A multiple-stimuli-responsive drug-conjugated cross-linked micelles was prepared by radical copolymerization. The chemical structure, morphology, and size of the cross-linked micelles were characterized, and the drug loading of the micelle was calculated. The experimental results indicated that the hydrodynamic size of the drug-loaded micelles were about 100 nm, and the as prepared micelles could be degraded and swelled in presence of reducing glutathione (GSH). The low critical solution temperature (LCST) of the micelle was around 39.4℃. According to the experimental results, the micelles will shrink at temperature above the LCST. Subsequently, the accumulative drug release rate was up to 91.78% under acidic (pH 5.0), reductive (GSH 10 mmol/L) and high temperature (42.0℃) conditions mimicking the tumor microenvironment, while a relatively low release rate of 1.12% was observed without stimulation. The drug-conjugated cross-linked micelles showed a strong cell uptake behavior. In the cytotoxicity assay, the micelles exhibited effective anti-cancer activity and excellent biocompatibility. In brief, the experimental results show that the as-prepared drug-conjugated cross-linked micelle exhibits multiple stimuli-responsiveness, which holds great promise for anti-cancer drug delivery.
This paper aims to explore the thermal feelings of different cover materials effect on wheelchair cushion comfortableness, and to build a mathematical model for motorized wheelchair cushion comfortableness. By measuring temperature and humidity between the contact face of motorized wheelchair cushion and human body as well as the setting posture adjustment time while cushion cover materials are nylon cloth, leather, fishnets cloth. At the same time, each volunteer took a questionnaire about the comfort of different cushion cover materials. Results showed that fishnets cloth was most comfortable, leather was worst, while nylon cloth was in between the two. The experimental objective data were consistent with the subjective data. We built a back propagation (BP) neural network mathematical model for motorized wheelchair cushion comfortableness. This study will provide objective reference to motorized wheelchair for the designers and users.
The effect of relaxation time in hyperbolic heat transfer model on the temperature field of microwave ablation of atrial fibrillation was investigated. And the results were compared with those calculated by Pennes model. A three-dimensional model of microwave ablation of atrial fibrillation was constructed. The relaxation time (τ) was 0, 1, 5, 8, 10, 15 and 20 s, respectively. And the temperature field of myocardial tissue was obtained. The results showed that the highest temperature of the hyperbolic model was 21.8 ℃ lower than that of the Pennes model at the beginning of ablation. With the increase of ablation time, the highest temperature tended to be the same. The lesion dimensions appeared at 3, 4, 6, 7, 8, 9, and 10 s, respectively after ablation. Therefore, the influence of hyperbolic model on temperature will decrease with the increase of the ablation time. At the beginning of ablation, the relaxation time will hinder the speed of myocardial thermal diffusion. The larger the relaxation time is, the slower the speed of thermal diffusion is. This study provides a reference for the application of hyperbolic model in microwave ablation of atrial fibrillation.
Objective To systematically review the effectiveness of forced air warming for the maintenance of perioperative core temperature, so as to provide clinical evidence for an appropriate warming plan during the perioperative period. Methods We electronically searched PubMed, The Cochrane Library, EMbase, Web of Science, CBM and CNKI from 2000 to 2012, so as to comprehensively collect randomized controlled trials (RCTs) about the effectiveness of different warming methods for the maintenance of perioperative core temperature (including forced air warming, resistive-heating blanket/electric heating pad, circulating water mattress, and infrared ray radiant heating system) for maintenance of perioperative core temperature. References of the included studies were also retrieved. Two reviewers independently screened literature according to the inclusion and exclusion criteria, extracted data and assessed the quality of the included studies. Then, meta-analysis was performed using RevMan 5.1 software. Results Eleven RCTs involving 577 patients were included. The results of meta-analysis indicated that, in the maintenance of core temperature during the perioperative period, forced air warming was superior to resistive-heating blanket/electric heating pad (SMD= –0.40, 95%CI –0.73 to –0.06), circulating water mattress (SMD= –1.10, 95%CI –1.55 to –0.66), and infrared ray radiant heating system (SMD= –0.69, 95%CI –1.06 to –0.32). In the incidence of hypothermia during the perioperative period, the group of forced air warming was lower than the group of blanket/electric heating pad (RR=1.76, 95%CI 1.15 to 2.69), but it was the same as the group of infrared ray radiant heating system (RR=1.37, 95%CI 0.83 to 2.27). In the incidence of shivering during the perioperative period, the group of forced air warming was the same as the group of blanket/electric heating pad (RR=0.75, 95%CI 0.18 to 3.21) and the group of infrared ray radiant heating system (RR=0.8, 95%CI 0.19 to 3.36). Conclusion Compared with resistive-heating blanket/electric heating pad, circulating water mattress, and infrared ray radiant heating system, forced air warming maintains patients’ core temperature better during the perioperative period, with a lower incidences of hypothermia. Due to the limited quantity and quality of the included studies, more high quality RCTs with large sample size are needed to verify the above conclusion.
