Cell Size Distribution Research Articles

Shape Memory Polymer Foam Based on Nanofibrillar Composites of Polylactide/Polyamide

This paper presents the novel development of a shape memory polymer foam based on polymer–polymer nanocomposites. Herein, polylactide (PLA)/biosourced polyamide (PA) foams are fabricated by in situ fibrillation of polymer blends and a subsequent supercritical CO2 foaming technique. In this system, PLA serves as a shape memory polymer to endow this foam with a shape memory effect (SME), and in situ generated PA nanofibers are employed to reinforce the PLA cell walls and provide an additional permanent phase. A concentration of PA, 5 wt.%, was chosen to form an entangled nanofibrillar network. Foams of PLA/PA nanoblends with the same content of constituents were fabricated to reveal the effect of minor phase morphology on the cell structure and shape memory behavior of polymer foams. Profiting from the reinforcing effect of PA nanofibers, the PLA/PA nanocomposite foam exhibits smaller foam cells, a narrower cell size distribution and a comparable cell concentration than the PLA/PA nanoblend foam. In addition, PA nanofibers, unlike PA nanodroplets, favor the shape fixation ratio and recovery ratio and shorten the shape recovery time.

Neural Network-Enabled Multiparametric Impedance Signal Templating for High throughput Single-Cell Deformability Cytometry Under Viscoelastic Extensional Flows.

Cellular biophysical metrics exhibit systematic alterations during processes, such as metastasis and immune cell activation, which can be used to identify and separate live cell subpopulations for targeting drug screening. Image-based biophysical cytometry under extensional flows can accurately quantify cell deformability based on cell shape alterations but needs extensive image reconstruction, which limits its inline utilization to activate cell sorting. Impedance cytometry can measure these cell shape alterations based on electric field screening, while its frequency response offers functional information on cell viability and interior structure, which are difficult to discern by imaging. Furthermore, 1-D temporal impedance signal trains exhibit characteristic shapes that can be rapidly templated in near real-time to extract single-cell biophysical metrics to activate sorting. We present a multilayer perceptron neural network signal templating approach that utilizes raw impedance signals from cells under extensional flow, alongside its training with image metrics from corresponding cells to derive net electrical anisotropy metrics that quantify cell deformability over wide anisotropy ranges and with minimal errors from cell size distributions. Deformability and electrical physiology metrics are applied in conjunction on the same cell for multiparametric classification of live pancreatic cancer cells versus cancer associated fibroblasts using the support vector machine model.

Microfluidic Fabrication of Gelatin-Nano Hydroxyapatite Scaffolds for Enhanced Control of Pore Size Distribution and Osteogenic Differentiation of Dental Pulp Stem Cells.

The combination of gelatin and hydroxyapatite (HA)has emerged as a promising strategy in dental tissue engineering due to its favorable biocompatibility, mechanical properties, and ability to support cellular activities essential for tissue regeneration, rendering them ideal components for hard tissue applications. Besides, precise control over interconnecting porosity is of paramount importance for tissue engineering materials. Conventional methods for creating porous scaffolds frequently encounter difficulties in regulating pore size distribution. This study demonstrates the fabrication of gelatin-nano HA scaffolds with uniform porosity using a T-type junction microfluidic device in a single-step process. Significant improvements in control over the pore size distribution are achieved by regulating the flow parameters, resulting in effective and time-efficient manufacturing comparable in quality to the innovative 3D bioprinting techniques. The overall porosity of the scaffolds exceeded 60%, with a remarkably narrow size distribution. The incorporation of nano-HAinto 3D porous gelatin scaffolds successfully induced osteogenic differentiation in stem cells at both the protein and gene levels, as evidenced by the significant increase in osteocalcin (OCN), an important marker of osteogenic differentiation. The OCN levels are 26 and 43 times higher for gelatin and gelatin-HA scaffolds, respectively, compared to the control group.

