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.

Self‐Beating Artificial Cells: Design of Cross‐Linked Polymersomes Showing Self‐Oscillating Motion

“…[7][8][9] Recently, there have been a number of studies on polymersomes for bioengineering and engineering applications, such as drug delivery systems and nanoreactors. [ 10,11 ] Polymersomes have also been studied as model systems to elucidate or mimic the characteristics of biological cell membranes. [ 12,13 ] A variety of synthetic technologies for well-designed block copolymers has enabled the introduction of elaborate cell-like functions to polymersomes.…”

Allosteric inhibition of individual enzyme molecules trapped in lipid vesicles

“…A very attractive alternative is to restrict individual molecules within small, optically transparent containers. Examples include lipid vesicles (20)(21)(22)(23)(24), selfassembled polymer nanocapsules (25,26), protein shells of viral capsids (27), and femtoliter chambers chemically etched into the surface of glass optical fibers (28,29).…”

Cascade Reactions in Multicompartmentalized Polymersomes

“…Such research is of fundamental biological and chemical relevance, because investigating how cellular reactions or interactions take place, in biomimetic, confined, and multicompartmentalized architectures, should improve the understanding of how the complexity of the eukaryotic cell is established step by step. Also, in materials chemistry, this level of control over chemical reactions can provide access to powerful new materials; reactions can be truly confined to provide increased efficacy, [39] and incompatible reactions can be separated and therefore conducted simultaneously. As such, miniaturized microreactors should allow control over attoliter or femtoliter volumes and increase safety and efficacy for biocatalysis/bioengineering purposes.…”