Design of in vitro biomimetic experimental system and simulation analysis for transvascular transport of nano-preparation.

Recently, the enhanced penetration and retention (EPR) effect of nano-preparations has been questioned. Whether the vascular endothelial cell gap (VECG) is the main transport pathway of nano-preparations has become a hot issue at present. Therefore, we propose an in vitro biomimetic experimental system that demonstrates the transvascular transport of nano-preparation. Based on the tumor growth process, the experimental system was used to simulate the change process of abnormal factors (vascular endothelial cell gap and interstitial fluid pressure (IFP)) in the tumor microenvironment. The influence of change in the abnormal factors on the enhanced penetration and retention effect of nano-preparation was explored, and simulation verification was performed. The results show that when the interstitial fluid pressure is close to the vascular fluid pressure (VFP), the transport of nano-preparation is obstructed, resulting in the disappearance of enhanced penetration and retention effect of the nano-preparation. This indicates that the pressure gradient between vascular fluid pressure and interstitial fluid pressure determines whether the enhanced penetration and retention effect of nano-preparations can exist.

Research progress on antibacterial activity of medical titanium alloy implant materials.

Titanium and its alloys are the preferred materials for medical implants. However, easy infection is a fatal shortcoming of Ti implants. Fortunately, the ongoing development of antibacterial implant materials is a promising solution, and Ti alloys with antibacterial properties hold immense potential for medical applications. In this review, we briefly outline the mechanisms of bacterial colonization and biofilm formation on implants; discuss and classify the major antimicrobials currently in use and development, including inorganic and organic antimicrobials; and describe the important role of antimicrobials in the development of implant materials for clinical applications. Strategies and challenges related to improving the antimicrobial properties of implant materials as well as the prospects of antibacterial Ti alloys in the medical field are also discussed.

Extraction, purification, structural characterization, and hepatoprotective effect of the polysaccharide from purple sweet potato.

BACKGROUND: Purple sweet potato Ipomoea batatas (L.) has long been used as a medicine and a food. It contains various bioactive substances such as polysaccharides, anthocyanins, and flavonoids. Purple sweet potato polysaccharides are known to have anti-oxidant, anti-tumor, and immunomodulatory functions. Nevertheless, studies on the structural characterization of purple sweet potato polysaccharides and their ability to prevent non-alcoholic fatty liver disease (NAFLD) have rarely been reported. RESULTS: A novel polysaccharide (PSPP-A) was extracted and isolated from purple sweet potato, and its structural characteristics and preventive effects on NAFLD were investigated. The results indicated that PSPP-A was composed of l-rhamnose, d-arabinose, d-galactose, d-glucose, and d-glucuronic acid with molar ratios of 1.89:8.45:1.95:1.13:1. Its molecular weight was 2.63 × 103 kDa. Methylation and nuclear magnetic resonance (NMR) analysis indicated that the glycosidic linkages were →3)-α-L-Araf-(1→, α-L-Araf-(1→, →2,4)-α-L-Rhap-(1→, 4-O-Me-ß-D-GlcAp-(1→, →4)-α-D-Glcp-(1→, →4)-ß-D-Galp-(1→, and →6)-ß-D-Galp-(1→. Scanning electron microscopy (SEM) indicated that the structure of PSPP-A was irregular. Subsequently, the protective effect of PSPP-A on NAFLD was investigated. The results indicated that bodyweight, liver index, and triglyceride (TG), total cholesterol (TC), aspartate transaminase (AST), and alanine transaminase (ALT) content were significantly reduced by intervention of purple sweet potato polysaccharide-A (PSPP-A) compared with the - high-fat diet group. Liver histopathological analysis indicated that PSPP-A attenuated irregular hepatocyte patterns and excessive lipid vacuoles. CONCLUSIONS: The novel polysaccharide, PSPP-A, mainly contains arabinose, which has certain preventive effects on NAFLD. This study provides a theoretical basis for further elucidating the hepatoprotective effect of purple sweet potatoes as a functional food. © 2022 Society of Chemical Industry.

