A novel composition of bioactive glass with potent haemostatic action and antibacterial competence

Haemorrhagic bleeding is a crucial area of concern related to military as well as civilian trauma. In recent years, bioactive glass is gaining attention in a number of healthcare applications, including haemostasis. Herewith, we report a unique composition of bioactive glass, 70 SiO₂: (30-x-y) CaO: x.Al₂O₃: y.ZnO, where x = 10–18 mole% and y = 0–8 mole%, (Al-BAG) exhibiting haemostatic property as well as antibacterial activity. The as-prepared glass was characterized using XRD, SEM-EDX, FTIR and TG-DSC along with in-vitro degradation study and biological studies e.g., cytocompatibility, haemocompatibility, in-vitro thrombus formation, in-vitro blood absorption capacity, blood coagulation assays (PT, aPTT), in-vitro antibacterial assay against Staph. aureus as well as in-vivo acute dermal toxicity followed by histopathological analysis) and in-vivo haemostasis efficacy were undertaken. The novel bioactive glass composition exhibits promises to be an efficient haemostatic agent with antibacterial activity.     

Antibacterial PES/Vancomycin ultrafiltration membranes with enhanced water flux and low BSA rejection

Polyethersulfone (PES) blended with glycopeptide Vancomycin was fabricated via phase inversion method. The fabricated membranes were characterized by scanning electron microscopy (SEM), fourier transform infrared spectroscopy (FTIR), contact angle (CA) and optical profilometry. The PES/Vancomycin membranes showed a notable increase in hydrophilicity, porosity, pore size, antibacterial activity and water flux in comparison with pristine membranes. The changes are due to the hydrophilic nature of Vancomycin molecules and ability to form hydrogen bond quickly. The surface hydrophilicity of PES/Vancomycin membranes decreased up to 48° with increase in surface roughness (R_a), that is, 0.347 μm, thus increasing the water flux of PES/Vancomycin membranes up to 340 L/m². h. The bovine serum albumin (BSA) rejection decreases, that is, pristine 70.9% to PES/Vancomycin 26% and BSA flux increases at constant ionic strength (0.1) and above the isoelectric point (IEP) of the BSA. Under these conditions, electrostatic interactions are expected to be minimum between protein and the membrane surfaces.     

Multiphase zinc and magnesium mono-substituted calcium phosphates derived from cuttlefish bone: A multifunctional biomaterials

Biomimetic calcium phosphate (CaP) systems mono-substituted with zinc (Zn²⁺) and magnesium (Mg²⁺) ions were prepared from a biogenic source (cuttlefish bone) by wet precipitation method. The results revealed that the as-prepared powders were composed of calcium-deficient carbonated hydroxyapatite (HAp), octacalcium phosphate (OCP), and amorphous calcium phosphate (ACP), while the heat-treated powders consisted of HAp, α-tricalcium phosphate (α-TCP), and β-tricalcium phosphate (β-TCP). In addition to Zn²⁺ and Mg²⁺ ions, the presence of CO₃^2?, Sr²⁺ and Na ⁺ ions was detected with elemental analysis, which can be attributed to the use of cuttlefish bone as a natural precursor of Ca²⁺ ions. The data obtained by XRD study demonstrated the decrease in lattice parameters in the OCP and β-TCP phases for Zn-substitution and Mg-substitution in the HAp, OCP, and β-TCP phases. Zn²⁺ occupies the Ca(1,3,4,6,7,8) sites in OCP and Ca(1,2,3,4) sites in β-TCP, while Mg²⁺ occupies the Ca(2) sites in HAp and the Ca(4,5) sites in β-TCP. Phase transformation study under simulated physiological conditions for 7 days showed the transformation of OCP and ACP into the thermodynamically more stable HAp. Characterization of the zeta-potential showed positively charged populations for all prepared CaP powders, while all samples showed high bovine serum albumin adsorption capacity. The culture of human embryonic kidney cells showed that the prepared CaPs are non-cytotoxic and that viability of the cells increases during the culture period. All powders obtained showed antibacterial activity towards Gram-negative Escherichia coli and low antibacterial effect against Gram-positive Staphylococcus aureus, as determined by viability analysis during 48 h. Inhibition zone analysis and observation of the morphology after 24 h showed no antibacterial properties.     

