Assessment of thermal effects of interstitial laser phototherapy on mammary tumors using proton resonance frequency method

In vivo photoacoustic image-guided tumor photothermal therapy and real-time temperature monitoring using a core-shell polypyrrole@CuS nanohybrid

Near-infrared (NIR) laser triggered theranostic platforms are increasingly used in clinical nanomedicine applications. In this work, a core-shell composite consisting of polypyrrole (PPy) coated copper sulfide (CuS) nanospheres with high photothermal efficiency and good photostability has been fabricated via a facile interfacial polymerization. The PPy@CuS nanohybrid had a hydrodynamic diameter of 58.5 nm with a CuS core and PPy shell and exhibited strong optical absorption and photon-to-heat conversion in the NIR region, leading to a sufficient photohyperthermic effect under irradiation with a 808 nm continuous wave laser. In vivo studies showed that the Ppy@CuS nanohybrids produced significant photoacoustic signals and exhibited remarkable photothermal therapeutic efficacy. Furthermore, the core-shell composites exhibited improved temperature elevation and photostability. The temperature-induced changes can be detected and monitored using photoacoustic imaging, thus allowing the control of the thermal dose while minimizing photothermal damage to surrounding healthy tissues. In summary, this study demonstrates that this novel platform could potentially be used for photoacoustic image-guided photothermal therapy and real-time temperature monitoring in cancer theranostics.

Synergistic interventional photothermal therapy and immunotherapy using an iron oxide nanoplatform for the treatment of pancreatic cancer

Pancreatic cancer (PC) is the most lethal malignancy due to its high metastatic ability and poor drug permeability. Here, a synergized interventional photothermal-immunotherapy strategy was developed with imaging guidance and temperature monitoring by magnetic resonance imaging (MRI) technique, for the local treatment of metastatic PC. A tumor microenvironment (TME)-responsive nanoplatform was fabricated via coating of DSPE-PEG and indocyanine green (ICG) onto imiquimod (IMQ) loaded amorphous iron oxide nanoparticles (IONs). This unique nanoplatform, IMQ@IONs/ICG, served as a contrast agent for MRI, a drug delivery vehicle for IMQ and ICG, and a catalyst for TME modulation. The biodegradable IMQ@IONs/ICG was also non-toxic, and improved the penetration of the loaded drugs in PC to maximize thermal ablation of the tumor and minimize damage to the surrounding healthy tissue. For the treatment of aggressive, metastatic Panc02-H7 pancreatic tumors in mice, ION-assisted MRI was employed to guide the administration of interventional photothermal therapy (IPTT) and monitor the temperature distribution in target tumor and surrounding tissue during treatment. The local IPTT treatment induced in situ immunogenic cell death (ICD), and, in combination with released IMQ, triggered a strong antitumor immunity, leading to decreased metastases and increased CD8+ in spleen and tumors. With precise local treatment and monitoring, treated primary tumors were completely eradicated, mesentery metastases were dramatically reduced, and the survival time was significantly prolonged, without damage to normal tissue and systemic autoimmunity. Overall, this synergistic strategy represents a promising approach to treat PC with significant potential for clinical applications. STATEMENT OF SIGNIFICANCE: Pancreatic cancer (PC) is one of the most lethal malignancies because it is non-permeable to drugs and highly metastatic. In this study, we designed a tumor microenvironment-responsive amorphous iron oxide nanoplatform (ION) to co-deliver photothermal agent (ICG) and toll-like-receptor-7 agonist (IMQ). This biodegradable nanoplatform IMQ@IONs/ICG improved the penetration of the loaded drugs in pancreatic tumor. With MR imaging guidance and temperature monitoring, the precise interventional photothermal therapy on mouse Panc02-H7 orthotopic tumors releases tumor antigens to initiate tumor-special immune responses, amplified by the released IMQ. Our results demonstrate that IMQ@IONs/ICG overcomes the obstacle of drug delivery to pancreatic tumors, and when combined with photothermal therapy, induces a systemic antitumor immunity to control metastatic tumors.

Laser-induced optothermal response of gold nanoparticles: From a physical viewpoint to cancer treatment application

Gold nanoparticles (GNPs)-based photothermal therapy (PTT) is a promising minimally invasive thermal therapy for the treatment of focal malignancies. Although GNPs-based PTT has been known for over two decades and GNPs possess unique properties as therapeutic agents, the delivery of a safe and effective therapy is still an open question. This review aims at providing relevant and recent information on the usage of GNPs in combination with the laser to treat cancers, pointing out the practical aspects that bear on the therapy outcome. Emphasis is given to the assessment of the GNPs' properties and the physical mechanisms underlying the laser-induced heat generation in GNPs-loaded tissues. The main techniques available for temperature measurement and the current theoretical simulation approaches predicting the therapeutic outcome are reviewed. Topical challenges in delivering safe thermal dosage are also presented with the aim to discuss the state-of-the-art and the future perspective in the field of GNPs-mediated PTT.

