Size-controlled spherical silver nanoparticles (Ag NPs) can be simply prepared by autoclaving mixtures of glass powder containing silver with glucose. Moreover, chitins with varying degrees of deacetylation (DDAc < 30%) and chitosan powders and sheets (DDAc > 75%) with varying surface structure properties have been evaluated as Ag NP carriers. Chitin/chitosan-Ag NP composites in powder or sheet form were prepared by mixing Ag NP suspensions with each of the chitin/chitosan-based material at pH 7.3, leading to homogenous dispersion and stable adsorption of Ag NPs onto chitin carriers with nanoscale fiber-like surface structures, and chitosan carriers with nanoscale porous surface structures. Although these chitins exhibited mild antiviral, bactericidal, and antifungal activities, chitin powders with flat/smooth film-like surface structures had limited antimicrobial activities and Ag NP adsorption. The antimicrobial activities of chitin/chitosan-Ag NP composites increased with increasing amounts of adsorbed Ag NPs, suggesting that the surface structures of chitin/chitosan carriers strongly influence adsorption of Ag NPs and antimicrobial activities. These observations indicate that chitin/chitosan-Ag NPs with nanoscale surface structures have potential as antimicrobial biomaterials and anti-infectious wound dressings.

Chitin nanofibers sheets (CNFSs) with nanoscale fiber-like surface structures are nontoxic and biodegradable biomaterials with large surface-to-mass ratio. CNFSs are widely applied as biomedical materials such as a functional wound dressing. This study aimed to develop antimicrobial biomaterials made up of CNFS-immobilized silver nanoparticles (CNFS/Ag NPs). CNFSs were immersed in suspensions of Ag NPs (5.17 ± 1.9 nm in diameter; mean ± SD) for 30 min at room temperature to produce CNFS/Ag NPs. CNFS/Ag NPs were characterized by transmission electron microscopy (TEM) and then tested for antimicrobial activities against Escherichia (E.) coli, Pseudomonas (P.) aeruginosa, and H1N1 influenza A virus, three pathogens that represent the most widespread infectious bacteria and viruses. Ultrathin sectioning of bacterial cells also was carried out to observe the bactericidal mechanism of Ag NPs. The TEM images indicated that the Ag NPs are dispersed and tightly adsorbed onto CNFSs. Although CNFSs alone have only weak antimicrobial activity, CNFS/Ag NPs showed much stronger antimicrobial properties against E. coli, P. aeruginosa, and influenza A virus, with the amount of immobilized Ag NPs onto CNFSs. Our results suggest that CNFS/Ag NPs interacting with those microbes exhibit stronger antimicrobial activities, and that it is possible to apply CNFS/Ag NPs as anti-virus sheets as well as anti-infectious wound dressings.

Low molecular weight heparin (LMWH)/protamine (P) nano/micro particles (N/MPs) (LMWH/P N/MPs) were applied as carriers for heparin-binding growth factors (GFs) and for adhesive cells including adipose-derived stromal cells (ADSCs) and bone marrow-derived mesenchymal stem cells (BMSCs). A mixture of LMWH and P yields a dispersion of N/MPs (100 nm–3 μm in diameter). LMWH/P N/MPs can be immobilized onto cell surfaces or extracellular matrix, control the release, activate GFs and protect various GFs. Furthermore, LMWH/P N/MPs can also bind to adhesive cell surfaces, inducing cells and LMWH/P N/MPs-aggregate formation. Those aggregates substantially promoted cellular viability, and induced vascularization and fibrous tissue formation in vivo. The LMWH/P N/MPs, in combination with ADSCs or BMSCs, are effective cell-carriers and are potential promising novel therapeutic agents for inducing vascularization and fibrous tissue formation in ischemic disease by transplantation of the ADSCs and LMWH/P N/MPs-aggregates. LMWH/P N/MPs can also bind to tissue culture plates and adsorb exogenous GFs or GFs from those cells. The LMWH/P N/MPs-coated matrix in the presence of GFs may provide novel biomaterials that can control cellular activity such as growth and differentiation. Furthermore, three-dimensional (3D) cultures of cells including ADSCs and BMSCs using plasma-medium gel with LMWH/P N/MPs exhibited efficient cell proliferation. Thus, LMWH/P N/MPs are an adequate carrier both for GFs and for stromal cells such as ADSCs and BMSCs, and are a functional coating matrix for their cultures.

Introduction: Paracrine effects can be exploited in cell-based therapies that secrete factors, such as chemokines and cytokines, and can recruit inflammatory cells to transplants. In this study, mouse adipose tissue-derived stromal cells (ASCs) and bone marrow-derived stromal cells (ST2 cells) were used to examine changes in paracrine interactions with inflammation cells. Methods: Green fluorescent protein positive (GFP⁺) bone marrow cells (BMCs) were injected into an irradiated mouse via the femoral vein, and ASCs and ST2 cells were transplanted intradermally. Subsequently, an in vivo imaging system was used to observe behaviors of GFP⁺ BMCs. To detect bone marrow-derived inflammatory cells which migrated to the ASC and ST2 cell transplantation area, the sections were immunostained using antibodies against Gr1, CD11c, and F4/80, and secretory proteins were detected in culture medium using enzyme-linked immunosorbent assay. Results: Many bone marrow-derived inflammatory cells migrated to ASC and ST2 cell transplantation sites. Among these, neutrophils were detected during the early period and macrophages were predominantly detected at a later point in time. Many chemokines, cytokines, growth factors, matrix metalloproteinases (MMPs), and tissue inhibitors of metalloproteinases (TIMPs) were secreted in abundance from ASCs, and the secretion increased by co-culturing with inflammatory cells, except for secretions of insulin-like growth factor-1, MMP-9 and MMP-13. Although secretions from ST2 cells were less than those from ASCs, co-culture with inflammatory cells increased these secretions to levels similar to those of ASCs. However, unlike ASCs, the ST2 cells did not secrete angiostatin, MMP-2, or MMP-3. Finally, ASCs secreted not only proinflammatory cytokines, angiogenic factors and MMPs but also anti-inflammatory cytokines, anti-angiogenesis factors, and TIMPs. Conclusions: The effects of cell-based therapies using ASCs and ST2 cells are depended on paracrine effects that are mediated by chemokines, cytokines, growth factors, MMPs, and TIMPs, which comprise responses to interactions between transplanted cells and inflammatory cells. Moreover, paracrine effects of transplanted cells are influenced by inflammatory cells, and are moderated by a balance of secreted inhibitors.

Low-molecular-weight heparin/protamine microparticles (LMW-H/P MPs) were produced as a carrier for heparin-binding growth factors (GFs) and for various adhesive cells. A mixture of low-molecular-weight heparin (MW: approximately 5000 Da, 6.4 mg/mL) and protamine (MW: approximately 3000 Da, 10 mg/mL) at a ratio of 7:3 (vol:vol) yields a dispersion of microparticles (0.5–3 µm in diameter). LMW-H/P MPs immobilize, control the release and protect the activity of GFs. LMW-H/P MPs can also bind to cell surfaces, causing these cells to interact with the LMW-H/P MPs, inducing cells/MPs-aggregate formation and substantially promoting cellular viability. Furthermore, LMW-H/P MPs can efficiently bind to tissue culture plates and retain the binding of important GFs, such as fibroblast growth factor (FGF)-2. The LMW-H/P MPs-coated matrix with various GFs or cytokines may provide novel biomaterials that can control cellular activity such as growth and differentiation. Thus, LMW-H/P MPs are an excellent carrier for GFs and various cells and are an efficient coating matrix for cell cultures.