Osteoblast growth and function in porous poly epsilon -caprolactone matrices for bone repair: a preliminary study

Calcium Phosphate (CaP) Composite Nanostructures on Polycaprolactone (PCL): Synergistic Effects on Antibacterial Activity and Osteoblast Behavior

Bone tissue engineering aims to develop biomaterials that are capable of effectively repairing and regenerating damaged bone tissue. Among the various polymers used in this field, polycaprolactone (PCL) is one of the most widely utilized. As a biocompatible polymer, PCL is easy to fabricate, cost-effective, and offers consistent quality control, making it a popular choice for biomedical applications. However, PCL lacks inherent antibacterial properties, making it susceptible to bacterial adhesion and biofilm formation, which can lead to implant failure. To address this issue, this study aims to enhance the antibacterial properties of PCL by incorporating calcium phosphate composite (PCL_CaP) nanostructures onto its surface via hydrothermal synthesis. The resulting "PCL_CaP" nanostructured surfaces exhibited improved wettability and demonstrated mechano-bactericidal potential against Escherichia coli and Bacillus subtilis. The flake-like morphology of the fabricated CaP nanostructures effectively disrupted bacteria membranes, inhibiting bacterial growth. Furthermore, the "PCL_CaP" surfaces supported the adhesion, proliferation, and differentiation of pre-osteoblasts, indicating their potential for bone tissue engineering applications. This study demonstrates the promise of calcium phosphate composite nanostructures as an effective antibacterial coating for implants and medical devices, with further research required to evaluate their long-term stability and in vivo performance.

Synthesis and Properties of Magnetic Fe3O4/PCL Porous Biocomposite Scaffolds with Different Sizes and Quantities of Fe3O4 Particles

In clinical practice, to treat diseases such as osteosarcoma or chondrosarcoma with broad surgical ostectomy, it would be ideal to have scaffolds that not only fill up the bone void but also possess the ability to regulate the subsequent regimes for targeted chemotherapy and/or bone regeneration. Magnetic targeting of therapeutic agents to specific sites in the body provides certain advantages such as minimal side-effects of anti-cancer drugs. The objective of this study was to characterize novel magnetic scaffolds that can be used as a central station to regulate the drug delivery of a magnetic nanoparticle system. Different sizes and quantities of Fe3O4 particles were mixed with poly-ε-caprolactone (PCL) to construct the magnetic scaffolds, and their mechanical properties, degradation performance, and cell biocompatibility were evaluated. It appeared that the presence of Fe3O4 particles influenced the magnetic, mechanical, and biological performances of the scaffolds. The prepared bio-nanocomposite scaffolds provided predominantly magnetic/superparamagnetic properties. Scaffolds with a micron-sized Fe3O4 to PCL weight (wt) ratio of 0.1:0.9 exhibited higher mechanical performances among samples, with Young’s modulus reaching 1 MPa and stiffness, 13 N/mm. Although an increased Fe3O4 particle proportion mildly influenced cell growth during the biocompatibility test, none of the Fe3O4/PCL scaffolds showed a cytotoxic effect.

Natural Fiber-Reinforced Polycaprolactone Green and Hybrid Biocomposites for Various Advanced Applications

Recent developments within the topic of biomaterials has taken hold of researchers due to the mounting concern of current environmental pollution as well as scarcity resources. Amongst all compatible biomaterials, polycaprolactone (PCL) is deemed to be a great potential biomaterial, especially to the tissue engineering sector, due to its advantages, including its biocompatibility and low bioactivity exhibition. The commercialization of PCL is deemed as infant technology despite of all its advantages. This contributed to the disadvantages of PCL, including expensive, toxic, and complex. Therefore, the shift towards the utilization of PCL as an alternative biomaterial in the development of biocomposites has been exponentially increased in recent years. PCL-based biocomposites are unique and versatile technology equipped with several importance features. In addition, the understanding on the properties of PCL and its blend is vital as it is influenced by the application of biocomposites. The superior characteristics of PCL-based green and hybrid biocomposites has expanded their applications, such as in the biomedical field, as well as in tissue engineering and medical implants. Thus, this review is aimed to critically discuss the characteristics of PCL-based biocomposites, which cover each mechanical and thermal properties and their importance towards several applications. The emergence of nanomaterials as reinforcement agent in PCL-based biocomposites was also a tackled issue within this review. On the whole, recent developments of PCL as a potential biomaterial in recent applications is reviewed.

Mechanical and Biological Properties of Magnesium- and Silicon-Substituted Hydroxyapatite Scaffolds

Magnesium (Mg)- and silicon (Si)-substituted hydroxyapatite (HA) scaffolds were synthesized using the sponge replica method. The influence of Mg²⁺ and SiO₄⁴⁻ ion substitution on the microstructural, mechanical and biological properties of HA scaffolds was evaluated. All synthesized scaffolds exhibited porosity >92%, with interconnected pores and pore sizes ranging between 200 and 800 μm. X-ray diffraction analysis showed that β-TCP was formed in the case of Mg substitution. X-ray fluorescence mapping showed a homogeneous distribution of Mg and Si ions in the respective scaffolds. Compared to the pure HA scaffold, a reduced grain size was observed in the Mg- and Si-substituted scaffolds, which greatly influenced the mechanical properties of the scaffolds. Mechanical tests revealed better performance in HA-Mg (0.44 ± 0.05 MPa), HA-Si (0.64 ± 0.02 MPa) and HA-MgSi (0.53 ± 0.01 MPa) samples compared to pure HA (0.2 ± 0.01 MPa). During biodegradability tests in Tris-HCl, slight weight loss and a substantial reduction in mechanical performances of the scaffolds were observed. Cell proliferation determined by the MTT assay using hBMSC showed that all scaffolds were biocompatible, and the HA-MgSi scaffold seemed the most effective for cell adhesion and proliferation. Furthermore, ALP activity and osteogenic marker expression analysis revealed the ability of HA-Si and HA-MgSi scaffolds to promote osteoblast differentiation.

