The successful treatment of cancer by boron neutron-capture therapy (BNCT) requires the selective concentration of boron-10 within malignant tumors. The potential of liposomes to deliver boron-rich compounds to tumors has been assessed by the examination of the biodistribution of boron delivered by liposomes in tumor-bearing mice. Small unilamellar vesicles with mean diameters of 70 nm or less, composed of a pure synthetic phospholipid (distearoyl phosphatidylcholine) and cholesterol, have been found to stably encapsulate high concentrations of water-soluble ionic boron compounds. The hydrolytically stable borane anions B,.H01, B,2H11SH2-, B20H170H4-B2]HT3, and the normal form and photoisomer of B2oH 2-were encapsulated in liposomes as their soluble sodium salts. The tissue concentration of boron in tumor-bearing mice was measured at several time points over 48 h after i.v. injection of emulsions of liposomes containing the borane anions. Although the boron compounds used do not exhibit an affinity for tumors and are normally rapidly cleared from the body, liposomes were observed to selectively deliver the borane anions to tumors. The highest tumor concentrations achieved reached the therapeutic range (>15 jtg of boron per g of tumor) while maintaining high tumor-boron/blood-boron ratios (>3). The most favorable results were obtained with the two isomers of B2OH _. These boron compounds have the capability to react with intracellular components after they have been deposited within tumor cells by the liposome, thereby preventing the borane ion from being released into blood.Boron neutron-capture therapy (BNCT), first proposed by Locher in 1936 (1), is based upon the propensity of the 10B nucleus to undergo the 10B + 1n -* 'Li + 'He reaction with thermal neutrons. This process releases 2.28 MeV of kinetic energy, which is distributed between the a-particle and the 7Li+ ion. The effective distance of travel of these two ions in tissue is limited to approximately one cell diameter. During their passage through the interior of a cell, the energetic fission products cause ionization-tracking and cellular damage with associated cytotoxicity. Since the neutron capture cross-section of the 10B nucleus is 103 to 104 greater than that of all elements of physiological importance, the selective concentration of 10B atoms within cancer cells, followed by irradiation with thermal neutrons, should result in the destruction of the tumor cells even in the presence of neighboring normal cells.The development of effective targeting strategies for the selective transport ofboron to cancer cells has been the single most urgent problem in the area of BNCT. Successful therapy requires the site-specific delivery of relatively large amounts (15-20 jig of B per g of tissue) of boron to tumors (2). Strategies employed have included the use of boron compounds with some natural affinity for tumors, such as 4-(dihydroxyboryl)phenylalanine (BPA) (3) or the mercaptoundecahydro-closo-dodecaborate dianion (B12H,,SH2-; BSH) (4); the attac...

Comprehensive investigation of lithium ion complexation with 15N-labeled polyphosphazenes 15 N-poly[bis(2-(2-methoxyethoxy)ethoxy)phosphazene] (15 N-MEEP) and 15 N-poly-[((2-allylphenoxy)0.12(4-methoxyphenoxy)1.02(2-(2-methoxyethoxy)ethoxy)0.86)phosphazene] (15 N-HPP)was performed by NMR, IR, and Raman spectroscopies. Previous studies characterized the ionic transport through the polymer matrix in terms of “jumps” between neighboring polymer strands utilizing the electron lone pairs of the etherial oxygen nuclei with the nitrogen nuclei on the polyphosphazene backbone not involved. However, noteworthy changes were observed in the NMR, IR, and Raman spectra with the addition of lithium trifluoromethanesulfonate (LiOTf) to the polyphosphazenes. The data indicate that the preferred association for the lithium ion with the polymer is with the nitrogen nuclei, resulting in the formation of a “pocket” with the pendant groups folding around the backbone. NMR temperature-dependent spin−lattice relaxation (T 1) studies (13C, 31P, and 15N) indicate significant lithium ion interaction with the backbone nitrogen nuclei. These studies are in agreement with molecular dynamics simulations investigating lithium ion movement within the polyphosphazene matrix.

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Determining the seasonal movement patterns of fish can provide insight into their spawning behaviors, predator–prey interactions, and habitat preferences. To investigate the seasonal movement patterns of adult yellow perch and how they are affected by lake habitat characteristics, we attached ultrasonic transmitters to two length‐groups (210–235 and 250–280 mm total length) of yellow perch from populations inhabiting two temperate lakes differing in habitat diversity and basin morphology. In the simple lake, yellow perch distributions differed between seasons, mean depth and distance from shore being greatest during the summer. The observed seasonal differences were similar between the two length‐groups. In the complex lake, yellow perch depth varied seasonally, the fish occupying deeper waters during the fall and shallower ones during the summer; however, the distance from shore was consistent among seasons. During the spring, males inhabited areas closer to shore than females in the complex lake, whereas the spatial distributions did not differ between sexes in the simple basin. Yellow perch from both lakes displayed similar seasonal variation in activity, movement rates being highest during the fall and lowest during the summer. Movement rates in the simple lake, however, were higher than those in the complex lake during all three seasons, which suggests that the effectiveness of passive sampling gears may vary in response to habitat complexity. These results reveal several seasonal differences in yellow perch habitat use, distribution, and activity in relation to basin complexity that may provide insight for managers considering sampling plans for individual lake types.

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