Chitosan: a versatile biopolymer for orthopaedic tissue-engineering

Challenges in Fabrication of Tissue-Engineered Cartilage with Correct Cellular Colonization and Extracellular Matrix Assembly

A correct articular cartilage ultrastructure regarding its structural components and cellularity is important for appropriate performance of tissue-engineered articular cartilage. Various scaffold-based, as well as scaffold-free, culture models have been under development to manufacture functional cartilage tissue. Even decellularized tissues have been considered as a potential choice for cellular seeding and tissue fabrication. Pore size, interconnectivity, and functionalization of the scaffold architecture can be varied. Increased mechanical function requires a dense scaffold, which also easily restricts cellular access within the scaffold at seeding. High pore size enhances nutrient transport, while small pore size improves cellular interactions and scaffold resorption. In scaffold-free cultures, the cells assemble the tissue completely by themselves; in optimized cultures, they should be able to fabricate native-like tissue. Decellularized cartilage has a native ultrastructure, although it is a challenge to obtain proper cellular colonization during cell seeding. Bioprinting can, in principle, provide the tissue with correct cellularity and extracellular matrix content, although it is still an open question as to how the correct molecular interaction and structure of extracellular matrix could be achieved. These are challenges facing the ongoing efforts to manufacture optimal articular cartilage.

Repair of Bone Defects with Chitosan-Collagen Biomembrane and Scaffold Containing Calcium Aluminate Cement

Innovative biomaterials can provide a promising new direction for the treatment of bone defects, stimulating a proper repair process, with no damage to adjacent tissues. The purpose of this in vivo study was to evaluate the biocompatibility and the osteoinductive capacity of chitosan-collagen biomembrane and scaffold containing calcium aluminate cement. Eighteen New Zealand white rabbits (Oryctolagus cuniculus) were distributed according to the experimental times of analysis (7, 15 and 30 days). Four bone defects were created in the rabbits calvaria, which were individually filled with the biomembrane, scaffold, blood clot (negative control) and autologous bone (positive control). Histopathological analysis was performed using optical microscope at 32´, 64´, 125´ and 320´ magnifications. Cell response to inflammation and new bone tissue formation was quantified using a score system. The biomembrane group presented greater inflammatory response at 15 days, with significant difference to autologous bone group (p<0.05). There was no statistically significant difference for foreign body type reaction among groups (p>0.05). Concerning new bone formation, linear closure of the defect area was observed more evidently in the group with autologous bone. The scaffold group presented similar results compared with the autologous bone group at 30 days (p>0.05). Both tested biomaterials presented similar biocompatibility compared with the control groups. In addition, the biomembrane and scaffold presented similar osteoinductive capacity, stimulating bone repair process in the course of the experimental time intervals.

Construction of Self-defensive Antibacterial and Osteogenic AgNPs/Gentamicin Coatings with Chitosan as Nanovalves for Controlled release

To solve the Ti implants-associated infection and poor osseointegration problems, we have constructed the AgNPs/gentamicin (Gen)-loaded silk fibroin (SF) coating with acceptable antibacterial and osteogenic aptitude. Nevertheless, due to uncontrollably sustained drug release, this bactericidal coating encountered some tricky problems, such as local high Ag concentration, short life-span and potential cytotoxicity. In this work, a chitosan (CS) barrier layer was constructed to prebuilt the SF-based film by two means, dip-coating (DCS) and spin-coating (SCS). Intriguingly, the CS barrier layer constructed by spin-coating highly improved the hydrophilic and protein-absorbed performances. As verified in the release profile, both coatings showed a prolonged and pH-dependent pattern of Ag⁺ with an accelerated release in acidic condition. Also, the multilayer coating with a SCS barrier layer showed an apparent bacteria-trigged antibacterial and biofilm-inhibited performances, whereas the improvements of antibacterial abilities of DCS coating were limited. The mechanisms could be explained that the pH decrease induced by the attachment and proliferation of bacteria triggered collapse of CS barrier layer, accelerating the release of bactericides. Moreover, benefitted from pH-dependent release behavior of Ag and bioactive SCS layer, functional coatings highly enhanced the initial adhesion, migration and proliferation of preosteoblast MC3T3-E1 cells, and subsequently accelerated osteoblast differentiation (alkaline phosphatase production). A relevant aspect of this work was to demonstrate the essential effect of reasonable construction of self-defensive barrier layer in achieving the balance between the high-efficiency bacterial killing and osteogenic activity, and highlighted its excellent potential in clinical applications.

