Sedimentation field-flow fractionation application to Toxoplasma gondii separation and purification

Pathogen enrichment from human whole blood for the diagnosis of bloodstream infection: Prospects and limitations

Blood culture represents the current reference method for the detection of bacteria or fungi in the circulation. To accelerate pathogen identification, molecular diagnostic methods, mainly based on polymerase chain reaction (PCR), have been introduced to ensure early and targeted antibiotic treatment of patients suffering from bloodstream infection. Still, these approaches suffer from a lack of sensitivity and from inhibition of PCR in a number of clinical samples, leading to false negative results. To overcome these limitations, various approaches aiming at the enrichment of pathogens from larger blood volumes prior to the extraction of pathogen DNA, thereby also depleting factors interfering with PCR, have been developed. Here, we provide an overview of current systems for diagnosing bloodstream infection, with a focus on approaches for pre-analytical pathogen enrichment, and highlight emerging applications of pathogen depletion for therapeutic purposes as a potential adjunctive treatment of sepsis patients.

Rapid separation of bacteria from blood-review and outlook

The high morbidity and mortality rate of bloodstream infections involving antibiotic-resistant bacteria necessitate a rapid identification of the infectious organism and its resistance profile. Traditional methods based on culturing the blood typically require at least 24 h, and genetic amplification by PCR in the presence of blood components has been problematic. The rapid separation of bacteria from blood would facilitate their genetic identification by PCR or other methods so that the proper antibiotic regimen can quickly be selected for the septic patient. Microfluidic systems that separate bacteria from whole blood have been developed, but these are designed to process only microliter quantities of whole blood or only highly diluted blood. However, symptoms of clinical blood infections can be manifest with bacterial burdens perhaps as low as 10 CFU/mL, and thus milliliter quantities of blood must be processed to collect enough bacteria for reliable genetic analysis. This review considers the advantages and shortcomings of various methods to separate bacteria from blood, with emphasis on techniques that can be done in less than 10 min on milliliter-quantities of whole blood. These techniques include filtration, screening, centrifugation, sedimentation, hydrodynamic focusing, chemical capture on surfaces or beads, field-flow fractionation, and dielectrophoresis. Techniques with the most promise include screening, sedimentation, and magnetic bead capture, as they allow large quantities of blood to be processed quickly. Some microfluidic techniques can be scaled up. © 2016 American Institute of Chemical Engineers Biotechnol. Prog., 32:823-839, 2016.

Field-flow fractionation and biotechnology

The gentle separation mechanism has made field-flow fractionation particularly suited to samples of biotechnological interest, from proteins and nucleic acids to viruses, subcellular units and whole cells. Recent progress in field-flow fractionation technology, as well as the development of coupled techniques combining field-flow fractionation capabilities with the specificity and sensitivity of well-established analytical methods, opens up new biotechnological applications for field-flow fractionation. The most recent appealing applications include: sorting and fingerprinting of bacteria for whole-cell vaccine production; noninvasive and tagless sorting of immature and stem cells; separation of intact proteins and enzymes in top-down proteomics; and the development of flow-assisted, multianalyte immunoassays using nano- and micron-sized particles with immobilized biomolecules.

Mouse Embryonic Stem Cell Sorting for the Generation of Transgenic Mice by Sedimentation Field-Flow Fractionation

Mouse embryonic stem (ES) cells are an important tool for generation of transgenic mice and genetically modified mice. A rapid and efficient separation of ES cells that respects cell integrity, viability, and their developmental potential while also allowing purified ES fraction collection under sterile conditions might be of great interest to facilitate the generation of chimeric animals. In this study, we demonstrated for the first time the effectiveness of a sedimentation field-flow fractionation (SdFFF) cell sorter to provide, with a characteristic DNA content, a purified ES cell fraction and with a high in vivo developmental potential to prepare transgenic mice by generation of chimeras having a high percentage of chimerism.

Sedimentation field flow fractionation purification of immature neural cells from a human tumor neuroblastoma cell line

The use of stem cells for therapeutic applications is now an important objective for the future. Stem cell preparation is difficult and time-consuming depending on the origin of cells. Sedimentation field flow fractionation (SdFFF) is an effective tool for cell separation, respecting integrity and viability. We used the human neuroblastic SH-SY5Y clone of the SK-N-SH cell line as a source of immature neural cells. Our results demonstrated that by using SdFFF cell sorter under strictly defined conditions, and immunological cell characterization, we are now able to provide, in less than 15 min, a sterile, viable, usable and purified immature neural cell fraction without inducting cell differentiation.

Hyphenation of sedimentation field flow fractionation with flow cytometry

Interest in the development of field flow fractionation (FFF) systems for cell sorting recently increased with the possibility of collecting and characterizing viable cellular materials. There are various tools for the analysis of cell characteristics, but the reference is small- and large-angle light scattering often coupled with fluorimetric measurements. The well-known flow cytometry (FC) cell analysis techniques can be associated with FFF leading to the possibility of collecting information provided by a remarkable separation technique for micron-sized particles (cells) operating in the steric-hyperlayer elution mode with multiparametric detection provided by flow cytometry. Moreover FFF derived cell characteristics can be correlated with FC characteristics to describe in a unique way the nature of the eluted materials. Experimental demonstrations are described herein using nucleated cells (HL-60 cell lineage) and human red blood cells (HRBC).

Cortical cell elution by sedimentation field-flow fractionation

As a cell sorter, Sedimentation field-flow fractionation (SdFFF) can be defined as an effective tool for cell separation and purification, respecting integrity and viability as well as providing enhanced recovery and purified sterile fraction collection. The complex cell suspension containing both neurons and glial cells of all types, obtained from cerebral cortices of 17-day-old rat fetuses, is routinely used as a model of primary neuronal culture. Using SdFFF, this complex cell mixture was eluted in sterile fractions which were collected and cultured. SdFFF cell elution was conducted under strictly defined conditions: rapid cell elution, high recovery (negligible cell trapping), short- and long-term cell viability, sterile collection. After immunological cellular type characterization (neurons and glial cells) of cultured cells, our results demonstrated the effectiveness of SdFFF to provide, in less than 6 min, viable and enriched neurons which can be cultured for further investigations.

Sedimentation field-flow fractionation device cleaning, decontamination and sterilization procedures for cellular analysis

In Sedimentation FFF (SdFFF) practice, it is known that a large number of cell elutions create aging phenomena of the separator, thereby reducing recovery and modifying elution characteristics. Systematic cleaning procedures are developed to enhance channel lifetime, together with microbial decontamination processes. Cells can be therefore reproducibly eluted for a large number of analyses and collected under sterile conditions, if needed. This is one of the most valuable aspect if further culture or transplantation is required. Decontamination was performed using, as contaminant probe, Staphylococcus aureus, highly adherent pathogenic bacteria that eluted from SdFFF as aggregates.