Although a conventional method of utilizing thermoresponsive grafted poly(N-isopropylacrylamide) (PNIPAAm) enables the harvest of a healthy confluent cell-to-cell junction preserved cell sheet while limiting the use of the trypsin enzyme, the absolute necessity in the delicate control of a sensitive nm-scale PNIPAAm chain length inevitably decelerates the advancement of cell sheet engineering. In this study, we demonstrate, for the first time, a thermoresponsive cell culture platform composed only of a ‘bulk’ form of a PNIPAAm hydrogel with the Young's modulus being increased up to the MPa scale. The surface roughness of the bulk PNIPAAm hydrogel initially modulated by the cross-linker concentration was altered from the nm- to μm-scale in response to a change in temperature above/below the low critical solution temperature (LCST) of 32 °C. The appropriate control of the surface roughness allowed the stable attachment (above the LCST) and easy detachment (below the LCST) of diverse cells and enabled the harvest of cell sheets composed of cell lines (C2C12 and NIH3T3) or even primary cells (human umbilical vein endothelial cells and keratinocytes). During their incubation at 37 °C, the cell lines were able to be attached on every surface of the prepared PNIPAAm cell culture platforms, whereas the primary cells were found to be only attached on a surface having a roughness below ∼30 nm. Furthermore, in the aspect of cell sheet detachment at the incubation temperature of 20 °C, the cell sheets composed of cell lines were fully detached from the surface of the platform having a roughness of ∼10 μm or higher, while the cell sheets composed of primary cells were entirely detached from the surface with a roughness of ∼19 μm or higher. Based on such behaviors of the diverse cells at a given surface roughness, this study further suggests a universal thermoresponsive cell culture platform which allows the harvest of all types of cells from cell lines to primary cells in a desired shape. Our suggested universal cell culture platform could play a powerful and versatile role in accelerating the advancement of cell sheet engineering.

Dental implant surgeries involve the insertion of implant fixtures into alveolar bones to replace missing teeth. When the availability of alveolar bone at the surgical site is insufficient, bone graft particles are filled in the insertion site for successful bone reconstruction. Bone graft particles induce bone regeneration over several months at the insertion site. Subsequently, implant fixtures can be inserted at the recipient site. Thus, conventional dental implant surgery is performed in several steps, which in turn increases the treatment period and cost involved. Therefore, to reduce surgical time and minimize treatment costs, a novel hybrid scaffold filled with bone graft particles that could be combined with implant fixtures is proposed. This scaffold is composed of a three-dimensionally (3D) printed polycaprolactone (PCL) frame and osteoconductive ceramic materials such as hydroxyapatite (HA) and β-tricalcium phosphate (β-TCP). Herein, we analyzed the porosity, internal microstructure, and hydrophilicity of the hybrid scaffold. Additionally, Saos-2 cells were used to assess cell viability and proliferation. Two types of control scaffolds were used (a 3D printed PCL frame and a hybrid scaffold without HA/β-TCP particles) for comparison, and the fabricated hybrid scaffold was verified to retain osteoconductive ceramic particles without losses. Moreover, the fabricated hybrid scaffold had high porosity and excellent microstructural interconnectivity. The in vitro Saos-2 cell experiments revealed superior cell proliferation and alkaline phosphatase assay results for the hybrid scaffold than the control scaffold. Hence, the proposed hybrid scaffold is a promising candidate for minimizing cost and duration of dental implant surgery.

Piezoelectric sensors have been developed due to the self-powered sensing and flexibility and the promising potential applications in the electronic skin (e-skin) inspired by human skin. However, although the piezoelectric sensors have an excellent performance in detecting human movements, it is difficult to distinguish external mechanical stimuli such as tapping in a single structure, together. Here, we suggest a self-powered e-skin based on electrospun poly(vinylidene fluoride-trifluoroethylene), nanofiber hybrid triboelectric–piezoelectric sensor (E-HTPS), that can identify between human motions and external touch based on both triboelectric effect and piezoelectric effect. Triboelectric effect-based sensors have a good electrical output characteristic with various advantages of high-flexibility and simple working operation. Hence, the E-HTPS consists of two layers, triboelectric layer as a tactile sensor and piezoelectric layer as a human motion sensor. Therefore, we demonstrate that the E-HTPS can detect human movements and even finger touch with attached to the target body part. Consequently, the E-HTPS could provide an effective approach to designing the self-powered e-skin as an artificial sensory system for healthcare monitoring and soft robotics.

The meniscus has poor intrinsic regenerative capability, and its injury inevitably leads to articular cartilage degeneration. Although there are commercialized off-the-shelf alternatives to achieve total meniscus regeneration, each has its own shortcomings such as individualized size matching issues and inappropriate mechanical properties. We manufactured a polycaprolactone-based patient-specific designed framework via a Computed Tomography scan images and 3D-printing technique. Then, we completed the hybrid-scaffold by combining the 3D-printed framework and mixture micro-size composite which consists of polycaprolactone and sodium chloride to create a cell-friendly microenvironment. Based on this hybrid-scaffold with an autograft cell source (fibrochondrocyte), we assessed mechanical and histological results using the rabbit total meniscectomy model. At postoperative 12-week, hybrid-scaffold achieved neo-meniscus tissue formation, and its shape was maintained without rupture or break away from the knee joint. Histological and immunohistochemical analysis results showed obvious ingrowth of the fibroblast-like cells and chondrocyte cells as well as mature lacunae that were embedded in the extracellular matrix. Hybrid-scaffolding resulted in superior shape matching as compared to original meniscus tissue. Histological analysis showed evidence of extensive neo-meniscus cell ingrowth. Additionally, the hybrid-scaffold did not induce osteoarthritis on the femoral condyle surface. The 3D-printed hybrid-scaffold may provide a promising approach that can be applied to those who received total meniscal resection, using patient-specific design and autogenous cell source.

Polycaprolactone (PCL) is one of the most widely used polymers in tissue engineering owing to its excellent biocompatibility, biodegradability, and processability. Nevertheless, most previous studies have primarily employed research-grade PCL, thereby limiting its clinical translation. In this study, four types of medical-grade PCL (RESOMER^® C203, C209, C212, and C217) were systematically evaluated for their applicability in three-dimensional (3D) printing, with respect to printability, mechanical characteristics, chemical stability, and biodegradation behavior. Among these, C209 and C212 exhibited superior printability and mechanical strength. FT-IR analysis showed that the chemical structure of PCL remained unchanged after both 3D printing and E-beam sterilization, while compressive testing demonstrated no significant differences in mechanical characteristics. In vitro degradation assessment revealed a time-dependent decrease in molecular weight. For kinetic analysis, both C209 and C212 were fitted using pseudo-first-order and pseudo-second-order models, which yielded comparable coefficients of determination (R²), suggesting that degradation may be governed by multiple factors rather than a single kinetic pathway. Taken together, these findings indicate that medical-grade PCL, particularly C209 and C212, is highly suitable for 3D printing. Furthermore, this study provides fundamental insights that may facilitate the clinical translation of PCL-based scaffolds for tissue engineering and biomedical implantation.