Low-viscosity Matrix Research Articles

Low-viscosity Matrix Suspension Culture for Human Colorectal Epithelial Organoids and Tumoroids.

Three-dimensional culture of human normal colorectal epithelium and cancer tissue as organoids and tumoroids has transformed the study of diseases of the large intestine. A widely used strategy for generating patient-derived colorectal organoids and tumoroids involves embedding cells in domes of extracellular matrix (ECM). Despite its success, dome culture is not ideal for scalable expansion, experimentation, and high-throughput screening applications. Our group has developed a protocol for growing patient-derived colorectal organoids and tumoroids in low-viscosity matrix (LVM) suspension culture. Instead of embedding colonic crypts or tumor fragments in solid ECM, these are grown suspended in medium containing only a low percentage of ECM. Compared with dome cultures, LVM suspension culture reduces the labor and cost of establishing and passaging organoids and tumoroids, enables rapid expansion, and is readily adaptable for high-throughput screening. Graphic abstract: Generation of organoids and tumoroids from human large intestine using LVM suspension culture (Created with BioRender.com).

Low-viscosity matrix suspension culture enables scalable analysis of patient-derived organoids and tumoroids from the large intestine

Cell embedment into a solid support matrix is considered essential for the culture of intestinal epithelial organoids and tumoroids, but this technique presents challenges that impede scalable culture expansion, experimental manipulation, high-throughput screening and diagnostic applications. We have developed a low-viscosity matrix (LVM) suspension culture method that enables efficient establishment and propagation of organoids and tumoroids from the human large intestine. Organoids and tumoroids cultured in LVM suspension recapitulate the morphological development observed in solid matrices, with tumoroids reflecting the histological features and genetic heterogeneity of primary colorectal cancers. We demonstrate the utility of LVM suspension culture for organoid and tumoroid bioreactor applications and biobanking, as well as tumoroid high-throughput drug sensitivity testing. These methods provide opportunities for the study and use of patient-derived organoids and tumoroids from the large intestine.

A mélange of subduction temperatures: Evidence from Zr-in-rutile thermometry for strengthening of the subduction interface

The Catalina Schist contains a spectacular, km-scale amphibolite facies mélange zone, thought to be part of a Cretaceous convergent margin plate interface. In this setting, blocks ranging from centimeters up to ≥100 m in diameter are surrounded by finer-grained matrix that is derived from the blocks. Blocks throughout the mélange represent a diversity of protoliths derived from basalts, cherts and other sediments, and hydrated mantle, but all contain assemblages consistent with upper amphibolite-facies conditions, suggesting a relatively restricted range of depths and temperatures over which material within the mélange was metamorphosed. This apparent uniformity of metamorphic grade contrasts with other mélanges, such as the Franciscan Complex, where coexisting rocks with highly variable peak metamorphic grade suggest extensive mixing of materials along the subduction interface. This mixing has been ascribed to flow of material within relatively low viscosity matrix. The Zr content of rutile in samples from across the amphibolite facies mélange of the Catalina Schist was measured to determine peak metamorphic temperatures, identify whether these temperatures were different among blocks, and whether the spatial distribution of temperatures throughout the mélange was systematic or random. Resolvably different Zr contents, between 290 and 720 (±10–40) ppm, are found among the blocks, corresponding to different peak metamorphic temperatures of 650 to 730 (±2–16) °C at an assumed pressure of 1 GPa. These results are broadly consistent with previous thermobarometric estimates. No systematic distribution of temperatures was found, however. Like other mélange zones, material flow within the Catalina Schist mélange was likely chaotic, but appears to have occurred on a more restricted scale compared to some other localities. Progressive metamorphism of mélange matrix is expected to produce rheologically stiffer matrix minerals (such as amphiboles and pyroxenes) at the expense of weaker matrix minerals (sheet silicates), affecting the overall rheological behavior of the mélange, and dictating the scale of flow. The Catalina Schist amphibolite facies mélange matrix appears to provide a snapshot of hotter, stiffer portions of a subduction interface, perhaps more representative of rheological behavior at depths approaching the subarc than is found in some other exhumed mélange zones.

