Hydroxyapatite Microparticles Research Articles

A Bioactive Coating Enhances Bone Allografts in Rat Models of Bone Formation and Critical Defect Repair.

Bone allografts are inferior to autografts for the repair of critical-sized defects. Prior studies have suggested that bone morphogenetic protein-2 (BMP-2) can be combined with allografts to produce superior healing. We created a bioactive coating on bone allografts using polycondensed deoxyribose isobutyrate ester (PDIB) polymer to deliver BMP-2 ± the bisphosphonate zoledronic acid (ZA) and tested its ability to enhance the functional utility of allografts in preclinical Wistar rat models. One ex vivo and two in vivo proof-of-concept studies were performed. First, PDIB was shown to be able to coat bone grafts (BGs). Second, PDIB was used to coat structural allogenic corticocancellous BG with BMP-2 ± ZA ± hydroxyapatite (HA) microparticles and compared with PDIB-coated grafts in a rat muscle pouch model. Next, a rat critical defect model was performed with treatment groups including (i) empty defect, (ii) BG, (iii) collagen sponge + BMP-2, (iv) BG + PDIB/BMP-2, and (v) BG + PDIB/BMP-2/ZA. Key outcome measures included detection of fluorescent bone labels, microcomputed tomography (CT) quantification of bone, and radiographic healing. In the muscle pouch study, BMP-2 did not increase net bone volume measured by microCT, however, fluorescent labeling showed large amounts of new bone. Addition of ZA increased BV by sevenfold (p < 0.01). In the critical defect model, allografts were insufficient to promote reliable union, however, union was achieved in collagen/BMP-2 and all BG/BMP-2 groups. Statement of clinical significance: These data support the concept that PDIB is a viable delivery method for BMP-2 and ZA delivery to enhance the bone forming potential of allografts. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:2278-2286, 2019.

Quanfima: An open source Python package for automated fiber analysis of biomaterials.

Hybrid 3D scaffolds composed of different biomaterials with fibrous structure or enriched with different inclusions (i.e., nano- and microparticles) have already demonstrated their positive effect on cell integration and regeneration. The analysis of fibers in hybrid biomaterials, especially in a 3D space is often difficult due to their various diameters (from micro to nanoscale) and compositions. Though biomaterials processing workflows are implemented, there are no software tools for fiber analysis that can be easily integrated into such workflows. Due to the demand for reproducible science with Jupyter notebooks and the broad use of the Python programming language, we have developed the new Python package quanfima offering a complete analysis of hybrid biomaterials, that include the determination of fiber orientation, fiber and/or particle diameter and porosity. Here, we evaluate the provided tensor-based approach on a range of generated datasets under various noise conditions. Also, we show its application to the X-ray tomography datasets of polycaprolactone fibrous scaffolds pure and containing silicate-substituted hydroxyapatite microparticles, hydrogels enriched with bioglass contained strontium and alpha-tricalcium phosphate microparticles for bone tissue engineering and porous cryogel 3D scaffold for pancreatic cell culturing. The results obtained with the help of the developed package demonstrated high accuracy and performance of orientation, fibers and microparticles diameter and porosity analysis.

Characterization of biomimetic silicate- and strontium-containing hydroxyapatite microparticles embedded in biodegradable electrospun polycaprolactone scaffolds for bone regeneration

A significant need exists today to develop novel alternatives to traditional bone grafts. Here, we report the potential use of mechanochemically synthesized hydroxyapatite (HA), silicate-, or strontium-containing HA microparticles and microparticle aggregates in combination with polycaprolactone (PCL) as hybrid scaffolds for filling bone defects. The detailed characterization of scaffolds was performed with high-resolution synchrotron radiation–based microcomputed laminography, XRD, EDX, and FTIR. An in vitro cell-scaffold interaction analysis showed a significant improvement of cell spreading in the case of hybrid scaffolds with silicate- and Sr-containing HA. Scaffolds with Sr- and silicate-containing HA affected the expression of several genes involved in morphogenesis and transcription. Scaffolds with Sr-containing HA increased the expression of markers of the primary component of the extracellular matrix, and scaffolds with Sr-containing HA facilitated cell mineralization via an increase in osteocalcin production. The hybrid scaffolds with silicate- and Sr-containing HA microparticles exerted the highest antibacterial activity against gram-positive bacterium Staphylococcus aureus compared to the unmodified PCL scaffolds. Based on these findings, the obtained scaffolds with Sr- or silicate-containing HA are believed to hold promise for bone tissue regeneration as compared to scaffolds containing pure HA.

