Hyperthermia using nanoparticles--Promises and pitfalls

Nanovehicles in the improved treatment of infections due to brain-eating amoebae

Pathogenic free-living amoebae are known to cause fatal central nervous system infections with extremely high mortality rates. High selectivity of the blood-brain barrier hampers delivery of drugs and untargeted delivery of drugs can cause severe side effects. Nanovehicles can be used for targeted drug delivery across the blood-brain barrier. Inorganic nanoparticles have been explored as carriers for various biomedical applications and can be modified with various ligands for efficient targeting and cell selectivity while lipid-based nanoparticles have been extensively used in the development of both precision and colloidal nanovehicles. Nanomicelles and polymeric nanoparticles can also serve as nanocarriers and may be modified so that responsiveness of the nanoparticles and release of the loads are linked to specific stimuli. These nanoparticles are discussed here in the context of the treatment of central nervous system infections due to pathogenic amoebae. It is anticipated that these novel strategies can be utilized in tandem with novel drug leads currently in the pipeline and yield in the development of much needed treatments against these devastating parasites.

Application of nanoparticles in cancer therapy with an emphasis on cell cycle

Owing to their unique characteristics, nanoparticles (NPs) could be incorporated into valuable therapeutic modalities for different diseases; however, there are many concerns about risk factors in human applications. NPs carry therapeutic chemicals that could improve the outcome of cancer therapies. Nowadays, NPs are being recognized as important and strategic agents in treatment of several disorders due to their unique properties in targeting malignant cells in tumor sites. Numerous investigations have shown that the majority of chemotherapeutic agents can be modified through entrapment in submicron colloidal systems. Still, there are problems and limitations in application of NPs in cancer therapy. The aim of the present study is to focus on potential NPs usage in cancer treatment with an emphasis on the cell cycle of malignant cells.

Inhibition of HSF1 and SAFB Granule Formation Enhances Apoptosis Induced by Heat Stress

Stress resistance mechanisms include upregulation of heat shock proteins (HSPs) and formation of granules. Stress-induced granules are classified into stress granules and nuclear stress bodies (nSBs). The present study examined the involvement of nSB formation in thermal resistance. We used chemical compounds that inhibit heat shock transcription factor 1 (HSF1) and scaffold attachment factor B (SAFB) granule formation and determined their effect on granule formation and HSP expression in HeLa cells. We found that formation of HSF1 and SAFB granules was inhibited by 2,5-hexanediol. We also found that suppression of HSF1 and SAFB granule formation enhanced heat stress-induced apoptosis. In addition, the upregulation of HSP27 and HSP70 during heat stress recovery was suppressed by 2,5-hexanediol. Our results suggested that the formation of HSF1 and SAFB granules was likely to be involved in the upregulation of HSP27 and HSP70 during heat stress recovery. Thus, the formation of HSF1 and SAFB granules was involved in thermal resistance.

Treatment of Hepatic Fibrosis in Mice Based on Targeted Plasmonic Hyperthermia

Liver fibrosis is a major health problem with multiple associated complications, which, to date, has no effective treatment. Hepatic stellate cells are the main responsible cells for fibrosis formation; upon their activation, excess accumulation of extracellular matrix and collagen deposits occurs. The mitogen platelet-derived growth factor (PDGF) and its receptor β (PDGFRβ) play a major role in hepatic stellate cells activation and are, therefore, promising targets for antifibrotic therapies. Gold nanorods hold great potential for diseased liver treatments, since their passive hepatic accumulation enhances active targeting strategies, hence increasing therapeutic efficiency. In addition, gold nanorods have photothermal properties that, combined with specific cell delivery, can be exploited to induce localized near-infrared light-mediated thermal ablation. Here, we demonstrate that gold nanorods coated with anti-PDGFRβ specifically target activated hepatic stellate cells in vivo. Additionally, gold nanorods-PDGFRβ-mediated photothermal therapy decreases fibrosis, hepatic inflammation, and hepatocyte injury in the experimental model of CCl₄-induced liver fibrosis in mice.

Protein-nanoparticle interactions and a new insight

The study of protein-nanoparticle interactions provides knowledge about the bio-reactivity of nanoparticles, and creates a database of nanoparticles for applications in nanomedicine, nanodiagnosis, and nanotherapy. The problem arises when nanoparticles come in contact with physiological fluids such as plasma or serum, wherein they interact with the proteins (or other biomolecules). This interaction leads to the coating of proteins on the nanoparticle surface, mostly due to the electrostatic interaction, called 'corona'. These proteins are usually partially unfolded. The protein corona can deter nanoparticles from their targeted functionalities, such as drug/DNA delivery at the site and fluorescence tagging of diseased tissues. The protein corona also has many repercussions on cellular intake, inflammation, accumulation, degradation, and clearance of the nanoparticles from the body depending on the exposed part of the proteins. Hence, the protein-nanoparticle interaction and the configuration of the bound-proteins on the nanosurface need thorough investigation and understanding. Several techniques such as DLS and zeta potential measurement, UV-vis spectroscopy, fluorescence spectroscopy, circular dichroism, FTIR, and DSC provide valuable information in the protein-nanoparticle interaction study. Besides, theoretical simulations also provide additional understanding. Despite a lot of research publications, the fundamental question remained unresolved. Can we aim for the application of functional nanoparticles in medicine? A new insight, given by us, in this article assumes a reasonable solution to this crucial question.

Plasmonically Modulated Gold Nanostructures for Photothermal Ablation of Bacteria

With the wide utilization of antibiotics, antibiotic-resistant bacteria have been often developed more frequently to cause potential global catastrophic consequences. Emerging photothermal ablation has been attracting extensive research interest for quick/effective eradication of pathogenic bacteria from contaminated surroundings and infected body. In this field, anisotropic gold nanostructures with tunable size/morphologies have been demonstrated to exhibit their outstanding photothermal performance through strong plasmonic absorption of near-infrared (NIR) light, efficient light to heat conversion, and easy surface modification for targeting bacteria. To this end, this review first introduces thermal treatment of infectious diseases followed by photothermal therapy via heat generation on NIR-absorbing gold nanostructures. Then, the usual synthesis and spectral features of diversified gold nanostructures and composites are systematically overviewed with the emphasis on the importance of size, shape, and composition to achieve strong plasmonic absorption in NIR region. Further, the innovated photothermal applications of gold nanostructures are comprehensively demonstrated to combat against bacterial infections, and some constructive suggestions are also discussed to improve photothermal technologies for practical applications.

