Saima Parveen

Highly sensitive fluorescent detection of trypsin based on BSA-stabilized gold nanoclusters

In this study, fluorescent metal nanoclusters are presented as novel probes for sensitive detection of protease for the first time. The sensing mechanism is based on trypsin digestion of the protein template of BSA-stabilized Au nanoclusters. The decrease in fluorescence intensity of BSA-Au nanoclusters caused by trypsin allows the sensitive detection of trypsin in the range of 0.01-100 μg/mL. The detection limit for trypsin is 2 ng/mL (86 pM) at a signal-to-noise ratio of 3. The present nanosensor for trypsin detection possesses red emission, excellent biocompatibility, high selectivity, and good stability. In addition, we demonstrated the application of the present approach in real urine samples, which suggested its potential for diagnostic purposes.

Oligonucleotide-stabilized fluorescent silver nanoclusters for turn-on detection of melamine.

Fluorescence nanoclusters have been used for the determination of melamine for the first time. The method is based on the fluorescence turn-on of oligonucleotide-stabilized silver nanoclusters (DNA-Ag NCs) by melamine. The enhancement factors (I-I(0))/I(0) increase linearly with melamine concentrations over the range 5.0×10(-8)-7.0×10(-6) M (R(2)=0.998). The detection limit is 1.0×10(-8) M, which is approximately 2000 times lower than the US Food and Drug Administration estimated melamine safety limit of 20.0 μM. Furthermore, the milk samples spiked with melamine are analyzed with excellent recoveries.

Immobilization of tris(1,10-phenanthroline)ruthenium with graphene oxide for electrochemiluminescent analysis

Electrochemiluminescence (ECL) of ruthenium complexes has broad applications and the immobilization of Ru(bpy)(3)(2+) has received extensive attention. In comparison with Ru(bpy)(3)(2+), Ru(phen)(3)(2+) can be immobilized more easily because of its better adsorbability. In this study, immobilization of Ru(phen)(3)(2+) for ECL analysis has been demonstrated for the first time by using graphene oxide (GO) as an immobilization matrix. The immobilization of Ru(phen)(3)(2+) is achieved easily by mixing Ru(phen)(3)(2+) with GO without using any ion exchange polymer or covalent method. The strong binding of Ru(phen)(3)(2+) with GO is attributed to both the π-π stacking interaction and the electrostatic interaction. The Ru(phen)(3)(2+)/GO modified electrode was characterized by using tripropylamine (TPA) as the coreactant. The linear range of TPA is from 3×10(-7) to 3×10(-2) mol L(-1) with the detection limit of 3×10(-7) mol L(-1). The ECL sensor demonstrates outstanding long-term stability. After the storage in the ambient environment for 90 days, the ECL response remains comparable with its original signal.

Vitamin C derivatives as new coreactants for tris(2,2'-bipyridine)ruthenium(II) electrochemiluminescence.

Vitamin C derivatives (VCDs) have been widely used as the alternative and stable sources of vitamin C, and accordingly exhibit many new applications, such as anti-tumor and central nervous system drug delivery. In this study, their Ru(bpy)(3)(2+) electrochemiluminescence (ECL) properties have been investigated for the first time using well-known ascorbyl phosphate and ascorbyl palmitate as representative VCDs. Ascorbyl phosphate and ascorbyl palmitate are VCDs with different substituted positions. Both of them increase Ru(bpy)(3)(2+) ECL, indicating that other VCDs may also enhance Ru(bpy)(3)(2+) ECL signal. The calibration plot for ascorbyl phosphate is linear from 3×10(-6) to 1.0×10(-3) M with a detection limit of 1.4×10(-6) M at a signal-to-noise ratio of 3. The relative standard deviation is 3.6% for six replicate measurements of 0.01mM ascorbyl 2-phosphate solution. The proposed method is about one order of magnitude more sensitive than electrochemical and UV-vis methods for the determination of ascorbyl phosphate, and is used successfully for the determination of ascorbyl phosphate in whitening and moisturising body wash.

Applications of Electrochemiluminescence

The development of electrochemiluminescence (ECL) applications is a growing field, having the potential advantages of ECL over conventional chemiluminescence. ECL has found various applications in immunoassays, DNA probe assays, and aptasensors by employing ECL-active species as labels on biological molecules. The recent use of ECL to detect many chemically, biochemically, clinically, and environmentally important analytes is reviewed.

Generation Pathways of Electrogenerated Chemiluminescence

ECL continues to be an area of active research. This chapter provides a brief way for understanding fundamentals of ECL. An overview of selected key ECL mechanisms for the production of ECL is given. Studies on finding new ECL co-reactants, disclosing the relationship between ECL efficiencies and structure of co-reactants, and improving ECL efficiencies are also discussed.

Coupling of ECL with Different Techniques

The perspectives and recent developments in the field of electrochemiluminescence (ECL) have grown exponentially in the last few decades. The state of the art of the developments, key strategies, and trends toward ECL detection coupled to capillary electrophoresis (CE), flow injection analysis (FIA), and solid phase microextraction (SPME) is described. New advances in homemade configurations, designs of ECL flow cells and probes, peculiarities of the operation of tandem systems using miniaturization (microchip/\( \upmu \)TAS) with detection by ECL are included. Due to its simplicity, low cost and high sensitivity and selectivity, ECL-based detection has become a quite useful detection tool in CE, FI, and SPME systems, making this technique an interesting field of research. Some emerging phenomena of ECL are discussed, such as light-emitting electrochemical swimmers.

Quenching of ECL

ECL quenching may play an important role in designing new methodologies for sensitive detection of analytes. Quenching proposes prospective advantages in the framework of ECL and has acquired considerable attention and is inextricably associated with the selectivity of luminophore and co-reactant. It can be used in diverse fields in the detection of many analytes, DNA detection, and hybridization, etc. Processes, reactions, and equations involving quenching are discussed as well.