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"Lei, Mei"
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The Antibacterial Mechanism of Silver Nanoparticles and Its Application in Dentistry
Nanotechnology has recently emerged as a rapidly growing field with numerous biomedical science applications. At the same time, silver has been adopted as an antimicrobial material and disinfectant that is relatively free of adverse effects. Silver nanoparticles possess a broad spectrum of antibacterial, antifungal and antiviral properties. Silver nanoparticles have the ability to penetrate bacterial cell walls, changing the structure of cell membranes and even resulting in cell death. Their efficacy is due not only to their nanoscale size but also to their large ratio of surface area to volume. They can increase the permeability of cell membranes, produce reactive oxygen species, and interrupt replication of deoxyribonucleic acid by releasing silver ions. Researchers have studied silver nanoparticles as antimicrobial agents in dentistry. For instance, silver nanoparticles can be incorporated into acrylic resins for fabrication of removable dentures in prosthetic treatment, composite resin in restorative treatment, irrigating solution and obturation material in endodontic treatment, adhesive materials in orthodontic treatment, membrane for guided tissue regeneration in periodontal treatment, and titanium coating in dental implant treatment. Although not all authorities have acknowledged the safety of silver nanoparticles, no systemic toxicity of ingested silver nanoparticles has been reported. A broad concern is their potential hazard if they are released into the environment. However, the interaction of nanoparticles with toxic materials and organic compounds can either increase or reduce their toxicity. This paper provides an overview of the antibacterial use of silver nanoparticles in dentistry, highlighting their antibacterial mechanism, potential applications and safety in clinical treatment.
Journal Article
لا ماء أنقى من الدموع : أغان من جبال ليانغ الصغيرة
يضم هذا الكتاب مجموعة من أروع القصائد الشعرية، التي كتبها شاعر مقاطعة \"يونان\" الصينية لورو دي جي Lure Diji) بلهجة الماندرين الصينية، مترجمة إلى اللغة العربية. وقد استمد لورو قصائده من المحيط البعيد للعالم الثقافي الصيني تناول خلالها الأرض الحمراء للهضبة العليا في المناطق الحدودية العالية في جنوب غرب الصين، والمنطقة التي تعلوها أعمال الطبيعة الحرة من أي قيود، بالإضافة إلى جبال الهيمالايا والغابات شبه الاستوائية العميقة، وجبال الثلج العملاقة والوديان ذات الانحدار الشديد، بالإضافة إلى روافد نهر يانغتسي، حيث تأخذ العديد من قصائد هذا الكتاب مكانها بين هذه التكوينات الطبيعية العظيمة، وتغوص في قصص الناس الذين يعيشون هناك، وتتناول الانطباعات التي تركوها على الأرض للحظات. إنها تحية وجدانية عظيمة مليئة بالوفاء والإكبار لإحدى براري الصين الأكثر جمالا ودفئا، من أحد أبنائها الأبرار.
Recent Developments in Food Packaging Based on Nanomaterials
The increasing demand for high food quality and safety, and concerns of environment sustainable development have been encouraging researchers in the food industry to exploit the robust and green biodegradable nanocomposites, which provide new opportunities and challenges for the development of nanomaterials in the food industry. This review paper aims at summarizing the recent three years of research findings on the new development of nanomaterials for food packaging. Two categories of nanomaterials (i.e., inorganic and organic) are included. The synthetic methods, physical and chemical properties, biological activity, and applications in food systems and safety assessments of each nanomaterial are presented. This review also highlights the possible mechanisms of antimicrobial activity against bacteria of certain active nanomaterials and their health concerns. It concludes with an outlook of the nanomaterials functionalized in food packaging.
