Preparation and characterization of novel poly(ε-caprolactone)/biphasic calcium phosphate hybrid composite microspheres

Desirably porous biodegradable hybrid composite microspheres were fabricated for use in bone graft and bone substitute applications. In this study, novel poly(ε-caprolactone)/biphasic calcium phosphate (70/30) composite microspheres (PCL/BCP MPs) were prepared using the emulsion solvent-evaporation method. Throughout this process, the ammonium bicarbonate (NH?HCO?) content was changed to obtain the desired porous structure. However, to maintain the spherical shape, the NH?HCO? content should not be higher than 5%. In the optical images of the PCL/BCP MPs, almost all the microparticles had a spherical shape, and the average diameter was about 600 μm. The scanning electron microscopy and cross-sectional optical images showed that the pore density and pore diameter of PCL/BCP MPs increased with increasing initial NH?HCO? concentrations. In the phase-composition analysis of the PCL/BCP MPs, which was characterized by X-ray diffraction and EDS, the two crystals BCP and PCL phases were shown to be miscible in PCL/BCP MPs. When the degradation of these microspheres was characterized, PCL/BCP MPs-0, PCL/BCP MPs-2, and PCL/BCP MPs-5 were found to display a sustained biodegradability, and the rate of degradation increased at higher initial NH?HCO? concentrations. Proliferation of cells on three different sample types was assessed and compared, and based on these results, the PCL/BCP MPs-5 was chosen to study MG-63 osteoblast-cell adhesion, growth, and proliferation. Furthermore, confocal images indicated that the cells effectively adhered, spread, and proliferated on PCL/BCP MPs-5 during a 5-day culture period.     

Bioactive silica–collagen composite xerogels modified by calcium phosphate phases with adjustable mechanical properties for bone replacement

The development of composites has been recognized as a promising strategy to fulfil the complex requirements of biomaterials. The present study reports on the modification of a novel silica–collagen composite material by varying the inorganic/organic mass ratio and introducing calcium phosphate cement (CPC) as a third component. The sol–gel technique is used for processing, followed by xerogel formation under specific temperature and relative humidity conditions. Cylindrical monolithic samples up to 400 mm³ were obtained without any sintering processes. Various hierarchical phases of the organic component were applied, ranging from tropocollagen and collagen fibrils up to collagen fibers, each characterized by atomic force microscopy. Focusing on the application of fibrils, various inorganic/organic mass ratios were used: 100/0, 85/15 and 70/30; their influence on the structure of the composite material was demonstrated by scanning electron microscopy. The composition was extended by the addition of 25 wt.% CPC which led to increased bioactivity by accelerating the formation of bone apatite layers in simulated body fluid. Synchrotron microcomputed tomography demonstrated the homogeneous distribution of the cement particles in the silica–collagen matrix. Compressive strength tests showed that the mechanical properties of the brittle pure silica gel are changed significantly due to collagen addition. The highest ultimate strength of about 115 MPa at about 18% total strain was registered for the 70/30 silica–collagen composite xerogels. Incorporation of CPC lowered the gel’s strength. By demonstrating differentiation of human monocytes into osteoclast-like cells, an important feature of the composite material regarding successful bone remodeling is fulfilled.     

Silicon-stabilized α-tricalcium phosphate and its use in a calcium phosphate cement: characterization and cell response

α-Tricalcium phosphate (α-TCP) is widely used as a reactant in calcium phosphate cements. This work aims at doping α-TCP with silicon with a twofold objective. On the one hand, to study the effect of Si addition on the stability and reactivity of this polymorph. On the other, to develop Si-doped cements and to evaluate the effect of Si on their in vitro cell response. For this purpose a calcium-deficient hydroxyapatite was sintered at 1250°C with different amounts of silicon oxide. The high temperature polymorph α-TCP was stabilized by the presence of silicon, which inhibited reversion of the β→α transformation, whereas in the Si-free sample α-TCP completely reverted to the β-polymorph. However, the β-α transformation temperature was not affected by the presence of Si. Si-α-TCP and its Si-free counterpart were used as reactants for a calcium phosphate cement. While Si-α-TCP showed faster hydrolysis to calcium-deficient hydroxyapatite, upon complete reaction the crystalline phases, morphology and mechanical properties of both cements were similar. An in vitro cell culture study, in which osteoblast-like cells were exposed to the ions released by both materials, showed a delay in cell proliferation in both cases and stimulation of cell differentiation, more marked for the Si-containing cement. These results can be attributed to strong modification of the ionic concentrations in the culture medium by both materials. Ca-depletion from the medium was observed for both cements, whereas continuous Si release was detected for the Si-containing cement.     

