Integrated Experimental and Mathematical Exploration of Modular Tissue Cultures for Developmental Engineering.

Developmental engineering (DE) involves culturing various cells on modular scaffolds (MSs), yielding modular tissues (MTs) assembled into three-dimensional (3D) tissues, mimicking developmental biology. This study employs an integrated approach, merging experimental and mathematical methods to investigate the biological processes in MT cultivation and assembly. Human dermal fibroblasts (HDFs) were cultured on tissue culture plastics, poly(lactic acid) (PLA) discs with regular open structures, or spherical poly(methyl methacrylate) (PMMA) MSs, respectively. Notably, HDFs exhibited flattened spindle shapes when adhered to solid surfaces, and complex 3D structures when migrating into the structured voids of PLA discs or interstitial spaces between aggregated PMMA MSs, showcasing coordinated colonization of porous scaffolds. Empirical investigations led to power law models simulating density-dependent cell growth on solid surfaces or voids. Concurrently, a modified diffusion model was applied to simulate oxygen diffusion within tissues cultured on solid surfaces or porous structures. These mathematical models were subsequently combined to explore the influences of initial cell seeding density, culture duration, and oxygen diffusion on MT cultivation and assembly. The findings underscored the intricate interplay of factors influencing MT design for tissue assembly. The integrated approach provides insights into mechanistic aspects, informing bioprocess design for manufacturing MTs and 3D tissues in DE.

Advances in ionogels for proton-exchange membranes.

To ensure the long-term performance of proton-exchange membrane fuel cells (PEMFCs), proton-exchange membranes (PEMs) have stringent requirements at high temperatures and humidities, as they may lose proton carriers. This issue poses a serious challenge to maintaining their proton conductivity and mechanical performance throughout their service life. Ionogels are ionic liquids (ILs) hybridized with another component (such as organic, inorganic, or organic-inorganic hybrid skeleton). This design is used to maintain the desirable properties of ILs (negligible vapor pressure, thermal stability, and non-flammability), as well as a high ionic conductivity and wide electrochemical stability window with low outflow. Ionogels have opened new routes for designing solid-electrolyte membranes, especially PEMs. This paper reviews recent research progress of ionogels in proton-exchange membranes, focusing on their electrochemical properties and proton transport mechanisms.

Investigation of cell infiltration and colonization in 3D porous scaffolds via integrated experimental and computational strategies.

This study aimed to integrate experimental and computational methods to systematically investigate cell infiltration and colonization within porous scaffolds. Poly(lactic acid) discs (Diameter: 6 mm; Thickness: 500 µm) with open pores (Diameter: 400-1100 µm), corners (Angle: 30-120°) and gaps (Distance: 100-500 µm), and cellulosic scaffolds with irregular pores (Diameter: 50-300 µm) were situated in tissue culture plates and cultured with human dermal fibroblasts (HDFs). Both phase contrast and scanning electron microscopy revealed that HDFs initially proliferated on scaffold surfaces, then infiltrated into the porous structures via cell bridging and stacking strategies, which was affected by the initial cell seeding densities, porous structures and culture times. Based on the density-dependent cell growths in two-dimensional cell cultures, power law models were developed to quantitatively simulate cell growths on scaffold surfaces. Model analysis predicted the effect of cell seeding efficiency on cell infiltrations into the porous scaffolds, which was further validated via series cell seeding experiments. The novelty of this research lies in the incorporation of multiple experimental and computational strategies, which enables the mechanistic insights of cell invasion and colonization in porous scaffolds, also facilitates the development of suitable bioprocesses for cell seeding and tissue manufacturing in Tissue Engineering and Regenerative Medicine.

Evaluation of Polymeric Particles for Modular Tissue Cultures in Developmental Engineering.

