Physiochemical and Biological Properties of Modified Collagen Sponge from Porcine Skin

The aim of the present study was to compare one-step method to EDC/NHS crosslinking （EDC/NHS group） and one-step simultaneous method to EDC/NHS crosslinking and heparin immobilization （EDC/NHS- Heparin group） in improving physiochemical and biological properties of native collagen sponge （Control group）. Modified collagen sponge overcome the disadvantages of native collagen sponge. IR spectra suggest the change of the functional groups. DSC data indicate that the stability of caloric transformation in EDC/NHS group is slightly higher than that of EDC/NHS-Heparin group. The crosslinking degree, stability against enzymes, stability in morphologically and biomechanical properties of EDC/NHS-Heparin group are higher than those of EDC/NHS group, whereas, the water-binding capacity in EDC/NHS-Heparin group is lower than that of EDC/NHS group. HUVECs in EDC/NHS-Heparin group scaffold proliferate fast, migrate well and distribute uniformly. One-step simultaneous method gains the better effects in above aspects, heparinized collagen matrices increase in angiogenic potential and suit for defect repairing and tissue engineering.

Extraction and Isolation of Type Ⅰ,Ⅲ and Ⅴ Collagens and Their SDS-PAGE Analyses

Type Ⅰ Ⅲ and Ⅴ collagens were extracted from bovine dermis and cornea by using pepsin treatment in acetic acid solution, followed by salt precipitation and dialysis, to purify and isolate each type of collagens. The preparation process was analyzed by using sodium dodecyl sulfate polyacrylamide gel electrophoresis （SDS-PAGE）. A reducing agent, 2-mercaptoethanol, was used to remove disulfide bonds and analyze the structure of the bonds involved between α chains in some types of collagens. The use of delayed reducing methods resulted in the difference between α1 （Ⅲ） and α1 （ Ⅰ ） chains in a mixture containing type Ⅰ and Ⅲ collagens. The structure of disulfide bonds among α chains exists potentially in type V collagen prepared from the pepsin-treatment extraction at 4 ℃, which differs from type Ⅲ collagen in relation to the locations of disulfide bonds. Compared with pepsin-treated collagen at 4 ℃, the relative molecular weights of α1 （V） and α2 （V） chains treated at room temperature decrease by 4.6% and 6.0%, respectively. It is concluded that type Ⅰ Ⅲ and Ⅴ collagens can be prepared from bovine dermis and cornea by the use of pepsin treatment, salt precipitation and dialysis. The interchain disulfide bonds lie potentially near the edges of termini of type V collagen molecules in extracellular matrix, and a small number of interchain crosslinks exist in type V collagen.

Study on biomechanical mechanism of bone remodeling

Background Bone is a dynamic tissue that constantly undergoes remodeling in which a coupled process of bone formation and resorption continues throughout life.This remodeling is necessary to maintain the structural integrity of the skeleton under conditions of changing mechanical forces.It is important to develop bone remodeling theory in order to explain bone development and to instruct bone disease therapy and rehabilitation.However,the process and mechanism are not fully understood.Our study was carried out to investigate biomechanical mechanism of bone remodeling with the respect to bone tissue/cell mechanobiology,computational biomechanics and animal model.

