Bioremediation technologies for treatment of PAH-contaminated soil and strategies to enhance process efficiency

The complex and diverse structural configurations of polycyclic aromatic hydrocarbons (PAHs), combined with their low bioavailability, hydrophobic nature, strong sorption phenomena, and high persistence in soil makes the design of effective bioremediation methodologies a challenge. The multi-phasic nature of the bioremediation process, restricted mass transfer and non-availability of degrading soil microflora further compound the problem. In this direction, this communication presents a focused review of bioremediation technologies used recently for the treatment of PAH-contaminated soils. The specific roles of important factors affecting bioremediation process efficiency are discussed. Finally some of the recently used strategies to enhance bioremediation process efficiency, including bioaugmentation, biostimulation, rhizoremediation, the use of chemotaxins, the biomimetic catalytic system approach, and integrated techniques, are reviewed.     

Bioactive nanofibers for fibroblastic differentiation of mesenchymal precursor cells for ligament/tendon tissue engineering applications

Mesenchymal stem cells and precursor cells are ideal candidates for tendon and ligament tissue engineering; however, for the stem cell-based approach to succeed, these cells would be required to proliferate and differentiate into tendon/ligament fibroblasts on the tissue engineering scaffold. Among the various fiber-based scaffolds that have been used in tendon/ligament tissue engineering, hybrid fibrous scaffolds comprising both microfibers and nanofibers have been recently shown to be particularly promising. With the nanofibrous coating presenting a biomimetic surface, the scaffolds can also potentially mimic the natural extracellular matrix in function by acting as a depot for sustained release of growth factors. In this study, we demonstrate that basic fibroblast growth factor (bFGF) could be successfully incorporated, randomly dispersed within blend-electrospun nanofibers and released in a bioactive form over 1 week. The released bioactive bFGF activated tyrosine phosphorylation signaling within seeded BMSCs. The bFGF-releasing nanofibrous scaffolds facilitated BMSC proliferation, upregulated gene expression of tendon/ligament-specific ECM proteins, increased production and deposition of collagen and tenascin-C, reduced multipotency of the BMSCs and induced tendon/ligament-like fibroblastic differentiation, indicating their potential in tendon/ligament tissue engineering applications.     

Dynamics of pattern formation in biomimetic systems

This paper is an attempt to conceptualize pattern formation in self-organizing systems and, in particular, to understand how structures, oscillations or waves arise in a steady and homogenous environment, a phenomenon called symmetry breaking. The route followed to develop these ideas was to couple chemical oscillations produced by Belousov-Zhabotinsky reaction with confined reaction environments, the latter being an essential requirement for any process of Life. Special focus was placed on systems showing organic or lipidic compartments, which represent more reliable biomimetic matrices.     

Aluminum inhibits the growth of hydroxyapatite crystals developed on a biomimetic methacrylic polymer

ProjectAluminum (Al) is an increasing problem in biomedicine since it can interact with phosphates. Bone is one of the preferential target tissues of Al deposition: Al interacts with mineralization and/or bone cell activities. We searched the influence of Al deposition in hydroxyapatite developed on a biomimetic polymer (carboxymethylated poly(2-hydroxyethyl-methacrylate)) which mimics bone mineralization in the absence of cells.ProceduresPellets of polymer were incubated for 5 days in a synthetic body fluid (SBF) to induce mineralization, then 21 days in SBF containing 20, 40 and 60 μg/L Al³⁺. Other pellets were incubated in SBF containing commercial Al foil (33 mg/vial) either in 1, 2 or 6 pieces. The mineral deposits were dissolved in HCl and Ca²⁺, PO₄^3? and Al³⁺ content was measured. Hydroxyapatite was characterized by SEM and X energy-dispersive X-ray analysis (EDX).ResultsThe amount of Al³⁺ was dose-dependently increased in Ca/P deposits on the polymer pellets. At high concentration (or with the 6 Al foils) growth of hydroxyapatite calcospherite was inhibited; only calcified plates emerging from the polymer were observed. Pellets incubated with 1 and 2 Al foils exhibited a reduction in calcospherite diameter and an increase in the Al³⁺/Ca²⁺ ratio. EDX identified Al in the mineral deposits.ConclusionsIn this acellular model, Al³⁺ altered the growth of calcospherites at low concentration and inhibited their development at high concentration. In SBF, a release of Al³⁺ from aluminum foils also inhibited mineralization. This study emphasizes the importance of Al in bone pathology and stresses the question of its release from biomaterials.     

