The increased emergence of drug resistant bacteria is one of the most serious problems in the modern medicine, and although new drugs are constantly being sought, the pace of development is slow compared to the evolution and spread of multidrug resistant species. In this study, the efficacy of the commercially available antibiotics (e.g. vancomycin and gentamicin) was synergistically enhanced by the enzymatic disruption of bacterial quorum sensing (QS) and ultrasound assisted nanotransformation of the antibacterial agents. The generated hybrid nano-antibacterials were deposited on silicone material in a Layer-by-Layer fashion. These nanocoatings disrupted bacterial QS signaling in reporter Chromobacterium violaceum and attenuated the virulence of P. aeruginosa, as demonstrated by the decrease of violacein, pyocyanin and alkaline protease production. Moreover, the multilayers eradicated Pseudomonas aeruginosa planktonic cells and inhibited up to 80 % the bacterium biofilm growth, without affecting the viability of human fibroblasts. Our results demonstrated that the hybrid nano-antibacterials, with complimentary modes of action, might be valuable alternatives to control drug-resistant biofilm occurrence on medical devices at reduced antibiotic dosages.
Bacteria-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 versatility and simplicity of the Layer-by- Layer (LbL) technique was used to functionalize polymer nanoparticles with antibacterial aminocellulose conjugate in a multilayer fashion. Stable polyelectrolyte-decorated particles with an average size of 250 nm and zeta potential of ± 40 mV were developed after five LbL assembly cycles. The antibacterial activity of these particles against Gram- positive Staphylococcus aureus and Gram-negative Escherichia coli increased significantly when the polycationic aminocellulose was applied as an uppermost layer. The large number of amino groups available on the particles surface improved the interaction with bacterial membrane phospholipids leading to membrane disturbance as was confirmed by Langmuir monolayer. The biopolymer decorated NPs were also able to inhibit the drug resistant biofilm formation, without affecting the human cells viability and therefore are promising alternatives for controlling bacterial infections occurrence.
The healing of chronic wounds requires intensive medical intervention at huge healthcare costs. Dressing materials should consider the multifactorial nature of these wounds comprising deleterious proteolytic and oxidative enzymes and high bacterial load. In this work, multifunctional hydrogels for chronic wound application were produced by enzymatic cross- linking of thiolated chitosan and gallic acid. The hydrogels combine several beneficial to wound healing properties, controlling the matrix metalloproteinases (MMPs) and myeloperoxidase (MPO) activities, oxidative stress, and bacterial contamination. In vitro studies revealed above 90% antioxidant activity, and MPO and collagenase inhibition by up to 98 and 23%, respectively. Ex vivo studies with venous leg ulcer exudates confirmed the inhibitory capacity of the dressings against MPO and MMPs. Additionally, the hydrogels reduced the population of the most frequently encountered in nonhealing wounds bacterial strains. The stable at physiological conditions and resistant to lysozyme degradation hydrogels showed high biocompatibility with human skin fibroblasts
The increased emergence of antibiotic-resistant bacteria is a growing public health concern, and although new drugs are constantly being sought, the pace of development is slow compared with the evolution and spread of multidrug- resistant species. In this study, we developed a novel broad-spectrum antimicrobial agent by simply transforming vancomycin into nanoform using sonochemistry. Vancomycin is a glycopeptide antibiotic largely used for the treatment of infections caused by Gram-positive bacteria but inefficient against Gram-negative species. The nanospherization extended its effect toward Gram-negative Escherichia coli and Pseudomonas aeruginosa, making these bacteria up to 10 and 100 times more sensitive to the antibiotic, respectively. The spheres were able to disrupt the outer membranes of these bacteria, overcoming their intrinsic resistance toward glycopeptides. The penetration of nanospheres into a Langmuir monolayer of bacterial membrane phospholipids confirmed the interaction of the nanoantibiotic with the membrane of E. coli cells, affecting their physical integrity, as further visualized by scanning electron microscopy. Such mechanism of antibacterial action is unlikely to induce mutations in the evolutionary conserved bacterial membrane, therefore reducing the possibility of acquiring resistance. Our results indicated that the nanotransformation of vancomycin could overcome the inherent resistance of Gram-negative bacteria toward this antibiotic and disrupt mature biofilms at antibacterial-effective concentrations.