Protein-based nanoplatform for detection of tumorigenic polyps in the colon via noninvasive mucosal routes

The use of nanoparticulate systems to diagnose and treat tumors has gained momentum with the rapid development of nanomedicine. Many nanotheranostics fail due to insufficient bioavailability and low accumulation at the tumor site, resulting in undesirable side effects. We describe the use of an engineered hepatitis E viral nanoparticle (HEVNP) with enhanced bioavailability, tissue retention and mucosal penetration capacities. HEVNP is a modular nanocapsule that can encapsulate heterologous nucleotides, proteins and inorganic metals, such as ferrite oxide nanoparticles. Additionally, the exterior protruding arms of HEVNP is composed of loops that are used for chemical coupling of targeting and therapeutic peptides. We propose the use of HEVNP to target colorectal cancer (i.e., polyps) with imaging-guided delivery using colonoscopy.

Recent Progress in the Synergistic Combination of Nanoparticle-Mediated Hyperthermia and Immunotherapy for Treatment of Cancer

Immunotherapy has demonstrated great clinical success in certain cancers, driven primarily by immune checkpoint blockade and adoptive cell therapies. Immunotherapy can elicit strong, durable responses in some patients, but others do not respond, and to date immunotherapy has demonstrated success in only a limited number of cancers. To address this limitation, combinatorial approaches with chemo- and radiotherapy have been applied in the clinic. Extensive preclinical evidence suggests that hyperthermia therapy (HT) has considerable potential to augment immunotherapy with minimal toxicity. This progress report will provide a brief overview of immunotherapy and HT approaches and highlight recent progress in the application of nanoparticle (NP)-based HT in combination with immunotherapy. NPs allow for tumor-specific targeting of deep tissue tumors while potentially providing more even heating. NP-based HT increases tumor immunogenicity and tumor permeability, which improves immune cell infiltration and creates an environment more responsive to immunotherapy, particularly in solid tumors.

Nanoparticles for Stem Cell Therapy Bioengineering in Glioma

Gliomas are a dismal disease associated with poor survival and high morbidity. Current standard treatments have reached a therapeutic plateau even after combining maximal safe resection, radiation, and chemotherapy. In this setting, stem cells (SCs) have risen as a promising therapeutic armamentarium, given their intrinsic tumor homing as well as their natural or bioengineered antitumor properties. The interplay between stem cells and other therapeutic approaches such as nanoparticles holds the potential to synergize the advantages from the combined therapeutic strategies. Nanoparticles represent a broad spectrum of synthetic and natural biomaterials that have been proven effective in expanding diagnostic and therapeutic efforts, either used alone or in combination with immune, genetic, or cellular therapies. Stem cells have been bioengineered using these biomaterials to enhance their natural properties as well as to act as their vehicle when anticancer nanoparticles need to be delivered into the tumor microenvironment in a very precise manner. Here, we describe the recent developments of this new paradigm in the treatment of malignant gliomas.

Immunogenicity of Externally Activated Nanoparticles for Cancer Therapy

Simple Summary

Recent advances in treating cancer via stimulating an anti-tumor immune system response have resulted in extraordinary results for lymphomas and leukemias; however these therapies have not performed well in solid tumors. External beam therapies, such as radiotherapy, hyperthermia, and photodynamic therapy, that are clinically used for solid tumors are now being explored in combination with nanoparticle systems to stimulate a long-term anti-tumor immune system response. In this review, we detail the novel nanoparticle complexes that are being researched to activate an anti-tumor immune response in combination with external beam therapy in both the preclinical and clinical settings.

Abstract

Nanoparticles activated by external beams, such as ionizing radiation, laser light, or magnetic fields, have attracted significant research interest as a possible modality for treating solid tumors. From producing hyperthermic conditions to generating reactive oxygen species, a wide range of externally activated mechanisms have been explored for producing cytotoxicity within tumors with high spatiotemporal control. To further improve tumoricidal effects, recent trends in the literature have focused on stimulating the immune system through externally activated treatment strategies that result in immunogenic cell death. By releasing inflammatory compounds known to initiate an immune response, treatment methods can take advantage of immune system pathways for a durable and robust systemic anti-tumor response. In this review, we discuss recent advancements in radiosensitizing and hyperthermic nanoparticles that have been tuned for promoting immunogenic cell death. Our review covers both preclinical and clinical results, as well as an overview of possible future work.

Mapping intracellular thermal response of cancer cells to magnetic hyperthermia treatment

Temperature is a key parameter for optimal cellular function and growth. Temperature perturbation may directly lead to cell death. This can be used in cancer therapies to kill cells in tumors, a therapeutic approach called hyperthermia. To avoid overheating of tumors that may damage healthy tissues, a knowledge of the intracellular temperature reached during the hyperthermia treatment of cancer cells is relevant. Recently, several luminescent intracellular nanothermometers have been proposed; however an application to sense temperature during a hyperthermia treatment is lacking. Here we present a technique to measure intracellular temperature changes in in vitro cancer cell models. For this purpose, we study for the first time the temperature dependence of the green fluorescent protein (GFP)'s fluorescence lifetime parameter. We find the fluorescence lifetime of GFP can be used for nanothermosensing. We use GFP in a bound form to actin filaments as an intracellular thermal reporter. Furthermore, we assess intracellular temperature during in vitro magnetothermal therapy on live HeLa cells incubated with polyacrylic acid-coated iron oxide nanoparticles. Compared to other thermosensitive materials and formulations reported so far, the GFP nanothermosensor is easily expressed via transfection and various GFP variants are commercially available. We foresee that the nanothermometer developed might find widespread applications in cancer therapy research and development.

Understanding Nanoparticle Toxicity to Direct a Safe-by-Design Approach in Cancer Nanomedicine

Nanomedicine is a rapidly growing field that uses nanomaterials for the diagnosis, treatment and prevention of various diseases, including cancer. Various biocompatible nanoplatforms with diversified capabilities for tumor targeting, imaging, and therapy have materialized to yield individualized therapy. However, due to their unique properties brought about by their small size, safety concerns have emerged as their physicochemical properties can lead to altered pharmacokinetics, with the potential to cross biological barriers. In addition, the intrinsic toxicity of some of the inorganic materials (i.e., heavy metals) and their ability to accumulate and persist in the human body has been a challenge to their translation. Successful clinical translation of these nanoparticles is heavily dependent on their stability, circulation time, access and bioavailability to disease sites, and their safety profile. This review covers preclinical and clinical inorganic-nanoparticle based nanomaterial utilized for cancer imaging and therapeutics. A special emphasis is put on the rational design to develop non-toxic/safe inorganic nanoparticle constructs to increase their viability as translatable nanomedicine for cancer therapies.

