Antimicrobial resistance is a significant threat to human health worldwide, forcing scientists to explore non-traditional antibacterial agents to support rapid interventions and combat the emergence and spread of drug resistant bacteria. Many new antibiotic-free approaches are being developed while the old ones are being revised, resulting in creating unique solutions that arise at the interface of physics, nanotechnology, and microbiology. Specifically, physical factors (e.g., pressure, temperature, UV light) are increasingly used for industrial sterilization. Nanoparticles (unmodified or in combination with toxic compounds) are also applied to circumvent in vivo drug resistance mechanisms in bacteria. Recently, bacteriophage-based treatments are also gaining momentum due to their high bactericidal activity and specificity. Although the number of novel approaches for tackling the antimicrobial resistance crisis is snowballing, it is still unclear if any proposed solutions would provide a long-term remedy. This review aims to provide a detailed overview of how bacteria acquire resistance against these non-antibiotic factors. We also discuss innate bacterial defense systems and how bacteriophages have evolved to tackle them.

The rapid progress in the development of surface plasmon resonance-based immunosensing platforms offers wide application possibilities in medical diagnostics as a label-free alternative to enzyme immunoassays. The early diagnosis of diseases or metabolic changes through the detection of biomarkers in body fluids requires methods characterized by a very good sensitivity and selectivity. In the case of the SPR technique, as well as other surface-sensitive detection strategies, the quality of the transducer-immunoreceptor interphase is crucial for maintaining the analytical reliability of an assay. In this work, an overview of general approaches to the design of functional SPR-immunoassays is presented. It covers both immunosensors, the design of which utilizes well-known and often commercially available substrates, as well as the latest solutions developed in-house. Various approaches employing chemical and passive binding, affinity-based antibody immobilization, and the introduction of nanomaterial-based surfaces are discussed. The essence of their influence on the improvement of the main analytical parameters of a given immunosensor is explained. Particular attention is paid to solutions compatible with the latest trends in the development of label-free immunosensors, such as platforms dedicated to real-time monitoring in a quasi-continuous mode, the use of in situ-generated receptor layers (elimination of the regeneration step), and biosensors using recombinant and labelled protein receptors.

Scientific interest in the investigation and application of multifunctional nanomaterials in medical diagnostics has been increasing. The employment of magnetocatalytic immunoconjugates as both analyte-capturing agents and enzyme-like catalytic labels may enable rapid preconcentration and determination of relevant antigens. In this work, we synthesized and comprehensively characterized two types of noble metal-decorated magnetic nanocubes (MDMCs) which were subsequently applied in the one-step, sandwich nanozyme-linked immunosorbent assay (NLISA). Magnetic cores allow for rapid separation from complex samples of biological origin. The catalytically active shell composed of Au-decorated Pt or Ru can effectively mimic the activity of horseradish peroxididase, retaining at the same time the ability to form stable bioconstructs through self-assembly of thiolated ligands. As a result, hybrid multifunctional nanoparticles were synthesized and used to detect C-reactive protein (CRP) in serum samples. We have also paid considerable attention to the mechanistic studies of the formation of sandwich immunocomplexes with nanoparticle labels by means of immunoenzymatic methods and surface plasmon resonance. Analytical parameters of the Pt-MDMCs-labeled NLISA (detection limit LOD = 0.336 ng mL^-1, recovery = 98.0%, linear response window covering two logarithmic units) turned out to be superior to the classical, one-step ELISA based on a horseradish peroxidase. In addition, our method offers further possibility of sensitivity adjustment by changing the parameters of magnetic preconcentration, together with good long-term stability of MDMCs conjugates and their good resistance to common interferences. We believe that the proposed simple synthetic protocol will guide a new approach to applying metal-decorated magnetic nanozymes as versatile and multifunctional labels for application in subsequent pre-analytical analyte concentration and immunoassays towards clinical applications.