Jacques Didelon

Improvement of meta-tetra(Hydroxyphenyl)chlorin-Like Photosensitizer Selectivity with Folate-Based Targeted Delivery. Synthesis and in Vivo Delivery Studies

The cell membrane folate receptor (FR) is a molecular target for tumor-selective drug delivery, including delivery of photosensitizers for anticancer photodynamic therapy (PDT). Tumor selectivity of meta-tetra(hydroxyphenyl)chlorin ( m-THPC), a photosensitizer used in PDT clinical trials, demonstrates a low tumor-to-normal epithelial uptake ratio. We report on the synthesis and on the photophysical properties of a m-THPC-like photosensitizer 1 conjugated to folic acid (compound 8). A comparative study of the accumulation of photosensitizers 1 and 8 is described. Nude mice were xenografted with FR-alpha-positive KB or HT-29 cells lacking FR-alpha as a negative control. Using optical fiber fluorimetry, we demonstrated that conjugate 8 exhibited enhanced accumulation in KB tumors compared to 1 4 h after injection. No significant difference between KB and HT-29 tumors was observed in case of compound 1. Tumor-to-normal tissue ratio exhibited a very interesting selectivity for conjugate 8 (5:1) in KB tumors 4 h postinjection.

Advantages and limitations of commonly used methods to assay the molecular permeability of gap junctional intercellular communication

The role of gap junctional intercellular communication (GJIC) in regulation of normal growth and differentiation is becoming increasingly recognized as a major cellular function. GJIC consists of intercellular exchange of low molecular weight molecules, and is the only means for direct contact between cytoplasms of adjacent animal cells. Disturbances of GJIC have been associated with many pathological conditions, such as carcinogenesis or hereditary illness. Reliable and accurate methods for the determination of GJIC are therefore important in cell biology studies. There are several methods used successfully in numerous laboratories to measure GJIC both in vitro and in vivo. This review comments on techniques currently used to study cell-to-cell communication, either by measuring dye transfer, as in methods like microinjection, scrape loading, gap-fluorescence recovery after photobleaching (gap-FRAP), the preloading assay, and local activation of a molecular fluorescent probe (LAMP), or by measuring electrical conductance and metabolic cooperation. As we will discuss in this review, these techniques are not equivalent but instead provide complementary information. We will focus on their main advantages and limitations. Although biological applications guide the choice of techniques we describe, we also review points that must be taken into consideration before using a methodology, such as the number of cells to analyze.

Biodistribution of hypericin in orthotopic transitional cell carcinoma bladder tumors: Implication for whole bladder wall photodynamic therapy

In a recent clinical study, we reported a selective uptake of hypericin in superficial bladder tumors. The results suggested that hypericin, a potent photosensitizer, could be used not only for diagnosis but also for photodynamic therapy (PDT) of superficial bladder tumors. In the present study, we investigated the biodistribution of hypericin in an orthotopic rat bladder tumor model by assessing the extent of hypericin penetration and the kinetics of accumulation into rat bladder tumors and normal bladder wall. Hypericin (8 or 30 μM) was instilled into the bladder via the catheter for 1, 2 or 4 hr. The fluorescence of hypericin in the bladder tumors and normal bladder was documented using fluorescence microscopy. In situ quantification of hypericin fluorescence in the tumor or normal bladder was performed using the laser‐induced fluorescence technique. There was much more hypericin fluorescence in the tumor than in the normal bladder, with the tumor‐to‐normal‐bladder ratio mounting to 12:1 after 4 hr of hypericin (30 μM) instillation. Moreover, hypericin was retained in the tumor for at least 1 hr before it was gradually lost from the tissue. Microscopically, the fluorescence of hypericin was restricted to the urothelial tumor and normal urothelium without fluorescence in the submucosa and the muscle layers. Subsequently no hypericin was detected in plasma, indicating that under these conditions systemic side effects should not be expected. Because the conditions used in this study were similar to those used in our previous clinical study, it is therefore likely that whole bladder wall PDT in the clinic under these conditions will produce selective urothelial tumor destruction without causing damage to the underlying muscle layers.

A Theoretical Approach of the Measurement of Osmotic Fragility of Erythrocytes by Optical Transmission

Abstract The osmotic fragility of the erythrocyte membrane to hypotonic solutions is investigated theoretically. The fragility curves exhibit a strong transmittance rise. This variation is assumed to result from changes in the scattering properties of erythrocytes under dialysis resulting from swelling and hemolysis. The refractive indices of erythrocytes are obtained through the Lorentz–Lorenz relation based on hemoglobin and water contents. The scattering cross sections (needed to calculate the collimated transmittance) and the forward scattered intensity (needed to calculate the incoherent transmittance) are expressed according to the simple algebraic relations of the anomalous diffraction approximation. It is shown that swelling (or shrinking) has no influence on the collimated transmittance. Hemolysis alone causes the abrupt sigmoidal increase of the collimated transmittance with time. The possible transmittance increase (decrease) observed during swelling (shrinking) is due to incoherent transmittance and depends on the detecting solid angle value of the experimental setup.

