Evaluation of knowledge-based planning models for male pelvic CBCT-based online adaptive radiotherapy on conventional linear accelerators.

PURPOSE: To assess the practicality of employing a commercial knowledge-based planning tool (RapidPlan) to generate adapted intact prostate and prostate bed volumetric modulated arc therapy (VMAT) plans on iterative cone-beam computed tomography (iCBCT) datasets. METHODS AND MATERIALS: Intact prostate and prostate bed RapidPlan models were trained utilizing planning data from 50 and 44 clinical cases, respectively. To ensure that refined models were capable of producing adequate clinical plans with a single optimization, models were tested with 50 clinical planning CT datasets by comparing dose-volume histogram (DVH) and plan quality metric (PQM) values between clinical and RapidPlan-generated plans. The RapidPlan tool was then used to retrospectively generate adapted VMAT plans on daily iCBCT images for 20 intact prostate and 15 prostate bed cases. As before, DVH and PQM metrics were utilized to dosimetrically compare scheduled (iCBCT Verify) and adapted (iCBCT RapidPlan) plans. Timing data was collected to further evaluate the feasibility of integrating this approach within an online adaptive radiotherapy workflow. RESULTS: Model testing results confirmed the models were capable of producing VMAT plans within a single optimization that were overall improved upon or dosimetrically comparable to original clinical plans. Direct application of RapidPlan on iCBCT datasets produced satisfactory intact prostate and prostate bed plans with generally improved target volume coverage/conformality and rectal sparing relative to iCBCT Verify plans as indicated by DVH values, though bladder metrics were marginally increased on average. Average PQM values for iCBCT RapidPlans were significantly improved compared to iCBCT Verify plans. The average time required [in mm:ss] to generate adapted plans was 06:09 ± 02:06 (intact) and 07:12 ± 01:04 (bed). CONCLUSION: This study demonstrated the feasibility of leveraging RapidPlan to expeditiously generate adapted VMAT intact prostate and prostate bed plans on iCBCT datasets. In general, adapted plans were dosimetrically improved relative to scheduled plans, emphasizing the practicality of the proposed approach.

Dosimetric comparison between proton beam therapy, intensity modulated radiation therapy, and 3D conformal therapy for soft tissue extremity sarcoma.

PURPOSE/OBJECTIVES: Proton beam therapy (PBT) may provide a dosimetric advantage in sparing soft tissue and bone for selected patients with extremity soft sarcoma (eSTS). We compared PBT with photons plans generated using intensity-modulated radiotherapy (IMRT) and three-dimensional conformal radiotherapy (3D-CRT). MATERIALS/METHODS: Seventeen patients previously treated with pencil beam scanning PBT were included in this study. Of these patients, 14 treated with pre-operative 50 Gy in 25 fractions were analyzed. IMRT and 3D-CRT plans were created to compare against the original PBT plans. Dose-volume histogram (DVH) indices were evaluated amongst PBT, IMRT, and 3D plans. Kruskal-Wallis rank sum tests were used to get the statistical significance. A p value smaller than .05 was considered to be statistically significant. RESULTS: For the clinical target volume (CTV), D2%, D95%, D98%, Dmin, Dmax, and V50Gy, were assessed. Dmin, D1%, Dmax, Dmean, V1Gy, V5Gy, and V50Gy were evaluated for the adjacent soft tissue. D1%, Dmax, Dmean, and V35-50% were evaluated for bone. All plans met CTV target coverage. The PBT plans delivered less dose to soft tissue and bone. The mean dose to the soft tissue was 2 Gy, 11 Gy, and 13 Gy for PBT, IMRT, and 3D, respectively (p < .001). The mean dose to adjacent bone was 15 Gy, 26 Gy, and 28 Gy for PBT, IMRT, and 3D, respectively (p = .022). CONCLUSION: PBT plans for selected patients with eSTS demonstrated improved sparing of circumferential soft tissue and adjacent bone compared to IMRT and 3D-CRT. Further evaluation will determine if this improved dosimetry correlates with reduced toxicity and improved quality of life.

