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Polylactic acid (PLA) fiber membrane needs to match the wound healing time when used as a medical adhesive membrane. In order to adjust the degradation cycle of PLA fiber, the composite microspheres of nano-SiO2/lipase/polycaprolactone (PCL) with degradation regulation function were designed and prepared. And then the composite microspheres were added into PLA fiber membrane to verify the degradation regulation function. The results showed that: the optimal preparation process of microspheres was obtained as follows: 5 mg/mL SiO2/lipase complex concentration, 10 mg/mL PCL concentration, 1000 r/min emulsification speed and 600 r/min curing speed. The amount of enzyme, loading in the microspheres, can be regulated in the range of 10.24%–11.29%. And the drug-loaded microspheres had a good sustained release effect. Finally, it was verified that the microspheres could accelerate the degradation rate of PLA fiber membrane. [ABSTRACT FROM AUTHOR]

In this paper, a novel data-driven model-free adaptive fractional-order sliding mode controller with prescribed performance is proposed for the shape memory alloy (SMA) actuator. Due to the strong asymmetric saturated hysteresis nonlinear characteristics of the SMA actuators, it is not easy to establish an accurate model and develop an effective controller. Therefore, we present a controller without using the model of the SMA actuators. In other words, the proposed controller depends merely on the input/output (I/O) data of the SMA actuators. To obtain the reasonable compensation for hysteresis, enhance the noise robustness of the controller, and reduce the chattering, a fractional-order sliding mode controller with memory characteristics is employed to improve the performance of the controller. In addition, the prescribed performance control (PPC) strategy is introduced in our work to guarantee the tracking errors converge to a sufficiently small boundary and the convergence rate is not less than a predetermined value which are significant and considerable in practical engineering applications of the SMA actuator. Finally, experiments are carried out, and results reveal the effectiveness and success of the proposed controller. Comparisons with the classical Proportional Integral Differential (PID), model-free adaptive control (MFAC), and model-free adaptive sliding mode control (MFAC-SMC) are also performed. [ABSTRACT FROM AUTHOR]

The upper-limb exoskeleton is capable of enhancing human arm strength beyond normal levels, whereas deriving the operator's desired action straightforward turns out to be one of the significant difficulties facing human-robot interaction research. In the study, the human-robot interface was presented to regulate the exoskeleton tracking human elbow motion trajectory that employed the contact force signals between the exoskeleton and its operator as the primary means of information transportation. The signals were recorded by adopting the novel soft skin sensors attached to the bracket on the exoskeleton linkage, which could reflect the human arm motion intention through the virtual admittance model and adaptive control. Subsequently, a 1-DOF upper-limb exoskeleton was designed to illustrate the performance of the proposed sensor and the interaction control method in the human-robot cooperation experiment. [ABSTRACT FROM AUTHOR]

Humanoid robotic hand actuated by shape memory alloy (SMA) represents a new emerging technology. SMA has a wide range of potential applications in many different fields, ranging from industrial assembly to biomedicine applications, due to the characteristic of high power-to-weight ratio, low driving voltages and noiselessness. However, nonlinearities of SMA and complex dynamic models of SMA-based robotic hands result in difficulties in controlling. In this paper, a humanoid SMA-based robotic hand composed of five fingers is presented with the ability of adaptive grasping. Reinforcement learning as a model-free control strategy can search for optimal control of systems with nonlinear and uncertainty. Therefore, an adaptive SA-Q-Learning (ASA-Q-learning) controller is proposed to control the humanoid robotic finger. The performance of ASA-Q-learning controller is compared with SA-Q-learning and PID controller through experimentation. Results have shown that ASA-Q-learning controller can control the humanoid SMA-based robotic hand effectively with faster convergence rate and higher control precision than SA-Q-learning and PID controller, and is feasible for implementation in a model-free system. [ABSTRACT FROM AUTHOR]

