Precision Synthesis of Polysarcosine via Controlled Ring-Opening Polymerization of N-Carboxyanhydride: Fast Kinetics, Ultrahigh Molecular Weight, and Mechanistic Insights.

The rapid and controlled synthesis of high-molecular-weight (HMW) polysarcosine (pSar), a potential polyethylene glycol (PEG) alternative, via the ring-opening polymerization (ROP) of N-carboxyanhydride (NCA) is rare and challenging. Here, we report the well-controlled ROP of sarcosine NCA (Sar-NCA) that is catalyzed by various carboxylic acids, which accelerate the polymerization rate up to 50 times, and enables the robust synthesis of pSar with an unprecedented ultrahigh molecular weight (UHMW) up to 586 kDa (DP ∼ 8200) and exceptionally narrow dispersity (D̵) below 1.05. Mechanistic experiments and density functional theory calculations together elucidate the role of carboxylic acid as a bifunctional catalyst that significantly facilitates proton transfer processes and avoids charge separation and suggest the ring opening of NCA, rather than decarboxylation, as the rate-determining step. UHMW pSar demonstrates improved thermal and mechanical properties over the low-molecular-weight counterparts. This work provides a simple yet highly efficient approach to UHMW pSar and generates a new fundamental understanding useful not only for the ROP of Sar-NCA but also for other NCAs.

Degradation behaviour of porous poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV) scaffolds in cell culture.

Exploring the degradation behaviour of biomaterials in a complex in vitro physiological environment can assist in predicting their performance in vivo, yet this aspect remains largely unexplored. In this study, the in vitro degradation over 12 weeks of porous poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV) bone scaffolds in human osteoblast (hOB) culture was investigated. The objective was to evaluate how the presence of cells influenced both the degradation behaviour and mechanical stability of these scaffolds. The molecular weight (Mw) of the scaffolds decreased with increasing incubation time and the Mw reduction rate (6.2 ± 0.4 kg mol-1 week-1) was similar to that observed when incubated in phosphate buffered saline (PBS) solution, implying that the scaffolds underwent hydrolytic degradation in hOB culture. The mass of the scaffolds increased by 0.8 ± 0.2 % in the first 4 weeks, attributed to cells attachment and extracellular matrix (ECM) deposition including biomineralisation. During the first 8 weeks, the nominal compressive modulus, E⁎, of the scaffolds remained constant. However, it increased significantly from Week 8 to 12, with increments of 55 % and 42 % in normal and lateral directions, respectively, attributed to the reinforcement effect of cells, ECM and minerals attached on the surface of the scaffold. This study has highlighted, that while the use of PBS in degradation studies is suitable for evaluating Mw changes it cannot predict changes in mechanical properties to PHBV scaffolds in the presence of cells and culture media. Furthermore, the PHBV scaffolds had mechanical stability in cell culture for 12 weeks validating their suitability for tissue engineering applications.

Uterine inflammation status modulates eggshell mineralization via calcium transport and matrix protein synthesis in laying hens.

This study explored the effects of uterine inflammation on eggshell mineralization, ultrastructure and mechanical properties in laying hens modified by a lipopolysaccharide (LPS) challenge or dietary essential oil (EO) addition. In trial 1, a total of 72 Hy-line Brown layers at 36 wk of age were randomly assigned to 3 treatment groups (n = 8), where they were intravenously injected with phosphate buffered saline, LPS at 1 mg/kg body weight, or LPS 3 times at 24-h intervals. In trial 2, a total of 288 Hy-line Brown layers at 60 wk of age were randomly divided into 4 groups (n = 8), where they were fed basal diets supplemented with EO at 0, 50, 100 and 200 mg/kg for 12 wk. A uterine inflammation model was constructed with LPS treatment, indicated by the elevated expression of IL-1ß and TNF-α (P < 0.05) and lymphocyte infiltration. Uterine inflammation caused remarkable decreases in eggshell thickness and mechanical properties with structure deteriorations (P < 0.05). Uterine inflammation stimulated the expression of matrix proteins ovotransferrin (TF) and ovalbumin (OVAL), while depressing the mRNA levels of calbindin-1 (CALB1) and osteopontin in uterine mucosa (P < 0.05). In contrast, EO addition alleviated uterine inflammation, evidenced by depressed levels of IL-1ß and IL-6 (P < 0.05). There was a significant elevation in shell thickness and breaking strength following EO intervention (P < 0.05), and these effects were maximized at addition of 100 mg/kg. Further, EO improved shell ultrastructure including more early fusion, less type B mammillae, and increased effective thickness (P < 0.05). The alleviated inflammation decreased the expression of OVAL and TF, whereas ion transport genes like CALB1 and solute carrier family 26 member 9 were upregulated (P < 0.05). Our findings suggest that inflammatory status can impact uterine functions in calcium transport and the synthesis of matrix proteins especially such as OVAL and TF, which in turn modulates calcium precipitation and ultrastructure formation, thereby determining eggshell mechanical properties. These findings provide a novel insight into the uterine inflammation-mediated modifications of eggshell quality.

