title: Block-copolymer vesicles as nanoreactors for enzymatic reactions.
abstract: The impact of the spatial confinement of polystyrene-block-poly(acrylic acid) (PS-b-PAA) block copolymer (BCP) vesicles on the reactivity of encapsulated bovine pancreas trypsin is studied. Enzymes, as well as small molecules, are encapsulated with loading efficiencies up to 30% in BCP vesicles with variable internal volumes between 0.014 aL (internal vesicle diameter, d(in) = 30 nm) and 8 aL (d(in) = 250 nm), obtained by manipulating the vesicle preparation conditions. The kinetics of the trypsin-catalyzed reaction of a fluorogenic substrate inside and outside the vesicles is quantitatively estimated using fluorescence spectroscopic analyses in conjunction with the use of NaNO(2) as selective quencher for non-encapsulated fluorophores. The values of the catalytic turnover number obtained for reactions in differently sized nanoscale reactors show a significant increase (up to approximately 5x) with decreasing BCP vesicle volume, while the values of the Michaelis-Menten constant decrease. The observed increase in enzyme efficiency by two orders of magnitude compared to bulk solution is attributed to an enhanced rate of enzyme-substrate and molecule-wall collisions inside the nanosized reactors, as predicted in the literature on the basis of Monte Carlo simulations.
authors.affiliation: Department of Materials Science and Technology of Polymers University of Twente, MESA+ Institute for Nanotechnology Postbus 217, 7500 AE Enschede, The Netherlands.
authors.forename: Qi
authors.initials: Q
authors.lastname: Chen
authors.forename: Holger
authors.initials: H
authors.lastname: Schönherr
authors.forename: G Julius
authors.initials: GJ
authors.lastname: Vancso
mesh_terms: D005453:Fluorescence; D007700:Kinetics; D018613:Microscopy, Confocal; D049329:Nanostructures / Q000737:chemistry* / Q000648:ultrastructure; D010316:Particle Size; D011108:Polymers / Q000737:chemistry*; D014357:Trypsin / Q000378:metabolism*
chemical_list: D011108:Polymers; D014357:Trypsin