Nanotechnology, Science and Applications最新文献

This article presents a simple, one-step, in situ generation of silver nanoparticle-functionalized fabrics with antibacterial properties, circumventing the conventional, multistep, time-consuming methods. Silver nanoparticle formation was studied with a library of capping agents (branched polyethylenimine [BPEI] of molecular weight [M_w] 10,000 and 25,000, polyvinylpyrrolidone, polyethylene glycol, polyvinylalcohol and citrate) mixed with silver nitrate. The mixture was then exposed to an assortment of light wavelengths (ultraviolet, infrared and simulated solar light) for studying the light-assisted synthesis of nanoparticles. The formation of nanoparticles corresponded with the reducing capabilities of the polymers wherein BPEI gave the best response. Notably, the irradiation wavelengths had little effect on the formation of the nanoparticle when the total irradiation energy was kept constant. The feasibility of utilizing this method for in situ nanoparticle synthesis on textile fabrics (towel [100% cotton], gauze [100% cotton], rayon, felt [100% polyester] and microfiber [15% nylon, 85% polyester]) was verified by exposing the fabrics soaked in an aqueous solution of 1% (w/v) AgNO₃ and 1% (w/v) BPEI (M_w 25,000) to light. The formation of nanoparticles on fabrics and their retention after washing was verified using scanning electron microscopy and quantified by inductively coupled plasma optical emission spectrometry. The functional property of the fabric as an antibacterial surface was successfully demonstrated using model bacteria such as Staphylococcus aureus, Enterococcus faecalis and Escherichia coli. The successful generation of silver nanoparticle-functionalized textile fabrics without the use of caustic chemicals, solvents and excessive heating presents a major step towards realizing a scalable green chemistry for industrial generation of functionalized fabrics for a wide range of applications.

Bacterial infections, especially by antimicrobial resistant (AMR) bacteria, are an increasing problem worldwide. AMR is especially a problem with health care-associated infections due to bacteria in hospital environments being easily transferred from patient to patient and from patient to environment, and thus, solutions to prevent bacterial transmission are needed. Hand washing is an effective tool for preventing bacterial infections, but other approaches such as nanoparticle-coated surfaces are also needed. In the current study, direct and indirect liquid flame spray (LFS) method was used to produce silver nanoparticle-coated surfaces. The antimicrobial properties of these nanoparticle surfaces were evaluated with the "touch test" method against Escherichia coli and Staphylococcus aureus. It was shown in this study that in glass samples one silver nanoparticle-coating cycle can inhibit E. coli growth, whereas at least two coating cycles were needed to inhibit S. aureus growth. Silver nanoparticle-coated polyethylene (PE) and PE terephthalate samples did not inhibit bacterial growth as effectively as glass samples: three nanoparticle-coating cycles were needed to inhibit E. coli growth, and more than 30 coating cycles were needed until S. aureus growth was inhibited. To conclude, with the LFS method, it is possible to produce nanostructured large-area antibacterial surfaces which show antibacterial effect against clinically relevant pathogens. Results indicate that the use of silver nanoparticle surfaces in hospital environments could prevent health care-associated infections in vivo.

Cellulose nanocrystals (CNCs) have emerged as promising candidates for a number of bio-applications. Surface modification of CNCs continues to gain significant research interest as it imparts new properties to the surface of the nanocrystals for the design of multifunctional CNCs-based materials. A small chemical surface modification can potentially lead to drastic behavioral changes of cell-material interactions thereby affecting the intended bio-application. In this work, unmodified CNCs were covalently decorated with four different organic moieties such as a diaminobutane fragment, a cyclic oligosaccharide (β-cyclodextrin), a thermoresponsive polymer (poly[N-isopropylacrylamide]), and a cationic aminomethacrylamide-based polymer using different synthetic covalent methods. The effect of surface coatings of CNCs and the respective dose-response of the above organic moieties on the cell viability were evaluated on mammalian cell cultures (J774A.1 and MFC-7), using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphe-nyltetrazolium bromide and lactate dehydrogenase assays. Overall, the results indicated that cells exposed to surface-coated CNCs for 24 h did not display major changes in cell viability, membrane permeability as well as cell morphology. However, with longer exposure, all these parameters were somewhat affected, which appears not to be correlated with either anionic or cationic surface coatings of CNCs used in this study.

