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Hydrogel scaffolds are attractive for tissue defect repair and reorganization because of their human tissue-like characteristics. However, most hydrogels offer limited cell growth and tissue formation ability due to their submicron- or nano-sized gel networks, which restrict the supply of oxygen, nutrients and inhibit the proliferation and differentiation of encapsulated cells. In recent years, 3D printed hydrogels have shown great potential to overcome this problem by introducing macro-pores within scaffolds. In this study, we fabricated a macroporous hydrogel scaffold through horseradish peroxidase (HRP)-mediated crosslinking of silk fibroin (SF) and tyramine-substituted gelatin (GT) by extrusion-based low-temperature 3D printing. Through physicochemical characterization, we found that this hydrogel has excellent structural stability, suitable mechanical properties, and an adjustable degradation rate, thus satisfying the requirements for cartilage reconstruction. Cell suspension and aggregate seeding methods were developed to assess the inoculation efficiency of the hydrogel. Moreover, the chondrogenic differentiation of stem cells was explored. Stem cells in the hydrogel differentiated into hyaline cartilage when the cell aggregate seeding method was used and into fibrocartilage when the cell suspension was used. Finally, the effect of the hydrogel and stem cells were investigated in a rabbit cartilage defect model. After implantation for 12 and 16 weeks, histological evaluation of the sections was performed. We found that the enzymatic cross-linked and methanol treatment SF5GT15 hydrogel combined with cell aggregates promoted articular cartilage regeneration. In summary, this 3D printed macroporous SF-GT hydrogel combined with stem cell aggregates possesses excellent potential for application in cartilage tissue repair and regeneration., Graphical abstract Image 1, Highlights • A novel macro-porous hydrogel scaffold for cartilage tissue engineering was optimized by enzymatically crosslinking of SF and GT molecules. • The advantages of this scaffold are excellent structural stability, suitable mechanical properties for cartilage regeneration. • Stem cells differentiated into hyaline cartilage by the cell aggregates seeding method while into fibrocartilage by the cell suspension seeding method.

Background: Localized delivery of antimicrobial agents such as antimicrobial peptides (AMPs) by a biomaterial should be on-demand. Namely, AMPs should be latent and biocompatible in the absence of bacterial infection, but released in an amount enough to kill bacteria immediately in response to bacterial infection. Methods: To achieve the unmet goal of such on-demand delivery, here we turned a titanium implant with titania nanotubes (Ti-NTs) into a Pandora's box. The box was loaded with AMPs (HHC36 peptides, with a sequence of KRWWKWWRR) inside the nanotubes and "closed" (surface-modified) with a pH-responsive molecular gate, poly(methacrylic acid) (PMAA), which swelled under normal physiological conditions (pH 7.4) but collapsed under bacterial infection (pH ≤ 6.0). Thus, the PMAA-gated Ti-NTs behaved just like a Pandora's box. The box retarded the burst release of AMPs under physiological conditions because the gate swelled to block the nanotubes opening. However, it was opened to release AMPs to kill bacteria immediately when bacterial infection occurred to lowering the pH (and thus made the gate collapse). Results: We demonstrated such smart excellent bactericidal activity against a panel of four clinically important bacteria, including Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, methicillin-resistant Staphylococcus aureus. In addition, this box was biocompatible and could promote the osteogenic differentiation of human mesenchymal stem cells. Both in vitro and in vivo studies confirmed the smart "on-demand" bactericidal activity of the Pandora's box. The molecularly gated Pandora's box design represents a new strategy in smart drug delivery.

Cell-material interactions are important to tissue engineering. Inspired by the natural topographic structures on the extracellular matrix, a growing number of studies have integrated engineering topography into investigations of cell behavior on biomaterials. Engineering topography has a significant influence on cell behaviors. These cell-topography interactions play an important role in regenerative medicine and tissue engineering. Similarly, cell-topography interactions are important to corneal reconstruction and regeneration. In this review, we primarily summarized the effects of topographic cues on the behaviors of corneal cells, including cell morphology, adhesion, migration, and proliferation. Furthermore, the integration of engineering surface topography into corneal tissue engineering was also discussed., Graphical abstract Image 1, Highlights • This article aims to provide insight into the potential applications of topography on corneal reconstruction and regeneration. • Discussed the relation between surface topography and corneal repair. • Reviewed the effect of topographic cues on corneal cell behaviors. • Reviewed the applications of topographic cues in corneal tissue engineering. • Discussed the underlying mechanism of the topographic effect on cell behaviors.

