Macropore design of tissue engineering scaffolds regulates mesenchymal stem cell differentiation fate

Craniosynostosis is a debilitating birth defect characterized by the premature fusion of cranial bones resulting from premature loss of stem cells located in suture tissue between growing bones. Mesenchymal stromal cells in long bone and the cranial suture are known to be multipotent cell sources in the appendicular skeleton and cranium, respectively. We are developing biomaterial constructs to maintain stemness of the cranial suture cell population towards an ultimate goal of diminishing craniosynostosis patient morbidity. Recent evidence suggests that physical features of synthetic tissue engineering scaffolds modulate cell and tissue fate. In this study, macroporous tissue engineering scaffolds with well-controlled spherical pores were fabricated by a sugar porogen template method. Cell-scaffold constructs were implanted subcutaneously in mice for up to eight weeks then assayed for mineralization, vascularization, extracellular matrix composition, and gene expression. Pore size differentially regulates cell fate, where sufficiently large pores provide an osteogenic niche adequate for bone formation, while sufficiently small pores (<125 μm in diameter) maintain stemness and prevent differentiation. Cell-scaffold constructs cultured in vitro followed the same pore size-controlled differentiation fate. We therefore attribute the differential cell and tissue fate to scaffold pore geometry. Scaffold pore size regulates mesenchymal cell fate, providing a novel design motif to control tissue regenerative processes and develop mesenchymal stem cell niches in vivo and in vitro through biophysical features.

Atrazine leaching from biochar-amended soils

The herbicide atrazine is used extensively throughout the United States, and is a widespread groundwater and surface water contaminant. Biochar has been shown to strongly sorb organic compounds and could be used to reduce atrazine leaching. We used lab and field experiments to determine biochar impacts on atrazine leaching under increasingly heterogeneous soil conditions. Application of pine chip biochar (commercially pyrolyzed between 300 and 550 °C) reduced cumulative atrazine leaching by 52% in homogenized (packed) soil columns (p=0.0298). Biochar additions in undisturbed soil columns did not significantly (p>0.05) reduce atrazine leaching. Mean peak groundwater atrazine concentrations were 53% lower in a field experiment after additions of 10 t ha(-1) acidified biochar (p=0.0056) relative to no biochar additions. Equivalent peat applications by dry mass had no effect on atrazine leaching. Plots receiving a peat-biochar mixture showed no reduction, suggesting that the peat organic matter may compete with atrazine for biochar sorption sites. Several individual measurement values outside the 99% confidence interval in perched groundwater concentrations indicate that macropore structure could contribute to rare, large leaching events that are not effectively reduced by biochar. We conclude that biochar application has the potential to decrease peak atrazine leaching, but heterogeneous soil conditions, especially preferential flow paths, may reduce this impact. Long-term atrazine leaching reductions are also uncertain.

An electrochemical troponin T aptasensor based on the use of a macroporous gold nanostructure

A specific troponin T (TnT) binding aptamer was identified and immobilized on an electrodeposited macroporous gold nanostructure using poly(ethylene glycol) 600, to fabricate a novel and ultrasensitive TnT aptasensor. The transducer surface on the gold disk electrode was characterized by field emission scanning electron microscopy, and immobilization of the aptamer was monitored by open circuit potential measurements. Binding of TnT by the aptamer was monitored by differential pulse voltammetry using ferro/ferricyanide as the redox probe. The aptamer has a high affinity and specificity, and the electrode is sensitive and selective. Best operated at a working potential of 0.23 V (vs. Ag/AgCl), the electrode can detected TnT in the 0.05 to 5.0 ng mL^-1 concentration range with a 23 pg mL^-1 detection limit. The method was applied to the determination of TnT in 99 spiked human serum samples, and the diagnostic sensitivity and specificity were 94 and 95%, respectively. Graphical abstract Schematic presentation of an electrochemical troponin T aptasensor. A macroporous gold nanostructure was electrodeposited followed by immobilization of a specific TnT aptamer. Binding of TnT by the aptamer was electrochemically monitored. MCH: mercaptohexanol; TnT: troponin T.

