Photodynamic therapy within edematous brain tissue: considerations on sensitizer dose and time point of laser irradiation

Nanomedicine and Early Cancer Diagnosis: Molecular Imaging using Fluorescence Nanoparticles

Incorporating nanotechnology into fluorescent imaging and magnetic resonance imaging (MRI) has shown promising potential for accurate diagnosis of cancer at an earlier stage than the conventional imaging modalities. Molecular imaging (MI) aims to quantitatively characterize, visualize, and measure the biological processes or living cells at molecular and genetic levels. MI modalities have been exploited in different applications including noninvasive determination and visualization of diseased tissues, cell trafficking visualization, early detection, treatment response monitoring, and in vivo visualization of living cells. High-affinity molecular probe and imaging modality to detect the probe are the two main requirements of MI. Recent advances in nanotechnology and allied modalities have facilitated the use of nanoparticles (NPs) as MI probes. Within the extensive group of NPs, fluorescent NPs play a prominent role in optical molecular imaging. The fluorescent NPs used in molecular and cellular imaging can be categorized into three main groups including quantum dots (QDs), upconversion, and dyedoped NPs. Fluorescent NPs have great potential in targeted theranostics including cancer imaging, immunoassay- based cells, proteins and bacteria detections, imaging-guided surgery, and therapy. Fluorescent NPs have shown promising potentials for drug and gene delivery, detection of the chromosomal abnormalities, labeling of DNA, and visualizing DNA replication dynamics. Multifunctional NPs have been successfully used in a single theranostic modality integrating diagnosis and therapy. The unique characteristics of multifunctional NPs make them potential theranostic agents that can be utilized concurrently for diagnosis and therapy. This review provides the state of the art of the applications of nanotechnologies in early cancer diagnosis focusing on fluorescent NPs, their synthesis methods, and perspectives in clinical theranostics.

Breakthroughs in medicine and bioimaging with up-conversion nanoparticles

Nanomedicine is a medical application of biochemistry incorporated with materials chemistry at the scale of nanometer for the purpose of diagnosis, prevention, and treatment. New models and approaches are typically associated with nanomedicine for precise multifunctional diagnostic systems at molecular level. Hence, employing nanoparticles (NPs) has unveiled new opportunities for efficient therapies and remedy of difficult-to-cure diseases. Among all types of inorganic NPs, lanthanide-doped up-conversion nanoparticles (UCNPs) have shown excellent potential for biomedical applications, especially for multimodal bioimaging including fluorescence and electron microscopy. Association of these visualization techniques plus the capability for transporting biomaterials and drugs make them superior agents in the field of nanomedicine. Accordingly, in this review, we firstly presented a fundamental understanding of physical and optical properties of UCNPs and secondly, we illustrated some of the prominent associations with bioimaging, theranostics, cancer therapy, and optogenetics.

THE ROLE OF PHOTODYNAMIC THERAPY IN THE TREATMENT OF PRIMARY, RECURRENT AND METASTATIC MALIGNANT BRAIN TUMORS

Photodynamic therapy is a relevant and promising area for research in the field of clinical neuroonocology. Application of modern developments in the field of laser technologies and new photosensitizers allows us to refer to this field as to high-tech. According to various authors, the inclusion of photodynamic therapy in combined and complex treatments of patients with malignant brain tumors allows achieving overall survival median of patients from 11 to 26 months for primary form of glioblastoma, and from 7.5 to 15 months - for recurrent forms of glioblastoma. Certain results have been achieved in the treatment of patients with metastatic brain lesion. In this publication the authors analyzed and systematized the results of the main clinical studies in the field of fluorescent diagnostics and intraoperative photodynamic therapy of primary, recurrent and metastatic forms of malignant brain tumors.

Aminolevulinic acid-mediated photodynamic therapy of human meningioma: an in vitro study on primary cell lines

OBJECTIVE

Five-aminolevulinic acid (5-ALA)-induced porphyrins in malignant gliomas are potent photosensitizers. Promising results of ALA-PDT (photodynamic therapy) in recurrent glioblastomas have been published. Recently, 5-ALA-induced fluorescence was studied in meningioma surgery. Here, we present an experimental study of ALA-PDT in an in vitro model of primary meningioma cell lines.

