foxe1 mutant zebrafish show indications of a hypothyroid phenotype and increased sensitivity to ethanol for craniofacial malformations.

BACKGROUND: FOXE1 mutations in humans are associated with cleft palate and hypothyroidism. We previously developed a foxe1 mutant zebrafish demonstrating mineralization defects in larvae. In the present study, we investigate the thyroid status and skeletal phenotype of adult foxe1 mutants. RESULTS: Mutant fish have increased expression of tshß in the pituitary, and of hepatic dio1 and dio2. In plasma, we found higher Mg levels. Together these findings are indicative of hypothyroidism. We further observed mineralization defects in scales due to enhanced osteoclast activity as measured by increased expression levels of tracp, ctsk, and rankl. Gene-environment interactions in the etiology of FOXE1-related craniofacial abnormalities remain elusive, which prompts the need for models to investigate genotype-phenotype associations. We here investigated whether ethanol exposure increases the risk of developing craniofacial malformations in foxe1 mutant larvae that we compared to wild types. We found in ethanol-exposed mutants an increased incidence of developmental malformations and marked changes in gene expression patterns of cartilage markers (sox9a), apoptotic markers (casp3b), retinoic acid metabolism (cyp26c1), and tissue hypoxia markers (hifaa, hifab). CONCLUSION: Taken together, this study shows that the foxe1 mutant zebrafish recapitulates phenotypes associated with FOXE1 mutations in human patients and a clear foxe1-ethanol interaction.

Histomorphometric Analysis of Flaplessly Placed and Early Loaded One-Piece Mini Dental Implants in Overdenture Patients.

Mini dental implants (MDIs) are an affordable alternative for overdentures in medically compromised patients with reduced bone volume. This human study reports the histomorphometric analysis of early loaded and flaplessly placed tapered, one-piece MDIs (ILZ, Southern Implants; Sa: 1.5 µm) after 7 to 11 months in function. Patients agreed to have an additional MDI placed and removed for evaluation. MDI stability was assessed via Periotest prior to implant removal. Histologic sections of four mandibular and three maxillary MDIs with surrounding bone were processed, and the bone-to-implant contact (BIC) was analyzed. At retrieval, the MDIs were in function for more than 6 months, were clinically healthy, and had mean probing pocket depths of 1.4 mm and 1.6 mm in the maxilla and mandible, respectively. Periotest values were < 5.5, indicating clinical stability. Most of the screw threads were filled with bone and revealed an intimate BIC, without any signs of intervening fibrous tissue layer. In both arches, the mean BIC was 68.5%. Large osteocytes could be identified in the calcified tissue, indicative of mature peri-implant bone. It can be concluded that MDIs, when loaded within 2 weeks in either arch, provide proper clinical stability and high BIC after 6 months.

Early bone ingrowth and segmental stability of a trussed titanium cage versus a polyether ether ketone cage in an ovine lumbar interbody fusion model.

BACKGROUND CONTEXT: Lumbar interbody fusion is an effective treatment for unstable spinal segments. However, the time needed to establish a solid bony interbody fusion between the two vertebrae may be longer than twelve months after surgery. During this time window, the instrumented spinal segment is assumed to be at increased risk for instability related complications such as cage migration or subsidence. It is hypothesized that the design of new interbody cages that enable direct osseointegration of the cage at the vertebral endplates, without requiring full bony fusion between the two vertebral endplates, might shorten the time window that the instrumented spinal segment is susceptible to failure. PURPOSE: To quantify the bone ingrowth and resulting segmental stability during consolidation of lumbar interbody fusion using two different cage types. STUDY DESIGN: Preclinical ovine model. METHODS: Seven skeletally mature sheep underwent bi-segmental lumbar interbody fusion surgery with one conventional polyether ether ketone (PEEK) cage, and one newly developed trussed titanium (TT) cage. After a postoperative time period of 13 weeks, non-destructive range of motion testing, and histologic analysis was performed. Additionally, sample specific finite element (FE) analysis was performed to predict the stability of the interbody fusion region alone. RESULTS: Physiological movement of complete spinal motion segments did not reveal significant differences between the segments operated with PEEK and TT cages. The onset of creeping substitution within the cage seemed to be sooner for PEEK cages, which led to significantly higher bone volume over total volume (BV/TV) compared with the TT cages. TT cages showed significantly more direct bone to implant contact (BIC). Although the mean stability of the interbody fusion region alone was not statistically different between the PEEK and TT cages, the variation within the cage types illustrated an all-or-nothing response for the PEEK cages while a more gradual increase in stability was found for the TT cages. CONCLUSIONS: Spinal segments operated with conventional PEEK cages were not different from those operated with newly developed TT cages in terms of segmental stability but did show a different mechanism of bone ingrowth and attachment. Based on the differences in development of bony fusion, we hypothesize that TT cages might facilitate increased early segmental stability by direct osseointegration of the cage at the vertebral endplates without requiring complete bony bridging through the cage. CLINICAL SIGNIFICANCE: Interbody cage type affects the consolidation process of spinal interbody fusion. Whether different consolidation processes of spinal interbody fusion result in clinically significant differences requires further investigation.

