| 1. |
- Allen, LT, et al.
(författare)
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Interaction of soft condensed materials with living cells: Phenotype/transcriptome correlations for the hydrophobic effect
- 2003
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - 0027-8424 .- 1091-6490. ; 100, s. 6331-6336
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Tidskriftsartikel (refereegranskat)abstract
- The assessment of biomaterial compatibility relies heavily on the analysis of macroscopic cellular responses to material interaction. However, new technologies have become available that permit a more profound understanding of the molecular basis of cell-biomaterial interaction. Here, both conventional phenotypic and contemporary transcriptomic (DNA microarray-based) analysis techniques were combined to examine the interaction of cells with a homologous series of copolymer films that subtly vary in terms of surface hydrophobicity. More specifically, we used differing combinations of N-isopropylacrylamide, which is presently used as an adaptive cell culture substrate, and the more hydrophobic, yet structurally similar, monomer N-tert-butylacrylamide. We show here that even discrete modifications with respect to the physiochemistry of soft amorphous materials can lead to significant impacts on the phenotype of interacting cells. Furthermore, we have elucidated putative links between phenotypic responses to cell-biomaterial interaction and global gene expression profile alterations. This case study indicates that high-throughput analysis of gene expression not only can greatly refine our knowledge of cell-biomaterial interaction, but also can yield novel biomarkers for potential use in biocompatibility assessment
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| 2. |
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| 3. |
- Andersson, M., et al.
(författare)
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A New Class of Labile Surfactants that Break Down to Non-surface Active Products upon Heating or after a Pre-set Time, without the Need for a pH Change
- 2007
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Ingår i: Tenside Surfactants Detergents. - : Walter de Gruyter GmbH. - 0932-3414 .- 2195-8564. ; 44:6, s. 366-372
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Tidskriftsartikel (refereegranskat)abstract
- A new class of labile surfactants that break down at a controllable rate without the need for a change in pH will be presented. The invention has been patented by YKI Institute for Surface Chemistry, and is based on use of β-keto acids or their salts as surface-active compounds. These surfactants spontaneously break down through decarboxylation, to form an oil-like ketone and CO 2/HCO 3 -/CO 32 - depending on pH. The rate of breakdown can be controlled within a wide range by temperature or by certain additives, but, unlike most cleavable surfactants, a change in pH is not needed. Furthermore the surfactants can be conveniently activated from a stabile precursor just before use, and one (of many possible) precursors of this kind is already available on the industrial scale in the form of a wellknown chemical that is FDA-approved in other, non-surfactant, applications. The compound in question, alkyl ketene dimer (AKD), is produced in large scale by a number of large chemical producers today, and used for hydrophobization of paper. The present article gives an overview of the surfactant chemistry, with focus on recent studies of the kinetics of activation of the surfactant precursor and breakdown kinetics of the labile surfactant at different conditions. Furthermore, possible industrial applications of the surfactant will be discussed, with one example taken from a recent feasibility study performed within the car washing area. © Carl Hanser Publisher.
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| 4. |
- Blute, I, et al.
(författare)
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Phase behaviour of alkyl glycerol ether surfactants
- 1998
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Ingår i: Tenside Surfactants Detergents. - 0932-3414 .- 2195-8564. ; 35, s. 207-212
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Tidskriftsartikel (refereegranskat)abstract
- In this paper the phase behaviour and physical properties of a series of alkyl (C6, C8, C12 and iso-C8) monoglycerol ethers and 2-hydroxyalkyl (C6, C8, C12) monoglycerol ethers are presented. The binary phase diagram for the surfactants shows very little dependence on temperature. It is shown that as the alkyl chain length increases the tendency to form lamellar liquid crystalline phases increases. The branched alkyl chain shows no formation of lamellar phase even at high concentrations of surfactant. The differences in phase behaviour between the surfactants is attributed to the variation in the critical packing parameter (CPP) of the surfactants. The presence of an additional hydroxyl group in the alkyl chain causes a temperature independent solubility behaviour. Ternary phase diagrams were prepared using dodecane as the oil phase. Hexyl glycerol ether was the only of the alkyl glycerol ethers which was sufficiently water soluble to determine the surface tension and CMC. The CMC was determined to 15 mM (and surface tension to 26 mN m-1).
