Fabrication of biocompatible porous scaffolds based on hydroxyapatite/collagen/chitosan composite for restoration of defected maxillofacial mandible bone

The Role of Crosslinking Agents in the Development of Collagen-Hydroxyapatite Composite Materials for Bone Tissue Engineering

The lack of bone grafts represents a major issue in the orthopedic field, reconstructive surgery, and dentistry. There are several bone conditions that often demand the use of grafts, such as fractures, infections, and bone cancer. The number of bone cancer cases increased in the past few decades and along with it, the need for bone grafting materials. To avoid the use of autografts and allografts there has been an increased interest towards synthetic grafts. This research aims to develop some collagen/hydroxyapatite (Coll/HAp) scaffolds cross-linked with three different agents that could be used in bone tissue engineering (BTE). These scaffolds were obtained with a freeze-drying method after the in situ formation of hydroxyapatite inside the collagen matrix. They were structurally and morphologically characterized and evaluated in terms of antimicrobial activity on E. coli and S. aureus bacterial strains. The results revealed that the scaffolds have porous structures with interconnected pores of suitable dimensions and well-distributed inorganic phases. Coll/HAp samples showed great antibacterial activity even without the use of typically used antibacterial agents. These findings allow us to conclude that these scaffolds are promising candidates for use in BTE and bone cancer treatment after the incorporation of specific antitumoral drugs.

Bio-Informed Porous Mineral-Based Composites

Certain biominerals, such as sea sponges and echinoderm skeletons, display a fascinating combination of mechanical properties and adaptability due to the well-defined structures spanning various length scales. These materials often possess high density normalized mechanical properties because they contain well-defined pores. The density-normalized mechanical properties of synthetic minerals are often inferior because the pores are stochastically distributed, resulting in an inhomogeneous stress distribution. The mechanical properties of synthetic materials are limited by the degree of structural and compositional control currently available fabrication methods offer. In the first part of this review, examples of structural elements nature uses to impart exceptional density normalized Young's moduli to its porous biominerals are showcased. The second part highlights recent advancements in the fabrication of bio-informed mineral-based composites possessing pores with diameters that span a wide range of length scales. The influence of the processing of mineral-based composites on their structures and mechanical properties is summarized. Thereby, it is aimed at encouraging further research directed to the sustainable, energy-efficient fabrication of synthetic lightweight yet stiff mineral-based composites.

Role of crosslinkers in advancing chitosan-based biocomposite scaffolds for bone tissue engineering: A comprehensive review

Bone tissue engineering (BTE) aims to repair and regenerate damaged bone tissue by combining cells, scaffolds, and signaling molecules. Various macromolecules, including natural polymers like chitosan (CS), collagen, hyaluronic acid, and alginate, as well as synthetic polymers such as polyethylene glycol and polylactic acid, are used in scaffold fabrication. Among these, CS holds significant potential in BTE due to its biocompatibility, biodegradability, and other features. The inherent mechanical weaknesses of CS-based scaffolds require the implementation of crosslinking strategies to improve their stability and overall performance. Physical crosslinkers like ultra-violet irradiation and freeze-thaw cycles are biocompatible but offer limited mechanical strength. Chemical crosslinkers like glutaraldehyde significantly improve mechanical strength, but they may induce cytotoxicity. We briefly outline here the critical role of physical and chemical crosslinkers in improving the physicochemical properties, mechanical strength, biocompatibility, and biological functions of CS-based scaffolds, including effective bone regeneration. The influence of crosslinking on the CS-based scaffolds' bioactivity, including the controlled release of bioactive molecules, is also discussed. A thorough understanding of crosslinker chemistry and application in CS-based scaffolds is essential for advancing bone regeneration therapies.

Enhanced Mandibular Bone Repair Using Poly Lactic-co-glycolic Acid Combined with Nanohydroxyapatite Scaffold Loaded by Mesenchymal Stromal/Stem Cells and Curcumin in Male Rats

This study aimed to investigate the healing effect of a polylactic-co-glycolic acid (PLGA) scaffold containing nanohydroxyapatite (NHA) along with curcumin (CCM), loaded with adipose-derived mesenchymal stem cells (AD-MSCs), on mandibular bone defects. The designed PLGA scaffolds containing NHA were evaluated for their mechanical and structural properties. Forty rats were divided into five groups (n = 8) based on the treatment: Sham, PLGA scaffolds containing NHA, PLGA scaffolds containing NHA + CCM, PLGA scaffolds containing NHA + AD-MSCs, and PLGA scaffolds containing NHA + CCM + AD-MSCs. After 8 weeks' follow-up, mandible bones were isolated for histomorphometry evaluation. Data were analyzed using SPSS version 21, with p-values <0.05 considered statistically significant. SEM evaluation showed that the designed nanocomposite scaffold had 80% porosity. Histomorphometry results indicated a significant difference in osteocyte, osteoblast, bone area, and vascular area parameters in the group treated with scaffolds loaded with AD-MSCs + CCM compared to the other groups (p < 0.05). The PLGA-containing NHA-CCM nanocomposite scaffold demonstrated good porosity and dispersion, suitable for treating bone defects. Rats treated with scaffolds containing AD-MSCs and CCM showed better therapeutic results than the other groups. Further research is needed to evaluate its anti-inflammatory, antioxidant properties, osteogenesis, and therapeutic effects in larger animal models.

