Rapid (FLASH-FLIM) imaging of protoporphyrin IX in a lipid mixture using a CMOS based widefield fluorescence lifetime imaging camera in real time for margin demarcation applications.

The fluorescence from protoporphyrin IX (PpIX) has been employed to characterise cellular activity and assist in the visualisation of tumour cells. Its formation can be induced by 5-aminolevulonic acid (5-ALA) which is metabolised by tumour cells to form PpIX. The PpIX is localised within the cells, rather than spreading into the vascular system.

Phenolic content and potential bioactivity of apple juice as affected by thermal and ultrasound pasteurization.

Thermal (T) and ultrasound (US) pasteurization processes were applied to apple juice and the phenolic compounds (TPC) were quantified before and after in vitro digestion by HPLC-DAD-ESI-MS, with their bioaccessibility ascertained. Digested samples were analysed for their inhibitory capacity against α-glucosidase. Since some of the compounds exhibit fluorescence, both steady state and time-resolved fluorescence methods were used to investigate the binding to a blood transport protein, human serum albumin (HSA).

Binding of Clitoria ternatea L. flower extract with α-amylase simultaneously monitored at two wavelengths using a photon streaming time-resolved fluorescence approach.

The binding of an extract from the flowers of Clitoria ternatea L. to the digestive enzyme α-amylase was investigated. This extract is a mixture of flavonoids, including anthocyanins, and has been previously shown to inhibit the activity this enzyme.

Time-resolved fluorescence observation of di-tyrosine formation in horseradish peroxidase upon ultrasound treatment leading to enzyme inactivation.

The application of ultrasound to a solution can induce cavitional phenomena and generate high localised temperatures and pressures. These are dependent of the frequency used and have enabled ultrasound application in areas such as synthetic, green and food chemistry. High frequency (100kHz to 1MHz) in particular is promising in food chemistry as a means to inactivate enzymes, replacing the need to use periods of high temperature.

Use of Lanthanide-Containing Polyoxometalates to Sensitise the Emission of Fluorescent Labelled Serum Albumin.

Monitoring the interaction of biomolecules is important, and the use of energy transfer is a principal technique in elucidating nanoscale interactions. Lanthanide compounds are promising luminescent probes for biological samples as their emission is longer-lived than any native autofluorescence. Polyoxometalates (POMs) are interesting structural motifs to incorporate lanthanides, offering low toxicity and a size pertinent for biological applications.

Use of time-resolved spectroscopy as a method to monitor carotenoids present in tomato extract obtained using ultrasound treatment.

Introduction: Compounds exhibiting antioxidant activity have received much interest in the food industry because of their potential health benefits. Carotenoids such as lycopene, which in the human diet mainly derives from tomatoes (Solanum lycopersicum), have attracted much attention in this aspect and the study of their extraction, processing and storage procedures is of importance. Optical techniques potentially offer advantageous non-invasive and specific methods to monitor them.

Use of Time-Resolved Fluorescence to Monitor Bioactive Compounds in Plant Based Foodstuffs.

The study of compounds that exhibit antioxidant activity has recently received much interest in the food industry because of their potential health benefits. Most of these compounds are plant based, such as polyphenolics and carotenoids, and there is a need to monitor them from the field through processing and into the body. Ideally, a monitoring technique should be non-invasive with the potential for remote capabilities.

Influence of cooking on the levels of bioactive compounds in Purple Majesty potato observed via chemical and spectroscopic means.

Tubers rich in phytochemicals can exhibit a potential health benefit. This work aims at studying the relative effect of different domestic cooking techniques by monitoring the level of total phenolic compounds (TP), total anthocyanins (TA) and anti-oxidant activity (AOA) on a variety of pigmented potatoes. Raw purple potatoes are a good source of anthocyanins (219 mg/kg FW) and the level of these compounds increased using different cooking techniques, with the exception of baking.

Pre-denaturing transitions in human serum albumin probed using time-resolved phosphorescence.

The investigation of protein dynamics has long been of interest, since protein interactions and functions can be determined by their structure and changes in conformation. Although fluorescence, occurring on the nanosecond timescale, from intrinsic fluorescent amino acids has been extensively used, in order to fully access conformational changes longer timescales are required. Phosphorescence enables processes on the microsecond to second timescale to be accessed.

