In situ sprayed hydrogels containing resiquimod-loaded liposomes reduce chronic osteomyelitis recurrence by intracellular bacteria clearance

Photodynamic gel-bombs enhance tumor penetration and downstream synergistic therapies

Nanoparticle-based drug delivery system remains a significant challenge in the current treatment of solid tumors, primarily due to their limited penetration capabilities. Herein, we successfully engineer photodynamic gel-bombs (DCM@OPR) capable of penetrating deeply into tumor tissues utilizing the photodynamic-triggered explosive energy and receptor-mediated transcytosis, significantly enhancing the therapeutic efficacy of breast cancer. The photodynamic gel-bombs were fabricated by loading powerful components of chlorin e6 and MnO2 nanoparticles, as well as Doxorubicin, into a crosslinked Ca2+-gel. Upon exposure to laser irradiation, the obtained photodynamic gel-bombs are capable of generating explosive energy, resulting in their fragmentation into numerous nanofragments. The photodynamic-triggered explosive energy subsequently drives these nanofragments to deeply penetrate into tumor tissues through gap leakage among tumor cells. In addition, the photodynamic-triggered explosive energy also promotes the escape of those therapeutic components (including chlorin e6, MnO2 nanoparticles, and doxorubicin) and nanofragments from lysosomes. In the subsequent stages, these nanofragments also exhibit excellent transcytosis capacity, facilitating deep penetration into tumor tissues. As expected, the enhanced penetration and accumulation of therapeutic components into tumor tissues can be achieved, significantly enhancing the anti-proliferation capacity against breast cancer.

Functional Hydrogel Interfaces for Cartilage and Bone Regeneration

Effective treatment of bone diseases is quite tricky due to the unique nature of bone tissue and the complexity of the bone repair process. In combination with biological materials, cells and biological factors can provide a highly effective and safe treatment strategy for bone repair and regeneration, especially based on these multifunctional hydrogel interface materials. However, itis still a challenge to formulate hydrogel materials with fascinating properties (e.g., biological activity, controllable biodegradability, mechanical strength, excellent cell/tissue adhesion, and controllable release properties) for their clinical applications in complex bone repair processes. In this review, we will highlight recent advances in developing functional interface hydrogels. We then discuss the barriers to  producing of functional hydrogel materials without sacrificing their inherent properties, and potential applications in cartilage and bone repair are discussed. Multifunctional hydrogel interface materials can serve as a fundamental building block for bone tissue engineering.

In Situ Application of Berberine-Loaded Liposomes on the Treatment of Osteomyelitis

Osteomyelitis is a major challenge in global healthcare, as it requires the simultaneous management of bone defects and bacterial infections, which poses considerable difficulties for orthopedic clinicians. In this study, we developed berberine liposome-modified bone cement specifically aimed at treating osteomyelitis induced by Staphylococcus aureus. We characterized the physical properties of this modified bone cement, conducted in vitro antibacterial assays to evaluate its efficacy in eradicating Staphylococcus aureus biofilm, established an in vivo rat model of osteomyelitis, and performed histopathological assessments alongside micro-CT analysis of bone parameters. The results indicated that the berberine liposome-modified bone cement exhibited favorable biodegradability and sustained-release characteristics, with a drug release rate of more than 90% within 14 days, while effectively eliminating bacterial biofilm with a biofilm eradication rate of up to 80% and facilitating bone repair with a bone volume fraction of 80%. This innovative treatment demonstrated both safety and efficacy in addressing tibial osteomyelitis in rats, thereby offering novel insights and methodologies for clinical interventions against osteomyelitis.

Challenges and considerations in liposomal hydrogels for the treatment of infection

INTRODUCTION

Liposomal hydrogels are novel drug delivery systems that comprise preformed liposomes incorporated in hydrogels destined for mostly localized drug therapy, herewith antimicrobial therapy. The formulation benefits from versatility of liposomes as lipid-based nanocarriers that enable delivery of various antimicrobials of different lipophilicities, and secondary vehicle, hydrogel, that assures better retention time of formulation at the infection site. Especially in an era of alarming antimicrobial resistance, efficient localized antimicrobial therapy that avoids systemic exposure of antimicrobial and related side effects is crucial.

