The synthesis of a polyacetal-block-polyurethane copolymer was achieved which possesses the ability to depolymerize both selectively and in response to orthogonal stimuli, heat and pH. To utilize heat as a stimulus, poly(phthalaldehyde) (PPA) was used as a block of the copolymer, while poly(benzyl-4-hydroxymethylphenylcarbamate) (PPC) end-capped with a tert-butoxycarbonyl protecting group (Boc group) were explored for viability as a pH-responsive block. The stimulus-induced depolymerization was studied using nuclear magnetic resonance (NMR), gel permeation chromatography (GPC), and attenuated total reflectance infrared spectroscopy (ATR-IR). These techniques confirmed that the depolymerization event did not affect the nature of the neighboring polymeric block. Depolymerization kinetics were measured for various chain lengths of each block. The results are presented and discussed to explore the ability of these materials to depolymerize in a controlled manner depending on the magnitude of the stimulus, as well as the ability for the blocks to remain unaffected by the orthogonal stimulus. This work shows promise for the development of advanced coatings systems and drug delivery applications.

Kappa (k-), iota (ɩ-), and lambda (λ-) Carrageenan (Car) microparticles were synthesized by crosslinking corresponding natural polymers with divinyl sulfone (DVS) via microemulsion polymerization/crosslinking methods for potential biomedical applications. Negatively charged e.g., -44 mV of Car particles were modified with diethylenetriamine (DETA) to generate positively charged modified (M-) ᴋ-Car particles with +23 mV zeta potential values. Cationic M-Car-DETA particles were found to be effectively antimicrobial material against gram negative bacteria, and some fungi species. Moreover, upon protonation of M-Car-DETA particles with HCl the effectiveness against all types of microorganisms are significantly increased. All types of Car based particles can be applicable for blood contacting material as low hemolysis ratio, 2.56% and high blood clotting capability, 86% were obtained. Furthermore, Car based particles found biocompatible against L929 fibroblast cells, and can induce necrotic cell death at 12.5 μg/mL concentration against DLD-1 colon cancer cells. M-ᴋ-Car-DETA particles were also demonstrated to be useful rending long term and linear drug release profiles using Rosmarinic Acid (RA) as a model drug.

The simultaneous capability of high-strain deformation and high shape recovery ratio constitutes a great challenge in design of the shape-memory polymers. Here we report on poly(carbonate-urea-urethane)s (PCUUs) synthesized by a precursor route, based on oligo(alkylene carbonate) diols, L-lysine diisocyanate (LDI), and water vapor. When programed with a strain of ε prog = 800%, the PCUU networks exhibited a one-way shape-memory effect (1W-SME) with excellent shape fixity (> 97%) and shape recovery (> 99%) ratios. The switching temperatures (T sw) varied between 50 and 56 °C and correlated to the melting transitions of the switching domains. The obtained PCUUs capable of high-strain are interesting candidate materials for degradable biomaterials as required in smart medical devices.

Spherical carbon particles (CPs) with controllable size and surface functionalities were prepared via hydrothermal treatment using sucrose as a precursor and then post modification methods. The CPs were prepared in two steps; firstly, dewatering of sucrose molecules at relatively low temperatures and secondly, carbonization at high temperatures. The micro/nano-sized CPs were functionalized by 2-Acrylamido-2-methylpropane sulfonic acid (AMPS), (3-Acrylamidopropyl)-trimethylammonium chloride (APTMACI), and N-isopropylacrylamide (NIPAM) in order to have the corresponding polymers on the surface of CPs. The monomers were polymerized via atom transfer radical polymerization (ATRP) by means of grafted initiator onto the CPs surface. Additionally, copolymer of these monomers was synthesized to introduce additional properties. The stability of the functionalized CPs in different solutions, and pH, temperature responsive behaviors of the newly prepared CP-polymers composite were evaluated.

