| 1. |
- Cruz, Javier, 1990-, et al.
(författare)
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Stable 3D Inertial Focusing by High Aspect Ratio Curved Microfluidics
- 2021
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Ingår i: Journal of Micromechanics and Microengineering. - : Institute of Physics Publishing (IOPP). - 0960-1317 .- 1361-6439. ; 31
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Tidskriftsartikel (refereegranskat)abstract
- Fine manipulation of particles is essential for the analysis of complex samples such as blood or environmental water, where rare particles of interest may be masked by millions of others. Inertial focusing is amongst the most promising techniques for this task, enabling label-free manipulation of particles with sub-micron resolution at very high flow rates. However, the phenomenon still remains difficult to predict due to the focus position shifting in tortuous ways as function of the channel geometry, flow rate and particle size. Here, we present a new line of microfluidics that exploit inertial focusing in High Aspect Ratio Curved (HARC) microchannels and overcome this limitation. Consisting of a single curved channel, HARC systems provide a highly predictable, single focus position near the centre of the inner wall, largely independent of the flow rate and particle size.An explanation of the mechanism of migration and focus of particles, together with its governing equations, is provided based on simulations in COMSOL Multiphysics and experimental results. HARC microchannels built in silicon-glass were used for experimental validation, achieving a high quality, single focus position for a range of microparticles with sizes of 0.7 - 1 µm and bacterial cells (Escherichia coli). The recovery of 1 µm particles was 99.84% with a factor four in concentration.With a stable focus position, we envision that HARC systems will bring the technology closer to implementation in laboratories for analysis of complex fluids with biological particles like cells and organelles.
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| 2. |
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| 3. |
- Hou, Zining, et al.
(författare)
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Time lapse investigation of antibiotic susceptibility using a microfluidic linear gradient 3D culture device
- 2014
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Ingår i: Lab on a Chip. - : Royal Society of Chemistry (RSC). - 1473-0197 .- 1473-0189. ; 14:17, s. 3409-3418
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Tidskriftsartikel (refereegranskat)abstract
- This study reports a novel approach to quantitatively investigate the antibacterial effect of antibiotics on bacteria using a three-dimensional microfluidic culture device. In particular, our approach is suitable for studying the pharmacodynamics effects of antibiotics on bacterial cells temporally and with a continuous range of concentrations in a single experiment. The responses of bacterial cells to a linear concentration gradient of antibiotics were observed using time-lapse photography, by encapsulating bacterial cells in an agarose-based gel located in a commercially available microfluidics chamber. This approach generates dynamic information with high resolution, in a single operation, e. g., growth curves and antibiotic pharmacodynamics, in a well-controlled environment. No pre-labelling of the cells is needed and therefore any bacterial sample can be tested in this setup. It also provides static information comparable to that of standard techniques for measuring minimum inhibitory concentration (MIC). Five antibiotics with different mechanisms were analysed against wild-type Escherichia coli, Staphylococcus aureus and Salmonella Typhimurium. The entire process, including data analysis, took 2.5-4 h and from the same analysis, high-resolution growth curves were obtained. As a proof of principle, a pharmacodynamic model of streptomycin against Salmonella Typhimurium was built based on the maximal effect model, which agreed well with the experimental results. Our approach has the potential to be a simple and flexible solution to study responding behaviours of microbial cells under different selection pressures both temporally and in a range of concentrations.
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| 4. |
- Zining, Hou, et al.
(författare)
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A microfluidic approach for dynamic investigation of the antibiotic susceptibility of bacteria
- 2013
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Ingår i: MME 2013 24th Micromechanics and Microsystems Europe Conference.
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Konferensbidrag (refereegranskat)abstract
- The possibility to study the effect on cell growth of a chemical is a valued tool for re- searchers in different areas, such as antibiotic resis- tance, cancer research and metabolic pathways. Traditional approaches need long time and no dynamic information is given. Microfluidics offers short diffusion lengths and steeper gradients for studies of antibiotic susceptibility, which could improve throughput greatly. By combining with time-lapse micrography, information on the dynam- ics may provide additional understanding. A micro- fluidic 3D cell culture chip was used to determine the MIC (minimum inhibitory concentration) and the dynamics of sub-MIC of E. coli against ampicillin and spectinomycin. And the same works have been done in Staphylococcus aureus and Salmonella. It is the first time to reveal this dynamic behaviour of bacteria against antibiotics quantitatively in a micro- fludic device. It is anticipated that it could be ex- tended to many other similar investigations in bio- logical and relevant pharmaceutical or clinical applications.
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| 5. |
- Andersson, Dan I, et al.