Nano-TiO2 Doped Chitosan Scaffold for the Bone Tissue Engineering Applications

The present focus is on the synthesis of highly effective, porous, biocompatible, and inert scaffold by using ceramic nanoparticles and natural polymer for the application in tissue engineering. Freeze-drying method was used to fabricate nano-TiO₂ doped chitosan sample scaffold. Nano-TiO₂/chitosan scaffold can considered as an effective solution for damaged tissue regeneration. The interaction between chitosan (polysaccharide) and nano-TiO₂ makes it highly porous and brittle that could be an effective substitute for bone tissue engineering. The TiO₂ nanoparticles have a great surface area and inert properties while chitosan is highly biocompatible and antibacterial. The physiochemical properties of TiO₂ nanoparticles and scaffold are evaluated by XRD and FTIR. The nanoparticles doped scaffold has given improved density (1.2870g/cm³) that is comparatively relevant to the dry bone (0.8 - 1.2 gm/cm³). The open and closed porosity of sample scaffold were measured by using Brunauer–Emmett–Teller analyzer (BET) and scanning electron microscopy (SEM). The mechanical properties are examined by stable microsystem (Texture Analyzer). The in vitro degradation of scaffold is calculated in PBS containing lysozyme at pH 7.4. Electron and fluorescence microscopy are used to study morphological characteristics of the scaffolds and TiO₂ nanoparticles. The growth factor and drug-loaded composites can improve osteogenesis and vascularization.

Application of nano-hydroxyapatite/chitosan scaffolds on rat calvarial critical-sized defects: A pilot study

BACKGROUND

The purpose of this pilot study was to evaluate for the first time the effect of 75/25 w/w nano-Hydroxyapatite/Chitosan (nHAp/CS) scaffolds on Guided Bone Regeneration (GBR) in rat calvarial critical-sized defects (CSDs).

MATERIAL AND METHODS

Six adult Sprague Dawley rats, 3 males and 3 females, were used. Two CSDs, full thickness and 5mm in diameter, were trephined in both sides of the parietal bone. The right CSD was filled with nHAp/CS scaffold, while the left CSD remained empty, as the control group. The wound was sutured in layers. Rats were euthanized with diethyl ether inhalation at 2, 4 and 8 weeks after surgical procedure. Histological and histomorphometric analysis was performed within distinct regions of interest (ROI): the lateral area inward of the middle sagittal seam; the lateral area outward of the middle sagittal seam and the central area.

RESULTS

The mean surface of newly formed bone (in μm2) in the lateral area inward of the middle sagittal seam of all rats was significantly higher (P=0.039) in the experimental group (91733.00±38855.60) than the control group (46762.17±25507.97). The NOex-c, defined as total number of osteocytes (OST) in newly formed bone surface in experimental group [experimental OST] minus the total number of osteocytes in newly formed bone surface in control group [control OST], was significantly greater (P=0.029) at 4th week post-surgery. Within the experimental group, a statistically significant increase (P=0.042) in the surface of newly formed bone was noticed in rats euthanized in 4th week compared with rats euthanized in 2nd week after surgery in the lateral area inward of the middle sagittal seam.

CONCLUSIONS

The results of this study suggest that 75/25 w/w nHAp/CS scaffolds should be considered as a suitable biomaterial for GBR.

Tailoring the Interface of Biomaterials to Design Effective Scaffolds

Tissue engineering (TE) is a multidisciplinary science, which including principles from material science, biology and medicine aims to develop biological substitutes to restore damaged tissues and organs. A major challenge in TE is the choice of suitable biomaterial to fabricate a scaffold that mimics native extracellular matrix guiding resident stem cells to regenerate the functional tissue. Ideally, the biomaterial should be tailored in order that the final scaffold would be (i) biodegradable to be gradually replaced by regenerating new tissue, (ii) mechanically similar to the tissue to regenerate, (iii) porous to allow cell growth as nutrient, oxygen and waste transport and (iv) bioactive to promote cell adhesion and differentiation. With this perspective, this review discusses the options and challenges facing biomaterial selection when a scaffold has to be designed. We highlight the possibilities in the final mold the materials should assume and the most effective techniques for its fabrication depending on the target tissue, including the alternatives to ameliorate its bioactivity. Furthermore, particular attention has been given to the influence that all these aspects have on resident cells considering the frontiers of materiobiology. In addition, a focus on chitosan as a versatile biomaterial for TE scaffold fabrication has been done, highlighting its latest advances in the literature on bone, skin, cartilage and cornea TE.

