Carbohydrate engineered cells for regenerative medicine

Improving Schwann Cell Differentiation from Human Adipose Stem Cells with Metabolic Glycoengineering

Schwann cells (SCs) are myelinating cells that promote peripheral nerve regeneration. When nerve lesions form, SCs are destroyed, ultimately hindering nerve repair. The difficulty in treating nerve repair is exacerbated due to SC's limited and slow expansion capacity. Therapeutic use of adipose-derived stem cells (ASCs) is emerging in combating peripheral nerve injury due to these cells' SC differentiation capability and can be harvested easily in large numbers. Despite ASC's therapeutic potential, their transdifferentiation period typically takes more than two weeks. In this study, we demonstrate that metabolic glycoengineering (MGE) technology enhances ASC differentiation into SCs. Specifically, the sugar analog Ac5ManNTProp (TProp), which modulates cell surface sialylation, significantly improved ASC differentiation with upregulated SC protein S100β and p75NGFR expression and elevated the neurotrophic factors nerve growth factor beta (NGFβ) and glial cell-line-derived neurotrophic factor (GDNF). TProp treatment remarkably reduced the SC transdifferentiation period from about two weeks to two days in vitro, which has the potential to improve neuronal regeneration and facilitate future use of ASCs in regenerative medicine.

Should Carbohydrate Intake Be More Liberal during Oral and Enteral Nutrition in Type 2 Diabetic Patients?

Carbohydrate (CHO) intake in oral and enteral nutrition is regularly reduced in nutritional support of older patients due to the high prevalence of diabetes (usually type 2-T2DM) in this age group. However, CHO shortage can lead to the lack of building blocks necessary for tissue regeneration and other anabolic processes. Moreover, low CHO intake decreases CHO oxidation and can increase insulin resistance. The aim of our current study was to determine the extent to which an increased intake of a rapidly digestible carbohydrate-maltodextrin-affects blood glucose levels monitored continuously for one week in patients with and without T2DM. Twenty-one patients (14 T2DM and seven without diabetes) were studied for two weeks. During the first week, patients with T2DM received standard diabetic nutrition (250 g CHO per day) and patients without diabetes received a standard diet (350 g of CHO per day). During the second week, the daily CHO intake was increased to 400 in T2DM and 500 g in nondiabetic patients by addition of 150 g maltodextrin divided into three equal doses of 50 g and given immediately after the main meal. Plasma glucose level was monitored continually with the help of a subcutaneous sensor during both weeks. The increased CHO intake led to transient postprandial increase of glucose levels in T2DM patients. This rise was more manifest during the first three days of CHO intake, and then the postprandial peak hyperglycemia was blunted. During the night's fasting period, the glucose levels were not influenced by maltodextrin. Supplementation of additional CHO did not influence the percentual range of high glucose level and decreased a risk of hypoglycaemia. No change in T2DM treatment was indicated. The results confirm our assumption that increased CHO intake as an alternative to CHO restriction in type 2 diabetic patients during oral and enteral nutritional support is safe.

Glycoengineering human neural stem cells (hNSCs) for adhesion improvement using a novel thiol-modified N-acetylmannosamine (ManNAc) analog

This study sets the stage for the therapeutic use of Ac₅ManNTProp, an N-acetylmannosamine (ManNAc) analog that installs thiol-modified sialoglycans onto the surfaces of human neural stem cells (hNSC). First, we compared hNSC adhesion to the extracellular matrix (ECM) proteins laminin, fibronectin, and collagen and found preferential adhesion and concomitant changes to cell morphology and cell spreading for Ac₅ManNTProp-treated cells to laminin, compared to fibronectin where there was a modest response, and collagen where there was no observable increase. PCR array transcript analysis identified several classes of cell adhesion molecules that responded to combined Ac₅ManNTProp treatment and hNSC adhesion to laminin. Of these, we focused on integrin α6β1 expression, which was most strongly upregulated in analog-treated cells incubated on laminin. We also characterized downstream responses including vinculin display as well as the phosphorylation of focal adhesion kinase (FAK) and extracellular signal-related kinase (ERK). In these experiments, Ac₅ManNTProp more strongly induced all tested biological endpoints compared to Ac₅ManNTGc, showing that the single methylene unit that structurally separates the two analogs finely tunes biological responses. Together, the concerted modulation of multiple pro-regenerative activities through Ac₅ManNTProp treatment, in concert with crosstalk with ECM components, lays a foundation for using our metabolic glycoengineering approach to treat neurological disorders by favorably modulating endpoints that contribute to the viability of transplanted NSCs.

The Applications of Metabolic Glycoengineering

Mammalian cell membranes are decorated by the glycocalyx, which offer versatile means of generating biochemical signals. By manipulating the set of glycans displayed on cell surface, it is vital for gaining insight into the cellular behavior modulation and medical and biotechnological adhibition. Although genetic engineering is proven to be an effective approach for cell surface modification, the technique is only suitable for natural and genetically encoded molecules. To circumvent these limitations, non-genetic approaches are developed for modifying cell surfaces with unnatural but functional groups. Here, we review latest development of metabolic glycoengineering (MGE), which enriches the chemical functions of the cell surface and is becoming an intriguing new tool for regenerative medicine and tissue engineering. Particular emphasis of this review is placed on discussing current applications and perspectives of MGE.

