In vivo laser-induced fluorescence imaging of a rat pancreatic cancer with pheophorbide-a

Push-pull pyropheophorbides for nonlinear optical imaging

Pyropheophorbide-a methyl ester (PPa-OMe) has been modified by attaching electron-donor and -acceptor groups to alter its linear and nonlinear optical properties. Regioselective bromination of the terminal vinyl position and Suzuki coupling were used to attach a 4-(N,N-diethylaminophenyl) electron-donor group. The electron-acceptor dicyanomethylene was attached at the cyclic ketone position through a Knoevenagel condensation. Four different derivatives of PPa-OMe, containing either electron-donor or electron-acceptor groups, or both, were converted to hydrophilic bis-TEG amides to generate a series of amphiphilic dyes. The absorption and emission properties of all the dyes were compared to a previously reported push-pull type porphyrin-based dye and a commercial push-pull styryl dye, FM4-64. Electrochemical measurements reveal that the electron donor group causes a greater decrease in HOMO-LUMO gap than the electron-acceptor. TD-DFT calculations on optimized geometries (DFT) of all four dyes show that the HOMO is mostly localized on the donor, 4-(N,N-diethylaminophenyl), while the LUMO is distributed around the chlorin ring and the electron-acceptor. Hyper-Rayleigh scattering experiments show that the first-order hyperpolarizabilities of the dyes increase on attaching either electron-donor or -acceptor groups, having the highest value when both the donor and acceptor groups are attached. Two-photon excited fluorescence (TPEF) and second harmonic generation (SHG) images of the bis-TEG amide attached dyes in lipid monolayer-coated droplets of water-in-oil reveal that the TPEF and SHG involve transition dipole moments in different orientations.

Phototoxic effect of na-pheophorbide a toward osteosarcoma cells in vitro using a laser diode

OBJECTIVE

The purpose of this study was to investigate the effectiveness of photodynamic therapy (PDT) with Na-pheophorbide A in anticancer treatment, using osteosarcoma cells in vitro.

BACKGROUND DATA

It has been reported that PDT with chlorophyll derivatives inhibits the proliferation of various cancer cells. However, there have been no reports that have evaluated the effectiveness of PDT in suppressing osteosarcoma cells.

MATERIALS AND METHODS

Uptake of Na-pheophorbide A into Hu09 cells (osteosarcoma cells) was assayed using fluorescence microscopy following incubation of the cells with 28 μmol/L of Na-pheophorbide A. The viability of Hu09 cells after PDT treatment was assessed using trypan blue dye staining and MTS assays. PDT-induced apoptosis was determined by evaluation of the activity of selected members of the caspase family and by terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) staining of cells.

RESULTS

Na-pheophorbide A uptake by cells was rapid, being observed after 60 min of treatment, and Na-pheophorbide A persisted in cells for >24 h. PDT treatment decreased cell viability compared with the control group, indicating high cytocidal activity of PDT. This cytocidal effect was dependent upon drug concentration, light dose, and the number of irradiation times. An increase in the number of cells positive for TUNEL staining and increases in the activity of caspases-3, -8 and -9 were observed in the first 2 h after PDT treatment.

CONCLUSIONS

A cytotoxic effect of PDT with Na-pheophorbide A on an osteosarcoma cell line in vitro was shown. Caspase activity assays suggested that PDT with Na-pheophorbide A induced an apoptotic change in HuO9 cells, mainly via activation of mitochondrial caspase -9 and -3 pathways.

Mid-infrared lifetime imaging for viability evaluation of lettuce seeds based on time-dependent thermal decay characterization

An infrared lifetime thermal imaging technique for the measurement of lettuce seed viability was evaluated. Thermal emission signals from mid-infrared images of healthy seeds and seeds aged for 24, 48, and 72 h were obtained and reconstructed using regression analysis. The emission signals were fitted with a two-term exponential model that had two amplitudes and two time variables as lifetime parameters. The lifetime thermal decay parameters were significantly different for seeds with different aging times. Single-seed viability was visualized using thermal lifetime images constructed from the calculated lifetime parameter values. The time-dependent thermal signal decay characteristics, along with the decay amplitude and delay time images, can be used to distinguish aged lettuce seeds from normal seeds.

