Ultra-stable zeolites—a tool for in-cell chemistry

Bile sequestration potential of an edible mineral (clinoptilolite) under simulated digestion of a high-fat meal: an in vitro investigation

Bile, important for cholesterol homeostasis, is a potential target of hypercholesterolemia management. Bile sequestration by orally administered resins, while mostly effective in reducing blood cholesterol, presents several side effects and disadvantages. Thus, widely available natural edible minerals such as clinoptilolite with adsorptive properties offer an alternative for bile sequestration. In an experimental setting mimicking the physiological conditions of digestion/absorption (pH, temperature, and retention times) with a series of assessment methods, scanning electron microscopy-energy dispersion X-ray analysis (SEM-EDX), X-ray diffraction (XRD), Fourier transform infrared analysis (FT-IR), thermogravimetric differential thermal analysis (TG-DTA), and molecular docking modeling, the ability of natural unmodified clinoptilolite to retain bile, while mixed with a simulated high-fat meal, was investigated. Our results demonstrate that clinoptilolite sequesters bile via adsorption of macromicelles at 75.4% efficiency, when the former is administered at a reasonable dose of 4% (w/w) of a meal's weight. This work provides the possibility of clinoptilolite utilization as a bile-sequestering/cholesterol-reducing agent.

Aluminium based adjuvants and their effects on mitochondria and lysosomes of phagocytosing cells

Aluminium oxyhydroxide, Al(OH)3 is one of few compounds approved as an adjuvant in human vaccines. However, the mechanism behind its immune stimulating properties is still poorly understood. In vitro co-culture of an aluminium adjuvant and the human monocytic cell line THP-1 resulted in reduced cell proliferation. Inhibition occurred at concentrations of adjuvant several times lower than would be found at the injection site using a vaccine formulation containing an aluminium adjuvant. Based on evaluation of the mitochondrial membrane potential, THP-1 cells showed no mitochondrial rupture after co-culture with the aluminium adjuvant, instead an increase in mitochondrial activity was seen. The THP-1 cells are phagocytosing cells and after co-culture with the aluminium adjuvant the phagosomal pathway was obstructed. Primary or early phagosomes mature into phagolysosomes with an internal pH of 4.5 - 5 and carry a wide variety of hydrolysing enzymes. Co-culture with the aluminium adjuvant yielded a reduced level of acidic vesicles and cathepsin L activity, a proteolytic enzyme of the phagolysosomes, was almost completely inhibited. THP-1 cells are an appropriate in vitro model in order to investigate the mechanism behind the induction of a phagocytosing antigen presenting cell into an inflammatory cell by aluminium adjuvants. Much information will be gained by investigating the phagosomal pathway and what occurs inside the phagosomes and to elucidate the ultimate fate of phagocytosed aluminium particles.

Surface-functionalized fluorescent silica nanoparticles for the detection of ATP

The design of two-dyed fluorescent silica nanoparticles for ATP detection is presented. The indicator dye possesses a dipicolyl-amine (DPA) unit complexed with Zn(II) as a receptor function for ATP while a rhodamine derivative is used as the reference dye. The nanoparticles were fully characterized regarding analytical performance, morphology and cytocompatibility.

Effect of composition, morphology and size of nanozeolite on its in vitro cytotoxicity

The extensive applications of nanoparticle materials in biomedical and biotechnological fields trigger the rapid development of nanotoxicology, because nanoparticles are reported to cause more damage than larger ones when human exposure to them. In the present manuscript, we prepared a series of zeolite nanocrystals with different frameworks, sizes, compositions and shapes, and provided the first report on their toxic difference. As our results, the toxicities of zeolite nanoparticles depend on their size, composition and shape when they are exposed to HeLa cells. The pure-silica nanozeolite silicalite-1 displays nontoxicity, but aluminum-containing nanozeolites, such as ZSM-5, LTL, and LTA, show a dose-dependent toxic manner. The different shapes of nanozeolites can lead to different cytotoxicities, while the influences of the surface charge differences of various nanozeolites on their toxicities are unconspicuous. More importantly, caspase-3 activity and LDH released assays showed that the toxic nanozeolites seem to induce cell necrosis rather than cell apoptosis by the damnification for the cell membranes. These results are expected to direct the applications of nanozeolites with different structures and shapes in biomedicine and clinic science.

Nanozeolite-driven approach for enrichment of secretory proteins in human hepatocellular carcinoma cells

Given the importance of secreted proteins as a source for early detection and diagnosis of disease, secreted proteins have been arousing considerable attention. However, the analysis of secreted proteins represents a challenge for current proteomic techniques. One of the difficulties in secretomic study is to concentrate proteins from large volume of growth media, particularly, the low abundant and low molecular weight proteins (molecular weight <30 kDa). Herein, we describe a novel strategy for harvesting secretory proteins. In this approach, proteins secreted from the human hepatocellular carcinoma cell line were enriched by zeolite LTL nanocrystals, followed by 1-D SDS-PAGE for protein fractionation and then by LC-ESI-MS/MS for protein identification. In total, 1474 unique proteins were confidently identified, including 505 low molecular weight proteins, and covered a broad range of pI and molecular weight. Furthermore, this study not only offered an efficient and powerful method for the enrichment of secretory proteins but also allowed in-depth study of secretome of hepatocellular carcinoma cells. The reported work is expected to represent one of the most comprehensive secretomic analyses so far.

