Hyperthermia produced by magnetic nanoparticles as an alternative method to control a major foodborne pathogen

NanoSpain 2017Salmonella enterica is responsible for the majority of the reported foodborne outbreaks, and that is why it is considered one of the most important foodborne pathogens nowadays [1]. Like many others bacteria, S. enterica can survive disinfection and resist a wide variety of biocidal agents [2]. Nowadays, the synthesis of superparamagnetic nanoparticles (MNPs) and its application in magnetic hyperthermia (MH) is of great interest, with MH being recently reported as a viable alternative to traditional disinfection methods against bacteria [3]. However, fundamental studies comprising the MH effect on different populations of planktonic cells and biofilm cells are scarce. Therefore, this work aimed at evaluating the effect of MH on different populations of planktonic cells and biofilms of S. enterica. The work was performed using a S. enterica collection strain (NCTC 13349), which different planktonic cell populations (lag, exponential, and stacionary phase) were adjusted to a final concentration of 1 × 108 cells/ml, while biofilms were formed in silicone coupons. Samples containing both magnetite nanoparticles and S. enterica cells or biofilms have been subjected to an alternating magnetic field of chosen amplitude 100 Oe with frequency of 873 kHz until different temperatures were reached. In order to evaluate the bactericidal effect of MH, survival of planktonic and biofilm cells was determined by colony forming unit (CFU) enumeration. Based on the most relevant results, cell membrane integrity and the effects of MH on cells surface and biofilm structure were analysed through microscopy techniques. Results showed that the high structural-magnetic quality magnetite nanoparticles used were effective against all planktonic cell populations and biofilms under an oscillating magnetic field. In fact, MNPs-based hyperthermia was able to promote a significant cell viability reduction on all planktonic cell populations both bacterial lyfe styles. Nonetheless, planktonic cells were more tolerant to MH than biofilms, possibly due to diffusion limitations along these bacterial communities. Microscopy images of planktonic cells and biofilms showed that MH can affect cell membrane integrity as well as the biofilms structure. In conclusion, this work presents evidences of the bactericidal effect of MH produced by MNPs against S. enterica, both regarding planktonic populations and biofilms. This ability of MH to control a major foodborne pathogen constitutes a novel contribution to the finding of new useful applications of hyperthermia.info:eu-repo/semantics/publishedVersio

Pseudomonas aeruginosa PAO 1 in vitro timekill kinetics using single phages and phage formulationsmodulating death, adaptation, and resistance

Pseudomonas aeruginosa is responsible for nosocomial and chronic infections in healthcare settings. The major challenge in treating P. aeruginosa-related diseases is its remarkable capacity for antibiotic resistance development. Bacteriophage (phage) therapy is regarded as a possible alternative that has, for years, attracted attention for fighting multidrug-resistant infections. In this work, we characterized five phages showing different lytic spectrums towards clinical isolates. Two of these phages were isolated from the Russian Microgen Sextaphage formulation and belong to the Phikmvviruses, while three Pbunaviruses were isolated from sewage. Different phage formulations for the treatment of P. aeruginosa PAO1 resulted in diversified timekill outcomes. The best result was obtained with a formulation with all phages, prompting a lower frequency of resistant variants and considerable alterations in cell motility, resulting in a loss of 73.7% in swimming motility and a 79% change in swarming motility. These alterations diminished the virulence of the phage-resisting phenotypes but promoted their growth since most became insensitive to a single or even all phages. However, not all combinations drove to enhanced cell killings due to the competition and loss of receptors. This study highlights that more caution is needed when developing cocktail formulations to maximize phage therapy efficacy. Selecting phages for formulations should consider the emergence of phage-resistant bacteria and whether the formulations are intended for short-term or extended antibacterial application.This study was supported by the Portuguese Foundation for Science and Technology (FCT) under the scope of the strategic funding of UID/BIO/04469/2020 unit. S.S. acknowledges funding by FCT through the individual scientific employment program contract (2020.03171.CEECIND).info:eu-repo/semantics/publishedVersio