Combined effect of undersized surgical technique and axial compression on the primary implant stability and host bone architecture.

AIM: The aim of this study was to investigate the combined effect of the lateral-compression of host-bone (undersized-osteotomy-preparation) and axial-compression of host-bone (not drilling the full length of the implant) on the primary-implant-stability and the host-bone-architecture. MATERIALS AND METHODS: In this experimental-study, 44 dental implants (diameter-4.2 mm; length-10 mm; Dyna®) were installed in the femoral-condyles of four cadaver-goats using four different surgical approaches (11 implant/surgical approach; n = 11). Approach-1: Standard preparation according to the manufacturer's guidelines. The bone-cavity was prepared up to 10 mm in depth and 4 mm in diameter. Approach-2: Preparation up to 8 mm in depth and 4 mm in diameter. Approach-3: Preparation up to 10 mm in depth. Approach-4: The bone-cavity was prepared up to 8 mm in depth and 3.6 mm in diameter. Insertion torque (n = 11), removal torque (n = 7) and % bone-implant contact (n = 4) measurements were recorded. Bone architecture was assessed by micro-computer tomography and histological analysis (n = 4). RESULTS: For approaches 2, 3, and 4 (P < .05), insertion-torque values were significantly higher as compared to approach 1. Regarding the bone-implant-contact percentage (%BIC), approach 3 and 4 were significantly higher compared to approach 1 and 2 (P<.05). For approach 2, the %bone volume (%BV) was significantly higher as compared to approach 1 (P<.05) for the most the inner zone of host bone in proximity of the implant. CONCLUSION: Lateral and axial compression improved the primary-implant-stability and therefore this new surgical-technique should be considered as an alternative approach especially for placing implants in low-density bone. Nevertheless, additional in vivo studies should be performed.

Three-dimensional evaluation of marginal and internal fit of 3D-printed interim restorations fabricated on different finish line designs.

PurposeTo evaluate the influence of fabrication method and finish line design on marginal and internal fit of full-coverage interim restorations. MethodsFour typodont models of maxillary central-incisor were prepared for full-coverage restorations. Four groups were defined; knife-edge (KE), chamfer (C), rounded-shoulder (RS), rounded-shoulder with bevel (RSB). All preparations were digitally scanned. A total of 80 restorations were fabricated; 20 per group (SLA/3D-printed n=10, milled n=10). All restorations were positioned on the master die and scanned using micro-computed tomography. The mean gaps were measured digitally (ImageJ). The results were compared using MANOVA (α=.05). ResultsInternal and marginal gaps were significantly influenced by fabrication method (P=.000) and finish-line design (P=.000). 3D-Printed restorations showed statistically significant lower mean gap compared to milled restorations at all points (P=.000). The mean internal gap for 3D-printed restorations were 66, 149, 130, 95µm and for milled restorations were 89, 177, 185, 154µm for KE, C, RS, RSB respectively. The mean absolute marginal discrepancy in 3D-printed restorations were (30, 41, 30, 28µm) and in milled restorations were (56, 54, 52, 38µm) for KE, C, RS, RSB respectively. ConclusionsThe fabrication methods showed more of an influence on the fit compared to the effect of the finish-line design in both milled and printed restorations. SLA-printed interim restorations exhibit lower marginal and internal gap than milled restorations. Nonetheless, for both techniques, all values were within the reported values for CAD/CAM restorations. Significance3D-printing can offer an alternative fabrication method comparable to those of milled restorations.

