| 1. |
- Alakpa, Enateri V., et al.
(författare)
-
Bioprinted schwann and mesenchymal stem cell co-cultures for enhanced spatial control of neurite outgrowth
- 2023
-
Ingår i: Gels. - : MDPI. - 2310-2861. ; 9:3
-
Tidskriftsartikel (refereegranskat)abstract
- Bioprinting nerve conduits supplemented with glial or stem cells is a promising approach to promote axonal regeneration in the injured nervous system. In this study, we examined the effects of different compositions of bioprinted fibrin hydrogels supplemented with Schwann cells and mesenchymal stem cells (MSCs) on cell viability, production of neurotrophic factors, and neurite outgrowth from adult sensory neurons. To reduce cell damage during bioprinting, we analyzed and optimized the shear stress magnitude and exposure time. The results demonstrated that fibrin hydrogel made from 9 mg/mL of fibrinogen and 50IE/mL of thrombin maintained the gel’s highest stability and cell viability. Gene transcription levels for neurotrophic factors were significantly higher in cultures containing Schwann cells. However, the amount of the secreted neurotrophic factors was similar in all co-cultures with the different ratios of Schwann cells and MSCs. By testing various co-culture combinations, we found that the number of Schwann cells can feasibly be reduced by half and still stimulate guided neurite outgrowth in a 3D-printed fibrin matrix. This study demonstrates that bioprinting can be used to develop nerve conduits with optimized cell compositions to guide axonal regeneration.
|
|
| 2. |
- Castelain, Mickaël, et al.
(författare)
-
Characterization of the Biomechanical Properties of T4 Pili Expressed by Streptococcus pneumoniae – A Comparison between Helix-like and Open Coil-like Pili
- 2009
-
Ingår i: ChemPhysChem. - : Wiley. - 1439-4235 .- 1439-7641. ; 10:9-10, s. 1533-1540
-
Tidskriftsartikel (refereegranskat)abstract
- Bacterial adhesion organelles, known as fimbria or pili, are expressed by Gram–positive as well as Gram–negative bacteria families. These appendages play a key role in the first steps of the invasion and infection processes, and they therefore provide bacteria with pathogenic abilities. To improve the knowledge of pili-mediated bacterial adhesion to host cells and how these pili behave under the presence of an external force, we first characterize, using force measuring optical tweezers, open coil-like T4 pili expressed by Gram–positive Streptococcus pneumoniae with respect to their biomechanicalproperties. It is shown that their elongation behavior can be well described by the worm-like chain model and that they possess a large degree of flexibility. Their properties are then compared with those of helix-like pili expressed by Gram–negative uropathogenic Escherichia coli (UPEC), which have different pili architecture. The differences suggest that these two types of pili have distinctly dissimilar mechanisms to adhere and sustain external forces. Helix-like pili expressed by UPEC bacteria adhere to host cells by single adhesins located at the distal end of the pili while their helix-like structures act as shock absorbers to dampen the irregularly shear forces induced by urine flow and to increase the cooperativity of the pili ensemble. Open coil-like pili expressed by S. pneumoniae adhere to cells by a multitude of adhesins distributed along the pili. It is hypothesized that these two types of pili represent different strategies of adhering to host cells in the presence of external forces. When exposed to significant forces, bacteria expressing helix-like pili remain attached bydistributing the external force among a multitude of pili, whereas bacteria expressing open coil-like pili sustain large forces primarily by their multitude of binding adhesins.
|
|
| 3. |
- Dahlberg, Tobias, et al.
(författare)
-
3D printed water-soluble scaffolds for rapid production of PDMS micro-fluidic flow chambers
- 2018
-
Ingår i: Scientific Reports. - : Nature Publishing Group. - 2045-2322. ; 8:1
-
Tidskriftsartikel (refereegranskat)abstract
- We report a novel method for fabrication of three-dimensional (3D) biocompatible micro-fluidic flow chambers in polydimethylsiloxane (PDMS) by 3D-printing water-soluble polyvinyl alcohol (PVA) filaments as master scaffolds. The scaffolds are first embedded in the PDMS and later residue-free dissolved in water leaving an inscription of the scaffolds in the hardened PDMS. We demonstrate the strength of our method using a regular, cheap 3D printer, and evaluate the inscription process and the channels micro-fluidic properties using image analysis and digital holographic microscopy. Furthermore, we provide a protocol that allows for direct printing on coverslips and we show that flow chambers with a channel cross section down to 40 x 300 μm can be realized within 60 min. These flow channels are perfectly transparent, biocompatible and can be used for microscopic applications without further treatment. Our proposed protocols facilitate an easy, fast and adaptable production of micro-fluidic channel designs that are cost-effective, do not require specialized training and can be used for a variety of cell and bacterial assays. To help readers reproduce our micro-fluidic devices, we provide: full preparation protocols, 3D-printing CAD files for channel scaffolds and our custom-made molding device, 3D printer build-plate leveling instructions, and G-code.