Biological Compatibility of a Polylactic Acid Composite Reinforced with Natural Chitosan Obtained from Shrimp Waste

The aim of this work is to evaluate the effect of chitosan content (1, 3 and 5 wt %) dispersed in polylactic acid (PLA) on the structure and properties of composites. Also, the hydrolytic degradation, and the cell viability and adhesion of human MG-63 osteoblasts are analyzed to determine the composites’ suitability for use in tissue engineering. For the manufacture of the materials, natural chitosan was extracted chemically from shrimp exoskeleton. The composites were fabricated by extrusion, because it is a low-cost process, it is reproducible, and it does not compromise the biocompatibility of the materials. FT-IR and XRD show that the chitosan does not change the polymer structure, and interactions between the composite components are discarded. In vitro degradation tests show that the composites do not induce significant pH changes in phosphate buffer solution due to their low susceptibility to hydrolytic degradation. The adhesion and morphological characteristics of the osteoblasts are evaluated using confocal microscopy and scanning electron microscopy. The cell viability is determined by the MTT assay. Osteoblasts adhesion is observed on the surface of PLA and composites. A higher amount of chitosan, higher number of cells with osteoblastic morphology, and mineralized nodules are observed on the composite surface. The highest metabolic activity is evidenced at 21 days. The results suggest that the Polylactic acid/chitosan composites are potentially suitable for use as a biomaterial.

Novel phytochemical Cissus quadrangularis extract–loaded chitosan/Na-carboxymethyl cellulose–based scaffolds for bone regeneration

Medicinal plants are attracting considerable interest as a potential therapeutic agent for bone tissue regeneration. Cissus quadrangularis L. is also a medicinal plant known with its osteogenic activity. In this study, a phytochemical scaffold was produced by incorporating Cissus quadrangularis with chitosan/Na-carboxymethyl cellulose blend by lyophilization technique. The effect of Cissus quadrangularis loading on the mechanical, morphological, chemical, and degradation properties as well as in vitro cytotoxicity, cell proliferation, and differentiation of the composites was investigated. Scanning electron microscopy images showed that porous Cissus quadrangularis–loaded scaffolds were obtained with an average pore size of 148–209 µm which is appropriate for bone regeneration. Cissus quadrangularis incorporation enhanced the compression modulus of scaffolds from 76 to 654 kPa. In vitro cell culture results indicated that Cissus quadrangularis/chitosan/Na-carboxymethyl cellulose scaffolds provided a favorable substrate for the osteoblast adhesion, proliferation, and mineralization. Results supported the osteoinductive property of the Cissus quadrangularis extract–incorporated scaffolds even without osteogenic media supplement. Cissus quadrangularis extract increased the alkaline phosphatase activity of the SaOS-2 cells on scaffolds on 7th and 14th days of incubation. The investigation of characterization and cell culture studies suggest that Cissus quadrangularis–loaded osteoinductive Cissus quadrangularis/chitosan/Na-carboxymethyl cellulose scaffold can serve as a potential biomaterial for bone tissue engineering applications.

Improvement of physico-chemical properties of dextran-chitosan composite scaffolds by addition of nano-hydroxyapatite

Nano-hydroxyapatite was incorporated into polymer matrix of Dextran/Chitosan to achieve a novel composite scaffold by freeze drying technique. The synthesized composite scaffolds were recognized by different performances such as: X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and Scanning electron microscope (SEM). The results revealed the complex formation between dextran and chitosan with an excellent dispersion of nHA inside the polymer matrix. The SEM images showed the presence of interconnected pore structure inside the scaffolds. The porosity of the composites was found to decrease from 82% to 67% by adding nanohydroxyapatite to the polymer matrix of Dextran/Chitosan. The mechanical properties of the scaffolds were measured by compression test. The obtained results verified that the presence of nHA can noticeably enhance young’s modulus and compressive strength of the composite scaffolds. All the obtained results essentially recommend that these composites can be a good candidate for bone tissue engineering applications.

Thermosensitive chitosan gels containing calcium glycerophosphate

In this paper the properties of thermosensitive chitosan hydrogels, formulated with chitosan chloride with β-glycerophosphate disodium salt hydrate and chitosan chloride with β-glycerophosphate disodium salt hydrate enriched with calcium glycerophosphate, are presented. The study focused on the determination of the hydrogel structure after conditioning in water. The structure of the gels was investigated by Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM). The crystallinity of the gel structure was determined by X-ray diffraction analysis (XRD) and the thermal effects were determined based on DSC thermograms.

Chitosan-grafted-poly(methacrylic acid)/graphene oxide nanocomposite as a pH-responsive de novo cancer chemotherapy nanosystem

The aim of this study was the design and development of a novel de novo drug delivery system for cancer chemotherapy. For this purpose, chitosan (CS) functionalized using phthalic anhydride followed by 4-cyano, 4-[(phenylcarbothioyl) sulfanyl] pentanoic acid as a chain transfer agent (CTA) to afford CS-CTA macroinitiator. The synthesized CS-CTA macroinitiator was then copolymerized with methacrylic acid (MAA) monomer using reversible addition-fragmentation chain transfer (RAFT) polymerization technique to produce chitosan-graft-poly(methacrylic acid) (CS-g-PMAA) graft copolymer. Afterward, graphene oxide (GO) nanosheets were incorporated into the synthesized copolymer through the physical interactions. The CS-g-PMAA/GO nanocomposite was loaded with doxorubicin hydrochloride (DOX) as a universal anticancer drug. The biocompatibility, DOX-loading capacity, and pH dependent drug release behavior of the developed nanocomposite were also investigated. As the experimental results, as well as superior biological and physicochemical features of CS and GO, we envision that the developed CS-g-PMAA/GO nanocomposite may be applied as de novo drug delivery nanosystem for cancer chemotherapy.

