Now showing 1 - 7 of 7
  • Publication
    Production of drug metabolites by immobilised Cunninghamella elegans: from screening to scale-up
    Cunninghamella elegans is a fungus that has been used extensively as a microbial model of mammalian drug metabolism, whilst its potential as a biocatalyst for the preparative production of human drug metabolites has been often proposed, little effort has been made to enable this. Here, we describe a workflow for the application of C. elegans for the production of drug metabolites, starting from well-plate screening assays leading to the preparative production of drug metabolites using fungus immobilised either in alginate or as a biofilm. Using 12- and 96-well plates, the simultaneous screening of several drug biotransformations was achieved. To scale up the biotransformation, both modes of immobilisation enabled semi-continuous production of hydroxylated drug metabolites through repeated addition of drug and rejuvenation of the fungus. It was possible to improve the productivity in the biofilm culture for the production of 4′-hydroxydiclofenac from 1 mg/l h to over 4 mg/l h by reducing the incubation time for biotransformation and the number of rejuvenation steps.
      495Scopus© Citations 24
  • Publication
    Nanoparticle–Biofilm Interactions: The Role of the EPS Matrix
    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.
      110Scopus© Citations 317
  • Publication
    Enhancing curcumin's solubility and antibiofilm activity via silica surface modification
    Bacterial biofilms are microbial communities in which bacterial cells in sessile state are mechanically andchemically protected against foreign agents, thus enhancing antibiotic resistance. The delivery of activecompounds to the inside of biofilms is often hindered due to the existence of the biofilm extracellularpolymeric substances (EPS) and to the poor solubility of drugs and antibiotics. A possible strategy toovercome the EPS barrier is the incorporation of antimicrobial agents into a nanocarrier, able topenetrate the matrix and deliver the active substance to the cells. Here, we report the synthesis ofantimicrobial curcumin-conjugated silica nanoparticles (curc-NPs) as a possibility for dealing with theseissues. Curcumin is a known antimicrobial agent and to overcome its low solubility in water it wasgrafted onto the surface of silica nanoparticles, the latter functioning as nanocarrier for curcumin intothe biofilm. Curc-NPs were able to impede the formation of modelP. putidabiofilms up to 50% anddisrupt mature biofilms up to 54% at 2.5 mg mL 1. Cell viability of sessile cells in both cases was alsoconsiderably affected, which is not observed for curcumin delivered as a free compound at the sameconcentration. Furthermore, proteomics of extracted EPS matrix of biofilms grown in the presence offree curcumin and curc-NPs revealed differences in the expression of key proteins related to celldetoxification and energy production. Therefore, curc-NPs are presented here as an alternative forcurcumin delivery that can be exploited not only to other bacterial strains but also to further biologicalapplications.
      294Scopus© Citations 24
  • Publication
    Interaction between Engineered Pluronic Silica Nanoparticles and Bacterial Biofilms: Elucidating the Role of Nanoparticle Surface Chemistry and EPS Matrix
    Nanoparticles (NPs) are considered a promising tool in the context of biofilm control. Many studies have shown that different types of NPs can interfere with the bacterial metabolism and cellular membranes, thus making them potential antibacterial agents; however, fundamental understanding is still lacking on the exact mechanisms involved in these actions. The development of NP-based approaches for effective biofilm control also requires a thorough understanding of how the chosen nanoparticles will interact with the biofilm itself, and in particular with the biofilm self-produced extracellular polymeric matrix (EPS). This work aims to provide advances in the understanding of the interaction between engineered fluorescent pluronic silica (PluS) nanoparticles and bacterial biofilms, with a main focus on the role of the EPS matrix in the accumulation and diffusion of the particles in the biofilm. It is demonstrated that particle surface chemistry has a key role in the different lateral distribution and specific affinity to the biofilm matrix components. The results presented in this study contribute to our understanding of biofilm-NP interactions and promote the principle of the rational design of smart nanoparticles as an important tool for antibiofilm technology.
