A polyphenolic biomacromolecule prepared from a flavonoid: Catechin as degradable microparticles

Catechin (CAT) was crosslinked with trimethylolpropane triglycidyl ether (TMPTGE) to obtain degradable poly(CAT) particles in a single step. Spherical p(CAT) particles with tens of micrometer size range and an isoelectronic point at pH 1.2 were obtained. The hydrolytic degradation of p(CAT) particles provided sustainable and extended release with 264 mg/g CAT release within 10 days at pH 7.4. The antioxidant capacity of 55.0 ± 0.9 μg/ml gallic acid equivalent in terms of total phenol content, and 0.88 ± 0.3 μmol/g trolox equivalent were estimated for p(CAT) particles displaying strong radical scavenging capability. Blood clotting and hemolysis assays demonstrated dose-dependent blood compatibility revealing higher blood compatibility for p(CAT) particles up to 10 μg/ml concentration. The cytotoxicity results show that p(CAT) particles have almost no toxicity for CCD841 normal colon cells at 250 μg/ml concentration in 24 h incubation time giving ~97% cell viability, whereas CAT molecules only provide ~34% cell viability.     

Very fast H2 production from the methanolysis of NaBH4 by metal‐free poly(ethylene imine) microgel catalysts

The polyethyleneimine (PEI) microgels prepared via microemulsion polymerization are protonated by hydrochloric acid treatment (p‐PEI) and quaternized (q‐PEI) via modification reaction with methyl iodide and with bromo alkanes of different alkyl chain lengths such as 1‐bromoethane, 1‐bromobutane, 1‐bromohexane, and 1‐bromooctane. The bare p‐PEI and q‐PEI microgels are used as catalysts directly without any metal nanoparticles for the methanolysis reaction of sodium borohydride (NaBH₄). Various parameters such as the protonation/quaternization reaction on PEI microgels, the amount of catalyst, the amount of NaBH₄, and temperature are investigated for their effects on the hydrogen (H₂) production rate. The reaction of self‐methanolysis of NaBH₄ finishes in about 32.5 min, whereas the bare PEI microgel as catalyst finishes the methanolysis of NaBH₄ in 22 min. Surprisingly, it is found that when the protonated PEI microgels are used as catalyst, the same methanolysis of NaBH₄ is finished in 1.5 min. The highest H₂ generation rate value is observed for protonated PEI microgels (10 mg) with 8013 mL of H₂/(g of catalyst.min) for the methanolysis of NaBH₄. Moreover, activation parameters are also calculated with activation energy value of 23.7 kJ/mol, enthalpy 20.9 kJ/mol, and entropy ?158 J/K.mol. Copyright © 2016 John Wiley & Sons, Ltd.     

Surface‐modified carbon black derived from used car tires as alternative,reusable, and regenerable catalysts for H2 release studies from sodium borohydride methanolysis

Carbon black (CB) obtained from used car tire rubbers were treated with concentrated sulfuric and nitric acids. The oxidized CB (CB‐COO‐Na⁺) is subsequently modified with epichlorohydrin (ECH) and amines including polyethylene imine (PEI). These modified CBs such as CB‐PEI are used as metal‐free catalysts in methanolysis of sodium borohydride (NaBH₄) to produce hydrogen. The hydrogen generation rate (HGR) of 3089 ± 44.69 mL.min^‐1.g^‐1 is accomplished at room temperature with CB‐PEI‐hydrochloric acid (HCl) catalyst. The resulting activation energy of 34.7 kJ/mol for the temperature range of ?20°C to +30°C compares favorably to most of alternative catalysts reported in literature while reaction catalyzing capabilities of CB‐PEI‐HCl particles extend to the subzero temperature range (?20°C‐0°C). The reuse and regeneration studies conducted for the CB‐PEI‐HCl catalyst showed that these catalysts do provide complete conversion at every use up to five consecutive runs and retain 50 ± 2.5% of the original hydrogen generation rate at the fifth consecutive reuse. The CBs‐based catalysts are fully regenerated with HCl treatment.     

Classification of ECG beats by using a fast least square support vector machines with a dynamic programming feature selection algorithm

In this paper, we present a new system for the classification of electrocardiogram (ECG) beats by using a fast least square support vector machine (LSSVM). Five feature extraction methods are comparatively examined in the 15-dimensional feature space. The dimension of the each feature set is reduced by using dynamic programming based on divergence analysis. After the preprocessing of ECG data, six types of ECG beats obtained from the MIT-BIH database are classified with an accuracy of 95.2% by the proposed fast LSSVM algorithm together with discrete cosine transform. Experimental results show that not only the fast LSSVM is faster than the standard LSSVM algorithm, but also it gives better classification performance than the standard backpropagation multilayer perceptron network.     