Collagen/chitosan/hyaluronic acid - based injectable hydrogels for tissue engineering applications - design, physicochemical and biological characterization

Studies on synthesis, physico-chemical and biological properties of novel biomimetic materials, potentially useful as injectable hydrogels are presented. These materials are in situ prepared chemically crosslinked collagen/chitosan/hyaluronic acid-based hydrogels exhibiting potential for tissue regeneration. Optimization of hydrogels involved testing the effect of various concentration of crosslinking agent (genipin) as well as different ratios of biopolymers used on their properties. The changes in the content of hyaluronic acid and in the genipin concentration used have been shown to be crucial. Employing the highest concentration of crosslinking agent studied (20 mM) the hydrogels of compact structure, characterized by good mechanical properties and prolonged degradation profile can be obtained. Changing the HA content in sol mixture the hydrogel of various wettability; more or less hydrophilic when compared to pure collagen/chitosan hydrogels can be fabricated. The in vitro cell culture study has shown that the surface of the prepared materials ensures suitable biocompatibility. These hydrogels can support the proliferation and adhesion of MG-63 cell line as it was demonstrated using Alamar Blue assay and SEM observations. It is believed that the collagen/chitosan/hyaluronic acid hydrogels crosslinked with genipin are particularly promising materials for bone regeneration procedures, especially attractive for regeneration of small bone losses. This is the first paper in the litearature presenting results of studies on that type of biopolymeric injectable hydrogels chemically crosslinked with genipin.

Chitosan/gelatin scaffolds support bone regeneration

Chitosan/Gelatin (CS:Gel) scaffolds were fabricated by chemical crosslinking with glutaraldehyde or genipin by freeze drying. Both crosslinked CS:Gel scaffold types with a mass ratio of 40:60% form a gel-like structure with interconnected pores. Dynamic rheological measurements provided similar values for the storage modulus and the loss modulus of the CS:Gel scaffolds when crosslinked with the same concentration of glutaraldehyde vs. genipin. Compared to genipin, the glutaraldehyde-crosslinked scaffolds supported strong adhesion and infiltration of pre-osteoblasts within the pores as well as survival and proliferation of both MC3T3-E1 pre-osteoblastic cells after 7 days in culture, and human bone marrow mesenchymal stem cells (BM-MSCs) after 14 days in culture. The levels of collagen secreted into the extracellular matrix by the pre-osteoblasts cultured for 4 and 7 days on the CS:Gel scaffolds, significantly increased when compared to the tissue culture polystyrene (TCPS) control surface. Human BM-MSCs attached and infiltrated within the pores of the CS:Gel scaffolds allowing for a significant increase of the osteogenic gene expression of RUNX2, ALP, and OSC. Histological data following implantation of a CS:Gel scaffold into a mouse femur demonstrated that the scaffolds support the formation of extracellular matrix, while fibroblasts surrounding the porous scaffold produce collagen with minimal inflammatory reaction. These results show the potential of CS:Gel scaffolds to support new tissue formation and thus provide a promising strategy for bone tissue engineering.

Mechanically enhanced nested-network hydrogels as a coating material for biomedical devices

Well-organized composite formations such as hierarchical nested-network (NN) structure in bone tissue and reticular connective tissue present remarkable mechanical strength and play a crucial role in achieving physical and biological functions for living organisms. Inspired by these delicate microstructures in nature, an analogous scaffold of double network hydrogel was fabricated by creating a poly(2-hydroxyethyl methacrylate) (pHEMA) network in the porous structure of alginate hydrogels. The resulting hydrogel possessed hierarchical NN structure and showed significantly improved mechanical strength but still maintained high elasticity comparable to soft tissues due to a mutual strengthening effect between the two networks. The tough hydrogel is also self-lubricated, exhibiting a surface friction coefficient comparable with polydimethylsiloxane (PDMS) substrates lubricated by a commercial aqueous lubricant (K-Y Jelly) and other low surface friction hydrogels. Additional properties of this hydrogel include high hydrophilicity, good biocompatibility, tunable cell adhesion and bacterial resistance after incorporation of silver nanoparticles. Firm bonding of the hydrogel on silicone substrates could be achieved through facile chemical modification, thus enabling the use of this hydrogel as a versatile coating material for biomedical applications.

