Development of phenol-grafted polyglucuronic acid and its application to extrusion-based bioprinting inks

In this present work, we developed a phenol grafted polyglucuronic acid (PGU) and investigated the usefulness in tissue engineering field by using this derivative as a bioink component allowing gelation in extrusion-based 3D bioprinting. The PGU derivative was obtained by conjugating with tyramine, and the aqueous solution of the derivative was curable through a horseradish peroxidase (HRP)-catalyzed reaction. From 2.0 w/v% solution of the derivative containing 5 U/mL HRP, hydrogel constructs were successfully obtained with a good shape fidelity to blueprints. Mouse fibroblasts and human hepatoma cells enclosed in the printed constructs showed about 95% viability the day after printing and survived for 11 days of study without a remarkable decrease in viability. These results demonstrate the great potential of the PGU derivative in tissue engineering field especially as an ink component of extrusion-based 3D bioprinting.

Preparation of Well-Dispersed Chitosan/Alginate Hollow Multilayered Microcapsules for Enhanced Cellular Internalization

Hollow multilayered capsules have shown massive potential for being used in the biomedical and biotechnology fields, in applications such as cellular internalization, intracellular trafficking, drug delivery, or tissue engineering. In particular, hollow microcapsules, developed by resorting to porous calcium carbonate sacrificial templates, natural-origin building blocks and the prominent Layer-by-Layer (LbL) technology, have attracted increasing attention owing to their key features. However, these microcapsules revealed a great tendency to aggregate, which represents a major hurdle when aiming for cellular internalization and intracellular therapeutics delivery. Herein, we report the preparation of well-dispersed polysaccharide-based hollow multilayered microcapsules by combining the LbL technique with an optimized purification process. Cationic chitosan (CHT) and anionic alginate (ALG) were chosen as the marine origin polysaccharides due to their biocompatibility and structural similarity to the extracellular matrices of living tissues. Moreover, the inexpensive and highly versatile LbL technology was used to fabricate core-shell microparticles and hollow multilayered microcapsules, with precise control over their composition and physicochemical properties, by repeating the alternate deposition of both materials. The microcapsules' synthesis procedure was optimized to extensively reduce their natural aggregation tendency, as shown by the morphological analysis monitored by advanced microscopy techniques. The well-dispersed microcapsules showed an enhanced uptake by fibroblasts, opening new perspectives for cellular internalization.

Usefulness of Alginate Lyases Derived from Marine Organisms for the Preparation of Alginate Oligomers with Various Bioactivities

Alginate-degrading enzyme, alginate lyase, catalyzes the cleavage of glycosidic 1-4 O-linkages between uronic acid residues of alginate by a β-elimination reaction leaving a 4-deoxy-l-erythro-hex-4-ene pyranosyluronate as nonreducing terminal end. The enzymes from a wide variety of sources such as marine molluscs, seaweeds, and marine bacteria have been discovered and studied not only from a point of view of enzymological interest of enzyme itself but also for elucidation of fine chemical structure of alginate, structure-activity relationship of alginate, and biological activities and physicochemical features of the enzymatic digestion products. Based on the substrate specificities, alginate lyases are classified into three groups: poly(β-d-mannuronate) lyase, poly(α-l-guluronate) lyase, and bifunctional alginate lyase, which are specific to mannuronate, guluronate, and both uronic acid residues, respectively. We have studied enzymological aspects of these three types of alginate lyases, and bioactivities of enzymatically digested alginate oligomers. In this chapter, we described the purification and characterization of three types of alginate lyases from different marine origins and overviewed the bioactivities of alginate oligomers.

Fabrication, Characterization, and Evaluation of Bionanocomposites Based on Natural Polymers and Antibiotics for Wound Healing Applications

The aim of our research activity was to obtain a biocompatible nanostructured composite based on naturally derived biopolymers (chitin and sodium alginate) loaded with commercial antibiotics (either Cefuroxime or Cefepime) with dual functions, namely promoting wound healing and assuring the local delivery of the loaded antibiotic. Compositional, structural, and morphological evaluations were performed by using the thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and fourier transform infrared spectroscopy (FTIR) analytical techniques. In order to quantitatively and qualitatively evaluate the biocompatibility of the obtained composites, we performed the tetrazolium-salt (MTT) and agar diffusion in vitro assays on the L929 cell line. The evaluation of antimicrobial potential was evaluated by the viable cell count assay on strains belonging to two clinically relevant bacterial species (i.e., Escherichia coli and Staphylococcus aureus).

Controllable Multicompartmental Capsules with Distinct Cores and Shells for Synergistic Release

A facile and flexible approach is developed for controllable fabrication of novel multiple-compartmental calcium alginate capsules from all-aqueous droplet templates with combined coextrusion minifluidic devices for isolated coencapsulation and synergistic release of diverse incompatible components. The multicompartmental capsules exhibit distinct compartments, each of which is covered by a distinct part of a heterogeneous shell. The volume and number of multiple compartments can be well-controlled by adjusting flow rates and device numbers for isolated and optimized encapsulation of different components, while the composition of different part of the heterogeneous shell can be individually tailored by changing the composition of droplet template for flexibly tuning the release behavior of each component. Two combined devices are first used to fabricate dual-compartmental capsules and then scaled up to fabricate more complex triple-compartmental capsules for coencapsulation. The synergistic release properties are demonstrated by using dual-compartmental capsules, which contain one-half shell with a constant release rate and the other half shell with a temperature-dependent release rate. Such a heterogeneous shell provides more flexibilities for synergistic release with controllable release sequence and release rates to achieve advanced and optimized synergistic efficacy. The multicompartmental capsules show high potential for applications such as drug codelivery, confined reactions, enzyme immobilizations, and cell cultures.

