Nanomaterials for controlling bacterial pathogens and resistance occurrence

lnfectious diseases are the leading cause of death worldwide while the constantly raising antimicrobial resistance (AMR) is a major concern for the public health. During the infection establishment bacteria! pathogens communicate via expression of signaling molecules, controlled through a phenomenon called quorum sensing (QS). As a result of this, bacteria produce virulence factors and form resistant biofilms on living and non-living surfaces causing persistent infections. The infection complexity, especially in chronic diseases, requires the use of broad-spectrum antibiotics responsive for the appearance and the spread of drug resistant species. lnfections caused by antibiotic-resistant pathogens are associated with high morbidity, mortality, and huge economic burden. Unlike the decrease over the past three decades of the number of novel marketed antimicrobial drugs, the number of antibiotic resistant bacteria! strains steadily increases. Thus, there is an urgent need for development of alternative strategies to manage difficult-to-treat infections. This thesis aims at the engineering of advanced nano-enabled materials and nanostructured coatings for controlling bacteria! pathogenesis and resistance occurrence. To achieve this, biopolymers, antibiofilm and anti-infective enzymes. and inorganic compounds were nano-hybridized as altemative modalities to the conventional antibiotics. The nanoform was able to provide enhanced interaction with bacteria! cell membranes and easier penetration into biofilms, increasing the antimicrobial efficacy at lower dosages, while preventing from development of antimicrobial resistance. Additionally, specific targeting moieties increased the nanomaterial's interaction with the pathogens, avoiding the drug resistance appearance and cytotoxicity. The first part ofthe thesis describes the functionalization of biologically inert nanoparticles (NPs) with membrane disturbing antimicrobial aminocellulose (AM) and biocompatible hyaluronic acid (HA) in an Lbl fashion for elimination of medically relevant pathogens. The generated nanoentities demonstrated high potential to inhibit the biofilm formation, without affecting the human cell viability. Further, the Lbl technique was applied to decorate antimicrobial, but potentially toxic silver (Ag) nano-templates with biocompatible AM and quorum quenching (QQ) acylase in order to obtain safe antibacterial and antibiofilm nanomaterials. The deposition of acylase and AM on the Ag core interfered with the QS signaling and bacteria! pathogenesis, and enhanced the NPs interaction with the bacteria! membrane. The integration of a triple mechanisms of action in the hybrid nanoentities resulted in complete bacteria and biofilm eradication and improved biocompatibility ofthe AgNPs. The thesís also describes the development of targeted nanocapsules (NCs) for selective elimination of Staphylococcus aureus. Herein, self-assembling nanoencapsulation technology using the biocompatible and biodegradable proteín zein was applied for the generation of zein NCs loaded with bactericida! oregano essential oil (EO). An antibody specifically targeting S. aureus was covalently grafted on the NCs surface. The obtained targeted NCs demonstrated antibacterial selectivity in a mixed bacteria! inoculum, and the treatment efficacy was validated in an in vitro coculture model of bacteria and mammalian cells. Finally, high intensity ultrasonochemistry (US) process was employed for engineering of durable antibacterial/antibiofilm coating on urinary catheters. The simultaneous deposition of zinc oxide (ZnO) NPs anda matrix-degrading amylase enzyme improved the NPs adhesion on the silicone material, and prevented its bacteria! colonization and biofilm formation in vitro. The hybrid nanostructured coating delayed the occurrence of early onset urinary tract infections (UTls) and showed excellent