Chitosan-mediated crystallization and assembly of hydroxyapatite nanoparticles into hybrid nanostructured films

Biomimetic Remineralized Three-Dimensional Collagen Bone Matrices with an Enhanced Osteostimulating Effect

Bone grafts with a high potential for osseointegration, capable of providing a complete and effective regeneration of bone tissue, remain an urgent and unresolved issue. The presented work proposes an approach to develop composite biomimetic bone material for reconstructive surgery by deposition (remineralization) on the surface of high-purity, demineralized bone collagen matrix calcium phosphate layers. Histological and elemental analysis have shown reproduction of the bone tissue matrix architectonics, and a high-purity degree of the obtained collagen scaffolds; the cell culture and confocal microscopy have demonstrated a high biocompatibility of the materials obtained. Adsorption spectroscopy, scanning electron microscopy, microcomputed tomography (microCT) and infrared spectroscopy, and X-ray diffraction have proven the efficiency of the deposition of calcium phosphates on the surface of bone collagen scaffolds. Cell culture and confocal microscopy methods have shown high biocompatibility of both demineralized and remineralized bone matrices. In the model of heterotopic implantation in rats, at the term of seven weeks, an intensive intratrabecular infiltration of calcium phosphate precipitates, and a pronounced synthetic activity of osteoblast remodeling and rebuilding implanted materials, were revealed in remineralized bone collagen matrices in contrast to demineralized ones. Thus, remineralization of highly purified demineralized bone matrices significantly enhanced their osteostimulating ability. The data obtained are of interest for the creation of new highly effective osteoplastic materials for bone tissue regeneration and augmentation.

Evaluation of quaternization effect on chitosan-HAP composite for bone tissue engineering application

This study attempts to improve the aqueous solubility of chitosan and utilizes it in the fabrication of composites with hydroxyapatite (HAP). The composites were evaluated as a curcumin delivery vehicle for bone regeneration. The chitosan was modified by quaternization, with a quaternization degree of 5 % for low quaternized chitosan (LQC) and 11 % for high quaternized chitosan (HQC). The modified chitosan, at alkaline pH 11, facilitated in situ HAP growth and formed LQC-HAP and HQC-HAP composites. The quaternization weakens intermolecular hydrogen bonds, facilitates interaction with the apatite precursor ions and promotes the growth of HAP. The modification significantly improved drug encapsulation (2.6 fold) but at the cost of a slight decrease in mechanical strength and increase in drug release. The in vitro studies with human osteoblast-like MG-63 cells established that the curcumin-loaded composites, LQC-HAP-C and HQC-HAP-C are biocompatible, encourage proliferation and promote a 2-fold increase in calcium mineralization over drug-free composites. The study exemplifies the reciprocity between quaternization degree and drug load/release properties and also illustrates that the magnitude of the latter reflects bioactivity. Thus, the quaternized chitosan-based HAP composite with tailorable bio-physicochemical properties becomes an interesting drug delivery system in bone regeneration.

Fungal-derived Selenium Nanoparticles and Their Potential Applications in Electroless Silver Coatings for Preventing Pin-tract Infections

Pin-tract infections (PTIs) are a common complication of external fixation of fractures and current strategies for preventing PTIs have proven to be ineffective. Recent advances show that the use of anti-infection coatings with local antibacterial activity may solve this problem. Selenium has been considered as a promising anti-infection agent owing to its antibacterial and antibiofilm activities. In this study, selenium nanoparticles (SeNPs) were synthesized via a cost-effective fungi-mediated biorecovery approach and demonstrated excellent stability and homogeneity. To investigate their anti-infection potential, the SeNPs were doped in silver coatings through an electroless plating process and the silver–selenium (Ag–Se) coatings were tested for antibacterial and antibiofilm properties against Staphylococcus aureus F1557 and Escherichia coli WT F1693 as well as corrosion resistance in simulated body fluid. It was found that the Ag–Se coating significantly inhibited S.aureus growth and biofilm formation on the surface, reducing 81.2% and 59.7% of viable bacterial adhesion when compared with Ag and Ag–PTFE-coated surfaces after 3 days. The Ag–Se coating also exhibited improved corrosion resistance compared with the Ag coating, leading to a controlled release of Ag⁺, which in turn reduced the risk of cytotoxicity against hFOBs. These results suggest that the fungal-derived SeNPs may have potential in use as implant coatings to prevent PTIs.

