nano-HA Content Research Articles

Fabrication and properties of a stable and porous YSZ/nano-HA structure by binder jetting processes

ABSTRACT In the preparation of porous ceramic structure by binder jetting process, the stability and strength of porous ceramic structure caused by different powder composition have attracted much attention. Therefore, a pore filling method was proposed in this paper, in which nano-hydroxyapatite (nano-HA) particles with different contents were filled into yttrium-stabilized zirconia (YSZ) ceramic powders to solve the poor porosity and weak mechanical properties of porous ceramic structure. The effects of nano-HA content on the pore formation, surface quality, phase stability, compressive strength and microstructure of porous YSZ/nano-HA structure were studied. The results showed that as the mass percentage of nano-HA increased to 25 wt.%, the surface roughness of the top, side, and bottom decreased, whereas the relative density increased from 39.3% to 48.8%. After sintering at 1450°C the porous YSZ/nano-HA structures revealed a decrease in shrinkage (18.1% −11.5%) and water absorption (4.4% −2.3%), but an increase in compressive strength (30.9 MPa − 41.2 MPa). The sintered phase of YSZ/nano-HA structure presented a new microstructure evolution process, in which t-ZrO2 and Ca3(PO4)2 acted as the main crystal phase, with trace amounts of Ca0.15Zr0.85O1.85 cubic solid solution.

Directed differentiation of BMSCs on structural/compositional gradient nanofibrous scaffolds for ligament-bone osteointegration.

Nanofibrous scaffolds with structural and compositional gradients exhibit great potential to modulate zonal differentiation of stem cells for the regeneration of soft-to-hard tissue interface. Here, the response of bone marrow stem cells (BMSCs) to electrospun gradient nanofibrous scaffolds was investigated to demonstrate their potential capabilities for interfacial tissue regeneration. The electrospun scaffolds showed gradient distribution of BMP-2/nanoHA contents and the fiber orientations gradually changed from random to align. Biomimetic mineralization demonstrated that calcium and phosphorus elements can deposit onto the surface of the nanofibers in a gradient manner similar to nanoHA content. BMSCs cultured on the gradient nanofibrous scaffolds exhibited high cell viability and cell morphology gradually changed from disorder to highly align similar to the underlying fiber orientation. BMP-2/nanoHA content gradients in the nanofibrous scaffolds were found to effectively promote the zonal expression of bone-specific genes like osteocalcin (OCN), Runt-related transcription factor 2 (Runx2) and alkaline phosphatase (ALP). Immunofluorescent staining of osteopontin (OPN) and OCN further confirmed osteoblastic phenotypic maturation on the regions of the scaffolds with a higher level of nanoHA and BMP-2 contents after cultured 28days. These results indicated that the gradient nanofibrous scaffolds enable to guide zonal differentiation of BMSCs in vitro, which might be useful to realize multitissue regeneration in one construct for the regeneration of soft-to-hard tissue interface.

Characterization of water hyacinth cellulose-g-poly(ammonium acrylate-co-acrylic acid)/nano-hydroxyapatite polymer hydrogel composite for potential agricultural application

Polymer nano-composite was prepared by grafting partially neutralized acrylic acid onto swollen cellulose isolated from water hyacinth in the presence of nano-hydroxyapatite (nano-HA) using N,N-methylene-bis-acrylamide (MBA) as the cross-linker and ammonium persulphate (APS) as the free radical initiator. Water absorption tests showed an increase in swelling ratio of the copolymer with increased nano-HA content to value of 120 g/g at 2.5% w/v above which it declined. FTIR spectrum of nano-composite revealed grafting of the monomer (acrylic acid/ammonium acrylate) onto cellulose and nano-HA. Transmission electron microscopy (TEM) images of nano-HA synthesized in the presence of Triton X-100 (non-ionic surfactant) displayed rod-shaped agglomerates and nano-particle dispersion within the copolymer matrix. Energy dispersive X-ray (EDX) spectra revealed the constituents of nano-composite to be mainly C, O, Ca and P, while N was not detected by this method. X-ray diffractograms (XRD) of cellulose grafted copolymer showed a more amorphous structure relative to that of dry water hyacinth cellulose and also presence of crystalline nano-HA within the copolymer. This polymer nano-composite could be beneficial in agriculture in aiding moisture retention as well as a source of P which occurs through microbial degradation of cellulose grafted copolymer and solubilization of nano-HA.