(författare)
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Mechanisms and clinical relevance of bacterial heteroresistance
- 2019
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Ingår i: Nature Reviews Microbiology. - : Nature Publishing Group. - 1740-1526 .- 1740-1534. ; 17:8, s. 479-496
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Forskningsöversikt (refereegranskat)abstract
- Antibiotic heteroresistance is a phenotype in which a bacterial isolate contains subpopulations of cells that show a substantial reduction in antibiotic susceptibility compared with the main population. Recent work indicates that heteroresistance is very common for several different bacterial species and antibiotic classes. The resistance phenotype is often unstable, and in the absence of antibiotic pressure it rapidly reverts to susceptibility. A common mechanistic explanation for the instability is the occurrence of genetically unstable tandem amplifications of genes that cause resistance. Due to their instability, low frequency and transient character, it is challenging to detect and study these subpopulations, which often leads to difficulties in unambiguously classifying bacteria as susceptible or resistant. Finally, in vitro experiments, mathematical modelling, animal infection models and clinical studies show that the resistant subpopulations can be enriched during antibiotic exposure, and increasing evidence suggests that heteroresistance can lead to treatment failure.
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| 6. |
- Arthurson, Veronica, et al.
(författare)
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Effects on Glomus mosseae root colonization by Paenibacillus polymyxa and Paenibacillus brasilensis strains as related to soil P-availability in winter wheat
- 2011
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Ingår i: Applied and Environmental Soil Science. - : Hindawi Limited. - 1687-7667 .- 1687-7675.
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Tidskriftsartikel (refereegranskat)abstract
- Greenhouse experiments were conducted to assess the effects of inoculating winter wheat (Triticum aestivum) with plant growth promoting rhizobacteria (PGPR) of the genusPaenibacillusunder phosphate P-limited soil conditions in the presence or absence of the arbuscular mycorrhizal fungus (AMF)Glomus mosseae. FourP. polymyxastrains and oneP. brasilensisstrain were compared at two cell concentrations (106and 108 cells g−1seeds) of inoculation, and surface sterilized AMF spores were added to pots. Mycorrhizal root colonization, plant growth, and plant uptake of phosphorus were analyzed. Bacterial phosphate solubilization was examined separatelyin vitro. MostP. polymyxastrains, isolated from wheat, had dramatic effectsper seon root growth and root P-content. No treatment gave significant effect on shoot growth. AMF root colonization levels and total plant uptake of P were much stimulated by the addition of mostP. polymyxastrains. The AM fungus alone and theP. brasilensis, alone or in combination with the fungus, did not affect total plant P-levels. Our results indicate that practical application of inoculation with plant host-specific rhizobacteria (i.e.,P. polymyxa) could positively influence uptake of phosphorus in P-deficient soils by wheat plants, provided that suitable AM fungi (e.g.,G. mosseae) are present.
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| 7. |
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| 8. |
- Biccler, Jorne Lionel, et al.
(författare)
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Relapse Risk and Loss of Lifetime After Modern Combined Modality Treatment of Young Patients With Hodgkin Lymphoma : A Nordic Lymphoma Epidemiology Group Study
- 2019
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Ingår i: Journal of Clinical Oncology. - : AMER SOC CLINICAL ONCOLOGY. - 0732-183X .- 1527-7755. ; 37:9, s. 703-713
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Tidskriftsartikel (refereegranskat)abstract
- PURPOSE: Estimates of short- and long-term survival for young patients with classic Hodgkin lymphoma (cHL) are of considerable interest. We investigated cHL prognosis in the era of contemporary treatment at different milestones during the follow-up.PATIENTS AND METHODS: On the basis of a Nordic cohort of 2,582 patients diagnosed at ages 18 to 49 years between 2000 and 2013, 5-year relapse risks and 5-year restricted losses in expectation of lifetime were estimated for all patients and for patients who achieved event-free survival (EFS) for 12 (EFS12), 24 (EFS24), 36 (EFS36) or 60 (EFS60) months. The median follow-up time was 9 years (range, 2.9 to 16.8 years).RESULTS: The 5-year overall survival was 95% (95% CI, 94% to 96%). The 5-year risk of relapse was 13.4% (95% CI, 12.1% to 14.8%) overall but decreased to 4.2% (95% CI, 3.8% to 4.6%) given that patients reached EFS24. Relapse risk for patients treated with six to eight courses of bleomycin, etoposide, doxorubicin, cyclophosphamide, vincristine, procarbazine, and prednisone (BEACOPP) was comparable to that of patients treated with six to eight courses of doxorubicin, bleomycin, vinblastine, and dacarbazine (ABVD) despite more adverse risk criteria among patients treated with BEACOPP. Both from diagnosis and if EFS24 was reached, the losses in expectation of lifetime during the following 5 years were small (from diagnosis, 45 days [95% CI, 35 to 54 days] and for patients who reached EFS24, 13 days [95% CI, 7 to 20 days]). In stage-stratified analyses of 5-year restricted loss in expectation of lifetime, patients with stages I to IIA disease had no noteworthy excess risk of death after they reached EFS24, whereas risk remained measurable for patients with stages IIB to IV cHL.CONCLUSION: Real-world data on young patients with cHL from the Nordic countries show excellent outcomes. The outlook is particularly favorable for patients who reach EFS24, which supports limited relapse-oriented clinical follow-up.
