An injectable and biomimetic multi‐phase nanocomposite for non‐invasive bone tissue engineering: fabrication and mechanistic evaluation

An injectable, non‐hardening nanocomposite bone graft has been developed using a combination of nanohydroxyapatite as bioactive and osseointegrative material; P‐15 peptide‐modified poly(lactic‐co‐glycolic acid) (PLGA) microspheres as biomimetic and osteoinductive agent; and PLGA–poly(ethylene glycol) (PEG)–PLGA as a carrier gel. Increase in lactic acid/glycolic acid ratio of PLGA–PEG–PLGA resulted in stronger gels with a wider gelation window. Addition of 2.5‐fold nanohydroxyapatite resulted in significant changes in injectability (3.5‐fold force of injection), swelling characteristics (2.5 times swelling index), rheological (shear viscosity from 2.1 × 10¹ Pa s for NC3_700 to 1.5 × 10⁶ Pa s for NC3_73.52 and from 3.9 × 10² Pa s for NC8_700 to 3.76 × 10⁶ Pa s for NC8_732; an increase in elasticity at the level of 1–1000 kPa), and thermal properties of the nanocomposites. A mechanistic study showed that nanohydroxyapatite exhibits a high degree of association with the gel and interferes with its gelation owing to changes in hydrogen bonding interactions between C=?O of polymer chains and P–OH groups of nanohydroxyapatite with water molecules of the gel. A schematic was developed demonstrating changes in bonding interactions among constituent phases with respect to nanohydroxyapatite content emphasizing the importance of material interactions while fabricating multi‐phase nanocomposites for various biomedical applications. Copyright © 2017 John Wiley & Sons, Ltd.     

A Copolymer Scaffold Functionalized with Nanodiamond Particles Enhances Osteogenic Metabolic Activity and Bone Regeneration

Functionalizing polymer scaffolds with nanodiamond particles (nDPs) has pronounced effect on the surface properties, such as improved wettability, an increased active area and binding sites for cellular attachment and adhesion, and increased ability to immobilize biomolecules by physical adsorption. This study aims to evaluate the effect of poly(l ‐lactide‐co‐ε‐caprolactone) (poly(LLA‐co‐CL)) scaffolds, functionalized with nDPs, on bone regeneration in a rat calvarial critical size defect. Poly(LLA‐co‐CL) scaffolds functionalized with nDPs are also compared with pristine scaffolds with reference to albumin adsorption and seeding efficiency of bone marrow stromal cells (BMSCs). Compared with pristine scaffolds, the experimental scaffolds exhibit a reduction in albumin adsorption and a significant increase in the seeding efficiency of BMSCs (p = 0.027). In the calvarial defects implanted with BMSC‐seeded poly(LLA‐co‐CL)/nDPs scaffolds, live imaging at 12 weeks discloses a significant increase in osteogenic metabolic activity (p = 0.016). Microcomputed tomography, confirmed by histological data, reveals a substantial increase in bone volume (p = 0.021). The results show that compared with conventional poly(LLA‐co‐CL) scaffolds those functionalized with nDPs promote osteogenic metabolic activity and mineralization capacity. It is concluded that poly(LLA‐co‐CL) composite matrices functionalized with nDPs enhance osteoconductivity and therefore warrant further study as potential scaffolding material for bone tissue engineering.

     

Digital volume correlation: Three-dimensional strain mapping using X-ray tomography

A three-dimensional extension of two-dimensional digital image correlation has been developed. The technique uses digital image volumes generated through high-resolution X-ray tomography of samples with microarchitectural detail, such as the trabecular bone tissue found within the skeleton. Image texture within the material is used for displacement field measurement by subvolume tracking. Strain fields are calculated from the displacement fields by gradient estimation techniques. Estimates of measurement precision were developed through correlation of repeat unloaded data sets for a simple sum-of-squares displacement-only correlation formulation. Displacement vector component errors were normally distributed, with a standard deviation of 0.035 voxels (1.22 m). Strain tensor component errors were also normally distributed, with a standard deviation of approximately 0.0003. The method was applied to two samples taken from the thigh bone near the knee. Strains were effectively measured in both the elastic and postyield regimes of material behavior, and the spatial patterns showed clear relationships to the sample microarchitectures.     

