Fetal nucleated red blood cell analysis for non-invasive prenatal diagnostics using a nanostructure microchip

Exploiting Sound for Emerging Applications of Extracellular Vesicles

Extracellular vesicles are nano- to microscale, membrane-bound particles released by cells into extracellular space, and act as carriers of biomarkers and therapeutics, holding promising potential in translational medicine. However, the challenges remain in handling and detecting extracellular vesicles for disease diagnosis as well as exploring their therapeutic capability for disease treatment. Here, we review the recent engineering and technology advances by leveraging the power of sound waves to address the challenges in diagnostic and therapeutic applications of extracellular vesicles and biomimetic nanovesicles. We first introduce the fundamental principles of sound waves for understanding different acoustic-assisted extracellular vesicle technologies. We discuss the acoustic-assisted diagnostic methods including the purification, manipulation, biosensing, and bioimaging of extracellular vesicles. Then, we summarize the recent advances in acoustically enhanced therapeutics using extracellular vesicles and biomimetic nanovesicles. Finally, we provide perspectives into current challenges and future clinical applications of the promising extracellular vesicles and biomimetic nanovesicles powered by sound.

Manufacturing methods, properties, and potential applications in bone tissue regeneration of hydroxyapatite-chitosan biocomposites: A review

Hydroxyapatite (HA) and chitosan (CS) biopolymer are the major materials investigated for biomedical purposes. Both of these components play an important role in the orthopedic field as bone substitutes or drug release systems. Used separately, the hydroxyapatite is quite fragile, while CS mechanical strength is very weak. Therefore, a combination of HA and CS polymer is used, which provides excellent mechanical performance with high biocompatibility and biomimetic capacity. Moreover, the porous structure and reactivity of the hydroxyapatite-chitosan (HA-CS) composite allow their application not only as a bone repair but also as a drug delivery system providing controlled drug release directly to the bone site. These features make biomimetic HA-CS composite a subject of interest for many researchers. Through this review, we provide the important recent achievements in the development of HA-CS composites, focusing on manufacturing techniques, conventional and novel three-dimensional bioprinting technology, and physicochemical and biological properties. The drug delivery properties and the most relevant biomedical applications of the HA-CS composite scaffolds are also presented. Finally, alternative approaches are proposed to develop HA composites with the aim to improve their physicochemical, mechanical, and biological properties.

Single-cell whole-genome sequencing, haplotype analysis in prenatal diagnosis of monogenic diseases

Monogenic inherited diseases are common causes of congenital disabilities, leading to severe economic and mental burdens on affected families. In our previous study, we demonstrated the validity of cell-based noninvasive prenatal testing (cbNIPT) in prenatal diagnosis by single-cell targeted sequencing. The present research further explored the feasibility of single-cell whole-genome sequencing (WGS) and haplotype analysis of various monogenic diseases with cbNIPT. Four families were recruited: one with inherited deafness, one with hemophilia, one with large vestibular aqueduct syndrome (LVAS), and one with no disease. Circulating trophoblast cells (cTBs) were obtained from maternal blood and analyzed by single-cell 15X WGS. Haplotype analysis showed that CFC178 (deafness family), CFC616 (hemophilia family), and CFC111 (LVAS family) inherited haplotypes from paternal and/or maternal pathogenic loci. Amniotic fluid or fetal villi samples from the deafness and hemophilia families confirmed these results. WGS performed better than targeted sequencing in genome coverage, allele dropout (ADO), and false-positive (FP) ratios. Our findings suggest that cbNIPT by WGS and haplotype analysis have great potential for use in prenatally diagnosing various monogenic diseases.

