Incubation Buffer Research Articles

Development of surface-attached thin film of non-fouling hydrogel from poly(2-oxazoline)

In this study poly(2-ethyl-2-oxazoline) (PEOXA) chains that contains 11 mol% of benzophenone molecules was synthesized and coated on either 3-ethoxybenzophenonesilane-modified inorganic or bare organic substrates. Upon irradiation under UV light, the photo-active benzophenone molecules enabled the formation of polymer network as well as attachment of the polymer network onto the substrates. Important variables for the generation of hydrogel film with high gel content and stability, such as the heat treatment for solvent removal, the UV wavelength (that determines the irradiation energy), and the input of energy dose were varied and their influence to the gel content and stability of the hydrogel film was studied. The thickness, lifetime of benzophenone, and chemical composition of the film were determined using ellipsometry, UV/Vis spectroscopy, and XPS methods, respectively. On a film that has been exposed to physiological buffer for 14 days, XPS results indicated that chemical degradation of the copolymer did not take place. Ellipsometry results, however, indicated that some portion of the film detached and the remaining thickness was dependent on the input of energy dose during the hydrogel preparation. It was shown that when suitable conditions are applied during preparation, a stable surface-attached PEOXA-based hydrogel, i.e. approximately 78% gel content and 75–90% stability after 30 days of incubation in physiological buffer, could be generated on the surface. Dry and swollen thicknesses of the stable surface-attached film measured from AFM experiments revealed a swelling factor of 1.7. Furthermore, the AFM morphology image showed a homogenous polymer film with an average roughness of 30 nm. Protein adsorption test revealed that the resulting surface-attached PEOXA-based hydrogel film on PMMA substrate hinders BSA adsorption to the same extent as the reference system generated from benzophenone-bearing poly(dimethylacrylamide) (PDMAA).

A New ELISA to Overcome the Pitfalls in Quantification of Recombinant Human Monoclonal Anti-HBs, GC1102, by Commercial Immunoassays

Several methods for the quantification of human anti-HBs, an antibody to hepatitis B surface antigen (HBsAg), have been developed based on enzyme reaction, chemiluminescence, fluorescence, and radioactivity for application to human serum or plasma. Commercial anti-HBs immunoassay kits use a sandwich method in which a bridge is formed by the anti-HBs between a HBsAg immobilized solid matrix and the labeled HBsAg. However, this direct sandwich enzyme-linked immunosorbent assay (ELISA) is insufficient to accurately evaluate the activity of the human monoclonal anti-HBs, GC1102. As an alternative, we developed an indirect anti-HBs ELISA (anti-HBs qELISA_v.1) that improved detection of anti-HBs. In this current study, we further optimized this indirect method to minimize nonspecific binding of human serum, by employing incubation buffers containing animal serum, Tween 20, skim milk, and a low pH washing buffer. This new and improved method, termed anti-HBs qELISA_v.2, showed accurate quantification of plasma-derived hepatitis B immune globulin (HBIG) and was comparable to results obtained with commercial ELISA (r = 0.93) and RIA (r = 0.85) kits. Further, the GC1102 in human serum could be precisely measured using the anti-HBs qELISA_v.2 without limitations of nonspecific binding.

Stannous chloride and stannous fluoride are inhibitors of matrix metalloproteinases

