Fibronectin-tethered graphene oxide as an artificial matrix for osteogenesis

Effect of Target Power on Microstructure, Tribological Performance and Biocompatibility of Magnetron Sputtered Amorphous Carbon Coatings

The tribological properties and preosteoblast behavior of an RF magnetron-sputtered amorphous carbon coating on a Si (100) substrate were evaluated. The graphite target power was varied from 200 to 500 W to obtain various coating structures. The amorphous nature of the coatings was confirmed via Raman analysis. The contact angle also increased from 58º to 103º, which confirmed the transformation of the a-C surface from a hydrophilic to hydrophobic nature with an increasing graphite target power. A minimum wear rate of about 4.73 × 10-8 mm3/N*mm was obtained for an a-C coating deposited at a 300 W target power. The 300 W and 400 W target power coatings possessed good tribological properties, and the 500 W coating possessed better cell viability and adhesion on the substrate. The results suggest that the microstructure, wettability, tribological behavior and biocompatibility of the a-C coating were highly dependent on the target power of the graphite. A Finite Element Analysis (FEA) showed a considerable increase in the Von Mises stress as the mesh size decreased. Considering both the cell viability and tribological properties, the 400 W target power coating was identified to have the best tribological property as well as biocompatibility.

Graphene/hydroxyapatite coating deposit on titanium alloys for implant application

Titanium (Ti) implants are widely used in medicine. Meanwhile, surface modification of Ti can strengthen the osseointegration of implants. In this study, we modified Ti implant surfaces, which was coated with GO, HA, HA-2wt%GO and HA-5wt%GO via electrophoresis deposition, to investigate their mechanisms and biological activity. Uncoated Ti was used as the control. Further, we examined the biological behavior and osteogenic performance of mouse bone marrow mesenchymal stem cells (BMSCs) cultured on coatings in vitro. We found that the HA-GO nanocomposite coating improved the roughness and hydrophilicity of the Ti surface. Compared with the uncoated Ti or Ti modified by HA or GO alone, cell adhesion and diffusion were enhanced on HA-GO-modified Ti surfaces. In addition, the proliferation and osteogenic differentiation of BMSCs in vitro were significantly improved on HA-GO-modified surfaces, whereas osteogenesis-related gene expression and alkaline phosphatase activity were slightly enhanced. Furthermore, we noted that bone regeneration was improved in the HA-2wt%GO group in vivo. Thus, the HA-2wt%GO nanocomposite coating might have potential applications in the field of dental implants.

Graphene-Reinforced Titanium Enhances Soft Tissue Seal

The integrity of soft tissue seal is essential for preventing peri-implant infection, mainly induced by established bacterial biofilms around dental implants. Nowadays, graphene is well-known for its potential in biocompatibility and antisepsis. Herein, a new titanium biomaterial containing graphene (Ti-0.125G) was synthesized using the spark plasma sintering (SPS) technique. After material characteristics detection, the subsequent responses of human gingival fibroblasts (HGFs) and multiple oral pathogens (including Streptococci mutans, Fusobacterium nucleatum, and Porphyromonas gingivalis) to the graphene-reinforced sample were assessed, respectively. Also, the dynamic change of the bacterial multispecies volume in biofilms was evaluated using absolute quantification PCR combined with Illumina high-throughput sequencing. Ti-0.125G, in addition to its particularly pronounced inhibitory effect on Porphyromonas gingivalis at 96 h, was broadly effective against multiple pathogens rather than just one strain. The reinforced material’s selective responses were also evaluated by a co-culture model involving HGFs and multiple strains. The results disclosed that the graphene-reinforced samples were highly effective in keeping a balance between the favorable fibroblast responses and the suppressive microbial growth, which could account for the optimal soft tissue seal in the oral cavity. Furthermore, the underlying mechanism regarding new material’s bactericidal property in the current study has been elucidated as the electron transfer, which disturbed the bacterial respiratory chain and resulted in a decrease of microbial viability. According to the Kyoto Encyclopedia of Genes and Genomes (KEGG) database, the PICRUSt tool was conducted for the prediction of microbial metabolism functions. Consequently, it is inferred that Ti-0.125G has promising potentials for application in implant dentistry, especially in enhancing the integrity of soft tissue and improving its resistance against bacterial infections around oral implants.