Alginate-nanohydroxyapatite hydrogel system: Optimizing the formulation for enhanced bone regeneration.

Ceramic/polymer-based biocomposites have emerged as potential biomaterials to fill, replace, repair or regenerate injured or diseased bone, due to their outstanding features in terms of biocompatibility, bioactivity, injectability, and biodegradability. However, these properties can be dependent on the amount of ceramic component present in the polymer-based composite. Therefore, in the present study, the influence of nanohydroxyapatite content (30 to 70 wt%) on alginate-based hydrogels was studied in order to evaluate the best formulation for maximizing bone tissue regeneration. The composite system was characterized in terms of physic-chemical properties and biological response, with in vitro cytocompatibility assessment with human osteoblastic cells and ex vivo functional evaluation in embryonic chick segmental bone defects. The main morphological characteristics of the alginate network were not affected by the addition of nanohydroxyapatite. However, physic-chemical features, like water-swelling rate, stability at extreme pH values, apatite formation, and Ca2+ release were nanoHA dose-dependent. Within in vitro cytocompatibility assays it was observed that hydrogels with nanoHA 30% content enhanced osteoblastic cells proliferation and expression of osteogenic transcription factors, while those with higher concentrations (50 and 70%) decreased the osteogenic cell response. Ex vivo data underlined the in vitro findings, revealing an enhanced collagenous deposition, trabecular bone formation and matrix mineralization with Alg-nanoHA30 composition, while compositions with higher nanoHA content induced a diminished bone tissue response. The outcomes of this study indicate that nanohydroxyapatite concentration plays a major role in physic-chemical properties and biological response of the composite system and the optimization of the components ratio must be met to maximize bone tissue regeneration.

Effect of nano-HA content on the mechanical properties, degradation and biocompatible behavior of Mg-Zn/HA composite prepared by spark plasma sintering

Recently, Mg-Zn alloy had been investigated as biodegradable material for fabricating orthopedic implants. In this paper, nano-hydroxyapatite (nano-HA) [Ca10(PO4)6(OH)2] was uniformly distributed on the surface of magnesium particles by ball milling process, and then the composite of Mg-5.5Zn/HA was successfully fabricated by spark plasma sintering (SPS). Effect of the nano-HA content on the compressive strength and the bioactivity in vitro (corrosion behavior, cytotoxicity) of the composite was analyzed. Results indicated that with the increasing of the nano-HA content (from 0 to 10 wt%), the compressive yield strength is improved remarkably. Comparing with Mg-5.5Zn alloy, of the nano-HA (10 wt%) can improve the compressive yield strength by 43% and bending strength by 14%. Furthermore, the in-vitro immersion tests revealed the positive and negative effects of nano-HA content on the corrosion behavior of Mg-5.5Zn/HA composite. The nano-HA can improve the degradation resistance of the Mg-5.5Zn matrix. Addition of 10 wt% HA can decrease the corrosion rate by 49%. Furthermore, the composite exhibits acceptable cytotoxicity to L-929 cells, and impressive potential to be used as an orthopedic implant material.

