This proof-of-concept study proposes a novel sensing mechanism for selective and label-free detection of 2,4,6-trinitrotoluene (TNT). It is realized by surface chemistry functionalization of silica nanoparticles (NPs) with 3-aminopropyl-triethoxysilane (APTES). The primary amine anchored to the surface of the silica nanoparticles (SiO2-NH2) acts as a capturing probe for TNT target binding to form Meisenheimer amine–TNT complexes. A colorimetric change of the self-assembled (SAM) NP samples from the initial green of a SiO2-NH2 nanoparticle film towards red was observed after successful attachment of TNT, which was confirmed as a result of the increased separation between the nanoparticles. The shift in the peak wavelength of the reflected light normal to the film surface and the associated change of the peak width were measured, and a merit function taking into account their combined effect was proposed for the detection of TNT concentrations from 10−12 to 10−4 molar. The selectivity of our sensing approach is confirmed by using TNT-bound nanoparticles incubated in AptamerX, with 2,4-dinitrotoluene (DNT) and toluene used as control and baseline, respectively. Our results show the repeatable systematic color change with the TNT concentration and the possibility to develop a robust, easy-to-use, and low-cost TNT detection method for performing a sensitive, reliable, and semi-quantitative detection in a wide detection range.
This work focuses on the development of optical sensors based on the LSPR phenomenon in nano-structured gold films suitable for detection of mycotoxins. A simple technology of annealing thin gold films was utilized for the formation of gold nano-islands exhibiting the LSPR effect. The morphology of gold nano-structures produced was studied with SEM and AFM while their optical properties were analysed with UV-vis absorption spectroscopy and spectroscopic ellipsometry (SE). A blue spectral shift of LSPR band caused by changes in the refractive index of medium constitutes the main principle of LSPR sensing. Bio-sensing tests were attempted using SE in total internal reflection mode (TIRE); a noticeable spectral shift was recorded on course of immune binding of aflatoxin B1 to specific antibodies immobilized on the surface of gold.
Detection of tiny quantities of nucleic acids, protein biomarkers and small organic molecules directly in complex matrices is of key relevance both in biomedical and in environmental fields. Moreover direct quantification of clinically relevant molecules (such as miRNA, DNA or proteins) in plasma is difficult due to its heterogeneous composition and the low amounts of target molecules. As for environmental pollutants (i.e. Aflatoxins), the direct detection is also hampered by the complexity of liquid samples (milk, wine, waste waters) lowering the sensitivities and requiring several steps of targets isolation and purification. Here we present our material platform based on microgels and hydrogel microparticles featuring high flexibility in performing detection and harvesting of different kind of targets in complex solutions.
This paper presents an LOC system combining microfluidic DEP channel with a CMOS image sensor for label and lens free detection and real-time counting of MCF-7 cells under continuous flow. Trapped and then released MCF-7 cells are accurately detected and counted under flow with a CMOS image sensor integrated underneath the DEP channel, for the first time in the literature. CMOS image sensor can capture 391 frames per second (fps) that allows detection of the released cells flowing through the channel with a flow rate up to 130 μl/min (0.468 m/s). Therefore, the proposed system is able to detect the cells under high flow where conventional techniques for cell quantification such as fluorescent tagging become unusable. Detected cells are automatically counted with a computer program and the counting accuracy of the whole system is 95%.
Okadaic acid (OA) is a representative diarrhetic shellfish poisoning toxin which is highly toxic and carcinogenic to human, and rich in polluted shellfish. In this work, a novel and high sensitive fluorescence immunosensor based on magnetic beads (MBs) and quantum dots (QDs) had been developed for OA detection. Carboxylic acid modified MBs were used as supporter to immobilize the OA-BSA, competed with the OA in the sample solution to bind with the anti-OA monoclonal antibody (OA-MAb). The CdTe QDs (EX600 nm) labeled IgG was served as secondary antibody to perform fluorescence detection. A portable flow cytometry, Moxi Flow was applied for OA on-site quantification. The results showed that the OA concentration was inversely proportional to the QDs fluorescence intensity. The limit of detection (LOD) was 0.05 μg/L with a linear range of 0.2–20 μg/L for OA detection, which was far lower than traditional id-ELISA strategy. Moreover, OA detection for the real sample could be completed within 1 hour. The matrix effect and the recovery rate were also assessed during real sample measurement, showing a high recovery.