Comprehensive Survey on Nanobiomaterials for Bone Tissue Engineering Applications

One of the most important ideas ever produced by the application of materials science to the medical field is the notion of biomaterials. The nanostructured biomaterials play a crucial role in the development of new treatment strategies including not only the replacement of tissues and organs, but also repair and regeneration. They are designed to interact with damaged or injured tissues to induce regeneration, or as a forest for the production of laboratory tissues, so they must be micro-environmentally sensitive. The existing materials have many limitations, including impaired cell attachment, proliferation, and toxicity. Nanotechnology may open new avenues to bone tissue engineering by forming new assemblies similar in size and shape to the existing hierarchical bone structure. Organic and inorganic nanobiomaterials are increasingly used for bone tissue engineering applications because they may allow to overcome some of the current restrictions entailed by bone regeneration methods. This review covers the applications of different organic and inorganic nanobiomaterials in the field of hard tissue engineering.

Linking graphene-based material physicochemical properties with molecular adsorption, structure and cell fate

Graphene, an allotrope of carbon, consists of a single layer of carbon atoms with uniquely tuneable properties. As such, graphene-based materials (GBMs) have gained interest for tissue engineering applications. GBMs are often discussed in the context of how different physicochemical properties affect cell physiology, without explicitly considering the impact of adsorbed proteins. Establishing a relationship between graphene properties, adsorbed proteins, and cell response is necessary as these proteins provide the surface upon which cells attach and grow. This review highlights the molecular adsorption of proteins on different GBMs, protein structural changes, and the connection to cellular function.

Topography enhances Runx2 expression in outgrowing cells from iPS cell-derived embryoid bodies

The effect of differing polystyrene substrate topographies on the osteogenic potential of the outgrowing cells (OGCs) formed from mouse-induced pluripotent stem (iPS) cells (miPSCs)-derived embryoid bodies (EBs) was investigated. Polystyrene substrates were sandblasted with 25, 50, and 150 μm aluminum oxide particles to obtain topographies with average Sa values of 0.6, 1.1, and 1.8 μm, respectively. 3D-SEM was used to evaluate substrate's topographies. Examination was done by scanning electron microscopy (SEM), by immunocytofluorescence (ICF) analysis for vinculin, Runx2 and collagen type I, and by quantitative RT-PCR (qRT-PCR) analysis for Runx2 and collagen type I. SEM and ICF analyses revealed that surface roughness caused cells elongation (2, 6, 8, 10 times for the NT, 0.6 μm, 1.1 μm, and 1.8 μm, respectively). Vinculin staining demonstrated how the Sa value affected cellular attachment to the substrate. FA points were randomly distributed on flat surfaces, but rough surfaces resulted in more concentrated FA points on the podia of the cells (11.7, 25.2, 26.7, 16.6 vinculin spots per 20 μm² for the NT, 0.6 μm, 1.1 μm, and 1.8 μm, respectively). qRT-PCR revealed that Runx2 expression was highest on day 16 on surfaces with Sa of 0.6 μm and 1.1 μm. Collagen type I expression increased from day 0 to day 16, no significance was found among the groups. In conclusion, surface topography affects cell shape and expression of early osteogenic potential in OGC, particularly surfaces with Sa values of 0.6 μm and 1.1 μm which showed the highest concentration of FA points on podia. These findings could be utilized in the development of inner surface topographies of scaffolds used with iPSCs. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B: 2288-2296, 2019.

Materials Science and Design Principles of Growth Factor Delivery Systems in Tissue Engineering and Regenerative Medicine

Growth factors (GFs) are signaling molecules that direct cell development by providing biochemical cues for stem cell proliferation, migration, and differentiation. GFs play a key role in tissue regeneration, but one major limitation of GF-based therapies is dosage-related adverse effects. Additionally, the clinical applications and efficacy of GFs are significantly affected by the efficiency of delivery systems and other pharmacokinetic factors. Hence, it is crucial to design delivery systems that provide optimal activity, stability, and tunable delivery for GFs. Understanding the physicochemical properties of the GFs and the biomaterials utilized for the development of biomimetic GF delivery systems is critical for GF-based regeneration. Many different delivery systems have been developed to achieve tunable delivery kinetics for single or multiple GFs. The identification of ideal biomaterials with tunable properties for spatiotemporal delivery of GFs is still challenging. This review characterizes the types, properties, and functions of GFs, the materials science of widely used biomaterials, and various GF loading strategies to comprehensively summarize the current delivery systems for tunable spatiotemporal delivery of GFs aimed for tissue regeneration applications. This review concludes by discussing fundamental design principles for GF delivery vehicles based on the interactive physicochemical properties of the proteins and biomaterials.

