Engineering the multifunctional surface on magnetic nanoparticles for targeted biomedical applications: a chemical approach

Gold-iron oxide (Au/Fe3O4) magnetic nanoparticles as the nanoplatform for binding of bioactive molecules through self-assembly

Nanomedicine plays a crucial role in the development of next-generation therapies. The use of nanoparticles as drug delivery platforms has become a major area of research in nanotechnology. To be effective, these nanoparticles must interact with desired drug molecules and release them at targeted sites. The design of these “nanoplatforms” typically includes a functional core, an organic coating with functional groups for drug binding, and the drugs or bioactive molecules themselves. However, by exploiting the coordination chemistry between organic molecules and transition metal centers, the self-assembly of drugs onto the nanoplatform surfaces can bypass the need for an organic coating, simplifying the materials synthesis process. In this perspective, we use gold-iron oxide nanoplatforms as examples and outline the prospects and challenges of using self-assembly to prepare drug-nanoparticle constructs. Through a case study on the binding of insulin on Au-dotted Fe3O4 nanoparticles, we demonstrate how a self-assembly system can be developed. This method can also be adapted to other combinations of transition metals, with the potential for scaling up. Furthermore, the self-assembly method can also be considered as a greener alternative to traditional methods, reducing the use of chemicals and solvents. In light of the current climate of environmental awareness, this shift towards sustainability in the pharmaceutical industry would be welcomed.

Synthesis and Characterization of Tetracycline Loaded Methionine-Coated NiFe2O4 Nanoparticles for Anticancer and Antibacterial Applications

In the present study, nickel ferrite (NiFe₂O₄)-based smart magnetic nanoparticles were fabricated and coated with methionine. Physiochemical characterization of the obtained Met-NiFe₂O₄ nanoparticles revealed the presence of methionine coating over the nanoparticle surface. Drug release study indicated that Tet-Met-NiFe₂O₄ nanoparticles possess pH-responsive controlled drug release behavior for tetracycline (Tet). The drug loading content for Tet was found to be 0.27 mg/L of nanoparticles. In vitro cytotoxicity test showed that the Met-NiFe₂O₄ nanoparticles is biocompatible. Moreover, this magnetic nanostructured material shown strong anticancer property as these nanomaterials significantly reduced the viability of A375 cells when compared to free Tet solution. In addition, Tet-Met-NiFe₂O₄ nanoparticles also showed strong antibacterial activity against different bacterial pathogens.

Formulation and Characterization of Poly (Ethylene Glycol)-Coated Core-Shell Methionine Magnetic Nanoparticles as a Carrier for Naproxen Delivery: Growth Inhibition of Cancer Cells

Simple Summary

Naproxen was loaded onto a magnetic nanoparticle coated with polyethylene glycol. Magnetic nanoparticles (MNPs) were used in this study to develop a smart naproxen delivery system. One of the most potent COX-1 and COX-2 inhibitors is naproxen, which belongs to the NSAID family of drugs. Although this drug has a short half-life, it has considerable toxicities and side effects on gastrointestinal tissues. The significant potential of our proposed nanocarrier for biomedical applications has been widely recognized; we modified MNPs to attach to this drug via disulfide bonds, promote the selective release of naproxen in inflammatory cells, and prevent adverse effects on the digestive system. It was found that the cytotoxicity of the drug was lowered by this change, which prevented unspecific protein binding.

Abstract

An efficient and selective drug delivery vehicle for cancer cells can remarkably improve therapeutic approaches. In this study, we focused on the synthesis and characterization of magnetic Ni_1−xCo_xFe₂O₄ nanoparticles (NPs) coated with two layers of methionine and polyethylene glycol to increase the loading capacity and lower toxicity to serve as an efficient drug carrier. Ni_1−xCo_xFe₂O₄@Methionine@PEG NPs were synthesized by a reflux method then characterized by FTIR, XRD, FESEM, TEM, and VSM. Naproxen was used as a model drug and its loading and release in the vehicles were evaluated. The results for loading efficiency showed 1 mg of Ni_1−xCo_xFe₂O₄@Methionine@PEG NPs could load 0.51 mg of the naproxen. Interestingly, Ni_1−xCo_xFe₂O₄@Methionine@PEG showed a gradual release of the drug, achieving a time-release up to 5 days, and demonstrated that a pH 5 release of the drug was about 20% higher than Ni_1−xCo_xFe₂O₄@Methionine NPs, which could enhance the intracellular drug release following endocytosis. At pH 7.4, the release of the drug was slower than Ni_1−xCo_xFe₂O₄@Methionine NPs; demonstrating the potential to minimize the adverse effects of anticancer drugs on normal tissues. Moreover, naproxen loaded onto the Ni_1−xCo_xFe₂O₄@Methionine@PEG NPs for breast cancer cell lines MDA-MB-231 and MCF-7 showed more significant cell death than the free drug, which was measured by an MTT assay. When comparing both cancer cells, we demonstrated that naproxen loaded onto the Ni_1−xCo_xFe₂O₄@Methionine@PEG NPs exhibited greater cell death effects on the MCF-7 cells compared with the MDA-MB-231 cells. The results of the hemolysis test also showed good hemocompatibility. The results indicated that the prepared magnetic nanocarrier could be suitable for controlled anticancer drug delivery.