This paper focuses on the trajectory tracking issue of the pneumatic artificial muscle (PAM) exoskeleton system. First of all, a new type of the PAM elbow exoskeleton was introduced to assist wearers in elbow flexion/extension movement. Moreover, a model-free adaptive control approach was combined with the prescribed performance control to ensure the tracking errors to be converged to the predefined requirements. Meanwhile, to suffer the influence of the unknown external disturbance on the exoskeleton, a terminal sliding mode control was adopted to reduce the tracking errors. From a theoretical perspective, the stability of the proposed controller can be proved by Lyapunov synthesis. After two sets of experiments, the proposed control method can further improve the tracking accuracy in the PAM elbow exoskeleton, compared with the other three model-free adaptive control methods. Simultaneously, the maximum absolute value of the tracking errors never exceeded the designed boundary. [ABSTRACT FROM AUTHOR]

This paper proposes a data-driven sliding mode control (SMC) method with tracking error constraint for a shape memory alloy (SMA) actuated system. More specifically, a new SMC method with prescribed performance is investigated by adopting the equivalent dynamic linearization technique and a novel transformed error algorithm to guarantee that the tracking error can converge into a preassigned region. Meanwhile, the proposed control method can effectively ensure the convergence rate and the steady-state error within a prescribed bound, merely depending on the input/output data without implicit or explicit information of the systems, which is more valuable for the practical application. The presented control method has been implemented on an SMA actuated system successfully and experimental results have shown that the proposed control is easily applicable and highly precise. In addition, the tracking error of the SMA actuated system can be constrained in a preassigned domain by the proposed control method. [ABSTRACT FROM AUTHOR]

Background: Beta-ketothiolase deficiency (BKTD) is an autosomal recessive disorder caused by biallelic mutation of ACAT1 that affects both isoleucine catabolism and ketolysis. There is little information available regarding the incidence, newborn screening (NBS), and mutational spectrum of BKTD in China.Results: We collected NBS, biochemical, clinical, and ACAT1 mutation data from 18 provinces or municipalities in China between January 2009 and May 2020, and systematically assessed all available published data from Chinese BKTD patients. A total of 16,088,190 newborns were screened and 14 patients were identified through NBS, with an estimated incidence of 1 per 1 million newborns in China. In total, twenty-nine patients were genetically diagnosed with BKTD, 12 of which were newly identified. Most patients exhibited typical blood acylcarnitine and urinary organic acid profiles. Interestingly, almost all patients (15/16, 94%) showed elevated 3-hydroxybutyrylcarnitine (C4OH) levels. Eighteen patients presented with acute metabolic decompensations and displayed variable clinical symptoms. The acute episodes of nine patients were triggered by infections, diarrhea, or an inflammatory response to vaccination. Approximately two-thirds of patients had favorable outcomes, one showed a developmental delay and three died. Twenty-seven distinct variants were identified in ACAT1, among which five were found to be novel.Conclusion: This study presented the largest series of BKTD cohorts in China. Our results indicated that C4OH is a useful marker for the detection of BKTD. The performance of BKTD NBS could be improved by the addition of C4OH to the current panel of 3-hydroxyisovalerylcarnitine and tiglylcarnitine markers in NBS. The mutational spectrum and molecular profiles of ACAT1 in the Chinese population were expanded with five newly identified variants. [ABSTRACT FROM AUTHOR]

In recent years, the growing popularity of artificial neural networks has urged more and more researchers to try introduce these methods to the machining field, with some of them actually producing good results. The acquisition of cutting data often means higher cost and time, limiting the application of neural network in the machining sector, to a certain extent. In this paper, for the task of cutting force prediction, a "transfer network" was established, based on data obtained by simulation, combined with the theory and method in the field of transfer learning. Compared to "ordinary network", that is, traditional back-propagation neural network based on experimental samples alone, transfer network exhibits obvious performance advantages. On one hand, this means that, using the same experimental samples, the prediction error of transfer network will be controlled; while on the other hand, when the same prediction error is achieved, the number of experimental samples required by the transfer network will be less. [ABSTRACT FROM AUTHOR]

