logo ban ban logo

Každý, kdo se přestane učit, je starý, ať je mu 20 nebo 80. Každý, kdo se stále učí, zůstává mladý. Je nejlepší v životě zůstat mladý.

Henry Ford

mendel

Výzkum

Electrochemical Behaviour of Doxorubicin Encapsulated in Apoferritin

Doxorubicin ((8S,10S)-10-(4-amino-5-hydroxy-6-methyl-tetrahydro-2H-pyran-2-yloxy)-6,8,11-trihydroxy-8-(2-hydroxyacetyl)-1-methoxy-7,8,9,10-tetrahydrotetracene-5,12-dione) called also as daunomycin and/or adriamycin is an anthracycline antibiotic (inset in Fig. 1A). It is commonly used in the treatment of a wide range of malignancies. The exact mechanism of action of doxorubicin is complex and still somewhat unclear. The current accepted mechanisms are intercalation into DNA and topoisomerase II inhibition [1-6]. However, its toxicity and association with the development as substantial cardiotoxicity decreases wider using if the drug in therapy [1,7-10]. Generating of reactive oxygen species causing lipoperoxidation that cause damaging of cell membranes, apoptotic changes via interaction with iron ions and activation of NF?B belongs to the other important effect of doxorubicin in vivo [1,3,11]. Thus, the main accent is to reduce the toxicity and find some transporter of this cytostatic to the cancer cells [12-14]. Successful process how to reach both points is encapsulation of anticancer drug into some transporter [15-17]. Numerous transporter systems like protein-based carriers [18], liposomes [19] and antibodies [20] have been suggested. It seems that intracellular protein apoferritin could be considered as a promising compound for transport [21-23], because contains a cage with internal and external diameters of 8 and 12 nm, respectively [24]. Apoferritin-binding sites [25] and endocytosis of apoferritin [26] have been identified in neoplastic cells and apoferritin may improve the drug selectivity for cell surfaces that express ferritin receptors. Due to the fact that it is possible to form complex apoferritin-doxorubicin by “opening” and “closing”, apoferritin receptors could be suitable candidate for anticancer drug delivering [27]. Encapsulated doxorubicin can be free by pH changing to the acidic and doxorubicin can attack cancer cells [28,29].

The electrochemical detection of doxorubicin (and other related drugs) is possible due to electroactivity of these molecules [30-43]. Doxorubicin is a complex molecule, where quinone and hydroquinone groups are electroactive and can be used to identify electrochemical reduction and/or oxidation of the drug [44,45]. Studies have been carried with mercury, carbon and other types of modified electrodes [46-49]. Polarographic behaviour of doxorubicin has been investigated by several authors with good sensitivity [31,50-53]. Carbon paste electrodes are superior to other solid electrodes in having a low residual current a noise [54] and due to the fact that their preparation is easy. These electrodes can be used for both cathodic and anodic based assays [55]. Basic electrochemical behaviour of doxorubicin at carbon paste electrode (CPE) has been investigated by several authors [56-60]. Application of carbon nanotubes (CNT) modified electrode for electrochemical detection of doxorubicin was also suggested too [59,61]. The interaction between the CNT and the anthracycline could enhance the electron transfer, which increased the detection sensitivity and lowered the detection limit [62]. It can be predicted that many more analogues could be monitored on such a platform with high sensitivity [63].

The main aim of this study was encapsulating of doxorubicin into apoferritin structure. It was achieved by reassembly route. At low pH (addition of HCl) apoferritin structure opens and the structure is reconstituted again after addition of base. In the presence of doxorubicin in solution some amount of doxorubicin is caught inside the cavity. This encapsulating/opening was detected using differential pulse voltammetry at expanded carbon paste electrode. Characterisation of electrochemical signal for doxorubicin. (A) Dependence of relative peak height on accumulation time for 100 µg/ml doxorubicin; in the left inset: scheme of doxorubicin with two outline position (quinone redox and hydroquinone redox centre). Inserted voltammogram of doxorubicin (100 µg/ml) has two characteristic peaks D1 at the potential -0.55 V and at the potential D2 -0.68 V, electrolyte has pH 5.5. (B) Dependence of relative peak height (green axis) on electrolyte pH, peak at -0.55 V ( ) and at -0.68 V ( ), change of peak position (orange axis) on electrolyte pH, peak at -0.55 V ( ) and at -0.68 V ( ), doxorubicin concentration 100 µg/ml. Inserted voltammogram shows changing of height or disappearance of some peak due to pH of electrolyte. This effect is demonstrated for pH 3.0, 3.5, 4.5 and 5.5. All experiments were measured by DPV with the following parameters: initial potential -1.0 V, end potential 0 V, amplitude 0.05 V, pulse width 0.2 s, pulse period 0.5 s, deposition potential -1.0 V and time of accumulation 120 s. Phosphate buffer with different pH (0.1 M) was used as a supporting electrolyte.

Podpořeno projekty: : CEITEC CZ.1.05/1.1.00/02.0068

Zemědělská 1/1665
613 00 Brno
Budova D		Tel.: +420 545 133 350
Fax.: +420 545 212 044