Synthesis of MIL-Modified Fe3O4 Magnetic Nanoparticles for Enhancing Uptake and Efficiency of Temozolomide in Glioblastoma Treatment

A nanometric hybrid system consisting of a Fe₃O₄ magnetic nanoparticles modified through the growth of Fe-based Metal-organic frameworks of the MIL (Materials Institute Lavoiser) was developed. The obtained system retains both the nanometer dimensions and the magnetic properties of the Fe₃O₄ nanoparticles and possesses increased the loading capability due to the highly porous Fe-MIL. It was tested to load, carry and release temozolomide (TMZ) for the treatment of glioblastoma multiforme one of the most aggressive and deadly human cancers. The chemical characterization of the hybrid system was performed through various complementary techniques: X-ray-diffraction, thermogravimetric analysis, FT-IR and X-ray photoelectron spectroscopies. The nanomaterial showed low toxicity and an increased adsorption capacity compared to bare Fe₃O₄ magnetic nanoparticles (MNPs). It can load about 12 mg/g of TMZ and carry the drug into A172 cells without degradation. Our experimental data confirm that, after 48 h of treatment, the TMZ-loaded hybrid nanoparticles (15 and 20 μg/mL) suppressed human glioblastoma cell viability much more effectively than the free drug. Finally, we found that the internalization of the MIL-modified system is more evident than bare MNPs at all the used concentrations both in the cytoplasm and in the nucleus suggesting that it can be capable of overcoming the blood-brain barrier and targeting brain tumors. In conclusion, these results indicate that this combined nanoparticle represents a highly promising drug delivery system for TMZ targeting into cancer cells.

Encapsulation of Photothermal Nanoparticles in Stealth and pH-Responsive Micelles for Eradication of Infectious Biofilms In Vitro and In Vivo

Photothermal nanoparticles can be used for non-antibiotic-based eradication of infectious biofilms, but this may cause collateral damage to tissue surrounding an infection site. In order to prevent collateral tissue damage, we encapsulated photothermal polydopamine-nanoparticles (PDA-NPs) in mixed shell polymeric micelles, composed of stealth polyethylene glycol (PEG) and pH-sensitive poly(β-amino ester) (PAE). To achieve encapsulation, PDA-NPs were made hydrophobic by electrostatic binding of indocyanine green (ICG). Coupling of ICG enhanced the photothermal conversion efficacy of PDA-NPs from 33% to 47%. Photothermal conversion was not affected by micellar encapsulation. No cytotoxicity or hemolytic effects of PEG-PAE encapsulated PDA-ICG-NPs were observed. PEG-PAE encapsulated PDA-ICG-NPs showed good penetration and accumulation in a Staphylococcus aureus biofilm. Penetration and accumulation were absent when nanoparticles were encapsulated in PEG-micelles without a pH-responsive moiety. PDA-ICG-NPs encapsulated in PEG-PAE-micelles found their way through the blood circulation to a sub-cutaneous infection site after tail-vein injection in mice, yielding faster eradication of infections upon near-infrared (NIR) irradiation than could be achieved after encapsulation in PEG-micelles. Moreover, staphylococcal counts in surrounding tissue were reduced facilitating faster wound healing. Thus, the combined effect of targeting and localized NIR irradiation prevented collateral tissue damage while eradicating an infectious biofilm.

