Biodegradable composites with improved barrier properties and transparency from the impregnation of PLA to bacterial cellulose membranes

Poly(lactic acid) (PLA) was impregnated in bacterial cellulose (BC) membranes. BC/PLA films were prepared by solvent casting and mechanical, optical and barrier properties, and biodegradation process were investigated. The transparency of processed films was higher than that of neat BC and increased with PLA content. Moreover, the incorporation of PLA to BC enhanced significantly the water vapor barrier properties of the BC membranes. The bionanocomposites contained a high percentage of cellulose due to the impregnation method that leads to the film with a BC content of 94%, which practically maintains the excellent mechanical properties of BC. However, when increasing the PLA content in the bionanocomposites the mechanical properties decreased slightly with respect to BC. Biodegradation under real soil conditions was determined indirectly through the study of the visual degradation and disintegration, demonstrating that the bionanocomposites were degraded faster than the neat PLA. The successful production of BC/PLA bionanocomposites suggested the possible application of them for active food packaging. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43669.     

Immobilization of lecithin on bacterial cellulose nanofibers for improved biological functions

In an attempt to improve the biological behavior of pristine bacterial cellulose (BC), lecithin (LEC) has been immobilized on the surface of BC nanofibers by solution immersion and subsequent chemical crosslinking with proanthocyanidin (PA). The as-prepared LEC-immobilized BCs (denoted as BC/LECs) were characterized by SEM, FTIR, and XRD, and their dynamic mechanical properties, thermal stability, and hydrophilicity were assessed. The presence of LEC on BC surface was confirmed by SEM and FTIR analyses. It has been found that BC/LECs retain the three-dimensional (3D) porous network structure of pristine BC. The BC/LECs still demonstrate favorable mechanical properties, surface hydrophilicity, and thermal stability. More importantly, preliminary cell studies suggest that the BC/LECs show improved cell behavior over pristine BC.     

Preparation and properties of bacterial cellulose/graphene oxide composite films using dyeing method

In this study, bacterial cellulose (BC) hydrogels were cultured from a kombucha SCOBY starter. The scanning electron microscopy (SEM) results indicated that the dried BC exhibited an interpenetrating fibrous mat. The BC films harvested for 5, 10, and 15 days were 15–19, 14.4–24, and 30–31 μm thick, respectively. Then, BC/graphene oxide (GO) composite films were prepared via the exhaust dyeing method. GO sheets penetrated the BC matrix, resulting in the formation of a BC/GO composite, as revealed by the SEM analysis results. The mechanical properties of the composite films were investigated. Compared with virgin BC, the tensile strength of the composite films was higher, while the %E at break was lower, resulting in a significant increase in the Young's modulus. The X-ray diffraction results indicated that an increase in the dyeing time (0.5–2 h) gradually induced cellulose crystalline conformation, which in turn affected the swelling ability, mechanical properties, and electrical properties of the BC/GO composite films. After the reduction of GO to reduced GO (rGO), flexible conductive BC/rGO films were obtained, as confirmed by their resistivity values. Thus, flexible conductive composite films with excellent mechanical properties were successfully fabricated.     

Influence of branching characteristics on thermal and mechanical properties of Ziegler–Natta and metallocene hexene linear low‐density polyethylene blends with low‐density polyethylene

The effect of the branch content (BC) and composition distribution (CD) of linear low‐density polyethylene (LLDPE) on the thermal and mechanical properties of its blends with LDPE were studied. All blends and pure resins were conditioned in a Haake PolyDrive blender at 190°C and in the presence of adequate amounts of antioxidant. Two metallocene LLDPEs (m‐LLDPE) and one Ziegler–Natta (ZN) hexene LLDPE were melt blended with the same LDPE. The effect of the BC was investigated by blending two hexene m‐LLDPEs of similar weight‐average molecular weights and molecular weight distributions but different BCs with the same LDPE. The effect of the CD was studied by using a ZN and an m‐LLDPE with similar weight‐average molecular weights, BCs, and comonomer type. Low‐BC m‐LLDPE blends showed separate crystallization whereas cocrystallization was observed in the high‐BC m‐LLDPE‐rich blends. However, ZN‐LLDPE/LDPE blends showed separate crystallization together with a third population of cocrystals. The influence of the crystallization behavior was reflected in the mechanical properties. The BC influenced the modulus, ultimate tensile strength, and toughness. The addition of a small amount of LDPE to a low‐BC m‐LLDPE resulted in a major improvement in the toughness, whereas the results for the high‐BC pair followed the additivity rule. ZN‐LLDPE blends with LDPE blends were found to be more compatible and exhibited superior mechanical properties compared to m‐LLDPE counterparts with the same weight‐average molecular weight and BC. All mechanical properties of ZN‐LLDPE blends follow the linear rule of mixtures. However, the CD had a stronger influence on the mechanical properties in comparison to the BC. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 2488–2498, 2005     