ObjectiveTo study the preparation and cytocompatibility of bone tissue engineering scaffolds by combining low temperature three dimensional (3D) printing and vacuum freeze-drying techniques. MethodsCollagen (COL)and silk fibroin (SF) were manufactured from fresh bovine tendon and silkworm silk. SolidWorks2014 was adopted to design bone tissue engineering scaffold models with the size of 9 mm×9 mm×3 mm and pore diameter of 500μm. According to the behavior of composite materials that low temperature 3D printing equipment required, COL, SF, and nano-hydroxyapatite (nHA)at a ratio of 9:3:2 and low temperature 3D printing in combination with vacuum freeze-drying techniques were accepted to build COL/SF/nHA composite scaffolds. Gross observation and scanning electron microscope (SEM) were applied to observe the morphology and surface structures of composite scaffolds. Meanwhile, compression displacement, compression stress, and elasticity modulus were measured by mechanics machine to analyze mechanical properties of composite scaffolds. The growth and proliferation of MC3T3-E1 cells were evaluated using SEM, inverted microscope, and MTT assay after cultured for 1, 7, 14, and 21 days on the composite scaffolds. The RT-PCR and Western blot techniques were adopted to detect the gene and protein expressions of COL I, alkaline phosphatase (ALP), and osteocalcin (OCN) in MC3T3-E1 cells after 21 days. ResultsCOL/SF/nHA composite scaffolds were successfully prepared by low temperature 3D printing technology and vacuum freeze-drying techniques; the SEM results showed that the bionic bone scaffolds were 3D polyporous structures with macropores and micropores. The mechanical performance showed that the elasticity modulus was (344.783 07±40.728 55) kPa; compression displacement was (0.958 41±0.000 84) mm; and compression stress was (0.062 15±0.007 15) MPa. The results of inverted microscope, SEM, and MTT method showed that a large number of cells adhered to the surface with full extension and good cells growth inside the macropores, which demonstrated a satisfactory proliferation rate of the MC3T3-E1 cells on the composite scaffolds. The RT-PCR and Western blot electrophoresis revealed gene expressions and protein synthesis of COL I, ALP, and OCN in MC3T3-E1 cells. ConclusionLow temperature 3D printing in combination with vacuum freeze-drying techniques could realize multi-aperture coexisted bionic bone tissue engineering scaffolds and control the microstructures of composite scaffolds precisely that possess good cytocompatibility. It was expected to be a bone defect repair material, which lays a foundation for further research of bone defect.
Patch clamp is a technique that can measure weak current in the level of picoampere (pA). It has been widely used for cellular electrophysiological recording in fundamental medical researches, such as membrane potential and ion channel currents recording, etc. In order to obtain accurate measurement results, both the resistance and capacitance of the pipette are required to be compensated. Capacitance compensations are composed of slow and fast capacitance compensation. The slow compensation is determined by the lipid bilayer of cell membrane, and its magnitude usually ranges from a few picofarads (pF) to a few microfarads (μF), depending on the cell size. The fast capacitance is formed by the distributed capacitance of the glass pipette, wires and solution, mostly ranging in a few picofarads. After the pipette sucks the cells in the solution, the positions of the glass pipette and wire have been determined, and only taking once compensation for slow and fast capacitance will meet the recording requirements. However, when the study needs to deal with the temperature characteristics, it is still necessary to make a recognition on the temperature characteristic of the capacitance. We found that the time constant of fast capacitance discharge changed with increasing temperature of bath solution when we studied the photothermal effect on cell membrane by patch clamp. Based on this phenomenon, we proposed an equivalent circuit to calculate the temperature-dependent parameters. Experimental results showed that the fast capacitance increased in a positive rate of 0.04 pF/℃, while the pipette resistance decreased. The fine data analysis demonstrated that the temperature rises of bath solution determined the kinetics of the fast capacitance mainly by changing the inner solution resistance of the glass pipette. This result will provide a good reference for the fine temperature characteristic study related to cellular electrophysiology based on patch clamp technique.