Development of a bovine collagen–apatitic calcium phosphate cement for potential fracture treatment through vertebroplasty

The aim of this study was to examine the potential of incorporating bovine fibres as a means of reinforcing a typically brittle apatite calcium phosphate cement for vertebroplasty. Type I collagen derived from bovine Achilles tendon was ground cryogenically to produce an average fibre length of 0.96 ± 0.55 mm and manually mixed into the powder phase of an apatite-based cement at 1, 3 or 5 wt.%. Fibre addition of up to 5 wt.% had a significant effect (P ? 0.001) on the fracture toughness, which was increased by 172%. Adding ?1 wt.% bovine collagen fibres did not compromise the compressive properties significantly, however, a decrease of 39–53% was demonstrated at ?3 wt.% fibre loading. Adding bovine collagen to the calcium phosphate cement reduced the initial and final setting times to satisfy the clinical requirements stated for vertebroplasty. The cement viscosity increased in a linear manner (R² = 0.975) with increased loading of collagen fibres, such that the injectability was found to be reduced by 83% at 5 wt.% collagen loading. This study suggests for the first time the potential application of a collagen-reinforced calcium phosphate cement as a viable option in the treatment of vertebral fractures, however, issues surrounding efficacious cement delivery need to be addressed.     

Bioactive composite bone cement based on α-tricalcium phosphate/tricalcium silicate

Silicon compounds are known as bioactive materials that are able to bond to the living bone tissue by inducing an osteogenic response through the stimulation and activation of osteoblasts. To improve the bioactive and mechanical properties of an α-Ca(3)PO(4)-based cement, the effects of the addition of Ca(3 SiO(5) (C(3)S) on physical, chemical, mechanical, and biological properties after soaking in simulated body fluid (SBF) were studied. The morphological and structural changes of the material during immersion were analyzed by X-ray diffraction and scanning electron microscopy. The results showed that it is possible to increase the compressive strength of the cement by adding 5% of C(3)S. Higher C(3)S contents enhance bioactivity and biocompatibility by the formation of a dense and homogeneous hydroxyapatite layer within 7 days; however, compressive strength decreases drastically as a consequence of delayed hydrolysis of α-Ca(3)(PO(4) (2). An increment in setting times and degradation rate of composites containing C(3)S was also observed.     

Controlled release of TGF-β1 from a biodegradable matrix for bone regeneration

Although bone has a remarkable capacity for regenerative growth, there are many clinical situations in which the bony repair process is impaired. TGF-β₁ is a 25 kD homodimeric protein which modulates the growth and differentiation of many cell types. The ability of TGF-β₁, to promote bone formation suggests that it may have potential as a therapeutic agent in disease of bone loss. However, there still exists a need for an effective method of delivering TGF-β₁ to the site of an osseous defect for the promotion of bone healing. This paper describes a novel biodegradable controlled release system for TGF-β₁ comprised of poly (DL-lactic-co-glycolic acid) (PLPG) and demineralized bone matrix (DBM). The amount and activity of TGF-β_I released was determined using several methods including ¹²⁵I-labeled TGF-β₁ as a tracer, an enzyme linked immunosorbent assay (ELISA) and a growth inhibitory assay (GIA). Protein was released from the devices for time periods of more than 600 h. The amount of TGF-β₁ released was directly proportional to both the TGF-β₁ loading and the weight percent of DBM in the device. The release kinetics could be further controlled by applying polymeric coatings of varying porosity to the devices. The GIA indicated that between 80 and 90% of the TGF-β₁ released from the delivery system retained its bioactivity. The PLPG and DBM existed in phase separated domains within the device as determined by differential scanning calorimetry. Scanning electron microscopy suggested that the devices were sufficiently porous to allow bone ingrowth.     

