Method of calculating porosity based on M44 element images of the Mueller matrix.

As a drug carrier, the porosity of porous electrospun fiber can greatly affect its drug loading ability and stability. In this work, a method to calculate the porosity of porous electrospun fiber with a polarization micrograph is described. Different porosities of porous electrospun fibers were measured by scanning electron microscope images and transmission Mueller matrix M44 element images, respectively. Mueller matrix M44 element images were obtained after polarization micrograph and normalization. The pore areas of M44 images were extracted by region growing, and the contour parts were obtained by performing morphological operation on pore areas. The porosity calculated by the polarization microscope image is in good consistency with that measured by the scanning electron microscope. Our results will promote practical application of electrospun porous fibers in the early stage of screening a large number of porous materials in the biomedicine field.

[Experimental studies for noninvasive assessment of portal vein pressure based on contrast enhanced subharmonic sonographic imaging].

Portal hypertension (PHT) is a common complication of liver cirrhosis, which could be measured by the means of portal vein pressure (PVP). However, there is no report about an effective and reliable way to achieve noninvasive assessment of PVP so far. In this study, firstly, we collected ultrasound images and echo signals of different ultrasound contrast agent (UCA) concentrations and different pressure ranges in a low-pressure environment based on an in vitro simulation device. Then, the amplitudes of the subharmonics in the echo signal were obtained by ultrasound grayscale image construction and fast Fourier transform (FFT). Finally, we analyzed the relationship between subharmonic amplitude (SA) and bionic portal vein pressure (BPVP) through linear regression. As a result, in the pressure range of 7.5-45 mm Hg and 8-20 mm Hg, the linear correlation coefficients (LCC) between SA and BPVP were 0.927 and 0.913 respectively when the UCA concentration was 1∶3 000, and LCC were 0.737 and 0.568 respectively when the UCA concentration was 1∶6 000. Particularly, LCC was increased to 0.968 and 0.916 respectively while the SAs of two UCA concentrations were used as the features of BPVP. Therefore, the results show a good performance on the linear relationship between SA and BPVP, and the LCC will be improved by using SAs obtained at different UCA concentrations as the features of BPVP. The proposed method provides reliable experimental verification for noninvasive evaluation of PVP through SA in clinical practice, which could be a guidance for improving the accuracy of PVP assessment.

Mueller matrix imaging of electrospun ultrafine fibers for morphology detection.

In the fields of tissue engineering, drug delivery, and filtering material, electrospun ultrafine fibers with micropores have important applications. A scanning electron microscope (SEM) is typically used to observe the microstructure of ultrafine fibers, but SEM has disadvantages, such as small field of vision, high cost, and ionization damage. Given this, 16 (4×4) full transmission Mueller matrices of electrospun fibers with three different morphologies, i.e., smooth surface, microporous, and beaded microspheres, were obtained. We find that the Mueller matrix element M44 is most sensitive to the micropores on fibers. In the M44 transformed image proposed in this paper, the different morphologies and contours of fibers can be clearly shown, providing a low-cost method for mass, nondestructive, and rapid morphology detection of fibers.

[A correction method for calculating resistance of Westerhof 's resistor].

The objective of the mock circulatory system (MCS) is to construct the characteristics of cardiovascular hemodynamics. Westerhof 's resistor that often regarded as the laminar flow resistance in the MCS, is commonly used to simulate the peripheral resistance of the cardiovascular system. However, the theoretical calculation value of fluid resistance of the Westerhof 's resistor shows distinguished difference with the actual needed value. If the theoretical resistance is regarded as the actual needed one and be used directly in the experiment, the experimental accuracy would not be acceptable. In order to improve the accuracy, an effective correction method for calculating the resistance of Westerhof 's resistor was proposed in this paper. Simulation software was also developed to compute accurately the capillary number, total length and resistance. The results demonstrate the proposed method is able to reduce the difficulty and complexity of the design of the resistor, which would obviously increase the manufactured precision of the Westerhof 's resistor. Simulation software would provide great support to the construction of various MCSs.

