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This work seeks to establish a theoretical model that links phagocytic capacity of phagocytes with geometries of phagocytes and phagocytic objects. The model is applied to four different types of phagocytic objects: a flat surface, a microsphere, a microdisk, and a population of microspheres. For the flat surface, the model assumes that a phagocyte maximizes its contact area between the flat surface and minimizes its non‐contact surface area under a constraint exerted by the volume of the phagocyte's cellular contents. For any of the other three types of objects, the model assumes that a phagocyte completely phagocytoses the object(s) by exhausting its available membrane area. It also assumes that the post‐phagocytosis phagocyte minimizes its surface area. Moreover, the volume of the phagocyte's cellular contents and the geometry of the object impose constraints on the model. For each case, two governing equations are established and combined to derive a single explicit equation with the phagocyte's phagocytic capacity as a function of other parameters. The equations are applied to experimental data for macrophages and neutrophils in the literature. Methods for extending the model and experimentally testing it are discussed. [ABSTRACT FROM AUTHOR]

DNA molecules in a solution can be immobilized and stretched into a highly ordered array on a solid surface containing micropillars by molecular combing technique. However, the mechanism of this process is not well understood. In this study, we demonstrated the generation of DNA nanostrand array with linear, zigzag, and fork-zigzag patterns and the microfluidic processes are modeled based on a deforming body-fitted grid approach. The simulation results provide insights for explaining the stretching, immobilizing, and patterning of DNA molecules observed in the experiments. [ABSTRACT FROM AUTHOR]

Abstract: Cationic lipid-coated magnetic nanoparticles (MPs) associated with transferrin were evaluated as gene transfer vectors in the presence of a static magnetic field. MPs were prepared by chemical precipitation and were surface-coated with cationic lipids, composed of DDAB/soy PC (60:40mole/mole). These cationic MPs were then combined with polyethylenimine (PEI) condensed plasmid DNA, followed by transferrin. The resulting magnetic electrostatic complexes retained relatively compact particle size and showed complete DNA condensation. Their transfection activity in the presence of a static magnetic field was evaluated by luciferase and green fluorescent protein (GFP) reporter genes. The magnetic complexes exhibited up to 300-fold higher transfection activity compared to commonly used cationic liposomes or cationic polymer complexes, based on luciferase assay. The enhancement in transfection activity was maximized when the cells were exposed to the vectors for a relatively short period of time (15min), or were treated in media containing 10% serum. Incorporation of transferrin further improved transfection efficiency of the cationic MPs. However, when cells were incubated for 4h in serum-free media, magnetic and non-magnetic vectors showed similar transfection efficiencies. In conclusion, transferrin-associated cationic MPs are excellent gene transfer vectors that can mediate very rapid and efficient gene transfer in vitro in the presence of a magnetic field. [Copyright &y& Elsevier]

Abstract: Soft lithographic techniques were used to fabricate polymeric microparticles for drug delivery applications. The microparticles were made of thermoplastics and thermosets from different types of precursors including reactive resin and polymer solutions in organic solvents or water. The microparticles produced using these methods were made of widely used polymers for drug delivery with highly uniform sizes, plate-like morphology, and well-defined lateral sizes and shapes, making them potentially useful for drug delivery applications and as platform for the construction of multi-functional drug delivery devices. [Copyright &y& Elsevier]

Abstract: A self-folding miniature device has been developed to provide enhanced mucoadhesion, drug protection, and targeted unidirectional delivery. The main part of the device is a finger like bilayered structure composed of two bonded layers. One is a pH-sensitive hydrogel based on crosslinked poly(methyacrylic acid) (PMAA) that swells significantly when in contact with body fluids, while the other is a non-swelling layer based on poly(hydroxyethyl methacrylate) (PHEMA). A mucoadhesive drug layer is attached on the bilayer. Thus, the self-folding device first attaches to the mucus and then curls into the mucus due to the different swelling of the bilayered structure, leading to enhanced mucoadhesion. The non-swelling PHEMA layer can also serve as a diffusion barrier, minimizing any drug leakage in the intestine. The resulting unidirectional release provides improved drug transport through the mucosal epithelium. The functionality of this device is successfully demonstrated in vitro using a porcine small intestine. [Copyright &y& Elsevier]

