Schematic of the phone-triggered drug delivery system.
Schematic of the phone-triggered drug delivery system.

A simple nanoscale delivery system based on gold nanoclusters loaded with a model drug (neutral red) can be triggered by a smartphone to suppress the growth of tumors, according to recent research [Kong et al., Materials Today (2021),]. The robust ‘all-in-one’ system offers tumor targeting, rapid renal clearance, and the effective production of reactive oxygen species (ROS), which kill cancer cells under low-levels of radiation from a smartphone torch.

“We have designed and fabricated a simple, renal-clearable nanoscale drug delivery system (NDDS) for effective photodynamic therapy of cancer via a smartphone torch light,” explains professor of nanochemistry at the University of Leeds, Dejian Zhou, who led the work with Weili Wang, Mei X. Wu of Harvard Medical School and Xavier Le Guével of Université Grenoble-Alpes, along with coworkers at Cardiff and Utrecht Universities.

Nanoparticle-based all-in-one drug delivery and imaging systems have become increasingly complex but, while they offer the advantages of multi-functionality, are typically too large for renal clearance, potentially leading to long-term toxicity – one of the major barriers to clinical translation and approval.

The atomic gold nanocluster (AuNC) NDDS, however, is small enough to be cleared rapidly via the kidneys. The system comprises three main components: a photosensitizer, in this case neutral red, which produces cancer cell-killing ROS when irradiated with a smartphone torch; the AuNC core, which acts as both a carrier for the neutral red and as a fluorescence agent for tumor imaging; and a layer of PEGylated crosslinkers that anchor neutral red to the core, enhance stability and reduce unwanted interactions while circulating in the body.

“We have found [that] the AuNC delivery system can accumulate effectively in tumor sites without a targeting ligand by simply exploiting a tumor’s enhanced permeability and retention effect,” explains Zhou.

The team believe that their delivery system could translate to the clinic because it is simple to produce, shows rapid renal clearance, which reduces potential long-term toxicity, is highly effective in vivo, and uses a readily accessible smartphone torch as a light source. This contrasts with current photodynamic therapies that, because they require expensive equipment and laser light sources, can only be performed in specialized hospitals. Although the new approach requires a relatively long treatment time, which can be uncomfortable and inconvenient for patients, a wearable smart phone mount could allow continuous irradiation of a tumor while the patient is free to move around. The approach could suffer from off-target phototoxicity, caution the researchers, but this could be mitigated by reducing the spot size of the torch light or improving tumor targeting of the system.

“We are now working on extending our approach to detect, visualize and treat tumors in deeper tissues,” says Zhou.