In situ forming chitosan hydrogels: Preliminary evaluation of the in vivo inflammatory response

Antioxidative, Anti-Inflammatory, Antibacterial, Photo-Cross-Linkable Hydrogel of Gallic Acid-Chitosan Methacrylate: Synthesis, In Vitro, and In Vivo Assessments

Chitosan (CS)-based photo-cross-linkable hydrogels have gained increasing attention in biomedical applications. In this study, we grafted CS with gallic acid (GA) by carbodiimide chemistry to prepare the GA-CS conjugate, which was subsequently modified with methacrylic anhydride (MA) modification to obtain the methacrylated GA-CS conjugate (GA-CS-MA). Our results demonstrated that the GA-CS-MA hydrogel not only exhibited improved physicochemical properties but also showed antibacterial, antioxidative, and anti-inflammatory capacity. It showed moderate antibacterial activity and especially showed a more powerful inhibitory effect against Gram-positive bacteria. It modulated macrophage polarization, downregulated pro-inflammatory gene expression, upregulated anti-inflammatory gene expression, and significantly reduced reactive oxygen species (ROS) and nitric oxide (NO) production under lipopolysaccharide (LPS) stimulation. Subcutaneously implanted GA-CS-MA hydrogels induced significantly lower inflammatory responses, as evidenced by less inflammatory cell infiltration, thinner fibrous capsule, and predominately promoted M2 polarization. This study provides a feasible strategy to prepare CS-based photo-cross-linkable hydrogels with improved physicochemical properties for biomedical applications.

Unraveling and Harnessing the Immune Response at the Cell-Biomaterial Interface for Tissue Engineering Purposes

Biomaterials are defined as "engineered materials" and include a range of natural and synthetic products, designed for their introduction into and interaction with living tissues. Biomaterials are considered prominent tools in regenerative medicine that support the restoration of tissue defects and retain physiologic functionality. Although commonly used in the medical field, these constructs are inherently foreign toward the host and induce an immune response at the material-tissue interface, defined as the foreign body response (FBR). A strong connection between the foreign body response and tissue regeneration is suggested, in which an appropriate amount of immune response and macrophage polarization is necessary to trigger autologous tissue formation. Recent developments in this field have led to the characterization of immunomodulatory traits that optimizes bioactivity, the integration of biomaterials and determines the fate of tissue regeneration. This review addresses a variety of aspects that are involved in steering the inflammatory response, including immune cell interactions, physical characteristics, biochemical cues, and metabolomics. Harnessing the advancing knowledge of the FBR allows for the optimization of biomaterial-based implants, aiming to prevent damage of the implant, improve natural regeneration, and provide the tools for an efficient and successful in vivo implantation.

Chitosan/polydopamine/octacalcium phosphate composite microcarrier simulates natural bone components to induce osteogenic differentiation of stem cells

Natural polymers and minerals can be combined to simulate natural bone for repairing bone defects. However, bone defects are often irregular and pose challenges for their repair. To overcome these challenges, we prepared Chitosan/Polydopamine/Octacalcium phosphate (CS/PDA/OCP) microcarriers that mimic bone composition and micro-size to adapt to different bone defect defects. CS/PDA microspheres were prepared by emulsion phase separation method and PDA in-situ polymerization. Finally, it was used to adsorb and immobilize OCP particles, resulting in the preparation of CS/PDA/OCP composite microcarriers. The microcarriers maintain an interconnected porous structure and appropriate porosity, which promotes cell adhesion, proliferation, and nutrient exchange. Subsequently, the protein adsorption capacity, simulated degradation, cell adhesion and proliferation capacity of the composite microcarriers were investigated. Additionally, their ability to simulate mineralization and induce osteogenic differentiation of BMSCs was characterized. The results demonstrated that the composite microcarrier had good biocompatibility and was conducive to cell adhesion and proliferation. Moreover, ALP and ARS staining revealed that the addition of OCP significantly enhanced the osteogenic differentiation of BMSCs. These results indicate that the composite microcarrier has promising prospects for bone repair applications.