Magnetic nanofibers based bandage for skin cancer treatment: a non-invasive hyperthermia therapy

BACKGROUND

The treatment of non-melanoma skin cancer and deadliest malignant melanoma skin cancer are the fifth and ninth most expensive treatments in Medicare, respectively. Moreover, the recurrence of cancer after currently available therapies, that is, surgery or radiotherapy, reduces the patient's life expectancy.

AIMS

In view of this, we fabricated magnetic nanofibrous mat-based bandage to treat skin cancer non-invasively using an external alternating current (AC) magnetic field induced hyperthermia.

METHODS

The Fe₃ O₄ nanoparticles incorporated polycaprolactone (PCL) fibers based bandages were fabricated using the electrospinning technique. The efficacy of the bandage was investigated in vitro using parental/doxorubicin hydrochloride (Dox)-resistant HeLa cells and in vivo using BALB/c mouse model in the presence of an external AC magnetic field (AMF).

RESULTS

The PCL-Fe₃ O₄ fibrous mat-based bandages dissipate heat energy locally on the application of an external AMF and increase the surrounding temperature in a controlled way up to 45°C in a few mins. The in vitro study confirms the elevated temperature could kill parental and Dox-resistant HeLa cells significantly. As the activity of Dox enhanced at a higher temperatures, more than 85% of parental HeLa cells were dead when cells incubated with Dox contained fibrous mat in the presence of AMF for 10 minutes. Further, we confirm the full recovery of chemically induced skin tumors on BALB/c mice within a month after five hyperthermic doses for 15 minutes. Also, there was no sign of inflammation and recurrence of cancer post-therapy.

CONCLUSION

The present study confirms the PCL-Fe₃ O₄ nanofibrous based bandages are unique and compelling to treat skin cancer.

Boron-Doped Nanodiamonds as Anticancer Agents: En Route to Hyperthermia/Thermoablation Therapy

Local targeted "inside-out" hyperthermia of tumors via nanoparticles is able to sensitize tumor cells to chemotherapy, radiation therapy, gene therapy, immunotherapy, or other effects, significantly reducing the duration and intensity of treatment. In this article, new nanomaterials are proposed to be used as anticancer agents: boron-doped nanodiamonds with sizes of about 10 nm synthesized for the first time by the high-temperature high-pressure (HTHP) method. The heating ability of boron-doped nanodiamonds was investigated under different heating conditions in different environments: water, chicken egg white, and MCF-7 breast cancer cells. It was discovered that, with the same conversion of the absorbed energy into heat, the ability to heat the environment when excited at a wavelength of 808 nm of boron-doped nanodiamonds is much higher than that of detonation nanodiamonds. It was established that boron-doped nanodiamonds are extremely promising for carrying out hyperthermia and thermoablation of tumors.

Study of absorption of radio frequency field by gold nanoparticles and nanoclusters in biological medium

Gold nanoparticles (AuNPs) and gold nanoclusters (AuNCs) are gaining interest in medical diagnosis and therapy as they are bio-compatible and are easy to functionalize. Their interaction with radiofrequency (RF) field for hyperthermia treatment is ambiguous and needs further investigation. A systematic study of the absorption of capacitive RF field by AuNPs and AuNCs dispersed in phosphate-buffered saline (PBS) is reported here in tissue mimicking phantom. The stability of AuNPs and AuNCs dispersed in PBS was confirmed for a range of pH and temperature expected during RF hyperthermia treatment. Colloidal gold solutions with AuNPs (10 nm) and AuNCs (2 nm), and control, i.e. PBS without nanogold, were loaded individually in 3 ml wells in a tissue phantom. Phantom heating was carried out using 27 MHz short-wave diathermy equipment at 200 and 400 W for control and colloidal gold solutions. Experiments were conducted for colloidal gold at varying gold concentrations (10-100 µg/ml). Temperature rise measured in the phantom wells did not show dependence on the concentration and size of the AuNPs. Furthermore, temperature rise recorded in the control was comparable with the measurements recorded in both nanogold suspensions (2, 10 nm). Dielectric property measurements of control and colloidal gold showed <3% difference in electrical conductivity between the control and colloidal gold for both nanoparticle sizes. From the measurements, it is concluded that AuNPs and AuNCs do not enhance the absorption of RF-capacitive field and power absorption observed in the biological medium is due to the ions present in the medium.

Integrating Loco-Regional Hyperthermia Into the Current Oncology Practice: SWOT and TOWS Analyses

Moderate hyperthermia at temperatures between 40 and 44°C is a multifaceted therapeutic modality. It is a potent radiosensitizer, interacts favorably with a host of chemotherapeutic agents, and, in combination with radiotherapy, enforces immunomodulation akin to “in situ tumor vaccination.” By sensitizing hypoxic tumor cells and inhibiting repair of radiotherapy-induced DNA damage, the properties of hyperthermia delivered together with photons might provide a tumor-selective therapeutic advantage analogous to high linear energy transfer (LET) neutrons, but with less normal tissue toxicity. Furthermore, the high LET attributes of hyperthermia thermoradiobiologically are likely to enhance low LET protons; thus, proton thermoradiotherapy would mimic ¹²C ion therapy. Hyperthermia with radiotherapy and/or chemotherapy substantially improves therapeutic outcomes without enhancing normal tissue morbidities, yielding level I evidence reported in several randomized clinical trials, systematic reviews, and meta-analyses for various tumor sites. Technological advancements in hyperthermia delivery, advancements in hyperthermia treatment planning, online invasive and non-invasive MR-guided thermometry, and adherence to quality assurance guidelines have ensured safe and effective delivery of hyperthermia to the target region. Novel biological modeling permits integration of hyperthermia and radiotherapy treatment plans. Further, hyperthermia along with immune checkpoint inhibitors and DNA damage repair inhibitors could further augment the therapeutic efficacy resulting in synthetic lethality. Additionally, hyperthermia induced by magnetic nanoparticles coupled to selective payloads, namely, tumor-specific radiotheranostics (for both tumor imaging and radionuclide therapy), chemotherapeutic drugs, immunotherapeutic agents, and gene silencing, could provide a comprehensive tumor-specific theranostic modality akin to “magic (nano)bullets.” To get a realistic overview of the strength (S), weakness (W), opportunities (O), and threats (T) of hyperthermia, a SWOT analysis has been undertaken. Additionally, a TOWS analysis categorizes future strategies to facilitate further integration of hyperthermia with the current treatment modalities. These could gainfully accomplish a safe, versatile, and cost-effective enhancement of the existing therapeutic armamentarium to improve outcomes in clinical oncology.