Physical Gold Nanoparticle-Decorated Polyethylene Glycol-Hydroxyapatite Composites Guide Osteogenesis and Angiogenesis of Mesenchymal Stem Cells

In this study, polyethylene glycol (PEG) with hydroxyapatite (HA), with the incorporation of physical gold nanoparticles (AuNPs), was created and equipped through a surface coating technique in order to form PEG-HA-AuNP nanocomposites. The surface morphology and chemical composition were characterized using scanning electron microscopy (SEM), atomic force microscopy (AFM), UV–Vis spectroscopy (UV–Vis), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and contact angle assessment. The effects of PEG-HA-AuNP nanocomposites on the biocompatibility and biological activity of MC3T3-E1 osteoblast cells, endothelial cells (EC), macrophages (RAW 264.7), and human mesenchymal stem cells (MSCs), as well as the guiding of osteogenic differentiation, were estimated through the use of an in vitro assay. Moreover, the anti-inflammatory, biocompatibility, and endothelialization capacities were further assessed through in vivo evaluation. The PEG-HA-AuNP nanocomposites showed superior biological properties and biocompatibility capacity for cell behavior in both MC3T3-E1 cells and MSCs. These biological events surrounding the cells could be associated with the activation of adhesion, proliferation, migration, and differentiation processes on the PEG-HA-AuNP nanocomposites. Indeed, the induction of the osteogenic differentiation of MSCs by PEG-HA-AuNP nanocomposites and enhanced mineralization activity were also evidenced in this study. Moreover, from the in vivo assay, we further found that PEG-HA-AuNP nanocomposites not only facilitate the anti-immune response, as well as reducing CD86 expression, but also facilitate the endothelialization ability, as well as promoting CD31 expression, when implanted into rats subcutaneously for a period of 1 month. The current research illustrates the potential of PEG-HA-AuNP nanocomposites when used in combination with MSCs for the regeneration of bone tissue, with their nanotopography being employed as an applicable surface modification approach for the fabrication of biomaterials.

Bone formation with functionalized 3D printed poly-ε-caprolactone scaffold with plasma-rich-fibrin implanted in critical-sized calvaria defect of rat

Background/purpose

Space-making is one of the essential factors for bone regeneration in severe bony defect. To test the hypothesis that an appropriately designed scaffold may be beneficial for the bone formation in defect, the new bone formed in the critical-size calvarial defect of rat was examined after implanted with a 3D-printed poly-ɛ-caprolactone (PCL) scaffold, retaining with and without plasma rich fibrin (PRF).

Materials and methods

Thirty-two rats were divided into four groups (control, PCL, PRF, and PCL-plus-PRF). A custom-made 3D-printed PCL scaffold, 900 μm in pore size, retaining with and without PRF, was implanted into a critical-sized calvarial defect, 6 mm in diameter. Animals were sacrificed at week-4 or 8 after implantation for assessing the new bone formation by dental radiography, micro-computed tomography (μ-CT), and histology.

Results

By radiography and μ-CT, significantly greater mineralization areas/volumes were observed in defects with 3D-printed scaffold groups compared to that without the scaffold in both two-time points. However, no advantage was found by adding PRF. Histology showed that bone tissues grew into the central zone of the critical defect when 3D-printed PCL scaffold was present. In contrast, for the groups without the scaffolds, new bones were formed mostly along defect borders, and the central zones of the defects were collapsed and healed with thin connective tissue.

Conclusion

Our results suggest that the use of a 900 μm pore size 3D-printed PCL scaffold may have the potential in facilitating the new bone formation.

Sinusoidal electromagnetic fields accelerate bone regeneration by boosting the multifunctionality of bone marrow mesenchymal stem cells

Background

The repair of critical-sized bone defects is always a challenging problem. Electromagnetic fields (EMFs), used as a physiotherapy for bone defects, have been suspected to cause potential hazards to human health due to the long-term exposure. To optimize the application of EMF while avoiding its adverse effects, a combination of EMF and tissue engineering techniques is critical. Furthermore, a deeper understanding of the mechanism of action of EMF will lead to better applications in the future.

Methods

In this research, bone marrow mesenchymal stem cells (BMSCs) seeded on 3D-printed scaffolds were treated with sinusoidal EMFs in vitro. Then, 5.5 mm critical-sized calvarial defects were created in rats, and the cell scaffolds were implanted into the defects. In addition, the molecular and cellular mechanisms by which EMFs regulate BMSCs were explored with various approaches to gain deeper insight into the effects of EMFs.

Results

The cell scaffolds treated with EMF successfully accelerated the repair of critical-sized calvarial defects. Further studies revealed that EMF could not directly induce the differentiation of BMSCs but improved the sensitivity of BMSCs to BMP signals by upregulating the quantity of specific BMP (bone morphogenetic protein) receptors. Once these receptors receive BMP signals from the surrounding milieu, a cascade of reactions is initiated to promote osteogenic differentiation via the BMP/Smad signalling pathway. Moreover, the cytokines secreted by BMSCs treated with EMF can better facilitate angiogenesis and osteoimmunomodulation which play fundamental roles in bone regeneration.

Conclusion

In summary, EMF can promote the osteogenic potential of BMSCs and enhance the paracrine function of BMSCs to facilitate bone regeneration. These findings highlight the profound impact of EMF on tissue engineering and provide a new strategy for the clinical treatment of bone defects.