A novel transdermal delivery route for energy supplements: Electrospun chitosan/polyvinyl alcohol nanofiber patches loaded with vitamin B12

Nanofibrous patches have attracted much attention as a solution to resolve drug delivery challenges. In this study, vitamin B₁₂- loaded polyvinyl alcohol (PVA)/chitosan (Cs) nanofiber patch (NFP) was electrospun and cross-linked by glutaraldehyde (GA). The physicochemical properties of the nanofiber patches were assessed by morphological studies, FTIR analysis, hydrophilicity test, mechanical tests, and in-vitro evaluations including biodegradability, MTT assay, and cumulative release test of vitamin. In-vivo studies were also carried out by measuring vitamin B₁₂ levels in the bloodstream and conducting histopathology studies on the animal models. The results showed that the mean diameter of Cs/PVA/B₁₂ and cross-linked patch were approximately 207 and 256 nm, respectively. Cross-linking of NFP led to the lower, slower, and more continuous release of the vitamin with a slight decrease in biodegradability, and an increase in the mechanical properties of the nanofiber patches. Furthermore, the cytocompatibility assay, MTT, and in vivo results revealed no cytotoxicity of Cs/PVA/B₁₂ NFP towards L929 cell line. No lesion or tissue damage was observed in the skin tissue of the animal models wearing these skin patches. Therefore, B₁₂-loaded NFP can be introduced as a potential candidate for commercial transdermal routes.

Using rheological monitoring to determine the gelation kinetics of chitosan-based systems

The modeling of polymeric reactions is a topic of large interest. The gelation reactions that may result from self-crosslinking or hybrid (agent based-) crosslinking are examples with interest specially in biomaterials applications. The composition of polymer entities during the reaction is hard to follow, and their concentration is not a good measure of the system dynamics. One alternative is monitoring the rheological behavior of the reacting mass, and relate the elastic modulus of the mixture with the rheological degree of conversion. In this paper we use rheological data to fit Malkin and Kulichikin (1996) [1] based models to describe the crosslinking of chitosan. First, the self-crosslinking of chitosan is considered. Then, the agent-based crosslinking reaction promoted by genipin is addressed. We use dynamical rheological data to fit the reaction models. The model fitting problem generated using Maximum Likelihood principle with heteroscedastic prediction error variance is formulated as a Dynamic Optimization problem and subsequently solved with a sequential approach. Parametric confidence regions are computed using the linear approximation of the covariance matrix at the optimum. Further, the parameters correlation matrix is also determined and used to qualitatively infer about the practical identifiability. The reaction order obtained for self-crosslinking kinetics is 1.3375 ± (0.0151) - approximately of first order -, and is 2.2402 ± (0.0373) for hybrid crosslinking (approximately of second order). In both cases we prove the error variance model is heteroskedastic and the model is identifiable. The approach proposed herein can be extended to other polymer systems.

Graphene Oxide Oxygen Content Affects Physical and Biological Properties of Scaffolds Based on Chitosan/Graphene Oxide Conjugates

Tissue engineering is a highly interdisciplinary field of medicine aiming at regenerating damaged tissues by combining cells with porous scaffolds materials. Scaffolds are templates for tissue regeneration and should ensure suitable cell adhesion and mechanical stability throughout the application period. Chitosan (CS) is a biocompatible polymer highly investigated for scaffold preparation but suffers from poor mechanical strength. In this study, graphene oxide (GO) was conjugated to chitosan at two weight ratios 0.3% and 1%, and the resulting conjugates were used to prepare composite scaffolds with improved mechanical strength. To study the effect of GO oxidation degree on scaffold mechanical and biological properties, GO samples at two different oxygen contents were employed. The obtained GO/CS scaffolds were highly porous and showed good swelling in water, though to a lesser extent than pure CS scaffold. In contrast, GO increased scaffold thermal stability and mechanical strength with respect to pure CS, especially when the GO at low oxygen content was used. The scaffold in vitro cytocompatibility using human primary dermal fibroblasts was also affected by the type of used GO. Specifically, the GO with less content of oxygen provided the scaffold with the best biocompatibility.

Nitrosalicyl-imine-chitosan hydrogels based drug delivery systems for long term sustained release in local therapy

The paper focuses on the synthesis and characterization of new drug delivery systems for local therapy. They were prepared by in situ hydrogelation of chitosan biopolymer with nitrosalicylaldehyde in the presence of a model drug, varying the crosslinking density. The structural, supramolecular and morphological characteristics of the systems were studied by FTIR spectroscopy, X-ray diffraction and, POM and SEM microscopy. In vitro release of the drug has been explored in simulated physiological conditions and in vivo release was investigated by the somatic pain model on rats. Information on the biodegradation of the systems was gain by simulating experiments of enzymatic degradation. The systems were biodegradable and showed a prolonged drug release, assuring an in vivo efficient therapeutic effect over 5 days, with no systemic toxicity. All these findings demonstrated that the new hydrogels based on nitrosalicyl-imine-chitosan provides a practical approach for sustained drug delivery for local chemotherapy.

