The negative consequences of biofilms are widely reported. A defining feature of biofilms is the extracellular matrix, a complex mixture of biomacromolecules, termed EPS, which contributes to reduced ...antimicrobial susceptibility. EPS targeting is a promising, but underexploited, approach to biofilm control allowing disruption of the matrix and thereby increasing the susceptibility to antimicrobials. Nanoparticles (NPs) can play a very important role as ’carriers’ of EPS matrix disruptors, and several approaches have recently been proposed. In this review, we discuss the application of nanoparticles as antibiofilm technologies with a special emphasis on the role of the EPS matrix in the physicochemical regulation of the nanoparticle–biofilm interaction. We highlight the use of nanoparticles as a platform for a new generation of antibiofilm approaches.
Self-adhering bacterial communities embedded in a matrix of hydrated macromolecules, known as biofilms, are prevalent and widespread. The matrix offers protection to the bacteria, reducing the cell susceptibility to antimicrobials.Functional nanoparticles are a promising technology to control or eradicate biofilms, providing the ability to enhance antimicrobial transport to the cell vicinity or alternatively to carry matrix dispersion agents.Critical to the development of novel strategies to control biofilm infections is an in-depth knowledge of the biofilm matrix which is still poorly understood due to its spatial and chemical variability and complexityA fundamental understanding of NP–EPS interactions has the potential to improve our ability to design more effective antibiofilm strategies.
The ubiquitous nature of bacterial biofilms combined with the enhanced resistance towards antimicrobials has led to the development of an increasing number of strategies for biofilm eradication. Such ...strategies must take into account the existence of extracellular polymeric substances, which obstruct the diffusion of antibiofilm agents and assists in the maintenance of a well-defended microbial community. Within this context, nanoparticles have been studied for their drug delivery efficacy and easily customised surface. Nevertheless, there usually is a requirement for nanocarriers to be used in association with an antimicrobial agent; the intrinsically antimicrobial nanoparticles are most often made of metals or metal oxides, which is not ideal from ecological and biomedical perspectives. Based on this, the use of polymeric micelles as nanocarriers is appealing as they can be easily prepared using biodegradable organic materials.
In the present work, micelles comprised of poly(lactic-co-glycolic acid) and dextran are prepared and then functionalised with curcumin. The effect of the functionalisation in the micelle's physical properties was elucidated, and the antibacterial and antibiofilm activities were assessed for the prepared polymeric nanoparticles against Pseudomonas spp. cells and biofilms. It was found that the nanoparticles have good penetration into the biofilms, which resulted in enhanced antibacterial activity of the conjugated micelles when compared to free curcumin. Furthermore, the curcumin-functionalised micelles were efficient at disrupting mature biofilms and demonstrated antibacterial activity towards biofilm-embedded cells.
Curcumin-functionalised poly(lactic-co-glycolic acid)-dextran micelles are novel nanostructures with an intrinsic antibacterial activity tested against two Pseudomonas spp. strains that have the potential to be further exploited to deliver a secondary bioactive molecule within its core.
Multidrug-resistant bacteria (MDRB) are extremely dangerous and bring a serious threat to health care systems as they can survive an attack from almost any drug. The bacteria's adaptive way of living ...with the use of antimicrobials and antibiotics caused them to modify and prevail in hostile conditions by creating resistance to known antibiotics or their combinations. The emergence of nanomaterials as new antimicrobials introduces a new paradigm for antibiotic use in various fields. For example, silver nanoparticles (AgNPs) are the oldest nanomaterial used for bactericide and bacteriostatic purposes. However, for just a few decades these have been produced in a biogenic or bio-based fashion. This review brings the latest reports on biogenic AgNPs in the combat against MDRB. Some antimicrobial mechanisms and possible silver resistance traits acquired by bacteria are also presented. Hopefully, novel AgNPs-containing products might be designed against MDR bacterial infections.
Biofilms are microbial communities embedded in an extracellular polymeric matrix and display an enhanced tolerance to the action of antimicrobials. The emergence of novel functionalised nanoparticles ...is considered a promising avenue for the development of biofilm-specific antimicrobial technologies. However, there is a gap in the understanding of interactions between nanoparticles and the biofilm matrix. Particularly, questions are raised on how nanoparticle charge and surface groups play a role in aggregation when in contact with biofilm components. Herein we present the synthesis of four types of silica nanoparticles and undertake an analysis of their interactions with Pseudomonas fluorescens biofilm matrix. The effect of the biofilm matrix components on the charge and aggregation of the nanoparticles was assessed. Additionally, the study focused on the role of matrix proteins, with the in-depth characterisation of the protein corona of each nanoparticle by Liquid Chromatography with Tandem Mass Spectrometry experiments. The protein corona composition is dependent on the nanoparticle type; non-functionalised nanoparticles show less protein selectivity, whereas carboxylate-functionalised nanoparticles prefer proteins with a higher isoelectric point. These outcomes provide insights into the field of biofilm-nanoparticle interactions that can be valuable for the design of new nano-based targeting systems in future anti-biofilm applications.
