Extensive Histopathological Characterization of Inflamed Bowel in the Dextran Sulfate Sodium Mouse Model with Emphasis on Clinically Relevant Biomarkers and Targets for Drug Development.

This study aims to develop a reliable and reproducible inflammatory bowel disease (IBD) murine model based on a careful spatial-temporal histological characterization. Secondary aims included extensive preclinical studies focused on the in situ expression of clinically relevant biomarkers and targets involved in IBD. C57BL/6 female mice were used to establish the IBD model. Colitis was induced by the oral administration of 2% Dextran Sulfate Sodium (DSS) for 5 days, followed by 2, 4 or 9 days of water. Histological analysis was performed by sectioning the whole colon into rings of 5 mm each. Immunohistochemical analyses were performed for molecular targets of interest for monitoring disease activity, treatment response and predicting outcome. Data reported here allowed us to develop an original scoring method useful as a tool for the histological assessment of preclinical models of DSS-induced IBD. Immunohistochemical data showed a significant increase in TNF-α, α4ß7, VEGFRII, GR-1, CD25, CD3 and IL-12p40 expression in DSS mice if compared to controls. No difference was observed for IL-17, IL-23R, IL-36R or F480. Knowledge of the spatial-temporal pattern distribution of the pathological lesions of a well-characterized disease model lays the foundation for the study of the tissue expression of meaningful predictive biomarkers, thereby improving translational success rates of preclinical studies for a personalized management of IBD patients.

Comparison of 99mTc-UBI 29-41, 99mTc-ciprofloxacin, 99mTc-ciprofloxacin dithiocarbamate and 111In-biotin for targeting experimental Staphylococcus aureus and Escherichia coli foreign-body infections: an ex-vivo study.

BACKGROUND: Diagnosis of implant-associated infection is challenging. Several radiopharmaceuticals have been described but direct comparisons are limited. Here we compared in vitro and in an animal model 99mTc-UBI, 99mTc-ciprofloxacin, 99mTcN-CiproCS2 and 111In-DTPA-biotin for targeting E. coli (ATCC 25922) and S. aureus (ATCC 43335). METHODS: Stability controls were performed with the labelled radiopharmaceuticals during 6 hours in saline and serum. The in vitro binding to viable or killed bacteria was evaluated at 37 °C and 4 °C. For in vivo studies, Teflon cages were subcutaneously implanted in mice, followed by percutaneous infection. Biodistribution of i.v. injected radiolabelled radiopharmaceuticals were evaluated during 24 h in cages and dissected tissues. RESULTS: Labelling efficiency of all radiopharmaceuticals ranged between 94% and 98%, with high stability both in saline and in human serum. In vitro binding assays displayed a rapid but poor bacterial binding for all tested agents. Similar binding kinetic occurred also with heat-killed and ethanol-killed bacteria. In the tissue cage model, infection was detected at different time points: 99mTc-UBI and 99mTcN-CiproCS2 showed higher infected cage/sterile cage ratio at 24 hours for both E. coli and S. aureus; 99mTc-Ciprofloxacin at 24 hours for both E. coli and at 4 hours for S. aureus; 111In-DTPA-biotin accumulates faster in both E. coli and S. aureus infected cages. CONCLUSIONS: 99mTc-UBI, 99mTcN-CiproCS2 showed poor in vitro binding but good in vivo binding to E. coli only. 111In-DTPA-biotin showed poor in vitro binding but good in vivo binding to S. aureus and poor to E. coli. 99mTc-Ciprofloxacin showed poor in vitro binding but good in vivo binding to all tested bacteria. The mechanism of accumulation in infected sites remains to be elucidated.

In-vivo imaging of tumor-infiltrating immune cells: implications for cancer immunotherapy.

