Ca/P concentration ratio at different sites of normal and osteoporotic rabbit bones evaluated by Auger and energy dispersive X-ray spectroscopy

Investigation of Calcium Phosphate-Based Biopolymer Composite Scaffolds for Bone Tissue Engineering

We present a novel method for preparing bioactive and biomineralized calcium phosphate (mCP)-loaded biopolymer composite scaffolds with a porous structure. Two types of polymers were investigated as matrices: one natural, cellulose acetate (CA), and one synthetic, polycaprolactone (PCL). Biomineralized calcium phosphate particles were synthesized via wet chemical precipitation, followed by the addition of organic biominerals, such as magnesium gluconate and zinc gluconate, to enhance the bioactivity of the pure CP phase. We compared the morphological and chemical characteristics of the two types of composites and assessed the effect of biomineralization on the particle structure of pure CP. The precipitated CP primarily consisted of nanocrystalline apatite, and the addition of organic trace elements significantly influenced the morphology by reducing particle size. FE-SEM elemental mapping confirmed the successful incorporation of mCP particles into both CA and PCL polymer matrices. Short-term immersion tests revealed that the decomposition rate of both composites is slow, with moderate and gradual ionic dissolution observed via ICP-OES measurements. The weight loss of the PCL-based composite during immersion was minimal, decreasing by only 0.5%, while the CA-based composite initially exhibited a slight weight increase before gradually decreasing over time.

Transdermal delivery of bisphosphonates using dissolving and hydrogel-forming microarray patches: Potential for enhanced treatment of osteoporosis

As of 2023, more than 200 million people worldwide are living with osteoporosis. Oral bisphosphonates (BPs) are the primary treatment but can cause gastrointestinal (GI) side effects, reducing patient compliance. Microarray (MAP) technology has the potential to overcome GI irritation by facilitating the transdermal delivery of BPs. This study examines the delivery of alendronic acid (ALN) and risedronate sodium (RDN) using dissolving and hydrogel-forming MAPs for osteoporosis treatment. In vivo testing on osteoporotic female Sprague Dawley rats demonstrated the efficacy of MAPs, showing significant improvements in mean serum and bone alkaline phosphatase levels, bone volume, and porosity compared to untreated bilateral ovariectomy (OVX) controls. Specifically, MAP treatment increased mean bone volume to 55.04 ± 2.25 % versus 47.16 ± 1.71 % in OVX controls and reduced porosity to 44.30 ± 2.97 % versus 52.84 ± 1.70 % in the distal epiphysis of the femur. In the distal metaphysis, bone volume increased to 43.32 ± 3.24 % in MAP-treated rats compared to 24.31 ± 3.21 % in OVX controls, while porosity decreased to 55.39 ± 5.81 % versus 75.69 ± 3.21 % in OVX controls. This proof-of-concept study indicates that MAP technology has the potential to be a novel, patient-friendly alternative for weekly osteoporosis management.

The Ways of Forming and the Erosion/Decay/Aging of Bioapatites in the Context of the Reversibility of Apatites

This study primarily focused on the acid erosion of enamel and dentin. A detailed examination of the X-ray diffraction data proves that the products of the acid-caused decay of enamel belong to the family of isomorphic bioapatites, especially calcium-deficient hydroxyapatites. They are on a trajectory towards less and less crystallized substances. The increase in Bragg's parameter d and the decrease in the energy necessary for the changes were coupled with variability in the pH. This was valid for the corrosive action of acid solutions with a pH greater than 3.5. When the processes of natural tooth aging were studied by X-ray diffraction, a clear similarity to the processes of the erosion of teeth was revealed. Scarce data on osteoporotic bones seemed to confirm the conclusions derived for teeth. The data concerning the bioapatite decays were confronted with the cycles of apatite synthesis/decay. The chemical studies, mainly concerning the Ca/P ratio in relation to the pH range of durability of popular compounds engaged in the synthesis/decay of apatites, suggested that the process of the formation of erosion under the influence of acids was much inverted in relation to the process of the formation of apatites, starting from brushite up to apatite, in an alkaline environment. Our simulations showed the shift between the family of bioapatites versus the family of apatites concerning the pH of the reaction environment. The detailed model stoichiometric equations associated with the particular stages of relevant processes were derived. The synthesis processes were alkalization reactions coupled with dehydration. The erosion processes were acid hydrolysis reactions. Formally, the alkalization of the environment during apatite synthesis is presented by introducing Ca(OH)2 to stoichiometric equations.

Inorganic Characterization of Feeds Based on Processed Animal Protein Feeds

The potential of utilizing inorganic constituents in processed animal proteins (PAPs) for species identification in animal feeds was investigated, with the aim of using these constituents to ensure the quality and authenticity of the products. This study aimed to quantify the inorganic content across various PAP species and assess whether inorganic analysis could effectively differentiate between PAP species, ultimately aiding in the identification of PAP fractions in animal feeds. Four types of PAPs, namely bovine, swine, poultry, and fish-based, were analyzed and compared to others made up of feathers of vegetal-based feed. Also, three insect-based PAPs (Cricket, Silkworm, Flour Moth) were considered in this study to evaluate the differences in terms of the nutrients present in this type of feed. Ionic chromatography (IC) was used to reveal the concentrations of NO3-, NO2, Cl-, and SO42-, and inductively coupled plasma optical emission spectroscopy (ICP-OES) to detect Al, Ca, Cd, Cr, Cu, Fe, K, Mg, Mn, Mo, Na, Ni, P, Si, Sr, Ti, and Zn. The application of multivariate chemometric techniques to the experimental results allowed us to determine the identification capability of the inorganic composition to identify correlations among the variables and to reveal similarities and differences among the different species. The results show the possibility of using this component for discriminating between different PAPS; in particular, fish PAPs are high in Cd, Sr, Na, and Mg content; swine PAPs have lower metal content due to high fat; feathers and vegetal feed have similar Al, Si, and Ni, but feathers are higher in Fe and Zn; and insect PATs have nutrient levels comparable to PAPs of other origins but are very high in Zn, Cu, and K.

Enamel Remineralisation with a Novel Sodium Fluoride-Infused Bristle Toothbrush

This study aims to investigate whether toothbrushes with fluoride-infused bristles have any (re)mineralisation effects on bovine enamel. Bovine incisors (N = 160) were extracted, and the buccal side of the crown was cut into dimensions of ~5 mm × 5 mm with a low-speed saw. These specimens were randomly allocated into four groups: half (80 teeth) were stored in demineralising solution (DM), and the other half were stored in deionised water (DW) for 96 h. Then, they were brushed with a force of 2.0 ± 0.1 N for five min with a manual toothbrush with either fluoride-infused (TF) or regular (TR) bristles. Microhardness (Vickers), X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDS), and scanning electron microscopy (SEM) were used to investigate the surfaces of the bovine enamel specimens before and after brushing. Two-way ANOVA was used to analyse the hardness data, and the pairwise comparison method was used to analyse the Ca/P ratio, for each group at α = 0.05. The results show that brushing with either of these toothbrushes increased the Vickers microhardness on DM and DW enamel (p < 0.001), whereas hydroxyapatite was revealed in all groups by XRD. The DM samples showed a significant increase (p < 0.05) in the Ca/P ratios after brushing with TR and TF. Conversely, under DW conditions, these ratios decreased significantly after brushing. In terms of the F atomic%, TF increased significantly. SEM revealed mineral deposition in the DM groups after toothbrushing. To conclude, toothbrushing effectively induces the microhardness of sound and demineralised enamel, while fluoride-infused bristles might be able to retain fluoride on the enamel surface.

