive peptide within a scaffold is known to enhance cell adhesion as well as neuronal differentiation in both 2‐dimensional and 3‐dimensional environments. The in vivo application of this peptide is also briefly described. 相似文献
We report the design and synthesis of new fully biodegradable thermoresponsive amphiphilic poly(γ‐benzyl L ‐glutamate)/poly(ethyl ethylene phosphate) (PBLG‐b‐PEEP) block copolymers by ring‐opening polymerization of N‐carboxy‐γ‐benzyl L ‐glutamate anhydride (BLG? NCA) with amine‐terminated poly(ethyl ethylene phosphate) (H2N? PEEP) as a macroinitiator. The fluorescence technique demonstrated that the block copolymers could form micelles composed of a hydrophobic core and a hydrophilic shell in aqueous solution. The morphology of the micelles as determined by transmission electron microscopy (TEM) was spherical. The size and critical micelle concentration (CMC) values of the micelles showed a decreasing trend as the PBLG segment increased. However, UV/Vis measurements showed that these block copolymers exhibited a reproducible temperature‐responsive behavior with a lower critical solution temperature (LCST) that could be tuned by the block composition and the concentration. 相似文献
The ability to mimic the chemical, physical and mechanical properties of the natural extra‐cellular matrix is a key requirement for tissue engineering scaffolds to be successful. In this study, we successfully fabricated aligned nanofibrous multi‐component scaffolds for bone tissue engineering using electrospinning. The chemical features were mimicked by using the natural components of bone: collagen and nano‐hydroxyapatite along with poly[(D ,L ‐lactide)‐co‐glycolide] as the major component. Anisotropic features were mimicked by aligning the nanofibers using a rotating mandrel collector. We evaluated the effect of incorporation of nano‐HA particles to the system. The morphology and mechanical properties revealed that,at low concentrations, nano‐HA acted as a reinforcement. However, at higher nano‐HA loadings, it was difficult to disrupt aggregations and, hence, a detrimental effect was observed on the overall scaffold properties. Thermal analysis showed that there were slight interactions between the individual components even though the polymers existed as a two‐phase system. Preliminary in vitro cell‐culture studies revealed that the scaffold supported cell adhesion and spreading. The cells assumed a highly aligned morphology along the direction of fiber orientation. Protein adsorption experiments revealed that the synergistic effect of increased surface area and the presence of nano‐HA in the polymer matrix enhanced total protein adsorption. Crosslinking with 1‐ethyl‐3‐(3‐dimethylaminopropyl) carbodiimide hydrochloride resulted in improved mechanical properties of the scaffolds and improved degradation stability, under physiological conditions.
Inverse opal scaffolds are finding widespread use in tissue engineering and regenerative medicine. Herein, the way in which the pore sizes and related physical properties of poly(D ,L ‐lactide‐co‐glycolide) inverse opal scaffolds are affected by the fabrication conditions is systematically investigated. It is found that the window size of an inverse opal scaffold is mainly determined by the annealing temperature rather than the duration of time, and the surface pore size is largely determined by the concentration of the infiltration solution. Although scaffolds with larger pore or window sizes facilitate faster migration of cells, they show slightly lower compressive moduli than scaffolds with smaller pore or window sizes. 相似文献