3D Printing of Cellulase-Laden Cellulose Nanofiber/Chitosan Hydrogel Composites: Towards Tissue Engineering Functional Biomaterials with Enzyme-Mediated Biodegradation

The 3D printing of a multifunctional hydrogel biomaterial with bioactivity for tissue engineering, good mechanical properties and a biodegradability mediated by free and encapsulated cellulase was proposed. Bioinks of cellulase-laden and cellulose nanofiber filled chitosan viscous suspensions were used to 3D print enzymatic biodegradable and biocompatible cellulose nanofiber (CNF) reinforced chitosan (CHI) hydrogels. The study of the kinetics of CNF enzymatic degradation was studied in situ in fibroblast cell culture. To preserve enzyme stability as well as to guarantee its sustained release, the cellulase was preliminarily encapsulated in chitosan–caseinate nanoparticles, which were further incorporated in the CNF/CHI viscous suspension before the 3D printing of the ink. The incorporation of the enzyme within the CHI/CNF hydrogel contributed to control the decrease of the CNF mechanical reinforcement in the long term while keeping the cell growth-promoting property of chitosan. The hydrolysis kinetics of cellulose in the 3D printed scaffolds showed a slow but sustained degradation of the CNFs with enzyme, with approximately 65% and 55% relative activities still obtained after 14 days of incubation for the encapsulated and free enzyme, respectively. The 3D printed composite hydrogels showed excellent cytocompatibility supporting fibroblast cell attachment, proliferation and growth. Ultimately, the concomitant cell growth and biodegradation of CNFs within the 3D printed CHI/CNF scaffolds highlights the remarkable potential of CHI/CNF composites in the design of tissue models for the development of 3D constructs with tailored in vitro/in vivo degradability for biomedical applications.     

骨用镁合金表面Ti-Cu涂层的腐蚀行为

背景：镁合金作为骨折内固定材料具有力学性能与骨相近、生物相容性好和可降解等突出优点,但其在体液中降解速度过快,成为其临床应用的瓶颈,因此综合利用表面处理提高其耐蚀性能具有重要意义。 目的：综合运用磁控溅射技术和碱热处理技术在镁合金表面制备兼具耐蚀性能和生物活性的涂层。 方法：首先采用熔炼技术制备Mg-Zn-Mn合金,利用磁控溅射技术在材料表面制备致密涂层,然后利用碱性溶液对表面涂层进行处理,利用模拟体液浸泡实验研究涂层的腐蚀行为,通过表面产物中钙和磷的含量推测涂层的生物活性。 结果与结论：经磁控溅射和碱热处理技术在镁合金表面制备兼具耐蚀性能和生物活性的涂层;经模拟体液浸泡24和168 h后涂层表面沉积含Ca,P产物,Ca/P比分别为1.54和2.11,接近类骨磷酸盐Ca/P比,涂层表面的浸泡24 h形成5-10 μm点腐蚀,随着浸泡时间增加点腐蚀逐渐长大,浸泡168 h后点腐蚀增加为100-800 μm。     

Characterization of Enzymatic Activity of MlrB and MlrC Proteins Involved in Bacterial Degradation of Cyanotoxins Microcystins

Bacterial degradation of toxic microcystins produced by cyanobacteria is a common phenomenon. However, our understanding of the mechanisms of these processes is rudimentary. In this paper several novel discoveries regarding the action of the enzymes of the mlr cluster responsible for microcystin biodegradation are presented using recombinant proteins. In particular, the predicted active sites of the recombinant MlrB and MlrC were analyzed using functional enzymes and their inactive muteins. A new degradation intermediate, a hexapeptide derived from linearized microcystins by MlrC, was discovered. Furthermore, the involvement of MlrA and MlrB in further degradation of the hexapeptides was confirmed and a corrected biochemical pathway of microcystin biodegradation has been proposed.     

A novel approach to temporary stenting: degradable cardiovascular stents produced from corrodible metal-results 6-18 months after implantation into New Zealand white rabbits

OBJECTIVE—To determine whether corrodible materials may be safely used as biodegradable cardiovascular implants.
DESIGN—Corrodible iron stents (> 99.8% iron) were produced from pure iron and laser cut with a stent design similar to a commercially available permanent stent (PUVA-AS16). A total of 16 NOR-I stents were implanted into the native descending aorta of 16 New Zealand white rabbits (mean luminal diameter at the implantation site 3.4 mm, balloon diameter to vessel diameter ratio 1.13).
RESULTS—No thromboembolic complications and no adverse events occurred during the follow up of 6-18 months. All stents were patent at repeat angiography after 6 (n = 9), 12 (n = 5), and 18 months (n = 2) with no significant neointimal proliferation, no pronounced inflammatory response, and no systemic toxicity.
CONCLUSIONS—This initial in vivo experience suggests that degradable iron stents can be safely implanted without significant obstruction of the stented vessel caused by inflammation, neointimal proliferation, or thrombotic events.