Asymptotic decoupling of population growth rate and cell size distribution

The rate at which individual bacterial cells grow depends on the concentrations of cellular components such as ribosomes and proteins. These concentrations continuously fluctuate over time and are inherited from mother to daughter cells, leading to correlations between the growth rates of cells across generations. Division sizes of cells are also stochastic and correlated across generations due to a phenomenon known as cell size regulation. Fluctuations and correlations from both growth and division processes affect the population dynamics of an exponentially growing culture. Here, we provide analytic solutions for the population dynamics of cells with continuously fluctuating growth rates coupled with a generic model of cell-size regulation. We show that in balanced growth, the effects of growth and division processes decouple; the population growth rate only depends on the single-cell growth rate process, and the population cell size distribution only depends on the model of division and cell size regulation. The population growth rate is always higher than the average single-cell growth rate and the difference increases with growth rate variability and its correlation time. This difference also sets the timescale for the population to reach its steady state. We provide analytical solutions for oscillations in population growth rate and traveling waves in size distribution during this approach to the steady state. Published by the American Physical Society 2024

Sensitive and real-time monitoring of microbial growth using a dielectric sensor with a 65-GHz LC-oscillator array and polytetrafluoroethylene membrane

In this study, we report a sensitive real-time microbial growth monitoring technique using a complementary metal-oxide semiconductor (CMOS) dielectric sensor with a polytetrafluoroethylene (PTFE) membrane. The sensor comprised an LC oscillator array operating at 65-GHz, whose resonant frequency was altered according to the dielectric properties of the region approximately 15 μm from the surface. We previously reported the rapid detection of viable Escherichia coli suspended in a liquid medium using the dielectric sensor; however, sensing growing cells was challenging owing to their tendency to float outside the effective sensing area in the suspended medium. To address this, we propose a new method to enhance the sensitivity of the device using a PTFE membrane that retains cells inside the effective area during measurement. Experiments using Escherichia coli suggested that the use of the membrane more than doubled sensitivity, reducing inspection times for practical applications. Furthermore, experiments with Lactococcus lactis, Staphylococcus epidermidis, and Saccharomyces cerevisiae demonstrated that this method can be used to monitor the growth of various microbes. In addition, variations in the output values of each oscillator facilitated the determination of microbial characteristics, such as cell size and growth distribution. This microbial growth monitoring technique is expected to find applications across a wide range of fields, such as food inspection, environmental hygiene monitoring, antibiotic susceptibility testing, new drug discovery, and the exploration of beneficial microbes.

Impact of compositionally diverse cereal flour water extracts on the gas cell size distribution and extensional rheology of model gluten-starch doughs

Impact of compositionally diverse cereal flour water extracts on the gas cell size distribution and extensional rheology of model gluten-starch doughs

Endothermic–Exothermic Hybrid Foaming of Recycled PET Blends

Over the past decades, the use of polyethylene terephthalate (PET) has seen significant growth, particularly in the packaging industry. However, its long decomposition time poses serious environmental challenges. The aim of this research was to develop a process for the foaming of large quantities of recycled PET (rPET) using endothermic and exothermic foaming agents. Various formulations with different ratios of endothermic and exothermic foaming agents were prepared, as well as their mixtures. The study found that the endothermic–exothermic hybrid foaming process resulted in a finer cell-size distribution and enhanced mechanical properties, making the foams highly suitable for widespread applications. The results support the potential use of exothermic foaming agents as nucleating agents in a hybrid foaming system. In particular, the ratio of 3% endothermic and 1% exothermic foaming agents proved optimal in terms of achieving a balance between porosity and mechanical strength, thereby enabling broad industrial applicability.

