Hemocompatibility of 2‐ N ‐3,6‐ O ‐sulfated chitosan films

Sulfated polysaccharide as biomimetic biopolymers for tissue engineering scaffolds fabrication: Challenges and opportunities

Sulfated polysaccharides play important roles in tissue engineering applications because of their high growth factor preservation ability and their native-like biological features. There are different sulfated polysaccharides based on different repeating units in the carbohydrate backbone, the position of the sulfate group, and the sulfation degree of the polysaccharide. These led to various sulfated polymers with different negative charge densities and resultant structure-property relationships. Since numerous reports are presented related to sulfated polysaccharide applications in tissue engineering, it is crucial to review the role of effective physicochemical and biological parameters in their usage; as well as their structure-property relationships. Within this review, we focused on the effect of naturally occurring and synthetic sulfated polysaccharides in tissue engineering applications reported in the last years, highlighting the challenges of the scaffold fabrication process, the position, and the degree of sulfate on biomedical activity. Additionally, we discussed their use in numerous in vitro and in vivo model systems.

Polysaccharide-based layer-by-layer nanoarchitectonics with sulfated chitosan for tuning anti-thrombogenic properties

The development of blood-interacting surfaces is critical to fabricate biomaterials for medical use, such as prostheses, implants, biosensors, and membranes. For instance, thrombosis is one of the leading clinical problems when polymer-based materials interact with blood. To overcome this limitation is necessary to develop strategies that limit platelets adhesion and activation. In this work, hyaluronan (HA)/chitosan (Chi) based-films, recently reported in the literature as platforms for tumor cell capture, were developed and, subsequently, functionalized with sulfated chitosan (ChiS) using a layer-by-layer technique. ChiS, when compared to native Chi, presents the unique abilities to confer anti-thrombogenic properties, to reduce protein adsorption, and also to limit calcification. Film physicochemical characterization was carried out using FTIR and XPS for chemical composition assessment, AFM for the surface morphology, and contact angle for hydrophilicity evaluation. The deposition of ChiS monolayer promoted a decrease in both roughness and hydrophilicity of the HA/Chi films. In addition, the appearance of sulfur in the chemical composition of ChiS-functionalized films confirmed the film modification. Biological assay indicated that the incorporation of sulfated groups limited platelet adhesion, mainly because a significant reduction of platelets adhesion to ChiS-functionalized films was observed compared to HA/Chi films. On balance, this work provides a new insight for the development of novel antithrombogenic biomaterials, opening up new possibilities for devising blood-interaction surfaces.

Low molecular weight sulfated chitosan efficiently reduces infection capacity of porcine circovirus type 2 (PCV2) in PK15 cells

Background

Porcine circovirus type 2 (PCV2)-associated diseases are a major problem for the swine industry worldwide. In addition to vaccines, the availability of antiviral polymers provides an efficient and safe option for reducing the impact of these diseases. By virtue of their molecular weight and repetitious structure, polymers possess properties not found in small-molecule drugs. In this perspective, we focus on chitosan, a ubiquitous biopolymer, that adjusts the molecular weight and sulfated-mediated functionality can act as an efficient antiviral polymer by mimicking PCV2-cell receptor interactions.

Methods

Sulfated chitosan (Chi-S) polymers of two molecular weights were synthesized and characterized by FTIR, SEM–EDS and elemental analysis. The Chi-S solutions were tested against PCV2 infection in PK15 cells in vitro and antiviral activity was evaluated by measuring the PCV2 DNA copy number, TCID50 and capsid protein expression, upon application of different molecular weights, sulfate functionalization, and concentrations of polymer. In addition, to explore the mode of action of the Chi-S against PCV2 infection, experiments were designed to elucidate whether the antiviral activity of the Chi-S would be influenced by when it was added to the cells, relative to the time and stage of viral infection.

Results

Chi-S significantly reduced genomic copies, TCID50 titers and capsid protein of PCV2, showing specific antiviral effects depending on its molecular weight, concentration, and chemical functionalization. Assays designed to explore the mode of action of the low molecular weight Chi-S revealed that it exerted antiviral activity through impeding viral attachment and penetration into cells.

Conclusions

These findings help better understanding the interactions of PCV2 and porcine cells and reinforce the idea that sulfated polymers, such as Chi-S, represent a promising candidates for use in antiviral therapies against PCV2-associated diseases. Further studies in swine are warranted.

Heparanized chitosans: towards the third generation of chitinous biomaterials

The functionalization of chitosans is an emerging research area in the design of solutions for a wide range of biomedical applications. In particular, the modification of chitosans to incorporate sulfate groups has generated great interest since they show structural similarity to heparin and heparan sulfates. Most of the biomedical applications of heparan sulfates are derived from their ability to bind different growth factors and other proteins, as through these interactions they can modulate the cellular response. This review aims to summarize the most recent advances in the synthesis, and structural and physicochemical characterization of heparanized chitosan, a remarkably interesting family of polysaccharides that have demonstrated the ability to mimic heparan sulfates as ligands for different proteins, thereby exerting their biological activity by mimicking the function of these glycosaminoglycans.

