Label-Free Detection of Escherichia coli from Mixed Bacterial Cultures Using Bacteriophage T4 on Plasmonic Fiber-Optic Sensor.

Consumption of water contaminated with pathogenic bacteria is a major cause of water-borne diseases. To address this challenge, we have developed a novel and sensitive sensing scheme for the rapid detection of bacteria (Escherichia coliB40) on a fiber-optic platform using bacteriophage (T4) as a bio-recognition element. The novelty of our sensing scheme is that instead of bacteriophages, bacteria (analyte) were first captured on the sensing surface and then the sensing surface was subjected to bacteriophages for specific detection of bacteria. The sensor was subjected to 100 to 107 cfu/mL of E. coliB40 spiked in a lake water matrix, and the least concentration of bacteria that could be easily detected was found to be 1000 cfu/mL. The control studies were performed with nonhost bacteria Pseudomonas aeruginosa. Bacteriophage T4, being specific to its host E. coliB40, did not interact with P. aeruginosa captured on the sensing probe, giving a negligible nonspecific response. Due to the specificity of bacteriophages to its host bacteria, it is possible to use this scheme to carry out the detection of specific bacteria in a mixed sample (containing a combination of bacteria) using bacteriophages specific to it. The sensor was able to detect E. coliB40 (target bacteria) even in the presence of a very high concentration (1000 times higher) of P. aeruginosa (nontarget bacteria).

Dendrimer as a multifunctional capping agent for metal nanoparticles for use in bioimaging, drug delivery and sensor applications.

Advances in nanoparticle research, particularly in the domain of surface-engineered, function-oriented nanoparticles, have had a profound effect in many areas of scientific research and aided in bringing unprecedented developments forward, particularly in the biomedical field. Surface modifiers/capping agents have a direct bearing on the major properties of metal nanoparticles (MNPs), ranging from their physico-chemical properties to their stability and functional applications. Among the different classes of capping agents, dendrimers have gained traction as effective multifunctional capping agents for MNPs due to their unique structural qualities, dendritic effect and polydentate nature. Dendrimer-coated metal nanoparticles (DC-MNPs) are typically produced by both (i) a one-pot strategy, where metal ions are reduced in the presence of dendrimer molecules and (ii) a multi-pot strategy, where a sequence of reactions involving the reduction of metal ions, activation, conjugation and purification steps are involved. These DC-MNPs have shown remarkable ability to stabilize MNPs by means of electrostatic interactions, coordination chemistry or covalent attachment, due to them entailing a large number of sites at which further molecular moieties can be conjugated. This review article is an attempt to consolidate the on-going work, particularly over the last five years, in the field of the synthesis of dendrimer-coated MNPs and their potential applications in bioimaging, drug delivery and biochemical sensors.