Synthesis,characterization, and biological activity of cross-linked chitosan biguanidine loaded with silver nanoparticles

Chitosan biguanidine hydrochloride (ChG) and glutaraldehyde cross-linked chitosan biguanidine (CChG) were synthesized and characterized by Fourier transform infrared spectroscopy, ¹H NMR and ¹³C NMR, X-ray diffraction, scanning electron microscopy (SEM) and thermal analyses (TGA and DTA). The results showed that ChG and CChG had a more amorphous structure than that of chitosan, and their thermal stability were slightly lower than that of chitosan. Colloidal silver nanoparticles (AgNPs) were prepared using borohydride reduction method and then investigated as fillers in partially cross-linked chitosan biguanidine. The obtained nanoparticles were uniform and spherical with average size of 9.6 ± 0.5 nm. The prepared CChG/AgNPs composites were characterized for their morphology, thermal properties, cytotoxicity and antimicrobial activity. The SEM images showed that the AgNPs are well imbedded in the CChG matrix. The thermal stability of CChG was improved with incorporation of AgNPs. The CChG and CChG/AgNPs showed less cytotoxicity to breast cancer cells (MCF-7). Compared with chitosan and CChG, the ChG and CChG/AgNPs showed better antimicrobial activity against Streptococcus pneumoniae and Bacillus subtilis as Gram-positive bacteria, Escherichia coli as Gram-negative bacteria and Aspergillus fumigatus, Geotricum candidum and Syncephalastrum recemosum as fungi.     

Hydrolytic stability of composite repair bond

The hydrolytic stability of composite repairs is a desirable property. In the present study, the composite repair microtensile bond strength, failure mode distribution, and nanoleakage occurrence before and after thermocycling were evaluated. Standardized, 1-month-old composite substrates were roughened, cleaned, and randomly assigned to seven groups according to the intermediate agent applied. Resin-based, silane-based, and combined silane/adhesive coupling agents were investigated. The same resin composite as the substrate was used for repair. For each group, repaired samples were wet stored for 24 h (37 degrees C) or thermocycled (5,000 cycles, 5-55 degrees C). Failure mode and silver nitrate penetration were examined by stereomicroscopy. Intermediate agent, experimental condition, and their interaction were significant factors. Hydrophobic flowable composites resulted in statistically higher repair strengths, lower occurrence of adhesive failures, and good quality interfacial coupling without any silver uptake in both conditions. Light-curing, hydrophilic resin monomer-based intermediate agents, although not affected by thermocycling, showed a more pronounced silver penetration. The composite repair strength of a self-curing silane/adhesive agent was significantly affected by thermal stresses, despite the absence of silver uptake. A prehydrolized silane agent recorded the lowest repair strength, with minimal or no evidence of interfacial silver impregnation after thermocycling. In conclusion, flowability and hydrophobic nature can be considered important properties when selecting intermediate agents for composite repair.     

Preoperative localization of sentinel lymph node in breast cancer patients by silver wire insertion or liquid charcoal injection guided by CT lymphography

Dual localization of SLN in breast cancer patients using isotope & dye is the best‐approved modality with limitations such as high cost of radioactive materials, complex logistic preparations & scheduling issues, especially in developing countries. We investigated the feasibility & accuracy of a novel technique for SLN localization using silver wire insertion or liquid charcoal injection guided by CT lymphography. 120 patients with clinically node‐negative breast cancer were enrolled. In the test group, SLN was localized using preoperative CTLG guided injection of liquid charcoal or by placing a 3 cm silver wire. In addition, intraoperative SLN mapping was performed using methylene blue dye followed by searching for the SLN localized by both methods. In the control group, SLN was localized by the blue dye only. Feasibility, accuracy, detection rates, and number of SLNs retrieved were reported as well as matching between the LN detected with the CTLG and that detected with the dye technique. SLN could be detected in 59 out of 60 patients (98.3%) in the test group and in 54 out of 60 patients (90%) in the control group (P = .057). In self‐controlled analysis of the test group comparing CTLG only to dye only was significant (P = .050). Comparing charcoal to silver wire in detection was statistically insignificant (P = .5). This novel method can offer advantages which are as follows: being more accurate than the dye alone, saving operative time, abandoning complex logistic preparations for the radioisotope, and solving the problem of timing.     

