| 1. |
- Björk, Per, et al.
(författare)
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Dynamics of complex formation between biological and luminescent conjugated polyelectrolytes - a surface plasmon resonance study
- 2005
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Ingår i: Biosensors and Bioelectronics. - : Elsevier BV. - 0956-5663. ; 20:9, s. 1764-1771
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Tidskriftsartikel (refereegranskat)abstract
- A water-soluble polythiophene, POWT, with zwitterionic peptide like side chains possess good characteristics for biosensor applications. The zwitterionic side chains of the polymer can couple to biomolecules via electrostatic and hydrogen bonding. This creates possibilities to imprint biomolecules to spin-coated polymer films with maintained functionality, and use the resulting matrix as a biosensor. Polymer-biomolecular interaction studies done with surface plasmon resonance (SPR) reveal a well performing sensor matrix with high affinity for DNA hybridizations as well as for protein detection. The responses are distinct and very specific. A directional dependence of antibodies binding to POWT layer has also been observed. The polymer films have also been characterized by optical methods. Emission and absorption measurements in different buffer systems confirm that the polymer matrix can undergo structural and conformational changes on surfaces. The dielectric function in the interval 300–800 nm of POWT is reported, based on variable angle spectroscopic ellipsometry. This modeling reveals that a considerable amount of water is included in the material. The polymer layer possesses the characteristics needed for biochip applications and micro array techniques.
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| 2. |
- Filippini, Daniel, et al.
(författare)
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Computer screen photo-assisted spectral fingerprinting of luminescent polythiophene pH reporter
- 2004
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Ingår i: IEEE Sensors. Proceedings. - : IEEE. - 1930-0395 .- 2168-9229. ; 3, s. 1377-1380
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Tidskriftsartikel (refereegranskat)abstract
- The capability of the computer screen photo-assisted technique (CSPT)for the spectral fingerprinting of a photoactive polythiophene derivative (POWT) used as pH reporter is demonstrated. POWT is part of a family of industrial scalable materials, well established for organic electronics and biomedical applications, which is used here to demonstrate the capability of CSPT for tracing key spectral features. The ability of CSPTfor substance classification, corroborated by principal component analysis (PCA), successfully compares to standard spectroscopy, especially considering the involved equipments: CSPT is only a computer set and a web camera.
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| 3. |
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| 4. |
- Karlsson, Fredrik, et al.
(författare)
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Interactions between a zwitterionic polythiophene derivative and oligonucleotides as resolved by fluorescence resonance energy transfer
- 2005
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Ingår i: Chemistry of Materials. - : American Chemical Society (ACS). - 0897-4756 .- 1520-5002. ; 17:16, s. 4204-4211
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Tidskriftsartikel (refereegranskat)abstract
- The interactions between a zwitterionic polythiophene derivative, POWT, and DNA oligonucleotides in solution have been studied by FRET (fluorescence resonance energy transfer). When POWT and ssDNA are bound alone in a complex, the distance between them is at its smallest. The distance increases when adding complementary DNA, but POWT is still mainly bound to the first DNA strand. We find that two POWT chains bind to one DNA strand, and the two POWT chains seem held together in pairs, unable to separate, as they can only bind to and quench half their own amount of labeled DNA. This POWT−POWT complex appears to dissociate at lower concentrations. ssDNA attached to POWT in a complex can also be substituted by other ssDNA in solution; this occurs to 50% when the free DNA is present in 10-fold concentration compared to the ssDNA bound to POWT. Titration studies at different concentrations show positive cooperativity in the binding of POWT and ssDNA into a complex. The hybridization of complementary DNA to the same complex involves no cooperativity. These observations indicate interesting possibilities for the use of POWT as a DNA sensor.
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| 5. |
- Åsberg, Peter, et al.