Aptamer-Mediated Enrichment of Rare Circulating Fetal Nucleated Red Blood Cells for Noninvasive Prenatal Diagnosis

Isolation of circulating fetal nucleated red blood cells (cfNRBCs) from maternal peripheral blood provides a superior strategy for noninvasive prenatal genetic diagnosis. Recent technical advances in single-cell isolation and genetic analyses have promoted the clinical application of circulating fetal cell-based noninvasive prenatal diagnosis. However, the lack of highly specific ligands for rare circulating fetal cell enrichment from massive maternal cells significantly impedes the clinical transformation progress. In this work, aptamers specific to NRBCs were developed through clinical sample-based cell-SELEX. Herein, the complex clinical system provides natural selection stringency through binding competition between target and background cells, and it empowers aptamers with high specificity. An aptamer-based strategy was also established to isolate cfNRBCs from maternal peripheral blood. Results show the remarkable selectivity and affinity of developed aptamers, enabling efficient enrichment of cfNRBCs from abundant maternal cells. Moreover, screening for fetal sex and trisomy syndrome achieved high accuracy through chromosome analysis of enriched cfNRBCs. To the best of our knowledge, this is the first report to develop aptamer ligands for cfNRBC enrichment, providing an efficient strategy to screen cfNRBC-specific ligands and demonstrating broad application potential for cfNRBC-based noninvasive prenatal diagnosis.

Microfluidic devices for the detection of disease-specific proteins and other macromolecules, disease modelling and drug development: A review

Microfluidics is a revolutionary technology that has promising applications in the biomedical field.Integrating microfluidic technology with the traditional assays unravels the innumerable possibilities for translational biomedical research. Microfluidics has the potential to build up a novel platform for diagnosis and therapy through precise manipulation of fluids and enhanced throughput functions. The developments in microfluidics-based devices for diagnostics have evolved in the last decade and have been established for their rapid, effective, accurate and economic advantages. The efficiency and sensitivity of such devices to detect disease-specific macromolecules like proteins and nucleic acids have made crucial impacts in disease diagnosis. The disease modelling using microfluidic systems provides a more prominent replication of the in vivo microenvironment and can be a better alternative for the existing disease models. These models can replicate critical microphysiology like the dynamic microenvironment, cellular interactions, and biophysical and biochemical cues. Microfluidics also provides a promising system for high throughput drug screening and delivery applications. However, microfluidics-based diagnostics still encounter related challenges in the reliability, real-time monitoring and reproducibility that circumvents this technology from being impacted in the healthcare industry. This review highlights the recent microfluidics developments for modelling and diagnosing common diseases, including cancer, neurological, cardiovascular, respiratory and autoimmune disorders, and its applications in drug development.

Recent Advances of Microfluidic Platform for Cell Based Non-Invasive Prenatal Diagnosis

The purpose of the present review is to try to highlight recent advances in the application of microfluidic technology on non-invasive prenatal diagnosis (NIPD). The immunoaffinity based microfluidic technology is the most common approach for NIPD, followed by size-based microfluidic methods. Immunoaffinity microfluidic methods can enrich and isolate circulating fetal extravillous trophoblasts (fEVTs) or fetal nucleated red blood cells (fnRBCs) for NIPD by using specific antibodies, but size-based microfluidic systems are only applied to isolate fEVTs. Most studies based on the immunoaffinity microfluidic system gave good results. Enough fetal cells were obtained for chromosomal and/or genetic analysis in all blood samples. However, the results from studies using size-based microfluidic systems for NIPD are less than ideal. In conclusion, recent advances in microfluidic devices make the immunoaffinity based microfluidic system potentially a powerful tool for cell-based NIPD. However, more clinical validation is needed.

Noninvasive prenatal diagnosis targeting fetal nucleated red blood cells

Noninvasive prenatal diagnosis (NIPD) aims to detect fetal-related genetic disorders before birth by detecting markers in the peripheral blood of pregnant women, holding the potential in reducing the risk of fetal birth defects. Fetal-nucleated red blood cells (fNRBCs) can be used as biomarkers for NIPD, given their remarkable nature of carrying the entire genetic information of the fetus. Here, we review recent advances in NIPD technologies based on the isolation and analysis of fNRBCs. Conventional cell separation methods rely primarily on physical properties and surface antigens of fNRBCs, such as density gradient centrifugation, fluorescence-activated cell sorting, and magnetic-activated cell sorting. Due to the limitations of sensitivity and purity in Conventional methods, separation techniques based on micro-/nanomaterials have been developed as novel methods for isolating and enriching fNRBCs. We also discuss emerging methods based on microfluidic chips and nanostructured substrates for static and dynamic isolation of fNRBCs. Additionally, we introduce the identification techniques of fNRBCs and address the potential clinical diagnostic values of fNRBCs. Finally, we highlight the challenges and the future directions of fNRBCs as treatment guidelines in NIPD.