The investigation of activated carbon by K2CO3 activation: Micropores- and macropores-dominated structure

In this study, the K₂CO₃ activation of bamboo was investigated in detail, and the structure and properties of the prepared activated carbons were tested for the feasibility of CO₂ capture application and the potential for both ion and bacteria adsorption for use in the field of hazardous wastewater treatment. Activated carbons were produced with different activator ratios, from 0.5 to 6 according to the sample mass ratio. The ratio of H or O to C (H/C or O/C) increased with the increasing amount of K₂CO₃ added for the activation. The samples had a highly-porous microporous structure, in which the micropore volume was calculated to be 0.6 cm³ g^-1 by the DR method of the CO₂ adsorption isotherm at 298 K. The BET surface area and total pore volume estimated from the N₂ adsorption isotherms at 77 K of the activated materials increased according to the increase of the K₂CO₃ impregnation ratio to a maximum value of 1802 m² g^-1 and 0.91 cm³ g^-1, respectively. Moreover, the K₂CO₃-activated samples had a specific morphology, that is, macropores which are presumed to be derived from bubbles. The X-ray-CT images showed that the bubble-like structure is not only on the surface but also inside the samples. The results of gas adsorption methods, mercury porosimetry, and SEM showed the co-existence of micropores (<2 nm) and macropores (100-10,000 nm). The results highlighted the unique pore structure, that is, the coexistence of micropores and macropores that would contribute to forming solutions for carbon sequestration in the atmosphere and wastewater treatment.

Macroporous bacterial cellulose grafted by oligopeptides induces biomimetic mineralization via interfacial wettability

Bacterial cellulose (BC) has a role in tissue repair and regenerative medicine, which has already attracted tremendous interest from researchers, especially those working in the field of hybrid materials. Herein, we designed BC-based macroporous functional materials by dialdehyde bacterial cellulose (DBC) cross-linking with oligopeptides under mild reactive conditions. The interfacial properties of the surface modified BC were examined by biomimetic mineralization. The results showed that a macroporous structure was achieved by using oligopeptides as chemical cross-linking agents with an interconnected macroporosity ranging from 20 μm to 80 μm. Their mechanical properties were barely altered compared to the pristine BC. Their enhanced surface charges stemmed from the carboxyl groups of the oligopeptides engaging in reactions with amine and aldehyde groups. The oligopeptides cross-linked DBC showed a faster initial induction towards minerals via interfacial wettability resulting in promotion of mineralization, the hybrid materials had excellent biocompatibility relative to the pristine BC. These findings are vital to the development of other biopolymers with essential macroporous structures as well as improved interfacial wettability, which enables their possible uses in tissue repair and regenerative medicine.

Biochar porosity: a nature-based dependent parameter to deliver microorganisms to soils for land restoration

Literature shows that biochar can potentially retain nutrients in agricultural soils, avoiding significant nutrient losses. Furthermore, biochar porosity and functional groups have been shown to enhance physico-chemical properties of soil when amended, which in turn has the ability to encourage inhabitation of specific microorganisms as biofertilizers or to enhance soil remediation. It supports scale-dependent parameters and provides both ecosystem services and soil-vegetation solutions relevant to nature-based solutions. However, detailed researches on the mechanisms of soil microbial interactions with biochar porous properties are required, along with the microbial attachment factors, sustenance, and detachment when applied to soils. Recent valuable works have impregnated plant growth-promoting bacteria unto biochar and have observed inconsistent results. Firstly, biochar intrinsic properties alter the fate of impregnation by inhibiting quorum sensing signals, and the macropore requirements for adsorption and/or biofilm formation have not been well considered. Additionally, the nutrient and supplement requirements for each microorganism as well as the adsorption capacity have not been well understood for biochar surfaces. Substantial information is required to understand the mechanisms of microbe adsorption and factors that influence the process, as well as sustenance of the matrix even when deployed in soils. Research directions should focus on determining molecular and chemical mechanisms responsible for the biochar-microbe interaction process and fate of microbe on biochar while expressing plant growth-promoting properties, which needs to be done in laboratory and field trials. Graphical abstract.

Facile fabrication of microparticles with pH-responsive macropores for small intestine targeted drug formulation

Oral drugs present the most convenient, economical, and painless route for self-administration. Despite commercialization of multiple technologies relying on micro- and nanocrystalline drugs, research on microparticles (MPs) based oral biopharmaceuticals delivery systems has still not culminated well enough in commercial products. This is largely due to the drugs being exposed to the destabilizing environment during MP synthesis process, and partly because of complicated process conditions. Hence, we developed a solvent swelling-evaporation method of producing pH-responsive MPs with micron-sized macropores using poly(methacrylic acid-co-ethyl acrylate) in 1:1 ratio (commercial name: Eudragit® L100-55 polymer). We investigated the effects of temperature and evaporation time on pore formation, freeze-drying induced pore closure, and the release profile of model drugs (fluorescent beads, lactase, and pravastatin sodium) encapsulated MPs in simulated gastrointestinal tract conditions. Encapsulated lactase/pravastatin maintained >60% of their activity due to the preservation of pore closure, which proved the potential of this proof-of-concept microencapsulation system. Importantly, the presence of macropores on MPs can be beneficial for easy drug loading, and solve the problem of bioactivity loss during the conventional MP fabrication-drug encapsulation steps. Therefore, pH-sensing MPs with macropores can contribute to the development of oral drug formulations for a wide variety of drugs and bio-macromolecules, having a various size ranging from genes to micron-sized ingredients with high therapeutic efficacy.