Bone physiology as inspiration for tissue regenerative therapies

The development, maintenance of healthy bone and regeneration of injured tissue in the human body comprise a set of intricate and finely coordinated processes. However, an analysis of current bone regeneration strategies shows that only a small fraction of well-reported bone biology aspects has been used as inspiration and transposed into the development of therapeutic products. Specific topics that include inter-scale bone structural organization, developmental aspects of bone morphogenesis, bone repair mechanisms, role of specific cells and heterotypic cell contact in the bone niche (including vascularization networks and immune system cells), cell-cell direct and soluble-mediated contact, extracellular matrix composition (with particular focus on the non-soluble fraction of proteins), as well as mechanical aspects of native bone will be the main reviewed topics. In this Review we suggest a systematic parallelization of (i) fundamental well-established biology of bone, (ii) updated and recent advances on the understanding of biological phenomena occurring in native and injured tissue, and (iii) critical discussion of how those individual aspects have been translated into tissue regeneration strategies using biomaterials and other tissue engineering approaches. We aim at presenting a perspective on unexplored aspects of bone physiology and how they could be translated into innovative regeneration-driven concepts.

Optimizing the nanostructure of graphene oxide/silver/arginine for effective wound healing

In this study, we introduce a novel graphene oxide/silver/arginine (GO/Ag/Arg) nanohybrid structure, which can act as an angiogenesis promoter and provide antibacterial nanostructure for improving the wound healing process. GO/Ag nanostructure has been optimized in terms of the GO/Ag mass ratio and pH values using central composite design and the response surface method to increase the Ag loading efficiency. Then, Arg was chemically introduced to the surface of GO/Ag nanostructure. Electrospun polycaprolactone (PCL)-GO/Ag/Arg nanocomposite was successfully fabricated and characterized. The synthesized nanocomposite demonstrated not only a great antibacterial effect on both Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) bacterial species, but appropriate biocompatibility against L929 fibroblastic cell lines. The results demonstrated that the preparation of the PCL-GO/Ag/Arg nanocomposite at a concentration of 1.0 wt% GO/Ag/Arg possessed the best biological and mechanical features. In vivo experiments also revealed that the use of optimized PCL-GO/Ag/Arg nanocomposite, after 12 d of treatment, led to significant increase in the healing process and also regeneration of the wound via reconstruction of a thickened epidermis layer on the wound surface, which was confirmed by histological analysis. In conclusion, the proposed approach can introduce a novel notion for preparing antibacterial material that significantly promotes angiogenesis.

Future Research Directions in the Design of Versatile Extracellular Matrix in Tissue Engineering

Native and artificial extracellular matrices (ECMs) have been widely applied in biomedical fields as one of the most effective components in tissue regeneration. In particular, ECM-based drugs are expected to be applied to treat diseases in organs relevant to urology, because tissue regeneration is particularly important for preventing the recurrence of these diseases. Native ECMs provide a complex in vivo architecture and native physical and mechanical properties that support high biocompatibility. However, the applications of native ECMs are limited due to their tissue-specificity and chemical complexity. Artificial ECMs have been fabricated in an attempt to create a broadly applicable scaffold by using controllable components and a uniform formulation. On the other hands, artificial ECMs fail to mimic the properties of a native ECM; consequently, their applications in tissues are also limited. For that reason, the design of a versatile, hybrid ECM that can be universally applied to various tissues is an emerging area of interest in the biomedical field.

