Recent Developments in Inertial and Centrifugal Microfluidic Systems along with the Involved Forces for Cancer Cell Separation: A Review

The treatment of cancers is a significant challenge in the healthcare context today. Spreading circulating tumor cells (CTCs) throughout the body will eventually lead to cancer metastasis and produce new tumors near the healthy tissues. Therefore, separating these invading cells and extracting cues from them is extremely important for determining the rate of cancer progression inside the body and for the development of individualized treatments, especially at the beginning of the metastasis process. The continuous and fast separation of CTCs has recently been achieved using numerous separation techniques, some of which involve multiple high-level operational protocols. Although a simple blood test can detect the presence of CTCs in the blood circulation system, the detection is still restricted due to the scarcity and heterogeneity of CTCs. The development of more reliable and effective techniques is thus highly desired. The technology of microfluidic devices is promising among many other bio-chemical and bio-physical technologies. This paper reviews recent developments in the two types of microfluidic devices, which are based on the size and/or density of cells, for separating cancer cells. The goal of this review is to identify knowledge or technology gaps and to suggest future works.

Unbiased Enrichment of Circulating Tumor Cells Via DNAzyme-Catalyzed Proximal Protein Biotinylation

Circulating tumor cells (CTCs) are noninvasive biomarkers with great potential for assessing neoplastic diseases. However, the enrichment bias toward heterogeneous CTCs remains to be minimized. Herein, a DNAzyme-catalyzed proximal protein biotinylation (DPPB) strategy is established for unbiased CTCs enrichment, employing DNA-framework-based, aptamer-coupled DNAzymes that bind to the surface marker of CTCs and subsequently biotinylated membrane proteins in situ. The DNA framework enables the construction of multivalent DNAzyme and serves as steric hindrance to avoid undesired interaction between DNAzymes and aptamer, leading to efficient binding and biotinylation. Compared with a biotinylated-aptamer strategy, fivefold lower bias of cell subpopulations was achieved by DPPB before and after capture, which enabled a 4.6-fold performance for CTCs analysis in clinic blood samples. DPPB is envisioned to offer a new solution for CTC-based cancer diagnostics.

Genomic Landscape of Hodgkin Lymphoma

Simple Summary

Hodgkin lymphoma (HL) is composed of many reactive and only a few cancer cells, so-called Hodgkin and Reed-Sternberg (HRS) or lymphocyte predominant (LP) cells. Due to the scarcity of these cells, it was difficult to perform high-throughput molecular investigations on them for a long time. With the help of recently developed methods, it is now possible to analyze their genomes. This review summarizes the genetic alterations found in HRS and LP cells that impact immune evasion, proliferation and circumvention of programmed cell death in HL. Understanding these underlying molecular mechanisms is essential, as they may be of prognostic and predictive value and help to improve the therapy especially for patients with recurrent or treatment-resistant disease.

Abstract

Background: Hodgkin lymphoma (HL) is predominantly composed of reactive, non-neoplastic cells surrounding scarcely distributed tumor cells, that is, so-called Hodgkin and Reed-Sternberg (HRS) or lymphocyte predominant (LP) cells. This scarcity impeded the analysis of the tumor cell genomes for a long time, but recently developed methods (especially laser capture microdissection, flow cytometry/fluorescence-activated cell sorting) facilitated molecular investigation, elucidating the pathophysiological principles of “Hodgkin lymphomagenesis”. Methods: We reviewed the relevant literature of the last three decades focusing on the genomic landscape of classic and nodular lymphocyte predominant HL (NLPHL) and summarized molecular cornerstones. Results: Firstly, the malignant cells of HL evade the immune system by altered expression of PDL1/2, B2M and MHC class I and II due to various genetic alterations. Secondly, tumor growth is promoted by permanently activated JAK/STAT signaling due to pervasive mutations of multiple genes involved in the pathway. Thirdly, apoptosis of neoplastic cells is prevented by alterations of NF-κB compounds and the PI3K/AKT/mTOR axis. Additionally, Epstein-Barr virus infection can simultaneously activate JAK/STAT and NF-κB, similarly leading to enhanced survival and evasion of apoptosis. Finally, epigenetic phenomena such as promoter hypermethylation lead to the downregulation of B-lineage-specific, tumor-suppressor and immune regulation genes. Conclusion: The blueprint of HL genomics has been laid, paving the way for future investigations into its complex pathophysiology.

