Chitosan-based microcapsules containing grapefruit seed extract grafted onto cellulose fibers by a non-toxic procedure

A novel non-toxic procedure is described for the grafting of chitosan-based microcapsules containing grapefruit seed oil extract onto cellulose. The cellulose was previously UV-irradiated and then functionalized from an aqueous emulsion of the chitosan with the essential oil. The novel materials are readily attained with durable fragrance and enhanced antimicrobial properties. The incorporation of chitosan as determined from the elemental analyses data was 16.08 ± 0.29 mg/g of sample. Scanning electron microscopy (SEM) and gas chromatography-mass spectroscopy (GC-MS) provided further evidence for the successful attachment of chitosan microcapsules containing the essential oil to the treated cellulose fibers. The materials thus produced displayed 100% inhibition of Escherichia coli and Staphylococcus epidermidis up to 48 h of incubation. Inhibition of bacteria by the essential oil was also evaluated at several concentrations.     

Synthesis of cellulose adipate derivatives

Cellulose esters containing adipates and other ester groups are synthesized by the reaction of commercially available cellulose esters in solution with the benzyl monoester of adipoyl chloride. The products, cellulose adipate esters in which the distal end of the adipate moiety is a benzyl ester, were easily converted to cellulose adipate derivatives by Pd-catalyzed hydrogenation. These cellulose adipate derivatives are promising biopolymers for drug delivery and other applications in which water-dispersion or swelling are desired.     

Palladium-bacterial cellulose membranes for fuel cells

Bacterial cellulose is a versatile renewable biomaterial that can be used as a hydrophilic matrix for the incorporation of metals into thin, flexible, thermally stable membranes. In contrast to plant cellulose, we found it catalyzed the deposition of metals within its structure to generate a finely divided homogeneous catalyst layer. Experimental data suggested that bacterial cellulose possessed reducing groups capable of initiating the precipitation of palladium, gold, and silver from aqueous solution. Since the bacterial cellulose contained water equivalent to at least 200 times the dry weight of the cellulose, it was dried to a thin membranous structure suitable for the construction of membrane electrode assemblies (MEAs). Results of our study with palladium-cellulose showed that it was capable of catalyzing the generation of hydrogen when incubated with sodium dithionite and generated an electrical current from hydrogen in an MEA containing native cellulose as the polyelectrolyte membrane (PEM). Advantages of using native and metallized bacterial cellulose membranes in an MEA over other PEMs such as Nafion 117 include its higher thermal stability to 130 degrees C and lower gas crossover.     

Multifunctional bionanocomposite films of poly(lactic acid), cellulose nanocrystals and silver nanoparticles

Nanocomposite films were prepared by the addition of cellulose nanocrystals (CNCs) eventually surfactant modified (s-CNC) and silver (Ag) nanoparticles in the polylactic acid (PLA) matrix using melt extrusion followed by a film formation process. Multifunctional composite materials were investigated in terms of morphological, mechanical, thermal and antibacterial response. The nanocomposite films maintained the transparency properties of the PLA matrix. Thermal analysis showed increased values of crystallinity in the nanocomposites, more evident in the s-CNC based formulations that had the highest tensile Young modulus. The presence of surfactant favoured the dispersion of cellulose nanocrystals in the polymer matrix and the nucleation effect was remarkably enhanced. Moreover, an antibacterial activity against Staphylococcus aureus and Escherichia coli cells was detected for ternary systems, suggesting that these novel nanocomposites may offer good perspectives for food packaging applications which require an antibacterial effect constant over time.     

Intrinsically antibacterial materials based on polymeric derivatives of eugenol for biomedical applications

Infections are the most common cause of biomaterial implant failure representing a constant challenge to the more widespread application of medical implants. This study reports on the preparation and characterization of novel hydrophilic copolymeric systems provided with antibacterial properties coming from eugenol residues anchored to the macromolecular chains. Thus, high conversion copolymers were prepared from the hydrophilic monomer 2-hydroxyethyl methacrylate (HEMA) and different eugenol monomeric derivatives, eugenyl methacrylate (EgMA) and ethoxyeugenyl methacrylate (EEgMA), by bulk polymerization reaction. Thermal evaluation revealed glass transition temperature values in the range 95-58 degrees C following the order HEMA-co-EgMA > PHEMA > HEMA-co-EEgMA and a clear increase in thermal stability with the presence of any eugenyl monomer in the system. In vitro wettability studies showed a reduction of water sorption capacity and surface free energy values with increasing the content of eugenol residues in the copolymer. The antimicrobial activity of copolymeric discs was evaluated by determining their capacity to reduce or inhibit colony formation by different bacterial species. All eugenyl containing materials showed bacteria growth inhibition, this one being higher for the EEgMA derivative copolymers.     

