Bacterial Enzyme Responsive Polymersomes: A Closer Look at the Degradation Mechanism of PEG-block-PLA Vesicles

Abstract

Stimuli-responsive polymersomes that are selectively cleaved by enzymes of pathogenic bacteria are herein reported. The local disruption of the polyester wall in poly(ethylene glycol)-block-poly(lactic acid) (PEG-b-PLA) polymersomes filled with reporter dyes owing to enzymatic degradation by proteinase K was monitored by fluorescence lifetime imaging microscopy. Capsule opening occurred on timescales of minutes to hours, leading to the release of the dye, followed by a slow capsule disintegration, and finally cleavage into monomeric lactic acid over several weeks. These nanocontainers represent a promising element in novel theranostic systems for potential application in advanced wound dressings.

Determination of the Wall Thickness of Block Copolymer Vesicles by Fluorescence Lifetime Imaging Microscopy

“…The intensity in this image is lower, although the excitation intensity is the same. This reduced intensity is attributed to vesicles that desorbed from the glass surface, in line with previous reports …”

“…This reduced intensity is attributed to vesicles that desorbed from the glass surface, in line with previous reports. [10] The time resolved fluorescence data of the dry and the rehydrated (wet) samples, shown in Figure 6, were then analyzed with triple and double-exponential decays, respectively. The lifetimes for the dry sample were τ solv = 3.9 ns, τ wall = 1.68 ns, and τ dry = 0.70 ns (Figure 9a), which match well with the data shown in Figure 5 and Table 1.…”

“…The thickness of the vesicle membrane has been reported to be to a first approximation invariant with size for PS n ‐ b ‐PAA m with small n and m . Hence we investigated, as reported here, PS 115 ‐ b ‐PAA 15 vesicles as a reference and compared them to the biodegradable vesicles of (poly(ethylene glycol)‐ block ‐poly(lactic acid)) PEG 114 ‐ b ‐PLA 167 …”

“…The thickness of the vesicle membrane has been reported to be to a first approximation invariant with size for PS n -b-PAA m with small n and m. [9] Hence we investigated, as reported here, PS 115 -b-PAA 15 vesicles as a reference and compared them to the biodegradable vesicles of (poly(ethylene glycol)-block-poly(lactic acid)) PEG 114 -b-PLA 167 . [10] In general, a water-filled vesicle with radius r and wall thickness w dries in a specific time, when exposed to ambient conditions. Smaller vesicles can be expected to require shorter drying times due to the increased surface area to volume ratio ( Figure 1).…”

Enzyme Degradable Polymersomes from Hyaluronic Acid-block-poly(ε-caprolactone) Copolymers for the Detection of Enzymes of Pathogenic Bacteria

“…As described previously, the lifetime of the dye depends strongly on its surrounding. 9 A typical time correlated single photon counting (TCSPC) decay is depicted in Figure 8, from which the lifetimes can be obtained. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 25 The size of the assemblies before and after treatment with hyaluronidase (for DLS data of neat hyaluronidase solution see Supporting Information, Figure 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 4...…”