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.

In this study, the interplay among the phospholipid 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) as a model membrane, the nonsteroidal anti-inflammatory drug naproxen, and the saponin β-aescin are investigated. The naproxen amount was fixed to 10 mol %, and the saponin amount varies from 0.0 to 1.0 mol%. Both substances are common ingredients in pharmaceutics; therefore, it is important to obtain deeper knowledge of their impact on lipid membranes. The size and properties of the DMPC model membrane upon naproxen and aescin addition were characterized with differential scanning calorimetry (DSC), small- and wide-angle X-ray scattering (SAXS, WAXS), and photon correlation spectroscopy (PCS) in a temperature-dependent study. The interaction of all substances was dependent on the lipid phase state, which itself depends on the lipid’s main phase transition temperature Tm. The incorporation of naproxen and aescin distorted the lipid membrane structure and lowers Tm. Below Tm, the DMPC–naproxen–aescin mixtures showed a vesicle structure, and the insertion of naproxen and aescin influenced neither the lipid chain–chain correlation distance nor the membrane thickness. Above Tm, the insertion of both molecules instead induced the formation of correlated bilayers and a decrease in the chain–chain correlation distance. The presented data clearly confirm the interaction of naproxen and aescin with DMPC model membranes. Moreover, the incorporation of both additives into the model membranes is evidenced.

While core-shell microgels have been intensively studied in their fully synthesized state, the formation mechanism of the shell has not been completely understood. Such insight is decisive for a customization...

Poly-N-n-propylacrylamide based microgels with embedded Pd-nanoparticles are synthesized with varying amounts (5-25 mol%) of methacrylic acid (MAc) comonomer. The microgels are characterized to investigate the influence of the comonomer content on catalytic activity of the hybrid particles. Since the acidity changes significantly upon copolymerization, the incorporated amount and apparent p K a value of the MAc via potentiometric titration are determined. The thermoresponsive properties of the microgels are characterized by means of photon correlation spectroscopy at pH values of 4 and 10, which correspond to the protonated and deprotonated state of the acidic copolymer according to the determined p K a values. MAc shows tremendous influence on the thermoresponsivity of the microgels not only related to the amount of MAc but especially upon change in pH. The prepared microgel systems are subsequently loaded with palladium nanoparticles. Their catalytic activity is investigated by the reduction of 4-nitrophenol. The catalytic degradation of the educt is monitored via UV-vis spectroscopy and the observed absorbance decay is analyzed by a pseudo-first order kinetic. Derived reaction rate constants are normalized with respect to the surface area of the palladium nanoparticles, revealing that the charge density and hydrophilicity within the microgel template greatly affect reactivity of embedded nanoparticles.

Front Cover: In article number 2200045, Thomas Hellweg and co‐workers describe the preparation of a variety of PNNPAM‐based microgels copolymerized with methacrylic acid and loaded with monodisperse catalytically active palladium nanoparticles. The copolymerized methacrylic acid leads to interesting pH‐ and thermoresponsive properties of the gel particles and shows ambivalent influences regarding the catalytic activity of the embedded nanoparticles. The cover page shows TEM images of the loaded system with the lowest and highest amount of methacrylic acid presented in the study. Both systems catalyze the reduction of 4‐nitrophenol to 4‐aminophenol, at which the system with more comonomer content shows a drastically decreased reaction rate as compared to the system with low amount of comonomer.