In vitro and in vivo advancement of multifunctional electrospun nanofiber scaffolds in wound healing applications: Innovative nanofiber designs, stem cell approaches, and future perspectives

The skin is one of the most essential tissues in the human body, interacting with the outside environment and shielding the body from diseases and excessive water loss. Hydrogels, decellularized porcine dermal matrix, and lyophilized polymer scaffolds have all been used in studies of skin wound repair, wound dressing, and skin tissue engineering, however, these materials cannot replicate the nanofibrous architecture of the skin's native extracellular matrix (ECM). Electrospun nanofibers are a fascinating new form of nanomaterials with tremendous potential across a broad spectrum of applications in the biomedical field, including wound dressings, wound healing scaffolds, regenerative medicine, bioengineering of skin tissue, and multifaceted drug delivery. This article reviews recent in vitro and in vivo developments in multifunctional electrospun nanofibers (MENs) for wound healing. This review begins with an introduction to the electrospinning process, its principle, and the processing parameters which have a significant impact on the nanofiber properties. It then discusses the various geometries and advantages of MEN scaffolds produced by different innovative electrospinning techniques for wound healing applications when used in combination with stem cells. This review also discusses some of the possible future nanofiber-based models that could be used. Finally, we conclude with potential perspectives and conclusions in this area.

What Molecular Recognition Systems Do Mesenchymal Stem Cells/Medicinal Signaling Cells (MSC) Use to Facilitate Cell-Cell and Cell Matrix Interactions? A Review of Evidence and Options

Mesenchymal stem cells, also called medicinal signaling cells (MSC), have been studied regarding their potential to facilitate tissue repair for >30 years. Such cells, derived from multiple tissues and species, are capable of differentiation to a number of lineages (chondrocytes, adipocytes, bone cells). However, MSC are believed to be quite heterogeneous with regard to several characteristics, and the large number of studies performed thus far have met with limited or restricted success. Thus, there is more to understand about these cells, including the molecular recognition systems that are used by these cells to perform their functions, to enhance the realization of their potential to effect tissue repair. This perspective article reviews what is known regarding the recognition systems available to MSC, the possible systems that could be looked for, and alternatives to enhance their localization to specific injury sites and increase their subsequent facilitation of tissue repair. MSC are reported to express recognition molecules of the integrin family. However, there are a number of other recognition molecules that also could be involved such as lectins, inducible lectins, or even a MSC-specific family of molecules unique to these cells. Finally, it may be possible to engineer expression of recognition molecules on the surface of MSC to enhance their function in vivo artificially. Thus, improved understanding of recognition molecules on MSC could further their success in fostering tissue repair.

Safety and Modulatory Effects of Humanized Galacto-Oligosaccharides on the Gut Microbiome

Complex dietary carbohydrate structures including β(1-4) galacto-oligosaccharides (GOS) are resistant to digestion in the upper gastrointestinal (GI) tract and arrive intact to the colon where they benefit the host by selectively stimulating microbial growth. Studies have reported the beneficial impact of GOS (alone or in combination with other prebiotics) by serving as metabolic substrates for modulating the assembly of the infant gut microbiome while reducing GI infections. N-Acetyl-D-lactosamine (LacNAc, Galβ1,4GlcNAc) is found in breast milk as a free disaccharide. This compound is also found as a component of human milk oligosaccharides (HMOs), which have repeating and variably branched lactose and/or LacNAc units, often attached to sialic acid and fucose monosaccharides. Human glycosyl-hydrolases do not degrade most HMOs, indicating that these structures have evolved as natural prebiotics to drive the proper assembly of the infant healthy gut microbiota. Here, we sought to develop a novel enzymatic method for generating LacNAc-enriched GOS, which we refer to as humanized GOS (hGOS). We showed that the membrane-bound β-hexosyl transferase (rBHT) from Hamamotoa (Sporobolomyces) singularis was able to generate GOS and hGOS from lactose and N-Acetyl-glucosamine (GlcNAc). The enzyme catalyzed the regio-selective, repeated addition of galactose from lactose to GlcNAc forming the β-galactosyl linkage at the 4-position of the GlcNAc and at the 1-position of D-galactose generating, in addition to GOS, LacNAc, and Galactosyl-LacNAc trisaccharides which were produced by two sequential transgalactosylations. Humanized GOS is chemically distinct from HMOs, and its effects in vivo have yet to be determined. Thus, we evaluated its safety and demonstrated the prebiotic's ability to modulate the gut microbiome in 6-week-old C57BL/6J mice. Longitudinal analysis of gut microbiome composition of stool samples collected from mice fed a diet containing hGOS for 5 weeks showed a transient reduction in alpha diversity. Differences in microbiome community composition mostly within the Firmicutes phylum were observed between hGOS and GOS, compared to control-fed animals. In sum, our study demonstrated the biological synthesis of hGOS, and signaled its safety and ability to modulate the gut microbiome in vivo, promoting the growth of beneficial microorganisms, including Bifidobacterium and Akkermansia.