Antibacterial functionalization of calfskin bioremediation film.

Decellularized calfskins are a well-established skin substitute that retains the dermal tissue's spatial structure, facilitating skin regeneration, and is already available in the market. However, their mechanical properties can change with degradation, leading to tearing at the suture. Moreover, decellularized calfskins do not possess inherent antimicrobial abilities, which can lead to wound infection and further injury during the healing process. With the objectives of supporting the clinical use of decellularized calfskins, minimizing the probability of decellularized calfskin fracture and damage during usage, and improving their anti-infective properties, this study utilized a post-loading method to load gentamicin sulfate onto the decellularized calfskin to functionalize it for antimicrobial purposes. In addition, the mechanical and physicochemical properties of the drug-carrying film were investigated to see if they could meet the clinical requirements. The results revealed that vancomycin sulfate could be loaded onto the decellularized calfskin without affecting collagen. The tensile strength of the drug-loaded membrane was determined to be in the range of 5.53-29.25 MPa, meeting the clinical requirements. Thermal analysis and pH analysis experiments demonstrated that the drug-loaded membrane did not undergo thermal denaturation or decomposition during skin repair and remained within the normal pH range of the skin, avoiding significant fluctuations in wound pH.

Research and analysis of the properties of bredigite-based 3D-printed bone scaffolds.

The use of bone tissue-engineered scaffolds for repairing bone defects has become extremely common. Bone tissue-engineered scaffolds should have good mechanical properties, a pore structure similar to that of natural bone, appropriate biodegradability, and good biocompatibility to provide attachment sites for growth factors and seed cells. They also need to exhibit special functions such as osteoconductivity and osteoinduction. In this study, the mechanical, degradation, and biological properties of bredigite were studied by using a triply periodic minimal surface (TPMS) model structure. Pressure tests on bone tissue-engineered scaffolds showed that the mechanical properties of TPMS scaffolds were significantly better than those of open-rod scaffolds with the same porosity. By analyzing the biological properties, we found that the TPMS model had better protein adsorption ability than the open-rod model, the cells could better adsorb on the surface of the TPMS scaffold, and the proliferation number and proliferation rate of the TPMS model were higher than those of the open-ended rod model.

Preparation and characterization of different micro/nano structures on the surface of bredigite scaffolds.

The preparation of controllable micro/nano structures on the surface of the bredigite scaffold is expected to exhibit the same support and osteoconductive capabilities as living bone. However, the hydrophobicity of the white calciµm silicate scaffold surface restricts the adhesion and spreading of osteoblasts. Furthermore, during the degradation process of the bredigite scaffold, the release of Ca2+ results in an alkaline environment around the scaffold, which inhibits the growth of osteoblasts. In this study, the three-dimensional geometry of the Primitive surface in the three-periodic minimal surface with an average curvature of 0 was used as the basis for the scaffold unit cell, and a white hydroxyapatite scaffold was fabricated via photopolymerization-based 3D printing. Nanoparticles, microparticles, and micro-sheet structures with thicknesses of 6 µm, 24 µm, and 42 µm, respectively, were prepared on the surface of the porous scaffold through a hydrothermal reaction. The results of the study indicate that the micro/nano surface did not affect the morphology and mineralization ability of the macroporous scaffold. However, the transition from hydrophobic to hydrophilic resulted in a rougher surface and an increase in compressive strength from 45 to 59-86 MPa, while the adhesion of the micro/nano structures enhanced the scaffold's ductility. In addition, after 8 days of degradation, the pH of the degradation solution decreased from 8.6 to around 7.6, which is more suitable for cell growth in the hµman body. However, there were issues of slow degradation and high P element concentration in the degradation solution for the microscale layer group during the degradation process, so the nanoparticle and microparticle group scaffolds could provide effective support and a suitable environment for bone tissue repair.