Fabrication of flat and sizeable nanocellular polymethyl methacrylate (PMMA) foam with tunable thermal conductivity

AbstractPolymeric nanocell foam is a promising material that faces manufacturing challenges. Producing sizable and thick foams for properties testing has been challenging. This study aims to scale up and understand the foaming mechanism of nanocellular foams by controlling the saturation temperature, pressure, and molecular weight distribution of the matrix to fine‐tune the glass transition temperature of the polymer/gas mixture. The hot‐press foamed samples possess a 100 × 70 × 6 ~ 8 mm3 dimension and a cell size of less than 200 nm. Bimodal structures can also be created by controlling the critical processing parameters. Introducing 37% microcells into unimodal nanocellular foam reduced the relative density from 0.29 to 0.19. The thermal conductivity of the foams was tuned by controlling the cell size distribution. Unimodal nanofoams have the lowest thermal conductivity for foams of the same density due to the Knudsen effect and tortuosity. The measured thermal conductivity is in agreement with theoretical models.Highlights PMMA nanofoam with a dimension of 100 × 70 × 6–8 mm3 and cell size below 200 nm. The morphology of nanofoams was tuned to be unimodal and bimodal. The foam density of the bimodal nanofoams was lowered below 0.238 g/cm3. The thermal conductivity of foams was tuned by controlling the cell structure.

Osmotic injury and cytotoxicity for hMSCs in contact with Me2SO: The effect of cell size distribution

The paper discusses the impact of cell size on cytotoxicity and expansion lysis during the osmotic excursions resulting from the contact of hMSCs from UCB with Me2SO. It builds upon the mathematical model recently presented by the authors, which pertains to a population of cells with uniform size. The objective is to enhance the model's relevance by incorporating the more realistic scenario of cell size distribution, utilizing a Population Balance Equations approach. The study compares the capability of the multiple-sized model to the single-sized one to describe system behavior experimentally measured through cytofluorimetry and Coulter counter when, first, suspending hMSCs in hypertonic solutions of Me2SO (at varying osmolality, system temperature, and contact times), and then (at room temperature) pelleting by centrifugation before suspending the cells back to isotonic conditions. Simulations demonstrate that expansion lysis and cytotoxic effect are not affected by cell size for the specific system hMSCs/Me2SO, thus confirming what was found so far by the authors through a single-size model. On the other hand, simulations show that, when varying the adjustable parameters of the model that are expected to change from cell to cell lineages, expansion lysis is sensitive to cell size, while cytotoxicity is not, being mainly influenced by external CPA concentration and contact duration. More specifically, it is found that smaller cells suffer expansion lysis more than larger ones. The findings suggest that different cells from hMSCs may require a multiple-sized model to assess cell damage during osmotic excursions in cryopreservation.

Layer-by-layer coated cellulose reduces the fire risk of polyurethane foam biocomposites

Cellulose implementation as filler in polyurethane foams (PUF) often leads to an increased the fire risk associated to the prepared biocomposite. To address this problem, this paper presents a novel approach where the cellulose filler is coated by a nanostructured layer-by-layer (LbL) assembly with flame retardant characteristics before its addition to the biocomposite. During PUF production, the presence of cellulose led to a reduced cell size distribution with improved thermal insulation properties. By forced combustion tests, the use of neat cellulose produced a detrimental effect by increasing the PUF heat release rates (up to +21 %). Conversely, the coated cellulose simultaneously decreased the peak of heat release rate (-22 %) and the total smoke release (-32 %) if compared with the reference PUF. The proposed approach represents a viable strategy for the production of PUF biocomposites where sustainability and fire protection are optimized.

Relationship of Cell Size Distribution and Biomechanics of Strawberry Fruit Under Varying Ca and N Supply

Relationship of Cell Size Distribution and Biomechanics of Strawberry Fruit Under Varying Ca and N Supply

Effect of partial substitution of wheat flour with freeze-dried olive pomace on the technological, nutritional, and sensory properties of bread