Magnetothermally Activated Nanometer-level Modular Functional Group Grafting of Nanoparticles

Nanoparticles with multifunctionality and high colloidal stability are essential for biomedical applications. However, their use is often hindered by the formation of thick coating shells and/or nanoparticle agglomeration. Herein, we report a single nanoparticle coating strategy to form 1 nm polymeric shells with a variety of chemical functional groups and surface charges. Under exposure to alternating magnetic field, nanosecond thermal energy pulses trigger a polymerization in the region only a few nanometers from the magnetic nanoparticle (MNP) surface. Modular coatings containing functional groups, according to the respective choice of monomers, are possible. In addition, the surface charge can be tuned from negative through neutral to positive. We adopted a coating method for use in biomedical targeting studies where obtaining compact nanoparticles with the desired surface charge is critical. A single MNP with a zwitterionic charge can provide excellent colloidal stability and cell-specific targeting.

Modulating the Heat Stress Response to Improve Hyperthermia-Based Anticancer Treatments

Simple Summary

Hyperthermia is a method to expose a tumor to elevated temperatures. Heating of the tumor promotes the effects of various treatment regimens that are based on chemo and radiotherapy. Several aspects, however, limit the efficacy of hyperthermia-based treatments. This review provides an overview of the effects and limitations of hyperthermia and discusses how current drawbacks of the therapy can potentially be counteracted by inhibiting the heat stress response—a mechanism that cells activate to defend themselves against hyperthermia.

Abstract

Cancer treatments based on mild hyperthermia (39–43 °C, HT) are applied to a widening range of cancer types, but several factors limit their efficacy and slow down more widespread adoption. These factors include difficulties in adequate heat delivery, a short therapeutic window and the acquisition of thermotolerance by cancer cells. Here, we explore the biological effects of HT, the cellular responses to these effects and their clinically-relevant consequences. We then identify the heat stress response—the cellular defense mechanism that detects and counteracts the effects of heat—as one of the major forces limiting the efficacy of HT-based therapies and propose targeting this mechanism as a potentially universal strategy for improving their efficacy.

Flash-cooling assisted sol-gel self-ignited synthesis of magnetic carbon dots-based heterostructure with antitumor properties

This work addresses current direction of the nanoparticles-based systems intended for cancer therapy by developing a newly-formulated innovative chemically-engineered anti-tumor composite consisting in a magnetic, fluorescent, lipophilic, and biologically-active carbon heterostructure capable by itself or through coupling with a chemotherapeutic agent to selectively induce tumor cell death. The anti-tumor compound was synthesized through a modified sol-gel method by addition of a low-cost molecule with recently proven anti-tumor properties which was combusted and flash-cooled along with magnetic iron oxides precursors at 250 °C. The synthesized compound consisted in carbon dots, graphene and hematite nanoparticles which endowed the composite with unique simultaneous fluorescence, magnetic and anti-tumor properties. The in-vitro cytotoxicity performed on tumor cells (human osteosarcoma) and normal cells (fibroblasts) showed a selective cytotoxic effect induced after 24 h of treatment by the drug-free composite, leading to a cell death of 37%, for a composite concentration of 0.01 mg/mL per 10⁴ tumor cells, whereas the composite loaded with an antitumor drug (mitoxantrone) boosted the cell death effect to 47% for similar exposure conditions. The method shows high potential as it boosts drug transfer within tumor cells. Different antitumor drugs already in clinical use can be used following their separate or in-cocktail controlled combustion.

The Interplay between Fe3O4 Superparamagnetic Nanoparticles, Sodium Butyrate, and Folic Acid for Intracellular Transport

Combined treatments which use nanoparticles and drugs could be a synergistic strategy for the treatment of a variety of cancers to overcome drug resistance, low efficacy, and high-dose-induced systemic toxicity. In this study, the effects on human colon adenocarcinoma cells of surface modified Fe₃O₄ magnetic nanoparticles (MNPs) in combination with sodium butyrate (NaBu), added as a free formulation, were examined demonstrating that the co-delivery produced a cytotoxic effect on malignant cells. Two different MNP coatings were investigated: a simple polyethylene glycol (PEG) layer and a mixed folic acid (FA) and PEG layer. Our results demonstrated that MNPs with FA (FA-PEG@MNPs) have a better cellular uptake than the ones without FA (PEG@MNPs), probably due to the presence of folate that acts as an activator of folate receptors (FRs) expression. However, in the presence of NaBu, the difference between the two types of MNPs was reduced. These similar behaviors for both MNPs likely occurred because of the differentiation induced by butyrate that increases the uptake of ferromagnetic nanoparticles. Moreover, we observed a strong decrease of cell viability in a NaBu dose-dependent manner. Taking into account these results, the cooperation of multifunctional MNPs with NaBu, taking into consideration the particular cancer-cell properties, can be a valuable tool for future cancer treatment.