Osteogenic differentiation of osteoblasts induced by calcium silicate and calcium silicate/β-tricalcium phosphate composite bioceramics

In this study, calcium silicate (CS) and CS/β-tricalcium phosphate (CS/β-TCP) composites were investigated on their mechanism of osteogenic proliferation and differentiation through regulating osteogenic-related gene and proteins. Osteoblast-like cells were cultured in the extracts of these CS-based bioceramics and pure β-TCP, respectively. The main ionic content in extracts was analyzed by inductively coupled plasma-atomic emission spectroscopy. The cell viability, mineralization, and differentiation were evaluated by MTT assay, Alizarin Red-S staining and alkaline phosphatase (ALP) activity assay. The expressions of BMP-2, transforming growth factor-β (TGF-β), Runx2, ALP, and osteocalcin (OCN) at both gene and protein level were detected by real-time polymerase chain reaction analysis and Western blot. The result showed that the extracts of CS-based bioceramics promoted cells proliferation, differentiation, and mineralization when compared with pure β-TCP. Accordingly, pure CS and CS/β-TCP composites stimulated osteoblast-like cells to express BMP-2/TGF-β gene and proteins, and further regulate the expression of Runx2 gene and protein, and ultimately affect the ALP activity and OCN deposition. This study suggested that the CS-based bioceramics could not only promote the expression of osteogenic-related genes but also enhance the genes to encode the corresponding proteins, which could finally control osteoblast-like cells proliferation and differentiation.     

The development of a nanocrystalline apatite reinforced crosslinked hyaluronic acid–tyramine composite as an injectable bone cement

We have developed an injectable bone cement composed of nanocrystalline apatite and crosslinked hyaluronic acid–tyramine conjugates (HA–Tyr). This bone cement was formed via the oxidative coupling of tyramine moieties catalyzed by hydrogen peroxide (H₂O₂) and horseradish peroxidise (HRP). The bone cement set within 60 s after H₂O₂ and HRP were added to the apatite/HA–Tyr pastes. The mechanical strength of the apatite/HA–Tyr cement was tuned by varying the apatite loading and H₂O₂ concentration. This rapid enzyme-mediated setting of our bone cement results in minimal heat release (ΔH = ?11.39 J/g) as compared to conventional bone cements. The crystalline phase and crystallite size (20 nm) of the apatitic phase in our bone cement matched that of trabecular bone. The storage modulus (G′), yield stress (σ_y), and compressive stiffness (E_c) of our bone cement prepared with different apatite loadings and H₂O₂ concentrations were measured, and optimized at G′ = 40 MPa, σ_y = 0.308 MPa and E_c = 2.270 MPa when the cement was formed with 0.4 g/ml of apatite, 0.61 units/ml of HRP and 6.8 mm of H₂O₂. Our biocompatible bone cement also successfully healed small bone and joint defects in mice within 8 weeks.     

Bioactivity and mechanical properties of collagen composite membranes reinforced by chitosan and β-tricalcium phosphate

In this study, we analyzed the effects of varying concentrations of chitosan (CS) and β-tricalcium phosphate [β-TCP, Ca(3) (PO(4) )(2) ] on the mechanical and cell-adhesion properties of a collagen (CG) matrix for use in guided bone regeneration (GBR). Three different CS concentrations (0.5, 1, and 2%) and five different contents of β-TCP (0, 17, 29, 38, and 44%) were investigated. The composite membranes were analyzed by scanning electron microscopy and cell-adhesion, flexural-strength, and tear-strength assays. The results show that the cell-adhesion and mechanical properties of the composite membranes improved with increasing β-TCP and CS contents, yielding suitable levels of the adhesion of cells and adequate mechanical stability to ensure successful GBR. The CS adhered to the microsized β-TCP, which was distributed uniformly in the composite membranes. The β-TCP and CS have no negative effect on the cell morphology, viability, and proliferation and possess good biocompatibility. This study demonstrates that β-TCP/CS/CG composite membranes are good candidates for GBR membranes in future applications. ? 2012 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2012.     