In vitro evaluation of porous poly(hydroxybutyrate-co-hydroxyvalerate)/akermanite composite scaffolds manufactured using selective laser sintering.

Incorporation of a bioactive mineral filler in a biodegradable polyester scaffold is a promising strategy for scaffold assisted bone tissue engineering (TE). The current study evaluates the in vitro behavior of poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV)/Akermanite (AKM) composite scaffolds manufactured using selective laser sintering (SLS). Exposure of the mineral filler on the surface of the scaffold skeleton was evident from in vitro mineralization in PBS. PHBV scaffolds and solvent cast films served as control samples and all materials showed preferential adsorption of fibronectin compared to serum albumin as well as non-cytotoxic response in human osteoblasts (hOB) at 24 h. hOB culture for up to 21 days revealed that the metabolic activity in PHBV films and scaffolds was significantly higher than that of PHBV/AKM scaffolds within the first two weeks of incubation. Afterwards, the metabolic activity in PHBV/AKM scaffolds exceeded that of the control samples. Confocal imaging showed cell penetration into the porous scaffolds. Significantly higher ALP activity was observed in PHBV/AKM scaffolds at all time points in both basal and osteogenic media. Mineralization during cell culture was observed on all samples with PHBV/AKM scaffolds exhibiting distinctly different mineral morphology. This study has demonstrated that the bioactivity of PHBV SLS scaffolds can be enhanced by incorporating AKM, making this an attractive candidate for bone TE application.

Coordination Chemistry Engineered Polymeric Carbon Nitride Photoanode with Ultralow Onset Potential for Water Splitting.

Construction of an intimate film/substrate interface is of great importance for a photoelectrode to achieve efficient photoelectrochemical performance. Inspired by coordination chemistry, a polymeric carbon nitride (PCN) film is intimately grown on a Ti-coated substrate by an in situ thermal condensation process. The as-prepared PCN photoanode exhibits a record low onset potential (Eonset ) of -0.38 V versus the reversible hydrogen electrode (RHE) and a decent photocurrent density of 242 µA cm-2 at 1.23 VRHE for water splitting. Detailed characterization confirms that the origin of the ultralow onset potential is mainly attributed to the substantially reduced interfacial resistance between the Ti-coated substrate and the PCN film benefitting from the constructed interfacial sp2 N→Ti coordination bonds. For the first time, the ultralow onset potential enables the PCN photoanode to drive water splitting without external bias with a stable photocurrent density of ≈9 µA cm-2 up to 1 hour.

Effect of Lycopene on the Growth Performance, Antioxidant Enzyme Activity, and Expression of Gene in the Keap1-Nrf2 Signaling Pathway of Arbor Acres Broilers.