As an attractive collector medium for hypervelocity particles, combined with outstanding physical properties and suitable compositional characteristics, SiO2 aerogel has been deployed on outer space missions and laser shock-loaded collection experiments. In this paper, impact experiments were conducted to understand the penetration process of irregular grains, irregular Al2O3 grains with two different sizes and speeds (~110 μm@7 km/s, ~251 μm@2.3 km/s) at various density silica aerogels. By classifying the shapes of projectile residues and tracks, the morphology of tracks was analyzed. It was observed that there were several kinds of typical tracks in the penetration of irregular grains, accompanied by residues with the shapes of near-sphere, polyhedron, streamlined body wedge, and rotator. The rotational behavior was demonstrated by the final status of one flake projectile as direct evidence. In addition, there was no obvious relationship between the track length and experimental parameters, which may be caused by the uncertain interaction between aerogels and irregular particles. In addition, it confirmed the existence of fragmentation, melting situation by observing the shape of the impact entrance hole. At the same time, optical coherence tomography was used to observe the detail of tracks clearly, which provided a method to characterize the tracks nondestructively. [ABSTRACT FROM AUTHOR]

Manual lifting tasks involve repetitive raising, holding and stacking movements with heavy objects. These arm movements are notable risk factors for muscle pain, fatigue, and musculoskeletal disorders in workers. An upper-limb wearable robot, as a 6-DOF dual-arm exoskeleton, which was designed to augment workers' strength and minimize muscular activation in the arm during repetitive lifting tasks. To adjust the robot joint trajectory, the user needs to apply an interactive torque to operate the robot during lifting tasks when a standard virtual mechanical impedance control structure is used. To reduce overshooting of the interactive torque on the user's joint, a three-tier hierarchical control structure was developed for the robot in this study. At the highest level, a human arm movement detection module is used to detect the user's arm motion according to the surface electromyography signals. Then, a Hammerstein adaptive virtual mechanical impedance controller is used at the middle level to reduce overshooting and yield an acceptable value of torque for the user's elbow joint in actual lifting tasks. At the lowest level, the actuator controller on each joint of the robot controls the robot to complete lifting tasks. Several experiments were conducted, and the results showed that the interactive torque on the user's elbow was limited and the muscular activations of erector spinae and biceps brachii muscles were effectively decreased. The proposed scheme prevents potential harm to the user due to excessive interactive torque on the human elbow joint, such as related muscle fatigue and joint injuries. [ABSTRACT FROM AUTHOR]

Brassica juncea is an important dietary vegetable cultivated and consumed in China for its edible stalks and leaves. The purple leaf mustard, which is rich in anthocyanins, is eye-catching and delivers valuable nutrition. However, the molecular mechanism involved in anthocyanin biosynthesis has not been well studied in B. juncea. Here, histological and transcriptome analyses were used to characterize the purple leaf color and gene expression profiles. Free-hand section analysis showed that the anthocyanin was mainly accumulated in the adaxial epidermal leaf cells. The anthocyanin content in the purple leaves was significantly higher than that in the green leaves. To investigate the critical genes and pathways involved in anthocyanin biosynthesis and accumulation, the transcriptome analysis was used to identify the differentially expressed genes (DEGs) between the purple and green leaves from the backcrossed BC3 segregation population in B. juncea. A total of 2,286 different expressed genes were identified between the purple and green leaves. Among them, 1,593 DEGs were up-regulated and 693 DEGs were down-regulated. There were 213 differently expressed transcription factors among them. The MYB and bHLH transcription factors, which may regulate anthocyanin biosynthesis, were up-regulated in the purple leaves. Interestingly, most of the genes involved in plant–pathogen interaction pathway were also up-regulated in the purple leaves. The late biosynthetic genes involved in anthocyanin biosynthesis were highly up-regulated in the purple leaves of B. juncea. The up regulation of BjTT8 and BjMYC2 and anthocyanin biosynthetic genes (BjC4H , BjDFR , and BjANS) may activate the purple leaf formation in B. juncea. This study may help to understand the transcriptional regulation of anthocyanin biosynthesis in B. juncea. [ABSTRACT FROM AUTHOR]