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| 5. |
- Blute, I, et al.
(författare)
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Solution behavior of a surfactant aldehyde – the oxidation product of an alcohol ethoxylate
- 1999
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Ingår i: Colloids and Surfaces A. - 0927-7757 .- 1873-4359. ; 150, s. 105-113
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Tidskriftsartikel (refereegranskat)abstract
- It has previously been shown that alcohol ethoxylates readily undergo autoxidation and that one of the major oxidation products is the surfactant aldehyde, i.e. an ethoxylate carrying a –CH2CHO group at the terminal end of the polyoxyethylene chain. In this work the cloud point, phase behavior and aggregation characteristics of the surfactant aldehyde produced by oxidation of C12H25(OCH2CH2)50H(CI2E5) are determined and compared with the values obtained with the parent surfactant. It was found that the physico-chemical behavior of the two species was very similar, which indicates that a considerable portion of the aldehyde group is in hydrated state, i.e. the surfactant aldehyde consists of a mixture of aldehyde in carbonyl form and the corresponding geminal diol. The cloud point of the surfactant aldehyde decreased rapidly with time, even when it was stored at low temperature. Also the parent surfactant and its homologue C12E6 exhibited a decrease in cloud point during storage. For instance, a 1% aqueous solution of C12E6 showed a cloud point decrease from 62 to 32°C after 4 months storage at 40°C. Such a change in solution behavior can have important practical implications.
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| 6. |
- Blute, I, et al.
(författare)
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Solution behaviour of a formate capped surfactant - the oxidation product of an alcohol ethoxylate.
- 1999
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Ingår i: Colloids and Surfaces A. - 0927-7757 .- 1873-4359. ; 160, s. 229-236
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Tidskriftsartikel (refereegranskat)abstract
- The solution behaviour has been investigated for an alcohol ethoxylate terminated with a formic acid ester. This compound has previously been reported to be an important degradation product in the auto-oxidation of alcohol ethoxylates. In this work we have investigated the solution behaviour of the formic acid ester surfactant C12H25(OCH2CH2)4OCHO (C12E4-OCHO). The pure formate was found to be sparsely soluble in water with no clear point at 0.1%. The critical micelle concentration was found to be 129 µM at 35°C, compared to 50 µM for the parent surfactant C12H25(OCH2CH2)5OH (C12E5). To mimic the behaviour of the oxidised surfactant, the formate was mixed in different ratios with C12E5 and the cloud point, surface tension and critical micelle concentration of these mixtures were studied. The gradual increase of formate was found to shift the cloud point and isotropic regions to lower temperatures. The cmc of the mixture was found to be lower than for the pure surfactant. The favourable interaction was analysed according to the non-ideal model by Rubingh and the interaction parameter, b, was determined to be -4, which is unusually large for a mixture of two nonionic surfactants. These results indicate that the reduction of cloud point observed during oxidation of nonionic surfactants can in part be attributed to the formation of formate esters.
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| 7. |
- Blute, I, et al.
(författare)
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The molecular mechanism for destabilization of foams by organic ions
- 1994
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Ingår i: Journal of the American Oil Chemists Society. - 0003-021X .- 1558-9331. ; 71, s. 41-46
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Tidskriftsartikel (refereegranskat)abstract
- The destabilization of foams by electrolytes with tetraalkylammonium ions has been investigated. The presence of large tetraalkylammonium ions at the oil/water interface perturbs the packing of surfactants, producing noncoherent films of low stability. A comparison between the foam destabilizing efficiency of tetraalkylammonium bromide salts with tributyl phosphate and 2-ethyl hexanol, which are used in many commercial antifoaming formulations, demonstrated that the organic salts have a potential for being useful in technical applications involving foam inhibition.
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| 8. |
- Carlfors, J, et al.