Graphene-based scaffolds for tissue engineering and photothermal therapy

Researchers have been creating 3D replicas of damaged tissues for millions of patients by using innovative biomaterials. While these scaffolds have regenerative properties, it would be beneficial if they could be utilized for local therapies, such as for cancer treatment. This report discusses the main advances in graphene scaffold design for near-infrared (NIR) photothermal therapy (PTT). NIR-PTT is a promising alternative for cancer cell killing, mediated by an increase of temperature due to NIR light-absorbers delivered to the tumor proximity. Graphene is a bidimensional material largely exploited in nanomedicine for its unique properties, such as high growth factor loading, which induces cell differentiation and its capacity to absorb NIR light. Here we cover aspects of future research in multifunctional graphene implants for cancer therapy and tissue regeneration.

Hyperthermia and protein homeostasis: Cytoprotection and cell death

Protein homeostasis or proteostasis, the correct balance between production and degradation of proteins, is an essential pillar for proper cellular function. Among the several cellular mechanisms that disrupt homeostatic conditions in cancer cells, hyperthermia (HT) has shown promising anti-tumor effects. However, cancer cells are also capable of thermoresistance. Indeed, HT-induced protein denaturation and aggregation results in the up regulation of heat shock proteins, a group of molecular chaperones with cytoprotective and anti-apoptotic properties via stress-inducible transcription factor, heat shock factor 1(HSF1). Heat shock proteins assist in the refolding of misfolded proteins and aids in their elimination if they become irreversibly damaged by various stressors. Furthermore, HSF1 also initiates the unfolded protein response in the endoplasmic reticulum (ER) to assist in the protein folding capacity of ER and also promotes the translation of pro-survival proteins' mRNA such as activating transcription factor 4 (ATF 4). Moreover, HT associated induction of microRNAs is also involved in thermal resistance of cancer cells via up-regulation of anti-apoptotic Bcl-2 proteins and down regulation of pro-apoptotic Bax and caspase 3 activities. Another cellular protection in response to stressors is Autophagy, which is regulated by the Mammalian target of rapamycin (mTOR) protein. Kinase activity in mTOR phosphorylates HSF1 and promotes its nuclear translocation for heat shock protein synthesis. Over-expression of heat shock proteins are reported to up-regulate Beclin-1, an autophagy initiator. Moreover, HT-induced reactive oxygen species (ROS) generation is sensitized by transcription factor NF-E2 related factor 2 (Nrf2) and activates the cellular expression of antioxidants and autophagy gene. Furthermore, ROS also potentiates autophagy via activation of Beclin-1. Inhibition of thermotolerance can potentiate HT-induced apoptosis. Here, we outlined that heat stress alters cellular proteins which activates cellular homeostatic processes to promote cell survival and make cancer cells thermotolerant.

Multicomponent Nanocomposites for Complex Anticancer Therapy: Effect of Aggregation Processes on Their Efficacy

Multicomponent nanocomposites for anticancer therapy were prepared, characterized, and tested for their antitumor efficacy. The water-soluble star-like dextran-graft-polyacrylamide copolymer was used as a nanoplatform for the creation of polymer-based multicomponent drug delivery systems for photodynamic and combined (photodynamic+chemotherapy) antitumor therapy. The three-component nanocomposites with incorporated gold nanoparticles and photosensitizer and the four-component ones additionally loaded by Doxorubicin into polymer nanoplatform were studied at 25 and 37°C by transmission electron microscopy and dynamic light scattering. Nanocomposites were tested for their photodynamic cytotoxicity for the cell line of breast cancer MCF-7/S. Three-component nanocomposites demonstrated higher efficacy than the four-component ones. The decrease in the activity of the four-component systems is explained by the aggregation process caused by the introduction of an additional component, which leads to a decrease in the hydrophilic-hydrophobic balance of the polymer macromolecule.

Magnetic Nanoparticles in Cancer Therapy and Diagnosis

There is urgency for the development of nanomaterials that can meet emerging biomedical needs. Magnetic nanoparticles (MNPs) offer high magnetic moments and surface-area-to-volume ratios that make them attractive for hyperthermia therapy of cancer and targeted drug delivery. Additionally, they can function as contrast agents for magnetic resonance imaging (MRI) and can improve the sensitivity of biosensors and diagnostic tools. Recent advancements in nanotechnology have resulted in the realization of the next generation of MNPs suitable for these and other biomedical applications. This review discusses methods utilized for the fabrication and engineering of MNPs. Recent progress in the use of MNPs for hyperthermia therapy, controlling drug release, MRI, and biosensing is also critically reviewed. Finally, challenges in the field and potential opportunities for the use of MNPs toward improving their properties are discussed.

Magnetic Temperature-Sensitive Solid-Lipid Particles for Targeting and Killing Tumor Cells