Monitoring tissue temperature during photothermal therapy for cancer

Phototherapies offer promising alternatives to traditional cancer therapies. Phototherapies mainly rely on manipulation of target tissue through photothermal, photochemical, or photomechanical interactions. Combining phototherapy with immunotherapy has the benefit of eliciting a systemic immune response. Specifically, photothermal therapy (PTT) has been shown to induce apoptosis and necrosis in cancer cells, releasing tumor associated antigenic peptides while sparing healthy host cells, through temperature increase in targeted tissue. However, the tissue temperature must be monitored and controlled to minimize adverse thermal effects on normal tissue and to avoid the destruction of tumor-specific antigens, in order to achieve the desired therapeutic effects of PTT. Techniques for monitoring PTT have evolved from post-treatment quantification methods like enzyme linked immunosorbent assay, western blot analysis, and flow cytometry to modern methods capable of real-time monitoring, such as magnetic resonance thermometry, computed tomography, and photoacoustic imaging. Monitoring methods are largely chosen based on the type of light delivery to the target tissue. Interstitial methods of thermometry, such as thermocouples and fiber-optic sensors, are able to monitor temperature of the local tumor environment. However, these methods can be challenging if the phototherapy itself is interstitially administered. Increasingly, non-invasive therapies call for non-invasive monitoring, which can be achieved through magnetic resonance thermometry, computed tomography, and photoacoustic imaging techniques. The purpose of this review is to introduce the feasible methods used to monitor tissue temperature during PTT. The descriptions of different techniques and the measurement examples can help the researchers and practitioners when using therapeutic PTT.

Characteristics of temperature changes in photothermal therapy induced by combined application of indocyanine green and laser

Photothermal therapy, a type of laser application, has the ability to eradicate tumor cells by a local thermal effect and elicit a tumor specific immune response. Indocyanine green (ICG), a photosensitizer, can effectively elevate the local temperature by absorbing energy from the laser. The present study aimed to investigate the characteristics of temperature changes during photothermal therapy with an infrared thermometer in an ICG solution and in tumor-bearing mice treated with a combination of laser and ICG. Additionally, the present study observed the morphological changes of tumor tissue by hematoxylin-eosin staining following photothermal therapy. In the solution experiment, when the laser power density was 1 W/cm² and the concentration of ICG was 0 or 0.0187 mg/ml, the temperature of the water was elevated by 3 and 28°C, respectively. In the tumor-bearing mice experiment, when the laser power density was 1 W/cm² and the concentration of ICG was 0 and 0.1 mg/ml, the temperature of the tumor-bearing mice was elevated by 6.9 and 28.5°C, respectively. With an increase in laser power density, including 0.6, 0.8 and 1.0 W/cm², the temperature was 23.3, 26.7 and 28.5°C, respectively. Pathological tissue sections demonstrated that a large number of tumor cells experienced necrosis, and the envelope of the tumor was destroyed. Numerous inflammatory cells, in particular lymphocytes, infiltrated into the tumor tissue following tumor tissue treatment with a combination of laser and ICG. These results indicated that a combination treatment with laser and ICG may significantly increase the temperature of the water solutions and in the tumor-bearing mice. The concentration of ICG and laser power density contributed to the temperature elevation, in particular to the concentration of ICG.

Simultaneous Evaluation of Thermal and Non-Thermal Effects of High-Intensity Focused Ultrasound on a Tissue-Mimicking Phantom

Physiologically relevant phantoms with high reliability are essential for extending the therapeutic applications of high-intensity therapeutic ultrasound. Here we describe a tissue-mimicking phantom capable of quantifying temperature changes and observing non-thermal phenomena by high-intensity therapeutic ultrasound. Using polydiacetylene liposomes, we fabricated agar-based polydiacetylene hydrogel phantoms (PHPs) that not only respond to temperature, but also have acoustic properties similar to those of human liver tissue. The color of PHPs changed from blue to red depending on the temperature in the range 40°C-70°C, where the red/blue ratio of PHP had a good linearity of 99.06% for the temperature changes. Furthermore, repeated high-intensity focused ultrasound led to histotripsy on the PHP with liquefied and damaged areas measuring 0.7 and 4.0 cm², respectively, at the signal generator amplitude setting voltage of 80 mV. Our results indicate not only the usability of the thermochromic phantom, but also its potential for evaluating non-thermal phenomena in various high-intensity focused ultrasound therapies.