Research Progress in Isolation and Enrichment of Fetal Cells from Maternal Blood

Prenatal diagnosis is an important means of early diagnosis of genetic diseases, which can effectively reduce the risk of birth defects. Free fetal cells, as a carrier of intact fetal genetic material, provide hope for the development of high-sensitivity and high-accuracy prenatal diagnosis technology. However, the number of fetal cells is small and it is difficult to apply clinically. In recent years, noninvasive prenatal diagnosis (NIPD) technology for fetal genetic material in maternal peripheral blood has developed rapidly, which makes it possible to diagnose genetic diseases by fetal cells in maternal peripheral blood. This article reviewed the current status of fetal cell separation and enrichment technology and its application in noninvasive prenatal diagnosis technology.

Fast label-free recognition of NRBCs by deep-learning visual object detection and single-cell Raman spectroscopy

A computer-assisted and label-free method to quickly recognize the rare nucleated red blood cells by combining visual object detection with single-cell Raman spectroscopy.

Sheathless acoustic based flow cell sorter for enrichment of rare cells

Cell enrichment is a powerful tool in many kinds of cell research, especially in applications with low abundance cell types. In this work, we developed a microfluidic fluorescence activated cell sorting device that was able to perform on-demand, low loss cell detection, and sorting. The chip utilizes three-dimensional acoustic standing waves to position all cells in the same fluid velocity regime without sheath. When the cells pass through a laser interrogation region, the scattering and fluorescent signals are detected, translated and transported to software. The target cells are then identified by gating on the plots. Short bursts of standing acoustic waves are triggered by order from PC to sort target cells within predefined gating region. For very low abundance and rare labeled lymphocytes mixed with high concentration unlabeled white blood cells (WBCs), (1-100 labeled lymphocytes are diluted in 10⁶ WBCs in 1 ml volume fluid), the device is able to remove more than 98% WBCs and recover labeled lymphocytes with efficiency of 80%. We further demonstrated that this device worked with real clinical samples by successfully isolating fetal nucleated red blood cells (FNRBCs) in the blood samples from pregnant women with male fetus. The obtained cells were sequenced and the expressions of (sex determining region Y) SRY genes were tested to determine fetal cell proportion. In genetic analysis, the proportion of fetal cells in the final picked sample is up to 40.64%. With this ability, the device proposed could be valuable for biomedical applications involving fetal cells, circulating tumor cells, and stem cells.

Isolation and characterization of fetal nucleated red blood cells from maternal blood as a target for single cell sequencing-based non-invasive genetic testing

PURPOSE

Although non-invasive prenatal testing (NIPT) based on cell-free DNA (cfDNA) in maternal plasma has been prevailing worldwide, low levels of fetal DNA fraction may lead to false-negative results. Since fetal cells in maternal blood provide a pure source of fetal genomic DNA, we aimed to establish a workflow to isolate and sequence fetal nucleated red blood cells (fNRBCs) individually as a target for NIPT.

METHODS

Using male-bearing pregnancy cases, we isolated fNRBCs individually from maternal blood by FACS, and obtained their genomic sequence data through PCR screening with a Y-chromosome marker and whole-genome amplification (WGA)-based whole-genome sequencing.

RESULTS

The PCR and WGA efficiencies of fNRBC candidates were consistently lower than those of control cells. Sequencing data analyses revealed that although the majority of the fNRBC candidates were confirmed to be of fetal origin, many of the WGA-based genomic libraries from fNRBCs were considered to have been amplified from a portion of genomic DNA.

CONCLUSIONS

We established a workflow to isolate and sequence fNRBCs individually. However, our results demonstrated that, to make cell-based NIPT targeting fNRBCs feasible, cell isolation procedures need to be further refined such that the nuclei of fNRBCs are kept intact.