Preparation,characterization and bioactivities of nano anhydrous calcium phosphate added gelatin–chitosan scaffolds for bone tissue engineering

Abstract

Gelatin, chitosan and nano calcium phosphate based composite scaffold with tailored architectures and properties has great potential for bone regeneration. Herein, we aimed to improve the physico chemical, mechanical and osteogenic properties of 3D porous scaffold by incorporation of dihydrogen calcium phosphate anhydrous (DCPA) nanoparticles into biopolymer matrix with variation in composition in the prepared scaffolds. Scaffolds were prepared from the slurry containing gelatin, chitosan and synthesized nano DCPA particle using lyophilization technique. DCPA nano particles were synthesized using calcium carbonate and phosphoric acid in water–ethanol medium. XRD pattern showed phase pure DCPA in synthesized nanopowder. Scaffolds were prepared by addition of DCPA nanoparticles to the extent of 5–10?wt% of total polymer into gelatin–chitosan solution with solid loading varying between 2.5 and 2.75?wt%. The prepared scaffold showed interconnected porosity with pore size varying between 110 and 200 micrometer. With addition of DCPA nanoparticles, average pore size of the prepared scaffolds decreased. With increase in nano ceramic phase content from 5?wt% to 10?wt% of total polymer, the compressive strength of the scaffold increased. Scaffold containing 10?wt% DCPA showed the highest average compressive strength of 2.2?MPa. Higher cellular activities were observed in DCPA containing scaffolds as compared to pure gelatin chitosan scaffold suggesting the fact that nano DCPA addition into the scaffold promoted better osteoblast adhesion and proliferation as evident from MTT assay and scanning electron microscopic (SEM) investigation of osteoblast cultured scaffolds. A higher degree of lamellopodia and filopodia extensions and better spreading behavior of osteoblasts were observed in FESEM micrographs of MG 63 cultured DCPA containing scaffold. The results demonstrated that both mechanical strength and osteogenic properties of gelatin–chitosan scaffold could be improved by addition of anhydrous dihydrogen calcium phosphate nanoparticles into it.     

Dispersion degree of a small-dose bone cement北大核心

BACKGROUND: During the percutaneous vertebroplasty, the optimal dose of bone cement that can bring favorable cement dispersion and remodel the biomechanical balance of the fractured vertebrae remains controversial. OBJECTIVE: To investigate the dispersion degree of small dose of bone cement in vertebroplasty. METHODS: In this experiment, 18 sheep selected with the same condition were randomly divided into three groups (group A, group B, group C), 6 in each group. A model of thoracolumbar vertebral compression fracture (T12, L1, L2) was made in each sheep. The injected volume of bone cement in groups A, B, C was 15%, 20%, 25% of the average volume of adjacent vertebral bodies, respectively. Postoperative CT images were used to evaluate the bone cement dispersion. Dispersion degree of bone cement among the three groups was compared by the Kruskal-Wallis test. RESULTS AND CONCLUSION: There was no statistical difference in the dispersion degree of bone cement among the three groups, and the excellent and good rate of dispersion was over 80%. To conclude, the optimal dose of bone cement injected into the fractured vertebra is 15% of the average volume of adjacent vertebral bodies, which can achieve good dispersion degree and restore the biomechanical stability of the vertebral body. © 2018, Journal of Clinical Rehabilitative Tissue Engineering Research. All rights reserved.     

Comparative clinical efficacy of polymethyl methacrylate and self-solidifying calcium phosphate cement in vertebroplasty: A meta-analysis北大核心