A multichannel electromyography dataset for continuous intraoperative neurophysiological monitoring of cranial nerve.

Continuous Intraoperative Neurophysiologic Monitoring (cIONM) is a widely used technology to improve surgical outcomes and prevent cranial nerve injury during skull base surgery. Monitoring of free-running electromyogram (EMG) plays an important role in cIONM, which can be used to identify different discharge patterns, alert the surgeon to potential nerve damage promptly, etc. In this dataset, we collected clinical multichannel EMG signals from 11 independent patients' data using a Neuromaster G1 MEE-2000 system (Nihon Kohden, Inc., Tokyo, Japan). Through innovative classification methods, these signals were categorized into seven different categories. Remarkably, channel 1 and channel 2 captured continuous EMG signals from the facial nerve (VII cranial nerve), while channel 3 to channel 6 focused on V, XI, X, and XII cranial nerves. This is the first time that intraoperative EMG signals have been collated and presented as a dataset and labelled by professional neurophysiologists. These data can be utilized to develop the architecture of neural networks in deep learning, machine learning, pattern recognition, and other commonly employed biomedical engineering research methods, thereby providing valuable information to enhance the safety and efficacy of surgical procedures.

Automatic Detection of Age-Related Macular Degeneration Based on Deep Learning and Local Outlier Factor Algorithm.

Age-related macular degeneration (AMD) is a retinal disorder affecting the elderly, and society's aging population means that the disease is becoming increasingly prevalent. The vision in patients with early AMD is usually unaffected or nearly normal but central vision may be weakened or even lost if timely treatment is not performed. Therefore, early diagnosis is particularly important to prevent the further exacerbation of AMD. This paper proposed a novel automatic detection method of AMD from optical coherence tomography (OCT) images based on deep learning and a local outlier factor (LOF) algorithm. A ResNet-50 model with L2-constrained softmax loss was retrained to extract features from OCT images and the LOF algorithm was used as the classifier. The proposed method was trained on the UCSD dataset and tested on both the UCSD dataset and Duke dataset, with an accuracy of 99.87% and 97.56%, respectively. Even though the model was only trained on the UCSD dataset, it obtained good detection accuracy when tested on another dataset. Comparison with other methods also indicates the efficiency of the proposed method in detecting AMD.

Superpixel-Oriented Label Distribution Learning for Skin Lesion Segmentation.

Lesion segmentation is a critical task in skin cancer analysis and detection. When developing deep learning-based segmentation methods, we need a large number of human-annotated labels to serve as ground truth for model-supervised learning. Due to the complexity of dermatological images and the subjective differences of different dermatologists in decision-making, the labels in the segmentation target boundary region are prone to produce uncertain labels or error labels. These labels may lead to unsatisfactory performance of dermoscopy segmentation. In addition, the model trained by the errored one-hot label may be overconfident, which can lead to arbitrary prediction and model overfitting. In this paper, a superpixel-oriented label distribution learning method is proposed. The superpixels formed by the simple linear iterative cluster (SLIC) algorithm combine one-hot labels constraint and define a distance function to convert it into a soft probability distribution. Referring to the model structure of knowledge distillation, after Superpixel-oriented label distribution learning, we get soft labels with structural prior information. Then the soft labels are transferred as new knowledge to the lesion segmentation network for training. Ours method on ISIC 2018 datasets achieves an Dice coefficient reaching 84%, sensitivity 79.6%, precision 80.4%, improved by 19.3%, 8.6% and 2.5% respectively in comparison with the results of U-Net. We also evaluate our method on the tasks of skin lesion segmentation via several general neural network architectures. The experiments show that ours method improves the performance of network image segmentation and can be easily integrated into most existing deep learning architectures.

A Novel Wearable Flexible Dry Electrode Based on Cowhide for ECG Measurement.