Developmental engineering (DE) aims to culture mammalian cells on corresponding modular scaffolds (scale: micron to millimeter), then assemble these into functional tissues imitating natural developmental biology processes. This research intended to investigate the influences of polymeric particles on modular tissue cultures. When poly(methyl methacrylate) (PMMA), poly(lactic acid) (PLA) and polystyrene (PS) particles (diameter: 5-100 µm) were fabricated and submerged in culture medium in tissue culture plastics (TCPs) for modular tissue cultures, the majority of adjacent PMMA, some PLA but no PS particles aggregated. Human dermal fibroblasts (HDFs) could be directly seeded onto large (diameter: 30-100 µm) PMMA particles, but not small (diameter: 5-20 µm) PMMA, nor all the PLA and PS particles. During tissue cultures, HDFs migrated from the TCPs surfaces onto all the particles, while the clustered PMMA or PLA particles were colonized by HDFs into modular tissues with varying sizes. Further comparisons revealed that HDFs utilized the same cell bridging and stacking strategies to colonize single or clustered polymeric particles, and the finely controlled open pores, corners and gaps on 3D-printed PLA discs. These observed cell-scaffold interactions, which were then used to evaluate the adaptation of microcarrier-based cell expansion technologies for modular tissue manufacturing in DE.

Antiplasticization of Polymer Materials: Structural Aspects and Effects on Mechanical and Diffusion-Controlled Properties.

Antiplasticization of glassy polymers, arising from the addition of small amounts of plasticizer, was examined to highlight the developments that have taken place over the last few decades, aiming to fill gaps of knowledge in the large number of disjointed publications. The analysis includes the role of polymer/plasticizer molecular interactions and the conditions leading to the cross-over from antiplasticization to plasticization. This was based on molecular dynamics considerations of thermal transitions and related relaxation spectra, alongside the deviation of free volumes from the additivity rule. Useful insights were gained from an analysis of data on molecular glasses, including the implications of the glass fragility concept. The effects of molecular packing resulting from antiplasticization are also discussed in the context of physical ageing. These include considerations on the effects on mechanical properties and diffusion-controlled behaviour. Some peculiar features of antiplasticization regarding changes in Tg were probed and the effects of water were examined, both as a single component and in combination with other plasticizers to illustrate the role of intermolecular forces. The analysis has also brought to light the shortcomings of existing theories for disregarding the dual cross-over from antiplasticization to plasticization with respect to modulus variation with temperature and for not addressing failure related properties, such as yielding, crazing and fracture toughness.

Modification of montmorillonite with aminopropylisooctyl polyhedral oligomeric silsequioxane.

Sodium montmorillonite (Na-MMT) was modified with various amounts of aminopropylisooctyl polyhedral oligomeric silsequioxane (POSS) and a second surfactant (alkyl ammonium based) via ion-exchange reactions. Interlayer spacing, interlamellar structure, and thermal and surface properties of these organoclays were characterized by wide angle X-ray diffraction, thermogravimetric analysis, and contact angle measurement. The interlayer space of POSS-modified clay (POSS-MMT) was strongly dependent on the arrangement of POSS surfactant but less dependent on the POSS concentration. The sodium ions in Na-MMT were only partially exchanged by protonized POSS due to the steric hindrance effect. In addition, the dual-surfactant-modified clays exhibited increased exchange ratios by controlling the amount of the second surfactant, resulting in a good balance in hydrophobicity and polarity of the modified clays. The resultant organoclays were mixed with polypropylene (PP) via a melt-compounding method. It was found that the dual-surfactant-modified clays with low polarity and similar hydrophobicity to PP were well dispersed in the PP matrix.

Surface characteristics of polyhedral oligomeric silsesquioxane modified clay and its application in polymerization of macrocyclic polyester oligomers.

Novel porous aminopropyllsooctyl polyhedral oligomeric silsesquioxane (POSS) modified montmorillonite clay complexes (POSS-Mts) with large interlayer distance and specific surface area have been successfully prepared via ion-exchange reaction and followed by freeze-drying treatment. The morphology of the POSS-Mts is highly influenced by the POSS concentration, pH of the suspension and drying procedure, but the interlayer distance of the POSS-Mts does not change much when the POSS concentration is above 0.4 CEC. The POSS-Mts were used as Sn-catalyst supporters to initiate the ring-opening polymerization of cyclic butylene terephthalate oligomers (CBT) for the first time. No diffraction peak was detected by wide-angle X-ray diffraction for the polymerized composites (pCBT/POSS-Mt), even at 10 wt % loading of POSS-Mt. A clay network rather than exfoliation structure was observed unexpectedly in the composites by transmission electron microscopy. The pCBT/POSS-Mt composite with 10 wt % POSS-Mt was further melt-compounded with commercial PBT resin as a master batch. The tensile properties of the resultant PBT/POSS-Mt composites were highly improved as compared to the pristine PBT due to the homogeneous dispersion of POSS-Mt in the PBT matrix.