A Biodegradable Tissue Adhesive for Post-Extraction Alveolar Bone Regeneration under Ongoing Anticoagulation-A Microstructural Volumetric Analysis in a Rodent Model

In addition to post-extraction bleeding, pronounced alveolar bone resorption is a very common complication after tooth extraction in patients undergoing anticoagulation therapy. The novel, biodegenerative, polyurethane adhesive VIVO has shown a positive effect on soft tissue regeneration and hemostasis. However, the regenerative potential of VIVO in terms of bone regeneration has not yet been explored. The present rodent study compared the post-extraction bone healing of a collagen sponge (COSP) and VIVO in the context of ongoing anticoagulation therapy. According to a split-mouth design, a total of 178 extraction sockets were generated under rivaroxaban treatment, of which 89 extraction sockets were treated with VIVO and 89 with COSP. Post-extraction bone analysis was conducted via in vivo micro-computed tomography (µCT), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDX) after 5, 10, and 90 days. During the observation time of 90 days, µCT analysis revealed that VIVO and COSP led to significant increases in both bone volume and bone density (p ≤ 0.001). SEM images of the extraction sockets treated with either VIVO or COSP showed bone regeneration in the form of lamellar bone mass. Ratios of Ca/C and Ca/P observed via EDX indicated newly formed bone matrixes in both treatments after 90 days. There were no statistical differences between treatment with VIVO or COSP. The hemostatic agents VIVO and COSP were both able to prevent pronounced bone loss, and both demonstrated a strong positive influence on the bone regeneration of the alveolar ridge post-extraction.

Elasticity and material anisotropy of lamellar cortical bone in adult bovine tibia characterized via AFM nanoindentation

The research focuses on the evaluation of the mechanical properties of osteonal cortical bone at the lamellar level. Elastic properties of the mid-diaphysis region of the bovine tibia are investigated via cantilever-based nanoindentation at the submicron length scale utilizing Atomic Force Microscopy, where the force-displacement curves are used for the elastic assessment using the Derjaguin-Muller-Toropov model to calculate indentation modulus. Variations of the modulus and the directional mechanical response of the osteonal bone at different distances from the Haversian canal are investigated. Additionally, the effects of demineralization on the indentation modulus are discussed. It was found that in the axial direction, the first and last untreated thick lamella layers show a significant indentation modulus difference compared to all other layers (4.26 ± 0.4 and 4.6 ± 0.3 GPa vs ∼3.5 GPa). On the other hand, the indentation modulus of transverse thick lamella layers shows a periodic variation between ∼3 ± 0.7 GPa and ∼4 ± 0.3 GPa from near the Haversian canal to near the interstitial bone. A periodic variation in the anisotropy ratio was found. Mineral content was quantified via energy-dispersive X-ray microanalysis at different levels of mineralization and shows a positive correlation with the indentation modulus.

Results of thermal osteonecrosis for implant removal on electron microscopy, implant stability, and radiographic parameters - a rat study

BACKGROUND

This rat study aimed to evaluate the feasibility of temperature thresholds that affect peri-implant bone cells and morphology and the potential usefulness of thermal necrosis for inducing implant removal for a subsequent in vivo pig study.

METHODS

On one side, rat tibiae were thermally treated before implant insertion. The contralateral side was used as the control group without tempering. Temperatures of 4 °C, 3 °C, 2 °C, 48 °C, 49 °C, and 50 °C were evaluated with a tempering time of 1 min. Energy-dispersive X-ray spectroscopy (EDX) and transmission electron microscopy (TEM) analyses were performed.

RESULTS

The EDX analysis revealed significant increases in element weights at 50 °C (e.g., calcium, phosphate, sodium, and sulfur; p < 0.01). The results of the TEM analysis showed that at all the applied cold and warm temperatures, signs of cell damage were observed, including vacuolization, shrinkage, and detachment from the surrounding bone matrix. Some cells became necrotic, leaving the lacunae empty.

CONCLUSIONS

Temperature of 50 °C led to irreversible cell death. The degree of damage was more significant at 50 °C and 2 °C than at 48 °C and 5 °C. Although this was a preliminary study, from the results, we identified that a temperature of 50 °C at a time interval of 60 min can lower the number of samples in a further study of thermo-explantation. Thus, the subsequent planned in vivo study in pigs, which will consider osseointegrated implants, is feasible.

Comparing the effect of demineralized versus hybrid dentin matrices on inducing bone regeneration in New Zealand white rabbits' Mandibular defect

OBJECTIVES

The aim of this study was to compare the effect of using demineralized dentin matrix (DDM) versus hybrid dentin matrices; Demineralized and undemineralized dentin particles (DDM +UDDM) on inducing bone regeneration in mandibular defects.

DESIGN

The study was conducted on fifty adult New Zealand rabbits, twenty for preparation of experimental materials and thirty for surgical procedures. They were randomly assigned into 3 equal groups as follow one control group: no treatment and two experimental groups including demineralized group: treated with DDM only; and hybrid group: treated with a hybrid of (50% DDM+50% UDD). A rounded critical size defect (10 mm in diameter- 5 mm in depth) was created in the body of mandible. After 3- and 6-weeks post-surgery, the bone regeneration was evaluated by light microscope, scanning electron microscope and histomorphometry.

RESULTS

Histological, histomorphometrical observation and SEM revealed that both dentin matrices had largely resorbed and induced new bone formation at both experimental groups compared to the control group, with statistically higher percentage of new bone formation in the hybrid group.

CONCLUSION

We concluded that although both dentin matrices induced new bone formation; however, hybrid dentin matrix yielded better results compared to DDM group.

Does anti-IgE therapy prevent chronic allergic asthma-related bone deterioration in asthmatic mice?

Current evidence on the association between allergic diseases and bone metabolism indicates asthma may be a potential risk factor for bone health. Using anti-IgE has been proven effective in allergic asthma treatment with a good safety profile; however, its effects on bone health are unknown. Thus, we aimed to investigate whether: (i) chronic allergic asthma (CAA) causes any meaningful changes in bone, and if any, (ii) anti-IgE therapy prevents any CAA-induced adverse alteration. A murine model was used to study CAA. Thirty-two BALB/c male-mice were assigned into four groups (eight-mice/group): Control, CAA (treated with saline), CAA + 100 µg of anti-IgE (CAA + 100AIgE), and CAA + 200 µg of anti-IgE (CAA + 200AIgE) groups. After immunization, saline or anti-IgE was performed intraperitoneally for 8-weeks (in five-sessions at 15-days interval). Three-point bending test was used for the mechanical analysis. Bone calcium (Ca²⁺) and phosphorus (P^3-) as well as Ca/P ratio were evaluated using inductively-coupled plasma-mass-spectrometer (ICP-MS). Compared to control, reductions observed in yield and ultimate moments, rigidity, energy-to-failure, yield and ultimate stresses, elastic modulus, toughness, and post-yield toughness parameters of the CAA group were found significant (P < 0.05). Similar declines were also detected regarding bone Ca²⁺, P^3- and Ca/P ratio (P < 0.05). Compared to control, we observed that 200 µg administration of anti-IgE in CAA + 200AIgE group hindered CAA-related impairments in mineral and mechanical characteristics of bone, while 100 µg in CAA + 100AIgE failed to do so. Our results showed CAA may cause bone loss, leading to a decrease in bone strength, and anti-IgE administration may dose-dependently inhibit these impairments in bone.

Surface and Structural Studies of Age-Related Changes in Dental Enamel: An Animal Model

In the animal kingdom, continuously erupting incisors provided an attractive model for studying the enamel matrix and mineral composition of teeth during development. Enamel, the hardest mineral tissue in the vertebrates, is a tissue sensitive to external conditions, reflecting various disturbances in its structure. The developing dental enamel was monitored in a series of incisor samples extending the first four weeks of postnatal life in the spiny mouse. The age-dependent changes in enamel surface morphology in the micrometre and nanometre-scale and a qualitative assessment of its mechanical features were examined by applying scanning electron microscopy (SEM) and atomic force microscopy (AFM). At the same time, structural studies using XRD and vibrational spectroscopy made it possible to assess crystallinity and carbonate content in enamel mineral composition. Finally, a model for predicting the maturation based on chemical composition and structural factors was constructed using artificial neural networks (ANNs). The research presented here can extend the existing knowledge by proposing a pattern of enamel development that could be used as a comparative material in environmental, nutritional, and pharmaceutical research.

