Batch injection analysis towards auxiliary diagnosis of periodontal diseases based on indirect amperometric detection of salivary α-amylase on a cupric oxide electrode

This study describes, for the first time, the use of a batch injection analysis system with amperometric detection (BIA-AD) to indirectly determine salivary α-amylase (sAA) levels in saliva samples for chronic periodontitis diagnosis. A chemical/thermal treatment was explored to generate a CuO film on a Cu electrode surface. This procedure offered good stability (RSD = 0.3%), good repeatability (RSD < 1.3%) and excellent reproducibility (RSD < 1.5%). The sAA concentration levels were determined based on the detection of maltose produced by enzymatic hydrolysis of starch. The analytical performance was investigated, and a linear correlation was observed for a maltose concentration range between 0.5 and 6.0 mmol L^-1 with a correlation coefficient equal to 0.999. The analytical sensitivity and the limit of detection were 48.8 μA/(mmol L^-1) and 0.05 mmol L^-1, respectively. In addition, the proposed system provided an excellent analytical frequency (120 analysis h^-1). The clinical feasibility of the proposed method was investigated by the determination of sAA levels in four saliva samples (two from healthy control persons (C1 and C2) and two from patients with chronic periodontitis (P1 and P2)). The accuracy provided by the BIA-AD system ranged from 93 to 98%. The sAA concentration levels achieved for each sample were compared to the values found by spectrophotometry and there was no statistically significant difference between them at a confidence level of 95%. Finally, the method reported herein emerges as a simple, low cost and promising tool for assisting periodontal diseases diagnosis.

A new insert sample approach to paper spray mass spectrometry: a paper substrate with paraffin barriers

The analytical performance for paper spray (PS) using a new insert sample approach based on paper with paraffin barriers (PS-PB) is presented. The paraffin barrier is made using a simple, fast and cheap method based on the stamping of paraffin onto a paper surface. Typical operation conditions of paper spray such as the solvent volume applied on the paper surface, and the paper substrate type are evaluated. A paper substrate with paraffin barriers shows better performance on analysis of a range of typical analytes when compared to the conventional PS-MS using normal paper (PS-NP) and PS-MS using paper with two rounded corners (PS-RC). PS-PB was applied to detect sugars and their inhibitors in sugarcane bagasse liquors from a second generation ethanol process. Moreover, the PS-PB proved to be excellent, showing results for the quantification of glucose in hydrolysis liquors with excellent linearity (R(2) = 0.99), limits of detection (2.77 mmol L(-1)) and quantification (9.27 mmol L(-1)). The results are better than for PS-NP and PS-RC. The PS-PB was also excellent in performance when compared with the HPLC-UV method for glucose quantification on hydrolysis of liquor samples.

Enhanced Performance of Colorimetric Biosensing on Paper Microfluidic Platforms Through Chemical Modification and Incorporation of Nanoparticles

This chapter describes two different methodologies used to improve the analytical performance of colorimetric paper-based biosensors. Microfluidic paper-based analytical devices (μPADs) have been produced by a stamping process and CO₂ laser ablation and modified, respectively, through an oxidation step and incorporation of silica nanoparticles on the paper structure. Both methods are employed in order to overcome the largest problem associated with colorimetric detection, the heterogeneity of the color distribution in the detection zones. The modification steps are necessary to improve the interaction between the paper surface and the selected enzymes. The enhanced performance has ensured reliability for quantitative analysis of clinically relevant compounds.

Highly sensitive colorimetric detection of glucose and uric acid in biological fluids using chitosan-modified paper microfluidic devices

This paper describes the modification of microfluidic paper-based analytical devices (μPADs) with chitosan to improve the analytical performance of colorimetric measurements associated with enzymatic bioassays. Chitosan is a natural biopolymer extensively used to modify biosensing surfaces due to its capability of providing a suitable microenvironment for the direct electron transfer between an enzyme and a reactive surface. This hypothesis was investigated using glucose and uric acid (UA) colorimetric assays as model systems. The best colorimetric sensitivity for glucose and UA was achieved using a chromogenic solution composed of 4-aminoantipyrine and sodium 3,5-dichloro-2-hydroxy-benzenesulfonate (4-AAP/DHBS), which provided a linear response for a concentration range between 0.1 and 1.0 mM. Glucose and UA were successfully determined in artificial serum samples with accuracies between 87 and 114%. The limits of detection (LODs) found for glucose and UA assays were 23 and 37 μM, respectively. The enhanced analytical performance of chitosan-modified μPADs allowed the colorimetric detection of glucose in tear samples from four nondiabetic patients. The achieved concentration levels ranged from 130 to 380 μM. The modified μPADs offered analytical reliability and accuracy as well as no statistical difference from the values achieved through a reference method. Based on the presented results, the proposed μPAD can be a powerful alternative tool for non-invasive glucose analysis.

