RESUMO
Enhanced vascular permeability in tumors plays an essential role in nanoparticle delivery. Prostate-specific membrane antigen (PSMA) is overexpressed on the epithelium of aggressive prostate cancers (PCs). Here, we evaluated the feasibility of increasing the delivery of PSMA-targeted magnetic nanoparticles (MNPs) to tumors by enhancing vascular permeability in PSMA(+) PC tumors with PSMA-targeted photodynamic therapy (PDT). Method: PSMA(+) PC3 PIP tumor-bearing mice were given a low-molecular-weight PSMA-targeted photosensitizer and treated with fluorescence image-guided PDT, 4 h after. The mice were then given a PSMA-targeted MNP immediately after PDT and monitored with fluorescence imaging and T2-weighted magnetic resonance imaging (T2-W MRI) 18 h, 42 h, and 66 h after MNP administration. Untreated PSMA(+) PC3 PIP tumor-bearing mice were used as negative controls. Results: An 8-fold increase in the delivery of the PSMA-targeted MNPs was detected using T2-W MRI in the pretreated tumors 42 h after PDT, compared to untreated tumors. Additionally, T2-W MRIs revealed enhanced peripheral intra-tumoral delivery of the PSMA-targeted MNPs. That finding is in keeping with two-photon microscopy, which revealed higher vascular densities at the tumor periphery. Conclusion: These results suggest that PSMA-targeted PDT enhances the delivery of PSMA-targeted MNPs to PSMA(+) tumors by enhancing the vascular permeability of the tumors.
Assuntos
Antígenos de Superfície/metabolismo , Glutamato Carboxipeptidase II/metabolismo , Nanopartículas de Magnetita/administração & dosagem , Fotoquimioterapia , Neoplasias da Próstata/tratamento farmacológico , Animais , Linhagem Celular Tumoral , Humanos , Imageamento por Ressonância Magnética/métodos , Masculino , Camundongos , Fármacos Fotossensibilizantes/uso terapêutico , Ensaios Antitumorais Modelo de XenoenxertoRESUMO
Magnetic nanoparticle (MNP)-induced hyperthermia is currently being evaluated for localized prostate cancer. We evaluated the feasibility of tumor-selective delivery of prostate-specific membrane antigen (PSMA)-targeted MNPs in a murine model with high-resolution magnetic resonance imaging (MRI) after intravenous administration of MNPs at a concentration necessary for hyperthermia. A PSMA-targeted MNP was synthesized and evaluated using T2-weighted MRI, after intravenous administration of 50 mg/kg of the MNP. Significant contrast enhancement ( P < 0.0002, n = 5) was observed in PSMA(+) tumors compared to PSMA(-) tumors 24 h and 48 h after contrast agent administration. Mice were also imaged with near-infrared fluorescence imaging, to validate the MRI results. Two-photon microscopy revealed higher vascular density at the tumor periphery, which resulted in higher peripheral accumulation of PSMA-targeted MNPs. These results suggest that the delivery of PSMA-targeted MNPs to PSMA(+) tumors is both actively targeted and passively mediated.
Assuntos
Antígenos de Superfície/química , Antígenos de Superfície/metabolismo , Meios de Contraste/química , Glutamato Carboxipeptidase II/química , Glutamato Carboxipeptidase II/metabolismo , Imageamento por Ressonância Magnética , Nanopartículas de Magnetita/química , Neoplasias da Próstata/diagnóstico por imagem , Neoplasias da Próstata/terapia , Animais , Antígenos de Superfície/genética , Estudos de Coortes , Sistemas de Liberação de Medicamentos , Estudos de Viabilidade , Glutamato Carboxipeptidase II/genética , Humanos , Hipertermia Induzida , Masculino , Camundongos , Camundongos Endogâmicos NOD , Camundongos SCID , Imagem Óptica , Células PC-3 , Transfecção , Carga Tumoral/efeitos dos fármacos , Ensaios Antitumorais Modelo de XenoenxertoRESUMO
Exogenous direct cell labeling with superparamagnetic iron oxide nanoparticles (SPIONs) is currently the most employed cell-labeling technique for tracking transplanted cells using magnetic resonance imaging (MRI). Although SPION-based cell labeling is effective for monitoring cell delivery and migration, monitoring cell survival is still a challenge. This unit describes an MRI technique that permits detection of the delivery, migration, and death of transplanted cells. This dual-contrast technique involves labeling cells with two different classes of MRI contrast agents, possessing different diffusion coefficients: SPIONs (T2 /T2* contrast agents, with lower diffusion coefficients) and gadolinium chelates (T1 contrast agents, with higher diffusion coefficients). In live cells, where both agents are in close proximity, the T2 /T2* contrast predominates and the T1 contrast is quenched. In dead cells, where the cell membrane is breached, gadolinium chelates diffuse from the SPIONs and generate a signature T1 contrast enhancement in the vicinity of dead cells. © 2017 by John Wiley & Sons, Inc.