Magnetic and temperature-sensitive solid lipid particles (mag. SLPs) were prepared in the presence of oleic acid-coated iron oxide (IO-OA) nanoparticles with 1-tetradecanol and poly(ethylene oxide)-block-poly(ε-caprolactone) as lipid and stabilizing surfactant-like agents, respectively. The particles, typically ~850 nm in hydrodynamic size, showed heat dissipation under the applied alternating magnetic field. Cytotoxic activity of the mag.SLPs, non-magnetic SLPs, and iron oxide nanoparticles was compared concerning the mammalian cancer cell lines and their drug-resistant counterparts using trypan blue exclusion test and MTT assay. The mag.SLPs exhibited dose-dependent cytotoxicity against human leukemia cell lines growing in suspension (Jurkat and HL-60/wt), as well as the doxorubicin (Dox)- and vincristine-resistant HL-60 sublines. The mag.SLPs showed higher cytotoxicity toward drug-resistant sublines as compared to Dox. The human glioblastoma cell line U251 growing in a monolayer culture was also sensitive to mag.SLPs cytotoxicity. Staining of U251 cells with the fluorescent dyes Hoechst 33342 and propidium iodide (PI) revealed that mag.SLPs treatment resulted in an increased number of cells with condensed chromatin and/or fragmented nuclei as well as with blebbing of the plasma membranes. While the Hoechst 33342 staining of cell suggested the pro-apoptotic activity of the particles, the PI staining indicated the pro-necrotic changes in the target cells. These conclusions were confirmed by Western blot analysis of apoptosis-related proteins, study of DNA fragmentation (DNA laddering due to the inter-nucleosomal cleavage and DNA comets due to single strand breaks), as well as by FACS analysis of the patterns of cell cycle distribution (pre-G1 phase) and Annexin V/PI staining of the treated Jurkat cells. The induction of apoptosis or necrosis by the particles used to treat Jurkat cells depended on the dose of the particles. Production of the reactive oxygen species (ROS) was proposed as a potential mechanism of mag.SLPs-induced cytotoxicity. Accordingly, hydrogen peroxide and superoxide radical levels in mag.SLPs-treated Jurkat leukemic cells were increased by ~20–40 and ~70%, respectively. In contrast, the non-magnetic SLPs and neat iron oxides did not influence ROS levels significantly. Thus, the developed mag.SLPs can be used for effective killing of human tumor cells, including drug-resistant ones.

Comparing the Effects of Intracellular and Extracellular Magnetic Hyperthermia on the Viability of BxPC-3 Cells

Magnetic hyperthermia involves the use of iron oxide nanoparticles to generate heat in tumours following stimulation with alternating magnetic fields. In recent times, this treatment has undergone numerous clinical trials in various solid malignancies and subsequently achieved clinical approval to treat glioblastoma and prostate cancer in 2011 and 2018, respectively. However, despite recent clinical advances, many questions remain with regard to the underlying mechanisms involved in this therapy. One such query is whether intracellular or extracellular nanoparticles are necessary for treatment efficacy. Herein, we compare the effects of intracellular and extracellular magnetic hyperthermia in BxPC-3 cells to determine the differences in efficacy between both. Extracellular magnetic hyperthermia at temperatures between 40–42.5 °C could induce significant levels of necrosis in these cells, whereas intracellular magnetic hyperthermia resulted in no change in viability. This led to a discussion on the overall relevance of intracellular nanoparticles to the efficacy of magnetic hyperthermia therapy.

Triple-Negative Breast Cancer: A Review of Conventional and Advanced Therapeutic Strategies

Triple-negative breast cancer (TNBC) cells are deficient in estrogen, progesterone and ERBB2 receptor expression, presenting a particularly challenging therapeutic target due to their highly invasive nature and relatively low response to therapeutics. There is an absence of specific treatment strategies for this tumor subgroup, and hence TNBC is managed with conventional therapeutics, often leading to systemic relapse. In terms of histology and transcription profile these cancers have similarities to BRCA-1-linked breast cancers, and it is hypothesized that BRCA1 pathway is non-functional in this type of breast cancer. In this review article, we discuss the different receptors expressed by TNBC as well as the diversity of different signaling pathways targeted by TNBC therapeutics, for example, Notch, Hedgehog, Wnt/b-Catenin as well as TGF-beta signaling pathways. Additionally, many epidermal growth factor receptor (EGFR), poly (ADP-ribose) polymerase (PARP) and mammalian target of rapamycin (mTOR) inhibitors effectively inhibit the TNBCs, but they face challenges of either resistance to drugs or relapse. The resistance of TNBC to conventional therapeutic agents has helped in the advancement of advanced TNBC therapeutic approaches including hyperthermia, photodynamic therapy, as well as nanomedicine-based targeted therapeutics of drugs, miRNA, siRNA, and aptamers, which will also be discussed. Artificial intelligence is another tool that is presented to enhance the diagnosis of TNBC.

3D cultures for modeling nanomaterial-based photothermal therapy

Photothermal therapy (PTT) is one of the most promising techniques for cancer tumor ablation. Nanoparticles are increasingly being investigated for use with PTT and can serve as theranostic agents. Based on the ability of near-infrared nano-photo-absorbers to generate heat under laser irradiation, PTT could prove advantageous in certain situations over more classical cancer therapies. To analyze the efficacy of nanoparticle-based PTT, preclinical in vitro studies typically use 2D cultures, but this method cannot completely mimic the complex tumor organization, bioactivity, and physiology that all control the complex penetration depth, biodistribution, and tissue diffusion parameters of nanomaterials in vivo. To fill this knowledge gap, 3D culture systems have been explored for PTT analysis. These models provide more realistic microenvironments that allow spatiotemporal oxygen gradients and cancer cell adaptations to be considered. This review highlights the work that has been done to advance 3D models for cancer microenvironment modeling, specifically in the context of advanced, functionalized nanoparticle-directed PTT.

pH-Sensitive nanotheranostics for dual-modality imaging guided nanoenzyme catalysis therapy and phototherapy

A theranostic nanosystem with a pH-sensitive structure showed charge conversion properties in the tumor acidic microenvironment. It could perform dual-modality imaging diagnosis and carry out catalysis therapy and phototherapy.

Recent Advances in Magnetite Nanoparticle Functionalization for Nanomedicine

Functionalization of nanomaterials can enhance and modulate their properties and behaviour, enabling characteristics suitable for medical applications. Magnetite (Fe3O4) nanoparticles are one of the most popular types of nanomaterials used in this field, and many technologies being already translated in clinical practice. This article makes a summary of the surface modification and functionalization approaches presented lately in the scientific literature for improving or modulating magnetite nanoparticles for their applications in nanomedicine.

Magnetic hyperthermia adjunctive therapy for fungi: in vitro studies against Candida albicans

The poor penetration of anti-fungal agents into the cornea through the intact epithelium layer makes it difficult to treat acute fungal corneal infections. Herein, we developed Amphotret (amphotericin B) antifungal drug contained polycaprolactone-Fe₃O₄ (PCL-FO) magnetic nanofibers (MNFs) using the electrospinning technique. These MNFs generate heat in the presence of AC magnetic field (AMF) and release drug upon heating. MNFs were compatible with human mesenchymal stem cells (hMSCs) and HeLa cells, which exhibited unaltered proliferation, ruling out any toxicity from the systems. Hyperthermia induced via MNFs from 42 °C to 50 °C compromised the viability of Candida albicans cells. Further, the efficacy of the systems was increased in the presence of both heat and drug simultaneously in vitro, leading to near 100% loss in viability of C. albicans cells at 50 °C with simultaneous drug release from MNFs. Thus, we propose magnetic hyperthermia as adjunctive therapy for fungal keratitis.

