Heparin Mimic Material Derived from Cellulose Nanocrystals

A review on multifaceted biomedical applications of heparin nanocomposites: Progress and prospects

Advances in polymer-based nanocomposites have revolutionized biomedical applications over the last two decades. Heparin (HP), being a highly bioactive polymer of biological origin, provides strong biotic competence to the nanocomposites, broadening the horizon of their applicability. The efficiency, biocompatibility, and biodegradability properties of nanomaterials significantly improve upon the incorporation of heparin. Further, inclusion of structural/chemical derivatives, fractionates, and mimetics of heparin enable fabrication of versatile nanocomposites. Modern nanotechnological interventions have exploited the inherent biofunctionalities of heparin by formulating various nanomaterials, including inorganic/polymeric nanoparticles, nanofibers, quantum dots, micelles, liposomes, and nanogels ensuing novel functionalities targeting diverse clinical applications involving drug delivery, wound healing, tissue engineering, biocompatible coatings, nanosensors and so on. On this note, the present review explicitly summarises the recent HP-oriented nanotechnological developments, with a special emphasis on the reported successful engagement of HP and its derivatives/mimetics in nanocomposites for extensive applications in the laboratory and health-care facility. Further, the advantages and limitations/challenges specifically associated with HP in nanocomposites, undertaken in this current review are quintessential for future innovations/discoveries pertaining to HP-based nanocomposites.

Control of tissue homeostasis by the extracellular matrix: Synthetic heparan sulfate as a promising therapeutic for periodontal health and bone regeneration

Proteoglycans are core proteins associated with carbohydrate/sugar moieties that are highly variable in disaccharide composition, which dictates their function. These carbohydrates are named glycosaminoglycans, and they can be attached to proteoglycans or found free in tissues or on cell surfaces. Glycosaminoglycans such as hyaluronan, chondroitin sulfate, dermatan sulfate, keratan sulfate, and heparin/heparan sulfate have multiple functions including involvement in inflammation, immunity and connective tissue structure, and integrity. Heparan sulfate is a highly sulfated polysaccharide that is abundant in the periodontium including alveolar bone. Recent evidence supports the contention that heparan sulfate is an important player in modulating interactions between damage associated molecular patterns and inflammatory receptors expressed by various cell types. The structure of heparan sulfate is reported to dictate its function, thus, the utilization of a homogenous and structurally defined heparan sulfate polysaccharide for modulation of cell function offers therapeutic potential. Recently, a chemoenzymatic approach was developed to allow production of many structurally defined heparan sulfate carbohydrates. These oligosaccharides have been studied in various pathological inflammatory conditions to better understand their function and their potential application in promoting tissue homeostasis. We have observed that specific size and sulfation patterns can modulate inflammation and promote tissue maintenance including an anabolic effect in alveolar bone. Thus, new evidence provides a strong impetus to explore heparan sulfate as a potential novel therapeutic agent to treat periodontitis, support alveolar bone maintenance, and promote bone formation.

Trackable and highly fluorescent nanocellulose-based printable bio-resins for image-guided tissue regeneration

Dynamic tracking of cell migration during tissue regeneration remains challenging owing to imaging techniques that require sophisticated devices, are often lethal to healthy tissues. Herein, we developed a 3D printable non-invasive polymeric hydrogel based on 2,2,6,6-(tetramethylpiperidin-1-yl) oxyl (TEMPO)-oxidized nanocellulose (T-CNCs) and carbon dots (CDs) for the dynamic tracking of cells. The as-prepared T-CNC@CDs were used to fabricate a liquid bio-resin containing gelatin methacryloyl (GelMA) and polyethylene glycol diacrylate (GPCD) for digital light processing (DLP) bioprinting. The shear-thinning properties of the GPCD bio-resin were further improved by the addition of T-CNC@CDs, allowing high-resolution 3D printing and bioprinting of human cells with higher cytocompatibility (viability ∼95 %). The elastic modulus of the printed GPCD hydrogel was found to be ∼13 ± 4.2 kPa, which is ideal for soft tissue engineering. The as-fabricated hydrogel scaffold exhibited tunable structural color property owing to the addition of T-CNC@CDs. Owing to the unique fluorescent property of T-CNC@CDs, the human skin cells could be tracked within the GPCD hydrogel up to 30 days post-printing. Therefore, we anticipate that GPCD bio-resin can be used for 3D bioprinting with high structural stability, dynamic tractability, and tunable mechanical stiffness for image-guided tissue regeneration.

