98 research outputs found
Antioxidant activity applying an improved ABTS radical cation decolorization assay
No full textmethod for the screening of antioxidant activity is reported as a decolorization assay applicable to both lipophilic and hydrophilic antioxidants, including flavonoids, hydroxycinnamates, carotenoids, and plasma antioxidants.
The pre-formed radical monocation of 2,29-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS•1) is generated by oxidation of ABTS with potassium persulfate and is reduced in the presence of such hydrogen-donating antioxidants.
The influences of both the concentration of antioxidant and duration of reaction on the inhibition of the radical cation absorption are taken into account when determining the antioxidant activity. This assay clearly improves the original TEAC assay (the ferryl myoglobin/ABTS assay) for the determination of antioxidant activity in a number of ways. First, the chemistry involves the direct generation of the ABTS radical monocation with no involvement of an intermediary radical. Second, it is a decolorization assay; thus the radical cation is pre-formed prior to addition of antioxidant test systems, rather than the generation of the radical taking place continually in the presence of the antioxidant. Hence the results obtained with the improved system may not always be directly comparable with those obtained using the original TEAC assay. Third, it is applicable to both aqueous and lipophilic systems
Acute Kidney Injury:Current and Future Therapies Involving Antioxidants and Antioxidant Formulations
Full text linkAcute kidney injury is characterised by abrupt failure of kidney function, sometimes leading to chronic kidney disease, and is associated with significant morbidity and mortality. However, there is no clear effective therapeutic solution and treatment is mainly based on either alleviation or removal of the possible cause and/or renal replacement therapy. Oxidative stress has been indicated as one of the main pathophysiological pathways in the development of acute kidney injury. Various treatments including antioxidants, inflammatory mediators and genetic modifiers have been proposed to for the treatment of this condition. Epidemiological studies show lower incidence of kidney failure with higher consumption of antioxidants. However, the data is inconclusive due to their physicochemical properties, bioavailability or toxicity. Novel drug delivery systems such as liposomes and nanoparticles have been proposed to overcome the pharmacodynamic and pharmacokinetic barriers. This review provides a brief introduction to acute kidney injury and the different factors involved in its pathology, focusing on oxidative stress. It also covers details of antioxidant use as preventive and/or treatment option. It will summarise their limitations as free drugs and the possible improvement in their bioavailability by two main novel drug delivery systems: liposomes and polymeric nanoparticles. Other therapies such as inflammatory mediators and genetic modifiers are also discussed briefly
Entrapment of Gold Nanoparticles in Liposomes for Controlled Intracellular Self-assembly
No full textBackground: Self-assembling nanomaterials (SANs) promise technological innovation at all stages of healthcare, encompassing fields of genomics, biosensors, immuno-analysis, drug delivery, detection, monitoring and treatment of diseases and infections. The generalised aim across these disciplines can be described as working towards the design of smart multifunctional nanosystems that interact, respond and provide treatment. To effectively exploit this approach, a high-level of behavioural understanding and control under biological conditions is required.Methods: Molecular recognition and electrostatic attraction, two different strategies of gold nanoparticle self-assembly were studied. Corresponding nanoparticles were incorporated into PEGylated liposomes using a novel method. Two formulations were manufactured and characterised with gold and lipid concentrations determined using analytical and microscopy techniques. Toxicity evaluation between liposomal systems and corresponding gold nanoparticles was performed in-vitro on hamster lung fibroblasts (V79), employing MTT and LDH assays. Cellular uptake and self-assembly of nanoparticles was investigated using a combination of electron microscopy and elemental analysis.Results: Both strategies facilitated spontaneous self-assembly of nanoparticles under aqueous conditions. However, within a