Bacterial infections caused by drug resistant strains are one of the world’s public health challenges and the development of alternative strategies is extensively being searched. Vancomycin is a glycopeptide antibiotic largely used for treatment of infections caused by Grampositive bacteria. However, it has little effect against Gramnegative bacteria due to its inability to penetrate their outer membrane, impermeable to such large molecules. The assemblies of molecules at nanometer dimensions confers unique properties, differing from those of the free molecules and the bulk materials with the same composition. The nanotransformation of the active agents themselves into nanosize has been applied in our group using the ultrasonic emulsification method to synthesize oilfilled nanospheres (NSs), in which the antimicrobial agent is located at the interface of the droplet. The nanotransformation does not alter the target of the drug or its chemical structure, while simply adding a support mechanism to its mode of action towards bacteria. This mode of action reduces the possibility of developing new resistant strains because bacterial membrane is highly evolutionarily conserved. The observed penetration of the NSs within a Langmuir monolayer composed by bacterial membrane phospholipids has confirmed that the vancomycin nanospheres were able to interact with the membrane and affect the physical integrity of Escherichia coli cells, which was further visualized by scanning electron microscopy. The ability of Vancomycin NSs to kill biofilm was visualised using fluorescence microscopy and antibacterial assays and quantified using CBDMBEC™ technique. The nanospherization of vancomycin boosted its capacity to inhibit the growth of Gramnegative Escherichia coli and Pseudomonas aeruginosa , making these bacteria up to 10 and 100 times, respectively, more sensitive to the antibiotic. Moreover, the antibiotic nanospheres eradicated biofilms of Gramnegative bacteria in the antibacterialeffective concentration
Bacteria that colonize and form biofilms on living tissues and medical devices are a global healthcare concern. They cause life threatening infections and are associated with increased mortality and morbidity in the hospitals. Although antibiotics have been successfully applied for treatment of bacterial diseases, the adaptive and genetic changes of the microorganisms within the biofilms make them inherently resistant to all known antibacterial agents. Therefore, novel antimicrobial strategies that do not exert selective pressure on bacterial population and minimize the risk of resistance occur- rence have been sought to prevent and treat biofilm related infections. A critical overview of the nu- merous groups and the rationale of advanced materials and surfaces with antibacterial and antibiofilm properties is the aim of this review. The development of antibiofilm coatings based on molecules in- terfering with bacterial cell-to-cell communication and biofilm integrity are discussed. Nano-scale transformation of obsolete antibiotics and surface functionalization with bacteriophages and natural antibacterials including enzymes, antimicrobial peptides, and polyphenols are also considered. Fi- nally, recent efforts to design new generation of integrated antibacterial materials are reported.
The increasing prevalence of bacterial strains with resistance to conventional antibiotics is a major global healthcare problem. Strategies based on the cellular response of bacteria to antimicrobial agents have been followed to reduce the adaptive pressure on these bacteria. One of these strategies consists in damaging the bacterial membrane, which leads to leakage of intracellular constituents into the extracellular environment and changes in intracellular pH. Langmuir technique has been used to evaluate the interaction of several antibacterial agents with cell membrane models at the molecular level.
In this work Vancomycin (VAC) a widely used antibiotic with acquired bacteria resistance – was transformed sonochemically into nanoparticles (NPsVAC) which antibacterial efficiency was further evaluated on biomimetic bacterial membranes. The results indicate a higher membraneVAC interaction when antibiotic is in nanoform rather than in solution.
On the other hand, nanoparticles (NPs) during circulation in biological fluids are affected by the protein corona phenomenon that consists in the adsorption of biomolecules on the NPs surface altering thereby their targeting and efficiency. Thus, the bacterial membraneNPsVAC interactions were also studied in corona effect conditions, in order to simulate the real application scenario.
'Early detection of an incipient wound infection is a challenge for the attending physician , since its early diagnosis allows the timely initiation of treatment, thus reducing the severity of the disease . Currently, however, wound infection is not diagnosed until becoming already evident. As a consequence, the treatment of the patient is further complicated and more likely to have a negative outcome4. Often wounds are treated with antibiotics before even the infection appears, leading to overdoses and development of bacterial resistance to antibiotics.
Considering that optimal efficiency is reached when a material serves multiple functions without compromise, consortium partners have discovered the means to convert wound dressings into a diagnostic tool capable to inform both patient and therapist about the wound status, thus directing towards the following therapeutic step. The proposed functional materials include a real time diagnostic reaction that positively influences the wound healing due to the timely intervention to treat infection or proteolytic stasis in the wound
The novel InFact technology will be translated into a low-cost, real-time diagnostic tool as a constituent part of a wound dressing material, i.e. the 'triple-P' materials concept:
- Protective - by a decoy substrate for destructive proteases
- Predictive – providing a cumulative wound status signal to predict the infection transition
- Proactive - changing the dressing according to a signal, rather than on a schedule base, will provide therapeutic response in time, and not too late.
More specifically, the functional materials (e.g. absorbent fibres and hydrocolloid pads) will incorporate immobilized substrates for three enzymes: myeloperoxidase, lysozyme and elastase. Upon infection, these enzymatic activities are highly elevated in wound fluids, and can be detected by the color change of the functional materials, visible via a window in the dressing.'