ObjectivesMatrix metalloproteinases (MMPs) in dentin and saliva can degrade collagen. Divalent metals are known inhibitors of MMPs, but stannous – such as in the form of stannous chloride (SnCl2) or stannous fluoride (SnF2) – is yet to be tested for a possible inhibitory effect. In this study, we tested the inhibitory effect on the proteolytic activity of MMP-2 and MMP-9. MethodsSodium chloride (NaCl), sodium fluoride (NaF), and chlorhexidine (CHX) were used as controls. Gelatin zymography was performed with recombinant human MMP-2 and MMP-9. SnCl2, SnF2, NaF, NaCl, and CHX were included either in the incubation buffer (M1) or added to the recombinant MMPs (M2) before the MMPs were analyzed using zymography. Furthermore, the effect of SnCl2, SnF2, and NaF on the enzymatic activity of MMP-2 and MMP-9 was measured in human dentin either before or after acid etching using 37%phosphoric acid. The effect of SnCl2, NaF, and CHX on the viability and of SnCl2 and NaF on the proliferation of human gingival fibroblasts and L929 mouse fibroblasts was also determined. ResultsFor M1, inhibitory concentrations (w/v%) of SnCl2 0.5% and 0.5%, SnF2 0.25% and 0.12%, NaF 0.12% and 0.5%, CHX 0.012% and 0.05%, were observed for MMP-2 and MMP-9, respectively. NaCl had no inhibitory effect. For M2, SnCl2 0.007% and 0.12%, and SnF2 0.03% and 0.5%, inhibited MMP-2 and MMP-9, respectively. NaF, NaCl and CHX had no effect. The enzymatic activity was slightly reduced when SnCl2 and NaF were applied on dentin before the acid attack. Regarding cell viability and proliferation of the cells after stimulation with the respective substances, NaF showed almost no effect, SnCl2 appeared to increase viability and proliferation of the cells, and CHX decreased the viability of cells. ConclusionsStannous ions caused a direct inhibition of the matrix metalloproteinases, whereas F− only had an inhibitory effect when added to the zymography buffer. Clinical significanceInhibition of MMPs using SnCl2 and SnF2 could play an important role in the prevention of dental erosion and caries. However, the clinical relevance of these findings needs to be proven.

Quantitative screening for endocrine-disrupting bisphenol A in consumer and household products using NanoAptamer assay

The NanoAptamer assay is a bisphenol A (BPA) quantification method that uses magnetic beads, quantum dot nanoparticles, and a BPA-specific aptamer. In this study, screening of various consumer and household products for BPA was demonstrated utilizing the NanoAptamer assay. First, the experimental conditions suitable for BPA detection using the NanoAptamer assay were examined in terms of incubation time, temperature, and buffer composition. The range of BPA quantification via the NanoAptamer assay was determined to be 0.005–1000 ng/mL of BPA. The selectivity was confirmed by detecting BPA in an analog mixture containing bisphenol S and bisphenol F. Finally, a leaching experiment using 20 consumer and household products classified into 4 categories was performed to demonstrate the capability of the NanoAptamer assay for BPA detection. The experiment was validated by high-performance liquid chromatography analysis (correlation coefficient, r = 0.99).

Optimization of Dothideomycetes sp. css035 chitosanase productivity and activity using response surface methodology

Among the methods used for the hydrolysis of chitosan, enzymatic hydrolysis using chitosanase was selected in order to produce high yield of specific chitooligosaccharides with less environmental pollutions. The production of Dothideomycetes sp. NRC-SSW extracellular chitosanase was statistically optimized in which a two - phase experimental design were applied. Plackett – Burman design was used to evaluate the relative importance of culture conditions and medium components for chitosanase production. Chitosan concentration, agitation speed and incubation period were found to be the most significant variables that affected the chitosanase production and their optimal values were obtained by applying Box-Behnken design. The optimized medium composed of (g/L) chitosan, 30; K2HPO4, 1.5; MgSO4, 0.4; KCl, 4.0; yeast extract, 18.5 and FeSO4,0.01; at pH 5.5, 30°C and 180rpm for 96h gave 13.9U/mL with 36.3% increase in the activity. The R2 value was 0.954 and this indicated the aptness of the model. The optimization of the hydrolytic conditions required for chitooligosaccharides production was also performed by Box-Behnken design. The highest yield of chitooligosaccharides was obtained with enzyme/ substrate ratio 0.05U/mg in 0.2M Tris HCl buffer incubation at 60οC for 5h. The cytotoxic activity of the chitooligosaccharides was tested in vitro against Hep-G2 and MCF7.

Digestion-Free Analysis of Peptides from 30-year-old Formalin-Fixed, Paraffin-Embedded Tissue by Mass Spectrometry Imaging.