Assuntos
Rastreamento de Células/métodos , Meios de Contraste/farmacologia , Gadolínio/farmacologia , Imageamento por Ressonância Magnética/métodos , Transplante de Células-Tronco , Células-Tronco/metabolismo , Animais , Xenoenxertos , Humanos , CamundongosRESUMO
Cell-based therapies are currently being developed for applications in both regenerative medicine and in oncology. Preclinical, translational, and clinical research on cell-based therapies will benefit tremendously from novel imaging approaches that enable the effective monitoring of the delivery, survival, migration, biodistribution, and integration of transplanted cells. Magnetic resonance imaging (MRI) offers several advantages over other imaging modalities for elucidating the fate of transplanted cells both preclinically and clinically. These advantages include the ability to image transplanted cells longitudinally at high spatial resolution without exposure to ionizing radiation, and the possibility to co-register anatomical structures with molecular processes and functional changes. However, since cellular MRI is still in its infancy, it currently faces a number of challenges, which provide avenues for future research and development. In this review, we describe the basic principle of cell-tracking with MRI; explain the different approaches currently used to monitor cell-based therapies; describe currently available MRI contrast generation mechanisms and strategies for monitoring transplanted cells; discuss some of the challenges in tracking transplanted cells; and suggest future research directions.
Assuntos
Terapia Baseada em Transplante de Células e Tecidos/métodos , Imageamento por Ressonância Magnética/métodos , Rastreamento de Células , Meios de Contraste/química , Humanos , Imagem MolecularRESUMO
Brain tumors are among the most lethal types of tumors. Therapeutic response variability and failure in patients have been attributed to several factors, including inadequate drug delivery to tumors due to the blood-brain barrier (BBB). Consequently, drug delivery strategies are being developed for the local and targeted delivery of drugs to brain tumors. These drug delivery strategies could benefit from new approaches to monitor the delivery of drugs to tumors. Here, we evaluated the feasibility of imaging 4-[bis(2-chloroethyl)amino]-l-phenylalanine (melphalan), a clinically used DNA alkylating agent, using chemical exchange saturation transfer magnetic resonance imaging (CEST MRI), for theranostic applications. We evaluated the physicochemical parameters that affect melphalan's CEST contrast and demonstrated the feasibility of imaging the unmodified drug by saturating its exchangeable amine protons. Melphalan generated a CEST signal despite its reactivity in an aqueous milieu. The maximum CEST signal was observed at pH 6.2. This CEST contrast trend was then used to monitor therapeutic responses to melphalan in vitro. Upon cell death, the decrease in cellular pH from â¼7.4 to â¼6.4 caused an amplification of the melphalan CEST signal. This is contrary to what has been reported for other CEST contrast agents used for imaging cell death, where a decrease in the cellular pH following cell death results in a decrease in the CEST signal. Ultimately, this method could be used to noninvasively monitor melphalan delivery to brain tumors and also to validate therapeutic responses to melphalan clinically.