Multispectral fluorescence lifetime imaging of feces-contaminated apples by time-resolved laser-induced fluorescence imaging system with tunable excitation wavelengths

We recently developed a time-resolved multispectral laser-induced fluorescence (LIF) imaging system capable of tunable wavelengths in the visible region for sample excitation and nanosecond-scale characterizations of fluorescence responses (lifetime imaging). Time-dependent fluorescence decay characteristics and fluorescence lifetime imaging of apples artificially contaminated with a range of diluted cow feces were investigated at 670 and 685 nm emission bands obtained by 418, 530, and 630 nm excitations. The results demonstrated that a 670 nm emission with a 418 nm excitation provided the greatest difference in time-dependent fluorescence responses between the apples and feces-treated spots. The versatilities of the time-resolved LIF imaging system, including fluorescence lifetime imaging of a relatively large biological object in a multispectral excitation-emission wavelength domain, were demonstrated.

Fluorescence characteristics of wholesome and unwholesome chicken carcasses

Each chicken carcass intended for U.S. consumers is mandated to be inspected by Food Safety and Inspection Service (FSIS) inspectors for its wholesomeness at the processing plants. Fluorescence responses of wholesome and unwholesome chicken carcasses were characterized and further evaluated for potential on-line applications for detection and classification of wholesome and unwholesome chicken carcasses. For this study, unwholesome chicken carcasses included cadaver and those with disease conditions such as airsacculitis and septicemia. Fluorescence characteristics from the epidermal layers in the breast areas of chicken carcasses were dynamic in nature. Emission peaks and ridges (maxima) were observed at 386, 444, 472, 512, and 554 nm and valleys (minima) were observed at 410, 460, 484, and 538 nm. One of the major factors affecting the line shapes of fluorescence responses from chicken carcass skin layers was absorption by hemoglobin. With the use of the normalized ratio spectra (NRS) approach, oxyhemoglobin was shown to be a major constituent in chicken carcasses affecting the fluorescence emission line shapes. Subtle line shape changes in the NRS also provided a qualitative means by which to assess the minute differences in oxy- and deoxyhemoglobin compositions perturbed by poultry diseases such as septicemia and airsacculitis. With the use of simple fluorescence band ratios as a multivariate model, wholesome and unwholesome chicken carcasses were correctly classified with 97.1% and 94.8% accuracies, respectively. On-line implementation of fluorescence techniques for the assessment of chicken carcass wholesomeness appears promising.

Detection of fecal contamination on apples with nanosecond-scale time-resolved imaging of laser-induced fluorescence

Detection of apples contaminated with feces is a public health concern. We found that time-resolved imaging of apples artificially contaminated with feces allowed optimization of timing parameters for detection. Dairy feces were applied to Red Delicious and Golden Delicious apples. Laser-induced fluorescence responses were imaged by use of a gated intensified camera. We developed algorithms to automatically detect contamination iteratively by using one half of the apples and validated them by applying the optimized algorithms to the remaining apples. Results show that consideration of the timing of fluorescence responses to pulsed-laser excitation can enhance detection of feces on apples.

Optimal fluorescence excitation and emission bands for detection of fecal contamination

Fecal contamination of food products is a critical health issue. To test the feasibility of the use fluorescent techniques to detect fecal contamination, fluorescence excitation and emission characteristics of fecal matter from cows, deer, swine, chickens, and turkeys in the UV to far-red regions of the spectrum were evaluated. To allow the optimization of the detection of fecal contamination on animal carcasses and cut meats, emission-excitation spectra of the feces were compared with spectra for animal meats. The feedstuffs for the swine, chickens, and turkeys were also analyzed. Excitation at approximately 410 to 420 nm yielded the highest level of fluorescence for both feces and feedstuffs. Emission maxima were in the red region (at 632 nm for chicken feces and at 675 nm for the feces of the other species). The major constituent responsible for emission at 632 nm was tentatively identified as protoporphyrin IX; emission at 675 nm most likely emanates from chlorophyll a or its metabolites. Animal meats emitted strong fluorescence in the blue-green regions, but no emission peaks were observed in the red region for these meats. These results suggest that fluorescence emissions from naturally occurring chlorophyll a and its metabolites are good markers for fecal contamination and that with excitation at 410 to 420 nm, the responses of fecal matter can easily be differentiated from the responses of animal meats. We suggest that the detection of fecal contamination can be enhanced by requiring a minimum chlorophyll a content in the finishing diets of all farm animals.

