Synthesis, structural characterization and study of antioxidant and anti-PrPSc properties of flavonoids and their rhenium(I)-tricarbonyl complexes.

This study aims at the synthesis and initial biological evaluation of novel rhenium-tricarbonyl complexes of 3,3',4',5,7-pentahydroxyflavone (quercetin), 3,7,4΄-trihydroxyflavone (resokaempferol), 5,7-dihydroxyflavone (chrysin) and 4΄,5,7-trihydroxyflavonone (naringenin) as neuroprotective and anti-PrP agents. Resokaempferol was synthesized from 2,2΄,4-trihydroxychalcone by H2O2/NaOH. The rhenium-tricarbonyl complexes of the type fac-[Re(CO)3(Fl)(sol)] were synthesized by reacting the precursor fac-[Re(CO)3(sol)3]+ with an equimolar amount of the flavonoids (Fl) quercetin, resokaempferol, chrysin and naringenin and the solvent (sol) was methanol or water. The respective Re-flavonoid complexes were purified by semi-preparative HPLC and characterized by spectroscopic methods. Furthermore, the structure of Re-chrysin was elucidated by X-ray crystallography. Initial screening of the neuroprotective properties of these compounds included the in vitro assessment of the antioxidant properties by the DPPH assay as well as the anti-lipid peroxidation of linoleic acid in the presence of AAPH and their ability to inhibit soybean lipoxygenase. From the above studies, it was concluded that the complexes' properties are mainly correlated with the structural characteristics and the presence of the flavonoids. The flavonoids and their respective Re-complexes were also tested in vitro for their ability to inhibit the formation and aggregation of the amyloid-like abnormal prion protein, PrPSc, by employing the real-time quaking-induced conversion assay with recombinant PrP seeded with cerebrospinal fluid from patients with Creutzfeldt-Jakob disease. All the compounds blocked de novo abnormal PrP formation and aggregation.

Organometallic rhenium tricarbonyl-enrofloxacin and -levofloxacin complexes: synthesis, albumin-binding, DNA-interaction and cell viability studies.

Organometallic rhenium complexes have recently been considered in the development of novel antitumor agents due to their suitable properties. A series of rhenium(I) tricarbonyl complexes was synthesized with the quinolone antimicrobial agents enrofloxacin (Herx) and levofloxacin (Hlfx) and solvent (e.g., methanol), imidazole (im) or pyridine (py) as co-ligands. The complexes were characterized by spectroscopic methods. The interaction of the rhenium complexes with bovine serum albumin was investigated by fluorescence emission spectroscopy and the corresponding binding constants were determined. The binding of the rhenium complexes to calf-thymus DNA was monitored by UV-Vis spectroscopy, viscosity measurements and competitive studies with ethidium bromide. These studies indicated that intercalation is the most possible mode of action and the corresponding DNA-binding constants of the complexes were calculated. The cytotoxicity of the Re-complexes against human K-562 erythroleukemia cells was found to be moderate to high. These preliminary results are promising and warrant the design of new Re-complexes with improved properties in future studies.

Synthesis and evaluation of Re/99mTc(I) complexes bearing a somatostatin receptor-targeting antagonist and labeled via a novel [N,S,O] clickable bifunctional chelating agent.