ObjectiveTo manufacture a polycaprolactone (PCL)/type Ⅰ collagen (COL Ⅰ) tissue engineered meniscus scaffold (hereinafter referred to as PCL/COL Ⅰ meniscus scaffold) by three-dimensional (3D) printing with low temperature deposition technique and to study its physicochemical properties.MethodsFirst, the 15% PCL/4% COLⅠ composite solution and 15% PCL simple solution were prepared. Then, 15% PCL/4% COL Ⅰmeniscus scaffold and 15% PCL meniscal scaffold were prepared by using 3D printing with low temperature deposition techniques. The morphology and microstructure of the scaffolds were observed by gross observation and scanning electron microscope. The compression modulus and tensile modulus of the scaffolds were measured by biomechanical test. The components of the scaffolds were analyzed by Fourier transform infrared spectroscopy (FTIR). The contact angle of the scaffold surface was measured. The meniscus cells of rabbits were cultured with the two scaffold extracts and scaffolds, respectively. After cultured, the cell proliferations were detected by cell counting kit 8 (CCK-8), and the normal cultured cells were used as controls. Cell adhesion and growth of scaffold-cell complex were observed by scanning electron microscope.ResultsAccording to the gross and scanning electron microscope observations, two scaffolds had orientated 3D microstructures and pores, but the surface of the PCL/COLⅠ meniscus scaffold was rougher than the PCL meniscus scaffold. Biomechanical analysis showed that the tensile modulus and compression modulus of the PCL/COL Ⅰ meniscus scaffold were not significantly different from those of the PCL meniscus scaffold (P>0.05). FTIR analysis results showed that COL Ⅰ and PCL were successful mixed in PCL/ COL Ⅰ meniscus scaffolds. The contact angle of PCL/COLⅠ meniscus scaffold [(83.19±7.49)°] was significantly lower than that of PCL meniscus scaffold [(111.13±5.70)°] (t=6.638, P=0.000). The results of the CCK-8 assay indicated that with time, the number of cells cultured in two scaffold extracts showed an increasing trend, and there was no significant difference when compared with the control group (P>0.05). Scanning electron microscope observation showed that the cells attached on the PCL/ COL Ⅰ meniscus scaffold more than that on the PCL scaffold.ConclusionPCL/COLⅠmeniscus scaffolds are prepared by 3D printing with low temperature deposition technique, which has excellent physicochemical properties without cytotoxicity. PCL/COLⅠmeniscus scaffold is expected to be used as the material for meniscus tissue engineering.
Numerical simulation is one of the most significant methods to predict the temperature distribution in high-intensity focused ultrasound (HIFU) therapy. In this study, the adopted numerical simulation was used based on a transcranial ultrasound therapy model taking a human skull as a reference. The approximation of the Westervelt formula and the Pennes bio-heat conduction equation were applied to the simulation of the transcranial temperature distribution. According to the temperature distribution and the Time Reversal theory, the position of the treatable focal region was corrected and the hot spot existing in the skull was eliminated. Furthermore, the influence of the exposure time, input power and the distance between transducer and skull on the temperature distribution was analyzed. The results showed that the position of the focal region could be corrected and the hot spot was eliminated using the Time Reversal theory without affecting the focus. The focal region above 60℃ could be formed at the superficial tissue located from the skull of 20 mm using the hot spot elimination method and the volume of the focal region increases with the exposure time and the input power in a nonlinear form. When the same volume of the focal region was obtained, the more power was inputted, the less the exposure time was needed. Moreover, the volume of the focal region was influenced by the distance between the transducer and the skull.
The temperature during the brain tumor therapy using high-intensity focused ultrasound (HIFU) should be controlled strictly. This research aimed at realizing uniform temperature distribution in the focal region by adjusting driving signals of phased array transducer. The three-dimensional simulation model imitating craniotomy HIFU brain tumor treatment was established based on an 82-element transducer and the computed tomography (CT) data of a volunteer's head was used to calculate and modulate the temperature distributions using the finite difference in time domain (FDTD) method. Two signals which focus at two preset targets with a certain distance were superimposed to emit each transducer element. Then the temperature distribution was modulated by changing the triggering time delay and amplitudes of the two signals. The results showed that when the distance between the two targets was within a certain range, a focal region with uniform temperature distribution could be created. And also the volume of focal region formed by one irradiation could be adjusted. The simulation results would provide theoretical method and reference for HIFU applying in clinical brain tumor treatment safely and effectively.
【Abstract】Objective To investigate the effects of preservative temperature on pancreatic function and determine the optimal preservative temperature for pancreatic transplantation. MethodsCold pancreatic preservation was performed and a homologous male Wistar rat model of heterotopic total pancreaticoduodenal transplantation was established. The pancreas was preserved for 6 h in UW solution at specific temperatures(0 ℃, 4 ℃, 8 ℃ and 12 ℃). After preservation, pancreatic tissue was taken for histologic examination in every group. ATP and total adenine nucleotides (TAN) were determined by using high performance liquid chromatography (HPLC). Blood glucose(BG), serum amylase and lipase were measured 24 h after transplantation. And the activity of myeloperoxidase (MPO) in the pancreatic grafts was also measured at the same time. Besides, histological observation was performed. Results Microscopic studies showed that the histomorphological changes of pancreas in 4 ℃ group were less obvious than those in other groups. Tissual concentrations of ATP and TAN decreased gradually in 4 ℃ group, 0 ℃ group, 8 ℃ group, and 12 ℃ group after 6 h of preservation(PH＜0.05). The levels of BG, serum lipase and MPO increased gradually in 4 ℃ group, 0 ℃ group, 8 ℃ group, and 12 ℃ group(PH＜0.05). The activity of MPO in 4 ℃ group （1.19±0.16 U/g ）was significantly lower than that of the control group（0.26±0.09 U/g，PH＜0.05). Conclusion The temperature of 4 ℃ is most appropriate for hypothermic pancreatic preservation and can considerably alleviate cold ischemic injury of rat pancreas.