The clinical use of photodynamic therapy (PDT) with rose bengal (RB) is emerging as an effective t reatment for a range of applications given its non-invasive and localised mode of delivery. In particular, rose bengal PDT has shown promising antifungal action in vitro. While focus has largely been on the physical and chemical impacts of PDT on the cell, an understanding of the role of genetics underpinning the cellular response is still limited. We have, therefore, reported a screen of the entire non-essential gene library of the model organism, Saccharomyces cerevisiae, using rose bengal PDT to ascertain the key genetic pathways affecting fungal tolerance to PDT. We also investigated the dosage of PDT required to eradicate Trichophyton rubrum spores, the main causative organism of onychomycosis infection. Following this, we conducted a pilot patient study of six patients (seven toenails) for the treatment of onychomycosis using rose bengal PDT (140 μM RB and ~763 J/cm2 green light), where the clinical treatment protocol was developed on the basis of the in vitro outcomes. The key biochemical pathways identified by the genetic screen as having altered tolerance to PDT included ergosterol biosynthesis, vacuolar acidification, and purine/S-adenosyl-L-methionine biosynthesis. The subsequent pilot patient study saw the complete cure of onychomycosis for all patients within three to five treatment sessions in the absence of pain or other local side effects. The outcome of the genetic screen for tolerance may thus inform the development of efficient clinical treatments using rose bengal PDT.
Peripheral nerve injuries are difficult to treat because axon regeneration is limited and functional recovery is often unsatisfactory in patients. Brief electrical stimulation of injured nerves is emerging as a new promising therapy that can relieve pain or induce better axon regeneration and functional recovery than untreated nerves. In this study, we report an innovative wireless and biocompatible stimulator that is also a scaffold for injured nerves when an autograft is applied to bridge a gap in rat sciatic nerves. We have named this device “graft-antenna” to highlight the double functionality of the implant. The scaffold is made of chitosan and incorporates a gold loop antenna (diameter ~1.3 mm, thickness ~70 nm) powered wirelessly by a transcranial magnetic stimulator (TMS). The device is bonded to tissue non-invasively and without sutures, exploiting the photo-adhesion properties of the chitosan scaffold. The stimulator did not migrate after implantation on healthy sciatic nerves in rats and was able to trigger a steady compound muscle action potential for 12 weeks (CMAP ~1.3 mV). No CMAP was elicited by the TMS when the wireless stimulator was not implanted on nerves. Axon regeneration was facilitated in sciatic nerves that were grafted with the graft-antenna and stimulated for 1 hour, once a week (magnetic field magnitude~0.72 T, pulse duration ~350 μs, repetition rate=1 pulse/sec). Eight weeks post-operatively, myelinated axon count, CMAP and nerve conduction velocity were statistically higher in the graft-antenna group (n=5) than in nerves grafted with the chitosan scaffold without antenna.
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