title: Light-responsive in situ forming injectable implants for effective drug delivery to the posterior segment of the eye.
abstract: Frequent intravitreal injections are currently the preferred treatment method for diseases affecting the posterior segment of the eye. However, these repeated injections have been associated with pain, risk of infection, hemorrhages, retinal detachment and high treatment costs. To overcome these limitations, light-responsive in situ forming injectable implants (ISFIs) may emerge as novel systems providing site-specific controlled drug delivery to the retinal tissues with great accuracy, safety, minimal invasiveness and high cost efficiency.
  
  
  
  Complex ocular barriers, routes for drug delivery, types of injectable implants, ocular application of light and benefits of light-responsive systems are discussed with regards to challenges and strategies employed for effective drug delivery to the posterior segment of the eye. In particular, we have highlighted photoresponsive moieties, photopolymerization mechanisms and different development strategies with their limitations as well as recent advancements in the field.
  
  
  
  Biodegradable light-responsive ISFIs are promising drug delivery systems that have shown a high degree of biocompatibility with sustained drug release in a number of applications. However, their use in intravitreal drug delivery is still in the very early stages. Issues related to the biocompatibility of the photoinitiator and the elimination of photo-degraded by-products from the ocular tissues need careful consideration, not only from a chemistry standpoint, but also from a biological perspective to improve the suitability of these systems for clinical applications.
authors.affiliation: a Buchanan Ocular Therapeutics Unit, Department of Ophthalmology, Faculty of Medical and Health Sciences , University of Auckland , Auckland , New Zealand.
authors.forename: Rohit
authors.initials: R
authors.lastname: Bisht
authors.affiliation: b Auckland Cancer Society Research Center, Faculty of Medical and Health Sciences , University of Auckland , Auckland , New Zealand.
authors.forename: Jagdish Kumar
authors.initials: JK
authors.lastname: Jaiswal
authors.affiliation: a Buchanan Ocular Therapeutics Unit, Department of Ophthalmology, Faculty of Medical and Health Sciences , University of Auckland , Auckland , New Zealand.
authors.forename: Ying-Shan
authors.initials: YS
authors.lastname: Chen
authors.affiliation: c School of Chemical Sciences, Faculty of Science , University of Auckland , Auckland , New Zealand.
authors.forename: Jianyong
authors.initials: J
authors.lastname: Jin
authors.affiliation: a Buchanan Ocular Therapeutics Unit, Department of Ophthalmology, Faculty of Medical and Health Sciences , University of Auckland , Auckland , New Zealand.
authors.forename: Ilva Dana
authors.initials: ID
authors.lastname: Rupenthal
mesh_terms: D003692:Delayed-Action Preparations / Q000008:administration & dosage; D016503:Drug Delivery Systems; D004343:Drug Implants; D005123:Eye / Q000378:metabolism*; D005128:Eye Diseases / Q000188:drug therapy*; D006801:Humans; D058449:Intravitreal Injections
chemical_list: D003692:Delayed-Action Preparations; D004343:Drug Implants
keywords: Injectable implants; light-responsive systems; ocular drug delivery; photocleavage; photodimerization; photoisomerization