The objective of this study was to determine the effect of dietary lycopene supplementation on the growth performance, antioxidant enzyme activity of serum and liver, and gene expressions associated with Kelch-like ech-associated protein-1 (Keap1)/Nuclear Factor E2-related factor 2 (Nrf2) pathway in liver of Arbor Acres broilers. A total of 288 1-day-old male broilers were randomly divided into 4 treatments with 6 replicates and 12 chickens for each replicate. The control group was fed with the basal diet, while the treated groups were fed with the basal diet with 10, 20, and 30 mg/kg lycopene in powder. Feed and water were provided ad libitum for 42 days. Compared with the control group, (a) the average daily gain increased (p = 0.002 vs. p = 0.001) and the feed conversion ratio decreased (p = 0.017 vs. p = 0.023) in groups treated with lycopene in the grower and whole phases, and the average daily feed intake was quadratically affected (p = 0.043) by lycopene in the grower phase; (b) the serum superoxide dismutase content was linearly affected (p = 0.035) by lycopene at 21 days; (c) the serum glutathione peroxidase content, superoxide dismutase content, and total antioxidant capability were higher (p = 0.014, p = 0.003, and p = 0.016, respectively) in the 30 mg/kg lycopene group at 42 days; (d) the liver glutathione peroxidase and superoxide dismutase contents in groups treated with lycopene were higher (p ≤ 0.001 vs. p ≤ 0.001) at 21 days; (e) the liver glutathione peroxidase content was higher (p ≤ 0.001) in the 20 and 30 mg/kg lycopene groups, at 42 days; (f) the mRNA expression levels of Nrf2, superoxide dismutase 2, NAD(P)H quinone dehydrogenase 1, and heme oxygenase 1 genes were higher (21 days: p = 0.042, p = 0.021, p = 0.035, and p = 0.043, respectively; 42 days: p = 0.038, p = 0.025, p = 0.034, and p = 0.043, respectively) in the 20 and 30 mg/kg lycopene groups at 21 and 42 days. The 30 mg/kg lycopene concentration improved the growth performance, antioxidant enzyme activity in serum and liver, and gene expression in the Keap1-Nrf2 signaling pathway of Arbor Acres broilers.

Threshold damage mechanisms in brittle solids and their impact on advanced technologies.

Threshold damage mechanisms in brittle covalent-ionic solids are outlined. Fracture and deformation modes are analyzed in terms of classical contact mechanics. Distinctions are made between brittle, ductile and quasiplastic mechanisms in both axial and translational contact. Special attention is devoted to the relatively unexplored subthreshold region where macrofracture is largely suppressed, a region of increasing relevance in the relentless move toward ever smaller devices and precision shaping technologies in the manufacturing sector. Cross-section micrographic images illustrate the fundamental nature of shear events within the hardness deformation zone responsible for crack initiation and propagation. Basic analytical relations for the strengths of surfaces with contact-induced damage in the postthreshold and subthreshold regions are presented, with emphasis on concept rather than fine detail. Strength data for a prototypical brittle material after sharp-indenter damage are presented to highlight the vital role of microstructure in determining transitions between brittle and quasiplastic responses. Pristine defect-free solids are shown to be highly vulnerable to contact damage, even in the subthreshold region. Heterogeneous solids with granular microstructures have lower initial strengths, but are more flaw tolerant. Brittle solids are also highly susceptible to degradation by surface removal processes in wear and machining settings, to a large extent depending again on microstructure. Implications of these findings concerning advanced technological applications of covalent-ionic solids are discussed.

Adhesion Evaluation of an Embedded SiN/GaAs Interface Using a Novel "Push-Out" Technique.

Adhesion assessments of an embedded interface in a multilayer system that contains a ductile layer are challenging. The occurrence of plastic deformation in the ductile layer often leads to additional complexity in analysis. In this study, an innovative "push-out" technique was devised to evaluate the interfacial toughness (Gin) of the embedded SiN/GaAs interface in a Au/SiN/GaAs multilayer system. Focus ion beam (FIB) milling was utilized to manufacture the miniaturized specimen and scratching with a conical indenter was used to apply load. This approach effectively minimized plastic deformation in the soft Au layer while inducing tensile stress to the embedded SiN/GaAs interface. As a result, the Au/SiN bilayer detached from the GaAs substrate with little plasticity. The energy associated with the interfacial delamination was derived from analyzing the load-displacement curves obtained from the scratching test. The Gin of the SiN/GaAs interface was calculated by means of energy analysis, and the average Gin was 4.86 ± 0.96 J m-2.

Liquid-phase sintering of lead halide perovskites and metal-organic framework glasses.