Development and characterization of CD54-targeted immunoPET imaging in solid tumors.

PURPOSE: Intercellular adhesion molecule-1 (ICAM-1, CD54) is an emerging therapeutic target for a variety of solid tumors including melanoma and anaplastic thyroid cancer (ATC). This study aims to develop an ICAM-1-targeted immuno-positron emission tomography (immunoPET) imaging strategy and assess its diagnostic value in melanoma and ATC models. METHODS: Flow cytometry was used to screen ICAM-1-positive melanoma and ATC cell lines. Melanoma and ATC models were established using A375 cell line and THJ-16T cell line, respectively. An ICAM-1-specific monoclonal antibody (R6-5-D6) and a nonspecific human IgG were radiolabeled with 64Cu and the diagnostic efficacies were interrogated in tumor-bearing mouse models. Biodistribution and fluorescent imaging studies were performed to confirm the specificity of the ICAM-1-targeted imaging probes. RESULTS: ICAM-1 was strongly expressed on melanoma and advanced thyroid cancer cell lines. 64Cu-NOTA-ICAM-1 immunoPET imaging efficiently delineated A375 melanomas with a peak tumor uptake of 21.28 ± 6.56 %ID/g (n = 5), significantly higher than that of 64Cu-NOTA-IgG (10.63 ± 2.58 %ID/g, n = 3). Moreover, immunoPET imaging with 64Cu-NOTA-ICAM-1 efficiently visualized subcutaneous and orthotopic ATCs with high clarity and contrast. Fluorescent imaging with IRDye 800CW-ICAM-1 also visualized orthotopic ATCs and the tumor uptake could be blocked by the ICAM-1 parental antibody R6-5-D6, indicating the high specificity of the developed probe. Finally, blocking with the human IgG prolonged the circulation of the 64Cu-NOTA-ICAM-1 in R2G2 mice without compromising the tumor uptake. CONCLUSION: ICAM-1-targeted immunoPET imaging could characterize ICAM-1 expression in melanoma and ATC, which holds promise for optimizing ICAM-1-targeted therapies in the future.

Chirality-Driven Transportation and Oxidation Prevention by Chiral Selenium Nanoparticles.

The chirality of nanoparticles directly influences their transport and biological effects under physiological conditions, but the details of this phenomenon have rarely been explored. Herein, chiral GSH-anchored selenium nanoparticles (G@SeNPs) are fabricated to investigate the effect of their chirality on their transport and antioxidant activity. G@SeNPs modified with different enantiomers show opposite handedness with a tunable circular dichroism signal. Noninvasive positron emission tomography imaging clearly reveals that 64 Cu-labeled l-G@SeNPs experience distinctly different transport among the major organs from that of their d-and dl-counterparts, demonstrating that the chirality of the G@SeNPs influences the biodistribution and kinetics. Taking advantage of the strong homologous cell adhesion and uptake, l-G@SeNPs have been shown here to effectively prevent oxidation damage caused by palmitic acid in insulinoma cells.

A Melanin-Based Natural Antioxidant Defense Nanosystem for Theranostic Application in Acute Kidney Injury.

Acute kidney injury (AKI) is frequently associated with oxidative stress and causes high mortality annually in clinics. Nanotechnology-mediated antioxidative therapy is emerging as a novel strategy for the treatment of AKI. Herein, a novel biomedical use of the endogenous biopolymer melanin as a theranostic natural antioxidant defense nanoplatform for AKI is reported. In this study, ultrasmall Mn2+-chelated melanin (MMP) nanoparticles are easily prepared via a simple coordination and self-assembly strategy, and further incorporated with polyethylene glycol (MMPP). In vitro experiments reveal the ability of MMPP nanoparticles to scavenge multiple toxic reactive oxygen species (ROS) and suppress ROS-induced oxidative stress. Additionally, in vivo results from a murine AKI model demonstrate preferential renal uptake of MMPP nanoparticles and a subsequent robust antioxidative response with negligible side effects according to positron emission tomography/magnetic resonance (PET/MR) bimodal imaging and treatment assessment. These results indicate that the effectiveness of MMPP nanoparticles for treating AKI suggests the potential efficacy of melanin as a natural theranostic antioxidant nanoplatform for AKI, as well as other ROS-related diseases.