Keywords: congenital heart disease; corrosion; stents; biodegradation     

医用壳聚糖膜的制备和性能研究

研究了壳聚糖膜的制备方法和性能。探讨了壳聚糖浓度、甘油和戊二醛用量对壳聚糖膜性能的影响，并考察了膜的体外降解过程。结果表明w=．02的壳聚糖溶液成膜效果较好；甘油和戊二醛能王著改善壳聚糖膜的力学性能和尺寸稳定性能；溶茼酶-林格氏液中浸泡40d后膜的降解率为41．98％。满足引导组织再生材料的基本要求。该膜作为一种潜在的生物医用材料，将具有较广阔的应用前景。     

In vitro gastrointestinal-resistant pectin hydrogel particles for β-glucuronidase adsorption

Pectin hydrogel particles (PHPs) were prepared by ionotropic gelation of low methylesterified pectin of Tanacetum vulgare L. with calcium ions. Wet PHPs prepared from TVF exhibited a smaller diameter and the lower weight as well as exhibited the best textural properties in terms of hardness and elasticity compared to the PHPs prepared from commercial low methylesterified pectin (CU701) used for comparison. Upon air drying, PHPs prepared from CU701 became small and dense microspheres whereas the dry PHPs prepared from TVF exhibited a drop-like shape. The morphology of dry PHPs determined by scanning electron microscopy revealed that the surface of the TVF beads exhibited fibred structures, whereas the PHPs prepared from CU701 exhibited a smooth surface. The characterization of surface roughness using atomic force microscopy indicated less roughness profile of the PHPs prepared from TVF than CU701. PHPs prepared from TVF were found to possess in vitro resistance to successive incubations in simulated gastric (SGF), intestinal (SIF), and colonic fluid (SCF) at 37 °C for 2, 4 and 18 h, respectively. The PHPs prepared from CU701 swelled in SGF and then lost their spherical shape and were fully disintegrated after 4 h of incubation in SIF. The PHPs from TVF, which were subjected to treatment with SGF, SIF and SCF, were found to adsorb microbial β-glucuronidase (βG) in vitro. The data obtained offered the prospect for the development of the PHPs from TVF as sorbents of colonic βG for the inhibition of re-absorption of estrogens.     

Lignin‐modifying enzymes in filamentous basidiomycetes – ecological,functional and phylogenetic review

Filamentous fungi owe powerful abilities for decomposition of the extensive plant material, lignocellulose, and thereby are indispensable for the Earth's carbon cycle, generation of soil humic matter and formation of soil fine structure. The filamentous wood‐decaying fungi belong to the phyla Basidiomycota and Ascomycota, and are unique organisms specified to degradation of the xylem cell wall components (cellulose, hemicelluloses, lignins and extractives). The basidiomycetous wood‐decaying fungi form brackets, caps or resupinaceous (corticioid) fruiting bodies when growing on wood for dissemination of their sexual basidiospores. In particular, the ability to decompose the aromatic lignin polymers in wood is mostly restricted to the white rot basidiomycetes. The white‐rot decay of wood is possible due to secretion of organic acids, secondary metabolites, and oxidoreductive metalloenzymes, heme peroxidases and laccases, encoded by divergent gene families in these fungi. The brown rot basidiomycetes obviously depend more on a non‐enzymatic strategy for decomposition of wood cellulose and modification of lignin. This review gives a current ecological, genomic, and protein functional and phylogenetic perspective of the wood and lignocellulose‐decaying basidiomycetous fungi. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Grain Growth upon Annealing and Its Influence on Biodegradation Rate for Pure Iron

Biodegradable pure iron has gained significant interest as a biomedical material. For biodegradable implant applications, the biodegradation behavior of pure iron is important. In this work, the influence of ferrite grain size on the biodegradation rate for pure iron was studied by means of heat treatment that was annealed below the austenized temperature using as-forged pure iron. Grains were coarsened and a spectrum of ferrite grain sizes was gained by changing the annealed temperature. Biodegradation behavior was studied through weight loss tests, electrochemical measurements and microscopic analyses. Hardness (HV) and biodegradation rate (P_i or P_w) were linearly ferrite grain size-dependent: HV=58.9+383.2d−12, and Pi=−0.023+0.425d−12 or Pw=0.056+0.631d−12. The mechanism by which the role of grain size on biodegradation rate was attributed to the ferrite grain boundary traits.     

三维多孔聚DL-乳酸/羟基磷灰石复合材料体外降解特征的研究

观察不同比例羟基磷灰石 (HA)复合聚DL 乳酸 (PDLLA)制备的泡沫材料的体外降解特性 ,将PDLLA、PDLLA/HA(5wt%)、PDLLA/HA(2 0wt%)及PDLLA/HA(35wt%)四种材料置入蒸馏水中降解 ,比较各组pH值、重量、分子量及抗压强度的变化。结果发现 ,复合材料PDLLA/HA(2 0wt%)降解各时期的各指标与其他组比较差异有显著性意义 (P <0 0 5 )。纯PDLLA的pH值呈逐渐下降的趋势 ,而PDLLA/HA(2 0wt%)在 6周后趋向于平稳 ,12周时pH值与原环境相近。说明HA的加入影响了PDLLA的体外降解性能 ,不同比例的复合材料性能不同 ,PDLLA/HA(2 0wt%)具有降解过程相对延迟、力学性能稳定和能缓冲酸性代谢产物的特点。