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Small photosensitizers for photodynamic therapy

Ultra-small photosensitizer molecules enable precise, minimally invasive photodynamic therapy with exceptional sensitivity and selectivity.

The molecules designed are the smallest reported photosensitizers (PS) to date, offering a minimally invasive precise approach to photodynamic therapy (PDT) with high sensitivity and selectivity.

Its compatibility with a wide range of biomolecules provides an opportunity to use it as a PS tailored to targeting various types of diseases – from infections to tumours.


This photosensitizer can be used in photodynamic therapy to target diseased cells with high precision.

Development Status

Preliminary data on use for cancer and antimicrobial PDT with good safety profiles.

IP Status

  • US patent granted
  • EP patent in National Phase examination

Commercial Offerings

  • License to the patent rights for further development of the technology.


The designed small molecule - benzoselenadiazole - is a photosensitizer (PS) with great potential as a novel photodynamic therapy (PDT). Unlike other bulkier fluorophores in the market which frequently target healthy surrounding cells, this PS has been designed to be remarkably small and non-charged, enabling more efficient incorporation into diseased cells.

The PS can be coupled to several biomolecules, ranging from small molecules to peptides or antibodies, making it a versatile PDT that can be tailored to precisely target your disease of interest – from infected cells to microtumours.


Benzoselenadiazole is the smallest reported photosensitizer (PS) designed to date. The small size of molecule causes the PS to mimic native biomolecules, recapitulating highly efficient uptake into cells with altered metabolic signatures reflective of disease.

Upon targeted exposure to non-toxic light, the highly sensitive and selective uptake of this PS enables its utility as a photodynamic therapy (PDT) to precisely target disease-causing cells even at early stages of metabolic dysfunction, while sparing healthy cells to minimize unwanted off-target effects.


  • Improved efficiency, offering unparalleled sensitivity and selectivity for diseased cells specifically
  • Broad compatibility for incorporation into many biomolecules, enabling versatility against different types of diseased cells
  • Precise activation only by exposure to non-toxic light for safety in vivo


Benson, S., de Moliner, F., Fernandez, A. et al. Photoactivatable metabolic warheads enable precise and safe ablation of target cells in vivo. Nat Commun 12, 2369 (2021).

Benson, S., Kiang, A., Lochenie, C., Lal, N., Mohanan, S.M.P.C., Williams, G.O.S., Dhaliwal, K., Mills, B., Vendrell, M. (2023). Environmentally sensitive photosensitizers enable targeted photodynamic ablation of Gram-positive antibiotic-resistant bacteria. Theranostics, 13(11), 3814-3825.

Quote: TEC1104067

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Emily Thompson

Technology Transfer Manager
Edinburgh Innovations Ltd
The University of Edinburgh