Carbohydrate-functionalized collagen matrices: design and characterization of a novel neoglycosylated biomaterial

Tyrosine glucosylation of collagen films exploiting Horseradish Peroxidase (HRP)

The development of human tissue models for regenerative medicine and animal-free drug screening requires glycosylated biomaterials such as collagen. An easy and fast biomaterial glycosylation method exploiting Horseradish Peroxidase (HRP) phenol coupling reaction is proposed. The protocol is adaptable to any polymer functionalized with phenol residues or tyrosine containing proteins. As a model the tyrosine residues on collagen films were functionalized with salidroside, a natural β-glucoside with a phenol in the aglycone. Scanning Electron Microscope (SEM) and contact angle analysis revealed the influence of glycosylation on the sample's morphology and wettability. Preliminary biological evaluation showed the cytocompatibility of the glucosylated collagen films.

Bioconjugation of Carbohydrates to Gelatin Sponges Promoting 3D Cell Cultures

Gelatin sponges are widely employed as hemostatic agents, and are gaining increasing interest as 3D scaffolds for tissue engineering. To broaden their possible application in the field of tissue engineering, a straightforward synthetic protocol able to anchor the disaccharides, maltose and lactose, for specific cell interactions was developed. A high conjugation yield was confirmed by ¹H-NMR and FT-IR spectroscopy, and the morphology of the resulting decorated sponges was characterized by SEM. After the crosslinking reaction, the sponges preserve their porous structure as ascertained by SEM. Finally, HepG2 cells cultured on the decorated gelatin sponges show high viability and significant differences in the cellular morphology as a function of the conjugated disaccharide. More spherical morphologies are observed when cultured on maltose-conjugated gelatin sponges, while a more flattened aspect is discerned when cultured onto lactose-conjugated gelatin sponges. Considering the increasing interest in small-sized carbohydrates as signaling cues on biomaterial surfaces, systematic studies on how small carbohydrates might influence cell adhesion and differentiation processes could take advantage of the described protocol.

Differential glycosylation of collagen modulates lung cancer stem cell subsets through β1 integrin-mediated interactions

In lung cancer, CD133+ cells represent the subset of cancer stem cells (CSC) able to sustain tumor growth and metastatic dissemination. CSC function is tightly regulated by specialized niches composed of both stromal cells and extracellular matrix (ECM) proteins, mainly represented by collagen. The relevance of collagen glycosylation, a fundamental post-translational modification controlling several biological processes, in regulating tumor cell phenotype remains, however, largely unexplored. To investigate the bioactive effects of differential ECM glycosylation on lung cancer cells, we prepared collagen films functionalized with glucose (Glc-collagen) and galactose (Gal-collagen) exploiting a neoglycosylation approach based on a reductive amination of maltose and lactose with the amino residues of collagen lysines. We demonstrate that culturing of tumor cells on collagen determines a glycosylation-dependent positive selection of CSC and triggers their expansion/generation. The functional relevance of CD133+ CSC increase was validated in vivo, proving an augmented tumorigenic and metastatic potential. High expression of integrin β1 in its active form is associated with an increased proficiency of tumor cells to sense signaling from glycosylated matrices (glyco-collagen) and to acquire stemness features. Accordingly, inhibition of integrin β1 in tumor cells prevents CSC enrichment, suggesting that binding of integrin β1 to Glc-collagen subtends CSC expansion/generation. We provide evidence suggesting that collagen glycosylation could play an essential role in modulating the creation of a niche favorable for the generation and selection/survival of lung CSC. Interfering with this crosstalk may represent an innovative therapeutic strategy for lung cancer treatment.

Neoglycosylated Collagen: Effect on Neuroblastoma F-11 Cell Lines

The regeneration of the nervous system is a challenging task. Currently, regenerative medicine approaches that exploit nature-inspired cues are being studied and hold great promise. The possibility to use protein-based matrices functionalized with small oligo- and monosaccharides is of interest since these can be finely tuned to better mimic the native environment. Collagen has been selected as a promising material that has the potential to be further tailored to incorporate carbohydrates in order to drive cell behavior towards neuroregeneration. Indeed, the grafting of carbohydrates to collagen 2D matrices is proved to enhance its biological significance. In the present study, collagen 2D matrices were grafted with different carbohydrate epitopes, and their potential to drive F-11 neuroblastoma cells towards neuronal differentiation was evaluated. Collagen functionalized with α-glucosides was able to differentiate neuroblastoma cells into functional neurons, while sialyl α-(2→6)-galactosides stimulated cell proliferation.

