Matrix Supported Poly(2-oxazoline)-Based Hydrogels for DNA Catch and Release

We describe the synthesis of matrix supported hydrogel structures based on amine containing poly­(2-oxazoline)­s and their use to bind and release genetic material for potential applications in diagnostics or pathogen detection. Amine containing poly­(2-oxazoline)­s were synthesized by copolymerization of 2-ethyl-2-oxazoline with a monomer bearing a <i>tert</i>-butyl oxycarbonyl (Boc) protected amine group in the 2-position and subsequent deprotection. The statistical copolymers were used to generate hydrogels and matrix supported hydrogels by cross-linking of a certain fraction of the amine groups with epichlorhydrin. Supported structures were prepared by soaking porous polyethylene (PE) or polypropylene (PP) filter materials in a copolymer/epichlorhydrin solution, which was cross-linked upon heating. Scanning electron microscopy (SEM) of the composites revealed a bead like structure of the gel phase, which could be attributed to a lower critical solution temperature (LCST) behavior of the initial polymer prior to gelation. The dependency of the LCST behavior on the content of amine groups was investigated. Swelling values and the ratio of hydrogel per composite was determined using water sorption analysis. Subsequently, the ability of the systems to absorb and release labeled DNA was tested. Uptake and stimulated release, triggered by changes in pH, temperature, and heparin concentration, were investigated using fluorescence microscopy. Polymerase chain reaction (PCR) proved the successful recovery of the DNA, demonstrating the potential of the presented system for a broad range of molecular biological applications

Conjugated Oligomers as Fluorescence Marker for the Determination of the Self-Healing Efficiency in Mussel-Inspired Polymers

Within the current study, a novel approach for the detailed determination of the scratch healing efficiency in mussel-inspired polymer films is presented. For this purpose, a sensor molecule was incorporated into a self-healing polymer network based on reversible zinc–histidine interactions. The fluorescence of the sensor molecule was monitored enabling a detailed depth- and time-resolved determination of the healing efficiency by means of confocal laser scanning microscopy (CLSM). Finally, this concept represents an efficient and detailed approach for the determination of the scratch self-healing efficiency in polymer films and can also be applied for other scratch self-healing systems, which are based on reversible dynamic bonds

Polymersomes with Endosomal pH-Induced Vesicle-to-Micelle Morphology Transition and a Potential Application for Controlled Doxorubicin Delivery

In order to obtain a novel, pH responsive polymersome system, a series of pH responsive block copolymers were synthesized via the reversible addition–fragmentation chain transfer (RAFT) polymerization of 3,4-dihydro-2<i>H</i>-pyran (DHP) protected 2-hydroxyethyl methacrylate (HEMA) (2-((tetrahydro-2<i>H</i>-pyran-2-yl)­oxy)­ethyl methacrylate (THP-HEMA)) and 2-(dimethylamino) ethyl methacrylate (DMAEMA) using p­(THP-HEMA) as a macro chain transfer agent (mCTA). The degree of polymerization (DP) of the p­(THP-HEMA) block was fixed to 35, whereas the DP of the p­(DMAEMA) block was systematically varied from 21 to 50. In aqueous solution, the block copolymer with the shortest p­(DMAEMA) block (DP = 21) self-assembled into vesicles, while the polymer with 30 units of p­(DMAEMA) formed a mixture of micelles and vesicles. The polymer with the longest p­(DMAEMA) block (DP = 50) formed exclusively micelles. The corresponding polymersomes exhibited a morphology transition from vesicles at neutral pH values to micelles upon lowering the pH value down to endosomal pH value as investigated by DLS and cryo-TEM. The capability of polymersomes to encapsulate both hydrophobic (e.g., Nile Red) and hydrophilic (e.g., doxorubicin hydrochloride (DOX·HCl)) cargos was verified by in vitro studies. Drug release studies demonstrated that the DOX·HCl release is significantly accelerated under acidic pH values compared to physiological conditions. Cytotoxicity studies revealed that DOX·HCl loaded polymersomes exhibited an efficient cell death comparable to free DOX·HCl. CLSM and flow cytometry studies showed that DOX·HCl loaded vesicles were easily taken up by L929 cells and were mainly located in the cytoplasm and cell nuclei

Tailoring Cellular Uptake and Fluorescence of Poly(2-oxazoline)-Based Nanogels

Controlling the size and charge of nanometer-sized objects is of upmost importance for their interactions with cells. We herein present the synthesis of poly­(2-oxazoline) based nanogels comprising a hydrophilic shell and an amine containing core compartment. Amine groups were cross-linked using glutaraldehyde resulting in imine based nanogels. As a drug model, amino fluorescein was covalently immobilized within the core, quenching excessive aldehyde functions. By varying the amount of cross-linker, the zeta potential and, hence, the cellular uptake could be adjusted. The fluorescence of the nanogels was found to be dependent on the cross-linking density. Finally, the hemocompatibility of the described systems was studied by hemolysis and erythrocyte aggregation assays. While cellular uptake was shown to be dependent on the zeta potential of the nanogel, no harmful effects to red blood cells was observed, rendering the present system as an interesting toolbox for the production of nanomaterials with a defined biological interaction profile

Star-Shaped Drug Carriers for Doxorubicin with POEGMA and POEtOxMA Brush-like Shells: A Structural, Physical, and Biological Comparison

The synthesis of amphiphilic star-shaped poly­(ε-caprolactone)-<i>block</i>-poly­(oligo­(ethylene glycol)­methacrylate)­s ([PCL₁₈-<i>b</i>-POEGMA]₄) and poly­(ε-caprolactone)-<i>block</i>-poly­(oligo­(2-ethyl-2-oxazoline)­methacrylate)­s ([PCL₁₈-<i>b</i>-POEtOxMA]₄) is presented. Unimolecular behavior in aqueous systems is observed with the tendency to form loose aggregates for both hydrophilic shell types. The comparison of OEGMA and OEtOxMA reveals that the molar mass of the macromonomer in the hydrophilic shell rather than the mere length is the crucial factor to form an efficiently stabilizing hydrophilic shell. A hydrophilic/lipophilic balance of 0.8 is shown to stabilize unimolecular micelles in water. An extensive in vitro biological evaluation shows neither blood nor cytotoxicity. The applicability of the polymers as drug delivery systems was proven by the encapsulation of the anticancer drug doxorubicin, whose cytotoxic effect was retarded in comparison to the free drug