Dynamic interactions between tumor cells and immune cells promote the initiation, progression, metastasis and therapy-resistance of cancer. With respect to immunotherapy, immune cell populations such as cytotoxic CD8+ T-cells, CD56+ NK cells and myeloid phagocytic cells play decisive roles. From an imaging perspective, the immune system displays unique challenges, which have implications for the design and performance of studies. The immune system comprises highly mobile cells that undergo distinct phases of development and activation. These cells circulate through several compartments during their active life span and accumulate in rather limited numbers in cancer lesion, where their effector phenotype further diversifies. Given these features, accurate evaluation of the tumor microenvironment and its cellular components during anti-cancer immunotherapy is challenging. In-vivo imaging currently offers quantitative and sensitive modalities that exploit long-lived tracers to interrogate, e.g. distinct immune cell populations, metabolic phenotypes, specific targets relevant for therapy or critical for their effector function. This review provides a comprehensive overview of current status for in-vivo imaging tumor-infiltrating immune cell populations, focusing on lymphocytes, NK cells and myeloid phagocytic cells, with emphasis on clinical translation.

Animal models for the study of inflammatory bowel diseases: a meta-analysis on modalities for imaging inflammatory lesions.

Inflammatory bowel diseases are lifelong disorders affecting the gastrointestinal tract characterized by intermittent disease flares and periods of remission with a progressive and destructive nature. Unfortunately, the exact etiology is still not completely known, therefore a causal therapy to cure the disease is not yet available. Current treatment options mainly encompass the use of non-specific anti-inflammatory agents and immunosuppressive drugs that cause significant side effects that often have a negative impact on patients' quality of life. As the majority of patients need a long-term follow-up it would be ideal to rely on a non-invasive technique with good compliance. Currently, the gold standard diagnostic tools for managing IBD are represented by invasive procedures such as colonoscopy and histopathology. Nevertheless, recent advances in imaging technology continue to improve the ability of imaging techniques to non-invasively monitor disease activity and treatment response in preclinical models of IBD. Novel and emerging imaging techniques not only allow direct visualization of intestinal inflammation, but also enable molecular imaging and targeting of specific alterations of the inflamed murine mucosa. Furthermore, molecular imaging advances allow us to increase our knowledge on the critical biological pathways involved in disease progression by characterizing in vivo processes at a cellular and molecular level and enabling significant improvements in the understanding of the etiology of IBD. This review presents a critical and updated overview on the imaging advances in animal models of IBD. Our aim is to highlight the potential beneficial impact and the range of applications that imaging techniques could offer for the improvement of the clinical monitoring and management of IBD patients: diagnosis, staging, determination of therapeutic targets, monitoring therapy and evaluation of the prognosis, personalized therapeutic approaches.

Image acquisition and interpretation criteria for 99mTc-HMPAO-labelled white blood cell scintigraphy: results of a multicentre study.

PURPOSE: There is no consensus yet on the best protocol for planar image acquisition and interpretation of radiolabelled white blood cell (WBC) scintigraphy. This may account for differences in reported diagnostic accuracy amongst different centres. METHODS: This was a multicentre retrospective study analysing 235 WBC scans divided into two groups. The first group of scans (105 patients) were acquired with a fixed-time acquisition protocol and the second group (130 patients) were acquired with a decay time-corrected acquisition protocol. Planar images were interpreted both qualitatively and semiquantitatively. Three blinded readers analysed the images. RESULTS: The most accurate imaging acquisition protocol comprised image acquisition at 3 - 4 h and at 20 - 24 h in time mode with acquisition times corrected for isotope decay. CONCLUSION: Using this protocol, visual analysis had high sensitivity and specificity in the diagnosis of infection. Semiquantitative analysis could be used in doubtful cases, with no cut-off for the percentage increase in radiolabelled WBC over time, as a criterion to define a positive scan.

In vivo and in vitro evidence that 99mTc-HYNIC-interleukin-2 is able to detect T lymphocytes in vulnerable atherosclerotic plaques of the carotid artery.