Water and solute transport in agricultural soils predicted by volumetric clay and silt contents

Solute transport through the soil matrix is non-uniform and greatly affected by soil texture, soil structure, and macropore networks. Attempts have been made in previous studies to use infiltration experiments to identify the degree of preferential flow, but these attempts have often been based on small datasets or data collected from literature with differing initial and boundary conditions. This study examined the relationship between tracer breakthrough characteristics, soil hydraulic properties, and basic soil properties. From six agricultural fields in Denmark, 193 intact surface soil columns 20cm in height and 20cm in diameter were collected. The soils exhibited a wide range in texture, with clay and organic carbon (OC) contents ranging from 0.03 to 0.41 and 0.01 to 0.08kgkg(-1), respectively. All experiments were carried out under the same initial and boundary conditions using tritium as a conservative tracer. The breakthrough characteristics ranged from being near normally distributed to gradually skewed to the right along with an increase in the content of the mineral fines (particles ≤50μm). The results showed that the mineral fines content was strongly correlated to functional soil structure and the derived tracer breakthrough curves (BTCs), whereas the OC content appeared less important for the shape of the BTC. Organic carbon was believed to support the stability of the soil structure rather than the actual formation of macropores causing preferential flow. The arrival times of 5% and up to 50% of the tracer mass were found to be strongly correlated with volumetric fines content. Predicted tracer concentration breakthrough points as a function of time up to 50% of applied tracer mass could be well fitted to an analytical solution to the classical advection-dispersion equation. Both cumulative tracer mass and concentration as a function of time were well predicted from the simple inputs of bulk density, clay and silt contents, and applied tracer mass. The new concept seems promising as a platform towards more accurate proxy functions for dissolved contaminant transport in intact soil.

Preferential flow modelling of chlorpyrifos leaching in two arid soils of irrigated agricultural production areas in Argentine Patagonia

An analysis was made of the transport and fate of the organophosphate pesticide chlorpyrifos in productive soils from the Alto Valle of the Río Negro in Argentine Patagonia. The climate of the region is arid, so traditional fruit production is under flood irrigation. The soils in the floodplain are predominantly Aridisols with textures ranging from sandy loam to clay loam. The calibration was performed with water table data and chlorpyrifos concentration in the soil horizons. Field experiments made with Brilliant Blue FCF at the profile scale enabled the parametrisation of the dual-permeability model MACRO. The model calibration was evaluated by a comparison of observed and simulated data and statistics. The simulation of the groundwater table depth was satisfactory and the chlorpyrifos leaching revealed a different pattern in the two soil types studied. The sandy loam texture soil produced more percolation of irrigation water, but the clay loam soil produced greater leaching of chlorpyrifos under similar application conditions, presumably due to preferential flow under non-equilibrium conditions. Productive management alternatives to reduce leaching into the underlying unconfined aquifer were simulated. Among these, the incorporation of organic matter was the best alternative.

Using Symmetrical Organic Cation Solutions to Study P2X7 Ion Permeation

P2X7 receptors are ATP-gated ion channels permeable to metal cations, such as Na⁺, K⁺, and Ca²⁺. They also exhibit permeability to various large molecular weight species, reaching up to 900 Da, in a process known as macropore formation, which is a unique functional hallmark across the P2X family. While well-documented in a range of different cell types, the molecular mechanism underlying this phenomenon is poorly understood, and has been clouded through the use of electrophysiological methodology prone to artifacts as a result of significant changes in ionic concentrations in asymmetric conditions. In this chapter, we discuss the permeation properties of P2X7, the related methodological challenges and the use of symmetrical organic cation solutions as a useful technique for probing P2X7 permeation.