Size-Optimized Ultrasmall Porous Silica Nanoparticles Depict Vasculature-Based Differential Targeting in Triple Negative Breast Cancer.

Rapid sequestration and prolonged retention of intravenously injected nanoparticles by the liver and spleen (reticuloendothelial system (RES)) presents a major barrier to effective delivery to the target site and hampers clinical translation of nanomedicine. Inspired by biological macromolecular drugs, synthesis of ultrasmall (diameter ≈12-15 nm) porous silica nanoparticles (UPSNs), capable of prolonged plasma half-life, attenuated RES sequestration, and accelerated hepatobiliary clearance, is reported. The study further investigates the effect of tumor vascularization on uptake and retention of UPSNs in two mouse models of triple negative breast cancer with distinctly different microenvironments. A semimechanistic mathematical model is developed to gain mechanistic insights into the interactions between the UPSNs and the biological entities of interest, specifically the RES. Despite similar systemic pharmacokinetic profiles, UPSNs demonstrate strikingly different tumor responses in the two models. Histopathology confirms the differences in vasculature and stromal status of the two models, and corresponding differences in the microscopic distribution of UPSNs within the tumors. The studies demonstrate the successful application of multidisciplinary and complementary approaches, based on laboratory experimentation and mathematical modeling, to concurrently design optimized nanomaterials, and investigate their complex biological interactions, in order to drive innovation and translation.

Efficient Uptake of 177 Lu-Porphyrin-PEG Nanocomplexes by Tumor Mitochondria for Multimodal-Imaging-Guided Combination Therapy.

The benefits to intracellular drug delivery from nanomedicine have been limited by biological barriers and to some extent by targeting capability. We investigated a size-controlled, dual tumor-mitochondria-targeted theranostic nanoplatform (Porphyrin-PEG Nanocomplexes, PPNs). The maximum tumor accumulation (15.6 %ID g-1 , 72 h p.i.) and ideal tumor-to-muscle ratio (16.6, 72 h p.i.) was achieved using an optimized PPN particle size of approximately 10 nm, as measured by using PET imaging tracing. The stable coordination of PPNs with 177 Lu enables the integration of fluorescence imaging (FL) and photodynamic therapy (PDT) with positron emission tomography (PET) imaging and internal radiotherapy (RT). Furthermore, the efficient tumor and mitochondrial uptake of 177 Lu-PPNs greatly enhanced the efficacies of RT and/or PDT. This work developed a facile approach for the fabrication of tumor-targeted multi-modal nanotheranostic agents, which enables precision and radionuclide-based combination tumor therapy.

Custom-Trained Deep Learning-Based Auto-Segmentation for Male Pelvic Iterative CBCT on C-Arm Linear Accelerators.