Formalin-fixed neuroendocrine tissues from American cockroaches (Periplaneta americana) embedded in paraffin more than 30 years ago were recently analyzed by matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI), to reveal the histological localization of more than 20 peptide ions. These represented protonated, and other cationic species of, at least, 14 known neuropeptides. The characterization of peptides in such historical samples was made possible by a novel sample preparation protocol rendering the endogenous peptides readily amenable to MSI analysis. The protocol comprises brief deparaffinization steps involving xylene and ethanol, and is further devoid of conventional aqueous washing, buffer incubations, or antigen retrieval steps. Endogenous secretory peptides that are typically highly soluble are therefore retained in-tissue with this protocol. The method is fully “top-down”, that is, without laborious in situ enzymatic digestion that typically disturbs the detection of low-abundance endogenous peptides by MSI. Peptide identifications were supported by accurate mass, on-tissue tandem MS analyses, and by earlier MALDI-MSI results reported for freshly prepared P. americana samples. In contrast to earlier literature accounts stating that MALDI-MSI detection of endogenous peptides is possible only in fresh or freshly frozen tissues, or exceptionally, in formalin-fixed, paraffin-embedded (FFPE) material of less than 1 year old, we demonstrate that MALDI-MSI works for endogenous peptides in FFPE tissue of up to 30 years old. Our findings put forward a useful method for digestion-free, high-throughput analysis of endogenous peptides from FFPE samples and offer the potential for reinvestigating archived and historically interesting FFPE material, such as those stored in hospital biobanks.

Incubation and its effect on Leishman stain.

BACKGROUND:Leishman stain is the universal stain used in staining of peripheral blood smears all over the world.AIM:To study the effect of incubation of buffer solution, slide alone and slide & buffer both on standard Leishman staining. The staining at times causes difficulty particularly in rainy season when there is increased moisture.METHOD:The study comprised of twenty peripheral blood smears selected consecutively in batches of ten each for two successive days . Minor modification in standard Leishman stain was done by either incubating slide or buffer solution or both. The staining characteristics were scored using system by NG et al and the statistical analysis was done.RESULTS:The highest mean score for background (1.5), nuclear (1.55), cytoplasmic features (1.5) and granules visualization (1.8) were seen in technique involving incubation of both slide and buffer. The results were statistically significant.CONCLUSION:We found that incubating glass slides or buffer solution or both yield better stained slide. Our study showed that there was better staining features seen in incubated slide verses routine method.

In vitro rumen biohydrogenation kinetics of mixed linoleic and alfa-linolenic acids

Background: Dietary linoleic (LA) and alpha-linolenic (LN) acids are extensively isomerized and hydrogenated by rumen microbes, and this activity can further contribute to the fatty acid profile of ruminant-derived food products. Objective: To evaluate the effects of LA:LN ratio in lipid supplements on the rumen biohydrogenation kinetics of LA and LN, as well as on the trans-vaccenic acid (VA) production, using an in vitro system. Methods: Rumen fluid was collected from a fistulated steer, diluted with incubation buffer, and then incubated with 500 mg of kikuyu grass (Cenchrus clandestinus) supplemented with 16.3 mg of different LA:LN mixtures (100:0, 75:25, 50:50, 25:75 or 0:100). Incubations were performed in triplicate for a period of 0, 2, 4, 6, 8 or 16 hours. Differences between treatments were evaluated in a completely randomized design. Alternatively, computational chemistry was used to determine the changes in the Gibbs free energy (ΔGrxn) at 39 °C for the principal steps of LA and LN ruminal biohydrogenation. Results: Partial replacement of LA by LN decreased the VA concentration and its accumulation rate; it also increased the stearic acid concentration and the rates of transfer from LA to conjugated linoleic acid (CLA), and from CLA to VA. The conversion from CLAto VA(ΔGrxn = -2.65 kJ/mol) was more spontaneousthan that from trans-11, cis-15 octadecadienoic acid (TA) to VA (ΔGrxn = -0.29 kJ/mol). Conclusion: The LA:LN ratio in lipids can modulate LA and LN biohydrogenation (BH) kinetics, as well as the VA production in the rumen.