STATEMENT OF SIGNIFICANCE

In this study, we developed a tough hydrogel by crosslinking HEMA monomers in alginate hydrogels and forming a well-organized structure of hierarchical nested network (NN). Different from most reported stretchable alginate-based hydrogels, the NN hydrogel shows higher compressive strength but retains comparable softness to alginate counterparts. This work further demonstrated the good integration of the tough hydrogel with silicone substrates through chemical modification and micropillar structures. Other properties including surface friction, biocompatibility and bacterial resistance were investigated and the hydrogel shows a great promise as a versatile coating material for biomedical applications.

Biocompatible scaffolds based on natural polymers for regenerative medicine

The chitosan and gelatine are commonly used biopolymers for the tissue engineering applications. In the previous methods for the cryogels synthesis, multistep preparation methods using toxic cross-linking agents such as glutaraldehyde are reported. Here, we present a two-step preparation method of gelatin macroporous cryogels and one-step preparation method of chitosan or gelatin cryogels. The physico-chemical properties of obtained scaffolds were characterized using FTIR, zeta potential, SEM and laser confocal microscopy. Non-toxic and biodegradable cross-linking agents such as oxidized dextran and 1,1,3,3-tetramethoxypropane are utilized. The one-step chitosan cryogels had degradation degree ~2 times higher compared to the cryogels prepared with a two-step method i.e. reduced by borohydride. Scaffolds cross-linked by glutaraldehyde had about 40% viability, whereas nine various compositions of cryogels showed significantly higher viability (~80%) of fibroblast cells in vitro. The cryogels were obtained without using the harmful compounds and therefore can be used straightforward as biocompatible and biodegradable scaffolds for the cell culturing purposes and other biomedical applications.

Piezoelectric smart biomaterials for bone and cartilage tissue engineering

Tissues like bone and cartilage are remodeled dynamically for their functional requirements by signaling pathways. The signals are controlled by the cells and extracellular matrix and transmitted through an electrical and chemical synapse. Scaffold-based tissue engineering therapies largely disturb the natural signaling pathways, due to their rigidity towards signal conduction, despite their therapeutic advantages. Thus, there is a high need of smart biomaterials, which can conveniently generate and transfer the bioelectric signals analogous to native tissues for appropriate physiological functions. Piezoelectric materials can generate electrical signals in response to the applied stress. Furthermore, they can stimulate the signaling pathways and thereby enhance the tissue regeneration at the impaired site. The piezoelectric scaffolds can act as sensitive mechanoelectrical transduction systems. Hence, it is applicable to the regions, where mechanical loads are predominant. The present review is mainly concentrated on the mechanism related to the electrical stimulation in a biological system and the different piezoelectric materials suitable for bone and cartilage tissue engineering.

Chitosan and chitooligosaccharides from shrimp shell waste: characterization, antimicrobial and shelf life extension in bread

Chitosan and chitooligosaccharides were extracted from white-leg shrimp shells by chemical treatment. Low molecular weight (13 kDa) and a high degree of deacetylation (54.83%) in chitooligosaccharides led to high water solubility compared to chitosan. Antimicrobial assays indicated that chitosan and chitooligosaccharides exhibited marked inhibitory activity against food-borne pathogenics, spoilage bacterial, and fungal strains tested. However, chitooligosaccharides revealed greater inhibitory effects than chitosan on tested microorganisms. The substitution of flour by chitosan or chitooligosaccharides in bread formulation (1 g/100 g total weight basis) showed antimicrobial effects against Bacillus cereus and Rhizopus sp. growth. Also, the fruity odor in bread containing chitosan or chitooligosaccharides was delayed. Interestingly, the bread containing chitooligosaccharides showed a stronger inhibitory effect against B. cereus and Rhizopus sp. compared to bread containing chitosan and control, where B. cereus and Rhizopus sp. were observed growing on the surface of bread after 4 days of incubation at 30 °C.

Gentamicin-loaded ceramic-biopolymer dual layer coatings on the Ti with improved bioactive and corrosion resistance properties for orthopedic applications

In orthopedic surgery, osteomyelitis (bone infection) is one of the most serious complications in the last few decades and the resident drug delivery is the key strategy to overcome this issue. Combination of bioactive materials with antibiotics is broadly developed for the handling of osteomyelitis which plays a dual role as bone cell growth and as local drug delivery systems for antibiotic delivery. TiO₂-SiO₂ mixtures were fabricated on Ti alloy by anodization method. Chitosan-Lysine (CS-LY) biopolymers were coated on composites by electrodeposition method and followed by gentamicin sulfate (GS) which was loaded as a model drug. The layers were characterized by AT-FTIR, XRD, FE-SEM and EDX methods. The mechanical, anticorrosion, antimicrobial effects and biocompatibility of the glazes were considered. In addition, drug loading, continued and prolonged liberation behaviors of GS from the fabricated coating were studied. The apatite development ability and cell viability are outstanding for CS-LY-3 coated composites. In vitro cell experimentations indicate that osteoblasts show good adhesion and high growth rates for CS-LY-3 coated TiO₂-SiO₂ composite substrate. In conclusion, the surface modification of TiO₂-SiO₂/CS-LY-3 coated Ti alloy could be used as a carrier for GS, not only to eradicate the osteomyelitis caused by Gram-negative and Gram-positive bacteria, but also to repair the bone defect initiated by the infection owing to the tunable nanocomposite degradation.

