Comparative investigation of porous nano-hydroxyapaptite/chitosan, nano-zirconia/chitosan and novel nano-calcium zirconate/chitosan composite scaffolds for their potential applications in bone regeneration

Zirconia based composite scaffolds and their application in bone tissue engineering

In the field of bone tissue engineering, biomimetic scaffold utilization is deemed an immensely promising method. The bio-ceramic material Zirconia (ZrO2) has garnered significant attention in the biomimetic scaffolds realm due to its remarkable biocompatibility, superior mechanical strength, and exceptional chemical stability. Numerous examinations have been conducted to investigate the properties and functions of biomimetic structures built from zirconia. Generally, nano-ZrO2 materials have showcased encouraging applications in bone tissue engineering, providing a blend of mechanical robustness, bioactivity, drug delivery capabilities, and antibacterial properties. This review aims to concentrate on the properties and preparations of ZrO2 and its composite materials, while emphasizing its role along with other materials as scaffolds for bone tissue repair applications. The study also discusses the constraints of materials and technology involved in this domain. Ongoing research and development in this area are anticipated to further augment the potential of nano-ZrO2 for advancing bone regeneration therapies.

Nitrogen Plasma Treatment of Composite Materials Based on Polylactic Acid and Hydroxyapatite

The effect of surface modification by an arc discharge plasma in a nitrogen flow with treatment durations of 5 and 10 min on the physicochemical properties and biocompatibility of the surface of composites based on polylactic acid and hydroxyapatite (PLA/HA) with different mass ratios (80/20, 70/30, 60/40) has been investigated. The aim of this work was to show the correlation between the changes of the physicochemical characteristics (chemical compound, morphology, wettability) of the surface layer of the PLA/HA composites and the cell viability (macrophages) in the presence of the plasma-modified materials. The dependence of alterations of the functional properties (wettability, biocompatibility) on the change in the chemical composition under the plasma exposure has been established. The chemical composition was studied using X-ray photoelectron spectroscopy (XPS), the surface morphology was researched with scanning electron microscopy (SEM), and the wettability of the composite's surface was analyzed by measuring the contact angle and surface energy calculation. In addition, the viability of macrophages was investigated when the macrophages from three donors interacted with a modified PLA/HA surface. It was found that the formation of the new functional groups, -C-N and N-C=O/C=O, improves the wettability of the surface of the composites and promotes the viability of macrophages in the presence of the composite materials. The fundamental principles for obtaining promising materials with the required properties for eliminating bone defects have been created.

Chitosan scaffolds with mesoporous hydroxyapatite and mesoporous bioactive glass

Bone regeneration is one of the most well-known fields in tissue regeneration. The major focus concerns polymeric/ceramic composite scaffolds. In this work, several composite scaffolds based on chitosan (CH), with low and high molecular weights, and different concentrations of ceramics like mesoporous bioactive glass (MBG), mesoporous hydroxyapatite (MHAp) and both MBG and MHAp (MC) were produced by lyophilization. The purpose is to identify the best combination regarding optimal morphology and properties. The tests of the scaffolds present a highly porous structure with interconnected pores. The compression modulus increases with ceramic concentration in the scaffolds. Furthermore, the 75%MBG (835 ± 160 kPa) and 50%MC (1070 ± 205 kPa) samples are the ones that mostly enhance increases in mechanical properties. The swelling capacity increases with MBG and MC, respectively, to 700% and 900% and decreases to 400% when MHAp concentration increases. All scaffolds are non-cytotoxic at 12.5 mg/mL. The CHL scaffolds improve cell adhesion and proliferation compared to CHH, and the MC scaffold samples, show better results than those produced with just MBG or MHAp. The composite scaffolds of chitosan with MBG and MHAp, have revealed to be the best combination due to their enhanced performance in bone tissue engineering.

Chitosan - zeolite scaffold as a potential biomaterial in the controlled release of drugs for osteoporosis

Chitosan scaffolds are a potential material in many biomedical applications. A particularly interesting application is their use in bone tissue engineering. Because of their biocompatibility and nontoxicity, they are an ideal material for this application. What is missing from chitosan scaffolds is controlled drug release. They can obtain this property by adding drug carriers. In this work, chitosan‑calcium zeolite scaffolds were prepared and used in the controlled release of the drug for osteoporosis - risedronate. Their properties have been compared with those of the popular chitosan-hydroxyapatite scaffold. The zeolite was evenly distributed throughout the scaffold. More drug was retained on the scaffold with the addition of zeolite compared to that with the hydroxyapatite. The new scaffolds have proven to be able to retain the drug and slowly release it in small doses. The results obtained are promising and show great potential for this material in bone tissue engineering.