Effect of down-stream processing parameters on the mechanical properties of bacterial cellulose

Bacterial cellulose (BC), a biodegradable polymer with high degree of crystallinity, produced by Gluconacetobacter xylinus, was used as reinforcement in biocomposites. The downstream process parameters involved in the preparation process of BC have important influence on its mechanical properties. The effect of some key processing parameters such as treatment temperature, drying stages, type of treatment solvent and pressure on biocellulose sheets was investigated during drying in order to modify the parameters responsible in mechanical properties. The rise in treatment temperature and drying processes of BC sheets showed about 8 and 11 % reduction in tensile strength, respectively. The addition of NaOH solutions during the treatment reduced the tensile strength of BC sheets sharply, though an increase in NaOH concentration produced treated samples with higher tensile modulus. The use of optimum NaClO solution as a cheap treatment solvent led to an increase of about 10–11 % in the mechanical properties of BC. A pressure increase during drying stage improved the tensile strength of biocellulose sheets by 7 % and resulted in highly enhanced tensile modulus of BC samples. The production process (microbial fermentation) and structural features (porous web-shaped structure) provide an ideal scenario for synthesis of BC composites. A number of schemes have been introduced to synthesize BC composites with different materials. Among these schemes, the initial addition of materials to BC culture media, the treatment of BC with solutions and suspensions, and the dissolution of BC in solvents are the most commonly used techniques.     

细菌纤维素/聚乳酸复合膜制备及性能

以聚乳酸(PLA)为原料,利用细菌纤维素(BC)生产菌株发酵制得BC/PLA复合膜。通过对BC/PLA复合膜制备过程中发酵时间、纺膜速率、PLA溶液用量等因素的考察,以BC/PLA复合膜载药率为指标,进行了BC/PLA复合膜制备工艺的优化;利用FTIR、TG、拉力实验、XRD及SEM对BC、PLA及BC/PLA复合膜化学基团、热性能、力学性能、结晶度及表面形貌进行了分析;对BC/PLA复合膜载药及释药过程进行了研究。结果表明,PLA溶液用量对BC/PLA复合膜载药率影响较小,BC/PLA复合膜最优制备工艺为:纺膜速率0.15 mm/s,发酵时间36h,所制备BC/PLA复合膜在15mg/L双氯芬酸钾药液中最大载药率为2.51mg/g。FTIR、TG、拉力实验、XRD及SEM结果表明,BC与PLA可以成功复合,从而改善PLA的热性能及力学性能,所制备BC/PLA复合膜具有三维网状多孔结构。载药BC/PLA复合膜药物释放过程符合一级释放动力学模型。     

Acrylic bone cements: Effects of the poly(methyl methacrylate) powder size and chitosan addition on their properties

The effect of the particle size of poly(methyl methacrylate) (PMMA) and the incorporation of chitosan (CH) on the mechanical and thermal properties and the biocompatibility of acrylic bone cements were investigated. Three groups of bone cements were prepared with different PMMA particles. Groups 1 (BC1) and 2 (BC2) contained ground and sieved PMMA with particle sizes in the ranges 50–150 μm and 1–50 μm, and group 3 (BC3) contained synthesized PMMA microspheres with a size of about 1 μm. The mechanical properties of the three groups were similar, but their curing properties were significantly affected. The presence of CH improved the mechanical and thermal properties. For the BC1 group, the compressive strength increased more than 10 MPa, and the curing temperature decreased 12°. The cement having the optimum properties (BC1) was applied to rats, where it enhanced the bone bonding ability, and bioactivity was observed. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39662.     