银质针治疗颈椎间盘突出症1例报告——11年随访研究

目的：探讨银质针治疗颈椎间盘突出症的远期效果。方法：报告银质针治疗1例颈椎间盘突出症患者，随访11年．观察临床症状变化和通过颈椎MRI观察突出的椎间盘演变过程。结果：疼痛视觉模拟评分明显减少，临床症状消失，颈椎MRI显示：治疗前椎间盘突出，硬膜囊明显受压，经过治疗，突出椎间盘逐渐与硬膜囊之间出现间隙，直至11年后，突出椎间盘还纳，硬膜囊压迫完全解除。结论：银质针治疗某些颈椎间盘突出症有效果，有可能引起椎间盘的变化。     

重组人表皮生长因子促进Ⅱ度烧伤创面愈合的临床观察

目的：观察重组人表皮生长因子（rhEGF）加纳米银敷料促进Ⅱ度烧伤创面愈合的疗效。方法选取2011年5月～2012年3月Ⅱ度烧伤患者90例,随机分成治疗组45例和对照组45例,治疗组创面换药时外用rhEGF,对照组创面换药时外用生理盐水,其他处理措施两组完全相同。观察两组患者创面局部和全身的不良反应、创面愈合时间及瘢痕生成情况。结果治疗组浅Ⅱ度和深Ⅱ度烧伤的愈合时间均显著短于对照组,差异均具有统计学意义（P均＜0.05）;治疗组深Ⅱ度烧伤患者的瘢痕发生率显著低于对照组,差异具有统计学意义（χ^2＝4.2198,P＜0.05）;治疗组外用rhEGF无明显不良反应。结论 rhEGF加纳米银敷料治疗Ⅱ度烧伤能加快烧伤创面的愈合速度,提高愈合质量,减少瘢痕的形成,无明显不良反应,安全性好。     

Aquacel Ag dressing versus Acticoat™ dressing in partial thickness burns: A prospective,randomized, controlled study in 100 patients. Part 1: Burn wound healing

Introduction

Studies comparing contemporary silver dressings in burns are scarce.

Methods

In a prospective, randomized, controlled study, counting 50 patients/research group, we compared two frequently used silver dressings, Acticoat™ and Aquacel^® Ag, in the management of partial thickness burns with a predicted healing time between 7 and 21 days as assessed by laser Doppler imaging between 48 and 72 h after burn. Variables investigated were related to baseline research group characteristics, wound healing, bacteriology, economics, nurse, and patient experience.

Results

Both research groups were comparably composed taking into account gender, age and burn characteristics. Similar results were obtained as to healing time and bacterial control with both silver dressings. A statistically significant difference in favor of the Aquacel^® Ag dressing was found for average ease of use (p < 0.001), average ease of application (p = 0.001), patient pain (p < 0.001), patient comfort with the dressing (p = 0.017), silver staining (p < 0.001), and cost effectiveness (p < 0.001).

Conclusion

Both silver dressings resulted in comparable healing times and bacterial control but the Aquacel^® Ag dressing significantly increased comfort for patients as well as nurses and was significantly more cost-effective than the Acticoat™ dressing for the given indication.     

Interaction of citrate‐coated silver nanoparticles with earthworm coelomic fluid and related cytotoxicity in Eisenia andrei

Understanding the interaction of nanoparticles with biological fluid is important for predicting the behavior and toxicity of nanoparticles in living systems. The earthworm Eisenia andrei was exposed to citrate‐coated silver nanoparticles (cAgNPs), and the interaction of cAgNPs with earthworm coelomic fluid (ECF), the cytotoxicity of cAgNPs in earthworm coelomocytes was assessed. The neutral red retention assay showed a reduction in lysosomal stability after exposure. The toxicity of silver ions dissolved from cAgNPs in the soil medium was not significant. The aggregation and dissolution of cAgNPs increased in ECF, which contains various electrolytes that alter the properties of nanoparticles, and their subsequent toxicity. Microscopic and dissolution studies demonstrated that the aggregation of cAgNPs rapidly increased, and readily dissolved in ECF. The bioavailability of cAgNPs to earthworms induced lysosomal cytotoxicity. This is the first report to test the interaction and lysosomal cytotoxicity of nanoparticles in earthworm biofluids. Copyright © 2014 John Wiley & Sons, Ltd.     