In the last years, olive pomace, a by-product of olive oil extraction, has shown great interest. The work aims to valorize the olive pomace of two Sardinian olive cultivars, Bosana and Semidana, by incorporating them into the formulation of functional baked products to improve their nutritional value. The freeze-dried pomace of the two varieties has been used to substitute the type 00 flour in percentages of 1, 2, and 3% (w/w). The olive pomace was characterized by macro-composition analysis, while the bread samples were characterized for their proximate, physical, technological, sensory characteristics and shelf life. The specific volume of fortified samples decreased significantly compared to the control, while antioxidant activity, and nutritional parameters were significantly improved using olive pomace. Moreover, fortified samples showed a reduction of browning and whiteness indices with respect to control. Textural profile analysis showed a firmer product, compared to the control, with higher levels of olive pomace which also positively affected the cell size distribution in the crumb. Sensorially, consumers were mostly appealed by the 1% levels of substitution of olive pomace, in particular that of the Bosana. Hardness of all samples increased significantly along 7 days of storage thus resulting in a shelf life of less than 3 days. Therefore, it can be concluded that the incorporation of olive pomace, especially at low levels (1%), into white bread significantly improves the nutritional and sensorial quality of bread without significantly affecting its technological properties.

Regional adiposity and insulin sensitivity - interactions with menopause and HIV in middle-aged Black African women.

To explore depot-specific functional aspects of adipose tissue, examining the putative role for menopause and HIV status on insulin sensitivity (SI) and beta-cell function in Black South African women. Women (n = 92) from the Middle-Aged Soweto Cohort, including premenopausal HIV-negative (n = 21); premenopausal women living with HIV (WLWH; n = 11); postmenopausal HIV-negative (n = 42); postmenopausal WLWH (n = 18) underwent the following tests: body composition (dual energy x-ray absorptiometry); fasting bloods for sex hormones, inflammation and adipokines; frequently sampled intravenous glucose tolerance test for SI and beta-cell function (disposition index, DI); abdominal (aSAT) and gluteal subcutaneous adipose tissue (gSAT) biopsies for cell size and mRNA expression of adipokines, inflammation, and estrogen receptors [ER]. Depot-specific associations between gene expression and insulin parameters did not differ by HIV or menopause status. Pooled analysis showed significant models for SI (P = 0.002) and DI (P = 0.003). Higher SI was associated with lower leptin and CD11c expression in aSAT and higher adiponectin in gSAT. Higher DI was associated with higher aSAT and gSAT expression of adiponectin, LPL, ERα, and PPARγ, and lower leptin in aSAT. WLWH had higher expression of adiponectin and lower expression of leptin in both aSAT (P = 0.002 and P = 0.005) and gSAT (P = 0.004 and P = 0.002), respectively, and a larger proportion of smaller cells in aSAT (P < 0.001). Insulin sensitivity and beta cell function were distinctively associated with aSAT and gSAT. While menopause did not influence these relationships, HIV had a significant effect on adipose tissue, characterised by variations in cell size distribution and transcript levels within the depots.

Extrusion foaming of Poly(lactic acid)/Rice straw composites: Opposing effects of eco-friendly physical/chemical treatment and compatibilization methods

In this study, the effects of two environmentally-friendly pulping methods along with two different reactive compatibilization methods on the foamability of poly (lactic acid) (PLA)/rice straw (RS) biocomposites have been investigated. RS as an annually renewable agricultural waste is low-cost and available. Melt-compounding and melt-foaming processes were performed through a twin-screw extrusion processing. The correlations between processing and microstructure were studied. The findings show that the RS pulping with sodium bicarbonate (SB) solution leads to the lignocellulosic particles with a porous structure. The structure causes the filler/matrix mechanical engagement and improves the interfacial adhesion and rheological properties, hence forming smaller cells with the narrowest cell size distribution. In contrast, applying ultrasound waves on the RS pulp brings the particles to very smooth surfaces. These surfaces have the highest activity at the cell nucleation stage and considerably increase the foam’s cell density. The reactive compatibilizers based on epoxy and maleic anhydride groups show opposing effects on the biocomposite microstructure, depending on the RS pulp type. The use of the reactive compatibilizers in the PLA/RS pulp treated with SB led to lighter foams with larger cells and higher cell densities and void fractions. Whereas the incorporation of the compatibilizers into the biocomposites containing RS pulp treated with SB and ultrasonic waves resulted in noticeably lower cell density and larger foam density. The extruded biocomposite foams with closed-cell microstructure can be used in insulation and packaging applications.