一种新型仿生抗菌剂的功能研究

抗菌剂α-炔丙基-γ-亚甲基-γ-丁内酯是以天然抗菌物质原白头翁素为基础,利用仿生技术合成出的新型抗菌剂.通过悬液杀菌法进行最小抑菌浓度测定、悬液定量法及活体菌落计数法进行最小杀菌浓度测定等生化试验对其抗菌效果进行了检验;通过细胞壁结构的完整性实验及透射电镜观察等理化实验对其抗菌机理做初步研究,为其应用于实践提供依据.抗菌剂α-炔丙基-γ-亚甲基-γ-丁内酯对大肠杆菌、金黄色葡萄球菌、白色念珠菌及马拉色菌均具有良好的抑菌作用,对马拉色菌的抑菌作用尤为突出,并对其具有良好的杀菌作用.其对马拉色菌的最小抑菌浓度为0.5mg/ml,当其浓度在10mg/ml时,对马拉色菌具有瞬杀作用(作用1min对球形马拉色菌的杀灭率可达到99.99％).通过胞壁完整性实验以及电镜观察实验表明该抗菌剂的抑菌机制并不是完全破坏胞壁结构,但是对细胞壁有一定影响.     

A novel tripolymer coating demonstrating the synergistic effect of chitosan, collagen type 1 and hyaluronic acid on osteogenic differentiation of human bone marrow derived mesenchymal stem cells

The biomimetic approach mimicking in vivo micro environment is the key for developing functional tissue engineered constructs. In this study, we used a tripolymer combination consisting of a natural polymer, chitosan and two extracellular matrix components; collagen type 1 and hyaluronic acid to coat tissue culture plate to evaluate their effect on osteogenic differentiation of human bone marrow derived mesenchymal stem cells (hMSCs). The polymers were blended at different mixing ratios and the tissue culture plates were coated either by polyblend method or by surface modification method. hMSCs isolated from adult bone marrow were directed to osteoblast differentiation on the coated plates. Our results showed that the tripolymer coating of the tissue culture plate enhanced mineralization as evidenced by calcium quantification exhibiting significantly higher amount of calcium compared to the untreated or individual polymer coated plates. We found that the tripolymer coated plates having a 1:1 mixing ratio of chitosan and collagen type 1, surface modified with hyaluronic acid is an ideal combination to achieve the synergistic effect of these polymers on in vitro osteogenic differentiation of hMSCs. These results thus, establish a novel biomimetic approach of surface modification to enhance osteoblast differentiation and mineralization. Our findings hold great promise in implementing a biomimetic surface coating to improve osteoconductivity of implants and scaffolds for various orthopaedic and bone tissue engineering applications.     

Solid-phase submonomer synthesis of peptoid polymers and their self-assembly into highly-ordered nanosheets