Synthesis and Biomedical Application of Hydroxyapatite as Carrier for Loading and Controlled Delivery of Antibiotics

The hydroxyapatite (HA) nano and microparticles were synthesized by wet-chemical precipitation in order to use them as drug carriers for biomedical applications. Scanning Electron Microscopy (SEM), Dynamic Light Scattering (DLS) and Fourier Transform Infrared Spectroscopy (FTIR) were performed to assess their size, external morphology and chemical composition. The properties of HA particles as drug carriers for antibiotics delivery were evaluated with doxycycline and chloramphenicol. The amount of drug loading and release was determined by UV-Visible spectrophotometry. The antibacterial properties of loaded HA particles were evaluated using gram-positive Bacillus subtilis bacteria and gram-negative Pseudomonas aeruginosa bacteria. The synthesized particles of HA exhibit a high adsorption capacity (around 99%) and good controlled release properties for doxycycline. The adsorption of chloramphenicol on HA was extremely low (about 2%). According to the results, the compatibility between the drug and substrate is an important factor in the absorption process, and the hydroxyapatite is a very promising carrier for controlled release of antibiotics.

Biochemical Gradients to Generate 3D Heterotypic‐Like Tissues with Isotropic and Anisotropic Architectures

AbstractAnisotropic 3D tissue interfaces with functional gradients found in nature are replicated in vitro for drug development and tissue engineering. Even though different fabrication techniques, based on material science engineering and microfluidics, are used to generate such microenvironments, mimicking the native tissue gradient is still a challenge. Here, the fabrication of 3D structures are described with linear/random porosity and gradient distribution of hydroxyapatite microparticles which are combined with a gradient of growth factors generated by a dual chamber for the development of heterotypic‐like tissues. The hydroxyapatite gradient is formed by applying a thermal ramp from the first to the second gel layer, and the porous architecture is controlled through ice templating. A 3D osteochondral (OC) tissue model is developed by codifferentiating fat pad adipose‐derived stem cells. Osteogenic and chondrogenic markers expression is spatially controlled, as it occurs in the native osteochondral unit. Additionally, a prevasculature is spatially induced by the perfusion of proangiogenic medium in the bone‐like region, as observed in the native subchondral bone. Thus, in this study, precise spatial control is developed over cell/tissue phenotype and formation of prevasculature which opens up possibilities for the study of complex tissues interfaces, with broader applications in drug testing and regenerative medicine.

Decellularized bovine small intestinal submucosa-PCL/hydroxyapatite-based multilayer composite scaffold for hard tissue repair

This study involved the development of a multilayer osteogenic tissue scaffold by assembling decellularized bovine small intestinal submucosa (bSIS) layers, together with synthetic hydroxyapatite microparticles (HAp) and poly(ε-caprolactone) (PCL) as the binder. As a first step, the surface and mechanical properties of the developed scaffold was determined, after which the biocompatibility was evaluated through seeding with isolated rat bone marrow mesenchymal stem cells (BM-MSCs). Then, a 21-day culture study was performed to investigate the in vitro osteoinductive potential of the scaffold on BM-MSCs under standard and osteogenic culture conditions. The SEM findings indicated that a uniform multilayer and perforated structure was acquired; that the HAp microparticles were homogenously distributed within the structure; and that the PCL-bound laminar scaffold had structural integrity. Mechanical tests revealed that the scaffold maintained its mechanical stability for at least 21 days in culture, with no changes in the first-day maximum strength and maximum stress values of 625.123 ± 70.531 N and 6.57762 ± 0.742 MPa, respectively. MTT and SEM analyses together revealed that BM-MSCs preserved their viability and proliferated during a 14-day culture period on the multilayer scaffold. Immunofluorescence analyses indicated that cells on the scaffold differentiated into the osteogenic lineage, by the culture-time-dependent increase in osteogenic markers' expression, i.e. Alkaline phosphatase, Osteopontin, and Osteocalcin. It was also clear that, the osteoinductive effect by the composite scaffold on BM-MSCs could be achieved even without the use of any external osteogenic inducers.