Osteogenesis around CaP-coated titanium implants visualized using 3D histology and micro-computed tomography.

Calcium phosphate (CaP) coatings can enhance the performance of bone implants in compromised conditions, such as osteoporosis. Therefore, this study compared non-coated vs. CaP-coated (n = 8) titanium implants in osteoporotic ovariectomized (OVX) rats. Bone volume (BV) was assessed using micro-computer tomography (micro-CT) and three-dimensional (3D) histology, in three zones from the implant surface. Bone remodeling was assessed using fluorochrome labels and osteoclast staining. Micro-CT and 3D histology showed a BV reduction in OVX animals, of respectively 22.4 and 10.5%. BV was significantly increased inside all zones around CaP coatings, especially in the inner zone of the OVX animals. Fluorochrome labels were predominantly seen when the coating was applied. Osteoclasts were mainly found in the area remote from the surface of non-coated implants in control animals. For the coated implants, osteoclasts were distributed evenly, and present in direct vicinity of the surface. In conclusion, 3D histology is a suitable technique to obtain data and insight into bone architecture around implants at relatively high resolution. Bone formation was significantly reduced in osteoporotic animals. CaP coatings resulted in a higher BV directly around implants installed in osteoporotic animals, enhanced turnover, and a shift of remodeling activity toward the implant surface.

Injectable self-gelling composites for bone tissue engineering based on gellan gum hydrogel enriched with different bioglasses.

Hydrogels of biocompatible calcium-crosslinkable polysaccharide gellan gum (GG) were enriched with bioglass particles to enhance (i) mineralization with calcium phosphate (CaP); (ii) antibacterial properties and (iii) growth of bone-forming cells for future bone regeneration applications. Three bioglasses were compared, namely one calcium-rich and one calcium-poor preparation both produced by a sol-gel technique (hereafter referred to as A2 and S2, respectively) and one preparation of composition close to that of the commonly used 45S5 type (hereafter referred to as NBG). Incubation in SBF for 7 d, 14 d and 21 d caused apatite formation in bioglass-containing but not in bioglass-free samples, as confirmed by FTIR, XRD, SEM, ICP-OES, and measurements of dry mass, i.e. mass attributable to polymer and mineral and not water. Mechanical testing revealed an increase in compressive modulus in samples containing S2 and NBG but not A2. Antibacterial testing using biofilm-forming meticillin-resistant staphylococcus aureus (MRSA) showed markedly higher antibacterial activity of samples containing A2 and S2 than samples containing NBG and bioglass-free samples. Cell biological characterization using rat mesenchymal stem cells (rMSCs) revealed a stimulatory effect of NBG on rMSC differentiation. The addition of bioglass thus promotes GG mineralizability and, depending on bioglass type, antibacterial properties and rMSC differentiation.

Resolution, sensitivity, and in vivo application of high-resolution computed tomography for titanium-coated polymethyl methacrylate (PMMA) dental implants.

OBJECTIVES: The aims of this study were (i) to determine the spatial resolution and sensitivity of micro- versus nano-computed tomography (CT) techniques and (ii) to validate micro- versus nano-CT in a dog dental implant model, comparative to histological analysis. MATERIAL AND METHODS: To determine spatial resolution and sensitivity, standardized reference samples containing standardized nano- and microspheres were prepared in polymer and ceramic matrices. Thereafter, 10 titanium-coated polymer dental implants (3.2 mm in Ø by 4 mm in length) were placed in the mandible of Beagle dogs. Both micro- and nano-CT, as well as histological analyses, were performed. RESULTS: The reference samples confirmed the high resolution of the nano-CT system, which was capable of revealing sub-micron structures embedded in radiodense matrices. The dog implantation study and subsequent statistical analysis showed equal values for bone area and bone-implant contact measurements between micro-CT and histology. However, because of the limited sample size and field of view, nano-CT was not rendering reliable data representative of the entire bone-implant specimen. CONCLUSIONS: Micro-CT analysis is an efficient tool to quantitate bone healing parameters at the bone-implant interface, especially when using titanium-coated PMMA implants. Nano-CT is not suitable for such quantification, but reveals complementary morphological information rivaling histology, yet with the advantage of a 3D visualization.