Polysaccharide-based C-dots and polysaccharide/C-dot nanocomposites: fabrication strategies and applications

C-dots are a new class of materials with vast applications. The synthesis of bio-based C-dots has attracted increasing attention in recent years. Polysaccharides being the most abundant natural materials with high biodegradability and no toxicity have been the focus of researchers for the synthesis of C-dots. C-dots obtained from polysaccharides are generally fabricated via thermal procedures, carbonization, and microwave pyrolysis. Small size, photo-induced electron transfer (PET), and highly adjustable luminosity behavior are the most important physical and chemical properties of C-dots. However, C-dot/polysaccharide composites can be introduced as a new generation of composites that combine the features of both C-dots and polysaccharides having a wide range of applications in biomedicines, biosensors, drug delivery systems, etc. This review demonstrates the features, raw materials, and methods used for the fabrication of C-dots derived from different polysaccharides. Furthermore, the properties, applications, and synthesis conditions of various C-dot/polysaccharide composites are discussed in detail.

Controlled Delivery and Photopatterning of Mechanical Properties in Polysaccharide Hydrogels Using Vanadium Coordination and Photochemistry

Incorporation of the transition metal ion V(V) into hydrogels has been used to impart photoresponsive behavior, which was used to tune materials properties during light irradiation. The photoreaction in QHE-cellulose/agarose hydrogels coordinated with vanadium was evidenced by a clear color change of yellow to blue through a green intermediate. This color change was attributed to the reduction of V(V) to V(IV) as described in our previous work. A concomitant oxidative breakdown of the polysaccharide chain was noticeable upon the reduction of V(V) with a decrease in stiffness (G') of the hydrogel material. This reduction of the metal ion and breakdown of polysaccharide chain induced irreversible changes in the microstructure of the hydrogel, enabling the controlled delivery of V(IV) and/or encapsulated cargo. Scanning electron microscopy studies showed an increase in pore sizes and guest cavity formation during irradiation. In addition to the significant drop in mechanical properties like storage and loss modulus in the gel materials, a viscosity drop in the polymer solution was observed through irradiation, indicating breakdown of the polysaccharide chain. A photomask can be used to create discrete patterns on these materials upon irradiation.

The Auxiliary Role of Heparin in Bone Regeneration and its Application in Bone Substitute Materials

Bone regeneration in large segmental defects depends on the action of osteoblasts and the ingrowth of new blood vessels. Therefore, it is important to promote the release of osteogenic/angiogenic growth factors. Since the discovery of heparin, its anticoagulant, anti-inflammatory, and anticancer functions have been extensively studied for over a century. Although the application of heparin is widely used in the orthopedic field, its auxiliary effect on bone regeneration is yet to be unveiled. Specifically, approximately one-third of the transforming growth factor (TGF) superfamily is bound to heparin and heparan sulfate, among which TGF-β1, TGF-β2, and bone morphogenetic protein (BMP) are the most common growth factors used. In addition, heparin can also improve the delivery and retention of BMP-2 in vivo promoting the healing of large bone defects at hyper physiological doses. In blood vessel formation, heparin still plays an integral part of fracture healing by cooperating with the platelet-derived growth factor (PDGF). Importantly, since heparin binds to growth factors and release components in nanomaterials, it can significantly facilitate the controlled release and retention of growth factors [such as fibroblast growth factor (FGF), BMP, and PDGF] in vivo. Consequently, the knowledge of scaffolds or delivery systems composed of heparin and different biomaterials (including organic, inorganic, metal, and natural polymers) is vital for material-guided bone regeneration research. This study systematically reviews the structural properties and auxiliary functions of heparin, with an emphasis on bone regeneration and its application in biomaterials under physiological conditions.

One step preparation of multifunctional poly (ether sulfone) thin films with potential for wound dressing

The increasing demand for higher-quality medical care has resulted in the obsolescence of traditional biomaterials. Medical care is currently transitioning from an era depending on single-functional biomaterials to one that is supported by multifunctional and stable biomaterials. Herein, long-lasting multifunctional poly(ether sulfone) thin films (MPFs) containing heparin-mimic groups and a quaternary ammonium compound (QAC) were prepared via semi-interpenetrating polymer network (SIPN) strategy. The MPFs, with rough surface and inner finger-like macrovoid, had better hydrophilicity and anti-protein fouling ability, as revealed by scanning electron microscopy (SEM), atomic force microscope (AFM) and water contact angle (WCA) and protein adsorption tests. The results of platelet adhesion and activation, and clotting time confirmed that the hemocompatibility of the MPFs was significantly improved. From cell culture and germ-culture test, it was noted that the overall trend of human umbilical vein endothelial cell (HUVEC) proliferation was enhanced by a combination of heparin-mimic groups and QAC, whereas the growth of Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) was significantly prohibited. In addition, the MPFs were capable of modulating the expression level of basic fibroblast growth factor (bFGF) and transforming growth factor-beta1 (TGF-β1) in fibroblast, which was beneficial to controlling the formation of hypertrophic scar. In summary, the MPFs had potential to be used in the field of wound management and the study might help guide the design of surface structure of wound dressing.