Alcian blue staining to track the intracellular fate of hyaluronic-acid-based nanoparticles at transmission electron microscopy

The main step in the assessment of nanomaterial safety and suitability for biomedical use is the location and the dynamic tracking of nanoparticles (NPs) inside cells or tissues. To precisely investigate the uptake mechanisms and intracellular fate of NPs, transmission electron microscopy is the technique of choice; however, the detection of NPs may sometimes be problematic. In fact, while NPs containing strongly electron dense (e.g. metal) components do not require specific detection methods at the ultrastructural level, organic NPs are hardly detectable in the intracellular environment due to their intrinsic moderate electron density. In this study, the critical-electrolyte-concentration Alcian Blue method set up by Schofield et al. in 1975 was applied to track hyaluronic-acidbased NPs in muscle cells in vitro. This long-established histochemical method proved to be a powerful tool allowing to identify not only whole NPs while entering cells and moving into the cytoplasm, but also their remnants following lysosomal degradation and extrusion.

Osteogenesis effects of magnetic nanoparticles modified-porous scaffolds for the reconstruction of bone defect after bone tumor resection

The treatment of bone defect after bone tumor resection is a great challenge for orthopedic surgeons. It should consider that not only to inhibit tumor growth and recurrence, but also to repair the defect and preserve the limb function. Hence, it is necessary to find an ideal functional biomaterial that can repair bone defects and inactivate tumor. Magnetic nanoparticles (MNPs) have its unique advantages to achieve targeted hyperthermia to avoid damage to surrounding normal tissues and promote osteoblastic activity and bone formation. Based on the previous stage, we successfully prepared hydroxyapatite (HAP) composite poly(lactic-co-glycolic acid) (PLGA) scaffolds and verified its good osteogenic properties, in this study, we produced an HAP composite PLGA scaffolds modified with MNPs. The composite scaffold showed appropriate porosity and mechanical characteristics, while MNPs possessed excellent magnetic and thermal properties. The cytological assay indicated that the MNPs have antitumor ability and the composite scaffold possessed good biocompatibility. In vivo bone defect repair experiment revealed that the composite scaffold had good osteogenic capacity. Hence, we could demonstrate that the composite scaffolds have a good effect in bone repair, which could provide a potential approach for repairing bone defect after bone tumor excision.

Targeting Integrins in Cancer Nanomedicine: Applications in Cancer Diagnosis and Therapy

Due to advancements in nanotechnology, the application of nanosized materials (nanomaterials) in cancer diagnostics and therapeutics has become a leading area in cancer research. The decoration of nanomaterial surfaces with biological ligands is a major strategy for directing the actions of nanomaterials specifically to cancer cells. These ligands can bind to specific receptors on the cell surface and enable nanomaterials to actively target cancer cells. Integrins are one of the cell surface receptors that regulate the communication between cells and their microenvironment. Several integrins are overexpressed in many types of cancer cells and the tumor microvasculature and function in the mediation of various cellular events. Therefore, the surface modification of nanomaterials with integrin-specific ligands not only increases their binding affinity to cancer cells but also enhances the cellular uptake of nanomaterials through the intracellular trafficking of integrins. Moreover, the integrin-specific ligands themselves interfere with cancer migration and invasion by interacting with integrins, and this finding provides a novel direction for new treatment approaches in cancer nanomedicine. This article reviews the integrin-specific ligands that have been used in cancer nanomedicine and provides an overview of the recent progress in cancer diagnostics and therapeutic strategies involving the use of integrin-targeted nanomaterials.

Presence of Gold Nanoparticles in Cells Associated with the Cell-Killing Effect of Modulated Electro-Hyperthermia

The efficacy of gold nanoparticle (AuNP)-assisted radiofrequency (RF)-induced hyperthermia employing the Kanzius device remains controversial. Different from the Kanzius device, modulated electro-hyperthermia (mEHT) utilizes the capacitive-impedance coupled 13.56 MHz radiofrequency (RF) current and has been approved for clinical cancer treatment. In this study, we investigated the heating characteristics of spherical-, urchin-, and rod-like AuNPs of a similar 50 nm size upon exposure to a 13.56 MHz radiofrequency using the LabEHY-105CL, an in vivo mEHT device. We found that, regardless of the AuNPs' sphere-, urchin- or rod-like shape, purified gold nanoparticle solution would not promote heat generation. The temperature elevation during radiofrequency irradiation was solely attributed to the ionic background of the solution. The AuNPs present in the medium (≤25 ppm) showed no effect on selective cell killing of malignant cells, whereas the AuNPs incorporated in the cells diminished the cell selectivity as well as cell death and acted as protectors in mEHT cancer treatment. Our study suggested that (1) the temperature elevation induced by 50 nm AuNPs in the 13.56 MHz radiofrequency field was negligible and was shape-independent, and (2) the presence of AuNPs would alter the cell-killing effect of modulated electro-hyperthermia.

The influence of female mice age on biodistribution and biocompatibility of citrate-coated magnetic nanoparticles

BACKGROUND

Magnetic nanoparticles (MNPs) have been successfully tested for several purposes in medical applications. However, knowledge concerning the effects of nanostructures on elderly organisms is remarkably scarce.

PURPOSE

To fill part of this gap, this work aimed to investigate biocompatibility and bio-distribution aspects of magnetic nanoparticles coated with citrate (NpCit) in both elderly and young healthy mice.

METHODS

NpCit (2.4 mg iron) was administered intraperitoneally, and its toxicity was evaluated for 28 days through clinical, biochemical, hematological, and histopathological examinations. In addition, its biodistribution was evaluated by spectrometric (inductively coupled plasma optical emission spectrometry) and histological methods.

