BMC biomedical engineering最新文献

Background: Mesenchymal stromal cells (MSCs) are widely used in clinical trials for bone repair and regeneration. Despite previous evidence showing a prominent osteogenic potential of 2D cultured CD271 enriched MSCs, the osteogenic potential of CD271 enriched cells cultured on 3D scaffold is unknown. Apatite-wollastonite glass ceramic (A-W) is an osteoconductive biomaterial shown to be compatible with MSCs. This is the first study comparing the attachment, growth kinetics, and osteogenic potential of two MSC populations, namely heterogeneous plastic adherence MSCs (PA-MSCs) and CD271-enriched MSCs (CD271-MSCs), when cultured on A-W 3D scaffold.

Results: The paired MSC populations were assessed for their attachment, growth kinetics and ALP activity using confocal and scanning electron microscopy and the quantifications of DNA contents and p-nitrophenyl (pNP) production respectively. While the PA-MSCs and CD271-MSCs had similar expansion and tri-lineage differentiation capacity during standard 2D culture, they showed different proliferation kinetics when seeded on the A-W scaffolds. PA-MSCs displayed a well-spread attachment with more elongated morphology compared to CD271- MSCs, signifying a different level of interaction between the cell populations and the scaffold surface. Following scaffold seeding PA-MSCs fully integrated into the scaffold surface and showed a stronger propensity for osteogenic differentiation as indicated by higher ALP activity than CD271-MSCs. Furthermore, A-W scaffold seeded uncultured non-enriched bone marrow mononuclear cells also demonstrated a higher proliferation rate and greater ALP activity compared to their CD271-enriched counterpart.

Conclusions: Our findings suggest that CD271-positive enrichment of a population is not beneficial for osteogenesis when the cells are seeded on A-W scaffold. Furthermore, unselected heterogeneous MSCs or BMMNCs are more promising for A-W scaffold based bone regeneration. This leads to a conclusion of broader clinical relevance for tissue engineering: on the basis of our observations here the osteogenic potential observed in 2D cell culture should not be considered indicative of likely performance in a 3D scaffold based system, even when one of the cell populations is effectively a subset of the other.

Background: Due to the presence of high noise level in tomographic series of energy filtered transmission electron microscopy (EFTEM) images, alignment and 3D reconstruction steps become so difficult. To improve the alignment process which will in turn allow a more accurate and better three dimensional tomography reconstructions, a preprocessing step should be applied to the EFTEM data series.

Results: Experiments with real EFTEM data series at low SNR, show the feasibility and the accuracy of the proposed denoising approach being competitive with the best existing methods for Poisson image denoising. The effectiveness of the proposed denoising approach is thanks to the use of a nonparametric Bayesian estimation in the Contourlet Transform with Sharp Frequency Localization Domain (CTSD) and variance stabilizing transformation (VST). Furthermore, the optimal inverse Anscome transformation to obtain the final estimate of the denoised images, has allowed an accurate tomography reconstruction.

Conclusion: The proposed approach provides qualitative information on the 3D distribution of individual chemical elements on the considered sample.

In this paper, we focus on robots used for laparoscopic surgery, which is one of the most active areas for research and development of surgical robots. We introduce research and development of laparoscope-holder robots, master-slave robots and hand-held robotic forceps. Then, we discuss future directions for surgical robots. For robot hardware, snake like flexible mechanisms for single-port access surgery (SPA) and NOTES (Natural Orifice Transluminal Endoscopic Surgery) and applications of soft robotics are actively used. On the software side, research such as automation of surgical procedures using machine learning is one of the hot topics.

Background: Currently there are no standard models with which to evaluate the biomechanical performance of calcified tissue adhesives, in vivo. We present, herein, a pre-clinical murine distal femoral bone model for evaluating tissue adhesives intended for use in both osseous and osteochondral tissue reconstruction.

Results: Cylindrical cores (diameter (Ø) 2 mm (mm) × 2 mm depth), containing both cancellous and cortical bone, were fractured out from the distal femur and then reattached using one of two tissue adhesives. The adhesiveness of fibrin glue (Tisseel^tm), and a novel, biocompatible, calcium phosphate-based tissue adhesive (OsStic^tm) were evaluated by pullout testing, in which glued cores were extracted and the peak force at failure recorded. The results show that Tisseel weakly bonded the metaphyseal bone cores, while OsStic produced > 30-fold higher mean peak forces at failure (7.64 Newtons (N) vs. 0.21 N). The failure modes were consistently disparate, with Tisseel failing gradually, while OsStic failed abruptly, as would be expected with a calcium-based material. Imaging of the bone/adhesive interface with microcomputed tomography revealed that, for OsStic, failure occurred more often within cancellous bone (75% of tested samples) rather than at the adhesive interface.

Conclusions: Despite the challenges associated with biomechanical testing in small rodent models the preclinical ex-vivo test model presented herein is both sensitive and accurate. It enabled differences in tissue adhesive strength to be quantified even for very small osseous fragments (<Ø4mm). Importantly, this model can easily be scaled to larger animals and adapted to fracture fragment fixation in human bone. The present model is also compatible with other long-term in vivo evaluation methods (i.e. in vivo imaging, histological analysis, etc.).