Calcium mobilizing effect of hawthorn leaf procyanidins in vascular endothelial cells

The hawthorn leaves have the effect of activating blood, removing blood stasis, regulating qi through the veins, dissolving turbidity and lowering lipid. Procyanidinis is one of its main active components and plays an important role in regulating vasoactivity. Previous studies showed that the regulating effect of procyanidins was related to its regulation on nitric oxide secretion from vascular endothelial cells, and this effect was dependent on the extracellular calcium concentration, suggesting that the changes in intracellular calcium ion concentration in endothelial cells may play a key role in this process. However, the research on this issue is still insufficient so far. This study is aimed to observe the effect of hawthorn leaf oligomeric procyanidins (HLP) on calcium mobilization of vascular endothelial cells, and investigate the underlying mechanism. Human umbilical vein endothelial cells (HUVEC) were cultured in vitro and labeled with Fura-2. HUVEC were treated with HLP at concentrations of 6.25, 12.5, 25 and 50 mg·L⁻¹, and the intracellular calcium concentrations were measured with a living cell microscope for 30 min. HLP increased the intracellular calcium concentration of HUVEC in a concentration dependent manner; and the intracellular calcium concentrations in 25 and 50 mg·L⁻¹ HLP groups were significantly higher than that in the normal group. With the use of calcium-free incubation buffer, addition of calcium chelating agent EGTA in incubation buffer, or use of inhibitors for sodium calcium exchanger, the effect of HLP was significantly inhibited. On the other hand, the effect of HLP could also be weakened by inhibiting the calcium release from the intracellular storage. In conclusion, these results suggest that HLP can elicit calcium mobilization in vascular endothelial cells, which may be one of the mechanisms for its vascular modulatory activity; and this calcium mobilizing effect may be achieved through promoting both extracellular calcium influx and intracellular calcium release, additionally the former may be related to activating the reverse transport of Na⁺-Ca²⁺ exchangers on the cell membrane.

Advances in enzyme substrate analysis with capillary electrophoresis.

Capillary electrophoresis provides a rapid, cost-effective platform for enzyme and substrate characterization. The high resolution achievable by capillary electrophoresis enables the analysis of substrates and products that are indistinguishable by spectroscopic techniques alone, while the small volume requirement enables analysis of enzymes or substrates in limited supply. Furthermore, the compatibility of capillary electrophoresis with various detectors makes it suitable for KM determinations ranging from nanomolar to millimolar concentrations. Capillary electrophoresis fundamentals are discussed with an emphasis on the separation mechanisms relevant to evaluate sets of substrate and product that are charged, neutral, and even chiral. The basic principles of Michaelis-Menten determinations are reviewed and the process of translating capillary electrophoresis electropherograms into a Michaelis-Menten curve is outlined. The conditions that must be optimized in order to couple off-line and on-line enzyme reactions with capillary electrophoresis separations, such as incubation time, buffer pH and ionic strength, and temperature, are examined to provide insight into how the techniques can be best utilized. The application of capillary electrophoresis to quantify enzyme inhibition, in the form of KI or IC50 is detailed. The concept and implementation of the immobilized enzyme reactor is described as a means to increase enzyme stability and reusability, as well as a powerful tool for screening enzyme substrates and inhibitors. Emerging techniques focused on applying capillary electrophoresis as a rapid assay to obtain structural identification or sequence information about a substrate and in-line digestions of peptides and proteins coupled to mass spectrometry analyses are highlighted.

