Proton-dynamic therapy following photosensitiser activation by accelerated protons demonstrated through fluorescence and singlet oxygen production.

We demonstrate excitation of photosensitisers (PSs) by accelerated protons to produce fluorescence and singlet oxygen. Their fluorescence follows a pattern similar to the proton energy loss in matter, while proton-derived fluorescence spectra match the photon-induced spectra. PSs excited in dry gelatin exhibit enhanced phosphorescence, suggesting an efficient PSs triplet state population. Singlet oxygen measurements, both optically at ~1270 nm and through the photoproduct of protoporphyrin IX (PpIX), demonstrate cytotoxic singlet oxygen generation by proton excitation. The singlet oxygen-specific scavenger 1,4-diazabicyclo[2.2.2]octane (DABCO) abrogates the photoproduct formation under proton excitation, but cannot countermand the overall loss of PpIX fluorescence. Furthermore, in two cell lines, M059K and T98G, we observe differential cell death upon the addition of the PS cercosporin, while in U87 cells we see no effect at any proton irradiation dose. Our results pave the way for a novel treatment combining proton therapy and "proton-dynamic therapy" for more efficient tumour eradication.

Guanidinylated dendritic molecular transporters: prospective drug delivery systems and application in cell transfection.

In the present review the crucial role of the guanidinium functional group in facilitating the transport of dendritic polymers through liposomal and cell membranes is discussed, along with other structural features of guanidinylated dendritic polymers that fine-tune their transport properties, and even determine their subcellular destinations. In this context, an ideal dendritic molecular transporter would need to possess a dendritic scaffold of the appropriate size and degree of guanidinylation, flexibility of the guanidinium moiety, and should exhibit a proper balance between hydrophilic and hydrophobic moieties located on the dendritic surface. All of the above are illustrated through selected paradigms from the relevant literature, which give a valuable insight into forging successful dendritic delivery systems for both drugs and genes. The main challenge for the future focus of the field is identified as the determination of the key structural and functional characteristics that will enhance cell internalisation, and secure localisation in specific subcellular organelles.

A system to monitor for fibre breakage during photodynamic therapy with diffuser fibres.

There is concern that the delicate fibres and cylindrical diffuser tips used for intraluminal PDT of blood vessels might break during the treatment. We have developed and tested a simple system to monitor for fibre breakage during PDT. Light from the laser is passed through a beam expander, then a beam splitter, and then is again contracted into the inlet of a diffuser fibre. Light reflected from the distal diffuser is also partially reflected by the beam splitter into a photodiode, which monitors changes in the intensity of the reflected light. The system was tested by simulating catastrophic failures in four fibres. In each case the output fell very significantly (DV=0.44-1.68 V, SD=0.01 V). Despite the small statistical sample, the average change in the reflected light intensity is still significant (p < 0.025, paired Student's t-test). Our conclusion was that this device can monitor the integrity of diffuser fibres during PDT.

Thermally induced irreversible conformational changes in collagen probed by optical second harmonic generation and laser-induced fluorescence.

Irreversible thermal conformational changes induced to collagen have been studied by optical methods. More specifically, second harmonic generation (SHG) from incident nanosecond Ng:YAG 1064 nm radiation and laser-induced fluorescence by 337 nm, pulsed nanosecond nitrogen laser excitation, at 405, 410 and 415 nm emission wavelengths were registered at eight temperatures (40 degrees, 50 degrees, 55 degrees, 60 degrees, 65 degrees, 70 degrees, 75 degrees and 80 degrees C) and normalised with respect to the corresponding values at the ambient temperature of 30 degrees C. The heating protocol used in this work, was selected to monitor only permanent changes reflecting in the optical properties of the samples under investigation. In this context, the SHG, directly related to the collagen fibril population in triple helix conformation, indicated on irreversible phase transition around 64 degrees C. On the other hand fluorescence related to the destruction of cross-linked chromophores in collagen, some of which are related to the triple helix tertiary structure, also indicated a permanent phase transition around 63 degrees C. These results are in agreement with previous results from studies with differential scanning calorimetry. However SHG and fluorescence, being non-invasive optical methods are expected to have a significant impact in the fields of laser ablative surgery and laser tissue welding.

Visual observation of infrared laser speckle patterns at half their fundamental wavelength.

In the course of work aimed to examine second harmonic generation in biological macromolecules, it was discovered that 1064 nm pulsed nanosecond infrared laser radiation, after scattering on the optically rough sample surface, was perceived as double the fundamental frequency green speckle pattern by the unaided eye. The threshold of this arresting phenomenon was found to be around 60 mJ/cm2 on hyaluronic acid potassium salt in dark ambient conditions. This effect is of a second order non-linear nature. After experiments with nearsighted, farsighted and normal vision observers in combination with second harmonic generation experiments on various lamb eye tissues, the effect was mainly attributed to second harmonic generation in the cornea arising from phase interference of the incident infrared radiation. The current work could possibly have implications in the fields of speckle interferometry and biomedicine.

Photochemical effects and hypericin photosensitized processes in collagen.

Emission and excitation spectra of collagen were recorded in the ultraviolet and visible regions. The existence of several types of chromophores absorbing and emitting throughout these spectral regions was observed. It was shown that laser irradiation at 355 and 532 nm caused collagen fluorescence photobleaching by 30%, when the delivered light doses were 9 and 18 J/cm2, respectively. This process of collagen fluorophores photodestruction was found to be a one-photon effect. The effect of hypericin (HYP), a polycyclic quinone, photosensitization on collagen was also studied. Addition of HYP aqueous solution to collagen produced quenching, redshift of the maximum, and broadening of the spectral form of its fluorescence. These effects became more prominent with increasing HYP concentration. The fluorescence of HYP sensitized collagen decreased in a spectrally nonproportional manner during laser irradiation at both 355 and 532 nm.