Combination effects of ultrasound and citral nanoemulsion against Shigella flexneri and the preservation effect on fresh-cut carrots

This present study evaluated the effect of ultrasound (US), citral nanoemulsion (CLON) and combined treatments on the inactivate effectiveness of Shigella flexneri in phosphate-buffered saline (PBS) and on the surface of fresh-cut carrots. In this study, CLON was produced by ultrasonic nanoemulsification. Results demonstrated that US + CLON treatment significantly (P < 0.05) improved the bactericidal effect against Sh. flexneri, especially 0.15 mg/mL of CLON combined with US (20 kHz, 345 W/cm²) treatment for 9 min decreased the number of Sh. flexneri by 8.55 log CFU/mL. The assay of reactive oxygen species (ROS) and malondialdehyde (MDA) levels indicated that US + CLON aggravated oxidative stress and lipid peroxidation in cell membranes. The leakage of cell constituents (proteins and nucleotide) demonstrated that the permeability and integrity of the cell membrane was significantly (P < 0.05) impaired. Field-emission scanning electron microscopy further showed that US + CLON exacerbates the disruption of the bacteria morphology. Confocal laser scanning microscopic and flow cytometry observed US + CLON treatment enhanced the changes of bacterial cell membrane integrity. Meanwhile, US + CLON was effective in reducing the presence of bacteria on the surface of fresh-cut carrots, and had no negative effects on the quality of fresh-cut carrots in terms of colour, hardness and weight during storage. Overall, this present study revealed ultrasound combined with CLON is a promising and viable cleaning method for improving the microbiological safety of fresh produce.     

一步热分解法形成的MoO3在无光条件下的抗菌性能

生物污损是威胁海工材料安全高效服役的重要因素，因此开发环保、成本低廉的防污材料非常必要。本文通过一步热分解法分别在450 ℃和750 ℃制备α-MoO3粉末材料，即S450和S750。采用X射线衍射（XRD）、扫描电子显微镜（SEM）、红外光谱（FTIR）对样品进行表征。结果显示，450 ℃和750 ℃获得的α-MoO3分别表现为纳米级板状结构和微米级长板状结构。利用平板计数法评价两种材料在无光条件下对铜绿假单胞菌（P. aeruginosa）的抗菌性能。结果显示，S450和S750在浓度为0.25，0.5，0.75，和1 mg/ml时，其抗菌率分别为27.3%，99%，100%，100%和16.1%，30.1%，52.3%，73.6%。表明两个条件下获得的α-MoO3在无光条件下均表现出良好的抗菌性能，并且溶液pH值随α-MoO3样品浓度的升高而降低，Mo离子溶出量随α-MoO3样品浓度的升高而增加。α-MoO3在无光条件下的抗菌活性源于H3O+和Mo离子溶出的协同作用影响。与S750相比，S450表现出更高的抗菌率，这可能源于S450在溶液中具有更高的溶解度，因而导致更多的H3O+和Mo离子溶出。     

新型氧化玉米淀粉-聚己内酯基抗菌膜材料的制备及性能研究

通过简便的“一锅法”对氧化玉米淀粉（OCS）进行线性接枝吲哚乙酸单体（IAA），成功制得新型氧化玉米淀粉基抗菌材料（OI）。然后进一步将OI与具有生物降解性的聚己内酯（PCL）进行共混成膜，制得氧化玉米淀粉-聚己内酯基抗菌薄膜（PO）。通过FTIR、UV-vis、XRD等对所制备的OI以及PO的化学结构和性能特征进行了结构表征和性能测试。结果表明：IAA与OCS主要通过酯化反应进行结合，所制备的OI的取代度为60%。将OI与PCL复配后，所制备的PO结晶度明显下降。随着复合膜中OI的增加，所制备的膜材料透光率下降，抗拉强度增加，接触角略有下降。特别当OI用量为10%（以总质量为基准，下同）时，所制备的PO-10表现出良好的生物相容性、非浸出性和抗菌活性。根据圆盘扩散试验，所制备的抗菌材料最低抑菌浓度为0.5 g/L，远低于传统抗生素和大分子壳聚糖抗菌材料的用量。因此，所制备的PO不仅具有良好的功能特性，且原料绿色无毒、价廉易得，是一种潜在的生物医用材料。     

乳链菌肽的抑菌机制

乳链菌肽(Nisin)是由乳酸乳球菌的某些菌株产生的1种羊毛硫细菌素。因其高效的抗菌性及对人体的低毒性而被广泛应用于食品防腐。孔道形成是Nisin抑菌作用的主要方式。Nisin可通过其带正电荷肽的C-端与带负电荷的磷脂之间的静电引力在细胞质膜上形成孔道,也能通过lipid Ⅱ的锚定作用形成lipid Ⅱ介导的孔道,同时Nisin与lipid Ⅱ结合抑制肽聚糖生物合成。Nisin对大肠杆菌的抑菌机制是对高盐敏感,而其对葡萄球菌的抑菌机制是对高盐不敏感。文章综述了Nisin的抑菌机制。