Modulatory properties of extracellular matrix glycosaminoglycans and proteoglycans on neural stem cells behavior: Highlights on regenerative potential and bioactivity

Despite the poor regenerative capacity of the adult central nervous system (CNS) in mammals, two distinct regions, subventricular zone (SVZ) and the subgranular zone (SGZ), continue to generate new functional neurons throughout life which integrate into the pre-existing neuronal circuitry. This process is not fixed but highly modulated, revealing many intrinsic and extrinsic mechanisms by which this performance can be optimized for a given environment. The capacity for self-renewal, proliferation, migration, and multi-lineage potency of neural stem cells (NSCs) underlines the necessity of controlling stem cell fate. In this context, the native and local microenvironment plays a critical role, and the application of this highly organized architecture in the CNS has been considered as a fundamental concept in the generation of new effective therapeutic strategies in tissue engineering approaches. The brain extracellular matrix (ECM) is composed of biomacromolecules, including glycosaminoglycans, proteoglycans, and glycoproteins that provide various biological actions through biophysical and biochemical signaling pathways. Herein, we review predominantly the structure and function of the mentioned ECM composition and their regulatory impact on multiple and diversity of biological functions, including neural regeneration, survival, migration, differentiation, and final destiny of NSCs.

Programming Cell-Cell Interactions through Non-genetic Membrane Engineering

The ability to direct targeted intercellular interactions has the potential to enable and expand the use of cell-based therapies for regenerative medicine, tissue engineering, and immunotherapy. While genetic engineering approaches have proven effective, these techniques are not amenable to all cell types and often yield permanent modifications with potentially long-lasting adverse effects, restricting their application. To circumvent these limitations, there is intense interest in developing non-genetic methods to modify cell membranes with functional groups that will enable the recognition of target cells. While many such techniques have been developed, relatively few have been applied to directing specific cell-cell interactions. This review details these non-genetic membrane engineering approaches-namely, hydrophobic membrane insertion, chemical modification, liposome fusion, metabolic engineering, and enzymatic remodeling-and summarizes their major applications. Based on this analysis, perspective is provided on the ideal features of these systems with an emphasis on the potential for clinical translation.

Biomimetic neural scaffolds: a crucial step towards optimal peripheral nerve regeneration

Peripheral nerve injury is a common disease that affects more than 20 million people in the United States alone and remains a major burden to society. The current gold standard treatment for critical-sized nerve defects is autologous nerve graft transplantation; however, this method is limited in many ways and does not always lead to satisfactory outcomes. The limitations of autografts have prompted investigations into artificial neural scaffolds as replacements, and some neural scaffold devices have progressed to widespread clinical use; scaffold technology overall has yet to be shown to be consistently on a par with or superior to autografts. Recent advances in biomimetic scaffold technologies have opened up many new and exciting opportunities, and novel improvements in material, fabrication technique, scaffold architecture, and lumen surface modifications that better reflect biological anatomy and physiology have independently been shown to benefit overall nerve regeneration. Furthermore, biomimetic features of neural scaffolds have also been shown to work synergistically with other nerve regeneration therapy strategies such as growth factor supplementation, stem cell transplantation, and cell surface glycoengineering. This review summarizes the current state of neural scaffolds, highlights major advances in biomimetic technologies, and discusses future opportunities in the field of peripheral nerve regeneration.

A library of chemically defined human N-glycans synthesized from microbial oligosaccharide precursors

Synthesis of homogenous glycans in quantitative yields represents a major bottleneck to the production of molecular tools for glycoscience, such as glycan microarrays, affinity resins, and reference standards. Here, we describe a combined biological/enzymatic synthesis that is capable of efficiently converting microbially-derived precursor oligosaccharides into structurally uniform human-type N-glycans. Unlike starting material obtained by chemical synthesis or direct isolation from natural sources, which can be time consuming and costly to generate, our approach involves precursors derived from renewable sources including wild-type Saccharomyces cerevisiae glycoproteins and lipid-linked oligosaccharides from glycoengineered Escherichia coli. Following deglycosylation of these biosynthetic precursors, the resulting microbial oligosaccharides are subjected to a greatly simplified purification scheme followed by structural remodeling using commercially available and recombinantly produced glycosyltransferases including key N-acetylglucosaminyltransferases (e.g., GnTI, GnTII, and GnTIV) involved in early remodeling of glycans in the mammalian glycosylation pathway. Using this approach, preparative quantities of hybrid and complex-type N-glycans including asymmetric multi-antennary structures were generated and subsequently used to develop a glycan microarray for high-throughput, fluorescence-based screening of glycan-binding proteins. Taken together, these results confirm our combined synthesis strategy as a new, user-friendly route for supplying chemically defined human glycans simply by combining biosynthetically-derived precursors with enzymatic remodeling.