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.

Crystalline polysaccharides: A review

The biodegradability and mechanical properties of polysaccharides are dependent on their architecture (linear or branched) as well as their crystallinity (size of crystals and crystallinity percent). The amount of crystalline zones in the polysaccharide significantly governs their ultimate properties and applications (from packaging to biomedicine). Although synthesis, characterization, and properties of polysaccharides have been the subject of several review papers, the effects of crystallization kinetics and crystalline domains on the properties and application have not been comprehensively addressed. This review places focus on different aspects of crystallization of polysaccharides as well as applications of crystalline polysaccharides. Crystallization of cellulose, chitin, chitosan, and starch, as the main members of this family, were discussed. Then, application of the aforementioned crystalline polysaccharides and nano-polysaccharides as well as their physical and chemical interactions were overviewed. This review attempts to provide a complete picture of crystallization-property relationship in polysaccharides.

Glycine-Chitosan-Based Flexible Biodegradable Piezoelectric Pressure Sensor

This paper presents flexible pressure sensors based on free-standing and biodegradable glycine-chitosan piezoelectric films. Fabricated by the self-assembly of biological molecules of glycine within a water-based chitosan solution, the piezoelectric films consist of a stable spherulite structure of β-glycine (size varying from a few millimeters to 1 cm) embedded in an amorphous chitosan polymer. The polymorphic phase of glycine crystals in chitosan, evaluated by X-ray diffraction, confirms formation of a pure ferroelectric phase of glycine (β-phase). Our results show that a simple solvent-casting method can be used to prepare a biodegradable β-glycine/chitosan-based piezoelectric film with sensitivity (∼2.82 ± 0.2 mV kPa-1) comparable to those of nondegradable commercial piezoelectric materials. The measured capacitance of the β-glycine/chitosan film is in the range from 0.26 to 0.12 nF at a frequency range from 100 Hz to 1 MHz, and its dielectric constant and loss factor are 7.7 and 0.18, respectively, in the high impedance range under ambient conditions. The results suggest that the glycine-chitosan composite is a promising new biobased piezoelectric material for biodegradable sensors for applications in wearable biomedical diagnostics.

Design, synthesis and characterization of hydroxyapatite-chitosan nanocomposite radiolabelled with 153Sm as radiopharmaceutical for use in radiosynovectomy

The aim of the present study was to introduction of hydroxyapatite/chitosan nanocomposite as a new radiosynovectomy agent with excellent properties. In this work, the nanocomposite was prepared through a reliable method and characterized using different techniques to elucidate its chemical structure and physiochemical properties. The prepared nanocomposite was successfully radiolabeled with 153Sm under optimal conditions and with high radiolabelling yield (99 %). The radiochemical purity of the prepared radiopharmaceutical was found to be >99 % as determined by ITLC technique. In vitro stability studies in saline solution and in human serum showed that the radiolabeled nanocomposite retained its stability for at least 6 days. The biodistribution and imaging studies in wild-type rats revealed high retention of the agent into the synovial joints of the knee even at 96 h post-injection, thereby indicating excellent in vivo stability of 153Sm labeled hydroxyapatite-chitosan nanocomposite. Therefore, the prepared radiopharmaceutical would be a potential therapeutic agent for use in radiosynovectomy procedure.

Biomimetic mineralization of a hydroxyapatite crystal in the presence of a zwitterionic polymer

The biomimetic mineralization of nano-hydroxyapatite using a zwitterionic polymer as a template to cognize the biomineralization of natural bone in vivo.