Dynamic Influence of pH on Metalloproteinase Activity in Human Coronal and Radicular Dentin

The aim of this study was to evaluate the effect of pH on the activation of matrix metalloproteinases (MMPs) of human coronal (CD) and radicular dentin (RD). CD and RD were pulverized to powder, and proteins were extracted with 1% phosphoric acid. The extracted proteins and the demineralized powder were separately incubated in the following solutions: 4-aminophenylmercuric acetate (control) or a buffer solution at different pHs (2.5, 4.5, 5.0, 6.0, and 7.0). After incubation, proteins were separated by electrophoresis to measure MMP activities by zymography. To assess the solubilized dentin collagen, the demineralized dentin powder was sustained in incubation buffer, and the amount of hydroxyproline (HYP) released was measured. Zymography revealed MMP-2 gelatinolytic activities for CD and RD in all experimental groups. For both substrates, the lowest pH solutions (2.5, 4.5, and 5.0) yielded higher gelatinolytic activity than those obtained by the highest pH solutions (6.0 and 7.0). For HYP analysis, no detectable absorbance values were observed for pHs of 2.5 and 4.5. The amount of HYP was higher for pH 7.0 than those of all other groups (p < 0.05), except for pH 6.0. No statistical differences were found between pHs 6.0 and 5.0 and control (p > 0.05). The MMP-2 enzyme from human CD and RD is dynamically influenced by pH: at low pH, the extracted enzyme activates this latent form, whereas collagen degradation by the matrix-bound enzyme is only observed when pHs are close to neutral.

Effects of incubation buffer conditions on in vitro primary cryopreserved hepatocyte phase I AND phase II metabolism

Effects of incubation buffer conditions on in vitro primary cryopreserved hepatocyte phase I AND phase II metabolism

Antibacterial Films Made of Ionic Complexes of Poly(γ-glutamic acid) and Ethyl Lauroyl Arginate

The biocide agent LAE (ethyl αN-lauroyl l-arginate chloride) was coupled with poly(γ-glutamic acid) (PGGA) to form stable ionic complexes with LAE:PGGA ratios of 1 and 0.5. The nanostructure adopted by these complexes and its response to thermal changes were examined in detail by Differential scanning calorimetry (DSC) and X-ray diffraction (XRD) using synchrotron radiation in real time. A layered biphasic structure with LAE filling the space between the polypeptidic sheets was adopted in these complexes. The complexes were stable up to above 250 °C, non-water soluble, and were able to form consistent transparent films. The release of LAE from the complexes upon incubation in aqueous buffer was examined and found to depend on both pH and complex composition. The antibacterial activity of films made of these complexes against Gram-positive (L. monocytogenes and S. aureus) and Gram-negative (E. coli and S. enterica) bacteria was preliminary evaluated and was found to be very high against the formers and only moderate against the later. The bactericide activity displayed by the LAE·PGGA complexes was directly related with the amount of LAE that was released from the film to the environment.

Polyvalent immunoglobulin binding is an obstacle to accurate measurement of specific antibodies with ELISA despite inclusion of blocking agents

Specific antibody concentrations are frequently measured in serum (and plasma and intravenous immunoglobulin) samples by enzyme-linked immunosorbent assay (ELISA). The standard negative control involves incubation of buffer alone on antigen-coated wells. The immunoreactivity that develops in antigen-coated wells in which diluted serum has been incubated is assumed to represent specific antibody binding. This approach can result in marked overestimation of specific antibody levels, because serum contains specific polyvalent antibodies which bind, primarily with low affinity, to multiple antigens (including those on ELISA plates) despite the use of blocking agents. Non-denaturing purification of serum IgG, followed by assessment of the antigen binding or antigen-binding affinity of this purified IgG, can reduce but not eliminate the problem of polyvalent antibody binding in indirect ELISAs. Alternatively, polyvalent antibody binding can be estimated by incubating a diluted serum sample on wells coated with an irrelevant protein (such as bovine serum albumin or a scrambled peptide sequence) or buffer alone, then subtracting this reactivity from the sample's binding to wells coated with the antigen of interest. Polyvalent binding of immunoglobulins must be accounted for in order to obtain accurate ELISA measurements of serum, plasma, or intravenous immunoglobulin antibodies.

