The mechanical properties of polyurethane foam wound dressing hybridized with alginate hydrogel and jute fiber

The purpose of this study is to fabricate a smart wound dressing by hybridizing hydrophilic polyurethane foam (PUF) and alginate hydrogel. Hydrophilic PUF is used to maintain damaged tissue in a moist environment. Despite its many strong points as a wound dressing, hydrophilic PUF cannot be loaded with ingredients such as growth factors and cytokines that would enhance wound healing. Therefore, we introduce a pH-sensitive alginate hydrogel with the ability to selectively release drugs within the pH range of wounded skin. Due to the small pore size of PUF and the high viscosity of the alginate solution, the two are not easily penetrable. As such, a vacuum method is used to insert alginate hydrogel into the PUF. The optimum conditions for the vacuum method chosen are to be proposed. However, the mechanical strength of PUF decreased after containing alginate hydrogel. Therefore, Na-alginate powder for PUF, various types of crosslinking agents and jute fiber for alginate hydrogel were introduced to improve the mechanical properties of hydrogel/PUF hybrid wound dressing. Three different types of crosslinking agents are used for the gel formation. The most suitable crosslinking agent and its concentration for alginate hydrogel is also determined by the experiments. The experimental results are discussed with proper schemes and reasonable explanations.     

The effect of bentonite concentration on the drug delivery efficacy of a pH-sensitive alginate/bentonite hydrogel

We produced a protein loaded, pH-sensitive alginate-bentonite hydrogel for wound dressings. Alginate is a nontoxic polysaccharide with favorable pH-sensitive properties that make it useful for the intestinal delivery of protein drugs. However, the use of alginate for drug delivery is limited by drug leaching and rapid dissolution of alginate at the higher pH, which may result in lower entrapment efficiency and a burst in the release of entrapped protein drugs. To overcome these problems, we created a novel cross-linked alginate-bentonite hydrogel by combining mineral-rich bentonite with the alginate matrix along with an additive to ensure controlled release. We analyzed the gel in the drug loading process in an aqueous environment by looking at the release profiles of a model protein drug (BSA) from the hydrogel at pH values of 4.5, 5.2 (skin area) and 7.4, 9.2 (wound area). The swelling ratio decreased with bentonite concentration, but did not fall below 6. The rate of drug release was slowest at a pH value of 4.5 and fastest at a pH value of 9.2. The rate of drug release decreased with bentonite concentration. The presence of bentonite prevents the rapid dissolution of alginate at the higher pH, ensuring the controlled release of the entrapped drug.     

Solution blowing of chitosan/PLA/PEG hydrogel nanofibers for wound dressing

In this study, a kind of hydrogel nanofibers were successfully fabricated via solution blowing of chitosan (CS) and polylactic acid (PLA) solutions mixed with various contents of polyethylene glycol (PEG) to offer hydration. The nanofibers with PEG content varying were average 341-376 nm in diameter with smooth surface and distributed randomly forming three-dimension (3D) mats. Glutaraldehyde (GA) vapor was then applied to impart stability, and the cross-linking reaction mainly occurred between GA and hydroxyl groups which was confirmed by XPS. The hydrogel nanofibers showed quick absorption behavior, high equilibrate water absorption and good air permeability which could help the mats absorbing excess exudates, creating a moist wound healing environment and oxygen exchanging in wound healing. The mats also exhibited good antibacterial activities against E. coil. The combination advantages of nanofibers mats and hydrogel will help it find promising application in wound healing.     

Influences of Molecular Weights on Physicochemical and Biological Properties of Collagen-Alginate Scaffolds

For tissue engineering applications, biodegradable scaffolds containing high molecular weights (MW) of collagen and sodium alginate have been developed and characterized. However, the properties of low MW collagen-based scaffolds have not been studied in previous research. This work examined the distinctive properties of low MW collagen-based scaffolds with alginate unmodified and modified by subcritical water. Besides, we developed a facile method to cross-link water-soluble scaffolds using glutaraldehyde in an aqueous ethanol solution. The prepared cross-linked scaffolds showed good structural properties with high porosity (~93%) and high cross-linking degree (50–60%). Compared with collagen (6000 Da)-based scaffolds, collagen (25,000 Da)-based scaffolds exhibited higher stability against collagenase degradation and lower weight loss in phosphate buffer pH 7.4. Collagen (25,000 Da)-based scaffolds with modified alginate tended to improve antioxidant capacity compared with scaffolds containing unmodified alginate. Interestingly, in vitro coagulant activity assay demonstrated that collagen (25,000 Da)-based scaffolds with modified alginate (C25-A63 and C25-A21) significantly reduced the clotting time of human plasma compared with scaffolds consisting of unmodified alginate. Although some further investigations need to be done, collagen (25,000 Da)-based scaffolds with modified alginate should be considered as a potential candidate for tissue engineering applications.     

