title: Nanoparticle suspensions enclosed in methylcellulose: a new approach for quantifying nanoparticles in transmission electron microscopy.
abstract: Nanoparticles are of increasing importance in biomedicine but quantification is problematic because current methods depend on indirect measurements at low resolution. Here we describe a new high-resolution method for measuring and quantifying nanoparticles in suspension. It involves premixing nanoparticles in a hydrophilic support medium (methylcellulose) before introducing heavy metal stains for visualization in small air-dried droplets by transmission electron microscopy (TEM). The use of methylcellulose avoids artifacts of conventional negative stain-TEM by (1) restricting interactions between the nanoparticles, (2) inhibiting binding to the specimen support films and (3) reducing compression after drying. Methylcellulose embedment provides effective electron imaging of liposomes, nanodiscs and viruses as well as comprehensive visualization of nanoparticle populations in droplets of known size. These qualities facilitate unbiased sampling, rapid size measurement and estimation of nanoparticle numbers by means of ratio counting using a colloidal gold calibrant. Specimen preparation and quantification take minutes and require a few microliters of sample using only basic laboratory equipment and a standard TEM.
authors.affiliation: School of Medicine, University of St Andrews, St Andrews, Fife, UK.
authors.forename: Christian
authors.initials: C
authors.lastname: Hacker
authors.affiliation: School of Medicine, University of St Andrews, St Andrews, Fife, UK.
authors.forename: Jalal
authors.initials: J
authors.lastname: Asadi
authors.affiliation: Centre for Biomolecular Sciences, University of St Andrews, St. Andrews, Scotland.
authors.forename: Christos
authors.initials: C
authors.lastname: Pliotas
authors.affiliation: School of Medicine, University of St Andrews, St Andrews, Fife, UK.
authors.forename: Sophie
authors.initials: S
authors.lastname: Ferguson
authors.affiliation: Biomedical Sciences Research Complex, University of St Andrews, North Haugh, St Andrews, United Kingdom.
authors.forename: Lee
authors.initials: L
authors.lastname: Sherry
authors.affiliation: Centre for Biomolecular Sciences, University of St Andrews, St. Andrews, Scotland.
authors.forename: Phedra
authors.initials: P
authors.lastname: Marius
authors.affiliation: School of Medicine, University of St Andrews, St Andrews, Fife, UK.
authors.forename: Javier
authors.initials: J
authors.lastname: Tello
authors.affiliation: Biomedical Sciences Research Complex, University of St Andrews, North Haugh, St Andrews, United Kingdom.
authors.forename: David
authors.initials: D
authors.lastname: Jackson
authors.affiliation: Centre for Biomolecular Sciences, University of St Andrews, St. Andrews, Scotland.
authors.forename: James
authors.initials: J
authors.lastname: Naismith
authors.affiliation: School of Medicine, University of St Andrews, St Andrews, Fife, UK.
authors.forename: John Milton
authors.initials: JM
authors.lastname: Lucocq