Series of Liquid Separation System Made of Homogeneous Copolymer Films with Controlled Surface Wettability

Exquisite surface wettability control of separation system surface is required to achieve separation of liquids with low surface tension difference. Here, we demonstrate a series of surface-energy-controlled homogeneous copolymer films to control the surface wettability of polyester fabric, utilizing a vapor-phase process, termed as initiated chemical vapor deposition (iCVD). The homogeneous copolymer films consist of a hydrophobic polymer, poly­(2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane), pV4D4, and a hydrophilic polymer, poly­(4-vinylpyridine), p4VP. Because the mixing of two or more components is always favorable in vapor phase, the iCVD process allows the formation of homogeneous copolymers from two immiscible, hydrophilic/hydrophobic monomer pairs, which is highly challenging to achieve in liquid phase. Simply by tuning the flow rate ratio of monomer pairs, a series of homogeneous copolymers with systematically controlled surface energy were formed successfully. The fabricated separation system could separate water (surface energy = 72.8 mJ/m²), glycerol (64 mJ/m²), ethylene glycol (48 mJ/m²), and olive oil (35.1 mJ/m²) sequentially with excellent selectivity, just by choosing a copolymer-coated polyester fabric with proper surface energy. Considering the small differences in the surface tension of the liquids used in this work, the surface-energy-controlled separation system can be a powerful tool to separate various kinds of liquid mixtures

Nanothin Coculture Membranes with Tunable Pore Architecture and Thermoresponsive Functionality for Transfer-Printable Stem Cell-Derived Cardiac Sheets

Coculturing stem cells with the desired cell type is an effective method to promote the differentiation of stem cells. The features of the membrane used for coculturing are crucial to achieving the best outcome. Not only should the membrane act as a physical barrier that prevents the mixing of the cocultured cell populations, but it should also allow effective interactions between the cells. Unfortunately, conventional membranes used for coculture do not sufficiently meet these requirements. In addition, cell harvesting using proteolytic enzymes following coculture impairs cell viability and the extracellular matrix (ECM) produced by the cultured cells. To overcome these limitations, we developed nanothin and highly porous (NTHP) membranes, which are ∼20-fold thinner and ∼25-fold more porous than the conventional coculture membranes. The tunable pore size of NTHP membranes at the nanoscale level was found crucial for the formation of direct gap junctions-mediated contacts between the cocultured cells. Differentiation of the cocultured stem cells was dramatically enhanced with the pore size-customized NTHP membrane system compared to conventional coculture methods. This was likely due to effective physical contacts between the cocultured cells and the fast diffusion of bioactive molecules across the membrane. Also, the thermoresponsive functionality of the NTHP membranes enabled the efficient generation of homogeneous, ECM-preserved, highly viable, and transfer-printable sheets of cardiomyogenically differentiated cells. The coculture platform developed in this study would be effective for producing various types of therapeutic multilayered cell sheets that can be differentiated from stem cells

Polymer Thin Films with Tunable Acetylcholine-like Functionality Enable Long-Term Culture of Primary Hippocampal Neurons

<i>In vitro</i> culture systems for primary neurons have served as useful tools for neuroscience research. However, conventional <i>in vitro</i> culture methods are still plagued by challenging problems with respect to applications to neurodegenerative disease models or neuron-based biosensors and neural chips, which commonly require long-term culture of neural cells. These impediments highlight the necessity of developing a platform capable of sustaining neural activity over months. Here, we designed a series of polymeric bilayers composed of poly­(glycidyl methacrylate) (pGMA) and poly­(2-(dimethylamino)­ethyl methacrylate) (pDMAEMA), designated pGMA:pDMAEMA, using initiated chemical vapor deposition (iCVD). Harnessing the surface-growing characteristics of iCVD polymer films, we were able to precisely engraft acetylcholine-like functionalities (tertiary amine and quaternary ammonium) onto cell culture plates. Notably, pGD3, a pGMA:pDMAEMA preparation with the highest surface composition of quaternary ammonium, fostered the most rapid outgrowth of neural cells. Clear contrasts in neural growth and survival between pGD3 and poly-l-lysine (PLL)-coated surfaces became apparent after 30 days <i>in vitro</i> (DIV). Moreover, brain-derived neurotrophic factor level continuously accumulated in pGD3-cultured neurons, reaching a 3-fold increase at 50 DIV. Electrophysiological measurements at 30 DIV revealed that the pGD3 surface not only promoted healthy maturation of hippocampal neurons but also enhanced the function of hippocampal ionotropic glutamate receptors in response to synaptic glutamate release. Neurons cultured long-term on pGD3 also maintained their characteristic depolarization-induced Ca²⁺ influx functions. Furthermore, primary hippocampal neurons cultured on pGD3 showed long-term survival in a stable state up to 90 daysfar longer than neurons on conventional PLL-coated surfaces. Taken together, our findings indicate that a polymer thin film with optimal acetylcholine-like functionality enables a long-term culture and survival of primary neurons

Chondroitin Sulfate-Based Biomineralizing Surface Hydrogels for Bone Tissue Engineering

Chondroitin sulfate (CS) is the major component of glycosaminoglycan in connective tissue. In this study, we fabricated methacrylated PEGDA/CS-based hydrogels with varying CS concentration (0, 1, 5, and 10%) and investigated them as biomineralizing three-dimensional scaffolds for charged ion binding and depositions. Due to its negative charge from the sulfate group, CS exhibited an osteogenically favorable microenvironment by binding charged ions such as calcium and phosphate. Particularly, ion binding and distribution within negatively charged hydrogel was dependent on CS concentration. Furthermore, CS dependent biomineralizing microenvironment induced osteogenic differentiation of human tonsil-derived mesenchymal stem cells in vitro. Finally, when we transplanted PEGDA/CS-based hydrogel into a critical sized cranial defect model for 8 weeks, 10% CS hydrogel induced effective bone formation with highest bone mineral density. This PEGDA/CS-based biomineralizing hydrogel platform can be utilized for in situ bone formation in addition to being an investigational tool for in vivo bone mineralization and resorption mechanisms