PURPOSE: Recent advances in basic science have established that inflammation plays a pivotal role in the pathogenesis of atherosclerosis. Inflammatory cells are thought to be responsible for the transformation of a stable plaque into a vulnerable one. Lymphocytes constitute at least 20 % of infiltrating cells in these vulnerable plaques. Therefore, the interleukin-2 (IL-2) receptor, being overexpressed on activated T lymphocytes, may represent an attractive biomarker for plaque vulnerability. The aim of this study was to evaluate the specificity of radiolabelled IL-2 [(99m)Tc-hydrazinonicotinamide (HYNIC)-IL-2] for imaging the lymphocytic infiltration in carotid plaques in vivo by planar and single photon emission computed tomography (SPECT)/CT imaging and ex vivo by microSPECT and autoradiography. METHODS: For the in vivo study, ten symptomatic patients with advanced plaques at ultrasound who were scheduled for carotid endarterectomy underwent (99m)Tc-HYNIC-IL-2 scintigraphy. The images were analysed visually on planar and SPECT images and semi-quantitatively on SPECT images by calculating target to background (T/B) ratios. After endarterectomy, immunomorphological evaluation and immunophenotyping were performed on plaque slices. For the ex vivo studies, four additional patients were included and, after in vitro incubation of removed plaques with (99m)Tc-HYNIC-IL-2, autoradiography was performed and microSPECT images were acquired. RESULTS: Visual analysis defined clear (99m)Tc-HYNIC-IL-2 uptake in seven of the ten symptomatic plaques. SPECT/CT allowed visualization in eight of ten. A significant correlation was found between the number of CD25+ lymphocytes and the total number of CD25+ cells in the plaque and the T/B ratio with adjacent carotid artery as background (Pearson's r = 0.89, p = 0.003 and r = 0.87, p = 0.005, respectively). MicroSPECT imaging showed clear (99m)Tc-HYNIC-IL-2 uptake within the plaque wall and not in the lipidic core. With autoradiography, only CD3+ lymphocytes were found to be labelled. CONCLUSION: These in vivo and ex vivo studies confirm the specificity of (99m)Tc-HYNIC-IL-2 for imaging activated T lymphocytes in carotid plaques. (99m)Tc-HYNIC-IL-2 is a true marker for the inflamed plaque and therefore of plaque instability.

Radiolabelled FGF-2 for Imaging Activated Fibroblasts in the Tumor Micro-Environment.

Tumor associated fibroblasts (TAFs) play a key role in tumor growth and metastatization. TAFs overexpress different biomarkers that are usually expressed at low levels in physiological conditions. Among them are the fibroblast growth factor receptors (FGFRs) that bind the fibroblast growth factors (FGFs). In particular, the overexpression of FGFR-2c in tumors has been associated with advanced clinical stages and increased metastatization. Here, we developed a non-invasive tool to evaluate, in vivo, the expression of FGFR-2c in metastatic cancer. This is based on 99mTc-labelled FGF-2. METHODS: 99mTc-FGF-2 was tested in vitro and in vivo in mice bearing allografts of sarcoma cells. Images of 99mTc-FGF-2 were acquired using a new portable high-resolution ultra-sensitive gamma camera for small animal imaging. RESULTS: FGF-2 was labeled with high specific activity but low labelling efficiency, thus requiring post-labeling purification by gel-filtration chromatography. In vitro binding to 2C human keratinocytes showed a Kd of 3.36 × 10-9 M. In mice bearing J774A.1 cell allografts, we observed high and rapid tumor uptake of 99mTc-FGF-2 with a high Tumor/Blood ratio at 24 h post-injection (26.1 %ID/g and 12.9 %ID) with low kidney activity and moderate liver activity. CONCLUSIONS: we labeled FGF-2 with 99mTc and showed nanomolar Kd in vitro with human keratinocytes expressing FGF-2 receptors. In mice, 99mTc-FGF-2 rapidly and efficiently accumulated in tumors expressing FGF-2 receptors. This new radiopharmaceutical could be used in humans to image TAFs.

Leukocyte and bacteria imaging in prosthetic joint infection.

There has been a significant increase in the number of joint prosthesis replacements worldwide. Although relatively uncommon, complications can occur with the most serious being an infection. Various radiological and nuclear imaging techniques are available to diagnose prosthetic joint infections (PJI). In this review article, we describe the pathophysiology of PJI, the principles of nuclear medicine imaging and the differences between Single Photon Emission Computed Tomography (SPECT) and Positron Emission Tomography (PET). The value of nuclear medicine techniques for clinical practice is also discussed. Then we provide an overview of the most often used radionuclide imaging techniques that may be helpful in diagnosing prosthetic joint infection: the (67)Ga-citrate, labelled white blood cells in vitro and in vivo (monoclonal antibodies directed against specific targets on the leukocytes), and (18)F-fluorodeoxyglucose ((18)F-FDG). We describe their working methods, the pitfalls, and the interpretation criteria. Furthermore, we review recent advances in imaging bacteria, a molecular imaging method that holds promises for the detection of occult infections. We conclude proposing two diagnostic flow-charts, based on data in the literature, that could help the clinicians to choose the best nuclear imaging method when they have a patient with suspicion of or with proven PJI.