Physically cross-linked scaffold composed of hydroxyapatite-chitosan-alginate-polyamide has potential to trigger bone regeneration in craniofacial defect

Recently, the fabrication of a scaffold from biomaterials has been increased due to the lack of adequate natural bone for grafting. In this study, hydroxyapatite-chitosan-alginate-polyamide (HCAP) synthetic scaffold was fabricated using the thermally induced phase separation (TIPS) technique. The scaffold was cross-linked with either a chemical cross-linker (calcium chloride, 2-hydroxyethyl methacrylate (HEMA), or glutaraldehyde (GTA)) or a physical cross-linker (gamma irradiation (IR)) resulting in scaffolds HCAP-CaCl2, HCAP-HEMA, HCAP-GTA, and HCAP-IR, respectively. The cross-linked scaffolds were characterized based on physicochemical properties, cytotoxicity, and biocompatibility. HCAP-GTA showed the highest density and the lowest swelling ratio and biodegradation rate closely matching with those of the HCAP-IR. Porosity and density of the HCAP, HCAP-IR, and HCAP-GTA scaffolds were 92.14, 87.26, and 83.33 %, and 0.241, 0.307, and 0.335 g/cm3, respectively. The swelling ratio for the same scaffolds was 149, 110, and 108 % after 72 h of observation. Brine shrimp cytotoxicity and RBC biocompatibility assay confirmed the non-toxic nature of HCAP-IR and HCAP-GTA scaffolds. The HCAP-IR scaffold was tested for bone regeneration in the rabbit mandible defect model. Histological analysis revealed the regeneration of new bone and restoration of bone defect at the site of injury. These findings indicate that radiation induced physically cross-linked HCAP scaffold could be used as an alternative in bone defect replacement therapy.

Strong, tough, and elastic poly(vinyl alcohol)/polyacrylamide DN hydrogels based on the Hofmeister effect for articular cartilage replacement

Traditional hydrogels are usually weak and brittle, which limit their application in articular cartilage replacement because cartilage is generally strong, tough, and elastic in nature. Therefore, it is highly desirable to construct hydrogels to mimic the mechanical properties of the native articular cartilage. Herein, in this work, poly(vinyl alcohol)/polyacrylamide (PVA/PAM) DN hydrogels were prepared by in situ polymerization, which were then treated with Hofmeister series ions (Cit3-, SO42-, and Cl-) to achieve H-PVA/PAM DN hydrogels. Among the three Hofmeister ions, the DN hydrogel treated with Cit3- (named PVA/PAM-Cit) showed the densest microstructure and the highest crystallinity degree. In this context, PVA/PAM-Cit exhibited a tensile strength of 18.9 ± 1.6 MPa, a compressive strength of 102.3 ± 7.9 MPa, a tensile modulus of 10.6 ± 2.1 MPa, a compressive modulus of 8.9 ± 0.8 MPa, and a roughness of 66.2 ± 4.2 MJ m-3, respectively, which were the highest strength and modulus, and the second highest toughness when compared with those of the reported PVA and PVA based DN hydrogels so far. It also showed an extreme high elasticity, which could maintain a stress of 99.2% after 500 cycles of fatigue testing. Additionally, PVA/PAM-Cit can promote the adhesion, spreading and proliferation of chondrocytes. These results verify that such a strong, tough, and elastic hydrogel could be a novel candidate material for articular cartilage replacement.

Synthesis and characterization of a bovine collagen: GAG scaffold with Uruguayan raw material for tissue engineering

Tissue engineering (TE) and regenerative medicine offer strategies to improve damaged tissues by using scaffolds and cells. The use of collagen-based biomaterials in the field of TE has been intensively growing over the past decades. Mesenchymal stromal cells (MSCs) and dental pulp stem cells (DPSCs) are promising cell candidates for development of clinical composites. In this study, we proposed the development of a bovine collagen type I: chondroitin-6-sulphate (CG) scaffold, obtained from Uruguayan raw material (certified as free bovine spongiform encephalopathy), with CG crosslinking enhancement using different gamma radiation doses. Structural, biomechanical and chemical characteristics of the scaffolds were assessed by Scanning Electron Microscopy, axial tensile tests, FT-IR and Raman Spectroscopy, respectively. Once we selected the most appropriate scaffold for future use as a TE product, we studied the behavior of MSCs and DPSCs cultured on the scaffold by cytotoxicity, proliferation and differentiation assays. Among the diverse porous scaffolds obtained, the one with the most adequate properties was the one exposed to 15 kGy of gamma radiation. This radiation dose contributed to the crosslinking of molecules, to the formation of new bonds and/or to the reorganization of the collagen fibers. The selected scaffold was non-cytotoxic for the tested cells and a suitable substrate for cell proliferation. Furthermore, the scaffold allowed MSCs differentiation to osteogenic, chondrogenic, and adipogenic lineages. Thus, this work shows a promising approach to the synthesis of a collagen-scaffold suitable for TE.

Biomaterial scaffolds in maxillofacial bone tissue engineering: A review of recent advances

Maxillofacial bone defects caused by congenital malformations, trauma, tumors, and inflammation can severely affect functions and aesthetics of maxillofacial region. Despite certain successful clinical applications of biomaterial scaffolds, ideal bone regeneration remains a challenge in maxillofacial region due to its irregular shape, complex structure, and unique biological functions. Scaffolds that address multiple needs of maxillofacial bone regeneration are under development to optimize bone regeneration capacity, costs, operational convenience. etc. In this review, we first highlight the special considerations of bone regeneration in maxillofacial region and provide an overview of the biomaterial scaffolds for maxillofacial bone regeneration under clinical examination and their efficacy, which provide basis and directions for future scaffold design. Latest advances of these scaffolds are then discussed, as well as future perspectives and challenges. Deepening our understanding of these scaffolds will help foster better innovations to improve the outcome of maxillofacial bone tissue engineering.

Antibacterial Activities of Ag/Cellulose Nanocomposites Derived from Marine Environment Algae against Bacterial Tooth Decay

Dental caries is an infectious oral disease caused by the presence of different bacteria in biofilms. Multidrug resistance (MDR) is a major challenge of dental caries treatment. Swabs were taken from 65 patients with dental caries in Makkah, Saudi Arabia. Swabs were cultivated on mitis salivarius agar and de Man, Rogosa, and Sharpe (MRS) agar. VITEK 2 was used for the identification of isolated bacteria. Antibiotic susceptibility testing of the isolated bacteria was performed using commercial antibiotic disks. Ulva lactuca was used as a reducing agent and cellulose source to create nanocellulose and Ag/cellulose nanocomposites. Fourier-transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray diffraction spectroscopy (XRD) were used to characterize nanocellulose and Ag/cellulose nanocomposites. The results showed that most bacterial isolates were Streptococcus spp., followed by Staphylococcus spp. on mitis salivarius media. Lactobacillus spp. and Corynebacterium group f-1 were the bacterial isolates on de Man, Rogosa, and Sharpe (MRS) media. The antibiotic susceptibility test revealed resistance rates of 77%, 93%, 0, 83%, 79%, and 79% against penicillin G, Augmentin, metronidazole, ampicillin, ciprofloxacin, and cotrimoxazole, respectively. Ag/cellulose nanocomposites and Ag/cellulose nanocomposites with fluoride were the most effective antibacterial agents. The aim of this work was to assess the antibacterial activity of Ag/cellulose nanocomposites with and without fluoride against bacteria isolated from the oral cavities of patients with dental caries. This study demonstrated that Ag/cellulose nanocomposites have antibacterial properties against multidrug-resistant bacteria that cause dental caries.