Implant Infection and Infection Resistant Materials: A Mini Review

Implant infection is an aggressive, often irreducible post-surgical infection. It remains the primary cause of implant failure. Bacterial contamination during surgery and subsequent adhesion onto biomaterial surface of opportunistic microorganisms, such as staphylococcal species, exopolysaccharidic slimes or specific adhesins, initiates the implant infection.

Pathogenesis of periprosthestic infection is the focus of studies aimed at developing infection resistant materials.

Bioactive Titanium Implant Surfaces with Bacterial Inhibition and Osteoblast Function Enhancement Properties

Infection in orthopedic implant surgery is a serious complication and a major cause of implant failure. Upon implant insertion, a contest between microbial colonization and tissue integration of the implant surface ensues. This race for the surface determines the probability of tissue integration or infection, and the surface properties of the substrate have an important role to play in determining the outcome. A number of strategies have been developed for the modification of implant surfaces to promote bone cell (osteoblast) functions and inhibit bacterial adhesion and growth. In this article, a review is given of these surface modification strategies, in particular those which can achieve the dual aim of bacterial inhibition and simultaneous enhancement of osteoblast functions. Surfaces of these types can be expected to have excellent potential for orthopedic applications. (Int J Artif Organs 2008; 31: 777–85)

Nanofibrous Poly(ε-Caprolactone)/Poly(Vinyl Alcohol)/Chitosan Hybrid Scaffolds for Bone Tissue Engineering using Mesenchymal Stem Cells

In the present study, based on a biomimetic approach, novel 3D nanofibrous hybrid scaffolds consisting of poly(ε-caprolactone), polyvinyl alcohol), and chitosan were developed via a multi-jet electrospinning method. The influence of chemical, physical, and structural properties of the scaffolds on the differentiation of mesenchymal stem cells into osteoblasts, and the proliferation of the differentiated cells were investigated. Osteogenically induced cultures revealed that cells were well-attached, penetrated into the construct and were uniformly distributed. The expression of early and late phenotypic markers of osteoblastic differentiation was upregulated in the constructs cultured in osteogenic medium.

Biomaterial Strategies to Reduce Implant-Associated Infections

Although the prophylaxis in controlling sterility within the operating room environment has been greatly improved, implant-associated infection is still one of the most serious complications in implant surgeries due to the existence of immune depression in the peri-implant area. The antibacterial ability of materials themselves logically becomes an important factor in preventing implant-associated infections. With the understanding of the pathogenesis of implant-associated infections, many approaches have been developed through providing an anti-adhesive surface, delivering antibacterial agents to disrupt cell-cell communication and preventing bacteria aggregation or biofilm formation, or killing bacteria directly (lysing the cell membrane). In this article, we review the current strategies in improving the antibacterial ability of materials to prevent implant infection and further present promising tactics in materials design and applications.

A phosphorylated chitosan armed hydroxyapatite nanocomposite for advancing activity onosteoblastandosteosarcomacells

Recently, applications of traditional medicine in tissue engineering have gained increasing attention.

The chitosan hydrogels: from structure to function

This review places an emphasis on chitosan intelligent hydrogels. The fabrication methods and mechanisms are introduced in this review and the interactions of the formation of hydrogels with both physical and chemical bonds are also introduced. The relationship between the structural characteristics and the corresponding functions of stimuli-responsive characteristics, self-healing functions and high mechanical strength properties of the chitosan hydrogels are discussed in detail.

Involvement of FAK-mediated BMP-2/Smad pathway in mediating osteoblast adhesion and differentiation on nano-HA/chitosan composite coated titanium implant under diabetic conditions

Nanophase HA/CS composite coated porous titanium implant exhibited superior biological performance under diabetic conditions compared to pure Ti.