Preferential flow characteristics of reclaimed mine soils in a surface coal mine dump

There are a large number of macropores/tubular channels of a few centimeters and plant roots in reclaimed dump soils, which are the main reasons for the formation of soil macropores and soil preferential flow. To systematically study the morphological characteristics and variation of soil preferential flow for different reclaimed vegetations in a dump, a dye-staining experiment and physical and chemical analysis were carried out to investigate the formation mechanism and influencing factors of soil preferential flow in the vegetation restoration process. The results indicate that there were differences in the soil water breakthrough curves for different plots. The macropore effluent rate generally increased at first and then tended to stabilize. The soil steady effluent rate decreased with increasing soil depth, which reached the maximum and minimum values at the depths of 0∼5 cm (0.0193∼0.0315 mm s^-1) and 50∼60 cm (0.0028∼0.0035 mm s^-1), respectively. Furthermore, the radius of soil macropores under different types of reclaimed vegetation ranged from 0.03 to 4.71 mm, most of which ranged from 0.11 to 2.36 mm. The soil macroporosity of different reclaimed vegetation types ranged from 0.03 to 16.58%, which was significantly greater than 5%. The soil macroporosity determined 65% of the variation in the steady effluent rate and 42% of the variation in the saturated hydraulic conductivity. Furthermore, the dye coverage ratio decreased as the soil layer depth increased in different plots, and there were some differences in each plot. The maximum dye coverage ratio occurred in the 0∼5 cm soil layer, which reached 90.37%. The dye coverage ratio at a depth of 0∼60 cm in six plots followed the order of Robinia pseudoacacia (26.48%) > Ulmus pumila (20.12%) > mixed forest (17.32%) > farmland (15.06%) > shrub (13.97%) > weeds (10.07%). The soil preferential flow mostly occurred in the 0∼40 cm soil depth layer, which occupied more than 93% of the total soil profile (0∼60 cm). Moreover, a Pearson correlation was used to analyze the relationship between environmental factors (soil, water, and plant factors) and the dye coverage ratio. The dye coverage ratio of soil preferential flow under different reclamation vegetations was very significantly or significantly positively correlated with the gravel content, mean radius of soil macropores, soil saturated hydraulic conductivity, root weight density, and root length density, which promoted the formation and development of soil preferential flow. This study will provide a scientific basis for understanding the formation mechanism and perfecting the research system of soil preferential flow, vegetation restoration, and reconstruction in a dump; furthermore, this research offers significance guidance in the construction of green mines and the development of regional economics.

Liquids with Permanent Macroporosity

Permanent macropores (>50 nm) had not been reported in the liquid state until a recent report by Tao Li and co-workers describing a synthetic strategy to form a porous liquid with dual micro-macroporosity. This is prepared by producing hierarchically porous particles that are surface coated and fluidised by dispersion. Surface micropores enable permanent porosity by steric exclusion of the fluid phase. The material has a considerable water uptake capacity (27 % w/w) due to large (480 nm) unoccupied macropores. This also enables switching of thermal conductivity on uptake of water. These are new properties translated from porous solids to the liquid state.

Controlled morphology and optical properties of n-type porous silicon: effect of magnetic field and electrode-assisted LEF

Fabrication of photoluminescent n-type porous silicon (nPS), using electrode-assisted lateral electric field accompanied with a perpendicular magnetic field, is reported. The results have been compared with the porous structures fabricated by means of conventional anodization and electrode-assisted lateral electric field without magnetic field. The lateral electric field (LEF) applied across the silicon substrate leads to the formation of structural gradient in terms of density, dimension, and depth of the etched pores. Apart from the pore shape tunability, the simultaneous application of LEF and magnetic field (MF) contributes to a reduction of the dimension of the pores and promotes relatively more defined pore tips as well as a decreased side-branching in the pore walls of the macroporous structure. Additionally, when using magnetic field-assisted etching, within a certain range of LEF, an enhancement of the photoluminescence (PL) response was obtained.

Multi-size optimization of macroporous cellulose beads as protein anion exchangers: Effects of macropore size, protein size, and ligand length

Multi-size optimization of ion exchangers based on protein characteristics and understanding of underlying mechanism is crucial to achieve maximum separation performance in terms of adsorption capacity and uptake kinetic. Herein, we characterize the effects of three different sizes, macropore size, protein size, and ligand length, on the protein adsorption capacity and uptake kinetic of macroporous cellulose beads, and provide insights into the underlying mechanism. In detail, (1) for smaller bovine serum albumin, macropore size has a negligible effect on the adsorption capacity, while for larger γ-globulin, larger macropores improve the adsorption capacity due to the high accessibility of binding sites; (2) there is a critical pore size (CPZ), at which the adsorption uptake kinetic is minimum. When pore sizes are higher than the CPZ, uptake kinetics are enhanced by pore diffusion. When pore sizes are lower than CPZ, uptake kinetics are enhanced by surface diffusion; (3) increasing ligand length improves the adsorption capacity by three-dimensionally extended polymer chains in pores and enhances uptake kinetic by improved surface diffusion. This study offers an integrated perspective to qualitatively assess the effects of multiple sizes, providing guidance for designing advanced ion exchangers for protein chromatography.