Viability of Saccharomyces cerevisiae incorporated within silica and polysaccharide hosts monitored via time-resolved fluorescence.

The viability of Saccharomyces cerevisiae in biocompatible polymers under different growth conditions and studied using time-resolved fluorescence techniques is presented. Two fluorophores, the viscosity sensitive probe 4-(4-(dimethylamino)styryl)-N-methyl-pyridiniumiodine (DASPMI) and the yeast viability stain 2-chloro-4-(2,3-dihydro-3-methyl-(benzo-1,3-thiazol-2-yl)-methylidene)-1-phenylquinolinium iodide (FUN-1) are used to elucidate information on the incorporated yeast cell viability. Variations in cell viscosity, which are indicative of the cell state, were obtained using DASPMI.

The binding of Curcuma longa extract with bovine serum albumin monitored via time-resolved fluorescence.

Turmeric (Curcuma longa L.) is obtained from the rhizome of the Zingberaceae family and has a long history as an ingredient in cooking. It has been used as a dye and recently research has concentrated on its possible health benefits, specifically because of its antioxidant activity.

Acridinyl methyl esters as photoactive precursors in the release of neurotransmitter amino acids.

An investigation of the use of an azaheterocycle, acridine, as an alternative photochemically removable protecting group for the carboxylic function of neurotransmitter amino acids was carried out. 9-Bromomethylacridine was used in the reaction with glycine, alanine, glutamic acid, β-alanine and γ-aminobutyric acid, to obtain model ester derivatives, which were irradiated at different wavelengths in a photochemical reactor. The process was followed by HPLC/UV, resulting in the release of the active molecule in short irradiation times.

The influence of silver nanostructures formed in situ in silica sol-gel derived films on the rate of Förster resonance energy transfer.

The efficiency of Förster resonance energy transfer (FRET) can be enhanced in the presence of a metal. Herein, we demonstrate the increased efficiency for a novel model sensor system where FRET is shown to occur between Rhodamine 6G in the bulk sol-gel matrix and Texas Red, which is held a fixed distance away by covalent attachment onto a silane spacer. Silver colloids are formed using light to initiate the reduction of a silver salt, which can be achieved at controlled locations within the film.

In situ formation of silver nanostructures produced via laser irradiation within sol-gel derived films and their interaction with a fluorescence tagged protein.

The presence of a conducting metal surface is known to affect the emission of a fluorophore in its proximity. This can lead to an enhancement in its fluorescence intensity along with a decrease in the fluorescence lifetime. This phenomenon, sometimes known as metal enhanced fluorescence, has implications in the area of sensing and "lab on a chip" applications.

The photophysics of europium and terbium polyoxometalates and their interaction with serum albumin: a time-resolved luminescence study.

Polyoxometalates (POMs) are emerging as useful materials for a variety of applications. Many show potential for use in the biological and medical fields. Those incorporating lanthanides, with their narrow emission bands, large Stokes' shift and tuneable emission are of particular interest for the labelling and imaging of biological molecules.

Monitoring sol-to-gel transitions via fluorescence lifetime determination using viscosity sensitive fluorescent probes.

The sol-to-gel transition was monitored via the use of time-resolved recording of the fluorescence emission of viscosity-sensitive probes. Two dyes were chosen for the study, water-soluble DASPMI and a hydrophobic BODIPY, and steady-state, time-resolved and time-tagged fluorescence measurements were performed. These techniques, coupled with the probes different solubility, allowed complementary fluorescence lifetime and intensity data to be obtained from the dyes introduced into the matrix-forming mixture to produce sol-gel derived monoliths.

Probing local effects in silica sol-gel media by fluorescence spectroscopy of p-DASPMI.

Stillbazolium salts present remarkable potential for application in several scientific areas. Their versatile behavior is explained by invoking the "twisted intramolecular charge-transfer" (TICT) mechanism, a model that describes the multiple fluorescence of DASPMI (4-(4-(dimethylamino)styryl)- N-methylpyridiniumiodine). One feature of their behavior is the sensitivity of the fluorescence lifetime to viscosity, thus identifying them as suitable probes for microheterogeneous systems, such as cells and sol-gel derived media.

