Isolation of fetal cells from the maternal circulation: prospects for the non-invasive prenatal diagnosis

Fundamentals and application of magnetic particles in cell isolation and enrichment: a review

Magnetic sorting using magnetic beads has become a routine methodology for the separation of key cell populations from biological suspensions. Due to the inherent ability of magnets to provide forces at a distance, magnetic cell manipulation is now a standardized process step in numerous processes in tissue engineering, medicine, and in fundamental biological research. Herein we review the current status of magnetic particles to enable isolation and separation of cells, with a strong focus on the fundamental governing physical phenomena, properties and syntheses of magnetic particles and on current applications of magnet-based cell separation in laboratory and clinical settings. We highlight the contribution of cell separation to biomedical research and medicine and detail modern cell-separation methods (both magnetic and non-magnetic). In addition to a review of the current state-of-the-art in magnet-based cell sorting, we discuss current challenges and available opportunities for further research, development and commercialization of magnetic particle-based cell-separation systems.

Label-free enrichment of adrenal cortical progenitor cells using inertial microfluidics

Passive and label-free isolation of viable target cells based on intrinsic biophysical cellular properties would allow for cost savings in applications where molecular biomarkers are known as well as potentially enable the separation of cells with little-to-no known molecular biomarkers. We have demonstrated the purification of adrenal cortical progenitor cells from digestions of murine adrenal glands utilizing hydrodynamic inertial lift forces that single cells and multicellular clusters differentially experience as they flow through a microchannel. Fluorescence staining, along with gene expression measurements, confirmed that populations of cells collected in different outlets were distinct from one another. Furthermore, primary murine cells processed through the device remained highly viable and could be cultured for 10 days in vitro. The proposed target cell isolation technique can provide a practical means to collect significant quantities of viable intact cells required to translate stem cell biology to regenerative medicine in a simple label-free manner.

MALDI-TOF MS in Prenatal Genomics

Prenatal diagnosis aims either to provide the reassurance to the couples at risk of having an affected child by timely appropriate therapy or to give the parents a chance to decide the fate of the unborn babies with health problems. Invasive prenatal diagnosis (IPD) is accurate, however, carrying a risk of miscarriage. Non-invasive prenatal diagnosis (NIPD) has been developed based on the existing of fetal genetic materials in maternal circulation; however, a minority fetal DNA in majority maternal background DNA hinders the detections of fetal traits. Different protocols and assays, such as homogenous MassEXTEND (hME), single allele base extension reaction (SABER), precise measuring copy number variation of each allele, and quantitative methylation and expression analysis using the high-throughput sensitive matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF MS), allow NIPD for single gene disorders, fetal blood group genotyping and fetal aneuploidies as well as the development of fetal gender-independent biomarkers in maternal circulation for management of pathological pregnancies. In this review, we summarise the use of MALDI-TOF MS in prenatal genomics.

A non-invasive test for prenatal diagnosis based on fetal DNA present in maternal blood: a preliminary study

BACKGROUND

Use of free fetal DNA to diagnose fetal chromosomal abnormalities has been hindered by the inability to distinguish fetal DNA from maternal DNA. Our aim was to establish whether single nucleotide polymorphisms (SNPs) can be used to distinguish fetal DNA from maternal DNA-and to determine the number of fetal chromosomes-in maternal blood samples.

METHODS

Formaldehyde-treated blood samples from 60 pregnant women and the stated biological fathers were analysed. Maternal plasma fractions were quantified at multiple SNPs, and the ratio of the unique fetal allele signal to the combined maternal and fetal allele signal calculated. The mean ratios of SNPs on chromosomes 13 and 21 were compared to test for potential fetal chromosomal abnormalities.

FINDINGS

The mean proportion of free fetal DNA was 34.0% (median 32.5%, range 17.0-93.8). We identified three samples with significant differences in the fetal DNA ratios for chromosome 13 and chromosome 21, indicative of trisomy 21; the remaining 57 samples were deemed to be normal. Amniocentesis or newborn reports from the clinical sites confirmed that the copy number of fetal chromosomes 13 and 21 was established correctly for 58 of the 60 samples, identifying 56 of the 57 normal samples, and two of the three trisomy 21 samples. Of the incorrectly identified samples, one was a false negative and one was a false positive. The sensitivity and positive predictive value were both 66.7% (95% CI 12.5-98.2) and the specificity and negative predictive values were both 98.2% (89.4-99.9).

INTERPRETATION

The copy number of chromosomes of interest can be directly established from maternal plasma. Such a non-invasive prenatal test could provide a useful complement to currently used screening tests.

Rare cell isolation using antibodies covalently linked to slides: application to fetal cells in maternal blood

We describe here a new type of method for isolation of rare cell populations in biological fluids. The method is based on the anthraquinone technology for covalent binding of molecules to a polymer surface. An anthraquinone molecule conjugated via a linker to an electrophilic group (AQ Immobilizer trade mark reagent, Exiqon A/S) is covalently bound to a polymer surface by UV irradiation. The electrophilic group of this AQ reagent can covalently bind a specific antibody directed against a specific cell marker. Applying a cell sample to the functional surface, the cells having the specific cell marker on the cell surface will bind to the antibody on the functional surface. Using this technique, even extremely small cell populations may be isolated. We succeeded in isolating fetal cells from maternal blood samples in the first trimester for chromosome defects genetic diagnosis.