Osseointegration of oral implants after delayed placement in rabbits: a microcomputed tomography and histomorphometric study.

PURPOSE: This study compared osseointegration of implants placed 14 days after implant site preparation with that of immediately placed implants in rabbit femurs. MATERIALS AND METHODS: Implants were placed bilaterally in the femoral condyles of 12 rabbits. On one side, the implants were placed 14 days after osteotomy, and the other side received implants immediately after osteotomy. Healing was assessed by microcomputed tomography and histomorphometry. RESULTS: The delayed implants (placed 14 days after osteotomy) showed better osseointegration than the immediately placed implants. Bone-to-implant contact and bone volume, as assessed by histomorphometry and microcomputed tomography, were significantly higher for the implants placed after 14 days. CONCLUSIONS: From this study, it can be concluded that early osteotomy bed preparation and placement of implants after a 2-week delay predisposes to better bone-implant interface healing.

The biological performance of injectable calcium phosphate/PLGA cement in osteoporotic rats.

Calcium phosphate cements (CPCs) including poly(D,L-lactic-co-glycolic) acid (PLGA) microparticles are promising candidates for bone regenerative applications. Previous studies with CPC/PLGA demonstrated that the material is non-toxic, biocompatible and osteoconductive. However, the outcome of these studies was based on healthy individuals and consequently does not provide information on bone substitute material performance in a compromised situation, such as osteoporosis. Therefore, this study comparatively evaluated the performance of injectable CPC/PLGA in healthy (SHAM) and osteoporotic rats (OVX) using a rat femoral condyle defect with implantation periods of 4 and 12 weeks. It was hypothesized that in OVX rats the degradation of CPC/PLGA would increase due to a higher osteoclastic activity present in osteoporotic animals and that the obtained space would be rapidly filled with newly formed bone. The results revealed an accelerated degradation of the used CPC/PLGA in osteoporotic animals, but bone formation was less compared to that in healthy animals at 4 and 12 weeks after implantation. In addition, after 4 weeks, the amount of newly formed bone under osteoporotic conditions was less in the femoral condyle defect compared to that present in a non-defect, osteoporotic control femoral condyle, but equal after 12 weeks. On the other hand, in healthy animals, the amount of newly formed bone in the femoral condyle defect was equal to that present in a non-defect control femoral condyle at 4 weeks, while higher after 12 weeks. This indicates that bone regeneration at a defect site under osteoporotic conditions is slower, but can reach native amounts after longer time periods. Consequently, bone regenerative treatments under osteoporotic conditions seem to require additional empowerment of bone substitute materials.

Processing and in vivo evaluation of multiphasic calcium phosphate cements with dual tricalcium phosphate phases.

Calcium phosphate cements (CPCs) use the simultaneous presence of several calcium phosphates phases. This is done to generate specific bulk and in vivo properties. This work has processed and evaluated novel multiphasic CPCs containing dual tricalcium phosphate (TCPs) phases. Dual TCPs containing α- and ß-TCP phases were obtained by thermal treatment. Standard CPC (S-CPC) was composed of α-TCP, anhydrous dicalcium phosphate and precipitated hydroxyapatite, while modified CPC (DT-CPC) included both α- and ß-TCP. Physicochemical characterization of these CPCs was based on scanning electron microscopy, X-ray diffraction, specific surface area (SSA) and particle size (PS) analysis and mechanical properties. This characterization allowed the selection of one DT-CPC for setting time, cohesion and biological assessment compared with S-CPC. Biological assessment was carried out using a tibial intramedullary cavity model and subcutaneous pouches in guinea pigs. Differences in the surface morphology and crystalline phases of the treated TCPs were detected, although PS analysis of the milled CPC powders produced similar results. SSA analysis was significantly higher for DT-CPC with α-TCP treated at 1100°C for 5h. Poorer mechanical properties were found for DT-CPC with α-TCP treated at 1000°C. Setting time and cohesion, as well as the in vivo performance, were similar in the selected DT-CPC and the S-CPC. Both CPCs created the desired host reactions in vivo.

