Polymer microbeads in immunology

Multiplexed microarrays based on optically encoded microbeads

In recent years, there has been growing interest in optically-encoded or tagged functionalized microbeads as a solid support platform to capture proteins or nucleotides which may serve as biomarkers of various diseases. Multiplexing technologies (suspension array or planar array) based on optically encoded microspheres have made possible the observation of relatively minor changes in biomarkers related to specific diseases. The ability to identify these changes at an early stage may allow the diagnosis of serious diseases (e.g. cancer) at a time-point when curative treatment may still be possible. As the overall accuracy of current diagnostic methods for some diseases is often disappointing, multiplexed assays based on optically encoded microbeads could play an important role to detect biomarkers of diseases in a non-invasive and accurate manner. However, detection systems based on functionalized encoded microbeads are still an emerging technology, and more research needs to be done in the future. This review paper is a preliminary attempt to summarize the state-of-the-art concerning diagnostic microbeads; including microsphere composition, synthesis, encoding technology, detection systems, and applications.

Immune-enhancing effects of Maitake (Grifola frondosa) and Shiitake (Lentinula edodes) extracts

BACKGROUND

The role of glucan in stimulation of immune reactions has been studied for several decades. In this report, we focused on the effects of orally administered glucan Maitake and Shiitake on immune reactions.

MATERIALS AND METHODS

We measured phagocytosis, NK cell activity, and secretion of IL-6, IL-12, IFN-γ as well as C-reactive protein (CRP) after 14 days of oral application of tested glucans. For comparison, active hexose correlated compound (AHCC) was used in all reactions.

RESULTS

We found significant stimulation of defense reaction. In all cases, the most active was the Maitake-Shiitake combination, with Maitake alone being the second strongest, followed by Shiitake on its own and AHCC.

CONCLUSIONS

Short-term oral application of natural immunomodulating glucans from Maitake and Shiitake mushrooms strongly stimulated both the cellular and humoral branch of immune reactions. These activities were significantly higher than those of AHCC.

Glucan and humic acid: synergistic effects on the immune system

Humic acids are compounds resulting from decomposition of organic matter. Despite their common presence, our knowledge of their biological effects is limited, and current findings are controversial. We decided to evaluate the immunological effects of two different types of humic acids, differing in source and biochemical characteristics. Using both components either alone or in combination with the well-established yeast-derived immunomodulator glucan, we measured their effects on both the cellular (phagocytosis and tumor suppression) and humoral (antibody production and cytokine secretion) branches of immune reactions. In summary, our results suggest that humic acids are biologically active immunodulators affecting both the humoral and cellular branches of immune reactions. In addition, the two humic acids studied here are working in synergy in stimulation of the immune reaction, supporting further studies of these natural immunomodulators.

Osteopontin functions as an opsonin and facilitates phagocytosis by macrophages of hydroxyapatite-coated microspheres: implications for bone wound healing

Osteopontin (OPN) is a secreted protein abundant in mineralized tissue extracellular matrices and bodily fluids. Previously we have shown that mineralized debris at surgical wound sites in bone and teeth are coated by macrophage-derived OPN and phagocytosed. Here, we have performed opsonophagocytosis assays to determine whether OPN acts as an opsonin and facilitates phagocytosis by macrophages of protein- and hydroxyapatite mineral-coated microspheres. Moreover, we have examined the opsonization effects of monomer OPN versus OPN polymerized (crosslinked) by tissue transglutaminase 2. Murine macrophages J774A.1 were exposed to polystyrene-latex microspheres having different surface chemistries (non-ionic, aldehyde amidine, carboxyl and aliphatic amine) which were coated with either serum albumin, immunoglobulin, monomer OPN or polymer OPN. Similar experiments with the same protein coatings were performed using hydroxyapatite-covered microspheres. Internalization of microspheres by phagocytosis into macrophages was confirmed by co-localization with the (phago)lysosomal markers lysosome-associated membrane protein-1 (Lamp-1) and LysoTracker, and by light microscopy and transmission electron microscopy after serial sectioning of plastic/resin-embedded cells containing microspheres. OPN significantly increased phagocytosis of both microspheres and hydroxyapatite-covered microspheres compared to negative controls (albumin-coated and uncoated microspheres), with phagocytic indices similar to, or greater than, those of the positive control (IgG-coated). The effect of OPN and hydroxyapatite on microsphere phagocytosis was synergistic. Polymer OPN further enhanced the phagocytosis of aliphatic amine and aldehyde amidine microspheres. Taken together, these results indicate that OPN is an effective opsonin able to facilitate particle uptake (including mineralized particles) by macrophages.

