TY - JOUR A1 - Folikumah, Makafui Yao A1 - Neffe, Axel T. A1 - Behl, Marc A1 - Lendlein, Andreas T1 - Thiol Michael-Type reactions of optically active mercapto-acids in aqueous medium JF - MRS advances : a journal of the Materials Research Society N2 - Defined chemical reactions in a physiological environment are a prerequisite for the in situ synthesis of implant materials potentially serving as matrix for drug delivery systems, tissue fillers or surgical glues. ‘Click’ reactions like thiol Michael-type reactions have been successfully employed as bioorthogonal reaction. However, due to the individual stereo-electronic and physical properties of specific substrates, an exact understanding their chemical reactivity is required if they are to be used for in-situ biomaterial synthesis. The chiral (S)-2-mercapto-carboxylic acid analogues of L-phenylalanine (SH-Phe) and L-leucine (SH-Leu) which are subunits of certain collagenase sensitive synthetic peptides, were explored for their potential for in-situ biomaterial formation via the thiol Michael-type reaction. In model reactions were investigated the kinetics, the specificity and influence of stereochemistry of this reaction. We could show that only reactions involving SH-Leu yielded the expected thiol-Michael product. The inability of SH-Phe to react was attributed to the steric hindrance of the bulky phenyl group. In aqueous media, successful reaction using SH-Leu is thought to proceed via the sodium salt formed in-situ by the addition of NaOH solution, which was intented to aid the solubility of the mercapto-acid in water. Fast reaction rates and complete acrylate/maleimide conversion were only realized at pH 7.2 or higher suggesting the possible use of SH-Leu under physiological conditions for thiol Michael-type reactions. This method of in-situ formed alkali salts could be used as a fast approach to screen mercapto-acids for thio Michael-type reactions without the synthesis of their corresponding esters. KW - biomaterial KW - biomedical KW - biomimetic (chemical reaction) KW - chemical synthesis Y1 - 2019 U6 - https://doi.org/10.1557/adv.2019.308 SN - 2059-8521 VL - 4 IS - 46-47 SP - 2515 EP - 2525 PB - Springer Nature Switzerland AG CY - Cham ER - TY - JOUR A1 - Neffe, Axel T. A1 - Löwenberg, Candy A1 - Julich-Gruner, Konstanze K. A1 - Behl, Marc A1 - Lendlein, Andreas T1 - Thermally-induced shape-memory behavior of degradable gelatin-based networks JF - International journal of molecular sciences N2 - Shape-memory hydrogels (SMH) are multifunctional, actively-moving polymers of interest in biomedicine. In loosely crosslinked polymer networks, gelatin chains may form triple helices, which can act as temporary net points in SMH, depending on the presence of salts. Here, we show programming and initiation of the shape-memory effect of such networks based on a thermomechanical process compatible with the physiological environment. The SMH were synthesized by reaction of glycidylmethacrylated gelatin with oligo(ethylene glycol) (OEG) alpha,omega-dithiols of varying crosslinker length and amount. Triple helicalization of gelatin chains is shown directly by wide-angle X-ray scattering and indirectly via the mechanical behavior at different temperatures. The ability to form triple helices increased with the molar mass of the crosslinker. Hydrogels had storage moduli of 0.27-23 kPa and Young's moduli of 215-360 kPa at 4 degrees C. The hydrogels were hydrolytically degradable, with full degradation to water-soluble products within one week at 37 degrees C and pH = 7.4. A thermally-induced shape-memory effect is demonstrated in bending as well as in compression tests, in which shape recovery with excellent shape-recovery rates R-r close to 100% were observed. In the future, the material presented here could be applied, e.g., as self-anchoring devices mechanically resembling the extracellular matrix. KW - shape-memory hydrogel KW - active polymer KW - biopolymer KW - mechanical KW - properties KW - degradation Y1 - 2021 U6 - https://doi.org/10.3390/ijms22115892 SN - 1422-0067 SN - 1661-6596 VL - 22 IS - 11 PB - Molecular Diversity Preservation International CY - Basel ER - TY - JOUR A1 - Julich-Gruner, Konstanze K. A1 - Löwenberg, Candy A1 - Neffe, Axel T. A1 - Behl, Marc A1 - Lendlein, Andreas T1 - Recent trends in the chemistry of shape-memory polymers JF - Macromolecular chemistry and physics N2 - Shape-memory polymers (SMPs) are stimuli-sensitive materials capable of performing complex movements on demand, which makes them interesting candidates for various applications, for example, in biomedicine or aerospace. This trend article highlights current approaches in the chemistry of SMPs, such as tailored segment chemistry to integrate additional functions and novel synthetic routes toward permanent and temporary netpoints. Multiphase polymer networks and multimaterial systems illustrate that SMPs can be constructed as a modular system of different building blocks and netpoints. Future developments are aiming at multifunctional and multistimuli-sensitive SMPs. KW - multifunctional polymers KW - networks KW - shape-memory polymers KW - stimuli-sensitive polymers KW - triple-shape effect Y1 - 2013 U6 - https://doi.org/10.1002/macp.201200607 SN - 1022-1352 VL - 214 IS - 5 SP - 527 EP - 536 PB - Wiley-VCH CY - Weinheim ER -