Pseudomonas aeruginosa has great intrinsic antimicrobial resistance limiting the number of effective antibiotics. Thus, other antimicrobial agents such as silver nanoparticles (AgNPs) are considered potential agents to help manage and prevent infections. AgNPs can be used in several applications against bacteria resistant to common antibiotics or even multi-resistant bacteria such as P. aeruginosa. This study assessed the antimicrobial activity of commercial 10 nm AgNPs on two hospital strains of P. aeruginosa resistant to a large number of antibiotics and a reference strain from a culture collection. All strains were susceptible to 5 µg/mL nanoparticles solution. Reference strains INCQS 0230 and P.a.1 were sensitive to AgNPs at concentrations of 1.25 and 0.156 µg/mL, respectively; however, this was not observed for hospital strain P.a.2, which was more resistant to all antibiotics and AgNPs tested. Cytotoxicity evaluation indicated that AgNPs, up to a concentration of 2.5 µg/mL, are very safe for all cell lines tested. At 5.0 µg/mL, AgNPs had a discrete cytotoxic effect on tumor cells HeLa and HepG2. Results showed the potential of using AgNPs as an alternative to conventional antimicrobial agents that are currently used, and a perspective for application of nanosilver with antibiotics to enhance antimicrobial activity.

Halloysite nanotubes (HNTs) were investigated as a platform for tunable nanoparticle composition and enhanced opacity in poly(methyl methacrylate) (PMMA) bone cement. Halloysite has been widely used to increase the mechanical properties of various polymer matrices, in stark contrast to other fillers such as barium sulfate that provide opacity but also decrease mechanical strength. The present work describes a dry deposition method for successively fabricating barium sulfate nanoparticles onto the exterior surface of HNTs. A sintering process was used to coat the HNTs in barium sulfate. Barium sulfate-coated HNTs were then added to PMMA bone cement and the samples were tested for mechanical strength and tailored opacity correlated with the fabrication ratio and the amount of barium sulfate-coated HNTs added. The potential cytotoxic effect of barium-coated HNTs in PMMA cement was also tested on osteosarcoma cells. Barium-coated HNTs were found to be completely cytocompatible, and cell proliferation was not inhibited after exposure to the barium-coated HNTs embedded in PMMA cement. We demonstrate a simple method for the creation of barium-coated nanoparticles that imparted improved contrast and material properties to native PMMA. An easy and efficient method for coating clay nanotubes offers the potential for enhanced imaging by radiologists or orthopedic surgeons.

In this study, nanoparticles (NPs) of poly(lactic-co-glycolic acid) (PLGA) loaded with fluconazole (FLZ) and FLZ-NPs coated with the cationic polymer polyethylenimine (PEI) (FLZ-NP-PEI) were synthetized in order to improve antimycotic activity against four strains of Candida spp. of clinical relevance. FLZ-NPs and FLZ-NP-PEI were synthesized by double emulsion solvent-diffusion (DES-D) and characterized. Minimum inhibitory concentration (MIC₅₀) and minimum fungicide concentration (MFC) were determined in vitro by culturing Candida strains in the presence of these nanocompounds. FLZ-NPs were spherical in shape with hydrodynamic sizes of ~222 nm and surface charge of -11.6 mV. The surface charges of these NPs were successfully modified using PEI (FLZ-NP-PEI) with mean hydrodynamic sizes of 281 nm and surface charge of 23.5 mV. The efficiency of encapsulation (~53%) and a quick release of FLZ (≥90% after 3 h) were obtained. Cytotoxicity assay showed a good cell viability for FLZ-NPs (≥86%), and PEI-modified NPs presented a decrease in cell viability (~38%). FLZ-NPs showed an increasing antifungal activity of FLZ for sensitive (Candida parapsilosis ATCC22019 and Candida albicans ATCC10231, MIC₅₀ =0.5 and 0.1 µg/mL, respectively) and resistant strains (Candida glabrata EMLM14 and Candida krusei ATCC6258, MIC₅₀ =0.1 and 0.5 µg/mL, respectively). FLZ-NP-PEI showed fungicidal activity even against C. glabrata and C. krusei (MFC =4 and 8 µg/mL, respectively). MIC₅₀ values showed best results for FLZ-NPs and FLZ-NP-PEI. Nevertheless, only FLZ-NP-PEI displayed fungicidal activity against the studied strains.