Hydroxyapatite-chitosan biocomposites synthesized in the simulated body fluid and their drug loading studies

Hydroxyapatite (HAp) is a bioceramic applied in the biomedical areas, such as matrices for drug release control. Chitosan (CTS), a natural polymer, is another material has been widely investigated for its potential use in the drug delivery systems. In this study, the composites of HAp-CTS are produced in order to investigate their drug loading and release studies. First of all, HAp-CTS composites are produced in the presence of simulated body fluid (SBF). Analysis confirmed the structure of HAp-CTS composites. Secondly, composites are encapsulated with 5-Fluorouracil (5-FU). The weight ratio of CTS is varied to realize its effect on drug loading of 5-Fluorouracil, a cancer drug, for the ratios of 1:1, 1:2 and 1:4 of HAp-CTS. The weight ratio giving the greatest drug load efficiency is selected for the last step of the study. Crosslinking agent, glutaraldehyde, are changed from 0 to 5% on the selected sample, then, drug loading is examined again in various environment owing different pH. Furthermore, drug release studies are conducted. To understand the structure and morphology of the samples, XRD, FTIR, SEM and Uv-Spectrum are applied. It is observed that weight ratio of polymer and crosslinking agent can be manipulated to adjust drug loading. Release kinetics are shown the Fickian diffusion. This new produced material can be applicable for drug delivery.

Natural polysaccharides leading to super adsorbent hydroxyapatite nanoparticles for the removal of heavy metals and dyes from aqueous solutions

Water pollution has created a major impact on the environment mainly due to contaminated industrial effluents with toxic substances such as heavy metals and textile dyes.

Chitosan-PLGA polymer blends as coatings for hydroxyapatite nanoparticles and their effect on antimicrobial properties, osteoconductivity and regeneration of osseous tissues

Composite biomaterials comprising nanostructured hydroxyapatite (HAp) have an enormous potential for natural bone tissue reparation, filling and augmentation. Chitosan (Ch) as a naturally derived polymer has many physicochemical and biological properties that make it an attractive material for use in bone tissue engineering. On the other hand, poly-D,L-lactide-co-glycolide (PLGA) is a synthetic polymer with a long history of use in sustained drug delivery and tissue engineering. However, while chitosan can disrupt the cell membrane integrity and may induce blood thrombosis, PLGA releases acidic byproducts that may cause tissue inflammation and interfere with the healing process. One of the strategies to improve the biocompatibility of Ch and PLGA is to combine them with compounds that exhibit complementary properties. In this study we present the synthesis and characterization, as well as in vitro and in vivo analyses of a nanoparticulate form of HAp coated with two different polymeric systems: (a) Ch and (b) a Ch-PLGA polymer blend. Solvent/non-solvent precipitation and freeze-drying were used for synthesis and processing, respectively, whereas thermogravimetry coupled with mass spectrometry was used for phase identification purposes in the coating process. HAp/Ch composite particles exhibited the highest antimicrobial activity against all four microbial strains tested in this work, but after the reconstruction of the bone defect they also caused inflammatory reactions in the newly formed tissue where the defect had lain. Coating HAp with a polymeric blend composed of Ch and PLGA led to a decrease in the reactivity and antimicrobial activity of the composite particles, but also to an increase in the quality of the newly formed bone tissue in the reconstructed defect area.

In situ strategy for bone repair by facilitated endogenous tissue engineering

Traditional tissue engineering procedures are expensive and time consuming. Facilitated endogenous tissue engineering (FETE) provides a solution that can avoid the ex vivo culture of autologous cells and initiate in situ reparative endogenous repair processes in vivo. This method involves fabricating a porous scaffold that mimics the environment present during the bone formation process, consisting of components that provide biomimetic interfacial interactions to cells. After the scaffold is implanted, progenitor cells provided by autologous bone marrow and surrounding tissues then differentiate to bone cells under the direction of the in situ scaffold. This paper reports a biomimetic method to prepare a hierarchically structured hybrid scaffold. Bone-like nano hydroxyapatite (HA) was crystallized from a collagen and chitosan (CC) matrix to form a porous scaffold. The in vivo study demonstrates that this nanohybrid scaffold supports excellent bone repair. This means that the FETE approach, in which the cell culture portion of traditional tissue engineering takes place in vivo, can promote the intrinsic regenerative potential of endogenous tissues.