Role and architectural significance of porous chitosan-based scaffolds in bone tissue engineering

In designing and fabricating scaffolds to fill the bone defects and stimulate new bone formation, the biomimetics of the construct is a crucial factor in invoking the bone microenvironment to promote osteogenic differentiation. Regarding structural traits, changes in porous characteristics of the scaffolds, such as pore size, pore morphology, and percentage porosity, may patronize or jeopardize their other physicochemical and biological properties. Chitosan (CS), a biodegradable naturally occurring polymer, has recently drawn considerable attention as a scaffolding material in tissue engineering and regenerative medicine. CS-based microporous scaffolds have been reported to aid osteogenesis under both in vitro and in vivo conditions by supporting cellular attachment and proliferation of osteoblast cells and the formation of mineralized bone matrix. This related notion may be found in numerous earlier research, even though the precise mechanism of action that encourages the development of new bone still needs to be understood completely. This article presents the potential correlations and the significance of the porous properties of the CS-based scaffolds to influence osteogenesis and angiogenesis during bone regeneration. This review also goes over resolving the mechanical limitations of CS by blending it with other polymers and ceramics.

Fabrication and characterization of ceramic-polymer composite 3D scaffolds and demonstration of osteoinductive propensity with gingival mesenchymal stem cells

The fabrication of biomaterial 3D scaffolds for bone tissue engineering applications involves the usage of metals, polymers, and ceramics as the base constituents. Notwithstanding, the composite materials facilitating enhanced osteogenic differentiation/regeneration are endorsed as the ideally suited bone grafts for addressing critical-sized bone defects. Here, we report the successful fabrication of 3D composite scaffolds mimicking the ECM of bone tissue by using ∼30 wt% of collagen type I (Col-I) and ∼70 wt% of different crystalline phases of calcium phosphate (CP) nanomaterials [hydroxyapatite (HAp), beta-tricalcium phosphate (βTCP), biphasic hydroxyapatite (βTCP-HAp or BCP)], where pH served as the sole variable for obtaining these CP phases. The different Ca/P ratio and CP nanomaterials orientation in these CP/Col-I composite scaffolds not only altered the microstructure, surface area, porosity with randomly oriented interconnected pores (80-450 μm) and mechanical strength similar to trabecular bone but also consecutively influenced the bioactivity, biocompatibility, and osteogenic differentiation potential of gingival-derived mesenchymal stem cells (gMSCs). In fact, BCP/Col-I, as determined from micro-CT analysis, achieved the highest surface area (∼42.6 m2 g-1) and porosity (∼85%), demonstrated improved bioactivity and biocompatibility and promoted maximum osteogenic differentiation of gMSCs among the three. Interestingly, the released Ca2+ ions, as low as 3 mM, from these scaffolds could also facilitate the osteogenic differentiation of gMSCs without even subjecting them to osteoinduction, thereby attesting these CP/Col-I 3D scaffolds as ideally suited bone graft materials.

The Diamond Concept Enigma: Recent Trends of Its Implementation in Cross-linked Chitosan-Based Scaffolds for Bone Tissue Engineering

An increasing number of publications over the past ten years have focused on the development of chitosan-based cross-linked scaffolds to regenerate bone tissue. The design of biomaterials for bone tissue engineering applications relies heavily on the ideals set forth by a polytherapy approach called the "Diamond Concept". This methodology takes into consideration the mechanical environment, scaffold properties, osteogenic and angiogenic potential of cells, and benefits of osteoinductive mediator encapsulation. The following review presents a comprehensive summarization of recent trends in chitosan-based cross-linked scaffold development within the scope of the Diamond Concept, particularly for nonload-bearing bone repair. A standardized methodology for material characterization, along with assessment of in vitro and in vivo potential for bone regeneration, is presented based on approaches in the literature, and future directions of the field are discussed.

Current advancements in bio-ink technology for cartilage and bone tissue engineering

In tissue engineering, the fate of a particular organ/tissue regeneration and repair mainly depends on three pillars - 3D architecture, cells used, and stimulus provided. 3D cell supportive structure development is one of the crucial pillars necessary for defining organ/tissue geometry and shape. In recent years, the advancements in 3D bio-printing (additive manufacturing) made it possible to develop very precise 3D architectures with the help of industrial software like Computer-Aided Design (CAD). The main requirement for the 3D printing process is the bio-ink, which can act as a source for cell support, proliferation, drug (growth factors, stimulators) delivery, and organ/tissue shape. The selection of the bio-ink depends upon the type of 3D tissue of interest. Printing tissues like bone and cartilage is always challenging because it is difficult to find printable biomaterial that can act as bio-ink and mimic the strength of the natural bone and cartilage tissues. This review describes different biomaterials used to develop bio-inks with different processing variables and cell-seeding densities for bone and cartilage 3D printing applications. The review also discusses the advantages, limitations, and cell bio-ink compatibility in each biomaterial section. The emphasis is given to bio-inks reported for 3D printing cartilage and bone and their applications in orthopedics and orthodontists. The critical/important performance and the architectural morphology requirements of desired bone and cartilage bio-inks were compiled in summary.

Histomorphometric evaluation of 3D printed graphene oxide-enriched poly(ε-caprolactone) scaffolds for bone regeneration

Objective

Restoring large boney defects using bone grafts alone is an unpredictable procedure. Biodegradable polymeric scaffolds suffer rapid biodegradation and lack sufficient osteo-conductivity. The aim of this study was to histomorphometrically evaluate three-dimensional printed graphene oxide-enriched poly(ε-caprolactone) (PCL) scaffolds for bone regeneration in a rabbit defect model using two different concentrations of graphene oxide. Basic characteristic properties and mount of new bone regeneration formation were evaluated.