Alginate Capsules with Cuttlebone-derived Fillers as an Integrated Solution for Bone Repair

Alginate capsules with cuttlebone-derived fillers were developed for bone repair applications. Prepared capsules were designed to be suitable for the treatment of small-sized bone loss provocative diseases, such as endodontic and periodontal diseases. Cuttlebone microparticles, as a source of calcium carbonate, or cuttlebone-derived hydroxyapatite microparticles were used as mineral fillers for the preparation of alginate capsules. The capsules were additionally covered with chitosan layer for the hard structure formation and improvement of adhesive properties. Encapsulation efficiency of dexamethasone as a model allopathic drug was 19 %, 24 % and 12 % for capsules with cuttlebone microparticles, capsules with cuttlebone-derived hydroxyapatite and capsules without any mineral filler (control group), respectively. We observed that chitosan coating and lyophilisation contributed for the preservation of spherical structure of alginate capsules with mineral fillers. Swelling study of dried capsules in simulated physiological environment (in phosphate buffer saline, pH = 7.2 at 37 °C temperature) showed that average swelling index of alginate-based capsules without mineral fillers was much higher in comparison to capsules with cuttlebone fillers: 121 %, 17 % and 3 % for control group, capsules with cuttlebone microparticles and capsules with cuttlebone-derived hydroxyapatite, respectively.DOI: http://dx.doi.org/10.5755/j01.ms.24.3.18858

Researches Regarding the Improvment of Different Dental Contemporary Composite Materials Structure

The purpose of this study was to test the structural improving that may be acquired by adding hydroxyapatite microparticles bearing or not silver nanoparticles to three different commercial products commonly used in dental practice. The practical part of this study consisted in the preparation of a common protocol of nine samples resulting from the creation of cavities and their filling similarly to the solving of different clinical situations of carious processes, extracted teeth belonging to both the anterior and the posterior area, with different architectures of the loss of dental substance. Before use, both HA and HA/AgNP have been subjected to calcination in an oven at 6000C for three hours in order to eliminate the residual organic matter. The structural changes have been studied on three types of composites known in the medical practice under the tradenames of Ceram X Duo, Swiss Tec and Herculite XRV Ultra. The structural changes materialized at the level of dentinal component are clearly visible in the SEM images recorded for each starting commercial material. Thus, the addition of HA with high polydispersity (within the range of tens of nanometers and several microns) was effective on lowering the surface rugosity and apparent macro-porosity, while enhancing the phase mixing and component cohesion, but only in the case of Ceram X Duo and Swiss Tec materials. For Herculite XRV Ultra these effects seems to be limited or even reversed, phenomenon that could be explained by the fact that this material already contains nano-fillers, and their concentration tends to saturation.

Increased Internal Porosity and Surface Area of Hydroxyapatite Accelerates Healing and Compensates for Low Bone Marrow Mesenchymal Stem Cell Concentrations in Critically-Sized Bone Defects

For clinical treatment of skeletal defects, osteoinductive scaffolds must have the ability to conform to the unique geometry of the injury site without sacrificing biologically favorable properties, including porosity. This investigation seeks to combine the osteoinductive properties of porous hydroxyapatite (HA) scaffolds with the beneficial handling characteristics of granules or putties, while evaluating the effects of mesenchymal stem cell (MSC) concentration on the composite grafts’ ability to regenerate bone in vivo. The results demonstrate that porous HA granules regenerate significantly larger volumes of bone compared to non-porous HA. Increased MSC concentrations in autologous bone marrow aspirate (BMA) contributed to greater bone regeneration. This effect was most predominant with non-porous HA. While the extent of bone regeneration using non-porous HA was strongly correlated with MSC concentration of the marrow, porous HA microparticles combined with autologous BMA were successful in faster treatment of critically-sized bone defects and with less dependence on the MSC concentration than non-porous HA.

3D biodegradable scaffolds of polycaprolactone with silicate-containing hydroxyapatite microparticles for bone tissue engineering: high-resolution tomography and in vitro study

To date, special interest has been paid to composite scaffolds based on polymers enriched with hydroxyapatite (HA). However, the role of HA containing different trace elements such as silicate in the structure of a polymer scaffold has not yet been fully explored. Here, we report the potential use of silicate-containing hydroxyapatite (SiHA) microparticles and microparticle aggregates in the predominant range from 2.23 to 12.40 µm in combination with polycaprolactone (PCL) as a hybrid scaffold with randomly oriented and well-aligned microfibers for regeneration of bone tissue. Chemical and mechanical properties of the developed 3D scaffolds were investigated with XRD, FTIR, EDX and tensile testing. Furthermore, the internal structure and surface morphology of the scaffolds were analyzed using synchrotron X-ray µCT and SEM. Upon culturing human mesenchymal stem cells (hMSC) on PCL-SiHA scaffolds, we found that both SiHA inclusion and microfiber orientation affected cell adhesion. The best hMSCs viability was revealed at 10 day for the PCL-SiHA scaffolds with well-aligned structure (~82%). It is expected that novel hybrid scaffolds of PCL will improve tissue ingrowth in vivo due to hydrophilic SiHA microparticles in combination with randomly oriented and well-aligned PCL microfibers, which mimic the structure of extracellular matrix of bone tissue.

