Measuring vitamin B 12 in food usually means bringing the sample to the laboratory. A new fluorescent sensor could help move part of that process onto something much simpler: a paper strip or cotton swab. A new study published in Biomedical Analysis describes a fluorescence-based strategy for portable vitamin B 12 (VB 12 ) detection in food samples. Researchers at Liaocheng University developed boron- and nitrogen-co-doped carbon dots (B, N-CDs) that emit bright blue fluorescence under ultraviolet light but become markedly dimmer when VB 12 is present. By transferring this sensing chemistry from a liquid assay onto filter-paper strips and a specially designed cotton-swab sensor, the team created two simple formats intended to make the detection step faster, cheaper, and easier to use outside conventional instrument-heavy workflows.
Common methods for measuring VB 12 , including chromatography and electrochemical analysis, can require complex instruments, lengthy sample handling, or carefully controlled conditions. Many fluorescence probes also remain tied to laboratory spectrometers. To address these limitations, the researchers synthesized B, N-CDs through a one-step hydrothermal process and evaluated their response to VB 12 . The probe showed a linear fluorescence response from 0 to 100 μM and a detection limit of 0.02 μM. In selectivity tests, VB 12 produced pronounced fluorescence quenching, while other tested B vitamins, amino acids, glucose, and common small molecules caused little comparable response.
The B, N-CDs were prepared from 3-aminophenylboronic acid and p-hydroxybenzaldehyde and formed water-dispersible nanoparticles averaging about 1 nm in diameter. They showed their strongest fluorescence emission at 475 nm under 390 nm excitation, with a quantum yield of 18.15%. Mechanistic experiments indicated that VB 12 associates with the carbon dots to form a non-luminescent ground-state complex, leading to static fluorescence quenching. Fluorescence-lifetime, UV-visible absorption, Raman, FT-IR, XPS, particle-size, and surface-charge measurements all supported this interaction, helping explain why the probe's blue fluorescence decreases as VB 12 concentration rises.
To translate the sensing response into portable formats, the team impregnated filter paper with B, N-CDs and designed a cotton-swab device that delivers the fluorescent probe to a sensing region during use. Under 365 nm UV light, both formats became progressively darker as VB 12 concentration increased. For the paper strip, image-based analysis of the green-to-blue (G/B) intensity ratio showed a strong linear relationship with VB 12 from 0 to 80 μM (R² = 0.9927). The swab format was designed to combine sample collection, transfer, mixing, and signal readout in one disposable device, and the sensing step can be completed rapidly once a suitable sample is available. Both the strips and swabs retained useful fluorescence and VB 12 -sensing performance for at least 20 days under the storage condition evaluated.
The researchers tested the analytical method using egg-yolk and goat-liver-powder samples and compared quantitative measurements with high-performance liquid chromatography (HPLC). In spiked recovery experiments, recoveries ranged from 97.09% to 101.22%, and the measured VB 12 concentrations closely matched the HPLC results, supporting the method's accuracy in the food matrices studied.
The work shows how carbon-dot fluorescence can be adapted into visually readable portable sensors without sacrificing sensitivity or selectivity. The authors also outline practical next steps, including replacing the laboratory UV lamp with a compact battery-powered UV-LED and adding smartphone-based image analysis for automated quantification. The current real-food workflow still involves laboratory sample pretreatment before measurement, so further simplification will be important for truly field-ready testing.
DOI： 10.1016/j.bioana.2026.08.003
Read the full article: https://www.sciencedirect.com/science/article/pii/S2950435X26000284
Biomedical Analysis invites submissions for its 2026 Special Issue, “POCT Technology Innovation and Application.” The issue welcomes original research articles and reviews on innovative point-of-care testing (POCT) technologies, materials and device development, multi-scenario applications, and intelligent and digital POCT.
The submission deadline is December 31, 2026 . Please refer to the Guide for Authors to prepare your manuscript and select the article type “VSI: POCT Technology Innovation and Application” when submitting your manuscript online.
Submit your manuscript at: https://www2.cloud.editorialmanager.com/bioana/default2.aspx
Biomedical Analysis is an international, peer-reviewed, open access journal published by Elsevier and KeAi and jointly sponsored by Sun Yat-sen University and the Guangzhou Analysis and Testing Center.
The journal publishes high-quality research in biomedical engineering, bioanalytical chemistry, biochemistry, genetics, biology, biomaterials, medicine, and related interdisciplinary fields, with a particular focus on biomedical testing, sensing technologies, and analytical innovation. Biomedical Analysis is indexed in Scopus, CAS, DOAJ, and EBSCO. Article processing charges (APCs) are currently waived for accepted manuscripts through the end of 2026.
Journal website: https://www.sciencedirect.com/journal/biomedical-analysis .
Biomedical Analysis
Experimental study
Not applicable
Portable detection of vitamin B12 using fluorescence quenching method of boron and nitrogen co-doped carbon dots
10-Sep-2026
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.