PURPOSE: The purpose of this investigation was to evaluate the clinical applicability of a commercial artificial intelligence-driven deep learning auto-segmentation (DLAS) tool on enhanced iterative cone beam computed tomography (iCBCT) acquisitions for intact prostate and prostate bed treatments. METHODS AND MATERIALS: DLAS models were trained using 116 iCBCT data sets with manually delineated organs at risk (bladder, femoral heads, and rectum) and target volumes (intact prostate and prostate bed) adhering to institution-specific contouring guidelines. An additional 25 intact prostate and prostate bed iCBCT data sets were used for model testing. Segmentation accuracy relative to a reference structure set was quantified using various geometric comparison metrics and qualitatively evaluated by trained physicists and physicians. These results were compared with those obtained for an additional DLAS-based model trained on planning computed tomography (pCT) data sets and for a deformable image registration (DIR)-based automatic contour propagation method. RESULTS: In most instances, statistically significant differences in the Dice similarity coefficient (DSC), 95% directed Hausdorff distance, and mean surface distance metrics were observed between the models, as the iCBCT-trained DLAS model outperformed the pCT-trained DLAS model and DIR-based method for all organs at risk and the intact prostate target volume. Mean DSC values for the proposed method were ≥0.90 for these volumes of interest. The iCBCT-trained DLAS model demonstrated a relatively suboptimal performance for the prostate bed segmentation, as the mean DSC value was <0.75 for this target contour. Overall, 90% of bladder, 93% of femoral head, 67% of rectum, and 92% of intact prostate contours generated by the proposed method were deemed clinically acceptable based on qualitative scoring, and approximately 63% of prostate bed contours required moderate or major manual editing to adhere to institutional contouring guidelines. CONCLUSIONS: The proposed method presents the potential for improved segmentation accuracy and efficiency compared with the DIR-based automatic contour propagation method as commonly applied in CBCT-based dose evaluation and calculation studies.

Characterization of actinide resin for separation of 51,52gMn from bulk target material.

We report an extraction chromatography-based method via Actinide Resin for the isolation of radio-manganese from both natural chromium and isotopically enriched iron targets for cyclotron production of 52gMn and 51Mn. For the separation of 52gMn from natCr, a decay-corrected radiochemical yield of 83.7 ± 8.4% was achieved. For 51Mn from 54Fe, a decay-corrected radiochemical yield of 78 ± 11% was achieved. This automatable method efficiently isolates both radionuclides from accelerator target material.

Automated, cassette-based isolation and formulation of high-purity [61Cu]CuCl2 from solid Ni targets.

BACKGROUND: A need for improved, cassette-based automation of 61Cu separation from irradiated Ni targets was identified given the growing interest in theranostics, and generally lengthy separation chemistries for 64Cu/64Ni, upon which 61Cu chemistry is often based. METHODS: A method for separating 61Cu from irradiated natNi targets was therefore developed, with provision for target recycling. Following deuteron irradiation, electroplated natNi targets were remotely transferred from the cyclotron and dissolved in acid. The dissolved target solution was then transferred to an automated FASTlab chemistry module, where sequential TBP and TK201 (Triskem) resins isolated the [61Cu]CuCl2, removed Ni, Co, and Fe, and concentrated the product into a formulation suitable for anticipated radiolabelling reactions. RESULTS: 61Cu saturation yields of 190 ± 33 MBq/µA from energetically thick natNi targets were measured. The average, decay-corrected, activity-based dissolution efficiency was 97.5 ± 1.4% with an average radiochemical yield of 90.4 ± 3.2% (N = 5). The isolated activity was collected approximately 65 min post end of bombardment in ~ 2 mL of 0.06 M HCl (HCl concentration was verified by titration). Quality control of the isolated [61Cu]CuCl2 (N = 5) measured 58Co content of (8.3 ± 0.6) × 10- 5% vs. 61Cu by activity, Ni separation factors ≥ (2.2 ± 1.8) × 106, EoB molar activities 85 ± 23 GBq/µmol and NOTA-based EoB apparent molar activities of 31 ± 8 MBq/nmol and 201 MBq/nmol for the 30 min and 3.3 h (N = 1) irradiations, respectively. CONCLUSION: High purity 61Cu was produced with the developed automated method using a single-use, cassette-based approach. It was also applicable for 64Cu, as demonstrated with a single proof-of-concept 64Ni target production run.

Tissue Factor-Targeted ImmunoPET Imaging and Radioimmunotherapy of Anaplastic Thyroid Cancer.

