Zinc oxide nanoparticles as contrast-enhancing agents for microwave imaging

Nanomaterials as electromagnetic sensors for tumour detection

AIM

Microwave (MW) imaging/sensing is a potential clinical diagnostic technique which exploits differences in the dielectric properties of tissues at MW frequencies. Notably, breast cancer detection has been identified as a key application for this modality; however, inherent contrast in tissue dielectric properties may not always be sufficient to allow imaging/sensing. Nanoparticles could provide the necessary enhancement, due to their effect on the dielectric properties of the target tissue and their ability to accumulate in tumours. This study aims to prepare novel zinc ferrites ZnFe2O4 nanoparticles and investigate their potential as contrast agents for MW imaging/sensing.

METHOD

Zinc ferrite nanoparticles were synthesized by thermal decomopositon and phase transferred using a co-polymer to improve biocompatibility. Dielectric properties were evaluated using the co-axial probe technique, progressing to ex vivo and in vivo studies in a triple-negative breast cancer xenograft mouse model.

RESULTS

Tumours regions injected subcutaneously with nanoparticles in vivo showed an increased dielectric constant of up to 49% compared with approximately 3% ex vivo. Significant increases in conductivity were also observed indicating potential application of the particles as MW hyperthermia sensitizers.

CONCLUSIONS

Crucially, this study presents the first in vivo evaluation of nanoparticles as contrast agents for MW imaging/sensing. Observed increases in the dielectric properties highlight their potential to improve tumour detection using MW technologies.

Oxidative stress modulating nanomaterials and their biochemical roles in nanomedicine

Many pathological conditions are predominantly associated with oxidative stress, arising from reactive oxygen species (ROS); therefore, the modulation of redox activities has been a key strategy to restore normal tissue functions. Current approaches involve establishing a favorable cellular redox environment through the administration of therapeutic drugs and redox-active nanomaterials (RANs). In particular, RANs not only provide a stable and reliable means of therapeutic delivery but also possess the capacity to finely tune various interconnected components, including radicals, enzymes, proteins, transcription factors, and metabolites. Here, we discuss the roles that engineered RANs play in a spectrum of pathological conditions, such as cancer, neurodegenerative diseases, infections, and inflammation. We visualize the dual functions of RANs as both generator and scavenger of ROS, emphasizing their profound impact on diverse cellular functions. The focus of this review is solely on inorganic redox-active nanomaterials (inorganic RANs). Additionally, we deliberate on the challenges associated with current RANs-based approaches and propose potential research directions for their future clinical translation.

Ampicillin-resistant bacterial pathogens targeted chitosan nano-drug delivery system (CS-AMP-P-ZnO) for combinational antibacterial treatment

Drug-resistant microorganisms are defeated using combinational drug delivery systems based on biopolymer chitosan (CS) and metal nanoparticles. Hence, PEGylated zinc oxide nanoparticles (P-ZnO NPs) decorated chitosan-based nanoparticles (CS NPs) were prepared to deliver ampicillin (AMP) for improved antibacterial activity. In comparison to ZnO NPs, P-ZnO NPs exhibit less aggregation and more stable rod morphologies in TEM. The size of the P-ZnO NPs decreased and was engulfed by the spherical CS-AMP NPs. The zeta potential of the CS-AMP-P-ZnO NPs was determined to be -32.93 mV and the hydrodynamic size to be 210.2 nm. Further, DEE and DLE of CS-AMP (2.0:0.2 w/w) showed 79.60 ± 2.62 % and 15.14 ± 2.11 %, respectively. The cumulative AMP release was observed at >50 % at 48 h at pH 5.4 and 7.4. Additionally, when compared to AMP, CS-AMP-P-ZnO NPs had better antibacterial activity against E. coli, due to the alternation of cell membrane permeability by CS and ZnO NPs. Moreover, the hemolytic properties of ZnO NPs were attenuated because of PEGylation and CS. Furthermore, due to the biocompatible effect of CS, CS-AMP-P-ZnO NPs did not exhibit toxicity on cells and chick embryos. Hence, this study concludes that CS-AMP-P-ZnO NPs could be a promising antibacterial agent.

Nanomaterials responding to microwaves: an emerging field for imaging and therapy

In recent years, new microwave-based imaging, sensing and hyperthermia applications have emerged in the field of diagnostics and therapy. For diagnosis, this technology involves the application of low power microwaves, utilising contrast between the relative permittivity of tissues to identify pathologies. This contrast can be further enhanced through the implementation of nanomaterials. For therapy, this technology can be applied in tissues either through hyperthermia, which can help anti-cancer drug tumour penetration or as ablation to destroy malignant tissues. Nanomaterials can absorb electromagnetic radiation and can enhance the microwave hyperthermic effect. In this review we aim to introduce this area of renewed interest and provide insights into current developments in its technologies and companion nanoparticles, as well as presenting an overview of applications for diagnosis and therapy.

Assessing Changes in Dielectric Properties Due to Nanomaterials Using a Two-Port Microwave System

Detecting changes in the dielectric properties of tissues at microwave frequencies can offer simple and cost effective tools for cancer detection. These changes can be enhanced by the use of nanoparticles (NPs) that are characterised by both increased tumour uptake and high dielectric constant. This paper presents a two-port experimental setup to assess the impact of contrast enhancement on microwave signals. The study focuses on carbon nanotubes, as they have been previously shown to induce high microwave dielectric contrast. We investigate multiwall carbon nanotubes (MWNT) and their -OH functionalised version (MWNT-OH) dispersed in tissue phantoms as contrast enhancing NPs, as well as salt (NaCl) solutions as reference mixtures which can be easily dissolved inside water mixtures and thus induce dielectric contrast changes reliably. MWNT and MWNT-OH are characterised by atomic force microscopy, and their dielectric properties are measured when dispersed in 60% glycerol–water mixtures. Salt concentrations between 10 and 50 mg/mL in 60% glycerol mixtures are also studied as homogeneous samples known to affect the dielectric constant. Contrast enhancement is then evaluated using a simplified two-port microwave system to identify the impact on microwave signals with respect to dielectric contrast. Numerical simulations are also conducted to compare results with the experimental findings. Our results suggest that this approach can be used as a reliable method to screen and assess contrast enhancing materials with regards to a microwave system’s ability to detect their impact on a target.