Fabrication method, structure, mechanical, and biological properties of decellularized extracellular matrix for replacement of wide bone tissue defects

The present paper was focused on the development of a new method of decellularized extracellular matrix (DECM) fabrication via a chemical treatment of a native bone tissue. Particular attention was paid to the influence of chemical treatment on the mechanical properties of native bones, sterility, and biological performance in vivo using the syngeneic heterotopic and orthotopic implantation models. The obtained data indicated that after a chemical decellularization treatment in 4% aqueous sodium chlorite, no noticeable signs of the erosion of compact cortical bone surface or destruction of trabeculae of spongy bone in spinal channel were observed. The histological studies showed that the chemical treatment resulted in the decellularization of both bone and cartilage tissues. The DECM samples demonstrated no signs of chemical and biological degradation in vivo. Thorough structural characterization revealed that after decellularization, the mineral frame retained its integrity with the organic phase; however clotting and destruction of organic molecules and fibers were observed. FTIR studies revealed several structural changes associated with the destruction of organic molecules, although all organic components typical of intact bone were preserved. The decellularization-induced structural changes in the collagen constituent resulted changed the deformation under compression mechanism: from the major fracture by crack propagation throughout the sample to the predominantly brittle fracture. Although the mechanical properties of radius bones subjected to decellularization were observed to degrade, the mechanical properties of ulna bones in compression and humerus bones in bending remained unchanged. The compressive strength of both the intact and decellularized ulna bones was 125-130 MPa and the flexural strength of humerus bones was 156 and 145 MPa for the intact and decellularized samples, respectively. These results open new avenues for the use of DECM samples as the replacement of wide bone tissue defects.

Effect of solvent; enhancing the wettability and engineering the porous structure of a calcium phosphate/agarose composite for drug delivery

Porous 3D degradable hydrophilic ceramic–polymer composites were fabricated for tissue engineering and drug delivery applications.

Investigating an organ-targeting platform based on hydroxyapatite nanoparticles using a novel in situ method of radioactive ¹²⁵Iodine labeling

In this study, we have investigated the synthesis of nanoparticles of hydroxyapatite (HAp) and hydroxyapatite coated with chitosan (HAp/Ch) and the chitosan-poly-d,l-lactide-co-glycolide polymer blend (HAp/Ch-PLGA) as an organ-targeting system. We have examined and defined the final destination, as well as the dynamics and the pathways of the synthesized particles following intravenous administration in vivo. The XRD, ZP, FT-IR and SEM analyses have confirmed that the hydroxyapatite nanoparticles with d50=72 nm are coated with polymers. Radioactive 125-Iodine ((125)I), a low energy gamma emitter, was used to develop a novel in situ method for the radiolabeling of particles and investigation of their biodistribution. (125)I-labeled particles exhibited high stability in saline and serum over the second day, which justified their use in the following in vivo studies. The biodistribution of (125)I-labeled particles after intravenous injection in rats differed significantly: HAp particles mostly targeted the liver, HAp/Ch the spleen and the liver, while HAp/Ch-PLGA targeted the lungs. Twenty-four hours post injection, HAp particles were excreted completely, while both (125)I-HAp/Ch and (125)I-HAp/Ch-PLGA were retained in the body for a prolonged period of time with more than 20% of radioactivity still found in different organs.

Prevention of infection in external fixator pin sites

Infection in external fixator pins is known to be a significant problem, with incidences between 3% and 80% reported in the literature. An infection occurs when planktonic bacteria adhere to external fixator pins and subsequently produce a biofilm which protects the bacteria from host defences. The most commonly implicated organisms are Staphylococcus aureus and Staphylococcus epidermidis. Once an infection occurs, treatment is difficult. Systemic antibiotics have limited benefits and considerable side-effects. The only definitive management is removal of the pin. This review will consider the current and potential future strategies for reducing pin site infection. Techniques to prevent infection must prevent bacterial adhesion, allow good osteointegration and have a low toxicity. Current areas of interest reviewed are titanium-copper alloys, nanosilver coatings, nitric oxide coatings, chitosan coatings, chlorhexidine and iodine, hydroxyapatite and antibiotic coatings. At present there is no consensus on the prevention of pin site infection, and there is a paucity of randomized controlled trials on which to draw a conclusion. Whilst a number of these strategies have potential future use, many of the above strategies need further studies in animal models to ensure no cytotoxicity and prevention of osteointegration. Following this, well-designed randomized controlled clinical trials are required to give future ways to prevent external fixator pin site infections.

