A natural fluorescent protein for ciprofloxacin sensing and mechanism study using molecular docking and circular dichroism.

Ciprofloxacin (CIP) is one of the common drug pollutants whose residues are often detected in the environment. In the current work, CIP was studied in aqueous environment based on a natural fluorescing compound called phycocyanin (PC). Using, a Spectro fluorophotometer, fluorescence detection of CIP was performed, and absorbance properties were studied using a UV-Visible spectrophotometer. In addition, a circular dichroism (CD) spectrophotometer and molecular docking analysis were implemented for further investigation. As the fluorometric measurement results showed, the fluorescence intensity of PC dropped linearly upon the addition of increasing amounts of CIP ranging from 0 to 120 µmol/L of final concentrations, with the limit of detection reaching down to 95 nM. In addition, the fluorescent sensor was found to be more selective towards CIP when tested against other six antibiotics and six pesticides. In the case of analysis of the PC-CIP interaction using a CD spectrophotometer the α-helix content of PC decreased in the presence of CIP, which is an indication of conformational changes in the secondary structure of PC. Moreover, the molecular docking analysis of the PC-CIP interaction assisted in locating the three sites where CIP binds with CIP, which in turn provided additional instances of the interaction mechanism between PC and CIP.

Ultrasensitive and selective detection of Hg2+ using fluorescent phycocyanin in an aqueous system.

Hg2+ toxicity is one of the most common chemical poisonings that occurs mainly from drinking polluted water. In the current work, Phycocyanin (PC) was exploited as a fluorescent sensor for sensitive and selective detection of Hg2+ in an aqueous system. PC-Hg2+ interaction was monitored using a spectro-fluorometer under different buffered solutions at pH values of 6,7,8,9, or 10 above the isoelectric point of PC (5.18). A remarkable decrease of PC fluorescence intensity was observed under Tris-buffer at pH 6 upon the addition of increasing Hg2+ concentrations (1-120 nM). Under the maintained experimental conditions, the current sensor showed a good linear relationship with R2 = 0.9971 and a limit of detection as low as 0.7 nM was achieved. In addition, a notable selectivity of Hg2+ over other nine heavy metals (Cu2+, Zn2+, Pb2+, Mg2+, Mn4+, Li+, Fe3+, Co2+, and Al3+) was achieved in the presence of 120 nM of each metal. Moreover, the current fluorescent detection assay was also tested in real samples of pond water, and recoveries as well as relative standard deviations within the acceptable limits were recorded.

Rapid and ultrasensitive detection of food contaminants using surface-enhanced Raman spectroscopy-based methods.

With the globalization of food and its complicated networking system, a wide range of food contaminants is introduced into the food system which may happen accidentally, intentionally, or naturally. This situation has made food safety a critical global concern nowadays and urged the need for effective technologies capable of dealing with the detection of food contaminants as efficiently as possible. Hence, Surface-enhanced Raman spectroscopy (SERS) has been taken as one of the primary choices for this case, due to its extremely high sensitivity, rapidity, and fingerprinting interpretation capabilities which account for its competency to detect a molecule up to a single level. Here in this paper, we present a comprehensive review of various SERS-based novel approaches applied for direct and indirect detection of single and multiple chemical and microbial contaminants in food, food products as well as water. The aim of this paper is to arouse the interest of researchers by addressing recent SERS-based, novel achievements and developments related to the investigation of hazardous chemical and microbial contaminants in edible foods and water. The target chemical and microbial contaminants are antibiotics, pesticides, food adulterants, Toxins, bacteria, and viruses. In this paper, different aspects of SERS-based reports have been addressed including synthesis and use of various forms of SERS nanostructures for the detection of a specific analyte, the coupling of SERS with other analytical tools such as chromatographic methods, combining analyte capture and recognition strategies such as molecularly imprinted polymers and aptasensor as well as using multivariate statistical analyses such as principal component analysis (PCA)to distinguish between results. In addition, we also report some strengths and limitations of SERS as well as future viewpoints concerning its application in food safety.