Organ-On-A-Chip Platforms: A Convergence of Advanced Materials, Cells, and Microscale Technologies

Significant advances in biomaterials, stem cell biology, and microscale technologies have enabled the fabrication of biologically relevant tissues and organs. Such tissues and organs, referred to as organ-on-a-chip (OOC) platforms, have emerged as a powerful tool in tissue analysis and disease modeling for biological and pharmacological applications. A variety of biomaterials are used in tissue fabrication providing multiple biological, structural, and mechanical cues in the regulation of cell behavior and tissue morphogenesis. Cells derived from humans enable the fabrication of personalized OOC platforms. Microscale technologies are specifically helpful in providing physiological microenvironments for tissues and organs. In this review, biomaterials, cells, and microscale technologies are described as essential components to construct OOC platforms. The latest developments in OOC platforms (e.g., liver, skeletal muscle, cardiac, cancer, lung, skin, bone, and brain) are then discussed as functional tools in simulating human physiology and metabolism. Future perspectives and major challenges in the development of OOC platforms toward accelerating clinical studies of drug discovery are finally highlighted.

Drug transport mechanisms and in vitro release kinetics of vancomycin encapsulated chitosan-alginate polyelectrolyte microparticles as a controlled drug delivery system

In this study, chitosan-alginate polyelectrolyte microparticles containing the antibiotic, vancomycin chloride were prepared using the ionotropic gelation (coacervation) technique. In vitro release and drug transport mechanisms were studied concerning the chitosan only and alginate only microparticles as a control group. Further, the effect of porosity on the drug transport mechanism was also studied for chitosan-alginate mixed particles produced by lyophilizing in contrast to the air-dried non-porous particles. According to the in vitro release data, alginate only and chitosan only microparticles showed burst release and prolonged release respectively. Chitosan-alginate lyophilized microparticles showed the best-controlled release of vancomycin with the average release of 22μg per day for 14days. Also, when increasing alginate concentration there was no increase in the release rate of vancomycin. The release data of all the microparticles were treated with Ritger-Peppas, Higuchi, Peppas-Sahlin, zero-order, and first-order kinetic models. The best fit was observed with Peppas-Sahlin model, indicating the drug transport mechanism was controlled by both Fickian diffusion and case II relaxations. Also, Fickian diffusion dominates the drug transport mechanism of all air-dried samples during the study period. However, the Fickian contribution was gradually reducing with time. Porosity significantly effects the drug transport mechanism as case II relaxation dominates after day 10 of the lyophilized microparticles.

Chitosan composite scaffold combined with bone marrow-derived mesenchymal stem cells for bone regeneration: in vitro and in vivo evaluation

The study aimed to develop a chitosan (CS)-based scaffold for repairing calvarial bone defects. We fabricated composite scaffolds made of CS and bovine-derived xenograft (BDX), characterized their physicochemical properties including pore size and porosity, absorption, degradation, and compressive strength, compared their efficacy to support in vitro proliferation and differentiation of human jaw bone marrow-derived mesenchymal stem cells (hJBMMSCs), and evaluated their bone regeneration capacity in critical-size rat calvarial defects. The CS/BDX (mass ratio of 40:60) composite scaffold with porosity of 46.23% and pore size of 98.23 μm exhibited significantly enhanced compressive strength than the CS scaffold (59.33 ± 4.29 vs. 18.82 ± 2.49 Kpa). The CS/BDX (40:60) scaffold induced better cell attachment and promoted more osteogenic differentiation of hJBMMSCs than the CS scaffold. The CS/BDX (40:60) scaffold seeded with hJBMMSCs was the most effective in supporting new bone formation, as evidenced by better histomorphometry results, larger new bone area, and more obvious mature lamellar bone formation compared to other groups in rat calvarial defects 8 weeks after implantation. These results suggest that CS/BDX composite scaffold combining with hJBMMSCs has the potential for bone defect regeneration.

Microbial resistance related to antibiotic-loaded bone cement: a historical review

PURPOSE

The use of antibiotic-loaded bone cement (ALBC) has a range of indications for use in orthopaedics. It has the advantage of delivering high loads of antibiotics to a targeted site, thereby avoiding the side effects associated with systemic administration. However, there is concern that the use of ALBC may precipitate the development of antibiotic-resistant bacteria.

METHODS

This review focuses on (1) the published research using both animal and human models examining the association between ALBC and the induction of microbial resistance (2) the mechanisms by which antimicrobial resistance develop (3) the research pertaining to specific classes of antibiotics commonly used in orthopaedic practice (4) the recent developments in calcium sulphate beads, nanoparticles and chitosan, as alternative antimicrobial treatments for periprosthetic joint infections.

CONCLUSION

The literature for and against a link between ALBC and the development of microbiological resistance is reviewed and presented. It is concluded that further research is needed to develop a defined set of indications for the use of ALBC in the management of periprosthetic joint infection. In addition, further research into alternative antimicrobial therapies in this area should be encouraged.