Lead halide perovskite (LHP) semiconductors show exceptional optoelectronic properties. Barriers for their applications, however, lie in their polymorphism, instability to polar solvents, phase segregation, and susceptibility to the leaching of lead ions. We report a family of scalable composites fabricated through liquid-phase sintering of LHPs and metal-organic framework glasses. The glass acts as a matrix for LHPs, effectively stabilizing nonequilibrium perovskite phases through interfacial interactions. These interactions also passivate LHP surface defects and impart bright, narrow-band photoluminescence with a wide gamut for creating white light-emitting diodes (LEDs). The processable composites show high stability against immersion in water and organic solvents as well as exposure to heat, light, air, and ambient humidity. These properties, together with their lead self-sequestration capability, can enable breakthrough applications for LHPs.

Dietary oregano essential oil supplementation improves intestinal functions and alters gut microbiota in late-phase laying hens.

BACKGROUND: Dietary essential oil (EO) supplementation can exert favorable effects on gut health in broilers. However, it is unknown whether EO could improve intestinal functions, consequently beneficial for egg performance and quality in late-phase laying hens. This study was aimed to investigate the potential effects of EO on production performance, egg quality, intestinal health and ileal microbiota of hens in the late phase of production. A total of 288 60-week-old Hy-line Brown laying hens were randomly divided into 4 groups and fed a basal diet (control) or basal diets supplemented with oregano EO at 100, 200 and 400 mg/kg (EO100, EO200 and EO400). RESULTS: Dietary EO supplementation resulted in a quadratic decrease (P < 0.05) in feed conversion ratio with lower (P < 0.05) feed conversion ratio in EO200 group than the control during weeks 9-12 and 1-12 of the trial. Compared to the control, EO addition resulted in higher (P < 0.05) eggshell thickness at the end of week. 4, 8 and 12 and higher (P < 0.05) chymotrypsin activity. There was a quadratic elevation (P < 0.05) in ileal chymotrypsin and lipase activity, along with a linear increase in villus height to crypt depth ratio. Quadratic declines (P < 0.05) in mRNA expression of IL-1ß, TNF-α, IFN-γ and TLR-4, concurrent with a linear and quadratic increase (P < 0.05) in ZO-1 expression were identified in the ileum with EO addition. These favorable effects were maximized at medium dosage (200 mg/kg) of EO addition and intestinal microbial composition in the control and EO200 groups were assessed. Dietary EO addition increased (P < 0.05) the abundances of Burkholderiales, Actinobacteria, Bifidobacteriales, Enterococcaceae and Bacillaceae, whereas decreased Shigella abundance in the ileum. CONCLUSIONS: Dietary EO addition could enhance digestive enzyme activity, improve gut morphology, epithelial barrier functions and modulate mucosal immune status by altering microbial composition, thus favoring feed efficiency and eggshell quality of late-phase laying hens.

Mechanisms associated with the depigmentation of brown eggshells: a review.

Eggshell color is an important shell quality trait that influences consumer preference. It is also of particular importance with respect to sexual signaling and the physiological and mechanical properties of shell pigment. Pigments include protoporphyrin IX, biliverdin, and traces of biliverdin zinc chelates, with brown eggs being notably rich in protoporphyrin IX, the synthesis of which has a marked effect on the intensity of brown eggshell color. This pigment is initially synthesized in the eggshell gland within the oviduct of laying hens and is subsequently deposited throughout the cuticular and calcareous layers of brown eggshell. In this review, we describe the factors affecting brown eggshell color and potential targets for the regulation of pigment synthesis. Protoporphyrin IX synthesis might be compromised by synthetase-mediated pigment synthesis, the redox status of the female birds, and regulation of the nuclear transcription factors associated with δ-aminolevulinic acid synthetase1. We believe that this review will provide a valuable reference for those engaged in studying eggshell depigmentation.

Mitochondrial transcription factor A induces the declined mitochondrial biogenesis correlative with depigmentation of brown eggshell in aged laying hens.

