Cellulose is the most abundant polysaccharide on Earth. It can be obtained from a vast number of sources, e.g. cell walls of wood and plants, some species of bacteria, and algae, as well as tunicates, which are the only known cellulose-containing animals. This inherent abundance naturally paves the way for discovering new applications for this versatile material. This review provides an extensive survey on cellulose and its derivatives, their structural and biochemical properties, with an overview of applications in tissue engineering, wound dressing, and drug delivery systems. Based on the available means of selecting the physical features, dimensions, and shapes, cellulose exists in the morphological forms of fiber, microfibril/nanofibril, and micro/nanocrystalline cellulose. These different cellulosic particle types arise due to the inherent diversity among the source of organic materials or due to the specific conditions of biosynthesis and processing that determine the consequent geometry and dimension of cellulosic particles. These different cellulosic particles, as building blocks, produce materials of different microstructures and properties, which are needed for numerous biomedical applications. Despite having great potential for applications in various fields, the extensive use of cellulose has been mainly limited to industrial use, with less early interest towards the biomedical field. Therefore, this review highlights recent developments in the preparation methods of cellulose and its derivatives that create novel properties benefiting appropriate biomedical applications.

Water is the liquid of life. Nature has therefore evolved countless enzymes that catalyse the addition of water to C=C bonds, isolated or conjugated. These reactions are regio- and enantioselective, they are part of primary metabolism as well as the secondary metabolism. The enzymes that catalyse these reactions (hydratases or hydro-lyases) are applied industrially in selected cases. However, they are not generally used in the laboratory although they outperform all currently available catalytic chemical methodologies. This feature article highlights the potential that hydratases have for chemistry compared to the acid catalysed addition of water.

The flavoenzyme vanillyl alcohol oxidase (VAO, EC 1.1.3.38) from Penicillium simplicissimum is active on a range of phenolic compounds [1,2]. It contains a covalently linked FAD cofactor, and the holoprotein forms stable octamers. VAO was the first histidyl-FAD-containing flavoprotein for which the crystal structure was determined [3], and serves as a prototype for a specific flavoprotein family [4]. Mutagenesis studies have shown that the covalent flavin-protein bond is crucial for efficient catalysis, and that covalent flavinylation of the apoprotein proceeds via an autocatalytic event [5,6]. As well as oxidizing alcohols, the fungal enzyme is also able to perform amine oxidations, enantioselective hydroxylations, and oxidative ether-cleavage reactions [7,8]. Several substrates can serve as vanillin precursors (e.g. vanillyl alcohol, vanillyl amine and creosol) [9,10]. Recently, VAO has been used in metabolic engineering experiments with the aim of creating a bacterial whole cell biocatalyst that is able to form vanillin from eugenol [11,12]. However, VAO is poorly expressed in bacteria, resulting in a relatively low intracellular VAO activity [12] and low yields of A gene encoding a eugenol oxidase was identified in the genome from Rhodococcus sp. strain RHA1. The bacterial FAD-containing oxidase shares 45% amino acid sequence identity with vanillyl alcohol oxidase from the fungus Penicillium simplicissimum. Eugenol oxidase could be expressed at high levels in Escherichia coli, which allowed purification of 160 mg of eugenol oxidase from 1 L of culture. Gel permeation experiments and macromolecular MS revealed that the enzyme forms homodimers. Eugenol oxidase is partly expressed in the apo form, but can be fully flavinylated by the addition of FAD. Cofactor incorporation involves the formation of a covalent protein-FAD linkage, which is formed autocatalytically. Modeling using the vanillyl alcohol oxidase structure indicates that the FAD cofactor is tethered to His390 in eugenol oxidase. The model also provides a structural explanation for the observation that eugenol oxidase is dimeric whereas vanillyl alcohol oxidase is octameric. The bacterial oxidase efficiently oxidizes eugenol into coniferyl alcohol (K M ¼ 1.0 lm, k cat ¼ 3.1 s )1 ).Vanillyl alcohol and 5-indanol are also readily accepted as substrates, whereas other phenolic compounds (vanillylamine, 4-ethylguaiacol) are converted with relatively poor catalytic efficiencies. The catalytic efficiencies with the identified substrates are strikingly different when compared with vanillyl alcohol oxidase. The ability to efficiently convert eugenol may facilitate biotechnological valorization of this natural aromatic compound.Abbreviations EUGO, eugenol oxidase; PCMH, p-cresol methylhydroxylase (EC 1.17.99.1); VAO, vanillyl alcohol oxidase (EC 1.1.3.38).

Papain, modified at Cys-25 with a monodentate phosphite ligand and complexed with Rh(COD)2BF4, is an active catalyst in the hydrogenation of methyl 2-acetamidoacrylate.