The enhancement of osseointegration using a graphene oxide/chitosan/hydroxyapatite composite coating on titanium fabricated by electrophoretic deposition

Titanium (Ti) has been commonly used as an implant material in dentistry and bone surgery for several decades. Meanwhile, surface modification of titanium can enhance the osseointegration of implants. In this study, a graphene oxide/chitosan/hydroxyapatite (GO/CS/HA) composite coating was fabricated by electrophoretic deposition on Ti substrates. Subsequently, the surface morphology, phase composition, wettability, and bonding strength of this composite coating were researched. Additionally, in vitro cytological examination was performed, including evaluations of cell adhesion, cell viability, cell differentiation, cell mineralization, and osteogenetic factor expression. Finally, the in vivo osteogenetic properties were evaluated through an animal study, including a histological analysis, a microcomputed tomography, and biomechanical tests. The results showed that a homogeneous and crack-free GO/CS/HA composite coating was coated on Ti, and the wettability and bonding strength of the GO/CS/HA composite coating were enhanced compared with HA, GO/HA, and CS/HA coatings. Furthermore, the GO/CS/HA coating greatly heightened the cell-material interactions in vitro. Additionally, this GO/CS/HA-Ti implant could enhance osseointegration in vivo. Consequently, GO/CS/HA-Ti may have potential applications in the field of dental implants. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2018. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B: 635-645, 2019.

High-efficiency generation of induced pluripotent mesenchymal stem cells from human dermal fibroblasts using recombinant proteins

Background

Induced pluripotent mesenchymal stem cells (iPMSCs) are novel candidates for drug screening, regenerative medicine, and cell therapy. However, introduction of transcription factor encoding genes for induced pluripotent stem cell (iPSC) generation which could be used to generate mesenchymal stem cells is accompanied by the risk of insertional mutations in the target cell genome.

Methods

We demonstrate a novel method using an inactivated viral particle to package and deliver four purified recombinant Yamanaka transcription factors (Sox2, Oct4, Klf4, and c-Myc) resulting in reprogramming of human primary fibroblasts. Whole genome bisulfite sequencing was used to analyze genome-wide CpG methylation of human iPMSCs. Western blot, quantitative PCR, immunofluorescence, and in-vitro differentiation were used to assess the pluripotency of iPMSCs.

Results

The resulting reprogrammed fibroblasts show high-level expression of stem cell markers. The human fibroblast-derived iPMSC genome showed gains in DNA methylation in low to medium methylated regions and concurrent loss of methylation in previously hypermethylated regions. Most of the differentially methylated regions are close to transcription start sites and many of these genes are pluripotent pathway associated. We found that DNA methylation of these genes is regulated by the four iPSC transcription factors, which functions as an epigenetic switch during somatic reprogramming as reported previously. These iPMSCs successfully differentiate into three embryonic germ layer cells, both in vitro and in vivo. Following multipotency induction in our study, the delivered transcription factors were degraded, leading to an improved efficiency of subsequent programmed differentiation.

Conclusion

Recombinant transcription factor based reprogramming and derivatization of iPMSC offers a novel high-efficiency approach for regenerative medicine from patient-derived cells.

Electronic supplementary material

The online version of this article (doi:10.1186/s13287-016-0358-4) contains supplementary material, which is available to authorized users.

Synthesis, toxicity, biocompatibility, and biomedical applications of graphene and graphene-related materials

Graphene is a two-dimensional atomic crystal, and since its development it has been applied in many novel ways in both research and industry. Graphene possesses unique properties, and it has been used in many applications including sensors, batteries, fuel cells, supercapacitors, transistors, components of high-strength machinery, and display screens in mobile devices. In the past decade, the biomedical applications of graphene have attracted much interest. Graphene has been reported to have antibacterial, antiplatelet, and anticancer activities. Several salient features of graphene make it a potential candidate for biological and biomedical applications. The synthesis, toxicity, biocompatibility, and biomedical applications of graphene are fundamental issues that require thorough investigation in any kind of applications related to human welfare. Therefore, this review addresses the various methods available for the synthesis of graphene, with special reference to biological synthesis, and highlights the biological applications of graphene with a focus on cancer therapy, drug delivery, bio-imaging, and tissue engineering, together with a brief discussion of the challenges and future perspectives of graphene. We hope to provide a comprehensive review of the latest progress in research on graphene, from synthesis to applications.

