Electrochemical catechol biosensor based on β-cyclodextrin capped gold nanoparticles and inhibition effect of ibuprofen

Herein, β-cyclodextrin-capped gold nanoparticle surface designed for tyrosinase (Tyr)-based nanosensor is proposed and demonstrated. Integration of the β-cyclodextrin-capped gold nanoparticles on graphite electrode surface was achieved via drop-casting method, Tyr was immobilized on the modified electrode and then used as drug inhibition platform with catechol as the substrate. All optimization studies that affect biosensor response were conducted, and catechol was detected in the linear range of 1.56 μM-25μM catechol concentration with a limit of detection of 0.42 μM and sensitivity of 2.094 μA.μM−1. cm-2. Tyr inhibition was followed with ibuprofen drug active compound with a 15 min incubation time, and the I50 value was found as 213 μM. The sensor is the first in the literature to use an electrochemical method for β-cyclodextrin-capped gold nanoparticles based Tyr biosensor and ibuprofen inhibition. This sensor presents an easy fabrication method, excellent sensor properties, and ibuprofen inhibition capabilities. As a result, it is proposed that the designed sensor is an ideal marker for detecting Tyr inhibition using electrochemical methods and an ibuprofen-based cosmetic cream formulation could be a viable option in the cosmetic market

Ponto-caspian and mediterranean faunal and floral records of upper pleistocene-holocene sediments from the Izmit Gulf (Marmara Sea, Turkey)

Izmit Gulf is located between Kocaeli and Armutlu peninsulas at east of Marmara Sea and the interaction area of North Anatolian Fault Zone (NAFZ) and Marmara Graben systems. In this study, the faunal and floral contents (ostracod, foraminifer, mollusc and diatom) of the samples belonging to seven drilling cores were studied and obtained the radiocarbon and optically stimulated luminescence (OSL) age data in order to establish on the Black Sea -Marmara Sea - Mediterranean water connections and palaeoenvironmental changes. The sediments in this study are Late Pleistocene-Holocene aged and only cover the Marine Isotope Stages MIS-5 (interglacial), MIS-3 (an interstadial period between MIS-4 and MIS-2 glacial epochs) and MIS-1. The determination of ostracod and mollusc fauna of the Mediterranean and Ponto-Caspian origin provide important clues to water exchange between the Mediterranean and the Black Sea. Although some Mediterranean originated ostracods occur sporadically with low abundance, absence of foraminiferal fauna and existence of Ponto-Caspian ostracods together with fresh water and cosmopolitan diatom flora indicate that the area strongly interacted with the Black Sea waters during MIS-5. The faunal and floral characteristics of the sediments deposited during MIS-3, clearly denote that the Izmit Gulf was connected with the Black Sea and the Mediterranean Sea at the beginning of MIS-3 (ca. 52.0 - 40.0 ky BP) and the shallow shelf areas were frequently affected by both the Black Sea discharge and Mediterranean input. A thick Holocene sedimentary sequence recovered from the southern Hersek Burnu drilling cores reflects the environmental changes after the latest Black-Mediterranean seas connection. The studied ostracod and mollusc assemblages are mainly characterized by the Mediterranean originated species with a few relict Ponto-Caspian fauna. Also, the benthic foraminiferal assemblages are dominated by normal marine and euryhaline species, reflecting the salinity fluctuations in the Holocene interval