biostudies-literatureRichardson SCWellcome TrustNIGMS NIH HHSEngineering and Physical Sciences Research Council1-11https://www.ebi.ac.uk/biostudies/studies/S-EPMC6661902biostudies-literatureUnknown127(1)Macromolecular therapeutics and nano-sized drug delivery systems often require localisation to specific intracellular compartments. In particular, efficient endosomal escape, retrograde trafficking, or late endocytic/lysosomal activation are often prerequisites for pharmacological activity. The aim of this study was to define a fluorescence microscopy technique able to confirm the localisation of water-soluble polymeric carriers to late endocytic intracellular compartments. Three polymeric carriers of different molecular weight and character were studied: dextrin (Mw~50,000 g/mol), a N-(2-hydroxypropyl)methacrylamide (HPMA) copolymer (Mw approximately 35,000 g/mol) and polyethylene glycol (PEG) (Mw 5000 g/mol). They were labelled with Oregon Green (OG) (0.3-3 wt.%; <3% free OG in respect oJournal of controlled release : official journal of the Controlled Release SocietyThe use of fluorescence microscopy to define polymer localisation to the late endocytic compartments in cells that are targets for drug delivery.PMC6661902R01 GM058202-11R01 GM058202EP/C013220/1Davies MWPiper RCDeacon SPWallom KLPowell AJDuncan RFerguson ELRichardson SCfalseThe use of fluorescence microscopy to define polymer localisation to the late endocytic compartments in cells that are targets for drug delivery.Macromolecular therapeutics and nano-sized drug delivery systems often require localisation to specific intracellular compartments. In particular, efficient endosomal escape, retrograde trafficking, or late endocytic/lysosomal activation are often prerequisites for pharmacological activity. The aim of this study was to define a fluorescence microscopy technique able to confirm the localisation of water-soluble polymeric carriers to late endocytic intracellular compartments. Three polymeric carriers of different molecular weight and character were studied: dextrin (Mw~50,000 g/mol), a N-(2-hydroxypropyl)methacrylamide (HPMA) copolymer (Mw approximately 35,000 g/mol) and polyethylene glycol (PEG) (Mw 5000 g/mol). They were labelled with Oregon Green (OG) (0.3-3 wt.%; <3% free OG in respect o2008-01-01T00:00:00Z2008 Apr2025-04-22T15:09:33.472Z2019-08-02T07:02:38ZS-EPMC66619021828112010.1016/j.jconrel.2007.12.015