Determination of temperature distribution in tissue for interstitial cancer photothermal therapy

BACKGROUND

Temperature increase in tumour tissue during photothermal therapy (PTT) is a significant factor in determining the outcomes of the treatment. Therefore, controlling and optimising temperature distribution in target tissue is crucial for PTT. In this study, we developed a unique ex vivo device to study the temperature distribution during PTT to be used as a guide for the desired photothermal effects for cancer treatment.

METHODS

Bovine liver tissue buried inside agarose gel served as a phantom tumour surrounded by normal tissue. A thermostatic incubator was used to simulate tissue environment in live animals. The temperature distributions were measured by thermocouples with needle probes at different locations inside the target tissue, during laser irradiation using an 805-nm laser.

RESULTS

The results obtained using the ex vivo device were verified by comparing the tissue temperature directly measured in animal tumours irradiated under the same conditions. With this model, the spatial distribution of temperature in target tissue can be monitored in real time. A two-dimensional temperature distribution in target tissue allows us to establish the correlations among laser parameters, temperature distribution and tumour size. In addition, the optimal temperature range for tumour destruction and immunological stimulation was determined using metastatic rat mammary tumour model.

CONCLUSION

The device and method developed in this study can provide guidance for choosing the appropriate treatment parameters for optimal photothermal effects, particularly when combined with immunotherapy, for cancer treatment.

Interstitial photoacoustic sensor for the measurement of tissue temperature during interstitial laser phototherapy

Photothermal therapy is an effective means to induce tumor cell death, since tumor tissue is more sensitive to temperature increases than normal tissue. Biological responses depend on tissue temperature; target tissue temperature needs to be precisely measured and controlled to achieve desired thermal effects. In this work, a unique photoacoustic (PA) sensor is proposed for temperature measurement during interstitial laser phototherapy. A continuous-wave laser light and a pulsed laser light, for photothermal irradiation and photoacoustic temperature measurement, respectively, were delivered to the target tissue through a fiber coupler. During laser irradiation, the PA amplitude was measured. The Grüneisen parameter and the bioheat equation were used to determine the temperature in strategic positions in the target tissue. Our results demonstrate that the interstitial PA amplitude is a linear function of temperature in the range of 22 to 55 °C, as confirmed by thermocouple measurement. Furthermore, by choosing appropriate laser parameters, the maximum temperature surrounding the active diffuse fiber tip in tissue can be controlled in the range of 41 to 55 °C. Thus, this sensor could potentially be used for fast, accurate, and convenient three-dimensional temperature measurement, and for real-time feedback and control of interstitial laser phototherapy in cancer treatment.

InCVAX--a novel strategy for treatment of late-stage, metastatic cancers through photoimmunotherapy induced tumor-specific immunity

A novel, promising potential cancer vaccine strategy was proposed to use a two-injection procedure for solid tumors to prompt the immune system to identify and systemically eliminate primary and metastatic cancers. The two-injection procedure consists of local photothermal application on a selected tumor intended to liberate whole cell tumor antigens, followed by a local injection of an immunoadjuvant that consists of a semi-synthetic functionalized glucosamine polymer, N-dihydro-galacto-chitosan (GC), which is intended to activate antigen presenting cells and facilitate an increased uptake of tumor antigens. This strategy is thus proposed as an in situ autologous cancer vaccine (inCVAX) that may activate antigen presenting cells and expose them to tumor antigens in situ, with the intention of inducing a systemic tumor specific T-cell response. Here, the development of inCVAX for the treatment of metastatic cancers in the past decades is systematically reviewed. The antitumor immune responses of local photothermal treatment and immunological stimulation with GC are also discussed. This treatment approach is also commonly referred to as laser immunotherapy (LIT).

Chitin, chitosan, and glycated chitosan regulate immune responses: the novel adjuvants for cancer vaccine

With the development of cancer immunotherapy, cancer vaccine has become a novel modality for cancer treatment, and the important role of adjuvant has been realized recently. Chitin, chitosan, and their derivatives have shown their advantages as adjuvants for cancer vaccine. In this paper, the adjuvant properties of chitin and chitosan were discussed, and some detailed information about glycated chitosan and chitosan nanoparticles was also presented to illustrate the trend for future development.