The deterioration of calcified cartilage integrity reflects the severity of osteoarthritis-A structural, molecular, and biochemical analysis

The calcified cartilage zone (CCZ) is a thin interlayer between the hyaline articular cartilage and the subchondral bone and plays an important role in maintaining the joint homeostasis by providing biological and mechanical support from unmineralized cartilage to the underlying mineralized subchondral bone. The hallmark of CCZ characteristics in osteoarthritis (OA) is less well known. The aim of our study is to evaluate the structural, molecular, and biochemical composition of CCZ in tissues affected by primary knee OA and its relationship with disease severity. We collected osteochondral tissue samples stratified according to disease severity, from 16 knee OA patients who underwent knee replacement surgery. We also used meniscectomy-induced rat samples to confirm the pathophysiologic changes of human samples. We defined the characteristics of the calcified cartilage layer using a combination of morphological, biochemical, proteomic analyses on laser micro-dissected tissue. Our results demonstrated that the Calcium/Phosphate ratio is unchanged during the OA progression, but the calcium-binding protein and cadherin binding protein, as well as carbohydrate metabolism-related proteins, undergo significant changes. These changes were further accompanied by thinning of the CCZ, loss of collagen and proteoglycan content, the occurrence of the endochondral ossification, neovasculature, loss of the elastic module, loss of the collagen direction, and increase of the tortuosity indicating an altered structural and mechanical properties of the CCZ in OA. In conclusion, our results suggest that the calcified cartilage changes can reflect the disease progression.

In vivo and in vitro analysis in a rat model using zoledronate and alendronate medication: microbiological and scanning electron microscopy findings on peri-implant rat tissue

Background

The aim of the present study was to assess the development of bacterial deposits and morphological parameters around dental zirconia and titanium implants compared with natural teeth during systemic bisphosphonate medication.

Materials and methods

Fifty-four rats were randomly allocated into one control group and two experimental groups (drug application of zoledronic and alendronic acid), with 18 animals in each group. After 4 weeks of drug delivery, either a zirconia or a titanium implant was immediately inserted. Microbiological analysis conducted 1 week, 8 weeks, and 12 weeks after surgery included total bacterial count and composition measurements. Samples were analyzed in a scanning electron microscope (SEM) equipped with energy-dispersive X-ray spectroscopy (EDX). Bone cell morphology was analyzed by transmission electron microscopy (TEM).

Results

One week after surgery, titanium and zirconia implants of the alendronic acid and control group showed a significantly higher bacterial count when compared to natural teeth in rats with zoledronic acid administration (p < 0.01). Less significant differences were recorded after 3 months, at which time no inter-material differences were evaluated (p > 0.05). I n the control group, TEM analysis showed that the osteoblasts had a strongly developed endoplasmic reticulum. In contrast, the endoplasmic reticulum of the osteoblasts in drug-treated animals was significantly less developed, indicating less activity.

Conclusions

Within the limits of this study, neither implant material was superior to the other at 3-month follow-up. With regard to the treatment and complications of patients with bisphosphonates, the implant material should not be an influencing factor. Bisphosphonates can be used in the rat model to reduce not only the activity of osteoclasts but also osteoblasts of the peri-implant bone.

Intrinsic osteoinductivity of PCL-DA/PLLA semi-IPN shape memory polymer scaffolds

Engineering osteoinductive, self-fitting scaffolds offers a potential treatment modality to repair irregularly shaped craniomaxillofacial bone defects. Recently, we innovated on osteoinductive poly(ε-caprolactone)-diacrylate (PCL-DA) shape memory polymers (SMPs) to incorporate poly-L-lactic acid (PLLA) into the PCL-DA network, forming a semi-interpenetrating network (semi-IPN). Scaffolds formed from these PCL-DA/PLLA semi-IPNs display stiffnesses within the range of trabecular bone and accelerated degradation relative to scaffolds formed from slowly degrading PCL-DA SMPs. Herein, we demonstrate for the first time that PCL-DA/PLLA semi-IPN SMP scaffolds show increased intrinsic osteoinductivity relative to PCL-DA. We also confirm that application of a bioinspired polydopamine (PD) coating further improves the osteoinductive capacity of these PCL-DA/PLLA semi-IPN SMPs. In the absence of osteogenic supplements, protein level assessment of human mesenchymal stem cells (h-MSCs) cultured in PCL-DA/PLLA scaffolds revealed an increase in expression of osteogenic markers osterix, bone morphogenetic protein-4 (BMP-4), and collagen 1 alpha 1 (COL1A1), relative to PCL-DA scaffolds and osteogenic medium controls. Likewise, the expression of runt-related transcription factor 2 (RUNX2) and BMP-4 was elevated in the presence of PD-coating. In contrast, the chondrogenic and adipogenic responses associated with the scaffolds matched or were reduced relative to osteogenic medium controls, indicating that the scaffolds display intrinsic osteoinductivity.

Polygalacto-fucopyranose biopolymer structured nanoparticle conjugate attenuates glucocorticoid-induced osteoporosis: An in vivo study

Naturally occurring polysaccharide-structured nanoparticles have developed as promising materials for treatment of bone health disorders. Silver nanoparticle (ST-AgNP) structured from sulfated polygalacto-fucopyranose comprising of recurring structural entities of 2-SO3-α-(1 → 3)-fucopyranose and 6-O-acetyl-β-(1 → 4)-galactopyranose isolated from marine macroalga Sargassum tenerrimum demonstrated potential activities associated with osteogenesis. Subsequent treatment with ST-AgNP, activity of alkaline phosphatase (63 mU/mg) was raised in osteoblast stem cells (human mesenchymal, hMSC) than that in control (30 mU/mg). Intense growth of mineralized nodule on the surface of hMSC was apparent following treatment with ST-AgNP. Increased population of bone morphogenic protein-2 (23%) and osteocalcin+ cells (50%) on M2 macrophages were apparent following treatment with ST-AgNP (0.25 mg/mL). Glucocorticoid-induced in vivo animal model studies of ST-AgNP exhibited significant recovery of serum biochemical parameters along with serum estradiol and parathyroid hormone compared to disease control. Disease-induced groups treated with ST-AgNP showed the disappearance of osteoporotic cavities in the trabecular bone. Following treatment with ST-AgNP, serum calcium and phosphorus contents were significantly recovered.

Elemental Composition in Female Dry Femora Using Portable X-Ray Fluorescence (pXRF): Association with Age and Osteoporosis

Pathophysiological conditions can modify the skeletal chemical concentration. This study analyzes the elemental composition in two anatomical regions from dry femoral bone using a portable X-Ray Fluorescence (pXRF) and evaluates its impact in the bone mineral density (BMD). The left femora of 97 female skeletons (21-95 years old individuals) from the Coimbra Identified Skeletal Collection were studied. Diagenetic biases were discarded at the outset and BMD was determined with Dual-energy X-ray absorptiometry. Chemical measurements were performed at the midpoint of the femoral neck and at the midshaft using a pXRF device, and comparisons were made considering the age and the BMD values. Only elements with a Technical Measurement Error ≤ 5% were selected: P, S, Ca, Fe, Zn, As, Sr, Pb and the Ca/P ratio. Statistically significant differences were found between regions, with higher concentrations of P, Ca, Zn and S at the midshaft, and the Ca/P ratio at the femoral neck. The concentration of P is higher in individuals < 50 years, while S and Ca/P ratio increase in individuals ≥ 50 years. The decrease of P with age can be simultaneously related to the decline of its concentration in osteoporosis. Decreased BMD is also associated with higher levels of S and Pb. Osteoporosis enhances the absorption of osteolytic elements in specific locations. This fast and non-destructive technique has proved effective for the comprehension of chemical changes related to bone mass loss. This study highlights the potential of identified skeletal collections to improve the knowledge about bone fragility.