Recent progress in the fabrication of flexible materials for wearable sensors.

Wearable sensors have been widely studied because of their small size, light weight, and potential for the noninvasive tracking and monitoring of human physiological information. Wearable flexible sensors generally consist of two parts: a flexible substrate in contact with the skin and a signal processing module. At present, wearable electronics cover many fields, such as machinery, physics, chemistry, materials science, and biomedicine. The design concept and selection of materials are very important to the function of a sensor. In this review, we summarize the latest developments in flexible materials for wearable sensors, including developments in flexible materials, electrode materials, and new flexible biodegradable materials, and describe the important role of innovation in material and sensor design in the development of wearable flexible sensors. Strategies and challenges related to the improvement of the performances of wearable flexible sensors, as well as the development prospects of wearable devices based on flexible materials, are also discussed.

Effect of in vitro simulated gastrointestinal digestion on the antioxidant activity, molecular weight, and microstructure of polysaccharides from Chinese yam.

In this study, we investigated the antioxidant properties and the changes of molecular weight (Mw), antioxidant activity, and microstructure of Chinese yam polysaccharides (CYP-A) during in vitro digestion. Results showed that the scavenging rate of 2, 2-diphenyl-1-picrylhydrazyl (DPPH) free radical of CYP-A was approximately 79% at the concentration of 6 mg/mL. Furthermore, the antioxidant ability positively correlated with the concentration of CYP-A. In addition, the Mw of CYP-A decreased (p < 0.05) after intestinal digestion. Fourier transform infrared showed that the degrees of esterification of CYP-A increased to 39.04% after 6 h of gastric digestion. Moreover, the structure of CYP-A changed after in vitro gastric digestion. The scanning electron microscope (SEM) images indicated that the surface morphology of CYP-A turned from smooth and irregular to a layered honeycomb after gastrointestinal digestion in vitro. Surprisingly, the activity of DPPH radical scavenging significantly increased (p < 0.05) in the intestinal digested samples of CYP-A, which showed a positive correlation with the concentration of CYP-A. However, the reducing power significantly decreased (p < 0.05) after in vitro intestinal digestion.

Progress in Excision Methods of Bone Materials.

Bone resection is a common technique in modern surgery, which can be divided into contact (such as mechanical osteotomy and ultrasonic osteotomy) and non-contact (such as laser osteotomy). Irrespective of the excision method, it causes processing damage to natural bone material, thus affecting bone healing. To reduce the machining damage in bone resection, different machining variables (cutting fluid temperature, feed rate, rotational speed, and ultrasonic frequency) were considered to explore the selection of various cutting conditions. This paper reviews the excision of natural bone materials including mechanical osteotomy, laser osteotomy, and ultrasonic osteotomy, especially traditional drilling and ultrasonic cutting, which represent the traditional and prospective methods of bone excision technology, respectively. Finally, the differences between methods are emphasized and the future trends in osteotomy technology and condition control during osteotomy are analyzed.

The impact of a novel Chinese yam-derived polysaccharide on blood glucose control in HFD and STZ-induced diabetic C57BL/6 mice.

Chinese yam, as a kind of traditional "medicine and food homologous food" in Asia, could assistance to digestion, nourish the lungs and relieve cough. Some research also suggested that Chinese yam could prevention of hyperglycemia, but the specific mechanism of action was not clear. In this paper, an acidic polysaccharide (CYPB) was isolated from Chinese yam with the molecular weight of 1.55 × 102 kDa. The determination of the monosaccharide composition of CYPB with ion chromatography showed that CYPB was composed of rhamnose, glucose, arabinose, galactose, glucose, xylose and glucuronic acid with the ratio of 6 : 3.73 : 7.31 : 10.95 : 4.56 : 1. The structural analysis indicated that the CYPB contain 1 → 3, 1 → 4, 1 → 2, 1 → 6 and 1 → 3, 6 glycoside bonds. The experimental results of diabetic mice model induced by high-fat diet (HFD) and streptozocin (STZ) indicated that CYPB could improve clinical symptoms and alleviate the glucose tolerance damage symptoms effectively. The underlying mechanism of regulate blood glucose of CYPB may be related to improve the ability of synthesize glycogen, insulin resistance and reduce gluconeogenesis by regulating the expression of InsR, PI3K, Akt and FoxO3, GLUT4 proteins in PI3K/Akt signaling pathway in T2DM mice.