Non-viral approaches for direct conversion into mesenchymal cell types: Potential application in tissue engineering

Acquiring adequate number of cells is one of the crucial factors to apply tissue engineering strategies in order to recover critical-sized defects. While the reprogramming technology used for inducing pluripotent stem cells (iPSCs) opened up a direct path for generating pluripotent stem cells, a direct conversion strategy may provide another possibility to obtain desired cells for tissue engineering. In order to convert a somatic cell into any other cell type, diverse approaches have been investigated. Conspicuously, in contrast to traditional viral transduction method, non-viral delivery of conversion factors has the merit of lowering immune responses and provides safer genetic manipulation, thus revolutionizing the generation of directly converted cells and its application in therapeutics. In addition, applying various microenvironmental modulations have potential to ameliorate the conversion of somatic cells into different lineages. In this review, we discuss the recent progress in direct conversion technologies, specifically focusing on generating mesenchymal cell types.

Graphene and graphene-based nanocomposites: biomedical applications and biosafety

Graphene is the first carbon-based two dimensional atomic crystal and has gained much attention since its discovery by Geim and co-workers in 2004.

Enhanced Osteogenesis by Reduced Graphene Oxide/Hydroxyapatite Nanocomposites

Recently, graphene-based nanomaterials, in the form of two dimensional substrates or three dimensional foams, have attracted considerable attention as bioactive scaffolds to promote the differentiation of various stem cells towards specific lineages. On the other hand, the potential advantages of using graphene-based hybrid composites directly as factors inducing cellular differentiation as well as tissue regeneration are unclear. This study examined whether nanocomposites of reduced graphene oxide (rGO) and hydroxyapatite (HAp) (rGO/HAp NCs) could enhance the osteogenesis of MC3T3-E1 preosteoblasts and promote new bone formation. When combined with HAp, rGO synergistically promoted the spontaneous osteodifferentiation of MC3T3-E1 cells without hindering their proliferation. This enhanced osteogenesis was corroborated from determination of alkaline phosphatase activity as early stage markers of osteodifferentiation and mineralization of calcium and phosphate as late stage markers. Immunoblot analysis showed that rGO/HAp NCs increase the expression levels of osteopontin and osteocalcin significantly. Furthermore, rGO/HAp grafts were found to significantly enhance new bone formation in full-thickness calvarial defects without inflammatory responses. These results suggest that rGO/HAp NCs can be exploited to craft a range of strategies for the development of novel dental and orthopedic bone grafts to accelerate bone regeneration because these graphene-based composite materials have potentials to stimulate osteogenesis.

Investigation of the changes of biophysical/mechanical characteristics of differentiating preosteoblasts in vitro

BACKGROUND

Topography, stiffness, and composition of biomaterials play a crucial role in cell behaviors. In this study, we have investigated biochemical (gene markers), biophysical (roughness), and biomechanical (stiffness) changes during the osteogenic differentiation of preosteoblasts on gelatin matrices.

RESULTS

Our results demonstrate that gelatin matrices offer a favorable microenvironment for preosteoblasts as determined by focal adhesion and filopodia formation. The osteogenic differentiation potential of preosteoblasts on gelatin matrices is confirmed by qualitative (Alizarin red, von kossa staining, immunofluorescence, and gene expression) and quantitative analyses (alkaline phosphatase activity and calcium content). The biomechanical and biophysical properties of differentiating preosteoblasts are analyzed using atomic force microscopy (AFM) and micro indentation. The results show sequential and significant increases in preosteoblasts roughness and stiffness during osteogenic differentiation, both of which are directly proportional to the progress of osteogenesis. Cell proliferation, height, and spreading area seem to have no direct correlation with differentiation; however, they may be indirectly related to osteogenesis.

CONCLUSIONS

The increased stiffness and roughness is attributed to the mineralized bone matrix and enhanced osteogenic extracellular matrix protein. This report indicates that biophysical and biomechanical aspects during in vitro cellular/extracellular changes can be used as biomarkers for the analysis of cell differentiation.