Effects of substrate stiffness on dental pulp stromal cells in culture.

Dental pulp stromal cells (DPSCs) can be differentiated down lineages known to either express bone or dentin specific protein markers. Since the differentiation of cells can be heavily influenced by their environment, it may be possible to influence the osteogenic/odontogenic potential of DPSCs by modulating the mechanical properties of substrate on which they are grown. In this study, human DPSCs were grown with and without hydroxyapatite (HA) microparticles on a range of substrates including fibronectin-coated hydrogels and glass substrates, which represented an elastic moduli range of approximately 3 kPa-50 GPa, over a 21-day period. Alkaline phosphatase activity, osteopontin production, and mineralization were monitored. The presence of HA microparticles increased the relative degree of mineralized matrix produced by the cells relative to those in the same substrate and media condition without the HA microparticles. In addition, cultures with cells grown on stiffer substrates had higher ALP activity and higher degree of mineralization than those grown on softer substrates. This study shows that DPSCs are affected by the mechanical properties of their underlying growth substrate and by the presence of HA microparticles. In addition, relatively stiff substrates (>75 kPa) may be required for significant mineralization of these cultures. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 1789-1797, 2018.

Dual non-viral gene delivery from microparticles within 3D high-density stem cell constructs for enhanced bone tissue engineering

High-density mesenchymal stem cell (MSC) aggregates can be guided to form bone-like tissue via endochondral ossification in vitro when culture media is supplemented with proteins, such as growth factors (GFs), to first guide the formation of a cartilage template, followed by culture with hypertrophic factors. Recent reports have recapitulated these results through the controlled spatiotemporal delivery of chondrogenic transforming growth factor-β1 (TGF-β1) and chondrogenic and osteogenic bone morphogenetic protein-2 (BMP-2) from microparticles embedded within human MSC aggregates to avoid diffusion limitations and the lengthy, costly in vitro culture necessary with repeat exogenous supplementation. However, since GFs have limited stability, localized gene delivery is a promising alternative to the use of proteins. Here, mineral-coated hydroxyapatite microparticles (MCM) capable of localized delivery of Lipofectamine-plasmid DNA (pDNA) nanocomplexes encoding for TGF-β1 (pTGF-β1) and BMP-2 (pBMP-2) were incorporated, alone or in combination, within MSC aggregates from three healthy porcine donors to induce sustained production of these transgenes. Three donor populations were investigated in this work due to the noted MSC donor-to-donor variability in differentiation capacity documented in the literature. Delivery of pBMP-2 within Donor 1 aggregates promoted chondrogenesis at week 2, followed by an enhanced osteogenic phenotype at week 4. Donor 2 and 3 aggregates did not promote robust glycosaminoglycan (GAG) production at week 2, but by week 4, Donor 2 aggregates with pTGF-β1/pBMP-2 and Donor 3 aggregates with both unloaded MCM and pBMP-2 enhanced osteogenesis compared to controls. These results demonstrate the ability to promote osteogenesis in stem cell aggregates through controlled, non-viral gene delivery within the cell masses. These findings also indicate the need to screen donor MSC regenerative potential in response to gene transfer prior to clinical application. Taken together, this work demonstrates a promising gene therapy approach to control stem cell fate in biomimetic 3D condensations for treatment of bone defects.

The effect of different hydroxyapatite microparticles on the osteogenic differentiation of MC3T3-E1 preosteoblasts.

Hydroxyapatite (HA) has been extensively explored for biomedical applications due to its advantages of facile synthesis and surface functions. Many studies have suggested that HA microparticles can induce osteogenic differentiation. However, how the size and shape of HA microparticles affected the differentiation response has not been elucidated. In this work, HA microparticles (HA whiskers and HA microspheres) with different sizes of 40, 50 and 80 μm were synthesized and their effects on the osteogenic differentiation of MC3T3-E1 preosteoblasts were investigated. All the HA microparticles showed cytocompatibility and did not show their influence on the proliferation at the studied concentrations. The osteogenic differentiation of MC3T3-E1 preosteoblasts was dependent on the size and shape of HA. Sphere-50 and sphere-80 significantly increased the alkaline phosphatase (ALP) activity, calcium deposition and expression of Runx2 and collagen I, while whisker-40, whisker-50 and whisker-80 reduced the ALP activity and calcium deposition. The results indicated that the size and shape of HA microparticles have an influence on the osteogenic differentiation of MC3T3-E1 preosteoblasts.