Thrombosis is the pathological clot formation under abnormal hemodynamic conditions, which can result in vascular obstruction, causing ischemic strokes and myocardial infarction. Thrombus growth under moderate to low shear (<1000 s−1) relies on platelet activation and coagulation. Thrombosis at elevated high shear rates (>10,000 s−1) is predominantly driven by unactivated platelet binding and aggregating mediated by von Willebrand factor (VWF), while platelet activation and coagulation are secondary in supporting and reinforcing the thrombus. Given the molecular and cellular level information it can access, multiscale computational modeling informed by biology can provide new pathophysiological mechanisms that are otherwise not accessible experimentally, holding promise for novel first-principle-based therapeutics. In this review, we summarize the key aspects of platelet biorheology and mechanobiology, focusing on the molecular and cellular scale events and how they build up to thrombosis through platelet adhesion and aggregation in the presence or absence of platelet activation. In particular, we highlight recent advancements in multiscale modeling of platelet biorheology and mechanobiology and how they can lead to the better prediction and quantification of thrombus formation, exemplifying the exciting paradigm of digital medicine. [ABSTRACT FROM AUTHOR]

Human Mesenchymal Stem Cells (hMSCs) and their derived products hold potential in tissue engineering and as therapeutics in a wide range of diseases. hMSCs possess the ability to aggregate into "spheroids", which has been used as a preconditioning technique to enhance their therapeutic potential by upregulating stemness, immunomodulatory capacity, and anti-inflammatory and pro-angiogenic secretome. Few studies have investigated the impact on hMSC aggregate properties stemming from dynamic and static aggregation techniques. hMSCs' main mechanistic mode of action occur through their secretome, including extracellular vesicles (EVs)/exosomes, which contain therapeutically relevant proteins and nucleic acids. In this study, a 3D printed microchannel bioreactor was developed to dynamically form hMSC spheroids and promote hMSC condensation. In particular, the manner in which dynamic microenvironment conditions alter hMSC properties and EV biogenesis in relation to static cultures was assessed. Dynamic aggregation was found to promote autophagy activity, alter metabolism toward glycolysis, and promote exosome/EV production. This study advances our knowledge on a commonly used preconditioning technique that could be beneficial in wound healing, tissue regeneration, and autoimmune disorders. [ABSTRACT FROM AUTHOR]

Cell population based toxicity assays cannot distinguish responses of single cells and sub-cellular organelles; while single cell assays are limited by low statistical power due to small number of cells examined. This article reports a new single cell array based toxicity assay, in which cell responses at population level, single cell level and sub-cellular level can be obtained simultaneously at high throughput. The single cell array was produced by microcontact printing and selected area cell attachment, and exposed to damaging X-ray radiation, which was followed by fluorescence imaging after staining. Two image processing softwares written in Python and MATLAB were used to determine the expressions of proteins associated with cell migration and invasion, and production of reactive oxygen species (ROS), respectively. The results showed significant differences in responses at single cell level and distinctive molecular heterogeneity at sub-cellular level in a large population of cells upon exposure to radiation. [ABSTRACT FROM AUTHOR]

Microcontactprinting (μCP) of polyelectrolytes is a facileand powerful method for surface micro/nanopatterning and functionalization.Poly(4-aminostyrene) (PAS) is a polyelectrolyte that can be convertedto aryldiazonium salt and exhibits pH-dependent hydrophobicity. Herewe demonstrate μCP of PAS and the expansion of this techniquein various directions. First, the microcontact-printed PAS can bediazotized to micropattern biomolecules including DNA and proteinand nanomaterials including single-walled carbon nanotubes and goldnanoparticles. Second, the diazotized PAS enables μCP of a metallicstructure on a carbon surface. Third, the hydrophobic nature of PASat the neutral pH allows the microcontact-printed PAS-based polyelectrolytemultilayer to be used as masks for wet etching. Lastly, this techniqueallows facile fabrication of highly engineered microparticles witha unique structure. Overall, this work has established a novel μCPplatform with various potential applications. [ABSTRACT FROM AUTHOR]

Paper indicators based on colorimetric assays are widely used for nitrite detection, but their application to liquids with strong colours is restricted. We report a novel paper indicator that allows for sensing nitrite by colorimetric assay, Raman spectroscopy, and electron paramagnetic resonance spectroscopy with non-overlapping signal wavelength ranges through non-contact means. The paper indicator was prepared by impregnating poly(4-aminostyrene), 2-naphthol and single-walled carbon nanotubes in a regular filter paper. All three ingredients were essential to realize the triple-modality sensing. This method is simple and inexpensive, and promises to have wider applicability than the existing paper indicators. [ABSTRACT FROM AUTHOR]

Highlights: [•] Aβ40 can be printed using a polydimethylsiloxane (PDMS) stamp. [•] Printing enables easy characterization of Aβ40 layer adsorbed on PDMS. [•] The intrinsic stability of the adsorbed layer is evaluated. [•] Stable microparticles of Aβ40 are obtained. [•] Aβ40 monomers and fibril fragments can be co-micropatterned. [ABSTRACT FROM AUTHOR]

We report the development of a low-cost method to generate a centimetre-scale periodic array of single plasmid DNA molecules of 11 kilobase pairs. The arrayed DNA molecules are amenable to enzymatic and physical manipulations. [ABSTRACT FROM AUTHOR]