The use of (18)F-FDG-PET/CT for diagnosis and treatment monitoring of inflammatory and infectious diseases.

FDG-PET, combined with CT, is nowadays getting more and more relevant for the diagnosis of several infectious and inflammatory diseases and particularly for therapy monitoring. Thus, this paper gives special attention to the role of FDG-PET/CT in the diagnosis and therapy monitoring of infectious and inflammatory diseases. Enough evidence in the literature already exists about the usefulness of FDG-PET/CT in the diagnosis, management, and followup of patients with sarcoidosis, spondylodiscitis, and vasculitis. For other diseases, such as inflammatory bowel diseases, rheumatoid arthritis, autoimmune pancreatitis, and fungal infections, hard evidence is lacking, but studies also point out that FDG-PET/CT could be useful. It is of invaluable importance to have large prospective multicenter studies in this field to provide clear answers, not only for the status of nuclear medicine in general but also to reduce high costs of treatment.

Radioimmune Imaging of α4ß7 Integrin and TNFα for Diagnostic and Therapeutic Applications in Inflammatory Bowel Disease.

Imaging using radiolabelled monoclonal antibodies can provide, non-invasively, molecular information which allows for the planning of the best treatment and for monitoring the therapeutic response in cancer, as well as in chronic inflammatory diseases. In the present study, our main goal was to evaluate if a pre-therapy scan with radiolabelled anti-α4ß7 integrin or radiolabelled anti-TNFα mAb could predict therapeutic outcome with unlabelled anti-α4ß7 integrin or anti-TNFα mAb. To this aim, we developed two radiopharmaceuticals to study the expression of therapeutic targets for inflammatory bowel diseases (IBD), to be used for therapy decision making. Both anti-α4ß7 integrin and anti-TNFα mAbs were successfully radiolabelled with technetium-99m with high labelling efficiency and stability. Dextran sulfate sodium (DSS)-induced colitis was used as a model for murine IBD and the bowel uptake of radiolabelled mAbs was evaluated ex vivo and in vivo by planar and SPECT/CT images. These studies allowed us to define best imaging strategy and to validate the specificity of mAb binding in vivo to their targets. Bowel uptake in four different regions was compared to immunohistochemistry (IHC) score (partial and global). Then, to evaluate the biomarker expression prior to therapy administration, in initial IBD, another group of DSS-treated mice was injected with radiolabelled mAb on day 2 of DSS administration (to quantify the presence of the target in the bowel) and then injected with a single therapeutic dose of unlabelled anti-α4ß7 integrin or anti-TNFα mAb. Good correlation was demonstrated between bowel uptake of radiolabelled mAb and immunohistochemistry (IHC) score, both in vivo and ex vivo. Mice treated with unlabelled α4ß7 integrin and anti-TNFα showed an inverse correlation between the bowel uptake of radiolabelled mAb and the histological score after therapy, proving that only mice with high α4ß7 integrin or TNFα expression will benefit of therapy with unlabelled mAb.

FMR1 deletion in rats induces hyperactivity with no changes in striatal dopamine transporter availability.

Autism Spectrum Disorder (ASD) is a pervasive neurodevelopmental disorder emerging in early life characterized by impairments in social interaction, poor verbal and non-verbal communication, and repetitive patterns of behaviors. Among the best-known genetic risk factors for ASD, there are mutations causing the loss of the Fragile X Messenger Ribonucleoprotein 1 (FMRP) leading to Fragile X syndrome (FXS), a common form of inherited intellectual disability and the leading monogenic cause of ASD. Being a pivotal regulator of motor activity, motivation, attention, and reward processing, dopaminergic neurotransmission has a key role in several neuropsychiatric disorders, including ASD. Fmr1 Δexon 8 rats have been validated as a genetic model of ASD based on FMR1 deletion, and they are also a rat model of FXS. Here, we performed behavioral, biochemical and in vivo SPECT neuroimaging experiments to investigate whether Fmr1 Δexon 8 rats display ASD-like repetitive behaviors associated with changes in striatal dopamine transporter (DAT) availability assessed through in vivo SPECT neuroimaging. At the behavioral level, Fmr1 Δexon 8 rats displayed hyperactivity in the open field test in the absence of repetitive behaviors in the hole board test. However, these behavioral alterations were not associated with changes in striatal DAT availability as assessed by non-invasive in vivo SPECT and Western blot analyses.