METHODS

We processed native tumor material obtained intra-operatively within 24 h for cell culture. Epithelial membrane antigen (EMA) immunohistochemistry was performed after the first passage to confirm that cells were meningioma cells. For 5-ALA-PDT treatment, about 5000 cells per well were seeded in 20 wells of a blank 96-well plate. Each block of 4 wells was inoculated with 150 µL of 0, 25, 50 and 100 µg/mL 5-ALA solutions; one block was used as negative control without 5-ALA and without PDT. Following incubation for 3 h PDT was performed using a laser (635 nm, 18.75 J/cm²). The therapeutic response was analyzed by the water soluble tetrazolium salt (WST-1) cell viability assay 90 min after PDT.

RESULTS

5-ALA-PDT was performed in 14 primary meningioma cell lines. EMA expression was verified in 10 primary cell cultures. The remaining 4 were EMA negative and PDT was without any effect in these cultures. All 10 EMA-positive cell lines showed a significant and dose-dependent decrease in viability rate (p < 0.001). Cell survival at 5-ALA concentrations of 12.5, 25, 50 and 100 μg/mL was 96.5% ± 7.6%, 67.9% ± 29.9%, 24.0% ± 16.7% and 13.8% ± 7.5%, respectively. For the negative controls (no 5-ALA/PDT and ALA/no PDT), the viability rates were 101.72% ± 3.5% and 100.17% ± 3.6%, respectively. The LD50 for 5-ALA was estimated between 25 and 50 µg/mL.

CONCLUSION

This study reveals dose-dependent cytotoxic effects of 5-ALA-PDT on primary cell lines of meningiomas. Either 5-ALA or PDT alone did not affect cell survival. Further efforts are necessary to study the potential therapeutic effects of 5-ALA-PDT in vivo.

The tumour is not enough or is it? Problems and new concepts in the surgery of cerebral metastases

Cerebral metastases are the most frequent cerebral tumours. Surgery of cerebral metastases plays an indispensible role in a multimodal therapy concept. Conventional white-light, microscopy assisted microsurgical and circumferential stripping of cerebral metastases is neurosurgical standard therapy, but is associated with an extraordinarily high recurrence rate of more than 50% without subsequent whole-brain radiotherapy. Therefore, neurosurgical standard therapy fails to achieve local tumour control in many patients. The present conceptual paper focuses on this issue and discusses the possible causes of the high recurrence rates such as intraoperative dissemination of tumour cells or the lack of sharp delimitation of metastases from the surrounding brain tissue resulting in incomplete resections. Adjuvant whole-brain radiotherapy reduces the risk of local and distant recurrences, but is associated with a well-documented impairment of neurocognitive function. New surgical strategies, such as supramarginal or fluorescence-guided resection, address the possibility of infiltrating tumour parts to achieve more complete resection of cerebral metastases. Supramarginal resection was shown to significantly reduce the risk of a local recurrence and prolongs two-year survival rates. Furthermore, radiosurgery in combination with surgery represents a promising approach.

Is it a glioblastoma? In dubio pro 5-ALA!

BACKGROUND

Differential diagnosis of unclear contrast-enhancing cerebral lesions includes cerebral metastases as well as malignant glioma. In the majority of cases, a definite preoperative diagnosis by neuroradiological assessment alone cannot be made. Since the introduction of 5-ALA-induced fluorescence-guided resection in the treatment of glioblastoma (GBM), the preoperative putative diagnosis of metastasis vs. GBM triggers a specific preoperative preparation of the patients. We analyzed the patient population with known cancer outside the central nervous system who underwent surgery for an assumed cerebral metastasis and for whom the intraoperative diagnosis was corrected to a malignant glioma.

METHODS

Retrospective analysis of patients with a known primary cancer who were operated on for an assumed cerebral metastasis, which turned out to be a GBM. The patients were treated at our center between January 2008 and June 2011.

RESULTS

We identified ten patients who underwent surgery for an assumed cerebral metastasis and for whom the diagnosis was corrected intraoperatively to a malignant glioma by frozen section. The median age was 68 years (41-82 years). The female-to-male ratio was 2:8. In all patients, the final histopathological analysis of the intracerbral tumors revealed a glioblastoma, while the patients suffered from diverse primary carcinomas.

CONCLUSION

A malignant glioma should always be considered as a differential diagnosis of an unclear contrast-enhancing cerebral lesion even for patients with a known malignancy. Furthermore, we make the case for a more liberal indication for 5-ALA.

