1,721,321 research outputs found
Current status of gene delivery: spotlight on nanomaterial-polymer hybrids
No full textGene therapy aims to treat human disorders by introducing genetic materials into specific target cells or tissues. Despite the curability for the origin of diseases by restoring missing functionalities, no technical feasibility of gene therapy has been established due to the lack of safe and efficient gene delivery systems. The emergence of nanotechnology has provided an opportunity to create nanomaterials that are suitable for the biomedical applications. Nanomaterials integrated with cationic polymers offer novel platforms that allow not only easy incorporation of genetic materials through electrostatic interactions but also further modifications to be upgraded to theranostics. In this article, current status of gene delivery utilizing hybrid nanomaterials that are composed of novel nanoplatforms and cationic polymers are highlighted. In particular, different strategies employed for the construction of nanomaterial-polymer hybrids are described.X111110sciescopu
EFFICIENT SIRNA DELIVERY WITH NON-VIRAL POLYMERIC VEHICLES
No full textSequence-specific gene silencing using small interfering RNA (siRNA) provides a potent and specific method for gene expression, thus is now being evaluated in clinical trials as a novel therapeutic strategy. As a results, there has been a significant surge of interest in the application of siRNA in therapeutics as a means of silencing the specific gene function. However, for siRNA technology to be valuable and effective, the development of efficient siRNA delivery strategy is essential for improving biological activities such as stability, cellular uptake, sequence-specificity, devoid of nonspecific knockdown and toxic side effects. Accordingly, a number of delivery systems, both viral and nonviral, have been reported and some of them successfully used for the introduction of siRNA into cells both in vitro and in vivo. Here, we discuss the current understanding of synthetic siRNA delivery mechanism and strategies of siRNA delivery by non-viral polymeric vehicles which are currently used in vitro and in vivo.X11121sciescopu
Biodegradable nanoparticles modified by branched polyethylenimine for plasmid DNA delivery
No full textThe main objective of this work is to build a comparative account of two PLGA nanoparticle (NP)-based gene delivery systems namely, plasmid DNA (pDNA) encapsulated PLGA NPs (PLGA-E) and surface adsorbed pDNA on PLGA-BPEI NPs (PLGA-BPEI), with respect to the extent of internalization and intracellular release of pDNA. Several formulations have also been evaluated systematically for determination of the optimal transfection efficiency. The zeta-potential, particle size measurements and DNase I protection assay established the importance of the BPEI chain length in regulating the effective loading and condensation of pDNA with PLGA-BPEI NPs and pDNA protection ability of PLGA-BPEI NPs. The colloidal stability of these formulations was also investigated as a function of serum concentration. The in vitro release of pDNA from both kind of formulations was studied at pH 7.4 and pH 5.0 by comparing the kinetics of pH-triggered release of pDNA from PLGA-BPEI-25K(5) and PLGA-E. In vitro time-dependent gene transfection efficiencies were studied in presence as well as in absence of serum for NIH3T3 and HEK293 cells. The cell viability and intracellular localization were also investigated using MTT assay and confocal microscopy study, respectively. (C) 2009 Elsevier Ltd. All rights reserved.X117472sciescopu
A Highly Entangled Polymeric Nanoconstruct Assembled by siRNA and its Reduction-Triggered siRNA Release for Gene Silencing
No full textA nanoconstruct (NC) is developed from a biocompatible natural polymer and siRNA conjugates to deliver small interfering RNA (siRNA) target-specifically without cationic condensation reagents. This study reports a novel siRNA-mediated cross-linked NC produced by hybridizing two complementary single-stranded siRNAs that are conjugated to the polymer dextran via a disulfide linkage. The reducible disulfide bond between the siRNA and polymer allow siRNA release from the NC in the reducible cytoplasmic region after the NC enters the cell. In addition, when the NC contains the prostate-carcinoma-binding peptide aptamer DUP-1, it can selectively deliver siRNA into prostate cancer cells of the PC-3 lines; thus, the newly formulated NC has reduced the cytotoxicity and improved the efficacy of target-specific siRNA delivery. Moreover, this new concept of NCs using biocompatible siRNA and a neutral polymer may provide insightful knowledge for future directions for designing NCs for stimuli-responsive and advanced target-specific siRNA delivery.X1124sciescopu
TARGETED POLYMERIC GENE DELIVERY FOR ANTI-ANGIOGENIC TUMOR THERAPY
No full textGene therapy has become a promising strategy for the treatment of genetically based diseases, such as cancer, which are currently considered incurable. A major obstacle in the field of cancer gene therapy is the development of a safe and efficient delivery system for therapeutic gene transfer. Non-viral vectors have attracted great interest, as they are simple to prepare, stable, easy to modify and relatively safe compared to viral vectors. In this review, an insight into the strategies developed for polyethylenimine (PEI)-based non-viral vectors has been provide, including improvement of the polyplex properties by incorporating hydrophilic spacer, poly(ethylene glycol) (PEG). Moreover, this review will summarize the strategies for the tumor targeting. Specifically, a targeted polymeric gene delivery system, PEI-g-PEG-RGD, will be introduced as an efficient gene delivery vector for tumor therapy, including its functional analysis both in vitro and in vivo.X117sciescopuskc
