Nuclear fast red-based colorimetric sensors for sensitive and selective detection of Ag ions.

The reduction of nuclear fast red (NFR) stain by sodium tetrahydroboron was catalyzed in the presence of silver ions (Ag+ ). The fluorescence properties of reduced NFR differed from that of NFR. The product showed fluorescence emission at 480 nm with excitation at 369 nm. Furthermore, the fluorescence intensity of the mixture increased strongly in the presence of Ag+ and Britton-Robinson buffer at pH 4.78. There was a good linear relationship between increased fluorescence intensity (ΔI) and Ag+ concentration in the range 5.0 × 10-9 to 5.0 × 10-8  M. The correlation coefficient was 0.998, and the detection limit (3σ/k) was 1.5 × 10-9  M. The colour of the reaction system changed with variation in Ag+ concentration over a wide range. Based on the colour change, a visual semiquantitative detection method for recognition and sensing of Ag+ was developed for the range 1.0 × 10-8  to 5.0 × 10-4  M, with an indicator that was visible to the naked eye. Therefore, a sensitive, simple method for determination of Ag+ was developed. Optimum conditions for Ag+ detection, the effect of other ions and the analytical application of Ag+ detection of synthesized sample were investigated.

Evaluation of efficacy of 1% Crystal Violet & Nuclear Fast Red stain compared to Haematoxyline & Eosin stain for assessing mitotic figures in oral premalignant and malignant lesions.

Various chromosomal arrangements in cells undergoing division are referred to as Mitotic figure (MF). The abnormal excess of mitotic figures is commonly seen in oral epithelial dysplasia (ED) and oral squamous cell carcinoma (OSCC). In present study, we compared the number of mitotic figures in normal oral mucosa, epithelial dysplasia & OSCC sections with haematoxyline & eosine (H&E) and 1%Crystal Violet & Nuclear Fast Red (CV&NFR) stain, also the efficacy of the CV&NFR stain as compared to H & E stain. We investigated the correlation between the number of mitotic figures & grades of OSCC. Study sample comprised of two serial sections of archival blocks of normal oral mucosa & diagnosed cases of epithelial dysplasia & OSCC. One slide stained with H& E & the other one with 1% CV & NFR. Mitotic figures were counted with the grid eyepiece. There was significant increase in number of MFs in oral ED and OSCC in comparison with normal oral mucosa. There was a highly significant increase in number of MFs in CV&NFR stained tissue sections when compared with H & E stain. Metaphase is the most commonly observed phase of mitosis. In summary, our study proposes the use of Crystal violet & Nuclear fast red stain as a selective stain for better contrast & easy identification MFs.

Nuclear fast red as highly sensitive "off/on" fluorescent probe for detecting guanine.

A novel fluorescence method for the determination of guanine was developed based on the fluorescence enhancement of Cu(2+)-nuclear fast red complex in the presence of guanine in Tris-HCl buffer. The complex of Cu(2+) with nuclear fast red resulted in a dramatic quenching of the fluorescence intensity. Nuclear fast red were dissociated from the complex with the addition of guanine due to the strong interaction between guanine and Cu(2+), which caused the fluorescence enhancement. The enhanced fluorescence intensity was well proportional to the concentration of guanine in the range of 4.96 × 10(-8)-1.09 × 10(-6)mol/L with the limit of detection 1.9 × 10(-8)mol/L. The method has been applied successfully to the determination of guanine in serum and DNA samples, and the recoveries were from 96.0% to 104.8%.

Investigation of interaction of nuclear fast red with human serum albumin by experimental and computational approaches.

For the first time, interaction of nuclear fast red (NFR) with human serum albumin (HSA) was studied by experimental and computational approaches. Firstly, experimental measurements including fluorescence spectroscopy (F), UVvis spectrophotometry (UVvis), cyclic voltammetry (CV), differential pulse voltammetry (DPV) and linear sweep voltammetry (LSV) were separately used to investigate the interaction of NFR with HSA and interesting thermodynamics information was obtained from these studies. Secondly, new information including electrochemical behavior of NFR-HSA complex species, relative concentrations of the various reacting species and effects of NFR on the sub-structure of HSA was obtained by applying multivariate curve resolution-alternating least squares (MCR-ALS). In this case, a row- and column-wise augmented matrix was built with DPV, LSV, F and UVvis sub-matrices and resolved by MCR-ALS. Surprisingly, by this method two NFR-HSA complex species with different stoichiometries and different electrochemical behaviors were found. Furthermore, by the use of the recorded voltammetric and spectroscopic data the binding constants of complex species were computed by EQUISPEC (a hard-modeling algorithm). Finally, the binding of NFR to HSA was modeled by molecular modeling and molecular dynamics (MD) simulations methods. Excellent agreement was found between experimental and computational results. Both experimental and computational results suggested that the NFR binds mainly to the sub-domain IIA of HSA.