Leaf morphology varies significantly among Brassica juncea. However, little is known regarding the causal gene that controls lobed leaf shape in B. juncea. In our study, the BjRCO gene, which is associated with leaf morphological variation, was cloned from chromosome A10 in B. juncea via BSR-seq. Blast analysis suggested that the BjRCO encodes a HD-Zip I transcription factor, which may serve as a positive regulator of lobed leaf formation in leaf mustard. Interestingly, the lobed leaf genes reported in the related species of Brassica (B. rapa, B. napus, and B. juncea) were located in A10. Phylogenetic analysis showed that BjRCO was also homologous to the lobed leaf gene BoLl reported on chromosome 9 in B. oleracea. In addition, qRT-PCR results showed that the expression levels of the BjRCO gene were higher expressed in the inner small lobed leaves than in the little sawtooth-like leaves (LSL). These results of this study indicate that the BjRCO gene is related to lobed leaf formation in B. juncea. These findings help to establish a solid foundation for future research investigating the molecular mechanism governing lobed leaf formation in B. juncea. [ABSTRACT FROM AUTHOR]

The key to battery management systems (BMS) is an accurate and real-time prediction on State of Charge (SOC) of the power battery. The methods of estimating SOC of power battery were analyzed. The gray neural network model was introduced into the field of SOC estimation. The model is used to establish the relationship of SOC, discharge current and rebound voltage. The model can be used to estimate SOC of battery on line by detecting the values of rebound voltage and discharge current during the discharge process. The model of SOC estimation is proved feasible by comparing the experimental data with calculated data. [ABSTRACT FROM AUTHOR]

Soft robotic grippers with compliance have great superiority in grabbing objects with irregular shape or fragility compared with traditional rigid grippers. The main limitations of such systems are small grasping force resulted from properties of soft actuators and lacking variable stiffness of soft robotic grippers, which prevent them from a larger wide range of applications. This article proposes a shape-memory alloy (SMA)-based soft gripper with variable stiffness composed of three robotic fingers for grasping compliantly at low stiffness and holding robustly at high stiffness. Each robotic finger mainly consisted of stiff parts and two variable stiffness joints is installed on the base with a specific angle. The paraffin as a variable stiffness material in the joint can be heated or cooled to change the stiffness of the robotic fingers. Results of experiments have shown that a single robotic finger can approximately achieve 18-fold stiffness enhancement. Each finger with two joints can actively achieve multiple postures by both changing the corresponding stiffness of joints and actuating the SMA wire. Based on these principles, the gripper can be applied to grasp objects with different shapes and a large range of weights, and the maximum grasping force of the gripper is increased to about 10 times using the variable stiffness joints. The final experiment is conducted to validate variable stiffness of the proposed soft grippers grasping an object. [ABSTRACT FROM AUTHOR]

Drug loaded PLA suture has been one most potential surgery material to help wounds healing. The loaded drug amounts and sustained drug release effect were a vital part for PLA suture. In this research drug-loaded microspheres and finishing bath were prepared to ensure more drug particles loaded on PLA suture. Moreover, sustained drug release effect and mechanical properties of PLA suture were also observed. The results suggested that PLA concentration and emulsifier amounts had more effect on the size of PLA drug-loaded microspheres and the optimal technology was: 0.03 g/mL of PLA concentration, 0.3 g of amount of emulsifier and the total amount of drug and emulsifier was 3 g. Moreover, drug release test showed a significant sustained release effect of the drug-loaded PLA suture. Mechanical measurements indicated the flexibility and strength were not impaired by such drug-loaded method. This research is expected to benefit the surgery fields further. [ABSTRACT FROM AUTHOR]

