Lianwen Sun

Bone mass and geometry of the tibia and the radius of master sprinters, middle and long distance runners, race-walkers and sedentary control participants: a pQCT study.

Mechanical loading is thought to be a determinant of bone mass and geometry. Both ground reaction forces and tibial strains increase with running speed. This study investigates the hypothesis that surrogates of bone strength in male and female master sprinters, middle and long distance runners and race-walkers vary according to discipline-specific mechanical loading from sedentary controls. Bone scans were obtained by peripheral Quantitative Computed Tomography (pQCT) from the tibia and from the radius in 106 sprinters, 52 middle distance runners, 93 long distance runners and 49 race-walkers who were competing at master championships, and who were aged between 35 and 94 years. Seventy-five age-matched, sedentary people served as control group. Most athletes of this study had started to practice their athletic discipline after the age of 20, but the current training regime had typically been maintained for more than a decade. As hypothesised, tibia diaphyseal bone mineral content (vBMC), cortical area and polar moment of resistance were largest in sprinters, followed in descending order by middle and long distance runners, race-walkers and controls. When compared to control people, the differences in these measures were always > 13% in male and > 23% in female sprinters (p < 0.001). Similarly, the periosteal circumference in the tibia shaft was larger in male and female sprinters by 4% and 8%, respectively, compared to controls (p < 0.001). Epiphyseal group differences were predominantly found for trabecular vBMC in both male and female sprinters, who had 15% and 18% larger values, respectively, than controls (p < 0.001). In contrast, a reverse pattern was found for cortical vBMD in the tibia, and only few group differences of lower magnitude were found between athletes and control people for the radius. In conclusion, tibial bone strength indicators seemed to be related to exercise-specific peak forces, whilst cortical density was inversely related to running distance. These results may be explained in two, non-exclusive ways. Firstly, greater skeletal size may allow larger muscle forces and power to be exerted, and thus bias towards engagement in athletics. Secondly, musculoskeletal forces related to running can induce skeletal adaptation and thus enhance bone strength.

3D-Printed Biopolymers for Tissue Engineering Application

3D printing technology has recently gained substantial interest for potential applications in tissue engineering due to the ability of making a three-dimensional object of virtually any shape from a digital model. 3D-printed biopolymers, which combine the 3D printing technology and biopolymers, have shown great potential in tissue engineering applications and are receiving significant attention, which has resulted in the development of numerous research programs regarding the material systems which are available for 3D printing. This review focuses on recent advances in the development of biopolymer materials, including natural biopolymer-based materials and synthetic biopolymer-based materials prepared using 3D printing technology, and some future challenges and applications of this technology are discussed.

Effects of physicochemical properties of nanomaterials on their toxicity.

Due to their unique size and properties, nanomaterials have numerous applications, which range from electronics, cosmetics, household appliances, energy storage, and semiconductor devices, to medical products such as biological sensors, drug carriers, bioprobes, and implants. Many of the promising properties of nanomaterials arise from their large surface to volume ratio and, therefore, nanobiomaterials that are implantable have a large contact area with the human body. Before, therefore, we can fully exploit nanomaterials, in medicine and bioengineering; it is necessary to understand how they can affect the human body. As a step in this direction, this review paper provides a comprehensive summary of the effects that the physicochemical properties of commonly used nanobiomaterials have on their toxicity. Furthermore, the possible mechanisms of toxicity are described with the aim to provide guidance concerning the design of the nanobiomaterials with desirable properties.

WISE-2005: Bed-rest induced changes in bone mineral density in women during 60 days simulated microgravity☆

