Delivery and stability of antisense oligonucleotide conjugates in vitro

The efficacy of antisense oligonucleotide (ODN) therapy is dependent on four major parameters: delivery to cells, intracellular stability and localisation and efficient action at the target site.The aim of this project was to study the delivery of ODNs to macrophages and to assess the stability of two ODN conjugates, in vitro. The first conjugate aimed to improve uptake of ODNs via mannose receptor mediated delivery, the second investigated the improved delivery of ODN conjugates via non-specific lipophilic interaction with the cell membrane. A mono-mannose phosphoramidite derivative was designed and synthesised and a mono-mannose ODN conjugate synthesised by standard phosphoramidite chemistry. Delivery of this conjugate was enhanced to RAW264.7 and J774 macrophage cell lines via a mechanism of receptor mediated endocytosis. The delivery of three lipophilic ODN conjugates, cholesterol (cholhex), 16-carbon alkyl chain (C16) and hexa-ethylene glycol (HEG) moieties and an unconjugated ODN were assessed in RAW264.7 macrophages. All three conjugates increased the lipophilicity of the ODN as assessed from partition coefficient data. Both the cholhex and unconjugated ODNs were found to have higher degrees of cellular association than the C16 and HEG conjugates. Cellular uptake studies implicated internalisation of these ODNs by an adsorptive endocytosis mechanism. Following endocytosis, ODNs must remain stable during their residence in endosomal/lysosomal compartments prior to exiting and exerting their biological action in either the cytosol or nucleus. Assessment of in vitro stability in a lysosomal extract revealed the cholhex conjugate and unconjugated ODNs to have a longer half-life than the C16 and HEG conjugated ODNs, highlighting the influence of conjugate moieties on lysosomal stability. The effects of base composition and length on stability in a lysosomal extract revealed the longest half-life for homo-cytidine ODNs and ODNs over 20 nucleotides in length. These studies suggest that the above conjugates can enhance cellular association and delivery of antisense ODNs to cultured macrophages. This may lead to their use in treating disorders such as HIV infection, which affects this cell type.

The stability of pharmaceutical powders: effect of additives and coating

The decomposition of drugs in the solid state has been studied using aspirin and salsalate as models. The feasibility of using suspension systems for predicting the stability of these drugs in the solid state has been investigated.. It has been found that such systems are inappropriate in defining the effect of excipients on 'the decomposition of the active drug due to chqnges in the degradation pathway. Using a high performance liquid chromatographic method, magnesium stearate was shown to induce the formation of potentlally immunogenic products in aspirin powders. These products which included salicylsalicylic acid .and acetylsalicyclsalicylic acid were not detected in aspirin suspensions which had undergone the same extent of decomposition. By studying the effect of pH and of added excipients on the rate of decomposition of aspirin in suspension systems, it has been shown that excipients such as magnesium stearate containing magnesium oxide, most probably enhance the decomposition of both aspirin and salsalate by alkalinising the aqueous phase. In the solid state, pH effects produced by excipients appear to be relatively unimportant. Evidence is presented to suggest that the critical parameter is a depression in melting point induced by: the added excipient. Microscopical examination in fact showed the formation of clear liquid layers in aspirin samples containing added magnesium stearate but not in control samples. Kinetic equations which take into account both the diffusive barrier presented by the liquid films and the. geometry of the aspirin crystals were developed. Fitting of the .experimental data to these equations showed good agreement. with the postulated theory. Monitorjng of weight issues during the decomposition of aspirin revealed that in the solid systems studied where the bulk of the decomposition product sublimes, it is possible to estimate the extent of degradation from the residual weight, provided the initial weight is known. The corollary is that in such open systems, monitoring of decomposition products is inadequate for assessing the extent of decomposition. In addition to the magnesium stearate-aspirin system, mapyramine maleate-aspirin mixtures were used to model interactive systems. Work carried out in an attempt to stabilise such systems included microencapsulation and film coating. The protection obtained was dependent on the interactive species used. Gelatin for example appeared to stabilise aspirin against the adverse effects of magnesium stearate but increased its decomposition in the presence of mapyramine maleate.