Polylactic acid (PLA) surgical sutures are a new type of absorbable sutures that can be degraded and absorbed in the body. However, there is high hydrophobicity for the surface of PLA sutures, which leads to poor biocompatibility and cellular affinity. In order to increase the hydrophilicity, the PLA sutures were etched by lipase firstly, and then grafted with chitosan. The results indicate that the optimal conditions of treating PLA sutures by lipase were as follows: 45℃ reaction temperature, 4.5 g/L concentration of lipase and 8 h reaction time. The sutures were etched by lipase and then formed some grooves and a number of hydroxyl (-OH) bonds, which led to increased surface area and hydrophilicity, but a drop in mass and strength. The optimal conditions of grafting chitosan onto PLA sutures were as follows: 4 h reaction time and 3 g/L concentration of chitosan. The chitosan grafted and loaded on the surface of PLA sutures, and in some areas of the sutures the chitosan reunited, which led to a rough surface and large friction coefficient. Finally, the hydrophilicity of the PLA sutures, treated by lipase and then grafted with chitosan, was greatly improved. [ABSTRACT FROM AUTHOR]

No studies have been focused on the inclusion of organic selenium in formulated feed of abalone when organic minerals are accepted by aquaculture feed industry. This experiment evaluated the effect of organic selenium on the growth, antioxidation, immunity and gene expressions of selenoproteins in abalone. Graded levels of organic selenium were included to the basal diet at 0.00, 0.15, 0.30 and 0.60 ppm providing 157.83, 322.51, 437.59 and 596.59 ug/kg of selenium in the diet. Accordingly, the diets were named as Se‐0.00, Se‐0.15, Se‐0.30 and Se‐0.60 respectively. Results had shown that survival rate, weight gain rate and shell length increase rate were lowest for Se‐0.60 group (p < 0.05). The concentration of selenium in the whole body generally increased with increasing level of dietary organic selenium (p < 0.05). The enzyme activities related to antioxidation increased initially with low levels of dietary selenium and decreased with higher levels, with the highest value in Se‐0.30 group (p < 0.05). The enzyme activities of immunity increased with the addition of dietary selenium. With the increase of dietary selenium, Myostain expression decreased initially and increased afterwards, with lowest value for Se‐0.30 group (p < 0.05). However, the expressions of other genes related to growth, antioxidation and selenoproteins firstly increased and then decreased, with the highest value recorded for Se‐0.15 group. In conclusion, the inclusion rate of 0.15 – 0.30 ppm Se in diet could promote growth, antioxidation, immunity and gene expressions of selenoproteins in abalone; however, excess selenium with 0.60 ppm inclusion lever in diet had toxic effects. [ABSTRACT FROM AUTHOR]

The drug-release time of suture should meet with the healing time of wound, so it is needed to control the drugrelease performance of polylactic acid (PLA) suture. In this paper, two biodegradable polymers with different degradation rates, such as polycaprolactone (PCL) and polyglycolide (PGA), were applied to carry the drug of tea polyphenol (TP). The drug-loading finishing solution which is made of PCL/PGA carriers and TP, was coated on the PLA suture. The drug-release rate and time of PLA suture could be regulated by adjusting the proportion of PCL/PGA carriers. The results indicate that the surface of drug-loaded PLA suture becomes rough. There is no obvious chemical reaction among the drug, carriers and PLA suture, just physical adhesion. With the increasing of PCL in drug-carriers, the strength of suture gradually increases. At 70/30 of PCL/PGA, the fracture elongation of suture reaches the highest point. In process of degradation, the surface of drugloaded PLA suture appears some holes after 25 weeks. The strength of sutures decreases gradually during degradation, and the effective strength time of sutures with various proportions of PCL/PGA is different. The drug-release rate of the suture is fast at early stage and slow at later stage and the higher the PGA proportion is, the faster the drug-release rate of the suture is. [ABSTRACT FROM AUTHOR]

The lithium ion battery is considered as the experimental object, and its discharge characteristics are studied. A model of the battery in different charge-states is established by a tool of neural network while battery's rebound voltage, temperature and load are set as input parameters. The validity of the model is tested based on the experimental data. The accuracy, adaptability and stability of the SOC in this model is validated in a variety of the working conditions, and the accuracy of the model is demonstrated to be higher than 5%. [ABSTRACT FROM AUTHOR]