Immune cell labelling and tracking: implications for adoptive cell transfer therapies.

BACKGROUND: The understanding of the role of different immune cell subsets that infiltrate tumors can help researchers in developing new targeted immunotherapies to reactivate or reprogram them against cancer. In addition to conventional drugs, new cell-based therapies, like adoptive cell transfer, proved to be successful in humans. Indeed, after the approval of anti-CD19 CAR-T cell therapy, researchers are trying to extend this approach to other cancer or cell types. MAIN BODY: This review focuses on the different approaches to non-invasively monitor the biodistribution, trafficking and fate of immune therapeutic cells, evaluating their efficacy at preclinical and clinical stages. PubMed and Scopus databases were searched for published articles on the imaging of cell tracking in humans and preclinical models. CONCLUSION: Labelling specific immune cell subtypes with specific radiopharmaceuticals, contrast agents or optical probes can elucidate new biological mechanisms or predict therapeutic outcome of adoptive cell transfer therapies. To date, no technique is considered the gold standard to image immune cells in adoptive cell transfer therapies.

Synthesis and Biodistribution of 99mTc-Labeled PLGA Nanoparticles by Microfluidic Technique.

The aim of present study was to develop radiolabeled NPs to overcome the limitations of fluorescence with theranostic potential. Synthesis of PLGA-NPs loaded with technetium-99m was based on a Dean-Vortex-Bifurcation Mixer (DVBM) using an innovative microfluidic technique with high batch-to-batch reproducibility and tailored-made size of NPs. Eighteen different formulations were tested and characterized for particle size, zeta potential, polydispersity index, labeling efficiency, and in vitro stability. Overall, physical characterization by dynamic light scattering (DLS) showed an increase in particle size after radiolabeling probably due to the incorporation of the isotope into the PLGA-NPs shell. NPs of 60 nm (obtained by 5:1 PVA:PLGA ratio and 15 mL/min TFR with 99mTc included in PVA) had high labeling efficiency (94.20 ± 5.83%) and >80% stability after 24 h and showed optimal biodistribution in BALB/c mice. In conclusion, we confirmed the possibility of radiolabeling NPs with 99mTc using the microfluidics and provide best formulation for tumor targeting studies.

In Vitro and In Vivo Evaluation of 99mTc-Polymyxin B for Specific Targeting of Gram-Bacteria.

BACKGROUND: Infectious diseases are one of the main causes of morbidity and mortality worldwide. Nuclear molecular imaging would be of great help to non-invasively discriminate between septic and sterile inflammation through available radiopharmaceuticals, as none is currently available for clinical practice. Here, we describe the radiolabeling procedure and in vitro and in vivo studies of 99mTc-polymyxin B sulfate (PMB) as a new single photon emission imaging agent for the characterization of infections due to Gram-negative bacteria. RESULTS: Labeling efficiency was 97 ± 2% with an average molar activity of 29.5 ± 0.6 MBq/nmol. The product was highly stable in saline and serum up to 6 h. In vitro binding assay showed significant displaceable binding to Gram-negative bacteria but not to Gram-positive controls. In mice, 99mTc-HYNIC-PMB was mainly taken up by liver and kidneys. Targeting studies confirmed the specificity of 99mTc-HYNIC-PMB obtained in vitro, showing significantly higher T/B ratios for Gram-negative bacteria than Gram-positive controls. CONCLUSIONS: In vitro and in vivo results suggest that 99mTc-HYNIC-PMB has a potential for in vivo identification of Gram-negative bacteria in patients with infections of unknown etiology. However, further investigations are needed to deeply understand the mechanism of action and behavior of 99mTc-HYNIC-PMB in other animal models and in humans.

In Vivo Imaging of Thyroid Cancer with 99mTc-TR1401 and 99mTc-TR1402: A Comparison Study in Dogs.