Optimising DNA extraction from a critically endangered marine alga

Prior to conducting genetic studies on critically endangered species, it is desirable to optimise DNA extraction to limit destructive sampling and reduce impacts on populations. We optimized DNA extraction for the critically endangered marine alga, Nereia lophocladia. Only gentle cryogenic homogenization using a mortar and pestle, followed by brief incubation in lysis buffer, produced high molecular weight DNA. However, this DNA still required post hoc cleanup to be of sufficient quantity for PCR and next generation sequencing. Importantly, sufficient DNA can be obtained from as little as 25 mg of algal material while still allowing contingencies for losses associated with cleanup. Optimisation of DNA extraction for this critically endangered species is paving the way for genomic studies to inform management strategies and conservation.

High-Affinity RGD-Knottin Peptide as a New Tool for Rapid Evaluation of the Binding Strength of Unlabeled RGD-Peptides to αvβ3, αvβ5, and α5β1 Integrin Receptors.

We describe a highly sensitive competition ELISA to measure integrin-binding of RGD-peptides in high-throughput without using cells, ECM-proteins, or antibodies. The assay measures (nonlabeled) RGD-peptides' ability to inhibit binding of a biotinylated "knottin"-RGD peptide to surface-immobilized integrins and, thus, enables quantification of the binding strength of high-, medium-, and low-affinity RGD-binders. We introduced the biotinylated knottin-RGD peptide instead of biotinylated cyclo[RGDfK] (as reported by Piras et al.), as integrin-binding was much stronger and clearly detectable for all three integrins. In order to maximize sensitivity and cost-efficiency, we first optimized several parameters, such as integrin-immobilization levels, knottin-RGD concentration, buffer compositions, type of detection tag (biotin, His- or cMyc-tag), and spacer length. We thereby identified two key factors, that is, (i) the critical spacer length (longer than Gly) and (ii) the presence of Ca2+ and Mg2+ in all incubation and washing buffers. Binding of knottin-RGD peptide was strongest for αvβ3 but also detectable for both αvβ5 and α5β1, while binding of biotinylated cyclo[RGDfK] was very weak and only detectable for αvβ3. For assay validation, we finally determined IC50 values for three unlabeled peptides, that is: (i) linear GRGDS, (ii) cyclo[RGDfK], and (iii) the knottin-RGD itself for binding to three different integrin receptors (αvβ3, αvβ5, α5β1). Major benefits of the novel assay are (i) the extremely low consumption of integrin (50 ng/peptide), (ii) the fact that neither antibodies/ECM-proteins nor integrin-expressing cells are required for detection, and (iii) its suitability for high-throughput screening of (RGD-)peptide libraries.

Implications for Ophthalmic Formulations: Ocular Buffers Show Varied Cytotoxic Impact on Human Corneal-Limbal and Human Conjunctival Epithelial Cells.

To investigate toxicity associated with buffers commonly used in topical ocular drug formulations using a human corneal-limbal epithelial (HCLE) and a human conjunctival epithelial (HCjE) cell model. HCLE and HCjE cells were incubated for 10, 30, or 60 minutes with 4 different buffers based on borate, citrate, phosphate, and Tris-HCl at 10, 50, and 100 mM concentrations. To detect possible delayed effects on cell viability, after 60 minutes of buffer incubation, cells were further incubated for 24 hours with a cell medium. Cell viability was determined using a colorimetric XTT-based assay. The morphology of cells was also investigated. HCjE cells showed more sensitivity to buffer incubation than HCLE cells. The 100 mM phosphate buffer displayed significant delayed effects on cell viability of HCLE 16.8 ± 4.8% and HCjE 39.2 ± 6.1% cells after 60 minutes of exposure (P < 0.05). HCjE cell viability was reduced after 60 minutes incubations with 50 and 100 mM citrate buffer to 42.8 ± 6.5% and 39.3 ± 7.9%, respectively, and even lower percentages at the delayed time point (both P < 0.05). HCLE cell morphology was distinctly altered by 100 mM phosphate and Tris buffers after 30 minutes, whereas HCjE cells already showed marked changes after 10 minutes of exposure to 100 mM citrate and phosphate buffers. We observed a time-dependent decrease of viability in both HCLE and HCjE cells exposed to higher buffer concentrations. Therefore, we propose further in vivo studies to translate these finding to humans to discern the real effects of the buffer concentration in eye drops on the ocular surface.