OBJECTIVE: Vertebroplasty is widely used in the treatment of osteoporotic vertebral fractures. At present, polymethyl methacrylate is still the most commonly used filling material for strengthening vertebral body, but it is not the most ideal filling material. Self-curing calcium phosphate cement is a new filling material developed in recent years, which can naturally heal with bone tissue and be absorbed and replaced by the human body. This meta-analysis systematically analyzed the clinical efficacy and safety of polymethyl methacrylate and self-solidifying calcium phosphate cement in vertebroplasty. METHODS: China National Knowledge Infrastructure, Wanfang database, Chinese Biomedical Medicine database, PubMed, EMbase, and Cochrane Library database were retrieved for clinical control studies regarding with polymethyl methacrylate and self-solidifying calcium phosphate cement treatment of osteoporotic vertebral compression fracture. The retrieval period was from the database inception to July 2020. The visual analogue scale score, vertebral kyphosis Cobb angle, vertebral body height, bone cement leakage rate, adjacent vertebral fracture rate, Oswestry dysfunction index, and clinical curative effect were used as the outcome indexes. All the literature screening, data extraction and research quality evaluation were carried out independently by two reviewers. In addition, the Cochrane Collaboration tool and the Newcastle-Ottawa scale were used to evaluate the quality of randomized controlled trials and cohort studies, respectively. RevMan 5.4 software was used for meta-analysis. RESULTS: (1) A total of nine studies involving 593 patients were included in the meta-analysis; five of which were randomized controlled trials, and four were retrospective cohort studies. All of the selected studies were of high quality. (2) Meta-analysis results showed that there was no significant difference between the two filling materials in the following aspects, including visual analogue scale score (SMD=-0.45, 95%CI:-1.10-0.21, P=0.18), Cobb angle of vertebral kyphosis (MD=-0.16, 95%CI:-0.43-0.11, P=0.24), height of vertebral body (SMD=0.13, 95%CI:-0.12-0.37, P=0.32), leakage rate of bone cement (OR=1.30, 95%CI:0.67-2.54, P=0.44), Oswestry disability index (MD=3.31, 95%CI:-1.34-7.97, P=0.16), and clinical effective rate (OR=1.00, 95%CI:0.14-7.27, P=1.00). However, in terms of new fractures of adjacent vertebrae, the calcium phosphate cement group was significantly better than the polymethyl methacrylate group (OR=2.17, 95%CI:1.04-4.51, P=0.04). CONCLUSION: The application of calcium phosphate cement in vertebroplasty has a significant advantage in reducing adjacent vertebral fractures compared with polymethyl methacrylate. The curative effect is similar in pain visual analogue scale score, vertebral kyphosis Cobb angle, vertebral body height, bone cement leakage rate, and Oswestry dysfunction index. However, more high-quality randomized controlled trials are needed to provide more sufficient evidence. © 2022, Publishing House of Chinese Journal of Tissue Engineering Research. All rights reserved.     

Controlled release of antihypertensive drug from the interpenetrating network poly(vinyl alcohol)–guar gum hydrogel microspheres

Poly(vinyl alcohol)-guar gum interpenetrating network microspheres were prepared by cross-linking with glutaraldehyde. Nifedipine, an antihypertesive drug, was loaded into these matrices before and after cross-linking to study its release patterns. The extent of cross-linking was analyzed by Fourier transform infrared spectroscopy and differential scanning calorimetry. Furthermore, the microspheres were characterized for drug entrapment efficiency, particle size, transport of water into the matrix and drug release kinetics. Scanning electron microscopic photographs confirmed the spherical nature and surface morphology. The mean particle size of the microspheres was found to be around 300 μm. The molecular transport phenomenon, as studied by the dynamic swelling experiments, indicated that an increase in cross-linking affected the transport mechanism from Fickian to non-Fickian. The in vitro release study indicated that the release from these microspheres is not only dependent upon the extent of cross-linking, but also on the amount of the drug loaded as well as the method of drug loading.     

Significance of calcium phosphate coatings for the enhancement of new bone osteogenesis – A review

A systematic analysis of results available from in vitro, in vivo and clinical trials on the effects of biocompatible calcium phosphate (CaP) coatings is presented. An overview of the most frequently used methods to prepare CaP-based coatings was conducted. Dense, homogeneous, highly adherent and biocompatible CaP or hybrid organic/inorganic CaP coatings with tailored properties can be deposited. It has been demonstrated that CaP coatings have a significant effect on the bone regeneration process. In vitro experiments using different cells (e.g. SaOS-2, human mesenchymal stem cells and osteoblast-like cells) have revealed that CaP coatings enhance cellular adhesion, proliferation and differentiation to promote bone regeneration. However, in vivo, the exact mechanism of osteogenesis in response to CaP coatings is unclear; indeed, there are conflicting reports of the effectiveness of CaP coatings, with results ranging from highly effective to no significant or even negative effects. This review therefore highlights progress in CaP coatings for orthopaedic implants and discusses the future research and use of these devices. Currently, an exciting area of research is in bioactive hybrid composite CaP-based coatings containing both inorganic (CaP coating) and organic (collagen, bone morphogenetic proteins, arginylglycylaspartic acid etc.) components with the aim of promoting tissue ingrowth and vascularization. Further investigations are necessary to reveal the relative influences of implant design, surgical procedure, and coating characteristics (thickness, structure, topography, porosity, wettability etc.) on the long-term clinical effects of hybrid CaP coatings. In addition to commercially available plasma spraying, other effective routes for the fabrication of hybrid CaP coatings for clinical use still need to be determined and current progress is discussed.     