Mechanical Stimulus Inhibits the Growth of a Bone Tissue Model Cultured In Vitro

Objectives To construct the cancellous bone explant model and a method of culturing these bone tissues in vitro, and to investigate the effect of mechanical load on growth of cancellous bone tissue in vtro. Methods Cancellous bone were extracted from rabbit femoral head and cut into I-ram-thick and 8-ram-diameter slices under sterile conditions. HE staining and scanning electron microscopy were employed to identify the histomorphology of the model after being cultured with a new dynamic load and circulating perfusion bioreactor system for 0, 3, 5, and 7 days, respectively. We built a three-dimensional model using microCT and analyzed the loading effects using finite element analysis. The model was subjected to mechanical load of 1000, 2000, 3000, and 4000 με respectively for 30 minutes per day. After 5 days of continuous stimuli, the activities of alkaline phosphatase （AKP） and tartrate-resistant acid phosphatase （TRAP） were detected. Apoptosis was analyzed by DNA ladder detection and caspase-3/8/9 activity detection. Results After being cultured for 3, 5, and 7 days, the bone explant model grew well. HE staining showed the apparent nucleus in cells at the each indicated time, and electron microscope revealed the living cells in the bone tissue. The activities of AKP and TRAP in the bone explant model under mechanical load of 3000 and 4000 με were significantly lower than those in the unstressed bone tissues （all P〈0.05）. DNA ladders were seen in the bone tissue under 3000 and 4000με mechanical load. Moreover, there was significant enhancement in the activities of caspase-3/8/9 in the mechanical stress group of 3000 and 4000 με （all P〈0.05）. Conclusions The cancellous bone explant model extracted from the rabbit femoral head could be alive at least for 7 days in the dynamic load and circulating perfusion bioreactor system, however, pathological mechanical load could affect the bone tissue growth by apoptosis in vitro. The differentiation of osteobiasts and osteoclasts might be inhibited after the model is stimulated by mechanical load of 3000 and 4000 με.

Preparation of Immobilized ε-Polylysine PET Nonwoven Fabrics and Antibacterial Activity Evaluation

A novel antibacterial material （L-PET） was prepared by immobilizing ε-polylysine on polyethylene terephthalate （PET） nonwoven fabrics. Surface modifications of the fabric were performed by using a chemical modification procedure where carboxyl groups were prepared on the PET surface, a coupling agent was grafted, and the ε-polylysine was immobilized. Scanning electron microscopy （SEM） was used to analyze the surface morphology of the fabrics, while the toluidine blue method and X-ray photoelectron spectroscopy （XPS） were used to evaluate the grafting densities. The antibacterial activities of the L-PET were investigated by using the shaking-flask method. The electron micrographs showed that the surface of the blank PET and the modified fabrics did not change. The results of XPS analysis confirmed that ε-polylysine was successfully grafted onto the surface of PET. The results of the antibacterial experiments showed that L-PET fabrics had excellent antibacterial activity against Escherichia coli and Staphylococcus aureus, and that L-PET fabrics were stable in storage for at least two years.

Oil Pollutants Degradation of Nano-MgO in Micro-Polluted Water

The removal of oil pollutants from water and purifying process of oil-polluted water are studied through catalytic degradation method with nano-MgO. The results indicated that catalytic degradation effect of nano-MgO on the oil pollutants was associated with dosage of nano-MgO, pH and water temperature. When oil content was 1.8 mg/L, 0.17 g nano-MgO was used and the removal rate of oil was 93.92%. Furthermore, nano-Mgo was a non-photosensitive catalyst. GC/MS analysis showed that the amount of petroleum-based pollutants in water was reduced 73.77% from the previous 61 kinds to 16 kinds, and the total peak area was reduced 96.05% after catalytic degradation of nano-MgO. Therefore, nano-MgO has an excellent effect on the catalytic degradation of oil pollutants and can be applied in the treatment of oil wastewaters.

Extraction of TypeⅤCollagen From Bovine Cornea and Its Structural Analysis

We used bovine cornea as starting material, pepsin treatment in acetic acid solution to extract the mixture of type I and V collagens, and salt precipitation and dialysis to purify and isolate each type of the collagens. The preparation was analyzed using sodium dodecyl sulphate polyacrylamide gel electrophoresis. 2-mercaptoethanol used as reducing agent cut off the disulfide bonds, which was utilized to analyze the structure of disulfide bonds involved between α chains in some types of collagens. At the same time, we discovered that the structure of disulfide bonds among α chains potentially existed in the type V collagen prepared from the pepsin-treatment extraction at 4℃. Through quantitative analysis, we obtained that, compared with those pepsin-treated at 4℃, the relative molecular weights of α1 （V） and α 2 （V） subunits pepsin-treated at room temperature decreased by 4.6% and 6.0%, respectively. It is concluded that type V collagen can be prepared from bovine coruea by use of pepsin treatment, salt precipitation and dialysis. The interchain and/or intermolecular disulfide bonds potentially lie near the edges of termini of type V collagen molecules existing in extracellular matrix, and there are few of the intermolecular and/or intramolecular crosslinks formed by lysine or hydroxylysine or histidine residues in type V collagen.