Cilnidipine loaded poly (ε-caprolactone) nanoparticles for enhanced oral delivery: optimization using DoE, physical characterization, pharmacokinetic, and pharmacodynamic evaluation

Cilnidipine (CND), an anti-hypertensive drug, possesses low oral bioavailability due to its poor aqueous solubility, low dissolution rate, and high gut wall metabolism. In the present study, an attempt has been made to prepare CND loaded polycaprolactone based nanoparticles (CND-PCL-NPs) by nanoprecipitation method applying the concepts of Design of Experiments. Critical factors affecting particle size and loading efficiency (LE%) were assessed by a hybrid design approach, comprising of Mini Run Resolution IV design followed by Box-Behnken design. Particle size, PDI, zeta potential and LE% of optimized formulations of CND-PCL-NPs were 220.3 ± 2.6 nm, 0.25 ± 0.1, -19.5 ± 0.9 mV, and 46.4 ± 1.8%, respectively. No significant changes were observed in the physical stability of nanoparticles when stored at 25 °C/60% RH over a period of 3 months. Oral pharmacokinetic studies revealed that Fabs of CND-PCL-NPs (0.55) were significantly higher than the CND suspension (0.26). Pharmacodynamic studies have revealed that the mean percent reduction in systolic blood pressure (% ΔSBP) was significantly higher in the case of CND-PCL-NPs (42%) as compared to CND suspension (24%). Optimized CND-PCL-NPs offer great potential in providing higher and sustained antihypertensive effect compared to conventional formulations of CND.

Exploiting ionisable nature of PEtOx-co-PEI to prepare pH sensitive, doxorubicin-loaded micelles

AIMS

This study was conducted to evaluate block copolymers containing two different poly(ethyleneimine) (PEI) amounts, as new pH-sensitive micellar delivery systems for doxorubicin.

METHODS

Micelles were prepared with block copolymers consisting of poly(2-ethyl-2-oxazoline)-co-poly(ethyleneimine) (PEtOx-co-PEI) and poly(ε-caprolactone) (PCL) as hydrophilic and hydrophobic blocks, respectively. Doxorubicin loading, micelle size, pH-dependent drug release, and in vitro cytotoxicity on MCF-7 cells were investigated.

RESULTS

The average size of drug-loaded micelles was under 100 nm and drug loading was between 10.7% and 48.3% (w/w). pH-sensitive drug release was more pronounced (84.7% and 68.9% (w/w) of drug was released at pH 5.0 and pH 7.4, respectively) for the micelles of the copolymer with the lowest PEI amount. The cell viability of doxorubicin-loaded micelles which were prepared by the copolymer with the lowest PEI amount was 28-33% at 72 h.

CONCLUSIONS

PEtOx-co-PEI-b-PCL micelles of this copolymer were found to be stable and effective pH-sensitive nano-sized carriers for doxorubicin delivery.

Effectiveness of Surface Treatment with Amine Plasma for Improving the Biocompatibility of Maxillofacial Plates

To date, no products have been presented for the surface treatment of metal plates used for repairing maxillofacial defects caused by trauma. Plasma surface treatment is a useful technique for chemically modifying the surfaces of biomaterials. Amine plasma-polymerization is an efficient way to prepare bioactive thin film polymers terminated with nitrogen-containing functional groups. The purpose of this study was to investigate the improvement in biocompatibility of titanium (Ti) plates treated with amine plasma-polymerization, and analyze their surfaces characteristics. To compare biocompatibility levels, in vitro test and animal study were performed using an amine plasma-polymerized Ti plate and an untreated Ti plate. After amine plasma-polymerization, the hydrophilicity of the Ti surface was remarkably improved. Biocompatibility was also improved for the Ti plates treated with amine plasma. The clinical application of this technique will not only shorten the time required for osseointegration, but will also improve the regeneration of bone.

Fabrication and Characterization of Scaffolds of Poly(ε-caprolactone)/Biosilicate® Biocomposites Prepared by Generative Manufacturing Process

Scaffolds of poly(ε-caprolactone) (PCL) and their biocomposites with 0, 1, 3, and 5 wt.% Biosilicate® were fabricated by the generative manufacturing process coupled with a vertical miniscrew extrusion head to application for restoration of bone tissue. Their morphological characterization indicated the designed 0°/90° architecture range of pore sizes and their interconnectivity is feasible for tissue engineering applications. Mechanical compression tests revealed an up to 57% increase in the stiffness of the scaffold structures with the addition of 1 to 5 wt.% Biosilicate® to the biocomposite. No toxicity was detected in the scaffolds tested by in vitro cell viability with MC3T3-E1 preosteoblast cell line. The results highlighted the potential application of scaffolds fabricated with poly(ε-caprolactone)/Biosilicate® to tissue engineering.

Histopathological Evaluation of Polycaprolactone Nanocomposite Compared with Tricalcium Phosphate in Bone Healing

INTRODUCTION

In recent years, the use of bone scaffolds as bone tissue substitutes, especially the use of such as hydroxyapatite and tricalcium phosphate, has been very popular. Today, the use of modern engineering techniques and advances in nanotechnology have expanded the use of nanomaterials as bone scaffolds for bone tissue applications.

MATERIAL AND METHODS

This study was performed on 60 adult male New Zealand rabbits divided into four experimental groups: the control group without any treatment, the second group receiving hydroxyapatite, the third group treated with β-tricalcium phosphate, and the fourth group receiving nanocomposite polycaprolactone (PCL) scaffold. In a surgical procedure, a defect 6 mm in diameter was made in a hind limb femur. Four indexes were used to assess histopathology, which were union index, spongiosa index, cortex index, and bone marrow.