Vancomycin-Loaded Collagen/Hydroxyapatite Layers Electrospun on 3D Printed Titanium Implants Prevent Bone Destruction Associated with S. epidermidis Infection and Enhance Osseointegration

The aim of the study was to develop an orthopedic implant coating in the form of vancomycin-loaded collagen/hydroxyapatite layers (COLHA+V) that combine the ability to prevent bone infection with the ability to promote enhanced osseointegration. The ability to prevent bone infection was investigated employing a rat model that simulated the clinically relevant implant-related introduction of bacterial contamination to the bone during a surgical procedure using a clinical isolate of Staphylococcus epidermidis. The ability to enhance osseointegration was investigated employing a model of a minipig with terminated growth. Six weeks following implantation, the infected rat femurs treated with the implants without vancomycin (COLHA+S. epidermidis) exhibited the obvious destruction of cortical bone as evinced via a cortical bone porosity of up to 20% greater than that of the infected rat femurs treated with the implants containing vancomycin (COLHA+V+S. epidermidis) (3%) and the non-infected rat femurs (COLHA+V) (2%). The alteration of the bone structure of the infected COLHA+S. epidermidis group was further demonstrated by a 3% decrease in the average Ca/P molar ratio of the bone mineral. Finally, the determination of the concentration of vancomycin released into the blood stream indicated a negligible systemic load. Six months following implantation in the pigs, the quantified ratio of new bone indicated an improvement in osseointegration, with a two-fold bone ingrowth on the COLHA (47%) and COLHA+V (52%) compared to the control implants without a COLHA layer (27%). Therefore, it can be concluded that COLHA+V layers are able to significantly prevent the destruction of bone structure related to bacterial infection with a minimal systemic load and, simultaneously, enhance the rate of osseointegration.

A Simple Method to Determine the Fractions of Labile and Mineral-Bound Microelements in Bone Tissue by Atomic Absorption Spectrometry

In this work a simple and inexpensive method to assess the concentration ratio of the labile and mineral-bound microelements of the bone tissue was developed. The approach is based on the separation of the components of bone tissue by their selective solubility with the subsequent determination of microelements with atomic absorption spectrometry. The total concentrations of Mg, Zn, Fe, Sr, Al, Cu, and Mn and the concentrations of these elements in aqueous solutions with pH 6.5, 10, and 12 after their ultrasonically activated interaction with the powder of dried bone were determined. Two quite different bone samples were analyzed: a cortical fragment of the femur of a mature healthy cow and the spongy part of a human femoral head affected by osteoporosis. Some common and individual features of the both type of bones in regard to the total concentrations and fractional distribution of microelements are discussed. The obtained concentrations of the "soluble" fractions of microelements were critically analyzed taking into account the possible reactions leading to new insoluble phases' formation in alkaline solutions. Based on the data obtained, the ability of elements to form labile fractions in the bone tissue could be arranged in the following descending series: Mg ≥ Zn > Al > Fe > Mn > Cu > Sr.

Solid-State Nuclear Magnetic Resonance Identifies Abnormal Calcium Phosphate Formation in Diseased Bones

The crystallites of calcium phosphate (CaP) in bones consist of hydroxyl apatite (HA) and amorphous calcium phosphate (ACP). These nanoscale structures of CaP are sculptured by biological bone formation and resorption processes and are one of the crucial factors that determine the overall strength of the constructs. We used one- and two-dimensional ¹H-³¹P solid-state nuclear magnetic resonance (SSNMR) to investigate the nanoscopic structural changes of CaP. Two quantitative measurables are deduced based on the heterogeneous linewidth of ³¹P signal and the ratio of ACP to HA, which characterize the mineral crystallinity and the relative proportion of ACP, respectively. We analyzed bones from different murine models of osteopetrosis and osteoporosis and from human samples with osteoporosis and osteoarthritis. It shows that the ACP content increases notably in osteopetrotic bones that are characterized by defective osteoclastic resorption, whereas the overall crystallinity increases in osteoporotic bones that are marked by overactive osteoclastic resorption. Similar pathological characteristics are observed for the sclerotic bones of late-stage osteoarthritis, as compared to those of the osteopetrotic bones. These findings suggest that osteoclast-related bone diseases not only alter the bone density macroscopically but also lead to abnormal formation of CaP crystallites. The quantitative measurement by SSNMR provides a unique perspective on the pathology of bone diseases at the nanoscopic level.

Lacunar-canalicular bone remodeling: Impacts on bone quality and tools for assessment

Osteocytes can resorb as well as replace bone adjacent to the expansive lacunar-canalicular system (LCS). Suppressed LCS remodeling decreases bone fracture toughness, but it is unclear how altered LCS remodeling impacts bone quality. The first goal of this review is to assess how LCS remodeling impacts LCS morphology as well as the composition and mechanical properties of surrounding bone tissue. The second goal is to compare tools available for the assessment of bone quality at length-scales that are physiologically-relevant to LCS remodeling. We find that changes to LCS morphology occur in response to a variety of physiological conditions and diseases and can be classified in two general phenotypes. In the 'aging phenotype', seen in aging and in some disuse models, the LCS is truncated and osteocytes apoptosis is increased. In the 'osteocytic osteolysis' phenotype, which is adaptive in some physiological settings and possibly maladaptive in others, the LCS enlarges and osteocytes generally maintain viability. Bone composition and mechanical properties vary near the osteocyte and change with at least some conditions that alter LCS morphology. However, few studies have evaluated bone composition and mechanical properties close to the LCS and so the impacts of LCS remodeling phenotypes on bone tissue quality are still undetermined. We summarize the current understanding of how LCS remodeling impacts LCS morphology, tissue-scale bone composition and mechanical properties, and whole-bone material properties. Tools are compared for assessing tissue-scale bone properties, as well as the resolution, advantages, and limitations of these techniques.

Implant removal using thermal necrosis-an in vitro pilot study

OBJECTIVES

The purpose of this pilot porcine cadaver study was to evaluate the feasible temperature thresholds, which affect osteocyte viability and bone matrix in a preclinical setup, assessing the potential of thermal necrosis for implant removal for further in vivo investigations.

MATERIALS AND METHODS

After implant bed preparation in the upper and lower jaw, temperature effects on the bone were determined, using two tempering pistons with integrated thermocouples. To evaluate threshold temperature and time intervals leading to bone necrosis, one piston generated warm temperatures at 49 to 56 °C for 10 s and the other generated cold temperatures at 5 to 1 °C for 30 s. Effects were assessed by a semi-quantitative, histomorphometrical scoring system, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and transmission electron microscopy (TEM).

RESULTS

The bone matrix was significantly degenerated starting at 51 °C for 10 s and 5 °C for 30 s. The osteocyte condition indicated significant bone damage beginning at cold temperatures of 2 °C. Temperature inputs starting at 53 °C led to decalcification and swollen mitochondria, which lost the structure of their inner cristae.

CONCLUSIONS

This study identified temperatures and durations, in both heat and cold, so that the number of samples may be kept low in further studies regarding temperature-induced bone necrosis. Levels of 51 °C for 10 s and 5 °C for 30 s have presented significant matrix degeneration.

CLINICAL RELEVANCE

Temperature thresholds, potentially leading to thermo-explantation of dental implants and other osseointegrated devices, were identified.