Postoperative infections remain a risk factor that leads to failures in oral and maxillofacial artificial bone transplantation. This study aimed to synthesize and evaluate a novel hydroxyapatite whisker (HAPw) / nano zinc oxide (n-ZnO) antimicrobial bone restorative biomaterial. A scanning electron microscope (SEM), energy dispersive spectroscopy (EDS) and x-ray diffraction (XRD) were employed to characterize and analyze the material. Antibacterial capabilities against Staphylococcus aureus, Escherichia coli, Candida albicans and Streptococcus mutans were determined by minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC), and kinetic growth inhibition assays were performed under darkness and simulated solar irradiation. The mode of antibiotic action was observed by transmission electron microscopy (TEM) and confocal laser scanning microscopy (CLSM). The MIC and MBC were 0.078-1.250 mg ml(-1) and 0.156-2.500 mg ml(-1), respectively. The inhibitory function on the growth of the microorganisms was achieved even under darkness, with gram-positive bacteria found to be more sensitive than gram-negative, and enhanced antimicrobial activity was exhibited under simulated solar excitation compared to darkness. TEM and CLSM images revealed a certain level of bacterial cell membrane destruction after treatment with 1 mg ml(-1) of the material for 12 h, causing the leakage of intracellular contents and bacteria death. These results suggest favorable antibiotic properties and a probable mechanism of the biomaterial for the first time, and further studies are needed to determine its potential application as a postoperative anti-inflammation method in bone transplantation.

Surface modification of titanium (Ti) implants are extensively studied in order to obtain prominent biocompatibility and antimicrobial activity, especially preventing implant-associated infection. In this study, Ti substrates surface were modified by graphene oxide (GO) thin film and silver (Ag) nanoparticles via electroplating and ultraviolet reduction methods so as to achieve this purpose. Microstructures, distribution, quantities and spectral peaks of GO and Ag loading on the Ti sheets surface were characterized. GO-Ag-Ti multiphase nanocomposite exhibited excellent antimicrobial ability and anti-adherence performance. Subsequently, morphology, membrane integrity, apoptosis and relative genes expression of bacteria incubated on the Ti samples surface were monitored to reveal the bactericidal mechanism. Additionally, the cytotoxicity of Ti substrates incorporating GO thin film and Ag nanoparticles were investigated. GO-Ag-Ti composite configuration that have outstanding antibacterial properties will provide the foundation to study bone integration in vitro and in vivo in the future.

To enhance the activity of transketolase towards nonphosphorylated substrates and enlarge the scope of its substrates, notably to long polyol aldehyde acceptors (D-ribose or D-glucose), a rational design-supported evolution strategy was applied. By using docking experiments, an in silico library, and iterative mutagenesis, libraries of single- and double-point mutants were designed and generated. A double-screening approach was implemented, coupling a preselection activity assay (HPLC method) and a selective assay (GC method) to find the best enzymes. Several mutants (R526N, R526Q, R526Q/S525T, R526K/S525T) showed improved activities towards nonphosphorylated substrates as the coupled products of lithium hydroxypyruvate (HPA) with glycolaldehyde (GO), D-ribose or D-glucose. These mutated enzymes were further characterised. They were shown to be up to four times more active than the wild-type (mutant R526Q/S525T) for nonphosphorylated substrates LiHPA/GO (V(m) /K(m) for LiHPA = 92.4 instead of 28.8×10(-3) min(-1) for the wild-type) and 2.6 times more active for substrates LiHPA/rib.

For most reported flavoproteins, the flavin cofactor is noncovalently but tightly bound by noncovalent interactions [1]. Nevertheless, a small but significant group of flavoproteins ( 5%) contains a covalently bound flavin. In most of these so-called covalent flavoproteins, the flavin cofactor is attached to the protein at the 8a-methyl of the isoalloxazine moiety, whereas some C6-linked flavins also have been found [2]. The most common linkage type involves coupling to a histidine residue, but proteins containing cysteinyl and tyrosyl linked flavins have also been reported. Recently, some covalent flavoproteins were even found to harbour a FAD cofactor that is tethered via two covalent linkages: a 8a-histidyl-C6-cysteinyl bound FAD [3]. The mechanism by which flavin cofactors are covalently incorporated is largely unknown, as is the rationale for covalent histidyl-flavin attachment. Previous studies have hinted at an autocatalytic process in which no helper enzymes or other additional factors are needed [2,[4][5][6]. This is in contrast to many other Vanillyl-alcohol oxidase (VAO; EC 1.1.3.38) contains a covalently 8a-histidyl bound FAD, which represents the most frequently encountered covalent flavin-protein linkage. To elucidate the mechanism by which VAO covalently incorporates the FAD cofactor, apo VAO was produced by using a riboflavin auxotrophic Escherichia coli strain. Incubation of apo VAO with FAD resulted in full restoration of enzyme activity. The rate of activity restoration was dependent on FAD concentration, displaying a hyperbolic relationship (K FAD = 2.3 lm, k activation = 0.13 min )1