RESULTS

The results showed that nanocomposite PCL and control groups always had the respective highest and lowest values among all the groups at all time intervals. The histopathological assessment demonstrated that the quantity of newly formed lamellar bone in the nanocomposite PCL group was higher than in other groups.

CONCLUSION

All these data suggest that PCL had positive effects on the bone healing process, which could have great potential in tissue engineering and clinical applications.

pH-Sensitive Nanocarrier-Mediated Codelivery of Simvastatin and Noggin siRNA for Synergistic Enhancement of Osteogenesis

The inexpensive hypolipidemic drug simvastatin (SIM), which promotes bone regeneration by enhancing bone morphogenetic protein 2 (BMP-2) expression, has been regarded as an ideal alternative to BMP-2 therapy. However, SIM has low bioavailability and may induce the upregulation of the BMP-2-antagonistic noggin protein, which greatly limits the osteogenic effect. Here, a pH-sensitive copolymer, monomethoxy-poly(ethylene glycol)- b-branched polyethyleneimine- b-poly( N-( N', N'-diisopropylaminoethyl)- co-benzylamino)aspartamide (mPEG-bPEI-PAsp(DIP-BzA)) (PBP), was synthesized and self-assembled into a cationic micelle. SIM and siRNA targeting the noggin gene (N-siRNA) were loaded into the PAsp(DIP-BzA) core and the cationic bPEI interlayer of the micelle via hydrophobic and electrostatic interactions, respectively. The SIM-loaded micelle effectively delivered SIM into preosteoblast MC3T3-E1 cells and rapidly released it inside the acidic lysosome, resulting in the elevated expression of BMP-2. Meanwhile, the codelivered N-siRNA effectively suppressed the expression of noggin. Consequently, SIM and N-siRNA synergistically increased the BMP-2/noggin ratio and resulted in an obviously higher osteogenetic effect than did simvastatin or N-siRNA alone, both in vitro and in vivo.

"Green-reduced" graphene oxide induces in vitro an enhanced biomimetic mineralization of polycaprolactone electrospun meshes

A novel green method for graphene oxide (GO) reduction via ascorbic acid has been adopted to realize bio-friendly reduced graphene oxide (RGO)/polycaprolactone (PCL) nanofibrous meshes, as substrates for bone tissue engineering applications. PCL fibrous mats enriched with either RGO or GO (0.25 wt%) were fabricated to recapitulate the fibrillar structure of the bone extracellular matrix (ECM) and the effects of RGO incorporation on the structural proprieties, biomechanics and bioactivity of the nano-composites meshes were evaluated. RGO/PCL fibrous meshes displayed superior mechanical properties (i.e. Young's Modulus and ultimate tensile strength) besides supporting noticeably improved cell adhesion, spreading and proliferation of fibroblasts and osteoblast-like cell lines. Furthermore, RGO-based electrospun substrates enhanced in vitro calcium deposition in the ECM produced by osteoblast-like cells, which was paralleled, in human mesenchymal stem cells grown onto the same substrates, by an increased expression of the osteogenic markers mandatory for mineralization. In this respect, the capability of graphene-based materials to adsorb osteogenic factors cooperates synergically with the rougher surface of RGO/PCL-based materials, evidenced by AFM analysis, to ignite mineralization of the neodeposited matrix and to promote the osteogenic commitment of the cultured cell in the surrounding microenvironment.

Tissue-engineered composite scaffold of poly(lactide-co-glycolide) and hydroxyapatite nanoparticles seeded with autologous mesenchymal stem cells for bone regeneration

OBJECTIVE

A new therapeutic strategy using nanocomposite scaffolds of grafted hydroxyapatite (g-HA)/ poly(lactide-co-glycolide) (PLGA) carried with autologous mesenchymal stem cells (MSCs) and bone morphogenetic protein-2 (BMP-2) was assessed for the therapy of critical bone defects. At the same time, tissue response and in vivo mineralization of tissue-engineered implants were investigated.

METHODS

A composite scaffold of PLGA and g-HA was fabricated by the solvent casting and particulate-leaching method. The tissue-engineered implants were prepared by seeding the scaffolds with autologous bone marrow MSCs in vitro. Then, mineralization and osteogenesis were observed by intramuscular implantation, as well as the repair of the critical radius defects in rabbits.

RESULTS

After eight weeks post-surgery, scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) revealed that g-HA/PLGA had a better interface of tissue response and higher mineralization than PLGA. Apatite particles were formed and varied both in macropores and micropores of g-HA/PLGA. Computer radiographs and histological analysis revealed that there were more and more quickly formed new bone formations and better fusion in the bone defect areas of g-HA/PLGA at 2-8 weeks post-surgery. Typical bone synostosis between the implant and bone tissue was found in g-HA/PLGA, while only fibrous tissues formed in PLGA.

CONCLUSIONS

The incorporation of g-HA mainly improved mineralization and bone formation compared with PLGA. The application of MSCs can enhance bone formation and mineralization in PLGA scaffolds compared with cell-free scaffolds. Furthermore, it can accelerate the absorption of scaffolds compared with composite scaffolds.

In vitro Bioactivity of Poly(∊-Caprolactone)-Apatite (PCL-AP) Scaffolds for Bone Tissue Engineering: The Influence of the PCL/AP Ratio

Porous poly(∊-caprolactone) (PCL) is used as long-term bioresorbable scaffold for bone tissue engineering. The bone regeneration process can be enhanced by addition of carbonated apatites (AP). This study was aimed at evaluating the influence of the PCL/AP ratio on the in vitro degradation and bioactivity of PCL-AP composites. To this purpose, PCL-AP samples were synthesised with the following PCL/AP weight/weight ratios: 50/50, 60/40 and 75/25.