Physical Crosslinked Poly(N-isopropylacrylamide)/Nano-Hydroxyapatite Thermosensitive Composite Hydrogels

Injectable and thermosensitive poly(N-isopropylacrylamide) (PNIPA)/nano-hydroxyapatite (nano-HA) composite hydrogels were synthesized by physical crosslinking of N-isopropylacrylamide with nano-HA as cross-linker to improve the mechanical property of hydrogels and avoid the use of chemical cross-linker. Internal morphology, thermosensitive, rheological, swelling, and hemocompatibility properties of the prepared hydrogels were investigated. The PNIPA/HA composite hydrogels had a phase transition from sol to gel, and the lowest critical solution temperature was about 32.5 °C. The PNIPA/HA composite hydrogels had regular pore structures and the nano-HA dispersed well throughout the network. Differential scanning calorimetry and thermogravimetric analysis showed that the addition of nano-HA had no significant effect on the LCST and thermal stability of the PNIPA/HA hydrogels. When the temperature was above 32.5 °C, the storage modulus (G′) and complex viscosity increased with the increasing nano-HA content. All PNIPA/HA composite hydrogels possessed the thinning behavior. The PNIPA/HA hydrogels exhibited a good water absorption capacity and the swelling ratio decreased with the increasing nano-HA content. As revealed by biocompatibility results, PNIPA/HA composite hydrogels were considered to be a non-hemolytic biomaterial. Therefore, PNIPA/HA hydrogels can be used as injectable materials for the potential applications of science and technology, such as tissue engineering scaffolds.

Hybrid Composites of Phosphate Glass Fibre/Nano-Hydroxyapatite/Polylactide: Effects of Nano-Hydroxyapatite on Mechanical Properties and Degradation Behaviour

Hydroxyapatite/polylactide (HA/PLA) composites have been intensively investigated for their potential as biodegradable fixation devices to heal bone fractures. However, most of these composites failed to achieve a bone-mimicking level of mechanical properties, which is an essential demand of the targeted application. In this study, the nano-hydroxyapatite/polylactide composites were used as the matrix and continuous phosphate glass fibres (PGF) served as the major reinforcement to obtain the nano-HA/PGF/PLA hybrid composites. While the PGF volume fraction remained constant (25%), the nano-HA content (in weight) varied from 0% to 20%. As nano-HA loading increased, the flexural modulus of the composites increased from 8.70 ± 0.35 GPa to 14.97 ± 1.30 GPa, and the flexural strengths were enhanced from 236.31 ± 10.83 MPa to 310.55 ± 22.88 MPa. However, it is found that the degradation rates are higher with more nano-HA loaded. Enhanced water absorption ability, as well as increased voids in the composites is possible reasons for the accelerated degradation of composites with higher nano-HA loading. The hybrid composites possess mechanical properties that are superior to most of the HA/PLA composites in previous research while maintaining the biodegradability. With a proper loading of nano-HA in composites of 10 weight percent, the composites are also found with improved mechanical properties without catastrophic degradation. The composites developed in this study have great potential as biodegradable bone fixation device with enhanced load-bearing ability as confirmed and superior bioactivity as anticipated.

Biodegradation, biocompatibility, and osteoconduction evaluation of collagen-nanohydroxyapatite cryogels for bone tissue regeneration.

Designing biomimetic biomaterials inspired by the natural complex structure of bone and other hard tissues is still a challenge nowadays. The control of the biomineralization process onto biomaterials should be evaluated before clinical application. Aiming at bone regeneration applications, this work evaluated the in vitro biodegradation and interaction between human bone marrow stromal cells (HBMSC) cultured on different collagen/nanohydroxyapatite cryogels. Cell proliferation, differentiation, morphology, and metabolic activity were assessed through different protocols. All the biocomposite materials allowed physiologic apatite deposition after incubation in simulated body fluid and the cryogel with the highest nanoHA content showed to have the highest mechanical strength (DMA). The study clearly showed that the highest concentration of nanoHA granules on the cryogels were able to support cell type's survival, proliferation, and individual functionality in a monoculture system, for 21 days. In fact, the biocomposites were also able to differentiate HBMSCs into osteoblastic phenotype. The composites behavior was also assessed in vivo through subcutaneous and bone implantation in rats to evaluate its tissue-forming ability and degradation rate. The cryogels Coll/nanoHA (30 : 70) promoted tissue regeneration and adverse reactions were not observed on subcutaneous and bone implants. The results achieved suggest that scaffolds of Coll/nanoHA (30 : 70) should be considered promising implants for bone defects that present a grotto like appearance with a relatively small access but a wider hollow inside. This material could adjust to small dimensions and when entering into the defect, it could expand inside and remain in close contact with the defect walls, thus ensuring adequate osteoconductivity.