Tri-modal imaging of gold-dotted magnetic nanoparticles for magnetic resonance imaging, computed tomography and intravascular ultrasound: an in vitro study

Aim: To examine the multimodal contrasting ability of gold-dotted magnetic nanoparticles (Au*MNPs) for magnetic resonance (MR), computed tomography (CT) and intravascular ultrasound (IVUS) imaging. Materials & methods: Au*MNPs were prepared by adapting an impregnation method, without using surface capping reagents and characterized (transmission electron microscopy, x-ray diffraction and Fourier-transform infrared spectroscopy) with their in vitro cytotoxicity assessed, followed by imaging assessments. Results: The contrast-enhancing ability of Au*MNPs was shown to be concentration-dependent across MR, CT and IVUS imaging. The Au content of the Au*MNP led to evident increases of the IVUS signal. Conclusion: We demonstrated that Au*MNPs showed concentration-dependent contrast-enhancing ability in MRI and CT imaging, and for the first-time in IVUS imaging due to the Au content. These Au*MNPs are promising toward solidifying tri-modal imaging-based theragnostics.

Applications of superparamagnetic iron oxide nanoparticles in drug and therapeutic delivery, and biotechnological advancements

Superparamagnetic iron oxide nanoparticles (SPIONs) have unique properties with regard to biological and medical applications. SPIONs have been used in clinical settings although their safety of use remains unclear due to the great differences in their structure and in intra- and inter-patient absorption and response. This review addresses potential applications of SPIONs in vitro (formulations), ex vivo (in biological cells and tissues) and in vivo (preclinical animal models), as well as potential biomedical applications in the context of drug targeting, disease treatment and therapeutic efficacy, and safety studies.

Delivery of miRNA-Targeted Oligonucleotides in the Rat Striatum by Magnetofection with Neuromag®

MicroRNAs (miRNAs) regulate gene expression at posttranscriptional level by triggering RNA interference. In such a sense, aberrant expressions of miRNAs play critical roles in the pathogenesis of many disorders, including Parkinson’s disease (PD). Controlling the level of specific miRNAs in the brain is thus a promising therapeutic strategy for neuroprotection. A fundamental need for miRNA regulation (either replacing or inhibition) is a carrier capable of delivering oligonucleotides into brain cells. This study aimed to examine a polymeric magnetic particle, Neuromag^®, for delivery of synthetic miRNA inhibitors in the rat central nervous system. We injected the miRNA inhibitor complexed with Neuromag^® into the lateral ventricles next to the striatum, by stereotaxic surgery. Neuromag efficiently delivered oligonucleotides in the striatum and septum areas, as shown by microscopy imaging of fluorescein isothiocyanate (FITC)-labeled oligos in astrocytes and neurons. Transfected oligos showed efficacy concerning miRNA inhibition. Neuromag^®-structured miR-134 antimiR (0.36 nmol) caused a significant 0.35 fold decrease of striatal miR-134, as revealed by real-time quantitative polymerase chain reaction (RT-qPCR). In conclusion, the polymeric magnetic particle Neuromag^® efficiently delivered functional miRNA inhibitors in brain regions surrounding lateral ventricles, particularly the striatum. This delivery system holds potential as a promising miRNA-based disease-modifying drug and merits further pre-clinical studies using animal models of PD.

Magnetic Nanoparticle-Mediated Gene Delivery to Two- and Three-Dimensional Neural Stem Cell Cultures: Magnet-Assisted Transfection and Multifection Approaches to Enhance Outcomes

Neural stem cells (NSCs) have high translational potential in transplantation therapies for neural repair. Enhancement of their therapeutic capacity by genetic engineering is an important goal for regenerative neurology. Magnetic nanoparticles (MNPs) are major non-viral vectors for safe bioengineering of NSCs, offering critical translational benefits over viral vectors, including safety, scalability, and ease of use. This unit describes protocols for the production of suspension (neurosphere) and adherent (monolayer) murine NSC cultures. Genetic engineering of NSCs with MNPs and the application of 'magnetofection' (magnetic fields) or 'multifection' (repeat transfection) approaches to enhance gene delivery are described. Magnetofection of monolayer cultures achieves optimal transfection, but neurospheres offer key advantages for neural graft survival post-transplantation. A protocol is presented which allows the advantageous features of each approach to be combined into a single procedure for transplantation. The adaptation of these protocols for other MNP preparations is considered, with emphasis on the evaluation of procedural safety. © 2017 by John Wiley & Sons, Inc.

