Design and synthesis of polypyrrole conductive ink based on sulfated chitosan for bactericide carbendazim detection

Conductive polymers (CPs) are typically insoluble in solvents, and devising biocompatible hydrophilic CPs is challenging and imperative to expand the applications of CPs. Herein, sulfated chitosan (SCS) is used as a green dopant instead of toxic poly(styrene sulfonate) (PSS), and SCS:polypyrrole (SCS:PPy) conductive ink is prepared by in situ polymerization. Due to the complex structure between PPy and SCS polyanion, the synthesized SCS:PPy dispersion forms a well-connected electric pathway and confers superior conductivity, dispersion stability, good film-forming ability, and high electrical stability. As proof of our concept, electrochemical sensing utilizing an SCS:PPy-modified screen-printed carbon electrode (SPCE) was performed towards carbendazim (CBZ). The SCS:PPy on the SPCE surface displayed greater sensitivity to CBZ because the conductive complex structure eased the electrocatalytic action of SCS:PPy by dramatically increasing the current intensity of CBZ oxidation and notably ameliorating stability. The sensor unveils the lowest detection value of 1.02 nM with a linear range of 0.05 to 906 μM for sensing trace CBZ by utilizing the pulse voltammetry technique. Interestingly, this senor shows excellent selectivity towards CBZ due to the formation of substantial interactions between SCS:PPy and CBZ, as demonstrated by molecular simulation studies. Furthermore, this sensor can precisely monitor CBZ in actual fruit and river water samples with satisfactory results. This study sheds light on the design and synthesis of sustainable hydrophilic CPs in the fabrication of sensors.

Sulfated Polysaccharide-Based Nanocarrier Drives Microenvironment-Mediated Cerebral Neurovascular Remodeling for Ischemic Stroke Treatment

Stroke is a leading cause of global mortality and severe disability. However, current strategies used for treating ischemic stroke lack specific targeting capabilities, exhibit poor immune escape ability, and have limited drug release control. Herein, we developed an ROS-responsive nanocarrier for targeted delivery of the neuroprotective agent rapamycin (RAPA) to mitigate ischemic brain damage. The nanocarrier consisted of a sulfated chitosan (SCS) polymer core modified with a ROS-responsive boronic ester enveloped by a red blood cell membrane shell incorporating a stroke homing peptide. When encountering high levels of intracellular ROS in ischemic brain tissues, the release of SCS combined with RAPA from nanoparticle disintegration facilitates effective microglia polarization and, in turn, maintains blood-brain barrier integrity, reduces cerebral infarction, and promotes cerebral neurovascular remodeling in a mouse stroke model involving transient middle cerebral artery occlusion (tMCAO). This work offers a promising strategy to treat ischemic stroke therapy.

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.

A versatile chitosan nanogel capable of generating AgNPs in-situ and long-acting slow-release of Ag+ for highly efficient antibacterial

Development of multifunctional antibacterial agent with long-lasting antibacterial activity and biofilm ablation performance is significant for the effective treatment of bacterial infections. Here, by utilizing the electrostatic interaction between sulfonated chitosan (SCS) and Ag⁺ and chitosan (CS), and the sodium borohydride reduction method, a versatile antibacterial agent (AgNPs@CS/SCS) capable of generating silver nanoparticles (AgNPs) in-situ and long-acting slow-release Ag⁺ was developed. AgNPs@CS/SCS has a good physiological stability and can long-acting slow-release of Ag⁺ due to the pH-dependent Ag⁺ release behavior of AgNPs. Noteworthy, AgNPs@CS/SCS can exert both excellent short- and long-term antibacterial and biofilm ablation activity. Importantly, it also exhibits superior antibacterial activity in the treatment of implant infections, accompanied by good biocompatibility. Together, this study suggest that AgNPs@CS/CSC is indeed a versatile antibacterial agent, and is expected to provide an effective treatment modality for implant infections in the clinic settings.