The electrocardiogram (ECG) electrode, as a sensor, is an important part of the wearable ECG monitoring device. Natural leather is rarely used as the electrode substrate. In this paper, wearable flexible silver electrodes based on cowhide were prepared by sputtering and brush-painting. A signal generator, oscilloscope, impedance test instrument, and ECG monitor were used to build the test platform evaluating the performance of electrodes with six subjects. The lossless waveform transmission can be achieved with our electrodes. Therefore, the Pearson's correlation coefficient calculated with input waveform and output waveform of the electrodes based on the top grain layer (GLE) and the split layer (SLE) of cowhide were 0.997 and 0.998 at 0.1 Hz respectively. The skin electrode impedance (Z) was tested, and the parameters of the equivalent circuit model of the skin electrode interface were calculated by a fitting method, indicating that the Z of the prepared electrodes was comparable with the standard gel electrode when the skin is moist enough. The signal-to-noise ratio of the ECG of the GLE and the SLE were 1.148 and 1.205 times that of the standard electrode in the standing posture, which meant the ECG measured by our electrodes was basically consistent with that measured by the standard electrode.

Hydrostatic pressures promote initial osteodifferentiation with ERK1/2 not p38 MAPK signaling involved.

Mechanical stress has been considered to be an important factor in bone remodeling and recent publications have shown that mechanical stress can regulate the direction of stem cell differentiation. The exact mechanobiological effects of pressure on initial osteodifferentiation of mesenchymal stem cells (MSCs) have not been determined. These mechanobiological mechanisms may be important both in biological responses during orthodontic tooth movement and in the development of new mechanobiological strategies for bone tissue engineering. We investigated the effects of static (23 kPa) or dynamic (10-36 kPa and at 0.25 Hz frequency) pressure on MSCs during the initial process of osteoblastic differentiation following treatment with dexamethasone, beta-glycerophosphate and ascorbic acid (for 0, 3, and 7 days, respectively). The following parameters were analyzed in the ALPase activity, mRNA level of osteogenesis-related transcription factors (Runx2, Osterix, Msx2, and Dlx5), and phosphorylation of ERK1/2 and p38 MAPK. The results showed that exposure to either dynamic or static pressure induced initial osteodifferentiation of MSCs. Particularly both types of pressure strongly stimulated the expression of osteogenesis-related factors of totally undifferentiated MSCs. ERK signaling participated in early osteodifferentiation and played a positive but non-critical role in mechanotransduction, whereas p38 MAPK was not involved in this process. Furthermore, the undifferentiated MSCs were highly sensitive to pressure exposure; whereas after osteoinduction MSCs reacted to pressure in a lower response state. The findings should lead to further studies to unveil the complex initial biological mechanisms of bone remodeling and regeneration upon mechanical stimuli.

[Facial expression recognition based on feature selection by quadratic mutual information].

To solve the problem of imprecise positioning of feature point and of the feature data redundancy in facial expression recognition by active appearance models (AAM), the automatic adjustment of initial model for AAM fitting is proposed in this paper. The specific aims are to improve the precision of positioning and to more effectively reflect the variation of expressions by acquired features. The problem of feature selection is resolved by adopting quadratic mutual information and reducing the feature dimension. The support vector machine (SVM) classifier is used for expression recognition. The experimental results on CAS-PEAL facial expression database show that the proposed method effectively improves the performance of facial expression recognition, the maximum recognition rate being 83.33%.

A Comprehensive Method for Accurate Strain Distribution Measurement of Cell Substrate Subjected to Large Deformation.

Cell mechanical stretching in vitro is a fundamental technique commonly used in cardiovascular mechanobiology research. Accordingly, it is crucial to measure the accurate strain field of cell substrate under different strains. Digital image correlation (DIC) is a widely used measurement technique, which is able to obtain the accurate displacement and strain distribution. However, the traditional DIC algorithm used in digital image correlation engine (DICe) cannot obtain accurate result when utilized in large strain measurement. In this paper, an improved method aiming to acquire accurate strain distribution of substrate in large deformation was proposed, to evaluate the effect and accuracy, based on numerical experiments. The results showed that this method was effective and highly accurate. Then, we carried out uniaxial substrate stretching experiments and applied our method to measure strain distribution of the substrate. The proposed method could obtain accurate strain distribution of substrate film during large stretching, which would allow researchers to adequately describe the response of cells to different strains of substrate.