Osteopontin regulates biomimetic calcium phosphate crystallization from disordered mineral layers covering apatite crystallites

Details of apatite formation and development in bone below the nanometer scale remain enigmatic. Regulation of mineralization was shown to be governed by the activity of non-collagenous proteins with many bone diseases stemming from improper activity of these proteins. Apatite crystal growth inhibition or enhancement is thought to involve direct interaction of these proteins with exposed faces of apatite crystals. However, experimental evidence of the molecular binding events that occur and that allow these proteins to exert their functions are lacking. Moreover, recent high-resolution measurements of apatite crystallites in bone have shown that individual crystallites are covered by a persistent layer of amorphous calcium phosphate. It is therefore unclear whether non-collagenous proteins can interact with the faces of the mineral crystallites directly and what are the consequences of the presence of a disordered mineral layer to their functionality. In this work, the regulatory effect of recombinant osteopontin on biomimetic apatite is shown to produce platelet-shaped apatite crystallites with disordered layers coating them. The protein is also shown to regulate the content and properties of the disordered mineral phase (and sublayers within it). Through solid-state NMR atomic carbon-phosphorous distance measurements, the protein is shown to be located in the disordered phases, reaching out to interact with the surfaces of the crystals only through very few sidechains. These observations suggest that non-phosphorylated osteopontin acts as regulator of the coating mineral layers and exerts its effect on apatite crystal growth processes mostly from afar with a limited number of contact points with the crystal.

A Novel Approach for Detecting Unique Variations among Infectious Bacterial Species in Endocarditic Cardiac Valve Vegetation

Infectious endocarditis (IE) remains one of the deadliest heart diseases with a high death rate, generally following thrombo-embolic events. Today, therapy is based on surgery and antibiotic therapy. When thromboembolic complications in IE patients persist, this is often due to our lack of knowledge regarding the pathophysiological development and organization of cells in the vegetation, most notably the primordial role of platelets and further triggered hemostasis, which is related to the diversity of infectious microorganisms involved. Our objective was to study the organization of IE vegetations due to different bacteria species in order to understand the related pathophysiological mechanism of vegetation development. We present an approach for ultrastructural analysis of whole-infected heart valve tissue based on scanning electron microscopy and energy-dispersive X-ray spectroscopy. Our approach allowed us to detect differences in cell organization between the analyzed vegetations and revealed a distinct chemical feature in viridans Streptococci ones. Our results illustrate the benefits that such an approach may bring for guiding therapy, considering the germ involved for each IE patient.

Effect of diode laser biostimulation compared to Teriparatide on induced osteoporosis in rats: an animal study from Egypt

Our aim in this study was to evaluate the effect of low-level laser therapy (LLLT) by means of diode laser bio-stimulation compared to Teriparatide in induced osteoporosis in rats. A total of 45 adult female Egyptian albino rats were used. Rats were divided into five groups: normal control, osteoporotic control, Teriparatide (TPTD) group (T), laser group (L), and laser and teriparatide (T+L) combination group. Osteoporosis was induced by performing double ovariectomy in rats. Lower jaws and left femurs were dissected. The specimens were tested using a Computed tomography unit, scanning EM (SEM) equipped with Energy Dispersive X-Ray Analyzer, and Rat PINP ELISA Kit. The histopathologic examination of experimental rat jaws and femurs revealed changes in bone architecture among the various groups throughout the experiment. CT examination showed a noticeable difference in radiodensity between jaw and femur bones. By SEM, bones of the Normal Control (NC) group showed normal bone porosity. However, bones of the Osteoporotic Control (OC) group showed a great difference as bone pores were large and numerous with irregular outlines. The ELISA test for PINP concentration showed a steady rise in the PINP concentrations in OC, T, L and T+L groups. We concluded that TPTD has osteogenic potential and is capable to enhance bone architecture by inducing the formation of new well-organized bone with narrower bone pore diameter. LLLT can be used as a good alternative local treatment strategy with minimal side effects and superior outcomes.

Design and development of a commercially viable in situ nanoemulgel for the treatment of postmenopausal osteoporosis

Aim: To investigate the potential of a thermosensitive intranasal formulation of raloxifene hydrochloride (RH) for systemic delivery with the possibility of enhanced bioavailability and anti-osteoporotic efficacy. Methods: In this work, a commercially scalable nanoemulsion in thermosensitive gel, aligned with better clinical acceptability, has been developed and evaluated. Results: A significant 7.4-fold improvement in bioavailability of RH was recorded when compared with marketed tablets. Likewise, in vivo pharmacodynamics studies suggested 162% enhanced bone density and significantly improved biochemical markers compared with per-oral marketed tablet. Conclusion: The formulation, being safe and patient compliant, successfully tuned anti-osteoporotic effects with improved therapeutic performance. Further, the work provided an exceptional lead to carry out the study in clinical settings.

Bone Mineral Composition Among Long-Term Parenteral Nutrition Patients: Postmortem Assessment of Calcium, Phosphorus, Magnesium, and Select Trace Elements

BACKGROUND

Patients receiving long-term parenteral nutrition (PN) treatment are at risk of developing metabolic bone diseases (MBDs). The bone compartment serves as a repository for a range of metal(loid)s that are administered intravenously to patients via PN solutions. Thus, the mineral composition of patient bones may be linked to the development of MBDs in this group.

METHODS

We measured 12 elements in bone samples obtained post mortem from 7 long-term (2-21 years) PN patients and 18 control bones obtained from hip/knee replacement surgery. The samples were cleaned, digested, and subsequently analyzed using a method based on inductively coupled plasma tandem mass spectrometry.

RESULTS

Compared with the control group, bones obtained from PN patients were significantly (P < 0.05) depleted in calcium (Ca), phosphorus (P), magnesium (Mg), chromium, and strontium and enriched in manganese (Mn), zinc, barium, cadmium (Cd), and uranium (U). No differences were observed for cobalt or lead.

CONCLUSIONS

Depletion of major components of bone mineral (Ca, P, and Mg) and enrichment in known toxicants (Cd, Mn, U) are concerns for PN patients.

In vivo behavior of biomicroconcretes based on α-tricalcium phosphate and hybrid hydroxyapatite/chitosan granules and sodium alginate

The current studies provide insights into how predictions based on results of physicochemical and in vitro tests are consistent with the results of in vivo studies. The new biomicroconcrete type materials were obtained by mixing the solid phase, composed of hybrid hydroxyapatite/chitosan granules and highly reactive α-tricalcium phosphate powder, used as the setting agent. This approach guaranteed a good adhesion of the continuous cement phase to the surface of granules. It has been demonstrated that developed biomicroconcretes are surgically handy, possessed favorable physicochemical and biological properties and can be considered as effective bone implant material. The hierarchical porosity and compressive strength (2-6 MPa) similar to cancellous bone made them suitable for low-load bearing applications. Despite the fact that final setting times of biomicroconcretes were longer than recommended in the literature (i.e., exceeded 15 min), their short cohesion time allows for a successful implantation in a rabbit femoral defect model. Histological analysis and Raman studies revealed newly formed bone tissues around the sides of implanted materials. Furthermore, the process of neovascularization and reconstruction of the bone tissue, as well as a reverse scaffolding process, was visible. No signs of inflammation or adverse tissue reactions were observed during the experiment.

SEM BSE 3D Image Analysis of Human Incus Bone Affected by Cholesteatoma Ascribes to Osteoclasts the Bone Erosion and VpSEM dEDX Analysis Reveals New Bone Formation

Bone erosion is considered a typical characteristic of advanced or complicated cholesteatoma (CHO), although it is still a matter of debate if bone erosion is due to osteoclast action, being the specific literature controversial. The purpose of this study was to apply a novel scanning characterization approach, the BSE 3D image analysis, to study the pathological erosion on the surface of human incus bone involved by CHO, in order to definitely assess the eventual osteoclastic resorptive action. To do this, a comparison of BSE 3D image of resorption lacunae (resorption pits) from osteoporotic human femur neck (indubitably of osteoclastic origin) with that of the incus was performed. Surface parameters (area, mean depth, and volume) were calculated by the software Hitachi MountainsMap© from BSE 3D-reconstructed images; results were then statistically analyzed by SPSS statistical software. Our findings showed that no significant differences exist between the two groups. This quantitative approach implements the morphological characterization, allowing us to state that surface erosion of the incus is due to osteoclast action. Moreover, our observation and processing image workflow are the first in the literature showing the presence not only of bone erosion but also of matrix vesicles releasing their content on collagen bundles and self-immuring osteocytes, all markers of new bone formation on incus bone surface. On the basis of recent literature, it has been hypothesized that inflammatory environment induced by CHO may trigger the osteoclast activity, eliciting bone erosion. The observed new bone formation probably takes place at a slower rate in respect to the normal bone turnover, and the process is uncoupled (as recently demonstrated for several inflammatory diseases that promote bone loss) thus resulting in an overall bone loss. Novel scanning characterization approaches used in this study allowed for the first time the 3D imaging of incus bone erosion and its quantitative measurement, opening a new era of quantitative SEM morphology.

