In vivo study on the biocompatibility of chitosan-hydroxyapatite film depending on degree of deacetylation

Factors influencing the antimicrobial mechanism of chitosan action and its derivatives: A review

Chitosan, a versatile amino polysaccharide biopolymer derived from chitin, exhibits broad-spectrum antimicrobial activity against various pathogenic microorganisms, including gram-negative and gram-positive bacteria, as well as fungi. Due to its ubiquitous use in medications, food, cosmetics, chemicals, and crops, it is an effective antibacterial agent. However, the antimicrobial performance of chitosan is influenced by multiple factors, which have been extensively investigated and reported in the literature. The goal of this review paper is to present a thorough grasp of the mechanisms of action and determining variables of chitosan and its derivatives' antibacterial activity. The article begins by providing a brief background on chitosan and its antimicrobial properties, followed by the importance of understanding the mechanism of action and factors influencing its activity".

In-Depth Characterization of Two Bioactive Coatings Obtained Using MAPLE on TiTaZrAg

TiZrTaAg alloy is a remarkable material with exceptional properties, making it a unique choice among various industrial applications. In the present study, two types of bioactive coatings using MAPLE were obtained on a TiZrTaAg substrate. The base coating consisted in a mixture of chitosan and bioglass in which zinc oxide and graphene oxide were added. The samples were characterized in-depth through a varied choice of methods to provide a more complete picture of the two types of bioactive coating. The analysis included Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), ellipsometry, and micro-Raman. The Vickers hardness test was used to determine the hardness of the films and the penetration depth. Film adhesion forces were determined using atomic force microscopy (AFM). The corrosion rate was highlighted by polarization curves and by using electrochemical impedance spectroscopy (EIS). The performed tests revealed that the composite coatings improve the properties of the TiZrTaAg alloy, making them feasible for future use as scaffold materials or in implantology.

Development of a membrane and a bilayer of chitosan, gelatin, and polyhydroxybutyrate to be used as wound dressing for the regeneration of rat excisional wounds

The skin is the largest organ in the human body that acts as a protective barrier from the outside environment. Certain dermatological pathologies or significant skin lesions can result in serious complications. Several studies have focused on the development of tissue-engineered skin substitutes. In this study, a new bilayer scaffold composed of a chitosan-gelatin membrane and a chitosan-polyhydroxybutyrate (PHB) porous matrix was synthesized and populated with human adipose-derived mesenchymal stem cells (hASCs) to be potentially used for wound dressing applications. By combining this membrane and porous matrix with the stem cells, we aimed to provide immunomodulation and differentiation capabilities for the wound environment, as well as mechanical strength and biocompatibility for the underlying tissue. The membrane was prepared from the mixture of chitosan and gelatin in a 2:1 ratio and the porous matrix was prepared from the mixture of chitosan and PHB, in equal proportions to form a final solution at 2.5% (m/v). Fourier transform infrared spectroscopy analysis showed the formation of blends, and micro-computed tomography, scanning electron microscopy and atomic force microscopy images demonstrated membrane roughness and matrix porosity. The MTT assay showed that the scaffolds were biocompatible with hASC. The membrane and the bilayer were used as dressing and support for cell migration in the dorsal excisional wound model in Wistar rats. Histological and gene transcriptional analyses showed that the animals that received the scaffolds regenerated the hair follicles in the deep dermis in the central region of the wound. Our results demonstrate the potential of these new biomaterials as dressings in wound healing studies, favoring tissue regeneration.

From Static to Dynamic: A Review on the Role of Mucus Heterogeneity in Particle and Microbial Transport

Mucus layers (McLs) are on the front line of the human defense system that protect us from foreign abiotic/biotic particles (e.g., airborne virus SARS-CoV-2) and lubricates our organs. Recently, the impact of McLs on human health (e.g., nutrient absorption and drug delivery) and diseases (e.g., infections and cancers) has been studied extensively, yet their mechanisms are still not fully understood due to their high variety among organs and individuals. We characterize these variances as the heterogeneity of McLs, which lies in the thickness, composition, and physiology, making the systematic research on the roles of McLs in human health and diseases very challenging. To advance mucosal organoids and develop effective drug delivery systems, a comprehensive understanding of McLs' heterogeneity and how it impacts mucus physiology is urgently needed. When the role of airway mucus in the penetration and transmission of coronavirus (CoV) is considered, this understanding may also enable a better explanation and prediction of the CoV's behavior. Hence, in this Review, we summarize the variances of McLs among organs, health conditions, and experimental settings as well as recent advances in experimental measurements, data analysis, and model development for simulations.