Interfacial rheology of coexisting solid and fluid monolayers.

Biologically relevant monolayer and bilayer films often consist of micron-scale high viscosity domains in a continuous low viscosity matrix. Here we show that this morphology can cause the overall monolayer fluidity to vary by orders of magnitude over a limited range of monolayer compositions. Modeling the system as a two-dimensional suspension in analogy with classic three-dimensional suspensions of hard spheres in a liquid solvent explains the rheological data with no adjustable parameters. In monolayers with ordered, highly viscous domains dispersed in a continuous low viscosity matrix, the surface viscosity increases as a power law with the area fraction of viscous domains. Changing the phase of the continuous matrix from a disordered fluid phase to a more ordered, condensed phase dramatically changes the overall monolayer viscosity. Small changes in the domain density and/or continuous matrix composition can alter the monolayer viscosity by orders of magnitude.

Effect of Matrix Viscosity on Rheological and Microwave Properties of Polymer Nanocomposites with Multiwall Carbon Nanotubes

Abstract Nanocomposites of multiwalled carbon nanotubes (MWCNTs) in epoxy resin and polypropylene (PP) are studied. The effect of matrix viscosity on the degree of dispersion of nanotubes is determined by rheological methods. Rheology and microwave properties are correlated to estimate the optimal limits of nanofiller content required for improving the performance of nanocomposites. Rheological percolation threshold is determined for both types nanocomposites, ϕp=0.27% for the epoxy/MWCNT and; ϕp=1.5% for the PP/MWCNT, as found critical for achieving a network structure of interacting nanotubes in the matrix polymer. Good electromagnetic shielding efficiency was obtained for nanocomposites at nanotube contents above the rheological percolation. Low viscosity matrix facilitates contacts between MWCNTs, resulting in appearance of electromagnetic shielding at very low percolation threshold.

Preparation of Au Nanoparticles and End‐Functionalized Poly(butadiene) Composites via Electrostatic Interaction

AbstractPolymer‐inorganic nanoparticle (NP) composites are prepared by immersing preformed end‐functionalized poly (butadiene) (PB) films, which have a lower glass transition temperature than room temperature, in an aqueous dispersion of Au NPs. Depending on the viscosity of the PB matrix, the Au NPs show different distributions in the end‐functionalized PB matrix. In the high viscosity matrix, the Au NPs are immobilized at the surface of the end‐functionalized PB, whereas in the low viscosity matrix, the Au NPs are incorporated into the matrix and are well dispersed. This incorporation of Au NPs occurs dynamically in three steps: (1) adsorption of the Au NPs on the surface of the PB matrix through electrostatic interactions; (2) stabilization of the Au NPs by the end functional groups of the PB molecules; (3) the diffusion of the Au NPs into the PB matrix because of the low viscosity of the matrix.

The role of non-covalent interactions and matrix viscosity on the dispersion and properties of LLDPE/MWCNT nanocomposites

Linear low density polyethylene (LLDPE)/multi-walled carbon nanotube (MWCNT) composites were prepared by melt compounding, following two different compatibilization strategies that involved non-covalent interactions between the matrix and the filler. The first approach involved grafting pyridine aromatic moieties on the maleated polyolefin backbone, which are able to interact by π–π stacking with the surface of the nanotubes. The second method implemented non-covalent/non-specific surface functionalization of the MWCNTs with a hyperbranched polyethylene (HBPE). The enhanced interfacial interactions established in the composites containing LLDPE functionalized with pyridine grafts improved the dispersion of the nanotubes within the polymer matrix. Dispersion was also favoured by higher matrix viscosity. Composites containing finely dispersed MWCNTs exhibited an increase in the rheological and electrical percolation thresholds, and a significant improvement in mechanical properties. On the contrary the composites based on the low viscosity matrix contained large amounts of aggregates, which promoted lower percolation thresholds. Manipulation of matrix viscosity and compatibilization resulted in composites with good mechanical properties, and low percolation thresholds.

