Biomedical subjects

Gro Smistad

Publications and source records attributed to Gro Smistad.

7 recordsLinked to original sources

PubMed2006

Multivariate toxicity screening of liposomal formulations on a human buccal cell line.

The influence of various formulation factors on the in vitro cellular toxicity of liposomes on human buccal cells (TR146), were studied by using the concept of statistical experimental design and multivariate evaluation. The factors investigated were the type of main phospholipid (egg-PC, DMPC, DPPC), lipid concentration, the type of charge, liposome size, and amount and nature of the charged component (diacyl-PA, diacyl-PG, diacyl-PS, stearylamine (SA), diacyl-TAP) in the liposomes. Both full factorial design and D-optimal designs were created. Several significant main factors and interactions were revealed. Positively charged liposomes were shown to be toxic. The toxicity of negatively charged liposomes was relatively low. Diacyl-TAP was less toxic than SA, and DPPC was less toxic than DMPC. Low level of positively charged component was favourable and essential when using egg-PC as the main lipid. The amount of negatively charged component, the liposome size, and the total lipid concentration did not affect the toxicity within the experimental room. DPPC appeared to be a good candidate when formulating both positively and negatively charged liposomes with low cellular toxicity. The concept of statistical experimental design and multivariate evaluation was shown to be a useful approach in cell toxicity screening studies.

Cell Line, Tumor↗

PubMed2005

Transfection efficiency and cytotoxicity of cationic liposomes in primary cultures of rainbow trout (Oncorhynchus mykiss) gill cells.

Immunisation of fish by immersion has been applied for inactivated, whole cell bacterins, where the gill epithelial cells are considered as one of the prime uptake sites. Antigen entry is a critical factor for delivery of vaccine antigens through the immersion route, also for DNA vaccines, and delivery systems like cationic liposomes may enhance uptake. In this study, the aim was to examine the efficiency of cationic liposomes as a means to transfect primary cultures of rainbow trout gill cells with plasmids encoding viral or reporter proteins. Furthermore, the effects of the concentration and composition of liposomes/lipoplex on the viability of the cells were evaluated. Transfection of the gill cells was possible with both plasmids following transfection with lipoplexes of a neutral charge. Low concentrations and neutral/negatively charged formulations were favourable with respect to the toxicity of the formulations. Given that the mucous barrier covering the gills is overcome, this system might be useful for the priming of the local immunity in the fish gills.

Animals↗

PubMed2004

Long-term stability of chitosan-based polyplexes.

PURPOSE: There is a lack of information about the long-term stability of chitosan-based polyplexes although a large amount is known as regards transfection efficiency and physicochemical characteristics. The aim of this work is to study the transfection efficiency and physicochemical properties of chitosan-based polyplexes over time when stored at different temperatures in an acetate-buffer at pH 5.5. METHODS: Aqueous samples of chitosan-based polyplexes were aged at 4 degrees C, 25 degrees C, and 45 degrees C for up to 1 year. Samples were taken at predetermined time-points and evaluated for in vitro transfection efficiency and physiochemical properties (particle size, zeta potential). RESULTS: One year of storage at 4 degrees C did not result in any major changes in the properties of the polyplexes. At 25 degrees C there were minor changes in the physicochemical characteristics of the polyplexes, and the in vitro transfection efficiency was reduced at 1 year of storage. Storage at 45 degrees C altered both the in vitro transfection efficiency and the physicochemical properties of the polyplexes after a short time. CONCLUSIONS: The biological and physicochemical stability of the chitosan-based polyplexes are maintained for 1 year of storage in acetate-buffer at 4 degrees C. The changes in the polyplex characteristics at elevated temperatures may be explained by degradation of both plasmid and chitosan.

Animals↗

PubMed2003

The influence of formulation variables on in vitro transfection efficiency and physicochemical properties of chitosan-based polyplexes.

The aim of this study was to investigate how a selection of formulation variables affects the in vitro transfection efficiency and physicochemical properties (particle size, zetapotential and chitosan-plasmid association) of chitosan-based polyplexes. Experimental designs in combination with multivariate data analysis were applied to reveal the effects of the formulation variables on the responses. The following formulation variables were studied: molecular weight and degree of acetylation of chitosan, pH and ionic strength of the buffer in which chitosan was dissolved, charge ratio of polyplexes, plasmid concentration and inclusion of a coacervation agent in the plasmid solution. The in vitro transfection efficiency in Epithelioma papulosum cyprini (EPC) cells was affected by the polyplex charge ratio, the DNA concentration in the complexes as well as the molecular weight and degree of acetylation of the chitosans. Two favourable formulations were identified in a more thorough investigation. These formulations were made of SC113 (theoretical charge ratio 10) and SC214 (theoretical charge ratio 3). The size of the complexes was affected by the degree of acetylation, concentration of DNA, pH, inclusion of a coacervation agent and the charge ratio. The charge ratio, pH and ionic strength determined the zetapotential of the particles, while the charge ratio was important for the association between the plasmid and chitosan.