(författare)
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Lidocaine in microemulsion - A dermal delivery system
- 1991
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Ingår i: Journal of Dispersion Science and Technology. - 0193-2691 .- 1532-2351. ; 12, s. 467-482
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Tidskriftsartikel (refereegranskat)abstract
- In order to obtain a microemulsion that is stable at skin tempeature, the regions of existance of microemulsions of water and isoproptyl myristate were studied as a function of hydrophilelipophile balance (HLB) of nonionic surfactant mixtures. The microemulsion dissolves large amount of the local anaesthetic lidocaine. The amount of dissolved lidocaine in the microemulsion was proportional to the isopropyl myristate content and limited to its solubility in this solvent. The addition of lidocaine lowered the phase inversion temperature (PIT) of the system and increased the temperature range for microemulsion stability. The structure of the microemulsion, as investigated by proton Fourier transform pulsed-gradient spin-echo NMR spectroscopy, was found to be bicontinous. The physico-chemical properties of the microemulsion as well as the low toxicity of its components result in formulation intendend for topical administation.
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| 9. |
- Friberg, SE, et al.
(författare)
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Foam Stability In A Glycerol System
- 1989
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Ingår i: Journal of Colloid and Interface Science. - 0021-9797 .- 1095-7103. ; 127, s. 573-582
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Tidskriftsartikel (refereegranskat)
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| 10. |
- Friberg, SE, et al.
(författare)
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Hydrotropes – performance chemicals
- 2004
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Ingår i: Journal of Dispersion Science and Technology. - 0193-2691 .- 1532-2351. ; 25, s. 243-251
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Tidskriftsartikel (refereegranskat)abstract
- The action of hydrotropes is reviewed emphasizing their influence in the formation of microemulsions, vesicle solutions and other products involving surfactant association structures. It is demonstrated that the hydrotropes, the association structures of which, realistically, can only be described as trivial, actually, are powerful and sophisticated performance chemicals playing an essential role in complex applied formulations utilizing more composite amphiphilic association structures
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| 11. |
- Friberg, S, et al.
(författare)
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Stability of hydrophobic foams
- 1986
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Ingår i: Langmuir. - 0743-7463 .- 1520-5827. ; 2, s. 659-664
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Tidskriftsartikel (refereegranskat)
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| 12. |
- Gilcreest, VP, et al.
(författare)
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Thermoresponsive poly(N-isopropylacrylamide) copolymers: Contact angles and surface energies of polymer films
- 2004
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Ingår i: Langmuir. - 0743-7463 .- 1520-5827. ; 20, s. 10138-10145
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Tidskriftsartikel (refereegranskat)abstract
- Surface properties of poly(N-isopropylacrylamide) (PNIPAM) copolymer films were studied by contact angle measurements and optical and atomic force microscopy. We prepared a series of copolymers of N-isopropylacrylamide with N-tert-butylacrylamide (NtBA) in order of increasing hydrophobicity. The measurements of the advancing contact angle of water at 37°C were hampered by the observation of a distinct stick/slip pattern on all polymers in the series with the exception of poly(NtBA) (PNtBA). We attributed this behavior to the film deformation by the vertical component of liquid surface tension leading to the pinning of the moving contact line. This was confirmed by the observation of a ridge formed at the pinned contact line by optical microscopy. However, meaningful contact (without the stick/slip pattern andwith a time-independent advancing contact angle) angles for this thermoresponsive polymer series could be obtained with carefully selected organic liquids. We used the Li and Neumann equation of state to calculate the surface energy and contact angles of water for all polymers in the series of copolymers and van Oss, Chaudhury, and Good (vOCG) acid-base theory for PNtBA. The surface energies of the thermoresponsive polymers were in the range of 38.9 mJ/m2 (PNIPAM) to 31 mJ/m2 (PNtBA) from the equation of state approach. The surface energy of PNtBA calculated using vOCG theory was 29.0 mJ/m2. The calculated contact angle for PNIPAM (74.5 ± 0.2°) is compared with previously reported contact angles obtained for PNIPAM-modified surfaces.
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| 13. |
- Lynch, I, et al.