Chitosan Nanoparticles: A Versatile Platform for Biomedical Applications

Chitosan is a biodegradable and biocompatible natural polymer that has been extensively explored in recent decades. The Food and Drug Administration has approved chitosan for wound treatment and nutritional use. Furthermore, chitosan has paved the way for advancements in different biomedical applications including as a nanocarrier and tissue-engineering scaffold. Its antibacterial, antioxidant, and haemostatic properties make it an excellent option for wound dressings. Because of its hydrophilic nature, chitosan is an ideal starting material for biocompatible and biodegradable hydrogels. To suit specific application demands, chitosan can be combined with fillers, such as hydroxyapatite, to modify the mechanical characteristics of pH-sensitive hydrogels. Furthermore, the cationic characteristics of chitosan have made it a popular choice for gene delivery and cancer therapy. Thus, the use of chitosan nanoparticles in developing novel drug delivery systems has received special attention. This review aims to provide an overview of chitosan-based nanoparticles, focusing on their versatile properties and different applications in biomedical sciences and engineering.

Synthesis and Biomedical Applications of Zirconium Nanoparticles: Advanced Leaps and Bounds in the Recent Past

Many synthetic routes manufacture zirconium nanoparticles in metal oxide, nitride, and other combination forms. Coupled with other variables such as concentration, pH, and form of precursor used, the various synthetic methods support synthesizing the zirconium metal oxide nanoparticles with changed features. Various synthetic methods were studied, such as sol-gel, hydrothermal, laser ablation, and precipitation. All have different synthetic routes, different precursors and solvents were sued, and the product was characterized by SEM, TEM, photo luminance spectroscopy, UV-absorption spectroscopy, and powder X-ray diffraction. X-ray diffraction determined the crystal structure by identifying the crystal shape, arrangement of atoms, and spacing between them. SEM and TEM studied the particle size and morphology of nanoparticles. UV-visible absorption spectroscopy and PL spectroscopy were used for the determination of optical properties of nanoparticles. Zirconium oxide nanoparticles have many applications in the medical field. The review study primarily focuses on the efficient combination of zirconium dioxide with other additive materials and functionalization techniques used to improve the material's properties, assisting the use of the material in hip arthroplasty and bone tissue applications. The development of sophisticated near-infrared (NIR) absorbing small molecules for useful phototheranostic applications was discussed in this paper.

Anisotropic Piezoelectric Properties of Porous (Ba0.85Ca0.15)(Zr0.1Ti0.9)O3 Ceramics with Oriented Pores through TBA-Based Freeze-Casting Method

Porous (Ba_0.85Ca_0.15)(Zr_0.1Ti_0.9)O₃ (BCZT) piezoelectric ceramics with an oriented directional hole structure were prepared by using the tertbutyl alcohol (TBA)-based freeze-casting method. The influences of sintering temperatures on the microstructure and piezoelectric properties of porous BCZT ceramics were investigated both perpendicular and parallel to the freezing direction. With the increase in sintering temperatures and the porosities decreased from 58% to 42%, the compressive strength increased from 14.0 MPa to 25.0 MPa. In addition, the d₃₃ value of 407 pC/N for the sample sintered at 1400 °C was obtained parallel to the freezing direction, which was 1.40 times that of the other direction.

Review on synthesis, properties and multifarious therapeutic applications of nanostructured zirconia in dentistry

Amongst dental ceramics, nano zirconia (ZrNp) has shown exceptional developments in the field of dentistry in recent years. Zirconia is an oxide that possess superior optical, mechanical, and biological properties. As a novel nanoparticle, it has been widely used in various fields of dentistry due to its improved mechanical properties, biocompatibility, and stable structure. Provision of metal free solutions is one of the prime requirements in dental materials. Many metal alloys used extensively possess unaesthetic colors and display chemical interactions in the oral cavity encouraging use of zirconia for dental use. Use of ZrNp based ceramics has increased due to its resistance to corrosion, superior color matching that enhances esthetics and improved strength compared to conventional biomaterials. This review discusses the recent scientific literature on the synthesis, properties and types, applications, and toxicity of ZrNp in the field of dentistry.