Overview and recent developments in cell-based noninvasive prenatal testing

Investigators have long been interested in the natural phenomenon of fetal and placental cell trafficking into the maternal circulation. The scarcity of these circulating cells makes their detection and isolation technically challenging. However, as a DNA source of fetal origin not mixed with maternal DNA, they have the potential of considerable benefit over circulating cell-free DNA-based noninvasive prenatal genetic testing (NIPT). Endocervical trophoblasts, which are less rare but more challenging to recover are also being investigated as an approach for cell-based NIPT. We review published studies from around the world describing both forms of cell-based NIPT and highlight the different approaches' advantages and drawbacks. We also offer guidance for developing a sound cell-based NIPT protocol.

The isolation and analysis of fetal nucleated red blood cells using multifunctional microbeads with a nanostructured coating toward early noninvasive prenatal diagnostics

Prenatal diagnostics holds great significance for pregnant women desiring healthy babies. Fetal nucleated red blood cells (fNRBCs), bearing the complete genome of the fetus, have been regarded as an important biomarker for noninvasive prenatal diagnostics (NIPD). The high-performance detection and enrichment of fNRBCs from maternal blood, especially during early pregnancy, is urgently needed for NIPD, which, unfortunately, remains a big challenge for early-pregnancy fNRBC isolation. In this study, we developed an innovative platform based on silica microbeads for fNRBC isolation and release in early pregnancy. Microbeads were coated with self-assembled MnO₂ nanoparticles (SiO₂@MnO₂) and then modified with a specific antibody. Benefiting from the three-dimensional nanostructure of the MnO₂ nanoparticles, the isolation efficiency of the fNRBCs was enhanced. Subsequently, fNRBCs were released via dissolving the MnO₂-nanoparticle coating using oxalic acid. We successfully isolated fNRBCs from the maternal peripheral blood samples of 20 pregnant women in the early pregnancy period, ranging from 41 to 62 gestational days. More importantly, the fetal origin of isolated cells was confirmed via fluorescent in situ hybridization and short tandem repeat analysis. This platform based on SiO₂@MnO₂ microbeads has verified the existence of fNRBCs in early-pregnancy maternal blood and is a promising approach for NIPD in early pregnancy.

Sequential Ensemble-Decision Aliquot Ranking Isolation and Fluorescence In Situ Hybridization Identification of Rare Cells from Blood by Using Concentrated Peripheral Blood Mononuclear Cells

Isolation and analysis of circulating rare cells is a promising approach for early detection of cancer and other diseases and for prenatal diagnosis. Isolation of rare cells is usually difficult due to their heterogeneity as well as their low abundance in peripheral blood. We previously reported a two-stage ensemble-decision aliquot ranking platform (S-eDAR) for isolating circulating tumor cells from whole blood with high throughput, high recovery rate (>90%), and good purity (>70%), allowing detection of low surface antigen-expressing cancer cells linked to metastasis. However, due to the scarcity of these cells, large sample volumes and large quantities of antibodies were required to isolate sufficient cells for downstream analysis. Here, we drastically increased the number of nucleated cells analyzed by first concentrating peripheral blood mononuclear cells (PBMCs) from whole blood by density gradient centrifugation. The S-eDAR platform was capable of isolating rare cells from concentrated PBMCs (10⁸/mL, equivalent to processing ∼20 mL of whole blood in the 1 mL sample volume used by our instrument) at a high recovery rate (>85%). We then applied the S-eDAR platform for isolating rare fetal nucleated red blood cells (fNRBCs) from concentrated PBMCs spiked with umbilical cord blood cells and confirmed fNRBC recovery by immunostaining and fluorescence in situ hybridization, demonstrating the potential of the S-eDAR system for isolating rare fetal cells from maternal PBMCs to improve noninvasive prenatal diagnosis.

