posted on 2024-02-23, 04:29authored byVishal Kansay, Varun Dutt Sharma, Gourav Chandan, Vasu Srivastava, Neera Batra, Amit Mittal, Sasanka Chakrabarti, Milan Kumar Bera
A portable,
low-cost, efficient, disposable, and simple nanosensor
for point-of-care or on-site monitoring of vitamin B12 remains
a challenge for quality control in the food, beverage, and pharmaceutical
industries. A solid-state fluorescence nanosensor probe based on N-,
K-, and Ca-doped carbon quantum dots (CQDs) embedded in a bioplastic
nanocomposite for quantitative detection of vitamin B12 with good sensitivity and accuracy is demonstrated here. A wide
range of morphological, physiochemical, compositional, crystallinity,
and functional groups have been investigated. The pH-responsive, tunable
solid-state fluorescence properties of the N-, K-, and Ca-doped CQDs
at bioplastic nanocomposite probes are reported. For on-site monitoring
of vitamin B12, a dual response via fluorescence and colorimetric
change has been demonstrated using a smartphone camera to capture
images in RGB (red, green, and blue) format and simultaneously analyzed
by a customized Android app, with quantitative results displayed on
the smartphone. It was possible to determine a linear range of 0.1
mM to 10 nM with limits of detection and quantification of 916 (1241.19
pg/mL) and 3054 pM (4138.21 pg/mL), respectively. Without sample pretreatment
or matrix-interfering effects, this approach was effectively used
to evaluate vitamin B12 in commercial beverages and pharmaceutical
supplements. The performance parameters of the developed nanosensor
were validated using a standard reference approach utilizing the Pearson's
correlation study, which indicates a good positive correlation (Pearson's
coefficient, r = 0.96, p < 0.001)
between the two methods. Moreover, potential fluoresce quenching mechanisms
have been suggested. Besides, the disposable and biodegradable nature
of the nanosensor probe was studied by discarding it into the soil
in the natural environment, where it degraded spontaneously by 80–85%
within 2 weeks.