Introduction The physique of college students is very important. The physique of college students is the prerequisite for the country’s revitalization, and health is the prerequisite for the transformation of intellectual capital. Object Aiming at the current college students’ physical education class arrangements and curriculum reform, the paper uses exercise prescriptions to make a brief plan for students’ physical exercise. Method The thesis uses the exercise prescription teaching method to carry out health intervention education for middle school students, which is used to analyze the physical requirements of students. Results After five months of fitness exercise prescription, the students’ physical fitness has increased significantly. We use fitness exercise prescriptions to make students feel good about exercise. Conclusion The application of physical and healthy exercise prescriptions can effectively improve the systematic and scientific nature of students’ participation in sports and help students learn and master healthy physical and mental self-exercise skills. Level of evidence II; Therapeutic studies - investigation of treatment results. RESUMO Introdução O físico dos estudantes universitários é muito importante. O físico dos universitários é o pré-requisito para a revitalização do país, e a saúde é o pré-requisito para a transformação do capital intelectual. Objeto Visando os arranjos das aulas de educação física dos atuais estudantes universitários e a reforma curricular, o artigo usa prescrições de exercícios para fazer um breve plano para os exercícios físicos dos alunos. Método A tese utiliza o método de ensino da prescrição de exercícios para realizar educação de intervenção em saúde para alunos do ensino médio, que é utilizada para analisar as exigências físicas dos alunos. Resultados Após cinco meses de prescrição de exercícios físicos, a aptidão física dos alunos aumentou significativamente. Usamos prescrições de exercícios físicos para fazer os alunos se sentirem bem com os exercícios. Conclusão A aplicação de prescrições de exercícios físicos e saudáveis pode efetivamente melhorar a natureza sistemática e científica da participação dos alunos em esportes e ajudá-los a aprender e dominar habilidades saudáveis de auto-exercício físico e mental. Nível de evidência II; Estudos terapêuticos - investigação dos resultados do tratamento. RESUMEN Introducción El físico de los estudiantes universitarios es muy importante. El físico de los estudiantes universitarios es el requisito previo para la revitalización del país, y la salud es el requisito previo para la transformación del capital intelectual. Objeto Con el objetivo de los arreglos de las clases de educación física de los estudiantes universitarios actuales y la reforma del plan de estudios, el documento utiliza prescripciones de ejercicios para hacer un plan breve para el ejercicio físico de los estudiantes. Método La tesis utiliza el método didáctico de prescripción de ejercicios para realizar la educación de intervención en salud para estudiantes de secundaria, que se utiliza para analizar los requisitos físicos de los estudiantes. Resultados Después de cinco meses de prescripción de ejercicios físicos, la aptitud física de los estudiantes ha aumentado significativamente. Usamos recetas de ejercicios físicos para que los estudiantes se sientan bien con el ejercicio. Conclusión La aplicación de prescripciones de ejercicio físico y saludable puede mejorar de manera efectiva la naturaleza sistemática y científica de la participación de los estudiantes en los deportes y ayudar a los estudiantes a aprender y dominar habilidades saludables de autoejercicio físico y mental. Nivel de evidencia II; Estudios terapéuticos: investigación de los resultados del tratamiento.

Modification of implants by antimicrobial peptides (AMPs) can improve the antimicrobial activity of the implants. However, AMPs have some cytotoxicity in vivo when they are exposed at body temperature. To tackle this challenge, we propose to develop a new approach to generating a smart antimicrobial surface through exposure of AMPs on the surface. A polydopamine film was first formed on the substrates, followed by the conjugation of a temperature-sensitive polymer, poly( N-isopropylacrylamide) (pNIPAM), to the film through atom transfer radical polymerization (ATRP). Then, AMPs were conjugated to the NIPAM on the resultant pNIPAM-modified surface through a click chemistry reaction. Because of the temperature-sensitive property of pNIPAM, the AMPs motif was more exposed to the external environment at room temperature (25 °C) than at body temperature (37 °C), making the surface present a higher antimicrobial activity at room temperature than at body temperature. More importantly, such a smart behavior is accompanied with the increased biocompatibility of the surface at body temperature when compared to the substrates unmodified or modified by AMPs or pNIPAM alone. Our in vivo study further verified that pNIPAM-AMP dual modified bone implants showed increased biocompatibility even when they were challenged with the bacteria at room temperature before implantation. These results indicate that the implants are antibacterial at room temperature and can be safely employed during surgery, resulting in no infection after implantations. Our work represents a new promising strategy to fully explore the antimicrobial property of AMPs, while improving their biocompatibility in vivo. The higher exposure of AMPs at room temperature (the temperature for storing the implants before surgery) will help decrease the risk of bacterial infection, and the lower exposure of AMPs at body temperature (the temperature after the implants are placed into the body by surgery) will improve the biocompatibility of AMPs.