Mechanical Strain Regulates Osteoblast Proliferation Through Ca^(2+)-CaMK-CREB Signal Pathway

Objective To investigate the effects of mechanical strain on Ca^(2+)-calmodulin dependent kinase(CaMK)-cA MP response element binding protein(CREB) signal pathway and proliferation of osteoblasts. Methods Using a four-point bending device, MC3T3-E1 cells were exposed to mechanical tensile strains of 2500 μs and 5000 μs at 0.5 Hz respectively. The intracellular free Ca^(2+)([Ca^(2+)]i) concentration and calmodulin activity were assayed by fluorospectrophotometry, CaMK II β, CREB, and phosphorylated(activated) CREB(p-CREB) were assessed by Western blot, and cells proliferation was assayed with MTT. Pretreatment with verapamil was carried out to block Ca^(2+) channel, and inhibitor U73122 was used to inhibit phospholipase C(PLC). Results Mechanical strains of 2500 μs and 5000 μs for 1 to 10 minutes both increased [Ca^(2+)]i level of the cells. The 2500 μs strain, a periodicity of 1 h/d for 3 days, activated calmodulin, elevated protein levels of CaMK II β and p-CREB, and promoted cells proliferation, which were attenuated by pretreatment of verapamil or U73122. The effects of 5000 μs strain on calmodulin, CaMK II β, p-CREB and proliferation were contrary to 2500 μs strain. Conclusion The mechanical strain regulates osteoblasts proliferation through Ca^(2+)-Ca MK-CREB signal pathway via Ca^(2+) channel and PLC/IP_3 transduction cascades.

Magnetic resonance imaging-three-dimensional printing technology fabricates customized scaffolds for brain tissue engineering

Conventional fabrication methods lack the ability to control both macro- and micro-structures of generated scaffolds. Three-dimensional printing is a solid free-form fabrication method that provides novel ways to create customized scaffolds with high precision and accuracy. In this study, an electrically controlled cortical impactor was used to induce randomized brain tissue defects. The overall shape of scaffolds was designed using rat-specific anatomical data obtained from magnetic resonance imaging, and the internal structure was created by computer- aided design. As the result of limitations arising from insufficient resolution of the manufacturing process, we magnified the size of the cavity model prototype five-fold to successfully fabricate customized collagen-chitosan scaffolds using three-dimensional printing. Results demonstrated that scaffolds have three-dimensional porous structures, high porosity, highly specific surface areas, pore connectivity and good internal characteristics. Neural stem cells co-cultured with scaffolds showed good viability, indicating good biocompatibility and biodegradability. This technique may be a promising new strategy for regenerating complex damaged brain tissues, and helps pave the way toward personalized medicine.

A Humerus Arterial Bleeding Simulation Model for Hemostasia

In our daily life, accident would happen with arterial haemorrhage,and death would be brought out by continuous arterial bleeding for little time if emergency has not been implemented in time. This paper presents a humerus arterial bleeding simulation model (HABSM) for hemostasia,which has a high-fidelity, practical model for the humerus arterial hemostasia operation that is not only for the surgeons and nurses, but also for commons in urgent bleeding accident. The functional components of HABSM are arm model, fluid circulated pipeline and circuit controlling system. The arm model is made of elastic material as human muscle. Fluid circulated pipeline contains wiggly pump, inlet pipe and outlet pipe. And circuit controlling system has single chip micyoco system (SCM), keyboard, pressure sensor and vision circuit. SCM controls pump and valve to realize humerus arterial blood circulation. Both surgeons and commons thought well of HABSM which provided a task trainer for humerus arterial hemostasia.