Enhanced Analytical Performance of Paper Microfluidic Devices by Using Fe3O4 Nanoparticles, MWCNT, and Graphene Oxide

Spheres, tubes, and planar-shaped nanomaterials as Fe3O4 nanoparticles (MNPs), multiwalled carbon nanotubes (MWCNT), and graphene oxide (GO) were used for the first time to treat microfluidic paper-based analytical devices (μPADs) and create a biocompatible layer with high catalytic surface. Once glucose measurements are critical for diabetes or glycosuria detection and monitoring, the analytical performance of the proposed devices was studied by using bienzymatic colorimetric detection of this carbohydrate. The limit of detection values achieved for glucose with μPADs treated with MNPs, MWCNT, and GO were 43, 62, and 18 μM, respectively. The paper surface modification solves problems associated with the lack of homogeneity on color measurements that compromise the sensitivity and detectability levels in clinical diagnosis.

Omega-3 enriched egg production: the effect of α -linolenic ω -3 fatty acid sources on laying hen performance and yolk lipid content and fatty acid composition

1. Diets high in total lipids, saturated fatty acids, trans fatty acids, and having high ω-6:ω-3 fatty acid ratios, have been shown to be related to increased instances of coronary heart disease, while diets high in ω-3 fatty acids have been shown to decrease the risk. 2. Feeding ω-3 fatty acid diets to laying hens has been shown to improve the quality of eggs produced in terms of saturation and ω-3 content. 3. A study was undertaken to determine if the ω-3 fatty acid source, when fed to hens, influences the amount transferred to eggs. 4. Flaxseed and flaxseed oil, along with chia seed and chia seed oil, were the two main sources of ω-3 fatty acid examined during the 84 d trial. 5. All α-linolenic enriched treatments yielded significantly higher ω-3 fatty acid contents per g of yolk and per yolk, than the non-α-linolenic enriched diets. Chia oil and chia seed yielded 54·5 and 63·5% more mg of ω-3 fatty acid per g of yolk for the 56 d test period, and 13·4 and 66·2% more for the 84 d test period, than flaxseed oil and flaxseed, respectively. 6. The differences in omega-3 content were significant, except for the chia oil compared with the flax oil, at the end of the trial. 7. This trial has shown that differences in conversion exist among ω-3 fatty acid sources, at least when fed to hens, and indicates that chia may hold a significant potential as a source of ω-3 fatty acid for enriching foods, thereby making these foods a healthier choice for consumers.

Beef lipids in relation to animal breed and nutrition in Argentina

Fatty acid (FA) composition of intramuscular fat (IMF) in M. Longissimus dorsi (LD) was measured in 72 steers from Angus (A), Charolais×Angus (CHA×A) and Holstein Argentine (HA) breeds. The steers were allotted to four dietary treatments of six animals each: T1, steers grazed on pasture; T2, steers supplemented with cracked corn grain (0.7% of live-weight) daily and free access to pasture; T3, steers supplemented with cracked corn grain (1% of live-weight) daily and free access to pasture; and T4, feedlot (concentrate based on corn, alfalfa hay and soybean meal without access to pasture). At slaughter weight, samples of LD at the 11th rib were used for intramuscular lipid analysis. The diet was shown to be more important than breed in determining FA composition. Pasture beef had higher percentages of saturated fatty acids (SFA), n-3 polyunsaturated fatty acids (PUFA) and conjugated linoleic acid (CLA) and lower percentages of IMF, monounsaturated fatty acids (MUFA), n-6 PUFA and n-6/n-3 ratios than feedlot beef. HA beef presented lower percentages of SFA and more MUFA with a higher n-6/n-3 ratio than A and CHA×A. Comparing grass and feedlot beef the amounts of FA in muscle (mg/100g) were, respectively 18:3 n-3 (44 vs. 11mg), CLA (20 vs. 12mg), 20:5 n-3 (20 vs. 11mg), 22:5 n-5 (20 vs. 11mg), 22:6 n-3 (12 vs. 6mg) and n-3 PUFA (84 vs. 32mg). Feedlot beef has more SFA (1372 vs. 1081mg), MUFA (1574 vs. 1078mg), PUFA (350 vs. 227mg) and n-6 PUFA (318 vs.143mg).

The isomerization of 2,5- and 9,12-octadecadienoic acids by an extract of Butyrivibrio fibrisolvens

A cell-free particulate preparation from Butyrivibrio fibrisolvens was used to study the relative rates of isomerization of all cis,cis-methylene-interrupted isomers of octadecadienoic acid. Only two isomers were found to be substrates, the 9,12-isomer was isomerized at 41 +/- 4 mumol/min per mg protein, and the 2,5-isomer at 11 +/- 1 mumol/min per mg. The product of the isomerization of the 2,5-isomer had an ultraviolet absorption maximum at 233 nm indicating that it was the 3,5-isomer. The isomerization of the 2,5-isomer was studied in detail. Its rate of isomerization was linear with protein concentration up to 0.047 mg/ml, and was linear with substrate concentration up to 48 muM. The pH optimum was 6.8. Below pH 6, the substrate was also subject to spontaneous isomerization. The inhibition of isomerization of the 9,12-isomer by the other isomers was studied. Those isomers in which the double bonds are close to the carboxyl group were the most effective inhibitors. The preparation was also found capable of hydrogenating the conjugated diene product from the 2,5-isomer to a monoene after prolonged incubation.