The somatostatin receptor subtype 2 (SSTR2) is often highly expressed on neuroendocrine tumors (NETs), making it a popular in vivo target for diagnostic and therapeutic approaches aimed toward management of NETs. In this work, an antagonist peptide (sst2-ANT) with high affinity for SSTR2 was modified at the N-terminus with a novel [N,S,O] bifunctional chelator (2) designed for tridentate chelation of rhenium(I) and technetium(I) tricarbonyl cores, [Re(CO)3]+ and [99mTc][Tc(CO)3]+. The chelator-peptide conjugation was performed via a Cu(I)-assisted click reaction of the alkyne-bearing chelator (2) with an azide-functionalized sst2-ANT peptide (3), to yield NSO-sst2-ANT (4). Two synthetic methods were used to prepare Re-4 at the macroscopic scale, which differed based on the relative timing of the click conjugation to the [Re(CO)3]+ complexation by 2. The resulting products demonstrated the expected molecular mass and nanomolar in vitro SSTR2 affinity (IC50 values under 30 nM, AR42J cells, [125I]iodo-Tyr11-somatostatin-14 radioligand standard). However, a difference in their HPLC retention times suggested a difference in metal coordination modes, which was attributed to a competing N-triazole donor ligand formed during click conjugation. Surprisingly, the radiotracer scale reaction of [99mTc][Tc(OH2)3(CO)3]+ (99mTc; t½â€¯= 6 h, 141 keV γ) with 4 formed a third product, distinct from the Re analogues, making this one of the unusual cases in which Re and Tc chemistries are not well matched. Nevertheless, the [99mTc]Tc-4 product demonstrated excellent in vitro stability to challenges by cysteine and histidine (≥98% intact through 24 h), along with 75% stability in mouse serum through 4 h. In vivo biodistribution and microSPECT/CT imaging studies performed in AR42J tumor-bearing mice revealed improved clearance of this radiotracer in comparison to a similar [99mTc][Tc(CO)3]-labeled sst2-ANT derivative previously studied. Yet despite having adequate tumor uptake at 1 h (4.9% ID/g), tumor uptake was not blocked by co-administration of a receptor-saturating dose of SS-14. Aimed toward realignment of the Re and Tc product structures, future efforts should include distancing the alkyne group from the intended donor atoms of the chelator, to reduce the coordination options available to the [M(CO)3]+ core (M = Re, 99mTc) by disfavoring involvement of the N-triazole.

Technetium-99m radiochemistry for pharmaceutical applications.

Technetium-99m (99m Tc) is a widely used radionuclide, and the development of 99m Tc imaging agents continues to be in demand. This overview discusses basic principles of 99m Tc radiopharmaceutical preparation and design and focuses on the 99m Tc radiochemistry relevant to its pharmaceutical applications. The 99m Tc complexes are described based on the most typical examples in each category, keeping up with the state-of-the-art in the field. In addition, the main current strategies to develop targeted 99m Tc radiopharmaceuticals are summarized.

Development and Pharmacological Evaluation of New Bone-Targeted (99m)Tc-Radiolabeled Bisphosphonates.

A novel bisphosphonate, 1-(3-aminopropylamino)ethane-1,1-diyldiphosphonic acid (3), was coupled to the tridentate chelators di-2-picolylamine, 2-picolylamine-N-acetic acid, iminodiacetic acid, 3-((2-aminoethyl)thio)-3-(1H-imidazol-4-yl)propanoic acid, and 2-((2-carboxyethyl)thio)-3-(1H-imidazol-4-yl)propanoic acid to form ligands 6, 9, 11, 15, and 19, respectively. Organometallic complexes of the general formula [Re/(99m)Tc(CO)3(κ(3)-L)] were synthesized, where L denotes ligand 6, 9, 11, 15, or 19. The rhenium complexes were prepared at the macroscopic level and characterized by spectroscopic methods. The technetium-99m organometallic complexes were synthesized in high yield and were identified by comparative reversed-phase HPLC with their Re analogues. The (99m)Tc tracers were stable in vitro and exhibited binding to hydroxyapatite. In biodistribution studies, all of the (99m)Tc complexes exhibited high bone uptake superior to that of 25, which is the directly (99m)Tc-labeled bisphosphonate 3, and comparable to that of (99m)Tc-methylene diphosphonate ((99m)Tc-MDP). The tracers [(99m)Tc(CO)3(6)] (26), [(99m)Tc(CO)3(9)] (27), [(99m)Tc(CO)3(11)] (28), and [(99m)Tc(CO)3(15)] (29) exhibited higher bone/blood ratios than (99m)Tc-MDP. 26 had the highest bone uptake at 1 h p.i. The new bisphosphonates showed no substantial growth inhibitory capacity in PC-3, Saos-2, and MCF-7 established cancer cell lines at low concentrations. Incubation of 26 with the same cancer cell lines indicated a rapid and saturated uptake. The promising properties of 26-29 indicate their potential for use as bone-imaging agents.