Inhibition of osteoclasts differentiation by CDC2-induced NFATc1 phosphorylation

Bone homeostasis is regulated by a balance of bone formation and bone resorption; dysregulation of bone homeostasis may cause bone-related diseases (e.g., osteoporosis, osteopetrosis, bone fracture). Members of the nuclear factor of activated T cells (NFAT) family of transcription factors play crucial roles in the regulation of immune system, inflammatory responses, cardiac formation, skeletal muscle development, and bone homeostasis. Of these, NFATc1 is a key transcription factor mediating osteoclast differentiation, which is regulated by phosphorylation by distinct NFAT kinases including casein kinase 1 (CK1), glycogen synthase kinase 3 (GSK3), and dual-specificity tyrosine-phosphorylation-regulated kinases (DYRKs). In this study, we report that cell division control protein 2 homolog (cdc2) is a novel NFAT protein kinase that inhibits NFATc1 activation by direct phosphorylation of the NFATc1 S263 residue. Cdc2 inhibitors such as Roscovitine and BMI-1026 induce reduction of phosphorylation of NFATc1, and this process leads to the inhibition of NFATc1 translocation from the nucleus to the cytoplasm, consequently increasing the nuclear pool of NFATc1. Additionally, the inhibition of cdc2-mediated NFATc1 phosphorylation causes an elevation of osteoclast differentiation or TRAP-positive staining in zebrafish scales. Our results suggest that cdc2 is a novel NFAT protein kinase that negatively regulates osteoclast differentiation.

Abnormal lacuno-canalicular network and negative correlation between serum osteocalcin and Cobb angle indicate abnormal osteocyte function in adolescent idiopathic scoliosis

Adolescent idiopathic scoliosis (AIS) is a prevalent spinal deformity occurring during peripubertal growth period that affects 1-4% of adolescents globally without clear etiopathogenetic mechanism. Low bone mineral density is an independent and significant prognostic factor for curve progression. Currently, the cause underlying low bone mass in AIS remains elusive. Osteocytes play an important role in bone metabolism and mineral homeostasis, but its role in AIS has not been studied. In the present study, iliac bone tissues were harvested from 21 patients with AIS (mean age of 14.3 ± 2.20 yr old) with a mean Cobb angle of 55.6 ± 10.61° and 13 non-AIS controls (mean age of 16.5 ± 4.79 yr old) intraoperatively. Acid-etched scanning electron microscopy (SEM) images of AIS demonstrated abnormal osteocytes that were more rounded and cobblestone-like in shape and were aligned in irregular clusters with shorter and disorganized canaliculi. Further quantitative analysis with FITC-Imaris technique showed a significant reduction in the canalicular number and length as well as an increase in lacunar volume and area in AIS. SEM with energy-dispersive X-ray spectroscopy analysis demonstrated a lower calcium-to-phosphorus ratio at the perilacunar/canalicular region. Moreover, microindentaion results revealed lower values of Vickers hardness and elastic modulus in AIS when compared with controls. In addition, in the parallel study of 99 AIS (27 with severe Cobb angle of 65.8 ± 14.1° and 72 with mild Cobb angle of 26.6 ± 9.1°) with different curve severity, the serum osteocalcin level was found to be significantly and negatively associated with the Cobb angle. In summary, the findings in this series of studies demonstrated the potential link of abnormal osteocyte lacuno-canalicular network structure and function to the observed abnormal bone mineralization in AIS, which may shed light on etiopathogenesis of AIS.-Chen, H., Zhang, J., Wang, Y., Cheuk, K.-Y., Hung, A. L. H., Lam, T.-P., Qiu, Y., Feng, J. Q., Lee, W. Y. W., Cheng, J. C. Y. Abnormal lacuno-canalicular network and negative correlation between serum osteocalcin and Cobb angle indicate abnormal osteocyte function in adolescent idiopathic scoliosis.

Human Mesenchymal Stem Cell Response to Lactoferrin-based Composite Coatings

The potential of mesenchymal stem cells (MSCs) for implantology and cell-based therapy represents one of the major ongoing research subjects within the last decades. In bone regeneration applications, the various environmental factors including bioactive compounds such as growth factors, chemicals and physical characteristics of biointerfaces are the key factors in controlling and regulating osteogenic differentiation from MSCs. In our study, we have investigated the influence of Lactoferrin (Lf) and Hydroxyapatite (HA) embedded within a biodegradable PEG-PCL copolymer on the osteogenic fate of MSCs, previous studies revealing an anti-inflammatory potential of the coating and osteogenic differentiation of murine pre-osteoblast cells. The copolymer matrix was obtained by the Matrix Assisted Pulsed Laser Evaporation technique (MAPLE) and the composite layers containing the bioactive compounds (Lf, HA, and Lf-HA) were characterised by Scanning Electron Microscopy and Atomic Force Microscopy. Energy-dispersive X-ray spectroscopy contact angle and surface energy of the analysed coatings were also measured. The characteristics of the composite surfaces were correlated with the viability, proliferation, and morphology of human MSCs (hMSCs) cultured on the developed coatings. All surfaces were found not to exhibit toxicity, as confirmed by the LIVE/DEAD assay. The Lf-HA composite exhibited an increase in osteogenic differentiation of hMSCs, results supported by alkaline phosphatase and mineralisation assays. This is the first report of the capacity of biodegradable composite layers containing Lf to induce osteogenic differentiation from hMSCs, a property revealing its potential for application in bone regeneration.

Skeleton bones in museum indoor environments offer niches for fungi and are affected by weathering and deposition of secondary minerals

Large skeleton specimens are often featured as iconic open displays in Natural History Museums, for example, the blue whale 'Hope' at the Natural History Museum, London. A study on Hope's bone surface was performed to assess the biodeterioration potential of fungi. Fungi were isolated, and a fungal internal transcribed spacer (ITS) clone library survey was performed on dust and bone material. Mineral particles derived from bone and dust were analysed using energy dispersive X-ray spectroscopy, variable pressure scanning electron microscopy (SEM) and high vacuum SEM. Results showed that bone material, although mainly mineral in nature, and therefore less susceptible than organic materials to biodeterioration phenomena in the indoor environments, offers niches for specialized fungi and is affected by unusual and yet not so well-documented mechanisms of alteration. Areas of bone surface were covered with a dense biofilm mostly composed of fungal hyphae, which produced tunnelling and extensive deposition of calcium and iron-containing secondary minerals. Airborne halophilic and xerophilic fungi including taxa grouping into Ascomycota and Basidiomycota, capable of displacing salts and overcome little water availability, were found to dominate the microbiome of the bone surface.