Enhancing effects of new biological response modifier beta-1,3 glucan sulfate PS3 on immune reactions

Glucans have a long history as non-specific biological modulators; however, but the search for optimal chemical configuration is still on. The objective of this study was to evaluate intraperitoneal application of PS3, a sulfated derivative of a (1-->3)-beta-D-glucan isolated from sporophytes of Laminaria digitata. PS3 showed significant stimulation of phagocytic activity as well as potentiation of synthesis and release of IL-2 by splenocytes. In addition, PS3 increased NK cell-mediated killing of tumor cells both in vitro and in vivo. When combined, our observations suggest that PS3 is similarly effective as native non-sulfated (1-->3)-beta-D-glucan and is generally more active than lentinan.

Parameters influencing the stealthiness of colloidal drug delivery systems

Over the last few decades, colloidal drug delivery systems (CDDS) such as nano-structures have been developed in order to improve the efficiency and the specificity of drug action. Their small size permits them to be injected intravenously in order to reach target tissues. However, it is known that they can be rapidly removed from blood circulation by the immune system. CDDS are removed via the complement system and via the cells of the mononuclear phagocyte system (MPS), after their recognition by opsonins and/or receptors present at the cell surface. This recognition is dependent on the physicochemical characteristics of the CDDS. In this study, we will focus on parameters influencing the interactions of opsonins and the macrophage plasma membrane with the surface of CDDS, whereby parameters of the polymer coating become necessary to provide good protection.

Glucan-like synthetic oligosaccharides: iterative synthesis of linear oligo-beta-(1,3)-glucans and immunostimulatory effects

Small reducing and linear oligo-beta-(1,3)-glucans, which are able to act as phytoallexin elicitors or as immunostimulating agents in anticancer therapy, were synthesized according to an iterative strategy that involved a unique key monosaccharidic donor. To avoid anomeric mixtures, the reducing entity of the target oligomers was first locked with benzyl alcohol and further selective deprotection of the 3-OH with DDQ afforded the desired building block as an acceptor. The latter was then used in a second cycle of glycosylation/deprotection to afford the desired disaccharide, and successive reiterations of this process provided the desired oligomers. Unusual conformational behaviors were observed by standard NMR sequences and supported by NOESY studies. Finally, removal of protecting groups afforded free tri-, tetra-, and pentaglucosides in good overall yields. Two oligosaccharides representing linear laminaritetraose and laminaripentaose were compared to the recently described beta-(1,3)-glucan phycarine. Following an intraperitoneal injection, the influx of monocytes and granulocytes into the blood and macrophages into the peritoneal cavity was comparable to that caused by phycarine. Similarly, both oligosaccharides stimulated phagocytic activity of granulocytes and macrophages. Using ELISA, we also demonstrated a significant stimulation of secretion of IL-1beta. Together these results suggest that the synthetic oligosaccharides have similar stimulatory effects as natural beta-(1,3)-glucans.

Effects of marine beta-1,3 glucan on immune reactions

Glucans have a long history as nonspecific biological modulators. A novel glucan-Phycarine-was isolated from sporophytes of Laminaria digitata. Phycarine showed significant stimulation of phagocytic activity as well as potentiation of synthesis and release of IL-1, IL-6 and TNF-alpha. In addition, Phycarine increased NK cell-mediated killing of tumor cells both in vitro and in vivo while acting via complement receptor type 3 (CR3) receptors.

Transdifferentiation of mouse aortic smooth muscle cells to a macrophage-like state after cholesterol loading

Mouse aortic smooth muscle cells (SMCs) were loaded for 72 h with cholesterol by using cholesterol:methyl-beta-cyclodextrin complexes, leading to approximately 2-fold and approximately 10-fold increases in the contents of total cholesterol and cholesteryl ester, respectively. Foam-cell formation was demonstrated by accumulation of intracellular, Oil Red O-stained lipid droplets. Immunostaining showed decreased protein levels of smooth muscle alpha-actin and alpha-tropomyosin and increased levels of macrophage markers CD68 and Mac-2 antigen. Quantitative real-time RT-PCR revealed that after cholesterol loading, the expression of SMC-related genes alpha-actin, alpha-tropomyosin, myosin heavy chain, and calponin H1 decreased (to 11.5 +/- 0.5%, 29.3 +/- 1.4%, 23.8 +/- 1.4%, and 3.8 +/- 0.5% of unloaded cells, respectively; P < 0.05 for all), whereas expression of macrophage-related genes CD68, Mac-2, and ABCA1 mRNA increased (to 709 +/- 84%, 330 +/- 11%, and 207 +/- 13% of unloaded cells, respectively; P < 0.05 for all), thereby demonstrating that the protein changes were regulated at the mRNA level. Furthermore, these changes were accompanied by a gain in macrophage-like function as assessed by phagocytotic activity. Expression of vascular cell adhesion molecule 1 and monocyte chemoattractant protein 1, known responders to inflammation, were not changed. In conclusion, cholesterol loading of SMC causes phenotypic changes regulated at the mRNA level that result in a transdifferentiation to a macrophage-like state. This finding suggests that not all foam cells in lesions may have a macrophage origin, despite what is indicated by immunostaining for macrophage-related markers. Furthermore, inflammatory changes in foam cells observed in vivo may not be simple consequences of cholesterol accumulation.