Bone formation analysis: effect of quantification procedures on the study outcome.

Quantification of the amount of newly formed bone is an essential part of bone regeneration studies. Histomorphometry, based on histological sections of plastic-embedded specimens, is the most frequently applied technique in this assessment. Before performing image analysis, a specific region of interest (ROI) has to be determined. Based on the histological procedure, different areas within the ROI can be discriminated and assigned to relevant tissue structures. However, in literature not much attention is paid to the effect of the histological procedures on the final outcome of the histomorphometrical measurements on bone regeneration. In this study, the histomorphometrical bone formation of the intramedullary cavity of the guinea pig tibia, filled with calcium phosphate cement, was quantified in plastic-embedded and paraffin-embedded specimens and in specimens analyzed with scanning electron microscopy in the backscattering mode (SEM-BS). The data showed that the histological procedure significantly affected the measured bone amount. Therefore, it is recommended that scaffold characteristics are carefully considered in selecting a proper technique for the analysis of bone formation in bone tissue engineering studies. The results of this study identified high-resolution SEM-BS and elastic van Gieson staining of decalcified histological sections as recommendable techniques for evaluating bone formation.

Scanning electron microscopy stereoimaging for three-dimensional visualization and analysis of cells in tissue-engineered constructs: technical note.

In tissue engineering research, various three-dimensional (3D) techniques are available to study cell morphology, biomaterials, and their relations. To overcome disadvantages of frequently used imaging techniques, in the current study stereoimaging scanning electron microscopy (SEM) is proposed. First, the 3D SEM application was validated using a series of standardized microspheres. Thereafter, MC-3T3 cell morphology was visualized and cell parameters as cell height were quantified on titanium and calcium-phosphate materials using 3D reconstruction software. Besides 3D visualization of the cells, quantitative assessment showed significant substrate dependency of cell spreading in time. Such quantification of cell spreading kinetics can be used for optimization of tissue engineering scaffold surface properties. However, further standardization of SEM image acquisition and 3D SEM software settings are still essential for 3D cell analysis.

In-vivo generation of bone via endochondral ossification by in-vitro chondrogenic priming of adult human and rat mesenchymal stem cells.

BACKGROUND: Bone grafts are required to repair large bone defects after tumour resection or large trauma. The availability of patients' own bone tissue that can be used for these procedures is limited. Thus far bone tissue engineering has not lead to an implant which could be used as alternative in bone replacement surgery. This is mainly due to problems of vascularisation of the implanted tissues leading to core necrosis and implant failure. Recently it was discovered that embryonic stem cells can form bone via the endochondral pathway, thereby turning in-vitro created cartilage into bone in-vivo. In this study we investigated the potential of human adult mesenchymal stem cells to form bone via the endochondral pathway. METHODS: MSCs were cultured for 28 days in chondrogenic, osteogenic or control medium prior to implantation. To further optimise this process we induced mineralisation in the chondrogenic constructs before implantation by changing to osteogenic medium during the last 7 days of culture. RESULTS: After 8 weeks of subcutaneous implantation in mice, bone and bone marrow formation was observed in 8 of 9 constructs cultured in chondrogenic medium. No bone was observed in any samples cultured in osteogenic medium. Switch to osteogenic medium for 7 days prevented formation of bone in-vivo. Addition of ß-glycerophosphate to chondrogenic medium during the last 7 days in culture induced mineralisation of the matrix and still enabled formation of bone and marrow in both human and rat MSC cultures. To determine whether bone was formed by the host or by the implanted tissue we used an immunocompetent transgenic rat model. Thereby we found that osteoblasts in the bone were almost entirely of host origin but the osteocytes are of both host and donor origin. CONCLUSIONS: The preliminary data presented in this manuscript demonstrates that chondrogenic priming of MSCs leads to bone formation in vivo using both human and rat cells. Furthermore, addition of ß-glycerophosphate to the chondrogenic medium did not hamper this process. Using transgenic animals we also demonstrated that both host and donor cells played a role in bone formation. In conclusion these data indicate that in-vitro chondrogenic differentiation of human MSCs could lead to an alternative and superior approach for bone tissue engineering.

