Radiochemical pharmacokinetic profile of P10 peptide with antifungal properties.

Paracoccidioidomycosis (PCM) is a chronic granulomatous disease that is caused by the thermally dimorphic fungus Paracoccidioides brasiliensis. It is endemic in some countries of Latin America and can cause a high-burden fungal infection with significant morbidity and mortality. The peptide P10, which demonstrates immune protection against experimental PCM, was radiolabeled with a radioisotope and evaluated in vivo. The radiolabeling was conducted to trace the pharmacokinetics of the molecule in principal organs and tissues. This was achieved with high radiochemical purity. Biodistribution and scintigraphic imaging showed fast blood clearance that was mainly renal; however, hepatobiliar excretion was also, with marked uptake in cervical lymph nodes. This profile may be useful for the development of a prophylactic drug or vaccine for patients exposed to PCM.

Effect of nanoemulsion modification with chitosan and sodium alginate on the topical delivery and efficacy of the cytotoxic agent piplartine in 2D and 3D skin cancer models.

Due to the limited options for topical management of skin cancer, this study aimed at developing and evaluating nanoemulsions (NE) for topical delivery of the cytotoxic agent piplartine (piperlongumine). NEs were modified with chitosan or sodium alginate, and the effects on the physicochemical properties, piplartine delivery and formulation efficacy were evaluated. The nanoemulsion droplets displayed similar size (96-112 nm), but opposite charge; the polysaccharides improved piplartine penetration into and across the skin (1.3-1.9-fold) in a similar manner, increasing the ratio "drug in the skin/receptor phase" by 1.4-1.5-fold compared to the plain NE and highlighting their relevance for cutaneous localization. Oleic acid addition to the chitosan-containing NE further increased drug penetration (~1.9-2.0-fold), as did increases in drug content from 0.5 to 1%. The cytotoxicity of piplartine was ~2.8-fold higher when the drug was incorporated in the chitosan-containing NE compared to its solution (IC50 = 14.6 µM) against melanoma cells. The effects of this nanocarrier on 3D melanoma tissues were concentration-related; at 1%, piplartine elicited marked epidermis destruction. These results support the potential applicability of the chitosan-modified nanoemulsion containing piplartine as a new strategy for local management of skin cancer.

Comparison of two peptide radiotracers for prostate carcinoma targeting.

OBJECTIVES: Scintigraphy is generally not the first choice treatment for prostate cancer, although successful studies using bombesin analog radiopeptides have been performed. Recently, a novel peptide obtained using a phage display library demonstrated an affinity for prostate tumor cells. The aim of this study was to compare the use of a bombesin analog to that of a phage display library peptide (DUP-1) radiolabeled with technetium-99m for the treatment of prostate carcinoma. The peptides were first conjugated to S-acetyl-MAG3 with a 6-carbon spacer, namely aminohexanoic acid. METHODS: The technetium-99m labeling required a sodium tartrate buffer. Radiochemical evaluation was performed using ITLC and was confirmed by high-performance liquid chromatography. The coefficient partition was determined, and in vitro studies were performed using human prostate tumor cells. Biodistribution was evaluated in healthy animals at various time points and also in mice bearing tumors. RESULTS: The radiochemical purity of both radiotracers was greater than 95%. The DUP-1 tracer was more hydrophilic (log P = -2.41) than the bombesin tracer (log P = -0.39). The biodistribution evaluation confirmed this hydrophilicity by revealing the greater kidney uptake of DUP-1. The bombesin concentration in the pancreas was greater than that of DUP-1 due to specific gastrin-releasing peptide receptors. Bombesin internalization occurred for 78.32% of the total binding in tumor cells. The DUP-1 tracer showed very low binding to tumor cells during the in vitro evaluation, although tumor uptake for both tracers was similar. The tumors were primarily blocked by DUP1 and the bombesin radiotracer primarily targeted the pancreas. CONCLUSION: Further studies with the radiolabeled DUP-1 peptide are recommended. With further structural changes, this molecule could become an efficient alternative tracer for prostate tumor diagnosis.

Radiotracers for different angiogenesis receptors in a melanoma model.

Early and reliable diagnosis of melanoma, a skin tumor with a poor prognosis, is extremely important. Phage display peptide libraries are a convenient screening resource for identifying bioactive peptides that interact with cancer targets. The aim of this study was to evaluate two technetium-99m tracers for angiogenesis detection in a melanoma model, using cyclic pegylated pentapeptide with RGD and NGR motifs conjugated with the bifunctional chelator mercaptoacetyltriglycine (MAG(3)). The conjugated peptides (10 µl of a µg/µl solution) were labeled with technetium-99m using a sodium tartrate buffer. Radiochemical evaluation was carried out by instant thin-layer chromatography and confirmed by high-performance liquid chromatography. The partition coefficient was determined and internalization assays were performed in two melanoma cell lines (B16F10 and SKMEL28). Biodistribution evaluation of the tracers was carried out in healthy animals at different time points and also in tumor-bearing mice, 120 min post injection. Blocking studies were also conducted by coinjection of cold peptides. The conjugates displayed a rather similar pharmacokinetic profile. They were radiolabeled with high radiochemical purity (>97%) and both were hydrophilic with preferential renal excretion. Yet, tumor uptake was higher for human than for murine melanoma cells, especially for [(99m)Tc]-MAG(3)-PEG(8)-c(RGDyk) (7.85±2.34%injected dose/g 120 min post injection). The performance of [(99m)Tc]-MAG(3)-PEG(8)-c(RGDyk) was better than the NGR tracer with regard to human melanoma uptake. In this sense, it should be considered for future radiotracer studies of tumor diagnosis.

Comparison of two peptide radiotracers for prostate carcinoma targeting

OBJECTIVES: Scintigraphy is generally not the first choice treatment for prostate cancer, although successful studies using bombesin analog radiopeptides have been performed. Recently, a novel peptide obtained using a phage display library demonstrated an affinity for prostate tumor cells. The aim of this study was to compare the use of a bombesin analog to that of a phage display library peptide (DUP-1) radiolabeled with technetium-99m for the treatment of prostate carcinoma. The peptides were first conjugated to S-acetyl-MAG3 with a 6-carbon spacer, namely aminohexanoic acid. METHODS: The technetium-99m labeling required a sodium tartrate buffer. Radiochemical evaluation was performed using ITLC and was confirmed by high-performance liquid chromatography. The coefficient partition was determined, and in vitro studies were performed using human prostate tumor cells. Biodistribution was evaluated in healthy animals at various time points and also in mice bearing tumors. RESULTS: The radiochemical purity of both radiotracers was greater than 95 percent. The DUP-1 tracer was more hydrophilic (log P = -2.41) than the bombesin tracer (log P = -0.39). The biodistribution evaluation confirmed this hydrophilicity by revealing the greater kidney uptake of DUP-1. The bombesin concentration in the pancreas was greater than that of DUP-1 due to specific gastrin-releasing peptide receptors. Bombesin internalization occurred for 78.32 percent of the total binding in tumor cells. The DUP-1 tracer showed very low binding to tumor cells during the in vitro evaluation, although tumor uptake for both tracers was similar. The tumors were primarily blocked by DUP1 and the bombesin radiotracer primarily targeted the pancreas. CONCLUSION: Further studies with the radiolabeled DUP-1 peptide are recommended. With further structural changes, this molecule could become an efficient alternative tracer for prostate tumor diagnosis.