      116Scopus© Citations 7
  • Publication
    Surface functionalization-dependent localization and affinity of SiO2 nanoparticles within the biofilm EPS matrix
    The contribution of the biofilm extracellular polymeric substance (EPS) matrix to reduced antimicrobial sus-ceptibility in biofilms is widely recognised. As such, the direct targeting of the EPS matrix is a promising biofilmcontrol strategy that allows for the disruption of the matrix, thereby allowing a subsequent increase in suscep-tibility to antimicrobial agents. To this end, surface-functionalized nanoparticles (NPs) have received considerableattention. However, the fundamental understanding of the interactions occurring between engineered NPs andthe biofilm EPS matrix has not yet been fully elucidated. An insight into the underlying mechanisms involvedwhen a NP interacts with the EPS matrix will aid in the design of more efficient NPs for biofilm control. Here wedemonstrate the use of highly specificfluorescent probes in confocal laser scanning microscopy (CLSM) toillustrate the distribution of EPS macromolecules within the biofilm. Thereafter, a three-dimensional (3D)colocalization analysis was used to assess the affinity of differently functionalized silica NPs (SiNPs) and EPSmacromolecules fromPseudomonasfluorescensbiofilms. Results show that both the charge and surface functionalgroups of SiNPs dramatically affected the extent to which SiNPs interacted and localized with EPS macromole-cules, including proteins, polysaccharides and DNA. Hypotheses are also presented about the possible physico-chemical interactions which may be dominant in EPS matrix-NP interactions. This research not only develops aninnovative CLSM-based methodology for elucidating biofilm-nanoparticle interactions but also provides a plat-form on which to build more efficient NP systems for biofilm control.
      271Scopus© Citations 22
  • Publication
    Tailoring Nanoparticle-Biofilm Interactions to Increase the Efficacy of Antimicrobial Agents Against Staphylococcus aureus
    Background: Considering the timeline required for the development of novel antimicrobial drugs, increased attention should be given to repurposing old drugs and improving anti-microbial efficacy, particularly for chronic infections associated with biofilms. Methicillin-susceptible Staphylococcus aureus (MSSA) and methicillin-resistant S. aureus (MRSA) are common causes of biofilm-associated infections but produce different biofilm matrices.MSSA biofilm cells are typically embedded in an extracellular polysaccharide matrix, whereas MRSA biofilms comprise predominantly of surface proteins and extracellular DNA (eDNA). Nanoparticles (NPs) have the potential to enhance the delivery of antimicro-bial agents into biofilms. However, the mechanisms which influence the interactions between NPs and the biofilm matrix are not yet fully understood. Methods:To investigate the influence of NPs surface chemistry on vancomycin (VAN) encapsulation and NP entrapment in MRSA and MSSA biofilms, mesoporous silica nano-particles (MSNs) with different surface functionalization (bare-B, amine-D, carboxyl-C,aromatic-A) were synthesised using an adapted Stöber method. The antibacterial efficacy of VAN-loaded MSNs was assessed against MRSA and MSSA biofilms. Results: The two negatively charged MSNs (MSN-B and MSN-C) showed a higher VAN loading in comparison to the positively charged MSNs (MSN-D and MSN-A). Cellular binding with MSN suspensions (0.25 mg mL−1) correlated with the reduced viability of both MSSA andMRSA biofilm cells. This allowed the administration of low MSNs concentrations while maintaining a high local concentration of the antibiotic surrounding the bacterial cells. Conclusion: Our data suggest that by tailoring the surface functionalization of MSNs,enhanced bacterial cell targeting can be achieved, leading to a novel treatment strategy for biofilm infections.
      204Scopus© Citations 35
  • Publication
    Simultaneous removal of malachite green and hexavalent chromium by Cunninghamella elegans biofilm in a semi-continuous system
    The present study was conducted to evaluate the potential of the fungus Cunninghamella elegans for simultaneous decolourisation of a triphenylmethane dye malachite green (MG) and hexavalent chromium [Cr(VI)] in the same media. This fungus can degrade MG through its reduction into leucomalachite green and then demethylation followed by oxidative cleavage. Along with MG degradation, C. elegans biofilm could effectively and repeatedly remove Cr(VI) from the liquid cultures even in the presence of high concentrations (40 g L−1) of NaCl and various other metal ions. C. elegans biofilm was also found to adsorb different dyes (reactive black-5, acid orange 7, direct red 81 and brilliant blue G) concurrently with Cr(VI). Based on its potential for simultaneous removal of dyes and Cr(VI) as well as reusability, C. elegans biofilm is envisaged as an efficient bioresource to devise strategies for treatment of wastewaters loaded with multiple pollutants.
      50Scopus© Citations 37