Whole-slide laser microdissection for tumour enrichment

The practical application of genome-scale technologies to precision oncology research requires flexible tissue processing strategies that can be used to differentially select both tumour and normal cell populations from formalin-fixed, paraffin-embedded tissues. As tumour sequencing scales towards clinical implementation, practical difficulties in scheduling and obtaining fresh tissue biopsies at scale, including blood samples as surrogates for matched 'normal' DNA, have focused attention on the use of formalin-preserved clinical samples collected routinely for diagnostic purposes. In practice, such samples often contain both tumour and normal cells which, if correctly partitioned, could be used to profile both tumour and normal genomes, thus identifying somatic alterations. Here we report a semi-automated method for laser microdissecting entire slide-mounted tissue sections to enrich for cells of interest with sufficient yield for whole genome and transcriptome sequencing. Using this method, we demonstrated enrichment of tumour material from mixed tumour-normal samples by up to 67%. Leveraging new methods that allow for the extraction of high-quality nucleic acids from small amounts of formalin-fixed tissues, we further showed that the method was successful in yielding sequence data of sufficient quality for use in BC Cancer's Personalized OncoGenomics (POG) program. © 2020 The Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Influence of Hydrodynamics and Hematocrit on Ultrasound-Induced Blood Plasmapheresis

Acoustophoretic blood plasma separation is based on cell enrichment processes driven by acoustic radiation forces. The combined influence of hematocrit and hydrodynamics has not yet been quantified in the literature for these processes acoustically induced on blood. In this paper, we present an experimental study of blood samples exposed to ultrasonic standing waves at different hematocrit percentages and hydrodynamic conditions, in order to enlighten their individual influence on the acoustic response of the samples. The experiments were performed in a glass capillary (700 µm-square cross section) actuated by a piezoelectric ceramic at a frequency of 1.153 MHz, hosting 2D orthogonal half-wavelength resonances transverse to the channel length, with a single-pressure-node along its central axis. Different hematocrit percentages Hct = 2.25%, 4.50%, 9.00%, and 22.50%, were tested at eight flow rate conditions of Q = 0:80 µL/min. Cells were collected along the central axis driven by the acoustic radiation force, releasing plasma progressively free of cells. The study shows an optimal performance in a flow rate interval between 20 and 80 µL/min for low hematocrit percentages Hct ≤ 9.0%, which required very short times close to 10 s to achieve cell-free plasma in percentages over 90%. This study opens new lines for low-cost personalized blood diagnosis.

Discriminated sgRNAs-Based SurroGate System Greatly Enhances the Screening Efficiency of Plant Base-Edited Cells

The development of CRISPR/Cas9-mediated base editing has made genomic modification more efficient. However, selection of genetically modified cells from millions of treated cells, especially plant cells, is still challenging. In this study, an efficient surrogate reporter system based on a defective hygromycin resistance gene was established in rice to enrich base-edited cells. After step-by-step optimization, the Discriminated sgRNAs-based SurroGate system (DisSUGs) was established by artificially differentiating the editing abilities of a wild-type single guide RNA (sgRNA) targeting the surrogate reporter gene and an enhanced sgRNA targeting endogenous sites. The DisSUGs enhanced the efficiency of screening base-edited cells by 3- to 5-fold for a PmCDA1-based cytosine-to-tyrosine base editor (PCBE), and 2.5- to 6.5-fold for an adenine base editor (ABE) at endogenous targets. These targets showed editing efficiencies of <25% in the conventional systems. The DisSUGs greatly enhanced the frequency of homozygous substitutions and expanded the activity window slightly for both a PCBE and an ABE. Analyses of the total number of single-nucleotide variants from whole-genome sequencing revealed that, compared with the no-enrichment PCBE strategy, the DisSUGs did not alter the frequency of genome-wide sgRNA-independent off-target mutations, but slightly increased the frequency of target-dependent off-target mutations. Collectively, the DisSUGs developed in this study greatly enhances the efficiency of screening plant base-edited cells and will be a useful system in future applications.

Enriching Stem/Progenitor Cells from Dental Pulp Cells by Low-density Culturing

BACKGROUND/AIM

Clonogenicity is a key feature of stem/progenitor cells. The present study aimed to enrich stem/progenitor cells from dental pulp cells by means of culturing the cells at a low clonal density with spatial separation and the evaluate differentiation potential of the surviving cells.

MATERIALS AND METHODS

Pulp cells derived from wisdom teeth were seeded into wells of a 96-plate at a mean density of 1 cell/well and cultured for 2 weeks. Surviving cells were harvested, pooled together and subjected to differentiation into adipocytes, osteoblasts and neurons using respective inducing conditions for 3 weeks. The former two types of cells were examined by staining with Oil Red O and Alizarin Red, respectively. Neuron-like cells were inspected for their morphology and immunostained for microtubule-associated protein 2 and β-tubulin III.

RESULTS

Vital cells were obtained in eight wells of a 96-well plate, corresponding to a survival rate of 8%. Since fewer than two wells would be expected to contain more than four cells at seeding, the majority of surviving cells likely grew from 1-3 cells, which is a very low density. These cells differentiated into functional adipocytes and osteoblasts, and morphologically neuron-like cells.

