Biomedical Engineering: Applications, Basis and Communications

Adult articular cartilage tissue has poor capability of self-repair. Therefore, a variety of tissue engineering approaches are motivated by the clinical need for articular repair. Alginate has been used as a biomaterial for cartilage regeneration. The alginate is a natural polymer that is extracted from seaweeds and purification. However, the main drawback is the immune rejection in vivo. To overcome this problem, we have developed the biocompability of alginate using modified Korbutt method. After alginate was purified, purified alginate microcapsules were used in cartilage regeneration. Chondrocytes were seeded in purified and nonpurified alginate microcapsules, and then cell viability, proliferation and phenotype were analyzed by 3-(4,5-dimethylthiazol-2-yl)-2,5 diphenyltetrazolium bromide (MTT) assay. Reverse transcriptase-polymerase chain reaction (RT-PCR) was conducted to confirm mRNA expression on collagen type I and collagen type II for chondrocytes phenotype. Hematoxylin and eosin (H&E) and Safranin-O histological staining showed tissue growth at the interface during the first 10 days. In this study, chondrocytes in purified alginate microcapsules had higher cell viability, proliferation and more phenotype expression than those in nonpurified alginate microcapsules. The results suggest that the purified alginate microcapsule is useful for cartilage regeneration.

Titanium (Ti) is widely used for making tissue engineering implants, due to its good corrosion resistance, biocompatibility and mechanical properties. However, bare Ti does not integrate well with natural bone tissue and releases ions and particles that are harmful to the extracellular matrix. To overcome these problems, the Ti substrate could be coated with various biocompatible materials including a composite of gelatin and hydroxyapatite (HA). However, few have characterized and evaluated the coating of gelatin/HA on Ti substrate and its effect on bone related cells. In this study, samples of Ti substrate coated with gelatin/HA composite were fabricated with gelatin concentration ranging from 0 to 200 mg/L. The porous surface structure of gelatin/HA composite formed on the Ti substrate was then examined and characterized for its composition and topography by X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), and image processing and analysis software (ImageJ), respectively. Subsequently, rat bone marrow-derived mesenchymal stromal cells (BMMSC) were cultured on the surface of gelatin/HA composite on Ti substrate, and evaluated for cell morphology, proliferation, and osteo-differentiation using SEM, MTT assay, and alkaline phosphatase (ALP) assay, respectively. It is shown that gelatin enhanced binding of HA onto Ti substrate, and the topography of the porous surface structures was influenced by gelatin concentration only for the large pore sizes. Furthermore, the results indicate that the porous surface structures of gelatin/HA on Ti substrate promoted proliferation and osteo–differentiation as compared to the naked pure Ti substrate, particularly on that with concentration of gelatin at 100 mg/L. These findings, taken together, suggest that Ti substrate can be coated with different porous surface structures of gelatin/HA composite with gelatin solution of different concentrations. Such coated Ti substrates can promote cytocompitibility and osteo-differentiation of BMMSC, and thus may be of potential in development of implants and devices for bone tissue engineering.

This study investigated center-of-pressure (COP) characteristics during volitional stepping in forward, backward, and sideways directions, along with the behavioral performance measures and COP measures of volitional stepping in these directions, and the relationships between these two types of measures in healthy older and young adults. Fifteen older and 15 young adults performed rapid stepping in the three directions using each leg. Behavioral performance measures included reaction time (RT), movement time (MT), step length, and step velocity in the MT phase. COP measures included the maximum anteroposterior (COP_AP) and mediolateral COP displacement (COP_ML) in the RT phase. Stepping in each direction demonstrated unique COP characteristics. The older adults presented slower RT, MT, step velocity, and smaller COP_AP in all three stepping directions (p < 0.05), as well as smaller COP_ML in the sideways stepping direction (p < 0.017), compared to the young adults. Step velocity correlated with COP_AP and/or COP_ML in all three stepping directions for both groups (r = 0.42–0.77, p < 0.05), suggesting that stepping performances during the movement execution phase correlated with COP control during the postural preparation phase. Results suggest that stepping training prescribed to older adults to improve their balance control may include multi-directional stepping.