Environmental concerns, along with oil shortages, have increased industrial interest in biomass conversion to produce biofuels and other valuable chemicals. A green option in biomass processing is ...the use of enzymes, such as cellulases, hemicellulases, and ligninolytic (laccase and peroxidases), which have outstanding specificity toward their substrates and can be reused if immobilized onto magnetic nanocarriers. Numerous studies report the biocatalysts’ performance after covalent binding or adsorption on differently functionalized magnetic nanoparticles (MNPs). Functionalization strategies of MNPs include silica-based surfaces obtained through a sol–gel process, graphene oxide-based nanocomposites, polymer-coated surfaces, grafting polymer brushes, and others, which have been emphasized in this review of the immobilization and co-immobilization of enzymes used for biomass conversion. Careful analysis of the parameters affecting the performance of enzyme immobilization for new hybrid matrices has enabled us to achieve wider tolerance to thermal or chemical stress by these biosystems during saccharification. Additionally, it has enabled the application of immobilized laccase to remove toxic organic compounds from lignin, among other recent advances addressed here related to the use of reusable magnetic carriers for bioderived chemical manufacturing.
Bacteria use quorum sensing (QS) to coordinate group behavior in response to cell density, and some bacterial viruses (phages) also respond to QS. In Staphylococcus aureus, the agr-encoded QS system ...relies on accumulation of auto-inducing cyclic peptides (AIPs). Other staphylococci also produce AIPs of which many inhibit S. aureus agr. We show that agr induction reduces expression of tarM, encoding a glycosyltransferase responsible for α-N-acetylglucosamine modification of the major S. aureus phage receptor, the wall teichoic acids. This allows lytic phage Stab20 and related phages to infect and kill S. aureus. However, in mixed communities, producers of inhibitory AIPs like S. haemolyticus, S. caprae, and S. pseudintermedius inhibit S. aureus agr, thereby impeding phage infection. Our results demonstrate that cross-species interactions dramatically impact phage susceptibility. These interactions likely influence microbial ecology and impact the efficacy of phages in medical and biotechnological applications such as phage therapy.
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•Lytic phage Stab20 infects S. aureus when agr quorum sensing is induced•Quorum-sensing induction reduces tarM-encoded α-GlcNAc glycosylation of WTA•α-GlcNAc glycosylated WTA hinders infection of Stab20 and related phages•Non-aureus staphylococci protect S. aureus from Stab20 killing by agr interference
Yang et al. show that α-GlcNAc glycosylation of wall teichoic acids is reduced by agr quorum-sensing induction in S. aureus. This reduction allows infection by the lytic phage Stab20. In mixed communities with non-aureus staphylococci producing inhibitory quorum-sensing auto-inducing cyclic peptides, agr interference protects S. aureus from infection.
Diabetes is a chronic metabolic disease which leads to high glucose levels in the blood, with severe consequences for human health. Due to the worldwide appeal for the reduction in calorie intake, ...this study presents the development of a nanomaterial able to capture sucrose selectively, thus providing a tool to remove naturally occurring sucrose from food, such as fruit juices, producing low-calorie juices for consumption. Magnetite nanoparticles (Fe
3
O
4
NPs) coated with an inert material (SiO
2
) and functionalised with the enzyme invertase were designed to remove sucrose from solutions. Fe
3
O
4
NPs were synthesised using the co-precipitation method, whereas the coating with a silica shell was done by the Stöber method. Its physicochemical characteristics were determined, with excellent stability over time. On the other hand, the invertase enzyme was extracted from dry Baker's yeast, purified and immobilised on the surface of the silica-coated Fe
3
O
4
NPs. pH-triggered sucrose capture occurred at pH 3.0 once invertase with protonated catalytic residues was able just to bind with sucrose in a highly selective way. After a short, 1 min interaction, approximately 13.5 mmol L
−1
of sucrose was captured per gram of nanomaterial and removed with the use of an external permanent magnet. The complex sucrose/nanomaterial was washed, and the released sucrose was put into buffered solution (pH = 4.8), where it underwent hydrolysis to yield inverted sugar. On the other side, sucrose-free nanomaterial was reused with no loss of enzymatic capability to capture sucrose at pH = 3.0 and maintained the invertase activity at pH 4.8 in ten consecutive rounds of re-use. As sucrose was recovered in the form of inverted sugar, not just low sugar beverage could be obtained, but also a high valued market product. Thus, the developed technology allows for the commercialisation of low-calorie food, offering healthier options to consumers and helping to fight diabetes and obesity.