Investigation of in vitro interactions between different polymeric surfaces and blood proteins via phagocytosis phenomena

The effect of various polymeric materials on blood components and their in vitro phagocytosis was the object of the present research. Polystyrene- (PS) and polymethylmetacrylate- (PMMA) based microspheres were produced by phase-inversion polymerization and chemically modified to obtain different surface hydrophilicities. The interactions between blood proteins and chemically- and biologically-modified surfaces were investigated and compared to plain microspheres. Adsorption properties of albumin, fibrinogen and total immunoglobulines on microspheres were tested. Hydrophilic surfaces have high ability for human serum albumin (HSA) adsorption, which also leads to less phagocytosis of microspheres in vitro. In the case of activated PMMA(PVA) microspheres, both protein adsorption and phagocytosis were significant. Interaction of blood proteins with microspheres did not cause any change in phagocytosis by leukocytes and monocytes. BSA adsorption on microspheres with different hydrophilicities showed the same blood protein adsorption results and phagocytosis was not detected. On the other hand, the highest level of phagocytosis was found with fibronectin-modified microspheres. The changes occurring in intrinsic and extrinsic coagulation mechanisms were determined by measuring the activated partial tromboplastin time (APTT) and the prothrombin time (PT). PT values of blood samples did not increase by treatment with microspheres, except for PS/HEMA, while chemical modification caused important prolongation in APTT.

Influence of the structure of support microspheres on leucocyte activation by RGDS-carrying microspheres

A cell adhesive peptide, Arg-Gly-Asp-Ser (RGDS), enhances leucocyte response to stimuli when insolubilized or conjugated with proteins. In order to investigate the contribution of the microsphere structure to leucocyte response. RGDS was immobilized onto several polymeric microspheres. The respiratory burst of polymorphonuclear leucocytes (PMNs) contacting contacting microspheres was enhanced by RGDS in cases where it was immobilized on polystyrene and, more effectively, a positively charged one. This was not observed in polyacrylamide-based or negative-charged microsphere systems. These results demonstrate that the property of supports strongly affects the regulation of the PMN response via an adhesive interaction.

Degradative capability of Pseudomonas putida on acetonitrile

Pseudomonas putida, capable of utilizing acetonitrile as a sole source of carbon and nitrogen, was isolated from contaminated soil and water samples collected from industrial sites. The P. putida cells were immobilized in calcium alginate beads. The degradation of acetonitrile by the immobilized cells of P. putida was investigated. The immobilized cells degraded different concentrations of acetonitrile into ammonia and carbon dioxide. The effect of aeration on the degradation rate was also studied. Oxygen limitation was suggested in the alginate-immobilized system. The rate of degradation of acetonitrile increased with increase in the rate of aeration.

Preparation of Encapsulated Microbial Cells for Environmental Applications

An improved method for the encapsulation of bacteria into microspheres of alginate, agarose, or polyurethane is described. Cell suspensions were passed through a low-pressure nozzle into an aqueous phase where matrix polymerization or gelation yielded beads 2 to 50 μm in diameter. Trials with a chlorophenol-degrading Flavobacterium species showed that cells entrapped by these procedures were as catabolically active as free cells. These types of beads should have numerous applications in the fields of environmental science and engineering.

Phagocytosis of protein coated colloidal-gold-agarose-gelatin microbeads by cultured uterine glandular epithelial and stromal cells

A procedure for fixing and immunostaining whole cells from primary cultures of ovine and bovine uterine gland fragments was used to identify keratin in intermediate filaments of epithelial cells to distinguish them from stromal cells. Colloidal gold encapsulated agarose-gelatin microbeads were coated with different proteins and used to investigate uptake by epithelial and stromal cells in culture. Microbeads were taken up by stromal cells and by epithelial cells on the outskirts of colonies. These cells formed ridges where they contacted and grew above stromal cells. Electron microscopy demonstrated that the microbeads had been internalized and appeared to be nontoxic. Individual cells could harbor more than 90 microbeads within their cytoplasm for at least seven to ten days with no apparent harm. Some cells with microbeads were seen to divide.