Multifunctional Hemostatic PVA/Chitosan Sponges Loaded with Hydroxyapatite and Ciprofloxacin

The present study describes the development of multifunctional hemostatic sponges to control bleeding. Chitosan (Ch) and poly(vinyl alcohol) (PVA) were selected as the basic polymeric matrix [Ch/PVA] for sponges. Glycerol and citric acid were used as crosslinkers [Ch/PVA/G(Cl)] to enhance the mechanical properties of the developed sponges. Ciprofloxacin (AB) was added to the developed sponge to impart antibacterial activity. Hydroxyapatite (HA) was also added, which would make the sponge suitable for bone surgery. Among the developed sponges, the Ch/PVA/G(Cl)-HA-AB sponge demonstrated enhanced cell viability, mechanical properties, and strong antimicrobial effect against Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus, in addition to platelet aggregation activity. The addition of ciprofloxacin and hydroxyapatite promotes a unique synergistic effect of antimicrobial activity and hemostasis. Thus, the present study introduces Ch/PVA/G(Cl)-HA-AB, a multifunctional hemostatic sponge that would be suitable for bone surgical applications.

Atomic Force Microscopy (AFM) on Biopolymers and Hydrogels for Biotechnological Applications-Possibilities and Limits

Atomic force microscopy (AFM) is one of the microscopic techniques with the highest lateral resolution. It can usually be applied in air or even in liquids, enabling the investigation of a broader range of samples than scanning electron microscopy (SEM), which is mostly performed in vacuum. Since it works by following the sample surface based on the force between the scanning tip and the sample, interactions have to be taken into account, making the AFM of irregular samples complicated, but on the other hand it allows measurements of more physical parameters than pure topography. This is especially important for biopolymers and hydrogels used in tissue engineering and other biotechnological applications, where elastic properties, surface charges and other parameters influence mammalian cell adhesion and growth as well as many other effects. This review gives an overview of AFM modes relevant for the investigations of biopolymers and hydrogels and shows several examples of recent applications, focusing on the polysaccharides chitosan, alginate, carrageenan and different hydrogels, but depicting also a broader spectrum of materials on which different AFM measurements are reported in the literature.

Biomimetic development of chitosan and sodium alginate-based nanocomposites contains zirconia for tissue engineering applications

Nanostructured materials possess unique structural and functional properties that play a crucial position in tissue engineering applications. Present investigation is aimed to synthesize chitosan-sodium alginate (CS) nanocomposite using hydrothermally prepared zirconia nanoparticles. In this, three different weight percentages of (0.5, 1, and 1.5) zirconia nanoparticles are utilized for the preparation of biomimetic nanocomposite scaffolds (CSZ) employing 4 wt% of CS by a solvent casting technique. Physico-chemical and thermal behavior of the prepared nanoparticles and their CSZ scaffolds are comprehensively characterized. Bioactivity of the prepared zirconia nanoparticles and CSZ scaffolds are explored in terms of in vitro biocompatibility, protein absorption in simulated body fluid (SBF), and phosphate buffered saline (PBS). Agar disc diffusion method is employed to identify the antibacterial property against Staphylococcus aureus and Escherichia coli. In vitro cytotoxicity of zirconia nanoparticles and CSZ scaffolds is identified against human urothelial carcinoma (UC6) and osteosarcoma (MG-63) cells. These studies explore that zirconia nanoparticles are suitable for biomedical applications while it is interacted with chitosan and sodium alginate (CS) due to their promising biocompatibility. Biomimetically obtained chitosan/sodium alginate scaffold contain 1 wt% zirconia nanoparticles show higher biocompatibility amenable for tissue engineering applications.