Assuntos
DNA/química , Imageamento por Ressonância Magnética/métodos , Melfalan/química , Alquilantes/química , Barreira Hematoencefálica/efeitos dos fármacos , Linhagem Celular Tumoral , Meios de Contraste , Células HEK293 , Humanos , Concentração de Íons de HidrogênioRESUMO
This paper reports the damaging effects of magnetic iron-oxide nanoparticles (MNP) on magnetically labeled cancer cells when subjected to oscillating gradients in a strong external magnetic field. Human breast cancer MDA-MB-231 cells were labeled with MNP, placed in the high magnetic field, and subjected to oscillating gradients generated by an imaging gradient system of a 9.4T preclinical MRI system. Changes in cell morphology and a decrease in cell viability were detected in cells treated with oscillating gradients. The cytotoxicity was determined qualitatively and quantitatively by microscopic imaging and cell viability assays. An approximately 26.6% reduction in cell viability was detected in magnetically labeled cells subjected to the combined effect of a static magnetic field and oscillating gradients. No reduction in cell viability was observed in unlabeled cells subjected to gradients, or in MNP-labeled cells in the static magnetic field. As no increase in local temperature was observed, the cell damage was not a result of hyperthermia. Currently, we consider the coherent motion of internalized and aggregated nanoparticles that produce mechanical moments as a potential mechanism of cell destruction. The formation and dynamics of the intracellular aggregates of nanoparticles were visualized by optical and transmission electron microscopy (TEM). The images revealed a rapid formation of elongated MNP aggregates in the cells, which were aligned with the external magnetic field. This strategy provides a new way to eradicate a specific population of MNP-labeled cells, potentially with magnetic resonance imaging guidance using standard MRI equipment, with minimal side effects for the host.
Assuntos
Campos Magnéticos , Nanopartículas de Magnetita/uso terapêutico , Neoplasias de Mama Triplo Negativas/terapia , Linhagem Celular Tumoral , Sobrevivência Celular , Feminino , Humanos , Imageamento por Ressonância Magnética , Nanopartículas de Magnetita/ultraestrutura , Microscopia Eletrônica de Transmissão , Temperatura , Neoplasias de Mama Triplo Negativas/patologiaRESUMO
Stem cell therapies are being developed for radiotherapy-induced brain injuries (RIBI). Magnetic resonance imaging (MRI) offers advantages for imaging transplanted stem cells. However, most MRI cell-tracking techniques employ superparamagnetic iron oxide particles (SPIOs), which are difficult to distinguish from hemorrhage. In current preclinical RIBI models, hemorrhage occurs concurrently with other injury markers. This makes the evaluation of the recruitment of transplanted SPIO-labeled stem cells to injury sites difficult. Here, we developed a RIBI model, with early injury markers reflective of hippocampal dysfunction, which can be detected noninvasively with MRI and behavioral tests. Lesions were generated by sub-hemispheric irradiation of mouse hippocampi with single X-ray beams of 80 Gy. Lesion formation was monitored with anatomical and contrast-enhanced MRI and changes in memory and learning were assessed with fear-conditioning tests. Early injury markers were detected 2 weeks after irradiation. These included an increase in the permeability of the blood-brain barrier, demonstrated by a 92 ± 20 % contrast enhancement of the irradiated versus the non-irradiated brain hemispheres, within 15 min of the administration of an MRI contrast agent. A change in short-term memory was also detected, as demonstrated by a 40.88 ± 5.03 % decrease in the freezing time measured during the short-term memory context test at this time point, compared to that before irradiation. SPIO-labeled stem cells transplanted contralateral to the lesion migrated toward the lesion at this time point. No hemorrhage was detected up to 10 weeks after irradiation. This model can be used to evaluate SPIO-based stem cell-tracking agents, short-term.
Assuntos
Escala de Avaliação Comportamental , Aprendizagem , Imageamento por Ressonância Magnética , Memória , Lesões Experimentais por Radiação/diagnóstico por imagem , Lesões Experimentais por Radiação/psicologia , Animais , Hipocampo/diagnóstico por imagem , Hipocampo/lesões , Hipocampo/efeitos da radiação , Hemorragias Intracranianas/diagnóstico por imagem , Hemorragias Intracranianas/etiologia , Hemorragias Intracranianas/psicologia , Masculino , Camundongos Endogâmicos BALB C , Lesões Experimentais por Radiação/terapia , Transplante de Células-Tronco , Células-Tronco , Raios XRESUMO
Stem cell therapies are currently being investigated for the repair of brain injuries. Although exogenous stem cell labelling with superparamagnetic iron oxide nanoparticles (SPIONs) prior to transplantation provides a means to noninvasively monitor stem cell transplantation by magnetic resonance imaging (MRI), monitoring cell death is still a challenge. Here, we investigate the feasibility of using an MRI dual-contrast technique to detect cell delivery, cell migration and cell death after stem cell transplantation. Human mesenchymal stem cells were dual labelled with SPIONs and gadolinium-based chelates (GdDTPA). The viability, proliferation rate, and differentiation potential of the labelled cells were then evaluated. The feasibility of this MRI technique to distinguish between live and dead cells was next evaluated using MRI phantoms, and in vivo using both immune-competent and immune-deficient mice, following the induction of brain injury in the mice. All results were validated with bioluminescence imaging. In live cells, a negative (T2/T2*) MRI contrast predominates, and is used to track cell delivery and cell migration. Upon cell death, a diffused positive (T1) MRI contrast is generated in the vicinity of the dead cells, and serves as an imaging marker for cell death. Ultimately, this technique could be used to manage stem cell therapies.