Sulfated chitosan rescues dysfunctional macrophages and accelerates wound healing in diabetic mice

Emerging evidence suggests that dysfunctional macrophages can cause chronic inflammation and impair tissue regeneration in diabetic wounds. Therefore, improving macrophage behaviors and functions may improve therapeutic outcomes of current treatments in diabetic wounds. Herein, we present a sulfated chitosan (SCS)-doped Collagen type I (Col I/SCS) hydrogel as a candidate for diabetic wound treatments, and assess its efficacy using streptozocin (STZ)-induced diabetic wound model. Results showed that Col I/SCS hydrogel significantly improved wound closure rate, collagen deposition, and revascularization in diabetic wounds. Flow cytometry analysis and immunofluorescent staining analysis showed that the Col I/SCS hydrogel accelerated the resolution of excessive inflammation by reducing the polarization of M1-like macrophages in chronic diabetic wounds. In addition, ELISA analysis revealed that the Col I/SCS hydrogel reduced the production of pro-inflammatory interleukin (IL)-6 and increased the production of anti-inflammatory cytokines including IL-4 and transforming growth factor-beta 1 (TGF-β1) during wound healing. Moreover, the Col I/SCS hydrogel enhanced the transdifferentiation of macrophages into fibroblasts, which enhanced the formation of collagen and the extracellular matrix (ECM) in wound tissue. We highlight a potential application of manipulating macrophages behaviors in the pathological microenvironment via materials strategy. STATEMENT OF SIGNIFICANCE: Improving the chronic inflammatory microenvironment of diabetic wounds by regulating macrophage behaviors has been of wide concern in recent years. We designed a Col I/SCS hydrogel based on Collagen type I and sulfated chitosan (SCS) without exogenous cells or cytokines, which could significantly improve angiogenesis and resolve chronic inflammation in diabetic wounds, and hence accelerate diabetic wound healing. The Col I/SCS hydrogel could facilitate the polarization of M1-to-M2 macrophages and activate the transdifferentiation of macrophages to fibroblasts. Additionally, the Col I/SCS hydrogel also equilibrated the content of pro-inflammatory and anti-inflammatory cytokines. This strategy may afford a new avenue to improve macrophage functions and accelerate diabetic chronic wound healing.

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.

Sulfated chitosan coated polylactide membrane enhanced osteogenic and vascularization differentiation in MC3T3-E1s and HUVECs co-cultures system

This study aimed to compare the effects of the two type chitosan derivatives, sulfated chitosan (SCS) and phosphorylated chitosan (PCS), coated on poly(d,l-lactide) (PDLLA) membrane via polydopamine, respectively, on vascularization and osteogenesis in vitro. Mouse preosteoblast cells (MC3T3-E1s) and human umbilical vein endothelial cells (HUVECs) were used as co-cultures system. The effects of two type membranes on calcium deposition, alkaline phosphatase (ALP) activity, vascularization related factors nitric oxide (NO) and angiogenic growth factor vascular endothelial growth factor (VEGF) were assessed. The changes of osteogenic and angiogenic related gene, and protein expression were evaluated too. In fact, SCS modified PDLLA membrane had the highest related gene and protein expression than other PDLLA membranes. Our results demonstrated that the SCS maybe a promising matrix for bone regeneration by co-cultures of ECs and OCs than PCS.

Chitosan, hydroxypropyltrimethyl ammonium chloride chitosan and sulfated chitosan nanoparticles as adjuvants for inactivated Newcastle disease vaccine

Chitosan (CS) and its water-soluble derivatives, hydroxypropyltrimethyl ammonium chloride chitosan (HACC) and sulfated chitosan (SCS), were used as adjuvants of inactivated Newcastle disease (ND) vaccine. First, NDV-loaded and blank CS, HACC/CS and SCS nanoparticles were prepared. The particle sizes were respectively 343.43 ± 4.12, 320.03 ± 0.84, 156.2 ± 9.29 nm and the zeta potentials were respectively +19.67 ± 0.58, +18.3 ± 0.5, -17.8 ± 2.65 mV under the optimal conditions. Then chickens were immunized with nanoparticles or commercial inactivated oil emulsion vaccine. After immunization, the humoral immunity levels of the chickens were evaluated. The cellular immunity levels were determined by the quantification of cytokines, lymphocyte proliferation assay, the percentages of CD4⁺ and CD8⁺ T lymphocytes. Finally, the chickens were challenged with highly virulent virus. The results demonstrated that the humoral immunity levels in NDV-loaded CS and HACC/CS nanoparticles groups were lower than commercial vaccine but the cellular immunity levels are better. Moreover, the prevention effects of NDV-loaded CS and HACC/CS nanoparticles against highly virulent NDV are comparable to commercial vaccine. Our study provides the basis of developing HACC and CS as effective vaccine adjuvants.

