Chemical and Physical Characterisation of Macroaggregated Human Serum Albumin: Strength and Specificity of Bonds with 99mTc and 68Ga.

BACKGROUND: Macroaggregated human serum albumin (MAA) properties are widely used in nuclear medicine, labelled with 99mTc. The aim of this study is to improve the knowledge about the morphology, size, dimension and physical-chemical characteristics of MAA and their bond with 99mTc and 68Ga. METHODS: Commercial kits of MAA (Pulmocis®) were used. Characterisation through experiments based on SEM, DLS and Stokes' Law were carried out. In vitro experiments for Langmuir isotherms and pH studies on radiolabelling were performed and the stability of the radiometal complex was verified through competition reactions. RESULTS: The study settles the MAA dimension within the range 43-51 µm. The Langmuir isotherm reveals for [99mTc]MAA: Bmax (46.32), h (2.36); for [68Ga]MAA: Bmax (44.54), h (0.893). Dual labelling reveals that MAA does not discriminate different radioisotopes. Experiments on pH placed the optimal pH for labelling with 99mTc at 6. CONCLUSION: Radiolabelling of MAA is possible with high efficiency. The nondiscriminatory MAA bonds make this drug suitable for radiolabelling with different radioisotopes or for dual labelling. This finding illustrates the need to continue investigating MAA chemical and physical characteristics to allow for secure labelling with different isotopes.

Chemical and Physical Characterisation of Human Serum Albumin Nanocolloids: Kinetics, Strength and Specificity of Bonds with 99mTc and 68Ga.

Nanoparticles of Human Serum Albumin (NC) labelled with 99mTc are widely used in Nuclear Medicine and represent the gold-standard for the intraoperative detection of the sentinel lymph node in many kinds of cancer, mainly breast cancer and melanoma. A significant amount of radionuclides can be incorporated into the HSA particle, due to the multiple binding sites, and HSA-based nanocolloid catabolism is a fast and easy process that results in innocuous degradation products. NCs labelled with different isotopes represent an interesting radiopharmaceutical for extending diagnostic accuracy and surgical outcome, but the knowledge of the chemical bond between NCs and isotopes has not been fully elucidated, including information on its strength and specificity. The aim of this study is to investigate and compare the physicochemical characteristics of the bond between NCs and 99mTc and 68Ga isotopes. Commercial kits of HSA-based nanocolloid particles (NanoAlbumon®) were used. For this purpose, we have primarily studied the kinetic orders of NC radiolabelling. Langmuir isotherms and pH effect on radiolabelling were tested and the stability of the radiometal complex was verified through competition reactions carried out in presence of different ligands. The future goal of our research is the development of inexpensive and instant kits, easily labelled with a wide spectrum of diagnostic and therapeutic isotopes, thus facilitating the availability of versatile and multipurpose radiopharmaceuticals.

Effects of Photons Irradiation on 18F-FET and 18F-DOPA Uptake by T98G Glioblastoma Cells.

The differential diagnosis between brain tumors recurrence and early neuroinflammation or late radionecrosis is still an unsolved problem. The new emerging magnetic resonance imaging, computed tomography, and positron emission tomography diagnostic modalities still lack sufficient accuracy. In the last years, a great effort has been made to develop radiotracers able to detect specific altered metabolic pathways or tumor receptor markers. Our research project aims to evaluate irradiation effects on radiopharmaceutical uptake and compare the kinetic of the fluorinate tracers. T98G glioblastoma cells were irradiated at doses of 2, 10, and 20 Gy with photons, and 18F-DOPA and 18F-FET tracer uptake was evaluated. Activity and cell viability at different incubation times were measured. 18F-FET and 18F-DOPA are accumulated via the LAT-1 transporter, but 18F-DOPA is further incorporated, whereas 18F-FET is not metabolized. Therefore, time-activity curves (TACs) tend to plateau with 18F-DOPA and to a rapid washout with 18F-FET. After irradiation, 18F-DOPA TAC resembles the 18F-FET pattern. 18F-DOPA activity peak we observed at 20 min might be fictitious, because earlier time points have not been evaluated, and a higher activity peak before 20 min cannot be excluded. In addition, the activity retained in the irradiated cells remains higher in comparison to the sham ones at all time points investigated. This aspect is similar in the 18F-FET TAC but less evident. Therefore, we can hypothesize the presence of a second intracellular compartment in addition to the amino acidic pool one governed by LAT-1, which could explain the progressive accumulation of 18F-DOPA in unirradiated cells.

99mTc-68Ga-ICG-Labelled Macroaggregates and Nanocolloids of Human Serum Albumin: Synthesis Procedures of a Trimodal Imaging Agent Using Commercial Kits.

