Stimuli-responsive microgels with cationic moieties: characterization and interaction with E. coli cells.

Stimuli-responsive microgel copolymer networks with ionizable functional groups have important applications for encapsulation of drugs, peptides, enzymes, proteins, or cells. Rational design of such networks can be based on characterization of stimuli-induced volume phase transition and spatial distribution of neutral and charged monomer units in crosslinked polymer chains. In this work we successfully synthesized poly(N-vinylcaprolactam-co-1-vinyl-3-methylimidazolium) (poly(VCL-VIM+)) microgels carrying permanent positive charges and demonstrate that 1H high-resolution NMR spectroscopy in combination with transverse (T2) magnetization relaxometry allows investigating separately the behavior of each functional group in the microgel network. The information about comonomer transition temperatures, width of transition, and change in transition entropy were reported and correlated with the concentration of charged functional groups and resulting electrophoretic mobility. A two-state approach was used to describe the temperature-induced volume phase transition separately for neutral and charged polymer segments. The core-corona architecture specific to each functional group was detected revealing that the charged methylated vinylimidazolium groups (VIM+) are concentrated mainly in the corona of the microgel. These biocompatible PVCL-based microgels functionalized with permanent positive charges are shown to serve as an antibacterial system against Gram-negative E. coli strains, due to the positive charge of the incorporated VIM+ comonomer in the polymer network.

MicroGelzymes: pH-Independent Immobilization of Cytochrome P450 BM3 in Microgels.

Microgels are an emerging class of "ideal" enzyme carriers because of their chemical and process stability, biocompatibility, and high enzyme loading capability. In this work, we synthesized a new type of permanently positively charged poly(N-vinylcaprolactam) (PVCL) microgel with 1-vinyl-3-methylimidazolium (quaternization of nitrogen by methylation of N-vinylimidazole moieties) as a comonomer (PVCL/VimQ) through precipitation polymerization. The PVCL/VimQ microgels were characterized with respect to their size, charge, swelling degree, and temperature responsiveness in aqueous solutions. P450 monooxygenases are usually challenging to immobilize, and often, high activity losses occur after the immobilization (in the case of P450 BM3 from Bacillus megaterium up to 100% loss of activity). The electrostatic immobilization of P450 BM3 in permanently positively charged PVCL/VimQ microgels was achieved without the loss of catalytic activity at the pH optimum of P450 BM3 (pH 8; ∼9.4 nmol 7-hydroxy-3-carboxy coumarin ethyl ester/min for free and immobilized P450 BM3); the resulting P450-microgel systems were termed P450 MicroGelzymes (P450 µ-Gelzymes). In addition, P450 µ-Gelzymes offer the possibility of reversible ionic strength-triggered release and re-entrapment of the biocatalyst in processes (e.g., for catalyst reuse). Finally, a characterization of the potential of P450 µ-Gelzymes to provide resistance against cosolvents (acetonitrile, dimethyl sulfoxide, and 2-propanol) was performed to evaluate the biocatalytic application potential.

[Delayed Occluding Membrane (DOM) - A New Concept to Prevent Spinal Cord Ischaemia During Endovascular Aortic Aneurysm Repair]. / Delayed Occluding Membrane (DOM) ­ ein neuer Ansatz zur Protektion der spinalen Ischämie bei endovaskulärem Aortenrepair.

INTRODUCTION: The risk of spinal cord ischemia is a relevant problem in in fields of open and endovascular thoracoabdominal aortic aneurysm repair (TAAA). Despite all efforts, no therapeutical concept exists, which enables a complete treatment of the TAAA without open branches or fenestrations, and reduces the risk for a spinal cord ischemia (SCI) to the minimum. In this article, we would like to present a new concept based on slow-occluding hydrogel-textile membrane, which could help to reduce the SCI risk during endovascular TAAA repair. CONCEPT: A hydrogel textile membrane is under development, which could be used a functional unit of endovascular stentprosthesis. If in contact with blood, glutathion induces swelling of the induces ongoing swelling of the membrane because of the triggered degradation of the crosslinker. Due to the resulting water uptake of the hydrogel textile membrane and mass increase of the gel, the swelling leads to a stabilization of the membrane. In vitro studies show, that the swelling of the hydrogel textile membrane should lead to a controlled decreasing flow into the aneurysm sac. After a pre-defined period, the membrane is occluded and the aneurysm sac perfusion stops. So, by using the hydrogel textile membrane, a complete treatment of the TAAA can be realized in one procedure without further re-intervention or pre-interventional measures. Furthermore, the risk of a SCI would be minimized. As this treatment concept is under development, only interim results are presented. CONCLUSION: The successful development and usage of a slow-occluding hydrogel textile membrane as a part of endovascular stentprosthesis could help to reduce the risk SCI during endovascular TAAA surgery.