Retrograde transport of radiolabelled botulinum neurotoxin type A to the CNS after intradetrusor injection in rats.

OBJECTIVE: To investigate the potential distribution of radiolabelled botulinum neurotoxin type A (BoNT/A) in the CNS after bladder injection in normal rats, by using the gamma-emitting radionuclide technetium-99 m ((99m) Tc). MATERIALS AND METHODS: BoNT/A was radiolabelled by pretreatment with 2-iminothiolane and incubation with (99m) Tc-gluconate. The labelled toxin (99m) Tc-BoNT/A was purified using size exclusion HPLC. Twenty-four female Wistar rats were evenly injected in the bladder wall with either (99m) Tc-ΒοΝΤ/Α (n = 12) or free (99m) Tc (n = 12). Four rats from each group were killed at 1, 3 and 6 h after injection, respectively. The bladder, L6-S1 spinal cord segment and L6-S1 dorsal root ganglia (DRG) were harvested and their radioactivity counted in a gamma scintillation detector. Results were calculated as % injected dose (I.D.) per gram of tissue. The paired t-test was used for comparison of means of (99m) Tc-ΒοΝΤ/Α radioactivity vs free (99m) Tc in the tissues of interest. RESULTS: Radiolabelled BoNT/A had a high radiochemical stability of 70% after 24 h. Gradual accumulation of (99m) Tc-ΒοΝΤ/Α was observed in the DRG up to 6 h after injection (P = 0.04 and P = 0.029 compared with 1 h and 3 h, respectively), while no accumulation was detected for free (99m) Tc. Consequently, (99m) Tc-ΒοΝΤ/Α radioactivity in the DRG was higher than free (99m) Tc radioactivity (3.18 ± 0.67% I.D./g vs 0.19 ± 0.10% I.D./g [P = 0.002] 6 h after injection). Values for (99m) Tc-ΒοΝΤ/Α radioactivity in the spinal cord were higher than those for free (99m) Tc, but not significantly. The bladder retained higher dosages of (99m) Tc-ΒοΝΤ/Α than free (99m) Tc at all time points. CONCLUSIONS: Significant accumulation of the radiolabelled toxin in the lumbosacral DRG, together with a less significant uptake in the respective spinal cord segment as opposed to free radioactivity provide first evidence of the retrograde transport of BoNT/A to the CNS after bladder injection in rats.

Synthesis, characterization, and biological evaluation of new biotinylated (99m) Tc/Re-tricarbonyl complexes.

The synthesis and biological evaluation of three new biotinylated fac-[(99m)Tc/Re(CO)3](+) complexes with the tridentate ligands L1, L2, and L3 are reported. L1-L3 contain the chelators 2-((5-aminopentyl)(pyridin-2-ylmethyl)amino)acetic acid, 2-(2-aminoethylthio)-3-(1H-imidazol-4-yl)propanoic acid, and 2-amino-3-(1-carboxy-2-(1H-imidazol-4-yl)ethylthio)propanoic acid, respectively, which are conjugated to biotin's carboxylate via their amine group. The fac-[Re(CO)3(L1-L3)] complexes were synthesized and characterized by NMR and IR, where the (N,N,O) coordination for ReL1 and the (N,S,O) coordination for ReL2 and ReL3 were confirmed. The tracer complexes fac-[(99m)Tc(CO)3(L1-L3)] were synthesized in high yield and were found highly stable in 10(-3) M L-histidine and L-cysteine over 24 h. Furthermore, they exhibited high binding affinity (>90%) for avidin. Rat plasma studies showed complete cleavage of biotin from (99m)TcL1 after 1 h and a low percentage of intact (99m)TcL2 and (99m)TcL3 with no biotin cleavage metabolites present, over 24 h. Similarly, rat urine analysis showed the presence of intact (99m)TcL2 and (99m)TcL3, while (99m)TcL1 was cleaved. Biodistribution studies of (99m)TcL2 and (99m)TcL3 revealed fast blood and tissue clearance.