biologically relevant medium considerable bio-complex formation occurred and only particles exploiting electrostatic interactions persisted to self-assemble. Nanoparticles were capable of being encapsulated within multilamellar liposomes by electrostatic exploiting interactions between oppositely charged components. The novel method resulted in variable internalised gold to lipid ratios, as a result of differing magnitudes of electrostatic attraction during preparation. Gold nanoparticles with cationic or anionic surfaces did not display cytotoxicity, although a significant difference in cytotoxicity was displayed as they underwent in-situ self-assembly. Liposomes with and without encapsulated gold nanoparticles exhibited significant dose-dependant cytotoxicity. Cellular internalisation of gold nanoparticles was evidenced within cellular vacuoles, although no confirmation of self-assembly was obtained.Conclusions: Nanomaterial-biological interactions preceding the process of self-assembly can hinder activity and result in unpredictable outcomes. Individual SANs can be incorporated within traditional drug delivery systems, which could be further investigated towards controlling self-assembly activity. Toxicity studies demonstrate that a unique biological response could arise when nanomaterials self-assemble. Intracellular evaluation of SANs is inherently difficult and current techniques and approaches would benefit from further development to enable routine and reliable assessment of analogous nanosystems
Comparison between Free and Encapsulated Form of Epicatechin in Liposomes and In Polymeric Nanoparticles Against the Paraquat-Induced Toxicity of NRK-52E Cells
Full text linkBoth liposomes and polymeric nanoparticles have lately been utilized as carriers of conventionally prescribed medications with the aim of improving their activity in various ways. Epicatechin is a flavonoid with a limited bioavailability that can be found in natural sources. It is somewhat water soluble. However, because of its poor absorption and quick metabolism, it cannot function as it is expected. This work sought to enhance the pharmacokinetic features of epicatechin by encapsulating it in polylactic acid nanoparticles and liposomes. Liposomes were formed by the hydration of a lipid film to prepare large multilamellar vesicles, followed by membrane extrusion to formulate smaller unilamellar vesicles. On the other hand, polymeric nanoparticles were produced by double emulsification solvent diffusion method using polylactic acid as the polymer. Both products were then characterized for their particle size, zeta potential, drug loading, antioxidant activity, toxicity on cell lines (NRK-52E cells) and protection against paraquat oxidation. The mean particle size of liposomes was 183.8 ± 80.1 nm and for polylactic acid nanoparticles it was 350.9 ± 87.4 nm. Their surface zeta-potentials were -11.3 ± 3.93 and -32.9 ± 7.54 mV; respectively. The encapsulation of epicatechin in liposomes was 10.23 ± 1.54% and in polylactic acid nanoparticles 5.35 ± 3.35% (%encapsulation efficiency = 18.09 ± 1.95%). Microscopic images presented both sorts of nanoparticles to be sphere-shaped. Encapsulation of epicatechin into both liposomes and polylactic acid nanoparticles enhanced the % internalisation remarkably from 4.18 ± 0.03% to 27.05 ± 1.07% and 36.29 ± 0.09%; respectively. The toxicity test found all three forms not to be harmful to the NRK-52E cells within the concentration ranges tested. Examining the in vitro activity results showed that the same concentration of epicatechin in the liposomal form showed more protection against paraquat than epicatechin in its free form. Moreover, a lower epicatechin concentration was used in the polylactic acid nanoparticle form and still found to be more protective. From these results it can be concluded that epicatechin-loaded liposomes and polylactic nanoparticles offer protection to NRK-52E cells against paraquat induced toxicity
Protective Effects of Resveratrol Encapsulated in Liposomes or PLA Nanoparticles against Oxidative Stress in NRK-52E Cells