Characterisation and oxidative stability of speciality plant seed oils

The past decade has seen an influx of speciality plant seed oils arriving into the market place. The need to characterise these oils has become an important aspect of the oil industry. The characterisation of the oils allows for the physical and chemical properties of the oil to be determined. Speciality oils were characterised based on their lipid and fatty acid profiles and categorised as monounsaturated rich (oleic acid as the major acyl components e.g. Moringa and Marula oil), linoleic acid rich (Grape seed and Evening Primrose oil) or linolenic acid rich (Flaxseed and Kiwi oil). The quality of the oils was evaluated by determining the free fatty acid content, the peroxide value (that measures initial oxidation) and p-anisidine values (that determines secondary oxidation products containing the carbonyl function). A reference database was constructed for the oils in order to compare batches of oils for their overall quality including oxidative stability. For some of the speciality oils, the stereochemistry of the triacylglycerols was determined. Calophyllum, Coffee, Poppy and Sea Buckthorn oils stereochemistry was determined. The oils were enriched with saturated and/or a monounsaturated fatty acids at position sn-1 and sn-3. The sn-2 position of the four oils was esterified with a polyunsaturated and/or a monounsaturated fatty acid indicating that they follow a typical acylation pathway and no novel acylation activity was evident from these studies (e.g enrichment of saturates at the sn-2 position). The oxidative stability of the oils was evaluated at 18oC and 60oC and the effect of adding a-tocopherol at commercially used level i.e 750ppm was assessed. The addition of 750ppm of a-tocopherol at 18oC increased the oxidative stability of Brown flax, Moringa, Wheat germ and Yangu oils. At 60oC Brown Flax, Manketti and Pomegranate oil polymerised after 48 hours. The addition of 750ppm a-tocopherol delayed the onset of polymerisation by up to 48 hours in Brown Flax seed oil. Pomegranate oil showed a high resistance to oxidation, and was blended into other speciality oils at 1%. Pomegranate oil increased the oxidative stability of Yangu oil at 18oC. The addition of Pomegranate oil to Wheat germ oil at 60oC, decreased the peroxide content by 10%. In Manketti and Brown Flaxseed oil at elevated temperatures, Pomegranate oil delayed the onset of polymerisation. Preliminary studies of Pomegranate oil blending to Moringa and Borage oil showed it to be more effective than a-tocopherol for certain oils. The antioxidant effects observed following the addition of Pomegranate oil may be due to its conjugated linolenic acid fatty acid, punicic acid.

Rotational and centration stability of an aspheric intraocular lens with a simulated toric design

Purpose: To assess the stability of the Akreos AO intraocular lens (IOL) platform with a simulated toric design using objective image analysis. Setting: Six hospital eye clinics across Europe. Methods: After implantation in 1 eye of patients, IOLs with orientation marks were imaged at 1 to 2 days, 7 to 14 days, 30 to 60 days, and 120 to 180 days. The axis of rotation and IOL centration were objectively assessed using validated image analysis. Results: The study enrolled 107 patients with a mean age of 69.9 years ± 7.7 (SD). The image quality was sufficient for IOL rotation analysis in 91% of eyes. The mean rotation between the first day postoperatively and 120 to 180 days was 1.93 ± 2.33 degrees, with 96% of IOLs rotating fewer than 5 degrees and 99% rotating fewer than 10 degrees. There was no significant rotation between visits and no clear bias in the direction of rotation. In 71% of eyes, the dilation and image quality was sufficient for image analysis of centration. The mean change in centration between 1 day and 120 to 180 days was 0.21 ± 0.11 mm, with all IOLs decentering less than 0.5 mm. There was no significant decentration between visits and no clear bias in the direction of the decentration. Conclusion: Objective analysis of digital retroillumination images taken at different postoperative periods shows the aspheric IOL platform was stable in the eye and is therefore suitable for the application of a toric surface to correct corneal astigmatism.

An investigation into the wavelength stability of polymer optical fibre Bragg gratings

The inscription of Bragg gratings has been demonstrated in PMMA-based polymer optical fibre. The water affinity of PMMA can introduce significant wavelength change in a polymer optical fibre Bragg grating (POFBG). In polymer optical fibre losses are much higher than with silica fibre. Very strong absorption bands related to higher harmonics of vibrations of the C-H bond dominate throughout the visible and near infrared. Molecular vibration in substances generates heat, which is referred to as the thermal effect of molecular vibration. This means that a large part of the absorption of optical energy in those spectral bands will convert into thermal energy, which eventually drives water content out of the polymer fibre and reduces the wavelength of POFBG. In this work we have investigated the wavelength stability of POFBGs in different circumstances. The experiment has shown that the characteristic wavelength of a POFBG starts decreasing after a light source is applied to it. This decrease continues until equilibrium inside the fibre is established, depending on the initial water content inside the fibre, the surrounding humidity, the optical power applied, and the fibre size. Our investigation has shown that POFBGs operating at around 850 nm show much smaller wavelength reduction than those operating at around 1550 nm in the same fibre; POFBGs with different diameters show different changes; POFBGs powered by a low level light source, or operating in a very dry environment are least affected by this thermal effect.