Luminescence enhancement of a europium containing polyoxometalate on interaction with bovine serum albumin.

Polyoxometalates (POMs) are useful in a wide range of biological applications, whilst rare-earth based POMs provide a potentially new biological optical label. As the luminescence of rare-earth materials is known to be sensitive to the environment, we report on investigations into the photophysics of a rare-earth (europium) POM with the protein bovine serum albumin (BSA). Via the use of luminescence anisotropy and time-resolved measurements the europium decatungstate was found to interact with BSA, which was accompanied by an observed enhancement in its luminescence.

Nile red synchronous scan fluorescence spectroscopy to follow matrix modification in sol-gel derived media and its effect on the peroxidase activity of cytochrome c.

The highly solvatochromic dye Nile red is used in conjunction with synchronous scan fluorescence spectroscopy to elucidate changes in the internal environment of cytochrome c, upon incorporation into differently modified sol-gel derived media. Nile red was first studied in a variety of solvents in order to quantify changes in polarity. Matrix modifications involved the addition of several silanes, intended to interact with any unreacted hydroxyl entities left from the matrix forming reaction, while polymers were used to help reduce shrinkage and modify the internal pore environment.

Effect of polymer strengtheners on the local environment of biocompatible glass as probed by fluorescence.

Mixed silica-calcite matrices were prepared by developing a "low" temperature (sol-gel) method in presence of several biocompatible polymers, thus providing samples with adequate porosity for the flow of biological fluids and also mechanically robust. In order to analyse and characterise the sample's microenvironments, the highly solvatochromic probe Nile red was used, which enabled the role of polymer addition upon local environmental effects in the host media to be elucidated. The polymers used were polyethylene glycol, polymethylmethacrylate and polyethylene.

Optical spectroscopy following the incorporation of a rare-earth containing (Eu) polyoxometalate into a sol-gel derived media.

Polyoxometalates (POMs) are an emerging class of materials which can be considered as inorganic complexes with distinct structural and optical characteristics. To be suitable in biomedical applications such as imaging, the materials may need to be embedded in a suitable host material, which may affect the optical properties of the emitting polyoxometalate. Here, we demonstrate that POMs can successfully be included into a sol-gel derived silica matrix.

Molecular diffusion within sol-gel derived matrices viewed via fluorescence recovery after photobleaching.

A suitable matrix to host enzymes for biosensor applications should encage and retain the bioactive species, while allowing it to be accessed to exploit its catalytic properties. Sol-gel derived monoliths are promising in this aspect. Molecular diffusion was monitored using fluorescence labelled proteins and unbound fluorescence dye molecules (representative of enzyme substrates) and their interaction with and mobility within the host assessed using time-resolved fluorescence anisotropy and fluorescence recovery after photobleaching observed via confocal microscopy.

Fluorescence probe techniques to monitor protein adsorption-induced conformation changes on biodegradable polymers.

The study of protein adsorption and any associated conformational changes on interaction with biomaterials is of great importance in the area of implants and tissue constructs. This study aimed to evaluate some fluorescent techniques to probe protein conformation on a selection of biodegradable polymers currently under investigation for biomedical applications. Because of the fluorescence emanating from the polymers, the use of monitoring intrinsic protein fluorescence was precluded.

Diffusion in a sol-gel-derived medium with a view toward biosensor applications.

Time-resolved fluorescence anisotropy and fluorescence recovery after photobleaching were applied to study the diffusion of dyes and a fluorescence-labeled enzyme in a sol-gel-derived medium. This type of medium exhibits attractive properties such as robustness, low processing temperature, high porosity, large internal surface area, and can act as protective immobilization media for biologically active molecules. This makes it a suitable candidate for biosensor applications.

Effect of the labelling ratio on the photophysics of fluorescein isothiocyanate (FITC) conjugated to bovine serum albumin.

The non-linearity of the fluorescence emission on increasing the probe to protein ratio has long been regarded as problematic and has lead to the development of dyes to overcome this effect. One of the causes of this non-linear response can be ascribed to the overlap of the label's own absorption and emission spectra. At higher labelling ratios, this affords the possibility of a reasonably efficient energy migration pathway, thus reducing the observed quantum yield of the dye.