Inhibition of Adherence and Biofilm Formation of Pseudomonas aeruginosa by Immobilized ZnO Nanoparticles on Silicone Urinary Catheter Grafted by Gamma Irradiation

Silicones for Maxillofacial Prostheses and Their Modifications in Service

The biomedical applications of silicones are countless due to their outstanding properties. In dentistry, silicone for maxillofacial and plastic surgery has become indispensable, from both physiological and aesthetic points of view. In this mini-review, silicone materials for dentistry and facial prostheses are discussed, focusing on their properties and alterations when exposed for long periods to different environments. A significant number of studies reported in the literature have been conducted in vitro, mimicking some of the main degradative factors which have been identified as triggers for discoloration and deterioration of the mechanical properties. Among these, in artificial aging and accelerated natural aging studies, UV radiation is considered the most important. Other weathering factors, biological contamination, and disinfection agents may have dramatic effects as well. Several general properties of silicones are described at the beginning, with a focus on biocompatibility, cross-linking mechanisms, and applications in dentistry and maxillofacial prosthetics. We discuss the ongoing cross-linking and/or possible exudation after manufacturing, which also affects the stability of the prosthesis over time, and possibly the patient. Next, the main environmental factors that affect the prostheses in service are presented, including the role of cigarettes smoke, which has been discussed very little so far. A few aspects, such as biofilm formation, its negative effects, and proposed solutions to overcome this phenomenon regarding silicones, are also described. We conclude by proposing a set of topics for future research and development based on the gaps that have been identified in the literature. Although silicones are probably irreplaceable in maxillofacial prosthetics, improvements in terms of base materials, additives, surface treatments, and maintenance are possible and necessary for long-lasting and safer prostheses.

Antimicrobial Functionalization of Silicone-graft-poly(N-vinylimidazole) Catheters

In this work, we present the modification of a medical-grade silicone catheter with the N-vinylimidazole monomer using the grafting-from method at room temperature and induced by gamma rays. The catheters were modified by varying the monomer concentration (20-100 vol%) and the irradiation dose (20-100 kGy). Unlike the pristine material, the grafted poly(N-vinylimidazole) chains provided the catheter with hydrophilicity and pH response. This change allowed for the functionalization of the catheters to endow it with antimicrobial features. Thus, the quaternization of amines with iodomethane and bromoethane was performed, as well as the immobilization of silver and ampicillin. The inhibitory capacity of these materials, functionalized with antimicrobial agents, was challenged against Escherichia coli and Staphylococcus aureus strains, showing variable results, where loaded ampicillin was amply better at eliminating bacteria.

An Overview of Biofilm-Associated Infections and the Role of Phytochemicals and Nanomaterials in Their Control and Prevention

Biofilm formation is considered one of the primary virulence mechanisms in Gram-positive and Gram-negative pathogenic species, particularly those responsible for chronic infections and promoting bacterial survival within the host. In recent years, there has been a growing interest in discovering new compounds capable of inhibiting biofilm formation. This is considered a promising antivirulence strategy that could potentially overcome antibiotic resistance issues. Effective antibiofilm agents should possess distinctive properties. They should be structurally unique, enable easy entry into cells, influence quorum sensing signaling, and synergize with other antibacterial agents. Many of these properties are found in both natural systems that are isolated from plants and in synthetic systems like nanoparticles and nanocomposites. In this review, we discuss the clinical nature of biofilm-associated infections and some of the mechanisms associated with their antibiotic tolerance. We focus on the advantages and efficacy of various natural and synthetic compounds as a new therapeutic approach to control bacterial biofilms and address multidrug resistance in bacteria.