Recent Development in the Fabrication of Collagen Scaffolds for Tissue Engineering Applications: A Review

Tissue engineering focuses on developing biological substitutes to restore, maintain or improve tissue functions. The three main components of its application are scaffold, cell and growthstimulating signals. Scaffolds composed of biomaterials mainly function as the structural support for ex vivo cells to attach and proliferate. They also provide physical, mechanical and biochemical cues for the differentiation of cells before transferring to the in vivo site. Collagen has been long used in various clinical applications, including drug delivery. The wide usage of collagen in the clinical field can be attributed to its abundance in nature, biocompatibility, low antigenicity and biodegradability. In addition, the high tensile strength and fibril-forming ability of collagen enable its fabrication into various forms, such as sheet/membrane, sponge, hydrogel, beads, nanofibre and nanoparticle, and as a coating material. The wide option of fabrication technology together with the excellent biological and physicochemical characteristics of collagen has stimulated the use of collagen scaffolds in various tissue engineering applications. This review describes the fabrication methods used to produce various forms of scaffolds used in tissue engineering applications.

A New Approach for Glyco-Functionalization of Collagen-Based Biomaterials

The cell microenvironment plays a pivotal role in mediating cell adhesion, survival, and proliferation in physiological and pathological states. The relevance of extracellular matrix (ECM) proteins in cell fate control is an important issue to take into consideration for both tissue engineering and cell biology studies. The glycosylation of ECM proteins remains, however, largely unexplored. In order to investigate the physio-pathological effects of differential ECM glycosylation, the design of affordable chemoselective methods for ECM components glycosylation is desirable. We will describe a new chemoselective glycosylation approach exploitable in aqueous media and on non-protected substrates, allowing rapid access to glyco-functionalized biomaterials.

Chemoenzymatic Synthesis of Branched Glycopolymer Brushes as the Artificial Glycocalyx for Lectin Specific Binding

The artificial glycocalyx fabricated by carbohydrates is of interest because it provides a platform to simulate the cell membranes that widely exist in the nature, and thus enable extensive applications to be implantable in bioengineering. Here, we present a green strategy combining two polymerization techniques, surface-initiated atom transfer radical polymerization (SI-ATRP) and enzyme-catalyzed elongation of polysaccharide, for fabricating densely packed branched glycopolymer brushes on the gold surface as the artificial glycocalyx. In this strategy, SI-ATRP is first performed to graft a linear polymer chain for anchoring maltose, which can be used as an enzyme acceptor for dextransucrase (DSase). Under DSase, a branched polysaccharide is efficiently formed through elongation of a sucrose substrate. Undoubtedly, enzymatic transglycosylation has unique advantages, such as being green, regio-, and stereo-selective, etc. The process of DSase-catalyzed polysaccharide is well monitored by a quartz crystal microbalance, and the grafting density of the glycopolymer brushes is estimated to be 0.7 chain nm^-2 with 23.0 nm dry thickness. The polysaccharide brushes display a branched structure consisting of α-d-glucose residues with 5% of α-1,3-linked shorter chain branches, and the branched structure is well characterized by X-ray photoelectron spectroscopy, time-of-flight secondary ion mass spectrometry, Fourier transform infrared/mirror reflection, water contact angle analysis, and atomic force microscopy. Compared with the linear maltose-anchored brushes, the branched glycopolymer analog prepared here shows high specific binding capacity of concanavalin A recognition, which should be of use in biomedical application.

Achieving Controlled Biomolecule-Biomaterial Conjugation

The conjugation of biomolecules can impart materials with the bioactivity necessary to modulate specific cell behaviors. While the biological roles of particular polypeptide, oligonucleotide, and glycan structures have been extensively reviewed, along with the influence of attachment on material structure and function, the key role played by the conjugation strategy in determining activity is often overlooked. In this review, we focus on the chemistry of biomolecule conjugation and provide a comprehensive overview of the key strategies for achieving controlled biomaterial functionalization. No universal method exists to provide optimal attachment, and here we will discuss both the relative advantages and disadvantages of each technique. In doing so, we highlight the importance of carefully considering the impact and suitability of a particular technique during biomaterial design.