Comparison of morphology, protein concentration, and size distribution of bone marrow and Wharton's jelly-derived mesenchymal stem cells exosomes isolated by ultracentrifugation and polymer-based precipitation techniques

Exosomes which are tiny extracellular vesicles (30–150 nm), transport vital proteins and gene materials such as miRNA, mRNA, or DNA, whose role in cell communication and epithelia regulation is critical. Many techniques have been developed as a result of studying exosomes' biochemical and physicochemical properties, although there is still no standard method to isolate exosomes simply with high yield. Commercial kits have gained popularity for exosome extraction despite concerns about their effectiveness in scientific research. On the other hand, ultracentrifugation remains the gold standard isolation method. This study compares these two common exosome isolation methods to determine their impact on the quality and quantity of exosomes isolated from bone marrow (BM) and Wharton's jelly (WJ)-derived mesenchymal stem cells. Isolated exosomes from the two sources of the cell's conditioned medium by two methods (polymer kit and ultracentrifuge) were characterized using western blotting, scanning electron microscopy (SEM), dynamic light scattering (DLS), and the Bradford assay. Western blot analysis confirmed separation efficiency based on CD81 and CD63 markers, with the absence of calnexin serving as a negative control. The Morphology of exosomes studied by SEM image analysis revealed a similar round shape appearance and their sizes (30–150 nm) were the same in both isolation techniques. The DLS analysis of the sample results was consistent with the SEM ones, showing a similar size range and very low disparity. The exosome protein content concentration analysis revealed that exosomes isolated by the polymer-based kits contained higher protein concentration density and purity (p <0.001). In general, though the protein yield was higher when the polymer-based kits were used, there were no significant differences in morphology, or size between WJ-derived and BM-derived exosomes, regardless of the isolation method employed.

A comparative study of surfactant-treated natural latex foam morphology, thermodynamic relationships and energy absorption: Talalay vs. dunlop processing

This study investigates the relationships between the morphology, energy absorption, and thermodynamic parameters of natural latex foams (NLFs) processed by the Dunlop and in-house Talalay methods, using different surfactant blends. Both methods involved mixing, moulding, and heating; the additional steps for the Talalay method involved cooling and gelation, a gel-freezing technique wherein the frozen foam is exposed to CO2 gas, inducing its transformation into a gel. The morphology of the internal structure of the NLFs was studied using 2D scanning electron micrographs and 3D micro- computerised tomography images. Two different surfactants, potassium laurate and pluronic, were used. Adding the blended surfactants reduced the porosity and increased the foam density of the NLF samples, improving mechanical properties. The cell size distribution of the NLF samples prepared using the Talalay method was broader than that of those prepared using the Dunlop method. In terms of the mechanical properties and energy absorption capabilities, the Talalay process resulted in samples with 20% lower compressive strength and 7% lower energy absorption than the control sample. A power-law relationship between the energy absorption per unit volume and the compression speed of the different foam samples was also observed. The ratio of the internal energy to the total compression force of the NLF samples prepared using the Talalay process was also lower than those prepared using the Dunlop process. The empirical insights derived from this study show how the mechanical properties and process technology associated with the producing of material foams could be improved.

Microstructure-Process-Property relationships of PLA-PBSA bimodal foams

This study delves into the physical and chemical blending of polylactic acid (PLA) and poly(butylene succinate-co-adipate) (PBSA), utilizing supercritical fluid-assisted injection molding. The research focuses on studying how the blend interphase influences the formation of unique bimodal cellular structures, thereby improving PLA’s mechanical properties. Employing scanning electron microscopy (SEM) and tensile testing, the study examines the correlation between cell morphology and mechanical strength. The research highlights the influence of compatibilization and cell size distribution leading to a increase in crystallinity and mechanical stiffness of the foams, offering critical insights for enhancing Microstructure-Process-Property (MP2) relationships for automotive and aerospace materials.