Vibrational IR and Raman spectroscopies coupled to thermogravimetry (TG) and differential scanning calorimetry (DSC) were used to investigate the in vitro degradation mechanism in different media: 0.01 M NaOH solution (pH = 12), saline phosphate buffer at pH 7.5 (SPB), esterase in SPB and simulated body fluid (SBF) at pH 7.5. The latter medium was used to evaluate the bioactivity of the composites. A control PCL sample was analysed before the addition of the AP component.

As regards the untreated samples, the method of synthesis utilised for preparing the composite was found to enhance the crystallinity degree. The AP component revealed to be constituted of a B-type carbonated hydroxyapatite with a 3% carbonate content. After 28 days of treatment, the samples showed different degradation patterns and extents depending on the degradation medium, the starting PCL crystallinity and composite composition. Weight measurements, Raman and TG analyses revealed deposition of an apatitic phase on all the composites immersed in SBF. Therefore, all the samples displayed a good bioactivity; the sample which showed the most pronounced apatitic deposition was 50/50, i.e. that containing the highest amount of AP.

Attachment and Growth of Fibroblasts on Poly(L-lactide/∊-caprolactone) Scaffolds Prepared in Supercritical CO2 and Modified by Polyethylene Imine Grafting with Ethylene Diamine-Plasma in a Glow-Discharge Apparatus

In this study, a copolymer of L-lactide and ∊-caprolactone (Mn: 73,523, Mw: 127,990 and PI: 1.74) was synthesized by ring-opening polymerization by using stannous octoate as the catalyst. FTIR, 1H-NMR and DSC confirmed the copolymer formation. The copolymer films were prepared and a novel method was developed to produce highly porous sponges for potential use in tissue engineering. Films were subjected to supercritical CO2 at 3300 psi and 70°C to create porous structures for production of possible tissue engineering scaffolds. The pore sizes were in the range of 40–80 mm. The copolymer films were pre-wetted with polyethylene imine (PEI) and then treated with ethylene diamine (EDA)-plasma in glow-discharge apparatus. Gas plasma surface modification of three-dimensional scaffolds fabricated by supercritical carbon dioxide technique was demonstrated to enhance cell adhesion, proliferation, and differentiation over 6 days in culture using L929 fibroblast cell line. Alkaline phosphatase (ALP) activity and glucose uptake in cell culture medium were followed in the cell culture experiments. Fibroblastic cell attachment and growth on the EDA-plasma treated scaffolds were rather low. However, both cell attachment and growth were significantly increased by PEI pre-treatment before EDA-plasma. The changes in ALP activity and glucose uptake also supported the cell growth behavior on these PEI and EDA-plasma treated scaffolds.

Cationic osteogenic peptide P15-CSP coatings promote 3-D osteogenesis in poly(epsilon-caprolactone) scaffolds of distinct pore size

P15-CSP is a biomimetic cationic fusion peptide that stimulates osteogenesis and inhibits bacterial biofilm formation when coated on 2-D surfaces. This study tested the hypothesis that P15-CSP coatings enhance 3-D osteogenesis in a porous but otherwise hydrophobic poly-(ɛ-caprolactone) (PCL) scaffold. Scaffolds of 84 µm and 141 µm average pore size were coated or not with Layer-by-Layer polyelectrolytes followed by P15-CSP, seeded with adult primary human mesenchymal stem cells (MSCs), and cultured 10 days in proliferation medium, then 21 days in osteogenic medium. Atomic analyses showed that P15-CSP was successfully captured by LbL. After 2 days of culture, MSCs adhered and spread more on P15-CSP coated pores than PCL-only. At day 10, all constructs contained nonmineralized tissue. At day 31, all constructs became enveloped in a "skin" of tissue that, like 2-D cultures, underwent sporadic mineralization in areas of high cell density that extended into some 141 µm edge pores. By quantitative histomorphometry, 2.5-fold more tissue and biomineral accumulated in edge pores versus inner pores. P15-CSP specifically promoted tissue-scaffold integration, fourfold higher overall biomineralization, and more mineral deposits in the outer 84 µm and inner 141 µm pores than PCL-only (p < 0.05). 3-D Micro-CT revealed asymmetric mineral deposition consistent with histological calcium staining. This study provides proof-of-concept that P15-CSP coatings are osteoconductive in PCL pore surfaces with 3-D topography. Biomineralization deeper than 150 µm from the scaffold edge was optimally attained with the larger 141 µm peptide-coated pores. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 2171-2181, 2017.

Antimicrobial peptide coatings for hydroxyapatite: electrostatic and covalent attachment of antimicrobial peptides to surfaces

The interface between implanted devices and their host tissue is complex and is often optimized for maximal integration and cell adhesion. However, this also gives a surface suitable for bacterial colonization. We have developed a novel method of modifying the surface at the material-tissue interface with an antimicrobial peptide (AMP) coating to allow cell attachment while inhibiting bacterial colonization. The technology reported here is a dual AMP coating. The dual coating consists of AMPs covalently bonded to the hydroxyapatite surface, followed by deposition of electrostatically bound AMPs. The dual approach gives an efficacious coating which is stable for over 12 months and can prevent colonization of the surface by both Gram-positive and Gram-negative bacteria.