Peptoids are a novel class of biomimetic, non-natural, sequence-specific heteropolymers that resist proteolysis, exhibit potent biological activity, and fold into higher order nanostructures. Structurally similar to peptides, peptoids are poly N-substituted glycines, where the side chains are attached to the nitrogen rather than the alpha-carbon. Their ease of synthesis and structural diversity allows testing of basic design principles to drive de novo design and engineering of new biologically-active and nanostructured materials. Here, a simple manual peptoid synthesis protocol is presented that allows the synthesis of long chain polypeptoids (up to 50mers) in excellent yields. Only basic equipment, simple techniques (e.g. liquid transfer, filtration), and commercially available reagents are required, making peptoids an accessible addition to many researchers' toolkits. The peptoid backbone is grown one monomer at a time via the submonomer method which consists of a two-step monomer addition cycle: acylation and displacement. First, bromoacetic acid activated in situ with N,N'-diisopropylcarbodiimide acylates a resin-bound secondary amine. Second, nucleophilic displacement of the bromide by a primary amine follows to introduce the side chain. The two-step cycle is iterated until the desired chain length is reached. The coupling efficiency of this two-step cycle routinely exceeds 98% and enables the synthesis of peptoids as long as 50 residues. Highly tunable, precise and chemically diverse sequences are achievable with the submonomer method as hundreds of readily available primary amines can be directly incorporated. Peptoids are emerging as a versatile biomimetic material for nanobioscience research because of their synthetic flexibility, robustness, and ordering at the atomic level. The folding of a single-chain, amphiphilic, information-rich polypeptoid into a highly-ordered nanosheet was recently demonstrated. This peptoid is a 36-mer that consists of only three different commercially available monomers: hydrophobic, cationic and anionic. The hydrophobic phenylethyl side chains are buried in the nanosheet core whereas the ionic amine and carboxyl side chains align on the hydrophilic faces. The peptoid nanosheets serve as a potential platform for membrane mimetics, protein mimetics, device fabrication, and sensors. Methods for peptoid synthesis, sheet formation, and microscopy imaging are described and provide a simple method to enable future peptoid nanosheet designs.     

Assembled capsules transportation driven by motor proteins

An active biomimetic system by integrating kinesin motor, microtubule, and man-made biomimetic microcapsule has been constructed. Biomimetic microcapsules were fabricated by using the layer-by-layer technique and could serve as cargos in this active biomimetic system. Both of the hollow and filled capsules as cargos can be transported by kinesin motors along microtubules. It may help to create kinesin-powered complex hybrid micro- and nanodevices.     

A first model for the oxidized active form of the active site in galactose oxidase: a free-radical copper complex

 Copper(II) complexes derived from the tripodal ligand bis(3′-t–butyl-2′-hydroxybenzyl)(2-pyridylmethyl)amine (LH₂) have been studied in order to mimic the redox active site of the free radical-containing copper metalloenzyme galactose oxidase. In non-coordinating solvents such as dichloromethane, only an EPR-silent dimeric complex was obtained (L₂Cu₂). The crystal structure of L₂Cu₂ revealed a "butterfly" design of the [Cu(μOR)₂Cu] unit, which is not flattened and leads to a short Cu–Cu distance, the t–butyl groups being localized on the same side of the [Cu(μOR)₂Cu] unit. The dimeric structure was broken down by acetonitrile or by alcohols, leading quantitatively to a brown mononuclear copper(II) complex. UV-visible and EPR data indicated the coordination of the solvent in these mononuclear complexes. Electrochemical as well as chemical (silver acetate) one-electron oxidation of acetonitrile solutions of the monomeric complex led to a yellow-green solution. Based on EPR, UV-visible and resonance Raman spectroscopy, the one-electron oxidation product was identified as a cupric phenoxyl radical system. It slowly decomposes into a product where the ligand has been substituted (dimerization) in the para position of the hydroxyl group, for one of the phenolic groups. The data for the one-electron oxidized species provides strong evidence for a free-radical copper (II) complex. Received: 19 July 1996 / Accepted: 16 October 1996     

Characterization of SynCAM surface trafficking using a SynCAM derived ligand with high homophilic binding affinity

In order to better probe SynCAM function in neurons, we produced a fusion protein between the extracellular domain of SynCAM1 and the constant fragment of human IgG (SynCAM-Fc). Whether in soluble form or immobilized on latex microspheres, the chimera bound specifically to the surface of hippocampal neurons and recruited endogenous SynCAM molecules. SynCAM-Fc was also used in combination with Quantum Dots to follow the mobility of transfected SynCAM receptors at the neuronal surface. Both immobile and highly mobile SynCAM were found. Thus, SynCAM-Fc behaves as a high affinity ligand that can be used to study the function of SynCAM at the neuronal membrane.