Bioactive Chitosan-Based Organometallic Scaffolds for Tissue Engineering and Regeneration

Captivating achievements in developing advanced hybrid biostructures through integrating natural biopolymers with inorganic materials (e.g., metals and metalloids) have paved the way towards the application of bioactive organometallic scaffolds (OMSs) in tissue engineering and regenerative medicine (TERM). Of various biopolymers, chitosan (CS) has been used widely for the development of bioactive OMSs, in large part due to its unique characteristics (e.g., biocompatibility, biodegradability, surface chemistry, and functionalization potential). In integration with inorganic elements, CS has been used to engineer advanced biomimetic matrices to accommodate both embedded cells and drug molecules and serve as scaffolds in TERM. The use of the CS-based OMSs is envisioned to provide a new pragmatic potential in TERM and even in precision medicine. In this review, we aim to elaborate on recent achievements in a variety of CS/metal, CS/metalloid hybrid scaffolds, and discuss their applications in TERM. We also provide comprehensive insights into the formulation, surface modification, characterization, biocompatibility, and cytotoxicity of different types of CS-based OMSs.

Effect of Hydroxyapatite Nanoparticles and Nitrogen Plasma Treatment on Osteoblast Biological Behaviors of 3D-Printed HDPE Scaffold for Bone Tissue Regeneration Applications

The need for the repair of bone defects has been increasing due to various causes of loss of skeletal tissue. High density polyethylenes (HDPE) have been used as bone substitutes due to their excellent biocompatibility and mechanical strength. In the present study, we investigated the preosteoblast cell proliferation and differentiation on the adding nano-hydroxyapatite (n-HAp) particles into HDPE scaffold and treating HDPE/n-HAp scaffolds with nitrogen (N₂) plasma. The three-dimensional (3D) HDPE/n-HAp scaffolds were prepared by fused modeling deposition 3D printer. The HDPE/n-HAp was blended with 10 wt% of n-HAp particle. The scaffold surface was reactive ion etched with nitrogen plasma to improve the preosteoblast biological response in vitro. After N₂ plasma treatment, surfaces characterizations were investigated using Fourier transform infrared spectroscopy, scanning electron microscopy, and atomic force microscopy. The proliferation and differentiation of preosteoblast (MC3T3-E1) cells were evaluated by MTT assay and alkaline phosphatase (ALP) activity. The incorporation of n-HAp particles and N₂ plasma surface treatment showed the improvement of biological responses of MC3T3-E1 cells in the HDPE scaffolds.

Treatment of Traumatic Cartilage Defects of Rabbit Knee Joint by Adipose Derived Stem Cells Combined with Kartogenin Hydroxyapatite Nano-Microsphere Complex

Kartogenin (KGN) can effectively promote the differentiation of adipose derived stem cells (ADSCs) into chondrocytes. With the help of three-dimensional slow-release technology, nano-microspheres are generated and used for cartilage repair. First, KGN solution was prepared, which was dissolved in distilled water, and NaOH solution, HEPES buffer, sodium chloride particles, and hydroxyapatite (HA) solution were added to prepare KGN-HA gel solution containing KGN. ADSCs were isolated from the posterior iliac of four-week-old New Zealand rabbits. After 0.5 mL of rabbit second-generation ADSCs suspension was taken, 2 mL KGN-HA gel solution was added, and they were mixed well to obtain ADSCs/KGN-HA gel. After drying treatment, ADSCs/KGN-HA nanospheres were precipitated. In the experiment, the minimum inhibitory concentration (MIC) of Staphylococcus aureus (MIC) > 2 μg/mL in each group of KGN-HA gel solution was reached within 30 days. Group K3 had the highest KGN encapsulation rate and the largest cumulative release. The biological activity of ADSCs was good in the ADSCs/KGN-HA nanoparticle solution. After two weeks of incubation, the nanospheres were positive for type II collagen staining/toluidine blue staining, that was, chondrocyte phenotype. The rabbit knee articular cartilage defect model was established. The defect part was filled with ADSCs/KGN-HA gel, which was similar in color to the surrounding tissues. The two sides of the tissue section and the surrounding cartilage tissue healed well, and no carrier material remained. Moreover, the cells were round, with cartilage lacuna formed around them, and after the simple periosteum was covered and repaired, the surface was sunken. The cell structure changed, and the healing with the surroundings was poor. In summary, under the slow release of KGN, ADSCs/KGN-HA nanospheres made ADSCs maintain a good biological form, which grew and proliferated normally. The ADSCs/KGN-HA nanoparticles cultured in vitro had a good repair effect on the animal model of articular cartilage defects.