The designed reusable nanomaterial was tailored for controlled sucrose removal from solutions and can benefit human health and low-calorie intake.
Biofilms are communities of microorganisms enclosed in a self-generated matrix of extracellular polymeric substances. While biofilm recalcitrance and persistence are caused by several factors, a ...reduction in antimicrobial susceptibility has been closely associated with the generation of pH gradients within the biofilm structure. Cells embedded within the biofilm create a localized acidic microenvironment, which is unaffected by the external pH. Therefore, pH monitoring is a promising approach for understanding the complexities of a three-dimensional heterogeneous biofilm. A fluorescent pH nanosensor was designed through the synthesis of mesoporous silica nanoparticles (47 ± 5 nm diameter) conjugated to a pH-sensitive dye (fluorescein) and a pH-insensitive dye (rhodamine B) as an internal standard (dye-MSNs). The fluorescence intensity of fluorescein (
) reduced significantly as the pH was decreased from 8.5 to 3.5. In contrast, the fluorescence intensity of rhodamine B (
) remained constant at any pH. The ratio of
/
produced a sigmoidal curve with respect to the pH, in a working pH range between 4.5 and 7.5. Dye-MSNs enabled the measurement of pH gradients within
WCS 365 biofilm microcolonies. The biofilms showed spatially distinct low-pH regions that were enclosed into large clusters corresponding to high-cell-density areas. Also present were small low-pH areas that spread indistinctly throughout the microcolony caused by the mass transfer effect. The lowest detected pH within the inner core of the microcolonies was 5.1, gradually increasing to a neutral pH toward the exterior of the microcolonies. The dye-MSNs were able to fully penetrate the biofilm matrix and allowed a quantitative ratiometric analysis of pH gradients and distribution throughout the biofilm, which was independent of the nanoparticle concentration.
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•A new method for comparing nanoparticle capture efficiencies of biofilms is reported.•Nanoparticle size and surface functionalisation play a significant role in the capture.•P. ...putida shows superior entrapment efficiency for of all nanoparticles tested.
The commercial use of nanoparticles has increased in recent years due to their unique characteristics, including high surface area, modifiable shape and surface charge and size-dependent properties. Consequently, a greater number of nanomaterials are now being released into the environment and inevitably interact with the natural ecosystem. Bacterial biofilms have the potential to capture and retain nanoparticles, however the factors determining the specific nanoparticle entrapment efficiencies of biofilms are not yet fully understood. Based on fluorescent intensity measurements we developed a simple and straightforward method that allowed the entrapment of different silica nanoparticles by two Pseudomonas strains to be quantified. It was determined that, regardless of nanoparticle size or surface functionalisation, Pseudomonas putida biofilms showed enhanced entrapment efficiencies compared to Pseudomonas fluorescens biofilms. It was also noted that both biofilms showed a higher entrapment capacity towards positively charged NPs. The method developed has the potential to be utilized for high throughput biofilm screening studies in order to develop a new understating of the relationship between nanoparticle characteristics and its uptake by bacterial biofilms.
biofilms pose a unique challenge in healthcare due to their tolerance to a wide range of antimicrobial agents. The high cost and lengthy timeline to develop novel therapeutic agents have pushed ...researchers to investigate the use of nanomaterials to deliver antibiofilm agents and target biofilm infections more efficiently. Previous studies have concentrated on improving the efficacy of antibiotics by deploying nanoparticles as nanocarriers. However, the dispersal of the extracellular polymeric substance (EPS) matrix in biofilm-associated infections is also critical to the development of novel nanoparticle-based therapies.
This study evaluated the efficacy of enzyme-functionalized mesoporous silica nanoparticles (MSNs) against methicillin-resistant
(MRSA) and methicillin-sensitive
(MSSA) biofilms. MSNs were functionalized with the enzyme lysostaphin, which causes cell lysis of
bacteria. This was combined with two other enzyme functionalized MSNs, serrapeptase and DNase I which will degrade protein and eDNA in the EPS matrix, to enhance eradication of the biofilm. Cell viability after treatment with enzyme-functionalized MSNs was assessed using a MTT assay and CLSM, while crystal violet staining was used to assess EPS removal.
The efficacy of all three enzymes against
cells and biofilms was significantly improved when they were immobilized onto MSNs. Treatment efficacy was further enhanced when the three enzymes were used in combination against both MRSA and MSSA. Regardless of biofilm maturity (24 or 48 h), near-complete dispersal and killing of MRSA biofilms were observed after treatment with the enzyme-functionalized MSNs. Disruption of mature MSSA biofilms with a polysaccharide EPS was less efficient, but cell viability was significantly reduced.
The combination of these three enzymes and their functionalization onto nanoparticles might extend the therapeutic options for the treatment of
infections, particularly those with a biofilm component.
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