Synthesis and self-assembly of polymer and polymer-coated ag nanoparticles by the reprecipitation of binary mixtures of polymers

Functional Silver Nanoparticle as a Benign Antimicrobial Agent That Eradicates Antibiotic-Resistant Bacteria and Promotes Wound Healing

With the increased prevalence of antibiotic-resistant bacteria infections, there is a pressed need for innovative antimicrobial agent. Here, we report a benign ε-polylysine/silver nanoparticle nanocomposite (EPL-g-butyl@AgNPs) with polyvalent and synergistic antibacterial effects. EPL-g-butyl@AgNPs exhibited good stability in aqueous solution and effective antibacterial activity against both Gram-negative (P. aeruginosa) and Gram-positive (S. aureus) bacteria without emergence of bacterial resistance. Importantly, the nanocomposites eradicated the antibiotic-resistant bacteria without toxicity to mammalian cells. Analysis of the antibacterial mechanism confirmed that the nanocomposites adhered to the bacterial surface, irreversibly disrupted the membrane structure of the bacteria, subsequently penetrated cells, and effectively inhibited protein activity, which ultimately led to bacteria apoptosis. Notably, the nanocomposites modulated the relative level of CD3⁺ T cells and CD68⁺ macrophages and effectively promoted infected wound healing in diabetic rats. This work improves our understanding of the antibacterial mechanism of AgNPs-based nanocomposites and offers guidance to activity prediction and rational design of effective antimicrobial nanoparticles.

Closing the gap: accelerating the translational process in nanomedicine by proposing standardized characterization techniques

On the cusp of widespread permeation of nanomedicine, academia, industry, and government have invested substantial financial resources in developing new ways to better treat diseases. Materials have unique physical and chemical properties at the nanoscale compared with their bulk or small-molecule analogs. These unique properties have been greatly advantageous in providing innovative solutions for medical treatments at the bench level. However, nanomedicine research has not yet fully permeated the clinical setting because of several limitations. Among these limitations are the lack of universal standards for characterizing nanomaterials and the limited knowledge that we possess regarding the interactions between nanomaterials and biological entities such as proteins. In this review, we report on recent developments in the characterization of nanomaterials as well as the newest information about the interactions between nanomaterials and proteins in the human body. We propose a standard set of techniques for universal characterization of nanomaterials. We also address relevant regulatory issues involved in the translational process for the development of drug molecules and drug delivery systems. Adherence and refinement of a universal standard in nanomaterial characterization as well as the acquisition of a deeper understanding of nanomaterials and proteins will likely accelerate the use of nanomedicine in common practice to a great extent.

The use of polyimide-modified aluminum nitride fillers in AlN@PI/epoxy composites with enhanced thermal conductivity for electronic encapsulation

Polymer modified fillers in composites has attracted the attention of numerous researchers. These fillers are composed of core-shell structures that exhibit enhanced physical and chemical properties that are associated with shell surface control and encapsulated core materials. In this study, we have described an apt method to prepare polyimide (PI)-modified aluminum nitride (AlN) fillers, AlN@PI. These fillers are used for electronic encapsulation in high performance polymer composites. Compared with that of untreated AlN composite, these AlN@PI/epoxy composites exhibit better thermal and dielectric properties. At 40 wt% of filler loading, the highest thermal conductivity of AlN@PI/epoxy composite reached 2.03 W/mK. In this way, the thermal conductivity is approximately enhanced by 10.6 times than that of the used epoxy matrix. The experimental results exhibiting the thermal conductivity of AlN@PI/epoxy composites were in good agreement with the values calculated from the parallel conduction model. This research work describes an effective pathway that modifies the surface of fillers with polymer coating. Furthermore, this novel technique improves the thermal and dielectric properties of fillers and these can be used extensively for electronic packaging applications.

Large-area fabrication of highly reproducible surface enhanced Raman substrate via a facile double sided tape-assisted transfer approach using hollow Au-Ag alloy nanourchins

Ideally, a SERS substrate should possess super signal amplification, high uniformity and reproducibility. Up to now, an emphasis on reproducibility and uniformity has been crucial to ensure consistent chemical detection sensitivity across the surface of a SERS substrate. Here we demonstrate a simple and facile double sided tape-assisted transfer method to fabricate surface enhanced Raman scattering (SERS) substrates with prominent performance using hollow Au-Ag alloy nanourchins (HAAA-NUs). Such a large area, closely-packed flat film of the HAAA-NUs with a high density of "hot spots" exhibits a high SERS activity and reproducibility, simultaneously. The AFM-correlated nano-Raman and the point by point scanning of SERS signals verify the excellent spatial uniformity and reproducibility with a low relative standard deviation (RSD) less than 15% using crystal violet as probe molecule at the concentrations of 1 × 10(-8) M and 1 × 10(-10) M. The SERS signals of Sudan dye at a 1 × 10(-8) M concentration also show high reproducibility with a low RSD of 13.8%. This facile protocol presented here could lead to a high quality SERS substrate and open tremendous potential for various applications.

Controlled orientation in a bio-inspired assembly of Ag/AgCl/ZnO nanostructures enables enhancement in visible-light-induced photocatalytic performance

In a bio-inspired approach, polyamine-mediated mineralization of ZnO was explored to develop an environmentally benign methodology for synthesizing Ag/AgCl/ZnO nanostructures. The assembling properties displayed by the polyamines to create composite structures was utilized to have the nanocomponents effectively interact with each other in a way that is desirable for the application envisaged. The polyamines, which act as a mineralizing agent for ZnO nanoparticles, also facilitate the formation of Ag/AgCl within ZnO under ambient conditions. Thus synthesized Ag/AgCl/ZnO nanostructures represent a multi-heterojunction system in which the nanocomponents lead in a synergistic way to enhancement in the photocatalytic activity under visible-light irradiation.

Synthetically directed self-assembly and enhanced surface-enhanced Raman scattering property of twinned crystalline Ag/Ag homojunction nanoparticles

A synthetically directed self-assembly strategy to the aqueous-phase synthesis of twinned crystalline silver/silver homojunction nanoparticles (Ag/Ag HJNPs) is demonstrated. In the self-assembly, ethylenediamine tetraacetic acid disodium (EDTA) and solution pH values play a crucial role in the formation of Ag/Ag HJNPs while the sizes of Ag nanoparticles (NPs) in the Ag/Ag HJNPs depend on the reductant concentrations of ascorbic acid. Surface-enhanced Raman scattering (SERS) measurements indicate that the SERS intensity acquired from the Ag/Ag HJNP colloidal solution is about 200 times stronger than that obtained from isolated Ag NP colloid solution. The plasmonic and SERS behaviors of Ag/Ag HJNPs were simulated by discrete-dipole approximation (DDA) and three-dimensional finite-difference time domain (3D-FDTD) methods, respectively. Theoretical calculation results disclose that surface plasmon resonance (SPR) properties of the Ag/Ag HJNPs are different from those of isolated Ag nanospheres, and their maximal SERS enhancement is about 2 orders of magnitude higher than that of isolated Ag nanospheres, which is in good agreement with the experimental results. The extra SERS enhancement can be explained by the hot spots at homojunction structures between Ag particles because of near-field coupling effect.