Today, single photon imaging represents one of the most challenging goals in the field of photonics. Many areas are
involved: nuclear and particle physics, astronomy, and, in the biophysics field, the newest technique to investigate the
state of several biological systems by detecting the ultra-weak luminescence emitted from the excited sample under
study. Aim of the work is the realization of a single photon imaging device able to identify the position and the arrival
time of the impinging photons from ultra low intensity sources. The main features of a 2-D array of Single Photon
Avalanche Diodes, manufactured by ST-Microelectronics, are shown.
The UVA induced Delayed Luminescence (DL), has been measured in vivo in the forearm skin of some healthy
volunteers of different sex and age during several periods of the year. An innovative instrument able to detect, in single
photon counting mode, the spectrum and the time trend of the DL emission has been used. The measured differences in
the time trends of the spectral components may be related to the sex and the age. The potential development of a new
analysis technique based on this phenomenon is discussed.
In this contribution we describe the realization of MUSES, a novel research equipment able to detect and identify
photons emitted, after laser irradiation, from biological samples (like micro-organisms and human cells) for fast
ultraweak luminescence analysis. MUSES has been entirely designed and realised at LNS-Southern National Laboratory
of the Italian INFN-Nuclear Physics National Institute. The excellent performances in terms of timing, wavelength and
angular identification make this multi-detector a unique device in biophotonics research field.
The new developments of SINPHOS project (SINgle PHOton Spectrometer) are reported. The realised device
is able to measure simultaneously with high accuracy time distribution and the wavelength spectrum of photons coming
several physical and biological systems. Such device is essentially composed by a grading spectrometer and an array of
SPADs (Single Photon Avalange Diodes).
Design and characterization of a new generation of single photon avalanche diodes (SPAD) array, manufactured by STMicroelectronics
in Catania, Italy, are presented. Device performances, investigated in several experimental conditions
and here reported, demonstrate their suitability in many applications. SPADs are thin p-n junctions operating above the
breakdown condition in Geiger mode at low voltage. In this regime a single charged carrier injected into the depleted
layer can trigger a self-sustaining avalanche, originating a detectable signal. Dark counting rate at room temperature is
down to 10 s-1 for devices with an active area of 10 μm in diameter, and 103 s-1 for those of 50 &mgr;m. SPAD quantum
efficiency, measured in the range 350÷1050 nm, can be comparable to that of a typical silicon based detector and reaches
the values of about 50% at 550 nm for bigger samples. Finally, the low production costs and the possibility of integrating
are other favorable features in sight of highly dense integrated 1-D or 2-D arrays.
New single photon avalanche detectors (SPAD), are presented. Device performances, as photo-detection efficiency, timing and dark counts, extracted in several experimental conditions and here reported, make them suitable in many applications. The integration possibility, in order to achieve a new concept of solid state photomultiplier, has been also successfully investigated within the 5x5 arrays manufacture.
Photobiological research in the last decades has shown the existence of Delayed Luminescence in biological tissue, which presents an excitation spectrum with a peak within the UVA region and can be detected with sophisticated photomultiplier systems. Based on these findings, a new and powerful tool able to measure the UV-A-laser-induced Delayed Luminescence emission of cultured cells was developed, with the intention to detect biophysical changes between carcinogenic and normal cells. Indeed noticeable differences have been found in the time resolved emission spectrum of delayed luminescence of cell cultures of human fibroblast and human melanoma. This new, powerful and non-invasive technique, in principle, could be applied in all fields of skin research, such as the investigation of skin abnormalities and to test the effect of products involved in regeneration, anti-aging and UV-light protection in order to prevent skin cancer.
SINPHOS is a monolithic micro-device, able to measure simultaneously time distribution and spectrum of photons coming from a weak source like Delayed Luminescence of biological systems. In order to achieve this challenging goal, we use: Deep Lithography with Ions (DLI) and microelectronic technologies for the fabrication of dedicated passive micro-optical elements and for the realization of Single Photon Avalanche Diode (SPAD) detectors, respectively
Photobiological research in the last 30 yr has shown the existence of ultraweak photon emission in biological tissue, which can be detected with sophisticated photomultiplier systems. Although the emission of this ultraweak radiation, often termed biophotons, is extremely low in mammalian cells, it can be efficiently increased by ultraviolet light. Most recently it was shown that UV-A (330 to 380 nm) releases such very weak cell radiation in differentiated human skin fibroblasts. Based on these findings, a new and powerful tool in the form of UV-A-laser-induced biophotonic emission of cultured cells was developed with the intention to detect biophysical changes between carcinogenic and normal cells. With suspension densities ranging from 1 to 8×106 cells/mL, it was evident that an increase of the UV-A-laser-light induced photon emission intensity could be observed in normal as well as melanoma cells. Using this new detection procedure of ultraweak light emission, photons in cell suspensions as low as 100 µL could be determined, which is a factor of 100 lower compared to previous procedures. Moreover, the detection procedure has been further refined by turning off the photomultiplier system electronically during irradiation leading to the first measurements of induced light emission in the cells after less than 10 µs instead of 150 ms, as reported in previous procedures. This improvement leads to measurements of light bursts up 107 photons/s instead of several hundred as found with classical designs. Overall, we find decreasing induction ratings between normal and melanoma cells as well as cancer-prone and melanoma cells. Therefore, it turns out that this highly sensitive and noninvasive device enables us to detect high levels of ultraweak photon emission following UV-A-laser-induced light stimulation within the cells, which enables future development of new biophysical strategies in cell research.