Rapid 3D Extrusion of Synthetic Tumor Microenvironments

The spatial positioning of 3D tumor-mimetic microenvironments, containing multiple cell types, is controlled with a simple concentric flow device in a single step. A range of geometric architectures are demonstrated, and the migration of segregated tumor cells and macrophages is explored using drugs that inhibit heterotypic interactions.

Formulation and preparation of stable cross-linked alginate-zinc nanoparticles in the presence of a monovalent salt

Polysaccharide-based nanoparticles can be formed, under the right conditions, when a counterion is added to a dilute polysaccharide solution. In this study, the possibility of preparing stable alginate nanoparticles cross-linked with zinc was investigated. The effects of the ionic strength of the solvent and the concentration of zinc were studied. The nanoparticles were characterized by dynamic light scattering, zeta potential and pH measurements. The results showed that an increase in the ionic strength of the solvent provided nanoparticles with considerably narrower size distributions compared to pure water, and a small size. The zinc content was shown to be an important factor for the formation of the nanoparticles. In fact, a critical zinc concentration was needed to obtain nanoparticles, and below this concentration particles were not formed. A stepwise increase in the amount of zinc revealed the process of formation of the nanoparticles. The stages of the nanoparticle formation process were identified, and differences according to the ionic strength of the solvent were also reported. Furthermore, the stability test of the most promising formulation showed a stability of over ten weeks.

Synthesis and evaluation of hydroponically alginate nanoparticles as novel carrier for intravenous delivery of propofol

Commercial lipid emulsion of propofol (CLE) has several drawbacks including pain on injection and emulsion instability. In this paper, a novel nanocarrier system is introduced to improve stability and solubility of the poorly soluble anesthetic drug, propofol, for intravenous administration. In this paper, alginate is modified using a facile method in which the carboxylic group of alginate is grafted to octanol. The octanol-grafted alginate (Alg-C8) is then employed to prepare nanoparticles which are subsequently used for encapsulation of propofol. The nanoparticles are analyzed for their pH, osmolarity, particle size, stability, morphology and sleep recovery and the results are compared with CLE as control. It is revealed that nanoparticles have the average particle size of 180 nm ± 1.2 and spherical morphology which is less than CLE while their pH, osmolarity and profile of release of formulated nanoparticles are similar to those of CLE. In addition, the results show good chemical and physical storage stability for the nanoparticles at room temperature for at least 6 months compared to CLE as control. The animal sleep recovery test on rats shows no significant difference in time of unconsciousness and recovery of the righting reflex between nanoparticles and CLE. It is concluded that encapsulated nanoparticles introduced here could be a promising clinical intravenous system for delivery of poorly soluble anesthetic propofol. In addition, this study provides an efficient and facile method for preparing a carrier system for water insoluble drugs.

Fabrication of novel oxygen-releasing alginate beads as an efficient oxygen carrier for the enhancement of aerobic bioremediation of 1,4-dioxane contaminated groundwater

Oxygen-releasing alginate beads (ORABs), a new concept of oxygen-releasing compounds (ORCs) designed to overcome some limitations regarding the fast oxygen release rate and the high pH equilibrium of ORCs, were fabricated to promote the stimulation of aerobic biodegradation in anaerobic groundwater. Slow oxygen-releasing rate and maintenance of constant pH were achieved by changing the parameters (ionic radius and valence) related to the cross-linking ions composing ORABs, and the best results were obtained for ORABs cross-linked with Al (Al-ORABs). Furthermore, the mechanism of the improved aerobic biodegradation using Al-ORABs under oxygen-limiting groundwater conditions was elucidated in batch and column studies with 1,4-dioxane and Mycrobacterium sp. PH-06 as a model contaminant and aerobic microbes, respectively. Maximum 1,4-dioxane degradations of 99% and 68.1% were achieved when Al-ORABs were applied in batch and column conditions, respectively, whereas 34.3% and 18% of 1,4-dioxane were degraded without Al-ORABs in batch and column conditions, respectively.

Synthesis and characterization of guar-alginate hybrid bead templated mercury sorbing titania spheres

Present communication reports on the synthesis and characterization of Hg(II) sorbing millimeter sized porous titania spheres (TSP). The synthesis utilizes guar gum-alginate hybrid beads as sacrificial template to polymerize titanium(IV) isopropoxide. The hybrid beads are crafted by pouring guar-alginate mixed solution to calcium bath. The mechanical strength of the beads depended on guar to alginate ratio in the mixed solution. The equal weight ratio of the two polysaccharides is appropriate for adequate mechanical strength beads. The unique performance of the templating beads is attributed to the synergistic interaction between guar gum and sodium alginate. FTIR, BET, SEM, TEM, XRD, TGA, and DTG analyses have been used for the characterization of the optimum performance TSP (TSPAG2). TSPAG2 is a mesoporous material that has higher surface area and narrower pore size distribution than pure alginate derived titania spheres (TSPA). TEM study demonstrated that TSPAG2 spheres are constituted of aggregated TiO2 nanoparticles of ∼ 10 nm size. TSPAG2 is able to capture >95% Hg(II) from synthetic Hg(II) solution in 10h at pH 5 as opposed to only 68% removal by TSPA.

Single and dual crosslinked oxidized methacrylated alginate/PEG hydrogels for bioadhesive applications

A degradable, cytocompatible bioadhesive can facilitate surgical procedures and minimize patient pain and post-surgical complications. In this study a bioadhesive hydrogel system based on oxidized methacrylated alginate/8-arm poly(ethylene glycol) amine (OMA/PEG) has been developed, and the bioadhesive characteristics of the crosslinked OMA/PEG hydrogels evaluated. Here we demonstrate that the swelling behavior, degradation profiles, and storage moduli of crosslinked OMA/PEG hydrogels are tunable by varying the degree of alginate oxidation. The crosslinked OMA/PEG hydrogels exhibit cytocompatibility when cultured with human bone marrow-derived mesenchymal stem cells. In addition, the adhesion strength of these hydrogels, controllable by varying the alginate oxidation level and measured using a porcine skin model, is superior to commercially available fibrin glue. This OMA/PEG hydrogel system with controllable biodegradation and mechanical properties and adhesion strength may be a promising bioadhesive for clinical use in biomedical applications, such as drug delivery, wound closure and healing, biomedical device implantation, and tissue engineering.