Eggshell color is an important characteristic for poultry eggs. Eggs from aged hens usually have poor shell color that is unacceptable for the table egg market. The objective of this study was to examine effects of pigment synthesis and mitochondrial biogenesis on brown eggshell color of aged laying hens. In this trial, 8 hens laying eggs with darker shell color and 8 hens laying eggs with lighter shell color were selected from 300 62-week-old Hy-Line brown-egg laying hens. Results showed that egg weight (P < 0.05), eggshell weight (P < 0.01), protoporphyrin IX (Pp IX) content of the eggshell and the shell gland (P < 0.001), and biliverdin content of the shell gland (P < 0.001) were significantly declined in the light-shell group compared with the dark-shell group. Relative mRNA expression of δ-aminolevulinic acid synthase1 (ALAS1) (P < 0.05), coproporphyrinogen oxidase (P < 0.01), ATP-binding cassette transporter ABCG2 (P < 0.01), and mitochondrial transcription factor A (P < 0.05) was reduced in hens laying lighter brown eggshell. Moreover relative mRNA expression of mitochondrial DNA copy number (P < 0.01), mitochondrial NADH dehydrogenase subunit 4 (P < 0.05), mitochondrial ATP synthase F0 subunit 8 (P < 0.05), and mitochondrial cytochrome c oxidase 1 (P < 0.01) was significantly decreased in the shell gland of the light-shell group. In addition, NAD+ contents of the shell gland were increased in the dark-shell group (P < 0.01). Brown eggshell depigmentation is a result of decreased Pp IX content in the eggshell and the shell gland. Decreased mitochondrial biogenesis may contribute to the depigmentation of brown eggshell by targeting ALAS1 and ALAS1-mediated Pp IX biosynthesis.

Purification, characterization, and chemical modification of Bacillus velezensis SN-14 fibrinolytic enzyme.

Fermented bean foods are a crucial source of fibrinolytic enzymes. The presented study aimed to purify, characterize, and chemically modify Bacillus velezensis SN-14 fibrinolytic enzyme. The fibrinolytic enzyme was purified using CTAB/isooctane/hexyl alcohol/n-butyl alcohol reverse micellar system, and the purified enzyme was chemically modified to improve its enzymatic activity and stability. Enzyme activity recovery and the purification fold for this enzyme were 44.5 ± 1.9% and 4.93 ± 0.05 fold, respectively. SDS-PAGE results showed that the molecular weight of the purified fibrinolytic enzyme was around 28 kDa. Besides, the optimum temperature and pH of the purified fibrinolytic enzyme were 37 °C and 8-9, respectively. Fe2+, mPEG5000, and pepsin were used for chemical modification and for improving the activity and stability of the purified enzyme. Thermal and acid-base stability of chemically modified enzymes increased significantly, whereas enzymatic activity increased by 7.3 times. After 30 d of frozen storage, the modified enzyme's activity was remarkably lower (33.2%) than the unmodified enzyme (60.6%). The current study on B. velezensis SN-14 fibrinolytic enzyme and chemical modification method using Fe2+, mPEG5000, and pepsin provide a reference for developing fibrinolytic drugs and foods.

Isolation of Bacillus spp. with High Fibrinolytic Activity and Performance Evaluation in Fermented Douchi.

ABSTRACT: Fibrinolytic enzymes are effective and highly safe in treating cardiovascular and cerebrovascular diseases. Therefore, screening fibrinolytic enzyme-producing microbial strains with excellent fermentation performance is of great value to industrial applications. The fibrin plate method was used in screening strains with high yields of fibrinolytic enzymes from different fermented food products, and the screened strains were preliminarily identified using molecular biology. Then, the strains were used for solid-state fermentation of soybeans. Moreover, the fermentation product douchi was subjected to fibrinolytic activity measurement, sensory evaluation, and biogenic amine content determination. The fermentation performance of each strain was comprehensively evaluated through principal component analysis. Finally, the target strain was identified based on strain morphology, physiological and biochemical characteristics, 16S rDNA sequence, and phylogenetic analysis results. A total of 15 Bacillus species with high fibrinolysin activity were selected. Their fibrinolytic enzyme-producing activity levels were higher than 5,500 IU/g. Through molecular biology analysis, we found 4 strains of Bacillus subtilis, 10 strains of Bacillus amyloliquefaciens, and 1 strain of Bacillus velezensis. The principal component analysis results showed that SN-14 had the best fermentation performance and reduced the accumulation of histamine and total amine, the fibrinolytic activity of fermented douchi reached 5,920.5 ± 107.7 IU/g, and the sensory score was 4.6 ± 0.3 (out of 5 points). Finally, the combined results of physiological and biochemical analyses showed SN-14 was Bacillus velezensis. The high-yield fibrinolytic and excellent fermentation performance strain Bacillus velezensis SN-14 has potential industrial application.

