NANOMATERIALS FOR BIOSENSING AND MITIGATION OF XENOBIOTICS

Abstract

Economically Motivated Adulteration (EMA) of milk and infant milk formula by hazardous chemicals like urea, detergent, and melamine has increased recently. Since milk and milk products are consumed by infants, adults and the geriatric population alike, such adulterations need to be tackled on priority. In the present study, we report a novel approach to detect anionic detergents (ADs) in milk by exploiting the optical and spectral properties of gold nanoparticles (AuNPs). The developed method is specific for AD detection and is free from the interference of other adulterants. The limit of detection for ADs like sodium dodecylbenzene sulfonate (SDBS) and commercial ADs in milk was 23 and 92 μg/ml, respectively. This method overcomes the complex sample preparation steps and is free from the use of harmful organic solvents. Urea is another major adulterant frequently used in fraudulent practices followed in the dairy industry. Urea is added in synthetic milk to enhance the nitrogen content in the milk, which gives a false measurement of protein content in synthetic milk. An Excess amount of urea intake poses severe health issues in pregnant women and infants. Urea can cause adverse effects, such as cancer, ulcers, renal failure, etc. Hence, there is a strong need to detect these hazardous adulterant milk. We modified an application of a portable spectrophotometer for the quantitative detection of urea and detergents on the mobile phone interface. This present study describes the application Prism plus, which was developed explicitly for portable phone technology and tested successfully for detecting SDBS, CAD and urea in milk samples. Furthermore, in context to the application of our developed method for rural parts of India, we designed a low cost, hand-powered CDfuge for processing milk samples. As commercial centrifuges are bulky, expensive and electricity-driven, the developed CDfuge opens up opportunities for its wide application at the field level, local diaries and unorganized dairy sector for the detection of an adulterant. Contamination of xenobiotics such as pesticides and detergents in water bodies is increasing and threatening the safety and health of human beings. The enhanced quality and effectiveness of nanomaterials make them more suitable for bioremediation as these materials possess high surface-area-to-volume ratio, lower toxicity, and can entrap microbes that can degrade toxic chemicals. To address this problem, we used adapted laboratory evolution (ALE) method for evolving the degradation ability of a proven pesticide degrading strain (Pseudomonas aeruginosa RPT-52). The strain was acclimatized for 3 months on 1) minimal medium (MM) containing endosulfan (α+β) and tween-80 and 2) MM containing endosulfan (α+β) and Sodium dodecylbenzene sulfonate (SDBS), as sole carbon and energy source. The acclimatized strain was entrapped in a unique hydrogel-based sandwich matrix made up of activated charcoal nanofibers (ACNFs), which was both selective and sensitive in capturing and degrading endosulfan and detergents. Applied voltage, flow rate, and tip–collector distance during electro-spinning were found critical for the development of nanofibers of ACNFs. Electro-spinning experiments performed at 13-14 kV with a flow rate of 0.5 mL/h and a distance of 15 cm from the collector were found to optimum conditions for the synthesis of nanofibers. SEM cross-section showed ACNFs with non-uniform distribution of fibers with a distance of <1μm between adjacent nanofibers strands. Space between the fibers obtained after electro-spinning significantly lowered the degree of leakage of Pseudomonas RPT-52 from the hydrogel-ACNFs sandwich matrix. Degradation studies using high-performance liquid chromatography revealed 32.81% and 38.2% of endosulfan-α in the presence of tween-80 and SDBS, respectively; 29.1% and 41.1% endosulfan-β was degraded in the presence of tween-80 and SDBS, respectively. These advances enable our developed nanofibers hydrogel-based system to be used for biosensing and mitigation of pesticides and detergents.