Cytocompatibility of PLA/Nano-HA composites for interface fixation

Objective: When preliminary tests have confirmed a nano-hydroxyapatite (Nano-HA) content of 20% of the polylactic acid (PLA) composite material of Nano-HA interface fixation material for biomechanical requirements, there is a need for further observation of its biocompatibility and clinical applications, to provide reference data. Methods: Preparation of Nano-HA content of 20% PLA composite Nano-HA bone substitute material and extract. The establishment of the negative control group (containing 10% fetal bovine serum in DMEM complete medium), experimental group (extract), the positive control group (mass concentration of 0.64% phenol), and a co-culture of rabbit bone marrow mesenchymal stem cells (rBMSC) and materials extraction liquid. Observation of the morphological changes in rBMSC in culture at time points of 3, 5, and 7 days, the use of the MTT assay, and determination of the relative growth in the above set of rBMSC in cell culture at 3, 5, and 7 days, to judge the material's cytotoxicity. Results: With time, the absorbance value of the three groups of cells were significantly increased (P < 0.01). The relative growth of the rBMSCs in experimental group in the first 3, 5, and 7 days was 95.3%, 96.8% and 97.6%; the cytotoxicity was according to the national standards I; the difference was not significant (P > 0.05) between the the experimental group and the negative control group; there was a significant difference between the positive control group and the other 2 groups (P < 0.05). Cells in the experimental group were seen having normal morphology, and spindle-shaped adherent growth. Conclusion: PLA composite artificial bone materials and Nano-HA show good cell compatibility, and the values for cytotoxicity, with reference to GB/T16886.5.2003 (China) standards, are in the safe range.

Electrospinning of nanofibrous scaffolds with continuous structure and material gradients

One of the major challenges in tissue engineering is to engineer biomaterial scaffolds with desirable gradients for the regeneration of composite tissues. Here we propose a unique electrospinning strategy to fabricate nanofibrous scaffolds with both structure and material composition gradients. The results demonstrate that the microstructural organization of nanofibers gradually changed from random to aligned patterns. Nanoparticles like nanohydroxyapatite (nano-HA) were encapsulated into these nanofibers and nano-HA content in the electrospun scaffolds gradually altered in a similar gradient manner to structural organization. This simple yet versatile method might be useful to engineer graded tissues by flexibly generating tissue-specific structure and material gradients.

Performance test of Nano-HA/PLLA composites for interface fixation

Objective: By in situ polymerization of poly-L-lactic acid (PLLA) and nano-hydroxyapatite (Nano-HA), and finding the best proportion of composite, so as to get ideal interface fixation material. Methods: According to a certain ratio (the mass fraction of Nano-HA, respectively, is 0%, 10%, 20%, 30% and 40%), composite PLLA and Nano-HA by in situ polymerization, and test the performance of this kind of new type of interface fixation such as, bending strength,compressive strength, elastic modulus, scanning electron microscopy (SEM) and degradation experiments in vitro. Then observe its mechanical properties, microstructure, the dispersion of Nano-HA in the PLLA and degradation rate of composite materials. Results: 1. Mechanical tests show that with the increase of Nano-HA content, the tensile strength decreases and the elastic modulus increases; with Nano-HA content of 20%, the bending strength of composite materials presents the peak value (156.8 MPa). 2. SEM scan shows the fracture surface of pure PLLA is relatively smooth; with Nano-HA content of 10%, the fracture surface shows a large number of dimples, and is obvious rough; with Nano-HA content of 20%, the fracture surface is uneven, forming a large number of dimples; with Nano-HA content of 30% or more, the fracture surface becomes more flat, and there are some small dimples. 3. Degradation experiments in vitro show the following: as the degradation time goes on, the pH values of degradation liquid is gradually reduced and the mechanical properties of composite materials also gradually have some decay. Conclusion: With Nano-HA content of 20%, the interface fixation material has a better mechanical properties and degradation properties. According to the best ratio, prepare Nano-HA/PLLA composite artificial materials with good performance.