Pinhole drying process is a slowly dryness in the air caused by capillary force. It was found useful to improve the transparency of silica aerogel. So in this work, pinhole drying was considered as a modification on the microstructure. We studied the effect of pinhole drying on the light transmission of aerogel. The effect of pinhole drying on the microstructure of aerogel was also investigated. The spherical transmittance ( τ ) and directional transmittance ( τ ) were measured by ultraviolet-Visible-infrared spectrophotometer, the scattering light at the 90° direction of the gel was measured by a nephelometer, and the microstructure of the aerogels were analyzed applying small angle X-ray scattering, nitrogen adsorption porosimetry, and scanning electron microscope. The results showed that pinhole dried silica aerogels and non-pinhole dried aerogels exhibited different microstructure and optical properties. The directional transmittance of the pinhole dried aerogel and non-pinhole dried aerogel at 600 nm wavelength was 57.9 and 40.9%, respectively, an improvement of 17.0%. The transparency ratio ( τ / τ ) of pinhole dried aerogel and non-pinhole dried aerogel at 400 nm wavelength was 0.26 and 0.07, respectively, an improvement of 0.19. Small angle X-ray scattering measurements showed that these improvements can be attributed to the smaller mean cluster size of pinhole dried aerogels than that of non-pinhole dried aerogels. 90° scattering light experiments indicated that the clusters of the gel were becoming smaller during the drying process caused by capillary force according to Rayleigh scattering theory. It is the reason why pinhole dried aerogels have smaller mean cluster size and relatively transparent. Graphical Abstract: [ABSTRACT FROM AUTHOR]

To study the ignition characteristics of semiconductor bridges (SCB) for automobile airbag igniters, a model was proposed to compute the electrical characteristics of SCB based on the structural characteristics, resistance properties, and the working process of the bridge. Numerical simulation was conducted to analyze the voltage and current trends at two ends of bridges with various geometric dimensions and those with identical geometric dimensions and oxide layers of different thicknesses. Voltage-current curves for bridges of three different dimensions were obtained through numerical simulation. Bridges of larger geometric dimensions were found to require higher voltage to reach the melting point, which means higher energy input is required. [ABSTRACT FROM AUTHOR]

A Semiconductor Bridge (SCB) explosive initiator has many advantages such as shorter action time, better ignition consistency and higher reliability. The development of a SCB has traditionally been guided by an experimental approach. Experiments conducted worldwide show that the melting and vaporization of a SCB when heated by an electrical current is a very complex physical process. In this process, the bridge goes through multi-phase changes, i.e., in order solid, liquid, gaseous and plasma-state. This paper discusses the numerical simulation of the SCB working process when driven with a short low-energy pulse. In an effort to elucidate the behaviors of the SCB working process, the temperature distribution before the SCB melting and SCB discharge are presented. The basic semiconductor equations and heat transfer equation are described to evaluate the temperature distribution in the SCB. The results are obtained from finite-difference implementations. The edge gasification effect of SCB is proved by the curve of temperature distribution, and the double temperature characteristic of SCB is shown. Finally, a SCB discharge model is established. The result shows that the bigger the external voltage, the longer is the discharge time. [ABSTRACT FROM PUBLISHER]

The semiconductor bridge (SCB) is a heavily n-doped semiconductor. The SCB device has advantages for reducing voltage and energy requirements compared with a conventional device. It also has very excellent safety. When driven with a short low-energy pulse, the SCB creates hot plasma to ignite energetic materials. The hot plasma permeates the energetic materials and deposits its latent heat of fusion to the grains, thereby heating the granular surfaces to energy states required for self-sustained reaction. The behavior of the SCB can be facilitated through the simulation of the electrical components. The resistance of the SCB is a key parameter during the process of producing the plasma. The dynamic resistance of a heavily doped semiconductor resistor was evaluated by observing the electrical mobility and conductivity of the resistor as a function of temperature covering the range from room temperature to the plasma temperature. In an effort to elucidate the dynamic resistance of the SCB, current was forced to flow through the bridge with an initial resistance of 1 \Omega. The energy stored in a 25- \mu\F capacitor was used to activate the plasma. Two peaks in the voltage–time curve were typically observed. Time histories of the resistance and voltage show the special features of the resistor. It appears that the resistance increases initially before the intrinsic temperature and then decreases due to negative resistance behavior, and then, the resistor is melted and vaporized to generate plasma. [ABSTRACT FROM PUBLISHER]