Reversibly Controlling Preferential Protein Adsorption on Bone Implants by Using an Applied Weak Potential as a Switch

A facile method is needed to control the protein adsorption onto biomaterials, such as, bone implants. Herein we doped taurocholic acid (TCA), an amphiphilic biomolecule, into an array of 1D nano‐architectured polypyrrole (NAPPy) on the implants. Doping TCA enabled the implant surface to show reversible wettability between 152° (superhydrophobic, switch‐on state) and 55° (hydrophilic, switch‐off state) in response to periodically switching two weak electrical potentials (+0.50 and ?0.80 V as a switch‐on and switch‐off potential, respectively). The potential‐switchable reversible wettability, arising from the potential‐tunable orientation of the hydrophobic and hydrophilic face of TCA, led to potential‐switchable preferential adsorption of proteins as well as cell adhesion and spreading. This potential‐switchable strategy may open up a new avenue to control the biological activities on the implant surface.     

Utilization of PVPA and its effect on the material properties and biocompatibility of PVA electrospun membrane

This study aims to investigate on the effect of the addition of polyvinylphosphonic acid (PVPA) on the material properties and biocompatibility of a polyvinyl alcohol (PVA) polymer tissue engineering scaffold fabricated by electrospinning process. Stabilization of the membranes was carried out by heat application. Fourier transform infrared spectroscopy confirmed the presence of P?O bonds and P–OH bonds and increase in the atomic percentage of phosphorus in Energy Dispersive Spectroscopy (EDS) indicated successful incorporation of PVPA to the PVA. Scanning electron microscope fiber morphology and microstructure showed that addition of PVPA reduced the average fiber diameter of the scaffold. After 1 hr of phosphate buffered saline immersion, scaffolds were observed to swell to almost 200% of their original weight. Increased tensile strength was observed at 0.1% PVPA addition but reduced values were observed when the concentration was greater than 0.1%. Cytocompatibility was examined with M3CT3‐E1 preosteoblast cells through cell viability after exposure to extract solutions and Live/Dead cell staining. Cell proliferation was quantified by MTT assay; cell adhesion was visualized by scanning electron microscope and confocal microscopy images. Bone regeneration was also observed and quantified using histomorphometric analysis and histological staining methods after implantation in rat calvarium for 4 weeks. Copyright © 2013 John Wiley & Sons, Ltd.     

Further insights into the assessment of cell cycle phases by FTIR microspectroscopy

Cell growth and replication occurs in an orderly manner through a set of tightly coordinated physiological events, classified as G0, G1, S, G2 and M in conformity to their characteristics. In a previous work, by combining the results of flow cytometry (FC) using propidium iodide (PI) staining, PI-FC, and Fourier Transform Infrared Microspectroscopy (FTIRM), we gathered information to classify live B16 cells into three different set of phases (G0/G1, S and G2/M), according to their nucleic acid content measured as the area integral of the Phosphate I band (PhI, 1274–1182 cm⁻¹). In this work, we demonstrate that, once built a calibration dataset for a cell line determining the intervals of the PhI area integral related to each phase of the cell cycle, such data can be used for assigning the stage to which a live cell belongs without the support of FC. In addition, we evaluate the spectral profile of early G1 B16 cells, and compare it with the one of G0 and late G1 cell cycle phases. FTIRM highlights that G0 and G1 phases are a continuum, where the content of RNA of early G1 cells is in between G0 and late G1, and the overall nucleic acid content varies accordingly. In the paper, we also pinpoint the effects on synchronization protocols on cellular biochemistry, further strengthening the potentialities of a totally label-free methodology for cell sorting. Finally, we demonstrate that the general concept behind the proposed approach may be extended to other mammalian cell lines: human bone osteosarcoma (U2OS) cells were tested.     

多发性骨髓瘤的骨髓形态学分析与临床应用

目的研究多发性骨髓瘤的骨髓形态学特征,探讨骨髓形态学在多发性骨髓瘤诊断中的临床应用价值。方法对广东医学院附属医院63例多发性骨髓瘤病人进行骨髓涂片及细胞染色和进行检验诊断分析。结果 94%的患者骨髓增生度都达到增生活跃以上,只有6%的是增生低下或极度低下,瘤细胞数量﹥15%,根据形态可分为四类;病人骨髓其他系包括巨核系、粒系、红系和淋巴系细胞都不同程度减少和受抑制。结论骨髓形态学分析是多发性骨髓瘤诊断和治疗疗效监测具有重要的临床应用价值,具有广泛开展的必要性和意义。     

马骨骼的承力机理研究

应用三维激光扫描仪、Pixform和ANSYS等软件建立了马掌骨和跖骨的三维有限元模型,分析了马掌骨的承力机理,研究证明生物体骨骼是一种等强度优化模型.在静态压力载荷下,斜椭圆孔模型更优,这正符合马跖骨代谢孔的形位特征,说明了生物体承力结构的进化合理性.