The preparation of polyurethane foam combined with pH-sensitive alginate/bentonite hydrogel for wound dressings

Polyurethane (PU) foam was combined with protein drug-loaded pH-sensitive alginate-bentonite hydrogel for wound dressings. Alginate is a linear copolymer composed of 1–4-linked β-D-mannuronic acid (M) and its c-5-epimer α-Lguluronic acid (G). The amount of (M) and (G) and their sequential distribution are varied depending on the alginate source. Soluble sodium alginate can become a hydrogel when cross-linked with divalent cations and has widespread applications in the food, drink, pharmaceutical and bioengineering industries. Recently, it has been also proposed as a biomaterial for drug delivery systems. Bentonites are the natural inorganic polymers consisting of a large proportion of expandable clay minerals with a three-layer structure such as montmorillonite, beidellite, nontronite, etc. They are important adjutants and supports for medical products, and they have many useful physicochemical, mechanical, and biological properties such as absence of toxicity, indifference to other raw materials, sorption, swelling, and complex formation properties. Alginate-bentonite hydrogels were prepared at concentration ratios of 10/0, 7/3, 5/5, 3/7. PU foams were prepared using hydrophilic polyols. We investigated the controlled release of a protein drug from PU foam combined with alginate-bentonite hydrogel at different pH values of 4.2, 5.2, 7.2, 8.2. The mechanical properties and cytotoxicity tests of this foam were also studied.     

Fabrication and Characterization of Nanocomposite Hydrogel Based on Alginate/Nano-Hydroxyapatite Loaded with Linum usitatissimum Extract as a Bone Tissue Engineering Scaffold

In the current paper, we fabricated, characterized, and applied nanocomposite hydrogel based on alginate (Alg) and nano-hydroxyapatite (nHA) loaded with phenolic purified extracts from the aerial part of Linum usitatissimum (LOH) as the bone tissue engineering scaffold. nHA was synthesized based on the wet chemical technique/precipitation reaction and incorporated into Alg hydrogel as the filler via physical cross-linking. The characterizations (SEM, DLS, and Zeta potential) revealed that the synthesized nHA possess a plate-like shape with nanometric dimensions. The fabricated nanocomposite has a porous architecture with interconnected pores. The average pore size was in the range of 100–200 µm and the porosity range of 80–90%. The LOH release measurement showed that about 90% of the loaded drug was released within 12 h followed by a sustained release over 48 h. The in vitro assessments showed that the nanocomposite possesses significant antioxidant activity promoting bone regeneration. The hemolysis induction measurement showed that the nanocomposites were hemocompatible with negligible hemolysis induction. The cell viability/proliferation confirmed the biocompatibility of the nanocomposites, which induced proliferative effects in a dose-dependent manner. This study revealed the fabricated nanocomposites are bioactive and osteoactive applicable for bone tissue engineering applications.     

Acrylamide/potassium 3-sulfopropyl methacrylate/sodium alginate/bentonite hybrid hydrogels: Synthesis,characterization and its application in lauths violet removal from aqueous solutions

In this report, it was to investigate that the swelling and dye sorption properties of a series of novel hybrid composite hydrogel sorbent systems containing polysaccharide/clay polyelectrolyte based on acrylamide/potassium 3-sulfopropyl methacrylate and sodium alginate, and clay such as bentonite were synthesized with free radical solution polymerization by using ammonium persulfate/N,N,N’,N’-tetramethylethylenediamine as redox initiating pair in presence of poly(ethylene glycol) diacrylate as a crosslinker. Swelling experiments were performed in water at 25 °C, gravimetrically. The hydrogels, the semi-interpenetrating polymer networks, and the hybrid composite hydrogel systems that synthesized in this study have showed high water absorbency. Some swelling and diffusion properties were calculated, and they were discussed for the hybrid hydrogel systems prepared under various formulations. The equilibrium percentage swelling degree of highly swollen hybrid composite hydrogel systems ranges are 718-2055 %. FT-IR analysis and SEM technique were applied for characterization. For sorption of water-soluble cationic dye such as lauths violet into the hydrogel systems was studied by batch sorption technique at 25 °C. For equilibrium sorption studies, dye sorption percentage, dye uptake performance, and partition coefficient of the hydrogel systems have been investigated. The values of dye sorption percentage of the hydrogels were changed among 87.11-96.39 %. Consequently, the hydrogel systems developed in this study could serve as a potential device for water and dye sorbent.     