Protocol for Evaluating In Vivo the Activation of the P2RX7 Immunomodulator

BACKGROUND

P2RX7 is a purinergic receptor with pleiotropic activities that is activated by high levels of extracellular ATP that are found in inflamed tissues. P2RX7 has immunomodulatory and anti-tumor proprieties and is therefore a therapeutic target for various diseases. Several compounds are developed to either inhibit or enhance its activation. However, studying their effect on P2RX7's activities is limited to in vitro and ex vivo studies that require the use of unphysiological media that could affect its activation. Up to now, the only way to assess the activity of P2RX7 modulators on the receptor in vivo was in an indirect manner.

RESULTS

We successfully developed a protocol allowing the detection of P2RX7 activation in vivo in lungs of mice, by taking advantage of its unique macropore formation ability. The protocol is based on intranasal delivery of TO-PRO™-3, a non-permeant DNA intercalating dye, and fluorescence measurement by flow cytometry. We show that ATP enhances TO-PRO™-3 fluorescence mainly in lung immune cells of mice in a P2RX7-dependant manner.

CONCLUSIONS

The described approach has allowed the successful analysis of P2RX7 activity directly in the lungs of WT and transgenic C57BL6 mice. The provided detailed guidelines and recommendations will support the use of this protocol to study the potency of pharmacologic or biologic compounds targeting P2RX7.

Distinct effects of biochar addition on soil macropore characteristics at different depths in a double-rice paddy field

Soil macropores largely control the water and nutrients transport as well as runoff processes in the soil. Biochar is frequently applied to soils to improve the macropore structure, but the effects remain controversial. To clarify depth-dependent soil macropore characteristics affected by biochar addition, the intact soil cores with a depth of 200 mm were collected from biochar-amended paddy field at addition rates of 0, 24, and 48 t ha^-1 (CK, BC1, and BC2, respectively). The two biochar treatments did not change the overall soil pore indices (e.g., macroporosity, pore number, fractal dimension, and circularity), but showed distinct effects at different soil depths. At a soil depth of 0-50 mm, the biochar treatments had higher macroporosity (8.59-8.85 %) than CK (4.94 %) (p < 0.05), but relatively lower pore circularity (0.83-0.84) than CK (0.88) (p < 0.05). The connectivity of biochar treatments (88-97) was 9.5-10.4 times higher than that of CK (9.3). At a soil depth of 100-200 mm, the biochar treatments exhibited lower macroporosity, macropore number, connectivity, and fractal dimension than CK (p < 0.05). The macropore indices (except circularity) of BC1 were relatively higher than those of BC2 in the most soil depths. Whether biochar altered the soil macropore indices depended on the addition rate of biochar and soil depth. The expansion and occupying effects of biochar were dominant at soil depths of 0-50 and 100-200 mm, respectively; and the two effects were stronger in BC1 than in BC2. A combination of the expansion and occupying effects occurred at a soil depth of 50-100 mm. The distinct effects of biochar on soil pore structure at different depths could mitigate methane emission and nutrient runoff loss from the double-rice paddy. Therefore, soil depth-dependent macropore structure should be considered when assessing the influence of biochar on soil properties and the associated environmental effects.

Macropore absorbent with bihydrophilic layers for the recovery of low-sulfur fuel oil

Conventional absorbent pads are widely employed for oil spill cleanup; however, their microporous structures face challenges in absorbing low-sulfur fuel oil (LSFO), especially at lower temperatures when LSFO solidifies owing to its high-viscosity shear stress. In this study, we developed a macroporous absorbent with bihydrophilic layers (MABL), i.e., a central hydrophobic layer sandwiched between two hydrophilic layers, with improved LSFO absorption efficiency. Unlike conventional hydrophobic absorbents, which remain predominantly afloat on the water surface with minimal submersion, the MABL achieves partial submersion owing to the wettability contrast of the bottom and central hydrophobic layers. This configuration ensures that the water surface aligns within the thickness range of MABL. The optimal pore size for LSFO absorption is determined to be 2.8 mm; pores smaller than 2.8 mm hinder LSFO absorption because of high-viscosity shear stress, while larger pores result in easy release of the absorbed LSFO. Notably, as the temperature decreases and LSFO solidifies, the MABL with 2.8-mm pores demonstrates significantly higher LSFO absorption capacity than conventional absorbent pads. Furthermore, a retention capability experiment reveals that the MABL with a pore size of 2.8 mm retains absorbed LSFO effectively under rotational flow in water and high-acceleration vibration in air, demonstrating its stability under dynamic conditions.