Effect of chitosan penetration on physico-chemical and mechanical properties of bacterial cellulose

Bacterial cellulose-chitosan composites (BC-Ch) were prepared in order to obtain the BC-Ch composites with improved physico-mechanical characteristics. BC sheets were immersed in a Ch solution hoping that the Ch penetrates into the BC sheet. Ch penetration was observed according to variations in temperature, operation mode and treatment time. The morphological changes due to enhanced penetration were observed through FE-SEM, FT-IR and XRD analysis. FE-SEM analyses confirmed the formation of three dimensional multilayered structures in BC-Ch, whose thickness increased with Ch penetration. The FT-IR analysis showed intermolecular hydrogen bonding interaction between the BC and Ch molecules. XRD results revealed a slight decrease in the crystallinity index of the BC-Ch composites compared to pure BC. The mechanical properties, water holding capacity (WHC) and water release rate (WRR) of the BC-Ch composites were significantly improved compared to pure BC. The superior mechanical properties, WHC and water release rate would make the BC-Ch composites suitable for wound dressing and other biomedical applications.     

Sustainable biocarbon as an alternative of traditional fillers for poly(butylene terephthalate)-based composites: Thermo-oxidative aging and durability

Sustainable biocomposites have gained considerable interest as an alternative to conventional composites in recent years due to their cost-effectiveness and environmental friendliness. The aim of this study was to investigate the performance and durability behavior of biocomposites from sustainable biocarbon (BC) as compared to conventional established fillers. The poly(butylene terephthalate) (PBT) and its composites reinforced with BC, talc, and glass fiber (GF) were prepared and the durability performances was investigated. The study showed that BC/PBT biocomposites provided a lighter weight alternative to traditionally used fillers. After undergoes thermo-oxidative aging, the mechanical properties of BC/PBT biocomposite were deteriorated. The GF/PBT showed the most stable in retaining its mechanical properties in comparison to the talc/PBT and BC/PBT. The aging behavior and mechanism of the PBT composites were discussed. This study provides further insight on the durability-related properties progression of biocomposites as compared to traditional used fillers. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47722.     

BC/PAM双网络水凝胶的制备及性能研究

为了改善细菌纤维素(BC)的物理及机械性能,扩大其在医用材料及功能材料等领域的应用,以细菌纤维素为基体,丙烯酰胺(AM)为单体,N,N-亚甲基双丙烯酰胺(MBA)为交联剂,采用自由基聚合的方法在BC骨架中引入聚丙烯酰胺(PAM)网络,获得BC/PAM双网络水凝胶。采用扫描电镜(SEM)、热重分析(TGA)对其形态结构及热稳定性进行研究,同时分别研究了单体和交联剂浓度对复合材料的溶胀、保水以及机械性能的影响。结果发现,随着单体和交联剂浓度的增加,BC/PAM水凝胶的溶胀和保水性均获得一定程度的改善。另外,增加单体浓度,复合材料的杨氏模量明显上升,形态结构更加致密,热稳定性显著提高。     

Bacterial cellulose: A comprehensive review

This review article provides a comprehensive overview of bacterial cellulose (BC), focusing on its physicochemical properties, production methods, purification techniques, and applications. It aims at providing a nuanced understanding of the current state of knowledge in those fields and bridging the gap between academic research and industrial applications. The physicochemical properties of BC, including its chemical structure, morphology, thermal properties, mechanical properties (such as tensile and compression properties), specific surface area, cytotoxicity, and biocompatibility, are discussed. Production methods of BC, including microorganism comparison, culture conditions, and vessel types, are thoroughly explored. Purification methods and sterilization techniques for BC are also addressed. Furthermore, the review highlights industries and applications that have shown interest in BC along with commercially available products, including medical, cosmetic, textile, food ingredients, and scaffolds in cell culture. A conclusion summarizes key findings and potential future directions in BC research and development.     