Alginate block fractions and their effects on membrane fouling

Alginate has been commonly used as a model foulant in studies of membrane organic fouling. As a complex polymer, alginate is composed of two different monomers, namely M ((1 → 4) linked β-D-mannopyranuronic acid) and G ((1 → 4) linked α-L-gulopyranuronic acid) which are randomly arranged into MG-, MM- and GG-blocks. So far, little information is available about fouling propensity of each block in microfiltration. In this study, microfiltration experiments were conducted respectively with MG-, MM- and GG-blocks separated from alginate under defined conditions. Results showed the severest fouling in the filtration of MG-block, and the least flux decline in the filtration of MM-block. The initial pore blocking was found to be responsible for the fouling observed in MG-block filtration, while the cake layer formed on membrane surface during the MM-block filtration could serve as a pre-filter that prevented membrane from further pore blocking. In order to look into fouling mechanisms, the effects of transparent exopolymeric particles (TEP) on membrane fouling were also studied. TEP were found to form through aggregation or cross-link of alginate blocks. As TEP were bigger than original alginate blocks, they could facilitate the formation of cake layer on membrane surface. It was observed that more TEP were produced from MM-blocks than from MG-blocks in solutions. This in turn explained why cake resistance was dominant in the filtration of MM-blocks as compared to MG-blocks. The analysis by the extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory further revealed that MM-blocks had lowest cohesive interaction energy among all three alginate blocks, which favoured aggregation of MM-blocks, and ultimately leading to the formation of more TEP. This study provided insights into the roles of different alginate blocks in development of membrane fouling, and suggested that the membrane fouling would be related to molecular structure of alginate.

A facile fabrication of alginate microbubbles using a gas foaming reaction

Microbubble particles have been extensively utilized as temporal templates for various biomedical applications. This study proposes a facile strategy to obtain microbubble-containing alginate particles (i.e., microbubbles inside alginate gel particles, called alginate microbubbles). The chemical reaction of sodium bicarbonate and hydrogen peroxide to produce gaseous carbon dioxide and oxygen was utilized to form microbubbles within alginate particles. Uniform alginate particles were obtained by a stable needle-based droplet formation process. Kinetic reaction of gas formation was monitored for 2% alginate particles. The gas formation increased with the concentrations of sodium bicarbonate (1-5 wt%) and hydrogen peroxide (0-36.5 wt%).

[Study of the preparation of silk fibroin gel and its morphology as drug release matrix in vitro and in vivo]

Silk fibroin (SF)/sodium alginate (SA) hydrogels can be used as drug injection materials. Homogenate was prepared by centrifugation of the pig myocardial extracellular matrix (PMM) and its modification of SF gel material. This paper observes and compares the different components SF, SF/SA, SF/SA/PMM to illustrate the SF/SA/PMM ternary material as a drug delivery composition material. This ternary material can shorten the gel time, and can make the gel form to be maintained better. Meanwhile, it makes the internal structure of the gel looser so that the hole wall becomes thinner and more conducive to the drug release. In addition, it has good biocompatibility proved by pathological analysis, and is able to enhance the mesenchymal stem cells growth activity, which has great significance in carrying out drug control release.

Development of pH-sensitive pectinate/alginate microspheres for colon drug delivery

The purposes of this study were to develop and evaluate calcium pectinate/alginate microspheres (PAMs) and to exploit their pH-sensitive properties for colon-targeted delivery of encapsulated cisplatin. PAMs were prepared using an electrospraying method. The PAMs, as cores, were then coated with Eudragit S100 using a polyelectrolyte multilayer coating technique in aqueous solution. The morphology of the microspheres was observed under scanning electron microscopy. In vitro drug release studies were performed in simulated gastrointestinal fluid, and the results indicated that approximately 5 % of the cisplatin was released from the Eudragit S100-coated PAMs, and 51 % of the cisplatin was released from the uncoated PAMs at 1 h. The release of cisplatin from the Eudragit S100-coated PAMs was more sustained in simulated gastric fluid than in simulated intestinal fluid due to the increased solubility of the coating polymer in media with pH >7.0. Drug release from the Eudragit S100-coated PAMs was best described by the Higuchi's square root model. From these results, it was concluded that Eudragit S100-coated PAMs are a potential carrier for delivery of cisplatin to the colon.

Alginate-PEGAc: a new mucoadhesive polymer

We have synthesized a novel mucoadhesive polymer, alginate-polyethylenglycol acrylate (alginate-PEGAc), in which an alginate backbone carries acrylated polyethylenglycol. This polymer combines the strength, simplicity and gelation ability of alginate with the mucoadhesion properties arising from the characteristics and acrylate functionality of PEG. The strong bonding to the mucus results from a combination of PEG's ability to interpenetrate the mucus surface and a Michael-type addition reaction between an acrylate end group on a polymer and the sulfide end group of the mucin-type glycoprotein. We have synthesized alginate-PEGAc, verified the formation of the desired product by nuclear magnetic resonance, demonstrated the lack of cytotoxicity, and evaluated the ability of this polymer to function as a novel mucoadhesive material for controlled drug release. Based on our findings we believe that modifying other polymers with PEG-acrylate can open the way for the development of many other multifunctional biomaterials for a variety of biotechnological and biomedical applications.

