Quantification of the Dissolved Inorganic Carbon Species and of the pH of Alkaline Solutions Exposed to CO₂ under Pressure: A Novel Approach by Raman Scattering

Dissolved inorganic carbon (DIC) content of aqueous systems is a key function of the pH, of the total alkanility (TA), and of the partial pressure of CO₂. However, common analytical techniques used to determine the DIC content in water are unable to operate under high CO₂ pressure. Here, we propose to use Raman spectroscopy as a novel alternative to discriminate and quantitatively monitor the three dissolved inorganic carbon species CO₂(aq), HCO₃^–, and CO₃^2– of alkaline solutions under high CO₂ pressure (from <i>P</i> = 0 to 250 bar at <i>T</i> = 40 °C). In addition, we demonstrate that the pH values can be extracted from the molalities of CO₂(aq) and HCO₃^–. The results are in very good agreement with those obtained from direct spectrophotometric measurements using colored indicators. This novel method presents the great advantage over high pressure conventional techniques of not using breakable electrodes or reference additives and appears of great interest especially in marine biogeochemistry, in carbon capture and storage and in material engineering under high CO₂ pressure

Synthesis, characterization, and In vitro studies of an reactive oxygen species (ROS)-responsive methoxy polyethylene glycol-thioketal- melphalan prodrug for glioblastoma treatment

Glioblastoma (GBM) is the most frequent and aggressive primary tumor of the brain and averages a life expectancy in diagnosed patients of only 15 months. Hence, more effective therapies against thismalignancy are urgently needed. Several diseases, including cancer, are featured by high levels of reactive oxygen species (ROS), which are possible GBM hallmarks to target or benefit from. Therefore, the covalent linkage of drugs to ROS-responsive molecules can be exploited aiming for a selective drug release within relevant pathological environments. In this work, we designed a new ROS-responsive prodrug by using Melphalan (MPH) covalently coupled with methoxy polyethylene glycol (mPEG) through a ROS-cleavable group thioketal (TK), demonstrating the capacity to self assembly into nanosized micelles. Full chemical-physical characterization was conducted on the polymeric-prodrug and proper controls, along with in vitro cytotoxicity assayed on different GBM cell lines and “healthy” astrocyte cells confirming the absence of any cytotoxicity of the prodrug on healthy cells (i.e. astrocytes). These results were compared with the non-ROS responsive counterpart, underlining the anti-tumoral activity of ROS-responsive compared to the non-ROSresponsive prodrug on GBM cells expressing high levels of ROS. On the other hand, the combination treatment with this ROS-responsive prodrug and X-ray irradiation on human GBM cells resulted in an increase of the antitumoral effect, and this might be connected to radiotherapy. Hence, these results represent a starting point for a rationale design of innovative and tailored ROS-responsive prodrugs to be used in GBM therapy and in combination with radiotherapy