Hierarchical Structure of Cellulose Nanofibril-Based Foams Explored by Multimodal X-ray Scattering

Structural characterization techniques are fundamental to correlate the material macro-, nano-, and molecular-scale structures to their macroscopic properties and to engineer hierarchical materials. Here, we combine X-ray transmission with scanning small- and wide-angle X-ray scattering (sSWAXS) to investigate ultraporous and lightweight biopolymer-based foams using cellulose nanofibrils (CNFs) as building blocks. The power of multimodal sSWAXS for multiscale structural characterization of self-assembled CNFs is demonstrated by spatially resolved maps at the macroscale (foam density and porosity), at the nanoscale (foam structural compactness, CNF orientation in the foam walls, and CNF packing state), and at the molecular scale (cellulose crystallite dimensions). Specifically, we compare the impact of freeze–thawing–drying (FTD) fabrication steps, such as static/stirred freezing and thawing in ethanol/water, on foam structural hierarchy spanning from the molecular to the millimeter scale. As such, we demonstrate the potential of X-ray scattering imaging for hierarchical characterization of biopolymers.

Hemocompatibility, biodegradability and acute toxicity of acetylated cellulose nanocrystals of different types in comparison

Promotion of promising cellulose nanocrystals (CNC) is largely dependent on the relationship between their morphology, surface chemical composition, and supramolecular structure with toxicity, hemocompatibility, and biodegradability. This paper outlines comparative and integrated analysis of the mentioned biocompatibility aspects of partially acetylated rod-, and disc-lake morphology of CNC with crystalline cellulose allomorphs I and II. These data have also included the study of CNC obtained from the sulfuric acid solutions. The aqueous solution of all types of tested CNC has not been toxic to mice after oral administration. Morphology of internal organs has not changed. However, in case of disc-like particles, the kidney mass coefficient noticeably changed. CNC have neither triggered platelet aggregation nor destroyed the red cell membrane. Intravenous administration to rabbits has not affected the plasma clotting time. Rod-like CNC are more resistant, and the disc-like particles are more susceptible to degradation under the influence of cellulases.

Synthesis and Cytotoxicity Studies of Wood-Based Cationic Cellulose Nanocrystals as Potential Immunomodulators

Polysaccharides have been shown to have immunomodulatory properties. Modulation of the immune system plays a crucial role in physiological processes as well as in the treatment and/or prevention of autoimmune and infectious diseases. Cellulose nanocrystals (CNCs) are derived from cellulose, the most abundant polysaccharide on the earth. CNCs are an emerging class of crystalline nanomaterials with exceptional physico-chemical properties for high-end applications and commercialization prospects. The aim of this study was to design, synthesize, and evaluate the cytotoxicity of a series of biocompatible, wood-based, cationic CNCs as potential immunomodulators. The anionic CNCs were rendered cationic by grafting with cationic polymers having pendant +NMe3 and +NH3 moieties. The success of the synthesis of the cationic CNCs was evidenced by Fourier transform infrared spectroscopy, dynamic light scattering, zeta potential, and elemental analysis. No modification in the nanocrystals rod-like shape was observed in transmission electron microscopy and atomic force microscopy analyses. Cytotoxicity studies using three different cell-based assays (MTT, Neutral Red, and LIVE/DEAD®) and three relevant mouse and human immune cells indicated very low cytotoxicity of the cationic CNCs in all tested experimental conditions. Overall, our results showed that cationic CNCs are suitable to be further investigated as immunomodulators and potential vaccine nanoadjuvants.

Selection of chromatographic methods for the purification of cell culture-derived Orf virus for its application as a vaccine or viral vector

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Estimation of the isoelectric point and size of Vero cell-derived Orf virus.

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Limited dynamic binding capacity of tested Orf virus to sulfated cellulose.

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Purification of Orf virus by steric exclusion chromatography lead to 84 % recovery.

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Hydrophobic interaction chromatography suitable for Orf virus purification.

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Promising unit operations for a scalable DSP to produce Orf virus viral vectors.

In recent years, the Orf virus has become a promising tool for protective recombinant vaccines and oncolytic therapy. However, suitable methods for an Orf virus production, including up- and downstream, are very limited. The presented study focuses on downstream processing, describing the evaluation of different chromatographic unit operations. In this context, ion exchange-, pseudo-affinity- and steric exclusion chromatography were employed for the purification of the cell culture-derived Orf virus, aiming at a maximum in virus recovery and contaminant depletion. The most promising chromatographic methods for capturing the virus particles were the steric exclusion- or salt-tolerant anion exchange membrane chromatography, recovering 84 % and 86 % of the infectious virus. Combining the steric exclusion chromatography with a subsequent Capto™ Core 700 resin or hydrophobic interaction membrane chromatography as a secondary chromatographic step, overall virus recoveries of up to 76 % were achieved. Furthermore, a complete cellular protein removal and a host cell DNA depletion of up to 82 % was possible for the steric exclusion membranes and the Capto™ Core 700 combination.

The study reveals a range of possible unit operations suited for the chromatographic purification of the cell culture-derived Orf virus, depending on the intended application, i.e. a human or veterinary use, and the required purity.