Investigation of 3-D mechanical properties of blood vessels using a new in vitro tests system: results on sheep common carotid arteries

In order to investigate the three-dimensional (3-D) mechanical properties of blood vessels, a new experimental device is described allowing in vitro static and dynamic measurements on segments of arteries with high technical performances. Static tests are applied to sheep common carotid arteries. Considering a thick-walled cylindrical model of orthotropic material under large deformations, a classical 3-D approach based on strain energy density is used to calculate the resulting mechanical behavior law in radial and circumferencial directions and stresses distribution throughout the wall thickness. Results are presented with reference to unloaded and zero-stress initial state thanks to simple measurements of inner and outer circumferences. A particular ratio relating the two main stresses (circumferential and longitudinal) is calculated that put into the forth the progressive modifications in the direction of the predominant stress in the wall and the specific radial location where these changes occur. The authors observe that this point location is a function of the test conditions of the specimen, i.e., stretching length and level of pressure.

System identification of the intracellular photoreaction process induced by photodynamic therapy

Photodynamic therapy (PDT) is an alternative treatment for cancer that involves the administration of a photosensitizing agent, which is activated by light at a specific wavelength. This illumination causes a sequence of photoreactions, which - in the presence of molecular oxygen - is supposed to be responsible for the death of the tumor cells. The PDT efficiency stems from the optimal interaction between these three factors (light, drug and oxygen). In this paper, a new approach is proposed to estimate photophysical parameters which characterize the ability of a photosensitizing drug to produce singlet oxygen. This approach is based on system identification techniques. This model-based method would allow biologists to estimate all the photophysical parameters from spectro-fluorescence data generated by only one experiment. Secondly, contrary to usual techniques which are restricted to in vitro studies, this approach can be directly applied to in vivo data.

Simultaneous Characterization of Optical and Rheological Properties of Carotid Arteries via Bimodal Spectroscopy: Experimental and Simulation Results

This study aimed at identifying potential correlations between rheological and optical properties of carotid artery rings before and after cryopreservation at different mechanical deformations using experimental and simulation results. Therefore, a uniaxial mechanical test bench was coupled to fibered optical spectroscopes measuring 410 nm excited autofluorescence and 650-850 nm elastically backscattered intensity spectra. Furthermore, we developed a statistical simulation program of light transport and fluorescence adapted to our specific experimental configuration. Both spectroscopies gave intensity spectra with higher amplitude for the cryopreserved samples. These observations are to be related to histological modifications affecting the arterial wall of postcryopreserved samples. We also observed significant spectral amplitude variations (increasing autofluorescence intensity and decreasing diffuse reflectance) as a function of the circumferential strains (0%-60%). Due to simulation, we identified values of absorption, diffusion, and anisotropy coefficients, and their variations as a function of state (fresh-cryopreserved), strains (0, 30%, 60%), and wavelengths (700, 740, 780 nm). The media and the adventice are, respectively, less and more absorbing for postcryopreserved rings, and it is the opposite for the fresh ones at higher wavelengths. Absorption and diffusion coefficients are slightly higher, whatever the wavelengths and strains, for the fresh than for the cryopreserved samples.

Salvage photodynamic therapy for extended carcinoma in situ of the oesophagus after subtotal oesophagectomy: 2 years follow up

he incidence of oesophageal cancer continuously increases nd 400 000 new cases/year are diagnosed worldwide. Total esophagectomy is recommended when multifocal disease, specially in case of Barrett’s oesophagus [1]. However, elected cases may benefit from subtotal oesophagectomy, ith 5-year survival rates ranging from 20% to 50% [1]. Local ecurrence after subtotal oesophagectomy is relatively high 30—40%) and regular endoscopic surveillance is mandatory. arly stage lesions are eligible for endoscopic minimally nvasive surgery such as endoscopic mucosal resection or issection (EMR, EMD), argon plasma photocoagulation, adiofrequency ablation or photodynamic therapy (PDT). hotodynamic therapy is now commonly applied to eradcate dysplasia and Barrett’s oesophagus but can also chieve destruction of squamous cell carcinoma. In the resent paper, we report a case of multifocal high grade ysplasia, in a patient with prior subtotal oesophagectomy, reated with PDT.

DIFFUSE REFLECTANCE SPECTROSCOPY MONTE-CARLO MODELING: ELONGATED ARTERIAL TISSUES OPTICAL PROPERTIES

Abstract Optical methods, such as reflectance and fluorescence spectroscopy, have shown the potential to characterize biological tissues. The goal of this study is to simulate the steady-state light transport in arterial tissues with optical parameters found in the literature, then to deduce optical properties of tissues through optimization and finally to experimentally verify Monte-Carlo modeling of steady-state diffuse reflectance. The optical properties found are roughly in the same order of magnitude than the optical parameters found in the literature and the results indicate that the simulated results agree reasonably well with the experimentally measured results.

IN VIVO CANCER DIAGNOSTICS BY SPACE RESOLVED DIFFUSE REFLECTANCE SPECTROSCOPY

In this paper we describe a compact, portable light-emitting diode (LED)-based fiber-optic system allowing in vivo diffuse reflectance spectra registration in visible and near IR spectral range at two distances between illuminating and collecting fibers. The construction of fiber optic probe is adapted for endoscopy application. We further report the preliminary results of in vivo discrimination between of the benign and malignant tissues and different types of malignant tissues in the animal models.