喷雾干燥法制备眼用壳聚糖/明胶复合微球**

背景：普通滴眼液由于泪液冲刷与鼻泪管吸收等因素,在眼表停留时间短,生物利用度低。 目的：以壳聚糖、明胶为载体材料,左氧氟沙星为模型药物,制备应用于眼表的缓控释微球并考察其理化性质与体外释放。 方法：采用喷雾干燥法制备左氧氟沙星壳聚糖/明胶微球,通过扫描电镜观察微球的表面形态,激光粒度仪测量微球粒径分布与zeta电位,高效液相色谱法检测微球的载药率与包封率,动态透析法研究微球体外药物释放情况。 结果与结论：所得微球形态良好,粒径分布窄,平均粒径为(1 267.4±115.3) nm,zeta电位为+(32.19±0.85) mV,载药量为(18.31±0.22)%,包封率为(91.53±1.12)%。载药微球体外释放符合一级释药方程Ln(1-Q)=-0.699 1t-0.086 4,r2=0.945 1。说明壳聚糖/明胶载药微球对左氧氟沙星具有缓释作用。实验采用喷雾干燥法成功制备了粒径及分布适宜、释放周期较理想、药物稳定性好的载左氧氟沙星壳聚糖明胶缓释微球。      

Gas-generating polymeric microspheres for long-term and continuous in vivo ultrasound imaging

Ultrasound (US) imaging is one of the most common biomedical imaging methods, due to the easy assessment and noninvasive way. For more precise and accurate US imaging, many contrast agents have been developed in a form of microbubbles composed of inner gas and shell materials. However, microbubbles showed undesirable short half-life under acoustic field during US imaging and insufficient in vivo stability in blood flow due to diffusion or bubble destruction. Therefore, the improvement of the half-life and stability of microbubbles under in vivo condition is highly needed for long-term in vivo US imaging. Herein, we developed rationally designed gas-generating polymeric microsphere (GGPM) that can produce microbubbles without encapsulation of gas for long-term and continuous US imaging. The poly(cholesteryl γ-butyrolactone-b-propylene oxide), poly(CB-PO), with carbonate side chains was synthesized as gas-generating polymer by ring-opening polymerization of cholestryl γ-butyrolactone (CB) and propylene oxide (PO). As optimal structure for intense US signal generation, porous GGPMs (p-GGPMs) with the average size about 3-5 μm were prepared with poly(CB-PO) by double emulsion method. These p-GGPMs generated continuous US signals over 70 min, while the signals from Sonovue^®, a commercial US contrast agent were completely attenuated within 15 min. This long-term signal duration of p-GGPM was also reproduced when they were subcutaneously injected under the skin of mouse. Moreover, as advanced in vivo application, the fine US imaging of heart in rat was enabled by intravenous injection of p-GGPM. Therefore, these overall results showed the great potential of p-GGPM as gas-generating US contrast agent for in vivo biomedical imaging and diagnosis.     

In vitro evaluation of the effectiveness and cytotoxicity of meglumine antimoniate microspheres produced by spray drying against Leishmania infantum

The aim of the present study was to evaluate the in vitro activity and cytotoxicity of meglumine antimoniate microspheres produced by spray drying on Leishmania infantum and the effect of the excipients used in them. The parasite strain shows sensitivity to the meglumine antimoniate microspheres prepared. All the antimony IC₅₀ values from encapsulated meglumine antimoniate (3.80 ± 0.34 to 9.53 ± 0.70 μg SbV/ml for promastigotes assay) are considerably lower compared to the mean value of IC₅₀ in Glucantime solution (112 ± 12.74 μg SbV/ml). Interesting IC₅₀ values for the excipient chitosan (112.64 ± 0.53 mg/ml for promastigotes and 100.81 ± 26.45 mg/ml for amastigotes) were obtained (without cytotoxic activity), whereas the rest of the excipients did not show any activity. This new delivery system could offer a new pharmacological tool for the treatment of leishmaniosis that reduces the doses required, lowering toxic side effects because of meglumine antimoniate.     

