In this study, we fabricated a poly(dimethylsiloxane) (PDMS) surface coated with polydopamine (PDA) to enhance cell adhesion. PDA is well known for improving surface adhesion on various surfaces due to the abundant reactions enabled by the phenyl, amine, and catechol groups contained within it. To confirm the successful surface coating with PDA, the water contact angle and X-ray photoelectron spectroscopy were analyzed. Human umbilical vein endothelial cells (HUVECs) and human-bone-marrow-derived mesenchymal stem cells (MSCs) were cultured on the PDA-coated PDMS surface to evaluate potential improvements in cell adhesion and proliferation. HUVECs were also cultured inside a cylindrical PDMS microchannel, which was constructed to mimic a human blood vessel, and their growth and performance were compared to those of cells grown inside a rectangular microchannel. This study provides a helpful perspective for building a platform that mimics in vivo environments in a more realistic manner.

Regulatory macrophages (Mreg) are a special cell type that present a potential therapeutic strategy for various inflammatory diseases. In vitro, Mreg generation mainly takes 7–10 days of treatment with chemicals, including cytokines. In the present study, we established a new approach for Mreg generation using a three-dimensional (3D) micropatterned polydimethylsiloxane (PDMS) surface coated with a natural biopolymer adhesive polydopamine (PDA) and the common cell adhesion peptide motif arginylglycylaspartic acid (RGD). The 3D PDMS surfaces were fabricated by photolithography and soft lithography techniques and were subsequently coated with an RGD+PDA mixture to form a surface that facilitates cell adhesion. Human monocytes (THP-1 cells) were cultured on different types of 2D or 3D micropatterns for four days, and the cell morphology, elongation, and Mreg marker expression were assessed using microscopic and flow cytometric analyses. The cells grown on the PDA+RGD-coated 3D micropatterns (20-µm width/20-µm space) exhibited the most elongated morphology and strongest expression levels of Mreg markers, such as CD163, CD206, CD209, CD274, MER-TK, TREM2, and DHRS9. The present study demonstrated that PDA+RGD-coated 3D PDMS micropatterns successfully induced Mreg-like cells from THP-1 cells within four days without the use of cytokines, suggesting a time- and cost-effective method to generate Mreg-like cells in vitro.

In our ongoing efforts to develop a biocompatible adhesive for thermoplastic bonding, we have introduced a chitosan–vitamin C (CSVC) hydrogel as a non-toxic adhesive reagent for bonding poly(methyl methacrylate) (PMMA). The bonding approach was successfully conducted using the CSVC hydrogel assisted by mild pressure for 20 min at room temperature. Hydrogen bonding and ionic cross-linking between CSVC and PMMA are suggested to be the prominent chemical interactions that accelerate the robust bonding of PMMA substrates. The hydrophilic modifications of PMMA by the CSVC hydrogel were confirmed by water contact angle analysis, Fourier-transform infrared spectroscopy, and scanning electron microscopy. Notably, the highest bond strength was achieved up to 1.48 MPa with perfect bonding performance characterized by clog-free and leak-proof microchannels. The bonded microdevices were applied to on-chip culturing of mesenchymal stem cells (MSCs), which can effectively promote the formation of MSC spheroids. Thus, the CSVC hydrogel is a promising nature-inspired adhesive that is expected to give a great impulse to the development of microdevices for advanced biomedical applications.

Chitosan (CS) is a natural polymer that exhibits many biological properties and is used as a biomaterial for antibacterial coatings, tissue engineering, cell research, drug delivery, and negatively charged molecule...