In vivo delivery, pharmacokinetics, biodistribution and toxicity of iron oxide nanoparticles

Iron oxide nanoparticles (IONPs) have been extensively used during the last two decades, either as effective bio-imaging contrast agents or as carriers of biomolecules such as drugs, nucleic acids and peptides for controlled delivery to specific organs and tissues. Most of these novel applications require elaborate tuning of the physiochemical and surface properties of the IONPs. As new IONPs designs are envisioned, synergistic consideration of the body's innate biological barriers against the administered nanoparticles and the short and long-term side effects of the IONPs become even more essential. There are several important criteria (e.g. size and size-distribution, charge, coating molecules, and plasma protein adsorption) that can be effectively tuned to control the in vivo pharmacokinetics and biodistribution of the IONPs. This paper reviews these crucial parameters, in light of biological barriers in the body, and the latest IONPs design strategies used to overcome them. A careful review of the long-term biodistribution and side effects of the IONPs in relation to nanoparticle design is also given. While the discussions presented in this review are specific to IONPs, some of the information can be readily applied to other nanoparticle systems, such as gold, silver, silica, calcium phosphates and various polymers.

Remote activation of the Wnt/β-catenin signalling pathway using functionalised magnetic particles

Wnt signalling pathways play crucial roles in developmental biology, stem cell fate and tissue patterning and have become an attractive therapeutic target in the fields of tissue engineering and regenerative medicine. Wnt signalling has also been shown to play a role in human Mesenchymal Stem Cell (hMSC) fate, which have shown potential as a cell therapy in bone and cartilage tissue engineering. Previous work has shown that biocompatible magnetic nanoparticles (MNP) can be used to stimulate specific mechanosensitive membrane receptors and ion channels in vitro and in vivo. Using this strategy, we determined the effects of mechano-stimulation of the Wnt Frizzled receptor on Wnt pathway activation in hMSC. Frizzled receptors were tagged using anti-Frizzled functionalised MNP (Fz-MNP). A commercially available oscillating magnetic bioreactor (MICA Biosystems) was used to mechanically stimulate Frizzled receptors remotely. Our results demonstrate that Fz-MNP can activate Wnt/β-catenin signalling at key checkpoints in the signalling pathway. Immunocytochemistry indicated nuclear localisation of the Wnt intracellular messenger β-catenin after treatment with Fz-MNP. A Wnt signalling TCF/LEF responsive luciferase reporter transfected into hMSC was used to assess terminal signal activation at the nucleus. We observed an increase in reporter activity after treatment with Fz-MNP and this effect was enhanced after mechano-stimulation using the magnetic array. Western blot analysis was used to probe the mechanism of signalling activation and indicated that Fz-MNP signal through an LRP independent mechanism. Finally, the gene expression profiles of stress response genes were found to be similar when cells were treated with recombinant Wnt-3A or Fz-MNP. This study provides proof of principle that Wnt signalling and Frizzled receptors are mechanosensitive and can be remotely activated in vitro. Using magnetic nanoparticle technology it may be possible to modulate Wnt signalling pathways and thus control stem cell fate for therapeutic purposes.