Paramagnetic hollow silica nanospheres for in vivo targeted ultrasound and magnetic resonance imaging

A series of hollow silica nanospheres (HSNSs) with sizes ranging from 100 to 400 nm were synthesized and used for primary ultrasound imaging (US) efficiency assessment. The 400 nm HSNSs were chosen as platform for conjugation with Gd-DTPA and cyclo-arginine-glycine-aspartic acid c(RGD) peptide to construct US and magnetic resonance imaging (MRI) dual-modal contrast agents (CAs): [HSNSs@(DTPA-Gd)-RGD]. The obtained CAs displayed good physiological stability, low cytotoxicity and negligible hemolytic activity in vitro. Furthermore, the passive accumulation and active-targeting of the HSNSs in the tumor site of mice was demonstrated by US and MR imaging, respectively. The qualitative and quantitative biodistribution of the HSNSs showed that they mainly accumulated in the tissues of liver, lung, tumor after intravenous administration and then be excreted from feces. In addition, histological, hematological, blood and biochemical analysis were used to further study toxicity of the HSNSs, and all results indicated that there were no covert toxicity of HSNSs in mice after long exposure times. Findings from this study indicated that the silica-based paramagnetic HSNSs can be used as a platform for long-term targeted imaging and therapy studies safely in vivo.     

Characterization and optimization of cell seeding in scaffolds by factorial design: quality by design approach for skeletal tissue engineering

Cell seeding into scaffolds plays a crucial role in the development of efficient bone tissue engineering constructs. Hence, it becomes imperative to identify the key factors that quantitatively predict reproducible and efficient seeding protocols. In this study, the optimization of a cell seeding process was investigated using design of experiments (DOE) statistical methods. Five seeding factors (cell type, scaffold type, seeding volume, seeding density, and seeding time) were selected and investigated by means of two response parameters, critically related to the cell seeding process: cell seeding efficiency (CSE) and cell-specific viability (CSV). In addition, cell spatial distribution (CSD) was analyzed by Live/Dead staining assays. Analysis identified a number of statistically significant main factor effects and interactions. Among the five seeding factors, only seeding volume and seeding time significantly affected CSE and CSV. Also, cell and scaffold type were involved in the interactions with other seeding factors. Within the investigated ranges, optimal conditions in terms of CSV and CSD were obtained when seeding cells in a regular scaffold with an excess of medium. The results of this case study contribute to a better understanding and definition of optimal process parameters for cell seeding. A DOE strategy can identify and optimize critical process variables to reduce the variability and assists in determining which variables should be carefully controlled during good manufacturing practice production to enable a clinically relevant implant.     

Rational development of GAG-augmented chitosan membranes by fractional factorial design methodology

To develop a novel biomaterial for chondrocyte culture, 8 glycosaminoglycan (GAG)/chitosan membranes (groups N1-N8) were prepared, with the aid of a 2-level 2(4-1) fractional factorial design, by co-immobilizing chondroitin-4-sulfate (CSA), chondroitin-6-sulfate (CSC), dermatan sulfate (DS), and heparin to chitosan membranes. The fractional factorial design allowed us to partly interpret the effects of individual GAGs and two-way interactions between GAGs. Within the level range of -1 and +1, low CSA level (2.6 mg) is favorable for collagen synthesis but not for cell proliferation. High CSC level (1.3 mg) is favorable for GAG production but not for cell proliferation. Conversely, high heparin (0.33 mg) and DS (0.13 mg) levels are desired for cell proliferation but not for the production of collagen and GAG. Moreover, the two-way interactions between GAGs influence the cell behavior. Among the 8 GAG/chitosan membranes, N1 and N4 (containing low CSA and heparin levels) lead to the maintenance of proper chondrocyte phenotype, as judged by the chondrocyte-like morphology, modest cell expansion, higher GAG and collagen production and proper cartilage marker gene expression. In conclusion, this approach provides a means of rationally predicting and evaluating the proper formulation of GAG/chitosan membranes and may facilitate the rational design of other tissue engineering scaffolds.     