Facile synthesis of biphasic calcium phosphate microspheres with engineered surface topography for controlled delivery of drugs and proteins

Biphasic calcium phosphate (BCP) microspheres are of great interest due to their high stability and osteoinductive properties at specific compositions. However, the need for optimal performance at a unique composition limits their flexibility for tuning drug release by modulation of bulk properties and presents the question of engineering surface topography as an alternative. It is necessary to have a facile method to control surface topography at a defined bulk composition. Here, we have produced BCP microspheres with different surface topographies that have the capability to be used as tunable drug release systems. We synthesized calcium deficient hydroxyapatite (CDHA) microparticles by precipitating calcium and phosphate ions onto ethylenediaminetetraacetic acid (EDTA) templates. The morphology and surface topography of CDHA microparticles were controlled using process parameters, which governed nucleation and growth. These parameters included template concentration, heat rate, and stirring speed. Under low heat rate and static conditions, we could obtain spherical microparticles with long and short nanosheets on their surfaces at low and high EDTA concentrations, respectively. These nanostructured microspheres were subsequently crystallized by thermal treatment to produce EDTA-free BCP microspheres with intact morphology. These biocompatible BCP microspheres were highly effective in loading and prolonged release of both small molecule [dexamethasone (Dex)] and protein [bovine serum albumin (BSA)] models. This strategy has enabled us to control the surface topography of BCP microspheres at defined compositions and holds tremendous promise for drug delivery and tissue engineering applications.

Incorporation of glass-reinforced hydroxyapatite microparticles into poly(lactic acid) electrospun fibre mats for biomedical applications

Tissue engineering is constantly evolving towards novel materials that mimic the properties of the replaced injured tissue or organ. A hybrid electrospun membrane of electroactive poly(l-acid lactic) (PLLA) polymer with glass reinforced hydroxyapatite (Bonelike®) microparticles placed among the polymer fibres in a morphology like “islands in the sea” was processed. The incorporation of 60 to 80wt% Bonelike® bone grafts granules with ≤150μm into the polymer solution lead to an amorphous polymeric fibre membranes, and a decrease of the average polymer fibre diameter from 550±150nm for neat PLA down to 440±170nm for the hybrid composite. The presence of Bonelike® in the polymer mats reduced the activation energy for thermal degradation from 134kJ·mol−1, obtained for the neat PLLA membranes down to 71kJ·mol−1, calculated for the hybrid composite membranes. In vitro cell culture results suggest that the developed processing method does not induce cytotoxic effects in MG 63 osteoblastic cells, and creates an environment that enhances cell proliferation, when compared to the neat PLLA membrane. The simplicity and scalability of the processing method suggests a large application potential of this novel hybrid polymer-microparticles fibre membranes for bone regenerative medicine.

Bone-specific poly(ethylene sodium phosphate)-bearing biodegradable nanoparticles

Chemotherapy is the most reliable treatment for osteoporosis and osseous metastases. To facilitate better drug delivery for bone treatments, a novel preparation of polymeric nanoparticles with high affinity to bone has been prepared. Two-step synthesis of cholesteryl-functionalized poly(ethylene sodium phosphate) (Ch-PEPn·Na) was performed via ring-opening polymerization of cyclic phosphoesters and the demethylation. The molecular weight of Ch-PEPn·Na could be well controlled by changing the ratio of cholesterol and cyclic phosphoesters. Because Ch-PEPn·Na exhibits an amphiphilic nature in aqueous media, Ch-PEPn·Na-bearing nanoparticles (PEPn·Na NPs) were prepared by a solvent evaporation technique. The size of the nanoparticles investigated in the current study is approximately 100nm, which was determined by dynamic light scattering (DLS) and transmission electron microscopy (TEM). Due to the presence of highly water-soluble polymer chains, dispersion of PEPn·Na NPs in aqueous media was stable for at least 1 week. Hemolytic activity of PEPn·Na NPs was found to be low and PEPn·Na NPs did not disintegrate mammalian cell membranes. Additionally, cytotoxicity of PEPn·Na NPs was not observed at concentrations below 100μg/mL. The adsorption of PEPn·Na NPs on hydroxyapatite (HAp) microparticles was studied in comparison with poly(ethylene glycol) nanoparticles (PEG NPs). Both PEPn·Na NPs and PEG NPs adsorbed well onto HAp microparticles in distilled water with binding equilibrium constants (KHAp) for PEPn·Na NPs and PEG NPs of 3.6×106 and 7.9×106, respectively. In contrast, only PEPn·Na NPs adsorbed onto HAp microparticles in a saline phosphate buffer. Moreover, the adsorption of PEPn·Na NPs onto HAp microparticles occurred even in the presence of 1.2mM calcium ions or low-pH media. The affinity of the nanoparticles to bovine bone slices was also studied, with the result that large quantities of adsorbed PEPn·Na NPs were observed on the slices by scanning electron microscope.