Nanomaterial-mediated autophagy: coexisting hazard and health benefits in biomedicine

BACKGROUND

Widespread biomedical applications of nanomaterials (NMs) bring about increased human exposure risk due to their unique physicochemical properties. Autophagy, which is of great importance for regulating the physiological or pathological activities of the body, has been reported to play a key role in NM-driven biological effects both in vivo and in vitro. The coexisting hazard and health benefits of NM-mediated autophagy in biomedicine are nonnegligible and require our particular concerns.

MAIN BODY

We collected research on the toxic effects related to NM-mediated autophagy both in vivo and in vitro. Generally, NMs can be delivered into animal models through different administration routes, or internalized by cells through different uptake pathways, exerting varying degrees of damage in tissues, organs, cells, and organelles, eventually being deposited in or excreted from the body. In addition, other biological effects of NMs, such as oxidative stress, inflammation, necroptosis, pyroptosis, and ferroptosis, have been associated with autophagy and cooperate to regulate body activities. We therefore highlight that NM-mediated autophagy serves as a double-edged sword, which could be utilized in the treatment of certain diseases related to autophagy dysfunction, such as cancer, neurodegenerative disease, and cardiovascular disease. Challenges and suggestions for further investigations of NM-mediated autophagy are proposed with the purpose to improve their biosafety evaluation and facilitate their wide application. Databases such as PubMed and Web of Science were utilized to search for relevant literature, which included all published, Epub ahead of print, in-process, and non-indexed citations.

CONCLUSION

In this review, we focus on the dual effect of NM-mediated autophagy in the biomedical field. It has become a trend to use the benefits of NM-mediated autophagy to treat clinical diseases such as cancer and neurodegenerative diseases. Understanding the regulatory mechanism of NM-mediated autophagy in biomedicine is also helpful for reducing the toxic effects of NMs as much as possible.

Microwave imaging of breast cancer with factorization method: SPIONs as contrast agent

Female breast at macroscopic scale is a nonmagnetic medium, which eliminates the possibility of realizing microwave imaging of the breast cancer based on magnetic permeability variations. However, by administering functionalized, superparamagnetic iron oxide nanoparticles (SPIONs) as a contrast material to modulate magnetic permeability of cancer cells, a small variation on the scattered electric field from the breast is achievable under an external, polarizing magnetic field.

PURPOSE

We demonstrate an imaging technique that can locate cancerous tumors inside the breast due to electric field variations caused by SPION tracers under different magnetic field intensities. Furthermore, we assess the feasibility of SPION-enhanced microwave imaging for breast cancer with simulations performed on a multi-static imaging configuration.

METHODS

The imaging procedure is realized as the factorization method of qualitative inverse scattering theory, which is essentially a shape retrieval algorithm for inaccessible objects. The formulation is heuristically modified to accommodate the scattering parameters instead of the electric field to comply with the requirements of experimental microwave imaging systems.

RESULTS

With full-wave electromagnetic simulations performed on an anthropomorphically realistic breast phantom, which is excited with a cylindrical imaging prototype of 18 dipole antenna arranged as a single row, the technique is able to locate cancerous tumors for a experimentally achievable doses.

CONCLUSIONS

The technique generates nonanatomic microwave images, which map the cancerous tumors depending on the concentration of SPION tracers, to aid the diagnosis of the breast cancer.

Qualitative microwave imaging of breast cancer with contrast agents

A microwave imaging (MWI) methodology for early diagnosis of breast cancer is presented. Instead of generating a tomographic image of the breast, the proposed technique aims to reconstruct a map of malignant tumours inside the breast by adopting an extended form of factorization method. The implementation of factorization method requires (i) two multi-static scattered field measurements around the breast, which correspond to two different states of the breast, and (ii) the inhomogeneous Green's function associated to the breast. For this purpose, the paper proposes the use of contrast agents, which selectively increase the dielectric properties of the malign tissues. Two multi-static field measurements are collected before and after the administration of contrast agents. Later, the inhomogeneous Green's function of the breast is estimated by back-propagating the scattered field measurements, which are taken before the contrast agent usage. The feasibility and efficiency of the proposed technique are demonstrated with numerical examples that are performed on a slice of the realistic breast phantoms, which are derived from real three dimensional magnetic resonance imaging (3D-MRI) measurements.

Design and Experimental Validation of a Multiple-Frequency Microwave Tomography System Employing the DBIM-TwIST Algorithm

We present a first prototype of a wideband microwave tomography system with potential application to medical imaging. The system relies on a compact and robust printed monopole antenna which can operate in the 1.0–3.0 GHz range when fully immersed in commonly used coupling liquids, such as glycerine–water solutions. By simulating the proposed imaging setup in CST Microwave Studio, we study the signal transmission levels and array sensitivity for different target and coupling liquid media. We then present the experimental prototype design and data acquisition process, and show good agreement between experimentally measured data and results from the CST simulations. We assess imaging performance by applying our previously proposed two-dimensional (2-D) DBIM TwIST-algorithm to both simulated and experimental datasets, and demonstrate that the system can reconstruct simple cylindrical targets at multiple frequencies.