细菌纤维素在医学方面的应用

细菌纤维素是由木葡糖酸醋杆菌等细菌合成的纤维素,在化学组成、分子结构上与植物纤维素相近,但具有传统的纤维素所无法比拟的优势,如高亲水性、持水性、生物适应性、可调控性以及高纯度、高透明度等,因而在医学上显示出了巨大的应用潜力。细菌纤维素可用作人造皮肤、外科敷料、人造血管、软骨组织、震动膜、缓释载体等,是最有前途的生物聚合材料之一。     

Preparation and characterization on mechanical and antibacterial properties of chitsoan/cellulose blends

Polysaccharides-based membranes of chitosan and cellulose blends were prepared using trifluoroacetic acid as a co-solvent. Morphology and mechanical property of prepared membranes were studied by Instron and dynamic mechanical thermal analysis. The mechanical and dynamic mechanical thermal properties of the cellulose/chitosan blends appear to be dominated by cellulose, suggests that cellulose/chitosan blends were not well miscible. It is believed that the intermolecular hydrogen bonding of cellulose is supposed to be break down to form cellulose–chitosan hydrogen bonding; however, the intra-molecular and intra-strand hydrogen bonds hold the network flat. The reduced water vapor transpiration rate through the chitosan/cellulose membranes indicates that the membranes used as a wound dressing may prevent wound from excessive dehydration. The chitosan/cellulose blend membranes demonstrate effective antimicrobial capability against Escherichia coli and Staphylococcus aureus, as examined by the antimicrobial test. These results indicate that the chitosan/cellulose blend membranes may be suitable to be used as a wound dressing with antibacterial properties.     

氧化石墨烯/十二烷基二甲基苄基氯化铵复合物的制备和抗菌性能研究

本文研究了氧化石墨烯/十二烷基二甲基苄基氯化铵( GO-1227)复合抗菌材料的制备及其抗菌性能。通过傅立叶红外光谱的检测,确定GO-1227复合物已经成功合成。为了研究复合物的抗菌活性,以大肠杆菌为代表,通过观察大肠杆菌的表面形貌变化和细菌体外离子浓度变化,证明GO-1227复合物具有相对于原材料更好的抗菌性能。     

Preparation and UV-protective properties of functional cellulose fabrics based on reactive azobenzene Schiff base derivative

Azobenzene Schiff base possesses excellent photochromic or thermochromic properties based on intermolecular proton transfer or cis-trans isomerization. The azobenzene Schiff base containing two reactive groups, N, N-bis{p-[(2′-sulphatoethyl)sulphonyl phenylazo] salicylidene}-1,2-ethylenediamine (BSPEA), was applied to modify cellulose materials. The functional cellulose fabrics containing azobenzene Schiff base groups were prepared. The chemical and morphological structures of functional cellulose fabrics were characterized by element analysis, FT-IR spectrum, and scanning electron microscopy (SEM). The UV-protection properties of the fabrics were investigated by the ultraviolet transmittance spectra and ultraviolet protection factor (UPF). The results show that the functional cellulose fabrics had excellent UV-protection properties with higher UPF value (UPF value reached 31.7) and lower ultraviolet transmittance (less than 5%). The modified cellulose fabrics had not significant influence on the physical properties. The functional cellulose fabrics based on reactive azobenzene Schiff base would have potential application in textile and functional materials.     

Biocompatibility evaluation of densified bacterial nanocellulose hydrogel as an implant material for auricular cartilage regeneration