彩色超声影像图文工作站的设计与实现

开发彩色超声图文工作站YNUPW2005,以获取、显示和处理超声动静态图像,自动生成并打印诊断报告。此彩色超声影像图文工作站改变了超声检测中图像的显示、处理和存储以及诊断报告生成的传统模式,为超声诊断、临床治疗和超声研究提供了精确的医学图文信息。     

Nanosheet-based titania microspheres with hollow core-shell structure encapsulating horseradish peroxidase for a mediator-free biosensor

Nanosheet-based titania (TiO(2)) microspheres with a hollow core-shell structure have been synthesized and employed to immobilize horseradish peroxidase (HRP) in order to fabricate a mediator-free biosensor. The morphology and structure of the TiO(2) microspheres were characterized by X-ray diffraction, scanning electron microscopy and transmission electronic microscopy. A possible growth mechanism has been proposed. Spectroscopic and electrochemical measurements revealed that the TiO(2) microspheres are an immobilization support with biocompatibility for enzymes, affording good enzyme stability and bioactivity. Due to the nanosheet-based hollow core-shell structure of the TiO(2) microspheres, the direct electron transfer of HRP is facilitated and the resulting biosensor displayed good performance for the detection of H(2)O(2), with both a low detection limit of 0.05 μM and a wide linear range of 0.4-140 μM, as well as a fast response and excellent long-term stability. The nanosheet-based TiO(2) microspheres with hollow core-shell structure, can be used for the efficient entrapment of other redox-active proteins and have wide potential applications in biosensors, biocatalysis, biomedical devices and bioelectronics.     

A new approach to prepare well-dispersed CaF(2) nanoparticles by spray drying technique

Previously, nano-sized calcium fluoride (CaF?) particles were prepared using a spray drying method by simultaneously feeding Ca(OH)? and NH?F solutions to a two-liquid nozzle. The aim of the present study was to prepare better-dispersed nano-CaF? particles by co-forming a soluble salt, sodium chloride (NaCl). NaCl of various concentrations were added to the NH(4) F solution, leading to formation of (CaF? +NaCl) composites with CaF? /NaCl molar ratios of 4/1, 4/4, and 4/16. Pure nano-CaF? was also prepared as the control. Powder X-ray diffraction analysis showed that the products contained crystalline CaF? and NaCl. Scanning electron microscopy examinations showed that both the CaF? /NaCl composite and pure CaF? particles were about (50-800) nm in size and consisted of primary CaF? particles of < 50 nm in size. BET surface area measurements showed similar primary particle sizes for all samples. Dynamic light scattering measurements showed that the washed (CaF?+NaCl) particles were much smaller than the pure CaF? as the dissolution of NaCl "freed" most of the primary CaF? particles, leading to a greater degree of particle dispersion. The well-dispersed nano-CaF? may be expected to be a more effective anticaries agent than NaF by providing longer lasting elevations of fluoride concentrations in oral fluids.     

3-Dimensional ultrasound imaging for meniscal lesions

PURPOSE: The aim of this prospective study was to evaluate preoperative three-dimensional ultrasound scans for the detection of meniscal lesions with a special focus on interobserver reliability. METHODS: Forty one patients with clinical signs of meniscal lesions were preoperatively examined by ultrasound using the 3-D technique (11.7 MHz linear transducer). The 3-D dataset was stored and examined by a second orthopaedic surgeon. The second ultrasound examiner was blinded to the results of the first. Any meniscal pathology was confirmed arthroscopically and documented. RESULTS: At arthroscopy eight lateral meniscal lesions and 57 medial meniscal lesions were detected at different locations. The sensitivity and specificity of the original ultrasound examination was acceptable whereas the results of the second ultrasound session were not as sensitive. CONCLUSION: Three-D-ultrasound with a high resolution transducer, in the hands of an experienced operator, provides acceptable results in the detection of meniscal lesions, however, analysis of the volume dataset from the 3-D ultrasound investigation indicates that it does not offer sufficient accuracy for clinical use.     