PTD-mediated delivery of α-globin chain into Κ-562 erythroleukemia cells and α-thalassemic (HBH) patients' RBCs ex vivo in the frame of Protein Replacement Therapy.

BACKGROUND: α-Thalassemia, a congenital hemoglobinopathy, is characterized by deficiency and/or reduced levels of α-globin chains in serious forms of α-thalassemia (HbH disease/Hb Bart's). This research work deals with a Protein Replacement Therapy approach in order to manage α-thalassemia manifestations, caused by the excess of ß-globin chain into HbH RBCs. The main goal was to produce the recombinant human α-globin chain in fusion with TAT, a Protein Transduction Domain, to ex vivo deliver it into HbH patients RBCs, to replace the endogenous missing α-globin chain. RESULTS: Cloning of the α-globin coding sequence, fused to the nucleotide sequence of TAT peptide was conducted and the human recombinant fusion proteins, 10xHis-XaSITE-α-globin-HA and 10xHis-XaSITE-TAT-α-globin-HA were produced. The ability of human recombinant 10xHis-XaSITE-α-globin-HA to interact in vitro with the previously produced 10xHis-XaSITE-TAT-ß-globin-HA and form α-/ß-globin heterodimers, was assessed and confirmed by size exclusion chromatography. The recombinant 10xHis-XaSITE-TAT-α-globin-HA was successfully delivered into human proerythroid K-562 cells, during the preliminary transduction evaluation experiments. Finally, the recombinant, TAT-fused α-globin was successfully transduced into RBCs, derived from HbH patients and reduced the formation of HbH-Inclusion Bodies, known to contain harmful ß4-globin chain tetramers. CONCLUSIONS: Our data confirm the successful ex vivo transduction of recombinant α-globin chains in HbH RBCs to replace the missing a-globin chain and reduce the HbH-inclusion bodies, seen in α-thalassemias. These findings broaden the possibility of applying a Protein Replacement Therapy approach to module sever forms of α-thalassemia, using recombinant α-globin chains, through PTD technology.

In vivo biodistribution study of TAT-L-Sco2 fusion protein, developed as protein therapeutic for mitochondrial disorders attributed to SCO2 mutations.

The rapid progress achieved in the development of many biopharmaceuticals had a tremendous impact on the therapy of many metabolic/genetic disorders. This type of fruitful approach, called protein replacement therapy (PRT), aimed to either replace the deficient or malfunctional protein in human tissues that act either in plasma membrane or via a specific cell surface receptor. However, there are also many metabolic/genetic disorders attributed to either deficient or malfunctional proteins acting intracellularly. The recent developments of Protein Transduction Domain (PTD) technology offer new opportunities by allowing the intracellular delivery of recombinant proteins of a given therapeutic interest into different subcellular sites and organelles, such as mitochondria and other entities. Towards this pathway, we applied successfully PTD Technology as a protein therapeutic approach, in vitro, in SCO2 deficient primary fibroblasts, derived from patient with mutations in human SCO2 gene, responsible for fatal, infantile cardioencephalomyopathy and cytochrome c oxidase deficiency. In this work, we radiolabeled the recombinant TAT-L-Sco2 fusion protein with technetium-99 m to assess its in vivo biodistribution and fate, by increasing the sensitivity of detection of even low levels of the transduced recombinant protein. The biodistribution pattern of [99mTc]Tc-TAT-L-Sco2 in mice demonstrated fast blood clearance, significant hepatobiliary and renal clearance. In addition, western blot analysis detected the recombinant TAT-L-Sco2 protein in the isolated mitochondria of several mouse tissues, including heart, muscle and brain. These results pave the way to further consider this PTD-mediated Protein Therapy Approach as a potentially alternative treatment of genetic/metabolic disorders.