Preparation of Cross-linked Chitosan Quaternary Ammonium Salt Hydrogel Films Loading Drug of Gentamicin Sulfate for Antibacterial Wound Dressing

Hydrogels, possessing high biocompatibility and adaptability to biological tissue, show great usability in medical applications. In this research, a series of novel cross-linked chitosan quaternary ammonium salt loading with gentamicin sulfate (CTMCSG) hydrogel films with different cross-linking degrees were successfully obtained by the reaction of chitosan quaternary ammonium salt (TMCS) and epichlorohydrin. Fourier transform infrared spectroscopy (FTIR), thermal analysis, and scanning electron microscope (SEM) were used to characterize the chemical structure and surface morphology of CTMCSG hydrogel films. The physicochemical property, gentamicin sulphate release behavior, cytotoxicity, and antibacterial activity of the CTMCSG against Escherichia coli and Staphylococcus aureus were determined. Experimental results demonstrated that CTMCSG hydrogel films exhibited good water stability, thermal stability, drug release capacity, as well as antibacterial property. The inhibition zone of CTMCSG hydrogel films against Escherichia coli and Staphylococcus aureus could be up to about 30 mm. Specifically, the increases in maximum decomposition temperature, mechanical property, water content, swelling degree, and a reduction in water vapor permeability of the hydrogel films were observed as the amount of the cross-linking agent increased. The results indicated that the CTMCSG-4 hydrogel film with an interesting physicochemical property, admirable antibacterial activity, and slight cytotoxicity showed the potential value as excellent antibacterial wound dressing.     

Purification and characterization of a bifunctional alginate lyase from Pseudoalteromonas sp. SM0524

An alginate lyase-producing bacterial strain, Pseudoalteromonas sp. SM0524, was screened from marine rotten kelp. In an optimized condition, the production of alginate lyase from Pseudoalteromonas sp. SM0524 reached 62.6 U/mL, suggesting that strain SM0524 is a good producer of alginate lyases. The bifunctional alginate lyase aly-SJ02 secreted by strain SM0524 was purified. Aly-SJ02 had an apparent molecular mass of 32 kDa. The optimal temperature and pH of aly-SJ02 toward sodium alginate was 50 °C and 8.5, respectively. The half life period of aly-SJ02 was 41 min at 40 °C and 20 min at 50 °C. Aly-SJ02 was most stable at pH 8.0. N-terminal sequence analysis suggested that aly-SJ02 may be an alginate lyase of polysaccharide lyase family 18. Aly-SJ02 showed activities toward both polyG (α-l-guluronic acid) and polyM (β-D-mannuronic acid), indicating that it is a bifunctional alginate lyase. Aly-SJ02 had lower K(m) toward polyG than toward polyM and sodium alginate. Thin layer chromatography and ESI-MS analyses showed that aly-SJ02 mainly released dimers and trimers from polyM and alginate, and trimers and tetramers from polyG, which suggests that aly-SJ02 may be a good tool to produce dimers and trimers from alginate.     

影响小麦幼穗组织培养特性基因的染色体定位

为了研究影响小麦幼穗组织培养特性的遗传规律，选用具有优良的组织培养特性的小麦品种(系)R1395和多花白与中国春小麦单体系列杂交，探讨了影响小麦组织培养特性如半愈期、成根愈率和成芽愈率的基因的染色体定位。结果表明，半愈期、成根愈率、成芽愈率等组织培养特性均显示了受多基因控制的倾向，但存在着主效基因的作用。染色体1D、1B、和5A对半愈期有显著的影响，其中1D染色体的作用最强；染色体3B、3D、2A和1D对成根愈率有显著的影响；染色体2B、2D和3A对成芽愈率有显著的影响，其中2B和2D显示了促进的作用，而3A表现了抑制的作用。     

Psyllium and acrylic acid based polymeric networks synthesized under the influence of γ-radiations for sustained release of fungicide

The present study deals with the utilization of psyllium and acrylic acid based hydrogels, synthesized under the influence of γ-radiations, in sustained delivery of copper sulfate, used as a fungicide in agricultural fields. Swelling behavior of the synthesized hydrogel was investigated in distilled water as functions of time, temperature, and pH. It was found that the hydrogel showed maximum of 10,578 % swelling at 25 °C for 24 h. The hydrogel was then checked for its sustained fungicide release behavior. It was observed that the hydrogel has been found to follow Non-Fickian type mechanism for the fungicide release. The ‘n’ and ‘k’ have been found to be 0.71 and 7.61×10⁻³, respectively.     

