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| 3. |
- Burns, NL, et al.
(författare)
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Influence of surface charge on protein adsorption at an amphoteric surface: effects of varying acid to base ratio
- 1996
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Ingår i: Journal of Colloid and Interface Science. - 0021-9797 .- 1095-7103. ; 177, s. 116-122
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Tidskriftsartikel (refereegranskat)abstract
- Plasma polymerization of 1,2-diaminocyclohexane (DACH) results in an amino functional surface which is not stable under ambient conditions. The aging process has previously been assumed to be an oxidation initiated by residual polymer radicals. We here propose that the surface process is not an oxidation but a carboxylation. Primary amino groups react with atmospheric carbon dioxide to give carbamate groups which are stabilized by salt formation with adjacent ammonium groups. We have used a novel electrokinetic technique to measure electroosmosis and monitor the aging process. While the total number of ionizable surface groups was constant, a gradual change in the ratio of basic to acid sites at the surface was found. After 64 days the ratio of was almost 1:1. This amphoteric surface which spontaneously changed its ratio of basic to acid sites was used as substrate to investigate effect of surface charge on adsorption of two proteins, human serum albumin (HSA) and lysozyme. It was found that lysozyme adsorbs in much higher amounts than HSA irrespective of the charge at the surface. Whereas adsorption of HSA was not dependent on the change in surface charge, adsorption of lysozyme decreased with aging, i.e. as the ratio of acid to base sites at the surface approached unity. An interesting finding was that more lysozyme was adsorbed the more positively charged the surface, even at pH values where the protein carried a strong net positive charge.
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| 4. |
- Burns, NL, et al.
(författare)
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Surface charge characterization and protein adsorption at biomaterials surfaces
- 1996
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Ingår i: Progress in Colloid and Polymer Science. - 0340-255X .- 1437-8027. ; 100, s. 271-275
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Tidskriftsartikel (refereegranskat)abstract
- In an effort to more fully understand the nature of protein adsorption, and the role adsorbed proteins have in mediating interfacial processes in biomaterial application, effect of surface charge is being explored. For this purpose, a novel electrokinetic technique whereby electroososmosis is measured at flat plates is being used to characterize surfaces with respect to effective surface charge and origin of charge. Protein adsorption is monitored by in situ ellipsometry or by an enzyme linked immunosorbent assay (ELISA). Correlations can then be made between the observed surface properties and biological response to the surface, including bacterial adherence and complement activation of blood proteins. Surfaces studied include a wide variety of radio frequency plasma polymers, and polysiloxane modified surfaces; all of interest as biomaterials. The plasma polymer surfaces are being used as model surfaces to study protein mediated bacterial adherence. Siloxane polymer coatings are being used to interfere with salivary pellicle and plaque formation on teeth, with different patterns in the adherence of oral bacteria observed with different polysiloxanes. In the above systems, patterns in protein adsorption related to surface charge and functionality, as well as other surface properties, can be identified. It appears that surface charge and charging properties are important factors in formation of biofilms.
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| 5. |
- Olsson, J, et al.
(författare)
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Modified pellicle formation and reduced in vitro bacterial adherence after surface treatment with different siloxane polymers
- 1995
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Ingår i: Colloids and Surfaces B. - 0927-7765 .- 1873-4367. ; 5, s. 161-169
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Tidskriftsartikel (refereegranskat)abstract
- Formation of salivary pellicles is a prerequisite of bacterial colonization on the tooth and the aim of this study has been to further the understanding of the role of surface properties in formation of the salivary pellicle and subsequent adhesion of oral bacteria. Surface modification as a means of interfering with pellicle and plaque formation has been investigated. Five different silicone-containing compounds were used for the surface treatments: polydimethylsiloxane containing aminoalkyl groups (I), polydimethylsiloxane containing partially neutralized aminoalkyl groups (II), ethyl silicate (III), potassium methyl siliconate (IV) and sodium silicate (V). Studies of water wetting, surface charge, oral bacterial adherence, pellicle and plaque formation were performed on glass slides, hydroxyapatite beads or teeth coated by the test compounds. No correlation was found between contact angle and surface charge, and evidently hydrophobicity, as expressed by water wetting, is not necessarily an indicaton of a low surface concentration of polar groups. All compounds reduced bacterial adherence after saliva contact, compound IV by around 90%. Different patterns were seen in the adsorption of pellicle proteins on the different polysiloxanes. Clinical experiments, however, did not reveal any significant differences in plaque formation.
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| 6. |
- Thomas, N, et al.
(författare)
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Osiris - The optical, spectroscopic and infrared remote imaging system for the Rosetta orbiter
- 1998
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Ingår i: SPACE EXPLORATION OF THE OUTER SPACE SOLAR SYSTEM AND COMETARY NUCLEI. - : PERGAMON PRESS LTD. - 0273-1177. ; 21:11, s. 1505-1515
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- The scientific objectives, design, and implementation of the Optical, Spectroscopic, and Infrared Remote Imaging System (OSIRIS) for the International Rosetta Mission are described. The instrument comprises two camera systems with a common electronics box
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- TINDELL, K, et al.
(författare)
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ANALYSIS OF HARD REAL-TIME COMMUNICATIONS
- 1995
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Ingår i: REAL-TIME SYSTEMS. - : KLUWER ACADEMIC PUBL. - 0922-6443. ; 9:2, s. 147-171
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- In a distributed hard real-time system, communications between tasks on different processors must occur in bounded time. The inevitable communication delay is composed of both the delay in transmitting a message on the communications media, and also the d
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