Oil-Membrane Protection of Electrochemical Sensors for Fouling- and pH-Insensitive Detection of Lipophilic Analytes

To take full advantage of the reagent- and label-free sensing capabilities of electrochemical sensors, a frequent and remaining challenge is interference and degradation of the sensors due to uncontrolled pH or salinity in the sample solution or foulants from the sample solution. Here, we present an oil-membrane sensor protection technique that allows for the permeation of hydrophobic (lipophilic) analytes into a sealed sensor compartment containing ideal salinity and pH conditions while simultaneously blocking common hydrophilic interferents (proteins, acids, bases, etc.) In this paper, we validate the oil-membrane sensor protection technique by demonstrating continuous cortisol detection via electrochemical aptamer-based (EAB) sensors. The encapsulated EAB cortisol sensor exhibits a 5 min concentration-on rise time and maintains a measurement signal of at least 7 h even in the extreme condition of an acidic solution of pH 3.

Clearable Theranostic Platform with a pH-Independent Chemodynamic Therapy Enhancement Strategy for Synergetic Photothermal Tumor Therapy

Chemodynamic therapy (CDT) is an emerging field, which utilizes intratumoral iron-mediated Fenton chemistry for cancer therapy. However, the slightly acidic tumor environment is improper for the classical Fenton reaction, which is generally energetic in a narrow pH range (e.g., pH = 3-4). Herein, a kind of ultrasmall bovine serum albumin (BSA)-modified chalcopyrite nanoparticles (BSA-CuFeS₂ NPs) was synthesized via a facile aqueous biomineralization strategy, which shows high dispersity and biocompatibility. Interestingly, the obtained BSA-CuFeS₂ shows a pH-independent Fenton-like reaction, which could exert Fenton-like activity to efficiently generate ^•OH under a weak acidic tumor environment. Combined with the extraordinarily high photothermal conversion (38.8%), BSA-CuFeS₂ shows the synergistic function of high photothermal therapy (PTT) and enhanced CDT, that is, PTT/CDT. Importantly, such ultrasmall BSA-CuFeS₂ NPs measuring around 4.9 nm can be quickly cleared out of the body through kidneys and liver, thus effectively avoiding long-term toxicity and systemic toxicity. Moreover, BSA-CuFeS₂ NPs can act as an efficient T₂-weighted magnetic resonance imaging (MRI) contrast agent to guide tumor ablation in vivo. This work offers a universal approach to boost production ^•OH by a pH-independent Fenton-like reaction strategy and achieves MRI-guided synergistic enhanced photothermal-CDT for highly efficient tumor treatment.

Sorption and desorption of Pb(II) to biochar as affected by oxidation and pH

The use of biochar for the removal of heavy metals from water has environmental benefits. In order to elucidate the potential application of highly functionalized biochar for the removal of Pb(II) in aqueous solution, maple wood biochar was oxidized using hydrogen peroxide. The pH values of oxidized biochar ranged from 8.1 to 3.7, with one set being adjusted to a pH of 7 as a comparison. It was found that oxidizing the biochars increased their Pb(II) adsorption capacity if the pH remained below 6 (strong oxidation), but decreased their Pb(II) adsorption ability above pH6 (weak oxidation). After adjusting the pH of oxidized biochar to pH7, the Pb(II) adsorption capacity further increased two to sixfold for oxidized biochars originally at pH3.7-6. The adsorption characteristics of Pb(II) were well described by the Langmuir equation. Adsorption of Pb(II) was not fully reversible in water. Less than 6% of Pb(II) desorbed in water in two consecutive steps than was previously adsorbed, for biochars with a pH below 7, irrespective of oxidation. Recovery using an extraction with 0.1M NaNO₃ increased from 0.7% to 32.7% of Pb(II) undesorbed by both preceding water extractions with increasing oxidation, for biochars with a pH below 7. Unextractable Pb(II) was lower at low oxidation but increased to 99.0% of initially adsorbed amounts at low pH, which indicated that the adsorption of Pb(II) on oxidized biochar is pH independent.