Receptor-mediated endocytosis of particles by peripheral dendritic cells

Human peripheral dendritic cells (DCs) are antigen-presenting cells with the ability to internalize antigen and present antigen-derived peptides to T cells. Human DCs express several receptors on the surface for endocytosis and other recognition receptors that bind to microbes or microbial products, which are internalized and processed. Here, we report the use of nanometer-size zeolite particles as a tool to study receptor-mediated endocytosis by the two subsets of immature DCs, myeloid (mDC) and plasmacytoid (pDC) dendritic cells. A major difference in receptor-mediated endocytosis was observed between the two populations of peripheral DCs. The pDC population demonstrated an almost complete lack of receptor-mediated endocytosis of zeolite particles, whereas the mDC population demonstrated a clear receptor-mediated endocytosis. Fc receptors are expressed by both peripheral DC populations and lipoteichoic acid (LTA) and lipopolysaccharide (LPS) are known ligands of the Toll-like receptor (TLR)-2 and TLR4, respectively, both TLRs expressed by human mDCs. An efficient receptor-mediated endocytosis of immunoglobulin G-, LTA-, and LPS-coated zeolite particles was observed by the mDC population and their endocytosing capacity depended strongly on the density of the ligand adsorbed onto the zeolite particles. In conclusion, an efficient receptor-mediated endocytosis was observed from the mDC population, whereas the pDCs demonstrated an almost complete lack of receptor-mediated endocytosis and nanometer-size dealuminated zeolite particles were a useful tool for studying receptor-mediated endocytosis in human peripheral DCs.

Controlled release of preservatives using dealuminated zeolite Y

This study demonstrates that dealuminated zeolite Y can act as a depot after adsorption of phenol derived preservatives. Upon suspension of zeolite loaded with the preservative m-cresol, equilibrium was quickly reached between free and adsorbed m-cresol. The equilibrium concentration of m-cresol was below 1 mM; however, it was enough to kill bacteria such as Escherichia coli and Staphylococcus aureus under metabolically active conditions. Killing of bacteria was not obtained under non-proliferating conditions and m-cresol was only released from the zeolite upon bacterial activity. Together, these results demonstrate an interesting potential use of dealuminated zeolite Y containing adsorbed preservatives for preventing microbial growth in numerous applications in industry and clinical setting.

De-aluminated Zeolite Y as a Tool to Study Endocytosis, A Delivery System Revealing Differences between Human Peripheral Dendritic Cells

We report the use of nanometre-sized zeolite particles as a novel approach to follow the endosomal acidification and proteolysis inside a viable cell. The method was verified by using human peripheral monocytes, a well known endocytosing cell population. Zeolite particles were subsequently used to investigate the endocytosing mechanisms of human peripheral dendritic cells (DC). Probes detecting pH neutral and acidic endosomes were adsorbed to de-aluminated zeolite Y, and used to detect endocytosis in immature human peripheral blood DC. Both the myeloid (mDC) and the plasmacytoid (pDC) dendritic cell subsets had an endocytosing capacity comparable with peripheral blood monocytes. However, the majority of both subsets of DC retained their endosomes at a neutral pH during the first hours after endocytosis and only a small number of the mDC showed any formation of acidic endosomes. Proteolytic degradation of endocytosed proteins was detected using self-quenched DQ-ovalbumin adsorbed to zeolite particles. Interestingly, a clear difference in proteolytic degradation of endocytosed ovalbumin was observed between the two subsets of DC. The mDC showed an efficient degradation of ovalbumin, while the pDC population displayed no or only minor proteolytic degradation. In conclusion, zeolite particles provide a useful tool to study the endocytosing mechanisms, and an efficient carrier of bio-molecules into the endosomal pathways of viable cells.

Sustained release of doxorubicin from zeolite-magnetite nanocomposites prepared by mechanical activation

Nanocomposites consisting of magnetite and FAU zeolite with a high surface area and adsorption capacity have been prepared by mechanical activation using high-energy milling at room temperature. FTIR results, as well as HRTEM, EFTEM, and XPS measurements, show that the resulting magnetic nanoparticles are covered by a thin aluminosilicate coating. A saturation magnetization as high as 16 emu g(-1) and 94.2 Oe of coercivity were observed for the obtained composites. The main advantages of this synthesis procedure are (i) simplicity of the preparation procedure, (ii) prevention of agglomeration of the magnetite nanoparticles to a large extent, and (iii) absence of free magnetite outside the zeolitic matrix. In addition, in vitro experiments revealed that the nanoparticles prepared were able to store and release substantial amounts of doxorubicin. In view of these advantages, these magnetic nanoparticles can be considered as potential candidates for drug-delivery applications.