Synthesis, characterization and biological evaluation of Pd(ii), Cu(ii), Re(i) and 99mTc(i) thiazole-based complexes.

A new thiazole-containing multidentate ligand 2-((2-phenylthiazol-4-yl)methylthio)ethanamine, L, was synthesized and used to prepare new complexes of the formula PdIILCl2 (Pd-L), CuIIL2Cl2 (Cu-L) and fac-[Re/99mTcI(CO)3(L)]+ (Re/99mTc-L). The ligand L and the metal complexes were characterized spectroscopically. Furthermore, the structures of Re-L and Cu-L were elucidated by X-ray crystallography. Ligand L acts as a bidentate (Nth, S) chelator in Pd-L, as a bidentate (N, S) chelator in Cu-L and as a tridentate (Nth, S, N) chelator in Re-L. The radiotracer 99mTc-L was synthesized in high yield and characterised by HPLC comparison with the Re-L analog. The synthesized compounds were evaluated for their anti-inflammatory and cytotoxic properties. The compounds exhibited low anti-inflammatory activity with Pd-L showing the highest activity among them. The cytotoxic activity of the ligand and the complexes against several human cancer cell lines (cervical adenocarcinoma HeLa, colorectal adenocarcinoma LS-174T, lung adenocarcinoma A549, breast adenocarcinoma MDA-MB-231 and normal human lung fibroblast cell line MRC-5) was examined using the MTT assay. The complex Cu-L exhibited the highest cytotoxicity and the complex Pd-L showed the best tumor selectivity. The changes in the cell cycle phase distribution were determined by flow cytometry and it was found that ligand L shows the highest apoptotic activity. The biodistribution studies of 99mTc-L in mice showed fast tissue clearance. Of all the thiazole-containing compounds, the palladium complex appears to be more promising for future efforts.

Synthesis and evaluation of 99mTc/Re-tricarbonyl complexes of the triphenylphosphonium cation for mitochondrial targeting.

INTRODUCTION: Lipophilic delocalized cations accumulate in tumor cell mitochondria due to their higher transmembrane potential. In this work, this strategy was adopted for the development of 99mTc tumor-targeted imaging agents. METHODS: Two tridentate ligands containing the triphenylphosphonium cation, L1 (S-cysteinyl) and L2 (N-iminodiacetate) as well as the respective 99mTc/ReL1 and 99mTc/ReL2 tricarbonyl complexes were synthesized. The effect of the ligands and the Re complexes on cell growth in U-87 MG glioblastoma cells was assessed. In vitro stability studies and measurement of logP of the 99mTc tracers was performed. The cellular and mitochondrial uptake of the 99mTc tracers in U-87 MG cells was evaluated. Biodistribution of 99mTcL1 and 99mTcL2 were performed on SCID mice bearing U-87 MG tumors. RESULTS: The ligands L1, L2 and the Re1 and ReL2 complexes were characterized spectroscopically. Single products 99mTcL1 and 99mTcL2, >90% stable in rat serum, were obtained. LogP was 0.40±0.14 for 99mTcL1 and -0.02±0.07 for 99mTcL2. L1, ReL1 and ReL2 caused no notable cytotoxicity and L2 was found to infer 40% inhibition of cellular growth at 10-5M as well as 80% cell death in culture at 10-4M. The cell uptake of 99mTcL1 and 99mTcL2 over 4h was 1.26±0.08% and 0.06±0.01% respectively, of which 13.41±3.63% and 18.61±6.19% was distributed in the mitochondria respectively. The initial tumor uptake in mice was found to be >1% ID/g for both 99mTc tracers. CONCLUSIONS: In vitro mitochondrial and in vivo tumor targeting was observed, better in 99mTcL1, however these properties should be optimized in future studies. Advances in Knowledge and Implications for Patient Care: Continuous efforts in this direction may lead to a suitable mitochondrial-targeted 99mTc imaging agent for tumor detection.