Methods

two concentrations of graphene oxide (1 and 3 wt%) were added to PCL scaffolds using hot blind technique while pure PCL scaffolds served as a control. Laboratory characterization included scanning electron microscopy (SEM), x-ray diffraction analysis (XRD), contact angle, internal porosity, in addition to density measurements. All scaffolds were subjected to biodegradation evaluation and cell cytotoxicity test. In vivo bone regeneration was evaluated in the tibia defect of a rabbit model by measuring the amount of new bone formation (n = 15, ά = 0.05).

Results

SEM images showed slight reduction in pore size and increase in filament width of scaffolds with increasing GO contents. However, the printed scaffolds matched well with the dimensions of the original design. XRD patterns revealed characteristic peaks identifying microstructure of scaffolds. Addition of GO increased crystallinity of the scaffolds. The contact angle and porosity readings indicated reduction in measurements with increased content of GO indicating improved wetting properties while the density followed an opposing pattern. Higher biodegradability values were associated with higher GO content resulting in acceleration of observed biodegradation. The results of cytotoxicity test showed reduction in cell viability with higher GO content. Bone regeneration was significantly enhanced for 1 wt% GO scaffolds compared to other groups as was evident by higher bone density observed in x-ray images and higher amount of new bone formation observed at different time intervals.

Significance

Graphene oxide improved the physical and biological properties of PCL scaffolds and significantly enhanced new bone regeneration.

Conductive Polyaniline Particles Regulating In Vitro Hydrolytic Degradation and Erosion of Hydroxyapatite/Poly(lactide-co-glycolide) Porous Scaffolds for Bone Tissue Engineering

In addition to biocompatibility and bioactivity, scaffolds with superior bone tissue regenerative capacity should possess excellent functionality (e.g., electroactivity and conductivity) and biodegradability matching with the rate of bone reconstruction. However, current conductive scaffolds display a reduced biodegradability rate and weakened biocompatibility. In this study, injectable conductive porous scaffolds were fabricated, incorporating camphor sulfonic acid-doped polyaniline (PANI) into hydroxyapatite/poly(lactide-co-glycolide) (HA/PLGA) scaffolds, using solvent-casting/particulate-leaching methodology. These scaffolds demonstrated excellent electroactivity, conductivity, hydrophilicity, thermodynamic properties, antibacterial properties, and biocompatibility. Their degradation behavior was explored by regulating the PANI content. The results demonstrated that adding an appropriate content of PANI would increase the pore size, porosity, and water absorption of the conductive scaffold and promote the formation of filamentous fiber byproducts with acidic hydrolysates, which accelerated the degradation rate of the scaffold. Owing to π-π stacking and hydrogen bonding, the conductive scaffold with 10 wt % PANI efficiently retarded the decrease in the thermal and mechanical properties of the scaffolds during a 16 week degradation. Thus, better regulation of degradation behavior and correlation would allow conductive porous scaffolds, such as bone implants, to achieve better bone ingrowth and restoration.

Antibacterial Activity of Ulva/Nanocellulose and Ulva/Ag/Cellulose Nanocomposites and Both Blended with Fluoride against Bacteria Causing Dental Decay

One of the most prevalent chronic infectious disorders is tooth decay. Acids produced when plaque bacteria break down sugar in the mouth cause tooth decay. Streptococcus mutans and Lactobacillus acidophilus are the most prominent species related to dental caries. Innovative biocidal agents that integrate with a biomaterial to prevent bacterial colonization have shown remarkable promise as a result of the rapid advancement of nanoscience and nanotechnology. In this study, Ulva lactuca was used as a cellulose source and reducing agent to synthesize nanocellulose and Ulva/Ag/cellulose/nanocomposites. The characterizations of nanocellulose and Ulva/Ag/cellulose/nanocomposites were tested for FT-IR, TEM, SEM, EDS, XRD, and zeta potential. Ulva/Ag/cellulose/nanocomposites and Ulva/nanocellulose, both blended with fluoride, were tested as an antibacterial against S. mutans ATCC 25175 and L. acidophilus CH-2. The results of the SEM proved that nanocellulose is filament-shaped, and FT-IR proved that the functional groups of Ulva/nanocellulose and Ulva/Ag/cellulose/nanocomposites and cellulose are relatively similar but present some small diffusion in peaks. The TEM image demonstrated that the more piratical size distribution of Ulva/Ag/cellulose/nanocomposites ranged from 15 to 20 nm, and Ulva/nanocellulose ranged from 10 to 15 nm. Ulva/Ag/cellulose/nanocomposites have higher negativity than Ulva/nanocellulose. Ulva/Ag/cellulose/nanocomposites and Ulva/nanocellulose possess antibacterial activity against S. mutans ATCC 25175 and L. acidophilus CH-2, but Ulva/Ag/cellulose/nanocomposites are more effective, followed by that blended with fluoride. It is possible to use Ulva/Ag/cellulose/nanocomposites as an antimicrobial agent when added to toothpaste. It is promising to discover an economic and safe nanocomposite product from a natural source with an antimicrobial agent that might be used against tooth bacteria.