A Strain Feedback Compensation Method during Cell Tensile Experiments

Cell tensile technique is an important and widely used tool in cell mechanical research. However, the strain control condition in traditional tensile experiments is not satisfied and would result in big errors. These strain errors will seriously impact the experimental accuracy and decrease the reliability and comparability of experimental results. In order to achieve the accurate strain control of the membrane during stretching, a strain feedback compensation method based on the digital image correlation is proposed in this paper. To evaluate the effect of the proposed compensation method, a series of stretching experiments in different strains ranging from 5% to 20% were performed. The results showed that our proposed method significantly decreased the errors of strain control. These results indicate that the strain feedback compensation method is very effective in controlling strain and can greatly improve the experimental accuracy.

A Strain Feedback Compensation Method during Cell Tensile Experiments.

Cell tensile technique is an important and widely used tool in cell mechanical research. However, the strain control condition in traditional tensile experiments is not satisfied and would result in big errors. These strain errors will seriously impact the experimental accuracy and decrease the reliability and comparability of experimental results. In order to achieve the accurate strain control of the membrane during stretching, a strain feedback compensation method based on the digital image correlation is proposed in this paper. To evaluate the effect of the proposed compensation method, a series of stretching experiments in different strains ranging from 5% to 20% were performed. The results showed that our proposed method significantly decreased the errors of strain control. These results indicate that the strain feedback compensation method is very effective in controlling strain and can greatly improve the experimental accuracy.

Fabrication of Eu-doped Gd(OH)3 Nanorods with Enhanced Magnetic- Resonance and Luminescence Imaging.

BACKGROUND: Multimodal bio-imaging is a new technique with more than one imaging modality. Eu3+ doping can tailor the multi-functions of Gd-based nanorods (NRs) to obtain the resolution the imaging at the cellular level. Silk fibroin with His and Lys can induce to fabricate metal compounds particles. However, one-step preparation of SFP-linked Eu-Gd(OH)3 NRs with cyto-compatibility is very challenging. METHODS: Eu-doped Gd(OH)3 nanorods with silk fibroin peptides (SFP-NRs) are synthesized via a simple and feasible biomimetic method in the assistance of SFPs. RESULTS: The measurement results showed that these hexagonal crystal NRs possessed 300 nm of the length. Compared with pure NRs, SFP-NRs exhibited better in vitro T1 signal-enhancement of magnetic resonance (MR) imaging due to their higher ratio of Eu and Gd and SFP coating on their surface, and the longitudinal relaxivity r1 value is 2.57 (Gd mM·s)-1 under a 7.0 T MR imaging system. Furthermore, a series of in vivo T1-weighted MR images between pre- and post-injection in tumor regions for 9 h indicated that average intensity of post-injection of SF-NRs was enhanced to 68%, higher the increased value of pure NRs (19.6%), but also SFP-NRs showed the good luminescence labeling of viable cell in the fluorescence observation. CONCLUSION: These results indicate that Eu-doped SFP-NRs have potential as T1 MR imaging contrast agents and optical imaging probe in tumor-detection field.

Fabrication of Aligned Conducting PPy-PLLA Fiber Films and Their Electrically Controlled Guidance and Orientation for Neurites.