(författare)
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Correlation of the adhesive properties of cells to N-iso-propylacrylamide/N-tert-butylacrylamide copolymer surfaces with changes in the surface structure using contact angle measurements, molecular simulations and Raman spectroscopy
- 2005
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Ingår i: Chemistry of Materials. - 0897-4756 .- 1520-5002. ; 17, s. 3889-3898
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Tidskriftsartikel (refereegranskat)abstract
- A series of copolymers of N-isopropylacrylamide (NIPAM) and the more hydrophobic comonomer N-tert-butylacrylamide (NTBAM), with increasing NTBAM content (i.e. increasing hydrophobicity) were prepared. The adhesion of human endothelial cells on polymer films prepared from copolymers of NIPAM:NTBAM was observed to increase with increasing polymer hydrophobicity. However, in the absence of serum, cell adhesion to the different surfaces was statistically indistinguishable. Thus, it appears that the copolymer films differentially support cell adhesion due to selective adsorption of proteins from the physiological environment (the serum). Using contact angle measurements, molecular simulations and Raman spectroscopy to characterize the different surfaces, we show evidence that the different behavior of the films of increasing hydrophobicity is actually due to the different chemical properties of the surfaces with increasing content of NTBAM in the copolymers. As the NTBAM content is increased, the number of NH residues at the surface decreases, due to the additional steric hindrance of the bulkier NTBAM group, which results in decreased hydrogen bonding and thus decreased adsorption of proteins such as albumin. However, in some cases, the adsorption is driven by hydrophobic interactions, and proteins such as fibronectin were found to adsorb more to the films with a higher content of NTBAM. There appears, thus, to be a direct correlation between surface composition and protein binding and the subsequent cell adhesion.
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| 14. |
- Lynch, Iseult, et al.
(författare)
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Correlation of the adhesive properties of cells to N-isopropylacrylamide/N-tert-butylacrylamide copolymer surfaces with changes in surface structure using contact angle measurements, molecular simulations, and Raman spectroscopy
- 2005
-
Ingår i: Chemistry of Materials. - : American Chemical Society (ACS). - 0897-4756 .- 1520-5002. ; 17:15, s. 3889-3898
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Tidskriftsartikel (refereegranskat)abstract
- A series of copolymers of N-isopropylacrylamide (NIPAM) and the more hydrophobic comonomer N-tert-butylacrylamide (NTBAM), with increasing NTBAM content (i.e., increasing hydrophobicity) were prepared. The adhesion of human epithelial cells on polymer films prepared from copolymers of NIPAM: NTBAM was observed to increase with increasing polymer hydrophobicity. However, in the absence of serum, cell adhesion to the different surfaces was statistically indistinguishable. Thus, it appears that the copolymer films differentially support cell adhesion due to selective adsorption of proteins from the physiological environment (the serum). Using contact angle measurements, molecular simulations, and Raman spectroscopy to characterize the different surfaces, we show evidence that the different behavior of cells on the films of increasing hydrophobicity is actually due to the different chemical properties of the surfaces with increasing content of NTBAM in the copolymers. As the NTBAM content is increased, the number of NH residues at the surface decreases, due to the additional steric hindrance of the bulkier NTBAM group, which results in decreased hydrogen bonding and thus decreased adsorption of proteins such as albumin. However, in some cases, the adsorption is driven by hydrophobic interactions, and proteins such as fibronectin were found to adsorb more to the films with a higher content of NTBAM. There appears, thus, to be a direct correlation between surface composition, i.e., the functional groups exposed at the surface, and protein binding and subsequent cell adhesion.
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| 15. |
- Piispanen, PS, et al.
(författare)
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Synthesis and characterization of surface-active compounds derived from cholesterol derivatives and glucose
- 2002
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Ingår i: Journal of Surfactants and Detergents (JSD). - 1097-3958 .- 1558-9293. ; 5, s. 345-351
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Tidskriftsartikel (refereegranskat)abstract
- The synthesis and characterization of surface-active compounds based on various steroid derivatives and glucose are presented. The hydrophobic and hydrophilic parts of the compounds were linked via glucosidic bonds. All compounds were found to have very low water solubility and only limited solubility in various organic solvents. The compounds were investigated according to their ability to interact with an anionic surfactant, sodium dodecylsulfate (SDS), in order to induce a decrease in the critical micelle concentration (CMC) of the surfactants. This synergistic effect was pronounced for cholestanol-6-on-ß-d-glucopyranoside and for cholestan-3,6-diol-ß-d-glucopyranoside. These two compounds lowered the CMC from 8 to 6 and 0.6 mM, respectively, for water solutions of SDS/glucoside with a molar ratio of 92:8. Furthermore, the ability of the compounds to stabilize lipid membranes, in liposomes, at varying concentrations of Ca2+, was studied. The compounds were, as expected, found to induce stabilization similar to that of cholesterol
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