Gaze tracking has drawn increasing attention and applied wildly in the areas of disabled aids, medical diagnosis, etc. In this paper, a remote gaze tracking system is proposed. The system is video-based, and the video is captured under the illumination of near infrared light sources. Only one camera is employed in the system, which keeps the equipment portable for the users. The corneal glints and the pupil center, whose extraction accuracy determines the performance of the gaze tracking system, are obtained according to the gray distribution of the video frame. And then, the positions of the points on the screen that the user fixating are estimated by the gaze tracking algorithm based on cross-ratio-invariant. Additionally, a calibration procedure is necessary to eliminate the error produced by the deviation of the optical and visual axes. The proposed remote gaze tracking system has a low computational complexity and high robustness, and experiment results indicate that it is tolerant of head movement and still works well for users wearing glasses as well. Besides, the angle error of the gaze tracking system is 0.40 degree of the subjects without glasses, correspondingly, 0.48 degree of the subjects with glasses, which is comparable to most of the existing commercial systems and promising for most of the potential practical applications.

To observe acute toxicity of naked Fe₃O₄-nanoparticles in mice, ICR mice were selected and exposed once to naked Fe₃O₄-nanoparticles by tail intravenous injection with different doses, i.e. 0, 102.4, 128, 160, 200, 250 mg/kg of body weight. 15 days later, Fe₃O₄ distribution and pathologic changes in main organs were investigated. By tail intravenous injection, LD₅₀ of naked Fe₃O₄-nanoparticles in mice was 163.60 mg/kg of body weight (147.58, 181.37 mg/kg of body weight, 95% confidence interval). Deaths of mice mainly caused by decompensation and twitching were observed. Immediately after injection, nanoparticles performed fast distribution in lung, liver, spleen etc, yet little were traced in brain, heart and kidney. 15 days after injection, apparent decline of nanoparticles content in lung and spleen was observed, whereas in liver the content rose. Pathologic detection indicated local particle denaturation and necrosis in the cardiac tissue. Protein cast was seen in several kidney tubules, and extravasated blood in carunculae papillaris, yet no pathologic changes were observed in other organs. LD₅₀ of Fe₃O₄ nanoparticles (9 nm) by means of tail intravenous injection is 163.60 mg/kg, and they mainly distributed in liver, spleen, lung and caused denaturation and necrosis in the cardiac muscle and malfunction of kidney. Also, the process of excreting the particles takes a long time.

Gene networks research has grown steadily because of its potential to represent, characterize and model a wide range of systems and phenomena on the molecular level. Especially the studies on the cancer-related gene networks through complex interactions can help to provide better understanding of the formation and development of cancer. In this work, using the expressions data of normal and lung adenocarcinoma stage, mutual information networks of cancer-related genes are constructed first. Then a model for cascading failures with DNA repair function of weighted gene networks is built. Furthermore, comparisons of numerical experiments show that deleting nodes in the networks of adenocarcinoma experimental group is more likely to cause larger scales of cascading failure than the one of control group. In addition, we find that 13 genes of control group and 12 genes of experimental group are of very strong destructibility for the two networks, respectively. The failures of these genes can lead to the paralysis of the whole network. Therefore, we conclude that these genes might play important roles in keeping normal level or developing lung adenocarcinoma of organisms. The results may have certain significance for the interpretation of lung cancer development and provide beneficial inspirations to clarify lung cancer occurrence of biological mechanism.