Journal Article
Proteomics of Staphylococcus aureus biofilm matrix in a rat model of orthopedic implant-associated infection
The matrix proteins of Staphylococcus aureus biofilm have not been well defined. Previous efforts to identify these proteins were performed using in vitro systems. Here we use a proteomic approach to identify biofilm matrix proteins directly from infected bone implants using a rat model of orthopedic implant-associated S. aureus infection. Despite heavy presence of host proteins, a total of 28 and 105 S. aureus proteins were identified during acute infection and chronic infection, respectively. Our results show that biofilm matrix contains mostly intracellular cytoplasmic proteins and, to a much less extent, extracellular and cell surface-associated proteins. Significantly, leukocidins were identified in the biofilm matrix during chronic infection, suggesting S. aureus is actively attacking the host immune system even though they are protected within the biofilm. The presence of two surface-associated proteins, Ebh and SasF, in the infected bone tissue during acute infection was confirmed by immunohistochemistry. In addition, a large number of host proteins were found differentially expressed in response to S. aureus biofilm formed on bone implants.
Journal Article
Anion-adaptive crystalline cationic material for 99TcO4− trapping
Efficient anion recognition is of great significance for radioactive
99
TcO
4
−
decontamination, but it remains a challenge for traditional sorbents. Herein, we put forward a tactic using soft crystalline cationic material with anion-adaptive dynamics for
99
TcO
4
−
sequestration. A cucurbit[8]uril-based supramolecular metal-organic material is produced through a multi-component assembly strategy and used as a sorbent for effective trapping of TcO
4
−
. Excellent separation of TcO
4
−
/ReO
4
−
is demonstrated by fast removal kinetics, good sorption capacity and high distribution coefficient. Remarkably, the most superior selectivity among metal-organic materials reported so far, together with good hydrolytic stability, indicates potential for efficient TcO
4
−
removal. The structure incorporating ReO
4
−
reveals that the supramolecular framework undergoes adaptive reconstruction facilitating the effective accommodation of TcO
4
−
/ReO
4
−
. The results highlight opportunities for development of soft anion-adaptive sorbents for highly selective anion decontamination.
Efficient anion recognition and trapping is of great significance for anion-specific separation processes but the design of an anion-adaptive sorbents remains a challenge. Here the authors use a cucurbit[8]uril based soft cationic supramolecular material as efficient sorbent for TcO
4
−
ions.
Journal Article
In-situ anodic precipitation process for highly efficient separation of aluminum alloys
Electrorefining process has been widely used to separate and purify metals, but it is limited by deposition potential of the metal itself. Here we report in-situ anodic precipitation (IAP), a modified electrorefining process, to purify aluminium from contaminants that are more reactive. During IAP, the target metals that are more cathodic than aluminium are oxidized at the anode and forced to precipitate out in a low oxidation state. This strategy is fundamentally based on different solubilities of target metal chlorides in the NaAlCl
4
molten salt rather than deposition potential of metals. The results suggest that IAP is able to efficiently and simply separate components of aluminum alloys with fast kinetics and high recovery yields, and it is also a valuable synthetic approach for metal chlorides in low oxidation states.
Traditional electrorefining process is limited by deposition potential of the metal itself. Here, the authors explore an in-situ anodic precipitation process based on different solubility of target metal chlorides that can efficiently separate components of aluminum alloys.
Journal Article
Intertwining DNA-RNA nanocapsules loaded with tumor neoantigens as synergistic nanovaccines for cancer immunotherapy
Nanomedicines that co-deliver DNA, RNA, and peptide therapeutics are highly desirable yet remain underdeveloped for cancer theranostics. Herein, we report self-assembled intertwining DNA-RNA nanocapsules (iDR-NCs) that efficiently delivered synergistic DNA CpG and short hairpin RNA (shRNA) adjuvants, as well as tumor-specific peptide neoantigens into antigen presenting cells (APCs) in lymph nodes for cancer immunotherapy. These nanovaccines were prepared by (1) producing tandem CpG and shRNA via concurrent rolling circle replication and rolling circle transcription, (2) self-assembling CpG and shRNA into DNA-RNA microflowers, (3) shrinking microflowers into iDR-NCs using PEG-grafted cationic polypeptides, and (4) physically loading neoantigen into iDR-NCs. CpG and shRNA in iDR-NCs synergistically activate APCs for sustained antigen presentation. Remarkably, iDR-NC/neoantigen nanovaccines elicit 8-fold more frequent neoantigen-specific peripheral CD8
+
T cells than CpG, induce T cell memory, and significantly inhibit the progression of neoantigen-specific colorectal tumors. Collectively, iDR-NCs represent potential DNA/RNA/peptide triple-co-delivery nanocarriers and synergistic tumor immunotherapeutic nanovaccines.