Regio- and stereospecific synthesis of mono-beta-d-glucuronic acid derivatives of combretastatin A-1

Synthetic routes have been established for the preparation of regio- and stereoisomerically pure samples of the mono-beta-d-glucuronic acid derivatives of combretastatin A-1, referred to as CA1G1 (5a) and CA1G2 (6a). Judicious choice of protecting groups for the catechol ring was required for the regiospecific introduction of the glucuronic acid moiety. The tosyl group proved advantageous in this regard. The two monoglucuronic acid analogues demonstrate low cytotoxicity (compared to CA1, 2) against selected human cancer cell lines, with CA1G1 being slightly more potent than CA1G2.

Facile single step fabrication of microchannels with varying size

In this report, we present a non-lithographic embedded template method for rapid and cost-effective fabrication of a monolithic microfluidic device with channels of various sizes. The procedure presented here enables the preparation of microchannels with varying dimensions in a single device without using any sophisticated micromachining instrumentation. In addition, this non-lithographic technique has also been used to fabricate a multilayer-multilevel biopolymer microdevice in a single step. To demonstrate the versatility of the presented method, we have fabricated microfluidic devices with four different materials under different curing/cross linking conditions. We have also demonstrated the application of the fabricated device to generate structured copper alginate microbeads, in vitro protein synthesis in three phase flow, and alternate plugs with liquid spacers.

Controlled delivery of VEGF via modulation of alginate microparticle ionic crosslinking

Clinical application of therapeutic angiogenesis is hampered by a lack of viable systems that demonstrate controlled, sustained release of vascular endothelial growth factor (VEGF). Alginate has emerged as a popular material for VEGF delivery; however most alginate-based systems offer limited means to control the rate of VEGF release beyond reducing the VEGF:alginate ratio to suboptimal efficiency. This study describes methods to control the release of VEGF from small (<10 microm mean diameter) alginate microparticles via the use of different ionic crosslinkers. Crosslinking with Zn(2+) versus Ca(2+) reduced VEGF diffusional release and the combination of discrete populations of either Zn(2+)- or Ca(2+)-crosslinked particles allowed for control over the sustained release profiles for VEGF. The particle preparations were non-toxic and VEGF was bioactive after release. These results demonstrate that ionic modulation of alginate crosslinking is a viable strategy for controlling release of VEGF while retaining the high protein:polymer ratio that makes alginate an attractive carrier for delivery of protein therapeutics.

Both ionically and enzymatically crosslinkable alginate–tyramine conjugate as materials for cell encapsulation

The swelling behavior of the structural material of cell-enclosing capsules is a key factor for the successful transplantation of these capsules in the treatment of diseases. The present study aimed to develop cell-enclosing capsules displaying minimal swelling under physiological conditions. We investigated the use of an alginate-tyramine conjugate synthesized by a carbodiimide/active-ester coupling reaction. The conjugate gel crosslinked by calcium ions and peroxidase-catalyzed oxidative coupling of phenols swelled less in saline than in unmodified alginate. The degree of swelling could be controlled by conjugate preparation conditions. The conjugate gel showed no obvious cytotoxicity for cells, including the process of oxidative coupling generation. Further, encapsulated cells could be cultured for up to 2 months and achieve approximately 5.2-fold greater mitochondrial activity after 51 days of encapsulation than after 1 day. These results show that this alginate-tyramine conjugate is a promising material for use in cell-enclosing capsules for cell therapy.

Preparation of calcium alginate microgel beads in an electrodispersion reactor using an internal source of calcium carbonate nanoparticles

An electrodispersion reactor has been used to prepare calcium alginate (Ca-alginate) microgel beads in this study. In the electrodispersion reactor, pulsed electric fields are utilized to atomize aqueous mixtures of sodium alginate and CaCO3 nanoparticles (dispersed phase) from a nozzle into an immiscible, insulating second liquid (continuous phase) containing a soluble organic acid. This technique combines the features of the electrohydrodynamic force driven emulsion processes and externally triggered gelations in microreactors (the droplets) ultimately to yield soft gel beads. The average particle size of the Ca-alginate gels generated by this method changed from 412 +/- 90 to 10 +/- 3 microm as the applied peak voltage was increased. A diagram depicting structural information for the Ca-alginate was constructed as a function of the concentrations of sodium alginate and CaCO3 nanoparticles. From this diagram, a critical concentration of sodium alginate required for sol-gel transformation was observed. The characteristic highly porous structure of Ca-alginate particles made by this technique appears suitable for microencapsulation applications. Finally, time scale analysis was performed for the electrodispersion processes that include reactions in the microreactor droplets to provide guidelines for the future employment of this technique. This electrodispersion reactor can be used potentially in the formation of many reaction-based microencapsulation systems.

Preparation of alginate–quaternary ammonium complex beads and evaluation of their antimicrobial activity

Alginate-quaternary ammonium complex beads with antimicrobial activity were prepared by the reaction of sodium alginate (SA) with 3-(trimethoxysilyl)propyl-octadecyldimethylammonium chloride (TSA) in acid solution, followed by crosslinking with CaCl(2). FTIR spectroscopy analysis showed that the resulting complex was formed mainly through covalent bonds between the hydroxyl groups of SA and the methoxysilyl groups of TSA. The complex beads exhibited a maximum swelling of 20% in water at 37 degrees C and were not hydrolyzed in water during experiments lasting for 30 days. The in vitro antimicrobial activity of the complex beads was evaluated against four species of bacteria and fungi. The test microorganisms were completely eliminated within 20 min when treated with 5% (v/v) complex beads, which showed a wide spectrum of excellent antimicrobial activity. The antimicrobial activity of the complex beads was retained after 10 cycles of washing and drying. The present results indicate that these SA-TSA complex beads are a new type of insoluble cationic polymer that can kill or remove microorganisms in water by mere contact without releasing the reactive agent.