No full textLiposomes and Polymeric nanoparticles are nanocarriers that can be used to enhance the pharmacokinetics of different drugs. The objective of the current study was to encapsulate resveratrol in DPPC liposomes and PLA nanoparticles; separately for the amelioration of PQ-induced oxidative stress on NRK-52E cells. Liposomes were produced by the hydration of a lipid film. Polymeric nanoparticles were prepared by double emulsification solvent diffusion method using PLA. They were then characterized for their particle size, zeta potential, drug loading, antioxidant activity, toxicity on NRK-52E cells, and protection against paraquat oxidation. The mean particle size for liposomes and PLA nanoparticles were respectively 197.4 ± 102.4 and 457.9 ± 56.1 nm and their surface zeta-potentials were -7.86 ± 6.36 and -21.6 ± 10.4 mV; respectively. LM and SEM images showed both types of nanoparticles to be spherical in shape. %LE efficiency for liposomes (12.04 ± 1.23%) was quite low compared to PLA nanoparticles (40.81 ± 29.14%). However, the % internalization for liposomes (5.95 ± 0.09%) was around 11 times higher than free resveratrol compared to PLA nanoparticles (0.93 ± 0.03%) which were only around two-fold higher. The toxicity tests showed that both liposomes and PLA nanoparticle forms of resveratrol showed less harmful effect on the cells than its free form mainly in the LDH assay. Furthermore, the benefit of encapsulation was also clear in the activity tests against PQ on the NRK-52E cell. From these results, it can be concluded that resveratrol-loaded liposomes and PLA nanoparticles can show more benefits over free resveratrol
Mimicking the nuclear pore complex using nanopores
No full textNuclear pore complexes acts as a gatekeeper for molecular transport between the nucleus and the cytoplasm in eukaryotic cells. The central NPC channel is filled with intrinsically disordered FG domains (phenylalanine (F), glycine (G)) that are responsible for the fascinating selectivity of NPCs, for which the underlying mechanism is still under considerable debate. In this thesis, a minimalistic mimic of (NPCs) was constructed using solid-state nanopore and DNA origami to study the spatial arrangement and transport process.BN/Cees Dekker La
Recent developments in formulation design for improving oral bioavailability of curcumin:A review
Full text linkCurcumin, a yellow-orange substance that is extracted from the spice turmeric (Curcuma longa, Zinziberaceae), has been attributed with a wide range of pharmacological activities for the prevention and treatment of several disease conditions such as arthritis, hypertension, diabetes, Alzheimer's, antibacterial and cancer to name a few. However, its potential for use as an orally delivered medicinal product is hindered by its poor solubility and bioavailability. The low oral bioavailability of curcumin is caused by several factors including low aqueous solubility, poor intestinal permeability, unstable at alkaline pH and rapid metabolism. To improve curcumin's poor oral bioavailability, different formulation strategies such as incorporation into nanoparticles, liposomes, micelles, micro/nano-emulsions and solid dispersions as well as co-administration with piperine have been investigated in both animal models as well as human supplementation studies. In this review, novel formulations of curcumin for oral delivery that were developed in recent years are reviewed and discussed.</p
Study of DNA origami plates on graphene nanopores
No full textCombining DNA origami with solid-state nanopores has been gaining an increasing amount of attention due to its potential for biosensing applications. Accordingly, origami plate dockings onto conventional solid-state silicon nitride pores with membranes of ?20nm thick were previously studied. Here, we examine whether graphene, with its single layer of carbon atoms, poses advantages over silicon-nitride pores. The conductance blockades due to origami plate dockings were characterized as a function of salt concentration and applied bias voltage and compared to the silicon-nitride data. As expected, it was found that conductance blockades increase with salt concentration and voltage. The relative conductance drop in graphene was however found to be similar to that for silicon nitride pores, whereas theory predicts that the blockade signal is larger in graphene pores. We have further compared the root-mean-squared noise levels of the ionic current through hybrid graphene-origami pores and bare pores, and found that the noise in the hybrid pores was slightly higher than in the bare pore current. Finally, it was tested whether the plates stick to the graphene pore in presence of EDTA. This was done by docking the plates and subjecting them to a negative ramping voltage. Without EDTA, no evidence of sticking was found, whereas with EDTA, 88.2\% of docked plates appeared to be sticking.Technische NatuurkundeBionanoscienceApplied Science
- …