Results of the IEA round robin on viscosity and stability of fast pyrolysis bio-oils

An international round robin study of the stability of fast pyrolysis bio-oil was undertaken. Fifteen laboratories in five different countries contributed. Two bio-oil samples were distributed to the laboratories for stability testing and further analysis. The stability test was defined in a method provided with the bio-oil samples. Viscosity measurement was a key input. The change in viscosity of a sealed sample of bio-oil held for 24 h at 80 °C was the defining element of stability. Subsequent analyses included ultimate analysis, density, moisture, ash, filterable solids, and TAN/pH determination, and gel permeation chromatography. The results showed that kinematic viscosity measurement was more generally conducted and more reproducibly performed versus dynamic viscosity measurement. The variation in the results of the stability test was great and a number of reasons for the variation were identified. The subsequent analyses proved to be at the level of reproducibility, as found in earlier round robins on bio-oil analysis. Clearly, the analyses were more straightforward and reproducible with a bio-oil sample low in filterable solids (0.2%), compared to one with a higher (2%) solids loading. These results can be helpful in setting standards for use of bio-oil, which is just coming into the marketplace. © 2012 American Chemical Society.

Stability of anthracycline cytotoxic agents in solution and infusion fluids

DUE TO COPYRIGHT RESTRICTIONS ONLY AVAILABLE FOR CONSULTATION AT ASTON UNIVERSITY LIBRARY AND INFORMATION SERVICES WITH PRIOR ARRANGEMENT

Magnetohydrodynamic stability of stochastically driven accretion flows

We investigate the evolution of magnetohydrodynamic (or hydromagnetic as coined by Chandrasekhar) perturbations in the presence of stochastic noise in rotating shear flows. The particular emphasis is the flows whose angular velocity decreases but specific angular momentum increases with increasing radial coordinate. Such flows, however, are Rayleigh stable but must be turbulent in order to explain astrophysical observed data and, hence, reveal a mismatch between the linear theory and observations and experiments. The mismatch seems to have been resolved, at least in certain regimes, in the presence of a weak magnetic field, revealing magnetorotational instability. The present work explores the effects of stochastic noise on such magnetohydrodynamic flows, in order to resolve the above mismatch generically for the hot flows. We essentially concentrate on a small section of such a flow which is nothing but a plane shear flow supplemented by the Coriolis effect, mimicking a small section of an astrophysical accretion disk around a compact object. It is found that such stochastically driven flows exhibit large temporal and spatial autocorrelations and cross-correlations of perturbation and, hence, large energy dissipations of perturbation, which generate instability. Interestingly, autocorrelations and cross-correlations appear independent of background angular velocity profiles, which are Rayleigh stable, indicating their universality. This work initiates our attempt to understand the evolution of three-dimensional hydromagnetic perturbations in rotating shear flows in the presence of stochastic noise. © 2013 American Physical Society.

Linear stability of flow past two circular cylinders in a side-by-side arrangement

The linear stability of flow past two circular cylinders in a side-by-side arrangement is investigated theoretically, numerically and experimentally under the assumption of a two-dimensional flow field, in order to explore the origin of in-phase and antiphase oscillatory flows. Steady symmetric flow is realized at a small Reynolds number, but becomes unstable above a critical Reynolds number though the solution corresponding to the flow still satisfies the basic equations irrespective of the magnitude of the Reynolds number. We obtained the solution numerically and investigated its linear stability. We found that there are two kinds of unstable modes, i.e., antisymmetric and symmetric modes, which lead to in-phase and antiphase oscillatory flows, respectively. We determined the critical Reynolds numbers for the two modes and evaluated the critical distance at which the most unstable disturbance changes from the antisymmetric to the symmetric mode, or vice versa. ©2005 The Physical Society of Japan.

