The colorimetric analysis of sialic acid in human saliva and bovine salivary mucin

Scalable Extraction of Airway Mucins from Porcine Trachea

Mucins are a major component of the innate defense system in the airways and their biological functions are important to consider in pulmonary disease research. However, the available mucus models for basic research relevant to the lung can be difficult to acquire in sufficient quantity to conduct such studies. Here, we present a new strategy to isolate airway mucins from pig trachea at the milligram to gram scale for use in pulmonary disease research. Using this protocol, we were able to isolate mucins with minimal DNA contamination consisting of ~70% by weight protein. Compared to porcine gastric mucins extracted with the same procedure, the porcine tracheal extract possessed significantly greater O-linked glycoprotein (mucin) content. Particle tracking microrheology was used to evaluate the biophysical properties of porcine trachea mucins. We found porcine tracheal mucins formed a much tighter mesh network and possessed a significantly greater microviscosity compared to lab extracted porcine gastric mucins. In comparison to mucus harvested from human airway tissue cultures, we found porcine tracheal mucins also possessed a greater microviscosity suggesting these mucins can form into a gel-like material at physiological total solids concentrations. These studies establish an accessible means to isolate airway mucins from porcine trachea at large scale for use in pulmonary disease research.

Oxidase mimicking Co/2Fe MOF included biosensor for sialic acid detection

A facile amperometric biosensor that included oxidase mimicking Co/2Fe metal-organic framework (MOF) for sialic acid (SA) detection was prepared. Amperometric SA biosensor was constructed on a gold screen-printed electrode via immobilization of Co/2Fe MOF and N-acetylneuraminic Acid Aldolase (NANA-Aldolase) enzyme, respectively. NANA-Aldolase enzyme converts free SA into pyruvate and N-acetyl-d-mannosamine. After this conversion, oxidase mimicking Co/2Fe bimetallic MOF converts pyruvate into acetylphosphate and O₂ into H₂O₂. Investigation of analytical characteristics resulted with the linear range of 0.02 mM-1.00 mM of SA concentration with limit of detection value of 0.026 mM. Sample application studies with developed SA biosensor were carried out with GD3 ganglioside and HeLa cancer cell lines which have high SA concentrations while A549 cell lines were also used as control group. Before detecting free SA, the bound SA was freed from SA sources where every step was monitored via electron impedance spectroscopy. Then, free SA was successfully detected with the amperometric SA biosensor and as a result, more practical and accurate system was developed.

Sialic acid content of infant saliva: comparison of breast fed with formula fed infants

Sialic acid is found in especially high concentrations in brain gangliosides, and supplementary sialic acid is associated with increased learning behaviour in animals. It was hypothesised that breast fed infants may have higher concentrations of sialic acid in body fluids and tissues because human milk is a rich source of sialylated oligosaccharides, while formulas contain very little. The aim therefore was to compare the sialic acid content of saliva collected from full term infants who were either solely breast fed or formula fed until weaning at 3-5 months of age. Thirty three infants, 18 breast fed and 15 formula fed, were studied at a mean (SD) age of 5 (2) months. The breast fed infants, when compared with formula fed infants, were found to have almost two times more free sialic acid in saliva (mean (SE) 16.0 (2.7) v 8.2 (2.1) mg/l, p < 0.036) and nearly 50% more total sialic acid (47.3 (3.9) v 32.2 (4.4) mg/l, p < 0.014). The findings provide a preliminary indication that an exogenous source of sialic acids derived from human milk may contribute to higher concentrations of sialic acid in body fluids. There are important implications for the formulation of human milk substitutes.

Determination of sialic acids in human serum by reversed-phase liquid chromatography with fluorimetric detection

A simple, rapid and highly sensitive reversed-phase liquid chromatographic method has been developed for the determination of sialic acids in human serum. The sialic acids, released by hydrolysis of serum, are converted in borate buffer with malononitrile to highly fluorescent compounds. The reaction mixture is separated isocratically within 5 min using an octadecyl-bonded silica column and a mobile phase of methanol and ammonium acetate buffer (15:85, v/v; pH 5.5). Measurement of the fluorescence intensity of the reaction mixture at 434 nm with irradiation at 357 nm allowed determination of 30-1000 ng/ml of sialic acids with high reproducibility. The limit of detection was 2 ng/ml. Intra-day and inter-day coefficients of variation for assaying 300 ng/ml N-acetylneuraminic acid (NANA) were 1.5% (n = 9) and 2.6% (n = 7), respectively. The recoveries of NANA were 98.5-101.1% for serum. The method has been used for clinical determinations.

Ion displacement following the adsorption of anionic macromolecules on hydroxyapatite

Certain small anionic molecules displace phosphate ions from the hydroxyapatite crystal hydration layer on adsorption. This follows the interaction of negatively charged groups with calcium ions in the crystal surface. The present study examines ion-exchange processes occurring during the adsorption of anionic macromolecules and attempts to determine the role of coulombic forces in the process. Various natural and synthetic polyanionic substances were added to a buffered hydroxyapatite slurry and adsorption measured by solution depletion. Calcium and phosphate ion displacement or uptake by apatite was determined after accounting for polymer-bound ions. Carboxymethylcellulose and a polyacrylamide sample in which 54% of amide groups had been hydrolyzed to carboxyl were adsorbed in the lowest amounts, but both caused consistent rises in the bulk solution phosphate level. Crude bovine submaxillary mucin and a polyacrylamide sample in which 28% of amide groups had been hydrolyzed were adsorbed in greater amounts but caused little or no phosphate displacement. In no case was there a stoichiometric relation between carboxyl adsorbed and phosphate displaced. The polyacrylamide samples also displaced Ca ions into the bulk solution, whereas the other macromolecules caused a decrease in solution Ca concentration. These results provide some evidence for the operation of an ion-exchange mechanism in the adsorption of polyanions on hydroxyapatite but do not exclude the involvement of other mechanisms, especially in the case of salivary mucin.