Injectable eggshell-derived hydroxyapatite-incorporated fibroin-alginate composite hydrogel for bone tissue engineering

Tissue engineering is a promising approach to repair and regenerate damaged or lost tissues or organs. In dental aspect, reconstruction of the resorbed alveolar bone after tooth extraction plays an important role in the success of dental substitution, especially in dental implant treatment. The hydroxyapatite (HA)-incorporated fibroin-alginate composite injectable hydrogel was fabricated to be used as scaffold for bone regeneration. HA was synthesized from eggshell biowaste. Fibroin was extracted from Bombyx mori cocoon. The synthesized HA, fibroin and alginate hydrogel were characterized. HA-incorporated fibroin-alginate hydrogel had decreased pore size and porosity compared with pure alginate hydrogel. Thermal analysis showed that hydrogel had a degradation peak of approximately 250 °C. Hydrogel could absorb water, with a swelling ratio of around 300% at 24 h. Hydrogel was degraded as time passed and almost completely degraded at day 7. Its compressive Young's modulus was approximately 0.04 ± 0.02 N/mm² to 0.10 ± 0.02 N/mm². Primary cytotoxicity test indicated non-toxic potential of the fabricated hydrogel. Increased ALP activity was observed in MC3T3-E1 cultured in HA-incorporated fibroin-alginate hydrogel. Results suggested the potential use of injectable HA fibroin-alginate hydrogel as dental scaffolding material. Further studies including in vivo examinations are needed prior to its clinical application.

Osteogenic Property Regulation of Stem Cells by a Hydroxyapatite 3D-Hybrid Scaffold With Cancellous Bone Structure

Cancellous bone plays an indispensable role in the skeletal system due to its various functions and high porosity. In this work, chitosan and hydroxyapatite nanowires (CS@HAP NWs) hybrid nanostructured scaffolds with suitable mechanical properties, high porosity and a fine porous structure were prepared to simulate the 3-dimensional structure of cancellous bone. The 3D-hybrid scaffolds promote cell adhesion and the migration of human adipose-derived stem cells (hADSCs) inside the scaffolds. The cavities in the scaffolds provide space for the hADSCs proliferation and differentiation. Moreover, the various contents of HAP and the induced mechanical property changes regulate the differentiation of hADSCs toward osteoblasts. Overall, cellular fate regulation of hADSCs via rationally engineered HAP-based hybrid scaffolds is a facile and effective approach for bone tissue engineering.

Micro + Nano: Conserving the Gold Standard Microroughness to Nanoengineer Zirconium Dental Implants

Zirconium has achieved popularity as a biomaterial for dental and orthopedic implants; however, its bioinertness can compromise implant-tissue integration, especially in compromised patient conditions. More recently, various nanoengineering strategies have been explored to enhance the bioactivity of Ti-based implants; however, nanoengineering of Zr-based implants has not been adequately explored. In this pioneering attempt, we report on the optimized fabrication of various nanostructures on microrough Zr surfaces and explore the influence of the underlying surface topography. In-depth optimization of electrochemical anodization (EA) is performed by tuning various parameters, including substrate topography, voltage/current and time, onto microrough (micromachined) and extremely rough Zr substrates, which represent clinically relevant implant surfaces. Variations of EA factors yielded various nanotopographies, including nanotubes, nanograss and nanotemplates, offering different topographical and chemical combinations. EA optimization and precise current-voltage recording was performed to arrive at clinically translatable and reproducible nanostructures on Zr surfaces. This study will pave the way toward the fabrication of the next generation of nanoengineered Zr-based orthopedic and dental implants.

Three-Dimensional Zirconia-Based Scaffolds for Load-Bearing Bone-Regeneration Applications: Prospects and Challenges

The design of zirconia-based scaffolds using conventional techniques for bone-regeneration applications has been studied extensively. Similar to dental applications, the use of three-dimensional (3D) zirconia-based ceramics for bone tissue engineering (BTE) has recently attracted considerable attention because of their high mechanical strength and biocompatibility. However, techniques to fabricate zirconia-based scaffolds for bone regeneration are in a stage of infancy. Hence, the biological activities of zirconia-based ceramics for bone-regeneration applications have not been fully investigated, in contrast to the well-established calcium phosphate-based ceramics for bone-regeneration applications. This paper outlines recent research developments and challenges concerning numerous three-dimensional (3D) zirconia-based scaffolds and reviews the associated fundamental fabrication techniques, key 3D fabrication developments and practical encounters to identify the optimal 3D fabrication technique for obtaining 3D zirconia-based scaffolds suitable for real-world applications. This review mainly summarized the articles that focused on in vitro and in vivo studies along with the fundamental mechanical characterizations on the 3D zirconia-based scaffolds.