Dynamic mechanical properties of bacterial cellulose nanofibres

In this work, dynamic mechanical properties of the grown bacterial cellulose (BC) nanofibers were investigated. BC pellicles were fabricated using bacterial fermentation (Gluconacetobacter xylinus). The morphology results confirmed that the dried BC at ambient conditions could be categorized as a xerogel. The thermal dynamic mechanical analysis results indicated that the bound water in bacterial cellulose structure had a very significant effect on thermal and dynamic mechanical properties of BC pellicles. The results of dehydration kinetics study showed that the main mechanism governing water loss of BC was Fickian diffusion. The glass transition temperatures (T_g) of the BC dried at 25 °C (ambient temperature) and 105 °C were estimated ??33 and ??18 °C, respectively. This discrepancy can be attributed to the plasticizing effect of the bound water of BC dried at ambient temperature. Furthermore, the results indicated that its modulus drop smaller than one order of magnitude can be attributed to its high crystalline nature. The storage modulus versus frequency increased due to the limitation of the relaxation process of the polymer chains. Moreover, the relaxation time distribution was achieved from the slope of the modulus master curve versus logarithmic frequency. As a result, BC exhibited a solid-like behavior.     

Cracking the Breast Cancer Glyco-Code through Glycan-Lectin Interactions: Targeting Immunosuppressive Macrophages

The immune microenvironment of breast cancer (BC) is composed by high macrophage infiltrates, correlated with the most aggressive subtypes. Tumour-associated macrophages (TAM) within the BC microenvironment are key regulators of immune suppression and BC progression. Nevertheless, several key questions regarding TAM polarisation by BC are still not fully understood. Recently, the modulation of the immune microenvironment has been described via the recognition of abnormal glycosylation patterns at BC cell surface. These patterns rise as a resource to identify potential targets on TAM in the BC context, leading to the development of novel immunotherapies. Herein, we will summarize recent studies describing advances in identifying altered glycan structures in BC cells. We will focus on BC-specific glycosylation patterns known to modulate the phenotype and function of macrophages recruited to the tumour site, such as structures with sialylated or N-acetylgalactosamine epitopes. Moreover, the lectins present at the surface of macrophages reported to bind to such antigens, inducing tumour-prone TAM phenotypes, will also be highlighted. Finally, we will discuss and give our view on the potential and current challenges of targeting these glycan-lectin interactions to reshape the immunosuppressive landscape of BC.     

细菌纤维素的功能化改性研究进展

细菌纤维素(BC)是微生物生长过程中产生的以葡萄糖为基本骨架的结构性碳水化合物,具有高纯度、高聚合度、高结晶度、高持水性、高抗张强度和良好的机械强度,在功能材料领域显示了巨大的应用潜力.综述了近年来BC合成菌种筛选的研究现状;分析了BC在透气、吸湿排汗、力学性能和染色与脱色性能调控方面的进展情况;重点总结了BC基材料在抗菌、防紫外线、防辐射、防静电、拒水拒油、导电和传感等功能化改性方面的研究进展;最后,指出BC大规模高效成模和成型技术、差异化高功能BC材料制备技术是未来的重点研发方向.     

含炭量对增强PP/BC复合材料的导电性能影响

以竹炭（BC）为填料,聚丙烯（PP）树脂为基体,采用熔融共混法制备了PP/BC复合材料,通过扫描电子显微镜、吸水率、显气孔率、力学性能和热稳定性进行综合分析,研究了BC含量对其导电性能的影响。结果表明,BC的引入可以显著降低PP/BC复合材料的体积电阻率,当BC含量大于30 %（质量分数,下同）时,增长效果尤为明显。     

Implications of melt compatibility/incompatibility on thermal and mechanical properties of metallocene and Ziegler–Natta linear low density polyethylene (LLDPE) blends with high density polyethylene (HDPE): influence of composition distribution and branch content of LLDPE