Synthesis of spherical calcium phosphate particles for dental and orthopedic applications

Calcium phosphate materials have been used increasingly in the past 40 years as bone graft substitutes in the dental and orthopedic fields. Accordingly, numerous fabrication methods have been proposed and used. However, the controlled production of spherical calcium phosphate particles remains a challenge. Since such particles are essential for the synthesis of pastes and cements delivered into the host bone by minimally-invasive approaches, the aim of the present document is to review their synthesis and applications. For that purpose, production methods were classified according to the used reagents (solutions, slurries, pastes, powders), dispersion media (gas, liquid, solid), dispersion tools (nozzle, propeller, sieve, mold), particle diameters of the end product (from 10 nm to 10 mm), and calcium phosphate phases. Low-temperature calcium phosphates such as monetite, brushite or octacalcium phosphate, as well as high-temperature calcium phosphates, such as hydroxyapatite, β-tricalcium phosphate or tetracalcium phosphate, were considered. More than a dozen production methods and over hundred scientific publications were discussed.

Photoacoustic FTIR spectroscopic study of undisturbed human cortical bone

Chemical pretreatment has been the prevailing sample preparation procedure for infrared (IR) spectroscopic studies on bone. However, experiments have indicated that chemical pretreatment can potentially affect the interactions between the components. Typically the IR techniques have involved transmission experiments. Here we report experimental studies using photoacoustic Fourier transform infrared spectroscopy (PA-FTIR). As a nondestructive technique, PA-FTIR can detect absorbance spectrum from a sample at controllable sampling depth and with little or no sample preparation. Additionally, the coupling inert gas, helium, which is utilized in the PA-FTIR system, can inhibit bacteria growth of bone by displacing oxygen. Therefore, we used this technique to study the undisturbed human cortical bone. It is found that photoacoustic mode (linear-scan, LS-PA-FTIR) can obtain basically similar spectra of bone as compared to the traditional transmission mode, but it seems more sensitive to amide III and ν(2) carbonate bands. The ν(3) phosphate band is indicative of detailed mineral structure and symmetry of native bone. The PA-FTIR depth profiling experiments on human cortical bone also indicate the influence of water on OH band and the cutting effects on amide I and mineral bands. Our results indicate that phosphate ion geometry appears less symmetric in its undisturbed state as detected by the PA-FTIR as compared to higher symmetry observed using transmission techniques on disturbed samples. Moreover, the PA-FTIR spectra indicate a band at 1747 cm(-1) possibly resulting from CO stretching of lipids, cholesterol esters, and triglycerides from the arteries. Comparison of the spectra in transverse and longitudinal cross-sections demonstrates that, the surface area of the longitudinal section bone appears to have more organic matrix exposed and with higher mineral stoichiometry.

An organic matrix-mediated processing methodology to fabricate hydroxyapatite based nanostructured biocomposites

An amorphous calcium phosphate precursor phase, which forms by adding orthophosphoric acid to a calcium hydroxide suspension, is transformed into crystalline hydroxyapatite by introducing polymer solutions. The nanostructured composite films formed by a solvent casting technique from the concentrated hybrid suspension are characterised for structure and mechanical properties.

Specific biofunctional performances of the hydroxyapatite-sodium maleate copolymer hybrid coating nanostructures evaluated by in vitro studies

The nanohybrid structures consisting of hydroxyapatite (HA) and sodium maleate-vinyl acetate copolymer (MP) deposited by Matrix Assisted Pulsed Laser Evaporation (MAPLE) technique on Ti surfaces were investigated for specific biological qualities required in bone implantology. The data from in vitro studies demonstrated that human primary osteoblasts (OBs) firmly adhered to Ti coated with HA-MP as indicated by cytoskeleton and vinculin dynamics. OBs spread onto biomaterial surface and formed groups of cells which during their biosynthetic activity expressed OB phenotype specific markers (collagen and non-collagenous proteins) and underwent controlled proliferation.