Influence of colloid particle profile on sentinel lymph node uptake

Positron emission tomography and single photon emission computed tomography imaging of tertiary lymphoid structures during the development of lupus nephritis

Lymphoid neogenesis occurs in tissues targeted by chronic inflammatory processes, such as infection and autoimmunity. In systemic lupus erythematosus (SLE), such structures develop within the kidneys of lupus-prone mice ((NZBXNZW)F1) and are observed in kidney biopsies taken from SLE patients with lupus nephritis (LN). The purpose of this prospective longitudinal animal study was to detect early kidney changes and tertiary lymphoid structures (TLS) using in vivo imaging. Positron emission tomography (PET) by tail vein injection of 18-F-fluoro-2-deoxy-D-glucose (¹⁸F-FDG)(PET/FDG) combined with computed tomography (CT) for anatomical localization and single photon emission computed tomography (SPECT) by intraperitoneal injection of ^99mTC labeled Albumin Nanocoll (^99mTC-Nanocoll) were performed on different disease stages of NZB/W mice (n = 40) and on aged matched control mice (BALB/c) (n = 20). By using one-way ANOVA analyses, we compared two different compartmental models for the quantitative measure of ¹⁸F-FDG uptake within the kidneys. Using a new five-compartment model, we observed that glomerular filtration of ^18FFDG in lupus-prone mice decreased significantly by disease progression measured by anti-dsDNA Ab production and before onset of proteinuria. We could not visualize TLS within the kidneys, but we were able to visualize pancreatic TLS using ^99mTC Nanocoll SPECT. Based on our findings, we conclude that the five-compartment model can be used to measure changes of FDG uptake within the kidney. However, new optimal PET/SPECT tracer administration sites together with more specific tracers in combination with magnetic resonance imaging (MRI) may make it possible to detect formation of TLS and LN before clinical manifestations.

Novel Experience in Hybrid Tracers: Clinical Evaluation of Feasibility and Efficacy in Using ICG-99mTc Nanotop for Sentinel Node Procedure in Breast Cancer Patients

PURPOSE

The clinical introduction of a radioactive and fluorescent hybrid tracer allowed for preoperative lymphatic mapping and intraoperative real-time fluorescence tracing of the sentinel lymph node (SLN) by a single injection. The aim of this feasibility study is to evaluate the first-in-human use of the hybrid tracer by combining indocyanine green (ICG) and radiocolloid based on Nanotop compound (99mTc Nanotop) for SLN biopsy (SLNB) in breast cancer patients.

METHODS

The day before surgery, ICG-99mTc Nanotop was injected periareolarly in breast cancer patients scheduled for SLNB. Planar lymphoscintigraphic (PL) and SPECT/CT images were then acquired. An intraoperative optonuclear probe was used to detect SLN gamma and fluorescent signals. The harvested SLNs were examined by hematoxylin-eosin staining, and patients were clinically evaluated 1 month after surgery.

RESULTS

Twenty-one consecutive patients were enrolled. The PL and SPECT/CT techniques identified at least 1 SLN in all patients for a preoperative sentinel detection rate of 100%. SPECT/CT revealed 3 additional lymph nodes in the same nodal basin, which had not been visualized on conventional PL (κ = 0.747; P < 0.005). All 30 preoperative SLNs were localized and excised up to 16 hours after injection. The counts measured via gamma tracing showed a very strong correlation with those measured via near-infrared fluorescent tracing (P < 0.005, r = 0.964). No adverse reactions were observed.

CONCLUSIONS

The SLNB technique used with the ICG-99mTc Nanotop tracer resulted to be feasible, reliable, and safe. This hybrid compound allowed us to obtain excellent performance in terms of both preoperative lymphatic mapping and intraoperative SLN detection in breast cancer patients.

Single Photon Emission Computed Tomography Tracer

Single photon emission computed tomography (SPECT) is the state-of-the-art imaging modality in nuclear medicine despite the fact that only a few new SPECT tracers have become available in the past 20 years. Critical for the future success of SPECT is the design of new and specific tracers for the detection, localization, and staging of a disease and for monitoring therapy. The utility of SPECT imaging to address oncologic questions is dependent on radiotracers that ideally exhibit excellent tissue penetration, high affinity to the tumor-associated target structure, specific uptake and retention in the malignant lesions, and rapid clearance from non-targeted tissues and organs. In general, a target-specific SPECT radiopharmaceutical can be divided into two main parts: a targeting biomolecule (e.g., peptide, antibody fragment) and a γ-radiation-emitting radionuclide (e.g., ^99mTc, ¹²³I). If radiometals are used as the radiation source, a bifunctional chelator is needed to link the radioisotope to the targeting entity. In a rational SPECT tracer design, these single components have to be critically evaluated in order to achieve a balance among the demands for adequate target binding, and a rapid clearance of the radiotracer. The focus of this chapter is to depict recent developments of tumor-targeted SPECT radiotracers for imaging of cancer diseases. Possibilities for optimization of tracer design and potential causes for design failure are discussed and highlighted with selected examples.