Manipulation of VEGF-induced angiogenesis by 2-N, 6-O-sulfated chitosan

Emerging evidence suggests that vascular endothelial growth facto (VEGF) is important in the treatment of various ischemic and cardiovascular diseases. However, it often suffers from high cost and easy deactivation with a short half-life. Here, we describe a synthetic 2-N, 6-O-sulfated chitosan (26SCS) with a high affinity to VEGF promoting the binding of the signaling protein to its VEGF receptor 2 (VEGFR2), activating receptor phosphorylation and pro-angiogenic related genes expression, and further stimulating downstream VEGF-dependent endothelial cell viability, migration, tube formation and rat aortic rings outgrowth. Interestingly, the obvious recruitment of mural cells were occurred to stabilize the sprouted microvessels. In addition, the pro-angiogenic potential of 26SCS composited VEGF was confirmed in vivo using the chick embryo chorioallantoic membrane (CAM) assay with an extensive perfusable vascular network. A longer monitoring was administered subcutaneously to mice in a biocompatible gelatin sponge and showed that VEGF with 26SCS had the capability to efficiently enhance neovascularization. These findings highlight that 26SCS, the semi-synthetic natural polymer, may be a promising coagent with VEGF for vascular therapy.

STATEMENT OF SIGNIFICANCE

Vascular endothelial growth factor (VEGF) is crucial for facilitating angiogenesis to supply oxygen and nutrient during wound healing and tissue regeneration. However, appropriate use of VEGF is an ongoing challenge due to its rapidly clearance and severe side effects at higher dosage. In this study, we described a synthetic 2-N, 6-O-sulfated chitosan (26SCS) with a high affinity to VEGF, which could significantly promote its binding capacity to VEGF receptor 2 and further stimulate the angiogenic behavior of endothelial cells. We further confirmed that 26SCS was spatially combined with VEGF in a "lying manner", and this spatial arrangement was more conducive to exposure of the receptor binding domain of VEGF. Additionally, it also promoted in vivo angiogenesis in a chicken chorioallantoic membrane assay and mouse subcutaneous implant model. This strategy may afford a new avenue to enhance pro-angiogenic capacity of VEGF.

Immunostimulatory effects of sulfated chitosans on RAW 264.7 mouse macrophages via the activation of PI3K/Akt signaling pathway

To investigate the immunostimulatory effects of chitosan sulfates, we prepared α- and β-chitosan sulfates with different molecular weights and compared their immunostimulatory activities in RAW 264.7 macrophages. Results suggest that β-chitosan sulfates were more active than α-chitosan in promoting nitric oxide (NO) production. Further study show that β-chitosan sulfate significantly promoted the production of NO, prostaglandin E₂, tumor necrosis factor (TNF)-α, interleukin-6 and interleukin-1β at the levels of transcription and translation. Moreover, Western blots revealed that it induced the phosphorylation of p85 and Akt, and the nuclear translocation of p50/p65 and c-Fos/c-Jun. The luciferase activity of cells pretreated with β-chitosan sulfate further confirmed the nuclear translocation of p50/p65 and c-Fos/c-Jun. Determination of Toll-like receptor (TLR) 4 expression suggested that β-chitosan sulfate at least partly bound to TLR4. In conclusion, β-chitosan sulfates activate RAW 264.7 cells through the PI3K-Akt pathway, which is dependent on activator protein-1 and nuclear factor-κB activation.

2-N, 6-O-sulfated chitosan-assisted BMP-2 immobilization of PCL scaffolds for enhanced osteoinduction

The aim of this study was to develop a 2-N, 6-O-sulfated chitosan (26SCS) modified electrospun fibrous PCL scaffold for bone morphogenetic protein-2 (BMP-2) delivery to improve osteoinduction. The PCL scaffold was modified by an aminolysis reaction using ethylenediamine (ED) and 26SCS was immobilized via electrostatic interactions (PCL-N-S). Scaffolds were characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and contact angle measurements. In vitro BMP-2 adsorption and release kinetics indicated that modified PCL-N-S scaffolds showed higher levels of binding of BMP-2 (about 30-100 times), moderative burst release (about one third), and prolonged releasing time compared to the unmodified PCL scaffold. The bioactivity of released BMP-2 determined by alkaline phosphatase (ALP) activity assay was maintained and improved 8-12 times with increasing concentration of immobilized 26SCS on the scaffolds. In vitro studies demonstrated that bone marrow mesenchymal stem cells (BMSCs) attached more readily to the PCL-N-S scaffolds with increased spreading. In conclusion, 26SCS modified PCL scaffolds can be a potent system for the sustained and bioactive delivery of BMP-2.