Enhanced Isolation of Fetal Nucleated Red Blood Cells by Enythrocyte-Leukocyte Hybrid Membrane-Coated Magnetic Nanoparticles for Noninvasive Pregnant Diagnostics

Fetal nucleated red blood cells (fNRBCs) in maternal peripheral blood containing the whole genetic information of the fetus may serve for noninvasive pregnant diagnostics (NIPD). However, the fetal cell-based NIPD is seriously limited by the poor purity of the isolated fNRBCs. Recently, the biomimetic cell membrane-camouflaged nanoparticles containing outstanding features have been widely used to detect and isolate rare cells from the peripheral blood samples. In this work, enythrocyte (RBC) and leukocyte (WBC) membranes are fused and coated onto magnet nanoparticles and then modified with anti-CD147 to isolate fNRBCs from the maternal peripheral blood with significant efficiency (∼90%) and purity (∼87%) in simulated spiked blood samples. Further, fNRBCs were isolated and identified from a series of maternal peripheral blood samples coming from pregnant women of 11-13 gestational weeks, and different chromosomal aneuploidies were diagnosed using fNRBCs isolated from maternal blood in early pregnancy. Our strategy may offer additional opportunity to overcome the limitations of current cell-based NIPD platforms.

Electrospun degradable Zn-Mn oxide hierarchical nanofibers for specific capture and efficient release of circulating tumor cells

Constructing biological affinity devices is considered as an effective strategy for isolating circulating tumor cells (CTCs), and electrospun nanofibers (ESNFs) have recently received attention. However, the current research focuses on polymer fibers, and fabricating stimuli-responsive inorganic nanofibers for cancer diagnosis and analysis is still challenging. In this work, Zn-Mn oxide nanofibers (ZnMnNFs) are used to capture and purify cancer cells after modification with specific antibodies. Then, the hierarchical nanofibers are degraded by reductive weak acid to release the captured cells efficiently without residues. Fusion of Zn and Mn, two transition metals, enhances the surface activity of oxides so that ZnMnNFs are easier to be degraded and modified. By using MCF-7 cancer cells, the cell capture efficiency of ZnMnNFs is up to 88.2%. Furthermore, by using citric acid, it is discovered that, by comparison with Mn oxide nanofibers, the cell release efficiency of ZnMnNFs is improved to 95.1% from 15.4%. In addition, the viability of released cells exceeds 90%. Lastly, the robustness of ZnMnNFs substrates is tested in peripheral blood from breast cancer patients (BCP) and colorectal cancer patients (CCP). Combined with fluorescence labeling, CTCs are confirmed to be isolated from all the clinical samples. This is the first trial of using ternary inorganic ESNFs for cancer cell capture. It is anticipated that the degradable ESNFs will provide biocompatible theranostic platforms and overcome the current limitations of cell release for high-precision gene analysis.

A novel method for noninvasive diagnosis of monogenic diseases from circulating fetal cells

OBJECTIVE

To establish a method for noninvasive fetal cell isolation from maternal blood and prenatal testing of monogenic diseases by a combination of direct sequencing and targeted NGS-based SNP haplotyping from single fetal cells.

METHOD

Peripheral blood of pregnant women in two families (congenital deafness and ichthyosis) was collected. After density-based separation and immunostaining with multiple biomarkers, candidate fetal cells were identified by high-throughput imagine analysis and picked up by automation. Individual fetal cells were subjected to STR-genotyping to identify their origin. Pathogenic mutations were identified by direct Sanger sequencing, and a combination of targeted NGS and SNP haplotyping using a custom panel. All the results were compared with amniotic fluid DNA.

RESULTS

Fetal trophoblasts were successfully harvested from maternal blood. STR-genotyping confirmed the fetal origin. Direct sequencing of pathogenic genetic mutations in fetal cells showed consistent results with amniotic fluid samples. For congenital deafness family, NGS-based SNP haplotyping also correctly identified the fetal haplotype. This single cell haplotyping method can be used to diagnose various genetic diseases.

CONCLUSION

We have established a method for noninvasive prenatal testing of monogenic diseases from circulating trophoblast cells. This cell-based NIPT can be further applied to the prenatal diagnosis of various monogenic diseases.