Differentiated thyroid cancer (DTC) cells may lose NIS expression and iodine uptake, but usually express TSH receptors (TSHR). Therefore, the aim of our study was to compare two radiolabeled superagonist TSH analogues for DTC imaging. These analogues (namely TR1401 and TR1402) have a higher TSHR binding affinity than recombinant human TSH (Thyrogen®). Radiolabeling was performed with technetium-99m using an indirect method via HYNIC conjugation and was followed by in vitro quality controls and binding assay on TSHR-positive cell lines (ML-1). An in vitro binding assay was also performed and compared with radiolabeled human recombinant TSH. In vivo imaging was performed in four dogs with spontaneous follicular thyroid carcinoma with solid poorly differentiated areas with 99mTc-TR1401 SPECT/CT, 99mTc-TR1402 SPECT/CT, and [18F]FDG PET/CT on different days within 2 weeks. TR1401 and TR1402 were labeled with high specific activity (8.3 ± 1.2 MBq/µg) and retention of their biological activity and structural integrity. Both agonists were able to efficiently bind TSHR receptors expressed by cell lines with dissociation constants (Kd) of 2.7 nM for 99mTc-TR1401 and 0.5 nM for 99mTc-TR1402 compared with 99mTc-Thyrogen (Kd = 8.4 nM). In tumor-targeting experiments, a focal uptake was observed in dogs with spontaneous intraglandular thyroid carcinoma, in which TSHR expression was confirmed by immunohistochemistry. 99mTc-TR1402 provided higher T/B than 99mTc-TR1401 and [18F]FDG (12.9 ± 1.3, 10.2 ± 0.7, and 3.8 ± 0.6, respectively; all p < 0.001). Given these results, 99mTc-TR1402 appears to be a useful tool for in vivo imaging of thyroid cancer.

Handling of Doubtful WBC Scintigraphies in Patients with Suspected Prosthetic Joint Infections.

Despite the application of EANM recommendations for radiolabelled white-blood-cells (WBC) scintigraphy, some cases still remain doubtful based only on visual analysis. The aim of this study was to investigate the role of semi-quantitative analysis and bone marrow scan (BMS) in solving doubtful cases. We retrospectively evaluated all [99mTc]HMPAO-WBC scintigraphies performed, in the last 7 years, for a suspected monolateral prosthetic joint infection (PJI). In doubtful cases, we used five different thresholds of increase of target-to-background (T/B) ratio, between delayed and late images, as criteria of positivity (5%, 10%, 15%, 20% and 30%). BMS were also analysed and sensitivity, specificity and accuracy of different methods were calculated according to final diagnosis. The sensitivity, specificity and accuracy were, respectively, 77.8%, 43.8% and 53.0% for the cut-off at 5%; 72.2%, 66.7% and 68.2% for the cut-off at 10%; 66.7%, 75.0% and 72.7% for the cut-off at 15%; 66.7%, 85.4% and 80.3% for the cut-off at 20%; 33.3%, 93.8% and 77.3% for the cut-off at 30%. BMS provided a significantly higher diagnostic performance than 5%, 10% and 15% thresholds. Conversely, we did not observe any statistically significant difference between BMS and the cut-off of more than 20%. Therefore, doubtful cases should be analysed semi-quantitatively. An increase in T/B ratio of more than 20% between delayed and late images, should be considered as a criterion of positivity, thus avoiding BMS.

Relevance of immune cell and tumor microenvironment imaging in the new era of immunotherapy.

Tumor-infiltrating immune cells play a key role against cancer. However, malignant cells are able to evade the immune response and establish a very complex balance in which different immune subtypes may drive tumor progression, metastatization and resistance to therapy. New immunotherapeutic approaches aim at restoring the natural balance and increase immune response against cancer by different mechanisms. The complexity of these interactions and the heterogeneity of immune cell subpopulations are a real challenge when trying to develop new immunotherapeutics and evaluate or predict their efficacy in vivo. To this purpose, molecular imaging can offer non-invasive diagnostic tools like radiopharmaceuticals, contrast agents or fluorescent dyes. These agents can be useful for preclinical and clinical purposes and can overcome [18F]FDG limitations in discriminating between true-progression and pseudo-progression. This review provides a comprehensive overview of immune cells involved in microenvironment, available immunotherapies and imaging agents to highlight the importance of new therapeutic biomarkers and their in vivo evaluation to improve the management of cancer patients.