RESULTS

NpCit presented age-dependent effects, inducing very slight and temporary biochemical and hematological changes in young animals. These changes were even weaker than the effects of the aging process, especially those related to the hematological data, tumor necrosis factor alpha, and nitric oxide levels. On the other hand, NpCit showed a distinct set of results in the elderly group, sometimes reinforcing (decrease of lymphocytes and increase of monocytes) and sometimes opposing (erythrocyte parameters and cytokine levels) the aging changes. Leukocyte changes were still observed on the 28th day after treatment in the elderly group. Slight evidence of a decrease in liver and immune functions was detected in elderly mice treated or not treated with NpCit. It was noted that tissue damage or clinical changes related to aging or to the NpCit treatment were not observed. As detected for aging, the pattern of iron biodistribution was significantly different after NpCit administration: extra iron was detected until the 28th day, but in different organs of elderly (liver and kidneys) and young (spleen, liver, and lungs) mice.

CONCLUSION

Taken together, the data show NpCit to be a stable and reasonably biocompatible sample, especially for young mice, and thus appropriate for biomedical applications. The data showed important differences after NpCit treatment related to the animals' age, and this emphasizes the need for further studies in older animals to appropriately extend the benefits of nanotechnology to the elderly population.

Anisotropic Gold Nanoparticle-Cell Interactions Mediated by Collagen

Gold nanoparticles (AuNPs) are the groundwork of a large variety of applications in the biomedical field. Further development and a better understanding of this versatile platform will lead to an expansion of potential applications. In this study, we propose a facile synthesis of AuNPs using hydrogen peroxide as a reducing agent and collagen as a stabilizing agent. Our synthetic approach results in "raspberry"-like AuNPs with a mean diameter of 60 nm, as revealed by electron microscopy. The optical properties of the AuNPs were assessed by UV-Vis and surface-enhanced Raman scattering (SERS), and their stability and in vitro cytotoxicity were evaluated as well. HeLa cell viability values were only modestly affected compared to control, with the highest concentration tested displaying a 20% decrease in cellular viability. The dose-dependent cellular internalization in the 20⁻60 nM range indicate the highest internalization rate at 60 nM and uptake values as high as 35%. This result correlated well with the viability results. These type of anisotropic AuNPs are proposed for biomedical applications such as hyperthermia, contrast agents or imaging. Therefore, our findings offer a platform for potential biological applications such as sensing and imaging, due to their unique physico-chemical features.

Gold Nanoparticles for Photothermal Cancer Therapy

Gold is a multifunctional material that has been utilized in medicinal applications for centuries because it has been recognized for its bacteriostatic, anticorrosive, and antioxidative properties. Modern medicine makes routine, conventional use of gold and has even developed more advanced applications by taking advantage of its ability to be manufactured at the nanoscale and functionalized because of the presence of thiol and amine groups, allowing for the conjugation of various functional groups such as targeted antibodies or drug products. It has been shown that colloidal gold exhibits localized plasmon surface resonance (LPSR), meaning that gold nanoparticles can absorb light at specific wavelengths, resulting in photoacoustic and photothermal properties, making them potentially useful for hyperthermic cancer treatments and medical imaging applications. Modifying gold nanoparticle shape and size can change their LPSR photochemical activities, thereby also altering their photothermal and photoacoustic properties, allowing for the utilization of different wavelengths of light, such as light in the near-infrared spectrum. By manufacturing gold in a nanoscale format, it is possible to passively distribute the material through the body, where it can localize in tumors (which are characterized by leaky blood vessels) and be safely excreted through the urinary system. In this paper, we give a quick review of the structure, applications, recent advancements, and potential future directions for the utilization of gold nanoparticles in cancer therapeutics.

MHI-148 Cyanine Dye Conjugated Chitosan Nanomicelle with NIR Light-Trigger Release Property as Cancer Targeting Theranostic Agent

PURPOSE

Paclitaxel (PTX) loaded hydrophobically modified glycol chitosan (HGC) micelle is biocompatible in nature, but it requires cancer targeting ability and stimuli release property for better efficiency. To improve tumor retention and drug release characteristic of HGC-PTX nanomicelles, we conjugated cancer targeting heptamethine dye, MHI-148, which acts as an optical imaging agent, targeting moiety and also trigger on-demand drug release on application of NIR 808 nm laser.

PROCEDURES

The amine group of glycol chitosan modified with hydrophobic 5β-cholanic acid and the carboxyl group of MHI-148 were bonded by 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide/N-hydroxysuccinimide chemistry. Paclitaxel was loaded to MHI-HGC nanomicelle by an oil-in-water emulsion method, thereby forming MHI-HGC-PTX.

RESULTS

Comparison of near infrared (NIR) dyes, MHI-148, and Flamma-774 conjugated to HGC showed higher accumulation for MHI-HGC in 4T1 tumor and 4T1 tumor spheroid. In vitro studies showed high accumulation of MHI-HGC-PTX in 4T1 and SCC7 cancer cell lines compared to NIH3T3 cell line. In vivo fluorescence imaging of the 4T1 and SCC7 tumor showed peak accumulation of MHI-HGC-PTX at day 1 and elimination from the body at day 6. MHI-HGC-PTX showed good photothermal heating ability (50.3 °C), even at a low concentration of 33 μg/ml in 1 W/cm² 808 nm laser at 1 min time point. Tumor reduction studies in BALB/c nude mice with SCC7 tumor showed marked reduction in MHI-HGC-PTX in the PTT group combined with photothermal therapy compared to MHI-HGC-PTX in the group without PTT.

CONCLUSION

MHI-HGC-PTX is a cancer theranostic agent with cancer targeting and optical imaging capability. Our studies also showed that it has cancer targeting property independent of tumor type and tumor reduction property by combined photothermal and chemotherapeutic effects.

Theoretical and experimental modeling of interstitial laser hyperthermia with surface cooling device using Nd3+-doped nanoparticles

To improve methods of laser hyperthermia for the treatment of bulk malignant neoplasms, an urgent task is the development of techniques and devices that automatically control heating at a given tissue depth and ensure its uniformity. The article proposes the concept of a system for performing hyperthermia with real-time spectroscopic temperature control and surface cooling, which allows to record spectra of diffusely scattered radiation and fluorescent signal from various depths of biological tissues by the means of the variation of the angle and distance between the fiber source of laser radiation and the receiving fiber. Theoretical and experimental modeling of the spatial distribution of diffusely scattered radiation and temperature inside the tissue with a fiber optic device providing surface cooling of the irradiated tissue, and recording spectral information from a given depth in real time, is presented. Simulation of radiation propagation in biological tissues, depending on the distance between the source and the receiver and the angle of their tilt, was carried out using the Monte Carlo method. Modeling of the temperature distribution inside the tissues was carried out by means of a numerical solution of the heat conduction equation. Experimental modeling was carried out on phantoms of biological tissues simulating their scattering properties as well as accumulation of the investigated nanoparticles doped with Nd³⁺ ions. It was shown that inorganic nanoparticles doped with rare-earth Nd³⁺ ions can be used as temperature labels for feedback to the therapeutic laser. According to the results of the theoretical simulation, optimal configurations of the relative arrangement of the fibers were chosen, as well as the optimum surface cooling temperatures for the given power densities. The heating of the phantom of the neoplasm containing the investigated nanoparticles doped with Nd³⁺ ions by laser radiation with an 805-nm wavelength and power density of 1 W/cm² up to 42 °C at a depth of 1 cm while maintaining the surface temperature within the limits of the norm was demonstrated.