Osteoblast Growth on Poly(L-lactic acid)-Negative Ion Powder Composite Films

Composite films made from poly(L-lactic acid) (PLLA) and negative ion powder (NIP, opal powder) were fabricated and the growth of human osteoblasts cultured in vitro on these composite films was assessed. The surface properties of the composite film and the control (100% PLLA) were investigated by contact angle and scanning electron microscopy (SEM). The former indicated that hydrophilicity did not change significantly, whereas the latter indicated that the surface of the composite films was not as smooth as the control, but without holes or caves. After osteoblast cells were seeded on the composite and control films, the cell densities and the morphology on these films were studied by light microscopy and SEM. The differential function of the cells was assessed by testing their alkaline phosphatase (ALP) activity. These results indicate that the addition of powder improved the adhesion between the osteoblasts and the composite films. The improvement came from the negative ions which were given off by the negative ion powder. The mechanism of negative ion was reviewed and a model of the mechanism was developed. This paper provides the first evidence that negative powder (functional material) can be used to fabricate composite films with PLLA for better cell growth.

Biocompatibility of Poly(ε-caprolactone) Scaffold Modified by Chitosan—The Fibroblasts Proliferation in vitro

In this study, the surface of poly("-caprolactone) (PCL) scaffold was modified by chitosan (CS) in order to enhance its cell affinity and biocompatibility. It is demonstrated by scanning electronic microscopy (SEM) that when 0.5-2.0 wt% chitosan solutions are used to modify the PCL scaffold, the amount of adhesion of the fibroblasts on the chitosan-modified PCL scaffolds dramatically increase when compared to the control after 7 days cell culture. The results indicate that the chitosan-modified PCL scaffolds are more favorable for cell proliferation by improving the scaffold biocompatibility. The improvement may be helpful for the extensive applications of PCL scaffold in heart valve and blood vessel tissue engineering.

Biodegradable mesoporous bioactive glass nanospheres for drug delivery and bone tissue regeneration

Bioactive inorganic materials are attractive for hard tissue regeneration, and they are used as delivery vehicles for pharmaceutical molecules, scaffolds and components for bio-composites. We demonstrated mesoporous bioactive glass (BG) nanospheres that exhibited the capacity to deliver pharmaceutical molecules. Mesoporous BG nanospheres with variable Ca to Si ratios were synthesized using sol-gel chemistry. By controlling the hydrolysis and condensation conditions, the diameter of the mesoporous BG nanospheres was changed from 300 nm to 1500 nm. The porous structure and surface area of the BG nanospheres were shown to be dependent on their composition. The surface area of the BG nanospheres decreased from 400 ± 2 m(2) g(-1) to 56 ± 0.1 m(2) g(-1) when the Ca/Si ratio increased from 5 to 50 at.%. When the mesoporous BG nanospheres were loaded with ibuprofen (IBU), they exhibited a sustained release profile in simulated body fluid (SBF). In the meantime, the IBU-loaded BG nanospheres degraded in SBF, and induced apatite layer formation on the surface as a result of their good bioactivity. When the BG nanospheres were used as a composite filler to poly (ε-caprolactone) (PCL), they were shown to be effective at improving the in vitro bioactivity of PCL microspheres.

Chemical and morphological gradient scaffolds to mimic hierarchically complex tissues: From theoretical modeling to their fabrication

Porous multiphase scaffolds have been proposed in different tissue engineering applications because of their potential to artificially recreate the heterogeneous structure of hierarchically complex tissues. Recently, graded scaffolds have been also realized, offering a continuum at the interface among different phases for an enhanced structural stability of the scaffold. However, their internal architecture is often obtained empirically and the architectural parameters rarely predetermined. The aim of this work is to offer a theoretical model as tool for the design and fabrication of functional and structural complex graded scaffolds with predicted morphological and chemical features, to overcome the time-consuming trial and error experimental method. This developed mathematical model uses laws of motions, Stokes equations, and viscosity laws to describe the dependence between centrifugation speed and fiber/particles sedimentation velocity over time, which finally affects the fiber packing, and thus the total porosity of the 3D scaffolds. The efficacy of the theoretical model was tested by realizing engineered graded grafts for osteochondral tissue engineering applications. The procedure, based on combined centrifugation and freeze-drying technique, was applied on both polycaprolactone (PCL) and collagen-type-I (COL) to test the versatility of the entire process. A functional gradient was combined to the morphological one by adding hydroxyapatite (HA) powders, to mimic the bone mineral phase. Results show that 3D bioactive morphologically and chemically graded grafts can be properly designed and realized in agreement with the theoretical model. Biotechnol. Bioeng. 2016;113: 2286-2297. © 2016 Wiley Periodicals, Inc.

Osteogenic activity of cyclodextrin-encapsulated doxycycline in a calcium phosphate PCL and PLGA composite

Composites of biodegradable polymers and calcium phosphate are bioactive and flexible, and have been proposed for use in tissue engineering and bone regeneration. When associated with the broad-spectrum antibiotic doxycycline (DOX), they could favor antimicrobial action and enhance the action of osteogenic composites. Composites of polycaprolactone (PCL), poly(lactic-co-glycolic acid) (PLGA), and a bioceramic of biphasic calcium phosphate Osteosynt® (BCP) were loaded with DOX encapsulated in β-cyclodextrin (βCD) and were evaluated for effects on osteoblastic cell cultures. The DOX/βCD composite was prepared with a double mixing method. Osteoblast viability was assessed with methyl tetrazolium (MTT) assays after 1day, 7day, and 14days of composite exposure; alkaline phosphatase (AP) activity and collagen production were evaluated after 7days and 14days, and mineral nodule formation after 14days. Composite structures were evaluated by scanning electron microscopy (SEM). Osteoblasts exposed to the composite containing 25μg/mL DOX/βCD had increased cell proliferation (p<0.05) compared to control osteoblast cultures at all experimental time points, reaching a maximum in the second week. AP activity and collagen secretion levels were also elevated in osteoblasts exposed to the DOX/βCD composite (p<0.05 vs. controls) and reached a maximum after 14days. These results were corroborated by Von Kossa test results, which showed strong formation of mineralization nodules during the same time period. SEM of the composite material revealed a surface topography with pore sizes suitable for growing osteoblasts. Together, these results suggest that osteoblasts are viable, proliferative, and osteogenic in the presence of a DOX/βCD-containing BCP ceramic composite.