A pilot study on using chlorine dioxide gas for disinfection of gastrointestinal endoscopes

Objectives： This pilot study of employing chlorine dioxide （CD） gas to disinfect gastrointestinal endoscopes was conducted to meet the expectations of many endoscopy units in China for a high-efficiency and low-cost disin- fectant. Methods： An experimental prototype with an active circulation mode was designed to use CD gas to disinfect gastrointestinal endoscopes. One type of testing device composed of polytetrafluoroethylene （PTFE） tubes （2 m long, inner diameter 1 mm） and bacterial carrier containers was used to simulate the channel of the endoscope. PTFE bacterial carriers inoculated with Bacillus atrophaeus with or without organic burden were used to evaluate the spor- icidal activity of CD gas. Factors including exposure dosage, relative humidity （RH）, and flow rate （FR） influencing the disinfection effect of CD gas were investigated. Moreover, an autoptic disinfecting test on eight real gastrointestinal endoscopes after clinical use was performed using the experimental prototype. Results： IRH, exposure dosage, or- ganic burden, and the FIR through the channel significantly （P〈0.05） affected the disinfection efficacy of CD gas for a long and narrow lumen. The log reduction increased as FR decreased. Treatment with 4 mg/L CD gas for 30 min at 0.8 L/min FR and 75% IRH, resulted in complete inactivation of spores. Furthermore, all eight endoscopes with a maximum colony-forming unit of 915 were completely disinfected. The cost was only 3 CNY （0.46 USD） for each endoscope. Conclusions： The methods and results reported in this study could provide a basis for further studies on using CD gas for the disinfection of endoscopes.

Positively charged microporous ceramic membrane for the removal of Titan Yellow through electrostatic adsorption

To develop a depth filter based on the electrostatic adsorption principle, positively charged microporous ceramic membrane was prepared from a diatomaceous earth ceramic membrane.The internal surface of the highly porous ceramic membrane was coated with uniformly distributed electropositive nano-Y2O3 coating. The dye removal performance was evaluated through pressurized filtration tests using Titan Yellow aqueous solution. It showed that positively charged microporous ceramic membrane exhibited a flow rate of 421 L/（m^2·hr） under the trans-membrane pressure of 0.03 bar. Moreover it could effectively remove Titan Yellow with feed concentration of 10 mg/L between pH 3 to 8. The removal rate increased with the enhancement of the surface charge properties with a maximum rejection of 99.6%. This study provides a new and feasible method of removing organic dyes in wastewater. It is convinced that there will be a broad market for the application of charged ceramic membrane in the field of dye removal or recovery from industry wastewater.

Effect of the same mechanical loading on osteogenesis and osteoclastogenesis in vitro

Purpose： To investigate the influence of the same mechanical loading on osteogenesis and osteoclastogenesis in vitro. Methods： Primary osteoblasts, bone marrow-derived mesenchymal stem cells （BMSCs, cultured in osteoinductive medium） and RAW264.7 cells cultured in osteoclast inductive medium were all subjected to a 1000μstrain （μs） at 1 Hz cyclic mechanical stretch for 30 min （twice a day）. Results： After mechanical stimulation, the alkaline phosphatase （ALP） activity, osteocalcin protein level of the osteoblasts and BMSCs were all enhanced, and the mRNA levels of ALP and collagen type I increased. Additionally, extracellular-deposited calcium of both osteoblasts and BMSCs increased. At the same time, the activity of secreted tartrate-resistant acid phosphatase, the number of tartrate-resistant acid phosphatase-positive multinucleated cells, matrix metalloproteinase-9 protein levels of RAW264.7 cells and the extracellular calcium solvency all decreased. Conclusion： The results demonstrated that 1000 μs cyclic mechanical loading enhanced osteoblasts activity, promoted osteoblastic differentiation of BMSCs and restrained osteoclastogenesis of RAW264.7 cells in vitro.