Research in Tissue Engineering Scaffold Materials for Alveolar Bone Repair.

An increasing number of scaffold materials are available for repairing alveolar bone defects. As each material has its own advantages and disadvantages, these characteristics should be carefully considered. This paper presents a review of the currently available materials for repairing alveolar bone defects, including artificial ceramics, polymers, and metals. The combination of seed cells or growth factors with these materials is the future trend for the treatment of alveolar bone defects. In this study, a comprehensive analysis of the advantages, disadvantages, and development status of various materials is carried out, providing a basis for future material selection.

Simulation study of the effects of interstitial fluid pressure and blood flow velocity on transvascular transport of nanoparticles in tumor microenvironment.

BACKGROUND AND OBJECTIVE: Although nanoparticle preparations have great potential in the treatment of tumors, nanoparticle preparations have not achieved the desired therapeutic effect. The reason is that the abnormal tumor microenvironment prevents nanoparticles from effective concentrating and reaching tumor area. Therefore, it's very necessary to better understand the effect of the abnormal tumor microenvironment on the transvascular transport of nanoparticles to overcome this critical problem. METHODS: In this paper, a tumor abnormal vascular-interstitial model was established, and the transvascular transport process of nanoparticles was simulated in the model by computational fluid dynamics (CFD) modeling. RESULTS: The simulation results showed that the transport efficiency of nanoparticles decreased with increasing interstitial fluid pressure (IFP), and nanoparticles could not cross the blood vessel wall when the IFP approached the blood vessel wall pressure. Interestingly, the transport efficiency of nanoparticles first increased with blood flow velocity, and then decreased with blood flow velocity. CONCLUSIONS: The results showed that with the continuous malignant development of tumors, the ability of nanoparticles to passively diffuse has almost disappeared. The enhanced permeability and retention (EPR) effect of the nanoparticles disappeared with the disappearance of the pressure gradient inside the tumor. These results provided guidance for future research on the vascular transport pathways and mechanisms of nanoparticles.

Advances in mathematical models of the active targeting of tumor cells by functional nanoparticles.

BACKGROUND AND OBJECTIVE: The process of nanoparticles (NPs) entering blood circulation to actively target tumor cells involves four stages-the transport of NPs in blood vessels, transvascular transport of NPs, transport of NPs in the tumor interstitial matrix and entry of NPs into tumor cells. These four stages are a complex process involving mechanical, physical, biochemical, and biophysical factors, the tumor microenvironment (TME) and properties of NPs play important roles in this process. Because this process involves a large number of factors and is very complex, it is difficult to study with conventional methods. METHODS: Using mathematical models for simulation is suitable for addressing this complex situation and can describe the complexity well. RESULTS: This work focuses on the theoretical simulation of NPs that target tumor cells to illustrate the effects of the abnormal microenvironment of tumors and properties of NPs on the transport process. Mathematical models constructed by different methods are enumerated. Through studying these mathematical models, different methods to overcome nanoparticle (NP) transport obstacles are illustrated. CONCLUSIONS: It is necessary to construct a theoretical model of active targeting nanodrug delivery under the coupling of micro-flow field and specific binding force field, and to simulate and analyze the delivery process at mesoscopic scale using computational fluid dynamics (CFD) method, so as to reveal the law and characteristics of drug delivery and cell uptake in the micro-environment of tumors in vivo. The methods and techniques discussed can serve as the basis for systematic studies of active targeting of functional nanoparticles to tumor cells.