Scalable MSC-derived bone tissue modules: In vitro assessment of differentiation, matrix deposition, and compressive load bearing

Enhancements to the mechanical properties of modular designs for bone tissue engineering could increase their clinical applications. In this study, bone marrow mesenchymal stem cells (MSCs) and hydroxyapatite (HAP) microgranules were encapsulated in polyelectrolyte complex membranes composed of chondroitin 4-sulfate (C4S), carboxymethyl cellulose (CMC) and chitosan. Microcapsules were formed with and without HAP microgranules, and cultured in either osteoinduction medium (Osteo) or expansion medium (Exp) to produce four microcapsule conditions: Osteo, Osteo+HAP, Exp, and Exp+HAP. Microcapsules facilitated alkaline phosphatase secretion and deposition of bone specific proteins (osteocalcin and osteopontin) by encapsulated MSCs over 28 days of osteogenic culture. SEM and micro-CT analysis showed cell-deposited mineral covering the surfaces of the HAP microgranules and interior of the microcapsule membrane. The mineralized microcapsules could be combined and fused into cylindrical constructs (4 × 5 mm, W × H), and uniaxial compression tests confirmed that microcapsule mineralization greatly enhanced the yield stresses of Osteo and Osteo+HAP fused constructs (10.4 ± 4.4 MPa and 6.4 ± 2.8 MPa), compared to only HAP microgranules (Exp+HAP, 0.5 ± 0.3 MPa). The C4S/CMC/Chitosan microcapsules provide a platform allowing pre-mineralization of microcapsules in vitro for later assembly of larger load-bearing constructs, or for use as an injectable bone regeneration strategy. STATEMENT OF SIGNIFICANCE: Clinical translation of bone tissue engineering is limited by the difficulty of generating space filling implants that both resist compressive loading, and simultaneously deliver cells throughout the bone defect. Here, we present the design of a microcapsule system containing both stem cells capable of rebuilding bone tissue, and a mechanically tough bone-like mineral, that imparts compression resistance to the microcapsules. The microcapsules support stem cell differentiation to an osteogenic phenotype, that can mineralize the microcapsule membrane and interior. The mineralized microcapsules can be assembled into larger bone constructs, and have mechanical properties on par with trabecular bone.

Material and regenerative properties of an osteon-mimetic cortical bone-like scaffold

The objective of this work was to fabricate a rigid, resorbable and osteoconductive scaffold by mimicking the hierarchical structure of the cortical bone. Aligned peptide-functionalize nanofiber microsheets were generated with calcium phosphate (CaP) content similar to that of the natural cortical bone. Next, the CaP-rich fibrous microsheets were wrapped around a microneedle to form a laminated microtube mimicking the structure of an osteon. Then, a set of the osteon-mimetic microtubes were assembled around a solid rod and the assembly was annealed to fuse the microtubes and form a shell. Next, an array of circular microholes were drilled on the outer surface of the shell to generate a cortical bone-like scaffold with an interconnected network of Haversian- and Volkmann-like microcanals. The CaP content, porosity and density of the bone-mimetic microsheets were 240 wt%, 8% and 1.9 g/ml, respectively, which were close to that of natural cortical bone. The interconnected network of microcanals in the fused microtubes increased permeability of a model protein in the scaffold. The cortical scaffold induced osteogenesis and vasculogenesis in the absence of bone morphogenetic proteins upon seeding with human mesenchymal stem cells and endothelial colony-forming cells. The localized and timed-release of morphogenetic factors significantly increased the extent of osteogenic and vasculogenic differentiation of human mesenchymal stem cells and endothelial colony-forming cells in the cortical scaffold. The cortical bone-mimetic nature of the cellular construct provided balanced rigidity, resorption rate, osteoconductivity and nutrient diffusivity to support vascularization and osteogenesis.

Biosynthesis and characterization of hydroxyapatite and its composite (hydroxyapatite-gelatin-chitosan-fibrin-bone ash) for bone tissue engineering applications

Hydroxyapatite (HAp) is a bioactive and biocompatible material possessing osteoconductive properties used widely in the biomedical sector. In the present study, synthesis of hydroxyapatite (HAp) using a Klebsiella pneumoniae SM24 (phosphate solubilizing bacteria) isolated from the slaughterhouse. HAp synthesized using biological source showed efficient and positive enzymatic activity in the National Botanical Research Institute Phosphate Medium (NBRIP). Characterization of HAp using FTIR revealed the presence of phosphate group hydroxyapatite and XRD spectra showed polycrystalline nature. The morphological characterization of HAp using FESEM revealed the mesoporous structure and EDX spectrum indicated presence of Ca and P as the major components. In addition, a new bone composite was prepared using the synthesized HAp, Gelatine (G), Chitosan (C), Fibrin (F) and Bone ash (HApGCF) using Simulated Body Fluid (SBF) solution. The confirmation of chemical and structural characteristics of HApGCF bone composite was achieved using FTIR, XRD and SEM analyses. The HApGCF bone composite was tested over osteoblast MG-63 cells showing effective biocompatibility and osteoblast attachment on the composite surface. Therefore, the present report proposes the in vitro application of HApGCF bone composite as a replacement for major bone damage and injury in a biocompatible and non-toxic way.

Developmental Transformation and Reduction of Connective Cavities within the Subchondral Bone

It is widely accepted that the subchondral bone (SCB) plays a crucial role in the physiopathology of osteoarthritis (OA), although its contribution is still debated. Much of the pre-clinical research on the role of SCB is concentrated on comparative evaluations of healthy vs. early OA or early OA vs. advanced OA cases, while neglecting how pure maturation could change the SCB’s microstructure. To assess the transformations of the healthy SCB from young age to early adulthood, we examined the microstructure and material composition of the medial condyle of the femur in calves (three months) and cattle (18 months) for the calcified cartilage (CC) and the subchondral bone plate (SCBP). The entire subchondral zone (SCZ) was significantly thicker in cattle compared to calves, although the proportion of the CC and SCBP thicknesses were relatively constant. The trabecular number (Tb.N.) and the connectivity density (Conn.D) were significantly higher in the deeper region of the SCZ, while the bone volume fraction (BV/TV), and the degree of anisotropy (DA) were more affected by age rather than the region. The mineralization increased within the first 250 µm of the SCZ irrespective of sample type, and became stable thereafter. Cattle exhibited higher mineralization than calves at all depths, with a mean Ca/P ratio of 1.59 and 1.64 for calves and cattle, respectively. Collectively, these results indicate that the SCZ is highly dynamic at early age, and CC is the most dynamic layer of the SCZ.

Halloysite-alkaline phosphatase system-A potential bioactive component of scaffold for bone tissue engineering

Alkaline phosphatase (ALP) was sucessfully incorporated into the halloysite (HAL) nanotubes, as confirmed by FTIR-ATR and XRD analyses. The loading efficiency (LE) of ALP was found to be 13.5%, while its encapsulation efficiency (EE) was estimated to be around 27%, as determined using the Bradford test. The influence of the immobilization in HAL on the enzyme activity was measured using standard ALP activity assay. Immobilized ALP effectively induced the bomineralization process, as showed by SEM, EDS, and XRD studies. As a result, calcium phosphate was produced in the form of hydroxyapatite cauliflower-like structures, with a slight content of calcium hydroxide. Interestingly, the encapsulation of ALP guest molecules in the HAL nanotubes considerably increased its thermal stability, most probably due to the heat sink effect. The activity of HAL-bound ALP was also found to be pH-independent in the wide range of pH values (3-10) due to the amphoteric nature of the aluminum oxide lining the HAL nanotube internal surface. Due to an increased resistance to the unfavorable conditions, which are often encountered during scaffold preparation or sterilization, ALP-HAL nanocomposite material may constitute an attractive bioactive component of the scaffolds for bone regeneration.

Zebrafish as a model to study bone maturation: Nanoscale structural and mechanical characterization of age-related changes in the zebrafish vertebral column

Zebrafish (Danio rerio) is a useful model for understanding biomedical properties of bone and are widely employed in developmental and genetics studies. Here, we have studied the development of zebrafish vertebral bone at the nanoscale from adolescence (6 months), early adulthood (10 months) to mid-life (14 months). Characterization of the bone was conducted using energy-dispersive X-ray spectroscopy (EDX), scanning electron microscopy (SEM) and PeakForce QNM atomic force microscopy (AFM) techniques. SEM and AFM revealed a lamellar structure with mineralized collagen fibrils. There was a significant increase in the wall thickness from 6 to 10 months (76%) and 10 months to 14 months (26%), which is positively correlated with nanomechanical behavior. An increase in the Ca/P ratio was found which was also positively correlated with nanomechanical properties. The change in mechanical properties and Ca/P are similar to those expected in humans when transitioning from adolescence to mid-life. We suggest that zebrafish serve as a suitable model for further studies on age-related changes in bone ultrastructure.