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| 9. |
- Blanco, Paula, et al.
(författare)
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Antimicrobial Peptide Exposure Selects for Resistant and Fit Stenotrophomonas maltophilia Mutants That Show Cross-Resistance to Antibiotics
- 2020
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Ingår i: mSphere. - : AMER SOC MICROBIOLOGY. - 2379-5042. ; 5:5
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Tidskriftsartikel (refereegranskat)abstract
- Antimicrobial peptides (AMPs) are essential components of the innate immune system and have been proposed as promising therapeutic agents against drug-resistant microbes. AMPs possess a rapid bactericidal mode of action and can interact with different targets, but bacteria can also avoid their effect through a variety of resistance mechanisms. Apart from hampering treatment by the AMP itself, or that by other antibiotics in the case of cross-resistance, AMP resistance might also confer cross-resistance to innate human peptides and impair the anti-infective capability of the human host. A better understanding of how resistance to AMPs is acquired and the genetic mechanisms involved is needed before using these compounds as therapeutic agents. Using experimental evolution and whole-genome sequencing, we determined the genetic causes and the effect of acquired de novo resistance to three different AMPs in the opportunistic pathogen Stenotrophomonas maltophilia, a bacterium that is intrinsically resistant to a wide range of antibiotics. Our results show that AMP exposure selects for high-level resistance, generally without any reduction in bacterial fitness, conferred by mutations in different genes encoding enzymes, transporters, transcriptional regulators, and other functions. Cross-resistance to AMPs and to other antibiotic classes not used for selection, as well as collateral sensitivity, was observed for many of the evolved populations. The relative ease by which high-level AMP resistance is acquired, combined with the occurrence of cross-resistance to conventional antibiotics and the maintained bacterial fitness of the analyzed mutants, highlights the need for careful studies of S. maltophilia resistance evolution to clinically valuable AMPs. IMPORTANCE Stenotrophomonas maltophilia is an increasingly relevant multidrug-resistant (MDR) bacterium found, for example, in people with cystic fibrosis and associated with other respiratory infections and underlying pathologies. The infections caused by this nosocomial pathogen are difficult to treat due to the intrinsic resistance of this bacterium against a broad number of antibiotics. Therefore, new treatment options are needed, and considering the growing interest in using AMPs as alternative therapeutic compounds and the restricted number of antibiotics active against S. maltophilia, we addressed the potential for development of AMP resistance, the genetic mechanisms involved, and the physiological effects that acquisition of AMP resistance has on this opportunistic pathogen.
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| 10. |
- Dahlin, Andreas P., et al.
(författare)
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Methodological aspects on microdialysis protein sampling and quantification in biological fluids : an in vitro study on human ventricular CSF.
- 2010
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Ingår i: Analytical Chemistry. - : American Chemical Society (ACS). - 0003-2700 .- 1520-6882. ; 82:11, s. 4376-4385
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Tidskriftsartikel (refereegranskat)abstract
- There is growing interest in sampling of protein biomarkers from the interstitial compartment of the brain and other organs using high molecular cutoff membrane microdialysis (MD) catheters. However, recent data suggest that protein sampling across such MD membranes is a highly complex process that needs to be further studied. Here, we report three major improvements for microdialysis sampling of proteins in complex biological matrixes. The improvements in this in vitro study using human ventricular cerebrospinal fluid as the sample matrix include increased fluid recovery control, decreased protein adsorption on the microdialysis membrane and materials, and novel quantitative mass spectrometry analysis. Dextrans in different concentrations and sizes were added to the perfusion fluid. It was found that dextrans with molecular mass 250 and 500 kDa provided a fluid recovery close to 100%. An improved fluid recovery precision could be obtained by self-assembly triblock polymer surface modification of the MD catheters. The modified catheters also delivered a significantly increased extraction efficiency for some of the investigated proteins. The final improvement was to analyze the dialysates with isobaric tagged (iTRAQ) proteomics, followed by tandem mass spectrometric analysis. By using this technique, 48 proteins could be quantified and analyzed with respect to their extraction efficiencies. The novel aspects of microdialysis protein sampling, detection, and quantification in biological fluids presented in this study should be considered as a first step toward better understanding and handling of the challenges associated with microdialysis sampling of proteins. The next step is to optimize the developed methodology in vivo.
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