Materials and Manufacturing Techniques for Polymeric and Ceramic Scaffolds Used in Implant Dentistry

Preventive and regenerative techniques have been suggested to minimize the aesthetic and functional effects caused by intraoral bone defects, enabling the installation of dental implants. Among them, porous three-dimensional structures (scaffolds) composed mainly of bioabsorbable ceramics, such as hydroxyapatite (HAp) and β-tricalcium phosphate (β-TCP) stand out for reducing the use of autogenous, homogeneous, and xenogenous bone grafts and their unwanted effects. In order to stimulate bone formation, biodegradable polymers such as cellulose, collagen, glycosaminoglycans, polylactic acid (PLA), polyvinyl alcohol (PVA), poly-ε-caprolactone (PCL), polyglycolic acid (PGA), polyhydroxylbutyrate (PHB), polypropylenofumarate (PPF), polylactic-co-glycolic acid (PLGA), and poly L-co-D, L lactic acid (PLDLA) have also been studied. More recently, hybrid scaffolds can combine the tunable macro/microporosity and osteoinductive properties of ceramic materials with the chemical/physical properties of biodegradable polymers. Various methods are suggested for the manufacture of scaffolds with adequate porosity, such as conventional and additive manufacturing techniques and, more recently, 3D and 4D printing. The purpose of this manuscript is to review features concerning biomaterials, scaffolds macro and microstructure, fabrication techniques, as well as the potential interaction of the scaffolds with the human body.

Mechanical strength improvement of chitosan/hydroxyapatite scaffolds by coating and cross-linking

Coating and cross-linking have been widely used to improve the properties of materials in tissue engineering. A chitosan/hydroxyapatite (CS/HA) comby scaffold with high porosity was prepared via a 3D printed pore-forming mold. The scaffold was then treated with gelatin (Gel) coating and was cross-linked by glutaraldehyde (GA) in order to improve the mechanical strength. The materials were characterized by infrared spectroscopy (IR) and X-ray diffraction (XRD). The structure of the scaffolds was observed by Scanning Electron Microscopy (SEM). Compression tests were carried out to evaluate the strength of the scaffolds. The behaviors and responses of preosteoblast cells on the scaffolds were studied as well. The results showed that gelatin coating and cross-linking significantly enhanced the mechanical strength of the porous scaffolds. Cell culture experiment indicated that the scaffold had good cytocompatibility. The combined application of 3DP structure construction and biopolymer coating/cross-linking would offer some new ideas in fabrication of porous scaffolds with enhanced strength and good biocompatibility for tissue engineering.

Recent trends in the application of widely used natural and synthetic polymer nanocomposites in bone tissue regeneration

The goal of a biomaterial is to support the bone tissue regeneration process at the defect site and eventually degrade in situ and get replaced with the newly generated bone tissue. Nanocomposite biomaterials are a relatively new class of materials that incorporate a biopolymeric and biodegradable matrix structure with bioactive and easily resorbable fillers which are nano-sized. This article is a review of a few polymeric nanocomposite biomaterials which are potential candidates for bone tissue regeneration. These nanocomposites have been broadly classified into two groups viz. natural and synthetic polymer based. Natural polymer-based nanocomposites include materials fabricated through reinforcement of nanoparticles and/or nanofibers in a natural polymer matrix. Several widely used natural biopolymers, such as chitosan (CS), collagen (Col), cellulose, silk fibroin (SF), alginate, and fucoidan, have been reviewed regarding their present investigation on the incorporation of nanomaterial, biocompatibility, and tissue regeneration. Synthetic polymer-based nanocomposites that have been covered in this review include polycaprolactone (PCL), poly (lactic-co-glycolic) acid (PLGA), polyethylene glycol (PEG), poly (lactic acid) (PLA), and polyurethane (PU) based nanocomposites. An array of nanofillers, such as nano hydroxyapatite (nHA), nano zirconia (nZr), nano silica (nSi), silver nano particles (AgNPs), nano titanium dioxide (nTiO₂), graphene oxide (GO), that is used widely across the bone tissue regeneration research platform are included in this review with respect to their incorporation into a natural and/or synthetic polymer matrix. The influence of nanofillers on cell viability, both in vitro and in vivo, along with cytocompatibility and new tissue generation has been encompassed in this review. Moreover, nanocomposite material characterization using some commonly used analytical techniques, such as electron microscopy, spectroscopy, diffraction patterns etc., has been highlighted in this review. Biomaterial physical properties, such as pore size, porosity, particle size, and mechanical strength which strongly influences cell attachment, proliferation, and subsequent tissue growth has been covered in this review. This review has been sculptured around a case by case basis of current research that is being undertaken in the field of bone regeneration engineering. The nanofillers induced into the polymeric matrix render important properties, such as large surface area, improved mechanical strength as well as stability, improved cell adhesion, proliferation, and cell differentiation. The selection of nanocomposites is thus crucial in the analysis of viable treatment strategies for bone tissue regeneration for specific bone defects such as craniofacial defects. The effects of growth factor incorporation on the nanocomposite for controlling new bone generation are also important during the biomaterial design phase.

