A cellulose-based colour test-strip for equipment-free drug detection on-site: application to sulfadiazine in aquatic environment

Abstract

This work develops a simple and innovative test-strip to monitor antibiotics in aquaculture facilities by an equipment-free approach. It consists of a low-cost disposable cellulose paper that was chemically modified to produce a colour change when in contact with a given antibiotic. In brief, the cellulose substrate was subject to oxidation with periodate, followed by amination with chitosan binding and modification with Cu(II). The test strip was then dipped in the target solution and the intensity of the colour generated therein revealed the concentration of antibiotic present for concentrations higher than 0.5 mM. The higher the concentration in sulfadiazine (SDZ), the more intense the pink colour formed in the final solution, which was also turbid due to the insolubility of the formed product. This colour intensity also varied linearly with the logarithm of the SDZ concentration (from 0.5 to 5 mM), when plotted against the sum of the RGB coordinates extracted from digital pictures. The linear equation of this response was represented by (R + G + B) = − 256.1 log(SDZ, mol/L) − 362.0, with an R-squared of 0.9913. The test-strip was stable for at least 15 days and was selective in the presence of tetracycline and difloxacin, while the response to other members of the sulfadiazine family requires prior evaluation. Overall, the test-strips developed herein are inexpensive and provide valuable (semi-) quantitative data for monitoring SDZ in waters, a most valuable approach to control and reduce the level of antibiotics in fish tanks, which in turn may reduce the costs of fish production and the environmental concerns linked to this practice. Moreover, the test strip uses a cellulose substrate that has little environmental impact upon discard.

Paper-Based Biosensors for COVID-19: A Review of Innovative Tools for Controlling the Pandemic

“…Generally, this includes reagents that react with a given compound or group of compounds, 26 metal nanoparticles (NPs) with catalytic or plasmonic features 27 , 28 or selective biorecognition elements that capture a wide range of target analytes, 29 − 31 including disease diagnosis. 32 − 35 These events may be translated by monitoring alterations in optical features, 36 which may involve changes in maximum wavelength reflection/absorption 37 or the enhanced Raman-scattering properties. 38 , 39 Translation by electrochemical properties has also been achieved 40 − 42 by having conductive inks casted on a cellulose substrate 43 or by hand-painting these inks 44 , 45 or using a printer for the same purpose.…”

“…There are many approaches that have been developed in time to achieve a successful biosensor on cellulose-based substrates, − including cellulose of bacterial origin, much before COVID-19, and they consist of immobilizing specific reagents on these substrates. Generally, this includes reagents that react with a given compound or group of compounds, metal nanoparticles (NPs) with catalytic or plasmonic features , or selective biorecognition elements that capture a wide range of target analytes, − including disease diagnosis. − These events may be translated by monitoring alterations in optical features, which may involve changes in maximum wavelength reflection/absorption or the enhanced Raman-scattering properties. , Translation by electrochemical properties has also been achieved − by having conductive inks casted on a cellulose substrate or by hand-painting these inks , or using a printer for the same purpose . Although the most well-known cellulose-based PoC approaches are lateral-flow methods, , with a well-known mode of operation that may be translated by naked-eye, optical, or electrochemical detectors.…”