Anaplastic thyroid cancer (ATC) is the most aggressive subtype of thyroid cancers with a dismal prognosis. It is aimed to explore a new biomarker and devise a marker-dependent theranostic pair for ATC. Flow cytometry is used to determine tissue factor (TF) expression in thyroid cancer cell lines. ALT-836, a TF-specific monoclonal antibody, is radiolabeled with 64Cu to develop 64Cu-NOTA-ALT-836. The diagnostic utility is assessed by immuno-positron emission tomography (immunoPET) imaging in ATC models. To facilitate total surgical removal of orthotopic ATCs, a near-infrared fluorescent imaging probe IRDye 800CW-ALT-836 is designed. As the therapeutic component, 131I-ALT-836 is further developed and the radioimmunotherapy (RIT) efficacy of this agent is interrogated in orthotopic ATC models. The results demonstrate that TF is highly expressed on the ATC cell line THJ-16T. 64Cu-NOTA-ALT-836 immunoPET imaging clearly delineates both subcutaneous and orthotopic ATCs, with a peak tumor uptake of 19.93 ± 2.17% ID per g (n = 3) and 37.20 ± 1.71% ID per g (n = 3), respectively. Fluorescent imaging with IRDye 800CW-ALT-836 facilitates the total resection of orthotopic ATCs. Moreover, 131I-ALT-836 RIT prolongs the survival of ATC-bearing mice. Taken together, TF is a promising marker for ATC and successive use of 64Cu-NOTA-ALT-836 and 131I-ALT-836 can realize precise management of ATC.

Spatiotemporal Distribution of Agrin after Intrathecal Injection and Its Protective Role in Cerebral Ischemia/Reperfusion Injury.

Intrathecal injection, drugs transporting along perivascular spaces, represents an important route for maintaining blood-brain barrier (BBB) integrity after cerebral ischemia/reperfusion (I/R) injury. However, after being directly injected into cerebrospinal fluid (CSF), the temporal and spatial changes in the distribution of therapeutic protein drugs have remained unknown. Here, with positron emission tomography (PET) imaging, the uptake of 89Zr-agrin is noninvasively and dynamically monitored. These data demonstrate the time-activity curve of drugs in the brain subregions and their spatial distribution in different organs after intrathecal administration. Furthermore, agrin treatment effectively inhibits BBB disruption by reducing the loss of tight-junctional proteins. Importantly, the infarct volume is reduced; the number of apoptotic neurons is decreased; and neurological function is improved in mouse I/R injury models. Thus, intrathecal injection of agrin provides the basis for a new strategy to research and develop protein drugs for reducing the aggravation of I/R injury.

ImmunoPET imaging of CD38 expression in hepatocellular carcinoma using 64Cu-labeled daratumumab.

CD38 is expressed on the surface of many immune cells, which are closely associated with antitumor immunity and immune tolerance of tumor cells. Therefore, monitoring CD38 expression has gained great attention for tracking the progression of tumors and cancer treatment. Herein, we aim to develop a PET tracer using an anti-CD38 monoclonal antibody (daratumumab) to monitor CD38 expression in hepatocellular carcinoma (HCC). In this study, daratumumab was radiolabeled with 64Cu (t1/2=12.7 h) to obtain 64Cu-NOTA-daratumumab. Relative CD38 expression in HepG2 and Huh7 HCC cell lines was assessed using western blot. The specificity of 64Cu-NOTA-daratumumab to both cell lines was examined using an in vitro cell-binding assay. PET imaging in subcutaneous models of HCC was performed to evaluate the capability and specificity of 64Cu-NOTA-daratumumab to target CD38 in vivo. Region-of-interest analysis and ex vivo biodistribution were performed to verify the tracer targeting capability of CD38. Through cellular studies of two HCC cell lines, CD38 expression was found to be higher in HepG2 and minimal in Huh7 cells. 64Cu-NOTA-daratumumab showed relatively high affinity to CD38 (Ka=18.21 ± 1.74 nM), while the affinity of Huh7 was in the micromolar range for daratumumab binding to the cells (Ka=3.98 ± 0.87 µM). At 48 h post-injection, PET imaging of subcutaneous models with 64Cu-NOTA-daratumumab revealed tumor uptakes of 12.23 ± 2.4 and 2.7 ± 1.2 %ID/g for HepG2 and Huh7, respectively (n=4), which correlated well with relative CD38 expression of the cells. Moreover, the 64Cu-NOTA-IgG nonspecific analogue showed a significantly lower uptake in HepG2 subcutaneous model in mice, suggesting a specific binding of daratumumab with CD38 in vivo. Our cellular studies and PET imaging confirmed the capability and specificity of 64Cu-NOTA-daratumumab for the imaging of CD38 in murine models of HCC. This study supports our claim that 64Cu-NOTA-daratumumab is an effective PET tracer for the non-invasive evaluation of CD38 expression and sensitive detection of CD38-positive tumor lesions in HCC.