In situ micro/nano-hydrogel synthesis from acrylamide derivates with lecithin organogel system

Acrylamide based hydrogel particles with variable charge were synthesized in different sizes using a biocompatible surfactant. We use microemulsion polymerization to synthesize the hydrogel particles in lecithin organogel systems. The phospholipid, lecithin, is a soybean extract that exhibits a rich phase behavior depending on various factors such as amount of water, co-solvent, additives and their concentrations. By UV irradiation of water-in-oil microemulsions of lecithin, containing different monomers, phospholipid coated hydrogels were synthesized in situ. The hydrogel particle size varies from a few hundred nanometers to tens of micrometer. The response time of these micron sized hydrogel particles, as measured by swelling experiments, is very fast (∼10⁰ s) in comparison with their corresponding bulk hydrogels (∼10¹ h). The positively charged cationic hydrogel microparticles were embedded/dispersed into another hydrogel matrix to render responsive behavior to a non-responsive matrix. Besides TEM and SEM studies, fluorescein dye absorption studies were also performed in order to visualize the hydrogel microparticles. Additionally, anionic hydrogel micro/nano-particles were also synthesized in the lecithin system.     

Super porous α-, β-, γ-cyclodextrin cryogels with high active agent loading and controllable release profiles

Cyclodextrins (CDs) are truncated cone-like structures that are natural cyclic oligosaccharides. Here, a simple preparation method for super porous poly(α-CD), poly(β-CD), and poly(γ-CD) cryogels crosslinking with divinyl sulfone at 150%, 100% and 125% mole ratios with respect to the α-CD, β-CD, and γ-CD molecules, respectively, under cryogenic conditions, is reported. The interconnected homogeneous pore distribution of CD-based cryogels with pore sizes in the range of 5–100 μm is confirmed by SEM analysis. The CD-based cryogels weighing 10 mg are determined as hemocompatible with <1% hemolysis ratios and >79% blood clotting indexes; whereas the same materials weighing 1 mg are biocompatible with >75% cell viability on L929 fibroblasts. Additionally, active agent adsorption/delivery efficiencies of CD-based cryogels utilizing two active agents, Bisphenol A (BPA, a carcinogenic compound) and Curcumin (CUR, a polyphenolic compound), are individually evaluated. It was revealed that p(γ-CD) cryogels exhibited the highest active agent loading capacity for BPA, 87 ± 13 mg/g, whereas p(α-CD) cryogels showed the highest loading capacity for CUR, 136 ± 4 mg/g. Moreover, the active agent release from p(α-CD), p(β-CD), and p(γ-CD) cryogel networks at pH 7.4 and 37°C were determined as 40.6 ± 2, 35.3 ± 2, and 34 ± 1 mg/g for BPA, and 1.07 ± 0.2, 1.27 ± 0.1, and 1.37 ± 0.1 mg/g for CUR, respectively, within 96 h.     

Design,synthesis, and characterization of hybrid micro-nano surface coatings for enhanced heat transfer applications

Metal particles coating is extensively used for surface coating a wide range of application including thermal management of electronics, concentrating photovoltaics, sensors and nuclear power plants. Both micro and nano-scale surfaces have been proven to show an enhanced two-phase heat transfer performance by varying surface properties like area, wettability, and roughness. To combine the unique features of both micro and nano-scale surface coatings, this study presents the design, synthesis, and characterization of new hybrid micro-nano scale surface coating by a new two steps approach. Five different types of surfaces; namely, plain nanocoated (PNC), uniform micro-porous (UMP), uniform hybrid micro-nano porous (UHMNP), 2-D modulated microporous (MMP) and modulated hybrid micro-nano (MHMNP) surfaces were fabricated. A new two steps approach of hot-pressing followed by nucleate boiling is used for the fabrication of these surfaces. Successful coating of hybrid micro-nano scale coating was achieved. Considering the critical surface properties of micro and nanoscale coatings, new hybrid micro-nano surfaces have been characterized for SEM, wettability, roughness test. The comparative analysis of these new hybrid coating is also performed with micro coated and uncoated surfaces. With the coating of nanoparticles, the average roughness of PNC surface increased by 4.67 times and that of hybrid micro-nano particle surface by 2.3 times. The deposition of nanoparticles resulted in an increase in contact angle for PNC surface, while the contact angle of hybrid micro-nano surfaces decreases from 126.4° to 82.1°.     

Improved mechanical strength of p(AAm) interpenetrating hydrogel network due to microgranular cellulose embedding

Here, polyacrylamide [p(AAm)]‐based hydrogels were synthesized via redox polymerization technique in the presence of various amounts of microgranular cellulose (MGCell) such as 0, 10, 25, 50, 100, and 150 mg MGCell/g. The synthesized p(AAm)‐MGCell interpenetrating hydrogels were characterized spectroscopically by FTIR, thermally by TGA analysis, and mechanically via dynamic mechanical measurements. Furthermore, the effect of the amount of MGCell in p(AAm) hydrogels on swelling% (S%) degree and mechanical strength was investigated. It was found that the S% was decreased from 727 ± 9 to 667 ± 6, 642 ± 8 and 619 ± 10, 568 ± 6 for p(AAm)‐MGCell interpenetrating network hydrogels containing 10, 50, 100, and 150 mg MGCell, respectively. On the other hand, the Young modulus of p(AAm)‐based hydrogels increased from 2.8 ± 0.2 kPa to 3.1 ± 0.03, 3.4 ± 0.1, 3.6 ± 0.3 and 4.3 ± 0.3 kPa with the incorporation of 10, 50, 100, and 150 mg MGCell into p(AAm) hydrogels. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44854.