biosafety in an in vivo animal model.Las enfermedades infecciosas son la principal causa de muerte en todo el mundo. Mientras que la resistencia a los antimicrobianos es una preocupación importante para la salud pública. Durante el establecimiento de la infección los patógenos bacterianos se comunican mediante la expresión de moléculas de señalización controladas mediante un fenómeno llamado detección de quórum (QS). Como resultado, las bacterias producen factores de virulencia y forman biopelículas resistentes que causan infecciones persistentes. Las infecciones causadas por patógenos resistentes a los antibióticos se asocian con una alta morbilidad mortalidad y una enorme carga económica. A diferencia de la disminución en las últimas tres décadas del número de nuevos medicamentos antimicrobianos comercializados el número de cepas bacterianas resistentes a los antibióticos aumenta constantemente. Por lo tanto existe la necesidad urgente de desarrollar estrategias alternativas para manejar infecciones diflciles de tratar. Esta tesis tiene como objeto de trabajo la ingenieria de materiales y recubrimientos avanzados nano estructurados para controlar la patogénesis bacteriana y la aparición de resistencias. Para lograrlo se combina polímeros anti biopelícula, enzimas anti infecciosas y compuestos inorgánicos como estrategias alternativas a los antibióticos convencionales. La nanoforma puede proporcionar una interacción mejorada con las membranas celulares bacterianas y una penetración más fácil en las biopelículas, aumentando la eficacia antimicrobiana en dosis más bajas al mismo tiempo que previene el desarrollo de resistencia antimicrobiana. Además las fracciones de orientación especificas aumentan la interacción del nano material con los patógenos evitando la aparición de resistencia al fármaco y la citotoxicidad.La primera parte de la tesis describe la funcionalización de nano partículas (NP) biológicamente inertes con aminocelulosa antimicrobiana (AM) perturbadora de la membrana y ácido hialurónico (HA) biocompatible en forma de LbL para la eliminación de patógenos médicamente relevantes. Las nanoentidades generadas demuestran un alto potencial para inhibir la formación de biopelículas sin afectar la viabilidad en las células humanas. Además, la técnica L.bL se aplica para decorar nanoplantillas de plata (Ag) antimicrobianas,pero potencialmente tóxicas con PNt biocompatible y acilasa de extinción de quórum (QQ) para obtener nanomateriales antibacterianos y anti biopelícula seguros. La deposición de acilasa y PNt en el núcleo de Ag interfiere con la señalización de QS y la patogénesis bacteriana y mejora la interacción de las NP con la membrana bacteriana. La integración de un triple mecanismo de acción en las nanoentidades híbridas da como resultado la erradicación completa de bacterias y biopelículas y una mejor biocompatibilidad de los AgNP. La tesis también describe el desarrollo de nanocápsulas dirigidas (NC) para la eliminación selectiva de Staphylococcus aureus. En este trabajo se aplica la tecnología de nanoencapsulación de autoensamblaje que utiliza la proteína Zeína biocompatible y biodegradable para la generación de NC de Zelna cargadas con aceite esencial de orégano bactericida.Un anticuerpo dirigido específicamente a S.aureus se injerta covalentemente en la superficie de las NC. Las NC dirigidos obtenidos demuestran selectividad antibacteriana en un inóculo bacteriano mixto.y la eficacia del tratamiento se valida en un modelo de cocultivo in vitro de bacterias y células de mamíferos.Finalmente, se emplea un proceso de ultrasonoqufmica de alta intensidad. Para la ingeniería de un recubrimiento antibacterlano/anti biopelícula duradero en catéteres urinarios. La deposición de NP de Óxido de Zinc y enzima amilasa que degrada la matriz.mejora la adhesión de las NP en el material de silicona evitando su colonización bacteriana y la formación de biopeliculas in vitroPostprint (published version