Preparation and characterization of collagen‐nanohydroxyapatite biocomposite scaffolds by cryogelation method for bone tissue engineering applications

Recent efforts of bone repair focus on development of porous scaffolds for cell adhesion and proliferation. Collagen-nanohydroxyapatite (HA) scaffolds (70:30; 50:50; and 30:70 mass percentage) were produced by cryogelation technique using 1-ethyl-3-(3-dimethyl aminopropyl) carbodiimide hydrochloride/N-hydroxysuccinimide as crosslinking agents. A pure collagen scaffold was used as control. Morphology analysis revealed that all cryogels had highly porous structure with interconnective porosity and the nanoHA aggregates were randomly dispersed throughout the scaffold structure. Chemical analysis showed the presence of all major peaks related to collagen and HA in the biocomposites and indicated possible interaction between nanoHA aggregates and collagen molecules. Porosity analysis revealed an enhancement in the surface area as the nanoHA percentage increased in the collagen structure. The biocomposites showed improved mechanical properties as the nanoHA content increased in the scaffold. As expected, the swelling capacity decreased with the increase of nanoHA content. In vitro studies with osteoblasts cells showed that they were able to attach and spread in all cryogels surfaces. The presence of collagen-nanoHA biocomposites resulted in higher overall cellular proliferation compared to pure collagen scaffold. A statistically significant difference between collagen and collagen-nanoHA cryogels was observed after 21 day of cell culture. These innovative collagen-nanoHA cryogels could have potentially appealing application as scaffolds for bone regeneration.

Stress relaxation behavior of nano-hydroxyapatite reinforced poly(vinyl alcohol) gel composites as biomaterial

Nano-hydroxyapatite reinforced poly(vinyl alcohol) (nano-HA/PVA) gel composites has been proposed as a promising biomaterial to replace diseased or damaged articular cartilage. In this paper, the stress relaxation mechanism of nano-HA/PVA gel composites was investigated. The various influence factors on the stress relaxation behavior of the composites were also evaluated. The results showed that the relaxation mechanism of the composites was mainly determined by the synergistic effect of two stress relaxation mechanisms analogous to those of the natural articular cartilage and the polymer. The relaxation rate of the composites increased with the rise of strain ratio, but it declined with the relaxation time. Under the given strain ratio, the relaxation rate of the composite presented a trend of rising first and then falling with the increasing amount of nano-HA content. Contrarily, the normalized equilibrium relaxation modulus of the composites decreased first and then presented increasing trend with the rise of nano-HA content. Furthermore, the normalized equilibrium relaxation modulus of the composites decreased with the rise of strain.

Swelling properties of nano-hydroxyapatite reinforced poly(vinyl alcohol) gel biocomposites

Nano-hydroxyapatite reinforced poly(vinyl alcohol) (nano-HA/PVA) gel composites is proposed as a promising biomaterial to replace diseased or damaged articular cartilage. Nano-HA/PVA gel composites were prepared by in situ synthesis of nano-HA particles in PVA solution and accompanied by freeze/thaw method. The influences of freeze/thaw cycle times, nano-HA content, PVA concentration and swelling media on the swelling characteristics of the gel composites were investigated. The results showed that the swelling ratio of the gel composites increased, but its swelling rate decreased with the rise of swelling time. Both the swelling ratio and equilibrium swelling ratio of the gel composites in the different swelling media presented an increasing trend with the rise of freeze/thaw cycle times. Contrarily, the equilibrium swelling ratio of the gel composites decreased with the rise of nano-HA and PVA concentration. Swelling media have significant influence on the swelling behaviour of the gel composites. The equilibrium swelling ratio of the gel composites in distilled water was the largest and it reached the lowest in bovine serum. Simultaneously, the equilibrium swelling ratio in bovine serum was far lower than that in inorganic swelling media, such as distilled water and physiological saline.