To better understand the effects of prolonged bed-rest in women, 24 healthy women aged 25 to 40 years participated in 60-days of strict 6° head-down tilt bed-rest (WISE-2005). Subjects were assigned to either a control group (CON, n=8) which performed no countermeasure, an exercise group (EXE, n=8) undertaking a combination of resistive and endurance training or a nutrition group (NUT, n=8), which received a high protein diet. Using peripheral quantitative computed tomography (pQCT) and dual X-ray absorptiometry (DXA), bone mineral density (BMD) changes at various sites, body-composition and lower-leg and forearm muscle cross-sectional area were measured up to 1-year after bed-rest. Bone loss was greatest at the distal tibia and proximal femur, though losses in trabecular density at the distal radius were also seen. Some of these bone losses remained statistically significant one-year after bed-rest. There was no statistically significant impediment of bone loss by either countermeasure in comparison to the control-group. The exercise countermeasure did, however, reduce muscle cross-sectional area and lean mass loss in the lower-limb and also resulted in a greater loss of fat mass whereas the nutrition countermeasure had no impact on these parameters. The findings suggest that regional differences in bone loss occur in women during prolonged bed-rest with incomplete recovery of this loss one-year after bed-rest. The countermeasures as implemented were not optimal in preventing bone loss during bed-rest and further development is required.

The use of nanoscaled fibers or tubes to improve biocompatibility and bioactivity of biomedical materials

Nanofibers and nanotubes have recently gained substantial interest for potential applications in tissue engineering due to their large ratio of surface area to volume and unique microstructure. It has been well proved that the mechanical property of matrix could be largely enhanced by the addition of nanoscaled fibers or tubes. At present, more and more researches have shown that the biocompatibility and bioactivity of biomedical materials could be improved by the addition of nanofibers or nanotubes. In this review, the efforts using nanofibers and nanotubes to improve biocompatibility and bioactivity of biomedical materials, including polymeric nanofibers/nanotubes, metallic nanofibers/nanotubes, and inorganic nanofibers/nanotubes, as well as their researches related, are demonstrated in sequence. Furthermore, the possible mechanism of improving biocompatibility and bioactivity of biomedical materials by nanofibers or nanotubes has been speculated to be that the specific protein absorption on the nanoscaled fibers or tubes plays important roles.

Evaluation of the mechanical properties of rat bone under simulated microgravity using nanoindentation

Exposure to microgravity causes a decrease in bone mass and altered bone geometry due to the lack of weight-bearing forces on the skeleton. The mechanical properties of bone are due not only to the structure and geometry, but also to the tissue properties of the bone material itself. To study the effects of microgravity on bone tissue, the mechanical properties of tail suspension rat femurs were investigated. Twelve Sprague-Dawley rats were randomly divided into two groups, tail suspension (TS) and control (CON). On days 0 and 14, the bone mineral density (BMD) of the femurs was determined by Dual Energy X-ray Absorptiometry. After 14 days, three-point bending was used to test the mechanical properties of the whole femur and nanoindentation was used to measure the mechanical properties of the bone materials. The BMD of femurs in TS was significantly lower than that in CON. In the three-point bending testing, the breaking load, stiffness and energy absorption all decreased significantly in the TS group. In the nanoindentation tests, there was no significant difference between TS and CON in elastic modulus (E), while hardness (H) was significantly decreased and E/H significantly increased in TS. Weightlessness affects the intrinsic mechanical properties of bone at the bone material level. It is necessary to investigate further the effect of microgravity on the collagen bone matrix. Nanoindentation is a relatively new technique that is useful for investigating the above changes induced by microgravity and for assessing the efficacy of intervention.

Effect of different labor forces on fetal skull molding

Fetal head molding is important for adapting the fetal head to the birth canal during vaginal delivery; however, excessive deformation of fetal head may lead to severe complications. Although labor force is one of the major factors which cause deformation of the fetal head, its effect on fetal head molding has not been quantitatively investigated yet. We examined this effect by using a finite element modeling approach. Firstly, a geometric model was created by scanning a polyethylene replica of fetal skull model with a white light three-dimensional scanner. Secondly, a nonlinear finite element model was proposed based on the geometric model. Next, the simulation results of the proposed model were verified against the experimental data reported in other literatures and they showed good agreement with the experimental observations. After this validation, the proposed model was used to simulate the fetal skull deformations under different labor forces. Simulation results illustrated that the fetal skull diameters and modified molding index (MMI) increased when the labor force was increased. Parietal bone around bregma and frontal bone around coronal suture undertook more stress, and parietal and frontal bones around coronal suture undertook more spatial and rotational displacement under larger labor force. The suboccipito-bregmatic diameter (SOBD) was more sensitive to the changes of labor force than other fetal skull diameters. The simulation results revealed the quantitative relationship between the labor force and fetal skull molding during delivery. In the future, if the degree of fetal skull molding is directly related to that of the head injury, the relationship investigated in this study may be used to predict the head injury by measuring the labor force during delivery.