Upconversion nanomaterials: synthesis, mechanism, and applications in sensing

Upconversion is an optical process that involves the conversion of lower-energy photons into higher-energy photons. It has been extensively studied since mid-1960s and widely applied in optical devices. Over the past decade, high-quality rare earth-doped upconversion nanoparticles have been successfully synthesized with the rapid development of nanotechnology and are becoming more prominent in biological sciences. The synthesis methods are usually phase-based processes, such as thermal decomposition, hydrothermal reaction, and ionic liquids-based synthesis. The main difference between upconversion nanoparticles and other nanomaterials is that they can emit visible light under near infrared irradiation. The near infrared irradiation leads to low autofluorescence, less scattering and absorption, and deep penetration in biological samples. In this review, the synthesis of upconversion nanoparticles and the mechanisms of upconversion process will be discussed, followed by their applications in different areas, especially in the biological field for biosensing.

5-aminolevulinic acid (5-ALA)-induced fluorescence in intracerebral metastases: a retrospective study

BACKGROUND

Microsurgical, circumferential stripping of intracerebral metastases often proves to be insufficient to prevent local tumor recurrence.

OBJECTIVE

We were interested in the potential impact of 5-aminolevulinic acid (5-ALA)-induced-fluorescence (5-AIF) as a diagnostic tool for the resection of intracerebral metastases.

METHODS

A retrospective analysis was performed for 52 patients who underwent 5-AIF-guided resection for intracerebral mass lesions that histologically corresponded to metastases from tumors outside the central nervous system. The presence of ALA fluorescence in the tumor was determined in each patient. In 42 patients, fluorescence of the resection cavity after tumor removal was additionally recorded. Data were correlated with neuropathological findings in tissue specimens.

RESULTS

A total of 32 of the 52 metastases (62%) exhibited 5-AIF in tumor parts. All 5-AIF-positive metastases exhibited an inhomogeneous fluorescence pattern. 5-AIF was neither associated with the histological type nor with the site of origin of the metastases. Residual fluorescence of the resection cavity was detected after macroscopically complete white light resection in 24 patients with 5-AIF positive metastases. Residual tumor tissue was histologically confirmed in 6 of 18 patients with available tissue specimens from such 5-AIF positive areas (33%).

CONCLUSIONS

The majority of metastases (62%) were 5-AIF positive, suggesting a potential impact of 5-AIF for improved visualization of metastatic tumor tissue within the brain. However, residual 5-AIF after macroscopically complete resection of a metastasis needs to be interpreted with caution because of the limited specificity for detection of residual tumor tissue.

Singlet oxygen-induced apoptosis of cancer cells using upconversion fluorescent nanoparticles as a carrier of photosensitizer

The photodynamic effect of upconversion nanoparticles loaded with a photosensitizer was studied on murine bladder cancer cells (MB49). Mesoporous silica was coated onto sodium yttrium fluoride upconversion nanocrystals to form a core-shell structure and then loaded with the photosensitizer zinc (II)-phthalocyanine into the porous silica. The nanoparticles displayed a uniform spherical shape with an average diameter of about 50 nm and showed good dispersibility in water. Intracellular uptake study in MB49 cells revealed a time- and concentration-dependent accumulation of these nanoparticles. Upon irradiation with 980-nm near-infrared light, their efficiency in activating the loaded zinc (II)-phthalocyanine to generate singlet oxygen molecules was confirmed in live cells. The cytotoxic effect of the released singlet oxygen from the nanoplatform was proven by cell viability assay, confocal microscopy, DNA agarose gel electrophoresis, cytochrome c-releasing assay, and prostate-specific antigen-enzyme-linked immunosorbent assay, all of which showed a strong photodynamic effect of the nanoparticles on MB49 cells. This suggests the efficacy of sodium yttrium fluoride upconversion nanoparticles as a carrier for photosensitizers and their use in photodynamic therapy of cancer and some other diseases.

FROM THE CLINICAL EDITOR

In this study, the photodynamic effect of upconversion nanoparticles loaded with a photosensitizer was investigated on murine bladder cancer cells, with strongly positive results, which may pave its way to future clinical use in malignant tumors and potentially other diseases.