Osteogenic biphasic calcium sulphate dihydrate/iron-modified α-tricalcium phosphate bone cement for spinal applications: In vivo study

In this study, the biocompatibility and the osteogenic features of a new iron-modified α-tricalcium phosphate (IM/α-TCP) and calcium sulphate dihydrate (CSD) biphasic cement (IM/α-TCP/CSD-BC) have been investigated in terms of the in vivo cement resorption, bone tissue formation and host tissue response on sheep animal model. Histological evaluation performed on undecalcified cement–bone specimens assessed the in vivo behaviour. It has been shown that the new IM/α-TCP/CSD-BC has the ability to produce firm bone binding in vivo (i.e. bioactivity). Qualitative histology proved cement biocompatibility, osteoconduction and favourable resorption, mainly through a macrophage-mediated mechanism. The results showed that the new cements have biocompatible and osteogenic features of interest as possible cancellous bone replacement biomaterial for minimally invasive spinal surgery applications.     

Calcium–strontium mixed phosphate as novel injectable and radio-opaque hydraulic cement

Sterile calcium hydrogenophosphate dihydrate (DCPD) (CaHPO₄·2H₂O), calcium oxide and strontium carbonate powders were mixed in various liquid phases. Among these, ammonium phosphate buffer (0.75 M, pH 6.9) led to a novel strontium-containing calcium phosphate cement. At a 6/2.5/1.5 M ratio and for a liquid to powder ratio (L/P) of 0.5 ml g^?1, the initial paste was fluid and remained injectable for 12 min at 25 °C. It was easily obtained by mixing sterile powders and the liquid phase using the push–pull technique, avoiding complex mixing apparatus. The cement set after 15 min at 37 °C and was hard after 1 h. The compressive strength was in the 20 MPa range, a value higher than that generally assigned to trabecular bone (5–15 MPa). This strength appeared sufficient for repairing non-loading sites or reinforcing osteoporotic vertebrae (vertebroplasty). After setting, the initial mixture formed a strontium–calcium-deficient carbonate apatite. The radio-opacity of the resulting cement was three times greater than that of cortical bone because of the presence of strontium ions, a feature that complies with the requirements for vertebroplasty. Furthermore, the cement powder remained stable and retained its properties for at least 4 years.     

Preparation and in vitro release of curcumin sustained-release microspheres北大核心

BACKGROUND: Curcumin can inhibit inflammation and promote axonal growth, but it has a short half-life and a fast clearance rate. OBJECTIVE: To prepare curcumin sustained-release microspheres to release curcumin slowly and continuously. METHODS: Curcumin sustained-release microspheres were synthesized by O/W emulsification volatilization method using polylactic acid-glycolic acid copolymer as raw material. The preset drug loading rates were 10% and 20%, respectively, and set as No. 1 and No. 2 microspheres. The curcumin sustained release microspheres were synthesized by O/W emulsification volatilization method using L-lactic acid-polycaprolactone copolymer as raw material. The preset drug loading rates were 10% and 20%, respectively, and the microspheres were set as No. 3 and No. 4. The surface morphology of the microspheres was observed by scanning electron microscopy, and the drug loading and encapsulation efficiency of the microspheres were determined by high performance liquid chromatography. Four groups of microspheres were immersed in PBS release solution containing 1% sodium dodecyl sulfate, and the sustained release of curcumin microspheres was detected under simulated physiological environment. RESULTS AND CONCLUSION: (1) Scanning electron microscopy showed that the particle size and morphology of No. 3 and No. 4 curcumin microspheres were better than those of No. 1 and No. 2 curcumin microspheres. (2) The encapsulation rate of No. 3 microspheres was higher than that of the other three groups (P < 0.05, P < 0.01), and there was no significant difference in the encapsulation rate of No. 1, 2 and 4 microspheres (P > 0.05). (3) The drug loading rates of No. 2, 3 and 4 microspheres were higher than that of No. 1 microsphere (P < 0.01), and the drug loading rates of No. 2 and 4 microspheres were higher than that of No. 3 microsphere (P < 0.01). (4) The in vitro release of No. 3 curcumin sustained-release microspheres lasted for 14 days, and the release of the other three kinds of microspheres lasted for 21 days. The cumulative release rate of No. 1 and No. 3 was higher than that of No. 2 and No. 4, and the curcumin release concentration of No. 3 was higher than that of No. 1. (5) The results showed that slow-release effect of the curcumin sustained-release microspheres with a preset loading rate of 10% prepared by L-lactic acid-polycaprolactone copolymer best meets the Zero order release requirements. © 2022, Publishing House of Chinese Journal of Tissue Engineering Research. All rights reserved.     