Background: Advancement in polymer technologies, facilitated predominantly through chemical engineering approaches or through the identification and utilization of novel renewable resources, has been a steady focus of biomaterials research for the past 50 years. Aliphatic polyesters have been exploited in numerous biomedical applications including the formulation of soft-tissue sutures, bone fixation devices, cardiovascular stents etc. Biomimetic 'soft' polymer formulations are of interest in the design of biological interfaces and specifically, in the development of implantable neuroelectrode systems intended to interface with neural tissues. Critically, soft polymer formulations have been shown to address the challenges associated with the disregulation of mechanotransductive processes and micro-motion induced inflammation at the electrode/tissue interface. In this study, a polyester-based poly(ε-decalactone)/silver nanowire (EDL:Ag) composite was investigated as a novel electrically active biomaterial with neural applications.Neural interfaces were formulated through spin coating of a polymer/nanowire formulation onto the surface of a Pt electrode to form a biocompatible EDL matrix supported by a percolated network of silver nanowires. As-formed EDL:Ag composites were characterized by means of infrared spectroscopy, scanning electron microscopy and electrochemical methods, with their cytocompatibility assessed using primary cultures of a mixed neural population obtained from the ventral mesencephalon of Sprague-Dawley rat embryos.

Results: Electrochemical characterization of various EDL:Ag composites indicated EDL:Ag 10:1 as the most favourable formulation, exhibiting high charge storage capacity (8.7 ± 1.0 mC/cm²), charge injection capacity (84.3 ± 1.4 μC/cm²) and low impedance at 1 kHz (194 ± 28 Ω), outperforming both pristine EDL and bare Pt electrodes. The in vitro biological evaluation showed that EDL:Ag supported significant neuron viability in culture and to promote neurite outgrowth, which had the average length of 2300 ± 6 μm following 14 days in culture, 60% longer than pristine EDL and 120% longer than bare Pt control substrates.

Conclusions: EDL:Ag nanocomposites are shown to serve as robust neural interface materials, possessing favourable electrochemical characteristics together with high neural cytocompatibility.

Background: In Photoacoustic imaging (PAI), the most prevalent beamforming algorithm is delay-and-sum (DAS) due to its simple implementation. However, it results in a low quality image affected by the high level of sidelobes. Coherence factor (CF) can be used to address the sidelobes in the reconstructed images by DAS, but the resolution improvement is not good enough, compared to the high resolution beamformers such as minimum variance (MV). In this paper, it is proposed to use high-resolution-CF (HRCF) weighting technique in which MV is used instead of the existing DAS in the formula of the conventional CF.

Results: The higher performance of HRCF is proved numerically and experimentally. The quantitative results obtained with the simulations show that at the depth of 40 mm, in comparison with DAS+CF and MV+CF, HRCF improves the full-width-half-maximum of about 91% and 15% and the signal-to-noise ratio about 40% and 14%, respectively.

Conclusion: Proposed method provides a high resolution along with a low level of sidelobes for PAI.

Magnetic resonance imaging (MRI) is an inherently slow imaging modality, since it acquires multi-dimensional k-space data through 1-D free induction decay or echo signals. This often limits the use of MRI, especially for high resolution or dynamic imaging. Accordingly, many investigators has developed various acceleration techniques to allow fast MR imaging. For the last two decades, one of the most important breakthroughs in this direction is the introduction of compressed sensing (CS) that allows accurate reconstruction from sparsely sampled k-space data. The recent FDA approval of compressed sensing products for clinical scans clearly reflect the maturity of this technology. Therefore, this paper reviews the basic idea of CS and how this technology have been evolved for various MR imaging problems.

Background: Frailty assessment is a critical approach in assessing the health status of older people. The clinical tools deployed by geriatricians to assess frailty can be grouped into two categories; using a questionnaire-based method or analyzing the physical performance of the subject. In performance analysis, the time taken by a subject to complete a physical task such as walking over a specific distance, typically three meters, is measured. The questionnaire-based method is subjective, and the time-based performance analysis does not necessarily identify the kinematic characteristics of motion and their root causes. However, kinematic characteristics are crucial in measuring the degree of frailty.

Results: The studies reviewed in this paper indicate that the quantitative analysis of activity of daily living, balance and gait are significant methods for assessing frailty in older people. Kinematic parameters (such as gait speed) and sensor-derived parameters are also strong markers of frailty. Seventeen gait parameters are found to be sensitive for discriminating various frailty levels. Gait velocity is the most significant parameter. Short term monitoring of daily activities is a more significant method for frailty assessment than is long term monitoring and can be implemented easily using clinical tests such as sit to stand or stand to sit. The risk of fall can be considered an outcome of frailty.

Conclusion: Frailty is a multi-dimensional phenomenon that is defined by various domains; physical, social, psychological and environmental. The physical domain has proven to be essential in the objective determination of the degree of frailty in older people. The deployment of inertial sensor in clinical tests is an effective method for the objective assessment of frailty.

Background: Long double-stranded RNAs (dsRNAs) are duplex RNAs that can induce immune response when present in mammalian cells. These RNAs are historically associated with viral replication, but recent evidence suggests that human cells naturally encode endogenous dsRNAs that can regulate antiviral machineries in cellular contexts beyond immune response.

Results: In this study, we use photochromic organic compound spiropyran to profile and quantitate dsRNA expression. We show that the open form of spiropyran, merocyanine, can intercalate between RNA base pairs, which leads to protonation and alteration in the spectral property of the compound. By quantifying the spectral change, we can detect and quantify dsRNA expression level, both synthetic and cellular. We further demonstrate that spiropyrans can be used as a molecular diagnostic tool to profile endogenously expressed dsRNAs. Particularly, we show that spiropyrans can robustly detect elevated dsRNA levels when colorectal cancer cells are treated with 5-aza-2'-deoxycytidine, an FDA-approved DNA-demethylating agent used for chemotherapy, thus demonstrating the use of spiropyran for predicting responsiveness to the drug treatment.

Conclusion: As dsRNAs are signature of virus and accumulation of dsRNAs is implicated in various degenerative disease, our work establishes potential application of spiropyrans as a simple spectral tool to diagnose human disease based on dsRNA expression.