Radiochemical purity of technetium-99m-nanocolloid rhenium sulphide is not influenced by heating

Despite a mistake during the preparation of technetium-99m (Tc)-nanocolloid rhenium sulphide (Nanocis) because of lack of heating, the apparent radiochemical purity (RCP) of this product was correct. The objectives of this study were to evaluate the impact of absence of heating on the RCP of Tc-nanocolloid rhenium sulphide and the effect of heating on particle size. Five Tc-Nanocis were prepared according to the manufacturer's instructions and five others were realized without any heating step. Quality controls were performed for each preparation. To evaluate the effect of heating on particle size, preparations were filtered through a 0.22 µm sterilizing membrane filter before and after 30 min of heating. The radioactivity was measured before and after the filtration. The results showed that absence of heating does not influence the apparent RCP of Tc-nanocolloid of rhenium sulphide. In terms of the particle size, 72% of particles had a diameter less than 0.22 µm before heating, as opposed to 21% after heating. To conclude, this study underlines a problem of quality control of the Tc-nanocolloid rhenium sulphide preparation, which cannot detect a lack of heating and can lead to the release of preparations that would not be suitable for scintigraphy.

Modification of PLGA nanoparticles for improved properties as a 99mTc-labeled agent in sentinel lymph node detection

We have earlier reported on the possible application of poly [lactide (co-glycolide)] (PLGA) nanoparticles of suitable size to serve as a (99m)Tc-labeled diagnostic tracer in sentinel lymph node detection (SLND). Additional efforts have now been made to improve both the radiolabeling yield and the biological efficacy by modifying the PLGA particles. Two approaches were taken, one based on in situ loading of mebrofenin inside PLGA nanoparticles and the second one based on functionalization of existing terminal carboxylic acid groups on the nanoparticle surface with p-aminobenzyl diethylenetriamine pentaacetic acid (p-NH2-Bz-DTPA) for enhanced availability of functional groups suitable for (99m)Tc complexation. The modified PLGA derivatives were purified and characterized. Radiolabeling of the modified PLGA nanoparticles was carried out with (99m)Tc using stannous chloride as the reducing agent. Mebrofenin encapsulated PLGA nanoparticles (mebrofenin-PLGA) did not show any significant improvement in the radiolabeling yield in comparison to the earlier reported "plain" PLGA nanoparticles, probably due to inaccessibility of the mebrofenin moiety to (99m)Tc upon encapsulation. DTPA-conjugated PLGA nanoparticles (DTPA-PLGA) showed appreciable improvement in radiolabeling yield under more moderate reaction conditions and better stability. In the biological evaluation performed in Wistar rat model, (99m)Tc-DTPA-PLGA nanoparticles showed a considerable increase in uptake in the sentinel node and the percentage popliteal extraction of the preparation was also higher. (99m)Tc-mebrofenin-PLGA did not show any improvement in SLN uptake over plain PLGA nanoparticles. The above results suggest that surface modification of PLGA by covalently coupling DTPA to PLGA nanoparticles prior to (99m)Tc labeling appears to be a superior approach to achieve a suitable (99m)Tc-labeled PLGA nanoparticle preparation for SLND.

Design and development of (99m)tc-'4+1'-labeled dextran-mannose derivatives as potential radiopharmaceuticals for sentinel lymph node detection