Collagen-chitosan-hydroxyapatite composite scaffolds for bone repair in ovariectomized rats

Lesions with bone loss may require autologous grafts, which are considered the gold standard; however, natural or synthetic biomaterials are alternatives that can be used in clinical situations that require support for bone neoformation. Collagen and hydroxyapatite have been used for bone repair based on the concept of biomimetics, which can be combined with chitosan, forming a scaffold for cell adhesion and growth. However, osteoporosis caused by gonadal hormone deficiency can thus compromise the expected results of the osseointegration of scaffolds. The aim of this study was to investigate the osteoregenerative capacity of collagen (Co)/chitosan (Ch)/hydroxyapatite (Ha) scaffolds in rats with hormone deficiency caused by experimental bilateral ovariectomy. Forty-two rats were divided into non-ovariectomized (NO) and ovariectomized (O) groups, divided into three subgroups: control (empty defect) and two subgroups receiving collagen/chitosan/hydroxyapatite scaffolds prepared using different methods of hydroxyapatite incorporation, in situ (CoChHa1) and ex situ (CoChHa2). The defect areas were submitted to macroscopic, radiological, and histomorphometric analysis. No inflammatory processes were found in the tibial defect area that would indicate immune rejection of the scaffolds, thus confirming the biocompatibility of the biomaterials. Bone formation starting from the margins of the bone defect were observed in all rats, with a greater volume in the NO groups, particularly the group receiving CoChHa2. Less bone formation was found in the O subgroups when compared to the NO. In conclusion, collagen/chitosan/hydroxyapatite scaffolds stimulate bone growth in vivo but abnormal conditions of bone fragility caused by gonadal hormone deficiency may have delayed the bone repair process.

Recent Advances in Hydroxyapatite-Based Biocomposites for Bone Tissue Regeneration in Orthopedics

Bone tissue is a nanocomposite consisting of an organic and inorganic matrix, in which the collagen component and the mineral phase are organized into complex and porous structures. Hydroxyapatite (HA) is the most used ceramic biomaterial since it mimics the mineral composition of the bone in vertebrates. However, this biomimetic material has poor mechanical properties, such as low tensile and compressive strength, which make it not suitable for bone tissue engineering (BTE). For this reason, HA is often used in combination with different polymers and crosslinkers in the form of composites to improve their mechanical properties and the overall performance of the implantable biomaterials developed for orthopedic applications. This review summarizes recent advances in HA-based biocomposites for bone regeneration, addressing the most widely employed inorganic matrices, the natural and synthetic polymers used as reinforcing components, and the crosslinkers added to improve the mechanical properties of the scaffolds. Besides presenting the main physical and chemical methods in tissue engineering applications, this survey shows that HA biocomposites are generally biocompatible, as per most in vitro and in vivo studies involving animal models and that the results of clinical studies on humans sometimes remain controversial. We believe this review will be helpful as introductory information for scientists studying HA materials in the biomedical field.

Three-layered PCL-collagen nanofibers containing melilotus officinalis extract for diabetic ulcer healing in a rat model

Active wound dressing with physicochemical and biological characteristics is more effective in healing diabetic foot ulcer (DFU). In this study, a 3-layer electrospun nanofiber wound dressings was fabricated, while its outer, middle and inner layers of the scaffold were made of PCL, PCL/collagen and collagen nanofibers, respectively. Various amounts of Melilotus officinalis extract were also loaded in the collagen nanofibers as a biologically active compound. The diameter and morphology of the obtained nanofibers were investigated by scanning electron microscopy (SEM) and FT-IR spectroscopy to analyse the composition of prepared dressings. The efficacy of the fabricated dressings as wound healing agent was assessed in streptozotocin-induced diabetic rats. The results demonstrated that the mean diameter of nanofibers are 373 ± 179 nm, 266 ± 108 nm, 160 ± 52 nm, and 393 ± 131 nm for PCL, PCL/collagen, pure collagen, and collagen nanofibers containing 0.08 g extract, respectively. The histo-pathology and histomorphometry assessments demonstrate the herbal extract-loaded electrospun dressings (especially containing 0.08 g of the extract) are promising in improving the diabetic ulcer healing. Our results indicated that the combination of drug did not compromise the physicochemical characteristics of wound dressing, while improving its biological activities.

Nanohydroxyapatite-Protein Interface in Composite Sintered Scaffold Influences Bone Regeneration in Rabbit Ulnar Segmental Defect

The healing physiology of bone repair and remodeling that occurs after normal fracture is well orchestrated. However, it fails in complex clinical conditions and hence requires augmentation by grafts. In this study, composite nanohydroxyapatite (nHA), poly(hydroxybutyrate) (PHB) and poly(ɛ-caprolactone) (PCL) constituted microspheres sintered three-dimensional scaffold were evaluated in rabbit ulnar segmental defect. A composite scaffold using PHB-PCL-nHA microspheres was developed with protein interface by solvent/non-solvent sintering to provide multiple cues such as biocomposition, cancellous bone equivalent meso-micro multi-scale porosity, and compressive strength. In vitro DNA quantification and alkaline phosphatase (ALP) assays revealed that the protein interfaced composite scaffolds supported osteoblast proliferation and mineralization significantly higher than scaffolds without protein and TCPS (p < 0.05). Scanning electron micrographs of osteoblasts cultured scaffolds demonstrated cell-matrix interaction, cell spreading, colonization and filopodial extension across the porous voids. Cylindrical scaffolds (5 × 10 mm) were implanted following segmental defect (10 mm) in rabbit ulnar bone and compared with untreated control. Radiography (4, 8 and 12 weeks) and µ-computed tomography (12 weeks) analysis showed directional bone tissue formation by bridging defective site in both scaffolds with and without protein interface. Whereas, undesired sclerotic-like tissue formation was observed in control groups from 8 weeks. Histology by hot Stevenel's blue and van Gieson's picrofuchsin staining has confirmed enhanced bone maturation in scaffold groups while presence of osteoids was observed in control after 12 weeks. Thus, the developed composite matrices exhibits osteoinductive, osteoconductive properties and demonstrates its bone regenerative potential owing to its compositional, micro & macro structural and mechanical properties. Graphical abstract.

Biocompatibility Studies on a Collagen-Hydroxyapatite Biomaterial

The current treatment of osteomyelitis includes systemic antibiotic therapy and a debridement procedure of the formed biofilm and necrotic tissue. Moreover, cements and three-dimensional scaffolds are used both for the delivery of therapeutic agents and as fillers for bone defects. The aim of our research was to test, on cellular cultures, the biocompatibility of a previously synthesized microporous biocomposite containing hydroxyapatite and a collagen matrix including a therapeutic agent (ciprofloxacin and gentamicin). The scaffold was obtained by direct mineralization namely co-precipitation of hydroxyapatite on a collagen matrix.