Rotated Lorenz Curves of Biological Size Distributions Follow Two Performance Equations

The Lorenz curve is used to describe the relationship between the cumulative proportion of household income and the number of households of an economy. The extent to which the Lorenz curve deviates from the line of equality (i.e., y = x) is quantified by the Gini coefficient. Prior models are based on the simulated and empirical data of income distributions. In biology, the Lorenz curves of cell or organ size distributions tend to have similar shapes. When the Lorenz curve is rotated by 135 degrees counterclockwise and shifted to the right by a distance of 2, a three-parameter performance equation (PE), and its generalized version with five parameters (GPE), accurately describe this rotated and right-shifted curve. However, in prior studies, PE and GPE were not compared with the other Lorenz equations, and little is known about whether the skewness of the distribution could influence the validity of these equations. To address these two issues, simulation data from the beta distributions with different skewness values and six empirical datasets of plant (organ) size distributions were used to compare PE and GPE with three other Lorenz equations in describing the rotated and right-shifted plant (organ) size distributions. The root-mean-square error and Akaike information criterion were used to assess the validity of the two performance equations and the three other Lorenz equations. PE and GPE were both validated in describing the rotated and right-shifted simulation and empirical data of plant (organ) distributions. Nevertheless, GPE worked better than PE and the three other Lorenz equations from the perspectives of the goodness of fit, and the trade-off between the goodness of fit and the model structural complexity. Analyses indicate that GPE provides a powerful tool for quantifying size distributions across a broad spectrum of organic entities and can be used in a variety of ecological and evolutionary applications. Even for the simulation data from hypothetical extreme skewed distribution curves, GPE still worked well.

Growth and Cell Size of Microalga Auxenochlorella protothecoides AS-1 under Different Trophic Modes.

Certain microalgal species can grow with different trophic strategies depending on the availability of nutrient resources. They can use the energy from light or an organic substrate, or both, and can therefore be called autotrophs, heterotrophs, or mixotrophs. We recently isolated a microalgal strain from the microplastic biofilm, which was identified as Auxenochlorella protothecoides, AS-1. Strain AS-1 grew rapidly in bacterial culture media and exhibited different growth rates and cell sizes under different trophic conditions. We compared the growth performance of AS-1 under the three different trophic modes. AS-1 reached a high biomass (>4 g/L) in 6 days under mixotrophic growth conditions with a few organic carbons as a substrate. In contrast, poor autotrophic growth was observed for AS-1. Different cell sizes, including daughter and mother cells, were observed under the different growth modes. We applied a Coulter Counter to measure the size distribution patterns of AS-1 under different trophic modes. We showed that the cell size distribution of AS-1 was affected by different growth modes. Compared to the auto-, hetero- and mixotrophic modes, AS-1 achieved higher biomass productivity by increasing cell number and cell size in the presence of organic substrate. The mechanisms and advantages of having more mother cells with organic substrates are still unclear and warrant further investigations. The work here provides the growth information of a newly isolated A. protothecoides AS-1 which will be beneficial to future downstream applications.

Decoupling cell size homeostasis in diatoms from the geometrical constraints of the silica cell wall.

Unicellular organisms are known to exert tight control over their cell size. In the case of diatoms, abundant eukaryotic microalgae, two opposing notions are widely accepted. On the one hand, the rigid silica cell wall that forms inside the parental cell is thought to enforce geometrical reduction of the cell size. On the other hand, numerous exceptions cast doubt on the generality of this model. Here, we monitored clonal cultures of the diatom Stephanopyxis turris for up to 2 yr, recording the sizes of thousands of cells, in order to follow the distribution of cell sizes in the population. Our results show that S. turris cultures above a certain size threshold undergo a gradual size reduction, in accordance with the postulated geometrical driving force. However, once the cell size reaches a lower threshold, it fluctuates around a constant size using the inherent elasticity of cell wall elements. These results reconcile the disparate observations on cell size regulation in diatoms by showing two distinct behaviors, reduction and homeostasis. The geometrical size reduction is the dominant driving force for large cells, but smaller cells have the flexibility to re-adjust the size of their new cell walls.