Control of bacterial cells growths by magnetic hyperthermia

In this work, we report the effectiveness of magnetic hyperthermia as a potential disinfection method against food spoilage microorganisms. High structural-magnetic quality magnetite nanoparticles have been found to be effective against bacterial microorganisms in solution under an oscillating magnetic field. Samples containing both magnetite nanoparticles and Pseudomonas fluorescens cells in aqueous solution have been subjected to an alternating magnetic field of chosen amplitude 100 Oe with frequency of 873 kHz for different times, achieving different maximum temperatures ranging from 35°C to 55°C. The subsequent colony forming units count evidenced an important decreasing of the cell survival with temperature in comparison to a conventional direct heating, ending in the total eradication of the microorganisms in relatively short times (~8 min). This ability of magnetic hyperthermia to control bacteria cells constitutes a novel contribution to the finding of new useful applications of hyperthermia different from biomedicine.This work was supported in part by the European Community’s under the FP7-Cooperation Programme through the MAGISTER project “Magnetic Scaffolds for in vivo Tissue Engineering” Large Collaborative Project FP7 and from European Regional Development Fund (ERDF) under the Northern Regional Operational Programme ON.2-O Novo Norte- for the acquisition of the main equipment used in this research. D. R. also acknowledges the financial support of Portuguese Foundation for Science and Technology (FCT) through the grant SFRH/BPD/72632/2010

Effect of magnetic hyperthermia on the structure of biofilm and cellular viability of a food spoilage bacterium

This work evaluated the effect of magnetic hyperthermia (MH) on planktonic cells and biofilms of a major food spoilage bacterium Pseudomonas fluorescens and its performance compared to a conventional direct heating (DH) technique. The results showed that MH had a greater and faster bactericidal effect, promoting a significant reduction in cell viability (≥3 Log CFU) in planktonic and biofilm cells, and leading to a complete eradication of planktonic cells at 55 °C (after only ~8 min). Accordingly, when comparing the same final temperatures, MH was more harmful to the integrity of cell membranes than DH, as observed in confocal laser scanning microscope images. Additionally, scanning electron microscope images revealed that exposure to MH had promoted modifications of the bacterial cell surface as well as of the structure of the biofilm. These results present the possibility of using MH out of the biomedical field as a potential disinfection method in food-related environments.This work was partly supported by the European Regional Development Fund (ERDF) under the Northern Regional Operational Programme ON.2-O Novo Norte- for the acquisition of the main equipment used in this research. DR also acknowledges the financial support of the Portuguese Foundation for Science and Technology (FCT) through [grant SFRH/BPD/72632/2010]. The authors are very grateful to Dr Edith Ariza and Dr Claudia Mota for their technical assistance in the SEM studies

The influence of colloidal parameters on the specific power absorption of PAA-coated magnetite nanoparticles

The suitability of magnetic nanoparticles (MNPs) to act as heat nano-sources by application of an alternating magnetic field has recently been studied due to their promising applications in biomedicine. The understanding of the magnetic relaxation mechanism in biocompatible nanoparticle systems is crucial in order to optimize the magnetic properties and maximize the specific absorption rate (SAR). With this aim, the SAR of magnetic dispersions containing superparamagnetic magnetite nanoparticles bio-coated with polyacrylic acid of an average particle size of ≈10 nm has been evaluated separately by changing colloidal parameters such as the MNP concentration and the viscosity of the solvent. A remarkable decrease of the SAR values with increasing particle concentration and solvent viscosity was found. These behaviours have been discussed on the basis of the magnetic relaxation mechanisms involved

Organic-inorganic magnetic hybrids as multifunctional imaging and therapeutic agents

Magnetic iron oxide nanoparticles (SPIONs) have become key elements in the design of functional nanostructures able to play an active role in different biomedical applications, e. g. as heat generating nanosources in magnetic hyperthermia, as contrast agents in magnetic resonance imaging (MRI), in drug delivery and cell separation, and in biosensing. On the other hand, polymeric nanostructures have received great interest as suitable bioactive encapsulating agents and carriers due to their biocompatibility, low toxicity and ability to influence the bioactive delivery profile [1]. In a further step, hybrid organic-inorganic nanocomposites have been explored as a synergistic approach that combines the modified bioactive release induced by the polymer/lipid encapsulation and the intrinsic physico-chemical properties from the inorganic counterpart [2]. In particular, magnetic hybrid self-assemblies have been found to open new perspectives for biomedical and environmental applications [3, 4]. Please click Additional Files below to see the full abstract

A review of the advances and challenges in measuring the thermal conductivity of nanofluids