Collagen and nano-hydroxyapatite interactions in alginate-based microcapsule provide an appropriate osteogenic microenvironment for modular bone tissue formation

The addition of nano-hydroxyapatite (nHA) and collagen (Col) to the alginate (Alg) microcapsule hydrogel reduced swelling and degradation ratios while the compressive strength increased compared to Alg, Alg-Col, and Alg-nHA groups. MTT assay and Calcein-AM staining revealed an enhanced MG-63 osteoblasts viability in the Alg-nHA-Col hydrogel compared to the other groups. SEM showed the attachment of MG-63 osteoblasts inside Alg-Col hydrogels. Non-significant differences were found in antioxidant capacity of cells inside the Alg-nHA-Col hydrogel compared to the Alg group. Hematoxylin-Eosin staining showed the distribution of MG-63 osteoblasts inside microspheres. Calcium deposits, alkaline phosphatase (ALP) activity with the increase of intracellular calcium were found in Alg-nHA-Col group. Western blotting showed that levels of osteocalcin, ColA2, Sox-9, and ColA1 also significantly increased compared to the Alg, Alg-Col, Alg-nHA groups. The present study demonstrated that the addition of mineral nHA and protein (Col) into the Alg improves osteogenic potential and provides a 3D platform for modular bone tissue engineering.

Chitosan-collagen-hydroxyapatite membranes for tissue engineering

Tissue engineering is growing in developing new technologies focused on providing effective solutions to degenerative pathologies that affect different types of connective tissues. The search for biocompatible, bioactive, biodegradable, and multifunctional materials has grown significantly in recent years. Chitosan, calcium phosphates collagen, and their combination as composite materials fulfill the required properties and could result in biostimulation for tissue regeneration. In the present work, the chitosan/collagen/hydroxyapatite membranes were prepared with different concentrations of collagen and hydroxyapatite. Cell adhesion was evaluated by MTS assay for two in vitro models. Additionally, cytotoxicity of the different membranes employing hemolysis of erythrocytes isolated from human blood was carried out. The structure of the membranes was analyzed by X-rays diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and thermal stability properties by thermogravimetric methods (TGA). The highest cell adhesion after 48 h was obtained for chitosan membranes with the highest hydroxyapatite and collagen content. All composite membranes showed good cell adhesion and low cytotoxicity, suggesting that these materials have a significant potential to be used as biomaterials for tissue engineering. Graphical abstract.

Collagen-based biocomposites inspired by bone hierarchical structures for advanced bone regeneration: ongoing research and perspectives

Bone is a hard-connective tissue composed of matrix, cells and bioactive factors with a hierarchical structure, where the matrix is mainly composed of type I collagen and hydroxyapatite. Collagen fibers assembled by collagen are the template for mineralization and make an important contribution to bone formation and the bone remodeling process. Therefore, collagen has been widely clinically used for bone/cartilage defect regeneration. However, pure collagen implants, such as collagen scaffolds or sponges, have limitations in the bone/cartilage regeneration process due to their poor mechanical properties and osteoinductivity. Different forms of collagen-based composites prepared by incorporating natural/artificial polymers or bioactive inorganic substances are characterized by their interconnected porous structure and promoting cell adhesion, while they improve the mechanical strength, structural stability and osteogenic activities of the collagen matrix. In this review, various forms of collagen-based biocomposites, such as scaffolds, sponges, microspheres/nanoparticles, films and microfibers/nanofibers prepared by natural/synthetic polymers, bioactive ceramics and carbon-based materials compounded with collagen are reviewed. In addition, the application of collagen-based biocomposites as cytokine, cell or drug (genes, proteins, peptides and chemosynthetic) delivery platforms for proangiogenesis and bone/cartilage tissue regeneration is also discussed. Finally, the potential application, research and development direction of collagen-based biocomposites in future bone/cartilage tissue regeneration are discussed.

Advocating Electrically Conductive Scaffolds with Low Immunogenicity for Biomedical Applications: A Review

Scaffolds support and promote the formation of new functional tissues through cellular interactions with living cells. Various types of scaffolds have found their way into biomedical science, particularly in tissue engineering. Scaffolds with a superior tissue regenerative capacity must be biocompatible and biodegradable, and must possess excellent functionality and bioactivity. The different polymers that are used in fabricating scaffolds can influence these parameters. Polysaccharide-based polymers, such as collagen and chitosan, exhibit exceptional biocompatibility and biodegradability, while the degradability of synthetic polymers can be improved using chemical modifications. However, these modifications require multiple steps of chemical reactions to be carried out, which could potentially compromise the end product's biosafety. At present, conducting polymers, such as poly(3,4-ethylenedioxythiophene) poly(4-styrenesulfonate) (PEDOT: PSS), polyaniline, and polypyrrole, are often incorporated into matrix scaffolds to produce electrically conductive scaffold composites. However, this will reduce the biodegradability rate of scaffolds and, therefore, agitate their biocompatibility. This article discusses the current trends in fabricating electrically conductive scaffolds, and provides some insight regarding how their immunogenicity performance can be interlinked with their physical and biodegradability properties.

Review of the Applications of Biomedical Compositions Containing Hydroxyapatite and Collagen Modified by Bioactive Components

Regenerative medicine is becoming a rapidly evolving technique in today's biomedical progress scenario. Scientists around the world suggest the use of naturally synthesized biomaterials to repair and heal damaged cells. Hydroxyapatite (HAp) has the potential to replace drugs in biomedical engineering and regenerative drugs. HAp is easily biodegradable, biocompatible, and correlated with macromolecules, which facilitates their incorporation into inorganic materials. This review article provides extensive knowledge on HAp and collagen-containing compositions modified with drugs, bioactive components, metals, and selected nanoparticles. Such compositions consisting of HAp and collagen modified with various additives are used in a variety of biomedical applications such as bone tissue engineering, vascular transplantation, cartilage, and other implantable biomedical devices.