The synthesis, labeling, and biological evaluation of a dextran derivative (DCM-30-iso) as potential radiopharmaceutical for sentinel lymph node imaging is presented. DCM-30-iso bears mannose as active moiety and isocyanide as ligand for technetium through the formation of a '4+1' Tc(III) mixed-ligand complex. A second derivative without mannose (DC-25-iso) was also prepared and evaluated as control. DCM-30-iso and DC-25-iso were synthesized from dextran in four steps (>50% overall yield) and characterized by spectroscopic methods. Labeling with (99m)Tc was achieved by reaction with 2,2',2''-nitrilotris(ethanethiol) and (99m)Tc-EDTA. Radiochemical purity was above 90% and was stable for at least 4 hours postlabeling at 37°C. The identity of the (99m)Tc complex was established through comparative HPLC studies using the well-characterized analogous Re-DC-25-iso complex. Biodistribution and imaging experiments of (99m)Tc-DCM-30-iso showed high uptake in the popliteal lymph node, which could be blocked with preinjection of mannose, and very low uptake in other nodes and organs. The nonmannosylated (99m)Tc-DC-25-iso derivative showed negligible uptake in all lymph nodes. The novel dextran-mannose derivative DCM-30-iso can be successfully labeled with (99m)Tc to give a well-characterized '4+1' complex with favorable biological properties as sentinel lymph node imaging agent.

Size and specificity of radiopharmaceuticals for sentinel lymph node detection

BACKGROUND

Biological performance of radiotracers for sentinel node detection analyzed in the light of molecular design and dimension is not widely available.

PURPOSE

To evaluate the effect of dextran molecular size and the presence of tissue-binding units (mannose) within the model of (99m)Tc-carbonyl conjugate for sentinel lymph node detection.

MATERIAL AND METHODS

Four dextran conjugates with and without mannose in the chemical backbone were included. All polymers were radiolabeled using the precursor [(99m)Tc(OH(2))(3)(CO)(3)](+). Radiolabeling conditions targeted the best radiochemical purity and specific activity for each radiopharmaceutical, and partition coefficients were also defined. Lymphoscintigraphy and ex-vivo biodistribution in popliteal lymph node, liver and kidneys were performed in Wistar rats. The effects of molecular weight and mannose presence were assessed by a two-level factorial design.

RESULTS

Radiochemical purity was indirectly related to molecular weight and presence of mannose in the polymer structure. All products were able to detect popliteal lymph node, however, uptake was strongly influenced by use of mannose (4-fold higher). Excretion was similarly modulated by differences in molecular weight. Mannose-enhanced lymph node uptake and higher molecule size in the range under study benefitted lymphoscintigraphic performance.

CONCLUSION

Screening of radiopharmaceuticals for lymphoscintigraphy might improve with attention to the mentioned physico-chemical features of the molecule.

(99m)Tc-labelled gold nanoparticles capped with HYNIC-peptide/mannose for sentinel lymph node detection

The aim of this research was to prepare a multifunctional system of technetium-99m-labelled gold nanoparticles conjugated to HYNIC-GGC/mannose and to evaluate its biological behaviour as a potential radiopharmaceutical for sentinel lymph node detection (SLND).

METHODS

Hydrazinonicotinamide-Gly-Gly-Cys-NH(2) (HYNIC-GGC) peptide and a thiol-triazole-mannose derivative were synthesized, characterized and conjugated to gold nanoparticles (AuNP, 20 nm) to prepare a multifunctional system of HYNIC-GGC-AuNP-mannose by means of spontaneous reaction of the thiol (Cys) present in HYNIC-GGC sequence and in the thiol-mannose derivative. The nanoconjugate was characterized by transmission electron microscopy (TEM), IR, UV-Vis, Raman, fluorescence and X-ray photoelectron spectroscopy (XPS). Technetium-99m labelling was carried out using EDDA/tricine as coligands and SnCl(2) as reducing agent with further size-exclusion chromatography purification. Radiochemical purity was determined by size-exclusion HPLC and ITLC-SG analyses. In vitro binding studies were carried out in rat liver homogenized tissue (mannose-receptor positive tissue). Biodistribution studies were accomplished in Wistar rats and images obtained using a micro-SPECT/CT system.

RESULTS

TEM and spectroscopy techniques demonstrated that AuNPs were functionalized with HYNIC-GGC-NH(2) and thiol-mannose through interactions with thiol groups and the N-terminal amine of cysteine. Radio-chromatograms showed radiochemical purity higher than 95%. (99m)Tc-EDDA/HYNIC-GGC-AuNP-mannose ((99m)Tc-AuNP-mannose) showed specific recognition for mannose receptors in rat liver tissue. After subcutaneous administration of (99m)Tc-AuNP-mannose in rats (footpad), radioactivity levels in the popliteal and inguinal lymph nodes revealed that 99% of the activity was extracted by the first lymph node (popliteal extraction). Biodistribution studies and in vivo micro-SPECT/CT images in Wistar rats showed an evident lymph node uptake (11.58 ± 1.98 %ID at 1 h) which was retained during 24 h with minimal kidney accumulation (0.98 ± 0.10 %ID) and negligible uptake in all other tissues.

