A cyclodextrin dimer has been synthesized with two ␤-cyclodextrins linked by a flexible chain containing a carbon-carbon double bond. This dimer binds and solubilizes a phthalocyanine-based photosensitizer that generates singlet oxygen on irradiation. When the complex is irradiated, the singlet oxygen cleaves the carbon-carbon link, and the cyclodextrins are released, liberating the photosensitizer into the light path. Ideas about how this phenomenon could be used to make photodynamic tumor therapy into a more selective process are described. In photodynamic therapy, a dye such as a porphyrin or a phthalocyanine is used in conjunction with irradiation, e.g., by visible light. The excited-state dye converts triplet oxygen to the singlet, which is lethal to cells. Light directed into the area of a tumor can lead to the destruction of cancer cells (1, 2). One problem in this field is of course the accessibility of tumors to irradiation. Another problem has to do with the desirability of localizing the photosensitizer at the tumor site to prevent unwanted side reactions elsewhere. An approach to the latter problem has been to target the photosensitizer by using cancerspecific antibodies (3), but this use of a foreign protein may not be ideal.A different approach has been proposed by Moser et al. (4). If a quite hydrophobic photosensitizer is bound to a cyclodextrin (CD) dimer, the complex will become much more hydrophilic, and the strongly bound sensitizer may not be easily taken up by tissues, including those that are not the target tumor cells. However, if the linker in the CD dimer can be cleaved by singlet oxygen, the photosensitizer should be released from the dimer and then enter nearby cells.If this cleavage occurs in the tumor region that is being irradiated, there should be two results. First of all, cleavage of the CD dimer will deliver the photosensitizer to the affected cells, as proposed by Moser et al. (4). Perhaps more interestingly, the destruction of the dimer-sensitizer complex by light will cause more of it to diffuse into the irradiated region, concentrating the sensitizer where it is needed. In other words, the sensitizer will be concentrated into the directed light beam.We have tested this concept by using an electron-rich carboncarbon double bond as the group that is cleavable by singlet oxygen. The oxygen adds to the double bond to form a dioxetane, which fragments to form two carbonyl groups (5). Sulfur substituents at each end of the double bond increase its reactivity. Materials and MethodsCD dimer 1 was synthesized by conversion of cystamine to its N-t-butoxycarbonyl derivative, then reduction of the disulfide link with sodium in ammonia and reaction of the thiolate with cis-1,2-dichloroethylene to form 2 (Scheme 1). All compounds were characterized by NMR and MS, and this olefin 2 had the characteristic infrared signal at 627 cm Ϫ1 for a cis double bond. Acid deprotection of 2 and then acylation with iodoacetic acid anhydride afforded a bis-iodide that was converted to a bisthioacetate. ...

The synthesis of a linear polymer with pendent γ‐cyclodextrins based on polyallylamine (PAA), a commercially available linear polymer, is described. After the reaction of the polyallylamine with mono‐functionalized γ‐cyclodextrin derivatives, linear polymers with pendent γ‐cyclodextrins were obtained. One compound was less water‐soluble than the starting materials. By masking the remaining unreacted amines, an uncharged, highly water‐soluble polymer was obtained.

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