Three-dimensional localization of implanted biomaterials in anatomical and histological specimens using combined X-ray computed tomography and three-dimensional surface reconstruction: a technical note.

For adequate histological processing of implanted biomaterials or tissue-engineered constructs, it is sometimes essential to obtain insight into the localization of structures inside the tissue samples. Observation of three-dimensional (3D) surface reconstruction, including basic photorealistic texture characteristics as surface pattern and color combined with X-ray computed tomography 3D reconstruction at different levels, is a useful approach to localize anatomical or implanted structures within experimental tissue samples. Because of the possible observation of structures of interest in a 3D environment, fusion of these techniques can greatly facilitate histological processing.

Micro-computed tomographical imaging of soft biological materials using contrast techniques.

The aim of this work was to introduce high-resolution computed tomography (micro-CT) for scaffolds made from soft natural biomaterials, and to compare these data with the conventional techniques scanning electron microscopy and light microscopy. Collagen-based scaffolds were used as examples. Unlike mineralized tissues, collagen scaffolds do not provide enough X-ray attenuation for micro-CT imaging. Therefore, various metal-based contrast agents were applied and evaluated using two structurally distinct scaffolds, one with round pores and one with unidirectional lamellae. The optimal contrast techniques for obtaining high-resolution three-dimensional images were either a combination of osmium tetroxide and uranyl acetate, or a combination of uranyl acetate and lead citrate. The data obtained by micro-CT analysis were in line with data obtained by light and electron microscopy. However, small structures (less than a few mum) could not be visualized due to limitation of the spot size of the micro-CT apparatus. In conclusion, reliable three-dimensional images of scaffolds prepared from soft natural biomaterials can be obtained using appropriate contrast protocols. This extends the use of micro-CT analysis to soft materials, such as protein-based biomaterials.

Optimal use of silver nitrate and marginal leakage at the sealant-enamel interface using micro-CT.

PURPOSE: To investigate the optimal silver nitrate concentration and tooth immersion period for assessing marginal leakage at the sealant-enamel interface, using micro-CT. METHODS: Two experiments were conducted, using eight teeth sealed with a resin composite without etching, in dried but not desiccated, pits and fissures. Five teeth were immersed in 50% silver nitrate for 0, 1, 2, 3, and 4 hours and scanned, using micro-CT, and two evaluators using a newly developed index assessed marginal leakage at the sealant-enamel interface (Experiment A). Experiment B was carried out in the same way as Experiment A, with the difference that teeth were immersed in 50% and 60% silver nitrate for 2 and 3 hours. Reliability of scores was estimated, using weighted kappa coefficient. ANOVA and t-test were applied to test for period and concentration effects. RESULTS: Reliability of collected data was substantial. A statistically significant difference was observed between 50% silver nitrate penetration scores at 0-1 and 2-4 hours of immersion (P < 0.0001) but not between 50% silver nitrate penetration scores at 2-, 3-, and 4-hours of immersion (P > 0.05) (experiment A). Analysis in experiment B showed a period effect (P = 0.03) but no concentration (P = 0.07) and interaction effect (P = 0.64). Combining all data from 50% silver nitrate immersion, analysis showed no statistically significant difference in penetration scores between 2, 3 and 4 hours of immersion (P = 0.33). The newly developed index showed substantial reliability.

High resolution magic angle spinning NMR spectroscopy for metabolic assessment of cancer presence and Gleason score in human prostate needle biopsies.