Osteogenic/angiogenic dual growth factor delivery microcapsules for regeneration of vascularized bone tissue

Growth factors (GFs) are major biochemical cues for tissue regeneration. Herein, a novel dual GF delivery system is designed composed of poly(lactic-co-glycolic acid) (PLGA) nanoparticles (NPs) and alginate microcapsules (MCs) via an electrodropping method. While bone morphogenetic protein (BMP)-2 is encapsulated in the PLGA NPs, vascular endothelial growth factor (VEGF) is included in the alginate MCs, where BMP-2-loaded PLGA NPs are entrapped together in the fabrication process. The initial loading efficiencies of BMP-2 and VEGF are 78% ± 3.6% and 43% ± 1.7%, respectively. When our dual GF-loaded MCs are assessed for in vitro osteogenesis of umbilical cord blood-derived mesenchymal stem cells (UCB-MSCs) on 2D and 3D environment, MCs contribute to much better UCB-MSCs osteogenesis as confirmed by von Kossa staining, immunofluorescence (osteocalcin, collagen 1), calcium content measurement, and osteogenic markers expression. In addition, when dual GF-encapsulated MCs are combined with collagen and then applied to 8 mm diameter rat calvarial defect model, the positive effects on vascularized bone regeneration are much more pronounced; micro computed tomography (CT) and histology analyses exhibit 82.3% bone healing coupled with 12.6% vessel occupied area. Put together, current study indicates a synergistic effect of BMP-2/VEGF and highlights the great potential of dual GF delivery modality (PLGA NPs-in-MC) for regeneration of vascularized bone.

Investigation of cellular responses upon interaction with silver nanoparticles

In order for nanoparticles (NPs) to be applied in the biomedical field, a thorough investigation of their interactions with biological systems is required. Although this is a growing area of research, there is a paucity of comprehensive data in cell-based studies. To address this, we analyzed the physicomechanical responses of human alveolar epithelial cells (A549), mouse fibroblasts (NIH3T3), and human bone marrow stromal cells (HS-5), following their interaction with silver nanoparticles (AgNPs). When compared with kanamycin, AgNPs exhibited moderate antibacterial activity. Cell viability ranged from ≤80% at a high AgNPs dose (40 µg/mL) to >95% at a low dose (10 µg/mL). We also used atomic force microscopy-coupled force spectroscopy to evaluate the biophysical and biomechanical properties of cells. This revealed that AgNPs treatment increased the surface roughness (P<0.001) and stiffness (P<0.001) of cells. Certain cellular changes are likely due to interaction of the AgNPs with the cell surface. The degree to which cellular morphology was altered directly proportional to the level of AgNP-induced cytotoxicity. Together, these data suggest that atomic force microscopy can be used as a potential tool to develop a biomechanics-based biomarker for the evaluation of NP-dependent cytotoxicity and cytopathology.

Mesenchymal Stromal/Stem Cell and Minocycline-Loaded Hydrogels Inhibit the Growth of Staphylococcus aureus that Evades Immunomodulation of Blood-Derived Leukocytes

Mesenchymal stromal/stem cells (MSCs) have demonstrated favorable wound healing properties in addition to their differentiation capacity. MSCs encapsulated in biomaterials such as gelatin and polyethylene glycol (PEG) composite hydrogels have displayed an immunophenotype change that leads to the release of cytokines and growth factors to accelerate wound healing. However, therapeutic potential of implanted MSC-loaded hydrogels may be limited by non-specific protein adsorption that facilitates adhesion of bacterial pathogens such as planktonic Staphylococcus aureus (SA) to the surface with subsequent biofilm formation resistant to immune cell recognition and antibiotic activity. In this study, we demonstrate that blood-derived primary leukocytes and bone marrow-derived MSCs cannot inhibit colony-forming abilities of planktonic or biofilm-associated SA. However, we show that hydrogels loaded with MSCs and minocycline significantly inhibit colony-forming abilities of planktonic SA while maintaining MSC viability and multipotency. Our results suggest that minocycline and MSC-loaded hydrogels may decrease the bioburden of SA at implant sites in wounds, and may improve the wound healing capabilities of MSC-loaded hydrogels.

Evaluation of UV radiation-induced toxicity and biophysical changes in various skin cells with photo-shielding molecules

Examining the real-time morphological, biophysical, and biomechanical changes associated with skin cell degeneration induced by UVR to understand the mechanisms.

Liposome-induced exfoliation of graphite to few-layer graphene dispersion with antibacterial activity

Liposome-induced exfoliation of graphite allowed to obtain few-layer graphene homogeneous in size and hydrophilic due to the non-covalent functionalization with phospholipids. The corresponding dispersions are stable for 48 h and demonstrate antimicrobial activity.