Osteoporosis is a kind of systemic skeletal disorder. Its core mechanism lies in imbalanced bone remodeling, which could result in progressive bone loss and structural compromise. Current clinical drugs and therapeutics are greatly limited, mostly due to their low bioavailability, poor bone-targeting specificity, and an overreliance on single molecular targets, hindering effective modulation of the disease's complex pathological microenvironment. In recent years, with the advent of nanotechnology, a transformative strategy has arisen to overcome these shortcomings in conventional osteoporosis management. This review begins with the pathophysiological mechanisms underlying osteoporosis and provides a comprehensive overview of nanomaterial-based therapeutic approaches, including nanocarriers engineered for targeted drug or biomacromolecule delivery, nanoplatforms designed to remodel the bone microenvironment, advanced scaffolds tailored to support severe bone defects and guide tissue regeneration, and bioactive systems aimed at regulating the gut-bone axis for systemic bone homeostasis. We summarize recent progress and advantages of these nanotechnologies, critically address persistent challenges and highlight emerging strategies to tackle them, and provide an outlook on potential future research directions and technologies.

While a variety of wound dressing materials are available, the effective combination of multiple active components into a single composite dressing to optimize wound healing outcomes presents a substantial challenge. Herein, we introduce a novel trilayer nanofiber membrane (SNM) for accelerated infected wound healing. The SNM, fabricated via electrospinning, comprises a hydrophilic inner layer enriched with epigallocatechin-3-gallate (EGCG) for antioxidant activity, an antimicrobial middle layer incorporating silver zeolitic imidazolate framework (Ag-ZIF), and a hydrophobic outer layer of waterborne polyurethane (WPU) for structural integrity. The SNM exhibits superior mechanical properties, with a tensile strength of 8.83 ± 0.99 MPa and an elongation at break of 262.57% ± 30.06%, alongside a water vapor transmission rate (WVTR) of 521 g/(m²·24h). The SNM composites demonstrate potent bactericidal effects, achieving a 93.50% ± 5.77% and 94.39% ± 4.29% reduction against E. coli and S. aureus, respectively. Furthermore, the SNM exhibits a high 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging efficiency of 95% at a concentration of 100 μg/mL. Animal studies indicate significant wound healing enhancement, with the SNM-treated group achieving a 52.78% healing rate on day 3, compared to 11.15% for the control group. This work offers a promising strategy for the development of multifunctional wound dressings with integrated antibacterial nanomaterials and natural bioactive components within a single composite material.

Natural enzymes are highly efficient catalysts with strong substrate specificity, making them ideal for biomedical applications. However, they often face issues such as variability, high costs, challenging preparation processes, and difficulties in large-scale production. This has led to significant efforts in developing effective nanoenzymes and exploring their application potential. In recent years, carbon dots (CDs) have gained attention due to their strong fluorescence, excellent biocompatibility, and low cytotoxicity. Cationic CDs, which possess a positively charged surface, have shown the ability to mimic natural enzyme applications. The positive charge on the surfaces of these nanomaterials significantly influences their fluorescence, biological activity, and interactions with other biomolecules. Therefore, understanding how surface charge affects the performance of CDs is crucial for enhancing their usability. Considerable progress has been made in the design, synthesis, and mechanistic research of enzyme-like cationic CDs, as well as their advanced applications. This article reviews the latest research on the design structure, catalytic mechanisms, biosensing capabilities, and biomedical applications of enzyme-like cationic CDs. First, we review the synthesis strategies for cationic CDs and how surface charge influences their physical and chemical properties. Next, we highlight various applications of these cationic CDs, demonstrating their use in areas such as detection, biomedical applications (including antibacterial agents, gene carriers, and therapeutic agents), catalysis, and more. Finally, we discuss the challenges and obstacles faced in the development of cationic CDs and look forward to exploring new applications in the future.