Using scaffolds as drug delivery systems to treat bone tumor

Surgery is the principal strategy to treat osteosarcoma and other types of bone tumors, but it causes bone defects that cannot be healed spontaneously. After surgery, patients still need to receive radiotherapy and/or chemotherapy to prevent tumor recurrence and metastasis, which leads to systemic side effects. Bone scaffolds exhibit the potentials to load cargos (drugs or growth factors) and act as drug delivery systems (DDSs) in the osteosarcoma postoperative treatment. This review introduces current types of bone scaffolds and highlights representative works using scaffolds as DDSs to treat osteosarcomas. Challenges and perspectives in the scaffold-based DDSs are also discussed. This review may provide references to develop effective and safe strategies for osteosarcoma postoperative treatment.

Early Application of Quaternized Chitin Derivatives Inhibits Hypertrophic Scar Formation

Various treatments for hypertrophic scars (HS) are applied after wound re-epithelialization. However, the lack of early intervention within the wound bed leads to poor HS treatment outcomes. In this study, quaternized chitin (QC) derivatives with different degrees of deacetylation (7.4% and 78.9%) are synthesized and their effects on HS formation are evaluated in a rabbit ear scar model. Early application of QC alleviates scar hypertrophy without delayed wound healing. Fibroblast count, collagen content, and α-smooth muscle actin expression are decreased, while matrix metalloproteinase-1 is upregulated on day 35 in the QC treatment group. QC suppresses inflammatory cell infiltration and IL-6 expression. A subsequent reduction in transforming growth factor β1 expression is also observed. The inhibitory effect of QC on HS formation is eliminated through the administration of exogenous IL-6. Taken together, early application of QC inhibits HS formation by downregulating IL-6 expression, and QC with a low degree of deacetylation tends to be more effective. Considering its potential for accelerating wound healing, inhibiting HS formation, and its antibacterial activity, QC may be used as an effective dressing in clinical wound management.

Zinc Oxide and Copper Chitosan Composite Films with Antimicrobial Activity

The role of the oral microbiome and its effect on dental diseases is gaining interest. Therefore, it has been sought to decrease the bacterial load to fight oral cavity diseases. In this study, composite materials based on chitosan, chitosan crosslinked with glutaraldehyde, chitosan with zinc oxide particles, and chitosan with copper nanoparticles were prepared in the form of thin films, to evaluate a new alternative with a more significant impact on the oral cavity bacteria. The chemical structures and physical properties of the films were characterized using by Fourier transform infrared spectroscopy (FTIR,) Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), elemental analysis (EDX), thermogravimetric analysis (TGA), X-ray diffraction (XRD), scanning electron microscopy (SEM), and contact angle measurements. Subsequently, the antimicrobial activity of each material was evaluated by agar diffusion tests. No differences were found in the hydrophilicity of the films with the incorporation of ZnO or copper particles. Antimicrobial activity was found against S. aureus in the chitosan film crosslinked with glutaraldehyde, but not in the other compositions. In contrast antimicrobial activity against S. typhimurium was found in all films. Based on the data of present investigation, chitosan composite films could be an option for the control of microorganisms with potential applications in various fields, such as medical and food industry.

Preparation and evaluation of an injectable curcumin loaded chitosan/hydroxyapatite cement

Curcumin (Cur) is an active ingredient of Curcuma longa. Cur has many pharmacological effects, such as anti-inflammation, anti-oxidation, anticoagulation, hypolipidemic, anti-angiogenesis and anti-cancer. An injectable curcumin loaded chitosan/hydroxyapatite bone cement (Cur-CS/HA) was prepared as a bone scaffold and drug delivery. Tween 20, a nonionic surfactant, was incorporated into the cement to improve the solubility of curcumin. Four types of Cur-CS/HA (Group0, Group1, Group5 and Group10) were prepared with different Tween 20 ratios (0, 1, 5 and 10%, respectively). The samples were characterized by infrared spectroscopy (IR), X-ray diffraction (XRD) and scanning electron microscope (SEM). Compression tests were carried out to evaluate the strength of the scaffolds. In addition, the inhibition assay was carried out on MG63 cells with the extracts of drug loaded materials. The results showed that Cur had an effect on the setting time (p < 0.05). Cur reduced the compressive strength of the CS/HA cement (p < 0.05). The release studies showed that Tween 20 could effectively improve the solubility of curcumin. When the Tween 20 content in cement increased from 0 to 10%, the cumulative release (30 d) of Cur increased from 5.5 to 10.6%. Moreover, the cement had good injectability, good anti-collapsibility and good biocompatibility to meet the clinical requirements. The result of inhibition assay showed that Cur-CS/HA could inhibit the proliferation of MG63 cells. Tween 20 incorporated Cur-CS/HA had great potential to use as a drug-loaded artificial bone material.