The applications of conductive nanomaterials in the biomedical field.

As their name suggests, conductive nanomaterials (CNMs) are a type of functional materials, which not only have a high surface area to volume ratio, but also possess excellent conductivity. Thus far, CNMs have been widely used in biomedical applications, such as effectively transferring electrical signals, and providing a large surface area to adsorb proteins and induce cellular functions. Recent works propose further applications of CNMs in biosensors, tissue engineering, neural probes, and drug delivery. This review focuses on common types of CNMs and elaborates on their unique properties, which indicate that such CNMs have a potential to develop into a class of indispensable biomaterials for the diagnosis and therapy of human diseases.

Use of micro-computed tomography to evaluate the effects of exercise on preventing the degeneration of articular cartilage in tail-suspended rats

Space flight has been shown to induce bone loss and muscle atrophy, which could initiate the degeneration of articular cartilage. Countermeasures to prevent bone loss and muscle atrophy have been explored, but few spaceflight or ground-based studies have focused on the effects on cartilage degeneration. In this study, we investigated the effects of exercise on articular cartilage deterioration in tail-suspended rats. Thirty-two female Sprague-Dawley rats were randomly divided into four groups (n=8 in each): tail suspension (TS), tail suspension plus passive motion (TSP), tail suspension plus active exercise (TSA), and control (CON) groups. In the TS, TSP, and TSA groups, the rat hindlimbs were unloaded for 21 days by tail suspension. Next, the cartilage thickness and volume, and the attenuation coefficient of the distal femur were evaluated by micro-computed tomography (μCT). Histological analysis was used to assess the surface integrity of the cartilage, cartilage thickness, and chondrocytes. The results showed that: (1) the cartilage thickness on the distal femur was significantly lower in the TS and TSP groups compared with the CON and TSA groups; (2) the cartilage volume in the TS group was significantly lower compared with the CON, TSA, and TSP groups; and (3) histomorphology showed that the chondrocytes formed clusters where the degree of matrix staining was lower in the TS and TSP groups. There were no significant differences between any of these parameters in the CON and TSA groups. The cartilage thickness measurements obtained by μCT and histomorphology correlated well. In general, tail suspension could induce articular cartilage degeneration, but active exercise was effective in preventing this degeneration in tail-suspended rats.

The effect of physical loading on calcaneus quantitative ultrasound measurement: a cross-section study

BackgroundPhysical loading leads to a deformation of bone microstructure and may influence quantitative ultrasound (QUS) parameters. This study aims at evaluating the effect of physical loading on bone QUS measurement, and further, on the potential of diagnosing osteoporosis using QUS method under physical loading condition.Methods16 healthy young females (control group) and 45 postmenopausal women (divided into 3 groups according to the years since menopause (YSM)) were studied. QUS parameters were measured at calcaneus under self-weight loading (standing) and no loading (sitting) conditions. Weight-normalized QUS parameter (QUS parameter measured under loading condition divided by the weight of the subject) was proposed to evaluate the influence of loading. T-test, One-Way analysis of variance (one way ANOVA) and receiver operating characteristic (ROC) analysis were applied for analysis.ResultsIn QUS parameters, mainly normalized broadband ultrasound attenuation (nBUA), measured with loading significantly differed from those measured without loading (p < 0.05). The relative changes of weight-normalized QUS parameters on postmenopausal women with respect to premenopausal women under loading condition were larger than those on traditional QUS parameters measured without loading. In ROC analysis, weight-normalized QUS parameters showed their stronger discriminatory ability for menopause.ConclusionsPhysical loading substantially influenced bone QUS measurement (mainly nBUA). Weight-normalized QUS parameters can discriminate menopause more effectively. By considering the high relationship between menopause and osteoporosis, an inference was drawn that adding physical loading during measurement may be a probable way to improve the QUS based osteoporosis diagnosis.