Long-sustaining response in a patient with non-resectable, distant recurrence of glioblastoma multiforme treated by interstitial photodynamic therapy using 5-ALA: case report

Glioblastoma multiforme continues to be a devastating disease despite modest improvements in survival achieved at present, and there is an urgent need for innovative treatment concepts. Five-aminolevulinic acid (ALA) is a drug which induces protoporphyrin IX accumulation in malignant gliomas and has been explored for fluorescence-guided resections of these tumors. ALA is also under investigation as a photosensitizer. We report a case of a patient with prior left frontal glioblastoma multiforme treated by surgery, radiation and chemotherapy, who developed a remote lesion in the left insula, which was refractory to secondary treatments. In a compassionate use setting she was treated by oral application of ALA (20 mg/kg bodyweight), and stereotactic phototherapy achieved by positioning four laser diffusors using 3-dimensional irradiation planning, and a 633 nm diode laser. The lesion disappeared 24 h after therapy. Circumferential contrast enhancement was observed at 72 h, which disappeared in the course of subsequent months. Edema resolved completely. The patient is still free of recurrence 56 months after treatment, demonstrating an impressive and long-lasting response to this novel mode of therapy.

Interstitial photodynamic therapy of nonresectable malignant glioma recurrences using 5-aminolevulinic acid induced protoporphyrin IX

BACKGROUND AND OBJECTIVE

Limited knowledge of the light and temperature distribution within the target volume in combination with non-selective accumulation of the applied photosensitizers (PS) has hampered the clinical relevance of interstitial photodynamic therapy (iPDT) for treatment of malignant glioma patients. The current pilot study focused on the development and the clinical implementation of an accurate and reproducible irradiation scheme for iPDT using 5-aminolevulinic acid (5-ALA) induced protoporphyrin IX (PPIX) as a selectively working PS.

STUDY DESIGN/MATERIALS AND METHODS

Monte Carlo simulations of fluence rate and heat transport simulations were performed using the optical properties of normal brain tissue infiltrated by tumor cells (absorption coefficient micro(a) = 0.2 cm(-1), reduced scattering coefficient: micro'(s) = 20 cm(-1)). A modified 3-D treatment-planning software was used to calculate both, the treatment-volume and the exact position of the light diffusers within the lesion. The feasibility and the risk of iPDT were tested in 10 patients with small and circumscribed recurrent malignant gliomas.

RESULTS

The optimum distance between the implanted light diffusers was determined to be 9 mm with regard to both fluence rate and temperature distribution. For this distance a temperature increase above 42 degrees C was not expected to occur. Up to six cylindrical light diffusers were stereotactically implanted to achieve a complete irradiation of the tumor volume, which was possible in every single patient (mean tumor volume: 5.9 cm3). The total applied light fluence was between 4,320 J and 11,520 J. Side effects of iPDT were not observed. Median survival was 15 months.

CONCLUSION

5-ALA iPDT in combination with a 3-D treatment-planning (which was based on optical and thermal simulations) is a safe and feasible treatment modality. The clinical impact of these findings deserves further prospective evaluation.

Acute morphological sequelae of photodynamic therapy with 5-aminolevulinic acid in the C6 spheroid model

OBJECTIVE

Aminolevulinic acid (ALA)-mediated photodynamic therapy (PDT) may represent a treatment option for malignant brain tumors. We used a three-dimensional cell culture system, the C6 glioma spheroid model, to study acute effects of PDT and how they might be influenced by treatment conditions.

METHODS

Spheroids were incubated for 4 h in 100 microg/ml ALA in 5% CO(2) in room air or 95% O(2) with subsequent irradiation using a diode laser (lambda = 635 nm, 40 mW/cm(2), total fluence 25 J/cm(2)). Control groups were "laser only", "ALA only", and "no drug no light". Annexin V-FITC, a marker used for detection of apoptosis, propidium iodide (PI), a marker for necrotic cells and H 33342, a chromatin stain, were used for morphological characterization of PDT effects by confocal laser scanning and fluorescence microscopy. Hematoxylin-eosin staining and TdT-FragEL (TUNEL) assay were used on cryosections. Growth kinetics were followed for 8 days after PDT.

RESULTS

PDT after incubation in 5% CO(2) provided incomplete cell death and growth delay in spheroids of >350 microm diameter. However, complete cell death and growth arrest occurred in smaller spheroids (<350 microm). Incubation in 95% O(2) with subsequent PDT resulted in complete cell death and growth arrest regardless of spheroid size. In incompletely damaged spheroids viable cells were restricted to spheroid centers. The rate of cell death in all control groups was negligible. Cell death was accompanied by annexin/PI costaining, but there was also evidence for annexin V-FITC staining without PI uptake.

CONCLUSIONS

PDT of experimental glioma results in rapid and significant cell death that could be verified as acute necrosis immediately after irradiation. This effect depended on O(2) concentration and spheroid size.