Synthesis of urine drug metabolites: glucuronic acid glycosides of phenol intermediates

The investigation of drug metabolism requires substantial amount of metabolites. Isolation from urine is tedious, therefore, the material obtained by synthesis is preferred. Substantial amounts of three tentative drug metabolites, phenolic glucuronides, have been prepared using easily available glycosyl donors. The final products [3(2-N-methyl-N-isopropylaminoethoxy)phenyl] beta-D-glucopyranosiduronic acid, 4-amino-3,5-dimethylphenyl beta-D-glucopyranosiduronic acid and [2(S)-propanoyl-6-O-naphthyl] beta-D-glucopyranuronic acid are useful as, for example, reference material in metabolite investigations.

A controlled-release strategy for the generation of cross-linked hydrogel microstructures

Microscale hydrogels of controlled sizes and shapes are useful for cell-based screening, in vitro diagnostics, tissue engineering, and drug delivery. However, the rapid cross-linking of many chemically and pH cross-linkable hydrogel materials prevents the application of existing micromolding techniques. In this work we present a method for fabricating micromolded calcium alginate and chitosan structures through controlled release of the gelling agent from a hydrogel mold. Replica molding was employed to generate patterned membranes, whereas microtransfer molding was used to produce microparticles of controlled shapes. To explore the viability of this technique for producing complex tissue engineering micro-architectures, this approach was used to generate cell-laden size- and shape-controlled 3D microgels as well as composite hydrogels with well-defined spatially segregated regions. In addition, shape-controlled microstructures that can exhibit differential release properties were loaded with macromolecules to verify the potential of this approach for drug delivery applications.

Manipulating the generation of Ca-alginate microspheres using microfluidic channels as a carrier of gold nanoparticles

In this paper the manipulation of Ca-alginate microspheres, using a microfluidic chip, for the encapsulation of gold nanoparticles is presented. Our strategy is based on hydrodynamic-focusing on the forming of a series of self-assembling sphere structures, the so-called water-in-oil (w/o) emulsions, in the cross-junction microchannel. These fine emulsions, consisting of aqueous Na-alginates, are then dripped into a solution of 20% calcium salt to accomplish Ca-alginate microspheres in an efficient manner. Experimental data show that microspheres with diameters ranging from 50 microm to 2000 microm with a variation less than 5% were precisely generated. The size and gap of the droplets are tunable by adjusting the relative sheath/sample flow rate ratio. Furthermore, we applied them to encapsulated gold nanoparticles, and this one shot operation performs the 'Lab on a Chip'.

Microencapsulation of hemoglobin in chitosan-coated alginate microspheres prepared by emulsification/internal gelation

Chitosan-coated alginate microspheres prepared by emulsification/internal gelation were chosen as carriers for a model protein, hemoglobin (Hb), owing to nontoxicity of the polymers and mild conditions of the method. The influence of process variables related to the emulsification step and microsphere recovering and formulation variables, such as alginate gelation and chitosan coating, on the size distribution and encapsulation efficiency was studied. The effect of microsphere coating as well its drying procedure on the Hb release profile was also evaluated. Chitosan coating was applied by either a continuous microencapsulation procedure or a 2-stage coating process. Microspheres with a mean diameter of less than 30 microm and an encapsulation efficiency above 90% were obtained. Calcium alginate cross-linking was optimized by using an acid/CaCO(3) molar ratio of 2.5, and microsphere-recovery with acetate buffer led to higher encapsulation efficiency. Hb release in gastric fluid was minimal for air-dried microspheres. Coating effect revealed a total release of 27% for 2-stage coated wet microspheres, while other formulations showed an Hb release above 50%. Lyophilized microspheres behaved similar to wet microspheres, although a higher total protein release was obtained with 2-stage coating. At pH 6.8, uncoated microspheres dissolved in less than 1 hour; however, Hb release from air-dried microspheres was incomplete. Chitosan coating decreased the release rate of Hb, but an incomplete release was obtained. The 2-stage coated microspheres showed no burst effect, whereas the 1-stage coated microspheres permitted a higher protein release.

Production of alkaline protease with immobilized cells of Bacillus subtilis PE-11 in various matrices by entrapment technique

The purpose of this investigation was to study the effect of Bacillus subtilis PE-11 cells immobilized in various matrices, such as calcium alginate, k-Carrageenan, ployacrylamide, agar-agar, and gelatin, for the production of alkaline protease. Calcium alginate was found to be an effective and suitable matrix for higher alkaline protease productivity compared to the other matrices studied. All the matrices were selected for repeated batch fermentation. The average specific volumetric productivity with calcium alginate was 15.11 U/mL/hour, which was 79.03% higher production over the conventional free-cell fermentation. Similarly, the specific volumetric productivity by repeated batch fermentation was 13.68 U/mL/hour with k-Carrageenan, 12.44 U/mL/hour with agar-agar, 11.71 U/mL/hour with polyacrylamide, and 10.32 U/mL/hour with gelatin. In the repeated batch fermentations of the shake flasks, an optimum level of enzyme was maintained for 9 days using calcium alginate immobilized cells. From the results, it is concluded that the immobilized cells of B subtilis PE-11 in calcium alginate are more efficient for the production of alkaline protease with repeated batch fermentation. The alginate immobilized cells of B subtilis PE-11 can be proposed as an effective biocatalyst for repeated usage for maximum production of alkaline protease.