|
|
| 4. |
- Dahlberg, Tobias, 1990-
(författare)
-
KNOW YOUR ENEMY : Characterizing Pathogenic Biomaterials Using Laser Tweezers
- 2022
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Diseases caused by pathogenic agents such as bacteria and viruses result in devastating costs on personal and societal levels. However, it is not just the emergence of new diseases that is problematic. Antibiotic resistance among bacteria makes uncomplicated infections difficult and lethal. Resilient disease-causing spores spread in hospitals, the food industry, and water supplies requiring effective detection and disinfection methods. Further, we face complex neurological diseases where no effective treatment or diagnostic methods exist. Thus, we must increase our fundamental understanding of these diseases to develop effective diagnostic, detection, disinfection, and treatment methods.Classically, the methods used for detecting and studying the underlying mechanics of pathogenic agents work on a large scale, measuring the average macroscopic behavior and properties of these pathogens. However, just as with humans, the average behavior is not always representative of individual behavior. Therefore, it is also essential to investigate the characteristics of these pathogens on a single cell or particle level. This thesis develops and applies optical techniques to characterize pathogenic biomaterial on a single cell or particle level. At the heart of all these studies is our Optical Tweezers (OT) instrument. OT are a tool that allows us to reach into the microscopic world and interact with it. Finally, by combining OT with other experimental techniques, we can chemically characterize biomaterials and develop assays that mimic different biological settings. Using these tools, we investigate bacterial adhesion, disinfection, and detection of pathogenic spores and proteins.Hopefully, the insights of these studies can lessen the burden on society caused by diseases by helping others develop effective treatment, diagnostic, detection, and disinfection methods in the future.
|
|
| 5. |
- Hanqing, Zhang, et al.
(författare)
-
A fast and robust circle detection method using isosceles triangles sampling
- 2016
-
Ingår i: Pattern Recognition. - : Elsevier. - 0031-3203 .- 1873-5142. ; 54, s. 218-228
-
Tidskriftsartikel (refereegranskat)abstract
- Circle detection using randomized sampling has been developed in recent years to reduce computational intensity. However, randomized sampling is sensitive to noise that can lead to reduced accuracy and false-positive candidates. To improve on the robustness of randomized circle detection under noisy conditions this paper presents a new methodology for circle detection based upon randomized isosceles triangles sampling. It is shown that the geometrical property of isosceles triangles provides a robust criterion to find relevant edge pixels which, in turn, offers an efficient means to estimate the centers and radii of circles. For best efficiency, the estimated results given by the sampling from individual connected components of the edge map were analyzed using a simple clustering approach. To further improve on the accuracy we applied a two-step refinement process using chords and linear error compensation with gradient information of the edge pixels. Extensive experiments using both synthetic and real images have been performed. The results are compared to leading state-of-the-art algorithms and it is shown that the proposed methodology has a number of advantages: it is efficient in finding circles with a low number of iterations, it has high rejection rate of false-positive circle candidates, and it has high robustness against noise. All this makes it adaptive and useful in many vision applications.
|
|
| 6. |
|
|
| 7. |
- Larsson, Jonas, et al.
(författare)
-
A hamiltonian derivation of interaction equations for Rossby waves
- 1999
-
Ingår i: Physica scripta. T. - 0281-1847. ; T82, s. 71-73
-
Tidskriftsartikel (refereegranskat)abstract
- The mode coupling equations for Rossby waves in a bounded periodic channel are derived by means of a Hamiltonian method. The streamfunction is used as field variable and we need not introduce Clebsch potentials or a lagrangian description. The Manley-Rowe relations follow from general hamiltonian theory.
|
|
| 8. |
- Lindberg, Ann-Sofie, et al.
(författare)
-
Firefighters' fit for duty score-model : Book of Abstracts
- 2016
-
Ingår i: 21st Annual Congress of the European College of Sport Science: Crossing borders through sport science. - : ECSS.