CONCLUSION

Low-density seeding with spatial separation enables statistical estimation of cell number in wells and provides an effective strategy for enriching stem/progenitor cells and for isolating clonal dental pulp cells.

Label-Free Rapid Separation and Enrichment of Bone Marrow-Derived Mesenchymal Stem Cells from a Heterogeneous Cell Mixture Using a Dielectrophoresis Device

Bone marrow-derived mesenchymal stem cells (BMSCs) are an important cell resource for stem cell-based therapy, which are generally isolated and enriched by the density-gradient method based on cell size and density after collection of tissue samples. Since this method has limitations with regards to purity and repeatability, development of alternative label-free methods for BMSC separation is desired. In the present study, rapid label-free separation and enrichment of BMSCs from a heterogeneous cell mixture with bone marrow-derived promyelocytes was successfully achieved using a dielectrophoresis (DEP) device comprising saw-shaped electrodes. Upon application of an electric field, HL-60 cells as models of promyelocytes aggregated and floated between the saw-shaped electrodes, while UE7T-13 cells as models of BMSCs were effectively captured on the tips of the saw-shaped electrodes. After washing out the HL-60 cells from the device selectively, the purity of the UE7T-13 cells was increased from 33% to 83.5% within 5 min. Although further experiments and optimization are required, these results show the potential of the DEP device as a label-free rapid cell isolation system yielding high purity for rare and precious cells such as BMSCs.

Selective Adhesive Cell Capture without Molecular Specificity: New Surfaces Exploiting Nanoscopic Polycationic Features as Discrete Adhesive Units

This work explored how molecularly non-specific polycationic nanoscale features on a collecting surface control kinetic and selectivity aspects of mammalian cell capture. Key principles for selective collector design were demonstrated by comparing the capture of two closely related breast cancer cell lines: MCF-7 and TMX2-28. TMX2-28 is a tamoxifen-selected clone of MCF-7. The collector was a silica surface, negatively-charged at pH 7.4, containing isolated molecules (~ 8 nm diameter) of the cationic polymer, poly(dimethyl-aminoethylmethacrylate), pDMAEMA. Important in this work is the non-selective nature of the pDMAEMA interactions with cells: pDMAEMA generally adheres negatively charged particles and cells in solution. We show here that selectivity towards cells results from collector design: this includes competition between repulsive interactions involving the negative silica and attractions to the immobilized pDMAEMA molecules, the random pDMAEMA arrangement on the surface, and the concentration of positive charge in the vicinity of the adsorbed pDMAEMA chains. The latter act as nanoscopic cationic surface patches, each weakly attracted to negatively-charged cells. Collecting surfaces engineered with an appropriate amount pDMAEMA, exposed to mixtures of MCF-7 and TMX2-28 cells preferentially captured TMX2-28 with a selectivity of 2.5. (This means that the ratio of TMX2-28 to MCF cells on the surface was 2.5 times their compositional ratio in free solution.) The ionic strength-dependence of cell capture was shown to be similar to that of silica microparticles on the same surfaces. This suggests that the mechanism of selective cell capture involves nanoscopic differences in the contact areas of the cells with the collector, allowing discrimination of closely related cell line-based small scale features of the cell surface. This work demonstrated that even without molecular specificity, selectivity for physical cell attributes produces adhesive discrimination.

Generation of novel monoclonal antibodies for the enrichment and characterization of human corneal endothelial cells (hCENC) necessary for the treatment of corneal endothelial blindness

Corneal transplantation is the primary treatment option to restore vision for patients with corneal endothelial blindness. Although the success rate of treatment is high, limited availability of transplant grade corneas is a major obstacle. Tissue-engineered corneal endothelial grafts constructed using cultivated human corneal endothelial cells (hCENC) isolated from cadaveric corneas may serve as a potential graft source. Currently, tools for the characterization of cultured hCENC and enrichment of hCENC from potential contaminating cells such as stromal fibroblasts are lacking. In this study, we describe the generation and characterization of novel cell surface monoclonal antibodies (mAbs) specific for hCENC. These mAbs could be used for enrichment and characterization of hCENC. Out of a total of 389 hybridomas, TAG-1A3 and TAG-2A12 were found to be specific to the corneal endothelial monolayer by immunostaining of frozen tissue sections. Both mAbs were able to clearly identify hCENC with good 'cobblestone-like' morphology from multiple donors. The antigen targets for TAG-1A3 and TAG-2A12 were found to be CD166/ALCAM and Peroxiredoxin-6 (Prdx-6), respectively, both of which have not been previously described as markers of hCENC. Additionally, unlike other Prdx-6 mAbs, TAG-2A12 was found to specifically bind cell surface Prdx-6, which was only expressed on hCENC and not on other cell types screened such as human corneal stromal fibroblasts (hCSF) and human pluripotent stem cells (hPSC). From our studies, we conclude that TAG-1A3 and TAG-2A12 are promising tools to quantitatively assess hCENC quality. It is also noteworthy that the binding specificity of TAG-2A12 could be used for the enrichment of hCENC from cell mixtures of hCSF and hPSC.

