Outer membrane vesicles from genetically engineered Salmonella enterica serovar Typhimurium presenting Helicobacter pylori antigens UreB and CagA induce protection against Helicobacter pylori infection in mice.

Helicobacter pylori causes globally prevalent infections that are highly related to chronic gastritis and even development of gastric carcinomas. With the increase of antibiotic resistance, scientists have begun to search for better vaccine design strategies to eradicate H. pylori colonization. However, while current strategies prefer to formulate vaccines with a single H. pylori antigen, their potential has not yet been fully realized. Outer membrane vesicles (OMVs) are a potential platform since they could deliver multiple antigens. In this study, we engineered three crucial H. pylori antigen proteins (UreB, CagA, and VacA) onto the surface of OMVs derived from Salmonella enterica serovar Typhimurium (S. Typhimurium) mutant strains using the hemoglobin protease (Hbp) autotransporter system. In various knockout strategies, we found that OMVs isolated from the ΔrfbP ΔfliC ΔfljB ΔompA mutants could cause distinct increases in immunoglobulin G (IgG) and A (IgA) levels and effectively trigger T helper 1- and 17-biased cellular immune responses, which perform a vital role in protecting against H. pylori. Next, OMVs derived from ΔrfbP ΔfliC ΔfljB ΔompA mutants were used as a vector to deliver different combinations of H. pylori antigens. The antibody and cytokine levels and challenge experiments in mice model indicated that co-delivering UreB and CagA could protect against H. pylori and antigen-specific T cell responses. In summary, OMVs derived from the S. Typhimurium ΔrfbP ΔfliC ΔfljB ΔompA mutant strain as the vector while importing H. pylori UreB and CagA as antigenic proteins using the Hbp autotransporter system would greatly benefit controlling H. pylori infection.

Outer membrane vesicles (OMVs), as a novel antigen delivery platform, has been used in vaccine design for various pathogens and even tumors. Salmonella enterica serovar Typhimurium (S. Typhimurium), as a bacterium that is easy to engineer and has both adjuvant efficacy and immune stimulation capacity, has become the preferred bacterial vector for purifying OMVs after Escherichia coli. This study focuses on the design of Helicobacter pylori ;(H. pylori) vaccines, utilizing genetically modified Salmonella OMVs to present several major antigens of H. pylori, including UreB, VacA and CagA. The optimal Salmonella OMV delivery vector and antigen combinations are screened and identified, providing new ideas for the development of H. pylori vaccines and an integrated antigen delivery platform for other difficult to develop vaccines for bacteria, viruses, and even tumors.

Four-Arm Polymer-Guided Formation of Curcumin-Loaded Flower-Like Porous Microspheres as Injectable Cell Carriers for Diabetic Wound Healing.

Stem cell injection is an effective approach for treating diabetic wounds; however, shear stress during injections can negatively affect their stemness and cell growth. Cell-laden porous microspheres can provide shelter for bone mesenchymal stem cells (BMSC). Herein, curcumin-loaded flower-like porous microspheres (CFPM) are designed by combining phase inversion emulsification with thermally induced phase separation-guided four-arm poly (l-lactic acid) (B-PLLA). Notably, the CFPM shows a well-defined surface topography and inner structure, ensuring a high surface area to enable the incorporation and delivery of a large amount of -BMSC and curcumin. The BMSC-carrying CFPM (BMSC@CFPM) maintains the proliferation, retention, and stemness of -BMSCs, which, in combination with their sustainable curcumin release, facilitates the endogenous production of growth/proangiogenic factors and offers a local anti-inflammatory function. An in vivo bioluminescence assay demonstrates that BMSC@CFPM can significantly increase the retention and survival of BMSC in wound sites. Accordingly, BMSC@CFPM, with no significant systemic toxicity, could significantly accelerate diabetic wound healing by promoting angiogenesis, collagen reconstruction, and M2 macrophage polarization. RNA sequencing further unveils the mechanisms by which BMSC@CFPM promotes diabetic wound healing by increasing -growth factors and enhancing angiogenesis through the JAK/STAT pathway. Overall, BMSC@CFPM represents a potential therapeutic tool for diabetic wound healing.

Fabrication of magnesium-doped porous polylactic acid microsphere for bone regeneration.

Biodegradable polymer microspheres that can be used as drug carriers are of great importance in biomedical applications, however, there are still challenges in controllable preparation of microsphere surface morphology and improvement of bioactivity. In this paper, firstly, poly(L-lactic acid) (PLLA) was synthesised by ring-opening polymerisation under anhydrous anaerobic conditions and further combined with the emulsion method, biodegradable PLLA microspheres (PM) with sizes ranging from 60-100 µm and with good sphericity were prepared. In addition, to further improve the surface morphology of PLLA microspheres and enhance their bioactivity, functionalised porous PLLA microspheres loaded with magnesium oxide (MgO)/magnesium carbonate (MgCO3) (PMg) were also prepared by the emulsion method. The results showed that the loading of MgO/MgCO3 resulted in the formation of a porous structure on the surface of the microspheres (PMg) and the dissolved Mg2+ could be released slowly during the degradation of microspheres. In vitro cellular experiments demonstrated the good biocompatibility of PM and PMg, while the released Mg2+ further enhanced the anti-inflammatory effect and osteogenic activity of PMg. Functionalised PMg not only show promise for controlled preparation of drug carriers, but also have translational potential for bone regeneration.

Microsphere-containing Hydrogel Scaffolds for Tissue Engineering.

Key Laboratory for Ultrafine Materials of Ministry of Education Centre for Biomedical Technologies Current tissue engineering technology aims to achieve the regeneration of human tissues, which integrates the key factors such as scaffolds, cells and biomolecules. Among these key factors, the development of high-performance scaffolds is the basis for the success of tissue engineering strategies. In the past decades, hydrogel scaffolds have been developed rapidly and widely used in biomedical field, however, their drawbacks have also been revealed, which shows that a single hydrogel scaffold cannot meet the excellent performance required in the field of tissue engineering. Recently, microspheres have been further engineered to fabricate structurally and functionally reliable artificial three-dimensional scaffolds of desired shape with enhanced specific biological functions. Therefore, the effective combination of hydrogel and microspheres can facilitate the development of high-performance scaffolds for tissue engineering and further fine-tuning the composite structure, which is expected to solve the dilemma faced by a single scaffold. In this review paper, we systematically summurized the type and preparation method for synthesis of hydrogel and microsphere materials commonly used in developing microsphere-containing hydrogel scaffolds. We then reviewed the broad application of these hybrid scaffolds in various fields of tissue engineering, followed by a summary and perspective on future directions.