(författare)
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Fluorescence quenching and excitation transfer between semiconducting and metallic organic layers
- 2004
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 96:6, s. 3140-3147
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Tidskriftsartikel (refereegranskat)abstract
- Here we present a simple approach to study the interaction of singlet excitons with polarons in conjugated polymers in organic electronic devices. Interlayer quenching constants KIL of 1.5 M−1 between a fluorescent molecule and a doped polymer in a layered sample demonstrates the importance of understanding the quenching of excited states in polymeric devices. A combination of Förster resonance energy transfer and quenching of photoluminescence between a fluorescent molecule and a conjugated polymer in its semiconducting and metallic states were studied. The polymer is a chiral 3-substituted polythiophene (POWT) and the fluorescent molecule is fluorescein bound to dextran (D-FITC). Bilayer samples with fluorescein on top of the POWT were fabricated and studied with absorption spectroscopy, fluorescence microscopy, and electrochemical doping methods. When POWT is electrochemically dedoped it is possible to enhance the photoluminescence in the polymer layer by excitation transfer from the fluorescein layer. Our results demonstrate that PL from the polythiophene disappears rapidly as soon as the layer is doped. As the doping of polymer layer increases the fluorescence from the fluorescein on top of the polymer decreases, due to excitation quenching. Models for excitation transfer and excitation quenching in POWT/FITC bilayer devices have been developed. This model predicts a linear relationship between the PL from the two molecules, in agreement with our experimental findings. These results are relevant for the development of electroluminescent devices or solar cells based on conjugated polymers.
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| 6. |
- Åsberg, Peter, 1973-, et al.
(författare)
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Surface energy modified chips for detection of conformational states and enzymatic activity in biomolecules
- 2006
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 22:5, s. 2205-2211
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Tidskriftsartikel (refereegranskat)abstract
- A novel patterning method for anchoring biomolecules and noncovalent assembled conjugated polyelectrolyte (CPE)/biomolecule complexes to a chip surface is presented. The surface energy of a hydrophilic substrate is modified using an elastomeric poly(dimethylsiloxane) (PDMS) stamp, containing a relief pattern. Modification takes place on the parts where the PDMS stamp is in conformal contact with the substrate and leaves low molecular weight PDMS residues on the surface resulting in a hydrophobic modification, and then biomolecules and CPE/biomolecule complexes are then adsorbed in a specific pattern. The method constitutes a discrimination system for different conformations in biomolecules using CPEs as reporters and the PDMS modified substrates as the discriminator. Detection of different conformations in two biomacromolecules, a synthetic peptide (JR2E) and a protein (calmodulin), reported by the CPE and resolved by fluorescence was demonstrated. Also, excellent enzyme activity in patterned CPE/horseradish peroxidase (HRP) enzyme was shown, demonstrating that this method can be used to pattern biomolecules with their activity retained. The method presented could be useful in various biochip applications, such as analyzing proteins and peptides in large-scale production, in making metabolic chips, and for making multi-microarrays.
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| 7. |
- Åsberg, Signild, et al.
(författare)
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Ischemic Stroke and Secondary Prevention in Clinical Practice : A Cohort Study of 14 529 Patients in the Swedish Stroke Register
- 2010
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Ingår i: Stroke. - 0039-2499 .- 1524-4628. ; 41:7, s. 1338-1342
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Tidskriftsartikel (refereegranskat)abstract
- Background and Purpose Secondary prevention is recommended after stroke, but adherence to guidelines is unknown. We studied the prescription of antiplatelet drugs, angiotensin-converting enzyme inhibitors, statins, and anticoagulant drugs and their relation to risk of death. Methods Patients with first-ever ischemic stroke in 2005 were registered in the Swedish Stroke Register. Odds ratios, hazard ratios, and 95% CIs were calculated using logistic and Cox proportional hazard regression models. Adjustments were performed for age, sex, cardiovascular risk factors, other drug therapies, and activities of daily living function. Results In total, 14 529 patients with a mean age of 75.0 (±11.6) years were included. They were followed for 1.4 (±0.5) years: 52% had hypertension, 26% atrial fibrillation, 19% diabetes, and 15% were smokers. The odds ratio for prescription of antiplatelet was 2.20 (95% CI, 1.86 to 2.60) among the oldest patients (≥85 years of age) compared with the youngest (18 to 64 years of age). The corresponding odds ratio was 0.38 (0.32 to 0.45) for prescriptions of angiotensin-converting enzyme inhibitors, 0.09 (0.08 to 0.11) for statins, and 0.07 (0.05 to 0.09) for anticoagulant therapy. Prescription of statin and anticoagulant therapy was associated with reduced risk of death (hazard ratio, 0.78 [0.65 to 0.91] and hazard ratio, 0.58 [0.44 to 0.76], respectively) but not the prescription of antiplatelet drugs or angiotensin-converting enzyme inhibitors. Conclusions The prescription of antiplatelet, angiotensin-converting enzyme inhibitors, statins, and anticoagulant therapy was strongly age related. Statin and anticoagulant therapy was associated with reduced risk of death and seemed to be underused among elderly patients. These findings should encourage physicians to follow today's guidelines for stroke care.
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