Electrically conductive biomaterial scaffolds have great potential in neural tissue regeneration. In this work, an aligned conductive fibrous scaffold was prepared by electrospinning PLLA on rotating collector and chemical oxidation polymerization of pyrrole (PPy) codoped with poly(glutamic acid)/dodecyl benzenesulfonic acid sodium. The characterization results of composition, structure and mechanics of fiber films show that the existence of weak polar van der Waals' force between PPy coating and PLLA fibers. The resistivity of aligned rough PPy-PLLA fiber film (about 800 nm of fiber diameter) at the perpendicular and parallel directions is 0.971 and 0.874 Ω m, respectively. Aligned rough PPy-PLLA fiber film could guide the extension of 68% PC12 neurites along the direction of fiber axis. Under electrostimulation (ES) of 100, 200, and 400 mV/cm, median neurite lengths of differentiated PC12 on aligned fiber-films are 128, 149, and 141 µm, respectively. Furthermore, under ES of 100, 200, and 400 mV/cm, the alignment rate of neurite along the electropotential direction (angle between neurite and electropotential direction ≤10°) on random fibers film are 17, 23, and 28%, respectively, and the alignment rate of neurites along the fiber axis (angle between neurite and fiber axis ≤10°) on aligned fibers film reach to 76, 83, and 79%, respectively, indicating that the combination of ES and rough conducting aligned structure could adjust the alignment of cellular neurites along the direction of the fiber axis or electropotential.

Fabrication and neuron cytocompatibility of iron oxide nanoparticles coated with silk-fibroin peptides.

Neuro-cytotoxicity of iron oxide nanoparticles (NPs) need to be considered. In this paper, magnetic Fe3O4 NPs are synthesized via a bio-mineralization process using silk fibroin (SF) as template. The prepared NPs with SF (SF-NPs) have more uniform grain size, better stability in weakly alkaline solution and higher saturation magnetization (about 82 emu/g) than pure NPs. After exposure to different concentration of SF-NPs (6.25-100 µg/mL), the reactive oxygen species generation in PC12 cells reduced compared with pure NPs. 1-5d treatment with SF-NPs did not destroy cell membrane and cyto-skeleton, and could improve the neurites extension in a dose-dependent manner at lower concentration (6.25-50 µg/mL), because SF peptide coating could delay the release of iron ions and the increase of surface crystal defects of NPs. Intact mitochondria in a neurite indicate the extension activity of neurites of cells treated with SF-NPs. Their high magnetic property and good neural-cytocompatibility provide the possibility of SF-NPs to be used as the contrast agents in brain MRI or the carrier of neural therapeutic drugs.

Physiological pulsatile flow culture conditions to generate functional endothelium on a sulfated silk fibroin nanofibrous scaffold.

Many studies have demonstrated that in vitro shear stress conditioning of endothelial cell-seeded small-diameter vascular grafts can improve cell retention and function. However, the laminar flow and pulsatile flow conditions which are commonly used in vascular tissue engineering and hemodynamic studies are quite different from the actual physiological pulsatile flow which is pulsatile in nature with typical pressure and flow waveforms. The actual physiological pulsatile flow leading to temporal and spatial variations of the wall shear stress may result in different phenotypes and functions of ECs. Thus, the aim of this study is to find out the best in vitro dynamic culture conditions to generate functional endothelium on sulfated silk fibroin nanofibrous scaffolds for small-diameter vascular tissue engineering. Rat aortic endothelial cells (RAECs) were seeded on sulfated silk fibroin nanofibrous scaffolds and cultured under three different patterns of flow conditioning, e.g., steady laminar flow (SLF), sinusoidal flow (SF), or physiological pulsatile flow (PPF) representative of a typical femoral distal pulse wave in vivo for up to 24 h. Cell morphology, cytoskeleton alignment, fibronectin assembly, apoptosis, and retention on the scaffolds were investigated and were compared between three different patterns of flow conditioning. The results showed that ECs responded differentially to different exposure time and different flow patterns. The actual PPF conditioning demonstrated excellent EC retention on sulfated silk fibroin scaffolds in comparison with SLF and SF, in addition to the alignment of cells in the direction of fluid flow, the formation of denser and regular F-actin microfilament bundles in the same direction, the assembly of thicker and highly crosslinked fibronectin, and the significant inhibition of cell apoptosis. Therefore, the actual PPF conditioning might contribute importantly to the generation of functional endothelium on a sulfated silk fibroin nanofibrous scaffold and thereby yield a thromboresistant luminal surface.