Detection of Bacteria Based on Quantum Dots by Using a Laboratory-Made System

This study investigated a method that simultaneously detects three bacteria, Salmonella typhimurium, Escherichia coli, and Staphylococcus aureus via an approach that uses antibody-conjugated quantum dots(QDs) as fluorescence markers,by using a laboratory-made system. QDs with different emission wavelenghs were immobilized with antibody. Antibody conjugated QDs capture the bacteria selectively and specifically so that "sandwich" complex were formed. The suspension of the labeled bacteria was trickled onto a microporous membrane. A 450 nm semiconductor laser was used as a part of the laboratory-made system to excite the QDs. Three PMT detectors were utilized to detect the fluorescence intensity. This method, of which the detection procedures are completed within 1 h, can be applied to the cost-effective and rapid detecting of bacterial contamination.

Relationship between surgical time and postoperative complications in senile patients with hip fractures

Objective：To elucidate the relationship between surgical time and postoperative complications in senile patients with hip fractures, and try to find out other factors which are related to these complications.Methods： Sixty-two patients, 28 males aged from 65 to 72 years with a mean age of 76.3 years and 34 females aged from 65 to 95 years with a mean age of 78.1 years, who had undergone orthopedic surgery because of hip fractures,were enrolled in a retrospective cohort study. The surgical time and pattern, the type of fracture, preoperative comorbidities, American Society of Anesthesiologists （ASA） score and the volume of blood transfusion during operation were obtained from these patients who were followed up by telephone calls for postoperative complications.All the patients were followed up at least for 1 year and were divided into subgroups according to their clinical characteristics and the results were analyzed by the Statistical Analysis System software.Results：There was no significant difference in the morbidity of postoperative eomplications with the gender,age,surgical time and pattern,or ASA score. There was significant difference in the morbidity of postoperative complications related to preoperative comorbidities and the volume of blood transfusion. There was a significant causality between preoperative comorbidities and postoperative complications. The morbidity of postoperative complications was 1.651 times higher in patients with preoperative comorbidities than those without.Conclusions：There is no relationship between the surgical time and postoperative complications in senile patients who received surgery for hip fracture within 1 year.No correlation is found between the postoperative complications and gender,age,type of fracture, surgical pattern,ASA score and the volume of blood transfusion. Preoperative comorbidities are an independent predictor for postoperative complications.

A Wavelet-Based Method to Predict Muscle Forces From Surface Electromyography Signals in Weightlifting

The purpose of this study was to develop a wavelet-based method to predict muscle forces from surface electromyography （EMG） signals in vivo. The weightlifting motor task was implemented as the case study. EMG signals of biceps brachii, triceps brachii and deltoid muscles were recorded when the subject carried out a standard weightlifting motor task. The wavelet-based algorithm was used to process raw EMG signals and extract features which could be input to the Hill-type muscle force models to predict muscle forces. At the same time, the musculoskeletal model of subject＇s weightlifting motor task was built and simulated using the Computed Muscle Control （CMC） method via a motion capture experiment. The results of CMC were compared with the muscle force predictions by the proposed method. The correlation coefficient between two results was 0.99 （p〈0.01）. However, the proposed method was easier and more efficiency than the CMC method. It has potential to be used clinically to predict muscle forces in vivo.

Computational Model for the Underlying Mechanisms Regulating Bone Loss by Mechanical Unloading and Estrogen Deficiency

The objective of this paper is to investigate the different effects of disuse and estrogen deficiency on bone loss and the underlying mechanisms.A mechanical-biological factors coupled computational model was built to simulate different patterns of bone loss induced in female rats by hind limb unloading,ovariectomy,or both in an animal study.A remodeling analysis was performed on a representative cross section of 6 mm2 of cancellous bone in the distal femoral metaphysis of the rats.The BMU activation frequency,the refilling rate,and the principal compressive strain in the state of mechanical unloading and estrogen deficiency were simulated to interpret the underlying mechanisms.Simulated bone loss patterns due to mechanical unloading,estrogen deficiency,or both all corresponded with the experimental observations.The results show that mechanical unloading and estrogen deficiency cause different bone loss patterns;moreover,mechanical unloading induces a greater degree of bone loss than estrogen deficiency,which can lead to improved treatment and prevention strategies for osteoporosis.