Synthesis and evaluation of a 99mTc tricarbonyl-labeled somatostatin receptor-targeting antagonist peptide for imaging of neuroendocrine tumors.

INTRODUCTION: A somatostatin receptor (SSTR)-targeting antagonist peptide (sst2-ANT) was radiolabeled with 99mTc tricarbonyl via a tridentate [N,S,N]-type ligand (L) to develop a radiodiagnostic agent, 99mTcL-sst2-ANT, for imaging of SSTR-expressing neuroendocrine tumors. METHODS: Receptor affinity was assessed in vitro with the nonradioactive analogue, ReL-sst2-ANT, via a challenge experiment in AR42J cells with 125I-SS-14 as the competing radioligand. Preparation of 99mTcL-sst2-ANT was achieved via reaction of [99mTc(CO)3(H2O)3]+ with L-sst2-ANT. To test the stability of the radiolabeled complex, challenge experiments were performed in phosphate-buffered saline solutions containing cysteine or histidine and also in mouse serum. Biodistribution and micro-SPECT/CT imaging studies were performed in AR42J tumor-bearing female ICR SCID mice. RESULTS: The half maximal inhibitory concentration (IC50 value) of ReL-sst2-ANT in AR42J cells was 15nM. Preparation of 99mTcL-sst2-ANT was achieved with ≥97% radiochemical yield (RCY) and was verified by HPLC co-elution with the ReL-sst2-ANT analogue. The radiolabeled complex remained intact for up to 24h in high concentration solutions of cysteine and histidine at 37°C. Furthermore, the radiotracer was 90% stable for 1h at 37°C in mouse serum. Micro-SPECT/CT images showed clear uptake in tumors and were supported by the biodistribution data, in which the 3.2% ID/g tumor uptake at 4h was significantly blocked by co-administration of nonradioactive SS-14. CONCLUSIONS: A [99mTc(CO)3(N,S,N)]+ chelate was employed for radiolabeling of an SSTR-targeting antagonist peptide. Synthesis of 99mTcL-sst2-ANT was achieved in high RCY, and the resulting complex displayed high in vitro stability. Somatostatin receptor affinity was retained in both cells and in tumor-bearing mice, where the complex successfully targeted SSTR-positive tumors via a receptor-mediated process. Advances in Knowledge and Implications for Patient Care. This first 99mTc-tricarbonyl-labeled SSTR antagonist peptide showed promising in vivo tumor targeting in mice. Future studies may lead to translation of a similar design into the clinic.

Octadecylamine-Mediated Versatile Coating of CoFe2O4 NPs for the Sustained Release of Anti-Inflammatory Drug Naproxen and in Vivo Target Selectivity.

Magnetic nanoparticles (MNPs) can play a distinct role in magnetic drug delivery via their distribution to the targeted area. The preparation of such MNPs is a challenging multiplex task that requires the optimization of size, magnetic, and surface properties for the achievement of desirable target selectivity, along with the sustained drug release as a prerequisite. In that context, CoFe2O4 MNPs with a small size of ∼7 nm and moderate saturation magnetization of ∼60 emu g(-1) were solvothermally synthesized in the presence of octadecylamine (ODA) with a view to investigate the functionalization route effect on the drug release. Synthetic regulations allowed us to prepare MNPs with aminated (AmMNPs) and amine-free (FAmMNPs) surface. The addition of the nonsteroidal anti-inflammatory drug with a carboxylate donor, Naproxen (NAP), was achieved by direct coupling with the NH2 groups, rendered by ODA, through the formation of an amide bond in the case of AmMNPs. In the case of FAmMNPs, indirect coupling of NAP was performed through an intermediate linker (polyethylenimine) and on PEG-ylated MNPs. FT-IR, (1)H NMR, (13)C NMR, and UV-vis data confirmed the addition of NAP, whereas diverse drug-release behavior was observed for the different functionalization approaches. The biological behavior of the MNPs@NAP was evaluated in vitro in rat serum and in vivo in mice, after radiolabeling with a γ-emitting radionuclide, (99m)Tc. The in vivo fate of MNPs@NAP carriers was in straightforward relation with the direct or indirect coupling of NAP. Furthermore, an inflammation was induced intramuscularly, where the directly coupled (99m)Tc-MNPs@NAP carriers showed increased accumulation at the inflammation site.