Abstract: A multi-inlet microfluidic hydrodynamic focusing (MF) system to prepare lipopolyplex (LP) containing Bcl-2 antisense deoxyoligonucleotide (ODN) was developed and evaluated. The lipopolyplex nanoparticles consist of ODN:protamine:lipids (1:0.3:12.5wt/wt ratio) and the lipids included DC-Chol:egg PC:PEG–DSPE (40:58:2mol/mol%). Using K562 human erythroleukemia cells, which contain an abundance of Bcl-2 and overexpression of transferrin receptors (TfR), and G3139 (oblimerson sodium or GenasenseTM) as a model cell line and drug, respectively, the Bcl-2 down-regulation at the mRNA and protein levels as well as cellular uptake and apoptosis was compared between the conventional bulk mixing (BM) method and the MF method. The lipopolyplex size and surface charge were characterized by dynamic light scattering (DLS) and zeta potential (ζ) measurement, respectively, while the ODN encapsulation efficiency was determined by gel electrophoresis. Cryogenic transmission electron microscopy (Cryo-TEM) was used to determine the morphology of LPs. Our results demonstrated that MF produced LP nanoparticles had similar structures but smaller size and size distribution compared to BM LP nanoparticles. MF LP nanoparticles had higher level of Bcl-2 antisense uptake and showed more efficient down-regulation of Bcl-2 protein level than BM LP nanoparticles. [Copyright &y& Elsevier]

Current brain spheroids or organoids derived from human induced pluripotent stem cells (hiPSCs) still lack a microglia component, the resident immune cells in the brain. The objective of this study is to engineer brain region-specific organoids from hiPSCs incorporated with isogenic microglia-like cells in order to enhance immune function. In this study, microglia-like cells were derived from hiPSCs using a simplified protocol with stage-wise growth factor induction, which expressed several phenotypic markers, including CD11b, IBA-1, CX3CR1, and P2RY12, and phagocytosed micron-size super-paramagnetic iron oxides. The derived cells were able to upregulate pro-inflammatory gene (TNF-α) and secrete anti-inflammatory cytokines (i.e., VEGF, TGF-β1, and PGE2) when stimulated with amyloid β42 oligomers, lipopolysaccharides, or dexamethasone. The derived isogenic dorsal cortical (higher expression of TBR1 and PAX6) and ventral (higher expression of NKX2.1 and PROX1) spheroids/organoids displayed action potentials and synaptic activities. Co-culturing the microglia-like cells (MG) with the dorsal (D) or ventral (V) organoids showed differential migration ability, intracellular Ca2+ signaling, and the response to pro-inflammatory stimuli (V-MG group had higher TNF-α and TREM2 expression). Transcriptome analysis exhibited 37 microglia-related genes that were differentially expressed in MG and D-MG groups. In addition, the hybrid D-MG spheroids exhibited higher levels of immunoreceptor genes in activating members, but the MG group contained higher levels for most of genes in inhibitory members (except SIGLEC5 and CD200). This study should advance our understanding of the microglia function in brain-like tissue and establish a transformative approach to modulate cellular microenvironment toward the goal of treating various neurological disorders. [ABSTRACT FROM AUTHOR]

Stem cell-derived cardiomyocytes and vascular cells can be used for a variety of applications such as studying human heart development and modelling human disease in culture. In particular, protocols based on modulation of Wnt signaling were able to produce high quality of cardiomyocytes or vascular cells from human pluripotent stem cells (hPSCs). However, the mechanism behind the development of 3D cardiovascular spheroids into either vascular or cardiac cells has not been well explored. Hippo/Yes-associated protein (YAP) signaling plays important roles in the regulation of organogenesis, but its impact on cardiovascular differentiation has been less evaluated. In this study, the effects of seeding density and a change in YAP signaling on 3D cardiovascular spheroids patterning from hPSCs were evaluated. Compared to 2D culture, 3D cardiovascular spheroids exhibited higher levels of sarcomeric striations and higher length-to-width ratios of α-actinin+ cells. The spheroids with high seeding density exhibited more α-actinin+ cells and less nuclear YAP expression. The 3D cardiovascular spheroids were also treated with different small molecules, including Rho kinase inhibitor (Y27632), Cytochalasin D, Dasatinib, and Lysophosphatidic acid to modulate YAP localization. Nuclear YAP inhibition resulted in lower expression of active β-catenin, vascular marker, and MRTF, the transcription factor mediated by RhoGTPases. Y27632 also promoted the gene expression of MMP-2/-3 (matrix remodeling) and Notch-1 (Notch signaling). These results should help our understanding of the underlying effects for the efficient patterning of cardiovascular spheroids after mesoderm formation from hPSCs. [ABSTRACT FROM AUTHOR]