New light on the brain: The role of photosensitizing agents and laser light in the management of invasive intracranial tumors

Invasive intracranial tumors, particularly malignant gliomas, are very difficult to eradicate surgically and carry a dismal prognosis. The vast majority relapse locally indicating that their cure is dependent on radical and complete local excision. However, their ability to invade and hide among normal brain tissue, our inability to visualize and detect them, the low tolerance of brain tissue to ionizing radiation and the presence of the blood brain barrier are the main causes of our failure to eradicate them. Photodynamic detection with 100% specificity and more than 80% sensitivity offers an excellent chance of visualizing camouflaged tumor nests. Also, photodynamic therapy offers a very good chance of targeted destruction of the remaining tumor cells safely following surgical excision and may double the survival of patients harboring these awful tumors. More work needs to be done to refine this promising technology to exploit it to its full potential.

Photoirradiation therapy of experimental malignant glioma with 5-aminolevulinic acid

OBJECT

Accumulation of protoporphyrin IX (PPIX) in malignant gliomas is induced by 5-aminolevulinic acid (5-ALA). Because PPIX is a potent photosensitizer, the authors sought to discover whether its accumulation might be exploited for use in photoirradiation therapy of experimental brain tumors, without injuring normal or edematous brain.

METHODS

Thirty rats underwent craniotomy and were randomized to the following groups: 1) photoirradiation of cortex (200 J/cm2, 635-nm argon-dye laser); 2) photoirradiation of cortex (200 J/cm2) 6 hours after intravenous administration of 5-ALA (100 mg/kg body weight); 3) cortical cold injury for edema induction; 4) cortical cold injury with simultaneous administration of 5-ALA (100 mg/kg body weight) and photoirradiation of cortex (200 J/cm2) 6 hours later; or 5) irradiation of cortex (200 J/cm2) 6 hours after intravenous administration of Photofrin II (5 mg/kg body weight). Tumors were induced by cortical inoculation of C6 cells and 9 days later, magnetic resonance (MR) images were obtained. On Day 10, animals were given 5-ALA (100 mg/kg body weight) and their brains were irradiated (100 J/cm2) 3 or 6 hours later. Seventy-two hours after irradiation, the brains were removed for histological examination. Irradiation of brains after administration of 5-ALA resulted in superficial cortical damage, the effects of which were not different from those of the irradiation alone. Induction of cold injury in combination with 5-ALA and irradiation slightly increased the depth of damage. In the group that received irradiation after intravenous administration of Photofrin II the depth of damage inflicted was significantly greater. The extent of damage in response to 5-ALA and irradiation in brains harboring C6 tumors corresponded to the extent of tumor determined from pretreatment MR images.

CONCLUSIONS

Photoirradiation therapy in combination with 5-ALA appears to damage experimental brain tumors selectively, with negligible damage to normal or perifocal edematous tissue.

Optimal light dose for interstitial photodynamic therapy in treatment for malignant brain tumors

BACKGROUND AND OBJECTIVE

The primary goal was to determine the maximal tolerable light dose that can be administered to patients undergoing multifiber interstitial photodynamic therapy (PDT) of malignant brain tumors at a fixed dose of photosensitizer.

STUDY DESIGN/MATERIALS AND METHODS

Eighteen patients (12 glioblastomas, 5 anaplastic astrocytoma, and 1 malignant ependymoma) were included in this study. The total light dose delivered to the tumor was divided into three groups of six patients each: 1,500-3,700 J, 3,700-4,400 J, and 4,400-5,900 J.

RESULTS

Five patients (all glioblastomas) demonstrated postoperative permanent neurologic deficits. None of the patients in 1,500-3,700 J, two patients in 3,700-4,400 J, and three patients in 4,400-5,900 J had neurologic deficits. Glioblastomas recurred more often than anaplastic astrocytomas. Increasing the light dose did not make a difference in local/regional control of glioblastomas. Patients with anaplastic astrocytomas survived (mean, 493 days) longer than patients with glioblastomas (mean, 116.5 days) after PDT. Four patients had prolonged survival (more than a year) after PDT.

CONCLUSIONS

Increasing the total light dose delivered to the tumor increases the odds of having a permanent neurologic deficit but does not increase survival or time to tumor progression. There was no difference in local or marginal recurrence with increasing light dose. Recurrent anaplastic astrocytomas tend to do better than recurrent glioblastomas with PDT.