Physicochemical Aspects of Metal Nanoparticle Preparation

Physicochemical properties, including optical properties or catalytic activity, and biological properties of metal nanoparticles are considerably influenced by their diameter. Therefore, a tailored synthesis of metal nanoparticles represents a key topic in the field of nanotechnology, and the number of research papers, concerning this topic, has been annually growing with an arithmetic progression. Metal nanoparticles are most frequently prepared via chemical reduction of metals in ionic form from their solutions. Using this synthetic approach, tailored parameters of the particles can be achieved via the adjustment of numerous factors: difference of potentials of the metal redox system and the reducing agent redox system, pH of the reaction mixture, and its temperature. The influence of these three factors on the diameter of the prepared metal nanoparticles will be discussed in the following chapter with respect to general laws and based on numerous examples from research practice

Quantification of purine basis in their mixtures at femto-molar concentration levels using FT-SERS

Surface-enhanced Raman scattering spectroscopy represents one of the unique techniques for studying nanoscale objects, and its distinctive properties can be used in the process of further analysis. The careful evaluation of the particular influence of selected key-role experimental parameters (e.g. pH value of measured sample mixture, size and distribution of used nanoparticles) and the influence of reduction agent used in the process of formation of desired nanoparticle objects presents an important task in the further study of surface-enhanced Raman scattering effect. A broad study of these experimental parameters was performed in this paper. The main aim of the presented work was to a demonstrate an application potential of selected experimental conditions in the determination of three purine bases: adenine, xanthine, and hypoxanthine. The resulting limits of detection are at femtomolar concentration levels for all three studied compounds

Silver Nanocoating Technology in the Prevention of Prosthetic Joint Infection

Prosthetic joint infection (PJI) is a feared complication of total joint arthroplasty associated with increased morbidity and mortality. There is a growing body of evidence that bacterial colonization and biofilm formation are critical pathogenic events in PJI. Thus, the choice of biomaterials for implanted prostheses and their surface modifications may significantly influence the development of PJI. Currently, silver nanoparticle (AgNP) technology is receiving much interest in the field of orthopaedics for its antimicrobial properties and a strong anti-biofilm potential. The great advantage of AgNP surface modification is a minimal release of active substances into the surrounding tissue and a long period of effectiveness. As a result, a controlled release of AgNPs could ensure antibacterial protection throughout the life of the implant. Moreover, the antibacterial effect of AgNPs may be strengthened in combination with conventional antibiotics and other antimicrobial agents. Here, our main attention is devoted to general guidelines for the design of antibacterial biomaterials protected by AgNPs, its benefits, side effects and future perspectives in PJI prevention

Comparative Study of Antimicrobial Activity of AgBr and Ag Nanoparticles (NPs)

<div><p>The diverse mechanism of antimicrobial activity of Ag and AgBr nanoparticles against gram-positive and gram-negative bacteria and also against several strains of candida was explored in this study. The AgBr nanoparticles (NPs) were prepared by simple precipitation of silver nitrate by potassium bromide in the presence of stabilizing polymers. The used polymers (PEG, PVP, PVA, and HEC) influence significantly the size of the prepared AgBr NPs dependently on the mode of interaction of polymer with Ag⁺ ions. Small NPs (diameter of about 60–70 nm) were formed in the presence of the polymer with low interaction as are PEG and HEC, the polymers which interact with Ag⁺ strongly produce nearly two times bigger NPs (120–130 nm). The prepared AgBr NPs were transformed to Ag NPs by the reduction using NaBH₄. The sizes of the produced Ag NPs followed the same trends – the smallest NPs were produced in the presence of PEG and HEC polymers. Prepared AgBr and Ag NPs dispersions were tested for their biological activity. The obtained results of antimicrobial activity of AgBr and Ag NPs are discussed in terms of possible mechanism of the action of these NPs against tested microbial strains. The AgBr NPs are more effective against gram-negative bacteria and tested yeast strains while Ag NPs show the best antibacterial action against gram-positive bacteria strains.</p></div

Kinetic curves for AgBr nanoparticles reduction by NaBH₄ in the presence of studied polymers (λ_max represent position of absorption maxima) and zoom of the first 60 seconds (inset).

<p>Kinetic curves for AgBr nanoparticles reduction by NaBH₄ in the presence of studied polymers (λ_max represent position of absorption maxima) and zoom of the first 60 seconds (inset).</p

Silver Nanoparticles Modified by Gelatin with Extraordinary pH Stability and Long-Term Antibacterial Activity

<div><p>The potential for application of any nanoparticles, including silver nanoparticles (AgNPs), is strongly dependent on their stability against aggregation. Therefore, improvement of this parameter is a key task, especially in the case of AgNPs, because a correlation between size and biological activity has been demonstrated. In the present work, a natural stabilizer, gelatin, was investigated for the stabilization of AgNPs in an aqueous dispersion. The particles were prepared via a modified Tollens process, and the gelatin modifier was added prior to the reducing agent. The stability against aggregation of the AgNPs prepared by this method was more than one order of magnitude higher (on the basis of the critical coagulation concentration (CCC)) than that of AgNPs prepared via a similar method but without the assistance of gelatin. Their high stability against aggregation was confirmed over wide pH range (from 2 to 13) in which the particles did not exhibit rapid aggregation; such stability has not been previously reported for AgNPs. Additionally, gelatin not only fulfills the role of a unique stabilizer but also positively influences the modified Tollens process used to prepare the AgNPs. The diameter of the gelatin-modified AgNPs was substantially smaller in comparison to those prepared without gelatin. The polydispersity of the dispersion significantly narrowed. Moreover, the gelatin-stabilized AgNPs exhibited long-term stability against aggregation and maintained high antibacterial activity when stored for several months under ambient conditions.</p></div

AFM images of AgBr nanoparticles prepared in the presence of a) PEG, b) PVP, c) PVA and d) HEC.

<p>AFM images of AgBr nanoparticles prepared in the presence of a) PEG, b) PVP, c) PVA and d) HEC.</p