Enrichment of Clavibacter michiganensis subsp. michiganensis in tomato seed extracts

An enrichment procedure was developed to improve detection of Clavibacter michiganensis subsp. michiganensis (Cmm) in tomato seed extracts. In the final procedure, seeds were soaked overnight in a buffer at 4°C and homogenised. Seed extracts were then filtered, supplemented with antibiotics and incubated for three days at 25°C. In seed extracts spiked with known amounts of Cmm suspensions, a 0- to 10,000-fold increase of Cmm populations was found in the incubation buffer supplemented with but not without the selective compounds, dependent on the seed lot. The procedure also enhanced enrichment of Cmm in seeds artificially infected with low or high numbers of a GFP-tagged strain of Cmm. The presence of the fluorescent bacteria in these internally-infected seeds was confirmed with epifluorescence stereo- and confocal laser scanning microscopy. Eight naturally-infected seed lots stored for three years were used for further evaluation of the procedure. Cmm was detected in seven out of eight lots by TaqMan, although Cmm was only detected by spread-plating in four lots. Enrichment resulted in an increase in Cmm population densities in two of these four seed lots.

Experimental Protocol for Detecting Cyanobacteria in Liquid and Solid Samples with an Antibody Microarray Chip.

Global warming and eutrophication make some aquatic ecosystems behave as true bioreactors that trigger rapid and massive cyanobacterial growth; this has relevant health and economic consequences. Many cyanobacterial strains are toxin producers, and only a few cells are necessary to induce irreparable damage to the environment. Therefore, water-body authorities and administrations require rapid and efficient early-warning systems providing reliable data to support their preventive or curative decisions. This manuscript reports an experimental protocol for the in-field detection of toxin-producing cyanobacterial strains by using an antibody microarray chip with 17 antibodies (Abs) with taxonomic resolution (CYANOCHIP). Here, a multiplex fluorescent sandwich microarray immunoassay (FSMI) for the simultaneous monitoring of 17 cyanobacterial strains frequently found blooming in freshwater ecosystems, some of them toxin producers, is described. A microarray with multiple identical replicates (up to 24) of the CYANOCHIP was printed onto a single microscope slide to simultaneously test a similar number of samples. Liquid samples can be tested either by direct incubation with the antibodies (Abs) or after cell concentration by filtration through a 1- to 3-μm filter. Solid samples, such as sediments and ground rocks, are first homogenized and dispersed by a hand-held ultrasonicator in an incubation buffer. They are then filtered (5 - 20 μm) to remove the coarse material, and the filtrate is incubated with Abs. Immunoreactions are revealed by a final incubation with a mixture of the 17 fluorescence-labeled Abs and are read by a portable fluorescence detector. The whole process takes around 3 h, most of it corresponding to two 1-h periods of incubation. The output is an image, where bright spots correspond to the positive detection of cyanobacterial markers.

Improvement of recovered activity and stability of the Aspergillus oryzae β-galactosidase immobilized on duolite A568 by combination of immobilization methods

The immobilization and stabilization of Aspergillus oryzae ?-galactosidase on Duolite??A568 was achieved using a combination of physical adsorption, incubation step in buffer at pH 9.0 and cross-linking with glutaraldehyde and in this sequence promoted a 44% increase in enzymatic activity as compared with the biocatalyst obtained after a two-step immobilization process (adsorption and cross-linking). The stability of the biocatalyst obtained by three-step immobilization process (adsorption, incubation in buffer at pH 9.0 and cross-linking) was higher than that obtained by two-steps (adsorption and cross-linking) and for free enzyme in relation to pH, storage and reusability. The immobilized biocatalyst was characterized with respect to thermal stability in the range 55-65 ?C. The kinetics of thermal deactivation was well described by the first-order model, which resulted in the immobilized biocatalyst activation energy of thermal deactivation of 71.03 kcal/mol and 5.48 h half-life at 55.0 ?C.