Multispectral laser-induced fluorescence imaging system for large biological samples

A laser-induced fluorescence imaging system developed to capture multispectral fluorescence emission images simultaneously from a relatively large target object is described. With an expanded, 355-nm Nd:YAG laser as the excitation source, the system captures fluorescence emission images in the blue, green, red, and far-red regions of the spectrum centered at 450, 550, 678, and 730 nm, respectively, from a 30-cm-diameter target area in ambient light. Images of apples and of pork meat artificially contaminated with diluted animal feces have demonstrated the versatility of fluorescence imaging techniques for potential applications in food safety inspection. Regions of contamination, including sites that were not readily visible to the human eye, could easily be identified from the images.

Feasibility, sensitivity, and reliability of laser-induced fluorescence imaging of green fluorescent protein-expressing tumors in vivo

Whole-body imaging of green fluorescent protein (GFP) can be used to test the efficiency of gene carriers for in vivo transduction. The aim of the current study was to determine the sensitivity and the accuracy of a GFP imaging procedure by in vivo investigation of GFP-expressing tumor cells. An improved method of whole-body GFP imaging made use of a laser excitation source and band-pass filters matched specifically to GFP and constitutive tissue fluorescence emission bands. Processing of the primary GFP fluorescence images acquired by the CCD camera subtracted background tissue autofluorescence. Our approach achieved 100% sensitivity and specificity for in vivo detection of 10%-transfected BxPc3 pancreatic tumor after subcutaneous grafting or orthotopical implantation in the pancreas of nude mice. It also detected less transfected tumors (i.e., 1 to 5%) but with a loss in sensitivity (50% of cases). The system was employed over a 5-week period to monitor the persistence of GFP expression in 10%-transfected BxPc3 tumors orthotopically implanted in the pancreas of two nude mice, allowing the direct visualization of tumor progression and spread. In facilitating the temporal-spatial follow-up of GFP expression in vivo, the optimized laser-induced fluorescence imaging device can support preclinical investigations of vectors for therapeutic gene transduction through regular, harmless, real-time monitoring of theirin vivo transductional efficacy and persistence.

Oxygen consumption through metabolism and photodynamic reactions in cells cultured on microbeads

Oxygen consumption by cultured cells, through metabolism and photosensitization reactions, has been calculated theoretically. From this result, we have derived the partial oxygen pressure PO2 in the perfusion medium flowing across sensitized cultured cells during photodynamic experiments. The PO2 variations in the perfusate during light irradiation are related to the rate of oxygen consumption through photoreactions, and to the number of cells killed per mole of oxygen consumed through metabolic processes. After irradiation, the reduced metabolic oxygen consumption yields information on the cell death rate, and on the photodynamic cell killing efficiency. The aim of this paper is to present an experimental set-up and the corresponding theoretical model that allows us to control the photodynamic efficiency for a given cell-sensitizer pair, under well defined and controlled conditions of irradiation and oxygen supply. To demonstrate the usefulness of the methodology described, CHO cells cultured on microbeads were sensitized with pheophorbide a and irradiated with different light fluence rates. The results obtained, i.e. oxygen consumption of about 0.1 microM s(-1) m(-3) under a light fluence rate of 1 W m(-2), 10(5) cells killed per mole of oxygen consumed and a decay rate of about 1 h(-1) of living cells after irradiation, are in good agreement with the theoretical predictions and with previously published data.

Human pancreatic carcinoma cells are sensitive to photodynamic therapy in vitro and in vivo

BACKGROUND

The aim of this study was to assess the efficiency of photodynamic therapy (PDT) on human pancreatic cancer cells in vitro and in an animal model.

METHODS

Human pancreatic tumour cell lines were submitted to PDT with pheophorbide a (Ph a), a chlorophyll derivative, in culture and after grafting into athymic mice. Ph a was tested in culture (10-10-10-5 mol/l) with a 5-J/cm2 energy treatment and on tumour-bearing Nude mice (30 mg/kg intraperitoneally) with a 100-J/cm2 PDT session. The effect of PDT was assessed in vitro using proliferative, apoptotic and clonogenic tests and in vivo on tumour growth and on the induction of tumour necrosis.

RESULTS

PDT inhibited tumour cell growth in culture by affecting DNA integrity. This tumour cell photodamage started at low concentration (10-7 mol/l) as corroborated by clonogenic and tumour growth tests. A strong necrosis was achieved in vivo with a single PDT session.

CONCLUSION

PDT destroyed human pancreatic carcinoma after low photosensitizer supply and weak energy application. It exerted this tumoricidal effect via apoptosis induction with a gentle protocol, and apoptosis and/or necrosis with a stronger protocol.