Development of Composite Scaffolds Based on Cerium Doped-Hydroxyapatite and Natural Gums-Biological and Mechanical Properties

Facile Synthesis of Ni-Doped ZnO Nanoparticles Using Cashew Gum: Investigation of the Structural, Optical, and Photocatalytic Properties

This work adopted a green synthesis route using cashew tree gum as a mediating agent to obtain Ni-doped ZnO nanoparticles through the sol-gel method. Structural analysis confirmed the formation of the hexagonal wurtzite phase and distortions in the crystal lattice due to the inclusion of Ni cations, which increased the average crystallite size from 61.9 nm to 81.6 nm. These distortions resulted in the growth of point defects in the structure, which influenced the samples' optical properties, causing slight reductions in the band gaps and significant increases in the Urbach energy. The fitting of the photoluminescence spectra confirmed an increase in the concentration of zinc vacancy defects (VZn) and monovacancies (Vo) as Zn cations were replaced by Ni cations in the ZnO structure. The percentage of VZn defects for the pure compound was 11%, increasing to 40% and 47% for the samples doped with 1% and 3% of Ni cations, respectively. In contrast, the highest percentage of VO defects is recorded for the material with the lowest Ni ions concentration, comprising about 60%. The influence of dopant concentration was also reflected in the photocatalytic performance. Among the samples tested, the Zn0.99Ni0.01O compound presented the best result in MB degradation, reaching an efficiency of 98.4%. Thus, the recovered material underwent reuse tests, revealing an efficiency of 98.2% in dye degradation, confirming the stability of the photocatalyst. Furthermore, the use of different inhibitors indicated that •OH radicals are the main ones involved in removing the pollutant. This work is valuable because it presents an ecological synthesis using cashew gum, a natural polysaccharide that has been little explored in the literature.

GelMA-based bioactive hydrogel scaffolds with multiple bone defect repair functions: therapeutic strategies and recent advances

Currently, the clinical treatment of critical bone defects attributed to various causes remains a great challenge, and repairing these defects with synthetic bone substitutes is the most common strategy. In general, tissue engineering materials that mimic the structural, mechanical and biological properties of natural bone have been extensively applied to fill bone defects and promote in situ bone regeneration. Hydrogels with extracellular matrix (ECM)-like properties are common tissue engineering materials, among which methacrylate-based gelatin (GelMA) hydrogels are widely used because of their tunable mechanical properties, excellent photocrosslinking capability and good biocompatibility. Owing to their lack of osteogenic activity, however, GelMA hydrogels are combined with other types of materials with osteogenic activities to improve the osteogenic capability of the current composites. There are three main aspects to consider when enhancing the bone regenerative performance of composite materials: osteoconductivity, vascularization and osteoinduction. Bioceramics, bioglass, biomimetic scaffolds, inorganic ions, bionic periosteum, growth factors and two-dimensional (2D) nanomaterials have been applied in various combinations to achieve enhanced osteogenic and bone regeneration activities. Three-dimensional (3D)-bioprinted scaffolds are a popular research topic in bone tissue engineering (BTE), and printed and customized scaffolds are suitable for restoring large irregular bone defects due to their shape and structural tunability, enhanced mechanical properties, and good biocompatibility. Herein, the recent progress in research on GelMA-based composite hydrogel scaffolds as multifunctional platforms for restoring critical bone defects in plastic or orthopedic clinics is systematically reviewed and summarized. These strategies pave the way for the design of biomimetic bone substitutes for effective bone reconstruction with good biosafety. This review provides novel insights into the development and current trends of research on GelMA-based hydrogels as effective bone tissue engineering (BTE) scaffolds for correcting bone defects, and these contents are summarized and emphasized from various perspectives (osteoconductivity, vascularization, osteoinduction and 3D-bioprinting). In addition, advantages and deficiencies of GelMA-based bone substitutes used for bone regeneration are put forward, and corresponding improvement measures are presented prior to their clinical application in near future (created with BioRender.com).

Studies of the Tarragon Essential Oil Effects on the Characteristics of Doped Hydroxyapatite/Chitosan Biocomposites