Biomechanical characterization of a low density silicone elastomer filled with hollow microspheres for maxillofacial prostheses

An ideal material for maxillofacial prostheses has not been found. We created a novel material: silicone elastomer filled with hollow microspheres and characterized its biomechanical properties. Expancel hollow microspheres were mixed with MDX4-4210 silicone elastomer using Q7-9180 silicone fluid as diluent. The volume fractions of microspheres were 0, 5, 15, and 30%?v/v (volume ratio to the total volume of MDX4-4210 and microspheres). The microspheres dispersed well in the matrix. The physical properties and biocompatibility of the composites were examined. Shock absorption was the greatest by the 5%?v/v composite, and decreased with increasing concentrations of microspheres. The density, thermal conductivity, Shore A hardness, tear and tensile strength decreased with increasing concentrations of microspheres, while elongation at break increased. Importantly, the tear strength of all composites was markedly lower than that of pure silicone elastomer. Cell viability assays indicated that the composite was of good biocompatibility. The composite with a volume fraction of 5% exhibited the optimal properties for use as a maxillofacial prosthesis, though its tear strength was markedly lower than that of silicone elastomer. In conclusion, we developed a novel light and soft material with good flexibility and biocompatibility, which holds a promising prospect for clinical application as maxillofacial prosthesis.     

Assessment of lower limb artery disease by ultrasound imaging

Lower limb artery ultrasound is portable and can be used in first aid outpatient clinics and at the bedside. In addition, I can assess blood vessel properties and evaluate bloodstream change non-invasively in real time, an inspection that is indispensable for the diagnosis and treatment of peripheral artery disease.     

超声成像的相位偏差校正

由于人体组织的各向异性，超声成像中存在相位偏差。相差制约了超声成像分辨率的进一步提高。互相关及其类似相位估计技术可以用于相差校正，jitter是此类算法的基本限制。并行自适应接收补偿算法可以校正较小的相差，结合互相关技术能够得到比较理想的相差校正效果。     

Synthesis and characterization of uniform radiopaque polystyrene microspheres for X-ray imaging by a single-step swelling process

Uniform radiopaque polystyrene microspheres of approximately 2.3 +/- 0.2 microm were prepared by a single-step swelling of 2.3 +/- 0.2 microm polystyrene template microspheres, dispersed in an aqueous solution with methylene chloride emulsion droplets containing 2,3,5-triiodobenzoylethyl ester. After completing the swelling process, the methylene chloride was evaporated in order to lock the 2,3,5-triiodobenzoylethyl ester in the polystyrene microspheres. The influence of the weight ratio [2,3,5-triiodobenzoylethyl ester]/[polystyrene] on the % of entrapped 2,3,5-triiodobenzoylethyl ester was elucidated. Characterization of the radiopaque polystyrene microspheres was accomplished by light microscope, FTIR, TGA, SEM, XPS, and elemental analysis. The radiopacity of the microspheres was demonstrated by an imaging technique based on X-ray absorption usually used in hospitals. This novel method of encapsulation of 2,3,5-triiodobenzoylethyl ester within polystyrene microspheres by a single-step swelling process may be used as a model for encapsulation of various hydrophobic radiopaque drugs within uniform polystyrene template particles of various diameters for different X-ray imaging needs, e.g., blood pool, body organs, embolization, dental composition, implants, protheses, and nanocomposites.     

基于超快超声平面波成像的医学超声探头改进

目的基于平面波发射/接收原理的超快超声成像技术近年来已成为国际医学超声领域的研究热点,有望取代传统的聚焦扫描式超声成像技术。传统方式受其成像模式的限制,无法实现高帧频成像,而通过平面波发射以及相干复合方法,可大大提高超声成像的帧频。本文提出一个新的设想,即采用高程方向无聚焦换能器(non-elevation-focused probe,NEFP),相对于传统的高程方向有聚焦换能器(elevation-focused probe,EFP),可能有助于进一步提高超快超声成像技术的成像效果。方法首先简要介绍平面波相干复合成像的原理和方法,进而通过FieldⅡ软件仿真,验证相干复合成像方法对平面波成像图像质量的提升效果。最后,通过仿真和实验实现探头高程方向的发射声束聚焦模式,并对上述2种模式换能器的平面波成像效果进行了对比分析。结果使用平面波复合成像算法得到很好的成像效果,两种探头经对比,NEFP探头成像图像的对比度相对于EFP探头明显增强。结论对于超快超声成像方法,使用NEFP超声探头可以取得更优的成像效果。     

