Circadian Clock Regulation via Biomaterials for Nucleus Pulposus

In Situ Remodeling of Efferocytosis via Lesion-Localized Microspheres to Reverse Cartilage Senescence

Efferocytosis, an intrinsic regulatory mechanism to eliminate apoptotic cells, will be suppressed due to the delayed apoptosis process in aging-related diseases, such as osteoarthritis (OA). In this study, cartilage lesion-localized hydrogel microspheres are developed to remodel the in situ efferocytosis to reverse cartilage senescence and recruit endogenous stem cells to accelerate cartilage repair. Specifically, aldehyde- and methacrylic anhydride (MA)-modified hyaluronic acid hydrogel microspheres (AHM), loaded with pro-apoptotic liposomes (liposomes encapsulating ABT263, A-Lipo) and PDGF-BB, namely A-Lipo/PAHM, are prepared by microfluidic and photo-cross-linking techniques. By a degraded porcine cartilage explant OA model, the in situ cartilage lesion location experiment illustrated that aldehyde-functionalized microspheres promote affinity for degraded cartilage. In vitro data showed that A-Lipo induced apoptosis of senescent chondrocytes (Sn-chondrocytes), which can then be phagocytosed by the efferocytosis of macrophages, and remodeling efferocytosis facilitated the protection of normal chondrocytes and maintained the chondrogenic differentiation capacity of MSCs. In vivo experiments confirmed that hydrogel microspheres localized to cartilage lesion reversed cartilage senescence and promoted cartilage repair in OA. It is believed this in situ efferocytosis remodeling strategy can be of great significance for tissue regeneration in aging-related diseases.

Injectable Nano-Micro Composites with Anti-bacterial and Osteogenic Capabilities for Minimally Invasive Treatment of Osteomyelitis

The effective management of osteomyelitis remains extremely challenging due to the difficulty associated with treating bone defects, the high probability of recurrence, the requirement of secondary surgery or multiple surgeries, and the difficulty in eradicating infections caused by methicillin-resistant Staphylococcus aureus (MRSA). Hence, smart biodegradable biomaterials that provide effective and precise local anti-infection effects and can promote the repair of bone defects are actively being developed. Here, a novel nano-micro composite is fabricated by combining calcium phosphate (CaP) nanosheets with drug-loaded GelMA microspheres via microfluidic technology. The microspheres are covalently linked with vancomycin (Van) through an oligonucleotide (oligo) linker using an EDC/NHS carboxyl activator. Accordingly, a smart nano-micro composite called "CaP@MS-Oligo-Van" is synthesized. The porous CaP@MS-Oligo-Van composites can target and capture bacteria. They can also release Van in response to the presence of bacterial micrococcal nuclease and Ca2+, exerting additional antibacterial effects and inhibiting the inflammatory response. Finally, the released CaP nanosheets can promote bone tissue repair. Overall, the findings show that a rapid, targeted drug release system based on CaP@MS-Oligo-Van can effectively target bone tissue infections. Hence, this agent holds potential in the clinical treatment of osteomyelitis caused by MRSA.

Therapeutic factors and biomaterial-based delivery tools for degenerative intervertebral disc repair

Intervertebral disc degeneration (IDD) is the main cause of low back pain (LBP), which significantly impacts global wellbeing and contributes to global productivity declines. Conventional treatment approaches, encompassing conservative and surgical interventions, merely serve to postpone the advancement of IDD without offering a fundamental reversal. Consequently, there is an urgent demand for an effective approach to prevent the progression of IDD. Recent investigations focusing on the treatment of IDD utilizing diverse bioactive substances integrated within various biomaterials have exhibited promising outcomes. Various bioactive substances, encompassing conventional small molecule drugs, small molecule nucleic acids, and cell therapies, exhibit distinct capacities for repairing IDD. Additionally, various biological material delivery systems, such as nano micelles, microspheres, and hydrogels, possess diverse biological and release characteristics. Consequently, these diverse materials and drugs hold promise for advancing the treatment of IDD. This article aims to provide a concise overview of the IDD process and investigate the research advancements in biomaterials and bioactive substances for IDD treatment, delving into their mechanisms.

Hydrogen Ion Capturing Hydrogel Microspheres for Reversing Inflammaging

Inflammaging is deeply involved in aging-related diseases and can be destructive during aging. The maintenance of pH balance in the extracellular microenvironment can alleviate inflammaging and repair aging-related tissue damage. In this study, the hydrogen ion capturing hydrogel microsphere (GMNP) composed of mineralized transforming growth factor-β (TGF-β) and catalase (CAT) nanoparticles is developed via biomimetic mineralization and microfluidic technology for blocking the NLRP3 cascade axis in inflammaging. This GMNP can neutralize the acidic microenvironment by capturing excess hydrogen ions through the calcium carbonate mineralization layer. Then, the subsequent release of encapsulated TGF-β and CAT can eliminate both endogenous and exogenous stimulus of NLRP3, thus suppressing the excessive activation of inflammaging. In vitro, GMNP can suppress the excessive activation of the TXNIP/NLRP3/IL-1β cascade axis and enhance extracellular matrix (ECM) synthesis in nucleus pulposus cells. In vivo, GMNP becomes a sustainable and stable niche with microspheres as the core to inhibit inflammaging and promote the regeneration of degenerated intervertebral discs. Therefore, this hydrogen ion-capturing hydrogel microsphere effectively reverses inflammaging by interfering with the excessive activation of NLRP3 in the degenerated tissues.