OBJECTIVES: Histopathology of prostate needle biopsies (PNBs) is an important part in the diagnosis, prognosis and treatment evaluation of prostate cancer. The determination of metabolite levels in the same biopsies may have additional clinical value. Here, we demonstrate the use of non-destructive high resolution magic angle spinning (HRMAS) proton NMR Spectroscopy for the assessment of metabolic profiles of prostate tissue in PNBs as commonly obtained in standard clinical practice. MATERIALS AND METHODS: PNBs that were taken routinely from 48 patients suspected of having prostate cancer were subjected to HRMAS proton NMR spectroscopy. Subsequent histopathology of the same biopsies classified the tissue either as cancer (n = 10) or benign (n = 30). RESULTS: Some practical aspects of this assessment were evaluated, such as typical spectral contamination caused by the PNB procedure. Significant metabolic differences were found between malignant and benign tissue using a small set of ratio's involving signals of choline compounds, citrate and lactate. Moreover, significant correlations were observed between choline, total choline, and citrate over creatine signal ratios and the Gleason scores of tumor in PNBs and of tumor in the whole prostate. CONCLUSION: This preliminary study indicates that HRMAS NMR of routinely obtained PNBs can provide detailed metabolic information of intact prostate tissue with clinical relevance.

In vivo biocompatibility of ultra-short single-walled carbon nanotube/biodegradable polymer nanocomposites for bone tissue engineering.

Scaffolds play a pivotal role in the tissue engineering paradigm by providing temporary structural support, guiding cells to grow, assisting the transport of essential nutrients and waste products, and facilitating the formation of functional tissues and organs. Single-walled carbon nanotubes (SWNTs), especially ultra-short SWNTs (US-tubes), have proven useful for reinforcing synthetic polymeric scaffold materials. In this article, we report on the in vivo biocompatibility of US-tube reinforced porous biodegradable scaffolds in a rabbit model. US-tube nanocomposite scaffolds and control polymer scaffolds were implanted in rabbit femoral condyles and in subcutaneous pockets. The hard and soft tissue response was analyzed with micro-computed tomography (micro CT), histology, and histomorphometry at 4 and 12 weeks after implantation. The porous US-tube nanocomposite scaffolds exhibited favorable hard and soft tissue responses at both time points. At 12 weeks, a three-fold greater bone tissue ingrowth was seen in defects containing US-tube nanocomposite scaffolds compared to control polymer scaffolds. Additionally, the 12 week samples showed reduced inflammatory cell density and increased connective tissue organization. No significant quantitative difference in polymer degradation was observed among the various groups; qualitative differences between the two time points were consistent with expected degradation due to the progression of time. Although no conclusions can be drawn from the present study concerning the osteoinductivity of US-tube nanocomposite scaffolds, the results suggest that the presence of US-tubes may render nanocomposite scaffolds bioactive assisting osteogenesis.

Evaluation of the biocompatibility of calcium phosphate cement/PLGA microparticle composites.

In this study, the biocompatibility of a calcium phosphate (CaP) cement incorporating poly (D,L-lactic-co-glycolic acid) (PLGA) microparticles was evaluated in a subcutaneous implantation model in rats. Short-term biocompatibility was assessed using pure CaP discs and CaP discs incorporating PLGA microparticles (20% w/w) with and without preincubation in water. Long-term biocompatibility was assessed using CaP discs incorporating varying amounts (5, 10, or 20% w/w) and diameter sizes (small, 0-50 mum; medium, 51-100 mum, or large, 101-200 mum) of PLGA microparticles. The short-term biocompatibility results showed a mild tissue response for all implant formulations, irrespective of disc preincubation, during the early implantation periods up to 12 days. Quantitative histological evaluation revealed that the different implant formulations induced the formation of similar fibrous tissue capsules and interfaces. The results concerning long-term biocompatibility showed that all implants were surrounded by a thin connective tissue capsule (<10 layers of fibroblasts). Additionally, no significant differences in capsule and interface scores were observed between the different implant formulations. The implants containing 20% PLGA with medium- and large-sized microparticles showed fibrous tissue ingrowth throughout the implants, indicating PLGA degradation and interconnectivity of the pores. The results demonstrate that CaP/PLGA composites evoke a minimal inflammatory response. The implants containing 20% PLGA with medium- and large-sized microparticles showed fibrous tissue ingrowth after 12- and 24-weeks indicating PLGA degradation and interconnectivity of the pores. Therefore, CaP/PLGA composites can be regarded as biocompatible biomaterials with potential for bone tissue engineering and advantageous possibilities of the microparticles regarding material porosity.