Animals↗

PubMed2003

Evaluation of different formulation studies on air-filled polymeric microcapsules by multivariate analysis.

Air-filled polymeric microcapsules have been prepared by freeze-drying of emulsions containing the wall-forming polymer in the organic phase of oil in water emulsions. Echogenic air-filled microcapsules were prepared from emulsions containing either (-)-camphene, cyclohexane or cyclooctane as the solvent in the organic phase. Formulation studies have been performed to improve the yield and acoustic quality of the microcapsule suspensions. The yield was measured as particle concentration or efficacy, i.e. normalised attenuation at 3.5 MHz, related to the amount of polymer used. No overall conclusion could be made for all the variables when visually comparing the results from the different investigations. Multivariate analyses (PCA and PLS) were therefore necessary to be able to reveal any relevant systematic information from all the investigations. Different parameters describing the formulation, the production process and parameters describing the characterisation of the intermediates and the final product were set as independent X-variables. Three to four percent (w/v) of polymer was found to be the appropriate concentration of wall forming polymer. Including PEG 3000 resulted in improved freeze-dried product and suspension. Quenching of the emulsions by freezing in dry ice/methanol prior to freeze-drying was not necessary. Process parameters for homogenising and freeze-drying should be optimised with regard to the single systems, due to the different physico-chemical properties of the different solvents, especially melting point and vapour pressure.

Air↗

PubMed2003

pH-sensitive paramagnetic liposomes for MRI: assessment of stability in blood.

The pH-dependent stability of dipalmitoyl phosphatidyl ethanolamine/palmitic acid (DPPE/PA) liposomal GdDTPA-BMA was investigated in human blood and after exposure to selected blood components. Relaxometry, visual observations and cryo-transmission electron microscopy (cryo-TEM) were employed for the assessment of stability. The liposomes were stable in buffer at physiological pH and the T(1)-relaxivity (r(1)) of the system was significantly lowered compared to that of non-liposomal GdDTPA-BMA, which could be explained by an exchange limited relaxation process. Lowering the pH, however, gave a marked increase in r(1), due to liposome aggregation and subsequent leakage of GdDTPA-BMA. After a few minutes incubation in human blood the liposomes were destabilised and leaky at both high and low pH, and blood components likely to cause the instability were studied. Physiological level of Na(+) (150 mM) did not affect the relaxometric behavior of the liposomes at pH 7.4, but shifted the pH-r(1) profile laterally to higher pH-values compared to a level of 50 mM Na(+). Increased screening of the surface charges and, concomitantly, a lowering of the energy-barrier against aggregation is a plausible explanation for this phenomenon. In contrast, both Ca(2+) and Mg(2+) (physiological level, both 2 mM) caused massive aggregation of the liposomes and leakage of contents, and were therefore much more detrimental to the stability of the liposomes than a physiological level of Na(+). This could be due to the higher screening ability of divalent cations, but aggregation could also be induced through an inter-liposomal "bridging" effect. Physiological level of both Na(+) and Ca(2+) caused less leakage than for lower Na(+) concentration (50 mM Na(+) and 2 mM Ca(2+)), probably due to competition for the negative surface charges. Albumin also destabilised the liposomes, and it was shown to be due to an interaction between albumin and PA in the liposomal membrane.

Contrast Media↗

PubMed2002

Immersion delivery of plasmid DNA. I. A study of the potentials of a liposomal delivery system in rainbow trout (Oncorhynchus mykiss) fry.

A successful regime for intramuscular injection of naked DNA is developed in fish, but the exploration of other ways of administration has not yet been studied in any detail. Immersion is a delivery route offering many advantages compared to conventional ways of administration. Applying cationic liposomes as a delivery system for DNA by this route, however, is met with severe toxicity problems. In this report, the underlying mechanisms of the acute toxicity were investigated in vivo and in vitro. The most critical factor was found to be the charge of the liposomes. Cationic liposomes above a certain threshold concentration had a lethal effect in rainbow trout fry. In contrast, similar concentrations of neutral or anionic liposomes were not toxic. Furthermore, large liposome-mucin complexes were formed upon addition of mucin to cationic liposomes. This was not observed with neutral or anionic liposomes. Lipoplexes were less toxic and interacted less with mucin compared to cationic liposomes. Hence, the mechanism of the acute toxicity in rainbow trout fry is suggested to be an interaction between the cationic liposomes and anionic components of gill mucin. The consequence is hypoxia and this is most likely the cause of acute toxicity observed in rainbow trout fry.

Animals↗