Magnetic poly(glycidyl methacrylate) microspheres for protein capture

The efficient isolation and concentration of protein antigens from complex biological samples is a critical step in several analytical methods, such as mass spectrometry, flow cytometry and immunochemistry. These techniques take advantage of magnetic microspheres as immunosorbents. The focus of this study was on the development of new superparamagnetic polymer microspheres for the specific isolation of the tumor suppressor protein p53. Monodisperse macroporous poly(glycidyl methacrylate) (PGMA) microspheres measuring approximately 5 μm and containing carboxyl groups were prepared by multistep swelling polymerization of glycidyl methacrylate (GMA), 2-[(methoxycarbonyl)methoxy]ethyl methacrylate (MCMEMA) and ethylene dimethylacrylate (EDMA) as a crosslinker in the presence of cyclohexyl acetate as a porogen. To render the microspheres magnetic, iron oxide was precipitated within their pores; the Fe content in the particles received ∼18 wt%. Nonspecific interactions between the magnetic particles and biological media were minimized by coating the microspheres with poly(ethylene glycol) (PEG) terminated by carboxyl groups. The carboxyl groups of the magnetic PGMA microspheres were conjugated with primary amino groups of mouse monoclonal DO-1 antibody using conventional carbodiimide chemistry. The efficiency of protein p53 capture and the degree of nonspecific adsorption on neat and PEG-coated magnetic microspheres were determined by western blot analysis.

Thermal potentiation of chemotherapy by magnetic nanoparticles

Clinical studies have demonstrated the effectiveness of hyperthermia as an adjuvant for chemotherapy and radiotherapy. However, significant clinical challenges have been encountered, such as a broader spectrum of toxicity, lack of patient tolerance, temperature control and significant invasiveness. Hyperthermia induced by magnetic nanoparticles in high-frequency oscillating magnetic fields, commonly termed magnetic fluid hyperthermia, is a promising form of heat delivery in which thermal energy is supplied at the nanoscale to the tumor. This review discusses the mechanisms of heat dissipation of iron oxide-based magnetic nanoparticles, current methods and challenges to deliver heat in the clinic, and the current work related to the use of magnetic nanoparticles for the thermal-chemopotentiation of therapeutic drugs.

Quantum dots conjugated with Fe3O4-filled carbon nanotubes for cancer-targeted imaging and magnetically guided drug delivery

A novel and specific nanoplatform for in vitro simultaneous cancer-targeted optical imaging and magnetically guided drug delivery is developed by conjugating CdTe quantum dots with Fe(3)O(4)-filled carbon nanotubes (CNTs) for the first time. Fe(3)O(4) is filled into the interior of the CNTs, which facilitates magnetically guided delivery and improves the synergetic targeting efficiency. In comparison with that immobilized on the external surface of CNTs, the magnetite nanocrystals inside the CNTs protect it from agglomeration, enhance its chemical stability, and improve the drug loading capacity. It also avoids magnetic nanocrystals-induced quenching of fluorescence of the quantum dots. The SiO(2)-coated quantum dots (HQDs) attached on the surface of CNTs exhibit favorable fluorescence as the hybrid SiO(2) shells on the QDs surface prevent its fluorescence quenching caused by the CNTs. In addition, the hybrid SiO(2) shells also mitigate the toxicity of the CdTe QDs. By coating transferrin on the surface of the herein modified CNTs, it provides a dual-targeted drug delivery system to transport the doxorubicin hydrochloride (DOX) into Hela cells by means of an external magnetic field. The nanocarrier based on the multifunctional nanoplatform exhibits an excellent drug loading capability of ca. 110%, in addition to cancer-targeted optical imaging as well as magnetically guided drug delivery.

T-cell receptor repertoires of tumor-infiltrating lymphocytes after hyperthermia using functionalized magnetite nanoparticles

AIM

Accumulating evidence has indicated that hyperthermia using magnetite nanoparticles induces antitumor immunity. This study investigated the diversity of T-cell receptors (TCRs) in tumor-infiltrating lymphocytes after hyperthermia using magnetite nanoparticles.

MATERIALS & METHODS

Functionalized magnetite nanoparticles, N-propionyl-4-S-cysteaminylphenol (NPrCAP)/magnetite, were synthesized by conjugating the melanogenesis substrate NPrCAP with magnetite nanoparticles. NPrCAP/magnetite nanoparticles were injected into B16 melanomas in C57BL/6 mice, which were subjected to an alternating magnetic field for hyperthermia treatment.

RESULTS

Enlargement of the tumor-draining lymph nodes was observed after hyperthermia. The TCR repertoire was restricted in tumor-infiltrating lymphocytes, and expansion of Vβ11(+) T cells was preferentially found. DNA sequences of the third complementaritydetermining regions revealed the presence of clonally expanded T cells.

CONCLUSION

These results indicate that the T-cell response in B16 melanomas after hyperthermia is dominated by T cells directed toward a limited number of epitopes and that epitope-specific T cells frequently use a restricted TCR repertoire.