Thermal stability of sputter-deposited 330 austenitic stainless-steel thin films with nanoscale growth twins

We have explored the thermal stability of nanoscale growth twins in sputter-deposited 330 stainless-steel (SS) films by vacuum annealing up to 500 °C. In spite of an average twin spacing of only 4 nm in the as-deposited films, no detectable variation in the twin spacing or orientation of twin interfaces was observed after annealing. An increase in the average columnar grain size was observed after annealing. The hardness of 330 SS films increases after annealing, from 7 GPa for as-deposited films to around 8 GPa for annealed films, while the electrical resistivity decreases slightly after annealing. The changes in mechanical and electrical properties after annealing are interpreted in terms of the corresponding changes in the residual stress and microstructure of the films. © 2005 American Institute of Physics.

Evaluation of the activity and stability of alkali-doped metal oxide catalysts for application to an intensified method of biodiesel production

A series of alkali-doped metal oxide catalysts were prepared and evaluated for activity in the transesterification of rapeseed oil to biodiesel. Of those evaluated, LiNO3/CaO, NaNO3/CaO, KNO3/CaO and LiNO3/MgO exhibited >90% conversion in a standard 3 h test. There was a clear correlation between base strength and activity. These catalysts appeared to be promising candidates to replace conventional homogeneous catalysts for biodiesel production as the reaction times are low enough to be practical in continuous processes and the preparations are neither prohibitively difficult nor costly. However, metal leaching from the catalyst was detected, and this resulted in some homogeneous activity. This would have to be resolved before these catalysts would be viable for large-scale biodiesel production facilities.

Stability of multi-agent systems

This work attempts to shed light to the fundamental concepts behind the stability of Multi-Agent Systems. We view the system as a discrete time Markov chain with a potentially unknown transitional probability distribution. The system will be considered to be stable when its state has converged to an equilibrium distribution. Faced with the non-trivial task of establishing the convergence to such a distribution, we propose a hypothesis testing approach according to which we test whether the convergence of a particular system metric has occurred. We describe some artificial multi-agent ecosystems that were developed and we present results based on these systems which confirm that this approach qualitatively agrees with our intuition.

Comparison of fitting stability of the different soft toric contact lenses

Purpose: To compare lens orientation and rotational recovery of five currently available soft toric lenses. Methods: Twenty subjects were recruited and trialed with each of the study lenses in a random order. Study lenses were PureVision® Toric (B&L), Air Optix® for Astigmatism (Alcon), Biofinity® Toric (CooperVision), Acuvue® Advance for Astigmatism (Vistakon), and Proclear® Toric (CooperVision). Lens orientation in primary position to determine the lens rotation form the vertical position and rotational recovery to primary gaze orientation following a 45° manual misorientation for the different lenses was compared. Results: The Biofinity Toric showed the lowest rotation from the vertical position and the Proclear Toric the highest. Also, the highest and the lowest reorientation speed were related to the Biofinity Toric and the Acuvue Advance for Astigmatism, respectively. The Repeated Measures ANOVA showed a significant difference in the lens rotation (P=. 0.004) and rotational recovery (P<. 0.001) among different contact lenses and the performed multiple comparisons indicated differences in rotation and also in reorientation speed were only seen between the Biofinity Toric when compared to four other lenses (P<. 0.05). Conclusion: Although there was appropriate fitting, based upon lens orientation and reorientation speed, with each of the study lenses it would appear that the optimized ballast technique used in the design of the Biofinity Toric helps reduce lens rotation and improve rotational recovery compared to others.

An investigation into the wavelength stability of polymer optical fibre Bragg gratings

The inscription of Bragg gratings has been demonstrated in PMMA-based polymer optical fibre. The water affinity of PMMA can introduce significant wavelength change in a polymer optical fibre Bragg grating (POFBG). In polymer optical fibre losses are much higher than with silica fibre. Very strong absorption bands related to higher harmonics of vibrations of the C-H bond dominate throughout the visible and near infrared. Molecular vibration in substances generates heat, which is referred to as the thermal effect of molecular vibration. This means that a large part of the absorption of optical energy in those spectral bands will convert into thermal energy, which eventually drives water content out of the polymer fibre and reduces the wavelength of POFBG. In this work we have investigated the wavelength stability of POFBGs in different circumstances. The experiment has shown that the characteristic wavelength of a POFBG starts decreasing after a light source is applied to it. This decrease continues until equilibrium inside the fibre is established, depending on the initial water content inside the fibre, the surrounding humidity, the optical power applied, and the fibre size. Our investigation has shown that POFBGs operating at around 850 nm show much smaller wavelength reduction than those operating at around 1550 nm in the same fibre; POFBGs with different diameters show different changes; POFBGs powered by a low level light source, or operating in a very dry environment are least affected by this thermal effect.