High-throughput isolation of fetal nucleated red blood cells by multifunctional microsphere-assisted inertial microfluidics

Being easy, safe and reliable, non-invasive prenatal diagnosis (NIPD) has been greatly pursued in recent years. Holding the complete genetic information of the fetus, fetal nucleated red blood cells (fNRBCs) are viewed as a suitable target for NIPD application. However, effective separating fNRBCs from maternal peripheral blood for clinic use still faces great challenges, given that fNRBCs are extremely rare in maternal blood circulation. Here, by combining the high-throughput inertial microfluidic chip with multifunctional microspheres as size amplification, we develop a novel method to isolate fNRBCs with high performance. To enlarge the size difference between fNRBCs and normal blood cells, we use the gelatin coated microspheres to capture fNRBCs with anti-CD147 as specific recognizer at first. The size difference between fNRBCs captured by the microspheres and normal blood cells makes it easy to purify the captured fNRBCs through the spiral microfluidic chip. Finally, the purified fNRBCs are mildly released from the microspheres by enzymatically degrading the gelatin coating. Cell capture efficiency about 81%, high purity of 83%, as well as cell release viability over 80% were achieved using spiked samples by this approach. Additionally, fNRBCs were successfully detected from peripheral blood of pregnant women with an average of 24 fNRBCs per mL, suggesting the great potential of this method for clinical non-invasive prenatal diagnosis.

Comparison between paramagnetic and CD71 magnetic activated cell sorting of fetal nucleated red blood cells from the maternal blood

Background

Fetal nucleated red blood cells (NRBC) from maternal circulation are rare events but can be enriched and used to evaluate the genetics of the fetus. We compared two simplified selection methods of the fetal cells from the maternal blood.

Methods

We isolated fetal cells from maternal blood through double‐density gradient centrifugation followed either by magnetic cell selection, based on the paramagnetic proprieties of the NRBC hemoglobin, converted to methemoglobin, or by a positive magnetic‐activated cell sorting (MACS) enrichment, using anti‐CD71 monoclonal antibodies. Finally, the cells were identified through fluorescence in situ hybridization (FISH) with specific chromosome X and Y probes.

Results

We processed 10 mL of peripheral blood samples from 27 pregnant women with singleton normal male fetuses. Hemoglobin‐based enrichment isolated significantly more NRBCs: 29.7 × 10⁴ cells than anti‐CD71 MACS: 10.1 × 10⁴ cells (P < .001). The FISH analysis found at least one XY cell in 81.5% and 61.5% of cases, respectively, for paramagnetic and anti‐CD71 selection. Also, the average number of XY cells identified through paramagnetic selection was 5.09 ± 2.5, significantly higher than those observed through CD71 sorting: 3.38 ± 1.7 cells (average ± SE) (P = .03).

Conclusion

The combination of density gradient centrifugation with paramagnetic selection has the advantage of simplicity and achieves a minimal manipulation and treatment of cells. It yields an increased number of NRBCs and FISH confirmed fetal cells, compared to the anti‐CD71 sorting.

High-purity isolation of rare single cells from blood using a tiered microchip system

We present a two-tiered microchip system to capture and retrieve rare cells from blood samples with high purity. The first module of the system is a high throughput microfluidic interface that is used to immunomagnetically isolate targeted rare cells from whole blood, and discard > 99.999% of the unwanted leukocytes. The second module is a microwell array that furthers the purification by magnetically guiding each cell into a separate well concurrently, and allows individual retrieval of each cell. We demonstrate the design of the system as well as its characterization by experiments using model cell lines that represent circulating fetal trophoblasts. Our results show that single cells can be retrieved with efficiencies and purities as high as 100% within 145 mins.

Silica microbeads capture fetal nucleated red blood cells for noninvasive prenatal testing of fetal ABO genotype

ABO hemolytic disease of the newborn (ABO-HDN), which may cause neonatal jaundice and polycythemia, or even stillbirth or neonatal death, is widespread in China. Prenatal testing for the fetal ABO blood group can reduce unnecessary concerns or ensure prompt treatment. Herein, we presented a method to employ high-density silica microbeads (SiO₂ MBs) for capturing fetal nucleated red blood cells (fnRBCs) in maternal peripheral blood, and we detected the ABO genotype of the fetus using these captured cells. We evaluated 52 patients using the SiO₂ MBs. Among 26 pregnant women with type O blood, 8 (30.8%) of the fetuses had type A blood, 5 (19.2%) had type B blood, and 13 (50%) had type O blood. SRY genes were detected in all 27 male fetuses. This study represents a simple and effective method for noninvasive prenatal detection of the fetal ABO genotype. We believe that this method has great potential for noninvasive prenatal testing of the fetal Rh blood group and other fetal diseases as well.

