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With the constant increase of electronic waste globally, society is demanding and governments are boosting the development of electronics with less pollutant materials and reduced environmental impact. One way to achieve this is to implement materials that are functional and structural at the same time, reducing material use and assembling parts. Further, printing techniques, such as screen printing, reduce considerably costs and time compared with conventional electronics; combined with methods to conform printed electronics to a 3D shape, such as thermoforming, allow to obtain nonplanar surface electronics simply and efficiently. Herein, screen‐printable inks made of styrene–ethylene/butylene–styrene and different aspect‐ratio carbon‐based materials for conformable electronics are reported. The inks are prepared with carbon black, carbon nanotubes, and reduced graphene oxide as conductive fillers, printed on a flexible substrate and thermoformed. Carbon black and carbon nanotube samples are functional after the process, with conductivities of 96 and 141 S m−1 for the best performing sample of each filler, respectively. Rheological, morphological, thermal, and electrical properties of the materials are also characterized. This study shows the influence of the filler's type and aspect ratio on the morphology and electrical conductivity of the printed materials before and after thermoforming. [ABSTRACT FROM AUTHOR]

Cytotoxicity is a critical parameter for materials intended for biological applications, such as food packaging. Shape-memory polyurethanes (SMPUs) have garnered significant interest due to their versatile properties and adaptability in synthesis. However, their suitability for biological applications is limited by the use of aromatic isocyanates, such as methylene diphenyl 4,4′-diisocyanate (MDI) and toluene diisocyanate (TDI), which are commonly used in SMPU synthesis but can generate carcinogenic compounds upon degradation. In this study, thermo-responsive shape-memory polyurethanes (SMPUs) were synthesized using poly(tetramethylene ether) glycol (PTMG) and castor oil (CO) as a chain extender with four different isocyanates—aromatic (MDI and TDI), aliphatic (hexamethylene diisocyanate [HDI] and isophorone diisocyanate [IPDI])—to evaluate their impact on polyurethane cytotoxicity. Cytotoxicity assays were conducted on the synthesized SMPU samples before and after exposure to light-induced degradation. The results showed that prior to degradation, all samples exhibited cell proliferation rates above 90%. However, after degradation, the SMPUs containing aromatic isocyanates demonstrated a drastic reduction in cell proliferation to values below 10%, whereas the samples with aliphatic isocyanates maintained cell proliferation above 70%. Subsequently, the influence of polyol chain length was assessed using PTMG, with molecular weights of 1000, 650, and 250 g·mol−1. The results indicated that the SMPUs with longer chain lengths exhibited higher cell proliferation rates both before and after degradation. The thermal and mechanical properties of the SMPUs were further characterized using thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and thermomechanical analysis (TMA), providing comprehensive insights into the behavior of these materials. [ABSTRACT FROM AUTHOR]

This article provides insights into hydrogels of the most promising biodegradable natural polymers and their mechanisms of degradation, highlighting the different possibilities of controlling hydrogel degradation rates. Since biodegradable hydrogels can be designed as scaffolding materials to mimic the physical and biochemical properties of natural tissues, these hydrogels have found widespread application in the field of tissue engineering and controlled release. In the same manner, their potential as water reservoirs, macro- and microelement carriers, or matrixes for the selective adsorption of pollutants make them excellent candidates for sustainable soil amendment solutions. Accordingly, this article summarizes the recent advances in natural biodegradable hydrogels in the fields of tissue engineering, controlled release, and soil remediation, emphasizing the new opportunities that degradability and its tunability offer for the design and applicability of hydrogels. [ABSTRACT FROM AUTHOR]

The study delves into the use of the thiol-yne click reaction to enhance (bio)conjugation methodologies, particularly focusing on immobilizing biomolecules onto PLLA surfaces. The thiol-yne click reaction, known for its efficiency, selectivity, and versatility in forming carbon-sulfur bonds under mild conditions without transition metal catalysts, is explored for conjugating the fluorophore dansyl onto PLLA surfaces. This approach aims to broaden bioconjugation strategies beyond traditional methods like the Michael-type reaction, expanding their applicability to diverse biomolecules. Utilizing a photoinitiator and specific light for photo-immobilization, the thiol-yne click reaction offers spatial and temporal control, with the absence of transition metal catalysts mitigating concerns of cytotoxicity and metal contamination, rendering it suitable for biomedical applications. The objectives of this research encompass demonstrating the feasibility of the thiol-yne click reaction for surface functionalization and enriching bioconjugation strategies for tailoring PLLA surfaces, ultimately advancing biomedical technologies through precise control over surface properties and functionality. For this purpose, PLLA surfaces were activated through hydrolysis and amidation to introduce the activated alkyne moiety (PLLA-Alkyne), followed by photo-induced dansyl immobilization (PLLA-Dns) with Irgacure 651. Various surface characterization techniques, including SEM, WCA, XPS, ATR-FTIR, and fluorescence microscopy and spectroscopy, validated the successful conjugation. This metal-free method preserves the material's bulk properties while enabling thiol-containing molecule immobilization. [ABSTRACT FROM AUTHOR]