Synthesis of zinc-crosslinked thiolated alginic acid beads and their in vitro evaluation as potential enteric delivery system with folic acid as model drug

The aim of this study is to explore the potential of synthetic modifications of alginic acid as a method to enhance the stability of its complexes with divalent cations under physiological conditions. A fraction of algin's carboxylic acid moieties was substituted with thiol groups to different substitution degrees through conjugating alginate to cysteine to produce alginate-cysteine (AC) conjugates. Infrared spectrophotometry and iodometry were used to characterize the resulting polymeric conjugates in terms of structure and degree of substitution. Moreover, zinc ions were used to crosslink the resulting AC polymers. Folic acid loaded beads were prepared from Zinc-crosslinked AC polymers (AC-Zn) of different cysteine substitution degrees. The generated beads were then investigated in vitro for their capacity to modify folic acid release. AC-Zn polymeric beads resisted drug release under acidic conditions (pH 1.0). However, upon transfer to a phosphate buffer solution (pH 7.0) they released most of their contents almost immediately. This change in drug release behavior is most probably due to the sequestering of zinc cations by phosphate ions within the buffer solution to form insoluble chelates and, to a lesser extent, the ionization of the carboxylic acid and thiol moieties. Removal of zinc ions from the polymeric matrix seems to promote polymeric disintegration and subsequent drug release. A similar behavior is expected in vivo due to the presence of natural zinc sequestering agents in the intestinal fluids. AC-Zn polymers provided a novel approach for enteric drug delivery as drug release from these matrices complied with the USP specifications for enteric dosage forms.

Papain entrapment in alginate beads for stability improvement and site-specific delivery: physicochemical characterization and factorial optimization using neural network modeling

This work examines the influence of various process parameters (like sodium alginate concentration, calcium chloride concentration, and hardening time) on papain entrapped in ionotropically cross-linked alginate beads for stability improvement and site-specific delivery to the small intestine using neural network modeling. A 3(3) full-factorial design and feed-forward neural network with multilayer perceptron was used to investigate the effect of process variables on percentage of entrapment, time required for 50% and 90% of the enzyme release, particle size, and angle of repose. Topographical characterization was conducted by scanning electron microscopy, and entrapment was confirmed by Fourier transform infrared spectroscopy and differential scanning calorimetry. Times required for 50% (T(50)) and 90% (T(90)) of enzyme release were increased in all 3 of the process variables. Percentage entrapment and particle size were found to be directly proportional to sodium alginate concentration and inversely proportional to calcium chloride concentration and hardening time, whereas angle of repose and degree of cross-linking showed exactly opposite proportionality. Beads with >90% entrapment and T(50) of <10 minutes could be obtained at the low levels of all 3 of the process variables. The inability of beads to dissolve in acidic environment, with complete dissolution in buffer of pH >or=6.8, showed the suitability of beads to release papain into the small intestine. The shelf-life of the capsules prepared using the papain-loaded alginate beads was found to be 3.60 years compared with 1.01 years of the marketed formulation. It can be inferred from the above results that the proposed methodology can be used to prepare papain-loaded alginate beads for stability improvement and site-specific delivery.

Mechanisms of formation and disintegration of alginate beads obtained by prilling

In this paper, compendial sodium alginate beads have been manufactured by laminar jet break-up technology. The effect of polymer concentration, viscosity and polymeric solution flow rate on the characteristics of beads was studied. Size distribution of alginate beads in the hydrated state was strongly dependent on the flow rate and viscosity of polymer solutions, since a transition from laminar jet break-up conditions to vibration-assisted dripping was observed. The re-hydration kinetics of dried beads in simulated gastric fluid (SGF) showed that the maximum swelling of beads was reached after 1-2 h, with an increase in volume of two to three times and a time lag dependent on the polymer concentration. The re-hydration swelling profiles in simulated intestinal fluid (SIF) showed no time lag and higher swelling volume; moreover, in this medium after the maximum swelling was reached, the bead structure was quickly disaggregated because of the presence in the medium of phosphate able to capture calcium ions present in the alginate gel structure.

Tailor-made alginate bearing galactose moieties on mannuronic residues: selective modification achieved by a chemoenzymatic strategy

1-Amino-1-deoxygalactose (12%, mole) has been chemically introduced on a mannuronan sample via an N-glycosidic bond involving the uronic group of the mannuronic acid (M) residues. The unsubstituted M residues in the modified polymer were converted into guluronic moieties (G) by the use of two C-5 epimerases, resulting in an alginate-like molecule selectively modified on M residues. The molecular details of the newly formed polymer, in terms of both composition and molecular dimensions, were disclosed by use of (1)H NMR, intrinsic viscosity, and high-performance size-exclusion chromatography-multiple-angle laser light scattering (HPSEC-MALLS). Circular dichroism has revealed that the modified alginate-like polymer obtained after epimerization was able to bind calcium due to the introduction of alternating and homopolymeric G sequences. The gel-forming ability of this M-selectively modified material was tested and compared with an alginate sample containing 14% galactose introduced on G residues. Mechanical spectroscopy pointed out that the modified epimerized material was able to form stable gels and that the kinetics of the gel formation was similar to that of the unsubstituted sample. In contrast, the G-modified alginate samples showed a slower gel formation, eventually leading to gel characterized by a reduced storage modulus. The advantage of the selective modification on M residues was confirmed by measuring the Young's modulus of gel cylinders of the different samples. Furthermore, due to the high content in alternating sequences, a marked syneresis was disclosed for the modified-epimerized sample. Finally, calcium beads obtained from selectively M-modified alginate showed a higher stability than those from the G-modified alginate, as evaluated upon treatment with nongelling ions.