Simultaneous ultrasound-assisted hybrid polyzwitterion/antimicrobial peptide nanoparticles synthesis and deposition on silicone urinary catheters for prevention of biofilm-associated infections

Nosocomial infections caused by antibiotic-resistant bacteria are constantly growing healthcare threats, as they are the reason for the increased mortality, morbidity, and considerable financial burden due to the poor infection outcomes. Indwelling medical devices, such as urinary catheters, are frequently colonized by bacteria in the form of biofilms that cause dysfunction of the device and severe chronic infections. The current treatment strategies of such device-associated infections are impaired by the resistant pathogens but also by a risk of prompting the appearance of new antibiotic-resistant bacterial mechanisms. Herein, the one-step sonochemical synthesis of hybrid poly(sulfobetaine) methacrylate/Polymyxin B nanoparticles (pSBMA@PM NPs) coating was employed to engineer novel nanoenabled silicone catheters with improved antifouling, antibacterial, and antibiofilm efficiencies. The synergistic mode of action of nanohybridized zwitterionic polymer and antimicrobial peptide led to complete inhibition of the nonspecific protein adsorption and up to 97% reduction in Pseudomonas aeruginosa biofilm formation, in comparison with the pristine silicone. Additionally, the bactericidal activity in the hybrid coating reduced the free-floating and surface-attached bacterial growth by 8 logs, minimizing the probability for further P. aeruginosa spreading and host invasion. This coating was stable for up to 7 days under conditions simulating the real scenario of catheter usage and inhibited by 80% P. aeruginosa biofilms. For the same time of use, the pSBMA@PM NPs coating did not affect the metabolic activity and morphology of mammalian cells, demonstrating their capacity to control antibiotic-resistant biofilm-associated bacterial infections.Peer ReviewedPostprint (published version

Layer-by-Layer coating of aminocellulose and quorum quenching acylase on silver nanoparticles synergistically eradicate bacteria and their biofilms

The emergence of antibiotic-resistant bacteria and the failure of the existing antibacterial therapeutics call for development of novel treatment strategies. Furthermore, the formation of bacterial biofilms restricts drug penetration and efficiency, causing life-threatening infections. Bacterial attachment and biofilm formation are regulated by the cell-to-cell communication phenomenon called quorum sensing (QS). In this work, antimicrobial silver nanoparticles (AgNPs) are decorated in a layer-by-layer fashion with the oppositely charged aminocellulose (AM) and acylase to generate hybrid nanoentities with enhanced antibacterial and antibiofilm activities as well as reduced cytotoxicity. Acylase, a quorum-quenching enzyme that degrades the QS signals in the extracellular environment of bacteria, disrupts the bacterial QS process and together with the bactericidal AM synergistically lowers fourfold the minimum inhibitory concentration of the AgNPs templates toward Gram-negative Pseudomonas aeruginosa (P. aeruginosa). The hybrid nanoparticles in eightfold-lower concentration than the AgNPs inhibit 45% of the QS-regulated virulence factors produced by the reporter Chromobacterium violaceum bacterial strain and reduce by 100% the P. aeruginosa biofilm formation. Moreover, the sequential deposition of antibacterial/antibiofilm active and biocompatible biopolymers onto the AgNPs allows the engineering of safe nanomaterials that do not affect the viability of human cells.Peer ReviewedPostprint (published version

Nano-formulation endows quorum quenching enzyme-antibiotic hybrids with improved antibacterial and antibiofilm activities against pseudomonas aeruginosa

The emergence of antibiotic resistant bacteria coupled with the shortage of efficient antibacterials is one of the most serious unresolved problems for modern medicine. In this study, the nano-hybridization of the clinically relevant antibiotic, gentamicin, with the bacterial pro-pathological cell-to-cell communication-quenching enzyme, acylase, is innovatively employed to increase its antimicrobial efficiency against Pseudomonas aeruginosa planktonic cells and biofilms. The sonochemically generated hybrid gentamicin/acylase nano-spheres (GeN_AC NSs) showed a 16-fold improved bactericidal activity when compared with the antibiotic in bulk form, due to the enhanced physical interaction and disruption of the P. aeruginosa cell membrane. The nano-hybrids attenuated 97 ± 1.8% of the quorum sensing-regulated virulence factors’ production and inhibited the bacterium biofilm formation in an eight-fold lower concentration than the stand-alone gentamicin NSs. The P. aeruginosa sensitivity to GeN_AC NSs was also confirmed in a real time assay monitoring the bacterial cells elimination, using a quartz crystal microbalance with dissipation. In protein-enriched conditions mimicking the in vivo application, these hybrid nano-antibacterials maintained their antibacterial and antibiofilm effectiveness at concentrations innocuous to human cells. Therefore, the novel GeN_AC NSs with complementary modes of action show potential for the treatment of P. aeruginosa biofilm infections at a reduced antibiotic dosage.Peer ReviewedPostprint (published version