CONCLUSIONS

This study demonstrated that (99m)Tc-AuNP-mannose remains within the first lymph node during 24 h and therefore might be useful as a target-specific radionanoconjugate for SLND using "1-day" or "2-day" conventional protocols.

Intraoperative laparoscopic fluorescence guidance to the sentinel lymph node in prostate cancer patients: clinical proof of concept of an integrated functional imaging approach using a multimodal tracer

BACKGROUND

Integration of molecular imaging and in particular intraoperative image guidance is expected to improve the surgical accuracy of laparoscopic lymph node (LN) dissection.

OBJECTIVE

To show the applicability of combining preoperative, intraoperative, and postoperative sentinel node imaging using an integrated diagnostic approach based on an imaging agent that is both radioactive and fluorescent.

DESIGN, SETTING, AND PARTICIPANTS

Before surgery, multimodal indocyanine green (ICG)-(99m)Tc-NanoColl was injected into the prostate. Subsequent lymphoscintigraphy and single-photon emission computed tomography/computed tomography (SPECT/CT) imaging of pelvic nodes was performed to determine the location of the sentinel lymph nodes (SLNs) preoperatively. During the surgical procedure a fluorescence laparoscope, optimized for detection in the near infrared range, was used to visualize the nodes identified on SPECT/CT. Eleven patients scheduled for robot-assisted laparoscopic prostatectomy (RALP) with an increased risk of nodal metastasis, based on Memorial Sloan-Kettering Cancer Center/Kattan nomogram estimation, participated in a pilot assessment (N09IGF).

SURGICAL PROCEDURE

Patients underwent RALP with LN dissection for prostate cancer.

MEASUREMENTS

Radioactive and fluorescent signals were monitored using different modalities, and the correlation between the two types of signals was studied. The location of preoperatively detected SLNs was documented.

RESULTS AND LIMITATIONS

Preoperatively, SLNs were identified by SPECT/CT, and the multimodal nature of the imaging agent also enabled intraoperative detection via fluorescence imaging. Fluorescence particularly improved surgical guidance in areas with a high radioactive background signal such as the injection site. Ex vivo analysis revealed a strong correlation between the radioactive and fluorescent content in the excised LNs. Fluorescence detection is limited by the severe tissue attenuation of the signal. Therefore, radio guidance to the areas of interest is still desirable.

CONCLUSIONS

Initial data indicate that multimodal ICG-(99m)Tc-NanoColloid, in combination with a laparoscopic fluorescence laparoscope, can be used to facilitate and optimize dissection of SLNs during RALP procedures.

(Non-targeted) radioactive/fluorescent nanoparticles and their potential in combined pre- and intraoperative imaging during sentinel lymph node resection

One clinical precedent for the use of nanosized imaging agents is the localization of the tumor draining sentinel lymph nodes. In this application, radiocolloids such as (99m)Tc-NanoColl are currently used to plan the surgical procedure and to provide acoustic guidance during the intervention. Additional injections of dyes are common to provide optical surgical guidance. Bimodal imaging agents, which are both radioactive and fluorescent, have the potential to be used for both surgical planning and intraoperative fluorescence guidance towards the sentinel lymph nodes. This review provides an overview of the radioactive, fluorescent, and size properties of (non-targeted) bimodal nanoparticles, and their (potential) value in sentinel lymph node detection.

Perspectives and potential applications of nanomedicine in breast and prostate cancer

Nanomedicine is a branch of nanotechnology that includes the development of nanostructures and nanoanalytical systems for various medical applications. Among these applications, utilization of nanotechnology in oncology has captivated the attention of many research endeavors in recent years. The rapid development of nano-oncology raises new possibilities in cancer diagnosis and treatment. It also holds great promise for realization of point-of-care, theranostics, and personalized medicine. In this article, we review advances in nano-oncology, with an emphasis on breast and prostate cancer because these organs are amenable to the translation of nanomedicine from small animals to humans. As new drugs are developed, the incorporation of nanotechnology approaches into medicinal research becomes critical. Diverse aspects of nano-oncology are discussed, including nanocarriers, targeting strategies, nanodevices, as well as nanomedical diagnostics, therapeutics, and safety. The review concludes by identifying some limitations and future perspectives of nano-oncology in breast and prostate cancer management.