TiB Nanowhisker Reinforced Titanium Matrix Composite with Improved Hardness for Biomedical Applications.

Titanium and its alloys have been employed in the biomedical industry as implants and show promise for more broad applications because of their excellent mechanical properties and low density. However, high cost, poor wear properties, low hardness and associated side effects caused by leaching of alloy elements in some titanium alloys has been the bottleneck to their wide application. TiB reinforcement has shown promise as both a surface coating for Ti implants and also as a composite reinforcement phase. In this study, a low-cost TiB-reinforced alpha titanium matrix composite (TMC) is developed. The composite microstructure includes ultrahigh aspect ratio TiB nanowhiskers with a length up to 23 µm and aspect ratio of 400 and a low average Ti grain size. TiB nanowhiskers are formed in situ by the reaction between Ti and BN nanopowder. The TMC exhibited hardness of above 10.4 GPa, elastic modulus above 165 GPa and hardness to Young's modulus ratio of 0.062 representing 304%, 170% and 180% increases in hardness, modulus and hardness to modulus ratio, respectively, when compared to commercially pure titanium. The TiB nanowhisker-reinforced TMC has good biocompatibility and shows excellent mechanical properties for biomedical implant applications.

Deformation behavior of porous PHBV scaffold in compression: A finite element analysis study.

Macroscopic mechanical properties of porous PHBV bone TE scaffolds have been well studied. However, their mechanical behavior at microscopic level has yet to be explored. In this study, the micro-mechanical behavior of a PHBV bone scaffold under compression was investigated using a numerical method that combines micro-computed tomography (µ-CT) and finite element analysis (FEA). It was found that the use of a linear-elastic model resulted in an overestimation of the stiffness of the scaffold, whereas a more realistic estimation of the scaffold's deformation behavior was obtained by utilizing a bilinear material model. The onset of plastic deformation occurred in the very early stage of loading resulting in significantly reduced stiffness of the scaffold. The non-uniform and arbitrary microstructure of the scaffold led to a heterogeneous stress distribution within the porous construct, which was subjected to a mixture of compressive and tensile stresses. Nevertheless, the resultant stress contours showed that the scaffold experienced primarily elastic deformation when it was loaded up to 0.003 strain, while localized plastic deformation occurred at sharp corners and necked regions of the micro-struts. The scaffold expanded slightly in the horizontal direction as it was compressed and the change in geometries of pores within the scaffold was insignificant. The proposed method provides a valuable tool to study the localized mechanical behavior of bone scaffolds in micrometer scale with arbitrary porous architecture. This approach could prove highly useful for guiding the fabrication of scaffolds that have anatomy specific mechanical properties and porous architecture.

Akermanite reinforced PHBV scaffolds manufactured using selective laser sintering.

Scaffold assisted tissue engineering presents a promising approach to repair diseased and fractured bone. For successful bone repair, scaffolds need to be made of biomaterials that degrade with time and promote osteogenesis. Compared to the commonly used ß-tricalcium phosphate scaffolds, Akermanite (AKM) scaffolds were found to degrade faster and promote more osteogenesis. The objective of this study is to synthesize AKM micro and nanoparticle reinforced poly(3-hydroxybutyrate-co-3-hydroxyvalerate; PHBV) composite scaffolds using selective laser sintering (SLS). The synthesized composite scaffolds had an interconnected porous microstructure (61-64% relative porosity), large specific surface areas (31.1-64.2 mm-1 ) and pore sizes ranging from 303 to 366 and 279 to 357 µm in the normal and lateral direction, respectively, which are suitable for bone tissue repair. The observed hydrophilic nature of the scaffolds and the swift water uptake was due to the introduction of numerous carboxylic acid groups on the scaffold surface after SLS, circumventing the need for postprocessing. For the composite scaffolds, large amounts of AKM particles were exposed on the skeleton surface, which is a requirement for cell attachment. In addition, the particles embedded inside the skeleton helped to significantly reinforce the scaffold structure. The compressive strength and modulus of the composite scaffolds were up to 7.4 and 103 MPa, respectively, which are 149 and 197% of that of the pure PHBV scaffolds. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B:2596-2610, 2019.