Bacterial nanocellulose (BNC), synthesized by the bacterium Gluconacetobacter xylinus, is composed of highly hydrated fibrils (99 % water) with high mechanical strength. These exceptional material properties make BNC a novel biomaterial for many potential medical and tissue engineering applications. Recently, BNC with cellulose content of 15 % has been proposed as an implant material for auricular cartilage replacement, since it matches the mechanical requirements of human auricular cartilage. This study investigates the biocompatibility of BNC with increased cellulose content (17 %) to evaluate its response in vitro and in vivo. Cylindrical BNC structures (Ø48?×?20 mm) were produced, purified in a built-in house perfusion system, and compressed to increase the cellulose content in BNC hydrogels. The reduction of endotoxicity of the material was quantified by bacterial endotoxin analysis throughout the purification process. Afterward, the biocompatibility of the purified BNC hydrogels with cellulose content of 17 % was assessed in vitro and in vivo, according to standards set forth in ISO 10993. The endotoxin content in non-purified BNC (2,390 endotoxin units (EU)/ml) was reduced to 0.10 EU/ml after the purification process, level well below the endotoxin threshold set for medical devices. Furthermore, the biocompatibility tests demonstrated that densified BNC hydrogels are non-cytotoxic and cause a minimal foreign body response. In support with our previous findings, this study concludes that BNC with increased cellulose content of 17 % is a promising non-resorbable biomaterial for auricular cartilage tissue engineering, due to its similarity with auricular cartilage in terms of mechanical strength and host tissue response.     

Synthesis and characterization of poly(butylene succinate-co-butylene malate): a new biodegradable copolyester bearing hydroxyl pendant groups

A new biodegradable copolyester, poly(butylene succinate-co-butylene malate) P(BS-co-BM), has been preliminarily prepared with optically active centers and lateral hydroxyl functional groups via a four-step synthetic strategy. First, an optically active benzyl-protected dimethyl malate was synthesized from a starting material of (S)-dimethyl malate and purified with good yield. Then, copolyester poly(butylene succinate-co-benzyl-protected butylene malate), P(BS-co-BBM), was prepared through a skilled condensation copolymerization of the benzyl-protected dimethyl malate, dimethyl succinate, and 1,4-butanediol in the presence of titanium tetraisopropoxide as the catalyst. Finally, a Pd/C catalyzed hydrogenation was applied to eliminate the benzyl protection group in a mixed solution of THF and methanol; thus the target copolyester P(BS-co-BM) was attained. On the other hand, physical properties of the synthesized copolyesters were systematically characterized by means of nuclear magnetic resonance spectrometer, Fourier transformed infrared spectrometer, gel permeation chromatography, optical polarimeter, quantitative hydroxyl titration, and thermal analytical instruments. The experimental evidence demonstrated a successful construction of the product P(BS-co-BM) bearing lateral hydroxyl functional groups. It was also revealed that the lower BBM unit content was in the benzyl-protected optically active P(BS-co-BBM) copolyester, the higher melting point T(m), crystallinity, the broader molecular distribution, and the lower glass transition temperature T(g) would be detected, and these results can be accounted for the presence of bulky lateral benzyl moieties. In contrast, the deprotected product P(BS-co-55 mol % BM) showed a higher T(m), crystallinity and lower T(g) than its counterpart P(BS-co-55 mol % BBM). Interestingly, a thermal stability as high as that of the linear PBS was observed for P(BS-co-55 mol % BM) while a strong BBM unit content dependence of thermal stability was detected for the benzyl-protected copolyester P(BS-co-BBM)s. Therefore, these results may be beneficial for the new optically active P(BS-co-BM) bearing hydrophilic hydroxyl functional groups as a potential biomaterial.     

Facile preparation of deoxy(thiocyanato)celluloses

Deoxy(thiocyanato)celluloses were prepared by treating chlorodeoxycellulose fabrics with potassium thiocyanate in N,N-dimethylformamide. Under optimal reaction-conditions, more than 80% of the chlorine atoms in the cellulose derivative were replaced by thiocyanate groups. Both the chlorodeoxy- and deoxy(thiocyanato)cellulose fabrics exhibited moderate antibacterial activities.Variables studied were thiocyanate concentration, reaction time and temperature, and degree of substitution of the chlorodeoxycellulose in the fabrics being treated. The effect that each of these variables had on the replacement of chlorine atoms by thiocyanate groups was investigated. The tensile, wrinkle-recovery, and biocidal properties of the chlorodeoxy- and deoxy(thiocyanato)cellulose fabrics were also compared.     

Effect of the structure of polymeric materials on the properties of immobilized enzymes

The relationship between the structure of triacetate cellulose fibres and films and properties of enzymes entrapped in these materials was investigated. Trypsin and penicillin amidase were entrapped in triacetate cellulose films and fibres during their formation. The effect of permeability of the films on the catalytic properties of entrapped trypsin was studied. The porous structure of triacetate cellulose fibres with entrapped penicillin amidase was studied, the fibres being produced by different methods. An increase of porosity and the specific surface of the fibre-biocatalyst reduced the Km value and the energy of activation of the hydrolytic decomposing of benzyl penicillin but increased the Vmax value.     