Covalent streptavidin immobilization on electrospun poly(m-anthranilic acid)/polycaprolactone nanofibers and cytocompatibility

An electrospun poly( m-anthranilic acid)/poly(ε-caprolactone) nanofiber mat was fabricated with functionalization of the surface with streptavidin which can enhance the cell attachment and proliferation. Poly(ε-caprolactone) as biodegradable, biocompatible, and electrospinnable polymer was blended with poly( m-anthranilic acid) because of the carboxylic acid (–COOH) groups on its backbone which allow the covalent immobilization of streptavidin onto nanofibers. 1-Ethyl-3-(dimethyl-aminopropyl) carbodiimide hydrochloride/ N-hydroxyl succinimide coupling reaction was used for immobilization and the presence of bound protein was investigated by Fourier transform infrared–attenuated total reflection spectroscopy and electrochemical impedance spectroscopy, as well as the confocal microscopy. Human osteoblast-like cells (SaOS2) were cultured on poly( m-anthranilic acid)/poly(ε-caprolactone) and streptavidin-immobilized poly( m-anthranilic acid)/poly(ε-caprolactone) nanofibers to evaluate the in vitro biocompatibility of nanofibers. Fluorescence staining of F-actin was performed to observe the cell morphology. The results confirmed the successful immobilization of streptavidin on the nanofibers and streptavidin immobilization enhanced the cell attachment and proliferation onto the poly( m-anthranilic acid)/poly(ε-caprolactone) nanofibers.

Effect of low-level mechanical vibration on osteogenesis and osseointegration of porous titanium implants in the repair of long bone defects

Emerging evidence substantiates the potential of porous titanium alloy (pTi) as an ideal bone-graft substitute because of its excellent biocompatibility and structural properties. However, it remains a major clinical concern for promoting high-efficiency and high-quality osseointegration of pTi, which is beneficial for securing long-term implant stability. Accumulating evidence demonstrates the capacity of low-amplitude whole-body vibration (WBV) in preventing osteopenia, whereas the effects and mechanisms of WBV on osteogenesis and osseointegration of pTi remain unclear. Our present study shows that WBV enhanced cellular attachment and proliferation, and induced well-organized cytoskeleton of primary osteoblasts in pTi. WBV upregulated osteogenesis-associated gene and protein expression in primary osteoblasts, including OCN, Runx2, Wnt3a, Lrp6 and β-catenin. In vivo findings demonstrate that 6-week and 12-week WBV stimulated osseointegration, bone ingrowth and bone formation rate of pTi in rabbit femoral bone defects via μCT, histological and histomorphometric analyses. WBV induced higher ALP, OCN, Runx2, BMP2, Wnt3a, Lrp6 and β-catenin, and lower Sost and RANKL/OPG gene expression in rabbit femora. Our findings demonstrate that WBV promotes osteogenesis and osseointegration of pTi via its anabolic effect and potential anti-catabolic activity, and imply the promising potential of WBV for enhancing the repair efficiency and quality of pTi in osseous defects.

Biodegradable Materials for Bone Repair and Tissue Engineering Applications

This review discusses and summarizes the recent developments and advances in the use of biodegradable materials for bone repair purposes. The choice between using degradable and non-degradable devices for orthopedic and maxillofacial applications must be carefully weighed. Traditional biodegradable devices for osteosynthesis have been successful in low or mild load bearing applications. However, continuing research and recent developments in the field of material science has resulted in development of biomaterials with improved strength and mechanical properties. For this purpose, biodegradable materials, including polymers, ceramics and magnesium alloys have attracted much attention for osteologic repair and applications. The next generation of biodegradable materials would benefit from recent knowledge gained regarding cell material interactions, with better control of interfacing between the material and the surrounding bone tissue. The next generations of biodegradable materials for bone repair and regeneration applications require better control of interfacing between the material and the surrounding bone tissue. Also, the mechanical properties and degradation/resorption profiles of these materials require further improvement to broaden their use and achieve better clinical results.

Biomodification of PCL Scaffolds with Matrigel, HA, and SR1 Enhances De Novo Ectopic Bone Marrow Formation Induced by rhBMP-2

The de novo formation of ectopic bone marrow was induced using 1.2-mm-thin polycaprolactone (PCL) scaffolds biomodified with several different biomaterials. In vivo investigations of de novo bone and bone marrow formation indicated that subcutaneous implantation of PCL scaffolds coated with recombinant human bone morphogenetic protein-2 (rhBMP-2) plus Matrigel, hydroxyapatite (HA), or StemRegenin 1 (SR1) improved formation of bone and hematopoietic bone marrow as determined by microcomputed tomography, and histological and hematopoietic characterizations. Our study provides evidence that thin PCL scaffolds biomodified with Matrigel, HA, and SR1 mimic the environments of real bone and bone marrow, thereby enhancing the de novo ectopic bone marrow formation induced by rhBMP-2. This ectopic bone marrow model will serve as a unique and essential tool for basic research and for clinical applications of postnatal tissue engineering and organ regeneration.

