In the present study, we show how acrylamide-based microgels can be employed for the uptake and release of the drug β-aescin, a widely used natural product with a variety of pharmacological effects. We show how aescin is incorporated into the microgel particles. It has an important influence on the structure of the microgels, by reducing their natural network-density gradient in the swollen state. Moreover, temperature-dependent measurements reveal how the incorporation of aescin stabilizes the microgel particles, while the volume phase transition temperature (VPTT) is almost constant, which is very important for the intended drug release. Finally, it is shown that upon increase of the temperature above the VPTT the particles are able to release aescin from their network, encouraging the use of this particular drug delivery system for hypothermia treatments.

While cationic microgels are potentially useful for the transfection or transformation of cells, their synthesis has certain drawbacks regarding size, polydispersity, yield, and incorporation of the cationic comonomers. In this work, a range of poly(N-isopropylacrylamide) (PNIPAM) microgels with different amounts of the primary amine N-(3-aminopropyl)methacrylamide hydrochloride (APMH) as the cationic comonomer were synthesized. Moreover, the pH-value during reaction was varied for the synthesis of microgels with 10 mol% APMH-feed. The microgels were analyzed by means of their size, thermoresponsive swelling behavior, synthesis yield, polydispersity and APMH-incorporation. The copolymerization of APMH leads to a strong decrease in size and yield of the microgels, while less than one third of the nominal APMH monomer feed is incorporated into the microgels. With an increase of the reaction pH up to 9,5 , the negative effects of APMH copolymerization were significantly reduced. Above this pH, synthesis was not feasible due to aggregation. The results show that the reaction pH has a strong influence on the synthesis of pH-responsive cationic microgels and therefore it can be used to tailor the microgel properties.

We investigate the internal structure of smart core–shell microgels by super-resolution fluorescence microscopy by combining of 3D single molecule localization and structured illumination microscopy using freely diffusing fluorescent dyes.

Cross-linkable microgels are synthesized by copolymerization of NIPAM with 2-hydroxy-4-(methacryloyloxy)–benzophenone (HMABP) and are subsequently UV-cross-linked to obtain smart membranes exhibiting switchable resistance.

In this work, we present a combination of a continuous flow reactor with in situ monitoring of the monomer conversion in a precipitation polymerization. The flow reactor is equipped with a preheating area for the synthesis of thermoresponsive microgels, based on N-isopropylacrylamide (NIPAM). The reaction progress is monitored with in situ FTIR spectroscopy. The monomer conversion at defined residence times is determined from absorbance spectra of the reaction solutions by linear combination with reference spectra of the stock solution and the purified microgel. The reconstruction of the spectra appears to be in good agreement with experimental data in the range of 1710 to 1530 cm− 1, in which prominent absorption bands are used as probes for the monomer and the polymer. With increasing residence time, we observed a decrease in intensity of the ν(C=C) vibration, originating from the monomer, while the ν(C=O) vibration is shifted to higher frequencies by polymerization. Differences between the determined inline conversion kinetics and offline growth kinetics, determined by photon correlation spectroscopy (PCS), are discussed in terms of diffusion and point to a crucial role of mixing in precipitation polymerizations.