Synthesis, characterization and biological evaluation of (99m)Tc/Re-tricarbonyl quinolone complexes.

New rhenium(I) tricarbonyl complexes with the quinolone antimicrobial agents oxolinic acid (Hoxo) and enrofloxacin (Herx) and containing methanol, triphenylphosphine (PPh3) or imidazole (im) as unidentate co-ligands, were synthesized and characterized. The crystal structure of complex [Re(CO)3(oxo)(PPh3)]∙0.5MeOH was determined by X-ray crystallography. The deprotonated quinolone ligands are bound bidentately to rhenium(I) ion through the pyridone oxygen and a carboxylate oxygen. The binding of the rhenium complexes to calf-thymus DNA (CT DNA) was monitored by UV spectroscopy, viscosity measurements and competitive studies with ethidium bromide; intercalation was suggested as the most possible mode and the DNA-binding constants of the complexes were calculated. The rhenium complex [Re(CO)3(erx)(im)] was assayed for its topoisomerase IIα inhibition activity and was found to be active at 100µM concentration. The interaction of the rhenium complexes with human or bovine serum albumin was investigated by fluorescence emission spectroscopy (through the tryptophan quenching) and the corresponding binding constants were determined. The tracer complex [(99m)Tc(CO)3(erx)(im)] was synthesized and identified by comparative HPLC analysis with the rhenium analog. The (99m)Tc complex was found to be stable in solution. Upon injection in healthy mice, fast tissue clearance of the (99m)Tc complex was observed, while both renal and hepatobiliary excretion took place. Preliminary studies in human K-562 erythroleukemia cells showed cellular uptake of the (99m)Tc tracer with distribution primarily in the cytoplasm and the mitochondria and less in the nucleus. These preliminary results indicate that the quinolone (99m)Tc/Re complexes show promise to be further evaluated as imaging or therapeutic agents.

Bioactive self-assembling lipid-like peptides as permeation enhancers for oral drug delivery.

Amphiphilic, lipid-like, self-assembling peptides are functional biomaterials with surfactant properties. In this work, lipid-like peptides were designed to have a hydrophilic head composed of aspartic acid or lysine and a six alanine residue hydrophobic domain and have a length similar to that of biological lipids. The aim of this work was to examine the potential of using ac-A6 K-CONH2 , KA6 -CONH2 , ac-A6 D-COOH, and DA6 -COOH lipid-like peptides as permeability enhancers to facilitate transport through the intestinal barrier. In vitro transport studies of the macromolecular fluorescent marker fluorescein isothiocyanate (FITC)-dextran (4.4 kDa) through Caco-2 cell monolayers show the permeation enhancement ability of the lipid-like peptides. We observed increased FITC-dextran transport across the epithelial monolayer up to 7.6-fold in the presence of lipid-like peptides. Furthermore, we monitored the transepithelial resistance and performed immunofluorescence studies of the cell tight junctions. Ex vivo studies showed increased mucosal to serosal absorption of FITC-dextran in rat jejunum in the presence of the ac-A6 D-COOH peptide. Furthermore, a small increase in the serosal transport of bovine serum albumin was observed upon addition of ac-A6 D-COOH. Lipid-like peptides are biocompatible and they do not affect epithelial cell viability and epithelial monolayer integrity. Our results suggest that short, lipid-like peptides may be used as permeation enhancers to facilitate oral delivery of diagnostic and therapeutic molecules.