Description of D-glucosamine immobilization kinetics onto poly(lactic acid) surface via a multistep physicochemical approach for preparation of novel active biomaterials

Poly(lactic acid) (PLA) has shown much success in the preparation of tissue engineering scaffolds as it can be fabricated with a tailored architecture. However, the PLA surface has drawbacks including the lack of biofunctional motifs which are essential for high affinity to biological cells. Therefore, this study describes a multistep physicochemical approach for the immobilization of d-glucosamine (GlcN), a naturally occurring monosaccharide having many biological functions, on the PLA surface aiming at enhancing the cell proliferation activity. In this approach, poly(acrylic acid) (PAAc) spacer arms are first introduced into the PLA surface via plasma post-irradiation grafting technique. Then, covalent coupling or physical adsorption of GlcN with/on the PAAc spacer is carried out. Factors affecting the grafting yield are controlled to produce a suitable spacer for bioimmobilization. X-ray photon spectroscopic (XPS) analyses confirm the immobilization of GlcN on the PLA surface. The XPS results reveal also that increasing the yield of grafted PAAc spacer on the PLA surface increases the amount of covalently immobilized GlcN, but actually inhibits the immobilization process using the physical adsorption method. Contact angle measurements and atomic force microscopy (AFM) show a substantial increase of surface energy and roughness of PLA surface, respectively, upon the multistep modification procedure. The cytocompatibility of the modified surfaces is assessed using a mouse embryonic fibroblast (MEF) cell line. Observation from the cell culture basically demonstrates the potential of GlcN immobilization in improving the cytocompatibility of the PLA surface. Moreover, the covalent immobilization of GlcN seems to produce more cytocompatible surfaces if compared with the physical adsorption method. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 3176-3188, 2017.

Extreme Activity of Drug Nanocrystals Coated with A Layer of Non-Covalent Polymers from Self-Assembled Boric Acid

Non-covalent polymers have remarkable advantages over synthetic polymers for wide biomedical applications. In this study, non-covalent polymers from self-assembled boric acid were used as the capping reagent to replace synthetic polymers in drug crystallization. Under acidic pH, boric acid self-assembled on the surface of drug nanocrystals to form polymers with network-like structures held together by hydrogen bonds. Coating driven by boric acid self-assembly had negligible effects on drug crystallinity and structure but resulted in drug nanocrystals with excellent dispersion properties that aided in the formation of a more stable suspension. Boric acid coating improved drug stability dramatically by preventing drug molecules from undergoing water hydrolysis in a neutral environment. More importantly, the specific reactivity of orthoboric groups to diols in cell glycocalyx facilitated a rapid cross-membrane translocation of drug nanocrystals, leading to efficient intracellular drug delivery, especially on cancer cells with highly expressed sialic acids. Boric acid coated nanocrystals of camptothecin, an anticancer drug with poor aqueous solubility and stability, demonstrated extreme cytotoxic activity (IC₅₀ < 5.0 μg/mL) to cancer cells compared to synthetic polymer coated CPT nanocrystals and free CPT. Surface coating using non-covalent polymers from self-assembled boric acid will have wide biomedical applications especially in biomaterials and drug delivery field.

Electrospinning of Cross-Linked Magnetic Chitosan Nanofibers for Protein Release

A poly(vinylalcohol) (PVA) electrospun/magnetic/chitosan nanocomposite fibrous cross-linked network was fabricated using in situ cross-linking electrospinning technique and used for bovine serum albumin (BSA) loading and release applications. Sodium tripolyphosphate (TPP) and glutaraldehyde (GA) were used as cross-linkers which modified magnetic-Fe3O4 chitosan as Fe3O4/CS/TPP and Fe3O4/CS/GA, respectively. BSA was used as a model protein drugs which was encapsulated to form Fe3O4/CS/TPP/BSA and Fe3O4/CS/GA/BSA nanoparticles. The composites were electrospun with PVA to form nanofibers. Nanofibers were characterized by field emission scanning electron microscopy (FESEM) and Fourier transform infrared spectroscopy (FTIR). The characterization results suggest that Fe3O4 nanoparticles with average size of 45 nm were successfully bound on the surface of chitosan. The cross-linked nanofibers were found to contain uniformly dispersed Fe3O4 nanoparticles. The size and morphology of the nanofibers network was controlled by varying the cross-linker type. FTIR data show that these two polymers have intermolecular interactions. The sample with TPP cross-linker showed an enhancement of the controlled release properties of BSA during 30-h experimental investigation. Graphical Abstract ᅟ.

Recent Developments in Synthetic Carbohydrate-Based Diagnostics, Vaccines, and Therapeutics

Glycans are everywhere in biological systems, being involved in many cellular events with important implications for medical purposes. Building upon a detailed understanding of the functional roles of carbohydrates in molecular recognition processes and disease states, glycans are increasingly being considered as key players in pharmacological research. On the basis of the important progress recently made in glycochemistry, glycobiology, and glycomedicine, we provide a complete overview of successful applications and future perspectives of carbohydrates in the biopharmaceutical and medical fields. This review highlights the development of carbohydrate-based diagnostics, exemplified by glycan imaging techniques and microarray platforms, synthetic oligosaccharide vaccines against infectious diseases (e.g., HIV) and cancer, and finally carbohydrate-derived therapeutics, including glycomimetic drugs and glycoproteins.

Progress in cell-based therapies for tendon repair

The last decade has seen significant developments in cell therapies, based on permanently differentiated, reprogrammed or engineered stem cells, for tendon injuries and degenerative conditions. In vitro studies assess the influence of biophysical, biochemical and biological signals on tenogenic phenotype maintenance and/or differentiation towards tenogenic lineage. However, the ideal culture environment has yet to be identified due to the lack of standardised experimental setup and readout system. Bone marrow mesenchymal stem cells and tenocytes/dermal fibroblasts appear to be the cell populations of choice for clinical translation in equine and human patients respectively based on circumstantial, rather than on hard evidence. Collaborative, inter- and multi-disciplinary efforts are expected to provide clinically relevant and commercially viable cell-based therapies for tendon repair and regeneration in the years to come.