A Straightforward Approach to Create Ag/SWCNT Composites

Flexible and conductive materials have a high application potential across many parts of modern life. In this work, thin free-standing films from single-walled carbon nanotubes (SWCNTs) were doped with Ag to enhance their electrical conductivity. A facile method to integrate these two materials is described herein. As a consequence, the material exhibited a six-fold boost to the electrical conductivity: an increase from 250 ± 11 S/cm to 1721 ± 125 S/cm. Interestingly, the specific conductivity remained at a comparable level upon doping, so the material was deemed promising in exploitation fields whereweight is of the essence. Furthermore, the material showed good bending characteristics, thereby revealing its applicability in flexible electronics.     

Chitosan/Silver Nanoparticle/Graphene Oxide Nanocomposites with Multi-Drug Release,Antimicrobial, and Photothermal Conversion Functions

In this work, we designed and fabricated a multifunctional nanocomposite system that consists of chitosan, raspberry-like silver nanoparticles, and graphene oxide. The room temperature atmospheric pressure microplasma (RT-APM) process provides a rapid, facile, and environmentally-friendly method for introducing silver nanoparticles into the composite system. Our composite can achieve a pH controlled single and/or dual drug release. Under pH 7.4 for methyl blue loaded on chitosan, the drug release profile features a burst release during the first 10 h, followed by a more stabilized release of 70–80% after 40–50 h. For fluorescein sodium loaded on graphene oxide, the drug release only reached 45% towards the end of 240 h. When the composite acted as a dual drug release system, the interaction of fluorescein sodium and methyl blue slowed down the methyl blue release rate. Under pH 4, both single and dual drug systems showed a much higher release rate. In addition, our composite system demonstrated strong antibacterial abilities against E. coli and S. aureus, as well as an excellent photothermal conversion effect under irradiation of near infrared lasers. The photothermal conversion efficiency can be controlled by the laser power. These unique functionalities of our nanocomposite point to its potential application in multiple areas, such as multimodal therapeutics in healthcare, water treatment, and anti-microbials, among others.     

Dry Sliding Behavior of an Aluminum Alloy after Innovative Hard Anodizing Treatments

This work evaluates the dry sliding behavior of anodic aluminum oxides (AAO) formed during one traditional hard anodizing treatment (HA) and two golden hard anodizing treatments (named G and GP, respectively) on a EN AW-6060 aluminum alloy. Three different thicknesses of AAO layers were selected: 25, 50, and 100 μm. Prior to wear tests, microstructure and mechanical properties were determined by scanning electron microscopy (VPSEM/EDS), X-ray diffractometry, diffuse reflectance infrared Fourier transform (DRIFT-FTIR) spectroscopy, roughness, microhardness, and scratch tests. Wear tests were carried out by a pin-on-disc tribometer using a steel disc as the counterpart material. The friction coefficient was provided by the equipment. Anodized pins were weighed before and after tests to assess the wear rate. Worn surfaces were analyzed by VPSEM/EDS and DRITF-FTIR. Based on the results, the GP-treated surfaces with a thickness of 50 μm exhibit the lowest friction coefficients and wear rates. In any case, a tribofilm is observed on the wear tracks. During sliding, its detachment leads to delamination of the underlying anodic aluminum oxides and to abrasion of the aluminum substrate. Finally, the best tribological performance of G- and GP-treated surfaces may be related to the existence of a thin Ag-rich film at the coating/aluminum substrate interfaces.