Biochemical Characterization and Cold-Adaption Mechanism of a PL-17 Family Alginate Lyase Aly23 from Marine Bacterium Pseudoalteromonas sp. ASY5 and Its Application for Oligosaccharides Production

As an important enzyme involved in the marine carbon cycle, alginate lyase has received extensive attention because of its excellent degradation ability on brown algae, which is widely utilized for alginate oligosaccharide preparation or bioethanol production. In comparison with endo-type alginate lyases (PL-5, PL-7, and PL-18 families), limited studies have focused on PL-17 family alginate lyases, especially for those with special characteristics. In this study, a novel PL-17 family alginate lyase, Aly23, was identified and cloned from the marine bacterium Pseudoalteromonas carrageenovora ASY5. Aly23 exhibited maximum activity at 35 °C and retained 48.93% of its highest activity at 4 °C, representing an excellent cold-adaptation property. Comparative molecular dynamics analysis was implemented to explore the structural basis for the cold-adaptation property of Aly23. Aly23 had a high substrate preference for poly β-D-mannuronate and exhibited both endolytic and exolytic activities; its hydrolysis reaction mainly produced monosaccharides, disaccharides, and trisaccharides. Furthermore, the enzymatic hydrolyzed oligosaccharides displayed good antioxidant activities to reduce ferric and scavenge radicals, such as hydroxyl, ABTS⁺, and DPPH. Our work demonstrated that Aly23 is a promising cold-adapted biocatalyst for the preparation of natural antioxidants from brown algae.     

Cultivable Alginate Lyase-Excreting Bacteria Associated with the Arctic Brown Alga Laminaria

Although some alginate lyases have been isolated from marine bacteria, alginate lyases-excreting bacteria from the Arctic alga have not yet been investigated. Here, the diversity of the bacteria associated with the brown alga Laminaria from the Arctic Ocean was investigated for the first time. Sixty five strains belonging to nine genera were recovered from six Laminaria samples, in which Psychrobacter (33/65), Psychromonas (10/65) and Polaribacter (8/65) were the predominant groups. Moreover, 21 alginate lyase-excreting strains were further screened from these Laminaria-associated bacteria. These alginate lyase-excreting strains belong to five genera. Psychromonas (8/21), Psedoalteromonas (6/21) and Polaribacter (4/21) are the predominant genera, and Psychrobacter, Winogradskyella, Psychromonas and Polaribacter were first found to produce alginate lyases. The optimal temperatures for the growth and algiante lyase production of many strains were as low as 10–20 °C, indicating that they are psychrophilic bacteria. The alginate lyases produced by 11 strains showed the highest activity at 20–30 °C, indicating that these enzymes are cold-adapted enzymes. Some strians showed high levels of extracellular alginate lyase activity around 200 U/mL. These results suggest that these algiante lyase-excreting bacteria from the Arctic alga are good materials for studying bacterial cold-adapted alginate lyases.     

橡胶树炭疽病生防内生菌的分离鉴定及抑菌作用研究

目前化学农药的缺点日益突显,研发环保的生防菌剂是当前绿色安全的一种方法,筛选具有抑制橡胶树炭疽病的生防菌株,为研发新型生防菌剂储备资源。本文采用组织培养法分离纯化橡胶树内生菌,平板对峙筛选拮抗菌株;通过菌株培养特征、生理生化、根据16S rRNA和gyrA基因序列构建系统发育树确定其分类地位;采用平板对峙法研究内生菌株的抗菌持久性、稳定性、广谱性;采用牛津杯法研究拮抗内生菌对杀菌剂的敏感性。从橡胶树健康的根组织中分离得到4株对橡胶树炭疽病具有抑制作用的细菌（Bac RZS3D4-1、Bac RZS3D4-2、Bac RZS3D4-3、Bac RZS3D4-4）,系统发育树分析结果显示这4株细菌与解淀粉芽孢杆菌（Bacillus amyloliquefaciens）亲缘关系很近,且培养性状和生理生化特征也与解淀粉芽孢杆菌相似。这4株内生菌的抗菌持久性强,抗菌稳定性好;对尖孢炭疽菌（Colletotrichum acutatum）DFMP1E和MLZZP3、小孢拟盘多毛孢（Pestalotiopsis microspora）MF375898均有较强的抑菌能力,对茄类镰刀菌（Fusarium solani）XJ160901的抑制作用较弱;对多菌灵、异菌脲、百菌清、苯醚甲环唑4种杀菌剂均不敏感,有望开发为生防菌剂。     