In this paper, the implications of melt compatibility on thermal and solid‐state properties of linear low density polyethylene/high density polyethylene (LLDPE/HDPE) blends were assessed with respect to the effect of composition distribution (CD) and branch content (BC). The effect of CD was studied by melt blending a metallocene (m‐LLDPE) and a Ziegler‐Natta (ZN) LLDPE with the same HDPE at 190 °C. Similarly, the effect of BC was examined. In both cases, resins were paired to study one molecular variable at a time. Thermal and solid‐state properties were measured in a differential scanning calorimeter and in an Instron mechanical testing instrument, respectively. The low‐BC m‐LLDPE (BC = 14.5 CH₃/1000 C) blends with HDPE were compatible at all compositions: rheological, thermal and some mechanical properties followed additivity rules. For incompatible high‐BC (42.0 CH₃/1000 C) m‐LLDPE‐rich blends, elongation at break and work of rupture showed synergistic effects, while modulus was lower than predictions of linear additivity. The CD of LLDPE showed no significant effect on thermal properties, elongation at break or work of rupture; however, it resulted in low moduli for ZN‐LLDPE blends with HDPE. For miscible blends, no effect for BC or CD of LLDPE was observed. The BC of LLDPE has, in general, a stronger influence on melt and solid‐state properties of blends than the CD. Copyright © 2004 Society of Chemical Industry     

利用糖蜜制备细菌纤维素的研究

细菌纤维素（BC）是一类由微生物产生的纤维素。细菌纤维素以其独特的物理和化学性质被广泛应用于医药、食品、造纸、纺织等领域。然而，BC应用的最大挑战是其生产成本，尤其是发酵生产碳源的成本相对较高。以相对廉价的糖蜜为原料，研究比较了不同预处理方法（硫酸-热处理、热处理和未处理）以及生产菌种（木葡糖醋杆菌和红茶菌）对细菌纤维素产量的影响。结果表明，硫酸-热处理之后的糖蜜获得的细菌纤维素产量最高，可达6．0g/L，比用葡萄糖制备细菌纤维素的产量提高了78％。当以红茶菌为菌种，细菌纤维素的产量可达12．0g/L，是木葡糖醋杆菌作为菌种的两倍。与葡萄糖和果糖相比，糖蜜制备的细菌纤维素同样具有三维网状结构，但是含水率较低，杨氏模量较小。     

细菌纤维素再生前后结构与性质上的差异

对比研究了细菌纤维素和再生细菌纤维素的结构与性质上的差异,揭示了细菌纤维素在氯化锂（LiCl）／二甲基乙酰胺（DMAc）溶剂体系下溶解,经水浴凝固再生前后的形貌、大分子结构、晶型及尺寸、物理机械性能、含水保湿性上的变化,为再生细菌纤维素的应用提供理论依据。     

医用双相磷酸钙陶瓷的制备工艺研究

医用双相磷酸钙（BCP）陶瓷是β-磷酸三钙（β-TCP）和羟基磷灰石（HA）的复合体,其成分与骨矿物组成类似,在生理环境下能发生不同程度的降解,被组织吸收。通过化学沉淀法制备纳米羟基磷灰石,然后通过可溶性钙盐和磷酸盐反应工艺制得的β-磷酸三钙,最后将二者进行机械复合而制得双相磷酸钙,将所得样品用X射线衍射仪（XRD）对样品进行了表征。结果显示：所得的双相磷酸钙中掺杂有β-焦磷酸钙,但是它的结晶较好,并且可以改善双相磷酸钙陶瓷的力学性能。     

Poly(lactic acid) biocomposites reinforced with ultrafine bamboo‐char: Morphology,mechanical, thermal,and water absorption properties

In this study, ultrafine bamboo‐char (BC) was introduced into poly(lactic acid) (PLA) matrix to improve mechanical and thermal properties of PLA based biodegradable composites. PLA/BC biocomposites were fabricated with different BC contents by weight. Uniform dispersion of BC in the PLA matrix and good interaction via physical and chemical interfacial interlocks were achieved. The maximum tensile strength and tensile modulus values of 14.03 MPa and 557.74 MPa were obtained when 30% BC was used. Impact strength of the biocomposite with 30% BC was increased by 160%, compared to that of pure PLA. DSC analysis illustrated that PLA/BC biocomposites had a better thermal property. Crystallization temperature decreased and maximal crystallinity of 30.30% was observed with 30% BC load. We did not notice significant thermal degradation differences between biocomposites with different BC loadings from TGA. Better water resistance was obtained with the addition of BC. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43425.