Radiochemical isolation method for the production of 52gMn from natCr for accelerator targets.

We report a novel, precipitation-based method for the isolation of Mn from Cr targets for cyclotron production of 52gMn. The separation produces no-carrier-added 52gMn with a decay corrected radiochemical yield of 85 ±â€¯3% and apparent molar activity for DOTA of 1.3 GBq/µmol. This method reduces stable metallic impurities in the purified 52gMn compared to previously reported chromatographic methods.

Simplified and automatable radiochemical separation strategy for the production of radiopharmaceutical quality 86Y using single column extraction chromatography.

We present a simplified, automatable single-column radiochemical separation method using the extraction chromatographic branched-DGA resin for the production of no-carrier-added 86Y with a radiochemical yield higher than 95%, an apparent molar activity of 1.4 ±â€¯0.4 Ci/µmol (DOTA) and 2.3 ±â€¯0.7 Ci/µmol (DTPA), and a run-to-run recycling efficiency of the isotopically-enriched target of 98 ±â€¯1%. These results enable the preparation of 86Y radiopharmaceuticals for 86Y/90Y-based cancer theranostic applications.

DNA origami nanostructures can exhibit preferential renal uptake and alleviate acute kidney injury.

Patients with acute kidney injury (AKI) frequently require kidney transplantation and supportive therapies, such as rehydration and dialysis. Here, we show that radiolabelled DNA origami nanostructures (DONs) with rectangular, triangular and tubular shapes accumulate preferentially in the kidneys of healthy mice and mice with rhabdomyolysis-induced AKI, and that rectangular DONs have renal-protective properties, with efficacy similar to the antioxidant N-acetylcysteine-a clinically used drug that ameliorates contrast-induced AKI and protects kidney function from nephrotoxic agents. We evaluated the biodistribution of DONs non-invasively via positron emission tomography, and the efficacy of rectangular DONs in the treatment of AKI via dynamic positron emission tomography imaging with 68Ga-EDTA, blood tests and kidney tissue staining. DNA-based nanostructures could become a source of therapeutic agents for the treatment of AKI and other renal diseases.

Molybdenum-based nanoclusters act as antioxidants and ameliorate acute kidney injury in mice.

Acute kidney injury (AKI) is a common reactive oxygen species (ROS)-related renal disease that causes numerous deaths annually, yet only supportive treatment is currently available in the clinics. Development of antioxidants with high accumulation rates in kidneys is highly desired to help prevent AKI. Here we report molybdenum-based polyoxometalate (POM) nanoclusters with preferential renal uptake as novel nano-antioxidants for kidney protection. These POM nanoclusters, with a readily variable valence state of molybdenum ions, possess the capability to scavenge detrimental ROS. Our results demonstrate that POM nanoclusters can efficiently alleviate clinical symptoms in mice subjected to AKI, as verified by dynamic PET imaging with 68Ga-EDTA, serum tests, kidney tissue staining, and biomarkers detection in the kidneys. The protective effect of POM nanoclusters against AKI in living animals suggests exploring their use for the treatment of AKI patients, as well as patients with other ROS-related diseases.

Renal-Clearable Ultrasmall Coordination Polymer Nanodots for Chelator-Free 64Cu-Labeling and Imaging-Guided Enhanced Radiotherapy of Cancer.