A Promising Potential of Brown Algae Sargassum polycystum as Irreversible Hydrocolloid Impression Material

This study aimed to investigate the potential use of brown algae Sargassum polycystum as irreversible hydrocolloid (alginate) impression material. Potassium alginate extracted from Sargassum polycystum was prepared in three different compositions (14%, 15%, and 16%) and mixed with other standard components to form an alginate impression material. Prior to that, the purity of potassium alginate was quantified with Fourier Transform Infrared Spectroscopy (FTIR) analysis. As a control material, the alginate impression material from a commercially available product was used. All alginate impression materials were then applied to a die stone model. Dimensional accuracy was measured by calculating the mesiodistal width of incisors in the generated dental cast using a digital caliper 0.01 accuracy (five replications). In addition, to evaluate the dimensional stability, the impression results were poured at four different periods (immediately, 5 min, 10 min, and 15 min). An independent t-test was performed to compare the measurement results with p < 0.05 considered significant. Analytical results confirm that the impression material containing 15% potassium alginate gives the best dimensional accuracy similar to control (p > 0.05). Meanwhile, the optimal dimensional stability was produced in the impression material containing 16% potassium alginate. Our study suggested that brown algae Sargassum polycystum has a promising potential to be used as an alginate impression material in clinical application.     

Crop Breeding in the Twenty-First Century

SUMMARY

One can predict a future in which professional plant breeding, especially in the private sector, will be significantly scaled back, and advanced biotechnologies (e.g., genetic engineering) will be forbidden for use in plant breeding. Alternatively, one can predict a future in which commercialism will rule all sectors. But a more optimistic outlook predicts that the current tripartite division of responsibilities will prevail: Private Sector, Public Sector, and Participatory (i.e., farmer-breeder partnerships). The global plant breeding system is composed of separate organs, each essential for the survival of the whole but each with a different function. All parts work together for the good of the whole.     

干热变性紫薯淀粉成膜工艺优化

紫薯中直链淀粉含量较高,具有较好的成膜性。以干热变性紫薯淀粉为基质,探究变性淀粉添加量、甘油添加量和海藻酸钠添加量对干热变性紫薯淀粉成膜特性的影响,通过响应面分析法确定干热变性紫薯淀粉最佳成膜工艺参数。结果表明:当变性淀粉添加量为3.99%,甘油添加量为1.52%,海藻酸钠添加量为0.60%时,干热变性紫薯淀粉膜的性能最优。研究成果将为干热变性紫薯淀粉可食用膜的工业化生产提供理论指导。     

食用胶对小麦粉面团流变学特性的影响

为明确食用胶在面制食品中的作用,以3种商业小麦粉(特一粉、富强粉、上白粉)为试验材料,分别添加不同比例的海藻酸钠、黄原胶、卡拉胶,分析其对面团流变学特性的影响。结果表明,小麦粉添加0.15%~0.25%的海藻酸钠,面团稳定时间显著提高,弱化度显著降低;添加0.10%、0.20%和0.25%的海藻酸钠,面团最大拉伸阻力显著提高。添加0.02%、0.06%和0.10%的黄原胶,面团最大拉伸阻力显著提高;添加0.10%黄原胶的面团拉伸面积也显著提高。添加0.10%的卡拉胶,面团稳定时间、拉伸面积显著提高,弱化度显著降低。食用胶因小麦粉品质不同对面团流变学特性的影响也不同,除添加0.25%的海藻酸钠外,其他添加量的3种食用胶均可降低特一粉的面团吸水率,提高上白粉的吸水率。研究认为,海藻酸钠、黄原胶、卡拉胶可显著改善小麦粉的面团流变学特性,增强面团筋力。