Sialidases as regulators of bioengineered cellular surfaces

Human sialidases (NEUs) catalyze the removal of N-acetyl neuraminic acids from the glycome of the cell and regulate a diverse repertoire of nominal cellular functions, such as cell signaling and adhesion. A greater understanding of their substrate permissivity is of interest in order to discern their physiological functions in disease states and in the design of specific and effective small molecule inhibitors. Towards this, we have synthesized soluble fluorogenic reporters of mammalian sialidase activity bearing unnatural sialic acids commonly incorporated into the cellular glycocalyx via metabolic glycoengineering. We found cell-surface sialidases in Jurkat capable of cleaving unnatural sialic acids with differential activities toward a variety of R groups on neuraminic acid. In addition, we observed modulated structure-activity relationships when cell-surface sialidases were presented glycans with unnatural bulky, hydrophobic or fluorinated moieties incorporated directly via glycoengineering. Our results confirm the importance of cell-surface sialidases in glycoengineering incorporation data. We demonstrate the flexibility of human NEUs toward derivatized sugars and highlight the importance of native glycan presentation to sialidase binding and activity. These results stand to inform not only metabolic glycoengineering efforts but also inhibitor design.

The 'sweet' spot of cellular pluripotency: protein glycosylation in human pluripotent stem cells and its applications in regenerative medicine

INTRODUCTION

Human pluripotent stem cells (hPSCs) promise for the future of regenerative medicine. The structural and biochemical diversity associated with glycans makes them a unique type of macromolecule modification that is involved in the regulation of a vast array of biochemical events and cellular activities including pluripotency in hPSCs. The primary focus of this review article is to highlight recent advances in stem cell research from a glycobiological perspective. We also discuss how our understanding of glycans and glycosylation may help overcome barriers hindering the clinical application of hPSC-derived cells.

AREAS COVERED

A literature survey using NCBI-PubMed and Google Scholar was performed in 2014.

EXPERT OPINION

Regenerative medicine hopes to provide novel strategies to combat human disease and tissue injury that currently lack effective therapies. Although progress in this field is accelerating, many critical issues remain to be addressed in order for cell-based therapy to become a practical and safe treatment option. Emerging evidence suggests that protein glycosylation may significantly influence the regulation of cellular pluripotency, and that the exploitation of protein glycosylation in hPSCs and their differentiated derivatives may lead to transformative and translational discoveries for regenerative medicine. In addition, hPSCs represent a novel research platform for investigating glycosylation-related disease.

Preparation of biointeractive glycoprotein-conjugated hydrogels through metabolic oligosacchalide engineering

In the current study, synthetic hydrogels containing metabolically engineered glycoproteins of mammalian cells were prepared for the first time and selectin-mediated cell adhesion on the hydrogel was demonstrated. A culture of HL-60 cells was supplemented with an appropriate volume of aqueous solution of N-methacryloyl mannosamine (ManMA) to give a final concentration of 5 mM. The cells were then incubated for 3 days to deliver methacryloyl groups to the glycoproteins of the cells. A transparent hydrogel was formed via redox radical polymerization of methacryloyl functionalized glycoproteins with 2-methacryloyloxyethyl phosphorylcholine and a cross-linker. Conjugation of the glycoproteins into the hydrogel was determined using Coomassie brilliant blue (CBB) and periodic acid-Schiff (PAS) staining. The surface density of P-selectin glycoprotein ligand-1 (PSGL-1) on the hydrogels was also detected using gold-colloid-labeled immunoassay. Finally, selectin-mediated cell adhesion on hydrogels containing glycoproteins was demonstrated. Selectin-mediated cell adhesion is considered an essential step in the progression of various diseases; therefore, hydrogels having glycoproteins could be useful in therapeutic and diagnostic applications.

Bifunctional dendrons for multiple carbohydrate presentation via carbonyl chemistry

The synthesis of new dendrons of the generations 0, 1 and 2 with a double bond at the focal point and a carbonyl group at the termini has been carried out. The carbonyl group has been exploited for the multivalent conjugation to a sample saccharide by reductive amination and alkoxyamine conjugation.

The potential roles of cell surface pHs in bioactive peptide activation

Glycolytic metabolism of cells produces protons that are removed from the cytosol by transport proteins to create a pH difference between the adjacent bulk solution and the cell membrane surface. Therefore, tissue cells have distinct surface pHs because of varied glycocalyx and proton production capability. In this study, we proved the role of cell surface pH in peptide-cell interaction and peptide activation using lytic peptides with pH-dependent activity as probes. Properly, selected peptides could sense the specific pH zones on cells and thus demonstrated varied activity to tissue cells with different surface pHs. For a specific cell, the activity of pH-sensitive peptides changed accordingly as the cell surface pH was tuned up or down by proton channel regulators. Mechanistic studies revealed that cell surface pH directly affected peptide insertion into membranes by altering the secondary structure and aggregation status of membrane-bound pH-sensitive peptides. A pH-sensitive lytic peptide-designed based on the cell surface pH difference between a normal-cancer cell pair showed good selectivity to cancer cells. Therefore, cell surface pHs may present new opportunities to design therapeutic peptides with high cell specificity and selectivity.

