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A partire dal 2010 le Indicazioni Nazionali hanno introdotto l’insegnamento della fisica moderna nelle Scuole Secondarie Superiori. Le Università e gli enti di ricerca devono quindi supportare i docenti nel loro sforzo di trattare questi argomenti avanzati in classe, proponendo il più possibile attività interattive e approcci originali. In questo documento è presentato un esempio di trattazione della fisica moderna attraverso l’astrofisica e la cosmologia. Le attività sono state proposte e testate durante il Corso di Aggiornamento in presenza dell’Università Roma Tre, con l’idea che esse possano poi essere applicate anche ad un Corso di Formazione iniziale.

Although photodynamic therapy (PDT), a therapeutic approach that involves a photosensitizer, light and O2, has been principally considered for the treatment of specific types of cancers, other applications exist, including the treatment of infections. Unfortunately, PDT does not always guarantee full success since it exerts lethal effects only in cells that have taken up a sufficient amount of photosensitizer and have been exposed to adequate light doses, conditions that are not always achieved. Based on our previous experience on the combination PDT/chemotherapy, we have explored the possibility of fighting bacteria that commonly crowd infected surfaces by combining PDT with an antibiotic, which normally does not harm the strain at low concentrations. To this purpose, we employed 5-aminolevulinic acid (5-ALA), a pro-drug that, once absorbed by proliferating bacteria, is converted into the natural photosensitizer Protoporphyrin IX (PpIX), followed by Gentamicin. Photoactivation generates reactive oxygen species (ROS) which damage or kill the cell, while Gentamicin, even at low doses, ends the work. Our experiments, in combination, have been highly successful against biofilms produced by several Gram positive bacteria (i.e., Staphylococcus aureus, Staphylococcus epidermidis, etc.). This original approach points to potentially new and wide applications in the therapy of infections of superficial wounds and sores.

Photofrin/photodynamic therapy (PDT) at sub-lethal doses induced a transient stall in proteasome activity in surviving A549 (p53(+/+)) and H1299 (p53(-/-)) cells as indicated by the time-dependent decline/recovery of chymotrypsin-like activity. Indeed, within 3 h of incubation, Photofrin invaded the cytoplasm and localized preferentially within the mitochondria. Its light activation determined a decrease in mitochondrial membrane potential and a reversible arrest in proteasomal activity. A similar result is obtained by treating cells with Antimycin and Rotenone, indicating, as a common denominator of this effect, the ATP decrease. Both inhibitors, however, were more toxic to cells as the recovery of proteasomal activity was incomplete. We evaluated whether combining PDT (which is a treatment for killing tumor cells, per se, and inducing proteasome arrest in the surviving ones) with Bortezomib doses capable of sustaining the stall would protract the arrest with sufficient time to induce apoptosis in remaining cells. The evaluation of the mitochondrial membrane depolarization, residual proteasome and mitochondrial enzymatic activities, colony-forming capabilities, and changes in protein expression profiles in A549 and H1299 cells under a combined therapeutic regimen gave results consistent with our hypothesis.

Objectives: Photodynamic treatment (PDT) of human lung carcinoma cells A549 (p53 (+/+)) and H1299 (p53 (−/−)) induces fast but transient stalling of proteasome activity. We have explored the possibility of prolonging this effect by combining PDT with drugs capable of sustaining the stall, and promote apoptosis of surviving cells. We show that aspirin can be used to accomplish this. Materials and methods: Cells were irradiated at doses ranging from 0.54 to 1.10 J cm(−2), and subsequently were incubated with aspirin at either high (10 and 5 mm) or low concentration (2.5 and 1.5 mm). Photofrin concentration and incubation time were constant (2.5 μg/ml and 16 h). Under these conditions, we analysed cell viability, colony‐forming efficiency, cycle profile, expression patterns of specific proteins and ubiquitination state, after individual or combined administration. Results: Treatment with either PDT or aspirin, rapidly induced proteasome malfunction and accumulation of cells in G(2)M, but did not induce apoptosis. However, when aspirin was added to cells (even at low concentrations) after PDT, the proteasome block was sustained. Moreover, significant cytotoxic effects, including apoptosis, were observed along with cytostatic effects (G(2)M accumulation/decreased colony formation). Conclusions: Combination of PDT and low‐toxicity drugs (such as aspirin) resulted in protracted inhibition of proteasome activity and induced apoptosis even in apoptosis‐resistant cancer cells.

We compared the effects of methyl levulinate (MAL)/photodynamic therapy (PDT) and adapalene, evaluated singly, versus combination therapy on HaCaT keratinocytes. Our aim was to determine whether the additive/synergistic outcomes of combination treatment were such that doses of each component could be reduced without affecting treatment efficacy. The analysis of data from specific PDT/adapalene combinations results indicating effects ranging from additive to clearly synergistic. We first evaluated the effects on cell viability, cell cycle and protein expression profiles of each individual treatment, then we tried to understand the reasons and the mechanisms whereby cells under combined treatment move more efficiently to death. Although we observed therapeutic strengthening by increasing either drug doses or light fluences, reinforcement was particularly marked in combinations in which PDT was predominant. Thus, if PDT is appropriately tuned, the dose of the drug can be reduced without compromising the therapeutic response. As both photodynamic therapy and adapalene have been and are therapeutic approaches to treat different dermatological pathologies such as acne, actinic keratosis etc., our data suggest that the adapalene-PDT combination may have important spin-off in clinical dermatology as a strategy to tackle this nasty condition.