Synthesis and Application of Scaffolds of Chitosan-Graphene Oxide by the Freeze-Drying Method for Tissue Regeneration

Several biomaterials, including natural polymers, are used to increase cellular interactions as an effective way to treat bone injuries. Chitosan (CS) is one of the most studied biocompatible natural polymers. Graphene oxide (GO) is a carbon-based nanomaterial capable of imparting desired properties to the scaffolds. In the present study, CS and GO were used for scaffold preparation. CS was extracted from the mycelium of the fungus Aspergillus niger. On the other hand, GO was synthesized using an improved Hummers-Offemann method and was characterized by Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, atomic force microscopy (AFM), X-ray diffraction (XRD), and dynamic light scattering (DLS). Subsequently, three formulations (GO 0%, 0.5%, and 1%) were used to prepare the scaffolds by the freeze-drying technique. The scaffolds were characterized by FTIR, thermogravimetric analysis (TGA), and scanning electron microscopy (SEM), to determine their thermal stability and pore size, demonstrating that their stability increased with the increase of GO amount. Finally, the scaffolds were implanted, recollected 30 days later, and studied with an optical microscope, which evidenced the recovery of the tissue architecture and excellent biocompatibility. Hence, these results strongly suggested the inherent nature of chitosan/graphene oxide (CS/GO) scaffolds for their application in bone tissue regeneration.

Macrophage phenotype switch by sequential action of immunomodulatory cytokines from hydrogel layers on titania nanotubes

Inflammatory response occurring between tissues and implants after implantation has attracted increasing attention because it can cause local tissue necrosis and even implant failure. Macrophages play a key role in all stages of inflammation. Pro-inflammatory (M1) and anti-inflammatory (M2) macrophages comprise two main phenotypes and the switch from M1 to M2 at specific time points is important for wound healing and tissue regeneration. Therefore, we hypothesized that biomaterial systems capable of facilitating macrophage phenotype switching should attenuate inflammation and enhance healing. To this end, a system of double hydrogel layers on titania nanotubes (TNT) was prepared as reservoir to modulate the release of interleukin-4 (IL-4) and interferon-γ (IFN-γ). In this system, IL-4, an anti-inflammatory cytokine, was loaded in TNT and IFN-γ, a pro-inflammatory cytokine, was located between two hydrogel layers of chitosan/β-glycerophosphate disodium and carboxymethyl chitosan/genipin. IFN-γ released rapidly in 3 days, whereas IL-4 exhibited a sustained release profile. In culture with mesenchymal stem cells and macrophages, this system displayed good cytocompatibility and significantly promoted cell proliferation. Macrophage phenotype switch was determined by ELISA, FACS and PCR. The results manifested that IFN-γ released from the system stimulated switching of macrophages to M1 in 3 days, whereas sustained release of IL-4 polarized macrophages to M2 after 4 days. This system can modulate macrophage phenotype switching from M1 to M2 by sequential action of the two cytokines, and might be used to research immune response between tissues and implants. The present study also provided a novel strategy for designing functional biomaterials.

Physicochemical and pharmacokinetic properties of polymeric films loaded with cisplatin for the treatment of malignant pleural mesothelioma

Background

Malignant mesothelioma is an invasive neoplasm arising from mesothelial surfaces of the pleural and peritoneal cavities. Mesothelioma treatment is unsatisfactory and recurrence is common. Here an innovative locoregional treatment for malignant pleural mesothelioma is presented.

Methods

Chitosan- and hyaluronate-based films were loaded with 0.5% and 4% w/w cisplatin and were studied for their physicochemical, mechanical and drug release characteristics. The performance of the drug delivery systems was assessed in vitro on A549 cells and on an orthotopic model of MPM recurrence in rats.

Results

Polysaccharide films produced were thin, flexible and resistant. Cisplatin was completely released from hyaluronic acid films within 96 hours, while drug release was found to be much more prolonged with chitosan films. The drug released from hyaluronate films was effective against A549 cell line, while for chitosan films the release was too slow to produce cytotoxicity. Similarly, cisplatin-loaded chitosan films in vivo released minimal quantities of cisplatin and induced inflammation and foreign body reaction. Cisplatin-loaded hyaluronate acid films on the contrary were able to prevent tumor recurrence. The cisplatin-loaded hyaluronate films provided higher C_max and AUC compared to a solution of cisplatin administered intrapleurally, but did not show any sign of treatment related toxicity.

Conclusions

Hyaluronate-based films appear as an optimal platform for the development of drug delivery systems suitable for the loco-regional post-surgical treatment of lung malignancies.