Human bone is composed of cortical bone and cancellous bone. The interior portion of natural bone is cancellous with a porosity of 50%–90%, but the outer layer is made of dense cortical bone, of which porosity was not higher than 10%. Porous ceramics were expected to be research hotspot in bone tissue engineering by virtue of their similarity to the mineral constituent and physiological structure of human bone. However, it is challenging to utilize conventional manufacturing methods to fabricate porous structures with precise shapes and pore sizes. Three-dimensional (3D) printing of ceramics is currently the latest research trend because it has many advantages in the fabrication of porous scaffolds, which can meet the requirements of cancellous bone strength, arbitrarily complex shapes, and individualized design. In this study, β-tricalcium phosphate (β-TCP)/titanium dioxide (TiO2 ) porous ceramics scaffolds were fabricated by 3D gel-printing sintering for the first time. The chemical constituent, microstructure, and mechanical properties of the 3D-printed scaffolds were characterized. After sintering, a uniform porous structure with appropriate porosity and pore sizes was observed. Besides, biological mineralization activity and biocompatibility were evaluated by in vitro cell assay. The results demonstrated that the incorporation of TiO2 (5 wt%) significantly improved the compressive strength of the scaffolds, with an increase of 283%. Additionally, the in vitro results showed that the β-TCP/TiO2 scaffold had no toxicity. Meanwhile, the adhesion and proliferation of MC3T3-E1 cells on scaffolds were desirable, revealing that the β-TCP/TiO2 scaffolds can be used as a promising candidate for repair scaffolding in orthopedics and traumatology.

The lower gastrointestinal tract is a complex ecological system involved in epithelial barrier maintenance, immune regulation, microbial metabolism, and host homeostasis. Disruption of this environment is closely associated with lower gastrointestinal disorders, including inflammatory bowel disease (IBD), irritable bowel syndrome (IBS), and colorectal cancer (CRC). Conventional therapies often face limitations such as poor drug stability, low solubility, insufficient intestinal retention, limited targeting efficiency, and systemic adverse effects. Oral hydrogel systems have emerged as promising platforms for lower gastrointestinal therapy because of their biocompatibility, tunable physicochemical properties, controlled-release behavior, and responsiveness to intestinal microenvironmental cues. However, most existing studies have been developed primarily from a disease-based therapeutic perspective, focusing on inflammation suppression, oxidative stress regulation, epithelial barrier repair, tumor inhibition, or symptom relief, while gut microbiota alterations are often evaluated as accompanying outcomes. In this review, we discuss oral hydrogel systems for lower gastrointestinal disorders from the perspective of the transition from disease-based therapy to microbiota-guided design. We summarize the physiological barriers and design basis of oral hydrogel systems, disease-oriented applications in IBD, CRC, gut–brain axis-related disorders, and microbiota-associated metabolic disorders, and emerging microbiota-oriented hydrogel strategies. We further discuss hydrogel–microbiota–host interactions, microbiota-related design principles, and translational challenges. This review aims to clarify how oral hydrogel systems can evolve from conventional drug delivery platforms toward microbiota-guided therapeutic systems for lower gastrointestinal disorders.

The structure, composition, and function of natural bone have long been the focus of bone tissue engineering. However, existing organic–inorganic 3D printing systems are limited by hydrogel stability and inorganic salt content, hindering the fabrication of robust three-dimensional scaffolds. In this study, we developed a hydrogel–inorganic particle bioink and implemented a multi-step crosslinking strategy. The organic phase, composed of sodium alginate, gelatin, and chitosan, was combined with β-tricalcium phosphate and crosslinked via ionic pre-crosslinking followed by Schiff base reaction to form a dual-crosslinked network. The resulting scaffolds exhibited excellent mechanical properties and biomimetic microarchitecture while maintaining shape stability under physiological conditions. Furthermore, the tunable swelling behavior of the hydrogel enabled efficient loading and controlled release of the small molecule EGCG. This composite scaffold demonstrated adjustable swelling, controllable degradation, and significantly enhanced cellular compatibility, providing a novel, efficient, and scalable strategy for the repair of complex bone defects and offering new insights for the design and application of 3D-printed bone scaffolds.