AREAS COVERED

We provide an overview of liposomal hydrogels that were developed for superior delivery of antimicrobials at different infections sites, with focus on skin and vaginal infections. The review summarizes the challenges of infection site and most common infection-causing pathogens and offers commentary on most relevant features the formulation needs to optimize to increase the therapy outcome. We discuss the impact of liposomal composition, size, and choice of polymer-forming hydrogel on antimicrobial outcome based on the literature overview and own experience in the field.

EXPERT OPINION

Liposomal hydrogels offer improved therapy outcome in localized antimicrobial therapy. By fine-tuning of liposomal as well as hydrogel properties, formulations with superior performance can be optimized targeting specific infection site.

Unlocking the Potential of Hybrid Nanocomposite Hydrogels: Design, Mechanical Properties and Biomedical Performances

Hybrid nanocomposite hydrogels consist of the homogeneous incorporation of nano‐objects in a hydrogel matrix. The latter, whether made of natural or synthetic materials, possesses a microporous, soft structure that makes it an ideal host for a variety of polymer and lipid‐based nano‐objects as well as metal‐ and silica‐based ones. By carefully choosing the composition and the proportions of the different constituents, hybrid hydrogels can display a wide array of properties, from simple enhancement of mechanical characteristics to specific bioactivity. This review aims to provide an overview of the state of the art in hybrid hydrogels highlighting key aspects that make them a promising choice for a variety of biomedical applications. Strategies for the preparation of hybrid hydrogels are discussed by covering the selection of individual components. The review will also explore the physico‐chemical and rheological characterization of these materials, which is essential for understanding their structure and function, ultimately satisfying specifications for the intended use. Successful examples of biomedical applications will also be presented, and the main challenges to be met will be discussed, with the aim of stimulating the research community to exploit the full potential of these materials.

Engineered macrophage-derived exosomes via click chemistry for the treatment of osteomyelitis

Osteomyelitis is a severe bone condition caused by bacterial infection that can lead to lifelong disabilities or fatal sepsis. Given that the infection is persistent and penetrates deep into the bone tissue, targeting and rapidly treating osteomyelitis remain a significant challenge. Herein, a triblock targeting peptide featuring ROS-cleavable linkage/antibacterial/bone-targeting unit was grafted onto the macrophage-derived exosomes (RAB-EXO). In vitro, the effective eradication of osteomyelitis pathogens MRSA/E. coli and induction of M2 macrophage differentiation were triggered by RAB-EXO. In vivo, after the intravenous administration of RAB-EXO, it can target the bone tissue and release antimicrobial peptides in the high ROS environment of osteomyelitis. The released antimicrobial peptides markedly inhibit bacterial growth at the infection sites. Moreover, M2 differentiation of the bone tissue macrophages are facilitated by EXO, thereby decreasing the inflammatory factors and achieving the anti-inflammatory effect. Finally, the complete healing of osteomyelitis without adverse effects associated with traditional treatments is achieved within 28 days in rat models. Our findings confirm that RAB-EXO, as a targeted treatment for osteomyelitis, offers promising directions for addressing other bacterial infection diseases, such as periodontitis and rheumatoid arthritis, through similar mechanisms.

Collagen patches releasing phosphatidylserine liposomes guide M1-to-M2 macrophage polarization and accelerate simultaneous bone and muscle healing