Carnosine-graphene oxide conjugates decorated with hydroxyapatite as promising nanocarrier for ICG loading with enhanced antibacterial effects in photodynamic therapy against Streptococcus mutans

Antimicrobial photodynamic therapy (aPDT) has been emerged as a noninvasive strategy to remove bacterial contaminants such as S. mutans from the tooth surface. Photosensitizer (PS), like indocyanine green (ICG), plays a key role in this technique which mainly suffers from the poor stability and concentration-dependent aggregation. An appropriate nanocarrier (NC) with enhanced antibacterial effects could overcome these limitations and improve the efficiency of ICG as a PS. In this study, various ICG-loaded NCs including graphene oxide (GO), GO-carnosine (Car) and GO-Car/Hydroxyapatite (HAp) were synthesized and characterized by Fourier Transform Infrared Spectroscopy (FT-IR), X-ray Diffraction (XRD), Filed Emission Scanning Electron Microscopy (FE-SEM), Energy Dispersive Spectroscopy (EDS), Zeta Potential and Ultraviolet-Visible spectrometry (UV-Vis). The colony forming unit and crystal violet assays were performed to evaluate the antimicrobial and anti-biofilm properties of PSs against S. mutans. The quantitative real-time PCR approach was also applied to determine the expression ratio of the gtfB gene in S. mutans. The zeta potential analysis and UV-Vis spectrometry indicated successful loading of ICG onto/into NCs. GO-Car/HAp showed highest amount of ICG loading (57.52%) and also highest aqueous stability after one week (94%). UV-Vis spectrometry analyses disclosed a red shift from 780 to 800 nm for the characteristic peak of ICG-loaded NCs. In the lack of aPDT, GO-Car@ICG showed the highest decrease in bacterial survival (86.4%) which indicated that Car could significantly promote the antibacterial effect of GO. GO@ICG, GO-Car@ICG and GO-Car/HAp@ICG mediated aPDT, dramatically declined the count of S. mutans strains to 91.2%, 95.5% and 93.2%, respectively (P < 0.05). The GO@ICG, GO-Car@ICG, GO-Car/HAp@ICG significantly suppressed the S. mutans biofilm formation by 51.4%, 63.8%, and 56.8%, respectively (P < 0.05). The expression of gtfB gene was considerably reduced to 6.0, 9.0 and 7.9-fold after aPDT in the presence of GO@ICG, GO-Car@ICG, GO-Car/HAp@ICG, respectively (P < 0.05). It could be concluded that the multi-functionalized GO as a novel nanocarrier could significantly enhance the ICG loading, stability, and improve its inhibitory effects as a photosensitizer in aPDT against S. mutans. These findings might provide opportunity for efficient treatment of local dental infections.

Low Doses of Simvastatin Potentiate the Effect of Sodium Alendronate in Inhibiting Bone Resorption and Restore Microstructural and Mechanical Bone Properties in Glucocorticoid-Induced Osteoporosis

By using an experimental model of dexamethasone-induced osteoporosis we investigated the effects of different therapeutic schemes combining sodium alendronate (SA) and simvastatin on bone mineral and protein composition, microstructural and mechanical remodeling. Wistar rats were randomized into eight groups: G1: non-osteoporotic; G2: osteoporotic; G3, G4, and G5: osteoporotic+SA (0.2, 0.4, and 0.8 mg/kg, respectively); G6, G7, and G8: osteoporotic+SA (0.2, 0.4, and 0.8 mg/kg, respectively)+simvastatin (0.4, 0.6, and 1 mg/kg, respectively). Osteoporosis was induced by dexamethasone (7 mg/kg, i.m.) once a week for 5 weeks. All treatments were administered for 8 weeks. Dexamethasone increased serum levels of alkaline phosphatase, calcium, phosphorus, and urea, especially in non-treated animals, which showed severe osteoporosis. Dexamethasone also induced bone microstructural fragility and reduced mechanical resistance, which were associated with a marked depletion in mineral mass, collagenous and non-collagenous protein levels in cortical and cancellous bone. Although SA has attenuated osteoporosis severity, the effectiveness of drug therapy was enhanced combining alendronate and simvastatin. The restoration in serum parameters, organic and inorganic bone mass, and mechanical behavior showed a dose-dependent effect that was potentially related to the complementary mechanisms by which each drug acts to induce bone anabolism, accelerating tissue repair.

Effects of glucose concentration on osteogenic differentiation of type II diabetes mellitus rat bone marrow-derived mesenchymal stromal cells on a nano-scale modified titanium

BACKGROUND AND OBJECTIVE

Diabetes mellitus (DM) is a common disease worldwide. Patients with DM have an increased risk of losing their teeth compared with other individuals. Dental implants are a standard of care for treating partial or full edentulism, and various implant surface treatments have recently been developed to increase dental implant stability. However, some studies have reported that DM reduces osseointegration and the success rate of dental implants. The purpose of this study was to determine the effects of high glucose levels for hard tissue formation on a nano-scale modified titanium surface.

MATERIAL AND METHODS

Titanium disks were heated at 600°C for 1 h after treatment with or without 10 m NaOH solution. All disks were incubated with type II DM rat bone marrow-derived mesenchymal stromal cells before exposure to one of four concentrations of glucose (5.5, 8.0, 12.0 or 24.0 mm). The effect of different glucose concentrations on bone marrow-derived mesenchymal stromal cell osteogenesis and inflammatory cytokines on the nano-scale modified titanium surface was evaluated.

RESULTS

Alkaline phosphatase activity decreased with increasing glucose concentration. In contrast, osteocalcin production and calcium deposition were significantly decreased at 8.0 mm glucose, but increased with glucose concentrations over 8.0 mm. Differences in calcium/phosphate ratio associated with the various glucose concentrations were similar to osteocalcin production and calcium deposition. Inflammatory cytokines were expressed at high glucose concentrations, but the nano-scale modified titanium surface inhibited the effect of high glucose concentrations.

CONCLUSION

High glucose concentration increased hard tissue formation, but the quality of the mineralized tissue decreased. Furthermore, the nano-scale modified titanium surface increased mineralized tissue formation and anti-inflammation, but the quality of hard tissue was dependent on glucose concentration.

Electrochemical preparation and characterization of PNIPAM-HAp scaffolds for bone tissue engineering

In the last decade, a variety of methods for fabrication of three-dimensional biomimetic scaffolds based on hydrogels have been developed for tissue engineering. However, many methods require the use of catalysts which compromises the biocompatibility of the scaffolds. The electrochemical polymerization (ECP) of acrylic monomers has received an increased attention in recent years due to its versatility in the production of highly biocompatible coatings for the electrodes used in medical devices. The main aim of this work was the use of ECP as scaffold fabrication technique to produce highly porous poly(N-isopropylacrylamide) (PNIPAM)/hydroxyapatite (HAp) composite for bone tissue regeneration. The prepared PNIPAM-HAp porous scaffolds were characterized by SEM, FTIR, water swelling, porosity measurements and X-ray diffraction (XRD) techniques. FTIR indicates that ECP promotes a successful conversion of NIPAM to PNIPAM. The water swelling and porosity were shown to be controlled by the HAp content in PNIPAM-HAp scaffolds. The PNIPAM-HAp scaffolds exhibited no cytotoxicity to MG63 cells, showing that ECP are potentially useful for the production of PNIPAM-HAp scaffolds. To address the osteomyelitis, a significant complication in orthopedic surgeries, PNIPAM-HAp scaffolds were loaded with the antibiotic oxacillin. The oxacillin release and the bacterial killing activity of the released oxacillin from PNIPAM-HAp against S. aureus and P. aeruginosa were demonstrated. These observations demonstrate that ECP are promising technique for the production of non-toxic, biocompatible PNIPAM-HAp scaffolds for tissue engineering.