Circular Dichroism Study of Orexin B under Oxidative Stress Conditions

The neuropeptides orexin A and B regulate various vital functions of the body, such as sleep/wake states, metabolism, and energy homeostasis. A loss of their physiological activity, with reduced ability to recognize their receptors, is suspected to be associated with oxidative stress conditions. These are related to excessive presence of reactive oxygen and nitrogen species, as well as of reactive lipoxidation byproducts. With the aim of evaluating the effects of oxidative stress on the secondary structure of orexin peptides, orexin B was synthesized and characterized by circular dichroism spectroscopy under different conditions. In aqueous solution it presents an unordered conformation, while in a membrane mimetic environment it assumes a helical structure. The effects of oxidative stress were evaluated exposing it to both oxygen and nitrogen radicals as well as to lipoxidation byproducts. The results showed that ROS, but not NRS, induced appreciable conformational changes, and only in the membrane mimetic environment. Lipoxidation byproducts, instead, led to secondary structure modifications much more evident than those induced by the direct action of ROS and RNS, and in both analyzed media. Additionally, MALDI-TOF analyses detected mass variations in the peptide attributable to oxidation of the C-terminal Met residue and deamination of asparagine in the Asn-His sequence. Taken together, all these data seem to confirm the involvement of oxidative processes in dysfunctions of the orexinergic system.

Development and validation of a selective SPR aptasensor for the detection of anticancer drug irinotecan in human plasma samples

In this work, a surface plasmon resonance (SPR)-based assay for the quantification of antineoplastic drug irinotecan in human plasma samples has been developed for the first time. The selective binding of irinotecan with an aptamer receptor, operating in human plasma, allowed to set-up a novel analytical methodology to detect the drug in the analytical range of interest by using SPR as detection technique. After hybridizing the aptamer to the sensing platform and optimizing the sample preparation procedure, a quantitative assay was validated according to FDA regulatory guidelines. The analytical working range was found between 100 and 7500 ng mL^-1 with negligible interferences from plasma components and co-medication associated with the administration of irinotecan. The utility of the new SPR assay was confirmed by analyzing plasma samples in parallel with LC-MS as reference technique, providing a new analytical tool for the therapeutic drug monitoring of irinotecan in patients under chemotherapy regimens.

An SPR investigation into the therapeutic drug monitoring of the anticancer drug imatinib with selective aptamers operating in human plasma

An ss-DNA aptamer-based biosensor was devised to detect the anticancer drug imatinib by means of surface plasmon resonance.

Practical fluorimetric assay for the detection of anticancer drug SN-38 in human plasma

The implementation of therapeutic drug monitoring in the routine clinical practice in oncology is mainly limited by the lack of therapeutic indexes for the majority of the anticancer drugs, and by the absence of suitable analytical tools, which can accurately quantify in real time the concentration of the administered drugs and their relevant metabolites in biological fluids. In this work, a simple and efficient fluorimetric determination of SN-38, the active metabolite of the anticancer drug irinotecan, was developed and applied to human plasma samples. The intrinsic fluorescence of SN-38 allowed its quantification in the range 10-500 ng mL^-1 with a LOQ of 5.0 ng mL^-1 and a LOD of 1.5 ng mL^-1. Low interferences due to main metabolites of irinotecan and comedications, commonly associated with administration of irinotecan, were observed. A validation study, according to FDA and EMA guidelines for bioanalytical method validation, was carried out and, finally, blind samples were analyzed in parallel with a HPLC-MS method obtaining an excellent agreement between the two techniques.

Enzyme-Based Electrochemical Biosensor for Therapeutic Drug Monitoring of Anticancer Drug Irinotecan

Therapeutic drug monitoring (TDM) is the clinical practice of measuring pharmaceutical drug concentrations in patients' biofluids at designated intervals, thus allowing a close and timely control of their dosage. To date, TDM in oncology can only be performed by trained personnel in centralized laboratories and core facilities employing conventional analytical techniques (e.g., MS). CPT-11 is an antineoplastic drug that inhibits topoisomerase type I, causing cell death, and is widely used in the treatment of colorectal cancer. CPT-11 was also found to directly inhibit acetylcholine esterase (AChE), an enzyme involved in neuromuscular junction. In this work, we describe an enzymatic biosensor, based on AChE and choline oxidase (ChOx), which can quantify CPT-11. ACh (acetylcholine) substrate is converted to choline, which is subsequently metabolized by ChOx to give betaine aldehyde and hydrogen peroxide. The latter one is then oxidized at a suitably polarized platinum electrode, providing a current transient proportional to the amount of ACh. Such an enzymatic process is hampered by CPT-11. The biosensor showed a ∼60% maximal inhibition toward AChE activity in the clinically relevant concentration range 10-10 000 ng/mL of CPT-11 in both simple (phosphate buffer) and complex (fetal bovine serum) matrixes, while its metabolites showed negligible effects. These findings could open new routes toward a real-time TDM in oncology, thus improving the therapeutic treatments and lowering the related costs.

Practical synthesis of aryl-2-methyl-3-butyn-2-ols from aryl bromides via conventional and decarboxylative copper-free Sonogashira coupling reactions

Two efficient protocols for the palladium-catalyzed synthesis of aryl-2-methyl-3-butyn-2-ols from aryl bromides in the absence of copper were developed. A simple catalytic system consisting of Pd(OAc)₂ and P(p-tol)₃ using DBU as the base and THF as the solvent was found to be highly effective for the coupling reaction of 2-methyl-3-butyn-2-ol (4) with a wide range of aryl bromides in good to excellent yields. Analogously, the synthesis of aryl-2-methyl-3-butyn-2-ols was performed also through the decarboxylative coupling reaction of 4-hydroxy-4-methyl-2-pentynoic acid with aryl bromides, using a catalyst containing Pd(OAc)₂ in combination with SPhos or XPhos in the presence of tetra-n-butylammonium fluoride (TBAF) as the base and THF as the solvent. Therefore, new efficient approaches to the synthesis of terminal acetylenes from widely available aryl bromides rather than expensive iodides and using 4 or propiolic acid rather than TMS-acetylene as inexpensive alkyne sources are described.

Gases as guests in benzocyclotrimer cage hosts

An imine-linked (+)-syn-benzotricamphor derivative gives access to chiral unimolecular cages exhibiting internal cavities of new shapes and volumes. One of these hosts hydrocarbon gases at low temperatures in solution through CH-pi attractive interactions. No encapsulation is observed when the cage structure is too narrow or too large for the guest.