Glycotherapy: new advances inspire a reemergence of glycans in medicine

The beginning of the 20(th) century marked the dawn of modern medicine with glycan-based therapies at the forefront. However, glycans quickly became overshadowed as DNA- and protein-focused treatments became readily accessible. The recent development of new tools and techniques to study and produce structurally defined carbohydrates has spurred renewed interest in the therapeutic applications of glycans. This review focuses on advances within the past decade that are bringing glycan-based treatments back to the forefront of medicine and the technologies that are driving these efforts. These include the use of glycans themselves as therapeutic molecules as well as engineering protein and cell surface glycans to suit clinical applications. Glycan therapeutics offer a rich and promising frontier for developments in the academic, biopharmaceutical, and medical fields.

Electro-spinning/netting: A strategy for the fabrication of three-dimensional polymer nano-fiber/nets

Since 2006, a rapid development has been achieved in a subject area, so called electro-spinning/netting (ESN), which comprises the conventional electrospinning process and a unique electro-netting process. Electro-netting overcomes the bottleneck problem of electrospinning technique and provides a versatile method for generating spider-web-like nano-nets with ultrafine fiber diameter less than 20 nm. Nano-nets, supported by the conventional electrospun nanofibers in the nano-fiber/nets (NFN) membranes, exhibit numerious attractive characteristics such as extremely small diameter, high porosity, and Steiner tree network geometry, which make NFN membranes optimal candidates for many significant applications. The progress made during the last few years in the field of ESN is highlighted in this review, with particular emphasis on results obtained in the author's research units. After a brief description of the development of the electrospinning and ESN techniques, several fundamental properties of NFN nanomaterials are addressed. Subsequently, the used polymers and the state-of-the-art strategies for the controllable fabrication of NFN membranes are highlighted in terms of the ESN process. Additionally, we highlight some potential applications associated with the remarkable features of NFN nanostructure. Our discussion is concluded with some personal perspectives on the future development in which this wonderful technique could be pursued.

Comparative evaluation of chitosan, cellulose acetate, and polyethersulfone nanofiber scaffolds for neural differentiation

Based on accumulating evidence that the 3D topography and the chemical features of a growth surface influence neuronal differentiation, we combined these two features by evaluating the cytotoxicity, proliferation, and differentiation of the rat PC12 line and human neural stem cells (hNSCs) on chitosan (CS), cellulose acetate (CA), and polyethersulfone (PES)-derived electrospun nanofibers that had similar diameters, centered in the 200-500 nm range. None of the nanofibrous materials were cytotoxic compared to 2D (e.g., flat surface) controls; however, proliferation generally was inhibited on the nanofibrous scaffolds although to a lesser extent on the polysaccharide-derived materials compared to PES. In an exception to the trend toward slower growth on the 3D substrates, hNSCs differentiated on the CS nanofibers proliferated faster than the 2D controls and both cell types showed enhanced indication of neuronal differentiation on the CS scaffolds. Together, these results demonstrate beneficial attributes of CS for neural tissue engineering when this polysaccharide is used in the context of the defined 3D topography found in electrospun nanofibers.

Experimental Design Considerations for In Vitro Non-Natural Glycan Display via Metabolic Oligosaccharide Engineering

Metabolic oligosaccharide engineering (MOE) refers to a technique where non-natural monosaccharide analogs are introduced into living biological systems. Once inside a cell, these compounds intercept a targeted biosynthetic glycosylation pathway and in turn are metabolically incorporated into cell-surface-displayed oligosaccharides where they can modulate a host of biological activities or be exploited as "tags" for bio-orthogonal and chemoselective ligation reactions. Undertaking a MOE experiment can be a daunting task based on the growing repertoire of analogs now available and the ever increasing number of metabolic pathways that can be targeted; therefore, a major emphasis of this article is to describe a general approach for analog design and selection and then provide protocols to ensure safe and efficacious analog usage by cells. Once cell-surface glycans have been successfully remodeled by MOE methodology, the stage is set for probing changes to the myriad cellular responses modulated by these versatile molecules. Curr. Protoc. Chem. Biol. 2:171-194 © 2010 by John Wiley & Sons, Inc.

Three-dimensional scaffold from decellularized human gingiva for cell cultures: glycoconjugates and cell behavior

OBJECTIVE

We studied both the presence of some carbohydrate compounds in a threedimensional (3D) matrix harvested from human gingiva and the cell behavior in this matrix.

MATERIALS AND METHODS

In this experimental research, in order to prepare 3D scaffolds, human palatal gingival biopsies were harvested and physically decellularized by freezethawing and sodium dodecyl sulfate (SDS). The scaffolds were placed within the rings of blastema tissues obtained from a pinna rabbit, in vitro. We evaluated the presence of glycoconjugatesand cellular behavior according to histological, histochemical and spectrophotometry techniques at one, two and three weeks after culture. One-way analysis of variance (ANOVA)comparedthe groups.

