Biocides are widely used for preventing the spread of microbial infections and fouling of materials. Since their use can build up microbial resistance and cause unpredictable long-term environmental problems, new biocidal agents are required. In this study, we demonstrate a concept in which an antimicrobial polymer is deactivated by the cleavage of a single group. Following the satellite group approach, a biocidal quaternary ammonium group was linked through a poly(2-methyloxazoline) to an ester satellite group. The polymer with an octyl-3-propionoate satellite group shows very good antimicrobial activity against Gram-positive bacterial strains. The biocidal polymer was also found to have low hemotoxicity, resulting in a high HC50 /MIC value of 120 for S. aureus. Cleaving the ester satellite group resulted in a 30-fold decrease in antimicrobial activity, proving the concept valid. The satellite group could also be cleaved by lipase showing that the antimicrobial activity of the new biocidal polymers is indeed bioswitchable.

Three amphiphilic diblock poly(2-oxazoline) copolymers composed of the hydrophilic poly(2-methyl-2-oxazoline) and hydrophobic poly(2-alkyl-2-oxazoline) with alkyl = pentyl (P1), heptyl (P2), and nonyl side chain (P3) lengths of the hydrophobic block were synthesized by ring-opening cationic polymerization. These polymers form micelles in water above their critical micelle concentration. The temperature-dependent stability of the micellar aggregates was analyzed by DLS and turbidity measurements as well as pyrene solubilization between 20 and 80°C in water. Moreover, the chemical composition of the block copolymers was determined by 1 H NMR spectroscopy. In particular, it was possible to quantify the degree of aggregations of the individual groups of both blocks by including the chemical composition into the derived equations. It could be shown by varying the temperature that both the chemical composition and the degree of micellization depend on the number of bonds of the considered structural groups of the side chain with respect to the backbone of the hydrophobic block as well as the length of the side chain. In addition, temperature-dependent T 1 and T 2 measurements were performed to determine the dynamics of the structural groups of the hydrophilic and hydrophobic blocks. Correlation times and activation energies were determined of the individual structural groups confirming the different mobilities. ■ INTRODUCTIONAmphiphilic block copolymers represent the most important extension of low molar mass amphiphiles with respect to structural diversity, chemical composition, and functionality. The simplest and still most abundant type of block copolymer consists of two block segments AB in a linear arrangement, each formed by a different monomer. 1,2 In selective solvents, amphiphilic block copolymers self-assemble and can form a variety of aggregated structures including vesicles, 3 polymersomes, 4 and micelles. 5 Especially polymer micelles have attracted much attention in the past due to their potential application in biomedicals, 6−12 surface modification, 13−15 and catalysis. 16−18 An interesting class of amphiphilic block copolymers is based on poly(2-oxazolines) that are prepared by ring-opening cationic polymerization. 19−21,30−32 The length of the alkyl side chains controls to a large extent the solubility in water of the poly(2-alkyl-2-oxazolines). Only polymers with 2-methyl-, 2-ethyl-, and 2-isopropyl-2-oxazolines lead to water-soluble materials at room temperature while longer alkyl side chains lead to water-insoluble polymers. 22 Moreover, it has been shown that aqueous solutions of certain homopolymers such as poly(2-isopropyl-2-oxazoline) (PIPOZ) and poly(2-ethyl-2-oxazoline) (PEOZ) undergo phase separation upon heating beyond their cloud point temperature, T CP . Depending on the polymer molecular weight and polymer concentration, T CP ranges from 36 to 80°C 23,24 and from ∼62 to 100°C 25 for solutions of PIPOZ and PEOZ, respectively. This property has also been used to design gradient copolyme...

Core‐crosslinked nanoparticles presenting secondary amine functional groups in the hydrophilic shell are synthesized by a bottom‐up approach. The route utilizes polymerization of 2‐oxazolines to prepare tailor‐made block copolymers with a primary or secondary amine end group in the hydrophilic block and alkynyl moieties in the hydrophobic part of the polymer. Upon solubilization in the aqueous media, these block copolymers form micelles that are photocrosslinked by a radical polymerization process to afford two types of core‐crosslinked nanoparticles, either with secondary amines, NP1, or primary amines, NP2, on the surface. The dimensions and stability of the core‐crosslinked nanoparticles are characterized by dynamic light scattering and fluorescence spectroscopy. The availability and reactivity of the amine groups in the hydrophilic shell are demonstrated by reaction with different aromatic model compounds resulting in a degree of surface functionalization of 4–47% for NP1 nanoparticles with secondary amino groups and a 20–95% degree of surface functionalization for NP2 with primary amine groups, as determined by UV–vis spectroscopy.

Nanoparticles represent the most widely studied drug delivery systems targeting cancer. Polymeric nanoparticles can be easily generated through a microemulsion polymerization. Herein, the synthesis, radiolabeling, and in vivo evaluation of nanoparticles (NPs) functionalized by an organosilicon fluoride acceptor (SiFA) are reported which can be radiolabeled without further chemical modifications. Four nanoparticles in the sub-100 nm range with distinct hydrodynamic diameters of 20 nm (NP1), 33 nm (NP2), 45 nm (NP3), and 72 nm (NP4), respectively, were synthesized under size-controlled conditions. The SiFA-labeling building block acted as an initiator for the polymerization of polymer P1. The nanoparticles were radiolabeled with fluorine-18 (F) through simple isotopic exchange (IE) and analyzed in vivo in a murine mammary tumor model (EMT6). The facile F radiolabeling SiFA methodology, performed in ethanol under mild reaction conditions, gave radiochemical yields (RCYs) of 19-26% and specific activities (SA) of 0.2-0.3 GBq/mg. Based on preclinical PET analysis, the tumor uptake and clearance profiles were analyzed depending on particle size. The nanoparticle size of 33 nm showed the highest tumor accumulation of SUV 0.97 (= 4.4%ID/g) after 4 h p.i. through passive diffusion based on the Enhanced Permeability and Retention (EPR) effect. Overall, this approach exhibits a simple, robust, and reliable synthesis of F radiolabeled polymeric nanoparticles with a favorable in vivo evaluation profile. This approach represents a straightforward synthetically accessible alternative to produce radiolabeled nanoparticles without any further surface modification to attach a radioisotope.

Surface-functional nanoparticles have been fabricated by utilizing bifunctional poly(2-oxazoline) macromonomers as surfactants in a microemulsion process.