The influence of matrix viscosity on MWCNT dispersion and electrical properties in different thermoplastic nanocomposites

Composites of MWCNTs having each three different levels of matrix viscosity with five different polymers (polyamide 12, polybutylene terephthalate, polycarbonate, polyetheretherketone and low density polyethylene) were melt mixed to identify the general influence of matrix viscosity on the electrical properties and the state of MWCNT dispersion. Huge differences in the electrical percolation thresholds were found using the same polymer matrix with different viscosity grades. The lowest percolation thresholds were always found in the composites based on the low viscosity matrix. The state of primary MWCNT agglomerate dispersion increased with increasing matrix viscosity due to the higher input of mixing energy. TEM investigations showed nanoagglomerated structures in the low viscosity samples which are obviously needed to achieve low resistivity values. The effect of nanotube shortening was quantified using two different viscosity grades of polycarbonate. Due to the higher mixing energy input the nanotube shortening was more pronounced in the high viscosity matrix which partially explains the higher percolation threshold.

Analysis of the influence of polymer viscosity on the dispersion of magnesium hydroxide in a polyolefin matrix

The dispersion of Mg(OH)2 agglomerates at low concentration in a polymer melt was investigated in a transparent counter-rotating shear cell. The influence of the viscosity of the matrix, the initial agglomerate size and the infiltration of the matrix was evaluated. Mg(OH)2 agglomerates have a low cohesion and a fractal structure. Two dispersive mechanisms already mentioned in the literature were identified: erosion and rupture. Critical conditions for rupture were measured and particle size analysis was performed in order to determine the kinetics of erosion. The infiltration of the matrix, which depends on the viscosity, was found to play a key role on dispersion mechanisms. In contrast to previous works, infiltration is more important with the high viscosity matrix. In infiltrated matrix, rupture was found to occur firstly through plastic deformation of the infiltrated agglomerate, and then the agglomerates split into small fragments. In the low viscosity matrix, fragments produced either by rupture or erosion are small aggregates.

Dispersion of carbon black in a continuous phase: Electrical, rheological, and morphological studies

This work investigates the dispersion of carbon black (CB) aggregates into various polymeric matrices to increase electric conductivity. The effect of matrix viscosity on CB morphology and, consequently, on the blend conductivity was thoroughly addressed. The electric conductivity increases from 10–9 to 10–4 when less than 3% CB aggregates were dispersed into the PDMS liquid of various viscosities. The CB threshold loading was found to increase from 1% to 3% as the viscosity rose from 10 cp to 60 000 cp. This finding shows that an ideal loading with CB aggregates is far below that (generally 15%) of a typical pelletized CB loading. Moreover, the microscope and RV tests reveal that CB aggregates diffuse and form an agglomerate-network when the conductivity threshold is reached in a low-viscosity matrix. However, a CB aggregate-network was observed when the threshold value was attained in a high-viscosity matrix. These two mechanisms can be distinguished at approximately 1000 cp. Finally, experimental observation shows that the increase of viscosity during curing does not influence the conductivity of the composite while the CB aggregates dispersed in a thermoset matrix. The minimum viscosity during curing, however, was found to be critical to CB dispersion morphology and, consequently, to ultimate electric conductivity.

Buckling versus folding: Importance of viscoelasticity

We present a dominant wavelength solution for a viscoelastic layer embedded in a low viscosity matrix under layer‐parallel compression based on the thin‐plate approximation. We show that the deformation mode approximates the elastic or viscous limits depending on a parameter, R, which is the ratio of dominant wavelength predicted by pure viscous theory to the one predicted by pure elastic theory. In contrast, conventional analyses based on the Deborah number incorrectly predict the deformation mode. The dominant viscoelastic wavelength closely follows the minimum out of viscous and elastic dominant wavelengths. The viscoelastic thin‐plate theory is verified by two‐dimensional modeling of large strain viscoelastic folding, for which we develop a new numerical algorithm based on a combined spectral/finite‐difference method. The robustness of the numerical code is demonstrated by calculation, for the first time, of the pressure field evolution during folding of a viscoelastic layer with up to 100% strain.

Separation of oligonucleotides and DNA fragments by capillary electrophoresis in dynamically and permanently coated capillaries, using a copolymer of acrylamide and beta-D-glucopyranoside as a new low viscosity matrix with high sieving capacity.