Synthesis of Structurally Defined Scaffolds for Bivalent Ligand Display Based on Glucuronic Acid Anilides. The Degree of Tertiary Amide Isomerism and Folding Depends on the Configuration of a Glycosyl Azide

[structures: see text] Syntheses and structural analyses of bivalent carbohydrates based on anilides of glucuronic acid are described. Secondary anilides predominantly adopted the Z-anti structure; there is also evidence for population of the Z-syn isomer. Bivalent tertiary anilides displayed two signal sets in their NMR spectra, consistent with the presence of (i) a major isomer where both amides have E configurations (EE) and (ii) a minor isomer where one amide is E and the other Z (EZ). Qualitative NOE/ROE spectroscopic studies in solution support the proposal that the anti conformation is preferred for E amides. The crystal structure of one bivalent tertiary anilide showed E-anti and E-syn structural isomers; intramolecular carbohydrate-carbohydrate stacking was observed and mediated by carbonyl-pyranose, azide-azide, and pyranose-aromatic interactions. The EE to EZ isomer ratio, or the degree of folding, for tertiary amides, was greatest for a bivalent compound containing two alpha-glycosyl azide groups; this was enhanced in water, suggesting that hydrophobic interactions are partially but not wholly responsible. Computational methods predicted azide-aromatic (N...H-C interaction) and azide-azide interactions for folded isomers. The close contact of the azide and aromatic protons (N...H-C interaction) was observed upon examination of the close packing in the crystal structure of a related monomer. It is proposed that the alpha-azide group is more optimally aligned, compared to the beta-azide, to facilitate interaction and minimize the surface area of the hydrophobic groups exposed to water, and this leads to the increased folding. The alkylation of bivalent secondary anilides induces a switch from Z to E amide that alters the scaffold orientation. The synthesis of a bivalent mannoside, based on a secondary anilide scaffold, for investigation of mannose-binding receptor cross-linking and lattice formation is described.

Synthesis and Structural Analysis of the Anilides of Glucuronic Acid and Orientation of the Groups on the Carbohydrate Scaffolding

[structures: see text] The synthesis of anilides derived from glucuronic acid is described. Secondary anilides had a Z configuration in the solid state and showed intramolecular and intermolecular hydrogen bonding. However, on the basis of NMR and IR studies, there was generally no evidence for the same hydrogen bonding in solution. Tertiary anilides showed a strong preference for the E configuration on the basis of NOE studies and molecular mechanics calculations. The alkylation of the secondary anilides induces a configurational switch that alters the orientation of the aromatic group with respect to the pyranose, which has relevance for presentation or orientation of pharmacophoric groups on carbohydrate scaffolds.

Synthesis of a glucuronic acid and glucose conjugate library and evaluation of effects on endothelial cell growth

Compounds that alter endothelial cell growth are of interest in the development of angiogenesis modulators. A structurally diverse series of saccharide derivatives (glycosylamide conjugates) have been synthesized and evaluated for their effects on bovine aortic endothelial cell (BAEC) growth. Heparin-albumin (HA) reduced BAEC growth by 32% at 10 microg/mL and a number of the novel saccharide conjugates from the library were found to mimic the effect of HA as they also inhibit endothelial cell survival under identical conditions. Two thiophene conjugates, thioglucamide (24% inhibition at 35 microM) and a related glucuronide (26% inhibition at 33 microM) were the most potent inhibitors of BAEC growth, as determined using a methylthiazol tetrazolium (MTT) assay. The effects of thioglucamide and HA on absolute cell number were also studied using cell counting experiments; thioglucamide (47% after 24 h) was more potent than indicated by the MTT assay and initially reduced the BAEC number to a greater extent than HA (30% after 24 h); however, its actions were over more rapidly than were HA's as cell growth had returned to levels of the control after 72 h where HA still caused 25% inhibition. The binding of the monosaccharide conjugates to fibroblast growth factor (FGF-2) in competition with heparin-albumin by ELISA was investigated to establish the possible mechanism by which glycoconjugates could alter growth but there was no general correlation between reduction in viable cell population and binding to FGF-2. No glycoconjugate reduced the proliferation of mouse mammary epithelial cells, nor did any alter gross cell morphology, supporting a proposal that the reduction in BAEC survival by monosaccharide conjugates such as thioglucamide is a result of the inhibition of cell proliferation rather than being an induction of cytotoxicity. These studies indicate that cell biological studies to determine the mechanism of action of the simple monosaccharide conjugates may be worthwhile.

Synthesis and Characterization of a Biotin-Alginate Conjugate and Its Application in a Biosensor Construction

Biotin was covalently coupled with alginate in an aqueous-phase reaction by means of carbodiimide-mediated activation chemistry to provide a biotin-alginate conjugate for subsequent use in biosensor applications. The synthetic procedure was optimized with respect to pH of the reaction medium (pH 6.0), the degree of uronic acid activation (20%), and the order of addition of the reagents. The biotin-alginate conjugate was characterized by titration with 2-anilinonaphthalene-6-sulfonic acid (2,6-ANS), 4-hydroxyazobene-2'-carboxylic acid (HABA) and by an HPSEC-MALLS analytical method as well as by FTIR and 13C NMR spectroscopy. As a compromise between the need for a high percent of molar modification of the alginate, on one hand, and sufficient gelling capability, on the other hand, an optimal modification of 10-13% of biotin-alginate was used. The new biotin-alginate conjugate was used for the encapsulation of bioluminescent reporter cells into microspheres. A biosensor was prepared by conjugating these biotinylated alginate microspheres to the surface of a streptavidin-coated optical fiber, and the performance of the biosensor was demonstrated in the determination of the antibiotic, mitomycin C as a model toxin.

Preparation of porous scaffolds by using freeze-extraction and freeze-gelation methods

Freeze-fixation and freeze-gelation methods are presented in this paper which can be used to prepare highly porous scaffolds without using the time and energy consuming freeze-drying process. The porous structure was generated during the freeze of a polymer solution, following which either the solvent was extracted by a non-solvent or the polymer was gelled under the freezing condition; thus, the porous structure would not be destructed during the subsequent drying stage. Compared with the freeze-drying method, the presented methods are time and energy-saving, with less residual solvent, and easier to be scaled up. Besides, the problem of formation of surface skin can be resolved and the limitation of using solvent with low boiling point can be lifted by the presented methods. With the freeze-extraction and freeze-gelation methods, porous PLLA, PLGA, chitosan and alginate scaffolds were successfully fabricated. In addition to the presentation of the morphologies of the fabricated scaffolds, preliminary data of cell culture on them are as well included in the present work.

