A paper-based point-of-care testing device for the colourimetric estimation of bilirubin in blood sample.

A paper-based colourimetric assay for the Point-of-Care Testing (PoCT) of bilirubin has been developed based on the formation of a green-coloured copper-bilirubin complex from a blue-coloured tetraamminecopper(II) sulphate complex. The reaction was studied and optimized by UV-Visible absorption spectroscopy and translated onto a paper strip. Hydrophobic circular well patterns on Whatman chromatography paper were created by wax printing. The tetraamminecopper(II) sulphate complex was drop cast and dried on the reagent zones in the wax-patterned paper. The images of reagent zones captured using a scanner were analyzed using ImageJ software. Bilirubin spiked blood serum was tested in the concentration range of 1.2 to 950 µM. The PAD exhibited sensitivities of 0.4197 a.u/µM and 0.1040 a.u/µM for concentration ranges of bilirubin 1.2 to 96 µM and 105 to 950 µM respectively and a low detection limit of 0.799 µM. The method is highly selective to bilirubin, even in the presence of other biomarkers in serum. A plasma separation membrane incorporated PAD was fabricated for the final testing and quantification of bilirubin from whole blood.

Paper based micro/nanofluidics devices for biomedical applications.

This chapter details the significance, fabrication and biomedical applications of paper-based microfluidic devices. The first part of the chapter describes the importance of paper diagnostic devices, highlighting pretreatment, dipsticks, lateral flow assays, and microPADs. Various methods followed for the fabrication of the paper analytical devices are discussed in the second part. The last part is about some of the important biomedical applications of paper analytical devices. Finally, the challenges and research gaps in the paper microfluidics for biomedical applications are presented.

Development of a paper-based analytical device for the colourimetric detection of alanine transaminase and the application of deep learning for image analysis.

A paper-based colourimetric assay for the detection of alanine transaminase has been developed. In the presence of alanine transaminase, 2,4-dinitrophenyl hydrazine changes to pyruvate hydrazone leading to a colour change from pale yellow to dark yellow. Reaction conditions were optimized using absorption spectroscopic studies. Hydrophobic patterns on the Whatman chromatographic paper were created by wax printing, and the reagents were drop cast at the reagent zone. On the paper device, the intensity of the yellow colour increases with ALT concentration in the range of 20-140 U/L in human serum. For the quantification of ALT, coloured images were captured using a digital camera and were processed with Image J software. The machine learning approach was also explored for the ALT analysis by training with colour images of the paper device and testing using a cross-validation procedure. The results obtained with real clinical samples on the paper device showed good accuracy of less than 5% relative error with the clinical lab results. Furthermore, the paper device shows high selectivity to ALT in the presence of various interfering species in blood serum with a sensitivity of 0.261 a.u/(U/L), a detection limit of 4.12 U/L, and precise results with an RSD of less than 7%. For the testing of whole blood, a plasma separation membrane was integrated with the patterned paper.

Trace metal distribution in the sediment cores of mangrove ecosystems along northern Kerala coast, south-west coast of India.

Core sediment samples were collected from five mangrove ecosystems along northern Kerala coast (Kunjimangalam: S1, Pazhayangadi: S2, Pappinissery: S3, Thalassery: S4, and Kadalundi: S5) to assess the status of heavy metal pollution. S1 recorded comparatively lower metal concentration at surface (except Pb) due to low organic content and sandy texture, while the reverse was true for S3. Higher metal contents were recorded at S5 (0-5 cm), which was attributed to its unique biogeochemical behavior. Enrichment factor and geoaccumulation index indicated moderate enrichment for Cd, and the pollution load index revealed progressive deterioration of sediment quality at S5 (0-5 cm). There was no harmful effect of trace metals on biological community (except Ni) according to Sediment Quality Guidelines. Major processes controlling trace metal accumulation in these systems are diagenetic processes, precipitation of heavy metals as sulfides, and the presence of Fe, Mn-oxy hydroxides, which act as adsorption sites for other metals.

Paper-based device for the colorimetric assay of bilirubin based on in-situ formation of gold nanoparticles.