In vitro degradation of a unique porous PHBV scaffold manufactured using selective laser sintering.

Biodegradable poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) scaffolds have shown great promise for bone tissue engineering applications. The investigation of their hydrolytic degradation is thus essential to understand the effect of hydrolysis on the complex biodegradation behavior of PHBV scaffolds. In this study, we investigated the degradation behavior of high molecular weight PHBV scaffolds manufactured using selective laser sintering (SLS) without using predesigned porous architectures. The manufactured scaffolds have high specific surface areas with great water-uptake abilities. After an incubation of 6 weeks in phosphate-buffered saline solution, the structural integrity of the scaffolds was unaffected. However, a significant decrease in molecular weight ranging from 39% to 46% was found. The measured weight loss was negligible, but their compressive modulus and strength both decreased, likely due to water plasticization. These findings suggest that hydrolytic degradation of PHBV by means of bulk degradation was the predominant mechanism, attributed to their excellent water absorptivity. Overall, the PHBV scaffolds manufactured using SLS exhibited adequate mechanical properties and satisfactory structural integrity after incubation. As a result, the scaffolds have great potential as candidates for bone repair in clinical practice. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 107A: 154-162, 2019.

Correlations of Molecular Weights of ß-Glucans from Qingke (Tibetan Hulless Barley) to Their Multiple Bioactivities.

ß-glucans have been considered the major bioactive components in Qingke (Tibetan hulless barley). However, the structure⁻function relationships of ß-glucans from Qingke have seldom been investigated. Whether the bioactivities of Qingke ß-glucans are closely correlated to their molecular weights remains unknown. Therefore, in order to explore Qingke ß-glucans as functional/healthy food ingredients for industrial applications, and to better understand their structure⁻function relationships, correlations of molecular weights of Qingke ß-glucans to their in vitro binding properties, inhibitory activities on digestive enzymes (α-amylase and pancreatic lipase), anti-inflammatory activities, and anticancer activities were systematically investigated. Results showed that the in vitro binding properties and the inhibitory activities on α-amylase and pancreatic lipase of Qingke ß-glucans were positively correlated to their molecular weights. However, the anti-inflammatory activities of Qingke ß-glucans increased as their molecular weights decreased. Furthermore, Qingke ß-glucans exhibited selectively anti-cancer activities in vitro. Positive and negative correlations of molecular weights to inhibitory effects against A549 cells and MDA-MB-231 cells were observed, respectively. However, the inhibitory effects of Qingke ß-glucans against HCT116 cells were not associated with their molecular weights. Results suggested that the molecular weights of Qingke ß-glucans significantly affected their bioactivities, which was beneficial for a better understanding of their structure⁻function relationships. Moreover, results showed that Qingke ß-glucans could be further explored as functional/healthy food ingredients for industrial applications due to their multiple health benefits.

The poisoning effect of PbO and PbCl2 on CeO2-TiO2 catalyst for selective catalytic reduction of NO with NH3.

The poisoning effect of PbO and PbCl2 on CeO2-TiO2 catalyst for selective catalytic reduction of NO with NH3 was investigated and compared. Both Pb species could deactivate the CeO2-TiO2 catalyst and PbO had a stronger poisoning effect than PbCl2. From the characterization results of BET, XRD, XPS, NH3-TPD and H2-TPR, it was concluded that the more serious deactivation by PbO could be ascribed to smaller BET surface area, fewer surface Ce3+ and chemisorbed oxygen, stronger interaction between PbO and CeO2-TiO2 catalyst, lower redox properties and surface acidity. The in situ DRIFT study results revealed that the NH3-SCR reaction over CeO2-TiO2 catalyst was governed by both E-R and L-H mechanisms, which wasn't changed over the Pb-poisoned samples. The greater loss of Brønsted acid sites attributed to fewer surface Ce3+ and more serious inhibition of NO oxidation to NO2 due to fewer surface chemisorbed oxygen were two key factors responsible for more serious deactivation by PbO. Furthermore, the presence of Pb species inhibited the NH3 adsorption on the Lewis acid sites, aggravating the deactivation of CeO2-TiO2 catalyst.