Combating Biofilms by a Self-Adapting Drug Loading Hydrogel

Recent advances in composite hydrogels: synthesis, classification, and application in the treatment of bone defects

Bone defects are often difficult to treat due to their complexity and specificity, and therefore pose a serious threat to human life and health. Currently, the clinical treatment of bone defects is mainly surgical. However, this treatment is often more harmful to patients and there is a potential risk of rejection and infection. Hydrogels have a unique three-dimensional structure that can accommodate a variety of materials, including particles, polymers and small molecules, making them ideal for treating bone defects. Therefore, emerging composite hydrogels are considered one of the most promising candidates for the treatment of bone defects. This review describes the use of different types of composite hydrogel in the treatment of bone defects. We present the basic concepts of hydrogels, different preparation techniques (including chemical and physical crosslinking), and the clinical requirements for hydrogels used to treat bone defects. In addition, a review of numerous promising designs of different types of hydrogel doped with different materials (e.g., nanoparticles, polymers, carbon materials, drugs, and active factors) is also highlighted. Finally, the current challenges and prospects of composite hydrogels for the treatment of bone defects are presented. This review will stimulate research efforts in this field and promote the application of new methods and innovative ideas in the clinical field of composite hydrogels.

Enhancement of Impaired MRSA-Infected Fracture Healing by Combinatorial Antibiotics and Modulation of Sustained Inflammation

Fracture healing is impaired in the setting of infection, which begets protracted inflammation. The most problematic causative agent of musculoskeletal infection is methicillin-resistant Staphylococcus aureus (MRSA). We hypothesized that modulation of excessive inflammation combined with cell-penetrating antibiotic treatments facilitates fracture healing in a murine MRSA-infected femoral fracture model. Sterile and MRSA-contaminated open transverse femoral osteotomies were induced in 10-week-old male C57BL/6 mice and fixed via intramedullary nailing. In the initial therapeutic cohort, empty, vancomycin (V), rifampin (R), vancomycin-rifampin (VR), or vancomycin-rifampin-trametinib (VRT) hydrogels were applied to the fracture site intraoperatively. Rifampin was included because of its ability to penetrate eukaryotic cells to target intracellular bacteria. Unbiased screening demonstrated ERK activation was upregulated in the setting of MRSA infection. As such, the FDA-approved mitogen-activated protein kinase kinase (MEK)1-pERK1/2 inhibitor trametinib was evaluated as an adjunctive therapeutic agent to selectively mitigate excessive inflammation after infected fracture. Two additional cohorts were created mimicking immediate and delayed postoperative antibiotic administration. Systemic vancomycin or VR was administered for 2 weeks, followed by 2 weeks of VRT hydrogel or oral trametinib therapy. Hematologic, histological, and cytokine analyses were performed using serum and tissue isolates obtained at distinct postoperative intervals. Radiography and micro-computed tomography (μCT) were employed to assess fracture healing. Pro-inflammatory cytokine levels remained elevated in MRSA-infected mice with antibiotic treatment alone, but increasingly normalized with trametinib therapy. Impaired callus formation and malunion were consistently observed in the MRSA-infected groups and was partially salvaged with systemic antibiotic treatment alone. Mice that received VR alongside adjuvant MEK1-pERK1/2 inhibition displayed the greatest restoration of bone and osseous union. A combinatorial approach involving adjuvant cell-penetrating antibiotic treatments alongside mitigation of excessive inflammation enhanced healing of infected fractures. © 2022 American Society for Bone and Mineral Research (ASBMR).

Synthesis of Bioactive Materials by In Situ One-Step Direct Loading of Syzygium aromaticum Essential Oil into Chitosan-Based Hydrogels

Hydrogel conjugates based on chitosan and an essential oil were synthetized by an ultrasound-assisted emulsification approach. Rheology studies revealed a gel-type structure with pronounced compactness and flexibility while SEM showed the formation of a two-level ordered network with highly interconnected pores. The swelling studies indicated a pH-dependent behavior with a significant overshooting effect. The synergistic effects of the components in clove essential oil led to a strong antioxidant character and an enhanced antimicrobial activity of the conjugate hydrogels. The bioactivity was maintained for 6 months, despite a slight decrease in the antimicrobial effect. Hydrogel conjugates were found to be very stable even after two months immersed in acidic solutions that would otherwise dissolve the chitosan matrix. Ultrasound emulsification was proved as an efficient one-step loading method of hydrophobic clove essential oil into hydrophilic chitosan matrix. It was found that clove oil and its components have a double role. Besides providing bioactivity, they also behave as gelation-inducing agents, acting as an alternative to the classical chemical cross-linkers to ensure the good physical and chemical stabilization of chitosan.

Advances in Ultrasound-Responsive Hydrogels for Biomedical Applications

Various intelligent hydrogels have been developed for biomedical applications because they can achieve multiple, variable, controllable and reversible changes in their shape and properties in a spatial and temporal manner,...