Study on compressive mechanical properties of nanohydroxyapatite reinforced poly(vinyl alcohol) gel composites as biomaterial

Nanohydroxyapatite reinforced poly(vinyl alcohol) (nano-HA/PVA) gel composites has been proposed as a promising biomaterial to replace diseased or damaged articular cartilage. In this paper, nano-HA/PVA gel composites were prepared by in situ synthesis nano-HA particles in PVA solution and accompanied with freeze/thaw method. The influence of nano-HA content, PVA concentration and freeze/thaw cycle times on the compressive mechanical behavior of nano-HA/PVA gel composites were evaluated using mechanical test equipment. The results showed that the compressive mechanical behavior of nano-HA/PVA gel composites was similar to that of natural articular cartilage, which held special viscoelastic characteristics. Both the compressive strength and modulus of the composites improved correspondingly with the rise of freeze/thaw cycle times and PVA concentration. The compressive strength and modulus of nano-HA/PVA gel composites firstly increased and then presented decreasing trend with the rise of nano-HA content. Furthermore, the compressive modulus of the composites improved exponentially with the rise of compressive strain ratio.

Electrospun Gelatin/Hydroxyapatite Nanocomposite Scaffolds for Bone Tissue Engineering

AbstractElectrospun composite scaffolds were prepared by mixing gelatin with nanoparticles of hydroxyapatite (nanoHA) in 2,2,2-trifluoroethanol (TFE) solution. The fibrous composite scaffolds with nanoHA content from 0 to 40 wt% were compared in terms of structure and morphology via x-ray diffraction (XRD) and scanning electron microscopy (SEM). Results show that dispersion of nanoHA in the scaffolds is uniform for 0%, 10%, 20%, and 30% nanoHA content, but significant nanoHA agglomeration can be observed for scaffolds with 40% nanoHA. In order to study the effect of nanoHA content on mechanical properties at the nanoscale level, the fibrous scaffolds were pressed into dense pellets and tested by nanoindentation to determine Young's modulus. Young's modulus was found to increase linearly with nanoHA content, reaching unexpectedly high values of 10.2 ± 0.8 GPa. Results are compared with other polymer/HA composites including those made with polycaprolactone or collagen.

Viscoelastic behavior of nano-hydroxyapatite reinforced poly(vinyl alcohol) gel biocomposites as an articular cartilage

Nanohydroxyapatite reinforced poly(vinyl alcohol) gel (nano-HA/PVA gel) composites has been proposed as an articular cartilage repair biomaterial. In this paper, nano-HA/PVA gel composites were prepared by in situ synthesis nano-HA particles in PVA solution and accompanied with freeze/thaw method. The influence of nano-HA content, PVA concentration, test frequency and freeze/thaw cycle times on the viscoelastic behavior of nano-HA/PVA gel composites were evaluated using dynamic mechanical thermal analysis (DMTA). The results showed that both storage modulus and loss modulus firstly increased and then presented decreasing trend with the rise of nano-HA content. Their maximum values were obtained while nano-HA content was 6%. Furthermore, the G' and G'' of the composites improve with the increase of PVA concentrations and freeze/thaw cycle times. This effect was more distinct at low freeze/thaw cycles. The phase angle (tan delta) of the pure PVA gel is larger than that of the nano-HA/PVA composites at the test frequency spectra, but all the phase angle values of the tested composites were close to that of nature bone.