Whitlockite Granules on Bone Regeneration in Defect of Rat Calvaria

Whitlockite (WH; Ca₁₈Mg₂(HPO4)₂(PO4)₁₂) is a calcium phosphate based ceramic that contains magnesium ions. As the second most abundant mineral in living bone, WH occupies 25-35 wt % of the inorganic portion of human bone. Compared to hydroxyapatite (HAp, Ca₁₀(PO₄)₆(OH)₂), WH possesses better mechanical properties, faster resorbability, and promotion behavior on the osteogenesis. In this article, we introduced a fabrication method of interconnected porous WH granules through vacuum filtration, followed by sintering treatment based on the thermal stability of WH synthesized using the tri-solvent system. This study presents a histological, radiological, and immunohistochemical evaluation of the bone healing potential of these WH granules in a 5 mm diameter calvarial bone defect in rats. The histological evaluation shows no inflammation or foreign body reaction in the WH group. The WH group displays newly formed bone at the same thickness as the original bone. On the contrary, bone formation is not observed in the nontreated (NT) group. Besides, immunohistochemistry (IHC) confirmed that WH granules promoted bone regeneration with the significantly higher expression of bone morphogenetic proteins-2 (BMP-2), alkaline phosphatase (ALP), osteopontin (OPN), and osteocalcin (OCN) compared to the NT group without the addition of exogenous cells or growth factors. These results suggest that WH has excellent potential for application in bone tissue regeneration.

Emission-tunable probes using terbium(III)-doped self-activated luminescent hydroxyapatite for in vitro bioimaging

Lanthanide ion (Ln³⁺)-doped nanoscale hydroxyapatites (nHAp) with tunable luminescence have attracted increasing attention due to their potential applications as useful biomedical tools (e.g., imaging and clinical therapy). In this study, we reported that doping Terbium (III) ions (Tb³⁺) in self-activated luminescent nHAp via a facile hydrothermal reaction, using trisodium citrate (Cit^3-), generates unique emission-tunable probes known as Cit/Tb-nHAp. The morphology, crystal phase, and luminescence properties of these Cit/Tb-nHAp probes are studied in detail. Moreover, the results demonstrate that the luminescence of self-activated nHAp originates from the carbon dots trapped within the nHAp crystals, in which partial energy transfer occurs from carbon dots (CDs) to Tb³⁺. The color tunability is successfully achieved by regulating the addition of Cit^3-. Biocompatibility study indicates that when co-cultured with C6 glioma cells in vitro for 3 days, ≤800 ppm Cit/Tb-nHAp is not cytotoxic for C6 glioma cells. We also present in vitro data showing efficient cytoplasmic localization of transferrin conjugated Cit/Tb-nHAp into C6 glioma cells by fluorescence cell imaging. We have successfully engineered Cit/Tb-nHAp, a promising biocompatible agent for future in vitro and in vivo fluorescence bioimaging.

Electrospun Biomaterials in the Treatment and Prevention of Scars in Skin Wound Healing

Electrospinning is a promising method for the rapid and cost-effective production of nanofibers from a wide variety of polymers given the high surface area morphology of these nanofibers, they make excellent wound dressings, and so have significant potential in the prevention and treatment of scars. Wound healing and the resulting scar formation are exceptionally well-characterized on a molecular and cellular level. Despite this, novel effective anti-scarring treatments which exploit this knowledge are still clinically absent. As the process of electrospinning can produce fibers from a variety of polymers, the treatment avenues for scars are vast, with therapeutic potential in choice of polymers, drug incorporation, and cell-seeded scaffolds. It is essential to show the new advances in this field; thus, this review will investigate the molecular processes of wound healing and scar tissue formation, the process of electrospinning, and examine how electrospun biomaterials can be utilized and adapted to wound repair in the hope of reducing scar tissue formation and conferring an enhanced tensile strength of the skin. Future directions of the research will explore potential novel electrospun treatments, such as gene therapies, as targets for enhanced tissue repair applications. With this class of biomaterial gaining such momentum and having such promise, it is necessary to refine our understanding of its process to be able to combine this technology with cutting-edge therapies to relieve the burden scars place on world healthcare systems.

