Laser-induced fluorescence detection of malignancies in the female genital tract via their natural emission and hypocrellin (HA) probing

Potential and Current Uses of Luminescence in Medical Diagnosis

Biological luminescence stimulated by optical excitation results in signals which are characteristic of the host tissue. The spectrum of the emitted light, the intensity, and the excited state lifetimes are modified as the result of disease or by activation through addition of cell selective phosphors. There is an opportunity to identify diseased tissue both by the spectral signals from activators or, in some cases, by the differences of the natural luminescence responses. For practical reasons, defined by the sensitivity range of standard luminescence detectors, much of the current work has focussed on the short wavelength emissions driven by laser activation. However, the techniques are poised to undergo a dramatic expansion in scope with the advent of higher sensitivity photocathodes with high efficiency responses at long wavelengths. It is now possible to utilise a greater range of emission features with improved discrimination. Further, movement to longer wavelength excitation, and emission, open the way to probe deeper beneath the surface of tissue. The current overview will focus on recent examples from detection of cancer to tooth caries and indicate how the non-destructive luminescence probes can distinguish between tissue changes at an early stage of development.

Glycoconjugated hypocrellin: synthesis of [(beta-D-glucosyl)ethylthiyl]hypocrellins and photosensitized generation of singlet oxygen

In order to improve the water solubility and specific affinity for malignant tumors of hypocrellin, glycoconjugated hypocrellins have been synthesized using an improved Königs-Knörr reaction from mercaptoethanol substituted hypocrellin B and 2,3,4,6-tetra-O-acetyl-alpha-D-glucopyranosyl bromide precursors. Deprotection of glucose moieties allows the production of derivatives which had improved solubility in neutral aqueous solution and covered a range of amphiphilic character. The structures of these new protected and unprotected compounds were characterized by UV-Vis, IR, 1H-NMR and MS data. The present strategy should prove applicable to the synthesis of other glycoconjugated perylenequinone compounds. In addition, the quantum yield of singlet oxygen generation photosensitized by these glycoconjugated hypocrellins has been determined.

Effect of liquid-nitrogen and formalin-based conservation in the in vitro measurement of laser-induced fluorescence from peripheral vascular tissue

In order to investigate the effects of conservation in liquid nitrogen and formalin on peripheral vascular tissue (abdominal aortic, femoral, flank, ham, fibular and tibial artery tissue), laser-induced fluorescence spectra have been recorded during the exposure of these tissues to helium-cadmium and argon ion radiation. The spectral distribution of tissue fluorescence allows the development of simple algorithms based on the intensity difference in order to discriminate the tissue samples when they are fresh and after they have been stored for 24 and 28 h in liquid nitrogen or formalin.

Spectral variations of laser-induced tissue emission during in vivo detection of malignancies in the female genital tract

A laser-based fluorescence-guided biopsy system has been developed for the screening and early detection of malignancies in the female inner/outer genital tract. Fluorescence spectra were recorded during in vivo exposure of normal and malignant tissue to He-Cd laser (442 nm) radiation. Spectral distribution of tissue natural fluorescence allowed for the development of simple algorithms, based on spectral intensity variations. A subsequent index of discrimination between normal and various malignant tissues has been calculated. This study focuses on the variability of the experimental data and the possible sources of spectral variations. These results suggest that monitoring of this index during colposcopy could enhance selective detection of the malignant tissue, reducing the risk of leaving pathologic tissue untreated during standard exploratory surgical procedures.