Due to the emergence of antibiotic-resistant pathogens, the need to find new, efficient antimicrobial agents is rapidly increasing. Therefore, in this study, we report the development of new biocomposites based on zinc-doped hydroxyapatite/chitosan enriched with essential oil of Artemisia dracunculus L. with good antimicrobial activity. Techniques such as scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX) and Fourier transform infrared spectroscopy (FTIR) were used in order to evaluate their physico-chemical properties. Our studies revealed that biocomposite materials with nanometric dimension and homogeneous composition could be obtained through an economic and cost-effective synthesis method. The biological assays demonstrated that ZnHA (zinc-doped hydroxyapatite), ZnHACh (zinc-doped hydroxyapatite/chitosan) and ZnHAChT (zinc-doped hydroxyapatite/chitosan enriched with essential oil of Artemisia dracunculus L.) did not exhibit a toxic effect on the cell viability and proliferation of the primary osteoblast culture (hFOB 1.19). Moreover, the cytotoxic assay also highlighted that the cell morphology of the hFOB 1.19 was not altered in the presence of ZnHA, ZnHACh or ZnHAChT. Furthermore, the in vitro antimicrobial studies emphasized that the samples exhibited strong antimicrobial properties against Escherichia coli ATCC 25922, Staphylococcus aureus ATCC 25923 and Candida albicans ATCC 10231 microbial strains. These results are encouraging for the following development of new composite materials with enhanced biological properties that could promote the osteogenic process of bone healing and also exhibit good antimicrobial properties.

Evaluation of cashew gum-polyvinyl alcohol (CG-PVA) electrospun nanofiber mat for scarless wound healing in a murine model

Modern-day treatment for burns and wounds demands scarless healing which is becoming a challenging clinical problem. Thus, to alleviate such issues, it becomes essential to develop biocompatible and biodegradable wound dressing material for skin tissue regeneration, which could heal the wound in a very short span leaving no scars. The present study focuses on the development of nanofiber of Cashew gum polysaccharide-Polyvinyl alcohol using electrospinning. The prepared nanofiber was optimized based on uniformity of fiber diameter (FESEM), mechanical property (Tensile Strength), and optical contact angle (OCA) and was subjected to evaluation of: antimicrobial activity against Streptococcus aureus and Escherichia coli, hemocompatibility, and in-vitro biodegradability. The nanofiber was also characterized using different analytical techniques including thermogravimetric analysis, Fourier-transform infrared spectroscopy, and X-ray diffraction. The cytotoxicity was also investigated on L929 fibroblast cells using an SRB assay. The in-vivo wound healing assay showed accelerated healing in comparison to untreated wounds. The in-vivo wound healing assay and histopathological slides of regenerated tissue confirmed that the nanofiber has the potential to accelerate healing properties.

In vitro hemocompatibility studies on small-caliber stents for cardiovascular applications

The doping of biologically meaningful ions into biphasic calcium phosphate (BCP) bioceramics, which exhibit biocompatibility with human body parts, has led to their effective use in biomedical applications in recent years. Doping with metal ions while changing the characteristics of the dopant ions, an arrangement of various ions in the Ca/P crystal structure. In our work, small-diameter vascular stents based on BCP and biologically appropriate ion substitute-BCP bioceramic materials were developed for cardiovascular applications. The small-diameter vascular stents were created using an extrusion process. FTIR, XRD, and FESEM were used to identify the functional groups, crystallinity, and morphology of the synthesized bioceramic materials. In addition, investigation of the blood compatibility of the 3D porous vascular stents was carried out via hemolysis. The outcomes indicate that the prepared grafts are appropriate for clinical requirements.

Lanthanides-Substituted Hydroxyapatite for Biomedical Applications

Lately, there has been an increasing demand for materials that could improve tissue regenerative therapies and provide antimicrobial effects. Similarly, there is a growing need to develop or modify biomaterials for the diagnosis and treatment of different pathologies. In this scenario, hydroxyapatite (HAp) appears as a bioceramic with extended functionalities. Nevertheless, there are certain disadvantages related to the mechanical properties and lack of antimicrobial capacity. To circumvent them, the doping of HAp with a variety of cationic ions is emerging as a good alterative due to the different biological roles of each ion. Among many elements, lanthanides are understudied despite their great potential in the biomedical field. For this reason, the present review focuses on the biological benefits of lanthanides and how their incorporation into HAp can alter its morphology and physical properties. A comprehensive section of the applications of lanthanides-substituted HAp nanoparticles (HAp NPs) is presented to unveil the potential biomedical uses of these systems. Finally, the need to study the tolerable and non-toxic percentages of substitution with these elements is highlighted.

Cerium Nitrate Treatment in the Management of Burns

Significance: The standard of care for deep burn wounds is eschar excision and autologous skin grafting within the first postburn days. However, when this is not practical due to medical reasons, unavailable surgical facilities, or lack of donor sites or other coverage, surgeons have used topical cerium nitrate (CN) in a cream with silver sulfadiazine (SSD) for over four decades to convert the eschar into a pliable and protective crust that facilitates the postponement or staging of eschar excision and grafting. CN+SSD treatment is reported to reduce dressing changes, improve patient comfort, and reduce bacterial burden, with unaffected epithelialization and few complications. Recent Advances: CN aqueous solutions applied topically alone or together with solid silver dressings in animal models have mitigated wound injury progression, wound microbial burden, and systemic immune dysfunction. Critical Issues: CN+SSD cream is not approved by U.S. Food and Drug Administration (FDA) and its efficacy in clinical trials has been challenging to demonstrate. One reason is that CN changes the eschar visibly, introducing unavoidable bias. Also, the market and patient population is small and burn wound presentation is highly variable. Future Directions: For use in settings wherein the once- or twice-daily CN+SSD cream dressing changes are least feasible (low-income, military, and mass casualty settings), it may be possible to develop a solid dressing containing cerium and silver that requires infrequent dressing changes. For future clinical studies, the trial design most suited to comparing silver-containing dressings with and without cerium may be paired difference of matched intrapatient wounds.