Nanostructured Substrates for Detection and Characterization of Circulating Rare Cells: From Materials Research to Clinical Applications

Circulating rare cells in the blood are of great significance for both materials research and clinical applications. For example, circulating tumor cells (CTCs) have been demonstrated as useful biomarkers for "liquid biopsy" of the tumor. Circulating fetal nucleated cells (CFNCs) have shown potential in noninvasive prenatal diagnostics. However, it is technically challenging to detect and isolate circulating rare cells due to their extremely low abundance compared to hematologic cells. Nanostructured substrates offer a unique solution to address these challenges by providing local topographic interactions to strengthen cell adhesion and large surface areas for grafting capture agents, resulting in improved cell capture efficiency, purity, sensitivity, and reproducibility. In addition, rare-cell retrieval strategies, including stimulus-responsiveness and additive reagent-triggered release on different nanostructured substrates, allow for on-demand retrieval of the captured CTCs/CFNCs with high cell viability and molecular integrity. Several nanostructured substrate-enabled CTC/CFNC assays are observed maturing from enumeration and subclassification to molecular analyses. These can one day become powerful tools in disease diagnosis, prognostic prediction, and dynamic monitoring of therapeutic response-paving the way for personalized medical care.

Noninvasive Prenatal Diagnostics: Recent Developments Using Circulating Fetal Nucleated Cells

PURPOSE OF REVIEW

The purpose of this review is to highlight recent research advances in noninvasive prenatal diagnostic methods.

RECENT FINDINGS

Recent studies developing noninvasive prenatal diagnostic (NIPD) methods have been focused on either fetal nucleated red blood cells (fNRBCs) or circulating trophoblasts (cTBs). Enriched cTBs were successfully utilized for whole genome profiling and short tandem repeat (STR) identification to confirm feto-maternal relationship. However, further analysis of isolated fNRBCs remains confined to examining fetal cytogenetics.

SUMMARY

Invasive prenatal diagnostic procedures, amniocentesis and chorionic villus sampling, are the gold standard for the diagnosis of fetal chromosomal abnormalities and genetic disorders. Meanwhile, noninvasive techniques of analyzing circulating cell-free fetal DNA (cffDNA) have been limited to screening tools and are highly fragmented and confounded by maternal DNA. By detecting circulating fetal nucleated cells (CFNCs) we are able to noninvasively confirm fetal chromosomal abnormalities, truly realizing the concept of "noninvasive prenatal diagnostics". The primary technical challenge is the enrichment of the low abundance of CFNCs in maternal peripheral blood. For any cell-based NIPD method, both fetal whole genome profiling and confirmation of the feto-parental relationship are essential. This has been successfully performed using enriched and isolated cTBs, making cTB a better candidate for NIPD. cTB enumeration also correlates with abnormal fetal or placental development. On the other hand, downstream analysis of fNRBCs remains limited to examining fetal sex and aneuploidies. Furthermore, trophoblast-based NIPD via an endocervical sample is also promising because of reduced dilution from hematologic cells.

Highly sensitive and rapid isolation of fetal nucleated red blood cells with microbead-based selective sedimentation for non-invasive prenatal diagnostics