Bilateral communication between bones and muscles is essential for healing composite bone-muscle injuries from orthopedic surgeries and trauma. However, these injuries are often characterized by exaggerated inflammation, which can disrupt bone-muscle crosstalk, thereby seriously delaying the healing of either tissue. Existing approaches are largely effective at healing single tissues. However, simultaneous healing of multiple tissues remains challenging, with little research conducted to date. Here we introduce collagen patches that overcome this overlooked issue by harnessing the plasticity of macrophage phenotypes. Phosphatidylserine liposomes (PSLs) capable of shifting the macrophage phenotype from inflammatory M1 into anti-inflammatory/prohealing M2 were coated on collagen patches via a layer-by-layer method. Original collagen patches failed to improve tissue healing under inflammatory conditions coordinated by M1 macrophages. In contrast, PSL-coated collagen patches succeeded in accelerating bone and muscle healing by inducing a microenvironment dominated by M2 macrophages. In cell experiments, differentiation of preosteoblasts and myoblasts was completely inhibited by secretions of M1 macrophages but unaffected by those of M2 macrophages. RNA-seq analysis revealed that type I interferon and interleukin-6 signaling pathways were commonly upregulated in preosteoblasts and myoblasts upon stimulation with M1 macrophage secretions, thereby compromising their differentiation. This study demonstrates the benefit of PSL-mediated M1-to-M2 macrophage polarization for simultaneous bone and muscle healing, offering a potential strategy toward simultaneous regeneration of multiple tissues. STATEMENT OF SIGNIFICANCE: Existing approaches for tissue regeneration, which primarily utilize growth factors, have been largely effective at healing single tissues. However, simultaneous healing of multiple tissues remains challenging and has been little studied. Here we demonstrate that collagen patches releasing phosphatidylserine liposomes (PSLs) promote M1-to-M2 macrophage polarization and are effective for simultaneous healing of bone and muscle. Transcriptome analysis using next-generation sequencing reveals that differentiation of preosteoblasts and myoblasts is inhibited by the secretions of M1 macrophages but promoted by those of M2 macrophages, highlighting the importance of timely regulation of M1-to-M2 polarization in tissue regeneration. These findings provide new insight to tissue healing of multiple tissues.

Nanoclay Hydrogel Microspheres with a Sandwich-Like Structure for Complex Tissue Infection Treatment

Addressing complex tissue infections remains a challenging task because of the lack of effective means, and the limitations of traditional bioantimicrobial materials in single-application scenarios hinder their utility for complex infection sites. Hence, the development of a bioantimicrobial material with broad applicability and potent bactericidal activity is necessary to treat such infections. In this study, a layered lithium magnesium silicate nanoclay (LMS) is used to construct a nanobactericidal platform. This platform exhibits a sandwich-like structure, which is achieved through copper ion modification using a dopamine-mediated metallophenolic network. Moreover, the nanoclay is encapsulated within gelatin methacryloyl (GelMA) hydrogel microspheres for the treatment of complex tissue infections. The results demonstrate that the sandwich-like micro- and nanobactericidal hydrogel microspheres effectively eradicated Staphylococcus aureus (S. aureus) while exhibiting excellent biocompatibility with bone marrow-derived mesenchymal stem cells (BMSCs) and human umbilical vein endothelial cells (HUVECs). Furthermore, the hydrogel microspheres upregulated the expression levels of osteogenic differentiation and angiogenesis-related genes in these cells. In vivo experiments validated the efficacy of sandwich-like micro- and nanobactericidal hydrogel microspheres when injected into deep infected tissues, effectively eliminating bacteria and promoting robust vascular regeneration and tissue repair. Therefore, these innovative sandwich-like micro- and nanobacteriostatic hydrogel microspheres show great potential for treating complex tissue infections.

Rifampicin-Loaded Polyelectrolyte Complex Eliminates Intracellular Bacteria through Thiol-Mediated Cellular Uptake and Oxidative Stress Enhancement

The poor accumulation of antibiotics in the cytoplasm leads to the poor eradication of intracellular bacteria. Herein, a polyelectrolyte complex (PECs@Rif) allowing direct cytosolic delivery of rifampicin (Rif) was developed for the treatment of intracellular infections by complexation of poly(α-lipoic acid) (pLA) and oligosaccharide (COS) in water and loading Rif. Due to the thiol-mediated cellular uptake, PECs@Rif delivered 3.9 times higher Rif into the cytoplasm than that of the free Rif during 8 h of incubation. After entering cells, PECs@Rif released Rif by dissociating pLA into dihydrolipoic acid (DHLA) in the presence of intracellular thioredoxin reductase (TrxR). Notably, DHLA could reduce endogenous Fe(III) to Fe(II) and provide a catalyst for the Fenton reaction to produce a large amount of reactive oxygen species (ROS), which would assist Rif in eradicating intracellular bacteria. In vitro assay showed that PECs@Rif reduced almost 2.8 orders of magnitude of intracellular bacteria, much higher than 0.7 orders of magnitude of free Rif. The bacteremia-bearing mouse models showed that PECs@Rif reduced bacterial levels in the liver, spleen, and kidney by 2.2, 3.7, and 2.3 orders of magnitude, respectively, much higher than free Rif in corresponding tissues. The direct cytosolic delivery in a thiol-mediated manner and enhanced oxidative stress proposed a feasible strategy for treating intracellular bacteria infection.