3D Printable Composite Biomaterials Based on GelMA and Hydroxyapatite Powders Doped with Cerium Ions for Bone Tissue Regeneration

The main objective was to produce 3D printable hydrogels based on GelMA and hydroxyapatite doped with cerium ions with potential application in bone regeneration. The first part of the study regards the substitution of Ca2+ ions from hydroxyapatite structure with cerium ions (Ca10-xCex(PO4)6(OH)2, xCe = 0.1, 0.3, 0.5). The second part followed the selection of the optimal concentration of HAp doped, which will ensure GelMA-based scaffolds with good biocompatibility, viability and cell proliferation. The third part aimed to select the optimal concentrations of GelMA for the 3D printing process (20%, 30% and 35%). In vitro biological assessment presented the highest level of cell viability and proliferation potency of GelMA-HC5 composites, along with a low cytotoxic potential, highlighting the beneficial effects of cerium on cell growth, also supported by Live/Dead results. According to the 3D printing experiments, the 30% GelMA enriched with HC5 was able to generate 3D scaffolds with high structural integrity and homogeneity, showing the highest suitability for the 3D printing process. The osteogenic differentiation experiments confirmed the ability of 30% GelMA-3% HC5 scaffold to support and efficiently maintain the osteogenesis process. Based on the results, 30% GelMA-3% HC5 3D printed scaffolds could be considered as biomaterials with suitable characteristics for application in bone tissue engineering.

Reactive oxygen species (ROS)-responsive nanoprobe for bioimaging and targeting therapy of osteoarthritis

Stimulus-responsive therapy that allows precise imaging-guided therapy is limited for osteoarthritis (OA) therapy due to the selection of proper physiological markers as stimulus. Based on that the over-production of Reactive Oxygen Species (ROS) is associated with the progression in OA, we selected ROS as markers and designed a cartilage targeting and ROS-responsive theranostic nanoprobe that can be used for effective bioimaging and therapy of OA. This nanoprobe was fabricated by using PEG micelles modified with ROS-sensitive thioketal linkers (TK) and cartilage-targeting peptide, termed TKCP, which was then encapsulated with Dexamethasone (DEX) to form TKCP@DEX nanoparticles. Results showed that the nanoprobe can smartly “turn on” in response to excessive ROS and “turn off” in the normal joint. By applying different doses of ROS inducer and ROS inhibitor, this nanoprobe can emit ROS-dependent fluorescence according to the degree of OA severity, helpful to precise disease classification in clinic. Specifically targeting cartilage, TKCP@DEX could effectively respond to ROS and sustained release DEX to remarkably reduce cartilage damage in the OA joints. This smart, sensitive and endogenously activated ROS-responsive nanoprobe is promising for OA theranostics.

Superabsorbent Hydrogels Based to Polyacrylamide/Cashew Tree Gum for the Controlled Release of Water and Plant Nutrients

Agricultural production is influenced by the water content in the soil and availability of fertilizers. Thus, superabsorbent hydrogels, based on polyacrylamide, natural cashew tree gum (CG) and potassium hydrogen phosphate (PHP), as fertilizer and water releaser were developed. The structure, morphology, thermal stability and chemical composition of samples of polyacrylamide and cashew tree gum hydrogels with the presence of fertilizer (HCGP) and without fertilizer (HCG) were investigated, using X-ray diffractometry (XRD), Fourier Transformed Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), Thermogravimetric Analysis (TGA/DTG) and Energy Dispersive Spectroscopy (EDS). Swelling/reswelling tests, textural analysis, effect of pH, release of nutrients and kinetics were determined; the ecotoxicity of the hydrogels was investigated by the Artemia salina test. The results showed that PHP incorporation in the hydrogel favored the crosslinking of chains. This increased the thermal stability in HCGP but decreased the hardness and adhesion properties. The HCGP demonstrated good swelling capacity (~15,000 times) and an excellent potential for reuse after fifty-five consecutive cycles. The swelling was favored in an alkaline pH due to the ionization of hydrophilic groups. The sustained release of phosphorus in HCGP was described by the Korsmeyer-Peppas model, and Fickian diffusion is the main fertilizer release mechanism. Finally, the hydrogels do not demonstrate toxicity, and HCGP has potential for application in agriculture.