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Physical capacity has previously been deemed important for firefighters’ physical work capacity, and evaluation of fitness for duty is common in the pre-hiring process. Various methods have been used to establish cut-off limits, i.e. normative data or expert judges. In accordance with government regulation, both full-time and part-time firefighters in Sweden have to pass a medical examination and a test of physical work capacity for permission to execute smoke diving. The physical work capacity test is a pass or fail test: dressed in firefighting protective clothes and breathing apparatus (total weight 24 ± 0.5 kg), six minutes walking with the incline at 8 degrees and treadmill speed of 4.5 km/h is performed. Inclusion of additional physical tests and appropriate cut-off limits is a decision taken by each individual municipality. The aim of the present study was to create a score model for evaluation of fitness for duty in the pre-hiring process of firefighters. Methods A total of 128 (64 men and 64 women) subjects: full-time firefighters, part-time firefighters and civilians, were included. Subjects performed five simulated firefighting work tasks and a selected battery six of physical tests including; 500 m rowing, grip strength, endurance bench press, track running 3000 m, standing broadjump and upright barbell row. The combined information from subjective evaluated cut-off limits, breakpoint estimation, checkpoint estimation and percentiles were used to create a score-model MO-PM30 Performance: Mixed Session 424 21ST ANNUAL CONGRESS OF THE EUROPEAN COLLEGE OF SPORT SCIENCE for evaluation of fit for duty. Results The models yielded various cut-off limits on the same physical test, depending on the work task investigated, but all tests were scored on a 1-11 scale. Consequently, the maximum total score was 66 and the minimum total score was 6. The recommended minimum total score of six tests is 36. Discussion In this study we created a score-model for evaluation of firefighters’ fit for duty in the pre-hiring process. When pre-hiring physical tests are performed, an easily conducted battery of physical tests is important in order to reduce costs but still maintain high validity and reliability. The score-model is easy to understand, performance gives the same score irrespectively of age and sex and makes it possible for the aspirants to prepare for the included physical tests. Since a specific physical test differs in importance in the prediction of simulated work task performance, the lack of performance in one physical test may not be fully compensated with a higher performance in another physical test. Simplifying and generalizing a method makes it practically usable at the detriment of accuracy on an individual level.
|
|
| 9. |
- Malyshev, Dmitry, et al.
(författare)
-
Laser induced degradation of bacterial spores during micro-Raman spectroscopy
- 2022
-
Ingår i: Spectrochimica Acta Part A - Molecular and Biomolecular Spectroscopy. - : Elsevier. - 1386-1425 .- 1873-3557. ; 265
-
Tidskriftsartikel (refereegranskat)abstract
- Micro-Raman spectroscopy combined with optical tweezers is a powerful method to analyze how the biochemical composition and molecular structures of individual biological objects change with time. In this work we investigate laser induced effects in the trapped object. Bacillus thuringiensis spores, which are robust organisms known for their resilience to light, heat, and chemicals are used for this study. We trap spores and monitor the Raman peak from CaDPA (calcium dipicolinic acid), which is a chemical protecting the spore core. We see a correlation between the amount of laser power used in the trap and the release of CaDPA from the spore. At a laser power of 5 mW, the CaDPA from spores in water suspension remain intact over the 90 min experiment, however, at higher laser powers an induced effect could be observed. SEM images of laser exposed spores (after loss of CaDPA Raman peak was confirmed) show a notable alteration of the spores' structure. Our Raman data indicates that the median dose exposure to lose the CaDPA peak was ∼60 J at 808 nm. For decontaminated/deactivated spores, i.e., treated in sodium hypochlorite or peracetic acid solutions, the sensitivity on laser power is even more pronounced and different behavior could be observed on spores treated by the two chemicals. Importantly, the observed effect is most likely photochemical since the increase of the spore temperature is in the order of 0.1 K as suggested by our numerical multiphysics model. Our results show that care must be taken when using micro-Raman spectroscopy on biological objects since photoinduced effects may substantially affect the results.
|
|
| 10. |
- Malyshev, Dmitry, et al.
(författare)
-
Mode of action of Disinfection chemicals on the bacterial spore structure and their Raman spectra
- 2021
-
Ingår i: Analytical Chemistry. - : American Chemical Society (ACS). - 0003-2700 .- 1520-6882. ; 93:6, s. 3146-3153
-
Tidskriftsartikel (refereegranskat)abstract
- Contamination of toxic spore-forming bacteria is problematic since spores can survive a plethora of disinfection chemicals and it is hard to rapidly detect if the disinfection chemical has inactivated the spores. Thus, robust decontamination strategies and reliable detection methods to identify dead from viable spores are critical. In this work, we investigate the chemical changes of Bacillus thuringiensis spores treated with sporicidal agents such as chlorine dioxide, peracetic acid, and sodium hypochlorite using laser tweezers Raman spectroscopy. We also image treated spores using SEM and TEM to verify if we can correlate structural changes in the spores with changes to their Raman spectra. We found that over 30 min, chlorine dioxide did not change the Raman spectrum or the spore structure, peracetic acid showed a time-dependent decrease in the characteristic DNA/DPA peaks and ∼20% of the spores were degraded and collapsed, and spores treated with sodium hypochlorite showed an abrupt drop in DNA and DPA peaks within 20 min and some structural damage to the exosporium. Structural changes appeared in spores after 10 min, compared to the inactivation time of the spores, which is less than a minute. We conclude that vibrational spectroscopy provides powerful means to detect changes in spores but it might be problematic to identify if spores are live or dead after a decontamination procedure.
|
|
