Role of Hydrogen Bonding of Cyclodextrin-Drug Complexes Probed by Thermodiffusion.

Temperature gradient-induced migration of biomolecules, known as thermophoresis or thermodiffusion, changes upon ligand binding. In recent years, this effect has been used to determine protein-ligand binding constants. The mechanism through which thermodiffusive properties change when complexes are formed, however, is not understood. An important contribution to thermodiffusive properties originates from the thermal response of hydrogen bonds. Because there is a considerable difference between the degree of solvation of the protein-ligand complex and its isolated components, ligand-binding is accompanied by a significant change in hydration. The aim of the present work is therefore to investigate the role played by hydrogen bonding on the change in thermodiffusive behavior upon ligand-binding. As a model system, we use cyclodextrins (CDs) and acetylsalicylic acid (ASA), where quite a significant change in hydration is expected and where no conformational changes occur when a CD/ASA complex is formed in aqueous solution. Thermophoresis was investigated in the temperature range of 10-50 °C by infrared thermal diffusion forced Rayleigh scattering. Nuclear magnetic resonance measurements were performed at 25 °C to obtain information about the structure of the complexes. All CD/ASA complexes show a stronger affinity toward regions of lower temperature compared to the free CDs. We found that the temperature sensitivity of thermophoresis correlates with the 1-octanol/water partition coefficient. This observation not only establishes the relation between thermodiffusion and degree of hydrogen bonding but also opens the possibility to relate thermodiffusive properties of complexes to their partition coefficient, which cannot be determined otherwise. This concept is especially interesting for protein-ligand complexes where the protein undergoes a conformational change, different from the CD/ASA complexes, giving rise to additional changes in their hydrophilicity.

Thermophoresis of cyclic oligosaccharides in polar solvents.

Cyclodextrins are cyclic oligosaccharides which are interesting as drug delivery systems, because they can be used as containers for pharmaceutical substances. We studied the Ludwig-Soret effect of [Formula: see text]-, [Formula: see text]-, [Formula: see text]- and methyl-[Formula: see text]-cyclodextrin in water and formamide by infrared thermal diffusion forced Rayleigh scattering (IR-TDFRS). In water the Soret coefficient, S T, of [Formula: see text]-, [Formula: see text]- and [Formula: see text]-cyclodextrin increases with increasing temperature and shows a sign change from negative to positive around T = 35 ° C, while S T of methyl-[Formula: see text]-cyclodextrin is positive in the entire investigated temperature. In formamide S T-values of all cyclodextrins coincide and show a slight decrease with temperature. We discuss the obtained results and relate the S T-values to the different hydrogen bonding capabilities of the cyclodextrins and the used solvents. It turns out that the change of S T with temperature correlates with the partition coefficient, logP, which indicates that more hydrophilic substances show a more pronounced temperature sensitivity of S T. Additionally we obtained a surprising result measuring the refractive index contrast factor with temperature, [Formula: see text] of cyclodextrins in formamide, which might be explained by a complex formation between cyclodextrins and formamide.

[A case of drug-induced interstitial pneumonitis after adjuvant chemotherapy with gemcitabine for bile duct cancer].

A 70-year-old man received pancreaticoduodenectomy for bile duct cancer and had been administered gemcitabine for 1 year as adjuvant chemotherapy. He complained of shortness of breath on effort and was admitted for gemcitabine-induced interstitial pneumonitis. His respiratory status was worsening after admission, so he was transferred in the intensive-care unit and required mechanical ventilator and steroid pulse therapy with 1,000 mg/day of methylprednisolone. His symptoms and radiological findings were dramatically improved. The patient could be discharged on the 24th day after admission. Interstitial pneumonitis induced by gemcitabine is rare, but could lead to severe complications, which could develop after long-term administration and should be treated by corticosteroid as soon as possible.

[Effect of hepatic arterial infusion chemotherapy for liver metastasis from gastric cancer].

We performed hepatic arterial infusion (HAI) chemotherapy for 4 patients with advanced gastric cancer who had undergone curative resection except for liver metastasis. The main antineoplastic drugs were 5-fluorouracil (5-FU), mitomycin C (MMC) and cisplatin (CDDP). A catheter was inserted into the hepatic artery by interventional radiological techniques in 3 patients and operatively in 1 patient. The response rate for 4 patients was 75% (CR2, PR1, PD1). The adverse events were Grade 3/4 nausea and/or vomiting in 2 cases. The HAI chemotherapy was effective and useful for patients with advanced gastric cancer who had no unresectable lesions except for liver metastasis.