Novel poss reinforced chitosan composite membranes for guided bone tissue regeneration

In this study, novel composites membranes composed of chitosan matrix and polyhedral oligomeric silsesquioxanes (POSS) were fabricated by solvent casting method. The effect of POSS loading on the mechanical, morphological, chemical, thermal and surface properties, and cytocompatibility of composite membranes were investigated and observed by tensile test, atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FTIR), thermal gravimetric analysis (TGA), protein adsorption assay, air/water contact angle analysis and WST-1 respectively. Swelling studies were also performed by water absorption capacity determination. Results showed that incorporation of Octa-TMA POSS^® nanofiller to the chitosan matrix increased the surface roughness, protein adsorption and swelling capacity of membranes. The addition of POSS enhanced significantly the ultimate tensile strength and strain at break of the composite membranes up to 3 wt% POSS loaded samples. An increase of about 76% in tensile strength and of strain at break 1.28% was achieved for 3 wt% POSS loaded nanocomposite membranes compared with chitosan membranes. The presence of POSS filler into polymer matrix increased the plasma protein adsorption on the surface. Maximum protein capacity and swelling was obtained for 10 wt% loaded samples. High cell viability results were obtained with indirect extraction of chitosan/POSS composites. Besides, cell proliferation and ALP activity results showed that POSS incorporation significantly increased the ALP activity of Saos-2 cells cultured on chitosan membranes. This novel composite membranes with tunable properties could be considered as a potential candidate for guided bone regeneration applications.

Chitosan-Graphene Oxide 3D scaffolds as Promising Tools for Bone Regeneration in Critical-Size Mouse Calvarial Defects

Limited self-regenerating capacity of human skeleton makes the reconstruction of critical size bone defect a significant challenge for clinical practice. Aimed for regenerating bone tissues, this study was designed to investigate osteogenic differentiation, along with bone repair capacity of 3D chitosan (CHT) scaffolds enriched with graphene oxide (GO) in critical-sized mouse calvarial defect. Histopathological/histomorphometry and scanning electron microscopy(SEM) analysis of the implants revealed larger amount of new bone in the CHT/GO-filled defects compared with CHT alone (p < 0.001). When combined with GO, CHT scaffolds synergistically promoted the increase of alkaline phosphatase activity both in vitro and in vivo experiments. This enhanced osteogenesis was corroborated with increased expression of bone morphogenetic protein (BMP) and Runx-2 up to week 4 post-implantation, which showed that GO facilitates the differentiation of osteoprogenitor cells. Meanwhile, osteogenesis was promoted by GO at the late stage as well, as indicated by the up-regulation of osteopontin and osteocalcin at week 8 and overexpressed at week 18, for both markers. Our data suggest that CHT/GO biomaterial could represent a promising tool for the reconstruction of large bone defects, without using exogenous living cells or growth factors.

Biologically anchored chitosan/gelatin-SrHAP scaffold fabricated on Titanium against chronic osteomyelitis infection

The obstacles faced to treat chronic osteomyelitis infection clinically led to the search for an ideal biomaterial, resulted in combining two major aspects of bone tissue engineering namely surface modified metallic implant and polymer nanocomposite scaffold. In the present study Gelatin - Strontium incorporated Hydroxyapatite (SrHAP) forming HG scaffold, vancomycin loaded chitosan -gelatin polyelectrolyte complex incorporated gelatin-SrHAP, forming HV scaffolds (HV1-0.5wt% and HV2-1wt% vancomycin) were investigated. The HG, HV1 and HV2 scaffolds were successfully fabricated on Cp-Ti through anchoring by treatment with dopamine, which forms a bidentate co-ordination through NH bonding. Interconnected porous morphology of the scaffolds was confirmed, besides the globular Sr-HAP found in HV2 scaffold. The total amount of vancomycin encapsulation for HV1 and HV2 scaffolds were determined to be 47.55±1.6μg and 82.45±3.5μg respectively. Among the scaffolds studied HV2 scaffold were found to have a significant antibacterial activity for both MRSA and MSSA strains compared to Cp-Ti, HG and HV1 scaffolds. The HV2 scaffold also had significantly higher% of cell viability compared to Cp-Ti, HG and HV1 scaffolds. Furthermore, the presence of the drug vancomycin had no toxic effect on the cells, rather it aided in enhanced cell proliferation and spreading.

Enzymatic degradation of hyaluronan hydrogels with different capacity for in situ bio-mineralization

In situ cross-linked hyaluronan (HA) hydrogels with different capacities for biomineralization were prepared and their enzymatic degradation was monitored. Covalent incorporation of bisphosphonates (BPs) into HA hydrogel results in the increased stiffness of the hydrogel in comparison with the unmodified HA hydrogel of the same cross-linking density. The rate of enzymatic degradation of HABP hydrogel was significantly lower than the rate of degradation of control HA hydrogel in vitro. This effect is observed only in the presence of calcium ions that strongly bind to the matrix-anchored BP groups and promote further mineralization of the matrix. The degradation of the hydrogels was followed by noninvasive fluorescence measurements enabled after mild and chemoselective labeling of cross-linkable HA derivatives with a fluorescent tag.