Enhanced DNA detection using a multiple pulse pumping scheme with time-gating (MPPTG).

Fluorescence signal enhancement induced by the binding of intercalators to DNA has been broadly utilized in various DNA detection methods. In most instances the increase in fluorescence intensity is associated with a concomitant increase of fluorescence lifetime. This increase of the fluorescence lifetime presents an additional opportunity to increase detection sensitivity. In this paper, we present a new approach to significantly enhance the sensitivity in detecting minute DNA concentrations. The approach is based on simultaneous use of time-gated detection and multi-pulse pumping. By using a calibrated burst of short pulses we greatly enhance the contribution of long-lived fluorescence species, thus enabling easy time-gated detection. Using a classic DNA intercalator - Ethidium Bromide (EtBr) - as an example with our novel multi-pulse pumping and time-gated detection technique, we were able to increase detection sensitivity over 70-fold with only 3 pulse excitation. This approach is generic and can be used with any analytical probe (exhibiting about 10 times change in lifetime) that shows an increase in fluorescence signal and fluorescence lifetime upon binding to a target.

Mechanothermally induced conformational switch of a porphyrin dimer in a polymer film.

Stretching a polymer film induces a conformational change (from the twisted to planar state) in the embedded porphyrin dimer, as evidenced by steady-state and time-resolved emission spectra.

A triazine-based BODIPY trimer as a molecular viscometer.

Photophysical behaviour of a novel trimeric BODIPY rotor with a high extinction coefficient is reported. Steady state and time resolved fluorescence measurements established that the trimer could be used as a viscometer for molecular solvents, membrane-like environments and several cancer cell lines.

Sandwich type plasmonic platform for MEF using silver fractals.

In this report, we describe a plasmonic platform with silver fractals for metal enhanced fluorescence (MEF) measurements. When a dye containing surface was brought into contact with silver fractals, a significantly enhanced fluorescence signal from the dye was observed. Fluorescence enhancement was studied with the N-methyl-azadioxatriangulenium chloride salt (Me-ADOTA·Cl) in PVA films made from 0.2% PVA (w/v) solution spin-coated on a clean glass coverslip. The Plasmonic Platforms (PP) were assembled by pressing together silver fractals on one glass slide and a separate glass coverslip spin-coated with a uniform Me-ADOTA·Cl in PVA film. In addition, we also tested ADOTA labeled human serum albumin (HSA) deposited on a glass slide for potential PP bioassay applications. Using the new PP, we could achieve more than a 20-fold fluorescence enhancement (bright spots) accompanied by a decrease in the fluorescence lifetime. The experimental results were used to calculate the extinction (excitation) enhancement factor (GA) and fluorescence radiative rate enhancements factor (GF). No change in emission spectrum was observed for a dye with or without contact with fractals. Our studies indicate that this type of PP can be a convenient approach for constructing assays utilizing metal enhanced fluorescence (MEF) without the need for depositing the material directly on metal structures platforms.

BSA Au clusters as a probe for enhanced fluorescence detection using multipulse excitation scheme.

Although BSA Au clusters fluoresce in red region (λmax: 650 nm), they are of limited use due to low fluorescence quantum yield (~6%). Here we report an enhanced fluorescence imaging application of fluorescent bio-nano probe BSA Au clusters using multipulse excitation scheme. Multipulse excitation takes advantage of long fluorescence lifetime (> 1 µs) of BSA Au clusters and enhances its fluorescence intensity 15 times over short lived cellular auto-fluorescence. Moreover we have also shown that by using time gated detection strategy signal (fluorescence of BSA Au clusters) to noise (auto-fluorescence) ratio can be increased by 30 fold. Thereby with multipulse excitation long lifetime probes can be used to develop biochemical assays and perform optical imaging with zero background.

Two Photon Induced Luminescence of BSA Protected Gold Clusters.

In this short letter, we have synthesized the BSA protected Au25 nanoclusters and studied their two photon luminescence behavior. We demonstrate that BSA Au25 nanoclusters can be used as a probe with two photon excitation capability. Our results show a quadratic relation between excitation power and emission intensity whereas with one photon excitation shows a linear dependence. The emission spectrum of BSA Au25 nanoclusters with one photon and two photon excitation shows no appreciable change. Due to its long wavelength emission (650 nm) and two photon excitation, BSA Au25 can be potentially used as a probe for deep tissue imaging.

Alendronate coated poly-lactic-co-glycolic acid (PLGA) nanoparticles for active targeting of metastatic breast cancer.

Delivery of therapeutic agents to bone is crucial in several diseases such as osteoporosis, Paget's disease, myeloproliferative diseases, multiple myeloma as well as skeletal metastasizing cancers. Prevention of cancer growth and lowering the cancer induced bone resorption is important in the treatment of bone metastasizing cancers. Keeping in mind the low diffusivity and availability of cell surface targets on cancer cells, we designed a targeted system to deliver chemotherapeutic agents to the bone microenvironment as an approach to tissue targeting using alendronate (Aln). We co-encapsulated curcumin and bortezomib in the PLGA nanoparticles to further enhance the therapeutic efficiency and overall clinical outcome. These multifunctional nanoparticles were characterized for particle size, morphology and drug encapsulation. The particles were spherical with smooth surface and had particle size of 235 ± 70.30 nm. We validated the bone targeting ability of these nanoparticles in vitro. Curcumin and bortezomib are known to have synergistic effect in inhibition of growth of cancer; however there was no synergism in the anti-osteoclastogenic activity of these agents. Surprisingly, curcumin by itself had significant inhibition of osteclastogenic activity. In vivo non-invasive bioimaging showed higher localization of Aln-coated nanoparticles to the bone compared to control groups, which was further confirmed by histological analysis. Aln-coated nanoparticles protected bone resorption and decreased the rate of tumor growth as compared to control groups in an intraosseous model of bone metastasis. Our data show efficient attachment of Aln on the surface of nanoparticles which could be used as a drug carrier for preferential delivery of multiple therapeutic agents to bone microenvironment.