Non-invasive prenatal diagnostics (NIPD) has been an emerging field for prenatal diagnosis research. Carrying the whole genome coding of the fetus, fetal nucleated red blood cells (FNRBCs) have been pursued as a surrogate biomarker traveling around in maternal blood. Here, by combining a unique microbead-based centrifugal separation and enzymatic release, we demonstrated a novel method for FNRBC isolation from the blood samples. First, the gelatin-coated silica microbeads were modified with FNRBC-specific antibody (anti-CD147) to capture the target cells in the blood samples. Then, the density difference between microbead-bound FNRBCs and normal blood cells enables the purification of FNRBCs via an improved high-density percoll-based separation. The non-invasive release of FNRBCs can then be achieved by enzymatically degrading the gelatin film on the surface of the microbeads, allowing a gentle release of the captured target cells with as high as 84% efficiency and ∼80% purity. We further applied it to isolate fetal cells from maternal peripheral blood. The released cells were analyzed by real-time polymerase chain reaction to verify their fetal origin and fluorescent in situ hybridization to detect fetal chromosome disorders. This straightforward and reliable alternative platform for FNRBC detection may have the potential for realizing facile NIPD.

Current Trends of Microfluidic Single-Cell Technologies

The investigation of human disease mechanisms is difficult due to the heterogeneity in gene expression and the physiological state of cells in a given population. In comparison to bulk cell measurements, single-cell measurement technologies can provide a better understanding of the interactions among molecules, organelles, cells, and the microenvironment, which can aid in the development of therapeutics and diagnostic tools. In recent years, single-cell technologies have become increasingly robust and accessible, although limitations exist. In this review, we describe the recent advances in single-cell technologies and their applications in single-cell manipulation, diagnosis, and therapeutics development.

Frequency-enhanced transferrin receptor antibody-labelled microfluidic chip (FETAL-Chip) enables efficient enrichment of circulating nucleated red blood cells for non-invasive prenatal diagnosis

Fetal aneuploidy and other chromosomal aberrations affect 9 in 1000 live births. Unlike the invasive diagnosis with high risk of miscarriage, non-invasive prenatal diagnosis (NIPD) sampling from maternal blood becomes a promising way for fetal genetic screening. However, fetal cell-based NIPD has a major challenge due to the small number of fetal cells present in maternal blood. We designed a frequency-enhanced transferrin receptor antibody-labelled microfluidic chip (FETAL-Chip) for efficient enrichment and identification of circulating fetal cells, i.e., circulating nucleated red blood cells (cNRBCs) from maternal blood. The FETAL-Chip can dramatically enhance the interaction of fetal cells with antibody-coated microposts to increase the capture efficiency while minimizing nonspecific adsorption. With the help of immunostaining, we can identify cNRBCs from as little as 2 milliliter maternal blood. Various numbers of cNRBCs were detected from volunteers as early as 7 weeks after conception and throughout the entire pregnancy. Gene analysis was also carried out to confirm the fetal origin of captured cells. With easy, non-invasive and highly efficient enrichment of cNRBCs, the method presented here offers great potential for non-invasive prenatal diagnosis.

Imprinted NanoVelcro Microchips for Isolation and Characterization of Circulating Fetal Trophoblasts: Toward Noninvasive Prenatal Diagnostics

Circulating fetal nucleated cells (CFNCs) in maternal blood offer an ideal source of fetal genomic DNA for noninvasive prenatal diagnostics (NIPD). We developed a class of nanoVelcro microchips to effectively enrich a subcategory of CFNCs, i.e., circulating trophoblasts (cTBs) from maternal blood, which can then be isolated with single-cell resolution by a laser capture microdissection (LCM) technique for downstream genetic testing. We first established a nanoimprinting fabrication process to prepare the LCM-compatible nanoVelcro substrates. Using an optimized cTB-capture condition and an immunocytochemistry protocol, we were able to identify and isolate single cTBs (Hoechst+/CK7+/HLA-G+/CD45-, 20 μm > sizes > 12 μm) on the imprinted nanoVelcro microchips. Three cTBs were polled to ensure reproducible whole genome amplification on the cTB-derived DNA, paving the way for cTB-based array comparative genomic hybridization (aCGH) and short tandem repeats analysis. Using maternal blood samples collected from expectant mothers carrying a single fetus, the cTB-derived aCGH data were able to detect fetal genders and chromosomal aberrations, which had been confirmed by standard clinical practice. Our results support the use of nanoVelcro microchips for cTB-based noninvasive prenatal genetic testing, which holds potential for further development toward future NIPD solution.