A large number of electronic devices could generate a lot of electromagnetic waves, which could interfere with other equipment and harm the human body. Therefore, an electromagnetic interference shielding (EMI) material is urgently needed to protect the human body and the electronic equipment. In this paper, the multi-wall carbon nanotubes (MWCNTs) and the nano-Fe3O4 were added into the polylactic acid (PLA) matrix to form the composite film with electromagnetic interference shielding performance. And the structure and properties of MWCNTs/Fe3O4/PLA composite films, such as the morphology, chemical structure, crystallization, mechanical property, conductive property, magnetic property and electromagnetic interference shielding property, were researched. The result shows that too much Fe3O4 could lead to agglomeration, and the coupling agent KH570 had grafted and modified the surface of MWCNTs. The MWCNTs and nano-Fe3O4 could increase the crystallinity of PLA matrix. With the increase of MWCNTs, the maximum tensile stress of composite films gradually increased, and the maximum tensile strain decreased, and the resistance value showed a significant downward trend. The Fe3O4 could improve the magnetic properties of composite film. The MWCNTs and Fe3O4 could improve the electromagnetic interference shielding efficiency (EMI SE). The MWCNTs played a more significant role than the Fe3O4 in the process of EMI, and the EMI SE of the composite film with 3:1 ratios of MWCNTs/Fe3O4 could rise to 22 dB. [ABSTRACT FROM AUTHOR]

Polylactic acid (PLA) surgical suture can be absorbed by human body. In order to avoid surgical site infections (SSIs), the drug is usually loaded on the PLA suture, and then the drug can release directly to the wound. Because the different types of wounds heal at different times, it is needed to control the drug release rate of PLA suture to consistent to the wound healing time. Two biopolymers, polyglycolide (PGA) and polycaprolactone (PCL), were selected as the carrier of ciprofloxacin (CPFX) drug, and then the CPFX-PCL/PGA was coated on the PLA suture. The degradation rate of drug-carrier can be controlled by adjusting the proportion of PCL/PGA, which can regulate the rate of CPFX drug release from PLA suture. The results show that the surface of PLA suture, coating with PCL/PGA, was very rough, which led to increased stitching resistance when we were suturing the wound. These materials, such as the PLA suture, the PCL/PGA carriers and the CPFX drug, were just physically mixed rather than chemically reacted, which was very useful for ensuring the original efficacy of CPFX drug. With the increasing of PCL in the carriers, both the breaking strength and elongation of these un-degraded sutures increased. During degradation, the breaking strength of all sutures gradually decreased, and the more PCL in the coating materials, the longer effective strength-time for the suture. With the increasing of PCL in the drug-carrier, the rate of drug releasing became lower. The drug release mechanism of CPFX-PCL/PGA was a synergistic effect of drug diffusion and PCL/PGA carrier dissolution. [ABSTRACT FROM AUTHOR]

Poly(lactic acid) (PLA) suture can be absorbed by the human body, and so have wide applications in modern surgery operations. The degradation period of PLA suture is expected to meet with the healing time of different types of wounds. In order to control the degradation period of the PLA suture, the carbon nanotubes (CNTs) were composited with PLA suture, and the degradation experiment in vitro was performed on sutures. The structure and properties of sutures during degradation, such as surface morphology, breaking strength, elongation, mass and chemical structure, were tracked and analyzed. The results indicated that the degradation brought about surface defects and resulted in 13.5 weeks for the strength valid time of the original PLA suture. By contrast, the strength valid time of the CNTs/PLA suture was increased to 26.6 weeks. Whilst the toughness of both the pure PLA and CNTs/PLA sutures decreased rapidly and almost disappeared after 3 to 4 weeks of degradation. The mass loss demonstrated that the time required for complete degradation of the two sutures was obviously different, the pure PLA suture 49 weeks, while CNTs/PLA sutures 63 to 73 weeks. The research proved that CNTs delayed PLA degradation and prolonged its strength valid time in degradation. [ABSTRACT FROM AUTHOR]