Antibacterial, antibiofilm, and antiviral farnesol-containing nanoparticles prevent Staphylococcus aureus from drug resistance development

Multidrug antimicrobial resistance is a constantly growing health care issue associated with increased mortality and morbidity, and huge financial burden. Bacteria frequently form biofilm communities responsible for numerous persistent infections resistant to conventional antibiotics. Herein, novel nanoparticles (NPs) loaded with the natural bactericide farnesol (FSL NPs) are generated using high-intensity ultrasound. The nanoformulation of farnesol improved its antibacterial properties and demonstrated complete eradication of Staphylococcus aureus within less than 3 h, without inducing resistance development, and was able to 100% inhibit the establishment of a drug-resistant S. aureus biofilm. These antibiotic-free nano-antimicrobials also reduced the mature biofilm at a very low concentration of the active agent. In addition to the outstanding antibacterial properties, the engineered nano-entities demonstrated strong antiviral properties and inhibited the spike proteins of SARS-CoV-2 by up to 83%. The novel FSL NPs did not cause skin tissue irritation and did not induce the secretion of anti-inflammatory cytokines in a 3D skin tissue model. These results support the potential of these bio-based nano-actives to replace the existing antibiotics and they may be used for the development of topical pharmaceutic products for controlling microbial skin infections, without inducing resistance development.Peer ReviewedPostprint (published version

Inhibition of quorum-sensing: A new paradigm in controlling bacterial virulence and biofilm formation

Bacterial pathogens coordinate the expression of multiple virulence factors and formation of biofilms in cell density dependent manner, through a phenomenon named quorum sensing (QS). Protected in the biofilm community, bacterial cells resist the antibiotic treatment and host immune responses, ultimately resulting in difficult to treat infections. The high incidence of biofilm-related infections is a global concern related with increased morbidity and mortality in healthcare facilities, prolonged time of hospitalization and additional financial cost. This has led to the urgent need for innovative strategies to control bacterial diseases and drug resistance. In this review, we outline the disruption of QS pathways as a novel strategy for attenuation of bacterial virulence and prevention of resistant biofilms formation on medical devices and host tissues. Unlike the traditional antibiotics, inhibiting the QS signaling in bacteria will not kill the pathogen or affect its growth, but will block the targeted genes expression, making the cells less virulent and more vulnerable to host immune response and lower dosage of antimicrobials. We summarize the recent successes and failures in the development of novel anti-QS drugs as well as their application in controlling bacterial infections in healthcare facilities. The inhibitory targeting of the production of QS signals, their transduction and recognition by the other cells in the surrounding are discussed. Special focus is also given to the anti-QS nanomaterials with improved effectiveness and specificity towards the pathogens

Antibody-enabled antimicrobial nanocapsules for selective elimination of Staphylococcus aureus