Protective effect against gastric mucosa injury of a sulfated agaran from Acanthophora spicifera

In this study, a polysaccharide from marine alga Acanthophora spicifera (PAs) was isolated and structurally characterized. Its protective potential against chemically-induced gastric mucosa injury was evaluated. The gel permeation chromatography experiments and spectroscopy spectrum showed that PAs is a sulfated polysaccharide with a high molecular mass (6.98 × 10⁵g/mol) and degree of sulfation of 1.23, exhibiting structural characteristic typical of an agar-type polysaccharide. Experimental results demonstrated that PAs reduced the hemorrhagic gastric injury, in a dose-dependent manner. Additionally, PAs reduced the intense gastric oxidative stress, measured by glutathione (GSH) and malondialdehyde (MDA) levels. PAs also prevented the reduction of mucus levels adhered to the gastric mucosa, promoted by the aggressive effect of ethanol. In summary, the sulfated polysaccharide from A. spicifera protected the gastric mucosa through the prevention of lipid peroxidation and enhanced the defense mechanisms of the gastric mucosa, suggesting as a promising functional food as gastroprotective agent.

Resveratrol as a plant type antioxidant modifier for polysulfone membranes to improve hemodialysis-induced oxidative stress

Resveratrol (RES) is a plant extract with excellent antioxidant, biocompatibility, anti-inflammatory and inhibition of platelet aggregation. RES-modified polysulfone (PSF) hemodialysis membranes have been fabricated using an immersion phase transformation method. The antioxidant properties of the blend membranes were evaluated in terms of their 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2'-azinobis-(3-ethylbenzothiazoline-6-sulfonate) (ABTS⁺), reactive oxygen species (ROS) free radicals scavenging, total antioxidant capacity (T-AOC) of serum and lipid peroxidation inhibition. The observed results of decreasing DPPH and ABTS⁺ levels, scavenging ROS, significant inhibition of lipid peroxidation and improving the T-AOC of serum all contribute to the recovery of oxidative balance and the use of RES as an antioxidant modifier. The antioxidant stability of PSF/RES blend membranes was also studied. Moreover, the results of blood compatibility experiments showed that the addition of RES improved the blood compatibility of PSF membrane, inhibited the adhesion of red blood cells and platelets; inhibited complement activation; and reduced the blood cells deformation rate. The dialysis simulation experiment indicated that PSF/RES membrane (M-3) can clear 90.33% urea, 89.50% creatinine, 74.60% lysozyme and retention 90.47% BSA. All these results showed the new PSF/RES blend membranes have potential to be used in the field of hemodialysis to improve oxidative stress status in patients.

Immunostimulatory effect of N-2-hydroxypropyltrimethyl ammonium chloride chitosan-sulfate chitosan complex nanoparticles on dendritic cells

In this study, we synthesized negatively charged chitosan sulfate and positively charged hydroxypropyltrimethyl ammonium chloride chitosan (HACC), and then prepared chitosan derivatives with positive and negative ions as nanoparticles (NPs) by ovalbumin encapsulation using the polyelectrolyte method. NPs with different substitution sites and molecular weights (MW) were prepared by varying conditions. We then determined the zeta potential average, diameter, encapsulation effect, and their immunostimulatory effects on dendritic cells (DCs). The results showed that chitosan-derivative NPs ranged in size from 153.33 to 320.90 nm; all NPs were positive, with charges ranging from 17.10 to 39.30 mV and the encapsulation rates of 65 %-75 %. Three NPs greatly promoted the expression and secretion of interleukin-6 (IL-6), tumor necrosis factor (TNF-α), and interleukin-1β (IL-1β) in DC cells: C2,3,6 chitosan sulfate-HACC (C2,3,6-HACC; 200 kDa), C3,6 chitosan sulfate-HACC (C3,6-HACC; 200 kDa) and C6 chitosan sulfate-HACC (C6-HACC; 50 kDa). We also found that 200-kDa C2,3,6-HACC and 50-kDa C6-HACC NPs greatly increased secretion of the major histocompatibility complex-II (MHC-II), CD40, CD80, and CD86, indicating that these NPs promote effective antigen presentation, further increasing immunity effects. Finally, we applied laser confocal photography and determined that NPs entered the cell to promote the regulation of cellular immune activity; this discovery lays a foundation for further research on their mechanism of their action. Therefore, C2,3,6-HACC and C6-HACC NPs have the potential as immunological adjuvants.