Theranostic Designed Near-Infrared Fluorescent Poly (Lactic-co-Glycolic Acid) Nanoparticles and Preliminary Studies with Functionalized VEGF-Nanoparticles.

Poly-lactic-co-glycolic acid nanoparticles (PLGA-NPs) were approved by the Food and Drug Administration (FDA) for drug delivery in cancer. The enhanced permeability and retention (EPR) effect drives their accumulation minimizing the side effects of chemotherapeutics. Our aim was to develop a new theranostic tool for cancer diagnosis and therapy based on PLGA-NPs and to evaluate the added value of vascular endothelial growth factor (VEGF) for enhanced tumor targeting. In vitro and in vivo properties of PLGA-NPs were tested and compared with VEGF-PLGA-NPs. Dynamic light scattering (DLS) was performed to evaluate the particle size, polydispersity index (PDI), and zeta potential of both preparations. Spectroscopy was used to confirm the absorption spectra in the near-infrared (NIR). In vivo, in BALB/c mice bearing a syngeneic tumor in the right thigh, intravenously injected PLGA-NPs showed a high target-to-muscle ratio (4.2 T/M at 24 h post-injection) that increased over time, with a maximum uptake at 72 h and a retention of the NPs up to 240 h. VEGF-PLGA-NPs accumulated in tumors 1.75 times more than PLGA-NPs with a tumor-to-muscle ratio of 7.90 ± 1.61 (versus 4.49 ± 0.54 of PLGA-NPs). Our study highlights the tumor-targeting potential of PLGA-NPs for diagnostic and therapeutic applications. Such NPs can be conjugated with proteins such as VEGF to increase accumulation in tumor lesions.

State of the Art of Natural Killer Cell Imaging: A Systematic Review.

Natural killer (NK) cell therapy is a promising alternative to conventional T cell-based treatments, although there is a lack of diagnostic tools to predict and evaluate therapeutic outcomes. Molecular imaging can offer several approaches to non-invasively address this issue. In this study, we systematically reviewed the literature to evaluate the state of the art of NK cell imaging and its translational potential. PubMed and Scopus databases were searched for published articles on the imaging of NK cells in humans and preclinical models. Study quality was evaluated following Quality Assessment of Diagnostic Accuracy Studies (QUADAS-2) criteria. We pooled studies as follows: Optical, magnetic resonance imaging (MRI) and nuclear medicine imaging with a total of 21 studies (n = 5, n = 8 and n = 8, respectively). Considering the limitation of comparing different imaging modalities, it appears that optical imaging (OI) of NK cells is very useful in a preclinical setting, but has the least translational potential. MRI provides high quality images without ionizing radiations with lower sensitivity. Nuclear medicine is the only imaging technique that has been applied in humans (four papers), but results were not outstanding due to a limited number of enrolled patients. At present, no technique emerged as superior over the others and more standardization is required in conducting human and animal studies.

PET Radiopharmaceuticals for Specific Bacteria Imaging: A Systematic Review.

BACKGROUND: Bacterial infections are still one of the main factors associated with mortality worldwide. Many radiopharmaceuticals were developed for bacterial imaging, both with single photon emission computed tomography (SPECT) and positron emission tomography (PET) isotopes. This review focuses on PET radiopharmaceuticals, performing a systematic literature review of published studies between 2005 and 2018. METHODS: A systematic review of published studies between 2005 and 2018 was performed. A team of reviewers independently screened for eligible studies. Because of differences between studies, we pooled the data where possible, otherwise, we described separately. Quality of evidence was assessed by Quality Assessment of Diagnostic Accuracy Studies (QUADAS) approach. RESULTS: Eligible papers included 35 published studies. Because of the heterogeneity of animal models and bacterial strains, we classified studies in relation to the type of bacterium: Gram-positive, Gram-negative, Gram-positive and negative, others. CONCLUSIONS: Results highlighted the availability of many promising PET radiopharmaceuticals for bacterial imaging, despite some bias related to animal selection and index test, but few have been translated to human subjects. Results showed a lack of standardized infection models and experimental settings.