Mechanical properties of nanohydroxyapatite reinforced poly(vinyl alcohol) gel composites as biomaterial

Nanohydroxyapatite reinforced poly(vinyl alcohol) gel (nano-HA/PVA gel) composites has been proposed as a promising biomaterial, especially used as an articular cartilage repair biomaterial. In this paper, nano-HA/PVA gel composites were prepared from mixing nano-HA particles modified by silicon coupling agent, with physiological saline solution (PSS) of PVA by freezing-thawing method. The effects of various factors on the mechanical properties of nano-HA/PVA gel composites were evaluated. It was shown that the mechanical behavior of nano-HA/PVA gel composites was similar to that of natural articular cartilage, which held special viscoelastic characteristics. The tensile strength and tensile modulus of the composites improved correspondingly with the increase of freezing-thawing times and concentration of PVA solution. The more concentration of PVA solution, the higher influence degree of concentration on the tensile strength of composites is. The tensile strength and tensile modulus of nano-HA/PVA hydrogel composites increased first and then decreased with the rising nano-HA content of the composites. The tensile modulus of the composites improved remarkably with the increase of elongation ratio.

Nanostructured Biocomposite Scaffolds Based on Collagen Coelectrospun with Nanohydroxyapatite

Nanofibrous biocomposite scaffolds of type I collagen and nanohydroxyapatite (nanoHA) of varying compositions (wt %) were prepared by electrostatic cospinning. The scaffolds were characterized for structure and morphology by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), atomic force microscopy (AFM) and X-ray diffraction (XRD) techniques. The scaffolds have a porous nanofibrous morphology with random fibers in the range of 500-700 nm diameters, depending on the composition. FT-IR and XRD showed the presence of nanoHA in the fibers. The surface roughness and diameter of the fibers increased with the presence of nanoHA in biocomposite fiber as evident from AFM images. Tensile testing and nanoindendation were used for the mechanical characterization. The pure collagen fibrous matrix (without nanoHA) showed a tensile strength of 1.68 +/- 0.10 MPa and a modulus of 6.21 +/- 0.8 MPa with a strain to failure value of 55 +/- 10%. As the nanoHA content in the randomly oriented collagen nanofibers increased to 10%, the ultimate strength increased to 5 +/- 0.5 MPa and the modulus increased to 230 +/- 30 MPa. The increase in tensile modulus may be attributed to an increase in rigidity over the pure polymer when the hydroxyapatite is added and/or the resulting strong adhesion between the two materials. The vapor phase chemical crosslinking of collagens using glutaraldehyde further increased the mechanical properties as evident from nanoindentation results. A combination of nanofibrous collagen and nanohydroxyapatite that mimics the nanoscale features of the extra cellular matrix could be promising for application as scaffolds for hard tissue regeneration, especially in low or nonload bearing areas.

Electrospun Bioactive Nanocomposite Scaffolds of Polycaprolactone and Nanohydroxyapatite for Bone Tissue Engineering

Nanocomposite scaffolds based on nanofibrous poly(epsilon-caprolactone) (PCL) and nanohydroxyapatite (nanoHA) with different compositions (wt%) were prepared by electrostatic co-spinning to mimic the nano-features of the natural extracellular matrix (ECM). NanoHA was found to be well dispersed in polymers up to the addition of 20 wt%, after ultrasonication. The composite scaffolds were characterized for structure and morphology using XRD, EDX, SEM, and DSC. The scaffolds have a porous nanofibrous morphology with fibers (majority) having diameters in the range of 450-650 nm, depending on composition, and interconnected pore structures. SEM, EDX, and XRD analyses have confirmed the presence of nanoHA in the fibers. As the nanoHA content in the fibers increases, the surface of fibers becomes rougher. The mechanical (tensile) property measurement of the electrospun composites reveals that as the nanoHA content increases, the ultimate strength increases from 1.68 MPa for pure PCL to 2.17, 2.65, 3.91, and 5.49 MPa for PCL/nanoHA composites with the addition of 5, 10, 15, and 20 wt% nanoHA, respectively. Similarly the tensile modulus also increases gradually from 6.12 MPa to 21.05 MPa with the increase of nanoHA content in the PCL/nanoHA fibers, revealing an increase in stiffness of the fibers due to the presence of HA. DSC analysis reveals that as nanoHA in the composite scaffolds increases, the melting point slightly increases due to the good dispersion and interface bonding between PCL and nanoHA.