Fluids containing colloidal suspensions of nanometer-sized particles (nanofluids) have been extensively investigated in recent decades with promising results. Driven by the increase in the thermal conductivity of these new thermofluids, this topic has been growing in order to improve the thermal capacity of a series of applications in the thermal area. However, when it comes to measure nanofluids (NFs) thermal conductivity, experimental results need to be carefully analyzed. Hence, in this review work, the main traditional and new techniques used to measure thermal conductivity of the NFs are presented and analyzed. Moreover, the fundamental parameters that affect the measurements of the NFs’ thermal conductivity, such as, temperature, concentration, preparation of NFs, characteristics and thermophysical properties of nanoparticles, are also discussed. In this review, the experimental methods are compared with the theoretical methods and, also, a comparison between experimental methods are made. Finally, it is expected that this review will provide a guidance to researchers interested in implementing and developing the most appropriate experimental protocol, with the aim of increasing the level of reliability of the equipment used to measure the NFs thermal conductivity.This work has been funded by Portuguese national funds of FCT/MCTES (PIDDAC) through the base funding from the following research units: UIDB/00532/2020, UIDB/04077/2020, UIDP/04077/2020 and UIDP/04436/2020. The authors are also grateful for the funding of FCT through the projects NORTE-01-0145-FEDER-030171, PTDC/EME-TED/7801/2020, POCI-01-0145- FEDER-016861, POCI-01-0145-FEDER-028159, funded by COMPETE2020, NORTE2020, PORTUGAL2020, and FEDER

Preliminary evaluation of zeolite-based platforms as potential dual drug delivery systems against microbial infections in the tumor microenvironment

Several zeolite-based delivery systems (ZDS) built with faujasite structure were prepared containing silver (Ag+) and 5-Fluorouracil (5-FU) as antimicrobial and antineoplastic agents, respectively. The idea behind this drug combination is an answer to the increasing evidence of colonization of tumor microenvironments by pathogenic microorganisms and their active role in tumor growth. Two ZDS with a fixed load of 5-FU and different silver loads, Ag7(5-FU).info:eu-repo/semantics/publishedVersio

Haemocompatibility of iron oxide nanoparticles synthesized for theranostic applications: a high-sensitivity microfluidic tool

The poor heating efficiency of the most reported magnetic nanoparticles (MNPs), allied to the lack of comprehensive biocompatibility and haemodynamic studies, hampers the spread of multifunctional nanoparticles as the next generation of therapeutic bio-agents in medicine. The present work reports the synthesis and characterization, with special focus on biological/toxicological compatibility, of superparamagnetic nanoparticles with diameter around 18 nm, suitable for theranostic applications (i.e. simultaneous diagnosis and therapy of cancer). Envisioning more insights into the complex nanoparticle-red blood cells (RBCs) membrane interaction, the deformability of the human RBCs in contact with magnetic nanoparticles (MNPs) was assessed for the first time with a microfluidic extensional approach, and used as an indicator of haematological disorders in comparison with a conventional haematological test, i.e. the haemolysis analysis. Microfluidic results highlight the potential of this microfluidic tool over traditional haemolysis analysis, by detecting small increments in the rigidity of the blood cells, when traditional haemotoxicology analysis showed no significant alteration (haemolysis rates lower than 2 %). The detected rigidity has been predicted to be due to the wrapping of small MNPs by the bilayer membrane of the RBCs, which is directly related to MNPs size, shape and composition. The proposed microfluidic tool adds a new dimension into the field of nanomedicine, allowing to be applied as a highsensitivity technique capable of bringing a better understanding of the biological impact of nanoparticles developed for clinical applications.This work was financially supported by: Project POCI-01-0145-FEDER-006984 – Associate Laboratory J Nanopart Res (2016) 18:194 Page 15 of 17 194 123 LSRE-LCM funded by FEDER funds through COMPETE2020 - Programa Operacional Competitividade e Internacionalizac¸a˜o (POCI) – and by national funds through FCT - Fundac¸a˜o para a Cieˆncia e a Tecnologia. R.O.R. acknowledges the Ph.D. scholarship SFRH/BD/97658/2013 Granted by FCT. A.M.T.S acknowledges the FCT Investigator 2013 Programme (IF/01501/ 2013), with financing from the European Social Fund and the Human Potential Operational Programme. M.B. would like to thank ERDF (European Regional Development Fund) under grant PO Norte CCDR-N/ON.2 Programme. J.G. also thanks the European Union’s Seventh Framework Programme for research, technological development and demonstration under grant agreement no. 600375.info:eu-repo/semantics/publishedVersio