细菌纤维素的研究进展

细菌纤维素是由醋酸杆菌属、根瘤菌属、土壤杆菌属、八叠球菌属等的某些细菌在一定条件下产生的,其中最有代表性的细菌是木醋杆菌。与传统植物纤维素相比,细菌纤维素具有很高的化学纯度。主要介绍细菌纤维素性质、生物合成的方法及其在食品工业、造纸工业和作为一种生物材料在医学工程等方面的应用。     

Extraction of chitosan from shrimp shells waste and application in antibacterial finishing of bamboo rayon

Chitosan can be best utilized as safe antibacterial agent for textiles but there is always a limitation of its durability. The chitin containing shellfish waste is available in huge quantities, but very low quantities are utilized for extraction of high value products like chitosan. In the current work chitosan was extracted from shrimp shells and then used as antibacterial exhaust finishing agent for grafted bamboo rayon. Chitosan bound bamboo rayon was then evaluated for antibacterial activity against both gram positive and gram negative bacteria. The product showed antibacterial activity against both types of bacterias which was durable till 30 washes.     

Structure-activity relationships of bioisosteres of a carboxylic acid in a novel class of bacterial translation inhibitors

The discovery and initial optimization of a novel anthranilic acid derived class of antibacterial agents which suffered from extensive protein binding has been previously reported. The structure-activity relationships around the carboxylic acid substituent are described herein. This acid was replaced by several alternative functional groups in attempts to retain bioactivity while reducing protein binding. Only groups with an acidic proton retained activity, and analogs containing those groups maintained the protein binding inherent to this class of antibacterial agents.     

Antibacterial cellulose fiber via RAFT surface graft polymerization

2-(dimethylamino)ethyl methacrylate (DMAEMA) was polymerized from cellulosic filter paper via reversible addition-fragmentation chain transfer (RAFT) polymerization. The tertiary amino groups of the grafted PDMAEMA chains were subsequently quaternized with alkyl bromides of different chain lengths (C8-C16) to provide a large concentration of quaternary ammonium groups on the cellulose surface. The antibacterial activity of the quaternized and nonquaternized PDMAEMA-grafted cellulosic fibers was tested against Escherichia coli. The antibacterial activity was found to depend on the alkyl chain length and on the degree of quaternization, i.e., the amount of quaternary amino groups present in the cellulose graft copolymers. The PDMAEMA-grafted cellulose fiber with the highest degree of quaternization and quaternized with the shortest alkyl chains was found to exhibit particularly high activity against E. coli.     

Synthesis and antibacterial activity of N4-mono alkyl derivatives of novel glycopeptide LYV07ww01

Thirty-one N(4)-mono alkyl derivatives of novel glycopeptide LYV07ww01 were synthesized by the reductive alkylation and their in vitro antibacterial activity was tested. The benzyl derivatives showed potent activity, especially against vancomycin-resistant enterococci and penicillin-resistant Streptococcus pneumoniae.     

Physicochemical characterisation of the ubiquitous bracken fern as useful biomaterial for preconcentration of heavy metals

Batch experiments with dry bracken fern have been done to determine cadmium and lead sequestering capacity of this biomaterial. Biomass characterisation was done by infrared spectroscopy and potentiometric analysis. The effect of pH of the metal containing solution, contact time and initial metal concentration has been studied, together with the acid-base properties of the biomaterial. Results obtained have been analysed using mathematical and modelling techniques. Effect of pH on metal sequestration has been correlated with observed acid-base properties of the natural substrate. Kinetic data analysis provided relevant information about metal sequestration rate, showing important differences between lead and cadmium. Maximum uptake was found to be the same for both metals 0.410 mmol/g. This value was also clearly correlated to the number of acidic groups determined for this material which was found to be 0.432 mmol of acidic groups per gram of fern. Results obtained indicate that acidic groups are the functional groups responsible of the sequestration of metal ions and that bracken fern is a promising material for metal preconcentration.     

Dyeing and diffusion properties of modified novel cellulose with triazine derivatives containing cationic and anionic groups

Cellulose is chemically modified with the compounds containing cationic and anionic groups. Dyeing and diffusion properties of modified cellulose are discussed. The exhaustion and fixation of reactive dyes on modified cellulose are higher than those on unmodified cellulose. Compared with unmodified cellulose, the dyed modified cellulose also gets good washing fastness. The diffusion coefficients of dyes at different temperature are calculated. Compared with unmodified cellulose, the diffusion of dyes in the modified cellulose shows significant change.