Progress in the Development of Chitosan-Based Biomaterials for Tissue Engineering and Regenerative Medicine

Over the last few decades, chitosan has become a good candidate for tissue engineering applications. Derived from chitin, chitosan is a unique natural polysaccharide with outstanding properties in line with excellent biodegradability, biocompatibility, and antimicrobial activity. Due to the presence of free amine groups in its backbone chain, chitosan could be further chemically modified to possess additional functional properties useful for the development of different biomaterials in regenerative medicine. In the current review, we will highlight the progress made in the development of chitosan-containing bioscaffolds, such as gels, sponges, films, and fibers, and their possible applications in tissue repair and regeneration, as well as the use of chitosan as a component for drug delivery applications.

Application of Chitosan in Bone and Dental Engineering

Chitosan is a deacetylated polysaccharide from chitin, the natural biopolymer primarily found in shells of marine crustaceans and fungi cell walls. Upon deacetylation, the protonation of free amino groups of the d-glucosamine residues of chitosan turns it into a polycation, which can easily interact with DNA, proteins, lipids, or negatively charged synthetic polymers. This positive-charged characteristic of chitosan not only increases its solubility, biodegradability, and biocompatibility, but also directly contributes to the muco-adhesion, hemostasis, and antimicrobial properties of chitosan. Combined with its low-cost and economic nature, chitosan has been extensively studied and widely used in biopharmaceutical and biomedical applications for several decades. In this review, we summarize the current chitosan-based applications for bone and dental engineering. Combining chitosan-based scaffolds with other nature or synthetic polymers and biomaterials induces their mechanical properties and bioactivities, as well as promoting osteogenesis. Incorporating the bioactive molecules into these biocomposite scaffolds accelerates new bone regeneration and enhances neovascularization in vivo.

A Precautionary Approach to Guide the Use of Transition Metal-Based Nanotechnology to Prevent Orthopedic Infections

The increase of multidrug-resistant bacteria remains a global concern. Among the proposed strategies, the use of nanoparticles (NPs) alone or associated with orthopedic implants represents a promising solution. NPs are well-known for their antimicrobial effects, induced by their size, shape, charge, concentration and reactive oxygen species (ROS) generation. However, this non-specific cytotoxic potential is a powerful weapon effective against almost all microorganisms, but also against eukaryotic cells, raising concerns related to their safe use. Among the analyzed transition metals, silver is the most investigated element due to its antimicrobial properties per se or as NPs; however, its toxicity raises questions about its biosafety. Even though it has milder antimicrobial and cytotoxic activity, TiO₂ needs to be exposed to UV light to be activated, thus limiting its use conjugated to orthopedic devices. By contrast, gold has a good balance between antimicrobial activity as an NP and cytocompatibility because of its inability to generate ROS. Nevertheless, although the toxicity and persistence of NPs within filter organs are not well verified, nowadays, several basic research on NP development and potential uses as antimicrobial weapons is reported, overemphasizing NPs potentialities, but without any existing potential of translation in clinics. This analysis cautions readers with respect to regulation in advancing the development and use of NPs. Hopefully, future works in vivo and clinical trials will support and regulate the use of nano-coatings to guarantee safer use of this promising approach against antibiotic-resistant microorganisms.