Heat transfer from nanoparticles for targeted destruction of infectious organisms

Whereas the application of optically or magnetically heated nanoparticles to destroy tumours is now well established, the extension of this concept to target pathogens has barely begun. Here we examine the challenge of targeting pathogens by this means and, in particular, explore the issues of power density and heat transfer. Depending on the rate of heating, either hyperthermia or thermoablation may occur. This division of the field is fundamental and implies very different sources of excitation and heat transfer for the two modes, and different strategies for their clinical application. Heating by isolated nanoparticles and by agglomerates of nanoparticles is compared: hyperthermia is much more readily achieved with agglomerates and for large target volumes, a factor which favours magnetic excitation and moderate power densities. In contrast, destruction of planktonic pathogens is best achieved by localised thermoablation and very high power density, a scenario that is best delivered by pulsed optical excitation.

Evaluation of in vitro cytotoxicity of superparamagnetic poly(thioether-ester) nanoparticles on erythrocytes, non-tumor (NIH3T3), tumor (HeLa) cells and hyperthermia studies

Magnetic nanoparticles encapsulated in biocompatible and biodegradable polymeric matrices are promising materials for biomedical applications, such as transport of antitumoral drugs and cancer treatment by hyperthermia. In this study, biobased poly(thioether-ester), PTEe, was obtained by thiol-ene polymerization and superparamagnetic nanoparticles, MNPs, were successfully incorporated in PTEe nanoparticles by miniemulsification followed by solvent evaporation. MNPs-PTEe nanoparticles with average diameter around 150 nm presented superparamagnetic behavior as confirmed by magnetization curves analysis. MNPs-PTEe nanoparticles did not present hemolytic damage on human red blood cells when incubated for 24 h. According to the cell viability assays, nanoparticles did not present any cytotoxic effect on murine fibroblast cell (NIH3T3) and human cervical cancer (HeLa). Hyperthermia assays were applied, demonstrating that AC magnetic field application (110 KHz-500 Oe) for 20 min significantly reduced the cells viability. The morphology evaluation of HeLa showed a hypoxia region one hour after hyperthermia application. Therefore, the results indicated that the superparamagnetic poly(thioether-ester) nanoparticles can be an excellent alternative for the targeted delivery of antitumor drugs and cancer treatment for hyperthermia.

Mn-Doping level dependence on the magnetic response of MnxFe3−xO4 ferrite nanoparticles

Manganese/iron ferrite nanoparticles with different Mn^2+/3+ doping grades have been prepared by a thermal decomposition optimized approach so as to ascertain the doping effect on the magnetic hyperthermia response.

Contemporary Polymer-Based Nanoparticle Systems for Photothermal Therapy

Current approaches for the treatment of cancer, such as chemotherapy, radiotherapy, immunotherapy, and surgery, are limited by various factors, such as inadvertent necrosis of healthy cells, immunological destruction, or secondary cancer development. Hyperthermic therapy is a promising strategy intended to mitigate many of the shortcomings associated with traditional therapeutic approaches. However, to utilize this approach effectively, it must be targeted to specific tumor sites to prevent adverse side effects. In this regard, photothermal therapy, using intravenously-administered nanoparticle materials capable of eliciting hyperthermic effects in combination with the precise application of light in the near-infrared spectrum, has shown promise. Many different materials have been proposed, including various inorganic materials such as Au, Ag, and Germanium, and C-based materials. Unfortunately, these materials are limited by concerns about accumulation and potential cytotoxicity. Polymer-based nanoparticle systems have been investigated to overcome limitations associated with traditional inorganic nanoparticle systems. Some of the materials that have been investigated for this purpose include polypyrrole, poly-(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS), polydopamine, and polyaniline. The purpose of this review is to summarize these contemporary polymer-based nanoparticle technologies to acquire an understanding of their current applications and explore the potential for future improvements.

NONINVASIVE ESTIMATION OF THE LOCAL TEMPERATURE OF BIOTISSUES HEATING UNDER THE ACTION OF LASER IRRADIATION FROM THE LUMINESCENCE SPECTRA OF Nd3+ IONS

Laser hyperthermia is one of the promising methods for treatment of oncological diseases. For routine clinical use of hyperthermia, it is necessary to control the uniformity and localization of heat within the tumor. Local heating can be achieved by using special thermal agents, such as nanoparticles doped with rare-earth ions. Measurement of the temperature of the thermal agents will allow timely regulation of the applied laser radiation excitation power and optimization of the hyperthermia process.

The paper presents the results of a study on the non-invasive determination of the YPO4 nanoparticles doped with Nd3+ temperature with sensitivity of 0.2% °С-1 in 30-60°С temperature range. The temperature of the nanoparticles was calculated from the Nd3+ luminescence spectra in the 800-1000 nm range under excitation into 4F5/2 energy state by 805 nm laser. A calibration procedure for recalculating the ratio of the luminescence intensities from the Stark sublevels of the 4F3/2 Nd3+ state into the values of the real NP temperature in accordance with the Boltzmann distribution is given. An algorithm for calculating luminescence intensities for individual Stark components is proposed. After calculating the intensities corresponding to each individual Stark component, all the intensities related to the transition from the upper and lower Stark sublevels of the 4F3/2 state are summed, and then their ratio is calculated. The resulting ratio is normalized to the value of the ratio at room temperature and, in accordance with the calibration dependence, is recalculated into the NP heating temperature. It was demonstrated that the investigated 1%Nd3+:YPO4 nanoparticles can be used as "primary” thermometers that do not require additional recalibration to evaluate the temperature in the range used for hyperthermia.