Gelatin-Based Photocurable Hydrogels for Corneal Wound Repair

In this study, an injectable, photocurable gelatin system, consisting of acrylated gelatin and thiolated gelatin, with tunable mechanical, biodegradation, and biological properties was used as a potential cell-supportive scaffold for the repair of focal corneal wounds. The mechanical property of hydrogels can be readily modified (postcure shear modulus of between 0.3 and 22 kPa) by varying the ratio of acrylate to thiol groups, photointensity, and solid content, and the biodegradation times also varied with the change of solid content. More importantly, the generated hydrogels exhibited excellent cell viability in both cell seeding and cell encapsulation experiments. Furthermore, the hydrogels were found to be biocompatible with rabbit cornea and aided the regeneration of a new tissue under a focal corneal wound (exhibiting epithelial wound coverage in <3d), and ultraviolet irradiation did not have any obvious harmful effect on the cornea and posterior eye segment tissues. Along with their injectability and tunable mechanical properties, the photocurable thiol-acrylate hydrogels showed promise as corneal substitutes or substrates to construct a new corneal tissue.

Sugared biomaterial binding lectins: achievements and perspectives

Lectins, a distinct group of glycan-binding proteins, play a prominent role in the immune system ranging from pathogen recognition and tuning of inflammation to cell adhesion or cellular signalling. The possibilities of their detailed study expanded along with the rapid development of biomaterials in the last decade. The immense knowledge of all aspects of glycan-lectin interactions both in vitro and in vivo may be efficiently used in bioimaging, targeted drug delivery, diagnostic and analytic biological methods. Practically applicable examples comprise photoluminescence and optical biosensors, ingenious three-dimensional carbohydrate microarrays for high-throughput screening, matrices for magnetic resonance imaging, targeted hyperthermal treatment of cancer tissues, selective inhibitors of bacterial toxins and pathogen-recognising lectin receptors, and many others. This review aims to present an up-to-date systematic overview of glycan-decorated biomaterials promising for interactions with lectins, especially those applicable in biology, biotechnology or medicine. The lectins of interest include galectin-1, -3 and -7 participating in tumour progression, bacterial lectins from Pseudomonas aeruginosa (PA-IL), E. coli (Fim-H) and Clostridium botulinum (HA33) or DC-SIGN, receptors of macrophages and dendritic cells. The spectrum of lectin-binding biomaterials covered herein ranges from glycosylated organic structures, calixarene and fullerene cores over glycopeptides and glycoproteins, functionalised carbohydrate scaffolds of cyclodextrin or chitin to self-assembling glycopolymer clusters, gels, micelles and liposomes. Glyconanoparticles, glycan arrays, and other biomaterials with a solid core are described in detail, including inorganic matrices like hydroxyapatite or stainless steel for bioimplants.

Concise Review: Biomimetic Functionalization of Biomaterials to Stimulate the Endogenous Healing Process of Cartilage and Bone Tissue

Musculoskeletal reconstruction is an ongoing challenge for surgeons as it is required for one out of five patients undergoing surgery. In the past three decades, through the close collaboration between clinicians and basic scientists, several regenerative strategies have been proposed. These have emerged from interdisciplinary approaches that bridge tissue engineering with material science, physiology, and cell biology. The paradigm behind tissue engineering is to achieve regeneration and functional recovery using stem cells, bioactive molecules, or supporting materials. Although plenty of preclinical solutions for bone and cartilage have been presented, only a few platforms have been able to move from the bench to the bedside. In this review, we highlight the limitations of musculoskeletal regeneration and summarize the most relevant acellular tissue engineering approaches. We focus on the strategies that could be most effectively translate in clinical practice and reflect on contemporary and cutting‐edge regenerative strategies in surgery. Stem Cells Translational Medicine2017;6:2186–2196

A model study for tethering of (bio)active molecules to biomaterial surfaces through arginine

A new approach for tethering of bioactive molecules via arginine is proposed and validated on collagen 2D matrices. The method involves the introduction of a methyl ketone on arginine side-chains, followed by reaction with model alkoxyamino derivatives.

Response of osteoblast-like MG63 on neoglycosylated collagen matrices

Collagen matrices modified in order to expose galactose residues to cells were studied for their interaction with osteosarcoma-derived cell line MG63.