New copolymers of acrylamide and beta-D-glucopyranoside were synthesized and characterized. The different reactivity of the two monomers towards radical polymerization meant we could control the growth of the polymer chains whose length was inversely related to the number of glucose residues incorporated in the copolymers. The properties of these polymers were investigated in the separation of oligonucleotides and double-stranded DNA by capillary electrophoresis (CE) in coated and uncoated capillaries. The new copolymers were a suitable matrix for CE due to their high-resolving capacity and low viscosity. We also looked into the advantages of a new method of dynamic suppression of electroosmotic flow based on the addition of small amounts (0.03-0.05%) of dimethylacrylamide to the sieving and to the running buffer. A complete test was run on the reproducibility and efficiency of separations carried out in a permanently and dynamically coated capillary, and the advantages and disadvantages of the two methods were compared.

Scale effects upon morphology development during mix melting of multiphase polymer blends in ZSK extruders

AbstractReplicate experiments were performed on ZSK‐30 and ZSK‐40 split barrel extruders concerning structure developments from PS‐PE pellet blends during the melting process. PS is the minor phase. PE grades were choosen to accommodate viscous and thin matrix phase viscosities. The large extruder displays a more diverse cross channel structure and retarded phase development for some blends. Inferior dispersion is especially obvious in the larger extruder when processing low viscosity matrix blends. Similar phase development occurs in the extruders for high viscosity matrix blends.

Effect of matrix crystallinity on the characteristics of the interfacial layer in SiC fiber-reinforced Si-Al-O-N composites

Glass or glass-ceramics have been used as matrix materials for fiber reinforcing by the slurry infiltration process, followed by hot pressing. These matrices have been used for two major reasons: (i) They oxidize the SiC fiber to form a C-rich interfacial layer between the fiber and matrix during hot pressing (2SiC(s) + O2(g) = 2C(s) + 2SiO(g)). Such carbon-rich layers cause low fiber-matrix interfacial shear strength resulting in high composite fracture toughness. (ii) A low viscosity matrix is required to minimize fiber damage during hot pressing. In the present study, the Si2N2O - AI2O3 system was used as a new host material for Nicalon SiC fiber: it has a more refractory nature and is able to provide a liquid phase (with the presence of a sintering agent, e.g., A12O3, CaO, etc.) to avoid fiber damage during densification. This matrix system can also provide oxygen to form a C-rich interphase. In this paper, the effect of matrix crystallinity on the interfacial characteristics is described.

The uplift of high-pressure-low-temperature metamorphic rocks

The uplift of high-P-low-Tmetamorphic rocks has been attributed to buoyancy, diapirism, or hydrodynamically driven return flow. Buoyancy forces can return material subducted into the mantle only if subduction slows or ceases, reducing the downward traction. The buoyancy forces will be reversed within the crust, because of the increased density of high-Passemblages, and therefore can not cause the subducted material to rise beyond the base of the crust. Diapirism and hydrodynamic flow processes require a low-density, low-viscosity matrix, and can only explain the emplacement of relatively small bodies of high-Prock entrained in the flowing material. The tectonic setting of coherent regional high-P—low-Tterrains can be explained in terms of the mechanical behaviour of an accretionary wedge with negligible yield strength, where underplating is the dominant mode of accretion. Underplating thickens the wedge from beneath and increases its surface slope. This causes the upper part of the wedge to extend horizontally, even though convergence is continuing. Continued underplating beneath and extension above can allow the oldest high-Procks to rise to within reach of a moderate amount of erosion on a time scale of the order of 10 Ma. As long as subduction continues beneath the wedge, the geothermal gradient will not relax to a normal value. This process explains (a) the evidence that high-P-low-Trocks are commonly uplifted while convergence is continuing; (b) the absence in many cases of significant overprinting by higher-Tassemblages; (c) the position of the oldest and highest pressure rocks in the upper rear of orogenic wedges; (d) the lack of adequate tectonic thicknesses of overlying rock to explain the metamorphism; and (e) the common occurrence of post-metamorphic faults that excise parts of the metamorphic zonation.