Flow-induced microstructure in aqueous cationic surfactant solution in the presence of structure-enhancing additives
No full textIn the present article, we report the flow-induced microstructure in a dilute wormlike micellar solution of cetyltrimethylammonium bromide (CTAB). The additive used here is sodium salicylate (NaSal) to enhance the supramolecular structure formation. The flow-induced microstructures in surfactant solution were reproduced by the in situ gelation of the substrate. A silicon alkoxide of tetramethylorthosilicate (TMOS) in aqueous hydrochloric acid was used as a silica precursor to capture the microstructure. The captured now-induced structures in the wormlike micellar solution show alignment to the direction of flow under a weak now. Meanwhile, at high shear rates, now-induced coagulation or layer fluctuations occur. The flow-induced morphologies are dependent on the surfactant concentration, molar ratio of NaSal to CTAB, and flow intensity. SEM images taken from the direct observations through in situ gelation are consistent with the rheological responses such as shear thinning or shear thickening behavior
UNIK-OPT/NN - Neural network based adaptive optimal controller on optimization models
No full textWhen the future information for an optimization model is not complete, the model tends to incorporate such uncertainties as some assumptions on the coefficients. As time passes and more precise information is accumulated, the initial optimal solution may no longer be optimal, or even feasible. At this point, model builders want to modify the assumed and controllable coefficients to obtain the desired values of designated decision variables. To aid this process, a neural network could effectively be applied. So we develop a tool UNIK-OPT/NN which can support the construction and recall of the neural network model on top of the knowledge assisted optimization model formulator UNIK-OPT and the semantic neural network building aid UNIK-NEURO. By adopting a commonly interpretable semantic representation of optimization and neural network models, UNIK-OPT/NN can effectively automate most of the neural network construction and recall procedure for optimal. control
Helical mesostructured tubules from Taylor vortex-assisted surfactant templates
No full textTemplates for helix-structured silica microtubules are generated by subjecting worm-shaped micelles of cetyltrimethylammonium bromide to so-called Taylor vortex flow conditions between a rotating and a stationary cylinder at controlled speed. Silica deposition from TEOS and template dissolution produce helical tubules about 100 nm in diameter and a few micrometers long (see Figure), potentially useful for chiral catalysis or optical applications
Effects of sodium salicylate on the microstructure of an aqueous micellar solution and its rheological responses
No full textIn this article, we consider the effects of sodium salicylate on the microstructure evolution and rheological responses of an aqueous cetyltrimethylammonium bromide (CTAB) solution. The experimental runs covered CTAB solutions ranging from dilute to semidilute, which were far above its critical micelle concentration. Sodium salicylate (NaSal) was used as a structure-forming agent with the molar ratio of NaSal to CTAB ranging from 0.1 to 10.0. The experimental results showed that the rheological responses of the surfactant solution were influenced strongly by both the CTAB concentration and the molar ratio. At low molar ratios, below 0.3, the surfactant solutions behaved like a Newtonian fluid. However, as the molar ratio increased, the deviation from Newtonian behavior became pronounced. Specifically, for 0.05 M CTAB solutions with molar ratios ranging from 1.0 to 5.0, an apparent yield stress developed at low shear rates and a stress plateau was displayed at intermediate shear rates. When the shear rate exceeded a certain threshold value, the shear stress increased, again passing over the plateau value. In addition, viscoelastic response and relaxation behavior were observed. The relaxation behavior after the cessation of flow was strongly dependent on the molar ratio, which was also confirmed by rheo-optical observations. The optical anisotropy measured by rheo-optical methods was closely related to flow-induced stretching and alignment of the wormy micelles and was consistent with the rheological responses. (C) 2000 Academic Press.Thiswork has been supported by a grant from theKorea Research Foundation.
The authors appreciate their support
High-strain-rate superplastic deformation behavior of a powder metallurgy-processed 2124 Al alloy
No full textHigh-strain-rate superplastic behavior of a powder-metallurgy processed 2124 alloy prepared through extrusion at a high ratio of 70 : 1 was investigated. A maximum tensile elongation of 700% was obtained at 823 K and at a strain rate of 10(-2) s(-1). Deformation behavior of this alloy was similar to those reported for other many HSR superplastic materials. Incorporation of threshold stress into the constitutive equation reveals that the true stress exponent is 2 and true activation energy for plastic flow is comparable to that for lattice diffusion in pure aluminum. Comparison of the present alloy with the 2124 Al composite indicates that the composite is weaker than the unreinforced alloy in the temperature range where grain boundary sliding is rate-controlled. (C) 2000 Kluwer Academic Publishers
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