title: Photosensitiser delivery for photodynamic therapy. Part 1: Topical carrier platforms.
abstract: BACKGROUND
  Photodynamic therapy (PDT) is a medical treatment in which a combination of a photosensitising drug and visible light causes destruction of selected cells. Due to the lack of true selectivity of preformed photosensitisers for neoplastic tissue and their high molecular weights, PDT of superficial skin lesions has traditionally been mediated by topical application of the porphyrin precursor 5-aminolevulinic acid (ALA).
  
  
  OBJECTIVE
  This article aims to review the traditional formulation-based approaches taken to topical delivery of ALA and discusses the more innovative strategies investigated for enhancement of PDT mediated by topical application of ALA and preformed photosensitisers.
  
  
  METHODS
  All of the available published print and online literature in this area was reviewed. As drug delivery of agents used in PDT is still something of an emerging field, it was not necessary to go beyond literature from the last 30 years.
  
  
  CONCLUSIONS
  PDT of neoplastic skin lesions is currently based almost exclusively on topical application of simple semisolid dosage forms containing ALA or its methyl ester. Until expiry of patents on the current market-leading products, there is unlikely to be a great incentive to engage in design and evaluation of innovative formulations for topical PDT, especially those containing the more difficult-to-deliver preformed photosensitisers.
authors.affiliation: School of Pharmacy, Medical Biology Centre, Queen's University Belfast, 97 Lisburn Road, Belfast, UK. r.donnelly@qub.ac.uk
authors.forename: Ryan F
authors.initials: RF
authors.lastname: Donnelly
authors.forename: Paul A
authors.initials: PA
authors.lastname: McCarron
authors.forename: Desmond I J
authors.initials: DI
authors.lastname: Morrow
authors.forename: Stéphane A
authors.initials: SA
authors.lastname: Sibani
authors.forename: A David
authors.initials: AD
authors.lastname: Woolfson
mesh_terms: D000287:Administration, Topical; D000818:Animals; D004337:Drug Carriers / Q000737:chemistry*; D006801:Humans; D010778:Photochemotherapy / Q000379:methods*; D017319:Photosensitizing Agents / Q000008:administration & dosage* / Q000627:therapeutic use*; D012869:Skin Absorption
chemical_list: D004337:Drug Carriers; D017319:Photosensitizing Agents