Novel spray dried pH-sensitive polyacrylamide-grafted-carboxymethylcellulose sodium copolymer microspheres for colon targeted delivery of an anti-cancer drug

Unique pH-sensitive spray dried microspheres were formulated employing hydrolyzed polyacrylamide-g-carboxymethylcellulose sodium (PAAm-g-NaCMC) co-polymer for colon targeted delivery of an anticancer drug, capecitabine. Synthesis of PAAm-g-NaCMC was carried out through free radical polymerization, which was supported with an inert atmosphere and then the alkaline hydrolysis was performed and subjected for characterization including FTIR spectroscopic analysis, ¹H NMR spectroscopic analysis, elemental analysis, viscosity measurement, neutralization equivalent and thermo-gravimetric investigation. The swelling data suggested that the PAAm-g-NaCMC possesses significant pH-sensitive property. The microspheres were in the range of 1.00 to 7.34 μ and the drug entrapment efficiency ranged between 70.98 and 94.41%. In vitro drug release suggested the failure of microspheres formulated using native NaCMC which failed to impede drug release in stomach and small intestine, while those prepared with pH-sensitive PAAm-g-NaCMC copolymer and cross-linked with glutaraldehyde are suitable for colon targeting because they retarded release of drug in physiologic atmosphere of stomach and small intestine. Only 12.97% of drug was released from CMC10 formulation by the end of 5th h and rest of drug has been targeted to colonic region. A sudden increase in release of drug was observed in rat caecal contents media because of colonic bacterial action on PAAm-g-NaCMC copolymer.     

Assessment of quadriceps muscle cross-sectional area by ultrasound extended-field-of-view imaging

This study aimed to test the validity and reliability of an extended-field-of-view ultrasonography (EFOV) method for quadriceps muscle cross-sectional area (CSA) assessment. The CSA was measured at 10, 20, 30, 40 and 50% of the distance from the superior border of the patella to the medial aspect of anterior superior iliac spine by EFOV imaging and compared to the CSA measured by computed tomography (CT). Validity was tested by intra-class correlation (ICC) between the two methods and intra- and inter-experimenter and inter-day reliability were also examined. The ICC computed between the two techniques ranged between 0.951 and 0.998 (P < 0.000), but the 95% confidence intervals of the ICCs were in the acceptable range only for 30, 40 and 50% sections (0.842–0.999, 0.943–0.997 and 0.992-0.999, respectively). The standard error of the EFOV technique when compared to CT was 2.4, 4.3, 1.2, 1.2 and 0.6%, for 10, 20, 30, 40 and 50% sections, respectively. The coefficient of variation, showing intra- and inter-experimenter reliability, ranged from 0.6 to 2.7%. ICCs computed to assess the inter-day reliability were between 0.982 and 0.998 (95% confidence interval 0.892–1). When CSA was compared between sections statistically significant differences were found between them, regardless of the imaging technique used. Small standard errors of the measurement and high ICCs with the small confidence intervals suggest that, at proximal and mid-thigh sections, EFOV is a valid and reliable method to measure quadriceps muscle size.     

Second harmonic inversion for ultrasound contrast harmonic imaging

Ultrasound contrast agents (UCAs) are small micro-bubbles that behave nonlinearly when exposed to an ultrasound wave. This nonlinear behavior can be observed through the generated higher harmonics in a back-scattered echo. In past years several techniques have been proposed to detect or image harmonics produced by UCAs. In these proposed works, the harmonics generated in the medium during the propagation of the ultrasound wave played an important role, since these harmonics compete with the harmonics generated by the micro-bubbles. We present a method for the reduction of the second harmonic generated during nonlinear-propagation-dubbed second harmonic inversion (SHI). A general expression for the suppression signals is also derived. The SHI technique uses two pulses, p' and p″, of the same frequency f(0) and the same amplitude P(0) to cancel out the second harmonic generated by nonlinearities of the medium. Simulations show that the second harmonic is reduced by 40?dB on a large axial range. Experimental SHI B-mode images, from a tissue-mimicking phantom and UCAs, show an improvement in the agent-to-tissue ratio (ATR) of 20?dB compared to standard second harmonic imaging and 13?dB of improvement in harmonic power Doppler.