Targeted bactericide nanosystems hold significant promise to improve the efficacy of existing antimicrobials for treatment of severe bacterial infections, minimizing the side effects and lowering the risk of antibiotic resistance occurrence. In this work, we developed antibody functionalized nanocapsules (NCs) containing antibacterial essential oil (EO) for selective and effective eradication of Staphylococcus aureus. Antibacterial EO NCs were produced via self-assembling nanoencapsulation in the plant-derived protein zein. The obtained EO NCs were decorated with aminocellulose to provide more reactive surface groups for carboxyl-to-amine immobilization of a specific against S. aureus antibody. The antibody-enabled EO NCs (Ab@EO NCs) demonstrated 2-fold higher bactericidal efficacy against the targeted bacterium compared to the pristine EO NCs at the same concentrations. The improved antibacterial effect of the Ab@EO NCs towards S. aureus was also confirmed in a real time assay by monitoring bacterial cells elimination using a quartz crystal microbalance. Furthermore, the Ab@EO selectively decreased the load and changed the cell morphology of the targeted S. aureus in a mixed inoculum with non-targeted P. aeruginosa. Applying the nanoformulated actives to an in vitro co-culture model of the bacteria and skin fibroblasts resulted in suppression of S. aureus growth, while preserving the human cells viability. The novel antibody-enabled antibacterial NCs showed potential to improve the treatment efficacy of staphylococcal infections, minimally affecting the beneficial microbiome and human cells.Peer ReviewedPostprint (author's final draft

Layer-by-layer decorated nanoparticles with tunable antibacterial and antibiofilm properties against both gram-positive and gram-negative bacteria

acteria-mediated diseases are a global healthcare concern due to the development and spread of antibiotic resistant strains. Cationic compounds are considered membrane active biocidal agents having a great potential to control bacterial infections, while limiting the emergence of drug resistance. Herein, the versatile and simple Layer-by-Layer (LbL) technique was used to coat alternating multilayers of an antibacterial aminocellulose conjugate and the biocompatible hyaluronic acid on biocompatible polymer nanoparticles (NPs), taking advantage of the nano-size of these otherwise biologically inert templates. Stable polyelectrolyte-decorated particles with an average size of 50 nm and zeta potential of + 40.6 mV were developed after five LbL assembly cycles. The antibacterial activity of these NPs against the Gram-positive Staphylococcus aureus (S. aureus) and Gram-negative Escherichia coli (E. coli) increased significantly when the polycationic aminocellulose was in the outermost layer. The large number of amino groups available on the particles surface, together with the nano-size of the multilayer conjugates, improved their interaction with bacterial membrane phospholipids leading to membrane disruption, as confirmed by a Langmuir monolayer model, and the 10 logs reduction for both bacteria. The biopolymer decorated NPs were also able to inhibit the biofilm formation of S. aureus and E. coli by 94 and 40%, respectively, without affecting human cells viability. The use of LbL coated NPs appears as a promising antibiotic-free alternative for controlling bacterial infections using low amount of antimicrobial agent.Peer Reviewe

Sonochemically engineered nano-enabled zinc oxide/amylase coatings prevent the occurrence of catheter-associated urinary tract infections

Catheter-associated urinary tract infections (CAUTIs), caused by biofilms, are the most frequent health-care associated infections. Novel antibiofilm coatings are needed to increase the urinary catheters' life-span, decrease the prevalence of CAUTIs and reduce the development of antimicrobial resistance. Herein, antibacterial zinc oxide nanoparticles (ZnO NPs) were decorated with a biofilm matrix-degrading enzyme amylase (AM) and simultaneously deposited onto silicone urinary catheters in a one-step sonochemical process. The obtained nano-enabled coatings inhibited the biofilm formation of Escherichia coli and Staphylococcus aureus by 80% and 60%, respectively, for up to 7 days in vitro in a model of catheterized bladder with recirculation of artificial urine due to the complementary mode of antibacterial and antibiofilm action provided by the NPs and the enzyme. Over this period, the coatings did not induce toxicity to mammalian cell lines. In vivo, the nano-engineered ZnO@AM coated catheters demonstrated lower incidence of bacteriuria and prevent the early onset of CAUTIs in a rabbit model, compared to the animals treated with pristine silicone devices. The nano-functionalization of catheters with hybrid ZnO@AM coatings appears as a promising strategy for prevention and control of CAUTIs in the clinicPeer ReviewedPostprint (published version