Synthesis of N-(fluoren-9-ylmethoxycarbonyl)glycopyranosylamine uronic acids

The synthesis of 10 N-(fluoren-9-ylmethoxycarbonyl)glycopyranosylamine uronic acids that are amenable to solid-phase synthesis is described. The general synthetic strategy involves initial incorporation of the protected amine, followed by selective TEMPO oxidation of C-6 hydroxyl groups to give the corresponding Fmoc-protected sugar amino acids. Amine incorporation may be accomplished from aminolysis of the free sugar or from glycosyl azide reduction. The reactions can be carried out on multigram scale, providing access to unique monomer units for future incorporation into combinatorial library syntheses.

Towards a fully synthetic substitute of alginate: Optimization of a thermal gelation/chemical cross-linking scheme (?tandem? gelation) for the production of beads and liquid-core capsules

Fully synthetic polymers were used for the preparation of hydrogel beads and capsules, in a processing scheme that, originally designed for calcium alginate, was adapted to a "tandem" process, that is the combination a physical gelation with a chemical cross-linking. The polymers feature a Tetronic backbone (tetra armed Pluronics), which exhibits a reverse thermal gelation in water solutions within a physiological range of temperatures and pHs. The polymers bear terminal reactive groups that allow for a mild, but effective chemical cross-linking. Given an appropriate temperature jump, the thermal gelation provides a hardening kinetics similar to that of alginate. With slower kinetics, the chemical cross-linking then develops an irreversible and elastic gel structure, and determines its transport properties. In the present article this process has been optimized for the production of monodisperse, high elastic, hydrogel microbeads, and liquid-core microcapsules. We also show the feasibility of the use of liquid-core microcapsules in cell encapsulation. In preliminary experiments, CHO cells have been successfully encapsulated preserving their viability during the process and after incubation. The advantages of this process are mainly in the use of synthetic polymers, which provide great flexibility in the molecular design. This, in principle, allows for a precise tailoring of mechanical and transport properties and of bioactivity of the hydrogels, and also for a precise control in material purification.

One-pot conversion of glycals to cis-1,2-isopropylidene-alpha-glycosides

Described is a general method for the conversion of glycals to the corresponding 1,2-cis-isopropylidene-alpha-glycosides. Epoxidation of glycals with dimethyldioxirane followed by ZnCl(2)-catalyzed addition of acetone converted a variety of protected glycals into 1,2-cis-isopropylidene-alpha-glycosides in good yield. The reaction is compatible with a range of protecting groups, including esters, benzyl ethers, and silyl ethers, as well as free hydroxyl groups. This method has been applied to develop a synthesis of protected glucuronic acid 1, a key intermediate in the synthesis of glycosaminoglycans. Compound 1 was produced in seven steps and 32% overall yield.

Synthesis of alpha-glucuronic acid and amide derivatives in the presence of a participating 2-acyl protecting group

[reaction: see text] Participating acyl groups located at C-2 in glucosyl and related donors generally promote formation of 1,2-trans-glycosides. Reactions of some glucuronic acid donors with TMSN(3)/SnCl(4) or ROH/SnCl(4) gave only the 1,2-cis-glycoside. The stereoselectivity is consistent with participation of the C-6 group. The methodology was used for the synthesis of a Kdn2en mimetic with the alpha-configuration.

Chemical transformation of lactose into 4-O-beta-D-galactopyranosyl-D-glucuronic acid (pseudolactobiouronic acid) and some derivatives thereof

The selective oxidation of the primary alcoholic function of the reducing unit of lactose was achieved in good overall yield (67%) starting from 2',6'-di-O-benzyl-2,3:3',4'-di-O-isopropylidenelactose dimethyl acetal (1) through a simple multi-step procedure based on the selective acetylation of OH-5 of 1 (methoxyisopropylation, acetylation, de-methoxyisopropylation) followed by a two-step oxidation at C-6 (TPAP-NMO then TEMPO-NaOCl) and finally, complete removal of the protecting groups.

[Synthesis of carbohydrate related compounds by using aldolase catalyzed reaction]

Enzymes proceed the reaction with high regio- and stereoselectivity under mild conditions, i.e. in an aqueous medium at room temperature. However, enzymatic reactions that catalyze carbon-carbon bond formation have not been utilized in organic synthesis until recently. We had an interest in an aldolase-catalyzed reaction which proceed carbon-carbon bond formation referred to aldol condensation, by which many bioactive compounds have been rationally synthesized. On the other hand, recent biological studies on cell recognition (cell adhesion) have disclosed the important roles of oligosaccharides on cell surfaces, especially which include glucuronic acid, 3-deoxy-D-manno-oct-2-ulosonic acid (KDO), and sialic acid in the structures e.g., sialyl Lewis X and endotoxins, in differentiation, induction, viral and bacterial infections, and immune response. As well as acidic oligosaccharides, basic ones have been utilized as practical medicines in the clinical level, like acarbose that acts as an amylase inhibitor. Based on these background, we embarked the synthesis of carbohydrate related compounds which can control the interaction between carbohydrates and carbohydrate recognition protein by the use of several aldolases. Azasugars, potent inhibitors toward glycosidases, were synthesized using fructose-1,6-diphosphate (FDP)-aldolase and other dihdroxyacetonephosphate (DHAP)-dependent aldolases in the key step. Sialyl Lewis X mimetic, peptidic mimetic of RNA having anti-Vero toxin activity, mycestericin D, and aza-idulonic acid were prepared by taking advantage of L-threonine aldolase catalyzed reaction, which afford beta-hydroxy-alpha-L-amino acids. A precursor of KDO, featured acidic sugar of endotoxins was provided by the reaction catalyzed with kynureninase, which generates beta-anion of L-alanine in its active site during the metabolic reaction from kynurenine to anthranilic acid.