Developing tumor-homing nanoparticles with integrated diagnostic and therapeutic functions, and meanwhile could be rapidly excreted from the body, would be of great interest to realize imaging-guided precision treatment of cancer. In this study, an ultrasmall coordination polymer nanodot (CPN) based on the coordination between tungsten ions (WVI) and gallic acid (W-GA) was developed via a simple method. After polyethylene glycol (PEG) modification, PEGylated W-GA (W-GA-PEG) CPNs with an ultrasmall hydrodynamic diameter of 5 nm were rather stable in various physiological solutions. Without the need of chelator molecules, W-GA-PEG CPNs could be efficiently labeled with radioisotope 64Cu2+, enabling positron emission tomography (PET) imaging, which reveals efficient tumor accumulation and rapid renal clearance of W-GA-PEG CPNs upon intravenous injection. Utilizing the radio-sensitizing function of tungsten with strong X-ray absorption, such W-GA-PEG CPNs were able to greatly enhance the efficacy of cancer radiotherapy in inhibiting the tumor growth. With fast clearance and little long-term body retention, those W-GA-PEG CPNs exhibited no appreciable in vivo toxicity. This study presents a type of CPNs with excellent imaging and therapeutic abilities as well as rapid renal clearance behavior, promising for further clinic translation.

Ultra-small iron-gallic acid coordination polymer nanoparticles for chelator-free labeling of 64Cu and multimodal imaging-guided photothermal therapy.

Cancer nanotechnology has become the hot topic nowadays. While various kinds of nanomaterials have been widely explored for innovative cancer imaging and therapy applications, safe multifunctional nano-agents without long-term retention and toxicity are still demanded. Herein, iron-gallic acid coordination nanoparticles (Fe-GA CPNs) with ultra-small sizes are successfully synthesized by a simple method for multimodal imaging-guided cancer therapy. After surface modification with polyethylene glycol (PEG), the synthesized Fe-GA-PEG CPNs show high stability in various physiological solutions. Taking advantage of high near-infrared (NIR) absorbance as well as the T1-MR contrasting ability of Fe-GA-PEG CPNs, in vivo photoacoustic tomography (PAT) and magnetic resonance (MR) bimodal imaging are carried out, revealing the efficient passive tumor targeting of these ultra-small CPNs after intravenous (i.v.) injection. Interestingly, such Fe-GA-PEG CPNs could be labeled with the 64Cu isotope via a chelator-free method for in vivo PET imaging, which also illustrates the high tumor uptake of Fe-GA CPNs. We further utilize Fe-GA-PEG CPNs for in vivo photothermal therapy and achieve highly effective tumor destruction after i.v. injection of Fe-GA-PEG CPNs and the following NIR laser irradiation of the tumors, without observing any apparent toxicity of such CPNs to the treated animals. Our work highlights the promise of ultra-small iron coordination nanoparticles for imaging-guided cancer therapy.

Intrabilayer 64Cu Labeling of Photoactivatable, Doxorubicin-Loaded Stealth Liposomes.

Doxorubicin (Dox)-loaded stealth liposomes (similar to those in clinical use) can incorporate small amounts of porphyrin-phospholipid (PoP) to enable chemophototherapy (CPT). PoP is also an intrinsic and intrabilayer 64Cu chelator, although how radiolabeling impacts drug delivery has not yet been assessed. Here, we show that 64Cu can radiolabel the stable bilayer of preformed Dox-loaded PoP liposomes with inclusion of 1% ethanol without inducing drug leakage. Dox-PoP liposomes labeled with intrabilayer copper behaved nearly identically to unlabeled ones in vitro and in vivo with respect to physical parameters, pharmacokinetics, and CPT efficacy. Positron emission tomography and near-infrared fluorescence imaging visualized orthotopic mammary tumors in mice with passive liposome accumulation following administration. A single CPT treatment with 665 nm light (200 J/cm2) strongly inhibited primary tumor growth. Liposomes accumulated in lung metastases, based on NIR imaging. These results establish the feasibility of CPT interventions guided by intrinsic multimodal imaging of Dox-loaded stealth PoP liposomes.