Fabrication of hydroxyapatite microparticles including silver nano-dots at grain boundary for long-term antimicrobial property

The antibacterial properties are useful to restrain inflammatory response caused by bacterial infection after implantation. The composites of hydroxyapatite (HAp) and silver nano-dots, silver oxide or silver phosphate have been investigated; however there are still some disadvantage in sintering; 1) silver nano-dots grow large, and are not homogenously distributed, 2) silver nano-dots melt and remove, and 3) silver phosphate and silver oxide formed exhibit higher solubility than metal silver. In this study, the distribution of silver nano-dots in HAp microparticles sintered was controlled at grain boundary with a modified silver mirror reaction as a novel route. HAp microparticles adsorbed formaldehyde by a vapor deposition method were soaked in an ammoniacal silver nitrate solution and were then sintered. There was a single phase of HAp including metal silver at 6.4 wt% even after sintering. The silver nano-dots were homogeneously distributed inside the microparticles. The release profiles of silver ions in phosphate buffer saline were compared with a reference; the HAp microparticles were soaked into silver nitrate solution and were then sintered. The distribution of silver in the reference was not homogeneous and large silver microparticles were grown outside the particles at 6.3wt%. The elution amount of silver ions from the microparticles at 12 hours was one-eighteenth of that from the reference. These results suggest that the HAp microparticles including silver nano-dots at grain boundary will be suitable for a long-term antibacterial material.

A Composite Material Based on Poly(2-hydroxyethyl methacrylate) with Hydroxyapatite Microparticle Inclusions

An organo-mineral composite bone-grafting material was developed and tested. The composite material is based on synthetic hydroxyapatite (HAP) (30-60 wt%) integrated into the matrix of poly(2-hydroxyethyl methacrylate) (pHEMA) hydrogel. The composite was shown to have a homogeneous and isotropic microstructure, mechanical strength of ~11 MPa, high degree of water absorption reaching 34%, and elastomeric properties under physio-logical conditions (strain at failure is 57%).

Immobilizing hydroxyapatite microparticles on poly(lactic acid) nonwoven scaffolds using layer-by-layer deposition

A composite porous scaffold for bone cell culture was fabricated by immobilizing HA (hydroxyapatite) (Ca10 (PO4)6 (OH)2) microparticles on PLA (poly(lactic acid)) nonwoven fibers using the layer-by-layer deposition technique. A nonwoven PLA of thickness 1 mm, with average pore size of 230 µm and a porosity of 94%, was used. The nonwoven was functionalized with aqueous 65% deacetylated chitosan followed by rinsing, and then a second padding with aqueous sodium alginate loaded with varying percentages of HA microparticles (0.01%, 0.1% and 0.2%), resulting in a composite porous nonwoven. Sodium alginate was revealed to be an efficient polymer for obtaining a stable dispersion of the HA microparticles in an aqueous medium. Atomic force microscopy and scanning electron microscopy images, zeta potential and wettability tests showed successfully the different surface modifications occurring at each step of surface functionalization. The chitosan coating cationized the PLA fiber surface, providing good adhesion of the HA-loaded anionic alginate coating. HA was almost homogeneously distributed at the PLA fiber surfaces with only a small reduction in the scaffold porosity, which reached 75%. The composite PLA/chitosan/alginate/HA nonwoven structures were tested as scaffold for adhesion and proliferation of rat pre-osteoblast MC3T3-E1 cells. The results showed that higher loading with HA improved the MC3T3 cell adhesion and proliferation after 3 and 6 days of culture.

Genotoxicity analysis of nano and micro particles of hydroxyapatite in human mesenchymal stem cells

Genotoxicity analysis of nano and micro particles of hydroxyapatite in human mesenchymal stem cells