Contributions of photochemistry to bio-based antibacterial polymer materials

Development of double network polyurethane-chitosan composite bioinks for soft neural tissue engineering

Three-dimensional (3D) bioprinting is an emerging manufacturing technology to print materials with cells for tissue engineering applications. In this study, we prepared novel ternary soft segment-based biodegradable polyurethane (tPU) using waterborne processes. The ternary soft segment included poly(ε-caprolactone) (PCL), polylactide, and poly(3-hydroxybutyrate) (PHB). tPU2 with a soft segment of PCL, poly(D,L-lactide), and PHB in a molar ratio of 0.7 : 0.2 : 0.1 demonstrated lower stiffness (∼2.3 kPa) and a greater tan δ value (∼0.64) and maintained good vitality (91.3%) of neural stem cells (NSCs) among various tPUs. The bioprinted tPU2 constructs facilitated cell proliferation (∼200% in 7 days) and neural differentiation of NSCs. Meanwhile, tPU2 formed double network composite hydrogels with gelatin or agarose, and the composite hydrogels showed good biocompatibility and achieved high-resolution (∼80 μm nozzle) bioprinting. In addition, a new series of double network polyurethane-chitosan composite (PUC) hydrogels were developed by combining tPU2 with a self-healing chitosan hydrogel. The PUC hydrogel demonstrated self-healing properties and bioprintability without the need for a post-crosslinking process. The bioprinted PUC composite hydrogel promoted cell proliferation (∼300% in 7 days) and neural differentiation of NSCs better than the tPU2 bioink. This study revealed new formulae of a polyurethane bioink and a polyurethane-chitosan composite bioink for 3D bioprinting and tissue engineering applications.

Research progress of stimulus-responsive antibacterial materials for bone infection

Infection is one of the most serious complications harmful to human health, which brings a huge burden to human health. Bone infection is one of the most common and serious complications of fracture and orthopaedic surgery. Antibacterial treatment is the premise of bone defect healing. Among all the antibacterial strategies, irritant antibacterial materials have unique advantages and the ability of targeted therapy. In this review, we focus on the research progress of irritating materials, the development of antibacterial materials and their advantages and disadvantages potential applications in bone infection.

Biobased polymer resources and essential oils: a green combination for antibacterial applications

To fight nosocomial infections, the excessive use of antibiotics has led to the emergence of multidrug-resistant microorganisms, which are now considered a relevant public health threat by the World Health Organization. To date, most antibacterial systems are based on the use of petro-sourced polymers, but the global supplies of these resources are depleting. Besides, silver NPs are widely accepted as the most active biocide against a wide range of bacterial strains but their toxicity is an issue. The growing interest in natural products has gained increasing interest in the last decade. Therefore, the design of functional antibacterial materials derived from biomass remains a significant challenge for the scientific community. Consequently, attention has shifted to naturally occurring substances such as essential oils (EOs), which are classified as Generally Recognized as Safe (GRAS). EOs can offer an alternative to the common antimicrobial agents as an inner solution or biocide agent to inhibit the resistance mechanism. Herein, this review not only aims at providing developments in the antibacterial modes of action of EOs against various bacterial strains and the recent advances in genomic and proteomic techniques for the elucidation of these mechanisms but also presents examples of biobased polymer resource-based EO materials and their antibacterial activities. Especially, we describe the antibacterial properties of biobased polymers, e.g. cellulose, starch, chitosan, PLA PHAs and proteins, associated with EOs (cinnamon (CEO), clove (CLEO), bergamot (BEO), ginger (GEO), lemongrass (LEO), caraway (CAEO), rosemary (REO), Eucalyptus globulus (EGEO), tea tree (TTEO), orange peel (OPEO) and apricot (Prunus armeniaca) kernel (AKEO) essential oils). Finally, we discuss the influence of EOs on the mechanical strength of bio-based materials.

Electron Paramagnetic Resonance Spin Trapping (EPR–ST) Technique in Photopolymerization Processes

To face economic issues of the last ten years, free-radical photopolymerization (FRP) has known an impressive enlightenment. Multiple performing photoinitiating systems have been designed to perform photopolymerizations in the visible or near infrared (NIR) range. To fully understand the photochemical mechanisms involved upon light activation and characterize the nature of radicals implied in FRP, electron paramagnetic resonance coupled to the spin trapping (EPR–ST) method represents one of the most valuable techniques. In this context, the principle of EPR–ST and its uses in free-radical photopolymerization are entirely described.