Nucleic acid nanomedicines are promising for cancer drug delivery. Here, the authors show using a mouse model the tumor immunotherapeutic efficacy of nanovaccines based on intertwining DNA-RNA nanocapsules loaded with DNA CpG,
Stat3
-silencing short hairpin RNA and tumor-specific peptide neoantigens.
Journal Article
Controllable photomechanical bending of metal-organic rotaxane crystals facilitated by regioselective confined-space photodimerization
Molecular machines based on mechanically-interlocked molecules (MIMs) such as (pseudo) rotaxanes or catenates are known for their molecular-level dynamics, but promoting macro-mechanical response of these molecular machines or related materials is still challenging. Herein, by employing macrocyclic cucurbit[8]uril (CB[8])-based pseudorotaxane with a pair of styrene-derived photoactive guest molecules as linking structs of uranyl node, we describe a metal-organic rotaxane compound, U-CB[8]-MPyVB, that is capable of delivering controllable macroscopic mechanical responses. Under light irradiation, the ladder-shape structural unit of metal-organic rotaxane chain in U-CB[8]-MPyVB undergoes a regioselective solid-state [2 + 2] photodimerization, and facilitates a photo-triggered single-crystal-to-single-crystal (SCSC) transformation, which even induces macroscopic photomechanical bending of individual rod-like bulk crystals. The fabrication of rotaxane-based crystalline materials with both photoresponsive microscopic and macroscopic dynamic behaviors in solid state can be promising photoactuator devices, and will have implications in emerging fields such as optomechanical microdevices and smart microrobotics.
The preparation of materials that display macro-mechanical responses to external stimuli is challenging. Here, the authors synthesize metal-organic rotaxane frameworks that contain photoactive axles as linkers; light irradiation triggers photodimerization of the ligands, which leads to macroscopic photomechanical bending of individual bulk crystals.
Journal Article
Caries remineralisation and arresting effect in children by professionally applied fluoride treatment – a systematic review
Background
As a low-cost and easily operated treatment, the use of professionally applied topical fluoride was approved for preventing dental caries and remineralising early enamel caries or white spot lesions. It is also used to arrest dentine caries. The aim of this study is to investigate the clinical efficacy of professional fluoride therapy in remineralising and arresting caries in children.
Method
A systematic search of publications from 1948 to 2014 was conducted using four databases: PubMed, Cochrane Library, ISI Web of Science and Embase. The key words used were (fluoride) AND (remineralisation OR remineralization OR arresting) AND (children caries OR early childhood caries). The title and abstract of initially identified publications were screened. Clinical trials about home-use fluorides, laboratory studies, case reports, reviews, non-English articles and irrelevant studies were excluded. The full texts of the remaining papers were retrieved. Manual screening was conducted on the bibliographies of the remaining papers to identify relevant articles.
Results
A total of 2177 papers were found, and 17 randomised clinical trials were included in this review. Ten studies investigated the remineralising effect on early enamel caries using silicon tetrafluoride, fluoride gel, silver diamine fluoride or sodium fluoride. Seven studies reported an arresting effect on dentine caries using silver diamine fluoride or nano-silver fluoride. Meta-analysis was performed on four papers using 5 % sodium fluoride varnish to remineralise early enamel caries, and the overall percentage of remineralised enamel caries was 63.6 % (95 % CI: 36.0 % - 91.2 %; p < 0.001). Meta-analysis was also performed on five papers using 38 % silver diamine fluoride to arrest dentine caries and the overall proportion of arrested dentine caries was 65.9 % (95 % CI: 41.2 % - 90.7 %; p < 0.001).
Conclusion
Professionally applied 5 % sodium fluoride varnish can remineralise early enamel caries and 38 % silver diamine fluoride is effective in arresting dentine caries.
Journal Article