Begoña Espiña

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.

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.

Combining CXCR4-targeted and nontargeted nanoparticles for effective unassisted in vitro magnetic hyperthermia

The use of targeted nanoparticles for magnetic hyperthermia (MHT) increases MHT selectivity, but often at the expense of its effectiveness. Consequently, targeted MHT is typically used in combination with other treatment modalities. This work describes an implementation of a highly effective monotherapeutic in vitro MHT treatment based on two populations of magnetic particles. Cells were sequentially incubated with two populations of magnetic particles: nonfunctionalized superparamagnetic nanoparticles and anti-CXCR4-functionalized particles. After removing the excess of free particles, an alternating magnetic field (AMF) was applied to produce MHT. The induced cytotoxicity was assessed at different time-points after AMF application. Complete loss of cell viability was observed 72 h after MHT when the iron loading of the anti-CXCR4-functionalized particles was boosted by that of a nontargeted population. Additionally, induction of necrosis resulted in more efficient cell death than did induction of apoptosis. Achieving a uniquely high effectiveness in monotherapeutic MHT demonstrates the potential of this approach to achieve complete loss of viability of cancer cells while avoiding the side effects of dual-treatment strategies that use MHT only as a sensitizing therapy.

Detection of Sulfide Using Mercapto Tetrazine-Protected Fluorescent Gold Nanodots: Preparation of Paper-Based Testing Kit for On-Site Monitoring

This work demonstrates the development of a highly sensitive method to detect and quantify sulfide ions (S2-) in water samples. First, we synthesized 6-mercapto-s-triazolo(4,3-b)-s-tetrazine (MTT) by the reaction between formaldehyde and 4-amino-3-hydrazino-5-mercapto-1,2,4-triazole at room temperature. The synthetic MTT was used as a capping ligand for the synthesis of gold nanodots (AuNDs) via a one-pot green method at room temperature with only a 10 min reaction time. Transmission electron microscopy images exhibited that the MTT-AuNDs have an average particle size of 1.9 nm and an emission maximum at 672 nm upon excitation at 360 nm. The synthesized highly red emissive MTT-AuNDs are used as specific fluorescent probes for the detection of S2-. The fluorescence of MTT-AuNDs was significantly and dose-dependently quenched by the addition of S2-. The observed fluorescence quenching was ascribed to the formation of an Au2S complex, which was determined by Raman and mass spectroscopy. A good linearity was achieved for the increasing concentration of S2- from 870 nM to 16 μM, and the detection limit was found to be 2 nM (S/N = 3). The S2- detection system that is described in this study was validated and agreed well with the standard methylene blue method. Furthermore, the present sensor was examined for its use in quantifying S2- in real water samples obtained from lakes and rivers. In addition, the specificity was checked against the most likely ion interferences in real water. Moreover, a cost-effective and viable paper-based S2- sensor was fabricated for environmental monitoring based on the use of MTT-AuNDs. The developed system would be an environmentally friendly and easy-to-use detection device for S2- in water.

Detection of Foodborne Pathogens Using Nanoparticles. Advantages and Trends

Abstract Due to their critical impact on public health, the detection of foodborne pathogens in food and water is an important issue for both, the food industry and control authorities. Fast and reliable analytical methods are needed in order to ensure the health of consumers, to easily determine whether a food product has been subjected to cross-contamination, and, simultaneously, to identify how and when this cross-contamination occurred in order to establish the proper corrective actions. Recent developments in nanotechnology are greatly impacting the advancement of some analytical techniques, including foodborne pathogen detection. Herein, the advantages and the recent applications of nanoparticles (NPs) in foodborne pathogen detection are reviewed. The most frequently used NPs in this context (gold nanoparticles, quantum dots, and magnetic nanoparticles) are described, and their applicability for food analysis is emphasized. Finally, this chapter provides an overview of the use of micro and nanofluidics, combined with nanoparticles, for food pathogen analysis, and the integration of nanomaterial-based sensors for pathogen detection in food packaging systems.

Green synthesis of fluorescent carbon dots from spices for in vitro imaging and tumour cell growth inhibition

Carbon dots have demonstrated great potential as luminescent nanoparticles in bioapplications. Although such nanoparticles appear to exhibit low toxicity compared to other metal luminescent nanomaterials, today we know that the toxicity of carbon dots (C-dots) strongly depends on the protocol of fabrication. In this work, aqueous fluorescent C-dots have been synthesized from cinnamon, red chilli, turmeric and black pepper, by a one-pot green hydrothermal method. The synthesized C-dots were firstly characterized by means of UV–vis, fluorescence, Fourier transform infrared and Raman spectroscopy, dynamic light scattering and transmission electron microscopy. The optical performance showed an outstanding ability for imaging purposes, with quantum yields up to 43.6%. Thus, the cytotoxicity of the above mentioned spice-derived C-dots was evaluated in vitro in human glioblastoma cells (LN-229 cancer cell line) and in human kidney cells (HK-2 non-cancerous cell line). Bioimaging and viability studies were performed with different C-dot concentrations from 0.1 to 2 mg·mL−1, exhibiting a higher uptake of C-dots in the cancer cultures compared to the non-cancerous cells. Results showed that the spice-derived C-dots inhibited cell viability dose-dependently after a 24 h incubation period, displaying a higher toxicity in LN-229, than in HK-2 cells. As a control, C-dots synthesized from citric acid did not show any significant toxicity in either cancerous or non-cancerous cells, implying that the tumour cell growth inhibition properties observed in the spice-derived C-dots can be attributed to the starting material employed for their fabrication. These results evidence that functional groups in the surface of the C-dots might be responsible for the selective cytotoxicity, as suggested by the presence of piperine in the surface of black pepper C-dots analysed by ESI-QTOF-MS.