Computational modelling of the mechanical environment of osteogenesis within a polylactic acid–calcium phosphate glass scaffold

A computational model based on finite element method (FEM) and computational fluid dynamics (CFD) is developed to analyse the mechanical stimuli in a composite scaffold made of polylactic acid (PLA) matrix with calcium phosphate glass (Glass) particles. Different bioreactor loading conditions were simulated within the scaffold. In vitro perfusion conditions were reproduced in the model. Dynamic compression was also reproduced in an uncoupled fluid-structure scheme: deformation level was studied analyzing the mechanical response of scaffold alone under static compression while strain rate was studied considering the fluid flow induced by compression through fixed scaffold. Results of the model show that during perfusion test an inlet velocity of 25 μm/s generates on scaffold surface a fluid flow shear stress which may stimulate osteogenesis. Dynamic compression of 5% applied on the PLA–Glass scaffold with a strain rate of 0.005 s^?1 has the benefit to generate mechanical stimuli based on both solid shear strain and fluid flow shear stress on large scaffold surface area. Values of perfusion inlet velocity or compression strain rate one order of magnitude lower may promote cell proliferation while values one order of magnitude higher may be detrimental for cells. FEM–CFD scaffold models may help to determine loading conditions promoting bone formation and to interpret experimental results from a mechanical point of view.     

Phase development during setting and hardening of a bone cement based on α-tricalcium and octacalcium phosphates

In this study, the phase development in the cement system α-TCP-OCP with phosphoric acid as a setting liquid was studied. The most promising formulation of α-TCP (60?wt%) and OCP (40?wt%) is proposed. This cement has the following characteristics: setting time 10?min, pH?=?6.7, the compressive strength about 30?MPa, and high dissolution rate in an isotonic solution; the final wt% composition of α-TCP/DCPD/HA/OCP equals 27/38/20/15. Energy dispersive X-ray diffraction techniques were used for in situ monitoring of the processes taking place in the cement in real time.     

Mesenchymal stem cell proliferation and differentiation on an injectable calcium phosphate – Chitosan composite scaffold

Calcium phosphate cement (CPC) can be molded or injected to form a scaffold in situ, has excellent osteoconductivity, and can be resorbed and replaced by new bone. However, its low strength limits CPC to non-stress-bearing repairs. Chitosan could be used to reinforce CPC, but mesenchymal stem cell (MSC) interactions with CPC-chitosan scaffold have not been examined. The objective of this study was to investigate MSC proliferation and osteogenic differentiation on high-strength CPC-chitosan scaffold. MSCs were harvested from rat bone marrow. At CPC powder/liquid (P/L) mass ratio of 2, flexural strength (mean ± sd; n = 5) was (10.0 ± 1.1) MPa for CPC-chitosan, higher than (3.7 ± 0.6) MPa for CPC (p < 0.05). At P/L of 3, strength was (15.7 ± 1.7) MPa for CPC-chitosan, higher than (10.2 ± 1.8) MPa for CPC (p < 0.05). Percentage of live MSCs attaching to scaffolds increased from 85% at 1 day to 99% at 14 days. There were (180 ± 37) cells/mm² on scaffold at 1 day; cells proliferated to (1808 ± 317) cells/mm² at 14 days. SEM showed MSCs with healthy spreading and anchored on nano-apatite crystals via cytoplasmic processes. Alkaline phosphatase activity (ALP) was (557 ± 171) (pNPP mM/min)/(μg DNA) for MSCs on CPC-chitosan, higher than (159 ± 47) on CPC (p < 0.05). Both were higher than (35 ± 32) of baseline ALP for undifferentiated MSCs on tissue-culture plastic (p < 0.05). In summary, CPC-chitosan scaffold had higher strength than CPC. MSC proliferation on CPC-chitosan matched that of the FDA-approved CPC control. MSCs on the scaffolds differentiated down the osteogenic lineage and expressed high levels of bone marker ALP. Hence, the stronger CPC-chitosan scaffold may be useful for stem cell-based bone regeneration in moderate load-bearing maxillofacial and orthopedic applications.