Peptide-conjugated glass slides for selective capture and purification of diagnostic cells: Applications in urine cytology

Obtaining a clear view of the cells of interest in diagnostic cytology can be challenging when specimens are contaminated with blood or other obscuring cells. In this study, we present a powerful technique for the selective capture of diagnostic epithelial cells directly on a microscope slide, highlighting its applications in urine cytology and immunocytochemistry (ICC). Using phage-display biopanning, we identified and synthesized a series of peptides that bind with high affinity to urothelial cells but not blood cells. We developed methods for conjugating the peptides to glass slides, and we used these slides to selectively capture both normal and cancerous epithelial cells from urine contaminated with blood cells. Unlike non-selective microscope slides, the peptide-conjugated slides selectively retained the cells of interest, recovering up to 75% of urothelial cells, while up to 98% of blood cells were washed away. The slides are compatible with Papanicolaou and hematoxylin and eosin (H&E) staining for cytology preparations, as well as ICC for detecting membrane-associated and nuclear cancer markers. We successfully detected the expression of carcinoembryonic antigen and survivin, two commonly measured bladder cancer markers. In addition to bladder cancer diagnostics, this technology has broad applications for increasing the quality of sample preparations in slide-based diagnostic testing.

Effect of pore structure of macroporous poly(lactide-co-glycolide) scaffolds on the in vivo enrichment of dendritic cells

The in vivo enrichment of dendritic cells (DCs) in implanted macroporous scaffolds is an emerging strategy to modulate the adaptive immune system. The pore architecture is potentially one of the key factors in controlling enrichment of DCs. However, there have been few studies examining the effects of scaffold pore structure on in vivo DC enrichment. Here we present the effects of surface porosity, pore size, and pore volume of macroporous poly(lactide-co-glycolide) (PLG) scaffolds encapsulating granulocyte macrophage colony-stimulating factor (GM-CSF), an inflammatory chemoattractant, on the in vivo enrichment of DCs. Although in vitro cell seeding studies using PLG scaffolds without GM-CSF showed higher cell infiltration in scaffolds with higher surface porosity, in vivo results revealed higher DC enrichment in GM-CSF loaded PLG scaffolds with lower surface porosity despite a similar level of GM-CSF released. The diminished compressive modulus of high surface porosity scaffolds compared to low surface porosity scaffolds lead to the significant shrinkage of these scaffolds in vivo, suggesting that the mechanical strength of scaffolds was critical to maintain a porous structure in vivo for accumulating DCs. The pore volume was also found to be important in total number of recruited cells and DCs in vivo. Varying the pore size significantly impacted the total number of cells, but similar numbers of DCs were found as long as the pore size was above 10-32 μm. Collectively, these results suggested that one can modulate in vivo enrichment of DCs by altering the pore architecture and mechanical properties of PLG scaffolds.

Shape-dependent optoelectronic cell lysis

We show an electrical method to break open living cells amongst a population of different cell types, where cell selection is based upon their shape. We implement the technique on an optoelectronic platform, where light, focused onto a semiconductor surface from a video projector creates a reconfigurable pattern of electrodes. One can choose the area of cells to be lysed in real-time, from single cells to large areas, simply by redrawing the projected pattern. We show that the method, based on the "electrical shadow" that the cell casts, allows the detection of rare cell types in blood (including sleeping sickness parasites), and has the potential to enable single cell studies for advanced molecular diagnostics, as well as wider applications in analytical chemistry.

Generation of tissue constructs for cardiovascular regenerative medicine: from cell procurement to scaffold design

The ability of the human body to naturally recover from coronary heart disease is limited because cardiac cells are terminally differentiated, have low proliferation rates, and low turn-over rates. Cardiovascular tissue engineering offers the potential for production of cardiac tissue ex vivo, but is currently limited by several challenges: (i) Tissue engineering constructs require pure populations of seed cells, (ii) Fabrication of 3-D geometrical structures with features of the same length scales that exist in native tissue is non-trivial, and (iii) Cells require stimulation from the appropriate biological, electrical and mechanical factors. In this review, we summarize the current state of microfluidic techniques for enrichment of subpopulations of cells required for cardiovascular tissue engineering, which offer unique advantages over traditional plating and FACS/MACS-based enrichment. We then summarize modern techniques for producing tissue engineering scaffolds that mimic native cardiac tissue.