A paper-based colorimetric assay for the determination of bilirubin has been developed. The method is based on the in-situ reduction of chloroauric acid to form gold nanoparticles. A chromatographic paper was patterned using a wax printer. Chloroauric acid was drop-cast onto the reagent zone. In the presence of bilirubin, gold(III) ions are reduced and form gold nanoparticles. This leads to a color change from yellow to purple. The intensity of the purple color (peak at 530 nm) increases with bilirubin concentration in the 5.0 to 1000 mg L-1 range. The detection limit is 1.0 mg L-1. For the quantification of bilirubin, images were captured using a digital camera, and data were processed with the help of machine learning-based supervised prediction using Random Forest classification. The method was applied to the determination of bilirubin in urine samples. The spiked urine samples exhibit more than 95% recovery. Graphical abstractSchematic representation of the paper-based colorimetric assay for the detection of bilirubin based on the in-situ formation of gold nanoparticles. A color band is generated for visual interpretation and used for the testing of bilirubin in urine.

Spatio-temporal variability in macrobenthic communities and trophic structure of a tropical estuary and its adjacent coastal waters.

Spatio-temporal distribution of the macrobenthic community (> 500 µm) and the trophic ecology of polychaetes were studied for a year in the Cochin estuary (CE) and its adjacent coastal waters. A profound influence of the southwest monsoon (SWM) was evident in the CE, a tropical monsoonal estuary, during the present study. The sediment texture and macrobenthic density exhibited a pronounced spatial variation in the estuary, while in the coastal waters temporal changes were more prominent. Polychaetes formed the dominant taxa in terms of density and diversity in the estuary (53 species belonging to 25 families) as well as in the adjacent coastal waters (39 species belonging to 20 families). The polychaete species Diopatra neapolitana dominated during nonmonsoonal periods was found to be replaced by the higher abundance of Pisione sp. in the CE during the monsoon period. On the other hand, in the coastal waters, Cossura coasta, the dominant species during the pre-monsoon period, was replaced by the surface deposit feeder Paraprionospio pinnata during the monsoon and post-monsoon periods. The study evidenced the combined influence of sediment texture, salinity, and food availability in determining the distribution and abundance of the macrobenthic fauna in the CE and adjacent coastal waters. Feeding guild analysis and trophic importance index showed that carnivores and surface and subsurface deposit feeders were the dominant and trophically important feeding guilds in the study area. Redundancy analysis showed that the sandy substratum supported a diversified functional composition in the estuary and its adjacent coastal waters, and motile, discretely motile polychaetes and filter feeders were more associated with the sandy substratum. Results of the present study revealed that the seasonally fluctuating polychaete community structure in the study area was predominantly controlled by their diversified feeding habits and the ecological descriptors of the polychaete feeding guilds were linked primarily to the substratum type and food availability.

Phosphorous fractionation in mangrove sediments of Kerala, south west coast of India: the relative importance of inorganic and organic phosphorous fractions.

The study of phosphorous dynamics in mangrove ecosystems of the northern Kerala coast aims to delineate its relationships with other biogeochemical parameters. Our intension is to check the validity of the hypothesis that these mangrove ecosystems act as an efficient trap of organic phosphorous by acting as P sink. The dissolved inorganic phosphate displayed higher concentration in monsoon that could be correlated with higher P leaching from mangrove litter as well as terrigenous input during wet season. Fe(OOH)≈P was much higher in monsoon (235.23 to 557.70 µg g(-1)) and lower in pre-monsoon (36.50 to 154.97 µg g(-1)), and displayed significant contribution towards the inorganic sedimentary P fractions. In monsoon, adsorption of P on iron hydroxides is enhanced by fresh water conditions, but pre-monsoon is characterised by the reductive dissolution of iron oxy hydroxides and the subsequent efflux of P to water column. CaCO3≈Pinorg may be present as an inert fraction in the sediment matrix, and did not display any interrelationship with other geochemical parameters. The abundant total organic P (25 to 73 %) fractions, largely derived from P bound with humic/fulvic acid, played a major role in immobilising P and regulating its dynamics in the nearby estuarine and coastal environment.