Effect of calcium phosphate coating and rhBMP-2 on bone regeneration in rabbit calvaria using poly(propylene fumarate) scaffolds

Various calcium phosphate based coatings have been evaluated for better bony integration of metallic implants and are currently being investigated to improve the surface bioactivity of polymeric scaffolds. The aim of this study was to evaluate the role of calcium phosphate coating and simultaneous delivery of recombinant human bone morphogenetic protein-2 (rhBMP-2) on the in vivo bone regeneration capacity of biodegradable, porous poly(propylene fumarate) (PPF) scaffolds. PPF scaffolds were coated with three different calcium phosphate formulations: magnesium-substituted β-tricalcium phosphate (β-TCMP), carbonated hydroxyapatite (synthetic bone mineral, SBM) and biphasic calcium phosphate (BCP). In vivo bone regeneration was evaluated by implantation of scaffolds in a critical-sized rabbit calvarial defect loaded with different doses of rhBMP-2. Our data demonstrated that scaffolds with each of the calcium phosphate coatings were capable of sustaining rhBMP-2 release and retained an open porous structure. After 6weeks of implantation, micro-computed tomography revealed that the rhBMP-2 dose had a significant effect on bone formation within the scaffolds and that the SBM-coated scaffolds regenerated significantly greater bone than BCP-coated scaffolds. Mechanical testing of the defects also indicated restoration of strength in the SBM and β-TCMP with rhBMP-2 delivery. Histology results demonstrated bone growth immediately adjacent to the scaffold surface, indicating good osteointegration and osteoconductivity for coated scaffolds. The results obtained in this study suggest that the coated scaffold platform demonstrated a synergistic effect between calcium phosphate coatings and rhBMP-2 delivery and may provide a promising platform for the functional restoration of large bone defects.

Effects on growth and osteogenic differentiation of mesenchymal stem cells by the strontium-added sol-gel hydroxyapatite gel materials

In the present study, strontium-modified hydroxyapatite gels (Sr-HA) at different concentrations were prepared using sol-gel approach and their effect on human-bone-marrow-derived mesenchymal stem cells, were evaluated. The effect of Strontium on physico-chemical and morphological properties of hydroxyapatite gel were evaluated. Morphological analyses (SEM and TEM) demonstrate that an increasing in the amount of Sr ions doped into HA made the agglomerated particles smaller. The substitution of large Sr2+ for small Ca2+ lead to denser atomic packing of the system causing retardation of crystals growth. The biological results demonstrated that hydroxyapatite gel containing from 0 to 20 mol% of Sr presented no cytotoxicity and promote the expression of osteogenesis related genes including an early marker for osteogenic differentiation ALP; a non-collagen protein OPN and a late marker for osteogenic differentiation OCN. Finally, the Sr-HA gels could have a great potential application as filler in bone repair and regeneration and used in especially in the osteoporotic disease.

Preparation and mechanical property of a novel 3D porous magnesium scaffold for bone tissue engineering

Porous magnesium has been recently recognized as a biodegradable metal for bone substitute applications. A novel porous Mg scaffold with three-dimensional (3D) interconnected pores and with a porosity of 33-54% was produced by the fiber deposition hot pressing (FDHP) technology. The microstructure and morphologies of the porous Mg scaffold were characterized by scanning electron microscopy (SEM), and the effects of porosities on the microstructure and mechanical properties of the porous Mg were investigated. Experimental results indicate that the measured Young's modulus and compressive strength of the Mg scaffold are ranged in 0.10-0.37 GPa, and 11.1-30.3 MPa, respectively, which are fairly comparable to those of cancellous bone. Such a porous Mg scaffold having a 3D interconnected network structure has the potential to be used in bone tissue engineering.

A porous tissue engineering scaffold selectively degraded by cell-generated reactive oxygen species

Biodegradable tissue engineering scaffolds are commonly fabricated from poly(lactide-co-glycolide) (PLGA) or similar polyesters that degrade by hydrolysis. PLGA hydrolysis generates acidic breakdown products that trigger an accelerated, autocatalytic degradation mechanism that can create mismatched rates of biomaterial breakdown and tissue formation. Reactive oxygen species (ROS) are key mediators of cell function in both health and disease, especially at sites of inflammation and tissue healing, and induction of inflammation and ROS are natural components of the in vivo response to biomaterial implantation. Thus, polymeric biomaterials that are selectively degraded by cell-generated ROS may have potential for creating tissue engineering scaffolds with better matched rates of tissue in-growth and cell-mediated scaffold biodegradation. To explore this approach, a series of poly(thioketal) (PTK) urethane (PTK-UR) biomaterial scaffolds were synthesized that degrade specifically by an ROS-dependent mechanism. PTK-UR scaffolds had significantly higher compressive moduli than analogous poly(ester urethane) (PEUR) scaffolds formed from hydrolytically-degradable ester-based diols (p < 0.05). Unlike PEUR scaffolds, the PTK-UR scaffolds were stable under aqueous conditions out to 25 weeks but were selectively degraded by ROS, indicating that their biodegradation would be exclusively cell-mediated. The in vitro oxidative degradation rates of the PTK-URs followed first-order degradation kinetics, were significantly dependent on PTK composition (p < 0.05), and correlated to ROS concentration. In subcutaneous rat wounds, PTK-UR scaffolds supported cellular infiltration and granulation tissue formation, followed first-order degradation kinetics over 7 weeks, and produced significantly greater stenting of subcutaneous wounds compared to PEUR scaffolds. These combined results indicate that ROS-degradable PTK-UR tissue engineering scaffolds have significant advantages over analogous polyester-based biomaterials and provide a robust, cell-degradable substrate for guiding new tissue formation.