Synthesis and cellular compatibility of Co-doped ZnO particles in silk-fibroin peptides.

Co-doped ZnO particles were successfully prepared via a facile biomineralization process in the template of silk-fibroin (SF) peptides at room temperature, and SF peptides were coated onto the surface of particles. The ratio of Zn/Co in reactive solution could substantially influence the morphology of as-prepared particles, and the rough spherical particles including some nanoparticles of 50 nm diameters could be obtained at 4:1 ratio of Zn/Co. The saturation magnetization of SF-coated Co-ZnO particles was 8.63 emu/g, much larger than that of Co-ZnO without SF. L929 cell test revealed that the Co-doped ZnO particles had a good cellular compatibility at the concentration of less than 0.25 mg/mL due to silk-peptide coating, indicating that the prepared Co-doped ZnO particles have a potential for the biomedical applications.

Synthesis and neuro-cytocompatibility of magnetic Zn-ferrite nanorods via peptide-assisted process.

In order to obtain magnetic nanorods (MNRs) with the neuro-cytocompatibility, silk-fibroin (SF)-coated Zn-ferrite NRs are successfully prepared via a mineralization process, and their saturation magnetization is 32emu g(-)(1). After the mineralization of 2d and 4d in the mixed solution of the concentrations of 15w/w% SF and 0.01M HCl, the lengths of NRs are ∼220nm and ∼2µm, respectively. Cell tests of NRs with 220nm length showed that the as-prepared Zn-ferrite NRs hardly produced toxicity on Escherichiacoli, Staphylococcusaureus, L929, and PC12 cells. The results of the outgrown neurites from PC12 cells indicated that the neurite length and the number of neurites were not significantly decreased at the low concentrations of SF-coated NRs (less than 0.25mg mL(-)(1)) in 1-5d culture time. TEM images of cell ultrathin sections indicated that, although Zn-ferrite NRs were split in the cytosol for 5d at the NR concentrations of 0.125mg mL(-)(1), some integrated mitochondria in a neurite suggested that SF-coated NRs inside cells did not influence the extension activity of neurites. Based on the good neuro-cytocompatibility and magnetic property of Zn-ferrite NRs, their potential applications in safe cell manipulation and axon guidance can be envisioned.

The influence of delayed compressive stress on TGF-ß1-induced chondrogenic differentiation of rat BMSCs through Smad-dependent and Smad-independent pathways.

Mechanical stimuli play important roles in regulating chondrogenic differentiation, but seldom studies have focused on when and how mechanical stimuli should be initiated. We have previously shown that Col2α1 mRNA was increased by delayed dynamic compressive stress initiated at the 8th day of chondrogenic culture. The current work is to further study the possibility of using delayed mechanical stress to relay chondrogenesis initiated by exogenous TGF-ß1. Mechanical stimulation was delivered from day 8 to day 14 of chondrogenic culture. It showed that delayed compressive stress not only stimulated gene expression and protein synthesis of chondrocyte-specific markers, but also stimulated the endogenous TGF-ß1 gene transcription, protein expression and the subsequent activation even when exogenous TGF-ß1 was discontinued. Furthermore, mechanical stress also promoted protein phosphorylation and nuclear translocation of Smad2/3, the TGF-ß1 downstream effectors. Inhibition TGF-ß with SB431542 significantly affected the stress-induced chondrogenic gene expression. In addition, phosphorylated-p38 and RhoB were upregulated by delayed loading in a TGF-ß-related manner. Phosphorylated-ERK1/2 and Wnt7a were also increased, but in a TGF-ß-independent way. It indicates that delayed compressive stress can be used as an effective substitute for TGF-ß1 supplement in inducing chondrogenic differentiation.