Recent Progress on Biodegradable Tissue Engineering Scaffolds Prepared by Thermally-Induced Phase Separation (TIPS)

Porous biodegradable scaffolds provide a physical substrate for cells allowing them to attach, proliferate and guide the formation of new tissues. A variety of techniques have been developed to fabricate tissue engineering (TE) scaffolds, among them the most relevant is the thermally-induced phase separation (TIPS). This technique has been widely used in recent years to fabricate three-dimensional (3D) TE scaffolds. Low production cost, simple experimental procedure and easy processability together with the capability to produce highly porous scaffolds with controllable architecture justify the popularity of TIPS. This paper provides a general overview of the TIPS methodology applied for the preparation of 3D porous TE scaffolds. The recent advances in the fabrication of porous scaffolds through this technique, in terms of technology and material selection, have been reviewed. In addition, how properties can be effectively modified to serve as ideal substrates for specific target cells has been specifically addressed. Additionally, examples are offered with respect to changes of TIPS procedure parameters, the combination of TIPS with other techniques and innovations in polymer or filler selection.

Amnion and collagen-based blended hydrogel improves burn healing efficacy on a rat skin wound model in the presence of wound dressing biomembrane

BACKGROUND

A burn wound is one of the most frequent and devastating injuries for patients which requires extensive care. Early treatment of burn wounds improves healing significantly.

OBJECTIVE

This study was designed to investigate the efficacy of amnion and collagen-based hydrogels on cutaneous burn wound healing in rats with covering membrane.

METHODS

We prepared a novel cell free hydrogel comprising human amnion, rabbit collagen, carboxymethyl cellulose sodium salt, citric acid, methyl paraben, propyl paraben, glycerin and triethanol amine. The wound covering membrane was developed from rabbit collagen and prawn shell chitosan. Beside swelling ratio, water absorption, equilibrium water content, gel fraction and spreadability analysis, in vitro cytotoxicity and biocompatibility tests were performed for the formulated hydrogels. Following the skin irritation study, second-degree burns were created on the dorsal region of the rats and the gels were applied with/without covering membrane to study the wound contraction and re-epithelialization period.

RESULTS

The formulated hydrogels were observed non-cytotoxic and compatible with human blood cells. No erythema and edema were found in skin irritation assay confirming the safety and applicability. Hydrogel consisting in a combination of amnion and collagen demonstrated significantly rapid wound healing, driven by complete re-epithelialization (16.75 ± 0.96 days) and closure by wound contraction (72 ± 3.27%, P < 0.0000009) when wound dressing membrane was used, whereas this gel alone healed about 62.5 ± 4.43% (P < 0.00001) and required 18.75 ± 0.50 days to complete re-epithelialization. Additionally, the gel with covering membrane treated group had maximum average body weight, food and water intake.

CONCLUSION

The amnion and collagen-based blended gel offers alternative possibilities to treat skin wounds when covered with film, which could overcome the limitations associated with modern therapeutic products such as high costs, long manufacturing times, complexities, storing, and presence of living biomaterials.

UV-assisted synthesis of hydroxyapatite from eggshells at ambient temperature: cytotoxicity, drug delivery and bioactivity

Hydroxyapatite [Ca10(PO4)6(OH)2], an important biomaterial, retains a chemical structure that is similar to the mineral phase of bone. Consequently, the ability of hydroxyapatite (Hap) to augment bone growth within bone tissue has made it a potential candidate for use as a hard tissue-implant material. In this work, adopting a UV-mediated solid-state method for the first time, hydroxyapatite was synthesized from eggshells and no thermal treatment was used but ambient temperature was maintained. This simple synthesis process involved a combination of ball milling of the starting materials followed by UV-irradiation. UV-excitation of the Ca and P precursors resulted in the desired Hap and X-ray diffraction (XRD), Fourier-transform infrared (FT-IR) and Raman spectroscopic techniques were used for characterization. The potency of UV-Hap as a biomaterial was examined via the bioactivity, cytotoxicity and the drug (ciprofloxacin) loading-releasing response, which was encouraging. The results of the cell viability assays complied an insignificant cytotoxicity and the simulated body fluid immersion test indicated the bioactivity was within the acceptable range. On the other hand, to better understanding the drug ejection and associated transport phenomenon, two kinetic models (Higuchi and Ritger-Peppas models) were used and a diffusion controlled ciprofloxacin release mechanism was observed using the Higuchi model. However, the experimental outcomes of a drug delivery response exposed UV-Hap as a favorable vehicle for drug loading and release. Hence, this research highlights the prospects of a UV-assisted synthesis method as a green route for the synthesis of Hap to be applied in biomedical fields.

Tissue engineering applications in otolaryngology-The state of translation

While tissue engineering holds significant potential to address current limitations in reconstructive surgery of the head and neck, few constructs have made their way into routine clinical use. In this review, we aim to appraise the state of head and neck tissue engineering over the past five years, with a specific focus on otologic, nasal, craniofacial bone, and laryngotracheal applications. A comprehensive scoping search of the PubMed database was performed and over 2000 article hits were returned with 290 articles included in the final review. These publications have addressed the hallmark characteristics of tissue engineering (cellular source, scaffold, and growth signaling) for head and neck anatomical sites. While there have been promising reports of effective tissue engineered interventions in small groups of human patients, the majority of research remains constrained to in vitro and in vivo studies aimed at furthering the understanding of the biological processes involved in tissue engineering. Further, differences in functional and cosmetic properties of the ear, nose, airway, and craniofacial bone affect the emphasis of investigation at each site. While otolaryngologists currently play a role in tissue engineering translational research, continued multidisciplinary efforts will likely be required to push the state of translation towards tissue-engineered constructs available for routine clinical use.

LEVEL OF EVIDENCE

NA.