Poly (lactic acid) (PLA) bioplastics are recyclable and biodegradable thermoplastics. They are derived from environmentally friendly sources such as potatoes, cornstarch and sugarcane. However, PLA is inherently brittle with low impact strength. The goal of this study is to improve mechanical properties of PLA by the addition of calcium carbonate (CaCO3) fillers. PLA composites were prepared by injection molding conventional limestone (LS) and white chicken eggshell (WES) powders with particle sizes of 63 μm and 32 μm in amounts of 5 wt. %, 10 wt. % and 20 wt. %. Mechanical properties such as, tensile strength, tensile modulus, and Charpy impact strengths were investigated. These three properties were evaluated and the results statistically analyzed using ANOVA F-test. For both particle sizes, the tensile strength decreased as the filler content increased, but was highest for a filler loading of 5 wt. %. In general, the 32 μm powder fillers had better tensile strengths than 63 μm sized fillers. The tensile modulus increased with filler content and was highest at 20 wt. % for both particle sizes. The LS/PLA composites had better toughness than the WES/PLA composites. The particle filler morphology and fractured surfaces were observed by scanning electron microscopy (SEM) and determined to have well dispersed particles with smooth fractured surfaces. Water absorption behavior of PLA/CaCO3 composites were studied by immersion in distilled water at room temperature for 56 days. Virgin PLA absorbed the least amount of water while the water absorption of CaCO3 composites were a function of powder type and content.

In this study, a multiblock copolymer containing oligo(3-methyl-morpholine-2,5-dione) (oMMD) and oligo(3-sec-butyl-morpholine-2,5-dione) (oBMD) building blocks obtained by ring-opening polymerization (ROP) of the corresponding monomers, was synthesized in a polyaddition reaction using an aliphatic diisocyanate. The multiblock copolymer (pBMD-MMD) provided a molecular weight of 40,000 g·mol−1, determined by gel permeation chromatography (GPC). Incorporation of both oligodepsipeptide segments in multiblock copolymers was confirmed by 1H NMR and Matrix Assisted Laser Desorption/Ionization Time Of Flight Mass Spectroscopy (MALDI-TOF MS) analysis. pBMD-MMD showed two separated glass transition temperatures (61 °C and 74 °C) indicating a microphase separation. Furthermore, a broad glass transition was observed by DMTA, which can be attributed to strong physical interaction i.e. by H-bonds formed between amide, ester, and urethane groups of the investigated copolymers. The obtained multiblock copolymer is supposed to own the capability to exhibit strong physical interactions.

The therapeutic effect of mesenchymal stem cells (MSCs) has been investigated in various clinical applications, in which their functional benefits are mainly attributed to the secretion of soluble factors. The enhancement of their therapeutic potential by physical and chemical properties of cell culture substrate is a safe and effective strategy, since they are highly sensitive to their microenvironment such as the elasticity and surface topography. In this study, we demonstrated that the geometry of polymeric substrate regulated the interleukin-6 (IL-6) secretion of human adipose derived MSCs. Polystyrene substrates comprising arrays of square-shaped (S50) or round-shaped (R50) microwells (side length or diameter of 50 μm and depth of 10 μm) were prepared by injection molding. Cellular apoptototic rate of MSCs was not affected by the microwell geometry, while the upregulated secretion of IL-6 and the enhancement of nuclear transcription factor STAT3 were detected in MSCs seeded on S50 substrate. The geometry-dependent modulatory effect was highly associated with ROCK signaling cascade. The inhibition of ROCK abolished the disparity in IL-6 secretion. These findings highlight the possibility to steer the secretion profile of stem cells via microwell geometry in combination with the manipulation of ROCK signaling pathway.

N-terminal methacrylation of peptide MAX1, which is capable of conformational changes by variation of the pH, results in a peptide, named VK20. Increasing the reactivity of this terminal group enables further coupling reactions or chemical modifications of the peptide. However, this end group functionalization may influence the ability of conformational changes of VK20, as well as its properties. In this paper, the influence of pH on the transition between random coil and ß-sheet conformation of VK20, including the transition kinetics, were investigated. At pH values of 9 and higher, the kinetics of ß-sheet formation increased for VK20, compared to MAX1. The self-assembly into ß-sheets recognized by the formation of a physically crosslinked gel was furthermore indicated by a significant increase of G’. An increase in pH (from 9 to 9.5) led to a faster gelation of the peptide VK20. Simultaneously, G’ was increased from 460 ± 70 Pa (at pH 9) to 1520 ± 180 Pa (at pH 9.5). At the nanoscale, the gel showed a highly interconnected fibrillary network structure with uniform fibril widths of approximately 3.4 ± 0.5 nm (N=30). The recovery of the peptide conformation back to random coil resulted in the dissolution of the gel, whereby the kinetics of the recovery depended on the pH. Conclusively, the ability of MAX1 to undergo conformational changes was not affected by N-terminal methacrylation whereas the kinetics of pH-sensitive ß-sheet formations has been increased.