Recent developments in sentinel lymph node (SLN) and radio occult lesion localization (ROLL) highlight the need for a multimodal contrast agent, providing better presurgical PET imaging and improved intraoperative mapping thanks to fluorescence detection. For this reason, we have studied a trimodal SLN/ROLL targeting agent (99mTc-68Ga-ICG) with commercially available kits of macroaggregated or nanocolloidal albumin (MA/NC-HSA). 68Ga PET imaging does provide better spatial resolution and makes it possible to predict signal intensity during surgery. The presence of 99mTc assesses the efficacy of these compounds in vitro and also during the surgery procedure. The aim of this study was to optimise the labelling and tagging of these two radiopharmaceuticals and assess their yields and stability. Kits of MA/NC-HSA particles (Pulmocis® and NanoAlbumon®) were used for sequential radiolabelling with 99mTc and 68Ga. Fluorescent tagging was performed using indocyanine green, a tricarbocyanine dye. The ITLC radiochemical purity of the trilabelled MA/NC-HSA was >95%. Fluorescent purity was measured by scanning the strips with a PhotoDynamicEye probe. Finally, in vitro stability tests, performed with DTPA and human serum solutions, assessed the efficacy of fluorescent tagging and radiolabelling.

Management of the axilla in patients with breast cancer and positive sentinel lymph node biopsy: An evidence-based update in a European breast center.

The surgical approach to the axilla in breast cancer has been a controversial issue for more than three decades. Data from recently published trials have provided practice-changing recommendations in this scenario. However, further controversies have been triggered in the surgical community, resulting in heterogeneous diffusion of these recommendations. The development of clinical guidelines for the management of the axilla in patients with breast cancer is a work in progress. A multidisciplinary team discussion was held at the research hospital Policlinico San Matteo from the Università degli Studi di Pavia with the aim to update recommendations for the management of the axilla in patients with breast cancer. An evidence-based approach is presented. Our multidisciplinary panel determined that axillary dissection after a positive sentinel lymph node biopsy may be avoided in cN0 patients with micro/macrometastasis to ≤2 sentinel nodes, with age ≥40y, lesions ≤3 cm, who have not received neoadjuvant chemotherapy and have planned breast conservation (BCS) with whole breast radiotherapy (WBRT). Cases with gross (>2 mm) ECE in SLNs are evaluated on individual basis for completion ALND, axillary radiotherapy or omission of both. Patients fulfilling the criteria listed above who undergo mastectomy, may also avoid axillary dissection after multidisciplinary discussion of individual cases for consideration of axillary irradiation. Women 70 years or older with hormone receptors positive invasive lesions ≤3 cm, clinically negative nodes, and serious or multiple comorbidities who undergo BCS with WBRT, may forgo axillary staging/surgery (if mastectomy or larger tumor, comorbidities and life expectancy are taken into account).

Intestinal T-cell lymphoma with enteropathy-associated T-cell lymphoma-like features arising in the setting of adult autoimmune enteropathy.

Enteropathy-associated T-cell lymphoma is regarded as a dismal, late complication of coeliac disease, though a single case of T-cell lymphoma with such features arising in the setting of autoimmune enteropathy of the adult has been reported to date. We aim to describe the case of a 41-year-old woman complaining of severe malabsorption syndrome, who was diagnosed with autoimmune enteropathy based on the presence of flat intestinal mucosa unresponsive to any dietary restriction and positivity for enterocyte autoantibodies. Steroid therapy led to a complete recovery of both mucosal and clinical findings over 12 years, when disease relapse was accompanied by the appearance of monoclonal rearrangement of T-cell receptor-γ and peculiar T-cell phenotypic abnormalities, leading to a rapid transition to an overt T-cell lymphoma with features of the enteropathy-associated subtype. Despite intensive treatment, the patient developed cerebral metastasis and died 9 months later. Our case enhances the concept of enteropathy-associated T-cell lymphoma as a disease that may arise in the setting of enteropathies other than coeliac disease, thus representing a heterogeneous entity. Moreover, our observations support the need of a close follow-up of these patients, coupled with comprehensive characterization of mucosal biopsies.

Usefulness of chronotropic incompetence to dipyridamole in predicting myocardial perfusion defects in heart transplant recipients.

The aim of this report was to assess the relation between heart rate response to dipyridamole infusion and perfusion defects at quantitative sestamibi single-photon emission computed tomographic imaging. We demonstrated in 166 heart transplant recipients that chronotropic incompetence to dipyridamole is the only significant and independent predictor of perfusion defects.