[Chitosan hydrogels biocompatibility improvement with the perspective of use as a base for osteoplastic materials in dentistry]

Using chitosan as the basis for osteoplastic material, we were dealt with its low biocompatibility. The critical assessment of it is poorly presented in the literature and does not have systematic approaches to solving. The aim of the study was to determine the effect of factors affecting chitosan charge and its free amino groups number on the biocompatibility of hydrogels. Biocompatibility of chitosan compositions were studied in male Wistar rats (n=90). The subcutaneous implantation of chitosan discs and hydrogel caused abundant leukocyte infiltration. The addition of β-glycerophosphate followed by dialysis slightly reduced the inflammatory response. Treatment with a solution of alkali NaOH and NaHCO3 buffer, on the contrary, intensified the inflammatory response. It is confirmed the effect of charged amino groups of chitosan on leukocyte taxis A decrease in the deacetylation degree (DD) of chitosan to 39.0% led to a statistically significant decrease in leukocyte infiltration. Saturation of chitosan hydrogels with PLA granules reduced by 16% the level of leukocyte infiltration, which was supposedly associated with a decrease in the volume of the hydrogel and an increase in the area of its interaction with blood plasma proteins, which reduce the positive charge of chitosan. The most significant reduction in leukocyte infiltration was achieved with a combination of deacetylated to 39.0% chitosan hydrogel with the addition of 16% by weight highly porous PLA granules.

Development of Electrospun Chitosan-Polyethylene Oxide/Fibrinogen Biocomposite for Potential Wound Healing Applications

Normal wound healing is a highly complex process that requires the interplay of various growth factors and cell types. Despite advancements in biomaterials, only a few bioactive wound dressings reach the clinical setting. The purpose of this research was to explore the feasibility of electrospinning a novel nanofibrous chitosan (CS)-fibrinogen (Fb) scaffold capable of sustained release of platelet-derived growth factor (PDGF) for the promotion of fibroblast migration and wound healing. CS-Fb scaffolds were successfully electrospun using a dual-spinneret electrospinner and directly evaluated for their physical, chemical, and biological characteristics. CS-polyethylene/Fb scaffolds exhibited thinner fiber diameters than nanofibers electrospun from the individual components while demonstrating adequate mechanical properties and homogeneous polymer distribution. In addition, the scaffold demonstrated acceptable water transfer rates for wound healing applications. PDGF was successfully incorporated in the scaffold and maintained functional activity throughout the electrospinning process. Furthermore, released PDGF was effective at promoting fibroblast migration equivalent to a single 50 ng/mL dose of PDGF. The current study demonstrates that PDGF-loaded CS-Fb nanofibrous scaffolds possess characteristics that would be highly beneficial as novel bioactive dressings for enhancement of wound healing.

Enhanced bioactivity and osteoinductivity of carboxymethyl chitosan/nanohydroxyapatite/graphene oxide nanocomposites

Tissue engineering approaches combine a bioscaffold with stem cells to provide biological substitutes that can repair bone defects and eventually improve tissue functions. The prospective bioscaffold should have good osteoinductivity. Surface chemical and roughness modifications are regarded as valuable strategies for developing bioscaffolds because of their positive effects on enhancing osteogenic differentiation. However, the synergistic combination of the two strategies is currently poorly studied. In this work, a nanoengineered scaffold with surface chemistry (oxygen-containing groups) and roughness (R_q = 74.1 nm) modifications was fabricated by doping nanohydroxyapatite (nHA), chemically crosslinked graphene oxide (GO) and carboxymethyl chitosan (CMC). The biocompatibility and osteoinductivity of the nanoengineered CMC/nHA/GO scaffold was evaluated in vitro and in vivo, and the osteogenic differentiation mechanism of the nanoengineered scaffold was preliminarily investigated. Our data demonstrated that the enhanced osteoinductivity of CMC/nHA/GO may profit from the surface chemistry and roughness, which benefit the β1 integrin interactions with the extracellular matrix and activate the FAK–ERK signaling pathway to upregulate the expression of osteogenic special proteins. This study indicates that the nanocomposite scaffold with surface chemistry and roughness modifications could serve as a novel and promising bone substitute for tissue engineering.

The CMC/nHA/GO scaffold with the surface chemistry and roughness dual effects and the release of phosphate and calcium ions synergistically assist the mineralization and facilitate the bone regeneration.