RESULTS

Extracellular matrix (ECM) remained after decellularization of tissue with 1% SDS. Glycoconjugate contents decreased meaningfully at a higher SDS concentration (p<0.0001). After culture of the ECM scaffold with blastema, we observed increased staining of alcian blue, periodic acid-Schiff (PAS) and toluidine blue in the scaffold and a number of other migrant cells which was caused by cell penetrationinto the scaffold. Spectrophotometry results showed an increase in glycosaminoglycans (GAGs) of the decellularized scaffolds at three weeks after culture.

CONCLUSION

The present study has shown that a scaffold generated from palatal gingival tissue ECM is a suitable substrate for blastema cell migration and activity.This scaffold maypotentially be useful as a biological scaffold in tissue engineering applications.

Biomimetic electrospun nanofibrous structures for tissue engineering

Biomimetic nanofibrous scaffolds mimicking important features of the native extracellular matrix provide a promising strategy to restore functions or achieve favorable responses for tissue regeneration. This review provides a brief overview of current state-of-the-art research designing and using biomimetic electrospun nanofibers as scaffolds for tissue engineering. It begins with a brief introduction of electrospinning and nanofibers, with a focus on issues related to the biomimetic design aspects. The review next focuses on several typical biomimetic nanofibrous structures (e.g. aligned, aligned to random, spiral, tubular, and sheath membrane) that have great potential for tissue engineering scaffolds, and describes their fabrication, advantages, and applications in tissue engineering. The review concludes with perspectives on challenges and future directions for design, fabrication, and utilization of scaffolds based on electrospun nanofibers.

Bacterial inclusion bodies as potential synthetic devices for pathogen recognition and a therapeutic substance release

Background

Adhesins of pathogens recognise the glycans on the host cell and mediate adherence. They are also crucial for determining the tissue preferences of pathogens. Currently, glyco-nanomaterials provide potential tool for antimicrobial therapy. We demonstrate that properly glyco-tailored inclusion bodies can specifically bind pathogen adhesins and release therapeutic substances.

Results

In this paper, we describe the preparation of tailored inclusion bodies via the conjugation of indicator protein aggregated to form inclusion bodies with soluble proteins. Whereas the indicator protein represents a remedy, the soluble proteins play a role in pathogen recognition. For conjugation, glutaraldehyde was used as linker. The treatment of conjugates with polar lysine, which was used to inactivate the residual glutaraldehyde, inhibited unwanted hydrophobic interactions between inclusion bodies. The tailored inclusion bodies specifically interacted with the SabA adhesin from Helicobacter pylori aggregated to form inclusion bodies that were bound to the sialic acids decorating the surface of human erythrocytes. We also tested the release of indicator proteins from the inclusion bodies using sortase A and Ssp DNAB intein self-cleaving modules, respectively. Sortase A released proteins in a relatively short period of time, whereas the intein cleavage took several weeks.

Conclusions

The tailored inclusion bodies are promising “nanopills” for biomedical applications. They are able to specifically target the pathogen, while a self-cleaving module releases a soluble remedy. Various self-cleaving modules can be enabled to achieve the diverse pace of remedy release.

The expanding world of tissue engineering: the building blocks and new applications of tissue engineered constructs

The field of tissue engineering has been growing in the recent years as more products have made it to the market and as new uses for the engineered tissues have emerged, motivating many researchers to engage in this multidisciplinary field of research. Engineered tissues are now not only considered as end products for regenerative medicine, but also have emerged as enabling technologies for other fields of research ranging from drug discovery to biorobotics. This widespread use necessitates a variety of methodologies for production of tissue engineered constructs. In this review, these methods together with their non-clinical applications will be described. First, we will focus on novel materials used in tissue engineering scaffolds; such as recombinant proteins and synthetic, self assembling polypeptides. The recent advances in the modular tissue engineering area will be discussed. Then scaffold-free production methods, based on either cell sheets or cell aggregates will be described. Cell sources used in tissue engineering and new methods that provide improved control over cell behavior such as pathway engineering and biomimetic microenvironments for directing cell differentiation will be discussed. Finally, we will summarize the emerging uses of engineered constructs such as model tissues for drug discovery, cancer research and biorobotics applications.

Glycocodon theory--the first table of glycocodons

Hydrophobic cellular membranes separate cells from an environment that is generally based on water. Therefore, it is not surprising that hydrophilic glycans and glycoproteins are exposed on the lipidic surface of membranes and that the glycocalyx has evolved in all basic cell types. During the evolution of multicellular life, the surface exposed protein-glycan interactions were taken as the origin of the language of cell-cell communication. The bioinformatics analysis presented here reveals that the amino acid triplets, the glycocodons, can be deduced for each glycan letter (monosaccharide). This theory proposes to distinguish between the "sugar code" (the sugar sequence) and the "glycocode" (evolutionary selected amino acids recognising the mono-sugar). Similarly to genetic code, original glycocodons are related to G, A, V, and D amino acids. Modern glycocodons can be deduced from GAVD-glycocodons using hydropathic similarity. In general, the amino acid triplets can be assembled from one dipeptide that is specific to a monosaccharide plus a polar amino acid. This theory may shed a different light on the reason for WWD conservation in the active sites of oligosaccharyltransferases and for GGQ in the active sites of ribosomes.