Assuntos
Meios de Contraste/química , Imageamento Tridimensional , Imageamento por Ressonância Magnética , Transplante de Células-Tronco Mesenquimais , Células-Tronco Mesenquimais/citologia , Animais , Lesões Encefálicas/diagnóstico , Lesões Encefálicas/patologia , Morte Celular , Movimento Celular , Rastreamento de Células , Gadolínio DTPA , Humanos , Ferro/metabolismo , Medições Luminescentes , Fenômenos Magnéticos , Camundongos Endogâmicos BALB C , Camundongos SCID , Imagens de Fantasmas , Lesões por Radiação/diagnóstico , Lesões por Radiação/patologia , Coloração e RotulagemRESUMO
Magnetic resonance (MR) imaging is advantageous because it concurrently provides anatomic, functional, and molecular information. MR molecular imaging can combine the high spatial resolution of this established clinical modality with molecular profiling inâ vivo. However, as a result of the intrinsically low sensitivity of MR imaging, high local concentrations of biological targets are required to generate discernable MR contrast. We hypothesize that the prostate-specific membrane antigen (PSMA), an attractive target for imaging and therapy of prostate cancer, could serve as a suitable biomarker for MR-based molecular imaging. We have synthesized three new high-affinity, low-molecular-weight Gd(III) -based PSMA-targeted contrast agents containing one to three Gd(III) â chelates per molecule. We evaluated the relaxometric properties of these agents in solution, in prostate cancer cells, and in an inâ vivo experimental model to demonstrate the feasibility of PSMA-based MR molecular imaging.
Assuntos
Antígenos de Superfície/análise , Meios de Contraste , Gadolínio/administração & dosagem , Gadolínio/química , Glutamato Carboxipeptidase II/análise , Imageamento por Ressonância Magnética/métodos , Linhagem Celular Tumoral , Humanos , MasculinoRESUMO
Mitochondria are attractive targets in photodynamic therapy. Two conjugates: TPP-Rh (a porphyrin-rhodamine B conjugate) and TPP-AO (a porphyrin-acridine orange conjugate), each possessing a single delocalized lipophilic cation, were designed and synthesized as photosensitizers. Their ability to target the mitochondria for photodynamic therapy was evaluated. The conjugates were synthesized by conjugating a monohydroxy porphyrin (TPP-OH) to rhodamine B (Rh B) and acridine orange base (AO), respectively, via a saturated hydrocarbon linker. To evaluate the efficiency of the conjugates as photosensitizers, their photophysical properties and in vitro photodynamic activities were studied in comparison to those of TPP-OH. Although fluorescence energy transfer (FRET) was observed in the conjugates, they were capable of generating singlet oxygen at rates comparable to TPP-OH. Biologically, exciting results were observed with TPP-Rh, which showed a much higher phototoxicity [IC(50), 3.95 microM: irradiation of 400-850 nm light (3 mW cm(-2)) for 1 h] than either TPP-OH or Rh B (both, IC(50), >20 microM) without significant dark toxicity at 20 microM. This improved photodynamic activity might be due to a greater cellular uptake and preferential localization in mitochondria. The cellular uptake of TPP-Rh was 8 and 14 times greater than TPP-OH and Rh B, respectively. In addition, fluorescence imaging studies suggest that TPP-Rh localized more in mitochondria than TPP-OH. On the other hand, TPP-AO showed some dark toxicity at 10 microM and stained both mitochondria and nucleus. Our study suggests that conjugation of photosensitizers to Rh might provide two benefits, higher cellular uptake and mitochondrial localization, which are two important subjects in photodynamic therapy.