Human bone and amniotic membrane banking in Bangladesh for grafting: the impact of the international atomic energy agency (IAEA) programme

The idea of establishing a human tissue bank in Bangladesh was started in 1985. However, in 2003, with the active cooperation of international atomic energy agency (IAEA) and Bangladesh Atomic Energy Commission, a tissue bank laboratory was upgraded as a unit for tissue banking and research. Due to increasing demand of allograft, this unit was transformed as an independent institute "Institute of Tissue Banking and Biomaterial Research (ITBBR)" in 2016. This is the only human tissue bank in Bangladesh, which processes human bone and amniotic membrane to provide safe and cost-effective allografts for transplantation. Importantly, banking of human cranial bone as autograft has also started at ITBBR. These processed grafts are sterilized using gamma radiation according to the IAEA Code of Practice for the radiation sterilization of tissues allografts. The amount of grafts produced by the ITBBR from 2007 to 2018 were 120,800 cc of bone chips, 45,420 cm² of amniotic membranes, 277 vials of de-mineralized bone granules (DMB), 95 pieces of massive bones, and 134 pieces of cranial bones. Overall, 112,748 cc of bone chips, 40,339 cm² of amniotic membranes, 174 vials of DMB, 44 pieces of massive bones, and 64 pieces of cranial bones were transplanted successfully. Nevertheless, to cope up with the modern advanced concepts of cell and tissue banking for therapeutic purpose, ITBBR is working to set up facilities for skin banking, stem cells banking including amniotic and cord blood derived stem cells and scaffold designing. To ensure the quality, safety, ethical and regulatory issues are sustainable in cell and tissue banking practices, ITBBR always works with the Government of Bangladesh for enhancing the national tissue transplantation programme within the contemporary facilities.

Chitosan/collagen based biomimetic osteochondral tissue constructs: A growth factor-free approach

Tissue engineering approach offers alternative strategies to develop multi-layered/multi-component osteochondral mimetic constructs to meet the requirements of the heterogeneous and layered structure of native osteochondral tissue. Herein, an iterative overlaying process to fabricate a multi-layered scaffold with a gradient composition and layer specific structure have been developed by combining the natural extracellular matrix (ECM) components-chitosan, type I collagen, type II collagen, nanohydroxyapatite- of the osteochondral tissue in biomimetic compositions. Subchondral bone layer was prepared by using freeze-drying method to obtain 3D porous scaffolds. The calcified cartilage and cartilage layers were prepared by thermal gelation method in the hydrogel form. Osteochondral scaffolds fabricated by iterative overlaying of each distinct layer exhibited a porous, continuous gradient structure and supported cell proliferation in a co-culture of MC3T3-E1 preosteoblasts and ATDC5 chondrocytes. Histology and biochemical analysis showed enhanced extracellular matrix production and demonstrated collagen and glycosaminoglycan deposition. Expression of genes specific for bone, calcified cartilage and cartilage were improved in the osteochondral scaffold. Overall, these findings suggest that iterative overlaying of freeze-dried scaffolds and hydrogel matrices prepared by using ECM components in biomimetic ratios to fabricate gradient, multi-layered structures can be a promising strategy without the need for growth factors.

Aloe vera-loaded nanofibrous scaffold based on Zein/Polycaprolactone/Collagen for wound healing

Recently, the use of nanofibers (NFs) for tissue engineering has been more developed. For this purpose, we fabricated the NFs (Zein/Polycaprolactone/Collagen) (Zein/PCL/Collagen) incorporated by zinc oxide NPs (ZnO NPs) and Aloe-vera (NFs/ZnO/Alv) using the electrospinning method. Prepared NFs were studied for their morphological, mechanical, thermal stability, and hydrophilic properties. Among the developed NFs, those loaded by ZnO (1 wt%) and Alv (8 wt%) and with Zein/PCL (70:30) displayed the suitable thermal stability and mechanical properties. The water contact angle of NFs improved by decreasing the Zein/PCL blending ratio. Cell culture results showed that the NFs had good cytocompatibility. The cell adhesion potential of this mats were certified with studying by fibroblast cells for various time intervals (24 h and 72 h). The NFs/ZnO/Alv sample revealed inhibition activity against S. aureus (19.23 ± 1.35 mm) and E. coli (15.38 ± 1.12 mm) bacteria. Thus, these results offered that the prepared NFs can be promised as an active scaffold for wound healing uses.

Novel bone-mimetic nanohydroxyapatite/collagen porous scaffolds biomimetically mineralized from surface silanized mesoporous nanobioglass/collagen hybrid scaffold: Physicochemical, mechanical and in vivo evaluations

Bone-mimetic scaffolds are receiving much interest as such scaffolds exhibit excellent biocompatibility and very close mimic to bone structure and composition. Here, novel bone-mimetic nanohydroxyapatite (nHA)/collagen (Col) porous scaffolds (nHA/Col) were prepared from surface silanized mesoporous nanobioglass (NBG)/Col hybrid scaffold by biomimetic mineralization. Surface silanized mesoporous NBG was prepared by ultrasound-assisted sol-gel method and post treatment with 3-aminopropyltriethylsilane (APTS). The surface silanized mesoporous NBG was characterized by transmission electron microscopy (TEM), transmission electron microscopy-selected area electron diffraction (TEM-SAED) and X-ray photoelectron spectroscopy (XPS). The physicochemical/mechanical characterizations of the scaffolds included scanning electron microscopy (SEM) and TEM imaging of micro/nanostructure, energy dispersive X-ray (EDX) analysis of chemical composition, TEM-SAED and X-ray diffraction/Attenuated total Reflectance-Fourier Infrared spectroscopy (XRD/ATR-FTIR) analyses of amorphous-to-crystalline transformations, thermogravimetric/differential scanning calorimetric (TGA/DSC) analyses of thermal behaviour , porosity and dynamic mechanical analyses. The presence of NBG in collagen fibrillar network enabled progressive growth of HA nanocrystals and generation of a novel bone-mimetic hybrid structures while preserving the highly porous structure of collagen scaffold. The crystallinity, crystallite size and crystal morphology of the grown HA nanocrystals were controllable by regulation of the mineralization time. Furthermore, the osteogenic properties of the non-mineralized (NBG/Col) and mineralized (nHA/Col) hybrid porous scaffolds were examined in vivo using critical-sized calvarial bone defect model in rat. Histological and micro-computed tomography (Micro-CT) analyses after 6 weeks of implantation revealed that the mineralized scaffolds possess excellent in vivo osteogenic potential compared to the non-mineralized one. Collectively, by using surface silanized mesoporous NBG hybridization with collagen fibrillar network, we successfully introduced a new approach for developing novel bone-mimetic nanohydroxyapatite/collagen hybrid scaffolds that possess significant potential for bone tissue regeneration.