Metabolic monosaccharides altered cell responses to anticancer drugs

Metabolic glycoengineering has been used to manipulate the glycochemistry of cell surfaces and thus the cell/cell interaction, cell adhesion, and cell migration. However, potential application of glycoengineering in pharmaceutical sciences has not been studied until recently. Here, we reported that Ac(4)ManNAc, an analog of N-acetyl-D-mannosamine (ManNAc), could affect cell responses to anticancer drugs. Although cells from different tissues and organs responded to Ac(4)ManNAc treatment differently, treated cells with increased sialic acid contents showed dramatically reduced sensitivity (up to 130 times) to anti-cancer drugs as tested on various drugs with distinct chemical structures and acting mechanisms. Neither increased P-glycoprotein activity nor decreased drug uptake was observed during the course of Ac(4)ManNAc treatment. However, greatly altered intracellular drug distributions were observed. Most intracellular daunorubicin was found in the perinuclear region, but not the expected nuclei in the Ac(4)ManNAc treated cells. Since sialoglycoproteins and gangliosides were synthesized in the Golgi, intracellular glycans affected intracellular signal transduction and drug distributions seem to be the main reason for Ac(4)ManNAc affected cell sensitivity to anticancer drugs. It was interesting to find that although Ac(4)ManNAc treated breast cancer cells (MDA-MB-231) maintained the same sensitivity to 5-Fluorouracil, the IC(50) value of 5-Fluorouracil to the same Ac(4)ManNAc treated normal cells (MCF-10A) was increased by more than 20 times. Thus, this Ac(4)ManNAc treatment enlarged drug response difference between normal and tumor cells provides a unique opportunity to further improve the selectivity and therapeutic efficiency of anticancer drugs.

Monolayer coated gold nanoparticles for delivery applications

Gold nanoparticles (AuNPs) provide attractive vehicles for delivery of drugs, genetic materials, proteins, and small molecules. AuNPs feature low core toxicity coupled with the ability to parametrically control particle size and surface properties. In this review, we focus on engineering of the AuNP surface monolayer, highlighting recent advances in tuning monolayer structures for efficient delivery of drugs and biomolecules. This review covers two broad categories of particle functionalization, organic monolayers and biomolecule coatings, and discusses their applications in drug, DNA/RNA, protein and small molecule delivery.

Designing a binding interface for control of cancer cell adhesion via 3D topography and metabolic oligosaccharide engineering

This study combines metabolic oligosaccharide engineering (MOE), a technology where the glycocalyx of living cells is endowed with chemical features not normally found in sugars, with custom-designed three-dimensional biomaterial substrates to enhance the adhesion of cancer cells and control their morphology and gene expression. Specifically, Ac(5)ManNTGc, a thiol-bearing analog of N-acetyl-d-mannosamine (ManNAc) was used to introduce thiolated sialic acids into the glycocalyx of human Jurkat T-lymphoma derived cells. In parallel 2D films and 3D electrospun nanofibrous scaffolds were prepared from polyethersulfone (PES) and (as controls) left unmodified or aminated. Alternately, the materials were malemided or gold-coated to provide bio-orthogonal binding partners for the thiol groups newly expressed on the cell surface. Cell attachment was modulated by both the topography of the substrate surface and by the chemical compatibility of the binding interface between the cell and the substrate; a substantial increase in binding for normally non-adhesive Jurkat line for 3D scaffold compared to 2D surfaces with an added degree of adhesion resulting from chemoselective binding to malemidede-derivatived or gold-coated surfaces. In addition, the morphology of the cells attached to the 3D scaffolds via MOE-mediated adhesion was dramatically altered and the expression of genes involved in cell adhesion changed in a time-dependent manner. This study showed that cell adhesion could be enhanced, gene expression modulated, and cell fate controlled by introducing the 3D topograhical cues into the growth substrate and by creating a glycoengineered binding interface where the chemistry of both the cell surface and biomaterials scaffold was controlled to facilitate a new mode of carbohydrate-mediated adhesion.

Lectin microarrays for glycomic analysis

Glycomics is the study of comprehensive structural elucidation and characterization of all glycoforms found in nature and their dynamic spatiotemporal changes that are associated with biological processes. Glycocalyx of mammalian cells actively participate in cell-cell, cell-matrix, and cell-pathogen interactions, which impact embryogenesis, growth and development, homeostasis, infection and immunity, signaling, malignancy, and metabolic disorders. Relative to genomics and proteomics, glycomics is just growing out of infancy with great potential in biomedicine for biomarker discovery, diagnosis, and treatment. However, the immense diversity and complexity of glycan structures and their multiple modes of interactions with proteins pose great challenges for development of analytical tools for delineating structure function relationships and understanding glyco-code. Several tools are being developed for glycan profiling based on chromatography, mass spectrometry, glycan microarrays, and glyco-informatics. Lectins, which have long been used in glyco-immunology, printed on a microarray provide a versatile platform for rapid high throughput analysis of glycoforms of biological samples. Herein, we summarize technological advances in lectin microarrays and critically review their impact on glycomics analysis. Challenges remain in terms of expansion to include nonplant derived lectins, standardization for routine clinical use, development of recombinant lectins, and exploration of plant kingdom for discovery of novel lectins.