Calcium carbonate aragonite polymorph nanoparticles derived from cockle shells were prepared using surface functionalization method followed by purification steps. Size, morphology, and surface properties of the nanoparticles were characterized using transmission electron microscopy, field emission scanning electron microscopy, dynamic light scattering, zetasizer, X-ray powder diffraction, and Fourier transform infrared spectrometry techniques. The potential of surface-functionalized calcium carbonate aragonite polymorph nanoparticle as a drug-delivery agent were assessed through in vitro drug-loading test and drug-release test. Transmission electron microscopy, field emission scanning electron microscopy, and particle size distribution analyses revealed that size, morphology, and surface characterization had been improved after surface functionalization process. Zeta potential of the nanoparticles was found to be increased, thereby demonstrating better dispersion among the nanoparticles. Purification techniques showed a further improvement in the overall distribution of nanoparticles toward more refined size ranges <100 nm, which specifically favored drug-delivery applications. The purity of the aragonite phase and their chemical analyses were verified by X-ray powder diffraction and Fourier transform infrared spectrometry studies. In vitro biological response of hFOB 1.19 osteoblast cells showed that surface functionalization could improve the cytotoxicity of cockle shell-based calcium carbonate aragonite nanocarrier. The sample was also sensitive to pH changes and demonstrated good abilities to load and sustain in vitro drug. This study thus indicates that calcium carbonate aragonite polymorph nanoparticles derived from cockle shells, a natural biomaterial, with modified surface characteristics are promising and can be applied as efficient carriers for drug delivery.

The structure and properties of nanocomposites of poly(ethylene oxide), with Ag and Au nanoparticles, surface modified with a 1:1 (by volume) oleylamine/oleic acid mixture, were investigated via transmission electron microscopy, scanning electron microscopy, thermogravimetric analysis, differential scanning calorimetry (DSC), infrared spectroscopy, dynamic mechanical analysis, and static mechanical testing. Results indicated that there was more oleylamine on Ag nanoparticles but more oleic acid on Au nanoparticles. This difference in surfactant populations on each nanoparticle led to different interfacial interactions with poly(ethylene oxide) and drastically influenced the glass transition temperature of these two nanocomposite systems. Almost all other properties were found to correlate strongly with dispersion and distribution state of Au and Ag nanoparticles, such that the property in question changed direction at the onset of agglomeration.

Durable superhydrophobic coatings were synthesized using a system of silica nanoparticles (NPs) to provide nanoscale roughness, fluorosilane to give hydrophobic chemistry, and three different polymer binders: urethane acrylate, ethyl 2-cyanoacrylate, and epoxy. Coatings composed of different binders incorporating NPs in various concentrations exhibited different superhydrophobic attributes when applied on polycarbonate (PC) and glass substrates and as a function of coating composition. It was found that the substrate surface characteristics and wettability affected the superhydrophobic characteristics of the coatings. Interfacial tension and spreading coefficient parameters (thermodynamics) of the coating components were used to predict the localization of the NPs for the different binders' concentrations. The thermodynamic analysis of the NPs localization was in good agreement with the experimental observations. On the basis of the thermodynamic analysis and the experimental scanning electron microscopy, X-ray photoelectron spectroscopy, profilometry, and atomic force microscopy results, it was concluded that localization of the NPs on the surface was critical to provide the necessary roughness and resulting superhydrophobicity. The durability evaluated by tape testing of the epoxy formulations was the best on both glass and PC. Several coating compositions retained their superhydrophobicity after the tape test. In summary, it was concluded that thermodynamic analysis is a powerful tool to predict the roughness of the coating due to the location of NPs on the surface, and hence can be used in the design of superhydrophobic coatings.