In pelvic surgery, CT images are commonly used for diagnosis and surgical planning. The images are often displayed and manipulated in a 2D environment, which is insufficient owing to the complex geometry of a pelvic structure. Moreover, a pre-bend of the reconstruction plates is necessary, but difficult to complete, because of the lack of appropriate templates. In this study, an integrated preoperative planning system is developed to provide 3D models and physical templates so that the surgeon can simulate and observe his planning and prepare better-fitted curved plates before surgery. The proposed method can be divided into the following four stages: 3D display, bone segmentation, bone reduction, and implant placement. As for the designed curved plates, they can be fabricated as templates by means of rapid prototyping technology. Several examples, including artificial bones, real CT images and real pelvic surgery, have been presented to demonstrate the feasibility of the proposed method.

Although auscultation of the heart remains central in the detection of abnormal heart sounds and murmurs that are frequently indicative of serious cardiac pathology, the application of electronic methods to this end remains rarely used in daily clinical practice. In this report we provide a series of examples showing how the phonocardiogram can be analyzed quantitatively using color spectrographic techniques and discuss how such methods may be of future value for noninvasive cardiac monitoring. Using a sound recording system, we recorded the heart sounds and data acquisition using the program Gold Wave (http://www.goldwave.com) to collect data from a high-speed USB interface. Sample color spectrogram analysis of the obtained signals was performed using custom software written in MATLAB. Data was collected from a number of infants and adults with cardiac structural disease as well as from some normal individuals. Our data is presented as a series of 13 cases. We expect the application of spectrographic techniques to phonocardiography to grow substantially as ongoing research and clinical experience demonstrates its utility in various settings. Our evaluation of a simple, low-cost phonocardiographic recording and analysis system to assist in determining the characteristic features of heart murmurs shows promise in helping distinguish normal heart sounds, innocent systolic murmurs and pathological murmurs in children. It expected to be useful in other clinical settings as well.

Loading evaluation in biomechanics is of the most concern if reliable results are expected. A key aspect in the mechanical design of an alveolar distractor is the accurate evaluation of physiological loading for computer simulation and effective modeling. Very few information and previous works are available about this subject. A stainless steel load cell with strain gauges has been developed and manufactured, in order to get accurate values of physiological loading. The cell was attached to splints, like those used in orthodontia. The load cell was calibrated and then an "in vivo" test was carried out on four partially-edentulous patients. Load digital registers were obtained for three cases in each patient: Tongue protrusion, lower or upper lips retraction and a combination of tongue and lips during the vocalization. Records show that it is possible to interpret quantitatively the load proportionality according to the tongue and lip physiological movements. From the loads magnitude differences in four patients, it can be observed that the morphological factor or occlusion differences affect both the loads size of the tongue protrusion muscles and lip retraction due to the orbicular muscles which can vary slightly or significantly. Further studies are been carried out by considering other kind of patients suffering different pathologies.

Wireless communication within body proximal has shown great promise for the construction of body sensor network (BSN) and body area network (BAN), wherein multiple master and slave nodes were typically deployed on different human body sites for physiological measurements or personal entertainment. We reported the in-situ experiments to characterize body-proximal electric coupling over various carrier frequencies (1–200 MHz), multiple subjects and different body postures. To improve the signal fidelity and minimize the ground return path, all experiments were performed in a shielded radiofrequency (RF) chamber with single electrode configuration and battery-operated transmitter/receiver — the setup has never been reported in other literatures. Results obtained from 15 subjects quantified the attenuation patterns of the RF signal coupling with human body. The average coupling loss was approximately 24 dB at 30 MHz whist the receiver electrode was attached at a distance of 10 cm from the transmitter electrode, and the on-body coupling loss followed a two-piecewise fitting over distance. In comparison, 30 MHz RF signals propagated 1 m from body to air and from air to air were attenuated 70 dB and 80 dB, respectively. The standard deviations representing different subjects and daily variations were less than 2 dB at 30 MHz when the coupling distance was 10 cm. The difference in signal attenuation was always less than 2 dB for various postures including standing, sitting and squatting. It concluded that the RF signal within the frequency range of 25–30 MHz is capable of providing a robust and subject-independent wireless link for body-proximal BSN/BAN applications.